S>ttxU fflolUgg of AgticulturB At (!(atneU Hntnecsity QC eos.Ds""""'"""''''''-""''^ Storage battery manual, including princip 3 1924 002 939 712 Cornell University Library The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924002939712 STORAGE BATTERY MANUAL STORAGE BATTERY MANUAL INCLUDING PRINCIPLES OF STORAGE BATTERY CONSTRUCTION AND DESIGN WITH THE APPLICATION OF STORAGE BATTERIES TO THE NAVAL SERVICE BY LUCIUS C. DUNN Lieutenant Commander, U. S. Navy g i m 1920 United States Naval Institute Annapolis, Maryland Copyright, 1920, bt J. W. CONROY Trustee for U. S. Naval Institute Annapolis, Md. CJe Both (§Atimoxt (pi-eee SALTIUORE, MD., U. s. j\. PEEPACB. Owing to the very rapidly increasing application of storage battery engi- neering to our naval service, and believing that there exists a growing need for a modern text-book on this subject, eifort has therefore been put forth in the productiou of this volume with the hope that it will prove of assistance in the instruction of our personnel in this very important and interesting branch of electrical engineering. Special effort has also been put forth in an attempt to present the subject matter of the text in as simple and as practical a manner as possible and with the use of only those involved formulae and mathematical expressions as have been deemed absolutely essential in developing and supporting the text. Great pains have also been taken in composing and selecting the various drawings and photographs used for clearly illustrating the text. My very sincere thanks are due and are extended to many of the battery engineers of the following companies for the numerous valuable and helpful hints received from them in relation to this subject and which have been crystallized into the production of the text of this volume, and also for the use of many of the illustrations used in connection with the text : The Electric Storage Battery Co., The Gould Storage Battery Co., The General Lead Batteries Co., The Philadelphia Storage Battery Co., The TJ. S. Light and Heat Corporation, The Willard Storage Battery Co., The Goodrich Bubber Co., The Brown Instrument Co., The Werner and Pfleiderer Co., and The Cutter Electrical and Mfg. Co. Lucius C. Dunn, Lieutenant Commander, TJ. S. Navy. U. S. Naval Forces Operating in European Waters. June, 1920 CONTENTS. CHAPTER PAGE I. Historical 1 II. Chemical Theory and Description of the Lead-Acid Storage Bat- tery Cell 5 III. Definitions and Nomenclature of Parts 14 IV. Description of Unit Assembly Type Cells 25 V. Application of the Storage Battery to the Naval Service 30 VI. Paste Type Assemblies 36 VII. Plants Type Assemblies 58 VIII. Capacity and BflBciency 74 IX. Electrolyte 88 X. Plate Insulation and Separators 105 XI. Jars 133 XII. Cell Covers and Soft Rubber Parts 153 XIII. Cross-Bars, Straps, Terminal Posts and Connectors 166 XIV. Cell Trays and Containers 190 XV. Watering Battery 202 XVI. Charging and Discharging Batteries 206 XVII. The " Trickling " Charge 238 XVIII. Floating the Storage Battery on the Line 250 XIX. Battery Ventilation 270 XX. Shipping Storage Batteries 281 XXI. Receiving Storage Batteries. Placing in Commission. Placing out of Commission 301 XXII. Faults. Methods of Detecting and Rectifying 314 XXIII. Repairs and General Overhaul 321 XXIV. Lead-Burning 344 XXV. Manual of Inspection 352 XXVI. Testing Storage Batteries 365 XXVII. The Cadmium Test 377 XXVIII. Miscellaneous Notes 383 CHAPTEE I. HISTORICAI. Discovery of the Voltaic Couple. In 1790 Alessandro Volta, an Italian physicist, discovered that if electrodes of two chemically dissimilar conducting substances are immersed in an electrolyte which is capable of attacking one or both of the electrodes, an electromotive force is produced which accordingly sets up a flow of current when the external circuit between the two electrodes is closed. Such a com- bination of electrodes and electrolyte has since been called a " Voltaic Couple," after its discoverer. In continuing his search in this direction, Volta also found that as long as the external circuit between the electrodes of the couple remained open, practically no chemical reaction between the electrolyte and the electrodes resulted ; but, as has been stated, as soon as the external circuit was closed, chemical reaction was instantly brought about between the electrolyte and the electrodes, with the resultant flow of electrical current through the external circuit. This chemical reaction resolved itself into either dissolving the affinitive electrode in the electrolyte, or its combining with the electrolyte to form another substance. This discovery having been made, it next became the logical step for man to so select and combine the electrodes and electrolyte composing this couple as to commercially utilize the resultant current and energy thus generated. PRIMARY BATTERY. The first commercial utilization of the voltaic couple as an electrical energy producing medium was in the form of the well-known primary cell or " primary battery," as it is commonly known. There have been various designs of this type cell developed and of which the Le Clanche cell and the various dry or " sparker " batteries are familiar examples. In this type of battery, the wasting away or exhaustion of the electrodes or the electrolyte necessitates a removal of the resultant substances thus formed, or even a renewal of the wasted or exhausted portion of the couple before the cell is capable of producing any further useful electrical energy. In other words, the voltaic couple in this type of cell is not reversible. 3 Storage Battery Manual secondary ok storage battery. PlantS's Discovery and Experiment Explained. Many years had elapsed since Volta gave his discovery to the world, and since which time many of the most prominent physicists of their respective times had diligently applied themselves to the task of evolving the theory and principles co-incident with the action of the voltaic couple, when in 1860 Gaston Plante, a French physicist, while engaged in certain related electro- lytic research work in his laboratory, had set up a small cell in connection with his work; the electrodes of this cell consisted of plain rolled sheets of pure lead, while the electrolyte consisted of dilute sulphuric acid. Also, in series with the external circuit of this cell was connected a galvanometer. During the course of his experiments and after he had been passing direct current through this small cell for some little time, Plante, while changing his connections, accidentally brought the terminals of the external circuit of this cell into contact with each other, whereupon he was surprised to observe the needle of the galvanometer swing to the opposite side of the scale, thus indicating that current was flowing through the external circuit in an oppo- site direction to that in which it had originally been flowing when passing current through the cell. Although it was noted that this secondary current lasted for a few seconds only, in following up his experiments Plante dis- covered that each time he repeated the operation, the duration of the secondary current increased, until after several such trials the secondary current became of quite appreciable magnitude. Furthermore, in con- tinuing his research along this line, Plante discovered that if the direction of charging current through the cell were reversed each time, the resulting secondary current was increased in magnitude much more rapidly. Upon further investigation Plante noted that whereas the surfaces of the lead plates were originally bright before placing them in the sulphuric acid, they immediately became coated with a white fllmy substance when placed in the acid. This feature of the experiment is accounted for by the fact that .■julphuric acid has a great afiinity for metals, and the white filmy substance on the surfaces of the lead plates was the lead-sulphate formed as a result of the action of the sulphuric acid on the lead. Plante also noted that when current had been passing through the cell for some little time the white coating on the surface of the positive plate became dark brown in color, and that on the negative plate a light gray. Subsequent chemical analysis proved the dark brown substance on the surface of the positive plate to be lead-peroxide, or a sort of lead rust, and the light gray substance of the negative plate, sponge lead, or metallic lead in a spongy state. Historical 3 Also, upon discharging the cell, Plante noted that these substances gradually changed in color until they again became white. Further exami- nation revealed the fact that at the end of the discharge the surfaces of both plates had again been converted into lead-sulphate. Also, each time this experiment was repeated, the coatings on the surfaces of the plates became thicker, which accounts for the increase in capacity of the cell noted during the course of his experiments. This type of plate has since been called a " Plante plate," after its discoverer. Thus it is seen that Plante, in passing a direct current through this small cell containing the pure lead electrodes and dilute sulphuric acid, had unconsciously converted it into a formidable voltaic couple, the active com- ponents of which were lead-peroxide (PbOj), sponge lead (Pb), and dilute sulphuric acid (HjSO^). Moreover, he had produced a voltaic couple, all elements of which were capable of restoration to their original state, after exhaustion, by passing current through the cell in the opposite direction, and it is as a result of this discovery and the principles involved that the modern storage battery has been developed. Difference Between Primary and Secondary Cell. As has been described in the preceding paragraphs, the fundamental prin- ciple of the secondary or storage battery cell is based on the reversibility feature of its voltaic couple. Furthermore, this feature of reversibility con- stitutes the radical difference between the primary and the secondary cell; in other words, the voltaic couple of the primary cell is not capable of reversibility, whereas that of the secondary cell is capable of such reversibility. It is, therefore, essential to a proper understanding of this subject that this distinction be thoroughly understood in the beginning and, since this dis- tinction has thus been explained in the preceding paragraphs, the succeeding text of this book will deal entirely with the reversible voltaic couple and its application to the storage battery or accumulator, as used in the naval service. Faure or Fasted Plates. Although Plante had discovered a reversible voltaic couple, months of charge, discharge and reversal were necessary with his process in order to form layers of lead-peroxide and sponge lead of sufficient thickness to produce a battery having any material capacity. Therefore it remained for the next important step in the development of the storage battery to be taken in the direction of a reduction in the time element necessary to complete this " forming process." 4 Storage Batteey Manual This kighly important and advanced step in the development of the storage battery vs^Ss achieved in 1880 vrhen a Frenchman, Camille Faure, in France, and an American, Charles F. Brush, in America, practically simul- taneously discovered a process by which a thick coating of lead-oxide, when mixed with sulphuric acid and worked up into a paste of putty-like con- sistency, could be applied to a skeleton framework or " grid," thus forming a plate, and that by placing these plates in dilute sulphuric acid and passing a single low rate charge through them, the lead-oxide on the respective positive and negative plates was converted into highly porous lead-peroxide and sponge lead. These plates have since been called " Faure " or " pasted plates." Since their discovery, these paste plates have undergone successive stages of development in the way of improved methods of combining and mixing the paste, as well as improvement in the design and construction of the grids, separators and other component parts. Improvement in Process of Forming Plante Plates. Although the development of the pasted type plate had insured the ulti- mate success of the storage battery as an efficient energy producing agent, the development of this art was not confined entirely to the paste type plates, as physicists, electrochemists and inventors were constantly engaged in trying to develop an improved method for the " forming process " of Plants plates. Happily, this field of endeavor was not without favorable results, as is indicated by the fact that the modern " forming " methods employed in the manufacture of Plante plates are capable of producing these plates about as quickly and as cheaply as those employed in producing Faure or " paste plates." Among these modern " forming " methods may be included the various fashioned grooving of the surfaces of these plates to increase their surface area in contact with the acid, and also the employment of various rapid electrochemical forming agents, such as hydrochloric acid, nitric acid, per- chloric acid and other lead corroding acids acting in conjunction with the sulphuric acid of the electrolyte. Moreover, the development of both of the above types of plates has pro- ceeded hand in hand, each having contributed its share to the successes achieved in this very important branch of electrical engineering. Each type of plate has its own particular field of efficient service, and in some instances these services require that both types be installed in the same cell. In this regard, it may be said, that, generally speaking, paste plates are used where maximum capacity per unit of weight is required and where life is not a governing factor, whereas, Plante plates are used for services in which weight is not a material factor and the desirability for long life is paramount. CHAPTEE II. CHEMICAI THEORY AND DESCRIPTION OF THE LEAD-ACID STORAGE BATTERY CELL. Development of the Storage Battery Cell. As explained in the preceding chapter, the storage battery cell, in its modern conception, consists of an application of the reversible voltaic couple in a highly developed stage of perfection. Moreover, in bringing the storage battery cell to this highly developed stage of perfection, such that it effi- ciently performs the many duties required of it in the modern electrical engineering world, it has been necessary for the storage battery engineer to carefutly consider three very important fundamental factors entering into the design and construction of this cell and to so arrange and combine these factors as to produce a well-balanced, practical and workable unit. These factors are as follows : 1. Mechanical. 2. Electrical. 3. Chemical. Mechanical Factor. The mechanical factor enters primarily into fulfilling the various struc- tural requirements of the battery, such as design and construction of the grids and plates and methods of retaining in position the active material of the plates; methods of connecting the plates to their corresponding straps and terminal posts, as well as securing the element in the jar ; various methods of plate separation and insulation ; design of the jar and cover and the various cover fittings, such as filling vents, terminal post bushings, gaskets, terminal post nuts, etc. ; design and construction of inter-cell connectors and methods of connecting the cell terminals to their corresponding service lines. In brief, obtaining necessary structural ruggedness and durability in the general design of the storage battery is the prime function of the mechanical factor. Electrical Factor. In the art of storage battery construction and design the electrical factor is equally as important as the mechanical factor. Upon the electrical factor largely depends the true and practical efficiency of the battery, since, as is true with other electrical apparatus, in order that the battery may satis- factorily perform its designed function, it is necessary that certain electrical characteristics be obtained. 6 Storage Battery Manual Therefore, in point of design, the electrical factor consists in so propor- tioning the grids, plates, straps, terminal posts, connectors, etc., that they will possess ample current carrying capacity, without undue voltage drop and heating, when the battery is subjected to the regular operating conditions of charge and discharge for which it was intended. In addition to the above general conditions to be fulfilled by the electrical factor, the following specific- points of design may also be included under this heading : (a) The design of the grid and plate and the distribution of the active material should be such as to produce uniform working of the plate over its entire surface. (b) The active material should be applied to the plate or grid in such manner that it will maintain proper contact with itself and the grid and thus produce maximum electrical conductivity. (c) In the larger type cells of high ampere-hour capacity, such as the submarine type, which require copper inserts in the straps, terminal posts and connectors, it is necessary that good electrical contact be obtained between the copper and the lead-alloy casting or plating around same in order that heating and the consequent loss of energy and efficiency may be prevented. The copper inserts should also possess a high degree of electrical conductivity. Improper contact between the copper and the lead-alloy casting has been a source of much trouble in the past in the storage battery engineering world, and this feature has been the subject of much study by battery engineers, and a great deal of development work has gone on, until now the modern methods employed produce a very satisfactory union between the copper and the lead-alloy castings. This subject will be taken up in detail in a later chapter. (d) Design of separators and methods of plate insulation should be such that internal resistance of the cell will be reduced to a minimum. This feature consists in selecting suitable woods for separators and specially treating these woods to lower their resistance to the passage of electrical current. Various methods of treating these woods have been devised. The design of the rubber separators, such as percentage of porosity, thickness, composition, etc., may also be properly placed uiider this heading. (e) Such details of the designs of the cells, jars, covers, connectors, trays, etc., as have to do with proper insulation and prevention of grounds. (f) Various methods and designs of attachments used in connecting the several cells to each other and to their service lines. Chemical Factor. Unlike practically all other types of electrical apparatus, the designs and methods of operation of which depend principally upon mechanical and The Lead-Acid Storage Battery Cell 7 electrical factors, the storage battery cell depends upon a third essential factor — the chemical factor. Moreover, it should be understood that in designing and operating the storage battery cell, the chemical factor is deserving of equal consideration with those other two factors, that is, the mechanical and the electrical factors. Also, although the application of the chemical factor involves many complex and intricate problems, both prac- tical and theoretical, when certain of the chemical fundamentals connected with the action of the storage battery cell are studied and understood, many of the apparent complex features of this subject will have been removed. It is therefore well in beginning the study of this subject to consider the prime constituents of the lead-acid storage battery cell and the fundamental equation of the reactions which take place in this cell during the cycle of charge and discharge. The active constituents of the lead-acid storage battery cell are as follows : (a) Positive plate; lead-peroxide (PbOj), which is of a velvety "choco- late " brown color. (b) Negative plate; finely divided sponge lead (Pb), which is of a " battleship " gray color. (c) Electrolyte; dilute sulphuric acid (H2SO4), consisting of chemically pure sulphuric acid diluted with pure distilled water. The generally accepted fundamental equation for the normal chemical action which takes place in this cell may be thus indicated as follows : » Pb-j-PbOj-fSHjSO^; cell in charged condition. SPbSO^-l-SHjO ; cell in discharged condition. Therefore, in combining the above, the fundamental equation of the com- plete reaction is written as follows : Pb-|-Pb02-F2H,SO, ( :> ) 2PbS0i-|-m„0. In other words, the conventional sign ( i ) indicates that this reaction is completely reversible ; that is, reading this equation from left to right ( ->- ) denotes the action which takes place during discharge of the cell, and reading from right to left (-<-), that which takes place during charge. It is therefore apparent from the above equation that during discharge the acid radical, SO4, of the electrolyte combines with the active materials of the positive and negative plates and converts both of these plates into lead-sulphate (PbSOj). Moreover, during charge the lead-sulphate is reduced by the charging current and the acid radical returned to the electro- lyte, the active materials of both plates being accordingly restored to their original states ; that is, to sponge lead and lead-peroxide. Storage Battery Manual CHAR.GED r^. ,- 3. DISCHARX3ING OHARX5ING DISCHAR^GED Fig. 1. — ^^The Four Stages of the Operating Cycle in tlie Storage Battery Cell. The Lead-Acid Stoeage Battery Cell 9 Graphical Illustration of the Cycle of Charge and Discharge. There is shown in Fig. 1 a diagrammatic illustration of the four stages constituting a complete cycle of charge and discharge, which stages are as follows : I. Cell in charged condition. II. Cell discharging. III. Cell in discharged condition. IV. Cell charging. The four stages enumerated above are given in the natural order in which they occur during the accomplishment of the cycle, and the illustration in Fig. 1 should be studied in conjunction with the text of the fundamental equation of the lead-acid storage battery cell and as outlined in the preceding paragraphs. The direction of flow of current through the cell is shown by the arrows in the drawings. The Characteristic Curves of Charge, — We have seen by the equations in the preceding paragraphs that when the cell is placed on discharge the acid radical (SO4) of the electrolyte combines with the active materials of the plates and accordingly converts them into lead-sulphate. We have also seen that when the cell is placed on charge the electrolytic action resulting from the charging current manifests itself in reducing the lead-sulphate contained in the plates, and of returning the acid radical (S'O^) to the electrolyte. Fig. 2 contains a set of curves illustrating the typical characteristics of the storage battery cell during charge, and an analysis of these curves will assist in obtaining a clear idea of the actions which take place in this cell during charge. Let us first consider the voltfige curve. It will be noted that at the begin- ning of the charge the cell voltage is around 2.15 to 8.17 volts, and as the charge progresses and as the sulphate is being reduced there is a gradual and regular increase in the voltage until approximately 2.35 volts is reached, at which time the voltage increases rapidly for the remainder of the charge, the voltage at the end of the charge averaging around 2.65 to 2.70 volts, which value represents the voltage of the fully charged cell. Moreover, if the charge be continued beyond this point, as will later be explained, practically all of the charging current is wasted since it is utilized in electrolysis or decomposing the water of the electrolyte. Now, at the beginning of the charge, since the plates are composed for the most part of lead-sulphate there is an abundant supply of this sulphate avail- able for reduction by the charging current; furthermore, during the early stages of the charge this supply of sulphate is easily accessible to the charging current since the surfaces of the plates are practically entirely composed of pure lead-sulphate. For this reason, therefore, the rise in the cell voltage during this period is relatively slight. 10 Storage Battery Manual However, as the charge progresses all of the lead-sulphate at the surfaces of the plates is reduced, and the remaining sulphate being located in the interior of the plates, it is accordingly less accessible to the charging current and in consequence its reduction is effected with increasingly greater diffi- culty, this feature being manifested by a gradual rise in the cell voltage, as is shown by the curve. This condition continues until a point is reached at which the charging current is in excess of that capable of being absorbed by the cell in the reduc- tion of sulphate, and the surplus current is therefore spent in electrolysis or 1 -J-- — — ~ _.^ — — 3.70 ___ — — 1 ea *ra tui e , r / — — ■ — — 3.50 / / 2.30 2.20 2.10 2.00 -< ^ --' — — —" Ci iti :al ^1 ss: ng P< iin t \ oil lag e __ ... — — "' __ " — - sj ec r' C ra ^it y — — ■ 1.50 1 nn 12 3 4 5 Hours Fig. 2. — Characteristic Curves o£ Charge. 110 H 100 i 90 "g 80 3 70 g 1.300 1.250 1.200 1.150 1.100 1.050 1.000 CD O p < decomposing the water of the electrolyte into its gaseous constituents, hydro- gen and oxygen. This condition obtains when the cell attains a voltage of approximately 3.35 volts, and this point is known as the critical gassing point of the cell and is plainly indicated on the curve in Fig. 2. From this point on, due to the fact that the amount of lead-sulphate re- maining in the plates is getting smaller all the time as well as less accessible to the charging current, there is a rapid increase in the cell voltage, until 2.65 to 2.70 volts is reached and at which time there is practically no lead-sulphate remaining in the plates, hence the specific gravity of the electrolyte ceases to rise and the cell may be said to be in a fully charged condition. If the charge The Lead-Acid Storage Battery Cell 11 be continued beyond this point the temperature of the cell rises rapidly and the cell in reality resolves itself into a hydrogen and oxygen generator, since practically all of the charging current at this stage goes to electrolysis. A study of the specific gravity and the temperature curves in conjunction with the foregoing analysis of the voltage curve should therefore enable the student to form a clear idea of the principal reactions vchich take place in the cell during charge. The Characteristic Curves of Discharge. — Having fully charged the cell as described above, we will next place it on discharge and note the characteristics during this operation. o 3.OO1 110 H 1.100 Fig. 3. — Characteristic Curves of Discharge. There is shown in Fig. 3 a set of curves representing the typical character- istics of the cell during a discharge and an analysis of these curves will assist in bringing out the salient features incident to the reactions which take place in the cell during discharge. As in the study of the reactions of charge, we will proceed to consider first the voltage curve in studying the discharge reactions. Starting then with the cell in a fully charged condition it will be noted from the curve that the instant the cell is cut in on discharge the cell voltage very rapidly drops from the normal full charge value (2.65 to 3.70 volts) to from 2.10 to 2.00 volts, after which the drop is comparatively slight over the 13 Storage Batteky Manual discharge period; but, during the latter stages of the discharge, that is, when the cell is from 60 to 75 per cent discharged, the voltage begins to drop off more rapidly until approximately 1.70 volts is reached and at which time the cell may be said to be for all practical purposes in a discharged condition. Of course, the discharge could be continued until complete discharge is accomplished, that is, until the cell voltage drops to zero, but for reasons which will later be explained, it is both inadvisable and uneconomical from an operating point of view to continue the discharge below 1.70 volts, espe- cially for discharges at the 3-hour rate and lower. For discharges higher than the 3-hour rate the discharge may be carried slightly below 1.70 volts. In analyzing the characteristic voltage curve of discharge let us first con- sider the conditions which obtain in the fully charged cell at the instant just preceding that of placing the cell on discharge. The pertinent conditions which obtain at this stage are that the pores of the active materials composing the plates are filled with high density acid, which is practically uniform in density with the bulk or main volume of electrolyte contained in the cell, and that the entire active surfaces of the plates are in intimate contact with the electrolyte. Now, at the instant that the cell is cut in on discharge and depending upon the magnitude of the discharge current rate, there is a certain immediate or initial drop in the cell voltage from the full charge value — in general the higher the current rate the greatei? the voltage drop, and vice versa; the amount of this initial drop in voltage may also be said to be a function of the internal resistance of the cell, the rate of formation of a thin layer of sulphate on the surfaces and in the pores of the plates, and the abstraction of the acid from the electrolyte which is in immediate contact with all portions of the active materials of the plates. After this initial drop in the cell voltage is effected, the drop thereafter is relatively slight over a considerable period of the discharge, and during this time the acid radical (SO4) of the electrolyte is combining with the active materials of the plates thus converting them into lead-sulphate. Also, during this period inasmuch as there is an abundant supply of both acid and active materials contained in the cell, the rate of diffusion of the acid into the pores of the plates and the consequent combining of this acid with the active material is comparatively rapid, thus maintaining a relatively constant cell voltage. However, as the discharge progresses there is a gradual drop in the voltage which is accounted for by the fact that the internal resistance of the cell gradually increases by virtue of the formation of the lead-sulphate in the plates, and also through the fact that the remaining uncombined active The Lead- Acid Storage Battery Cell 13 material being located in the interior or core of the plates, it accordingly becomes more and more inaccessible to the action of the electrolyte and, since the density of the electrolyte is in turn gradually growing weaker, it follows that the rate of difPusion of the lectrolyte into the pores of the plates is decreased ; diffusion of the electrolyte into the pores of the plates is further retarded as a result of the clogged or congested condition of the pores of the active material incident to the formation of the mass of sulphate in the plates. This condition continues throughout the remainder of the discharge, with the exception that the drop in cell voltage becomes more rapid after the cell reaches a stage of from 60 to 75 per cent discharged, and from which time on due to the fact that the mass of lead-sulphate is steadily increasing while the density of the electrolyte is growing weaker, there is an increasing rate to the drop in cell voltage. As has been stated, the discharge should be discontinued when the cell voltage is reduced to 1.70 volts, as any discharging beyond this point is uneconomical, and also owing to the fact that lead- sulphate is less dense than either lead-peroxide or sponge lead, there is danger of overstraining the grids and cracking or " buckling " them if it be attempted to convert all of the active material into lead-sulphate. Therefore, it has been found that 1.70 volts is the safe limit of the discharge such that an excessive strain will not be put upon the grids through over-expansion of the sulphated mass of active material. However, the rate of discharge establishes the minimum final voltage limit during discharge, and each battery manu- facturer establishes this limit for his own particular make of battery. This subject of minimum final voltage limit on discharge will be taken up in more detail in a later chapter. A study of the specific gravity and the temperature characteristic curves in conjunction with the analysis of the voltage curve as outlined above will serve to form a clear idea of the prime reactions which take place in the cell during discharge. It will be noted that during a normal discharge there is a comparatively slight rise in the cell temperature, this rise being not as great as during charge. Eeferring to the characteristic curve of specific gravity it will be noted that the drop in the specific gravity of the electrolyte is practically directly pro- portional to the ampere-hours of discharge, and for this reason the specific gravity readings are in general more to be relied upon in determining the true state of discharge of the cell than are the voltage readings. However, in order to intelligently operate the storage battery cell routine readings should be taken of the voltage as well as the specific gravity. CHAPTEE Hi. DEFINITIONS AND NOMENCLATURE OF PARTS. Acid. — The active component of the electrolyte as used in the lead-acid storage battery cell, and consists of chemically pure sulphuric acid (H2SO4). Acid Testing: Outfit. — The accessories used for testing the specific gravity of the electrolyte. These testing outfits usually consist of beakers, hydrom- eters, hydrometer syringes and thermometers. Alternating Current. — A current which alternates regularly in direction. Should never be used for charging storage batteries unless some form of rectifier is used with it to convert it into direct current. FiQ. 4. — Storage Battery Ammeter. Ammeter. — An instrument used for measuring the rate of current in amperes fiowing through an electrical circuit. As used with the storage battery these meters measure the rate of charging current passing through, the battery, and also for measuring the rate of current passing from the storage battery on discharge. The ammeters used with storage batteries are usually of the two-way reading type ; that is, the zero mark of the ammeter is placed in the center of the are of the scale and the graduations are made to the right and to the left of the zero mark. Thus, on charge the needle registers on that portion of the scale to the right of the zero mark, while on discharge it registers to the left of the zero mark. This type of meter facilitates using either during charge or discharge of the battery without changing the terminal leads to the instrument, as would otherwise be neces- sary to compensate for the change in direction of current in the circuit if it Definitions and Nomenolatdeb of Paets 15 contained only one scale of graduations. Fig. 4 contains an illustration of this type of ammeter. Ampere. — The practical unit of electric current. Ampere-Hour.' — A unit of quantity used in measuring the quantity of electric current passing through a circuit, and is obtained by multiplying the rate in amperes by the time. Thus, 10 amperes flowing for 5 hours equals 50 ampere-hours. Ampere-Hour Meter. — An instrument used for measuring the quantity of current (ampere-hours) passing through an electrical circuit. Ampere-hour meters are used in connection with storage batteries for two purposes, which are as follows: First, for recording the ampere-hours discharged from the battery, thus indicating the degree of discharge of the battery. Second, for recording the ampere-hours of charge put into the battery, thus indicating the degree of charge of the battery. Antimony. — A metal extensively used in the manufacture of lead-acid storage batteries. It is used principally for combining with lead to produce the lead-antimony alloy of which the grids for the plates are cast. The antimony adds rigidity to the grid. Average Voltage. — The average value of the electromotive force of a given charge or discharge, and is an essential factor in computing the mimber of kilowatts developed on a given charge or discharge. Battery. — Any number of complete cells assembled in one or more trays. Boosting. — A term applied to a special charge given to one or more cells whose state of charge has, through any cause, fallen below that of the other cells of the battery. Thus, such cells are given a " boosting " charge to restore them to the same degree of charge as the other cells of the battery. Buckled Plates. — Plates which have become distorted in shape as a result of excessive overcharging and discharging. High temperatures in the cell and over-sulphation of the active material of the plates constitute the chief factors which produce buckled plates. Capacity. — The capacity of a storage battery cell is rated in terms of ampere-hours, which means that the plates in the cell, when fully charged, are capable of delivering a given number of amperes for a given length of time, the time usually being stated in hours. The capacity of a storage battery varies with the rate of discharge; in other words, a battery will deliver more ampere-hours when discharging at a lower rate in amperes than it will deliver when discharging at a higher rate. Capacity of storage bat- teries is also expressed in kilowatts. Cell. — The battery unit, consisting of a jar containing completely assembled element and electrolyte, and with cover and vent. 16 Storage Battery Manual Cell Connector. — The metal link used for connecting the positive post of one cell to the negative post of the adjacent cell. These connectors are of various types and designs, but, generally speaking, they consist of a strip of pure copper around which is either cast or plaited a pure lead envelope. For the small portable types of batteries these connectors are usually cast from lead-antimony alloy. Characteristic Curves. — The curves showing the various factors of the normal charge and discharge of the battery, and are essential to an intelli- gent operation of the battery. These curves show the various rates of charge and discharge, with the corresponding initial, average and final voltages, as well as the kilowatts developed at the various rates. The specific gravity of the electrolyte at full charge and upon which these various factors are based is also included in these characteristic curves. Charging. — The process of passing direct current through a battery in th? direction opposite to that of discharge in order to restore the energy used on discharge. Charging Curve. — The curve prepared by the battery manufacturer and showing the starting, intermediate. and finishing rates for charging the par- ticular type battery to which it applies. Charging Eate. — The proper rate of current to use in charging a battery. It is expressed in amperes and varies with the size and number of the plates in the cell. Chemical Action. — The joint action taking place between the electrolyte and the active material composing the electrodes of the storage battery cell. Corrosion. — The result of the action of the acid of the electrolyte on the metal parts of the battery, and is principally due to lack of care in cleaning the battery. Coulomb. — The practical unit of quantity of electricity, and is that quantity of electricity conveyed by one ampere in one second; sometimes referred to as the ampere-second. Cross Bar. — The portion of the cross-bar, strap and terminal post casting to which is lead-burned the lugs of the plates of the cell. Cell Cover. — The hard rubber cover which closes each individual cell. These covers cpntain the various fittings, such as filling cylinders, vent plugs, etc., and are securely sealed to the jar by means of sealing compound. Cycle. — The complete operation of discharging a fully charged cell and again returning it to a state of full charge. It is usual to reckon the life of a battery in cycles. Direct Current. — An electrical current whose direction of flow is constant. Habitually used for charging a storage battery. Definitions and Nomenclaturie of Parts 17 Discharge. — The flow of an electric current from a battery through a circuit as a result of closing this circuit, and is in the opposite direction to " charge." Faure Plates. — Commonly known as " paste plates," and named after their inventor, Camille Faure. The active material of these plates is held in a framework or " grid." Filling Plug. — The hard rubber plug which fits into and closes the orifice of the filling cylinder in the cell cover. Final Voltage. — ^The electromotive force of a cell or battery at the end of a discharge. Finishing Bate. — The reduced charging rate used when nearing the com- pletion of the charge of a battery, and is such as to produce a minimum amount of gassing in the cell at this stage of the charge. Flooding. — The act of filling to overflowing a cell when adding water or electrolyte and should be prevented as much as possible, as it is conducive to rotting of the trays, short circuits, etc. Freshening Charge. — A charge given to a battery, which has been standing idle, to insure that it is maintained in a fully charged and healthy condition. On batteries which are subjected to protracted periods of idleness it is good practice to give them a " freshening charge " at least every two weeks if possible. Gassing. — The bubbling of the electrolyte incident to the evolution of gas formed by electrolysis of the water in the electrolyte when nearing the end of the charge. Gravity. — A contracted term used in reference to the " specific gravity " of the electrolyte. Grids. — The lead-antimony alloy castings which form the lattice-work frames for holding the active material of paste plates. Many types and designs of grids have been developed and used by the various storage battery manufacturers. Ground. — A connection made between an electrical circuit and the earth. If such a ground occurs on both the positive and the negative legs of a circuit a " short circuit " is the result. It is especially important to a satisfactory operation that all storage battery circuits be kept as clear as possible of such grounds. Group. — A complete set of positive or negative plates joined to the cor- responding cross-bar and strap. Such a group of negative plates is called a " negative group," and a similar group of positive plates, a " positive group." Groups do not include separators. Hold-Downs. — The brackets and rods attached to the ends of a tray for securing the battery in position. .18 Stoeage Battery Manual Hydrometer. — An instrument used for checking and measuring the specific gravity of the electrolyte. Hydrometer Syringe. — The glass barrel and attached rubber bulb used for drawing up electrolyte for test with the hydrometer. Hydrogen Gas. — Liberated at the negative plate of a storage battery during charge. A 3 per cent mixture of hydrogen in air is dangerous, and it is essential to safety in operating storage battery cells to keep the hydrogen mixture below 2 per cent. Initial Voltage. — ^The electromotive force of a cell or battery at beginning of discharge. Intake Vent. — An orifice located in the hard rubber cover of a cell and through which air is drawn into the cell for ventilation purposes. Internal Resistance. — The resistance to the flow of current offered by the plates, separators and electrolyte in the storage battery cell. Jar. — The container for the element and electrolyte of the storage battery cell. Hard rubber is now used for the jars of lead-acid storage battery cells to the practical exclusion of all other materials, except, however, glass is sometimes used for certain limited services. Kilowatt. — One thousand watts ; 746 watts equals one horsepower. Lead. — The basic metal forming the voltaic couple as applied to the lead- acid storage battery cell. Lead Drops. — Drops of molten lead which become detached from the main bulk of the metal during the process of lead-burning the plate lugs to the straps, etc. In order to lessen the likelihood of short circuits it is very essential that none of these lead drops be allowed to lodge between the plates. Lead-Peroxide (PbO,). — The active material composing the positive plates of the lead-acid storage battery cell. Lead-Sulphate (PbSO^). — The compound formed as a result of the action of the sulphuric acid on lead. Lead-Burning Outfit. — An outfit consisting of the various accessories used in the process of lead-burning the various parts of lead-acid storage bat- teries. These outfits consist essentially of hydrogen or oxygen generators for supporting the fiame used in melting the lead or lead-alloy used in this process. Lean Plates. — A term applied to plates in which, through shedding, either normal or abnormal, the amount of active material has been reduced to the point such that little efficiency is obtained with further working of the plates. In other words, plates which have become " lean " have practically reached the end of their useful life. There is shown in Fig. 5 an illustration of a " lean " plate. Definitions and Nomenclatuee of Pakts 19 Maximum Gravity. — The highest specific gravity attained by the electro- lyte of the cell through continued charging, thus indicating that no acid remains in the plates and constitutes an important factor in determining when the cell is fully charged. Minimum Final Voltage. — The minimum permissible value of the voltage reached by a cell on discharge. Negative Plate. — The sponge lead (Pb) component of the voltaic couple as used in the lead-acid storage battery cell. A fully formed negative plate is of a " battleship " gray color. Negative Group. — The unit formed by burning the complete set of nega- tive plates of the cell to their corresponding straps, cross-bars and terminals. >., ""■■::■ Fig. 5. — Lean Plate. A negative group contains one more plate than does the corresponding posi- tive group. Ohm. — The practical unit of resistance. Ohm's Law. — The law which expresses the relation between electromotive force, current and resistance in a closed electrical circuit in which the current is continuous. This law takes its name from its enunciator, Georg Simon Ohm, a German mathematician, and states that the current is directly proportional to the electromotive force and inversely proportional to the resistance, and is symbolically expressed as follows : C'=-jj , where C = Current, jE'= Electromotive Force, and R = Eesistance. 80 Storage Battery Manual Oil of Vitriol. — Concentrated sulphuric acid, the specific gravity of which is about 1.835. Parallel Grouping. — The method of connecting together the several cells of a battery, such that the positive terminals of all cells are connected to a common bus, and similarly the negative terminals of all cells. Plante Plates. — Plates which are formed from pure lead by Plante's process, and are named after their discoverer, Gaston Plante, a Frenchman, who discovered the reversible voltaic couple in 1860. Plates. — The electrodes of the storage battery cell, the positive plate con- sisting of lead-peroxide (PbOj), and the negative plate of metallic sponge lead (Pb). Plate Lugs. — The lug or neck formed at the upper corner of the plate, and which is used for lead-burning the plate to its terminal post strap. The plate lug thus serves to conduct the current to and from the plate to its terminal post. Porcelain Insulators. — The porcelain skids on which the cell trays rest, and which act as an insulating medium to prevent moisture grounds, etc. Positive Plate. — The lead-peroxide component of the voltaic couple as used in the lead-acid storage battery cell. A fully formed positive plate is of a velvety " chocolate fudge " color. Positive Group. — The unit formed by burning the complete set of positive plates of the cell to their corresponding cross-bars, straps, and terminals. A ■positive group contains one plate less than does the corresponding negative group. Eating, — The measure of the current in amperes capable of being deliv- ered by a storage battery cell for a specific interval. Thus, if a cell is capable of producing 14 amperes continuously for 10 hours, to the specified final voltage, its " 10-hour rate " is 14 amperes. Similarly we speak of the 1-hour rate, 3-hour rate, 5-hour rate, etc. Rectifier. — An electrical apparatus used for converting alternating current into direct current. As applied to the storage battery, it is used for convert- ing alternating current into direct current for charging purposes. Eesistance. — Any inaterial of relatively low conductivity, such as lamp banks, wire, carbon, water, etc., which is inserted in a circuit for the pur- pose of retarding the flow of current. By varying the resistance, the amount of current can be regulated. As applied to the storage battery, these various types of resistances form a part of the charging and discharging panels for these batteries. Reversed Cell. — A cell whose voltage reading has become reversed through charging in the wrong direction. Under ordinary operating conditions, cells should never be allowed to become reversed. Definitions and Nomunclatuee op Paets 21 Rubber Separators. — The perforated sheets of hard rubber placed between the plates to prevent the positive and negative plates from coming in contact with each other. For most batteries used in the naval service these rubber separators are used in conjunction with treated wood separators, one such rubber sheet and one wood separator forming the insulation between each adjacent positive and negative plate. In such a combination the perforated rubber sheet is habitually placed against the positive plate. Sealing Compound. — The thick, black, acid-proof compound used for seal- ing and making a tight joint between the jar and cover of the unit assembly- type storage battery cell. Sediment. — Particles of active material which have become detached from the plates and deposited on the bottom of the jar. This sediment has a thick, muddy appearance and is frequently referred to as " mud " by the operating personnel. Sediment Space. — The clearance space between, the bottom of the jar and the bottoms of the plates for receiving the sediment which is " shed " from the plates. This sediment space should be sufficient to receive all sediment shed from the plates during the useful life of the cell and without causing any short circuits across the bottom edges of the plates. Separator. — An insulator placed between the plates of opposite polarity in the storage battery cell to prevent the plates from coming in contact with each other. For batteries of the naval service they usually consist of specially treated sheets of wood, perforated sheets of hard rubber or a combination of both of these types. Separators are generally corrugated or ribbed to insure proper plate separation and to facilitate ample circulation of the electrolyte. Separator Supports. — Usually of hard rubber and placed in the bottom of the jar for supporting the separators in the element. In the small navy type portable batteries, the " bridges " in the bottom of the jar act as separator supports as well as supporting the plates of the element. Spray. — Fine particles of electrolyte carried up by the bubbles formed as a result of the evolution of gas in the cell. Series Grouping. — The method of grouping the cells of a battery such that the positive terminal of one cell is connected to the negative terminal of the adjacent cell and so on throughout the entire circuit. The effect obtained by grouping the cells in series is that the terminal voltage is the sum of the voltages of all cells so connected; hence, the power developed is increased over that of a single cell. However, when so connected, the ampere-hour capacity of the entire battery is that of a single cell. Series-Parallel Switch. — A specially constructed switch for connecting the cells of a battery either in series Or parallel grouping, depending upon the power required or other conditions to be met in operation. 23 Storage Battery Manual Shedding. — The normal act of the loosening and falling away from the plates of the worn out particles of active material incident to the working of the cell. This shedding of the active material occurs in a degree with every charge and discharge of the storage battery cell and continues throughout the useful life of the cell ; in fact, " shedding " is a function of the life of the cell. Short Circuits. — As applied to the storage battery, it is usually a condition of metallic connection between the positive and negative plates of a cell. The plates may be in actual contact or material may bridge across the plates. A defective separator constitutes the most frequent cause of such a short circuit. With proper assembly of the cell, if the separators are maintained in good condition, the occurrence of such a short circuit is unlikely. Silver Nitrate Solution. — A solution used for making a qualitative test for chlorine in water intended for use in storage batteries. When a few drops of silver nitrate solution are placed in water containing chlorine, the water instantly becomes cloudy and milky; whereas, when placed in water free from chlorine, the water remains clear. Specific Gravity. — ^The density of the electrolyte of the storage battery cell as compared with water as a standard, the specific gravity of pure distilled water being unity. Usually referred to as " gravity." An important factor in operation of the storage battery. Sponge lead (Pb). — The active material of the negative plate in the lead- acid storage battery cell. Starting Rate. — The rate used in beginning the charge of a battery by the constant current method, and varies with the size and type of the battery. It is usual for the battery manufacturer to assign a " starting rate " for each type of battery, and to place this starting rate on the battery name-plate for the information of the operating personnel. The " starting rate " is usually approximately twice the " finishing rate." Strap. — The lead-antimony casting composing the terminal post and cross- bar and to which the lugs of all plates of like polarity in the cell are burned. In the larger type cells these straps are of copper, the lead-antimony being cast around the copper as a protective coating to prevent the copper from entering the cell. Sulphate. — As applied to the lead-acid storage battery cell it refers to lead-sulphate (PbS04), and is the substance into which the active material of both the positive and negative plates is converted during discharge. Sulphated. — A term used in describing the character of the plates con- taining an abnormal amount of lead-sulphate (PbSO^) as a result of the cell being in an underchanged condition, from either overdischarging without Definitions and JSTomenolatuee op Paets 33 correspondingly long charges or from standing idle for protracted periods and becoming self -discharged. Sulphate Reading, — A peculiarity of cell voltage attained when charging a cell, the plates of which are considerably sulphated. In this case the charg- ing voltage shows abnormally high before gradually dropping to the normal charging voltage. Temperature Coefficient. — The amount of the increase or decrease in the electromotive force of the cell as a result of an increase or decrease in the temperature of the cell. The temperature coefficient is positive for increased temperatures and negative for decreased temperatures. Practically speaking, it manifests itself in an increase or decrease in the ampere-hours given out by a cell to a stated final voltage. For example, all storage battery data of the naval service are based on the electrolyte having an initial temperature of 80° Fahrenheit; thus, if the initial temperature of the electrolyte is above 80° F., an increase in the ampere-hour capacity obtained from the cell to the normal final voltage, based on 80° F., will result. Conversely, if the initial temperature of electrolyte be below 80° F., a decrease in ampere-hour capacity obtained from the cell will result. Appropriate curves, called " Temperature Coefficient Curves for Capacity," are supplied by the battery manufacturers, and usually include temperatures ranging from 40° F. to 110° F., the 80° F. point on these curves representing the rated 100 per cent of capacity of the battery at the particular discharge rate as shown on the curve. Terminal Post. — The portion of the positive or negative group whicli extends through the cell cover and by means of which the cell is connected to other cells or the required service circuits. Terminal Post Gaskets. — The soft rubber gaskets used by some battery manufacturers for making an acid-tight joint around the terminal post where it passes through the hole in the cell cover. Terminal Post Nuts. — The alloy or hard rubber nuts used by some battery manufacturers for securing the cell cover to the terminal post. In addition to assisting in making an effective seal between the cell cover and the ter- minal post, it also serves to prevent the element from shifting position in the jar. Terminal Volts. — The combined voltages of all cells of a group connected in series. For example, if a tray contains five cells, all of which are con- nected in series, the terminal voltage of this tray of batteries is the sum of the voltages of these five cells. Tray. — ^The container or case which holds the cells. The tray and cells which it contains are usually assembled as one complete unit. A battery may consist of one or more such trays. 34 Storage Batteey Manual Tray Cover. — The cover provided for closing the battery tray, as described above, and is designed primarily for protecting the tops of the cells against damage when working around the battery as well as keeping it free as possible from dirt, dust, foreign substances, etc. Tray Terminals. — The attachments installed on each end of a battery tray, by means of which the positive terminals of one end cell and the negative terminals of the other end cell are connected to another tray, or the regular service line. Trickling Charge. — 'When the storage batteries are connected across the supply mains and the conditions are such that the batteries are at all times receiving just enough current to counteract local action and thus keep them in a full charged condition, they are said to be receiving a " trickling charge." A fraction of an ampere only is required for this " trickling ciharge," and aside from the advantages obtained in counteracting local action in the cell the battery at all times has its entire capacity available for instant use if required. All batteries which are assigned primarily for stand-by circuits should be so connected up to the supply mains that they constantly receive a " trickling charge " as described above. Vent Trap. — Consists of a series of perforated rubber sheets or baffle discs placed in the exhaust vent of a cell having forced ventilation, and is designed to trap the acid of the electrolyte which has been thrown up by the spray and return it to the cell. Voltage. — Electrical potential or pressure, the unit of which is the volt. Watering Battery. — The act of adding distilled or other pure water to the storage battery cell jn order to replenish the water which has been lost through spraying and evaporation of the electrolyte. The batteries should be watered regularly as necessary. The level of the electrolyte should never be allowed to get below the tops of the plates before watering. Water Rheostat. — A rheostat consisting of a box or barrel of water into which are placed two metal plates; one plate is connected by a wire to the positive terminal and the other one to the negative terminal of a storage battery. This type of rheostat is frequently used for test discharges of storage batteries. The water should be slightly acidulated in order to increase its conductivity. By varying the distance between the plates, the current regulation during discharge may be adjusted. Other types of water rheostats consist of pipe coils through which water is circulated under pressure. By making connections at various points along the length of the coil the resistance is varied and the desired current regulation is obtained. Wood Separator. — A sheet of specially treated wood used for insulating from each other the positive and negative plates of the storage battery cell. Various kinds of wood are used for the separators, including bass wood, red- wood, cypress, white cedar and Douglas fir. CHAPTER IV. DESCRIPTION OF UNIT ASSEMBLY TYPE CELLS. The Unit Assembly Type Cell Defined. The unit assembly type of cell, as its name implies, is one in which the jar. element, electrolyte and cover are assembled and sealed as one complete unit, and is such that it may be transported or handled entirely as a separate unit if desired, or it may be connected up in series or parallel grouping with other cells if required. Various features of design applying particularly to cell ventilation and non-spillage of electrolyte are characteristic of this type cell. Application to the Naval Service. Although in some few instances other types of cells are used for certain special services, principally on shore stations, the modern application of the lead-acid storage battery on board ship and in the general naval service is confined practically entirely to the unit assembly type of cell and the descriptive matter of this chapter will be confined to cells of this type. How- ever, description of the other types, the so-called " open " or " tandem " types, will be covered in another chapter. Component Parts of Unit Assembly Type Cell. The unit assembly type cell in its modern application to our naval service is composed of the following parts, all of which are shown in Fig. 6 : (Positive Plates. Cross-bar, Straps and Termi- nal Posts. I Negative Plates. I. Element. { (b) Negative Group ... J Cross-bar, Straps and Termi- I nal Posts. fWood. 1 Rubber, (d) Separator Hold-downs. (b) Negative Group (c) Separators II. Electrolyte. III. Jar. IV. Cell Cover and Parts. V. Connectors. VI. Sealing Compound. 3 26 Storage Battery Manual CellA^emUy Posi iive Cr oss Bar Ji^::^t-^T^ Terminal Bushmcj -^^^ ^ H Separator Reiaimr MATERIAL UST | MRTMO NAME OF PART MATERIAL WW 1 CELL t Jar HPlRUBBER 1 3 Cover HORueSER 1 •q- VENT Plus KoflUBBER 1 5 TehminalBushins S Rubber 4- 6 ft>3iTivE Group 1 7 Positive Plate 4 s PosmvE Cross BAR Pure Lead 1 9 negative Sroup 1 10 NEG.PlATEl»IEllMEl)lliIE 3 11 NEG.PLATE-OUTSIOE • a 12 Negative Cross Bar ti^iMJTl-lfcWl 1 13 Perforated Sheet Hu Rubber s lrvice. After casting the grids, they are next trimmed and inspected. This inspection consists in examining the grids for broken bars, cracked lugs, blow-holes and other such imperfections in casting. After discarding the imperfect grids as a result of this inspection, the perfect ones are then Paste Type Assemblies 45 delivered to the pasting room where the active material in paste form, as has been described, is applied to them. The defective grids are usually melted up and recast, but in some instances, if the blow-holes and other imperfections are not too bad, these grids may be reclaimed by flame-puddling the blow-holes, lead-burning, etc. Also, owing to the oxidization which takes place on the grids when they are exposed to the air for a considerable length of time, they should be pasted as soon as practicable after casting, in order to obtain a satisfactory contact between the grid and paste; if the grids are oxidized to a considerable extent the proper bond or contact between the paste and the grid is not obtained. Requirements of a Satisfactory Grid. In regard to the constructive features of these grids, the design should bb such as to fulfill the following requirements : (a) The grid should be of sufficient cross-section and so proportioned as to carry, without undue loss, the current generated by the battery under operating conditions and also obtain uniform current distribution over the entire surface of the plate. (b) The grid should be so designed as to offer maximum electrical contact with the active material throughout the life of the plate, and also form a receptacle for the active material, such that sloughing-off or shedding of the active material is reduced to a minimum. (c) The composition of the grid should be such as to not be injuriously affected by the electrolyte. Also, this composition should be such as to afford a minimum of local action between itself, and the contained active material. (d) The grid should be so designed as to allow maximum diffusion of electrolyte through the active material. (e) The grid should be as light as possible consistent with the function which it has to perform. (f) The grid should be of sufficient rigidity to resist huckling, as a result of oversulphating of the active material which it contains. Grid Casting Equipment Should Be Maintained at Uniform Temperature. In order that uniformity may be obtained in the grade of castings pro- duced from the moulds, it is necessary when casting the grids that these moulds, as well as the molten metal used in these castings, be maintained at an even temperature during this process. This is especially important in casting the larger types of grids, such as are used in submarine storage batteries and other battery installations requiring plates of this size. There- fore, in order to maintain 'this even temperature in the melting pots and 46 Storage Batteet Manual mould equipment, and thus assist in securing uniform castings, it is cus- tomary practice in the leading storage battery manufacturing plants to operate this equipment continuously throughout the entire 34 hours per day until the casting of the particular lot* of grids has been completed, thereby preventing the fluctuations in the temperature of this equipment, which would otherwise occur, if allowed to remain idle and cool off during the casting process. Also, as a further expedient in maintaining this equipment at even tem- peratures, various types of thermo-electric pyrometers, thermometers and other temperature recording instruments are installed for the guidance of the workmen operating this equipment. Description of Thermo-Electric Pyrometer Equipment as Applied to the Operation of Grid Casting. A form of temperature indicating apparatus used extensively with storage battery grid casting equipments is known as the thermo-electric pyrometer, and consists essentially of a thermo-couple in circuit with which is connected a millivoltmeter having its dial graduated in degrees Fahrenheit instead of in electrical units. The principle upon which the operation of this form of apparatus is based is that of the electrical current which is generated when the junction of two dissimilar metals, that is, a thermo-couple, is submerged in a pot of molten metal ; as the temperature of the molten metal rises and falls, the temperature of the thermo-electric couple accordingly rises and falls, and the thermo-electric current thus generated accordingly increases or decreases, and is indicated on the millivoltmeter, which, as stated, has its dial graduated in degrees of temperature instead of in electrical units. This form of apparatus has proved very successful in maintaining the melting pots at a uniform temperature. In some storage battery manufac- turing plants this system is elaborated upon somewhat, in that in addition to the indicating apparatus installed in the immediate vicinity of the melting pot for the guidance of the operator in controlling the temperature of his pot, there are also central stations connected up with the thermo- couples installed in the several melting pots, and by a suitable master switch the temperature of each individual pot may be readily read upon the central station instrument. There are also various types of recording devices incor- porated in this apparatus by which an accurate record of each individual melting pot may be obtained throughout the entire run. In some plants there are unskilled operators of the mould equipment who cannot read the temperature indicating apparatus, and for the benefit of these men a series of colored lights are installed in the circuits with the thermo-couples for their guidance in controlling the temperature of the Paste Type Assemblies 47 48 Storage Battery Manual melting pots. Por instance, in a certain plant the series of colored lights consists of a green light, a red light and a white light ; correct working temperature of the molten metal is indicated when the white light is on, temperature too low when the green light is on, and temperature too high when the red light is on. It is thus only necessary for the operator to keep his white light burning in order to maintain his pot of metal at the correct temperature. Fig. 8 contains a series of illustrations representing the pyrometer equip- ment, such as is used in connection with the casting of storage battery grids and other parts. Eeferring to this illustration, the various parts are shown as follows: A represents the thermo-couple proper; B shows the thermo- FiQ. 9. — " Exlde " Type Grid and Plates. couple submerged in the molten lead pot, the connections to the indicator and the recording instruments being clearly shown in this section of the illustration; C shows the wiring diagram and the method of connecting the recording and indicating instruments with the several melting pots,. and D shows the head moulder reading the temperature of the several pots. Various Types of Grids. With present stage of the art, the designs of the grids used in storage battery plates may be divided into two main classes, as follows : (a) Those whose members are arranged in rectangular relation with each other. (b) Those whose members are arranged in rectangular and diagonal relation with each other. Paste Type Assemblies 49 Of the former class the following types are examples : " Exide " grid. " Gould " grid. ^ "U-S-L"grid. " Willard " grid. Of the latter class the following types are examples : " Diamond " grid. " Herring-Bone " grid. " Titan " grid. The " Exide " Grid. — In Fig. 9 is shown an illustration of an " Exide " grid, which is the trade name adopted for it by the Electric Storage Battery Company. There is also shown in this figure illustrations of positive and negative plates using this type of grid. Ill-'- Fig. 10. — Section of " Exide " Grid. Eeferring to the illustration it will be noted that this grid consists of a skeleton framework or lattice-work composed of a series of vertical and hori- zontal bars. The vertical bars are of the full thickness of the grid and thus extend from side to side of the grid, while the horizontal bars, which are staggered on opposite sides of the grid, are of just sufficient thickness to form a cage for the active material and also to collect the current from the adjacent active material and conduct it to the vertical bars. In Fig. 10 is shown a cross-section of this grid. Eeferring' to this figure it will be noted that when the active material is properly compacted into this grid, it is then in the form of a ribbon which " zig-zags " from side to side of the grid, the width of this ribbon being the width of the space between the two adjacent vertical bars. By thus staggering the horizontal bars on oppo- sites sides of the grid, they form an interlock for holding the active material in position, and also allow ample space for proper diffusion of the electrolyte into the active material. 50 Storage Battery Manual The horizontal bars, although individually of parabolic cross-section in shape, are uniform in cross-section throughout the entire grid, while the vertical bars are taper in cross-section from top to bottom of the grid, the larger cross-section being at the top, since this is the location of maximum current density. The " Gould " Grid. — ^There is shown in Pig. 11 a photographic illustration of a paste type plate manufactured by the Gould Storage Battery Company, and in which plates the " Gould " type grid is used. Both positive and negative plates are shown in this illustration. In Fig. 12 is shown a photographic illustration of a " Gould " grid such as is used in submarine storage batteries. The details of the vertical and hori- zontal bars are clearly shown in this illustration. Fig. 11. — " Gould " Type Grid and Pl-ates, The " TI-S-I " Grid. — There is shown in Fig. 13 an illustration of plates and grids of the " TJ-S-L " type and as manufactured by the U. S. Light and Heat Corporation. Both positive and negative plates as well as grids are shown in this illustration. The assembly of a " U-S-L " type group is also shown in this photograph. Special attention is directed to the taper post strap of this group, the detailed method of assembly of which will be described in another part of the text. The " Titan " Grid. — Another type of grid containing the rectangular and diagonal feature of design is the " Titan " grid, an illustration of which is shown in Fig. 14, and as manufactured by the General Lead Batteries Company. In this illustration is also shown a positive and a negative plate composed of this grid. A notable feature of this grid is that it can be bent double on either side of the vertical axis without being broken in twain, for whereas the vertical members of the grid will part during this Paste Type Assemblies 51 Fib. 12.— "Gould" Grid— Submarine Type. 52 Storage Battery Manual operation, the diagonal members will not part and accordingly act as striiigers in holding the grid together. This feature is conducive to offering resistance to buckling of the plate, which is especially desirable for the so-called " thin " type of plates. The "Diamond" Grid. — There is shown in Fig. 15 an illustration of a " Diamond " grid, the trade name as given to it, on account of its shape, by the manufacturers, the Philadelphia Storage Battery Company. In developing this grid, it will be noted that the designer has made use of certain features of the principle of bridge truss construction in that the U-S-L Grouti lih I'oM SiTtp U-S-L Nrmiive Plate Fig. 13.—" U-S-L " Type Grids and Plates. framework consists of a series of vertical and diagonal bars. The diagonal bars form a series of " diamond " crosses, which crosses are staggered on opposite sides of the grid in order to produce an effective interlock for main- taining the active material in position. The vertical bars are of the full thickness of the grid and thus extend from face to face of the plate. Also, these vertical bars are of taper cross-section from top to bottom, the larger cross-section being properly at the top of the grid, the location of maximum current density. This type of grid has many excellent features, chief among which are the strength and rigidity obtained through the network of truss construction, in Paste Type Assemblies 53 which each member helps to support every other member. Eeferring to Fig. 15, consider, for instance, the diagonal member, shown in dotted line, starting at the lower left-hand corner of the grid at A; this member runs diagonally across to the other side of the grid at B, thence back to other side at C, and finally, across the grid again to the upper diagonally opposite corner at D. Each other diagonal member follows a similar and parallel Negative Plate. Positive Plate. Pig. 14. — " Titan " Type Grid and Plates. path. Thus a strain on any member of the grid is transmitted to and resisted by every other member of the grid, a feature which is very desirable in resisting any tendency to hucMing of the plate when installed in the cell. In Fig. 16 is shown a detailed section and cross-section of this grid, which gives a clear idea of its construction. In considering further the construction of this grid, it will be noted in Fig. 16 that the face of each diamond on one side of the grid is backed-up by 54 Stoeage Battebt Manual a cross formed by the members of four diamonds on the opposite side of the grid. Furthermore, on each diamond there are four places where members on one face of the grid cross members on the opposite face. Thus it will be noted that every particle of active material contained within this grid is close to a conductor, which feature not only serves to assist in maintaining the active material in position, but, in addition, forms many short paths for Pig. 15. — Philadelphia " Diamond " Grid. collecting the current and conducting it to the vertical members of the grid, thereby increasing the efficiency of the plate in absorbing and delivering energy. Therefore, it is seen that this grid contains three prime requisites of a good grid; namely, strength, loclcing ability, and conductivity, and is considered one of the best grids at present used in storage batteries for the naval service. Although these grids as used in batteries for the naval service are in most cases i inch thick, the manufacturers supply them for special services and io Paste Type Assemblies 55 the commercial trade in much thinner units. In fact, this grid was one of the pioneers in the field of the so-called " thin plate " batteries. In Fig. 17 there is shown a complete plate made up from one of these grids. This grid is used only for positive plates, since that plate is the one active iTtater.ia.X is Xocl^d-'beiweeTU crosses 1 pTate plata v/heve -me-mhers cross eacliotl^r Fio. 16. — Section of " Diamond " Grid Fig. 17. ' Diamond " Grid, Positive Plate. Fig. 18. ' Herring-Bone " Negative Grid and Plate. which requires the greater structural strength. The negative plates used with this grid are of a different design and are known as the " Herring- Bone " grid. In Fig. 18 there is shown a photographic illustration of the " Herring-Bone " grid as used by the Philadelphia Storage Battery Company. 56 Storage Battery Manual The " Ironclad " Type Assembly. — Within comparatively recent time another type of paste assembly has been developed in this country and is meeting with extensive application both in the naval service and in the com- mercial trade. This type of assembly is known as the " Ironclad-Exide " assembly, and derives its name from the special construction of the positive plate which is used in conjunction with the " Exide " type pasted grid. This Spine. Active Material. Tube, Enlarged Section •* Ironclad " Tube. Showing Slotted Tube. ■ WOOD itnumt-f ^ m mr- - * Ironclad " Assembly. FiQ. 19.— Details of ' '' Flat Paste '* Assembly. Ironclad " Assembly. type of assembly is founded upon the principle developed in France about the year 1898 by Phillipart, and which principle has been commercially developed in this country by the Electric Storage Battery Company. The positive plate consists of a number of hard rubber tubes which are filled with the paste active material. Eunning through the center of each tube is a lead-antimony core or spine, which is firmly anchored in the paste by means of semicircular leaves equally spaced along the length of the spine. This spine is lead-burned to the top bar and bottom bar forming Paste Type Assemblies 67 the frame of the plate, and acts as a conductor for transmitting the electrical energy to and from the plate. The hard rubber tubes are " slotted " circum- ferentially by fine saw-cuts of about 1/100 of an inch in width; these slots are designed to effect diffusion of the acid of the electrolyte into the pores of the active material, and serve the same purpose as the perforations in the hard rubber separators used in the ordinary flat paste type assembly. An unribbed veneer separator only is used with this type of assembly, there being Fig. 20. — " Ironclad " Plate and " Paste " Negative — Submarine Type. vertical ribs on diagonally opposite sides of the tubes to effect proper plate separation. There is shown in Fig. 19 a sectional plan view of the regular " flat paste " type assembly and the " Ironclad " type assembly. The essential differences m designs of the two types of assemblies are plainly shown in this drawing. A section of an " Ironclad " tube and the slotted hard rubber tube are also shown in this drawing. Pig. 20 contains a photographic illustration of an " Ironclad " positive plate and the corresponding " Exide " type negative, such as are used in submarine batteries. Long life of the positive plate is especially character- istic of this type of assemblj. 5 CHAPTEE VII. PLANTE TYPE ASSEMBLIES. Methods of Manufacture and Types of Plante Plates. As was explained in Chapter I, the method originally employed by Plante in forming his plates consisted in placing two plain sheets of pure lead in a jar containing sulphuric acid, and then by connecting the terminals of these lead sheets to direct current buses and passing direct current through the cell the respective surfaces of the lead sheets were thus converted into lead-peroxide and sponge lead, thereby forming the positive and negative plates. Also, as has been previously pointed out, such plates, on account of their comparatively limited surface areas exposed to the action of the electrolyte, were possessed of correspondingly limited capacity. Moreover, in order to obtain even this small amount of capacity it was necessary to subject the plates to numerous cycles of charge and discharge, including many reversals, which extended over a considerable period of time and was otherwise a com- paratively expensive method of producing these plates. Therefore, the general trend of development in the art of manufacturing this type of plate has accordingly been along the lines of effecting a reduction in the time element required for the forming process, which includes the various modern forming agents now employed, as well as that of increasing, by various im- proved manufacturing methods, the plate surface areas in contact with the electrolyte. In general, the various modern types of Plante assemblies depend mainly upon the methods employed in constructing the plates prior to subjecting them to the forming process. In some instances, however, the forming process or special formation used by the manufacturer governs the type of plate produced. Mechanically considered, the principal methods now used in Plante plate construction may be classified as follows : (1) Casting. (3) Building-up. (3) Spinning. (4) Ploughing. ( 5 ) Swedging. Each of the above classifications refers to the particular mechanical method employed in increasing the surface area of that portion of the plate in con- Plante Type Assemblies 59 tact with the electrolyte and which constitutes the so-called active portion of the plate. Eepresentative types of Plante plates, constructed by each of the above-named methods will be described. Cast Type. — The plates manufactured by the casting method are known as cast type plates, and are cast under pressure in appropriately designed moulds, pure soft lead being used in the casting process. Of this particular type of plate the " Tudor " type is a familiar example, this type having been commercially developed and used extensively in European countries. Fig. 81 contains a detailed illustration of a cast " Tudor " plate. Eeferring to this illustration it will be noted that the plate construction consists of a series of numerous, thin, vertical leaves, and also of a smaller Conducting Lug. Hanging Lug Front Elevation. Fig. 21.— Cast Type " Tudor " Plante Plate. number of horizontal bars or ribs which are integrally joined to the vertical leaves; these particular features of construction being cleaxly shown in the end elevation of a section of the plate on the right-hand side of the illus- tration. Consistent with proper mechanical strength required for supporting the plate, this grid-like construction is designed to produce maximum surface area of the plate in contact with the electrolyte. The construction of the hanging and the conducting lugs is also plainly shown in the illus- tration of this plate. After these plates are cast they are next subjected to a forming process, whereupon thin layers of lead-peroxide and sponge lead are formed on the respective surfaces of the positive and negative plates. It will thus be seen that the number of leaves in such a plate constitutes a function of the 60 Storage Batteet Manual capacity of the plate. For reasons which will be explained later, the negative plates of the Plante type. are usually cast slightly heavier than the positive ones. In forming these plates, all plates are usually formed as positives after which the required number are reversed and converted into negatives. It may be said that the east type " Tudor " plate has never met with extensive application in this country, due primarily to the manufacturing dif&culties encountered in the casting process, as it appears that the molecu- lar construction of the lead obtained in this country is not conducive to the same degree of uniformity in the casting of these plates as that obtainable from European leads. Other types of Plante plates have therefore been developed in this country, all of which types will be fully described in the succeeding text. " Built-TJp " Type. — There are several types of Plante plates manufac- tured by the huilding-up method of construction; these plates are usually referred to as the built-up type. Although the details of constructing this type of plate vary somewhat, generally speaking, all of them consist of a lead-antimony alloy casting or grid which constitutes the supporting frame- work for the pure lead active members of the plate ; these pure lead members being of various shapes and types, principally as regards surface area, depending upon the particular details as worked out in the design of the plate. Due to the fact that an alloy composed of lead and antimony is prac- tically unattacked by the acid of the electrolyte, the east grids or frameworks used for these plates take no part in the primary working of the plate other than that of conducting current to and from the plate. These grids should be sufficiently rugged in design as to withstand the strain put upon them as a result of the growing action incident to the normal Plante formation which takes place on the pure lead members of which the grids form a sup- port; this feature resolves itself into a function of resisting buckling of the plate. It may be said that, as a general rule, plates of this type find chief appli- cation in stationary storage battery installations and other classes of service where the subject of weight is relatively unimportant, as due to the large percentage of the plate as regards weight devoted to the grid, the weight efficiency of plates of this type is comparatively low as compared to other types of Plante and paste plates. However, this type of plate is noted for its ruggedness and its capability to withstand much repeated abuse in the operation of the battery. Plante Type Assemblies 61 The following are familiar examples of built-up type Plante plates as manufactured in this country and used in modern storage battery instal- lations requiring plates of this type : (a) " Manchester " positive. (b) " IJ-S-L Unit " positive. Bach of the above types will be described in detail in the succeeding text. (a) " Manchester " Positive. — The " Manchester " positive Plante plate was one of the pioneers in the commercial application of storage batteries in this country, and is also now used extensively for certain classes of storage battery installations, principally on shore stations for radio equipment, stationary " stand-by " installations, isolated farm lighting sets, etc. Section of Fully Formed Plate. Gria. Fig. 22.- Corrugated Tape Buttons. ' Manchester " Positive Plants Plate. This type of plate consists of a lead-antimony casting or grid containing numerous holes and into which are hydraulically pressed pure lead " but- tons " or " rosettes," which are made up from corrugated strips of pure lead tape. The holes in the grids are slightly beVelled or countersunk on each face of the grid in order that when the buttons expand or grow due to the forming action which takes place during the operation of the cell, this expansive action will tend to rivet the buttons in position, thereby main- taining good electrical contact with the grid as well as preventing them from becoming detached from the grid. Pig. 22 contains an illustration which clearly shows the details of the component parts of this plate. Eeferring to this illustration, the con- struction of the lead-antimony grid will be readily understood, as will also that of the corrugated tape " buttons " or " rosettes." Th« section of the fully formed plate gives a clear idea of the method of installing the buttons 62 Storage Battery Manual in the grid. The corrugations in the tape from which the buttons are made are designed primarily to assist diffusion of the electrolyte into the active material of the plate. Due to the large percentage of grid comprising this type of plate, the weight efficiency is comparatively low, but for certain classes of service, such as stationary stand-by installations where the question of weight is not a CoTidiicting Lui Perforated Sheets of Pure Lead Enclos- ing Ac'ti\e Material in the Compartments nf Plate. Lead-Antimony Frame. Fig. 23.— "Box" Negative Plate. governing factor, these plates render highly satisfactory service ; ruggedness is an especially characteristic feature of this type of plate. This plate has been commercially developed in this country by the Electric Storage Battery Company, and was used in some of the early submarine storage battery installations in our naval service. " Box " Negative. — Although, properly speaking, the " box " negative type plate does not belong to the Plante group, it being a special type of " paste " plate, it will nevertheless be here described inasmuch as it is now Plant^; Type Assemblies 63 chiefly used in conjunction with the " Manchester " type positive Plante plate described in the preceding paragraphs. This plate is of the so-called built-up type construction and derives its name from the cellular or " box-like " features of design. Fig. 23 contains a sketch of this type of plate and from which a clear idea of the various details of construction may be had. The frame composing the supporting members of this plate consists of a lead-antimony casting in the form of a series of crossed bars, all of which are integrally joined together, thus pro- ducing the compartmentation or' cellular construction for holding the paste active material. These cells or compartments are closed on each face of the plate by means of perforated sheets of pure, soft rolled lead held in position by riveting to the lead-antimony casting forming the frame of the plate. The perforations in the lead sheets comprising the two faces of the plate are designed to afford proper circulation of the electrolyte in and around the paste active material compacted into the several compartments of the plate. The paste for this type of plate consists of litharge and lampblac^k, or carbon in some other finely divided form, in order to increase its conductivity as well as to maintain the proper degree of porosity in the paste. Although this type of plate produces good results for certain classes of service, it may be said that, due to the very advanced stage which has been attained in the art of paste plate construction, it is gradually being superseded by other later types. After these plates are made up they are given a forming charge in the same manner as was described in the preceding chapter applying to paste type assemblies. (b) " TJ-S-L Unit Positive " Plante Plate. — Another typical example of the built-up type of Plante plate is known aS the " U-S-L Unit Positive," an illustration of which is shown in Fig. 34. This plate is manufactured by the U. S. Light and Heat Corporation and consists of a lead-antimony framework or grid casting which supports the pure lead units constituting the active members of the plate. The lead-antimony grid is cast under pressure and is sufficiently rugged in design as to afford ample strength and rigidity during the life of the plate. The lead units which compose the active members of the plate are swedged from blank slabs of chemically pure rolled lead ; this swedging process consists in working up the surfaces of the blank slabs into leaves or laminations in order to increase the surface areas of the active units in contact with the electrolyte. The pure lead units are secured to the grid by means of lead-burning, and in order to prevent buckling of the plate, as a result of the normal growth or expansive action which takes place to a certain degree in all positive Plante plates, ample clearance space is left between the sides and bottoms 64 Storage Battery Manual of the lead units and the inside edges of the grid to accommodate this growth. This feature of design is plainly shown in the illustration, Fig. 34. The lead-antimony grid used with the paste type negative which operates in con- junction with the Plante positive plate described herein is also shown in this illustration. In the manufacture of these plates it is essential that a good electrical contact be obtained in lead-burning the pure lead units to the grid ; these lead-burned joints should also be of sufficient cross-section and current- carrying capacity as to accommodate the various rates capable of being developed by the active members during the operation of the plate. After ' U-S-L " Unit Type Built-Up Plants Plate (Positive). Neg-ative Grid Used with \ Positive Plate. Negative Gnd (Paste). Unit Positive. Fig. 24.—" U-S-L " Unit Type Plante Plate. the units are lead-burned to the grid the plates are then placed in the forming tanhs and given their formation charge. This type of plate is now used mostly for stationary battery installations and where weight is not a governing factor. This is considered a very rugged and diirable plate and for its particular line of service gives good results. " Spun " Type Plante Plate. — This type of plate is manufactured by the spinning method of construction and is a type largely used in this country, both in the naval service and commercial fields. Pig. 35 contains a photographic illustration of this type of plate and as manufactured by the Gould Storage Battery Company. Increasing the surface area of this type of plate is effected by passing a pure lead blank through a spinning machine Plante Type Assemblies . 65 specially designed for this purpose by the manufacturers. The general details entering into the manufacture of this plate are as follows : The pure lead blank is formed by easting a fiat ingot of pure lead of from 4 to 5 inches in thickness, and then passing this ingot back and forth between the steel pressure rolls of a rolling mill, and in this maimer is rolled until the desired thickness of the lead blank is obtained; this thickness in practice varies from 0.186 to 0.288 inch. It will therefore be seen that when the lead blank is removed from the rolling mill it has been transformed into an Pig. 25.—" Spun " Type Plants Plate. exceedingly dense and homogeneous sheet of pure lead, qualities which are especially to be desired in the manufacture of Plante plates. These lead sheets having been removed from the rolling ■ mill are next carried to the punching machine where they are die-punched into blank plates of the desired size and form, with hanging and conducting lugs attached. The next operation is that of the spinning process, which is as follows : The blank plates after being punched out as outlined above are next set-up in the frame of the spinning machine; when the machine is put in motion this frame carrying the blank plates reciprocates between a series of revolving mandrels, one set located on each side of the plate, each of which is fitted out with steel discs separated from each other by spacing washers. 66 Storage Battery Manual As the frame carrying the blank plate passes back and forth between these discs a uniform pressure is continuously exerted against these discs and in turn against the blank plate by means of compressed air, and ridges or ribs and grooves accordingly begin to a,ppear on each face of the plate. As the spinning operation progresses the discs are thus fed and depressed ' GOULD " TYPE SPUN PLATE. Horizontal Ri-b Vertical Rit We-b Well' Lead Blank, First Stage. Intermediate Stage. Finished Stage. / Various Stages of the Spinning Process. Pig. 26. — Showing Various Views of " Gould " Type Spun Plate. deeper and deeper into the plate, thus causing the lead to flow into the spaces between the discs, forming the ribs on each face of the plate. It is therefore apparent that the thickness of the ribs thus spun on the plate is governed by the width of the spacing washers interposed between the discs, and that the amount of space between the ribs is governed by the thickness of the discs on the mandrels. Plante Type Assemblies: 67 Fig. 2fi contains a set of illustratione which clearly show the various stages of the spinning process in the manufacture of these plates, as well as sectional views of the plate after the spinning operation is complete. The series of drawings at the bottom of this illustration show the various stages of the spinning operation from the pure lead blank to the completely spun plate ; the development of the grooves and ribs are plainly indicated in this portion of the illustration. In plates of large size manufactured by this method, it is desirable to leave a certain portion of the blank plate intact to form horizontal and vertical ribs for strengthening and current-conducting purposes. The horizontal ribs are obtained by spinning the plate in sections, thus leaving between the spun sections a diamond shaped cross-bar of solid metal extending the full width of the plate. This feature of the design as worked out on this plate is shown in the upper views of Fig. 26. The vertical ribs are obtained by means of the heavier washers, periodically spaced along the mandrel, which subdivide each section, thus forming the heavier vertical ribs, these ribs varying in number and size according to the dimensions of the plate. These heavier vertical ribs are also shown in the drawings, Fig. 26. By limiting the depth that the discs are fed into the blank plate a web of solid metal of any desired thickness remains as a central conductor, plate support, and current equalizer ; the web thus formed is shown in Fig. 26. It will thus be noted that the spinning of the ribs on the plate resolves itself into a flowing process; that is, due to the pressure exerted upon the discs as they are fed into the plates, the metal flows into the spaces between the discs, thus forming the ribs on the surface of the plate and increasing the surface area of the plate many times that of the original blank plate. In this regard, it is claimed by some storage battery engineers that this method of rib formation is superior to other methods, such as gouging, cutting, bending, etc., in that on account of the crystalline structure of lead those methods open up the pores of the lead in some of the ribs, thus allowing penetration of the electrolyte into those pores with the result that on account of the Plante action which takes place in the pores, abnormal shedding or sloughing-oil of the lead ribs is produced ; whereas, on the other hand, it is claimed that ribs formed by the spinning process are manifestly more dense than the original blank lead plates, thus excluding abnormal penetration of the electrolyte into the lead. It is apparent that any sucli difference, if there be a difference, in character of the ribs formed by the two methods resolves itself into a function of the useful life of the plate. After the spinning operation is complete, the plates are next thoroughly cleaned of all oil and other foreign substances preparatory to conducting the 68 Storagk Ba'i'tkhy "Maam^ai, r* Space for. Electrolyte Active ^4ATERIAL * Reserve Lead SPUN PLATE (FORMED) SPUN PLATE (liNFORMEDH Pig. 27. — Showing Sections of Completely Spun and Fornied " Gould ' Plants Plate. Plante Type Assemblies 69 Fia. 28. — " Gould " Type Spun Plate — Submarine Type. 70 Stokage Battery Manual formation charge. This charge . consists in connecting the plates up in the forming tanks containing the forming solution or lead corroding agents, and then passing direct current through the plates, thus depositing a thin layer of active material on the surfaces of all ribs of the plates. Fig. 27 contains a set of illustrations from which a clear idea of the plate in the various stages of fabrication may be obtained, these stages including all operations beginning vfith the lead blank to the fully formed plate. The lower view in this illustration shows a section of a plate magnified about five times. This type of plate as manufactured by the Gould Storage Battery Company is known as the " C. P." plate, deriving its name from the " ch,emi- cally.pure" (C. P.) characteristics of the forming solution used in: the forrtfartion charge. Pig. 28 contains a photographic illustration of this^type of piate as designed for submarine storage batteries. The unspun seclions forming the vertical and horizontal conducting and strengthening ribs are clearly shown in this photograph. Ploughed Type. — Plante plates of this type are manufactured by a plough- ing process, which process derives its name from the plough-shaped tool used in developing the leaves on the surface of the plate. This method consists in placing a sheet of pu^^ rolled lead in a machine, called a ploughing machine and resembling an ordinary shaper, and ploughing up leaves or laminations from the surface of the lead sheet, thereby increasing its surface area. The ploughing tool of this machine is of such design as to produce a leaf of the desired form and size when the machine is put in operation ; this tool is mounted in the head of the shaper arm, and at each stroke of this arm a leaf is ploughed up from the flat surface of the sheet of lead. An auto- matic feed. carries the tool across the width of the plate, this feed properly spacing the leaves apart at the end of each stroke. The strengthening and conducting ribs of the plate are formed by jumping the feed the proper amount at the desired positions along the width of the plate, thus leaving unploughed sections of the plate which constitute these ribs. This method of manufacturing Plante plates is featured by the Willard Storage Battery Company. After the ploughing operation is completed, the plates are next placed in the forming tanks and given their formation charge, after which they are ready for assembling in groups and installing- in the jars. Generally speaking, jars for this type of plate consist either of glass or lead-lined tanks. Swedged Type. — This type of plate is manufactured by the swedging process, which consists in gradually developing the flat surface of a chem- ically pure, rolled sheet of lead into ribs or leaves by means of progressive and equally distributed pressure applied to the master forming or swedg- Plante Type Assemblies 71 ing. block of the swedgiiig machine. This block consists of a steel slab having laminations, leaves, grooves, and strengthening ribs very accurately machined on its surface such that the desired form of the surface of the plates is impressed or developed on the rolled lead sheet when the machine is put in operation and pressure applied to the swedging block; obviously, the developed or machined' surfaces of the swedging block is the reverse of that of the plates formed from it ; that is, a groove on the swedging block develops a rib or leaf on the rolled lead sheet and vice versa. This swedging process is accomplished through the swedging block of the machine being suc- PlanW Negative. Pig. 29.— Plante Positive. U-S-L " Swedged Type Plante Plates. ^cessively passed over the surface of the lead sheet; an automatic feeding arrangement is provided such that the swedging block is progressively fed into the lead sheet until the desired depth has been attained, thus developing the increased surface area of the lead sheet. This method of manufacturing Plante plates produces very uniform and homogeneous plates. Fig. 39 contains a photographic illustration of a pair of plates as manu- factured by this method by the U. S. Light and Heat Corporation. It will be noted that the plates in this illustration are practically identical in form with the exception that the design of the negative plate dispenses with all vertical and horizontal ribs, except the center ones, thus increasing the active area of thfe negative plates. This special feature of design in respect to the increased surface area of the negative plates over that of the corresponding 72 Stobage Battery Manual positive plates may be said to be characteristic of all types of Plante plates, the reasons for which will be explained in another part of the text. As in the case of other types of Plante plates, these plates are used in installations where the subject of weight per unit of power developed is not an important one. After the swedging process is completed, the plates are next placed in the forming tanks and given their formation charge, which consists in forming a thin layer of sponge lead and lead-peroxide on the respective surfaces of the negative and positive plates. Special Characteristics of Plante Plates. Capacity and Weight. — As was stated in the preceding paragraphs, the capacity of Plante assemblies per pound of battery is considerably less than that for paste type assemblies, which also accounts for the fact that paste plates are now used practically entirely for the so-called portable types of storage batteries and wherein the subject of weight is of necessity a very important one. This feature of increased weight of Plante assemblies over that of the paste type is due primarily to the fact that it is necessary to initially provide a reserve of lead in both the positive and negative plates of the Plante type in order to produce a well-balanced unit; the reasons for this may be briefly summarized as follows : Positive Plates.^ — Inasmuch as the active material of Plante plates is formed or produced from the original lead constituting the plates, and due to the fact that it is an inherent characteristic of all types of positive . plates to shed a certain amount of this active material with each suc- cessive cycle of charge and discharge, it is therefore apparent that it accord- ingly becomes necessary to provide a reserve amount of base metal to com- pensate for that amount of active material shed from the plates during their normal operation in order that their rated capacity may be maintained throughout their useful life; in other words, this reserve amount of base lead must be provided in order that new active material may be progressively formed from it as necessary to replace that lost as a result of shedding. Negative Plates. — Although after the original formation of active material is completed on the negative plates, practically no further forming action takes place on the basic lead of these plates, yet in view of the fact that all sponge lead has a tendency to contract or shrink during the normal action which takes place in the cells, thereby effecting a reduction in the capacity of the negative plates, it therefore becomes necessary to initially provide an excess of active material in order that when this shrinkage occurs the service Plante Type Assemblies 73 capacity available in the plates may balance that of the corresponding positive plates. As a general rule, it may be said that this shrinkage of the negative active material takes place at a comparatively rapid rate during the early operating days of the battery, after vphich it gradually decreases until practically no further shrinkage occurs. It is for this reason that Plante negative plates are designed with more initial surface area than the corresponding positive plates. This feature of design is plainly illustrated in Fig. 29, where the number of horizontal rihs is reduced in the negative plate as compared to that of the positive plate in order to increase the surface area of the negative plate. In further consideration of the subject of reserve metal provided for Plante type plates, it should be noted that whereas in the positive plates the reserve lead is provided in the form of basic lead in order to replace the active material lost in shedding, in the negative plates the reserve lead is provided in the form of active material in order to compensate for shrinkage in the original amount provided. In other words, the capacity of the positive plate remains practically constant from the beginning of and during its useful life, whereas an excess of capacity (active material) must be initially provided in the negative plate in order that at the end of the shrinkage period ample capacity to balance that of the positive shall remain. This distinction between the two forms of the reserve metal as provided in these plates should be clearly drawn in the mind before passing on to the succeeding text, as a thorough understanding of this feature of the subject is necessary to a proper study of Plante plates. CHAPT.EK VIII. CAPACITY AND EFFICIENC"^ Capacity Defined. In order that storage battery installations may be ■ intelligently and satis- factorily operated it is necessary that the term capacity, as relating to storage battery engineering, be thoroughly understood. Capacity when considered in this sense may be defined as the amount of electrical energy capable of being delivered by a cell or battery from the beginning of discharge until the gradually diminishing electromotive force of the cell reaches some predetermined value, which value depends upon the rate of the discharge as well as the design of the particular battery in question. The above definition assumes that the discharge is a continuous one, and that it is begun vrhen the battery is fully charged and at a standard initial temperature. The standard initial temperature upon which the capacity of storage batteries for the naval service is based is 80 degrees Fahrenheit. The Unit of Capacity. The unit of capacity is the ampere-hour, which represents the product obtained by multiplying the rate of discharge in amperes by the time of dis- charge in hours. Thus, if a cell is capable of delivering 50 amperes steadily for 10 hours, to the predetermined final voltage, the capacity of this battery is 500 ampere-hours at that rate. Watt-Hour Capacity. Considered from a storage battery engineering point of view, the real energy capacity or true measure of a battery's energy producing capabilities is known as the watt-hour capacity, and is obtained by multiplying the ampere-hour capacity of the battery by the average value of the voltage during the discharge and is represented by the expression, CtEa, where : =Eate of discharge in amperes. t = Time of discharge in hours. ^a = Average voltage during discharge. Thus, considering the same battery as outlined in the preceding paragraph, if this battery is discharged at the 10-hour rate (50 amperes) for 10 hours. Capacity and Efficiency 75 and the average voltage obtained during this discharge is 1.85 volts, then the watt-hour capacit}' of this battery is : 500x1.85 = 9.25 watt-hours. Capacity Varies with Eate of Discharge. Other things being equal, the capacity of a battery may be said to vary inversely as the rate of discharge; that is, the number of ampere-hours capable of being delivered by a battery when discharged at low rates is greater than that obtainable when discharged at higher rates. Theoretically considered, the capacity of a battery should be the same for all rates of discharge inasmuch as there is a definite amount of active material contained in the plates as well as a definite amount of sulphuric acid in the electrolyte, which combination should produce a definite number of ampere-hours irrespective of the rate of discharge. Practically considered, however, such is not the case, for, as has been pointed out, it is an established fact that the number of ampere-hours pro- duced by a battery during a continuous discharge does vary with the rate of discharge. Considering that the ampere-hour capacity of the battery is 100 per cent at the 1-hour rate, the following tabulation gives the relative percentage of ampere-hour capacity at other rates up to and including the 20-hour rate : Rate of discharge. Ampere-hour capacity. l-hour 100 per cent 3-hour 135 5-hour 150 10-hour 172 15-hour 193 20-hour 197 This variation in capacity for different rates of discharge is due primarily to the fact that as the discharge progresses the acid concentration in the electrolyte becomes progressively less by virtue of its combining with the active material of the plates to form lead-sulphate, and since the ampere- hours delivered by a cell on discharge is a function of the rate of diffusion of the acid into the pores of the plate and the consequent combining of this acid with the active material with which it comes in contact, it follows that the sulphating action is greatest at the surface of the plate where the active material is readily accessible to the acid. Obviously, therefore, at higher rates of discharge, since the sulphating action is greatest at the surface of the plate, the sulphate crystals tend to clog up or congest the oUter pores of the plate, thus retarding the diffusion of the acid into the interior of the 76 Storage Battery Manual plate, with the result that the electrochemical action between the electrolyte and the interior active material of the plate is retarded, thus effecting a reduction in the number of ampere-hours delivered by the battery. Also, as has been stated, since the capacity is established by the end or final voltage, when the surface pores of the active material become congested and reduce the rate of diffusion of the acid into the interior pores, it is apparent that the acid which is entrained in the pores becomes weak, thus increasing the internal resistance of the cell, which is reflected by a reduction in the cell voltage, until the end or minimum final voltage for this rate is reached. On the other hand, however, at lower rates of discharge the diffusion of the acid into the pores of the plate is more even, and consequently sulphate is not formed so rapidly at the surface and the acid has a better chance of access into the inner pores of the plate, consequently the voltage remains higher, and the number of ampere-hours obtainable at low rates of dis- charge is greater than at high rates. Another interesting feature in regard to the capacity of storage batteries is that although when discharged at high rates to the minimum final voltage, if allowed to stand for a short while, the voltage comes up or recovers itself again and the battery is then capable of producing an appreciable number of ampere-hours at lower rates of discharge ; this additiontil capacity obtain- able at lower rates after a higher rate discharge is commonly referred to as recuperative capacity. Capacity Established by End or Final Voltage. The low voltage limit reached by the cell at the end of discharge and as referred to in the preceding paragraphs is usually fixed by the battery manu- facturers and is based primarily upon the degree to which the plates of the cells may be sulphated without injury during the discharge This condition arises from the fact that lead-sulphate is less dense than either lead-peroxide or sponge lead, the prime constituents of the active material of the positive and negative plates. Therefore, during a discharge, the active material of both sets of plates expands as it is converted into lead-sulphate, thus making it necessary to discontinue the discharge when a definite degree of sulphation has been attained in order to not subject the grids, adjacent active material and other parts of the plates to excessive strain incident to such expansion. The relative densities of sponge lead, lead-peroxide, and lead-sulphate are approximately as follows : Sponge lead 10.5 Lead-peroxide 8.0 Lead-sulphate 6.5 Capacity and Efficiency 77 Generally speaking, the following tabulation represents the low voltage limits capable of being safely reached by a battery of good design without injury to the plates during a continuous discharge at the designated rate : Rate of discharge. Final volts per cell. l-hour 1.50 3-hour 1.70 5-hour 1.72 10-hour 1.75 15-hour 1.77 20-hour 1.80 It will be noted in the above table that the limiting final voltage has a smaller value at the higher rates of discharge than at the lower rates. This feature is accounted for by the fact that inasmuch as at the higher rates of discharge the number of ampere-hours obtainable from a cell is smaller than at the lower rates, the degree of sulphation in the plates is therefore less at the higher rates and the expansive action of the sulphated active material is accordingly not as great. Factors Which Affect Capacity. Other than the rate of discharge, the factors which directly affect the capacity of storage batteries may be summarized as follows : (a) Quantity of active material. (b) Arrangement of active material. (c) Condition of active material. (d) Quantity and density of the electrt)lyte. (e) Circulation of the electrolyte. (f) Temperature. (g) Age of the cell. Each of the above factors may be briefly commented upon as follows : Quantity of Active Material. — Inasmuch as the lead-peroxide of the posi- tive plates and the sponge lead of the negative plates are each converted into lead-sulphate during a discharge, and also since it is as a result of this electrochemical action that electrical energy is produced on discharge, it follows that the greater the amounts of these active materials contained in the plates the greater the capacity of the battery. The relation between the quantity of active material used in a cell and the quantity of electricity obtainable from it may be determined from the appli- cation of Faraday's electrochemical law, which law states that : I. The amount of a substance liberated at an electrode is proportional to the total quantity of electricity passed through the cell. 78 Stoeage Batteht Manual II. The amount of a substance liberated by a given quantity of electricity is proportional to the electrochemical equivalent of the corresponding ion. III. The amount of a substance liberated is equal to the electrochemical equiv- alent of the corresponding ion multiplied by the total quantity of electricity. In brief, the above law states in effect that the amount of each substance performing a function in an electrochemical reaction is proportional to the quantity of electricity which passes through the circuit. And when various substances enter into an electrochemical reaction, their amounts are pro- portional to their chemical equivalent weights. In the application of this law it is necessary that certain electrical units be utilized, principal among which are the ampere and the coulomb, the former being the unit of current and the latter the practical unit of quantity of electricity, one coulomb being the quantity of electricity which passes through a circuit when a current of 1 ampere has been flowing constantly for 1 second. The electrochemical equivalent or the chemical equivalent weight of a sub- stance as used in the above law is the ratio of quantity, by weight, of a sub- stance which is decomposed by 1 ampere-hour (3600 coulombs) of electricity, to the quantity of hydrogen liberated by the passage of 1 ampere-hour of elec- tricity. Numerically considered, it is equal to the atomic weight of the sub- stance divided by its valency. Inasmuch as the atomic weight and valency of hydrogen are each equal to 1, the electrochemical equivalent of hydrogen is unity. As a result of a series of very accurately conducted experiments it has been established that when 1 ampere of current has been flowing constantly for 1 second through a voltameter or an electrolytic cell in which silver is being deposited from a silver nitrate solution (AgNOj), under standard specifica- tions, this quantity of electricity (1 coulomb) deposits 0.001118 gm. of silver. The atomic weight of silver is 107.93; silver ion being univalent, the electrochemical equivalent or the chemical equivalent weight of silver is therefore i^^ =107.93 gm. Then, since 1 coulomb of electricity deposits 0.001118 gm. of silver, the number of coulombs required to deposit 107.93 gm. will be - - ' =96,540 coulombs. .UUlllo Therefore, since this same number of coulombs will deposit the electro- chemical equivalent or the chemical equivalent weight of any other metal which can be electroplated in the same manner as described above for silver, Capacity and Efficiency 79 this quantity of electricity (96,540 coulombs) has for convenience been adopted as the electrochemist's unit of quantity of electricity and will be used accordingly in the succeeding text and calculations relating to this subject. Now, in calculating the amount of active material required to produce a given quantity of electricity in the lead-acid storage battery cell, the pro- cedure is as follows : , . , . , fPb, negative plate. Active materials., i -r,-,^ -,• , , 1 PbOj, positive plate. The atomic weight of lead is 306.9 and, since it is bivalent, its electro- chemical equivalent or chemical equivalent weight is — -2i_ gm. 2 S06 9 Hence, if 96,540 coulombs of electricity will deposit — g^— gm. of lead, then 1 coulomb or 1 ampere-second of electricity will deposit ■^ ^96^ =.00107 gm. of lead; and since 1 ampere-hour is equal to 3600 coulombs, then 1 ampere-hour of electricity will deposit 3600 X .00107 = 3.89 gm.of lead. Therefore, 3.89 gm. of lead will be required in the negative plates for every ampere-hour of electricity produced by the battery. Next, considering the positive plate, the atomic weight of lead-peroxide (PbOj) is 206.9-1-33, and its electrochemical equivalent or chemical equiva- lent weight is 306.9-f33 338.9 3 gm. 338 9 Then, since 96,540 coulombs of electricity will deposit — „— gm, of lead- peroxide, 3600 coulombs, or 1 ampere-hour of electricity will deposit 338.9 1 3600 . .„ „ , -, •■, — g— X 9g-g4Q X ^— =4.45 gm. of lead-peroxide; or, 4.45 gm. of lead-peroxide will be required in the positive plates for every ampere-hour of electricity produced by the battery. Although the above calculations represent the theoretical amounts of active materials required in the plates for each ampere-hour of electricity produced by the battery, when practically considered, it is found that from two to five times the theoretical amounts of active material are- required, depending upon the type of plates used, for the reason that the porosity of 80 Storage Battjsky Manual the active material is necessarily limited in all types of plates, and therefore some of the active material is inaccessible to the action of the electrolyte. Furthermore, for other reasons which have been stated elsewhere in this chapter, the discharge is discontinued when a predetermined minimum final voltage is reached, thus accounting for a certain amount of the active material present in the plates and which is not utilized in producing ampere- hours. These facts taken in conjunction with other characteristic features of design of storage batteries satisfactorily explain why the theoretical amounts of active materials contained in the plates are exceeded. Arrangement of Active Material. — Since it is essential to the production of electrical energy in the cell that the acid of the electrolyte and the active materials of the plates be in contact with each other, it is readily apparent that the arrangement of the active materials in relation to that of the electrolyte constitutes a very important factor in respect to the capacity of the battery. In other words, the greater the degree of contact between the electrolyte and the particles of active materials contained in the plates, the greater the capacity of the battery. Also, it is essential to a proper design of the battery that the active materials be so arranged in the plates as to produce uniform working over all portions of the plate in order to prevent bucMing and undue strain over any part of the plate. Therefore, in point of design, the battery engineer strives to produce a battery, the plates of which present maximum surface area in contact with the electrolyte in order that an increase in capacity as outlined above may be effected. Moreover, by installing in the cells a large number of thin plates having surface areas as great as is consistent with good design, the capacity of the battery is accordingly increased. Especially is this true of batteries designed for high discharge rates, as, for instance, in submarine storage batteries, automobile starting batteries, and other batteries designed for similar classes of service. On the other hand, however, since the rate of diffusion of the electrolyte into the pores of the plate is a function of the capacity of the plate, it may be said that for batteries designed for low rate discharge work, thick plates with smaller surface areas are more practicable, inasmuch as low rates of discharge do not require such a rapid rate of diffusion of the electrolyte into the pores of the plates as is necessary in the case of high rates of discharge ; thick plates, therefore, afford ample rates of diffusion for the required low rate capacity. Furthermore, thick plates are in general possessed of longer life than is characteristic of thin plates. In further consideration of the subject of the arrangement of the active materials in the plates and the effect of such arrangement upon capacity, it Capacity and Efficiency 81 may be said that Plants type plates present striking examples, as in these plates the active materials are formed or deposited in very thin layers over a comparatively large surface area of plate, with the result that they respond rapidly to very high rates of discharge ; that is, the layers of active materials being relatively thin, the rate of diifusion of the acid into the pores of the plates is correspondingly rapid, thus making the plate capable of readily responding to the high rates of discharge. Also, due to the per- fection attained in the contact betvi^een the active material and the con- ducting members of Plante plates, the conductivity is high, the internal resistance of the cell is correspondingly low, and with the result that the voltage of the cell during discharge is high, thus increasing the watt-hour capacity of the cell. Moreover, since the internal resistance of the cell is reduced as a result of the good contact between the active material and the conducting members of the plate, it is apparent that the ampere-hour and the watt-hour efficiencies of Plante plates are relatively high in comparison with paste plates. Condition of Active Material. — Inasmuch as it is impossible for all par- ticles of active materials composing the plates to be assembled at the sur- face, it obviously becomes necessary that some means be provided whereby the acid of the electrolyte may be readily accessible and plentifully supplied to the particles of active materials located in the interior of the plate in order that full capacity may be obtained during a discharge. This feature or expedient resolves itself into effecting a sufficient degree of porosity in the active material through the use of other agents, such as carbon, barium sul- phate and other substances, during the mixing of the paste and the manu- facture of the plate. In general, it may be said that the greater the degree of porosity of the active material the greater the capacity of the plate ; that is, a porous plate is capable of producing greater capacity, especially at high rates of discharge, than a dense, hard plate. However, there is a practical limit to the degree of porosity which is to be desired in a plate, as too much porosity is conducive to excessive shedding of the active material and a consequent short life of the place. After a proper degree of porosity has once been obtained in the active material during the manufacture of the plates, it is essential to satisfactory operation of the battery that this porosity be maintained as far as possible throughout the useful life of the plates. In order to maintain this porosity it is therefore necessary that the battery be kept in a state of practically full charge, especially when lying idle and subjected to protracted periods of inactivity, since if it is allowed to remain in an uncharged condition the lead- sulphate crystals become hard and it is with difficulty that such crystals are 83 Storage Battery Manual reduced during charge, if indeed at all in cases of excessive sulphation. Hence, in such cases the internal resistance of the cell increases, the pores of the active material become clogged or congested, thus preventing proper diffusion of the electrolyte and with the consequent result that the capacity falls off, the efficiency is reduced and the battery deteriorates rapidly in general. Furthermore, if this condition is allowed to exist without taking steps to remedy it, it then becomes only a matter of a comparatively short while until the capacity is beyond restoration, at which time the battery is ready for the scrap heap. The subject of the trichling charge and its rela- tion to maintaining the active material of the plates in proper condition as regards capacity is covered fully in a later chapter and should be carefully studied. Quantity and Density of the Electrolyte. — Having considered the active materials composing the plates and their relation to the capacity of tho storage battery cell, we will next consider the electrolyte and its relation to capacity. In the beginning it should be thoroughly understood that the electrolyte plays equally as important a part in the operation of the cell as do the active materials of the plates, for if it were not for the presence of the electrolyte no electrochemical action would take place in the cell and, con- sequently, no electricity could be produced by it. The necessity for the presence of the electrolyte having thus been estab- lished, the next point to be considered is the amount of electrolyte required in the cell to produce a given capacity or quantity of electricity; this can be ascertained through the application of Faraday^s law, the procedure being similar to that followed in determining the amounts of the active materials contained in the plates. In this connection let us therefore again review the fundamental equation of the chemical reaction which takes place in the lead-acid storage battery cell. This equation is written as follows : Pb 4- 3H,S0, -f- PbO^ = 2PbS0^ -|- SH^O. In applying Faraday's law to the above equation, such that the amount of electrolyte can be ascertained, it becomes necessary to obtain the electro- chemical equivalent of the 2H2SO4 member. Therefore, since the atomic weight of sulphur is 31.83, the atomic weight of the electrolyte as chemically expressed above is 3[2-|-31.83 -I- (4x16)] =195.66, and being bivalent the electrochemical equivalent or chemical equivalent . , , . 195.66 weight IS — ^g — gm. As has been previously pointed out, since 96,540 coulombs of electricity will deposit the chemical equivalent .weight of any substance entering Capacity and Efficiency 83 into an electrochemical reaction, then the amount of HjSO^ deposited by 1 ampere-hour or 3600 coulombs of electricity will be : 195.66 1 3600 „ ^, ^-2- X gpiO ^ ^r =3.64gm.; and therefore 3.64 gm. of H2SO4 will be required in the cell for every ampere-hour of electricity produced by it. In summarizing the theoretical amounts of active materials used up in the lead-acid storage battery cell in the production of 1 ampere-hour of electricity, it will be seen that these amounts are as follows : Lead (Pb) 3.89 grams. Lead-peroxide (PbO,) 4.45 grams. Electrolyte (HjSO.) 3.64 grams. As was stated in the case of the active materials composing the plates, that for a given capacity the actual amounts of these materials required exceed the theoretical amounts, so also does the actual amount of electrolyte required in the cell in practice exceed the theoretical amount. In point of design the chief reasons for exceeding the theoretical amount of electrolyte in actual practice may be stated as follows : (a) It is necessary that the tops of the negative plates be covered with electrolyte in order to prevent them from oxidizing and drying out and thus losing their capacity. Strictly speaking, in so far as the actual production of ampere-hours is concerned, all acid which is positioned above the tops of the plates is not utilized, although, as will be later described, the additional acid head resulting from the acid above the tops of the plates constitutes a function of the rate of diffusion and circulation of the electrolyte in the pores of the plates. (b) AH acid in the space below the bottoms of the plates, which is com- monly known as the sediment space, plays no useful part in the production of ampere-hours. Next, in considering the subject of density of the electrolyte, it may be said that this factor has a considerable effect upon the capacity of the storage battery, as within certain limits the voltage of the cell increases with the density of the electrolyte, thus manifesting itself accordingly in an increase of capacity obtainable from the cell. Another necessary consideration to be given to the density of the electrolyte is that of the effect it has upon the life of the cell. In respect to this feature of the subject, it has been found that the chemical activity of the electrolyte at densities above 1.300 is such as to rapidly attack and seriously injure the grids and other parts of the battery, making it impracticable to use acid of a higher specific gravity than 1.300. 84 Storage Battery Manual As stated above, within certain limits the voltage of the cell increases with an increase in the density of the electrolyte ; this is due primarily to the fact that the conductivity of the electrolyte varies with the density of the acid, it being greatest at a density of about 1.230, as shown on the curve in Pig. 30. It will also be noted from this curve that the conductivity decreases from this point as the density of the electrolyte is increased or decreased; that is, the resistance of the electrolyte in the cell increases as the density is increased or decreased from 1.320. However, owing to the increased chemi- cal activity, and therefore capacity, especially at high rates of discharge, which results through the use of high density acid, a compromise has there- fore been effected, and the normal full charge gravity reading adopted for batteries of the naval service and designed for high rates of discharge ranges from 1.250 to 1.280; whereas, those designed for intermittent service at comparatively low discharge rates use acid of 1.220 specific gravity at full charge. These limits are considered satisfactory for batteries designed for this service. Circulation of the Electrolyte. — ^The circulation of the electrolyte also bears an important relation to the subject of capacity obtainable from the storage battery cell. In order that the chemical action may be ample and continuous in supporting the discharge it is necessary that the facilities for affording circulation of the electrolyte be such as to allow the stronger acid to replace the weaker acid in contact with the active material of the plates. Mechanically considered, this feature resolves itself into providing and installing separators containing sufficient porosity; necessary acid space between the plates and the separators, as well as ample space between the separators — these having been very fittingly termed the breathing spaces of the cell; necessary height of the electrolyte above the tops of the plates as to produce a sufficient acid head for assisting in increasing the capacity of the battery through increased rate of diffusion, hence circulation, of the electrolyte into the pores of the plates ; and such other mechanical expedients as will tend to improve, generally, the circulation of the acid in the cell. Temperature. — The subject of temperature is important with regard to capacity in that the rate of diffusion of the electrolyte is quite appreciably increased by virtue of a rise in temperature, and since the diffusion of the acid into- the pores of the plates is a function of capacity, it follows that the capacity is increased by a rise in temperature in the cell. The increased diffusion is brought about by expansion of the acid, as well as the increased size of the pores in the separators and plates resulting from this rise in temperature of the cell, all of which tends to assist in improving the circula- tion of the electrolyte. It has been found that the density of the electrolyte varies inversely by approximately one point (.001) for every 3 degrees Capacity and Efficiency 85 Fahrenheit; in other words, for every 3 degrees Fahrenheit rise in tem- perature, the density of the electrolyte will register .001 point lower on the hydrometer scale. Therefore, in taking specific gravity readings of a cell, the correction for temperature should be made in order to ascertain the true state of charge or discharge of the battery with respect to the standard temperature upon which the capacity is based. The standard temperature upon which the capacity of all storage batteries for the naval service is based is 80 degrees Fahrenheit. Moreover, all chemical action is accelerated by a rise in temperature, and the chemical activity of the storage battery cell is thus increased as a result of rise in temperature, which manifests itself in an increase in capacity developed by the battery.' It may also be said that the voltage of the cell is increased on discharge by a certain amount as a result of increased tem- perature in the cell, and since capacity is established by end or final voltage, it follows that the capacity is accordingly increased by a certain amount. Under normal operating conditions 110 degrees Fahrenheit has been adopted as the maximum permissible limit to be reached by a battery, as on account of the increased activity of the chemical action at temperatures above this point, it is considered detrimental to the battery to exceed this limit; particularly is this true in respect to the wood separators, as the acid at high temperatures has a very bad effect upon them. For occasional dis- charges, however, this limit may be safely raised to 135 degrees Fahrenheit. At low temperatures the capacity of the battery falls off rapidly, and for temperatures of 50 degrees Fahrenheit and below the capacity approaches 50 per cent of normal, and the efficiency at low temperatures is correspond- ingly reduced. It is customary to require the battery manufacturers to supply tempera- ture coefficient curves for variation in capacity on all types of batteries supplied to the naval service for the guidance of the operating personnel. The 100 per cent capacity point on this curve is the normal capacity obtain- able at 80 degrees Fahrenheit. The effect of temperature upon capacity may be said to vary with the rate of discharge, it being greatest at the lower rates of discharge. Age of the Cell. — The age of the cell is another factor which should be considered in the general discussion of the subject of capacity of storage batteries. When operated under normal conditions it is an inherent char- acteristic of the storage battery to increase in capacity over a certain period of its early life until a maximum has been attained ; from this point there is a gradual decline in the capacity until it is so low as to not justify further operation. 86 Storage Batteey Manual Owing to the fact that in the manufacture of storage batteries all of the active material of the plates is not fully formed during the initial charge and discharge, it therefore requires several cycles of charge and discharge, depending upon the type of battery, to place all of the active material in condition for supporting the discharge; or, in other vpords, the battery has not been developed to the point of producing its maximum capacity. On the other hand, however, after all of the active material in the plates has been developed, such that the cell is capable of producing maximum capacity, it is also an inherent characteristic for the plates, especially the positive ones, to shed a certain amount of their active material with each cycle of charge and discharge, thus accounting for the gradual decline in the capacity of the battery. Generally speaking, a battery may be said to be worn out and unsuitable for further operation when its capacity 'has been reduced to from 60 to 70 per cent of its normal rated capacity. It is usual practice to require the battery manufacturers to guarantee a certain period of operation of the battery (in years) before the capacity is reduced below a certain per cent of its normal rated capacity. For batteries supplied to the naval service the guarantee is drawn up on basis of 80 per cent of the normal rated capacity, the time factor depending upon the type of battery supplied. Efficiency. Efficiency Defined. — The efficiency of a storage battery is the ratio of out- put to input; that is, for a given cycle the ratio of the amount of the dis- charge to that of the preceding charge. Efficiency may be properly divided into two classes, viz. : (1) Quantity efficiency. (3) Energy efficiency. Where : _ ... „~, . Ampere-hours given out on discharge Quantity Efficiency = -r — ^ r ° , . t^ — ^ -. ^ J ■> Ampere-hours put in on preceding charge „„ . _ Watt-hours given out on discharge °^ •' '~ Watt-hours put in on preceding charge ' The quantity efficiency runs very high, which for batteries of good design may be as high as 95 per cent, though the average value is around. 9_0 per cent. The energy efficiency, which is the true measure of a battery's efficiency from a storage battery engineering point of view, does not run as. high as the quantity efficiency, in that the average charging voltage is higher than the average voltage produced by the battery on discharge, due primarily to the resistance offered by the battery to the flow of charging current, as a result Capacity and Efficiency 87 of polarization. An 80 per cent watt-hour efficiency is considered very good, the average running around 70 per cent. Owing to the loss of charge as a result of local action or self discharge taking place in the cell, and which is characteristic of all storage batteries, it may be said that the elapsed interval of time between the discharge and the preceding charge is necessarily a function of the efficiency of the cell, the longer this interval the lower the efficiency. Moreover, inasmuch as the capacity of a battery is also a function of its efficiency, the remarks con- tained in the preceding text in respect to capacity bear an important rela- tion to efficiency. The actual operation of determining the efficiency of a 'battery requires a very accurately calibrated set of instruments as well as uniform condi- tions, in respect to temperature, rates of charge and discharge, etc., and in order to determine an average value for efficiency at a given rate of dis- charge, the data taken on several cycles conducted under uniform conditions should be used. CHAPTEE IX, ELECTROLYTE. Electrolyte Defined. Any non-metallic liquid possessed of electrical conductivity and which is chemically decomposed, or whose component elements are disassociated when an electrical current is passed through it is called an electrolyte. Composition. Electrolytes are composed of metallic salts, acids and bases when in solu- tion with water; such aqueous solutions of salt, sulphuric acid, potassium hydrate, sodium hydrate, etc., are familiar examples of this class of electro- lytes. Also, many metallic salts, acids and bases when maintained in a molten state perform equally well the functions of an electrolyte. Ionic Theory as Applied to Electrolytes. As has been stated, an electrolyte must be possessed of relatively good electrical conductivity and its component parts must also be in a stable equilibrium. Moreover, in order that such a substance may be possessed of good electrical conductivity, it must be very susceptible to ionization, since a current can only pass through a solution when two ions are available to convey it. Eelative to this feature, of ionization, although water in itself is not a conductor, or if it be one, due to its high resistance it is an exceedingly poor one, it nevertheless possesses a remarkable power for aiding in the ionizing of substances held in solution with it, and for this reason it therefore meets with extensive application for forming numerous solutions of high conductivity and may be said to constitute the basis of all electrolytes used in the storage battery cell. The electrolyte which is used to the practical exclusion of all others in the lead-acid storage battery cell consists of a relatively concentrated solution of sulphuric acid in water. It, therefore, contains concentrations of hydrogen ions (cations) and SO^ ions (anions), and these ions in passing back and forth through the solution between the electrodes convey the current to the electrodes and from thence the electricity passes out through the circuit. It should, therefore, be thoroughly understood that the electrolyte plays a relatively important part in the action of the storage battery cell, and in order that its purity and efEectiveness of action may be safeguarded it is deserving of a just amount of attention in the operation of the storage battery cell. Electrolyte 89 Navy Specifications for Electrolyte. In order to insure that a pure grade of sulphuric acid is obtained for the electrolyte of lead-acid storage batteries, the present specifications require that the concentrated acid shall be of the highest grade of commercial sul- phuric acid. It must be water white in color, and of at least 1.835 specific gravity (or 65.7 Baume) at 15.5 degrees Centigrade (or 60 degrees Fahren- heit). It should average at least 76.37 per cent of SO3 (sulphuric anhy- dride), or 93.43 per cent H2SO4 (sulphuric acid). Also, it must not contain the slightest trace of platinum and but the smallest trace of copper, selenium, arsenic, tin, manganese, thallium. Cadmium and magnesium are permissible. It must not show more than one one-hundredth of 1 per cent zinc ; one twenty-fifth of 1 per cent antimony ; one one-hundredth of 1 per cent iron ; one one-thousandth of 1 per cent chlorine ; one one-thousandth of 1 per cent nitrogen in any form, as ammonia, nitrate, etc.; one six-hundredths of 1 per cent copper. The acid must not contain appreciable quantities of the sulphates of calcium, sodium, potassium, or aluminum, nor of sulphur, sulphur dioxide, or pyrosulphuric acid. It should further be free from organic matter, acetates, chlorates, citrates, and from silicates or sediment in any sensible quantity. Composition of Electrolyte Used in the lead-Acid Storage Battery Cell. The electrolyte used in the lead-acid storage battery cell is composed of dilute sulphuric acid, H,SOi, and pure water, preferably distilled. This electrolyte should be prepared from concentrated acid (oil of vitriol) of 1.835 specific gravity and having a purity which conforms with the specifi- cations as outlined in the preceding- paragraph. The so-called " commercial acid," which is ordinarily obtainable at drug stores, etc., is not satisfactory for use in storage batteries, and it is essential that " chemically pure " (C. P.) acid only be used for this purpose. It is also essential that the special precautions for handling and mixing the acid for the electrolyte, and as outlined elsewhere in this chapter, be rigidly adhered to in order that satisfactory results in operation of the battery may be obtained. Too much emphasis cannot be put upon the subject of purity of the acid and water used in making up the electrolyte for the storage battery, as it is especially true in this case that " an ounce of prevention is worth a pound of cure." Effects of Impurities in Electrolyte. In order that the importance of safeguarding the purity of the electrolyte may be realized, a brief outline of the effects that certain impurities have 90 Storage Battery Manual upon the operation of the storage battery cell will be given. These impu- rities may in general terms be stated under three headings, as follows : I. Foreign metals, or salts of such metals, especially those which appear after lead in the electrochemical series; or, in other words, those which are less electronegative than lead; for example, copper, silver and platinum. Due to the electrochemical action which takes place in the cell, these metals are immediately transferred to the active material of the negative plate where innumerable electrical couples are formed, and at which points local action is produced, with the result that the spongy lead of the negative plate is converted by this action into lead-sulphate (PbSO^j), and free hydrogen is evolved at the foreign metal. This action is more pronounced in proportion to the increase in the quantity of the metallic impurity contained in the electrolyte, and consequently the more readily is hydrogen gas evolved from the surface of the foreign metal. The result of this local action, as described above and caused by such impurities in the electrolyte, is manifested by a gradual decrease in the capacity of the negative plate. Generally speaking, it may be said that platinum, as a rule, is the worst of the metals in this respect. Another instance of the decrease in capacity of the negative plate as a result of the local action which takes place in a cell due to impurities is in the case of antimony. Antimony is soluble in sulphuric acid; hence, is carried over and deposited on the sponge lead of the negative plate with the consequent local action and loss of capacity of the negative plate caused by the sponge lead-antimony couple thus formed. This antimony is deposited or plated on the negative plate by the electrolytic action, and not only causes a reduction in capacity of the negative plate by local action, as described above, but the pores of the sponge lead active material become filled up and congested with the antimony, thus causing a further loss in capacity through restricted and decreased diffusion of the acid of the electro- lyte. In this regard, although the grids of pasted plates contain a certain proportion of antimony, which probably is responsible for some local action taking place in the cell, yet it is practically negligible, inasmuch as it is alloyed with the lead. Furthermore, the surfaces of the grids, especially the positive ones, become corroded by the action of the acid of the electrolyte, and this coating acts as a protection to a certain extent against the antimony content going into solution. II. Metals, such as iron or manganese, whose salts are readily oxidized or reduced; for example, iron or ferrous sulphate when in contact with lead- peroxide (PbOj) of the positive plate is readily oxidized to ferric sulphate, while this ferric sulphate, when it comes in contact with the sponge lead (Pb) of the negative plate is again reduced to ferrous sulphate. Each of Electrolyte 91 these reactions is accompanied with loss of charge of the corresponding plate, with the consequent formation of lead-sulphate (PbSOi) on each plate. It will, therefore, be understood that the presence of a considerable quantity of iron or manganese in the electrolyte will rapidly discharge a battery in accordance with the reactions outlined above. The presence of iron in the electrolyte of a storage battery cell when placed on charge is indicated by heating of the cell, as well as by the fact that the specific gravity and voltage will not attain their normal maximum. III. Foreign acids or salts of these acids or acid forming substances. The presence of these substances in the electrolyte is manifested by a rapid corrosion of the grids. The presence of even the minutest quantity of such acids or substances should, therefore, be avoided. Eelation Between Density and Conductivity of Electrolyte. The density of the electrolyte is an important factor in the operation of the storage battery cell. Owing to its high resistance, concentrated sulphuric acid, which is a heavy, oily liquid, does not form a satisfactory electrolyte, and this constitutes one of the chief reasons why the electrolyte used in the lead-acid storage battery cell consists of dilute sulphuric acid and pure water. The conductivity of dilute sulphuric acid (H2SO4) is greatest at a density of about 1.330. In Fig. 30 is shown a graphical representation of the relative conductivity of electrolyte of various densities ranging from that having a specific gravity of 1.030 to that of concentrated sulphuric acid of 1.835 specific gravity. It will be noted that the curve is parabolic in shape, the relative conductivity decreasing as the density is increased or decreased from 1.230. Specific Gravity Defined. The specific gravity of a liquid or any substance is its relative density or weight as compared with water as a standard. It expresses numerically how much heavier or how much lighter any volume of liquid or substance is than an equal volume of pure water. The specific gravity of pure water is therefore considered as unity, usually written 1.000 and spoken of as " ten hundred." Therefore, concentrated sulphuric acid, which is a solution with a specific gravity of 1.835, is one and eight-hundred and thirty-five thousandths times as heavy as an equal volume of pure water, and in terms of specific gravity is spoken of as " eighteen thirty-five." In other words, sulphuric acid being heavier than water, its presence in electrolyte accounts for the fact that the specific gravity of the electrolyte used in the lead-acid 93 Storage Battery Manual storage battery cell is greater than 1.000. The specific gravity of the electro- lyte is obtained by the use of a special instrument called an hydrometer, the description of which and method of using will be taken up later. o 5. ^§5S|§§§§X s 5)5! ? t- 'a, is 5i 5 * ^000 : : : " :::::::::;?!;::::::::::":":"":::::":::;:":;:": A N : :.: : :::S _ ;i I - - _::::!::::::.:: i\ w , — ;":":!:: e ;: : :::::::: — :;::::: """:; \ " ::::: ::::::::;;: : ...J _.::;:::: — ._/ . r / \ j_ — 3 r \ 1::: c : : -i::::::::::::!;:. ::.:;;:::: r \ 1 ^ r..:: : : t:::::;: \" ""::::::: X ::.::::.. \ \ \ \ N ,m> jtfrv/9^ious Of^s/r/ES. Fig. 30. — Resistance ot Sulphuric Acid at Various Densities. Specific Gravity of Electrolyte Used in Lead-Acid Storage Batteries — Navy Type. The specifications for the " Navy Type " lead-acid storage batteries require that the specific gravity of the electrolyte used in these batteries shall be from Electrolyte 93 1.210'to 1.220 (average 1.215) when fully charged and at a temperature of 80 degrees Fahrenheit. In view of the fact that the portable storage batteries used in the naval service are, as a general rule, subjected to intermittent periods of duty, they thus remaining idle for protracted periods, the low specific gravity (1.215) of the electrolyte has been adopted, since it affords ample capacity and satis- factory operation of the batteries used on this type of service. By using electrolyte of this low specific gravity, local action, or self-discharge in the cell is reduced, the effect of over-sulphation is minimized, the effects of impurities in the electrolyte are not so pronounced, and the effects of high temperatures attained under regular service conditions of operation are not so injurious as would be the case if electrolyte of greater density were used. In other words, the life of the battery is increased as well as its reliability of operation, by using electrolyte of the low density. High specific gravity electrolyte increases local action within the cell as a result of the increased activity of the chemical action. There is also a progressive increase in the capacity of a storage battery cell through increasing the specific gravity of the electrolyte within given limits. Specific Gravity of Electrolyte — Submarine Cells. Since the main storage batteries of the submarine resolve themselves into the prime movers or source of power when operating submerged, it is thus necessary that the specific gravity of the electrolyte be increased over that used in the portable types of batteries described above. Under ordinary peace time conditions of operation, the electrolyte used in the submarine service is of 1.250 specific gravity at end of full charge and at a temperature of 80 degrees Fahrenheit. However, for boats operating in tropical waters, electrolyte of 1.215 specific gravity at end of full charge and at 80 degrees Fahrenheit is used. For the same reasons as given in the preceding para- graph relative to the portable types of storage batteries, the low specific gravity of electrolyte for tropical service is used in order to counteract the deleterious effects due to high temperature. Also, under conditions of war time operations, since it is necessary that maximum capacity be available in the storage batteries of this service, it is advisable to increase the specific gravity of the electrolyte to 1.280 or 1.300. In regard to increased capacity as a result of increasing the specific gravity of electrolyte, it may be said that this applies more particularly to batteries of the paste-paste type, since this increase in capacity is not so pronounced with the storage batteries having Plante plates. The difference m the character and distribution of the active material in the two types of 94 Stokage Battery Mandal plates, which is also a function of the rate of acid diffusion during discharge, accounts for this difference in capacity through increasing the specific gravity of the electrolyte. Method of Preparing Electrolyte. In order to properly prepare electrolyte from sulphuric acid of 1.835 specific gravity, it is necessary that certain essential precautions be observed, as follows : (a) Use a glass, china, glazed earthenware, lead or rubber vessel for mixing the acid and the water. Never use a metallic vessel other than lead, since practically all other metals readily dissolve in sulphuric acid, and if allowed to enter the cell would ruin the plates. (b) Use only sulphuric acid of known purity and which rigidly conforms with the specifications as previously outlined in this chapter. (c) Use only pure water, preferably distilled water if obtainable. It is especially important that pure water be used, in view of the fact that certain organic acids or chemical compositions frequently found in water of some localities will attack the plates and ruin them in a comparatively short time. (d) Carefully pour the acid into the watej and never the water into the acid, since during this process of dilution a chemical combination is pro- duced and not an ordinary mechanical mixture ; therefore, heat being liber- ated, the solution accordingly becomes hot. Care should be taken to prevent splashing, as strong acid will cause painful burns. Should the water be poured into the acid, the accompanying chemical combination between the larger volume of concentrated acid is much more rapid and pronounced than if the acid be poured into the water. Fig. 31 contains a photographic illus- tration of the operation of mixing sulphuric acid with water to form electro- lyte. Note that the workman is pouring the acid into the water. (e) Stir thoroughly with a wooden paddle and allow the solution to cool before taking the specific gravity with the hydrometer. Sulphuric acid and water do not mix readily ; the water, being lighter than the acid, tends to remain on top. When mixing, the density of the solution cannot be accurately measured until both the acid and the water are thoroughly mixed. However, having once been thoroughly mixed they remain so. (f) Since all storage battery, data for the naval service are based on an electrolyte temperature of 80 degrees Fahrenheit, the specific gravity of the solution after mixing should be taken at this temperature, or corrected to this temperature, in order to obtain the required density of the mixture. (g) Provide the personnel mixing the electrolyte with rubber boots, rubber aprons, rubber gloves and goggles. Electrolyte 95 Mixing Large Quantities of Electrolyte. In mixing large quantities of electrolyte, such as for a renewal of electro- lyte in a submarine battery, putting a new submarine battery in commission Fig. 31. — Mixing Sulphuric Acid with Water to Form Storage Battery Electrolyte. Acid Poured from Pitcher into the Crock Containing the Water, and Stirred with Wooden Paddle During Process of Mixing. "or preparing electrolyte for a large number of small batteries, a large lead- ''lined tank is preferred, but should such a tank not be available, a tank of sufficient size to accommodate the required quantity of electrolyte to be 96 Storage Battery Manual prepared should be constructed of well-seasoned lumber and, after com- pletion, given a couple of coats of asphaltum or other acid-proof paint on the inside in order to protect the electrolyte from the contaminating effects of the injurious acids contained in the wood of the tank. This coating of the interior of the tank with acid-proof paint is especially important should the water be placed in the tank while hot, as in the case of water made on board ship, submarine tenders, etc., where it is customary to pump the water direct from the distillers to the mixing tank, since on account of the increased activity of the chemical action at high temperatures, the water is thus more susceptible to contamination by the injurious wood acids. The effect when using cold water is, therefore, not so marked. Should neither a lead-lined tank nor acid-proof paint be available, the wood tank should be constructed as described above and filled with water containing caustic soda or other alkali and the solution brought te a boiling point by means of a steam coil or other method, and thus allowed to boil for five or six hours in order to neutralize the injurious wood acids on the inside lining of the tank. This having been done, rinse out the tank thor- oughly with pure water and again fill with the necessary amount of cold water and proceed with mixing the electrolyte as outlined in the preceding paragraphs. Table for Preparation of Electrolyte of Various Densities. The following table may be conveniently used in the preparation of electrolyte of various densities when using acid of 1.835 specific gravity, as well as that of 1.400 specific gravity. This table gives the parts of pure water to be added to one part of acid of each of the above-mentioned specific gravities, at 80 degrees Fahrenheit, to form electrolyte of a given density, as shown in the left-hand column of the table ; this table is also made up on a basis of parts of acid by volume as well as by weight. In most cases it will be found that the table of 1.400 specific gravity acid will suffice, as it is now customary for battery manufacturers as well as the various navy yards and shore stations to carry a supply of 1.400 specific gravity acid for use in mixing storage battery electrolyte, and the acid for this density is now commonly known as battery acid. The purity of the 1.400 acid should be equal to that outlined elsewhere in this chapter, and no acid should be used for storage battery electrolyte until it has been tested and found satisfactory. Neither should water be used in mixing the electro- lyte until it has been analyzed and found suitable for the purpose. A rigid adherence to these simple directions will do much towards a satisfactory operation of the battery. Electrolyte 97 TABLE FOR MIXING ELECTROLYTE. (Specific Gravity Ranging from 1.200 to 1.300.) Based on 1 Pakt Sqlphueic Acid (1.835 S. G. ) AND (1.400 S. G. ) AT 80° F. Specific Parts of pure water to one part of acid at 80 " F. gravity of mixture 1.835 acid. 1.400 acid. desirjed at 80' F. Parts by Parts by Parts by Parts by volume. weiglit. volume. weight. 1.200 4.33 2.36 1.14 .83 1.205 4.15 2.. 30 1.09 .79 1.210 4.07 2.22 1.04 .75 1.215 3.00 2.15 .99 .71 1.220 3.84 2.09 .94 .63 1.225 3.70 2.05 .89 .65 1.230 3.60 1.97 .85 .61 1.235 3.48 1.92 .81 .58 1.240 3.40 1.86 .77 .55 1.245 3.30 1.80 .73 .52 1.250 3.22 1.76 .69 .50 1.255 3.10 1.70 .66 .47 1.260 3.05 1.66 .63 .44 1.265 2.95 l.fS .59 .42 1.270 2.90 1.57 .56 .40 1.275 2.80 1.55 .52 .38 1.280 2.75 1.49 .49 .35 1.285 2.68 1.48 .46 .33 1.290 2.60 1.41 .43 .31 1.295 2.55 1.40 .40 .29 1.300 2.47 1.34 .37 .27 The Hydrometer. The specific gravity or density of the electrolyte is measured with an instrument called the hydrometer, which consists of a closed hollow glass tube or bulb float, the top end of which terminates in a long, narrow stem which contains the graduated scale for measuring the specific gravity of the solution. The hydrometer floats upright in the electrolyte and the point on the graduated scale which coincides with the surface of the liquid measures its density or specific gravity, and it is usually spoken of as " gravity." There is shown at (7, Fig. 32, one of these hydrometers as described above. The Hydrometer Syringe. For greater convenience in testing the electrolyte, the hydrometer has been combined with other parts, the complete combination of which is called a hydrometer syringe. In Fig. 32 is shown one of these hydrometer syringes. 98 Storage Battekt Manual which consists of the following parts, as indicated in the figure : A, rubber bulb; B, glass barrel; C, hydrometer; D, rubber suction tube; E, suction tube plug valve ; Fj hydrometer scale. Method of Using the Hydrometer Syringe. When it is desired to test the specific gravity of the electrolyte, take the hjdrometer syringe and squeeze the rubber bulb A, insert the end of the Fig. 32. Hydrometer Syringe. rubber suction tube D in the electrolyte, and well below the surface of the liquid. Then, by slowly releasing the rubber bulb A, the electrolyte is drawn through the plug valve E, and up into the glass barrel B, until the hydrom- eter C floats freely and clear of the plug valve E in the bottom of the glass barrel. The point on the hydrometer scale F at which the stem emerges from the solution is the measure of the specific gravity of the solution. In order to get an accurate reading and to prevent the hydrometer from sticking to the side of the glass barrel, it is necessary that the hydrometer syringe be held in a vertical position. Also, the reading should be taken Electeolytb 99 when there is no compression on the rubber bulb. The accuracy of the calibration of the hydrometer should be ascertained before using by checking against another hydrometer known to have correct graduations. It should also be understood that before taking the hydrometer reading the acid and water of the electrolyte should be thoroughly mixed, since the water being lighter than the acid will tend to remain on top, and if it has not been thoroughly mixed with the acid, a reading taken under these con- ditions will be misleading and incorrect. Effect of Temperature on Specific Gravity Readings. Since electrolyte, like most other substances, expands when heated, and contracts when cooled, its specific gravity is accordingly affected by a change in temperature. This variation in specific gravity as a result of temperature change amounts to approximately .001 points of gravity for every 3 degrees (Fahrenheit) change in temperature. Thus, if electrolyte has a given specific gravity at a temperature of 80 degrees Fahrenheit and then be heated, the heat will cause the electrolyte to expand, and, although the actual strength of the solution will remain unchanged, yet the expansion will cause it to register a lower specific gravity of approximately one point (.001) for each 3 degrees rise in temperature. For example, if electrolyte has a specific gravity of 1.215 at 80 degrees Fahrenheit and the temperature be raised to 89 degrees Fahrenheit, this increase in temperature will cause the electrolyte to expand and the specific gravity to drop three points (3x .001 = . 003) ; hence, the specific gravity of the electrolyte would then be 1.218 instead of 1.215. Similarly, if the tem- perature of the electrolyte be lowered from 80 degrees Fahrenheit to 71 degrees Fahrenheit, this would cause the electrolyte to contract and the specific gravity would then rise from 1.215 to 1.218. Therefore, since the change of temperature does not afliect the actual strength of the electrolyte, the specific gravity only being changed, in order to refer all specific gravity readings to an adopted standard, these readings should be corrected one point for each 3 degrees change in temperature. Eighty degrees Fahrenheit is the adopted standard for all battery data of the naval service; therefore, all specific gravity readings should be cor- rected to this point as a standard. Sea-Going or Practical Tests for Storage Battery Electrolyte Although it is realized that under operating conditions and those which obtain in general on board ship, the testing of storage battery electrolyte cannot be obtained with the same degree of accuracy as is possible in a well- 100 Storage Battery Manual equipped chemical laboratory, yet it is considered that with a little detailed care and attention to this subject a practical working test may be obtained with a fair degree of accuracy by establishing a " sea-going laboratory " in the battery service stations on board ship and on submarine tenders. Laboratory Equipment Required. — The equipment for this " sea-going laboratory " should consist essentially of the following : 1 Test tube rack. 12 Test tubes, size 6 inches by f inch (approximately). 2 Test tube cleaners. 2 60-c. c. glass flasks. 2 250-c. c. glass flasks. 2 10-c. e. glass graduates. 2 100-c. c. glass graduates. 12 Glass stirring rods, 6 to 7 inches long. 1 Dropping bottle for potassium permanganate. 1 Chemical balance. 1 Bunsen burner. 1 Iron tripod. 1 Wire gauze for tripod. 1 350-c. c. beaker. 1 4-inch watch glass (for covering beaker). 1 1-liter flask with glass stopper. 1 Eeagent bottle with glass stopper and ground glass label for each of the following reagents : Silver nitrate. Potassium ferrocyanide. Lead acetate. Nitrate acid (C. P.). Sulphuric acid (C. P.). Starch solution. Standard iron solution. Standard iodine solution. Reagents Required. — The following reagents for making practical tests of the electrolyte should be included in this laboratory equipment: Silver nitrate (AgNOj), 5 per cent solution. Sulphuric acid (HjSO^), 1.835 specific gravity, chemically pure. Nitric acid (HNO3), 1.400 specific gravity, chemically pure. Granulated zinc (Zn), 20 rnesh, chemically pure. Lead acetate, 10 per cent solution. Potassium permanganate, 0.3 per cent solution. Potassium ferrocyanide (K^FejCye), 4.0 per cent solution. Electrolyte 101 Ferrous Sulphate (Saturated Solution). — This reagent is made up by dis- solving the chemically pure crystals of ferrous sulphate in a small quantity of distilled water in a test tube, care being taken to use an excess of crystals in order to insure that the solution is saturated. A fresh supply of the reagent as outlined above must be made up each day as used, hence a supply of chemically pure ferrous sulphate crystals should be kept on hand. Starch Solution. — To prepare this reagent, place 300 c. c. of distilled water in a 850-c. c. beaker and bring to the boiling point over a Bunsen burner, the beaker being supported by iron wire gauze resting on an iron tripod. Next, 1 gram of ordinary starch mixed to a thin paste with cold distilled water is slowly poured into the boiling distilled water. Continue boiling this mixture for two minutes after the starch is added, then cover the beaker and allow to stand over night. Then pour into the starch reagent bottle the clearer portion of the solution, discarding the thick portion found collected in the bottom of the beaker. Standard Iodine Solution. — In preparing this reagent mix 2.4 grams of chemically pure iodine and 15 grams of potassium iodide in 1 liter of distilled water. Standard Iron Solution. — This reagent should be made up to contain the maximum allowable amount of iron for comparative tests. Therefore, a sufficient amount of pure iron wire to give the allowable limit of iron in 1 liter of solution is carefully weighed and dissolved in chemically pure sulphuric acid of 1.250 specific gravity (or any other gravity of acid as required for the test). Next, an excess of hydrogen peroxide (5 c. c. 3 per cent) solution is added and then the entire solution boiled until gas ceases to be evolved, the beaker being covered with a watch glass to prevent loss. When cold, transfer the solution to a 1-liter measuring flask, care being taken to wash all of the solution out of the beaker in which it was boiled, and the flask then filled up to the mark with chemically pure sulphuric acid of 1.250 specific gravity (or any other specific gravity, depending upon the specific gravity of the electrolyte to be tested). Electrolyte Tests. The tests outlined below apply primarily to the testing of new electrolyte of 1.250 specific gravity. If it is desired to test electrolyte of higher specific gravity, it should first be diluted or cut back to 1.250 by the addition of dis- tilled water. In diluting acid of any strength higher than 1.400 specific gravity, care should be taken that the acid is poured into the water and not the water into the acid; this to avoid excessive heating and possible injury to personnel resulting therefrom. If electrolyte of lower specific gravity 103 Storage Battery Manual than 1.250 is to be tested, the proper allowance for the maximum allowable impurities should be made. When electrolyte from a cell which has been in use is to be tested, the standard iron solution should be made up to correspond to the increased amount of iron allowable in old electrolyte. Color. — The sample should be clear and practically colorless. A small amount of lead-sulphate, which shows as a white sediment, will do no harm. Oil of vitriol (1.835 specific gravity) is sometimes dark in color as a result of the presence of traces of organic matter, and this is not cause for rejection unless the color is very dark. Odor. — Electrolyte which is suitable for storage batteries should be odor- less. To test the odor, shake up a closed flask or bottle partially filled with electrolyte and then uncork and note whether or not there is any odor. Sometimes sulphurous or nitric acid can be detected in this manner and further testing eliminated. Iron. — To 100 c. c. of the electrolyte in a test tube add the potassium permanganate solution, drop by drop, stirring each time. As each drop enters the test sample a pink color will be observed, which may disappear as the permanganate solution becomes mixed with the sample. Continue adding the permanganate solution until a slight pink color becomes perma- nent; then add 2 c. c. of potassium ferrocyanide solution, when the presence of iron will be indicated by a blue color. Next, make a comparative test by using 10 c. c. of the standard iron solution instead of the electrolyte being- tested. If the sample being tested shows a deeper blue color than the standard iron solution, the sample should be rejected. Owing to the disastrous effect of iron upon a cell, the test for iron is a very important one, and furthermore, on account of the ever-present likeli- hood of iron entering the cell through the use of contaminated water, or other cause, a periodic test for iron should be made on the electrolyte from time to time. EflFects of Iron in a Cell. — Iron being one of the injurious metallic impu- ritites generally found in various quantities in electrolyte, not more than .01 per cent should be allowed in new filling acid, relative to the amount of concentrated HjSO^ constituting the solution. All iron contained in the lead parts and active materials of the cell only gradually dissolve out into the electrolyte, and therefore in old cells the amount may reach the per- missible maximum of .01 per cent. Iron is contained in the cells as oxides and as sulphate, the latter condition, however, owing to the electrolytic action in the cells, is not maintained. In sulphuric acid iron cannot exist as metal, although during charge the existing tendency is for it to deposit Elbcteolytb 103 as such on the negatives, but owing to its high solubility as metal in dilute HjSO^ this is prevented, and the efBciency during the charge is thereby pri- marily reduced. Moreover, the presence of iron in the electrolyte produces a local action very similar to most of the other metallic impurities, in that it affects both electrodes ; that is, the positive and negative plates. For the reason that the higher oxidized ions on reaching the negative plates give off part of their oxygen, while the lesser oxidized ions, which are in contact with the positive plates, absorb oxygen, it is thus seen that we have to deal with a continuously reversible reaction when iron is present in the storage battery cell. Also, unlike some other cases of impurities in the electrolyte, it appears that the total amount of iron contained in all parts of the cell, after once going into solution, remains permanent for the life of the cells, and all iron which from time to time enters the cell is cumulative in effect, as nothing is lost by .decomposition or liberated in a gaseous state. The normal amount of charge for cells containing no appreciable quan- tities of metallic impurities is approximately 105 per cent; that is, the ampere-hour efficiency is approximately 95 per cent. On the other hand, the amount of charge required for cells containing large quantities of iron may reach as high as 135 to 150 per cent, depending upon the amount of iron they contain, and furthermore, such cells may, on open circuit, lose their charge entirely, due to the very active reversible reaction, in from 3 to 6 weeks. Therefore, the reasons for at all times taking special precautions against iron entering a storage battery cell are readily apparent. Chlorine. — To test for chlorine in new electrolyte, add a few drops of nitric acid, then a little silver nitrate solution to a sample of the electrolyte in a test tube. If pure, the addition of the silver nitrate will have no effect. If slightly impure, the addition of the silver nitrate turns the sample slightly cloudy, and the sample can be passed as 0. K. If totally impure, the addition of the silver nitrate turns the sample a very milky color, which is accompanied by a heavy precipitate of silver chloride, and such a sample is unsuitable for storage batteries. If the electrolyte has been in a cell, the above test will not show chlorine unless recently introduced. Chlorine in a worked cell is changed to per- chloric acid, and requires a special method for its detection. A never failing test for chlorine is by smell. Nitric Acid (Oxides of Nitrogen). — Nitric acid and other oxides of nitrogen are very harmful to the plates of storage battery cells. To make a test for these impurities, to 5 c. c. of the electrolyte to be tested add 15 c. c. of chemically pure sulphuric acid (1.835 specific gravity) and allow to cool. 104 Storage Battery Manual Then add 2 drops of a saturated solution of ferrous sulphate, and stir with a glass rod until thoroughly mixed. The presence of oxides of nitrogen will be indicated by a pink color. If this color is very pale or slight after stand- ing for 10 minutes, the sample of electrolyte can be passed as suitable for storage batteries. In order to offer contrast- in determining the color, the sample should be judged against a piece of white paper in a good light. Sulphurous Acid. — In order to detect the presence of sulphurous acid in electrolyte, first place 15 c. c. of the sample in a small, narrow-necked flask of 60 c. c. capacity, and add a sufficient amount of chemically pure granu- lated zinc to cover the bottom of the flask. Then moisten a piece of filter paper or other absorbent paper (white blotting paper will answer the pur- pose) with lead acetate solution, and lay this absorbent paper over the mouth of the flask. The gas evolved by the zinc will strike the paper and turn it brown if sulphurous acid is present. If the paper remains white, sulphurous acid is not present, and the sample can be passed in so far as this impurity is concerned. If the above zinc-lead acetate test shows a discoloration of the paper, the following test should be made to determine whether or not the electrolyte should be accepted or rejected : Measure exactly 5 c. c. of standard iodine solution into a 350-c. c. flask and add 3 or 4 drops j3f the starch solution. This reaction is accompanied by a deep blue color. JNow, add 100 c. c. of the sample of electrolyte to be tested and shake until thoroughly mixed. If the blue color disappears, sul- phurous acid is present in sufficient quantity to reject the electrolyte. If any blue color remains after a thorough shaking, sulphurous acid content is low enough to be passed. The above tests cover the detection of impurities most likely to be found in electrolyte and which are more or less a common source of trouble in the operation of storage batteries, particularly incident to the naval service. It has been found very convenient to place all of the reagents and labora- tory equipment as outlined in the preceding text in a cabinet constructed very much on the order of the boiler testing cabinets now supplied to vessels. In time it is hoped that a regular standard equipment for such a laboratory will be supplied to all submarine tenders and other ships. CHAPTER X. PLATE INSULATION AND SEPARATORS. Function of Separators. In developing the storage battery to meet the requirements of its various modern applications, it has been necessary to install in the cells a maximum number of plates, consistent with proper mechanical strength, life and dura- bility, in order to obtain maximum capacity in current per unit of space. Therefore, in so doing, the thickness of the plates has been necessarily reduced and the plates have been placed closer together, much more so, in POS IT I Vet PLRTET- 1^1/pftgR i<"EPKR TrrOK^ -ifeQ KTlVC Jt^: Fig. 33. — Showing Plate Centers and Arrangement of Plates and Separators. fact, than in the early days of storage battery construction and design; or, in the words of the battery engineer, when speaking of placing the plates closer together, " the plate centers liave been decreased," which means in effect that the distance between the vertical axes of two adjacent positive or negative plates has been decreased. This point is illustrated in Fig. 33, which shows a portion of the plan view of a cell with positive plates, negative plates and the corresponding separators. In this figure the positive plate centers are indicated at A and the negative plate centers at B. Obviously, if both positive and negative plates are of the same thickness, then their plate centers are the same, or A would then equal B. 106 Storage Batteey Manual By thus placing the plates closer together it will therefore be appreciated that for a proper functioning of the cell and in order to safeguard it against damage as a result of internal short circuits, it is necessary that the insu- lating medium or separators placed between the plates of the cell be of a high order of perfection. In addition to serving as an insulating medium, these separators must fulfill the following requirements : (a) They must be impervious to the action of the acid of the electrolyte. (b) They must he strong enough to withstand the mechanical chafing and compression incident to the normal expansion and contraction of the plates while working. (c) They must be unaffected by the temperatures attained by the cell during ordinary conditions of operation. (d) They must also contain no substances which have a deleterious eSect upon any portion of the cell. (e) They must possess a fairly high degree of porosity in order to facili- tate proper circulation and diffusion of the acid of the electrolyte into the plates during a discharge and, conversely, form paths for the return of the acid to the electrolyte on charge. (f ) Although requiring a high degree of porosity, the individual pores of these separators should be so minute as to prevent as much as possible the entraining of gas bubbles therein, thus reducing the effects of polarization to a minimum. Modem Types of Separators. It is therefore apparent that many problems present themselves in obtain- ing an insulator which fulfills all of the foregoing requirements, and much time, thought and ingenuity have been devoted to this subject by battery engineers. -Many different combinations of as many different kinds of materials have been tried and used for these insulators or separators, but with the present stage of the art it may be said that in so far as the naval service is concerned nothing has been found quite so good for the purpose as the combination consisting of a sheet of specially treated wood when used in conjunction with a thin, finely perforated sheet of hard rubber, which type is known as the " wood and rubber combination " separator. However, at the present writing another type of separator, known as the " Threaded Eubber Separator," has been placed on the market by the Willard Storage Battery Company, and this new type is said to be producing good results for certain classes of service; this type will be described elsewhere in this chapter. Also, the " Ironclad " type assembly uses a thin wood veneer sepa- rator in conjunction with the slotted rubber tubes of the positive plates; this type will also be described. .KuBBEn Plate Insulation and Separators 107 The following topical outline represents in a general way the various types of separators used in modern storage battery installations : {Plain Sawed and Ribbed. Unribbed Veneer. Quarter-Sawed and Ribbed. Modern Types of Separatois ] fPerforated Rubber Sheet, (ribbed or unribbed) . Slotted Rubber Sheet, (ribbed or unribbedj . "Ironclad" Slotted Rubber Tube. Threaded Rubber. It will be noted in the above outline that these separators consist of either wood or rubber, or both, and that each of these two types is further sub- divided into other types, differing mainly in the methods of manufacture as well as the particular type of battery in which they are installed. The methods of manufacture and special characteristics of each of these types will be described in detail. WOOD SEFAKATORS. Historical. — In the comparatively early days of the commercial applica- tion of storage batteries, as for instance in the large central power station .installations, untreated cherry wood separators placed between two thin sheets of asbestos were used for the plate insulating or separating medium; these cherry wood separators as used in such installations also contained a series of large auger holes drilled through them in order to reduce the internal resistance of the cell and to facilitate proper circulation and diffusion of the acid of the electrolyte into the plates. For many years this combination of separators was used for this service and until they were superseded by other wood separators which incorporated improved methods of treating the woods and which methods with the present stage of the art have reached a high degree of perfection. The circumstances leading up to the development of the wood treating process, which now forms the basis of all treatment of separators by this method, is of interest in the study of the general subject of wood separators. It appears that one day while working in the laboratory, one of the research engineers of one of the large storage battery manufacturing companies had on hand some old storage battery cells, the plates of which were supposed to have lost their capacity, and as judged from the standards at that time. S 108 Storage Battery Manual were due for the scrap-heap; however, while he was examining these old cells the idea occurred to him to place some thin sheets of cherry wood, containing no auger holes, between the plates of these cells and to charge them up and conduct a series of tests upon them. This he did, and as a result he was very much surprised to find that these old, apparently worn out cells gave a considerable amount of their original rated capacity and, in fact, much more than they had given when they were turned in to him as being worn out. This result was responsible for his continuation of research along this line and with the view of ascertaining, if possible, just what caused this rejuvenation of the old, apparently worn out plsites. After an extensive series of experiments along this line it was finally concluded that the wood acids (acetic) contained in these cherry wood separators were helpful to the active material of the negative plates and tended to accelerate the sulphating action upon the negative active material during a discharge, which satisfactorily accounted for the noted increase in capacity of these old cells. The next stage in the development of this subject came when it was attempted to use woods other than cherry for these separators, as on account of the scarcity of cherry wood and the expense attached to its use for this purpose, other more abundant and less expensive woods were to be preferred if they could be satisfactorily used. The next wood which suggested itself was poplar, as this wood was plenti- ful, less expensive than cherry, belonged to the soft-wood family, and, con- taining a comparatively small amount of resinous matter, its use for separa- tors eflfected a reduction in the internal resistance of the cell as compared to that of other available woods. Accordingly, many batteries were manufactured and equipped with poplar wood separators, but after these batteries had been in service for a short while it became readily apparent that something was radically wrong with the cells. Upon opening these cells and removing the elements it was found that the grids, lugs, and other lead parts had been seriously attacked, and in some instances the grids fell apart and the lugs were so badly attacked that they disintegrated, thus allowing the plates to fall away from the cross-bars and straps. After much research it was finally established that the acetic acid contained in these poplar wood separators was responsible for the destructive attack as noted upon the lead parts of these cells. Therefore, the next important problem which presented itself in the devel- opment of this subject was that of devising some method of treating these wood separators such that portions of the injurious wood acids should be removed, but allowing to remain such of them as proved beneficial to the negative active material. The first logical step in the solution of this Plate Insulation and Sbpakatoes 109 problem was that of neutralizing the undesirable amount of wood acids con- tained in the wood; another series of tests on these separators was accord- ingly arranged with this end in view, until finally a method of treating the wood was evolved which, as has been stated, now forms the basis of the general scheme of treating practically all wood separators by this method. This method was known as the alkali treatment. The details of this treat- ment will be described later. Woods Used; Eelative Life, Conductivity, Etc. — Of the various woods which, after receiving the proper treatment, have been found suitable for storage battery separators and which are now more or less generally used, the following may be included : (a) Basswood. (b) Poplar. (d) Douglas fir. (d) California redwood. (e) White cedar. (f) Cypress. The above list is given in the approximate relative order of life of each of the woods when operated under uniform conditions in the storage battery cell; considering the life of basswood as 100 per cent, the following table represents approximately the relative lives of the other woods when used as separators : Wood. Lite. Basswood 100 per cent. Poplar 100 " " Douglass flr 175 " " California redwood 180 " " White cedar 190 " Cypress 200 " " It will be noted in the table that cypress is possessed of about double the life of either basswood or poplar; however, it may be said that cypress, on account of its dense, close grain, has a higher factor of internal resistance, hence less conductivity, than basswood or poplar, and for a given battery installation the voltage characteristic is not as good when using cypress as when basswood or poplar is used. Other things being equal, it may be said that the conductivity factor in woods used for separators varies inversely as the life ; that is, the longer the life the less the conductivity, and vice versa. The subject of selection of woods for separators therefore resolves itself into choosing between life and conductivity, and in making such selection the particular type and design of the battery as well as the special services for which it is intended must necessarily be taken into consideration. In other 110 Storage Battery Manual words, if a battery is designed for very high discharge rates and the require- ments of the service demand a high voltage characteristic even at the expense of life of the separator, then one of the soft woods, such as basswood or poplar, should be used. On the other hand, if long life and reliability against deterioration of separators, with the consequent sacrifice of a certain amount of voltage characteristic, is desired, then one of the coniferous woods should be used. Furthermore, it may be said that, as a general policy, the coniferous woods as outlined in the above table are considered better suited to the requirements of the naval service than the softer woods; it is also believed that, with present stage of the art, the trend in commercial applica- tions of storage batteries is in favor of the coniferous woods. With further reference to the general subject of selection of woods for separators, it should be stated that air-dried lumber produces better separa- tors than kiln-dried stock, for the reason that the process of kiln-drying destroys a certain amount of the strength and endurance qualities of the wood, thus shortening its life, and air-dried lumber should therefore be used for this purpose whei^ obtainable. Hence, it follows that timber to be used for separator stock should be cut in the autumn or winter seasons, as at such time the sap is " down," and the lumber obtained from such stock is capable of air-drying more quickly, and can be fabricated into separators at an earlier date after cutting. By air- drying is meant the reduction, without the use of heat, of the percentage of moisture contained in the stock to that of the normal humidity of the sur- rounding air. By kiln-drying is meant the reduction of the moisture through the application of heat to the stock, as from a kiln, etc. Moreover, by cutting the separator stock during the seasons when the sap is " down," many of the so-called impurities, gums, resins, and other con- stituents which increase the resistance of the separator and have a deleterious effect upon the cell are eliminated. This feature of the subject will be later considered in more detail in connection with the treating processes used in the manufacture of separators. Method of Sawing Wood for Separators. — The manner of sawmg the wood used for separator stock constitutes an important factor in the efficiency of the separator produced. Generally speaking, there are two approved methods of cutting this stock for use in the manufacture of wood separators, these methods referring to the manner of sawing the stock out of the logs at the saw mill rather than the subsequent sawing, grooving or other machining done in the fabrication of the finished separator. For convenience these methods may be classified as follows : (a) Quarter-sawed. (b) Plain sawed. Plate Insolation^ and Separators 111 In describing these methods and the relative eflficiencies of the separators produced, it is necessary to consider certain fundamentals which are char- acteristic of tree growth^ inasmuch as the principles upon which these methods are based depend upon these fundamentals. In this regard, the prime feature to be considered is that of the annual growth ring, or annual ring, as commonly referred to in plant anatomy ; each year of a tree's growth is marked by a cellular formation which con- stitutes an integral part of the main trunk structure and by which the diameter of the trunk is increased from year to year. This ring is con- centric with the main axis of the trunk and is circumferentially divided into two sections, one of which is highly porous and of light fibrous structure, while the other is of a dense resinous consistency ; these ring-like sections of the annual ring are often referred, to as winter and summer growth rings. It is with reference to these rings and their relative positions in respect to the plane of sawing the separator stock that the above-mentioned methods of sawing are classified. Quarter-Sawed Method. — Fig. 34 contains a set of drawings which are intended to illustrate the principles embodied in this subject. The circular drawing to the left of this illustration represents a section taken diametri- cally across the trunk of a tree to be cut up for separator stock. Each annual ring is represented by a plain and a shaded circle, the resinous section being shown as shaded, whereas the lighter and more porous section is un.shaded. The cross-section of the trunk is divided into quadrants, each of which is numbered for clearness in illustrating the text. Referring to quadrant 3, the dotted lines on each side of and parallel to the 45-degree radius represent saw cuts taken through the trunk. Now, it will be noted that the annual rings in the block included between these two dotted lines, as indicated at c, make right-angles with these dotted lines or the plane of the saw cuts ; this angle is known as the annual ring angle. Also, this method of cutting the stock out of the trunk is called quarter- sawed method, and all separators produced from the block c are of .the quarter-sawed type. As will be later explained, this method produces the best type of separators. Plain Sawed Method. — It will be further noted, as shown in the parallel lines of quadrant 4, that as the cuts are taken beyond the limits of the dotted lines of block c, the angles made between the annual rings and the plane of sawing decrease. All sawing beyond the limits of block c is called ■plain sawing, and stock produced from this portion of the quadrant is known as plain sawed stock. Quadrant 3 shows a modification of each of these methods in which the plane of sawing is taken parallel to the diaaneters instead of the 45-degree radius ; this method of sawing produces a maximum 118 Storagr Battery ^Manial Jr^ -J^=^^ - errs—-. □3 "^ ^is^^^ ^::^:^- ( << rxr^ £^''^~ ~ :^^^-_r o r:::=^- ^ =r- 5 (3 ■o o to '%■ o ,!3 CQ Plate Insulation and Separators 113 number of large pieces of stock having annual ring angles less than 45 degrees. In the plain sawed method of sawing, no stock having annual ring angles less than 45 degrees should be used in the manufacture of separators. Quadrant 1 represents the poorest method of sawing wood as far as sepa- rator stock is concerned, and wood sawed by this method should not he used for separators. This particular method of sawing is known as the tan- gential method, the plane of the saw cuts being parallel to the dotted line ab, which is perpendicular to the 45-degree radius of this quadrant, hence tangent to the annual ring ; or, in other words, the annual ring angle in this stock is zero. Characteristics of Separators Obtained from Each Class of Stock. The portions of the illustration shown at A, B, and G in Fig. 34 represent enlarged and exaggerated cross-sections in end elevation of wood separators. Owing to the thinness of the separators, the arcs of the annual rings are pro- jected as straight lines. A represents a separator manufactured from stock cut by the tangential method, and as shown in quadrant 1. In this case it will be noted that the annual ring runs practically parallel with the sawing plane or effective face of the separator. Moreover, as shown by the arrow,, in order for the electro- lyte to diffuse' through this separator it is necessary for it to traverse both the resinous and the lighter fibrous sections of the sheet, poor facilities for aiding diffusion of the electrolyte being especially characteristic of the dense resinous section. Therefore, this type of separator offers the greatest resist- ance to the diffusion and circulation of the electrolyte in the cell which accordingly manifests itself in a reduction of the cell voltage with a cor- responding reduction in efficiency. As has been stated, such stock should never be used in the manufacture of separators. B represents a separator produced from stock obtained by the plain sawed method, such as has been described in connection with quadrants 2 and 4. The path of the acid in diffusing through the sheet is also shown by the arrow, and it will be noted that this separator was obtained from a block, the annual ring angle of which is 45 degrees. Although the diffusion and circu- lation of the acid through this sheet is improved to a great extent over that shown in A, owing to the longer path which the acid has to traverse in passing through the sheet, the rate of diffusion is not as rapid as is that for the separator shown in C. As the annual ring angle increases from 45 degrees to 90 degrees (quarter-sawed type), the efficiency of the separator increases in direct proportion. C shows a separator produced from stock obtained by the quarter-sawed method, and such as shown in block c of quadrant 3, the similarity of the 114 Storage Batteet Manual cross-section of this separator and block c being readily apparent. The path of the acid in diffusing through the sheet is also shown by the arrow, and inasmuch as this path is the shortest possible distance across the sheet, it follows that the rate of diffusion through this separator is greatest, and hence its efficiency is likewise greater than that of A or B. This method pro- duces the ideal separator in so far as diffusion and circulation of the electro- lyte are concerned. Fig. 35. — Quarter-Sawed Wood Separator. Fig. 35 contains a photographic illustration of a quarter-sawed separator as manufactured by the Philadelphia Storage Battery Company. The alternate light and dark streaks in this photograph represent the light and the resinous sections of the annual ring, and due to the uniformity of spacing of these sections and the short path of the acid through the sheet, it is evident that this separator is conducive to uniform working of the entire area of the plates for which it forms an insulator. Owing to the toughness of the resinous section of the annual ring it also follows that the strength and durability of the separator are increased through disposing these resinous sections so uniformly across the width of the sheet. Plate Insulation and Sepahatoes 115 Methods and Object of Treating Wood Separators. Having considered the types of wood suitable for use as separators and the methods of sawing the stock from the logs, we will next consider the methods of treating the wood used for this purpose and the object of the treating process. In brief, the object of treating the wood used as separators may be stated as follows : 1. To neutralize a portion of the acetic or other wood acids which have a deleterious effect upon certain parts, especially those of lead, in the cell. 2. To dilate the fiber and thus increase the porosity, which accordingly decreases the resistance and aids in accelerating the circulation and the diffusion of the electrolyte into the pores of the plates. The treating process saponifies the fats, dissolves the resins, gums, etc., thus developing to a considerable extent the porosity of the wood. In producing the effects outlined above, various methods have been used, but with present stage of the art the following methods may be said to constitute the ones now most generally used, and although some of the processes may vary slightly in detail from those stated below, the general principles involved are the same : (a) Acid-alkali bath. (b) Steam bath. Acid-Alkali Bath Process. — ^The process of treating wood separators by this method consists of three stages, viz : 1. Acid bath. 2. Alkali bath. 3. Washing. (1) Acid Bath. — The separators, having been planed, grooved or machined by other approved methods, are placed in a vat containing a sulphuric acid water solution of about 1.200 specific gravity and at a temperature of from 70 to 80 degrees Fahrenheit, and are allowed to thus soak for a period of from 2 to 4 days. However, if higher temperatures of the bath are used, such as from 100 to 110 degrees Fahrenheit, the specific gravity of the solution may be reduced to 1.100, but the duration of the treatment remains practically the same in either case. (2) Alkali Bath. — The separators after receiving the acid bath described above are next placed in a second set of vats containing an alkaline bath consisting of . a 3 per cent solution of caustic potash, or another such alkali in water, and at a temperature ranging from 70 to 80 degrees Fahrenheit ; the separators are allowed to thoroughly soak in this bath for a period of from 34 to 48 hours. 116 Storage Battery Manual (3) Washing. — The last stage of the process is that of washing the separa- tors and thoroughly clearing them of all acid or alkali absorbed in the pre- ceding stages of the treating process. This is usually done by placing them in a third series of vats and allowing them to soak for from 12 to 24 hours in running water; or if this arrangement cannot be had, the separators should be washed in not less than 15 changes of water, the separators being allowed to remain in each change of water for from 3 to 5 hours. Also, the water used for the washing process should be of approved quality suitable for storage batteries, in order that water containing impurities detrimental to the battery will not be introduced in the cells when installing the wood separators. After the separators have been treated as outlined above, they are placed in the trimming machine where they are trimmed to the exact size; this is necessary in view of the fact that the treating process has a tendency to soften and swell the fiber, thus rendering the separator in most cases larger than before beginning the treatment. The separators are now ready for installing in the cells. If they are not required upon completion of the treating process, they are packed up in boxes containing excelsior which has been thoroughly moistened with approved battery water to prevent the separators from drying out. If they are to be stored for a considerable period before using, the excelsior should be again moistened periodically by pouring the water into the packing cases. It is also advisable to store the packing cases in such manner that the separators are horizontal, as this pre- vents to a certain degree the water from draining out of the pores of the wood. If allowed to dry out, the separators become shrunken, buckled, or cracked, and are thus rendered unfit for installation in the cells. Steam Bath Process. — Some authorities maintain that the apaounts of wood acids and other acid-forming materials usually contained in the lignone are not present in sufficient quantities in certain of the coniferous woods, such as white pine, Douglas fir, and the common species of cedar, as to cause any injurious effects upon the positive plates or any other portions of the cell, but, on the other hand, these materials are actually helpful to the negative plates. Therefore, no attempt is made to eliminate or neutralize such materials contained in the wood by the treating process herein described; however, the internal resistance of the above-mentioned woods is relatively high, and this treating process, known as the steam bath process, is designed primarily to lower the resistance of the wood through the elimination of certain of its gums and resinous constituents, thus increas- ing the porosity of the wood as a result of softening and swelling of the fiber. This process consists in subjecting the wood, after it has been sawed, grooved and fabricated into the separator sheet, to a steam bath treatment Plate Insulation and Sepaeatoes 117 under pressure for a period of from 12 to 18 hours. The same results may be obtained, however, by boiling the wood in a bath of pure, fresh water, preferably at atmospheric pressure, for a period of from 24 to 48 hours. In order to reduce the time of the treating process some manufacturers prefer to boil the wood under a pressure of from 80 to 90 pounds per square inch, the time required to complete the process under these conditions ranging from 5 to 10 hours; in general, however, the duration of the process will vary with the type of wood and the pressure employed. In conducting the above described treating process the separators are usually packed vertically in tiers in large vats, the steam being admitted at the bottom of the vat.. The advocates of this method of treating separators maintain that a better quality of separator is produced than in the alkali acid process previously described, in that the removal of the acetic acids and acid-forming materials from the lignone tends to weaken the structure of the wood fiber, thus weakening and impairing the insulating qualities of the separator ; whereas, in the steam bath process they claim that such is not the case since practically none of these materials are removed from the wood. However, in so far as the batteries for the naval service are concerned, the experience has been that each of these methods of treating the woods is equally satisfactory. Notes on Design and Manufacture of Wood Separators. In manufacturing wood separators the stock is usually received at the separator plant in planks, the thickness of which ranges from | inch to 1 inch, while the length and width vary with the type and size of the separator to be produced. After these planks have been inspected for knots, cracks, and other imperfections, they are then passed through the rip-saw machine where they are worked up in sheets of the desired thickness; they are then ready to be passed through the grooving and ribbing machines, which machines resemble in general an ordinary planer and the knives or saws which effect the grooving and ribbing process are mounted on a revolving mandril, the spacing of these cutters depending upon the desired width of grooves and ribs. In order to protect the leading edge of the sheet, which is relatively thin, from splitting as it passes under the cutters, the ends of the sheets or boards are usually dipped in molten paraffin before passing them through the grooving and ribbing machine. Fig. 36 contains an illustration of a type of wood separator commonly used in battery installa- tions, the details of the ribs and grooves being plainly shown. The thin portion of the sheet included between the ribs is known as the web of the 118 Storage Battery Manual separator. In order to give added strength to the separator it is usual practice to design the outboard or marginal ribs slightly wider than the intermediate ribs. When used in conjunction with a ribbed rubber sepa- rator the ribs on the rubber sheet are positioned such that they will rest Single Ribbed. Double Ribbed. Pig. 36. — Treated Wood Separators (Single and Double Ribbed). against that portion of the web of the wood separator lying midway between two wood ribs; also, the wood separator usually contains from two to three times the number of ribs as does the corresponding rubber separator. If an unribbed rubber separator is used the number of ribs on the wood sepa- rator is increased and they are placed closer together to increase the strength of the combination. Plate Insulation and Separators 119 It will also be noted that the lower portion of the drawing in Fig. 36 eon- tains end elevations in section showing a wood separator which is ribbed only on one side {single ribbed), and one which is ribbed on both sides {double ribbed). Both types are commonly used, though it may be said that the single ribbed type is more generally used. The advantage in using the double ribbed type rests in the fact that a great volume of acid and cor- respondingly better circulation of the electrolyte is effected around the negative plates, which is conducive to improved characteristics of the nega- tive plates in point of capacity, especially at high rates of discharge. How- ever, it may be said that special precautions are necessary in mixing the negative paste for plates used in such installations in order to guard against over-expansion of the negative active material in service, as on account of the expanding agent contained in the paste there is a tendency for over- expansion to take place and thus cause this active material to be forced out from the grid and into the grooves of the separators, and which in time results in a gradual decrease in the capacity of the negatives. The chief reason for this loss in capacity of the negative plates is that such active mate- rial which is forced out into the grooves of the separators loses proper contact with the grid and the adjacent active material and with the consequent result that on account of the poor conductivity offered it fails to receive the proper amount of charging current to reduce the sulphate, and thus in time becomes inactive and contributes nothing towards the capacity of the plate on discharge. Such plates may be detected by a cadmium test, as they will be found to have a gradually increasing cadmium reading on succeeding charges. For batteries of the naval service it may be said that the single ribbed type are considered preferable to the double ribbed type, inasmuch as the flat side of the single ribbed type is placed in contact with the negative plates, which tends to maintain the negative active material in position in the grid, thus reducing the likelihood of loss of capacity as outlined above. As to the method of installing separators in storage battery cells it may be said that for batteries containing a single wood separator, the ribs are placed next to the positive plates and the plain or ungrooved side next to the negative plates for the reason that, as has been stated, the wood has a healthful effect upon the capacity of the negative plates ; furthermore, the positive active material oxidizes the wood and accelerates decay, and since the ribs are the strongest portions of the separator they are placed in con- tact with the positive plates. In batteries equipped with the " wood and rubber combination " type separators, the wood separator is also placed in contact with the negative plates, while the flat side of the rubber separator is placed in contact with tho 120 Storage Battery Manual positive plates. Fig. 37 contains a photographic illustration of a complete cell assembly in which the " wood and rubber combination " method of plate insulation is used ; the relative positions of positive plates, negative plates, Terminal Post. Cover. Plate Lug. Wood Separator. Perforated Rubber Separator. Negative Plate. Jtr. Sediment Space.' Fig. 37. — Assembly of Cell Showing Wood and Rubber Separators Installed. wood and rubber separators, and other portions of the cell are plainly shown in this illustration. As to the deterioration of wood separators in service, it may be said that, other things being equal, high temperatures have the greatest effect in shortening their life. Plate Insulation and Sepaeatohs 121 Wood Veneer Separator. A special form of the " wood and rubber combination " separator is used in the " Ironclad " type paste-paste assembly cell. The wood member of this combination consists of a treated veneer or unribbed sheet, which is placed next to the negative plates, the thickness of this, sheet being about the same as that of the web portion of the ordinary ribbed type wood sepa- rator. Fig. 38 contains a detailed illustration of this assembly and from which a clear idea of the relative positions of the plates and separators may be had. It will be noted that the hard rubber tubes of the positive plates Negative Plate. Wood Veneer. _ Rubber Tube. ■^■^■ Wood Veneer. Negative Plate. Fig. 38. — Showing Wood Veneer Separator In " Ironclad " Assembly. contain projections on each side which serve as ribs for maintaining proper plate separation and spacing, these ribs extending the full length of the tube. HARD RITBBES SEFARATOKS. Perforated Rubber Separators. — In the " wood and rubber combina- tion " method of plate insulation or separation, the rubber member con- sists of a thin, finely perforated sheet of hard rubber, and the arrange- ment of this combination is such that there is one such rubber sheet placed against each face or surface of each positive plate in the cell; and, although thus serving primarily as an insulator, this separator also acts in a secondary capacity as a support for retaining in position the active material of the positive plate, since in addition to possessing little or no mechanical strength, the lead-peroxide of these plates becomes softened or " muddy " during the normal operation of the cell, this would otherwise cause it to fall away from the grid in comparatively large lumps if it were not held in place by the rubber separator. Furthermore, in order that the internal resistance of the cell may be reduced to a minimum, thereby increasing the voltage characteristic of the 123 Storage Battery Manual cell and with the consequent increased electrical efficiency, the porosity of these Tubber separators is made as high as possible consistent with proper mechanical strength and stability of the sheet. Moreover, the fineness of the porosity of these rubber sheets constitutes an essential factor in retaining the active material of the positive plates in position, as has been described above. This porosity, as used in the rubber separators for the naval service, runs from 35 to 36 per cent, which means that in every square inch of sur- face area of the separator sheet, the perforated area in this square inch amounts to from 35 to 35 per cent. There is shown in Fig. 39 an illustration of a pair of separators such as are used in the "wood and rubber combina- tion " type. There are various types of these rubber separators, some of which contain vertical reinforcing ribs, while others contain no ribs. It may be said that. Wood. Rubber. Fig. 39. — Pair of " Wood and Rubber Combination " Separators. as a general rule, the separators for the small portable types of batteries con- tain no ribs, whereas some of those used in the larger cells, such as the sub- marine type, contain the vertical reinforcing ribs. Pig. 40 contains a detailed illustration of a type of rubber separator containing the vertical reinforcing ribs ; these ribs consist of narrow strips of hard rubber which are vulcanized to the hard rubber sheets after they have passed through the perforating machines. The portion of the perforated sheet located between the vertical ribs is known as the web of the separator. The strength and durability of these separators is increased by leaving an unperforated margin of from ^ to f of an inch all around the .sheet; this feature is also shown in the drawing. In the manufacture of rubber separators it is very essential that all impurities, particularly as regards metals, he not present in the separator stock. Some manufacturers make a practice of passing the separator stock, after it comes from the calendering machines, through a high voltage Plate Insulation and Separators 133 dielectric testing machine in order to detect the presence of any conducting substances or any other defects which cause a breakdown in the insulating qualities of the stock, and all such pieces are discarded. This is considered an excellent procedure and is recommended for all plants manufacturing separators. Also, some manufacturers cure the rubber separator stock between sheets of tin-foil in order to effect a smooth, polished surface in the finished sheet, Uiiperforated Margin. ooooooo oooooo ooooo ooooo OOOO oo oo ooo OOOO- Web. oo ooo oo .. Rib. oooo ooo ooo o oooo ooo ooo o o ooo -ooo KIO. =^ Fig. 40.— Perforated Hard Rubber Separator (Ribbed). and although it is considered that this method produces an excellent sepa- rator and one which is to be desired, great care should be taken when inspect- ing the separators to see that none of the tin-foil adheres to the sheet, and to thus guard against any particles of tin-foil entering the cell when the separators are installed; this in order that the likelihood of short-circuits resulting from the presence of the tin-foil may be eliminated. " Slotted Rubber " Separator. — Another type of hard rubber separator which has recently made its appearance in storage battery installations is 124 Storage Battery Manual known as the " slotted rubber " type, and lias been developed and brought out by the Philadelphia Storage Battery Company. This separator differs mainly from the ordinary perforated type just described in that instead of perforations this rubber sheet contains fine rectangular slots, the die which is used in the punching or slotting machine being of rectangular cross-section instead of round ; otherwise, the general design, method of installing in the cell and process of manufacture are practically identical with the perforated type- However, certain merits are claimed for this separator as against those of the perforated type. These claims may be summarized as follows: 1. Increased life of positive plates; the slots are much more efficient than the perforations in preventing the loss of active material from the plates, thus materially increasing the life of the positive plates without any decrease in capacity or efficiency of the cell. 2. Increased life of wood separators; owing to the fact that all positive active material which comes in contact with the wood separators has a tendency to disintegrate and decay the wood, it is claimed that inasmuch as this separator retards shedding of the positive active material to a greater degree than does the perforated type, a smaller amount of positive active material therefore comes in contact with the wood separators, with the con- sequent increase in their life. 3. The combined effect of the increased life of positive plates and wood separators as a result of using slotted rubber separators is that the life of the battery is increased 25 per cent or more. The theory upon which the merits claimed for this separator are based is that whereas the perforations in the ordinary separator are on the order of .045 to .050 of an inch in diameter, the slots in this new type separator are y% of an inch long by .012 of an inch wide, the porosity running about 27 per cent; and, inasmuch as it is claimed that the particles of active material which are " shed " or flake off from the positive plates during the normal operation of the battery have a diameter of approximately 1/50 of an inch (.020"), these particles are therefore small enough to pass through the perforations in the ordinary separator, but too large to pass through the slotted rubber sheet. In other words, the shedding of the positive plates is retarded and the size of the particles of active material which do pass through the slots is so small as to cause them to readily fall to the bottom of the cell without lodging on the wood separators and disintegrating them, the net results being that the life of the battery is increased by 25 per cent or more through the use of the slotted rubber separators. Tests are now in progress in our navy to determine the comparative merits of this separator when operated under regular service conditions. Plate Insulation and Sepaeators 135 Slotted Rubljer Tube for "Ironclad" Assembly. — The rubber member of the " wood and rubber combination " separator, as used in the " Iron- clad" type paste-paste cell assembly, consists of a slotted hard rubber tube into which is packed the active material of the positive plates. The slots in this tube are on the order of 1/100 of an inch wide, and they extend circumferentially around the tube from rib to rib. These ribs are placed diametrically opposite each other and take up against the wood veneer separator, thus acting as a spacing rib for maintaining proper plate separation and spacing. Each tube also contains an unslotted Spine. Fig. 41. — Showing General Principles of " Ironclad " Tute Construction. margin or cuff of from ^^ to | inch wide at the bottom and the top for the purpose of reinforcing and protecting the ends of the tubes. These tubes are made of a very high grade of hard rubber stock and are die-pressed in very much the same manner as the process used in the manufacture of fountain pen stock. After the tubes come from the die-pressing machine they are next placed in the vulcanizers and are cured to the proper degree. The next step in their manufacture is that of the slotting operation, which consists in passing them through a slotting machine, after which they are ready to be filled with the active material and fabricated in the plate. Fig. 41 contains an illustration which shows the general principle upon which this type of plate is based. The drawing is slightly exaggerated 126 Storage Battery Manual as to size in order that the principles incorporated in the design may be clearly shown. The relative positions of negative plates, wood veneers, and slotted tubes are shown in the illustration of Fig. 38. " Threaded Rubber " Separator. — Another type of separator or insulator which has comparatively recently made its appearance in the storage battery world and which is now being used extensively in the commercial field, espe- cially in the automobile industry, is known as the " threaded rubber " sepa- rator, and is a product developed by the laboratories of the Willard Storage Battery Company. THREADED \ \ RUBBER ^ Fig. 42. — Threaded Rubber Separator or Insulator. This separator takes its name from the great number (about 300,000 per separator) of small cotton strands which pass thrbugh the rubber sheet from face to face, and by which circulation and diffusion of the electrolyte in the cell is effected. Fig. 43 contains a group of illustrations of this separator. Eeferring to this illustration, A represents a detailed line draw- ing of the separator and which gives a clear idea of the shape of the sheet and strengthening ribs. It will be noted that the sheet is of corrugated cross-section in order to afford proper circulation and contact of the electro- lyte with and around the plates; also the corrugations act as channels for the liberation of gas bubbles formed in the plates. The hard rubber spacing Plate Insulation and Separators 187 and strengthening ribs whicli extend the full length of the sheet are vul- canized to it. These ribs are designed to maintain proper plate spacing and also to act as reinforcing strips for the threaded sheet. Three ribs are shown in this particular illustration, but the number varies with the width of separator used ; B shows a photographic representation of this particular size of separator using three ribs ; C is a greatly enlarged micro-photograph of a section of the separator. The white spots in this photograph represent the numerous cotton strands which thread through the sheet. Each of these threads is about ^V of an inch in length and of so small a diameter as to be practically invisible to the naked eye. During the late war this type of separator was used extensively for storage batteries in the aviation branch of our service, and are said to have proven entirely satisfactory. One of the chief merits claimed for this separator is that it affords a much higher voltage curve than a wood separator, par- ticularly at low temperatures, for the reason that at low temperatures the pores of the wood contract and increase the internal resistance of the cell which manifests itself in a reduction in the cell voltage, whereas no such action is apparent with the threaded rubber. The contractors claim to have made some very conclusive comparative tests in starting automobile engines with the surrounding air around freezing, and in each case the voltage characteristic of the batteries equipped with threaded rubber sepa- rators was higher than similar batteries of identical design and equipped with wood separators. Another very important feature claimed for this separator is that bat- teries when assembled with this separator can remain practically indefi- nitely, and with no deterioration of the plates or separators, without the necessity of pouring electrolyte and periodically charging the battery, such as is characteristic of all other types of current separator installations. If this claim be correct, it would appear that, other things being equal, this separator should prove especially suited to the requirements of the naval service, wherein it is necessary to maintain a large stock of storage bat- teries in store at navy yards, shore stations, etc. Tests are now in progress to determine the suitability of this separator for the general naval service, and with present stage of the tests it may be said that the results are con- sidered favorable to the separator. Methods of Installing Separators. Depending upon the type of battery, method of shipment, and length of time which will elapse before the battery is put in commission after assembly, various methods of installing separators have been adopted, chief among which may be included the following : 128 Storage Battery Manual " Wet " Method. — In this method the treated wood separators and the rubber separators are installed in the battery at the time of assembling the plates and lead-burning them together. Also, the electrolyte is poured practically immediately, or within a space of a few hours, after the element is installed in the jar. The cell is then placed in the charging room and given its initial charge and test discharge, specific gravity of the electro- lyte equalized, height of the electrolyte adjusted as necessary, and the battery thoroughly cleaned up preparatory to packing for shipment. This method, in so far as the naval service is concerned, is the one most com- monly used. Batteries shipped by this method require a periodic freshen- ing charge at least every 100 days when not in use, but better results will obtain if batteries shipped by this method are placed on trickling charge and maintained in a state of practically full charge at all times. The sub- ject of trickling charge will be taken up in detail in a later chapter. " Unfilled " Method. — This method consists in installing the treated wood separators and the rubber separators in the battery in the same manner as was described in the preceding paragraph for the dry method with the exception, however, that the cell is hermetically sealed and no electro- lyte is poured. The object of hermetically sealing the cell is to prevent the wood separators from drying out. Batteries shipped by this method will remain for at least 10 months with- out filling with electrolyte and conducting the initial charge. After the electrolyte is poured in the cell it is then treated in the same manner as regards charging, etc., as a wet cell. " Dumped " Method. — This method consists in assembling the cell with treated wood and rubber separators, pouring electrolyte and conducting the initial charge and test discharge, after which the battery is fully charged and then the cells turned upside down and the electrolyte dumped out. The cells are then thoroughly rinsed out with fresh water, care being taken to remove as much of the acid as possible. All of the water having been removed from the cells, they are then sealed up, with the exception of a small pin-hole left in the filling plug for breathing purposes to allow any gases which may be evolved in the cell to escape. When it is desired to put the battery in commission it is necessary to pour the electrolyte and recharge it. This is considered a very undesirable method of preparing batteries for shipment and is not recommended for the naval service. " Dry " Method. — This method consists in installing untreated wood separators and the regular rubber separators in a battery and not pouring the electrolyte until it is desired to give the battery its initial charge and place it in commission at a later date. This method is known as the dry Plate Insulation and Sepaeatoes 129 method, as both wood separators and plates are dry when installed in the jar. This method is rarely used, the objection being in the fact that the wood separators have not been treated, thus causing the likelihood of the following : 1. Excessive amount of acetic acid contained in the wood and ill effects incident to this. 2. Wood has not been treated to increase its conductivity; hence the internal resistance is higher, and cell voltage will be reduced thereby. 3. Possibility of warping, drawing, cracking or buckling of wood sepa- rators due to drying out through lack of moisture in the jar. When this occurs, it is necessary to remove the separators and replace them with good ones. In any event, it is always advisable, when time permits, to remove such elements from a jar and examine the separators for cracks, etc. Better still, if the time and treated .separators are available, it will pay in the long run to remove the dry untreated separators and replace them with the treated separators before pouring the electrolyte and running the initial charge. " Bone Dry " Method. — This method is used by the Willard Storage Bat- tery Company in conjunction with their " threaded rubber " separator which has been previously described. In so far as the naval service is con- cerned, to date this method has not been in vogue sufficiently long to form any conclusions, but it is understood that this method is producing satis- factory results in the commercial field. Surely if there is no deterioration to plates or separator for an indefinite period when shipping batteries by this method, it would appear that this method constitutes a very desirable one, especially when it is desired to store batteries for long periods of time and at places where proper charging facilities, etc., are not available for taking care of batteries filled with electrolyte. Notes on Shipping Separators. The methods of packing and shipping separators, particularly those of wood, are very important in respect to preserving them and maintaining them in suitable condition for installation in the cells. It is especially essential that precautions be taken against allowing treated wood separators to dry out, .since in drying out they become warped, shrunken, and cracked and are thus rendered unfit for installation in the cells. It is the present policy in supplying separators for spare cells, especially those of the sub- marine type, to require the battery manufacturers to pack such separators in hermetically sealed cases; this method will preserve them for practically an indefinite period without further attention. However, whenever the case is once unsealed it is then necessary to pour fresh water in the packing 130 Stor-age Battery Manual case periodically to keep the separators moist. The cases .should therefore be not unsealed until ready to install the separators. It has been found very convenient to pack the separators for each spare submarine cell in a separate case and to allow 35 per cent in excess for breakage in handling incident to installation, etc. In such cases the boxes containing the separa- tors should be appropriately marked with the name of the submarine, individual cell number, the type of cell, and other identifieation markings which will facilitate expeditious handling in the store rooms at navy yards and on board ship. These cases should also be marked : " Treated wood separators " ; " Do not open until ready to use," etc. In .shipping spare submarine cells it is also usual practice to install the rubber separators in the element and to use dry wood spacing boards to take the place of the treated wood separators until desired to install them and put the cell in commission. For the smaller types of batteries the wood separators are usually packed in boxes containing moist excelsior, and then pouring fresh water in the cases from time to 1;ime to prevent the separators from drying out. Also, at battery service stations on board ship and at navy yards it has been found very satisfactory to provide an earthenware jar or crock equipped with a tight-fitting cover for storing such separators as are required during the regular course of battery repairs and separator renewals, the supply in the crock being replenished from the main supply in the packing cases as required. History of Separator Development in the Naval Service. The history of the development of the wood separator as used in the naval service dates back to the early days of storage battery applications to sub- marines, and in which the old tandem type battery installations were used, which period also antedates the development in this country of the unit assembly type such ^ is now used practically entirely in these installations. In those days a .single basswood separator was used, as no perforated separators were designed for use with them ; also, these basswood separators contained no vertical ribs, such as is now current practice, but " straddle " type hard rubber pins or ribs were placed between the separator and the plates to protect the separator from the chafing action caused by the move- ment of the plates in the cell which was an especially characteristic feature in these old, loose assembly tandem installations. However, these hard rubber pins or ribs proved of little if any value, as the chafing action result- ing from the movement of the plates in the cells was sufficient to grind through the wood separators, thereby causing no end of serious battery troubles through short-circuiting of the plates. Moreover, basswood being Plate Insulation and Separators 131 of admittedly short life in electrolyte, this wood proved especially unsatis- factory for this service. Therefore, on account of the very unsatisfactory results obtained through using hassvpood .separators, it was decided by the submarine electrical experts of that time to abandon the use of wood separators and to substitute therefor a thin perforated sheet of hard rubber. These hard rubber sepa- rators contained a series of vertical hard rubber ribs vulcanized to the sheets and equally spaced across the width of the separator; these ribs were designed to maintain proper plate spacing and to prevent short-circuiting of the plates. This method of plate separation proved little if any better than the single wood separators, as experience proved that it was only a question of time before the active material of the plates bridged across the separating space and through the perforations in the rubber .separators, thus producing the damaging short-circuits in the cell. It was at about this time that the first unit assembly type cell for sub- marines was developed in our country, and the electrical experts of the submarine builders concluded that as there would be practically no relative motion between the plates in the cells of this type of assembly, a single, perforated and ribbed hard rubber separator would prove satisfactory as a plate insulating or separating medium. However, such conclusion was destined to bring about sore disappointment, for it was found that although the chafing or grinding actions between the plates and which had proved so disastrous in tandem installations, had been eliminated through adopting the unit assembly type cell, the destructive short-circuits between the plates were not eliminated, as in time, on account of the heat generated in the cell, these separators became soft and pliable, and the web portions of the sheets sagged against the plates thus producing pockets for catching the sediment which was shed from the plates. In time these pockets became loaded up with active material which forced its way through the perforations in the rubber sheets and produced the above-mentioned short-circuits. The author served as commanding officer of one of the first submarines in our navy to be equipped with the unit assembly type cell containing the single rubber separators^ and he can offer first-hand testimony as to the very unsatis- factory results obtained with these separators. The next step in trying to eliminate the short-circuits was to use two perforated rubber separators between the plates. These separators were of practically identical design as the single rubber separators used in these cells and which have been described. Moreover, the double rubber .separa- tors proved no better than the single rubber, as experience proved that it was only a matter of time before the short-circuits occurred, since it was impos- 132 Storage Battery Manual sible to prevent the ultimate bridging across of the active material between the plates and through the perforations in both rubber sheets. Therefore, the pendulum of separator application having swung between the two extremes, that is, on the one side to that of the single wood separator and on the other to that of the double rubber, and in each case no success against short-circuits having been attained, the next step was to balance the swing of the pendulum. This was done through selecting a wood separator from one side of the field and a perforated rubber separator from the other and to combine these two, thus producing what is known as the " wood-and- rubber " combination. In justice to some of our battery engineering talent it should be stated that there was considerable opposition on the part of a portion of the submarine personnel against ever using the double rubber separators after it was found that the single rubber separator had proved a failure; but this opposition was practically overruled and the decision in favor of trying out the double rubber separators was made, and it was only after experience proved that the double rubber separators produced nothing towards the satisfactory solution of the separator problem that the " wood-and-rubber " combination was finally adopted. However, since this combination has been adopted and, also, since it is producing the most satisfactory results thus far obtained in the operation of batteries in our service, it is hoped that we will retain this combination as a standard policy, or until such time as it is proved beyond all doubt that a better design has been evolved. Furthermore, it is believed that it can be safely asserted without question that, to date, fully 90 per cent of the .serious battery troubles in our naval service can be attributed primarily to separator troubles, and, as stated, since with present stage of the art the " wood-and-rubber " combination is considered the very best yet evolved for this service, let us take care that in the future the swinging of the pendulum of separator application is maintained at the balance. CHAPTEE XI. JARS. Types of Storage Battery Jars. There are five general types of Jars used in lead-acid storage battery instal- lations, which types are as follows : (a) Hard rubber. (b) Glass. (c) Lead-lined wooden tanks. (d) Gummite. (e) Celluloid. The designs of each of the above types of jars vary with the special instal- lations for which they are intended, and incorporate the various individual features corresponding with the particular batteries in which they are used and as developed by the various storage battery manufacturers. Types as Applied to the Naval Service. At the present writing, in so far as the storage battery installations in the naval service are concerned, it may be said that the hard rubber type of jars meets with more extensive application than either of the other types. However, in a few special cases, principally in remote shore stations for stand-by purposes, glass jars are sometimes used ; these installation's usually comprising the stand-by batteries for radio installations, etc., and in some instances battery installations which were put into operation before the development of the present extensively used hard rubber jar. Also, in the early days of submarine boat construction and design, lead-lined wooden tanks were used, but this practice was discontinued when development of the art of hard-rubber manufacture had reached the stage such that a hard- rubber jar of the type and size used in submarine boat storage battery installations could be satisfactorily manufactured. Also, at the present writing, experiments with the manufacture of " gummite " jars are going on in this country, but as yet this type has not attained the stage of extensive commercial exploitation, though in European countries, principally in France, this type of jar has been successfully manufactured on a broad com- mercial scale for several years. From present indications, however, it is believed that before these notes are published this type of jar will also have reached the stage of successful commercial manufacture and application in this country. 134 Storage Batteey Maxdal hard rubber mrs. Specifications for Hard Rubber Jars (Small Portable Types). The hard rubber jars used for the small portable type batteries in the naval service are very similar in design to the jars used in the regular com- mercial trade, such as in the automobile starting, lighting and ignition systems, electric vehicle installations, etc. However, it may be said that the naval specifications for these jars are somewhat more rigid in requirements than those for the commercial trade, and especially so in the grade of the hard rubber used. Fig. 43. — Hard Rubber Jar, Portable Type. Except for some special jars having a thinner wall, as in gun-firing, aviation and other such special types of storage batteries, the specifications for the jars going into the production of batteries for the naval service require that they be of hard rubber not less than ^ inch thick, and shall be made of rubber compound with not less than 5000 pounds tensile strength per square inch, with not less than 6 per cent elongation. Also, the specifi- cations require that all such jars shall be given a dielectric break-down test at the works of the battery manufacturer prior to installation of the element in the jar; for the ^ inch thick jars this dielectric test should be not less than 10,000 volts, and for the thinner wall jars it should be not less than Jars 135 nsOO volts. The object of the dielectric test is to detect foreign conducting matter which may be present in the rubber compound, or cracks, fissures and other such imperfections in manufacture. The specifications also require the rubber manufacturers, as well as the battery manufacturers, to have their Dames vulcanized on one side of the jar, which is conducive to maintaining a high standard in the manufacture of these jars, as well as serving to assist Fig. 44. — Hard Rubber Jar, Portable Type, the various service stations and the general naval service in detecting and readily identifying a manufacturer's product, whether good or bad. Plain Wall-Bridge Bottom Type Jar. There is shown in Fig. 43 a photographic illustration in section of a very extensively used design of hard rubber jar going into the production of portable storage batteries for the naval service, which design also meets with extensive application in commercial storage battery installations. This 136 Storage Battery Maxdal type is known as the " plain wall-bridge bottom type," and derives this name from the fact that the four walls of the jar are entirely plain, there being no element-supporting ledges attached thereto, while the bottom of the jar contains the element-supporting bridges. These bridges are vulcanized to the bottom of the jar during process of manufacture, thus forming an integral part with the bottom. In Fig. 44 is also shown a line drawing of this jar, a portion of which is in section ; it will be noted that there are two n / — \ Fig. 45. — Jar Containing Pour Bridges. bridges shown at A in this drawing. However, the number of bridges contained in these jars varies in different types of batteries, the width of the plates used in the particular jar usually being a function of the number of bridges which it contains ; that is, a narrow plate requires only two bridges, whereas, a wider plates requires more, usually not in excess of four. Jar Containing Four Bridges. Some battery manufacturers design their elements such that all positive plates in the cell are supported by an individual set of bridges, and likewise Jaes 137 all negative plates in the cell. This is considered a very desirable feature, as it reduces the likelihood of short-circuits occurring between the adjacent positive and negative plates, as a result of sediment collecting on top of these bridges. There is shown in Fig. 45 an illustration of a type of cell con- taining four bridges and embodying this feature of design. It will be noted Fig. 46. — Side Wall Element Support Type Jar. that the two positive and negative supporting bridges shown at BB and AAj respectively, are " staggered," thus facilitating uniform points of support for the positive and negative plates. Another desirable feature of design illus- trated in this drawing is that of the reinforced " feet " on the bottom of the plates, shown at C ; these feet protect the bottom edges of the plates from damage against the jar bridges cutting through the bottom edge of the grid, as a result of the bumps and knocks which the cell is subjected to under 138 Storage Battery Manual service operating conditions. Endurance tests conducted on bumping plat- forms have demonstrated the desirability of casting these reinforced feet on the bottoms of the grids, and especially so for services using comparatively thin plates in their storage batteries. Fig. 47. — Cell Assembly in Side Wall Support Jar. Side Wall Element Support Type Jar. Another type of hard rubber jar used for storage batteries designed for thu naval service is shov^n in Fig. 46. This jar is known as the " side wall element support " type, and derives its name from the fact that two of the opposite inside walls of the jar are off-set, thus forming ledges for supporting the element. Suitable lugs are oast on the plates, or in some cases, the cross-bars are designed such that they are capable of supporting Jars 139 the element by engaging on top of the ledges in the jar walls, as described above. The bridges on the bottom of the jar for supporting the separators are also shown in this drawing ; however, in some types of installations the separators are supported by hard rubber pins which pass through holes in suitable lugs cast on the bottoms of the plates. Fig. 47 contains a detailed illustration of a cell assembly using this type of jar and developed by the Gould Storage Battery Company for use in the naval service. All features of this assembly, such as plate support lugs, separator support bridges in the bottom of the jar, wood and rubber separa- tors, separator retainers, etc., are shown in this drawing. Special notice should be had of the method of insulating the plate support lugs from each other on top of the support ledges in the jar walls; this insulation is obtained in this particular installation by use of the hard rubber lug spacing pieces which are plainly shown in the drawing. These lug spacing or separating pieces and method of supporting the element by the plate lugs are plainly shown at E in the drawing. It will be noted that the design of these lug spacing pieces is such that each plate lug is separated from the adjacent lug of opposite polarity by a hard rubber partition, each lug thus resting in an individual compartment of its own, and it is thus that proper insulation between the lugs is obtained. It will be further noted that these lug separating pieces are about double the height of the plate lugs, and that the partitions also extend the full height of the separating pieces; this is done to guard against short circuiting of the plate lugs by the lead sponge or mossy growth which collects on top of the negative plates and which is char- acteristic of all negative plates after they have been in service for some little time. Specifications for Submarine Type Hard Rubber Jars. Owing to the large size of the jars used in submarine storage batteries, as well as the large factors of safety and reliability required for this service, it is necessary that the very best grade of materials and workmanship be used in their manufacture. Although at the present writing these jars are not considered of as high a type in respect to workmanship and materials as is desired for such an important class of service, it should nevertheless be stated that a very great advancement has been made within comparatively recent time in the art of their manufacture, and this advancement is steadily going ahead at a satisfactory rate. Moreover, it is believed that, when the rubber manufacturers have had more experience in the mixing and the fabri- cation of their stock for this large work, together with the improved methods of manufacture which will doubtless result from the very considerable 140 Storage Batteky Manual amount of research which is now being carried on in respect to this special product, an entirely satisfactory submarine jar will be produced. The current navy specifications for these jars have therefore been framed to improve this stock and the general character of the product as rapidly as possible, and also to insure that the workmanship keeps pace with any improved characteristics which may be developed in the material; these specifications are therefore subject to change and, like all other specifications and regulations, are really a growth or development in themselves. With present stage of the art, the following constitute the more important features of the current specifications : Dimensions. — Hard rubber jars shall conform to the dimensions shown on drawings specified in requisition or schedule covering the special installation in which the material is to be used ; but on account of the high coefficient of hard rubber, a tolerance will be allowed of 0.006 of an inch plus, per 1 inch for width, length, and height on inside dimensions, measurement to be taken at the corners. 0.0095 inch minus tolerance per inch in height may be taken when it is necessary to reheat the jar for straightening purposes, after the jar has been finished to the proper height; such jars must then be altered on the underside of the bottom to compensate for one-half the above tolerance, so that the over-all height of the jar will conform to not less than within 0.0047 per 1 inch of height to dimensions shown on the drawings. When jars are supplied with outside reinforcing ribs, they must be made to the tolerance specified on drawings. Materials. — The materials used in the preparation of the hard rubber shall be limited to rubber, reclaimed rubber, sulphur, hard rubber dust and the various ingredients required to produce a material having the physical and chemical properties specified below. Specific Gravity. — Specific gravity shall not exceed 1.50. Impurities. — The hard rubber shall be free from metallic particles, such as copper, brass, and tin ; from all granular matter, and from all lumps or aggre- gations of mineral matter which have not been thoroughly incorporated into the rubber compound during mixing on the compounding mill, and from all other substances soluble in sulphuric acid of 1.4 specific gravity. The iron present as such, and in combination, shall not exceed 0.30 per cent. Tensile Strength. — Eectangular test pieces ^ inch by ^ inch by 4 inches, cut from a test slab as described below, shall be turned in a lathe for a space of 2 inches centrally located on the test pieces. These test pieces, when broken in the testing machine at a temperature between 70 degrees and 80 degrees Fahrenheit, shall show a tensile strength of not less than 3000 pounds per square inch. Jaes 141 Transverse Strength, — CyliBdrical rods 4 inches long and J inch in diameter shall be prepared from a test slab as described below. One test shall be made from these rods maintained at an average temperature of 40 degrees Fahrenheit, and when placed on supports 3^ inches apart shall be capable of supporting a load (centrally applied) of 33 pounds, showing a deilection of not under 0.07 inch. A second similar test will be made at a temperature of 100 degrees Fahrenheit ; the test rods must support 33 pounds, showing a deflection of not over 0.50 inch. Test Slabs. — (a) The test slabs from which the tensile and the transverse strength test pieces are prepared shall be taken from such lots of mixture after the same has been calendered and made ready to build into a jar. (b) These test pieces shall be vulcanized under the same conditions as the jar itself. (c) One test slab shall be prepared for each 10 jars, or less, to be manu- factured, and the size of each of these test slabs shall be such as to produce at least six test pieces (two for tensile strength test and four for transverse strength test) of dimensions specified above for those test pieces. Dielectric Break-Down Test. — Jars of all types will be subject to the fol- lowing test : First. — Fill the jar with water, allow same to stand filled from 8 to 10 hours. Second. — A wood block covered with metal (the size of which shall not be less than y% of an inch smaller than the inside dimension of the jar) is to be used by inserting it in the jar after the water has been emptied from it. Third. — Water will then be poured in the jar, covering the metal-covered block until there is no air gap between the jar and the block, to within IJ inches of the top of the jar. Fourth. — The metal of the block shall then be connected to one terminal of a high voltage transformer of not less than 24,000 volts, and not less than 4 kilowatt capacity ; the other terminal of the transformer shall be connected to a wire brush (the wire brush having bristles, at least 4 inches long, and so constructed that the brushes will readily fall into every corner of the jar). Current shall then be turned on and the wire brush passed very slowly and carefully over every part of the exterior of the jar up to the point where dis- charge over the top of the jar begins. If the jar should puncture at any point the jar will be rejected, and shall not be presented for retest. Hydrostatic Test," — Jars intended for installation in submarines in which each jar is wedged, shall be filled with liquid up to operating level and containing the weight, 35 per cent in excess of the weight in jar when com- pletely assembled, and kept standing in this position supported on a fair level surface for six hours. This test shall be made in a room where the 10 143 Storage Batthhy Manual temperature is not under 75 degrees Fahrenheit, the temperatiare of the liquid in the jar being maintained at an average of 120 degrees Fahrenheit by means of electric or steam coils at the option of the manufacturer. At the end of this test, when the jar has assumed the normal temperature of the room, liquid or weight having been removed from the jar, caliper measure- ments shall be taken on the outside of the ribs on both the length and width of the jar, and no permanent set greater than f of an inch in total dimen- sions shall be shown. Jars tested under this paragraph shall be limited to five jars. After type of jars has satisfactorily withstood above tests, jars on future orders of same type will be considered satisfactory if material test for tensile strength and dielectric strength are complied with. Finish. — (a) The surface of the jars, both inside and outside, shall present a neat, smooth, and finished appearance, and shall be free from JDitting, blow- holes, rough spots, rubber scale, blisters, and other deformations which may be caused by the presence of air pockets in the compound, or other air pockets which may be formed between the rubber and mandrel as a result of improper venting during process of manufacture. (b) All vertical and horizontal ribs forming and strengthening the outer walls of jars shall be true with the surface of the jar and shall be perfectly joined to each other and to the adjacent surfaces of the jar. Marking Jars. — The following data shall be vulcanized on the outside of each jar near the top so as to be plainly legible : Name of jar manufacturer. Date of manufacture. Government's, battery manufacturer's, or shipbuilder's contract number on which jars were built. Types of Submarine Jars. In respect to the methods of manufacture, hard rubber jars of the sub- marine type may be divided into two general classes, viz. : (a) Built-up. (b) Moulded. Built-Up Type. — In the built-up type the walls, strengthening ribs, bands, etc., are assembled successively around a cast iron mandrel, the shape of which conforms to the shape of the inside of the jar, and after each piece is in turn thoroughly worked into its respective position by means of hand rollers used by the workmen, they are placed in the vulcanizers where they are subjected to the vulcanizing process. After this process has been com- pleted, the jars are removed to the extracting machine where the mandrels are extracted, after which they are sent to the grinding machine where they are ground to the finished size ; they are then ready to be finished up prepara- Jaks 143 tory to subjecting them to the inspection and tests in accordance witli approved specifications. Fig. 48 contains a photographic illustration of a built-up jar. The strengthening ribs and bands are plainly shown in this picture, as are also the lifting eyes for use in lifting the cell by means of the lifting device, which is equipped with a series of lifting pins designed to engage in the lift- ing eyes: Fig. 48.— Built-Up Type Hard Rubber Jar for Sub- marine Battery. In the manufacture of jars by this method it is very essential, when assembling the various pieces of stock around the mandrel, that all air entrapped between the sides of the mandrel and the stock be driven out by means of the hand rollers used by the workmen. It is likewise essential that good adhesion be obtained between all ribs, bands and other parts which are assembled on the stock forming the walls, and also to exercise care in rolling out any air that may have been entrapped between any of these parts during the course of building up the jar. This is necessary for the reason that any air that remains in any part of the stock is converted into steam during the vulcanizing process and hence expands and forms blisters, blow-holes, open 144 Storage Battery Mandal seams, and other such imperfections which render the jar unfit for use. It may be said that this feature of entrapped air and the subsequent injurious effects which it has upon the jar during the vulcanizing process, constitutes one of the chief sources of trouble and difficulty in the manufacture of jars by this method. Moulded Type. — In the moulded type jar, the stock forming the walls, ribs, bands, lifting ears, insulator feet, etc., is placed in a very ruggedly constructed and accurately machined press-mould, after which this press- mould is assembled around a cast iron mandrel, the outside shape of which conforms to the desired shape of the interior of the jar. The various parts forming this press-mould are then forced or pressed by hydraulic pressure, or any other means, against the mandrel, thus forcing the rubber stock into the various compartments of the mould and accordingly effecting the desired formation of the jar. The next operation is that of vulcanizing tfie jar, which consists in bringing the interior of the mandrel and the parts of the press-mould to the required temperature by means of steam, there being steam leads into the interior core of the mandrel as well as steam jackets around the parts of the press-mould. When the vulcanizing process has been completed the press-mould is disassembled from around the mandrel thus leaving the newly formed jar. The next operation is that of extracting the mandrel from the jar, after which another mandrel is inserted in the jar to preserve the proper form and size during the cooling period. After the jar has properly cooled it is taken to the grinding machine, where all rough edges are removed and any other necessary work done to prepare the jar for the required inspection and tests. Owing to the very satisfactory grade of jars obtained by this method, it may be said that this process of manufacture is considered superior to the built-up method, the main advantages of the moulded over the built-up type being as follows : (a) Greater uniformity in finish, shape and size, which is especially important from the point of view of installation in the submarine. (b) No open seams or imperfectly formed seams. .(c) Fewer blow-holes, blisters, cracks and other imperfections. (d) Smaller percentage of loss incident to manufacture. (e) Requires less time to manufacture and is especially adapted to quan- tity production. (f ) Possible to obtain better lines, fillets, and other finer details of design than in the built-up type. (g) Requires fewer skilled workmen in the actual fabrication of the jar. The design shown in Fig. 49 represents a type of jar which has been very successfully manufactured by the moulded method, and contains many improved features of design over the built-up type of jar shown in Fig. 48. Jars 145 -'J lu- 1 J 4 ; 4 --^ r.—~ — ^^ SOFT RUBBER EAR BUSHING MILD STEEL LIFTING EAR INSERT Ilifting ear bushing 1 to be vulcanized in R SOFT 8TEEL-*ffl . \ 1 ]l 11 J 1 [\ 1 1 1 1 ! 1 i! J! ^'a_ALL AAa±M \-"^- — ^ 7' 'cq fHi il HARD RCfffEtm m PART OF JAR-^ eElSH^ V ""^^^ PETTICOAT INSULATOR FOOT Fig. 49. — Hard Rubber Jar, Submarine Type. 146 Storage Battery Manual It will be noted that this jar contains a series of horizontal bands pro- gressively spaced from the bottom of the jar in order to prevent excessive' bulging of the sides of the jar when subjected to the working temperatures of the cell. This jar also contains a series of vertical ribs, which in addition to increasing the rigidity of the jar, also serve as wedging ribs or guides by which the jars are wedged or secured in position in the battery tank, paraffin impregnated maple wood wedges appropriately grooved to slide over these wedging ribs on the jar being used for this purpose. In respect to this feature it will be further noted that each wedging rib contains a square shoulder or stop at the bottom of the jar in order to prevent the wedge from being driven too far down and injuring the lead lining of the battery tank. Another improvement which will be noted in the jar under present consid- eration is that it is equipped with two steel reinforced lifting ears, the eyes of which are fitted with soft rubber bushings designed to equalize the strain of the lifting device pins in the lifting ear eyes when lifting the cell. Although when it is desired to lift the cell, the lifting device is also made fast to the terminal posts of the cell in addition to the lifting ears of the jar, such that the weight of the element is not borne entirely by the lifting ears, the specifi- cations nevertheless require that these lifting ears be strong enough to support the weight of the fully-charged cell when filled with electrolyte and without attaching the lifting device to any other part of the cell. The details of the soft rubber bushings and the metal inserts for the lifting ears are shown in the upper right-hand corner of the illustration. The steel inserts are plated with a lead-antimony coating to protect them against the corrosive action of the acid of the electrolyte should the inner wall of the jar become cracked or contain other fissures or imperfections which would allow the acid to come in contact with the metal insert ; this expedient also serves as a precaution against damage to the cell through the iron going into solution with the electrolyte. The soft rubber feet on the bottom of the jar are of the petticoat insulator type, the soft rubber strips or cushions being serrated on their under side to compensate for any irregularities of construction in the bottom of the battery tank, thus equalizing the supporting strain across the bottom of the jar. It will be noted that the element is hung from two support ledges formed on the inside walls of the jar. It is considered that this jar incorporates the best features of design of any yet evolved. GLASS JARS. As far as the battery installations of the naval setvice are concerned, those using glass jars are confined practically entirely to stand-by batteries at shore stations, principally for radio work. However, in the commercial field Jars 147 these jars are extensively used for certain classes of service, such as isolated farm-lighting sets, certain types of stand-by batteries, and other such instal- lations which are confined practically entirely to the stationary type. For such classes of service these jars give very satisfactory results, and due to the fact that the element is at all times visible, the height of the electrolyte and general condition of plates, separators, and other parts of the interior of the cells may be readily observed. S.epara-tor Retainer Bort Connector Ne-< E >; ki lO ^ w kr □S C ij c .d JS JS .q ja h J3 l-r J3 t- in M ^ J3 A <■« .q J3 HM M JH -«» M ampere- -W HM nW iH ■-• N N N 05 CQ •" ■« in >o -) denotes the action which takes place during discharge of the cell, and reading from right to left ( -< — ), that which takes place during charge. It is, therefore, apparent from the above equation that during discharge the acid radical, SO^, of the electrolyte combines with the active materials of the positive and negative plates and converts both of these plates into lead-sulphate (PbSO^). Moreover, during charge the lead-sulphate is reduced by the charging current and the acid radical returned to the electro- lyte, the active materials of both plates being accordingly restored to their original states ; that is, to sponge lead and lead-peroxide. Self -discharge of an Idle Battery. — It is an established fact that if a fully charged or a partially charged battery be allowed to stand idle long enough it will eventually become completely discharged of its' own accord. This is manifested by a reduction in the cell voltage, drop in the specific gravity of the electrolyte and the formation of lead-sulphate in the positive and nega- tive plates. In other words, although the circuit connecting the terminals of the battery has not been closed during the idle period and, consequently, no current drawn from the battery, the acid radical of the electrolyte has nevertheless combined with the active materials of both sets of plates, con- verting them into lead-sulphate in the same manner as though the battery had been subjected to a regular useful service discharge. A fully charged battery will completely discharge itself in approximately 100 days if allowed to remain idle without receiving a freshening charge during this period. However, the degree of acid concentration in the electro- lyte and the temperature to which the battery is subjected are governing factors in the time element required for a battery to become discharged through self-discharge, high-acid concentration and high surrounding tem- peratures tending to lessen the time element necessary for a complete self- discharge as outlined above. Factors Which Produce Self -discharge. — There are several factors which are in various degrees responsible for the internal or self-discharge which takes place in an idle storage battery. These factors, when considered either individually or collectively, are, in battery parlance, usually referred to under the general term local action. Chief among these several factors may be stated the following : (1) Impurities in the electrolyte. The "Trickling Chaege" 241 (2) Impurities in the materials composing the grids, and defective grid- casting. (3) Local couples formed in the manufacture of the positive plates. (4) Local couples formed in the manufacture of the negative plates. (5) Leakage of current between the cell terminals as a result of moisture grounds, etc. Each of the above factors may be briefly commented upon as follows : Impurities in the Electrolyte. — As a general rule any metallic impu- rities present in the electrolyte will cause a loss of charge at the negative plates. During charge such metallic impurities are deposited upon the negative plates where they form innumerable local couples with the active materials of these plates, with the consequent result that in the presence of the electrolyte discharge takes place, thus liberating hydrogen at the negative plates and with a loss of charge at these plates. Such metallic impurities include antimony, arsenic, copper, iron, plati- num and tin. Iron is in general the most active and destructive of the above-mentioned impurities, for, due to the fact that the ions of this metal can exist in two different stages of oxidation, each stage of which is capable of being converted from one to the other, these ions continually oscillate from one group of plates to the other, when the cell is placed on open circuit, thus causing a consequent loss of charge at each group. It requires only a comparatively small amount of iron in a cell to com- pletely discharge it in a very short while when the cell is left on open circuit. Therefore, great care should be ' exercised when operating the storage bat- tery that iron is prevented from ent>.-.'ing the cell, such as through using electrolyte or water which contains iron, dropping into the cell iron nuts, bolts, washers, nails, tools, etc., or through any other cause. Furthermore, all iron which enters a cell from time to time is cumulative in effect, as none of this metal is lost by electrolytic decomposition or liberated in a gaseous state, as is the case with certain other impurities. Impurities in the Materials Composing the Grids and Defective Grid- Casting. — The alloy used in casting the grids of the storage battery cell con- sists of lead and antimony. If these metals are not refined to a very high degree the other metallic impurities contained will set up small local couples in the presence of the electrolyte, thus causing a loss of charge of the plates. Also, if the lead-antimony alloy is not a homogeneous mixture, or if there are segregations of pure antimony and pure lead in spots with blow-holes or shrinkage cracks in the casting as a result of improper cooling or insuffi- cient mixing of the alloy before pouring into the moulds, other local couples are formed which accounts for a further loss of charge of the plates. 242 Storage Battery Manual Local Couples Formed in the Manufacture of Positive Plates. — As outlined above, the grids are composed of lead-antimony alloy, whereas the active material of the positive plates consists of lead-peroxide. We thus have a couple formed by the lead-peroxide and the grid in the presence of the electrolyte, which results in a certain amount of discharge of the positive plate, the amount of which depending upon the surface contact area between the positive active material and the grid. However, the discharge from this cause is of comparatively short duration, since a layer of lead-sulphate is eventually formed between the grid and the active material of the positive plate, thus forming an insulating medium which prevents further discharge. Also, another source of internal or self-discharge of the positive plates, especially in the Plante type, is the failure to remove all of the forming agents which were used in forming the plates. If these plates are not thoroughly cleared of all such forming agents, the loss of charge from this cause is likely to prove quite appreciable in amount. Local Couples Pormed in the Manufacture of Negative Plates. — As in the case of the positive plates, we have in the negative plates local couples formed by the lead-antimony alloy grid in contact with the sponge lead active material, and in the presence of the electrolyte a certain amount of discharge takes place in the negative plates from this cause. Also, as was described in the preceding paragraph relating to the positive plates, a thin insulating layer of lead-sulphate is similarly formed between the negative grid and the active material of this plate, thus preventing a further loss of charge from this cause. Another loss of charge at the negative plate is due to the local action which takes place between the various materials used for obtaining porosity, increasing conductivity and the various expanders used in the manufacture of these plates. Leakage of Current Between Cell Terminals. — Although, properly speaking, loss of discharge from this cause is not due to local action in the strict meaning of the term, it is, nevertheless, included here, since it accounts for quite an appreciable amount of loss of charge in an idle stor- age battery cell if such a condition is allowed to exist sufficiently long with- out rectifying it; in fact, the loss of charge through this cause is in some cases equal to, if not greater than, the combined loss of charge due to the other factors outlined above, provided the leakage of current between the terminals is of protracted duration. Method of Conducting "Trickling Charge." — Having considered the effects of the various factors of local action in producing self-discharge of the idle storage battery cell, the object of the " trickling charge " in reducing to a minimum the effects of this local action, as well as maintaining the bat- tery iQ a fully charged, healthy condition is, therefore, readily apparent. The "Teicklksig Charge" 343 As was explained in defining the term "trickling charge" in the early part of this chapter, only a fraction of an ampere of current is sufficient to counteract this local action, the amount of the current depending upon the type of the battery in respect to the size and the number of plates installed in the cells. Lamp-bank Method. — A very satisfactory and simple method of conduct- ing the "trickling charge," and one which is very conveniently applied on board ship, is known as the lamp-bank method, and consists in connecting lamp-banks in series with the battery and the charging buses of the ship's main supply lines, the number of lamps used depending upon the following : (a) Type of battery; size and number of plates in the cells. (b) Number of cells in the battery. (c) Voltage of the charging buses. The function of the lamp-banks is that of a resistance to absorb the excess voltage in the main charging line over that required for the small amount of " trickling charge " current passing through the battery. Fig. 103 contains an illustration of the equipment and necessary con- nections required for conducting a "trickling charge" by the lamp-bank method on navy type storage batteries. The lamp-banks connected in series with the battery and the main charg- ing buses are plainly shown in this illustration, as is also the double-pole snap-switch used for cutting on or off the " trickling charge " current, as desired. The direction of the current in passing through the battery on charge is as indicated by the arrows in the drawing. In this regard, as in all other cases of charging storage batteries, it is essential that only direct current be used for this purpose, and that the positive terminal of the battery be connected to the positive charging bus and the negative terminal of the battery to the negative bus. To do otherwise will result in serious harm to the battery. In conducting the " trickling charge " by the lamp-bank method, the life of the lamps will be increased if the arrangement of the lamp-banks is such as to reduce the voltage sufficiently to cause the lamps to burn at a low incandescence. Also, as a general rule, on account of their high efficiency and long Hfe, tungsten filament lamps should be used, if obtainable, in prefer- ence to carbon filament lamps, as they afford a finer degree of current and voltage regulation than the carbon filament lamps. However, if the con- ditions are such that it is not practicable to use tungsten filament lamps, carbon filament lamps may be used. The advantage in using lamp-banks as a resistance, instead of using regular commercial resistance units in conjunction with a low-reading ammeter, rests in the fact that lamp-banks at all times atEord a reliable !344 Storage Battery Manual D.P.Snap Switch CONNECTIDNS FOR TRICKLIN& CHARGE tM VMVJiMjmp i Lamp Banks In Series Fig. 103. — Showing Connections for Trickling Charge. The "TiiioKLiNG Chaege" 345 visual indication that current is "trickling " through the hattery, whereas, the needle of the ammeter does not present so striking an indication of the charging current; in other words, as long as the lights are burning it is definitely known that current is passing through the battery, and anybody on watch in the vicinity, v/hether he be a coal-passer or an ordinary seaman, can tell when the charging current is on or off. At navy yards, shore stations and regular battery service stations, where the organization is such that someone is in constant attendance with the storage batteries on charge, commercial resistance units may well be used in connection with ammeters and voltmeters, as at such places proper facilities are at hand for using at all times accurately calibrated instru- ments, etc. Standard commercial resistance units of identica] rating as standard size lamps may now be obtained; those resistance units are also designed to screw into the standard incandescent lamp sockets. All storage batteries designed for stand-by circuits on board ship, as well as spare submarine cells kept in the battery service stations on submarine tenders, should be maintained in a charged condition by the " trickling charge " method. Also, spare submarine batteries stored at navy yards for emergency installation can be kept in good serviceable condition and with comparatively little cost of upkeep and maintenance by this method, and its practice should be encouraged. Computing the " Trickling Charge " Rate. — The number of positive plates contained in the cell constitutes the basis for computing the " trickling charge " rate for a given battery installation. For the portable types of storage batteries used in the naval service and having positive plates ^ inch in thickness, a trickling charging rate of .025 amperes per positive has been found to be suflBcient to counteract local action and maintain the plate in a fully charged, liealthy condition. Thus, if such a cell contains n positive plates, the " trickling charge '' rate for this cell would be n x .035 amperes. For all portable type cells having positive plates less than J inch in thick- ness .0135 ampere per positive plate, or one-half of ^ inch plate rating, should be used in absence of any other specific rating designated by the battery manufacturer. In respect to this featu.re, the navy specifications for portable types of storage batteries require that each storage battery manu- facturer submit detailed drawings of every type cell supplied on government contracts; in addition to containing detailed drawings of parts for the infor- mation and use of the battery service stations and operating personnel in ordering spare parts, making repairs, etc., these drawings also specify the number and size of the plates installed in the cells. For submarine type cells the battery manufacturers also supply the required " trickling charge " rate for each type. 246 Storage Battehy Mandal Therefore, in order to ascertain the " trickling charge " rate for a given cell or battery installation, it is only necessary to consult these detailed drawings supplied by the battery manufacturers. The required "trickling charge " rate should also be found on the metal name-plate attached to the cell tray. It has also been found that the charge voltage of a cell through which is passing the required amount of "trickling charge " current averages from 3.15 to 2.30 volts. Therefore, when calculating the " trickling charge " rate for a given installation, if 2.15 volts per cell is used the results will be sufficiently accurate for practical application. Example. — The storage battery charging buses on board ship are con- nected across the 115-volt supply mains, and it is desired to place a set of auxiliary lighting batteries on " trickling charge " ; each cell of this battery contains 9 plates, 4 positives and 5 negatives, and the entire battery consists of 12 cells, all of which are connected in series. Find the " trickling charge " rate for this battery, and the amount of the resistance to be placed in series with the battery in order to conduct the " trickling charge " at the required rate. Solution. — This type of cell conforms to the navy standard for these bat- teries and contains four :|-inch positive plates. Hence, the "trickling charge " rate for this cell is 4 X .025 ampere = .1 ampere. Also, since there are 12 cells connected in series, the counter-electromotive force produced by this battery when on " trickling charge " at the required rate is 12 X 2.15 volts= 25.8 volts. Therefore, 115 — 25.8 volts = 89.2 volts, which must be absorbed by a resistance placed in series with this battery. Now, by Ohm's law : ^ E , 89.2 B = 892 ohms, the amount of the resistance to be inserted in series with the battery in order to allow a " trickling charge '' of .1 ampere to pass through the battery. Therefore, in order to translate this resistance in terms of lamp-banks it is only necessary to select lamps of such rating and to so combine them that the value of the resistance offered by the entire lamp-bank will be 892 ohms; various combinations of lamps may be utilized for such a lamp- bank. For the particular problem outlined above, it has been found that a bank consisting of three 25-watt metallic filament lamps placed in series with The "Trickling Chaegb" 247 each other, and this lamp-bank in turn placed in series with the battery, will allow a " trickling charge " of .1 ampere to pass through the battery. Gassing and Ventilation of Batteries During " Trickling Charge " and Care of Compartment in Which They Are Located. — Although, as has been stated, when the " trickling charge " is properly conducted, the amount of gas evolved from the storage batteries is relatively small, yet, as a precaution during this charge, the trays of these batteries should be left uncovered and the compartment in which they are located should also be well ventilated, periodically, at least, in order that any gas which is evolved will be dis- sipated before an explosive mixture is formed. In this regard, tests conducted are conclusive that a 4 per cent mixture of hydrogen in air is dangerous, and it is the established policy in operating storage batteries requiring forced ventilation in our service, such as the sub- marine types, to design the ventilating apparatus on a basis of sufficient capacity to keep the amount of hydrogen present in the air at any instant below 2 per cent, thus insuring a substantial factor of safety in the oper- ation of these batteries. The compartment in which the batteries are located should be kept free from sweating and otherwise as dry as possible, in order to reduce the likeli- hood of moisture grounds occurring around the batteries. The tops of the cells, sides and tops of the trays, stowage racks, etc., should also be kept dry and free from acid spray, as in addition to causing leakage between the cell terminals and other such grounds, the cell trays and other woodwork around the batteries will become acid soaked, and which will eventually result in rotting of the woodwork of the trays and other parts. It is good practice to give the cell trays and other woodwork around the batteries a coating of asphaltum or other acid-resisting paint periodically as necessary. All metal work in the compartment in which the batteries are installed should also be coated with acid-resisting paint to protect it from the cor- rosive action of the acid fumes, and spray given off from the batteries. It is essential to successful operation of the batteries that the compartment be kept clean and no metals, tools or other materials stored- around or on top of the batteries. Watering Battery and Routine Overcharge. — In conducting the " trick- ling charge," the cells should be watered regularly with pure distilled or other approved battery water to replace that lost in evaporation. Under no conditions should acid be added to replace evaporation. Also, for the best results, the battery should, as a routine practice, be given an " overcharge " at the prescribed " finishing " rate at least once a month, in order to thoroughly mix the added water with the electrolyte and to pre- vent the injurious effects of stratification of the acid in the electrolyte. In 248 Storage Battery Manual this regard, cells which are allowed to remain inactive for protracted periods, that is, not being subjected to regular cycles of charge and discharge, are sub- ject to this acid stratification in the electrolyte, in that the heavier and more concentrated acid tends to settle to the bottom of the cell with the result that effect of local action on the plates is more pronounced in the lower part of the cell. Although, as has been pointed out, the " triekUng charge " is designed to reduce the effect of local action to a minimum, the " trickling charge " rate is not sufficient to produce enough gassing in the cell to stir up or agi- UIRINE5 -FDR- I TRICKLIMEt chare^e HIIIIIIIIH Pig. 104. — Wiring Diagram for Trickling Charge. tate the electrolyte, and for this reason the periodic overcharge is helpful in dissipating any tendency to stratification of the acid. The duration of this overcharge should be sufficiently long to insure that a maximum specific gravity reading has been obtained, and as .shown by four successive readings taken at equal intervals for a period of one hbur. Such a maximum gravity reading insures that practically all acid has been driven out of the plates, if the cells have received the proper attention during pre- vious operation. There is shown in Fig. 104 a composite wiring diagram of the complete 'equipment required for charging or discharging a set of storage batteries on The "Trickling Chaege" 249 board ship. In addition to the " trickling charge " equipment, which has already been described, this diagram also includes the necessary connections and equipment for giving the storage battery a normal charge, and " over- charge,'' as vi^ell as the connections for discharging the battery through the discharge service lines. It will be noted in this diagram that the regular charging equipment consists of a variable rheostat, connected in circuit with the main current supply lines, for regulating the charging current to correspond with the prescribed " starting " and " finishing " rates for the particular types of battery used in the installation. Connections to ammeter and voltmeter are also shown in the diagram. Charging and discharging is effected by means of the double-pole double- throw switch .8, which may be closed on either side of the circuit, as desired. Manifestly, when discharging the battery, the double-pole snap switch on the " trickling charge " circuit should be in the " open " position ; also, when the battery is receiving a "trickling charge" switch S should be thrown in the " open " position. In conclusion it is safe to say that the storage battery has come to stay in our naval service, and the "trickling charge " will accordingly occupy a prominent place in the operation, care and maintenance of these batteries. CHAPTER XVIII. FLOATING THE STORAGE BATTERY ON THE LINE. Although the practice of floating the storage battery on the line has been adopted commercially for a number of years and has registered a marked success in the storage battery engineering world, its general adoption for naval use and its application to the submarine electrical plant are of com- paratively recent date. However, owing to the rapidly increasing use of the storage battery as a stand-by agent for the various power circuits, as well as other electrical circuits on board ship, floating the storage battery on the line will likewise meet with increased application and will eventually become a regular routine engineering practice in the battery service stations and electrical plants of practically all naval vessels. In fact, tiiis practice has already been adopted as routine on board practically all of our submarines, and this chapter deals mainly with its application to this special branch of our service; but inasmuch as the general principles involved are identical, the subject-matter herein contained is, with a few minor exceptions, equally applicable to the electrical plants of all naval vessels equipped for floating their storage batteries on the line. ^ Ploating the storage battery on the line, or the operation of maintaining the battery in a practically constant degree of charge while directly con- nected in parallel across the bus-bars of the main power units normally sup- plying current for the exterior load, is best accomplished in the submarine electrical plant through the application of the principle of electromagne- tism, which principle is contained in the action of the reverse-current circuit- breaker. The method of using the reverse-current breaker for this purpose is identical with that employed in running dynamos in parallel and, as is well known, when this practice first came into general use, experience proved it highly essential that some means be provided for protecting the machines against serious damage should either of them fail, through break-down or any other cause, to deliver its designated share of the power required on the line. It being obviously true that when dynamos are working in multiple, the failure of any one of the machines t^ take its share of the exterior load forces the other machine or machines, as the case may be, to take the addi- tional load, with the possibility of causing the disabled machine to run as a motor. Moreover, depending upon the nature of the break-down and the load on the line in comparison with the ratings of the machines, these may be sufficient to wreck the power units and put th6 entire plant out of commission. Floating the Stokage Bati'Eev on the Line 351 Fig. 105. — Reverse Current Circuit-Breaker. 352 Storage Battery Manual Hence, the evolution and development of the reverse-current circuit breaker came as a natural result in offering a protective means against damage to the dynamos and other equipment through accidents of this kind, and, as stated, it is the reverse-current circuit-breaker which has been adapted for use and performs a similar function in the operation of floating the storage battery on the line in the submarine electrical plant. The Reverse-Current Circuit-Breaker. The reverse-current circuit-breaker, as its name implies, serves to auto- matically open the circuit when the direction of current flow in the Une is reversed. In Fig. 105 is shown a photographic illustration of one of these circuit-breakers, and in Fig. 106 is shown the corresponding wiring diagram for this breaker and the method of connecting it in circuit with the generator and bus-bars. In the photograph, Fig. 105, the reverse-current circuit- breaker is shown with portions of the frame-work removed in order that the essential parts necessary to the reversal feature may be clearly shown. The reversal feature of this breaker consists of two separate electromagnetic systems as follows : (1) A series magnetic system. (3) A shunt magnetic system. The series magnetic system consists of the following parts : (a) Series magnetic cpil A in series with the main switch member of the breaker and designed to carry the entire line current. (b) Series magnetic core B surrounded by the series coil A, while to each end of this core is attached a pole piece, one of which, marked E, may be plainly seen in the photograph. The core B is mounted on frictionless bear- ings which allow a slight angular movement about its axis. One of these bearings, marked F, is also shown in the photograph. The shunt magnetic system consists of the following parts : (a) Shunt magnetic coils C and C" shunted across the main bus members of the circuit. These coils, connected in series with each other, are wound with high resistance wire and are adapted to receive the full line voltage. The spring contact P automatically closes the shunt coil circuit when the circuit-breaker is closed and likewise opens the shunt coil circuit when the circuit-breaker is opened. (b) Shunt magnetic cores D and D' surrounded by the corresponding shunt coils C and C". These cores are shown mounted opposite the outer extremities of the series pole pieces and the windings of shunt coils C and C" are so related to each other that the magnetic poles at corresponding ends of the shunt cores D and D' are opposite in sign and hence tend to create a strong magnetic flow across the gaps separating the respective poles. Floatihg the Storage Batteky on the Line 253 It is the action of the magnetic cores B, D and D' under the influence of their respective coil fields which mechanically operates the tripping mechan- F U\L^V\T\NJ^ BN^'^ -aVv^^ (<5 ^ 1 k-V^^UNNJ'L ^\^^ ^Wf^ ^ ^ VIRINCt li — ^ niAq-RAM F i DF If 1 REVERSE I 1^ ^ V ■ v\ — 1 CURRENT I CIRCUIT Ti^ \ ! BREAKER c ^ il ' \^ S--L, -»- J^J^ » X p/lp= H' -• ^r\^ Fig. 106. — Wiring Diagram of Reverse Current Circuit-Brealter. ism T for opening the circuit upon reversal of direction of current flow. These cores are made of Norway iron, an especsially high-grade of soft iron containing practically no impurities, and due to its softness, permeability, and low retentivity or capacity for retaining a minimum amount of residual 17 854 Storage Battery Manual magnetism when demagnetized upon cessation of a current flowing through its coils, this particular grade of iron is especially adapted for use in the magnetic cores of this type. Eelative to the low retentivity feature, when a magnetizing current passing through a coil is reversed, the residual mag- netism or remanence in the core must necessarily be neutralized or deadened by a coercive force before the induced magnetism is of sufficient strength to react in the core. Fig. 107. — Reverse Current Circuit-Breaker (Closed Position). Hence, it follows that the smaller the amount of residual magnetism pres- ent in a core, the smaller the amount of coercive force required to neutralize same and, consequently, the more responsive will be the core reaction in the coil field. This feature explains the advantage gained in using Norway iron for these cores, and is best appreciated when the core reactions of the reverse-current circuit-breaker are considered. In this instance it is essential that the series magnetic core undergo an instantaneous and abrupt change of polarity in order that the tripping mechanism for opening the breaker may be instantly operated upon reversal of current. These core reactions may be Floating the Stobage Battery on the Line 355 understood by a study of the elementary wiring diagrams shown in Figs. 107 and 108. For clearness in following through the design and operation of the reverse-current circuit-breaker, the descriptive lettering of the various parts in Figs. 107 and 108 are identical with those of Figs. 105 and 106. In Fig. 107 the reverse-current circuit-breaker is shown closed in the circuit with its series coil A connected in series with the main circuit. The shunt coils C and C, oppositely wound, are connected in series with each Pig. 108. — Reverse Current Circuit-Breaker (Open Position). other and in parallel across the main positive and negative buses. The bat- teries are shown connected in parallel, and in this manner are floated on the line while the generator is supplying current for the load on the line. The direction of the current flowing through the circuit is as indicated by the arrows. 'Now with the generator running and the current passing from same through the series coil A and the shunt coils C and C", their respective mag- netic cores B, D and D' are thus inductively magnetized by virtue of the coil fields formed by the generator current; the polarities of these cores are as 256 Storage Batteky Manual indicated and are in accordance with the direction of current flowing through their coils. Thus, in the diagram the induced south pole of pole piece E, connected to magnetic core B, is shown attracted by the induced north pole of core D, while it is repelled by the induced south pole of core D', and in this position the breaker remains closed so long as the direction of current flow is not changed. Now, as illustrated in Fig. 108, should the engine or generator motive power become disabled or stopped for any reason, the generator current immediately ceases and the battery begins to discharge back into the line; the current in the line then flows in the opposite direction with a consequent reversal of the polarity in the series core B, thus occasioned by the change in the field of the series coil A. Also, since the shunt coils C and C are con- nected in parallel with the main circuit, it follows that the direction of current flow in these coils remains constant, irrespective of the direction of current flow in the main circuit, and the polarities of the shunt coil cores D and D' accordingly remain constant. Furthermore, due to the change of polarity in the series coil core B, there occurs a similar change of polarity in the pole piece E, and as shown in Fig. 108 the induced north pole of the pole piece E is attracted by the south pole of core D' and repelled by the north pole of core D. This electrical reaction thus resolves itself into mechanically operating the tripping mechanism T of the circuit-breaker, which automatically opens the circuit and prevents the current from the battery from running the generator as a motor. For proper operation of the breaker it is,, obviously, of great importance that the shunt coil leads across the main power buses he connected up in circuit with due regard for polarity. Commercial Application of Floating the Storage Battery on the line. Before proceeding further with the subject, as a matter of historical ref- erence and in order to properly develop the subject-matter of this chapter for service application, it is well to consider some of the prominent appli- cations of the principle of floating the battery on the line and the ultimate means to an end which have prompted its adoption commercially in the electrical world. In this connection it may be stated that the practice of floating the battery first came into favor and met with extensive use on a large scale in the field of commercial power and lighting stations, electrically operated railways, and plants of that type. In the early days, in addition to their regular generating sets for carrying the normal load on the line, these central power stations were equipped with additional auxiliary or stand-by machines which were constantly kept in readiness for immediately connecting in on the line in cases of emergency, Floating the Storage Battery on the Line 257 such as break-downs, periodic high-rate power demands or " peaks " on the line, etc. This was found to be highly essential in maintaining a plant of this type,, as otherwise the break-down might prove of such a serious nature, or the power demand be of such magnitude as to materially impair the effi- ciency of the plant, or even put the plant entirely out of commission, with a consequent paralysis of the various other industrial plants, department stores, office buildings, etc., depending upon their sources of power through the feeder lines from this station. However, as the science of electro-chemical engineering progressed, and when the storage battery had finally been developed to the point of proving a real commercial success, it immediately fell heir to a very important berth in the equipment of these central power and lighting stations. The storage battery in this instance largely replaced the old .stand-by machines and per- formed the function of a stand-by agent, for, owing to its capacity for either giving out or receiving electrical energy, it thus proved a very flexible unit and one which was entirely capable, within certain definite limitations of its inherent capacity, of readily responding to all conditions of load on the line. When operated in this manner it is usual to connect the batteries in parallel with the main generating sets of these stations in order that the batteries may readily be available for emergency discharge or to assist the generating sets in supplying current for the " peaks," thus maintaining constant voltage on the exterior line for any fluctuation of the load; and conversely, when thus connected, the batteries may receive charge when the load on the line ip light or below normal, thereby increasing the plant efficiency. Moreover, when the generators are supplying only enough current at the required voltage to meet the demand on the line, the batteries are neither receiving nor giving out electrical energy, and it is thus that the term Aoating the battery on the line is derived. In other words, the operation of floating the storage battery on the line is a function of the change in the line drop in the circuit between the generating set and the battery terminals. Thus, in the following elementary analytical description, let JE' = Generator voltage. E^ = Battery terminal voltage on open circuit. (7= Current in the circuit. B = Eesistance of circuit between generator and battery terminals. Then (RC) represents the drop in the circuit between the generator and the battery terminals. Hence, (E—RC) represents the line voltage at the battery terminals. Therefore, it follows that : (a) When Ej^= (E — RC), the battery is neither receiving nor giving out electrical energy and is " floating on the line." 858 Storage Battery Manual (b) When E-i-■-, © ® IT ® ir ® ir o ly ® © [] !•• .1, -o ii ® )i * ft M IM * A * A t ^ -M © 296 Storage Battery Manual This case as at present developed consists of four uprights or corner posts, shown at 1 and 2, which form the supports for the sides of the case, and by which the side boards are drawn up against the walls of the jar by means of the adjustable tie-rods, 7 and 8; these tie-rods also permit of adjusting the sides of the case against the jar in order to compensate for the contraction or expansion incident to the drying out or checking of the lumber, as well as the heating of the cell during the initial charge and test discharges. It is therefore possible by this means to maintain the sides of the packing case firmly against the walls of the jar, thus preventing relative motion between the cell and the packing case, which is desirable in preventing damage in transit and subsequent handling; it is also possible by this means to pre- vent bulging or other distortion of the jar when conducting the development charges and discharges. After the cell has received its development charges and discharges and given the necessary re-charge, it is usual practice to go over all of the tie-rods of the packing case and to take-up on them as necessary, but care should be taken in this operation to not set-up on them too tightly, as to do so puts an unnecessary and unequal compression on the jar, which might prove conducive to fracturing the jar in transit. In other words, the tie-rods should be set- up on just sufBciently to prevent relative motion between the cell and the packing case. Some battery manufacturers make a practice of nailing the sides of these packing cases to the uprights after setting-up on the tie-rods, and then removing the tie-rods before shipping the cases; other manufacturers leave the tie rods in position after setting-up on them for the last time before ship- ment, and accordingly do not nail the sides of the case to the uprights. It now appears that either of these methods is equally satisfactory. However, in shipping spare cells in the dry condition, these tie-rods should not be removed, nor should the sides of the cases be nailed to the uprights, as it is necessary to give these spare dry cells their development charges and discharges on board submarine tenders, at naval stations, etc., before placing these cells in commission, and the packing case should therefore permit of the same adjustment during this period for these spare cells as was explained in the case of the development of the other cells prior to shipment from the works of the manufacturers. It will be further noted that the cover of this packing ease is secured to the uprights by means of screws, which feature is conducive to the exercise of care when removing the packing case cover incident to unpackng the cell, as at such times it is very important that special care be taken to prevent damage to the intake vents, filling cylinder, and other fragile parts of the Shipping Storage Batteries 297 298 Storage Battery Manual cell cover. The filler pieces, shown at A, are placed on the under side of the cover and are designed to seat on top of the cell terminal posts when the packing ease cover is secured in position, thus preventing vertical motion of the cell in the case while in transit. The skids, shown at 6, on the bottom of the packing case, are intended to permit of using a small automatic jacking truck or conveyor, of standard commercial design, for transporting these cells in an upright position around the dock, shipping platforms, or other places as desired. The notches, shown at B, on the bottom of the packing case are designed for passing a cargo strap around the case when it is desired to sling it for hoisting on board ship, etc., these notches are also conveniently used for accommodating the special lifting rods or irons used in placing these packing cases in the foreign shipment crates, which crates will later be described. The usual shipping markings, such as " Handle with Care," " Fragile," " This Side Up," etc., should be stenciled in plain lettering on the outside of this packing case, as should also the particular cell number in the given battery installation, type of cell, name of vessel or station for which intended, and in short all information which will promote careful and expe- ditious handling to its ultimate destination. In preparing the spare cells, which are assembled in a " dry " condition, for shipment, it is standard practice to paint the packing case covers of these cells a " battleship gray " in order to easily identify them as spare cells ; the instructions for placing these spare cells in commission are contained in a heavy envelope attached to one of the terminal posts of the cell. These spare cells should not be filled with electrolyte until proper examination of the element has been made and the other preliminary instructions relative to placing these cells in commission have been carried out. Shipping Submarine Batteries by Rail. Special precautions should be taken in loading the packing cases contain- ing submarine cells in the railroad cars. Care should also be taken to not load the car beyond its rated full load capacity, and when practicable a steel frame car, which is in good condition, should be selected for the battery shipment. Each cell should be so stowed in the car and in such relative position with respect to the adjacent cells as will prevent as much as possible any motion of the cells in the car. It has been found that best results are obtained by stowing the cells in an " egg-crate " fashion, that is, each cell is held in posi- tion by a series of athwartship and longitudinal braces composed of lumber of approximately 3" x 3" stock, these braces thus forming a skeleton crib- bing in the car for holding the cells rigidly in position. Shipping Storage Batteeies 299 This method of loading usually resolves' itself into stowing the cells in two groups, one group of cells and the corresponding cribbing being located on each side of the ear doors ; the success of this method depends largely upon the manner of loading the first row of cells in each end of the car, which cells should be stowed firmly or jam-up against the end of the walls of the car, so that each succeeding row of cells can be just as firmly secured in posi- tion, thus preventing lost motion in the whole group. The space in the car in wake of the side doors and between the two groups of cells outlined above should be utilized for the stowage of other battery parts, such as connectors, bolts, nuts, ventilation ducts and fittings, separators, sealing compound, or any other parts; this space between tlie two groups of cells should also be utilized in bracing the two groups of cells against each other by means of athwartship filler pieces consisting of lumber on the order of 4" x 6" stock, this to prevent fore and aft movement of the two groups of cells. It is also a good plan to chart the location of each individual cell in the car such that should the car be damaged in a wreck or other accident, a record of the cells contained in the car will be on file at the factory, and steps can therefore be immediately taken to assemble replacement cells, should the urgency of the occasion demand it. Moreover, it is highly desirable that, when practicable, arrangements be made with the carrier company to bill the shipment through to destination, thus obviating as much as possible the necessity of transferring the cells from one car to another in transit, as a transfer of this kind is usually accompanied by damage unless special care is taken in handling, reloading and securing the cells in the car. Fig. 117 contains a photographic illustration of a condition such as might be ex- pected when the cells are not properly stowed and secured in the car. This particular photograph was taken of a carload of batteries upon their receipt at destination after having been transferred from the original car en route. Obviously, therefore, when the value of the parts, as reckoned in labor, material, and strategic importance, is considered, it is apparent that every effort should be put forth to insure safe and sound delivery at destination, and the subject of properly packing these batteries should be accordingly looked after in great detail. Before loading submarine cells in the cars they should be given a freshen- ing charge at least within two weeks of the date of loading, and they should be watered as late as practicable before securing the packing case covers in ■ position for shipment. It is also a good plan to ship inter-cell connectors, bolts, nuts, washers, cell lifting-devices, etc., with the first carload of cells shipped in order to facilitate expeditious handling at destination, and also to have these part, 300 Stoeage Batteey Manual at hand in case it is desired to connect the cells up for giving them a freshening charge upon receipt at destination. It will usually be found advantageous to ship the cells in the consecutive order in v^hich they are numbered in the battery installation, as in such cases the work of installation can be begun prior to receipt of all of the cells. There are numerous details of shipment, such as have been outlined above, which if studied and con- sidered for each individual shipment will result in efficient and satisfactory service for all hands concerned. Packing Submarine Cells for Foreign Shipment. In making foreign shipments of submarine cells a system of double pack- ing cases is used. The inside case is of the same design as is used for domes- tic shipments which has previously been described and as shown in Fig. 116. This case is placed in another case of much heavier general design and of sufficient dimensions as to allow at least six inches of tightly packed sawdust between the top, bottom, and all four sides of the inside case and the walls of the outer case ; in other words, the inner case containing the cell " floats " in a tightly packed bed of sawdust. In order to prevent the sawdust from entering the cell, the inner packing case should have a sufficient amount of oil-cloth or other such heavy material tacked around it in such manner as to prevent the sawdust from sifting through the cracks and other openings in the inner case. The outer case is equipped with skids to facilitate moving the cell around in an upright position. This case also contains an iron strap or sling securely fastened to the sides and in such manner as to prevent slinging the cell in the cargo falls for hoisting on board ship, etc., in any other but an upright position. The usual conventional shipping markings, such as " This Side Up," " Handle with Care," " This Case Contains Acid," etc., should be plainly stenciled on the outside of this packing case; other identification markings such as the type of the battery, individual number of the cell in the instal- lation, gross and net weights of the case, name of boat or station for which intended, and such other information as will assist in carefully and expe- ditiously handling the cell to its ultimate destination. CHAPTEE XXI. RECEIVING STORAGE BATTERIES. PLACING IN COMMISSION. PLACING OUT OF COMMISSION. Receiving Storage Batteries. Unpack with Care, — The very first step in unpacking a battery upon arrival at destination is to exercise due care in order to not damage the fragile parts of which it is composed. The specifications for batteries supplied to the naval service require that the covers for the packing cases shall be secured in position with screws, and not with nails, in order that these covers may be removed by means of a screw-driver, thus facilitating the unpacking of the battery with a minimum amount of rough handling. After removing the packing case cover carefully lift the tray or cell out of the case, care being taken to maintain the tray or cell in an upright posi- tion, in order to prevent the weight of the element from being carried by the cell cover, and also to prevent spilling the electrolyte, should the cells be shipped in a -filled condition. In ease the battery is too large and heavy for lifting out of the case, it will usually be found convenient to remove one side of the packing case and slide the battery out of the case. For unpacking submarine cells a special lifting-device is provided for attaching to the jar and the cell terminal posts, such that the cell may easily be lifted out of the case by means of a chain fall or other suitable lifting gear. However, on ac- count of their large size and weight submarine cells should not be removed from their packing cases until ready for installation, or if they are tempora- rily removed from the packing cases for purpose of inspection they should be returned to the packing cases as soon as the inspection has been completed in order that the case may form a support for the cell and prevent distortion of the jar walls. Having removed the battery from the packing case clear the tray and cells o.f all saw-dust, excelsior and other packing material and clean the tops of the tray and cell of all dust and foreign matter preparatory to making a thorough inspection of the battery. Should the packing case, excelsior, or other parts show signs of being acid-soaked it is likely that the battery contains one or more leaky jars, in which case it is necessary that they be renewed before placing the battery in commission. Inspection. — After unpacking the battery the next step is to make a thorough inspection of all parts for breakage or other damage which may have occurred in transit. In making this inspection the filling plugs of all 20 302 Storage Battery Manual cells should be removed for the purpose of ascertaining the height of the electrolyte above the tops of the plates and separators ; pure distilled or other approved battery water should accordingly be added to the cells as may be found necessary to bring the level of the electrolyte to the proper height. Should a cracked or broken jar be found, the cell containing such jar should be disconnected from the other cells and removed from the tray in order to renew the broken jar; in renewing the jar the cell connectors should be removed, and the sealing compound lifted with a hot putty-knife in order to unseal and remove the cell cover for lifting out the element. After re- moving the element it should be thoroughly inspected for ascertaining the condition of the plates and separators, and renewals of these parts made as may be found necessary. In case it is found that the element is dried out, or that the plates are in a badly sulphated condition, it will usually be found necessary to give the cell a special treating charge in order to restore its capacity. This treating charge is usually conducted at the prescribed finishing rate of the particular type cell in question. Before watering, hydrometer readings should be taken of all cells in order to determine their states of charge. After watering, the cells should be connected up and given a freshening charge at the earliest practicable opportunity. It is especially important in maintaining the plates in good condition that the freshening charge be given within 100 days from the date on which the battery was last charged. Storage. — In case it is not desired to place the cells in service immediately upon their receipt, after having made the detailed inspection as outlined above, they should be stored in a dry place, preferably in a building in which the temperature is moderate and where ample ventilation is ^.fEorded. Dur- ing the storage period the cells should be watered regularly as necessary to keep the level of the electrolyte at the proper height, and also a freshening charge should be given to the cells within every 100 days that they remain in storage. The tops of the cells, including the connectors, terminal posts, etc., should also be cleaned periodically during the storage period in order to keep them in a neat serviceable condition. Placing in Commission. Procedure Depends Upon Method of Shipping. — The procedure to be fol- lowed in placing storage batteries in commission depends upon the special method employed in assembling the cells and preparing them for shipment, that is, whether they were shipped filled, unfilled, dumped, dumped and washed, dry or hone-dry. Also, in each case the detailed instructions issued by the battery manufacturers should be studied and carefully followed in placing the batteries in commission. Rbobiving Storage Battekie8 303 Batteries Which Have Eeceived Their Initial Charge Prior to Shipment.— As a matter of policy batteries which have received their initial charge prior to shipment should in general be given a freshening charge at the earliest practicable opportunity after their arrival at destination, whether they were shipped with or without electrolyte, the latter case obviously re- quiring that the cells be filled with electrolyte before conducting the fresh- ening charge. In this regard great care should be taken to insure that only chemically pure sulphuric acid and distilled or other approved battery water are used in mixing the electrolyte for the cells, as this feature constitutes one of the most important ones looking to the satisfactory operation of the bat- tery. The subject of preparation of electrolyte as well as that of watering battery have been covered in detail in other chapters. Batteries Which Have Not Received Their Initial Charge Prior to Ship- ment. — Before attempting to place in commission batteries which have not received their initial charge, the necessary facilities for conducting the initial charge through to completion should first be made available. This includes proper charging equipment, facilities for mixing and pouring the electrolyte, accurately calibrated instruments such as ammeters and volt- meters, the usual acid testing sets such as hydrometers and thermometers, and an ample supply of appropriate forms for recording the various data as the initial charge progresses. It should here be stated that much of the future success in operating the battery depends upon the manner in which the initial charge is conducted, and special attention should therefore be devoted to this subject. The details in connection with conducting the initial charge are outlined elsewhere in this volume and should be studied carefully in con- junction with the special instructions issued for placing the particular type of battery in commission. Spare Cells — Submarine Type. — With present stage of the art it is the accepted policy in the submarine service to supply for these batteries the spare cells assembled in a dry condition; that is, no wood or rubber separators are installed between the plates at the time of assembly, but these separators are shipped in separate containers and are to be installed later when placing the cell in commission. Wooden spacing boards of the combined thickness of the regular wood and rubber separators are installed between the plates when assembling the plate groups in order to preserve the proper plate separation and to thus prevent relative motion of the plates and the probable damage incident thereto in handling the cell prior to installation of the regular separators. In some instances, however, the rubber separators are installed with the dry wood spacing boards at the time of assembling the plate groups, in which case the thickness of these wood spacing boards is the same as that of the 304 Storage Batteet Manual treated wood separators, thus preserving the proper amount of spacing between the plates as well as maintaining the proper compactness in the groups until ready to install the regular treated wood separators. The treated wood separators are packed in hermetically sealed cases in order to prevent them from drying out and these cases should therefore be not unsealed until ready to install the separators. If the treated wood sepa- rators be allowed to dry out they are thus rendered unfit for installation in the cells. When it is desired to place in commission a spare cell which has been assembled in the manner described above, it is necessary that .special prepar- FiG. 118. — A Set of Element Clamps. ations be made and certain equipment be provided in order to obtain best results in this operation. The following equipment and method of pro- cedure when used in conjunction with any special instructions or equipment issued with a given type of battery will in general prove satisfactory for placing in commission these spare cells. Equipment Eequired. — (a) Element and cell lifting device. (b) Differential chain hoist or other tackle capable of supporting the completely assembled cell when filled with electrolyte. (c) At least two, and preferably three, sets of element clamps for prevent- ing the " fanning " or spreading motion of the plates when the element is removed from the jar. These clamps can easily be made on board ship or Ebceiving Storage Batteeies 305 other place as necessary, each set consisting of two hard wood boards, two tie-rods of i" or f " in diameter threaded at both ends, and a corresponding set of four washers and nuts. The boards should be approximately 2 inches thick, 3 or 4 inches wide, and about 13 inches longer than the width of the element, such that the boards extend about 6 inches beyond the vertical edges of the element when the clamps are secured in their proper positions. A hole of sufficient diameter to freely accommodate the tie-rods should be bored at about 2 inches from each end of the boards. The tie-rods should be at least 8 inches longer than the combined thickness of the boards and the element, and threaded sufficiently on each end to permit of ample spreading of the plates when removing the spacing boards and installing the regular wood and rubber separators, as well as to afford the proper amount of draw or compression of the plates and separators when it is desired to re-install the element in the Jar. Fig. 118 contains an illustration of a set of these clamps from which a clear idea of their construction and use may be obtained. (d) Two sets. of sheet brass or copper element guides for use in re-instal- ling the element in the jar. Each set of guides consists of two pieces of sheet copper or brass, one set being used for guiding the edges of the plates, while the other set is for guiding the flat faces of the element into the jar. The set for guiding the edges of the plates should be at least |" less than the inside length of the jar, while the other set should be at least ^" less than the inside width of the jar. Thus it will be seen that these guides serve the pur- pose of " shoe-horning " the element into the jar. (e) The required number of treated wood separators. As a rule from 10 to 15 per cent in excess of the number actually required should be provided to make up for breakage in handling, etc., as the wood separators are com- paratively frail. (f ) The required number of rubber separators. (g) The required number of hard rubber plate support and separator support pins or rods. (h) Terminal sealing nut wrench. (i) Lead-lined, rubber, or earthenware tank for containing the electrolyte. (j) Rubber buckets, gloves, and aprons for handling the acid. (k) Necessary amount of sealing compound. (1) Appropriate vessels for melting and pouring the sealing compound. (m) Necessary amount of oakum and soft rubber tape for use with the sealing compound in sealing the cell cover in position. Method of Procedure. — The spare cells assembled as described above have not been sealed with sealing compound, and it is therefore only necessary to remove the oakum from the channel-way formed between the walls of the jar and the dome of the cover. After removing the oakum, next remove the 306 Storage Batteet Manual terminal sealing nuts by means of the terminal sealing nut wrench, and, after attaching the cell lifting device to the cell terminal posts, lift the element from the jar by means of the chain fall or other suitable lifting gear. Fig. 119 contains an illustration of a type of terminal sealing nut wrench used with these batteries. Kow, remove the separator support pins from the bottom of the element, and then remove the dry wood spacing boards from between the plates, being careful to not " fan " or spread the plates far enough apart as to place an undue strain upon the plate lugs. Care should also be taken when removing Fig. 119. — Terminal Sealing Nut Wrench. the spacing boards to prevent as much as possible the dislodgment of the active material from the plates, as due to the dry condition of the plates some of the pellets of active material may become loose in the grid, and special care should therefore be taken to guard against loss of active material during this operation. In general, such pellets as may become loose through drying out, as mentioned above, usually expand and again tighten themselves in the grids when the acid is poured in the cell and during the development charges and discharges an subsequent cycles. Having removed the wood spacing boards, next begin the installation of the regular separators by taking a treated wood separator and a rubber sepa- rator and placing them together in their proper relative positions as installed Ebceiving Stoease Battekies 307 in the cell, that is, the ribhed side of the wood separator is placed against the rubber separator; by thus handling each pair of these separators as a single unit the next step is to place them in position between the plates. Starting at one end of the element, with a diagonal motion slip the separator unit up between the first two plates, the rubber separator being habitually placed in contact with the positive plates, while the wood is placed in contact with the negative plates during the entire course of the separator installation. Continue this diagonal sliding motion until the separators are placed in their proper positions, the bottom and side edges of the separators being lightly tapped with a mallet and block of wood as necessary to exactly line them up with the edges of the plates as well as the separator support pins. It is especially important that no separators be allowed to project beyond their positions in respect to the edges of the plates, as on account of the small clear- ance allowed between the edges of the plates and the walls o| the jars, such separators will be injured when installing the element in the jar. Upon completion of the installation of separators, next install the hard rubber separator support pins and secure the element clamps in position preparatory to lowering the element into the jar. In order that no unequal strains will be put upon any portion of the plates during this operation, all clamps should be set up on uniformly in succession, that is, by setting up a little on one set and then a little on the other set, and so on until the element is sufficiently compressed for lowering away into the jar. Before installing the element, a thorough inspection should be made of the jar in order to detect any defects, and especially to insure that the interior of the jar is clean and free of all bolts, nuts, washers, nails, tools, or any other objectional foreign matter. Now, ship these two sets of element guide sheets into position around the top edges of the jar, the upper edges of these sheets being turned over in such manner as to permit of hanging or supporting them in position from the top edges of the jar. This done we are now ready for installing the element in the jar. Begin this installation by slacking off on the chain falls and thus gently lowering away the element, having care to guide the bottom edges and feet of the plates into position as they enter the jar. When the bottom of the element has entered the jar sufficiently then remove the element guide sheets and continue lowering away the element until the bottom set of element clamps is about level with the top of the jar. If the element is easily entering the jar, the bottom set of element clamps may be removed entirely, but in case there is a tendency for the element to " stick " or jam against the walls of the jar, it will usually be found better to progressively shift up the position of the clamps as necessary to effect proper installation of the element. In regard to this feature it should be stated that if properly designed with 308 Storage Battery Manual respect to plate clearances, thickness of separators, etc., each element should be capable of installation in the Jar without the application of any force other than the weight of the element itself, in other words, the weight of the element should be sufficient to force it home into the jar. However, should the element be found to bind slightly against the jar walls, it will usually be found that it will slide home by gently rocking the jar or by raising and lowering the element a little at the time, by taking up on and slacking off on the chain falls, thus gently working the element down into the jar. The main objection to using force other than the weight of the element itself when installing it in the jar rests in the fact that such installation places an unnecessary bursting strain on the inside of the jar which may prove conducive to cracking the jar when the cell is placed in commission and installed in the boat, and since the question of a broken jar may, under cer- tain conditions of operation, prove a very serious one, it is therefore very important that every possible precaution be taken to guard against the occurrence of a broken jar. With properly designed element it may be found that the binding or jamming of the element is caused by some or all of the separators running a little full in thickness, in which case a suitable set of separators of the proper thickness should be selected and installed before proceeding with the installation of the element. The element having been installed such that it rests firmly and squarely upon the supporting ledges of the jar, the next step is that of installing and sealing the cell cover in position. Place the cell cover in position such that it rests squarely upon the soft rubber terminal post gaskets which are seated on top of the shoulders cast on the post straps, care being taken when doing this to insure that the edges of the cover do not bind at any point against the walls of the jar. Having thus shipped the cover, screw on the terminal sealing nuts and set up on them gradually and uniformly in succession in order to not strain the cover at any point. These nuts should be set up on sufficiently to seat the cover firmly in position against the soft rubber gaskets and such that an acid tight joint is effected between the cover and the post- straps. Now, lay the soft rubber tape around the channel-way formed between the cover and the jar walls, after which pack a layer of oakum on top of this soft rubber tape. The cover is now ready for sealing by pouring the sealing compound. Although, when it is properly done, pouring the sealing compound is a comparatively simple operation, it nevertheless requires a certain amount of care and technique in order to effect a neat and satisfactory seal around the jar, which is very important from an operating point of view, since after all it is the sealing compound that makes the cell both acid and water tight. Eecbiving Stoeage Batteeies 309 When pouring the compound it should be just hot enough to run freely into all crevices around the channel-way of the cover, thus filling all openings through which acid and water could pass. If the compound be too hot while pouring it will be found that it contracts considerably in cooling, forming hollow spots or honey-combs in the body of the compound which impairs its sealing properties. Also, pouring an excessive amount of compound should be guarded against, since the surplus compound must be trimmed off, leaving a ragged surface which must be smoothed off with a hot putty-knife or flame. A clever workman thus has his sealing compound at the proper temperature and only pours sufficient compound to properly seal the cell, leaving a smooth finished surface to the compound upon completion of the sealing operation. The surface of the compound should be finished off flush with the flat top of the cell cover in order to eliminate any pockets in which moisture, acid, or dirt could collect. Having sealed the cell as outlined above, next pour the electrolyte into the cell, this electrolyte being of the required density to produce the desired full charge specific gravity upon completion of the initial charge. In gen- eral, due to the water contained in the treated wood separators, it will be found that the specific gravity of the electrolyte poured into the cell will have to be from 30 to 30 points (.030 to .030) higher than the required full charge value of the electrolyte. After pouring the electrolyte the cell should be allowed to stand until the electrolyte has cooled sufficiently for beginning the initial charge ; the tem- perature of the electrolyte should not be above 100 degrees Fahrenheit, and preferably lower, when beginning the initial charge. The method of conducting the initial charge is covered in detail in another chapter. Placing Out of Commission. Method of Placing Out of Commission. — Should it be desired or found necessary to lay-up or. store away a battery for an indefinite period, or for a period which exceeds 10 or 13 months, it will in general be found both con- venient and economical to place the battery out of commission, since when out of commission the usual upkeep routine such as freshening charges, periodic watering, cleaning, etc., is not required. A satisfactory method of placing out of commission batteries of the unit assembly type may be outlined as follows : First. — The battery should be given a thorough equalizing charge in order that all acid contained in the plates may be driven out preparatory to remov- ing the elements from the jars. Second. — Disconnect each cell by removing all inter-cell and terminal con- nectors. Also remove aU terminal post nuts, gaskets, etc. 310 Storage Battery Manual Third. — Unseal the cell by passing a hot putty-knife through the sealing compound, and, after clearing away all sealing compound from around the cover, remove the cell cover. Fourth. — Lift all cells out of the trays. Fifth. — Lift the elements out of the jars, after which gently separate the positive and the negative groups, being careful to not injure the active material. Sixth. — Eemove the separators from between the plates. It will usually be found to not prove worth while to attempt to save the wood separators, and consequently they should be discarded. However, the rubber separators will usually be found to be in good condition, and in most cases can be saved for re-installation. Seventh. — Eemove the acid from the positive and negative groups by rins- ing them sufficiently in fresh water. Then rectify any defects in these groups, such as straightening out the grids, pressing the active material back in position, etc. These features will be taken up in detail later. Eighth. — Eemove all acid from the jars by dumping out the old electrolyte and rinsing them out thoroughly with fresh water. Place the jars bottom side upward in order to allow all acid and water to drain out preparatory to re-installing the groups for storage. Ninth. — Soak the trays in a strong caustic soda solution contained in a tub, barrel or other vessel in order to neutralize all acid contained in and around the trays ; then thoroughly clean and dry them preparatory to storing them away in a clean, dry place. Tenth. — After thoroughly cleaning all parts as outlined above, assemble or enmesh the positive groups in pairs in the jars, and likewise the negative groups preparatory to storing them away. In some instances it may prove desirable to place the jars containing the groups in the trays and thus storing them away together. Preparation of the Various Parts for Storage. — In the preceding para- graphs we have considered in a general way the successive steps which are necessary in placing a battery out of commission, so we will now take up in detail the preparation of the various parts for storage. As previously ex- plained, the plates should be fully charged before disassembling the battery for placing out of commission, and the detailed account of the treatment of the various parts will be begun with the plates. Negative Plates. — Due to the fact that charged negative plates heat up as a result of the oxidization of the surface active material when exposed to the air, the negative groups should therefore be taken care of first after separating them from the positive groups. Receiving Stoeage Batteeies 311 The negative groups should first be rinsed off in clean fresh water and then placed on a clean bench or table to allow the acid and water to drain from them. For reasons which have been stated above, it will generally be found that the negative plates will show signs of heating and will steam when first placed on the bench, in which case they should be sprayed or sprinkled with fresh water to cool them off, continuing this spraying at intervals as necessary until the plates cease to show signs of heating. The negative groups should then be examined to determine the condition of the plates and other parts. If it is found that the pellets of active material have expanded or bulged out beyond the surfaces of the grids, this active material should be pressed back into position while soft and before it becomes dry. A very convenient method of pressing this active material back into position is by placing clean, smooth wooden boards, of the proper size and thickness, between the plates and pressing them together in a plate press, or if a special plate press be not available, an ordinary bench vise will very well answer the purpose. It is especially important that this over-expanded or bulged active material be pressed back into position in order that proper contact with the grid may be restored, since if proper contact with the grid is not made, the plate will not give its required capacity. It is also important that the spacing boards be of sufficient size to entirely fill the space between the plates in order to prevent fracturing the plates when they are pressed together. Should any of the edges or corners of the plates be buckled, they should be straightened, a pair of fiat nose pliers being very convenient for this work. After straightening and pressing the plates as described above, the groups should then be immersed in sulphuric acid of about 1.250 specific gravity, or. the old electrolyte removed from the battery may be conveniently used for this purpose. The groups should be allowed to remain in this acid for from 3 to 5 hours, after which they should be removed from the acid and allowed to dry without further washing. Then, placing the groups together in pairs, place them in jars preparatory to storing away. This process produces the required amount of sulphating action in the plates to maintain them in good condition while stored away. In some cases it will prove very convenient after straightening and press- ing the plates to place a pair of negative groups in each Jar, and then to pour the acid over them and thus allow them to stand for from 3 to 5 hours, after which pour off the acid and store the jars and groups away without removing the groups from the jars. Positive Plates. — The positive groups should be rinsed off by gently dip- ping them in clean fresh water, in order to remove the acid, sediment, and 312 Storage Battery Manual any foreign matter from them, having care in this operation to dislodge as little of the active material as possible. This active material is usually soft and of relatively frail structure when first removed from the jar, and for this reason under no circumstances should a hose or any other method be used in rinsing tlie groups which will tend to wash this soft " muddy " active material out of the plates. Should it be found that any of the pellets of active material are bulging out beyond the surfaces of the grids, they should be pressed back into posi- tion by either using a wooden paddle or by placing them in a plate press or vise in the same manner as was described for the negative plates. After removing the groups from the press set them on end on the bench and allow them to dry. Then place the positive groups together in pairs and place a pair of groups thus assembled in each jar for storing away. If any of the positive plates show signs of excessive wear they should be cut away from the cross-bars and scrapped, and new plates burned into the groups. As a general rule it will be found that more plate renewals are required in the positive than in the negative groups. For best results all plates should be stored away in a dark place where they will not come in contact with the light. Wood Separators. — Only in rare instances will it be found practicable to attempt to save the treated wood separators ; however, in instances where it appears to prove worth while to save them, the separators should be thor- oughly rinsed off in fresh water, after which they should be packed away in hermetically sealed cases to prevent them from drying out. Rubber Separators. — After scraping oflE all of the sediment, active ma- terial, parts of the wood separators, and any other matter which may have lodged on the rubber separators, they should be thoroughly washed oflE in fresh water or by turning a hose on them. They should then be made up in bundles, by stacking them between wooden boards of approximately the same dimensions as the separators. Another satisfactory method of storing them away is to pack them in appropriate size wooden boxes or cases. Hard Rubber Covers, — Thoroughly rinse the covers off in fresh water or wash them off by turning a hose on them. Should they be found to be warped when removed from the cells they may be straightened by first soaking them in hot water. For storing them away either pack them in suitable cases or place them in their normal position on the jars. Connectors. — Wash the connectors in a bicarbonate of soda solution to neutralize all acid contained on them; then rinse them off in fresh water. After thoroughly cleaning them in this manner make them up in bundles or pack them away in suitable cases. Receiving Storage Batteries 313 Jars. — After removing the elements and emptying the electrolyte from the jars, the jars should be thoroughly washed out with fresh water, being careful to remove all sediment which may have been deposited on the bottom and sides of the jar.- This done, the jars are now ready to receive the groups, as has already been described. Electrolyte. — If the electrolyte is sufficiently pure it should be emptied from the cells into carTjoys, earthenware crocks, or other suitable contain- ers for storage. This electrolyte may also be utilized in preparing the nega- tive groups for storage, as outlined above. If the electrolyte be not pure enough to be used again, it should be thrown away. CHAPTEE XXII. FAULTS. METHODS OF DETECTING AND RECTIFYING. Faults Classified. — The faults which develop in storage batteries may be said to resolve themselves into three general classes, or a combination of them, as follows: (a) Mechanical. (b) Electrical. (c) Chemical. Thus by having the above classes in mind^ and by pursuing a systematic course of inspection and reasoning, the cause for troubles which develop with- the battery should be comparatively easily determined. Moreover, after having determined the cause, appropriate steps for rectifying or remedying these faults can then be taken. The following table contains a list of the faults which are commonly en- countered in operating the storage battery. The methods of detecting and remedying these faults are also appropriately placed in the columns of this table to serve as a guide in determining and rectifying these faults : 1. Broken jar. 2. Poor contact between terminal posts and connectors. 3. Insufficient ventilation. 4. Too much electrolyte in the cells. 5. Leaky or improperly sealed cover. Huw detected. Habitually low electrolyte in the cell. Trays and other parts show signs of being- acid soaked. Low cell voltage. Heating of terminals or connectors. Poor lead-burniniff apparent. Corroded terminals and connectors. Battery overheats. Hydrogen content in surrounding air increases. Visual inspection. Flooding of electrolyte over tops of cells with the consequent grounds and corroded terminal posts and connectors. Cell shows tendency to heat up owing to restricted ventilation. Visual inspection. Signs of corrosion around cell ter- minals, connectors, etc. Top of cover acid soaked as a result of " creeping" of the electrolyte. Moisture grounds ; cell loses charge on standing idle. How rectified. Renew jar. Clean terminals and connectors. Renew joint between terminal posts and connectors. Keep battery clean. Improve the ventilation. Add only a sufficient amount of water to bring level of electro- lyte to proper height above the tops of the plates and separa- tors. Seal cover properly. Faults. Methods op Detecting and Eectifying 315 Faults. How detected. How rectified. 6. Insufficient amount of Visual inspection. Add a sufficient amount of water. electrolyte. Cell heats on charge. Tops of wood separators in charred condition. Tops of plates in sulphated condi- tion. Unable to obtain hydrometer read- ings. 7. Plates short-circuiteil. Battery heats on charge. Lift the element from the jar and Battery will not hold charge. eliminate the short circuit. Gradual reduction in capacity. Presence of defective separator. Presence of lead-drops or other con- ducting material between plates. Buckled plates. 8. Excessive sulphation of Hich cell voltage during charge. Special "treating" charge re- the plates. Low cell voltage during discharge. Loss in capacity. Drop in the specific gravity of the electrolyte. Plates not of norrfial color ; positive plates become a reddish brown while negative plates become a dead whitish giay. Both plates contain white spots of sulphate. quired. 9. Charging at too high a. Abnormal heating of cell. Reduce the changing rate. rate. Abnormal evaporation of electrolyte. Excessive gassing as shown by the " boiling " of the electrolyte. Abnormal shedding of active ma- terial from the plates. 10. Internal or self-dis- Battery will not hold charge on Renew the electrolyte. charge. standing idle. Renew separators if defective. Impurities in electrolyte. Eliminate any short-circuits. Gradually loses catiacity. Keep battery clean, especially the Gradual drop in specific gravity of top of the cell around terminal electrolyte. posts and connectors. Abnormal sulphated condition of plates. Gradual drop in cell voltage. Gassing while standing idle. 11. Buckled plates Visual inspection. Remove element from jar and Plates short-circuited through cut- straighten plates by pressing ting of separators when the buck- them between clean flat boards. ling takes place. If too badly buckled cut plates May be caused by habitually dis- out and renew. charging battery below low volt- Do not discharge below low volt- age limit. Also it may be caused age limit. by charging battery at too high a Use correct charging rate. rate, thus causing the cell to heat abnormally. 12. Lean plates Visual inspection. Cut out lean plates and renew Abnormal amount of sediment in provided remainder of plates in bottom of the jar. group are in satisfactory condi- Marked reduction in capacity. tion. 13. Excessive overcharging. Reduction in capacity through ex- cessive shedding of the active ma- terial from the plates. Wood separators damaged through the high temperatures incident to overcharging. Frequent watering. Reduce amount of overcharging. 14. Repeatedly under- Gradual reduction in capacity. Give the battery an equalizing charged. Gradual drop in specific gravity of electrolyte. Plates -ibnormally sulphated. Reduction in cell voltage. Cadmium readings. charge every two weeks. 316 Storage Battery Manual Faults. 15, Specific gravity will not come up on charge. 16. Acid added instead of water. 17, ■ Salt water in the cell.. 18. Impurities in electro- lyte. 19. Battery frozen . 20. Battery tray an'd other wood parts rotted. How detected. By hydrometer readings. Electrolyte density too low. Excessive sediment in jars. Loose or dirty connectors. Plates abnormally sulphated. / High speciSc gravity of the electro- lyte. Increased local action in cell. Marked Increase in operating tem- perature of cell, \ Unmistakable signs of chlorine gas. Reduction- in capacity. Battery will not hold charge. Abnormal heating of cell. Frozen "slush" formed on the sur- face of electrolyte. Due to allow- ing battery to stand in discharged condition in freezing weather. Visual inspection. Caused by allowing acid to slop on the wood parts. How rectified. Give battery a "treating" charge, then add acid as neces- sary to bring specific gravity to required value. Reduce the specific gravity of the electrolyte. Dump out the electrolyte and give the cell special treatment. Renew electrolyte. Give cell special treatment as required. Keep battery charged. Have electrolyte of proper den- sity. Keep battery clean. Keep wooden parts coated with an acid resisting paint. Series of Photographs Representing Battery Faults. The following series of photographs will give a clear idea of some of the faults which may be expected with storage batteries if they are not given the proper care and attention. Faults. Methods of Detecting and EECTirYiNo 317 ' Fig. 119a. — Showing " Buckled " Plates Which Require Straightening and Pressing. 21 318 Storage Bati^:»x ^i^ Pig. 119b.— Showing the Effects ol Low Electrolyte in the Cell. Note the White Line of Sulphate on Upper Portion of the Plates. Fio. 119c. — Showing the Effects of Freezing on a Group. . If fl I 320 Storage Battehy Manual Pig. 119f. — Showing the Effects of Allowing Electrolyte to Slop-over on the Tray, and General Neglect in Keeping Battery Clean. Note the Corrosion of Connectors and How Tray is Rotted Away. CHAPTEE XXIII. REPAIKS AND GENERAL OVERHAUL. General Remarks on Repairs. — As is the case with all other types of machinery and electrical apparatus the storage battery from time to time during its useful life requires a certain amount of repairs in order to enable it to efficiently perform its allotted duties, and, although these repairs are in general of a minor nature, providing that the battery is operated intelligently and given the proper attention, it is nevertheless necessary that certain tech- nique and principles be employed in order that the repairs may be satisfac- torily made. It is therefore the purpose of this chapter to point out the methods and principles involved in performing certain vifork incident to effecting satisfactory repairs, and since these methods and principles have resulted from a long period of practical experience in operating and repair- ing storage batteries, they represent the best methods and ways of effecting the various repairs, and they should be closely followed in order to obtain best all around results Provide Necessary Tools and Equipment. — Before proceeding further with the subject of repairs and general overhaul, a list of the tools and equipment required for this work will be given, for in order for the battery repair gang to turn out first class work it is necessary that suitable tools and equipment be provided for them. Of course, the amount of Such tools and equipment to be provided will depend largely upon the size of the battery service station, the amount of work to be done, and the extent to which it is desired to equip a given station. ^ The following list, however, represents the tools and other equipment which will in general be found satisfactory for practically all classes of bat- tery repairs, and every well regulated battery repair and service station should be provided with them : 1 Source of direct current with suitable rheostats, charging panels, includ- ing instruments, etc., for charging the batteries. 1 Acid testing set, including hydrometers and thermometers. 1 Portable voltmeter, low reading type. 1 Cadmium stick and prod for taking cadmium readings of the plates. 1 Discharge panel with suitable rheostats for conducting test discharges on batteries before and after repairing. 1 Source of distilled or other approved battery water. 1 Large lead-lined tank for storing battery water. 1 Set of chemical reagents for testing electrolyte (see Chapter IX). 332 Storage Battery Manual 1 Soft rubber bulb syringe for adjusting the.height of the electrolyte in cells. 1 Set of carboys for storing electrolyte. 1 Supply of battery acid (1.400 specific gravity). 1 Eubber apron to protect the clothes from the acid. 1 Pair rubber gloves to protect the hands when handling acid. 1 Pair rubber boots. 1 Pair goggles for wear when mixing and handling electrolyte. 1 Set of rubber buckets for handling electrolyte. 1 Glass or earthenware crock for use in mixing electrolyte. 10 Pounds of bicarbonate of soda for making up neutralizing solution, for washing the hands and other parts of the body while and after hand- ling electrolyte. Fine sawdust saturated with this soda solution has been found very convenient and effective for this purpose. 1 Supply of sealing compound. 1 Metal pot for melting sealing compound. 1 iletal ladle for pouring sealing compound. 1 Putty-knife for working the sealing compound when sealing or unsealing the cell cover. 1 Ball peen hammer for general work. 1 Set of Stillson WTenches, assorted sizes. 1 Set of monkey wrenches, assorted sizes. 1 Set of open end wrenches, assorted sizes. 1 Ratchet brace and assortment of twist drills for drilling the connectors loose from their terminal posts, etc. 1 Center punch for use with ratchet and drills. 2 Sets of square nose pliers for pulling the elements from the jars, removing separators, straightening plates, etc. 1 Set of screw drivers of various sizes for general work around the tray and other parts of the battery. 1 Adjustable hacksaw frame and set of saw blades for general work. 1 Differential chain hoist for handling submarine and other large type cells. 1 Element lifting device for lifting submarine and other large type cells. 3 Sets of element clamps for use with submarine and other large type cells. 1 Lead-lined drip pan for catching the acid drained from the element after removal from the jar. 1 Sink with running water for washing jars, separators, connectors, and other parts. 1 Assortment of wood chisels for cutting out plates, trimming up the cross- bars and other parts after burning-in plates, etc. 1 Wood mallet for use with wood chisels, adjusting separators, etc. 1 Set of end cutting nippers for cutting plate lugs, terminal posts, straps, cross-bars, connectors, etc. Eepaius and General Ovekpiadl 323 ] Lead-burning outfit complete. i Pair colored glasses for use when lead-burning. 1 Triangular scraper for scraping plate lugs, cross-bars, and other lead parts preparatory to lead-burning. ], Assortment of coarse files or rasps, including handles, for dressing-up plate lugs, cross-bars, and other lead parts. 1 Steel file brush for cleaning files. 1 Wire brush for brightening up lead parts preparatory to lead-burning. 1 Supply of lead-antimony and lead-solder sticks for use in lead-burning. 1 Adjustable plate burning rack for lead-burning plates to their cross-bars, straps, and terminal posts. 1 Hand bellows for clearing the element and other parts of lead filings, etc. 1 Bench vise or other type of press for use in pressing the plates after re- moval from the jars. 1 Supply of clean flat boards of appropriate sizes for pressing and straight- ening out certain plates as necessary. 1 Lead lined case for holding a supply of treated wood separators. 1 Assortment of positive and negative plates of various types and sizes. 1 Assortment of rubber separators for the various types and sizes of bat- teries. 1 Assortment of treated wood separators of various sizes. 1 Assortment of cell covers and sundry parts such as soft rubber gaskets, filling plugs, terminal nuts, intake vents, etc., to fit the various types and sizes of cells. 1 Assortment of cell connectors to fit the various types and sizes of cells. 1 Assortment of cross-bar, strap and terminal post castings of various types and sizes. 1 Assortment of rubber jars. 1 Assortment of porcelain insulator skids for cell trays. 1 Supply of acid-resisting, paint for painting cell trays and other wood parts. 1 Complete set of blue-prints of all types of cells, showing all part numbers for use in ordering spare parts, assembling batteries, etc. 1 Set of characteristic curves for all types of batteries for use in conducting test discharges, charging batteries, etc. 1 Set of steel numeral stencils for stamping the numbers on cells, etc. 1 Set of steel stencils marked " Pos " and " Neg " for marking the battery terminal posts. 1 Set of battery record blanks for keeping a record of charges and dis- charges on the various cells. 324 Storage Battery Manual First Make Preliminary Surface Inspection of Battery. — Before attempt- ing to dismantle a battery preparatory to doing any repair work, the battery should first be given a thorough surface inspection, as it is often the case that satisfactory repairs can be made or proper treatment administered with- out even breaking the connections between the cells. Also, when taken in conjunction with this surface inspection it is often possible that by con- sidering the reports or repair letters forwarded to the repair station with the battery, or in questioning the operating personnel, the exact nature of the battery trouble is readily apparent and schedule of the necessary repairs or treatment can then be arranged accordingly. Attention is here invited to the table of faults and methods of detecting and rectifying them as outlined in the preceding chapter. Furthermore, in making this preliminary surface inspection it is very essential that the exterior of the battery be in all respects thoroughly clean, especially on the tops of the cells, around the terminal posts, connectors, etc., and, if the battery is not clean in this respect when received at the repair station, then the very first step in the preliminary inspection is that of clean- ing the battery. This cleaning can be very satisfactorily done by wiping off these parts with a rag dipped in a boiling solution of bicarbonate of soda and water, as this solution not only cleanses the parts, but it neutralizes any acid contained on the exterior of the battery. It is also well in rnaking this preliminary inspection to consider the data contained on the name-plate secured to the battery, as tliisi name-plate should contain the date on which the battery was shipped from the works of the manufacturers, and also the terms of the guarantee. Batteries for the naval service are purchased on a guarantee basis of developing not less than 80 per cent of the rated capacity for a given period (in years) from the date of shipment from the works of the manufacturers. In this regard it may be stated that provided the surface inspection does not indicate any abnormal condition or defects, and if test discharges conducted on the battery show it to be as low as 70 per cent of rated capacity, the chances are that the plates are worn out, in which case the battery should either be replaced or, if prac- ticable, such parts as are ia satisfactory condition salvaged and battery re- built. The successive steps in making the preliminary inspection and arrang- ing a schedule of any repairs or treatment found necessary and as outlined above may be summarized as follows : First. — See that the exterior of the battery is thoroughly clean. Second. — Make inspection for loose or defective connectors and terminal posts, poor lead-burning, defective sealing of the cell cover, height of the electrolyte in the cell and note how much water is required to bring it to the proper level over the tops of the plates and separators, specific gravity of the electrolyte, and cracked jar, cover or other broken parts. Eepaiks and General Ovebhadl 325 Third. — Consult any letters, records or reports submitted with the battery, or, if possible, question the operating personnel. Fourth. — Also consult the data contained on the battery name-plate. If no defects are apparent from the surface inspection, see battery charged and conduct test discharges for available capacity for comparison with normal rat^d capacity. Fifth. — If the inspection of the battery shows that the cause of the trouble is external or that the faults can be rectified without unsealing the cell, then FiG. 120. — Drilling Connector Loose from Terminal Post. take necessary steps to rectify them by eifecting repairs or administering proper treatment. Sixth. — If trouble lies within the cell and cannot be rectified by treatment, unseal the cell and proceed with necessary repairs. Drilling Conne.ctors Loose from Terminal Posts. — In order to disconnect cells having their connectors lead-burned to the terminal posts it has in gen- eral been found that the best method consists in using a ratchet brace and twist drill, the drill to be slightly larger in diameter than that portion of the terminal post which passes through and is lead-burned to the connector. The hole should be carefully centered with the terminal post and should be 326 Storage Battery Manual drilled to a depth which is slightly in excess of the thickness of the lead- burned portion of the connector in order to allow the connector to be lifted or pried off of the terminal post. In order to reduce the amount of labor required when building-up and re-burning the connector to the terminal post, the hole should be drilled no deeper than is necessary for freely remov- ing the connector. Fig. 120 contains an illustration of this operation. After removing the connectors clean oft' the top of the cell and remove all lead shavings or drillings deposited while drilling the connectors loose, having care to prevent any of these lead particles from entering the cell. Unsealing Cell and Removing Cover. — After removing the connectors as described in the preceding paragraph the next step in opening up the cell for inspection and repairs is that of unsealing the cell and removing the cover. Take a hot putty-knife, such as shovra in Fig. 121, and by passing it with a gouging or scooping motion remove all sealing compound from the channel- way formed between the dome of the cover and the inside walls of the jar. Pig. 121. — Putty-Knife Used in Removing Sealing Compound. In performing this operation it is very essential that the inside walls of the jar be thoroughly scraped clear of all compound in order to prevent the edges of the cover from binding when removing from the jar. In case soft rubber tape and oakum are used in sealing the cell, these materials should also be removed from around the cover before attempting to remove the cover. In some instances it will be found convenient to heat the compound with a flame, such as that from a lead-burning tip or from a blow-torch, but in such instances, and in order to prevent an explosion, care should be taken to insure that the interior of the cells are cleared of all gases before bringing the flame near the battery; an air hose or a hand bellows will be found satis- factory for this purpose. Care should also be taken in using this flame not to injure the cover, jar, or any other parts of the cell. ISTow, take two pairs of flat nose pliers and by gripping the top of a ter- minal post of each group of plates, lift the element and cover vertically until they are clear of the jar. In this regard provided the cover, terminal posts, gaskets, etc., are found in good condition, it will generally be found best to Eepaies and Geneeal Oveehadl 337 remove the cover and element intact from the jar,. since if the trouble is found to be with separators or of any other nature which can be remedied without detaching the cover from the element, much unnecessary labor and probable breakage will manifestly be saved. The above description applies to the portable types of cells, as the method of procedure for unsealing submarine and other large type cells is contained elsewhere in the text. Dis-assembly and Inspection of Element. — Having removed the element from the jar and after allowing all electrolyte to drain from the plates and separators, in preparing the element for inspection place it on a clean flat top table or work-bench, the element thus resting on the normal vertical edges of the plates. This done, it will usually be found that the plates are best inspected after removing the separators. To remove the separators, gently spread or " fan " the plates apart, having care to not spread them any further apart than is actually necessary for removing the separators; the separators can be very conveniently removed by pushing them out with a putty-knife, or by pulling them out from the bottom of the element by means of a pair of flat nose pliers. The rubber separators will usually be found in satisfactory condition for re-installation after thoroughly washing them, but in most cases it will prove more satisfactory in the end to not attempt to re-install the old treated wood separators, and a fresh supply of these separators should therefore be kept on hand for repair purposes. If upon inspection it is found that some of the plates will have to be re- newed, then remove the terminal sealing nuts and lift the cover from the element, after which gently separate the groups. We are now ready to pro- ceed with cutting out the defective plates and burning in new ones. It should here be stated that the negative plates will generally show signs of heating when they are removed from the jar and exposed to the air, in which case they should be kept cool by dipping or spraying them as necessary with pure fresh water. If only the positive group requires plate renewals, then the plates of the negative group should be immersed in fresh water or electrolyte until ready to re-assemble the element. Cutting Out Plates. — As a guide in the inspection of the groups to ascer- tain if any plate renewals are necessary, a few of the principal points in connection with this work will be given. In this regard it may be said that during the normal operation of the battery there is in general more wear on the positive plates than on the negatives, and for this reason it wiE. usually be found that more plate renewals are required in the positive than in the negative groups. 328 Storage Battery Manual Let us begin by first considering the visual characteristics of plates which are in normal healthy condition, and from which a comparison can be made with plates which are not up to standard. Positive plates which are in a fully charged, healthy condition and which have just been removed from the electrolyte, are of a dark brown chocolate " fudge " color, and the active material is of a firm consistency and is in good contact with the grid. When in a discharged condition these plates are of a rusty, reddish color. Negative plates which are in a fully charged, healthy condition, and when just removed from the electrolyte, are of a " battleship-gray " color, and the active material is in good contact with the grid. If when scratched with the linger nail or with a knife the scratched surface of the plate presents a lustre or a shiny appearance such as that from a mark made by a soft lead pencil, it is an indication that the negative active material is in good healthy con- dition. When in a discharged condition these plates are of a lighter color than when fully charged. Both the positive and negative plates, when dried out but in good con- dition, are of a lighter color than described above. However, it does not necessarily follow that all plates, which do not have the appearance of the normal, healthy plates described above, will have to be cut out and renewed, for many plates which are in poor condition as regards capacity and which do not present a good appearance can sometimes be restored to satisfactory condition by administering proper treatment. Each case of a battery overhaul involving plate renewals will have to be decided upon its own merits when taking into consideration the nature of the duty to be performed by the battery, the facilities for making repairs, and the spare plates and other parts which are available. As a general rule, however, it may be said that plates which answer to the following description should be cut out and renewed : (a) Plates in which the active material is worn away to the extent that the bases of the grid-bars are exposed; in other words lean plates, as very little capacity is obtainable from such plates. (b) Plates which are so badly buckled that they cannot be satisfactorily straightened. (c) . Plates having cracked grids. (d) Plates which are so badly sulphated that their capacity cannot be restored with the usual " treating cycles " which are described elsewhere in the text. (e) Positive plates having abnormally soft " muddy " active material. (f) Negative plates in which the active material is bulged or expanded to such an extent that it has lost its conductivity through improper contact Eepaies and Gbnbeal Overhaul 329 with the grid, and which cannot be satisfactorily restored by pressing the plates. (g) Negative plates the active material of which has shrunken or con- tracted to the extent that conductivity is lost through improper contact with the grid. (h) Plates in which the pores of the active material have become clogged or congested through the deposit of metallic or other impurities contained in the cell. The work of cutting out defective plates from portable types of batteries can be very conveniently done by sawing the plate lug loose from the cross- bar by means of a hack-saw, or sometimes a pair of end cutting nippers such as are shown in Pig. 122 will be found very handy for this operating. Por cutting plates out of submarine and other large type cells a wood-chisel and mallet will usually prove satisfactory. Straightening and Pressing the Plates. — As has been stated, sometimes it will be fouud that plates which are buckled or which have their active Fig. 122. — End Cutting Nippers for Cutting Plate Lugs, Cross-Bars, Etc. material loose in the grid can be placed in satisfactory condition by straight- ening them or by suitably pressing them. Plates which are buckled should be straightened by means of a pair of flat nose pliers, care being taken to prevent cracking the grid in this operation. Plates in which the pellets of active material have expanded or bulged out beyond the surface of the grid-bars should be pressed back into position while soft and before it becomes dry. The plates should be gently rinsed off before pressing them, and in view of the relatively frail structure of the positive active material when soft, these plates should be rinsed off by gently dipping them in clean fresh water, and under no circumstances should a hose or any other method be used in rinsing the positive plates which will tend to wash this soft " muddy " active material out of the plates. The structure of the negative active material being of a more durable nature, these plates can be rinsed by spraying them with a hose, but care should be observed to not dis- lodge any of the active material in this process. As stated elsewhere in the text, the negative plates will usually show signs of heating, when exposed to the air and appropriate steps such as spraying or dipping them in fresh water should be taken to keep them cool. 330 Storage Battery Manual A very convenient method of pressing the active material back into posi- tion and of restoring proper contact with the grid consists in placing clean smooth wooden boards, of the proper size and thickness, between the plates and pressing them together in a plate press, or if a special plate press be not available, an ordinary bench vise will very well answer the purpose. The spacing boards should be of sufficient size to entirely fill the space between the plates of the groups in order to prevent fracturing the plates when they are pressed together. I II II II W II II I I II Fig. 123. — Plate Burning Rack. In the case of submarine or other large type cells, it is a good plan to place the plate on a table or bench, and after placing a piece of card-board or can- vas on the plate, press the active material back into position by passing a roller of sufficient size and weight back and forth over the plate, then turn the plate over and repeat the operation. Burning-in the Plates. — After cutting out any defective plates which may have been found and as outlined in the preceding paragraph, the next opera- tion in order is that of replacing the defective plates by lead-burning them to the cross-bars. A special form of rack, called a plate-burning rach, is used for this purpose, an illustration of one of these racks being shown in EepairS and General Ovehhaul 331 Fig. 123. It will be noted from this drawing that this rack consists of a grooved or notched stand upon which the plates are placed, these grooves being used for properly spacing the plates apart. The comb-shaped burning bar at the top of this rack is also slotted for receiving the plate lugs, the slots being so placed that they line up with the grooves in the base of the rack. It will also be noted that the cross-bar, strap and terminal post casting is placed on top of the burning bar such that the plate lugs line up with corres- ponding slots or notches in the cross-bar, and in this manner the plates are lead-burned to the cross-bar. The method of placing the plates in the rack and also that of the cross-bar casting are indicated by dotted outlines in the drawing. These burning racks are usually designed such that they easily permit of adjustment for height and plate separation to accommodate the various sizes of plates and batteries. Pig. 124. — Triangular Lead Scraper Used for Scraping Plate Lugs, Etc. Prom an operating point of view it should be stated that the work of lead- burning the plate lugs to the cross-bar is one of the most important features entering into the construction of the battery, and great care should therefore be observed to insure that a good Job of lead-burning is obtained in this operation, since all current delivered or received by the plate must pass through the plate lug. and also through the lead-burned joint between the lug and the cross-bar. The plate lugs and the inside of the slots and other burning portions of the cross-bar casting should be scraped bright and clean with a triangular lead scraper before beginning the lead-burning operation. A triangular scraper such as is conveniently used in this work is shown in Fig. 121. The sticks of lead or lead-antimony should also be scraped clean before using them in order to permit only clean lead to enter the fused or lead-burned joint. In the case of submarine or other large type cells in which the cross-bar is built up in successive stages while lead-burning the plates into groups it is necessary to scrape the surfaces of each successive layer of the fused lead 333 Storage Battery Manual as it is built up in order that a clean bright surface of metal is always avail- able for fusing or lead-burning to the next layer of metal. Although the triangular lead scraper is also used in this operation, it will be found that in cleaning and brightening up large surfaces of metal for lead-burning, such as in the present case, a wire brush will prove very satisfactory and conveni- ent; a type of wire brush extensively used in this work is shown in Fig. 125. The subject of lead-burning, however, is covered more fully in a separate chapter. Re-assembling Groups, Installing Separators, and Replacing Element in Jar. — After repairing or renewing any plates as found necessary, we are now ready to reassemble the groups and to install the separators. To assemble the groups set a positive group and the corresponding negative group on the work-bench, terminal posts out-board and pointing up, and with the groups facing each other in the normal positions for assembly. Then gently bring the groups together and enmesh the plates in their proper rela- tive positions, being careful to prevent as much as possible the plates from Fig. 125. — Wire Brush Used for Cleaning Lead Parts for Lead-Burning. scraping or chafing against each other in order to not injure or dislodge the active material. The negative group contains one more plate than does the corresponding positive group, and when properly assembled the outside plates of the groups are therefore negatives. Having thus assembled the groups and lined up the edges of the plates with each other, place the groups on edge on a block of wood, terminal posts point- ing away from you and bottoms of the plates facing you. The groups are now in position for installing the separators. To install the separators, take a rubber separator and the corresponding treated wood separator, and after placing them together, ribbed side of the wood in contact with the rubber, gently spread the plates apart and slide the pair of separators into position between the plates, the wood separator being habitually placed next to the negative plate for the reason that the positive active material rots or disintegrates the wood, whereas the treated wood hat a healthful eSect upon the negative active material. It will usually be found that the best results will be obtained by installing the first pair of separators between the plates in the middle of the element, and then wOrk alternately and outward on each side of the first pair of separators installed until the Eepairs and Geneeal Oveehadl 333 installation of all separators is completed. All separators should then be accurately positioned and lined up with the edges of the plates by tapping them with a block of wood or a wood mallet. This done, the element is now ready for installation in the jar. After having thoroughly cleaned the jar and inspected it for any defects, set the jar on the work-bench preparatory to receiving the element. Now, take the element in the hand and set it squarely in the jar such that the plates rest firmly upon the bridges or supporting ledges in the jar. We are now ready for installing the cover and sealing the cell. In case it is desired to run test discharges or to give the plates special treatment after installation in the jar, it may prove desirable to pour the electrolyte into the cell and to conduct the test discharges or the treating cycles before installing the cover. Lifting and Inspecting Element, Renewing Separators, Etc, — Submarine Type. — ^Whenever it is desired to lift the element of a submarine or other large type cell for inspection or repairs, such as for renewing plates or separators, etc., the same equipment should be provided as was described for placing, a spare cell in commission. Chapter XXI, 'srith the addition of a large drip pan for catching any electrolyte or sediment drained from the element. The connectors, cover fittings, etc., should be removed and cover unsealed as has already been described. Provision should also be made for spraying or othervidse cooling the element while out of the jar, and all necessary preparations should be made in advance of lifting the element as will serve to expedite the work of inspection and repair, in order that the element may be returned to the jar as early as possible. If a plate is to be renewed, tap the separator support pins and the plate support pinp out far enough with the aid of another set of such pins as to permit the removal of the plate and the separators on each side of it, these pins thus holding and supporting the other plates and separators of the element in position during the repair work. Cut the plate out by means of a wood chisel or other appropriate tools. Then install the new plate and lead- burn it into position, care being taken to not damage the other plates and separators with the flame, and also to prevent any lead-drops or run-downs from lodging between the plates or separators. Next, drive the plate support pins home and lower the element into the jar. In case it is desired to renew any separators the method of procedure in handling the element is in general the same as described above. Whenever an element is removed from a jar, it .is a good plan to make an inspection of it and to enter all notes in the battery record book for future reference. Soundings should be taken to ascertain the amount of sediment deposited on the bottom of the jar. This data will in general prove useful in estimating the condition of the other cells of the battery. 22 334 Storage Battery Manual After installing the element and sealing the cell, all connectors should be thoroughly cleaned before reinstalling and all cover fittings should also be cleaned and put in good condition as necessary. It is especially a good time to clean the bafBe discs of the ventilation fittings and to overhaul the connec- tions to the ventilation system. Installing the Cover and Pouring the Sealing Compound. — The element having been installed such that it rests firmly and squarely upon the support- ing ledges or the bridges in the bottom of the jar, the next step is that of installing the cover and pouring the sealing compound. Place the cell cover in position such that it rests squarely upon the soft rubber terminal post gaskets which are seated on top of the shoulders cast on the post straps, care being taken when doing this to insure that the edges of the cover do not bind at any point against the walls of the jar; if there should be any tendency for the cover to bind, it should be removed and the edges dressed down as necessary with a mill file. Having thus shipped the cover, screw on the terminal sealing nuts and set up on them gradually and uniformly in succession in order to not strain the cover at any point. , These nuts should be set up on sufficiently to seat the cover firmly in position against the soft rubber gaskets and such that an acid-tight joint is effected between the cover and the termi,nal post straps. Always use the special wrench provided with these nuts in order to not injure or score them when screwing them home. The top of the thread on the post strap should be upset with a center-punch or a nail after setting up on the nuts in order to prevent the nuts from backing off. In installing covers on those types of batteries which contain lead-antimony bushings vulcanized in the cover for lead-burning directly to the terminal posts and connectors, it is necessary that these covers be squarely and firmly placed in position such that an acid-tight joint is effected between the bush- ing and the post strap before attempting to lead-burn these parts together. The cover having been firmly secured in position as outlined above, we are now ready to seat the cell by pouring the sealing compound. Although, when properly done, pouring the sealing compound is a com- paratively simple operation, it nevertheless requires a certain amount of care and skill in order to effect a neat and satisfactory seal around the jar, which is very important from an operating point of view, since after all it is the sealing compound that assists in making the cell both acid and water tight. When pouring the sealing compound it should be just hot enough to run freely into all crevices around the channel-way of the cover, thus filling all openings through which acid and water could pass. If the compound be too hot while pouring, it will be found that it contracts considerably in cooling, thereby forming hollow spots or honey-combs in the body of the compound, Eepairs and General Ovbhhaul 335 which impairs its eilective sealing properties. Also, pouring an excessive amount of compound should be guarded against, since the surplus compound must be trimmed off, leaving a ragged surface which must be smoothed off with a hot putty-knife or flame. Therefore, a clever workingman will have his sealing compound at the proper temperature and will be careful to pour FiQ. 125a. — Pouring the Sealing Compound Around the Cell Cover. only the required amount of compound to properly seal the cell, thus leaving a smooth, finished surface to the compound upon completion of the sealing operation. In this regard it should be stated that the surface of the com- pound should be finished off iiush with the flat top of the cell cover in order to eliminate any pockets or recesses in which moisture, acid, or dirt could collect. Fig. 125 A contains an illustration of pouring the sealing com- pound around the cell cover. 336 Storage Batteey Manual SEixing and Renewing Electrolsrte. — ^When overhauling storage batteries it is a good plan to renew the electrolyte of all cells, since it is one of the prime requisites of satisfactory battery operation that the electrolyte be kept pure. A supply of sulphuric acid of 1.400 specific gravity, commonly known as " battery acid," should therefore be kept on hand for this purpose. Complete details of the equipment required and the method of mixing the acid with the water in order to obtain electrolyte of any desired density will be found in Chapter IX ; it is especially important that no acid which does not conform with the purity specifications, as contained in this chapter, be used. Removing a Single Cell from Tray. — In case it is desired to remove for repairs only one cell from the tray of batteries it will be found necessary in most cases to drill the iater-eell connectors loose from the terminal posts of the adjacent cells as well as from the cell to be removed, especially if rigid type connectors are used. If flexible type connectors are used it will sometimes be found that it is only necessary to drill the connectors loose Fig. 126. — Alligator Pincers Used for Removing Jars from Trays, Etc. from the terminal posts of the cell to be removed, and then to. bend the con- nectors back over the tops of the adjacent cells in order to permit removal of the one cell. Should a Jar show a tendency to stick or bind in the tray it will usually prove advisable to first remove the element, and then after drawing off the electrolyte, fill the Jar with boiling water, which wUl usually soften the rubber and the sealing compound such as to allow the Jar to be withdrawn by means of gripping the top edges with two pairs of pliers or alligator pincers and lifting vertically on the Jar. A pair of alligator pincers such as are con- veniently used for this purpose are shown in Fig. 136. Jars to be Washed Out. — After removing the element and drawing off or dumping the electrolyte, the Jars should be washed out thoroughly with fresh water, being careful to remove all sediment deposited in the bottom of the Jar and on the inside walls. If Jars have been removed from the tray thoroughly examine them for cracks or other defects. In order to test them for leaks fill them with fresh water and after insuring that they are thor- oughly dry on the outside, set them on a piece of dry paper in a warm room and allow them to thus stand for a period of about 5 hours, at the expiration Ebpaies and Genekal Oveehaul 337 of which time any " leakers." will be detected by moisture spots on the paper. A good rule to follow is to never re- install a jar if it is not in the very best of condition, or if there is the least suspicion that it is not up to standard, as it is best in the end to scrap a good jar rather than run the risk of battery trouble later on as a result of a defective jar. Overhauling Trays. — After removing the cells the trays should be gone over and given a thorough overhaul before re-installing the cells. This overhaul should consist mainly in soaking the trays in a warm bicarbonate of soda solution to neutralize any acid contained in the wood and on the tray fittings, after which thoroughly rinse the la-ays oS in clean fresh water and allow them to dry. Then go over all of the tray fittings such as porcelain insulator skids, tie-rods, handles, hold-down attachments, and repair or renew these parts as found necessary. All rotten or damaged wood work about the trays should also be repaired and all wood-screws tightened up. All repairs having been made as outlined above, the trays should then be given a couple of coats, both inside and outside, of asphaltum or other acid-resisting paint, and when this paint has thoroughly set the trays are then ready for re-instal- lation of the cells. " Treating Cycles." — In order to restore the capacity of badly sulphated plates or of plates in which the active material has lost contact vidth the grid and has had to be pressed back into position, a special cycle of charge and dis- charge, called a treating cycle, or a series of such cycles, is used. This treatment consists in charging the cells for a long time at a very low rate, this rate to be low enough to produce a maximum gravity reading of the electrolyte with a minimum amount of gassing ancj rise in temperature of the cells. After completing this charge, then discharge the cells at approxi- mately the 10-hour rate and to a final voltage of not less than 1.80 volts per cell, then re-charge as described above ; this treatment thus allows the minute particles of active materials to re-adjust themselves in the plates and to assume their normal healthy condition. By taking cadmium readings of the plates, and also by noting the increase in the capacity developed and in comparing this with the normal rated capac- ity of the plates, the time for discontinuing the treating cycles can be determined. In administering such treatment to badly sulphated plates the specific gravity of the electrolyte should not be higher than 1.200 during the early stages of the treatment or for the first few cycles, as the lead-sulphate con- tained in the plates is more easily reduced in low gravity electrolyte than that of high specific gravity. However, after the plates begin to show signs of satisfactorily responding to treatment, such as by increase of capacity, the specific gravity of the 338 Storage Battery Manual electrolyte can then be brought up to the normal full charge value for con- ducting the test discharges for capacity. If the plates are abnormally sulphated to the degree that they respond very slowly to this treatment, they should be scrapped. Working Drawings and Characteristic Curves. — In order to have at hand a ready reference of the details of construction of the various types of bat- teries used in the naval service, each battery repair station should be equip- ped with a complete set of detailed drawings of these batteries. Each manu- facturer supplying batteries for the naval service is therefore required to furnish with these batteries complete sets of working drawings; these draw- ings in addition to showing the various details of construction and assembly of the batteries also give a stock list of the individual parts, the materials of which they are composed, the number of such parts required per battery, as well as the manufacturer's individual part number for use in easily identify- ing the various parts when it is desired to order spares. Thus, with each drawing numbered, and also with each individual part on the drawing carry- ing an individual number, it is comparatively easy to identify any part as 4esired. Characteristic curves are also supplied by the manufacturers with all batteries issued to the naval service. These curves are for the guidance of the operating personnel and show the ampere-hour and the kilowatt-hour capacities for the various rates of discharge; capacity correction curves for temperature coefficient; initial, average, and final voltages for the various discharge rates; charging curves and various data relating to the different conditions of operation. A typical set of these characteristic curves is shown in Fig. 97. These characteristic curves are especially useful for conducting capacity tests in the battery repair stations in order to ascertain the available capacity of a battery and for comparison with the normal rated capacity, or that as shown by the characteristic curves. Proper charging rates are also obtained from these curves. General Overhaul — Submarine Battery. — With the present practically excliTsive application of the unit assembly type cell for submarine battery installations, the subject of the general overhaul of the battery does not require as much time and labor, in so far as the crew of the boat are con- cerned, as was formerly the case when the old tandem type installations were used. In fact, in so far as the boat is concerned what was originally termed a battery general overhaul period now resolves itself into a battery renewal or replacement period, since when the battery is so far gone as torequire a general overhaul, this battery should be removed from the boat and a new one installed. The old battery should then be sent to the battery repair and Eepaies and Gbneeal Overhaul 339 service station to be put in proper condition for reinstallation in the boat at another time or for replacing a battery in another boat as the case may be. In the ease of trouble developing with certain individual cells of a sub- marine battery, such cells should be removed from the boat and replaced by cells which are kept on trickling charge on board the submarine tender and ready for immediate installation in a boat when required. The defec- tive cells or hospital cells thus removed from the boat should be placed on board the tender and overhauled by the battery repair gang in the battery service station on board. When these cells are again in normal healthy con- dition they should be placed on trichling charge and thereafter kept in condition for immediate installation as replacement cells on board a sub- marine when required. In this way cells are always kept in readiness on board the tender for installation in the submarine and the submarine battery is accordingly kept in full commission. In case of an accident in which so many cells and other materials are damaged that the tender cannot supply the replacement cells and material, an immediate summary of the extent of the damage and the amount of re- placement material required should be dispatched to the navy yard or station which the submarine is to visit in order that this material or replacement cells may be made available upon arrival of the boat and such that repairs may be effected at the earliest moment. It should be borne in mind that when her battery is out of commission a submarine is of little or no military value, and the necessity for perfecting organization to the end that submarine bat- teries be at all times kept in commission and in good condition is therefore very apparent. Moreover, it is the duty of everyone having any connection with the operation of the storage batteries on board a submarine to familiar- ize himself with all details of the construction of the battery, and also with all rules and instructions which are issued for the proper care and mainte- nance of these batteries. Method of Locally Lead-Plating Copper Connectors, Terminal Posts, Etc. — By using the process and equipment described below it will often be found convenient and comparatively easy to locally lead-plate or touch-up exposed copper spots on lead-plated copper terminal posts, connectors, etc., which may have become worn or damaged, without disconnecting or removing the cells from the battery. Preparation of the Plating Solution. — The plating solution for this opera- tion is made up by taking some clean sand and thoroughly saturating it with hydroilouric acid, after which neutralize this mixture with lead carbonate, litmus paper being conveniently used as an indicator in this process. Then to this mixture add about 20 per cent, by volume, of hydroilouric acid and 340 Storage Battery Ma^jual 1 per cent, by volume, of a good grade of glue or gelatine. This solution should then consist of approximately 30 per cent free hydroflouric acid, 4 per cent lead, and 1 per cent glue or gelatin, the glue or gelatin being put into the solution to prevent the lead from being deposited or plated in the form of " lead trees " on the copper parts. The ingredients for making up this solution can usually be obtained from any navy yard chemist or from any commercial chemist. In preparing this solution be very careful to prevent the mixture from coming in contact with the hands and body. The Plating Process. — ^A six volt battery or direct current from any other source and of any voltage may be satisfactorily used in this process, but in order to obtain best results the current rate should be relatively low. It should also be stated that the success of the operation depends as much apon the density of the current and the concentration of the plating solution as it does upon the skill of the operator. In conducting this process connect the positive terminal of the source of current to a piece of pure lead bar or wire around the plating end of which is secured a piece of muslin or other cloth wrapped in bag-like form and ■ containing some of the plating solution; this cloth should also be, kept thor- oughly saturated with the solution during the plating process. Connect the negative terminal of the source of current with the object to be plated and apply the saturated cloth of the positive terminal to the' spot to be plated. Now, with the current flowing, and by firmly rubbing the saturated cloth bag of plating solution back and forth over these bare spots the lead-plating will take place on them. This operation should be continued until the desired thickness of the plating is attained. If current from a 125 volt line is used it will be ncessary to have quite a heavy wrapping of cloth around the pure lead plating wire or stock in order to provide the required amount of resistance for reducing the current to a value small enough for properly conducting the process. Also, if current density and the concentration of the solution be not correct, the plating will take place in the form of a granular structure, and not in the smooth sheet form which is desired and such as will be the case when all details of the process are correct. Fig. 127 contains an illustration from which a clear idea of the details of this process may be obtained. Protective Coating for Steel Decks of Battery Repair and Service Stations. — A very effective method of preparing and coating the steel decks of battery repair and service stations, on board submarine tenders and other ships, in Ebpaies and Geneeal Ovbehaul 341 order to protect the steel from the corrosive action of the acid contained in the electrolyte of storage batteries, consists of the following : First. — Sufficient concrete should be laid upon the steel plates of the deck as to present a perfectly smooth and level surface over the whole deck, a trowel or other suitable tool being used in effecting this even surface. It is Plating Solution in cloth Terminal Post 6 Volt Battery Pig. 127.- -Showing Method of Locally Lead-Plating Copper Terminal Posts, Connectors, Etc. especially important that this layer of concrete be thick enough to entirely cover all rivet heads, butt and lap-joints, and other irregular places in the deck in order to form a smooth even base upon which to lay the sheet lead covering. Second. — On top of this concrete base lay a covering of 6 pound sheet lead, care being taken to cut the lead such that it contains as few seams as possible. After placing this sheet lead covering in position lead-burn all of the seam?, 342 Storage Battery Manual special pains being taken to make a good job of the lead-burning of these seams, as the effectiveness of this method of preserving the steel deck depends largely upon the acid-proof qualities of the sheet lead covering. The out«r edges of this lead covering should be turned up for at least from 1 to 2 feet in order to form a protection for the steel bulkheads of the com- partment. Third. — On top of the sheet lead are to be laid two layers of an acid-resist- ing felt, all joints between the two layers to be lapped. The bottom layer of felt is to be laid on the sheet lead after thoroughly and heavily coating the surface of the lead and the under side of the first layer of felt with an acid- resisting asphaltum compound, this compound to be very hot when applied to the felt and the lead, and the felt should be laid while the compound is hot, weights being used on top of the felt until the compound cools and sets in order to effect a good seal or union between the felt and the lead. iS^'ext, lay the second layer of felt on top of the first layer, lapping all joints between the two layers as pointed out above. Fourth. — After laying the second layer of felt apply to it a heavy coating of the hot asphaltum compound, then while hot pave the top of this compound with vitrified paving bricks, care being taken to press or embed them firmly into the hot compound'. These bricks should be spaced from f " to i" apart on all sides, then place wooden filler pieces in the spaces between the bricks to prevent them from shifting positions, these filler pieces to be of the exact width of the spaces between the bricks in order to effect compactness in the flooring. The height of the wooden filler pieces should be about 1 inch less than the height of the bricks in order to leave a space for a hot layer of the eompoimd to be poured between the bricks and on top of the wooden filler pieces. In filling the joints between the bricks with the hot compound, it is necessary to use great care in all the details of the process in order to obtain a perfectly acid-tight job. The bricks must be absolutely dry, otherwise the compound will not adhere to them. Also, after the joints are poured it is necessary to go over each one of them with a blow torch in order to thoroughly heat the bricks and to bring the compound to the running point such that it will flow into all of the minute crevices all around the bricks and wooden filler pieces. The compound will generally be found to settle considerably during this heating process, in which case a sufiicient amount of hot compound will have to be added to bring it on a level with the top surfaces of the brick paving as it is especially impor- tant that all of these compound joints be brought up on a level with the pav- Eepaies and Genehal Oveehadl 343 ing in order to eliminate all low spots or pockets which would collect dirt, water, acid, etc. The above method if carefully carried out in all details of its construction will be found to constitute a very satisfactory one for preserving the steel deck, and at the same time will produce a very practical and serviceable flooring for the battery repair and service station. Fig. 128.- Vltrlflea PaTlng Brick. / Aephaltum Gompoujid. ,Wood ELller riEces, ^Asphaltmn Compound. --Aold-reelEtlng Pelt, ^sphaitum Compound. [^^"tr^ fi lb. Sheet lead, ement. -■ Steel Deck Plates.. -Method of Preparing Steel Deck of Battery Service Station to Protect the Steel from Acid. rig. 138 contains an illustration of the details of construction of this flooring. Lead drain boxes may be conveniently installed in this flooring as found necessary. All drain pipes and aprons of such drain boxes should be securely lead-burned to the 6 pound sheet lead covering in order to form a perfectly acid-proof joint. Hot compound should also be freely applied between these drain boxes and the brick paving in order to produce an acid-proof joint around the drains. CHAPTEE XXIV. LEAD-BURNING. lead-Burning Defined. The art of fusing or melting together the com- ponent lead parts of the storage battery, as by means of a flame, electric arc, or any other method of applied heat, is technically termed lead-burning. Various Methods in Use. Depending upon the source and the type of the applied heat, the various methods of lead-burning may be stated as follows : (a) Hydrogen gas and compressed air. (b) Compressed hydrogen and oxygen. (c) Oxygen and illuminating gas. (d) Electric arc. (e) Soldering iron. (f) The compound ladle. A description of the equipment used in each of the above methods, including special notes on each of them, will now be given. Hydrogen Gas and Compressed Air. — This method consists in using an hydrogen flame for fusing or lead-burning the parts together and is con- sidered a very satisfactory method, and is one which is in extensive use both in the naval service and in the commercial world. It is especially convenient to use this method when the hydrogen can be obtained in suitable tanks. .Also, special portable lead-burning outfits, including a hydrogen generator, are designed for use with this method and these outfits may be obtained from the regular trade and are very convenient for use where tanks of hydrogen are not obtainable. The principle upon which the hydrogen generator supplied with these outfits operates is that when sulphuric acid is brought in contact with zinc, the acid radical, SO^, combines with the zinc thus liberating hydrogen. The primary reaction involved in this instance being chemically expressed as follows : • Zn -I- H^SO, = Hj H- ZnSO^. Pig. 129 contains an illustration of one of these portable lead-burning outfits, and from which a clear idea of its construction and method of oper- ation may be obtained. Eeferring to this illustration it will be noted that the acid reservoir, shown at A, consists of a lead-lined tank and located such that the sulphuric acid which it contains is fed by gravity through the acid downtake C, and into the lead-lined gas generating compartment B, where Leab-Buening 345 it comes into contact with the small particles of zinc contained in this com- partment, whereupon the hydrogen gas is liberated in accordance with the equation outlined above. The charge of zinc is placed in the gas generating compartment through the hand-hole 2, after which this hand-hole should be closed air-tight by means of the hand-hole plate 10, and the hand-hole plate dog 1. The hydrogen gas being generated as explained above, in tracing its path through the system it will be noted that it passes out of the generating com- partment at 11, then through the rubber hose 4, and into the bottom of the BURNING PIPE BURNING Pipe TIP CAS GENERATOR WASH BOTTLE IN PAIL AIR TANK HAND AIR PUMP A. Sulphuric Acid Reservoir. 6 Hydrogen Generating Compartment. C. Acid Down-take. 1. Dog for Hand-hole Plate. 2. Hand-hole to Generating Compartment. 3. Generating Compartment Drain. 4. GaB Hose. 5. Wash Bottle Hose Connection (supply). 6. Wash Bottle Hose Connection (e:diaust). 7. Gas Hose. 8. Gas Regulating Valve. 9. Air Regulating Valve. 10. Hand-hole Plate. 11. Generating Compartment Hose Connection. Fig. 129. — Hydrogen Generator and Lead-Burning Outfit. wash bottle where it is cooled and purified by passing through the water contained in the wash bottle ; it then passes out of the wash bottle at 6, into the rubber hose 7, through the regulating valve 8, where it mixes with the air from the compressed air tank, and then passes on to the burning tip where it is ignited, thus supporting the hydrogen flame for the lead-burning process. It will also be noted that the wash bottle is immersed in a pail of water for cooling purposes, and this water should be renewed from time to time as it becomes warm. The wash bottle should be about three-fourtha filled with fresh water. 346 Storage Battekt Manual In preparing the flame for lead-burning have the air regulating valve 9 closed, and the gas regulating valve 8 wide open, then apply a match or a lighted candle to the end of the burning tip until the hydrogen is ignited, after which crack open the air regulating valve 8, and adjust both the gas regulating and the air regulating valves until the correct mixture of air and gas are obtained for the desired type of flame. A little experience will enable one to correctly regulate the valves for the desired flame. It is a good plan to have a standing light, as from a torch or a gas Jet, for use in igniting the burning tip from time to time during the lead-burning process, as this eliminates the necessity of igniting the tip with a match each time; a lighted candle will serve the same purpose. The amount of zinc, sulphuric acid, and water required depends upon the size or capacity of the gas generator ; the instructions accompanying a given set should state the required proportions of these materials to use. Old elec- trolyte from storage batteries may be very well used in these hydrogen gener- ating outfits. The density of the acid should be not above 1.335 nor below 1.160; any density between these limits will in general be found satisfactory. If the acid used is oil of vitriol, then it should be diluted by mixing with the proper proportion of water. In mixing the acid with the water follow the rules and precautions as laid down in Chapter IX. The charge of zinc should be replenished from time to time as necessary to maintain the required amount in the gas generating compartment. Should zinc be not obtainable, iron filings may be used instead in this type of gas generator, although in general it may be said that the gas derived from iron is not as pure as that from zinc. When the gas generator is to be laid up overnight the old solution should be allowed to drain from the generating compartment at the drain hole 3, after which the entire set should be thoroughly cleansed by pouring fresh water into the acid reservoir and allowing it to drain from the bottom of the gas generating compartment. A new charge of materials should then be placed in the generator when it is to be used again. If compressed air from another source is available, the hand pump and air tank need not be used with these sets, though in such case it will prob- ably be necessary to interpose a reducing valve between the source of supply and the air regulating valve of the set. Compressed Hydrogen and Oxygen. — The gases used in supporting the lead-burning flame in this method consist of hydrogen and oxygen supplied from separate tanks. After passing by means of a hose through the regu- lating valves these gases are mixed in proper proportions and pass on to the burning tip where they are ignited and support the flame in a very similar manner as was described in the preceding method. A very hot flame is pro- duced by these gases and is characteristic of this method. Lead-Bdening 347 Oxygen and Illuminating Gas. — This method consists in using illumin- ating gas and oxygen for supporting the flame at the burning tip, and may be said to constitute a very satisfactory method, as both gases can usually Fig. 130.- -Oxygen and Illuminating Gas Lead- Burning Outfit. ■ be obtained in all localities. The illuminating gas is obtained from the regular gas jets or lines, while the oxygen is commercially supplied in tanks. Fig. 130 contains an illustration showing the equipment and the arrange- ment of this equipment as used in this method. 348 Storage Battery Manual Electric Arc. — This method consists in using a carbon, heated by means of an electric current, to fuse the metal and thus lead-burn the parts together. In some instances this method may prove very convenient since, if desired, the battery to be repaired can be used as the source of current for heating the carbon, provided, of course, that the battery is in a charged condition, thus requiring no additional equipment for the lead-burning operation. However, it may be said that this method is in general satisfactory only for light jobs of lead-burning, such as fqr burning connectors to terminal posts of portable types of batteries, and is not suitable for heavier work, such as that of burning plates into groups, etc. carbon pencil Fig. 131. — Electric Arc Lead-Burning Outfit. The apparatus used in this method consists of a carbon point, a combi- nation carbon holder and handle, the necessary lengths of flexible cable, and the corresponding contact clamps for conveying the current from the source to the carbon and to the parts to be lead-burned. Fig. 131 contains an illustration which will give a clear idea of the special equipment employed in this method of lead-burning. The carbon, the carbon holder and the handle, as well as the flexible cable and correspond- ing clamps, are plainly shown in this drawing. For best results in using this method the carbon should be at a bright cherry red heat when used and the source of current or the number of cells Connected across the carbon and the parts to be lead-burned should accord- ingly be sufficient to produce this degree of heat. The arrangement of the parts in the circuit should be such that when the carbon point is placed in contact with the parts to be lead-burned, these parts Lead-Burning 349 as well as the carbon point and the source of current are connected in series with each other. That is, the clamp on the end of the flexible cable attached to the handle of the carbon holder is connected to one terminal of the battery or source of current, while the other terminal of the battery or source of cur- rent is connected with one end of the extra length of flexible cable, the other end of this cable being connected to the parts to be lead-burned, thus when the carbon is placed in contact with these parts the circuit is completed and the carbon heated thereby. A six volt battery will usually prove sufficient for any job of lead-burning to be done by this method, and for some work four volts will be found ample. The carbon should be sharpened to a pencil point and should be secured such that it projects from 2-J to 3 inches from the holder. It is especially important that good electrical contact be made between all parts and the clamps of the flexible cable, these parts to be scraped bright and clean as necessary to accomplish this. Due to the film of scale which will form on the surface of the carbon, it will be found that when used tor a time the pencil will cease to heat properly, in which case it will therefore be necessary to scrape this scale ofl! with a knife, triangular lead scraper, file, or other such tool. It will also be neces- sary to dip the carbon and the holder in a bucket of water from time to time to cool them ofl:. The carbon should be kept in motion during the whole lead-burning process and over the whole surface of the parts to be burned together in order to prevent stratification of the metal and to obtain an homogeneous joint. Soldering Iron. — Although a soldering iron is not suited for general lead- burning work or where an extensive amount of lead-burning is required, it may be said that for emergency work and in instances, in which no other lead-burning apparatus is available, a satisfactory job can be obtained by this method if due care is exercised. In fact, a very creditable job of lead- burning can be accomplished with a soldering iron, provided that the re- quired amount of pains and technique are put into the work. An ordinary soldering iron may be used for this purpose but the shape of the point should be long and narrow in order to get into small places, such as for lead-burning connectors to terminal posts, etc. In order to obtain best results two soldering irons should be used in this work for it is necessary that the iron in use be very hot when working the molten metal. The iron should be at a cherry red heat when used, and on account of its low melting point lead solder wire or bar should be used instead of lead-antimony burning stock. The irons should also be well tinned and thoroughly cleaned in solderinu- acid before attempting to use them. A tallow candle is used for the solder- 23 350 Storage Battery Manual ing flux and should be rubbed on the parts to be lead-burned before applying the soldering iron. The parts to be lead-burned must also be scraped bright and clean by means of a triangular lead scraper or a wire brush before attempting to do any lead-burning. The lead-burning stock or soldering wire is fused by rubbing against the sides of the hot soldering iron while at the same time fusing the parts to be burned together with the point of the iron ; by thus carefully working the iron and the burning stock a satisfactory job can be obtained, but it should be borne in mind that the iron must be at a cherry red heat. The Compound Ladle. — This method is used where the work to be done is of a very delicate nature and where a flame cannot be conveniently used such as in repairing small sections of grids, plates, etc. In using this method a special form of ladle, called a compound ladle, is employed, this ladle being fitted with a burning tip with necessary flexible hose connection to the gas lines for supporting the flame which heats the metal Contained in the ladle. Burning Tip. Fig. 132. — Compound Ladle for Use in Delicate Jobs of Lead-Burning. The lead in the ladle is brought to a red heat and then poured on or around the parts to be lead-burned together, the heat of the molten metal thus being sufficient to fuse the parts to be lead-burned together, the molten metal com • bines with them and effects the required lead-burned joint. A suitable form or mould is usually employed in conjunction with the ladle, this form being placed around the parts to be lead-burned in order to retain the molten metal when poured from the ladle, thus producing the desired shape or form of the lead-burned joint. Fig. 133 contains an illustration of a type of compound ladle such as has been described above. Special Notes on lead-Burning. — In discussing the special notes on lead- burning it should first be stated that no matter which of the methods of lead- burning is used, it is essential to first-class workmanship that all parts to be burned together be scraped bright and clean before attempting the burning process. The tools used in cleaning these parts, such as triangular scrapers, wire-brushes, files, etc., have been described in the preceding chapter. Also, for best results, not only should the lead-burning sticks be clean and bright Lead-Bukninq 351 but they should as far as practicable be composed of the same grade of alloy as the parts to be burned together. In order to prevent damage to covers, jars, trays and other parts it is a good plan to place strips of asbestos around these parts when burning con- nectors to terminal posts, etc. Fig. 132a. — Building-Up a Terminal Post by Lead-Burning Process. Before attempting to do any lead-burning work around a battery be sure that all cells have been well ventilated and cleared of all gases in order to prevent an explosion when using the flame. Fig. 133A contains an illustra- tion of a method of building-up a battery terminal post by means of the lead-burning process. The burning tip, flame, lead alloy burning stock, and iron forms around the terminal posts are plainly shown in this illustra- tion. Attention is especially invited to the method of holding the burning tip in relation to the alloy burning stock. CHAPTEE XXV. MANUAL OF INSPECTION. (Storage Batteries and Farts.) Manual Divided into Two Parts. — The subject of inspection of storage batteries and parts for the naval service may be properly divided into two main parts, as follows : I. Storage Batteries — Submarine Type. II. Storage Batteries — Portable Type. The subject matter of this manual of inspection will, therefore, be taken up in the order outlined above. FART I. STORAGE BATTERIES— STTBUARINE TYPE. General Outline of Assembly and Inspection of Submarine Cells. — In order that a clear understanding may be had of the various important details which should be observed in conducting an inspection of storage batteries and parts designed for the submarine service, a general outline of the suc- cessive stages which the cell passes through during process of manufacture is given as a guide in studying the various important features of inspection required for this type of cell and other parts making up the submarine bat- tery. The following outline, therefore, includes the various successive stages passed through in the manufacture of the unit assembly type cell : I Casting Room — (Paste Plates). — (a) Grids cast in specially con- structed moulds ; moulds kept hot with gas flame or electrical heating units during moulding process. Soap-stone or talcum powder used on the moulds to obtain a smooth easting. Moulds clamped together tightly before molten metal is poured and then opened up and grid removed from the mould when metal has cooled and set sufficiently. Molten metal maintained at an even temperature in the melting pots in order to obtain uniform grade of castings. Fig. 133B contains a typical illustration of a scene in a grid casting room. (b) Grids trimmed, straightened and made ready for burning on the plate lugs. Grids inspected for broken gridbars, blow-holes and .other imperfec- tions in castings. Grids which cannot be reclaimed are melted up and re- cast. All blow-holes in grids should be removed by flame-puddling process before going to pasting room. This is necessary in order to prevent the paste from entering the blow-holes and the consequent forming which will take place in the blow-holes during the formation charge. It is practically impossible to obtain a satisfactory plate if the grids are pasted and formed before removing the blow-holes with the flame-puddling process. (c) Plate lugs burned on. Some manufacturers design their moulds such that the plate lugs, are cast integral with the grids. Manual of Inspection 353 354 Storage Battery Manual II. Spinning Room — (Plante Plates). — (a) Lead blanks stamped out from the sheets of rolled lead. (b) Blanks then carefully weighed and inspected for proper thickness. (c) Blanks placed in the spinning machines where the grooves are spun in the plate. Fig. 132c. — Typical Scene in Grid Pasting Room. (d) Spun plates removed from the spinning machine and inspected for imperfections in the spinning process. Plates which cannot be reclaimed are melted up and re-spun. (e) Plates removed to cleaning machines where all oil used in the spin- ning process is removed and plates thoroughly washed and cleaned. This is a fery important step, as any oil or other foreign matter remaining on the Manual of Inspection 355 plates will seriously interfere with the forming process during the formation charge. III. Pasting Eoom — (Paste Plates). — (a) Paste mixed in the mixing machines. Positive paste consists of red-lead and dilute sulphuric acid. Negative paste consists of litharge, dilute sulphuric acid and the various materials commonly used for an expander. Fig 132d. — Placing Plates in Drying Rooms after Pasting (b) Grids pasted. Fig. 132C shows a typical scene in grid pasting room. (c) After pasting the grids, they are dipped in dilute sulphuric acid in order to increase the degree of sulphation in the active material, which is commonly referred to as the cementing process. (d) Plates are then sent to the drying ovens to be thoroughly dried before placing in the forming tanks. Pig. 133D shows a method of placing the plates in the drying ovens after pasting. IV. Forming Room. — (a) Plates placed in the forming tanks which con- sist of lead-lined wood tanks or glazed earthenware jars containing dilute 356 Storage Batteet Manual sulphuric acid or any other forming agents used by various manufacturers. Fig. 133E illustrates a method of placing the plates in the forming tanks. (b) The plates are connected lip in groups of required polarity for receiv- ing their " forming charge." Some manufacturers form positive and nega- tive plates in the same tank, whereas, other manufacturers have a constant Pig. 132e. — Placing Plates in the Forming Tanks. set of electrodes installed in the tanks and only form one set of plates of like polarity at the time. In the formation of Plante plates, it is usual to form all plates as positives, after which the required number of negatives are formed from these positives. Fig. 132F shows a typical scene in " form- ing " room. Manual oe Inspection 357 (e) After plates have received their forming charge they are then re- moved from the tanks, washed and dried and sent to the store-room where they remain until ready to be assembled in groups. V. Assembly Room. — (a) Plate lugs scraped, cleaned and drilled prepar- atory to assembling and lead-burning in groups. (b) All plates inspected for cracks, loss of active material, defective lugs, improper formation, blow-holes in grids and other imperfections. (c) All wood separators inspected for cracks, knots, thin spots and other imperfections in manufacture. Fig. 1336 shows method of inspecting wood separators. Pig. 132f.- -Taking Voltage, Specific Graviiy, and Temperature Readings During " Forming " Charge. (d) All rubber separators inspected for imperfect perforations, slots, broken separators and other imperfections in manufacture. (e) Cross-bar, strap and terminal post castings inspected for imperfec- tions in casting and lead plating. (f ) Plates and separators assembled in the jig and clamped for burning the plate lugs to cross-bars, straps and terminal posts. (g) Jig containing the plates and separators placed on the burning plat- form and plate lugs burned to the cross-bar, strap and terminal post castings. 358 Storage Battery Manual (h) Element removed from the assembly jig and swung vertically in a chain hoist where the hard rubber separator and plate support pins are inserted. The element is then given a minute inspection for the following: 1. Improper lead-burning. 2. Lead drops and run-downs. 3. Plates and separators examined for purpose of ascertaining whether or not they have been injured during process of assembly and renewals made where necessary. 4. If this inspection proves that the element is satisfactorily assem- bled, the element is then ready for installing in the jar. Fig. 132g. — Inspecting Wood Separators for Imperfections. Note the Illumi- nating Box with Ground Glass Cover as Used in this Work. (i) Jars washed out, inspected and crated in packing cases. Fig. 13211 illustrates how the hard rubber jars axe tested dielectrieally before the ele- ment is installed. (j) Element installed in the jar. Care should be taken that no nails, bolts, nuts, washers, tools, dirt or any other foreign matter are present in the jar when the element is installed. (k) Cell covers inspected for cracks, imperfections in moulding, such as defective threads, etc. Manual of Inspection 359 (1) Cell cover placed on the jars and terminal post gaskets, washers and hold-down nuts secured in position. Cover sealed to the jar by means of pouring sealing compound around the edges. Pig. 132h. — Testing Hard Rubber Jars Dielectrically Before Installing the Element. (m) Cell given proper number in accordance with the approved layout prints of cell ventilation system. (n) Cell carried to the charging and testing room 360 Storage Battery Manual VI. Charging and Testing Room. — (a) Cell placed in position and con- necting up in circuit for receiving the initial charge. (b) Electrolyte poured and cell allowed to stand until temperature has dropped sufficiently for conducting the initial charge. (c) Placed on initial charge at the required charging rates correspond- . ing to the special type of cell. Eoutine readings of cell voltage, temperature, gravity and charging current recorded as the initial charge progresses. If temperature becomes excessive during the initial charge artificial ventilation is resorted to. (d)" Equalize specific gravity readings of the electrolyte as necessary preparatory to conducting the official test discharges. (e) When initial charge is completed and cell temperatures are at 80 degrees Fahrenheit (unless tests are to be conducted in accordance with approved temperature correction curves for capacity) the cells are ready for running the 3-hour official test discharge. Take voltage, gravity and temperature readings as per routine. Select pilot cells and record routine readings of same during discharge. The pilot cells should be selected after the discharge has begun in order that cells representing high, intermediate and low voltages may be obtained for these readings. No terminal cells should be selected as pilot cells. Essential that proper current rate be main- tained throughout the discharge. (f) Check average and final voltages with the approved characteristic curves to see if rated capacity has been obtained. (g) Select the two cells of each circuit having the lowest final voltage at end of the 3-hour discharge for the 1-hour official discharge. (h) During 1-hour official test discharge record voltage, gravity and tem- perature readings as per routine. (i) Check average and final voltages with approved characteristic curve to see if rated capacity has been obtained. (j) Eecharge all cells preparatory to shipment. This charge is known as the " Shipping Charge " and should be conducted sufficiently long to insure that all acid has been driven out of the plates as these cells may be required to stand idle without receiving a " freshening charge " for some little time. Cells watered as necessary before shipping. (k) Electrolyte of each individual cell subjected to chemical analysis to insure that iron content and other impurities are not above the permissible amount. (1) If chemical analysis of electrolyte shows 0. K., cells are then dis- connected and taken out of circuit preparatory to cleaning up for final inspection before crating for shipment. Manual of Inspection 361 VII. Final Inspection. — (a) Cell covers and terminals thoroughly cleaned. Covers inspected for cracks, warping and other defects which have developed since assembly. All intake and exhaust vents and baffle discs inspected and renewed as necessary. Terminal posts inspected for poor lead-plating and damage to terminals through connecting up and disconnecting in the charg- ing and testing room. (b) Cell numeral discs installed on top of cell covers. (c) Cell terminals coated with vaseline. (d) After cell has thus been given a thorough inspection, the crate cover is placed in position, care being taken to not damage the cell cover and parts in this operation. The crate cover should not be secured in position until the cell crate tie-rods have been set up on to take any lost motion out of the crate such that it takes-up firmly against all four sides of the jar. (e) Stencil cell number, battery identification markings, " Handle with Care,'' and other such markings on the top and sides of the packing case. (f ) If for foreign shipment the cells are then crated in another packing case and packed in sawdust. In such instances the cover of the inside pack- ing crate should be securely covered with oil-cloth to prevent the sawdust from entering the cell.. (g) Cells then loaded in the railroad cars. They should be securely packed in the cars and well braced with timbers to prevent motion and damage en route. The foreign shipment packing crates contain an iron strap for slinging the crates in cargo falls for loading on board ship. These iron straps are so placed on the crates that it is impossible to sling the cells upside down. PART II. STORAGE BATTERIES— PORTABLE TYPE. Test for Capacity. When portable storage batteries are submitted for inspection at the works of the manufacturer it is customary to select at random one complete battery of each type and to conduct capacity tests on it. The procedure for con- ducting such tests is in general as follows : 1. The following readings taken while battery is on charge and just prior to discharging: (a) Voltage of each cell. (b) Specific gravity of each cell. (c) Temperature of each cell. 2. Cut the battery in on discharge, regulate the current to the proper value as quickly as possible. 3. After discharge has run for from five to fifteen minutes take voltage reading of each cell. Select cells having lowest voltage for use as pilot cells. 363 Storage Battery Manual 4. Take individual cell voltage, specific gravity, and temperature readings every 30 minutes. . 5. During thfi last hour of the discharge take overall readings as above every 15 minutes. 6. Upon completion of the test take overall readings as above. 7. If the battery fails to deliver the required capacity all other batteries of the type on the order are held up pending a satisfactory test for capacity. Pig. 132i. — Assembling the Elements. — Portable Type Batteries. If the batteries are properly rated, and contain no defects, the capacity should be obtained v?ithin the first three cycles of charge and discharge. Check Dimensions, Construction and Weight. — The dimensions, con- struction and weight of the batteries should be checked up to see that they conform to the specifications. An approved drawing or blueprint is usually provided for this purpose by the battery manufacturer. Pig. 1321 shows operation of assembling the elements of portable types of batteries by plac- ing the groups of plates together. Manual op Inspection 363 Surface Inspection of Batteries. — If the capacity tests are satisfactory and the batteries conform to specifications, they are then ready for the surface inspection. In making the surface inspection of the batteries it is well to place to- gether in line all trays belonging to a set of batteries, as in this way the record of the inspection is easily kept track of. Fig. 132j. — Showing Celluloid Instruction Sheet Secured to Inside of Battery Tray Cover Now, in order to insure that all cells in each tray are in good condition and that they are connected up properly with regard to polarity the terminal voltage of each tray should be checked. If a cell should happen to be re- versed, short-circuited, or contain any other serious defect, the voltage read- ing will usually serve as a means of detecting the defective cell. In portable batteries manufactured for the naval service the positive terminal should be 364 Storage Battery Manual to the right hand when facing the front of the tray, the front being the side on which is secured the battery name-plate. Specific gravity readings of the electrolyte should be taken to see that the acid is of the prescribed full charge density. Also see that the height of the electrolyte above tops of plates is correct. The covers and tops of all cells should be inspected for breakage. The cells should be inspected to see that they are installed in the trays correctly. It sometimes happens that the proper spacing boards have not been used, and that the cells are loose in the trays. Such defects should be rectified before the batteries are accepted. All connectors and terminal posts should be inspected for poor lead-burn- ing. The terminal connectors should be inspected to see that they are of the correct type and size, and that they line up properly with the cable holes in the trays. All parts of the battery should be thoroughly clean and the trays and other wood parts neatly covered with acid-resisting paint. All trays should contain suitable instructions for care and operation. It is customary to secure the celluloid sheet containing these instructions to the inside of the tray cover. Fig. 138 J contains a photograph illustrating this feature. Porcelain insulator skids should be inspected for breakage. Be sure that the polarity of the terminals is plainly marked on each tray. Having inspected the batteries as outlined above, they are now ready for packing for shipment. Special notes on the various methods of preparing the batteries for shipment have been given in another chapter. CHAPTER XXVI. TESTING STORAGE BATTERIES. Object of Testing. — In general it may be said that the testing of storage batteries has as its primary object that of ascertaining the following: (1) Voltage characteristic. (2) Ampere-hour capacity. (3) Watt-hour capacity. Other factors such as the various efficiencies, weight and size per unit of capacity, temperature characteristics, etc., may be obtained in conjunction with the three fundamental test factors enumerated above. Also, the test- ing of storage batteries serves the purpose of bringing out any defects in design, or of other local defects, such as short-circuits, bad plates or sepa- rators, impurities in the electrolyte, poor lead-burning, etc. The method of conducting the tests will now be described. Method of Conducting Tests, — In order to obtain uniform and accurate results in conducting tests on storage batteries it is necessary that consider- able attention be devoted to certain of the minute details which are charac- teristic of storage battery operation, and which will later be described. The method outlined below is therefore given to serve as a guide in conducting such tests, and if carefully followed, the three fundamental test factors as enumerated in the preceeding paragraph, as well as any other pertinent factors, may be comparatively easily and accurately obtained. The rate at which it is customary to test a battery naturally depends largely upon the type of the battery and the purpose for which it is used. For example, automobile starting batteries and batteries of similar types designed for high discharge rates of short duration are frequently tested at as high as the 20-second discharge rate and sometimes at even higher rates than this, whereas, other types such as are designed for very low-rate discharges are tested at as low as the 30-hour discharge rate. However, with proper facilities, a test may be conducted on a battery at any rate of discharge of which it is capable of producing and it is customary for the manufacturers to prepare and supply to the naval service characteristic curves which include all rates of discharge within the scope that the particular type of battery will likely be called upon to perform. The characteristic curves of submarine batteries include all discharge rates from zero to 20 hours, while the curves for the smaller types of batteries include rates from zero to 10 hours. Thus, it is only necessary to consult these curves to ascertain the discharge charac- teristics for any desired discharge rate and to check the performance of the 24 366 Storage Batteky Manual battery on a given test discharge against the characteristics as contained on these curves. Curves such as are here described are shown in Eig. 97. For purpose of illustrating the method of conducting a test, a three-hour test will here be used, that is, the test will be conducted at the three-hour discharge rate of the given battery. However, the principle involved in the method is the same for tests at all other rates of discharge. Before beginning the test consult the approved drawings and character- istic curves of the battery in order to obtain necessary data as well as to establish uniform conditions for conducting the test. The following out- line represents in general what should be done in this respect before begin- ning the test : (a) Ascertain from the curves the three-hour discharge rate. (b) Ascertain from the curves the average cell voltage during discharge at the three-hour rate. (c) Ascertain from the curves the minimum final cell voltage for the three-hour rate of discharge. (d) Ascertain from the curves the temperature correction for capacity if initial temperature of cell is above or below 80 degrees Fahrenheit, the standard temperature upon which all battery data of batteries for the naval service is based. If temperature is above 80 degrees, the discharge should run for a certain period of time, as shown by the temperature correction curve, more than three hours to the prescribed minimum final voltage; if below 80 degrees the discharge should run less than three hours to the same final voltage. (e) See that the level of the electrolyte is at the proper height above the tops of plates and separators, as shown by the approved battery drawings. (f ) See that the specific gravity of the electrolyte of all cells is within the permissible limits of tlie full charge value. It is customary to allow a toler- ance of 10 points in specific gravity, 5 points below to 5 points above the normal full charge value. Thus if the normal full charge value of the specific gravity is 1.250, then the permissible specific gravity range at the beginning of the test is from 1.345 to 1.255. If the battery is conservatively rated the variation in capacity between the above limits of specific gravity may be said to be negligible for all practical purposes. (g) Be sure that battery is fully charged before beginning the test. (h) See that all voltmeters, ammeters, ampere-hour meters, hydrometers, thermometers, and all other instruments used in connection with the test are accurately calibrated. (i) If an ampere-hour meter is to be used in connection with the test see that it is either set at zero, or that a record is made of the reading which it registers at the beginning of the test. Testing Storage Batteries 367 Having obtained the data and satisfied tlie conditions outlined above, next place the battery on charge at the finishing rate for about 5 minutes, and while thus on charge take a voltage reading of all cells, after which close the switch between the battery and the discharge lines and regulate the discharge current to the proper value, 3-hour rate, as quickly as possible. This dis- charge fate should be maintained as constantly as possible throughout the test, as this constitutes one of the most important details in connection with a satisfactory test. After the test has been running for five minutes take another set of over- all voltage readings and from which select the pilot cells to be used during the test. At least two each of the high, the intermediate, and the low cells, as shown by this set of overall voltage readings, should be selected for pilot cells, as the readings taken on such cells will give a clear indication of the condition of all cells of the battery in respect to their states of discharge as the test progresses. In this regard it should be stated that care should be taken to not select a cell located at the end of a row for use as a pilot cell, as due to better ventilation on account of its location, or due to any heat from terminal connectors the temperature of an end cell may vary some- what from the other cells of the battery, which in turn will cause a variation in the cell voltage reading, and for this reason such a cell is not suitable for a pilot cell. Having thus selected the cells to be used as pilot cells, the routine readings for the test, consisting of voltage, specific gravity, and temperature, should be begun on these cells; the first set of such readings should be taken and recorded after the test has been running for 15 minutes, and thereafter at 15 minute intervals. The ampere-hour meter on the discharge circuit should also be read and recorded at these intervals. In addition to the above pilot cell readings an overall set of voltage, spe- cific gravity, and temperature readings should be taken and recorded every hour during the test, as this serves as an additional check on the perform- ance of each cell in the battery. After the test has been in progress for 2 hours and 30 minutes, the low pilot cells should in general indicate the condition of the low cells in the circuit, and if the low cells at this time are within .035 to .030 volts of the limiting final voltage, an overall set of voltage readings should be taken at intervals of 5 minutes during the remainder of the test in order to determine at what period of the test the low cells, if any, go below the specified limiting final voltage. This is important from a point of view of standardization of cells, as it is usual practice to include a fixed standard in the specifications for the various types of batteries, and a certain tolerance is often allowed in the number of cells which pass below the specified limiting final voltage on the test. This tolerance is generally limited to 10 per cent of the cells of the battery, and the final voltage of such cells -must not be more than .10 volt 368 Storage Battery Manual below the specified limiting final voltage at the end of the test. Especially is this true in the case of testing new cells, as during the first few cycles of a cell's life, there is a certain amount of irregularity in its performance, and this tolerance on the tests is designed to take care of such irregularities and at the same time to insure that only normal cells are permitted to remain in the battery. If cells do not come within the tolerance allowed in the approved specifications, they should be replaced by cells which conform to the standard, and the cells which are below standard should be examined and necessary steps taken to rectify any defects which may be found. At the expiration of 3 hours take and record an overall reading of voltage, specific gravity, and temperature, whereupon the test is completed, and the discharge may be stopped. This, of course, providing that the initial tem- perature of the cells was at 80 degrees Fahrenheit; if above or below this value, the duration of the test should be changed accordingly. Temperature Coefficient Curves. — Fig. 133 contains an illustration of a typical set of Temperature Coeffieieut Curves such as are used in conducting capacity tests. This set of curves includes the temperature coefficients for the one, three, and ten hour rates of discharge. It will be noted that the 100 per cent of capacity for each of the above discharge rates is based on a tem- perature of 80° Fahrenheit, and that these curves include all temperatures from 40° to 120° Fahrenheit. Thus, should the initial temperature of the battery be 54°, then in referring to the three-hour rate curve it will be noted that the test will only be required to run for 2 hours and 30 minutes, to the specified final voltage. It will further be noted that as the rate of the discharge in amperes de- creases, the variation in capacity due to temperature increases ; this feature is plainly shown by the relative pitch of the three curves contained in the drawing. ■ Moreover, it will be noted that the element of time for a test in- creases or decreases, respectively, with an increase or decrease in initial temperature from 80° Fahrenheit. It is customary to include the temper- ature coefficient curves on the same sheet with the other characteristic curves of a battery. Becordinif the Test Data. All readings- and other data obtained during the test should be systemat- ically recorded. This data is essential in computing the ampere-hour and the watt-hour capacities, as well as other factors. When prepared in the proper form such data constitutes an important portion of the history of the battery and should therefore be preserved with the other battery records for further use, should they be required. Figs. 134 and 135 contain typical examples of a method of preparing and recording test data which has been found very satisfactory and which can be Testing Storage Batteries 369 'j.i3HN3UHVJ - 833iJoaa Ml aunivuadiAiaj. 370 Storage Battery Manual RECORD OF 3 HOUR INITIAL DISCHARGE OF BATTERY FOR U S. BAVY -Juns-SilV. TEMPERATURE OF ROOM 1!!'°" ""^""^^ (After Diicb«rge.Z£L. , 19l_a_ .3 -Hour Rated dpedty—SSJIO A. R . .__. a.. Hour Acblel Capuity_SSS0„ A. H. TYPE OF BATTERY PASTE- PASTE ASSEMBLY AT.r«.Du.h«,.R...g5g^ Amperes INTTIAL CHARGE .. ^L HOUR INTTtAL DISCHARGE ' CELL No. C.^ ^TT Vd™. Volt. St«t Volu Fuul Gtavio Final ■ unRiul Cn.ky Tm>p.,.. Vdi. REMARKS 1 1.279 81 2.61 1.935 1.73 1.192 97 1.284 75 2.59 2 1.280 80 2.62 L.93 1.735 1.184 100 1.284 74 2.62 Pilot 3 1.278 80 2.63 L.92 1.73 1.184 97 1.280 75 2.60 4 1.280 80 2.60 1.92 1.70 1.187 95 1.281 75 2.61 5 1.2S0 81 2.61 L.92S 1.73 1.183 96 1.284 74 2.63 6 1.279 80 2.59 1.91 1.705 1.178 98 1.279 78 2.58 7 1.280 81 2.62 1.94 1.725 1.183 100 1.278 79 2.61 Pilot 8 1.280 81 2.60 1.92 1.725 1,180 98 1.S81 78 2.60 9 1.279 80 2.61 1.92 1.71 1.180 102 1.283 77 2.60 10 1.280 81 2.62 1.905 1.70 1.182 98 1.283 75 2.59 11 1.279 80 2.58 1.92 1.725 1.179 97 1.280 77 2.60 12 1.279 80 2.61 1.935 1.715 l.lVl 99 1.280 76 2.61 13 1.278 80 2.63 1.92 1.705 1.180 99 1.284 75 2.63 14 1.279 79 2;60 1.91 l.«9 1.187 101 1.2 84 74 2.60 15 1.278 80 2.61 1.90 1.679 1.183 97 1.274 95 2.62 f 16 1.280 80 2.59 1.94 1.72 1.180 100 1.283- 76 2.59 Pilot 17 1.278 81 2.62 1.915 1,70 1.179 99 1.279 76 2.61 18 1.279 ■80 2.60 1,935 1,745 1.185 102 1.281 1.282 75 2.62 19 1.279 80 2.61 1.915 1,71 1.191 99 74 2.63 20 1.283 79 2.59 1.91 1.70 1.178 97 1.280 84 2.54 21 1.280 78 2.60 1.91 1.69 1.183 98 1.281 75 2.58 22 1.2 79 78 2.61 1.92 1.705 1.194 98 1.283 75 2.63 23 1.278 80 2.62 1.915 1.695 1.178 98 1.280 .ii 2.58 24 1.278 80 2.59 1.89 1.73 1.18: 103 li279 79 2.68 Pilot 25 1.279 81 2.S8 1.93 i;72 1.180 96 1.280 78 2.60 26 '1.277 80 2.60 1.915 1.72 1.189 98 1.278 79 2.61 27 1.279 80 2.61 1.90 1.68 1.185 99 1.278 79 2,59 28 1.278 81 2.62' 1.925 1.736 1.193 97 1.278 79 2.62 29 1.276 81 2.60 1.905 1.705 1.184 98 1.277 80 2.60 30 1.279 80 2.61 1.93 1.74 1.186 101 i;278 80 2.60 Pilot 31 1.280 80 2.59 1.92 1.72 1.195 96 1.278 80 2.61 32 1.278 81 2.62 1.905 1.71 1.189 99 1.278 80 2,63 33 1.278 81 8.60 1.93 1.74 1.182 98 1.877 84 2.58 34 1.277 81 2.61 1.915 1.93 1.72 1.186 97 1.280 84 2.60 35 1.278 81 2.59 1.74 1.194 97 1.280 80 2.61 36 1.278 80 2.58 1.92 1.68S 1,202 101 1.279 79 2.47 f 37 1,279 81 2.62 L.915 1.70 1.186 101 1.280 79 2.62 38 1.279 80 2.61 1,925 1.726 1.190 97 1.280 79 2;59 39 1.282 80 2.59 1.93 1.74 1.193 98 1.283 78 2.58 40 1.278 80 2.58 1.925 1.71S 1.185 101 1,278 79 2.57 At. 1.278 80.20 2.602 1.919 #DsnoteB 1.714 1 hour 1.185 pilol 98.55 8 L.SSO 77.85 2.601 Seoond cycle. Oell #36 was replace d. this cell was so low In oa laolty that it waa.aot UBod. Cell #36 was run as a one and th: •ee hour pilot; records of the 3e teal :a are not shown Paj since e 1 call wi as dls< iarded Fio. 134. — Battery Test Record Sheet. Testing Storage Batteries 371 Record of Pilot Cell Readings Taken During 2__Hour Official Discharge OF BATTERY FOR U. S. H A V y DUeharte Rate....29S.Q._Alnp«u DATE..Junfi....2a.,...19La.. TYPE OF BATTERY aSTE-EASTE ASSEMBLY _ PILOT CELL No.j?....._ PILOT CELL No ...7..... PILOT CELL NO.....X& ^ Voluw Cw«a VoltM. c™«w v.i™. C™rt, Ohg. 2.62 1.280 80 2.62 1.280 81 2.59 1.280 80 5 1.93 1.94 1.94 ^ 15 1.925 1.274 82 1.935 1,274 82 1.93 1.275 82 ZO 1.91 1.270 84 i.92 1.266 84 1.91 1,269 84 45 1.896 1.264 86 1.905 1.260 86 1,895 1,266 86 '60 1.88 1.258 88 1.89 1,253 88 1,88 1,253 88 75 1.865 1.250 90 1.875 1,248 90 1,865 1,249 90 90 1.85 1.240 92 1.86 1.239 92 1.85 1,280 92 105 1,835 1.233 94 1.84 1.232 93 1.83 1,231 94 180 1.815 1,223 95 1.82 1.223 95 ^,805 1,221 96 135 1.795 1.214 96 1.80 1.218 96 1.79 1.213 98 150 1.78 1.203 97 ■ •1.78 1.207 97 1.77 1.203 98 165 1.76 1.193 96 1.76 1.197 98 1.77 1.203 98 180 1.735 1.184 100 1,725 1.183 100 1.72 1.180 100 AT, . 1.846i 1,851 I 1.842C PILOT CELL Na.24._ PILOT CELL No ■30- PILOT CELL No. 4Q_ V,ltM. Cr.vilr VJu,. C.Tit, V.1™. Cwvit.. Chg. 2.59 1.278 80 2.51 1.279 80 2.59 1.280 79 5 1.89 1.93 1-.905 15 1>88S 1.275 82 1.925 1.276 82 1.895 1.276 81 30 1.875 1.268 84 1.91 1.270 84 1.885 1.271 82 45 1.86 1.263 86 l.SO 1.264 86 1,87 1.264 85 60 1.845 1.258 88 1.885 1.258 88 1.855 1.259 86 75 1.83 1.249 90 1.87 1.251 90 1.835 1.251 88 90 1.82 1,239 92 1.855 1.241 92 1.825 1.243 90 105 1.80 1.230 94 1.34 1.233 94 1.805 1.238 ISO 1.78 1.223 96 1.825 ;-.226 96 1.79 1.228 91 135 1,765 1.213 98 1.805 1.218 98 1.775 1.222 92 150 1,77 1.203 100 1.785 1.208 99 1.755 1.210 93 165 1.77 1.203 100 1.765 1.195 101 1.735 1.203 93 180 1.73 1.183 103 1.74 1.186 101 1.71 1.188 96 Av. 1.8151 1.850 3 Pa te 2 1.819! Pig. 135.— Pilot Cell Record Sheet. 373 Stoeage Battery Manual used to advantage as a guide in the preparation of battery test data in record form. It will be noted that Pig. 134 contains a record of the final readings taken on the initial charge of a battery consisting of 40 cells, also the final readings taken during a 3-hour test discharge, as well as the record of the final read- ings of the re-charge following this 3-hour test discharge. Fig. 135 contains the discharge records of the pilot cells which were used for this 3-hour test. It will be noted that the first set of readings of the pilot cells was taken while the battery was being charged at the finishing rate, and just prior to beginning the test; the second set of readings was 2.80 2.60 . 9 ±(i 3 HOUF DISCHARGE ^> D ISCH/ iRGE RATE = 140( amp i. "^ ^. 111 U u. 2.20 O UI S 2.00 ti p S* 1.90 1.80 SPEC .ipio a UVITY OURV ,^ ^^ ■^ ^ "^ "^ VOLT AGE C jrve' ^"~ . ^ ::^ 1.60 TEI UPERA- rURE c ■"7 URVE CHG. L280 1.260 1.240 1 1.220 t 1.200 1.180 100 90° 15 30 45 60 75 90 105 120 135 ISO 165 180 195 TIME IN UINUTES Fig. 136. — Typical Set of Battery Characteristic Curves. 80° taken after the test had been running for 5 minutes, while the other read- ings were taken at 15-minute intervals and as has already been explained in the early part of this chapter. Fig. 136 contains an illustration of a typical set of curves which have been plotted from the records of the readings taken during a 3-hour test discharge. The relative characteristics of voltage, specific gravity, and tem- perature of battery during the test are plainly indicated by these curves. Other forms for the preparation of battery data are shown in Figs. 98, 99, and 100. Fig. 136A shows a scene in the testing room during the pre- liminary test on cells before assembling them in trays and before the final acceptance tests are conducted. Testing Storage Batteries 373 Computing Ampere-Honr and Watt-Hour Capacities. As has been stated, it is one of the primary objects of testing storage bat- teries to obtain the ampere-hour and the watt-hour capacity developed on such a test. Inasmuch as the pilot cells selected for the test comprise those which are representative of the high, the intermediate, and the low cells of the battery, it is customary to use the readings taken on such pilot cells for Fig. 136a. — Taking Voltage Readings on Cells During Preliminary Tests Before Assembling Them in Trays. Note the Voltmeter and Prods in the Hands of the Testers. computing these capacities, as this method is sufficiently accurate for all practical purposes. However, should a battery consist of comparatively few cells, readings can be taken on all cells of the battery during the entire test and the capacity of each cell computed individually, but, for large battery installations, such as for the submarine service, etc., it is more practical to select pilot cells and to compute the capacity of the entire battery from the pilot cells readings. 374 Storage Battery Manual "Ampere-Hour Capacity." — The ampere-hour capacity developed by a battery is represented by the product obtained by multiplying the average value of .the discharge current during the test by the time of the discharge expressed in hours, and is expressed as follows: AH = Cxt. Where : ^J7= Ampere-hour capacity. C = Average value of the discharge current during the test. i = Duration of the discharge test expressed in hours. Thus, as a function of design, having determined the limiting final voltage for the given rate of discharge, the ampere-hour capacity developed by a particular type of battery during a test is represented by the product of the discharge rate and the length of time the discharge runs before the given limiting final cell voltage is reached. Eeferring to Pig. 134 it will be noted that the average value of the dis- charge current during the test was 2950 amperes, and that the duration of the test was 3 hours; hence the ampere-hour capacity developed by the bat- tery on this test was 3x2950 = 8850 ampere-hours. " Watt-Hour Capacity." — The„watt-hour capacity developed by a battery is represented by the product obtained by multiplying the ampere-hour capacity by the average value of the battery voltage and the number of cells in the battery, and is represented by the following expression : WH = AHxVaXN. Where ; TFfl'= "Watt-hour capacity. .i4fl'= Ampere-hour capacity. yo= Average cell voltage during the discharge. iV^ = Number of cells in the battery. Thus, in referring to Pigs. 134 and 135, the ampere-hour capacity during this test is 8850 ampere-hours, the average value of the cell voltage as obtained by averaging the average voltage readings of the pilot cells is 1.8372 volts, and the number of cells in the battery is 40. Hence, the watt-hour capacity developed on this test is: 8850 X 1.8372 X 40 = 650368.8 watt-hours. Now, for convenience it is customary to express large numerals like this in terms of kilowatts, and since a kilowatt is a unit 1000 times as great as a watt, it follows that the value of the above capacity expressed in kilowatts is 650.36 kilowatt-hours. Testing Storage Batteries 375 The Water Rheostat. For making test discharges on storage batteries it is usually necessary to provide a special resistance for current regulation purposes. A form of resistance extensively used for this purpose and one which can be very con- veniently constructed is known as the water rheostat. The principle upon which this form of rheostat is constructed is that of utilizing water as a resistance, there being two metal plates immersed in a tank of water and to which plates are connected the wires of the discharge circuit. Thus, by varying the distance between the two plates the resistance offered by the water to the flow of current is also varied and the discharge current is CO c4^ ^ C3^0 d^ C±=Z) c=i=3 ci c^ 5T~^5TSwfoT^^T^l-' »^> 1 — rv_y '^^— I •^ V^ 1 "^ — ^.-^ ■ 1 >w/ Fig. 137. — Showing Connections for Discharging Through Water Rheostat. accordingly regulated by this means; that is, the closer the plates are together the smaller the resistance offered to the flow of current, and vice versa. The conductivity of the water is increased by making it slightly acidulated through the addition of a small amount of salt or of sulphuric acid. Fig. 137 contains an illustration of a type of water rheostat described above, 'and the proper connections necessary for conducting a test discharge by this method of current regulation. Eeferring to this illustration it will be noted that the wires of the discharge circuit are each connected to one of the plates in the tank containing the acidulated water. The plates in this 376 Storage Battekt Manual instance consist of unpasted grids, but plain sheets of lead or of iron will well answer the purpose. The tank may be of wood, earthenware, glass, iron or any such material, but, in general, a water tight tank constructed of wood will be found very satisfactory. It is especially important that care be exercised to prevent plates from coming in contact with each other while current is flowing through the circuit; in this regard it is a good plan to place a thin wooden board or a perforated rubber separator between the plates to prevent them from coming in contact with each other during the discharge. In conducting a test discharge with the apparatus shown in this illustra- tion it will be noted that it is only necessary to place the plates, which are sus- pended from the top of the tank, at the proper distance apart and to then close the single- throw double-pole switch 8; the current is then regulated during discharge by varying the distance between the plates as may be found necessary. After the current has once been regulated to the proper value it is a good plan to keep a small stream of fresh water running into the tank by means of a hose in order to keep the water in the tank at as near a con- stant temperature as possible, as the water will show a tendency to heat dur- ing the discharge. The connections to voltmeter and ammeter are also plainly shown in the diagram of the switchboard in this illustration, as are also the connections from the trays of batteries to the single-throw double- pole switch 8. Another type of water rheostat used for conducting test discharges on the larger types of cells consists of circulating water through a series of coils of brass pipes, the proper degree of current regulation being effected by making connections with the discharge circuit at various points as necessary along the length of the pipe coils, thus varying the resistance to the flow of current through the coils. CHAPTEE XXVII. THE CADMIUM TEST. Object of the Cadmium Test. — Although it has been stated that the read- ings taken of the voltage and specific gravity give an indication of the state of charge or discharge of a cell, it should also be said that these readings are only valuable in this respect for cells vi^hose plates are in a normal condition as regards delivering the full capacity of which they are capable. That is to say, a battery may show normal values for the voltage and specific gravity readings at the end of a charge, yet if one or both groups of plates are not in a state of full charge the capacity of the battery is limited by the poorest group of plates. It is therefore the object of the cadmium test to ascertain the relative states of charge of the'two groups of plates in the cell, and to thus detect the plates which are not in normal condition as regards capacity in order that they may be given appropriate treatment and placed in such condition that they will deliver the full capacity of which they are capable. Description of the Cadmium Stick. — In order to detect the relative states of charge of the two groups of plates in the storage battery cell, a neutral or inert electrode is generally used, cadmium being extensively used for this purpose. Cadmium is an element which occupies a position between lead-peroxide and sponge lead in the electro-chemical series , hence, it is possible to measure the potential difference between cadmium, and the lead-peroxide (positive) plates, as well as that between cadmium and the sponge lead (negative) plates, and in this way the plates which are below normal as regards capacity may be detected. That is to say, with the fully charged cell, cadmium is electro-negative to the positive plates, whereas, it is electro-positive to the negative plates ; on the other hand, however, when the cell is in a discharged condition, the cadmium electrode becomes electro-negative to the negative plates, but the positive plates remain electro-positive to cadmium. ' By a very carefully conducted series of tests the values for the potential difference between cadmium and the two sets of perfectly normal and healthy plates of the lead-acid storage battery cell have been accurately established under conditions of both charge and discharge. Therefore, by comparing the readings obtained on a cadmium test with these established normal values, the condition of the plates as regards capacity may be determined. 378 Storage Battery Manual CHARGE! p. 0J .(+) I 2.05 I 2.10 1.75... g^ 1,80 r^ I DISCHARGE Fig. 138. — Chart Showing Normal Cadmium Readings. The' Cadmium Test 379 The following table represents the normal values of the differences of potential between cadmium and the positive and the negative plates : TABLE OF NORMAL CADMIUM READINGS. Condition of plates. Potential difference between Cadmium Cell voltage Positive plate (Pb0„). Negative plate (Pb). Charged Discharged (+) 2.45 to (+) 2.55 volts. (+) 2.05 to (+) 2.10 volts. (— ) .05 to (— ) .10 volts. (+) .25 to (+) .30 volts. (+) 2.50 to (+) 2.65 volts. (+) 1.75 to (+) 1.80 volts. It will be noted in the above table that the cell voltage at any time is represented by the algebraic sum of the differences of potential between ?.\:s\ Fig. 139. — Apparatus for Taking Cadmium Readings. cadmium and the positive and negative plates respectively. The values given in this table may also be graphically illustrated by the chart in Fig. 138 which clearly shows the normal cadmium readings for both charge and dis- charge. Fig. 139 contains an illustration of the equipment required for making a cadmium test. This equipment consists of a stick of cadmium of approxi- 380 Storage Battery Manual mately -J inch in diameter enclosed in a perforated rubber tube, the cadmium being secured to a hard rubber handle and connected with one end of the flexible cable which forms one of the voltmeter leads. The other voltmeter lead is connected with a regular copper pointed prod which is also secured to a hard rubber handle. The clips for connecting the flexible leads to the bind- ing posts of the voltmeter are also plainly shown in the illustration. Method of Making the Cadmium Test. — For conducting the cadmium test, either during charge or discharge, current of the desired rate should be flowing through the circuit to or from the battery. It is also important in obtaining uniform readings that the cadmium stick be free from impurities, and that the surface of the cadmium be kept in a corroded condition and never scraped or polished. In measuring the voltage between the set of plates, the cadmium stick should be placed in the electrolyte between the plates to be tested, having care to prevent the cadmium from coming in contact with either plate. Each time that a reading is taken it is necessary that the cadmium occupy the same relative position in the cell in order that uniform and accurate readings may be obtained. In making the cadmium test the method of making the connections between the leads of the cadmium stick, the copper pointed prod, and the binding posts of the voltmeter depends upon the type of the voltmeter used. If the! voltmeter is of the type which has its zero point in the center of the arc of the scale, commonly known as the two-way reading type, it is not necessary to shift the leads to the binding posts when taking the respective readings between cadmium and the positive and negative plates. However, if the voltmeter is of the type which has its zero mark located at the left hand end of the arc of the scale, it then becomes necessary at times to shift the binding post leads in order to measure the difference of potential between cadmium and one set of the plates. Thus, if the leads are properly connected for measuring the difference of potential between cadmium and the positive plate, it would then be necessary to shift the binding post leads in order to measure the difference of potential between cadmium and a completely charged negative plate, for the reason that the negative plate when in this condition is electro-negative to cadmium; this of course, pro- viding that the negative plate is in a perfectly normal condition. A little practice with taking cadmium readings will assist in determining when it is necessary to shift the binding post leads if the one-way reading type volt- meter is used. Let us now proceed to take a set of cadmium readings on a cell. The cell is being charged at the normal rate, and it is near the completion of the The Cadmium Test 381 charge. The two-way reading type voltmeter is to be used. We will begin by taking a reading between cadmium and the positive plates. First, connect the clip, which is attached to the end of the flexible cable of the copper pointed prod, with the positive binding post of the voltmeter, and then connect the clip, attached to the end of the cadmium stick cable, with the negative binding post of the voltmeter. We are now ready to take cadmium readings. Next, insert the cadmium stick in the electrolyte and close to the positive plate to be tested, but exercise great care to prevent the cadmium from com- ing in contact with any of the plates in the cell. Now, press the copper pointed prod against the lug of the positive plate to be tested, and at which time it will be noted that the needle of the voltmeter will be deflected and will register on the positive side of the scale the difference of potential between cadmium and the positive plate. Now, in order to test the negative plate proceed in the same manner as described for the positive plate, with the exception, however, that the copper pointed prod is placed in contact with the lug of the negative plate to be tested. It will then be noted that the needle will register on the negative side of the scale the difference of potential between cadmium and the negative plate, since the negative plate is electro-negative to cadmium when nearing a condition of full charge. Thus, as has been pointed out, having at hand the normal values which have been established for the differences of potential between the plates under certain given conditions, if these values are not obtained on the cadmium test when taken under the given conditions, then the plates or group of plates which do not show normal values for the difference of potential are faulty and should be given appropriate treatment in order to restore them to a normal condition. For example, suppose that at the end of a charge it is found by test that the potential difference between cadmium and the negative plates of a cell show that the negative plates are electro-positive to cadmium ; this would indicate that a large portion of lead-sulphate in the negative plates had not been reduced to sponge lead during the charge, and this group of plates would therefore become completely discharged very quickly after being placed on discharge, which would accordingly reduce the capacity of the cell ; in this regard it should be stated that like the chain which is no stronger than its weakest link, the capacity of the storage battery cell is no better than the poorest group of plates which it contains. Thus it is that the cadmium test is designed to indicate the relative states of charge of the individual plates or group of plates in the cell, in order that the plates which limit the capacity of the cell may be detected and any defects which may exist rectified. 382 Storage Battery Manual Pig. 140 contains a photographic illustration of two groups of plates taken from cells, and such as would prove below normal on a cadmium test. It will be noted that both groups of plates are in a very badly sulphated con- dition, and there is also very poor conductivity between the grids and the pellets of active material on account of the poor contact between the grids and the active material. A cadmium test on these groups at the end of a charge would show that the readings between the positive group and cadmium would be abnormally low, and that the negative group would be electro-positive to cadmium. Very little capacity would be obtainable from these plates in their present con- dition. Fig. 140.— Badly Sulphated Groups Which Would Show Below Normal on Cadmium Test. The treatment required to restore the capacity of such plates is a series of charges and discharges (treating cycles) at a very low rate and in electrolyte of comparatively low specific gravity (1.200). The " Standard Negative " Electrode Test. — For laboratory work in con- nection with ascertaining the relative states of charge of storage battery plates some battery engineers prefer to use a standard negative electrode instead of the cadmium stick described in the preceding paragraphs. This electrode consists of an ordinary negative plate which at all times is kept in a perfectly healthy and fully charged condition. The method of using such an electrode for this purpose is practically identical with that which has already been described for making the cadmium test, with the exception, however, that the values of the differences of potential are obviously not the same as in the cadmium test. CHAPTEE XXVIII. MISCELLANEOUS NOTES. Health Hints. When working around storage batteries or in the manufacture of various parts composing the cells, certain precautions for preserving the health should be observed. These health hints may be divided into two classes, as follows : (1) Protection against the injurious effects of sulphuric acid. (3) Protection against lead poisoning. Protection Against Injurious Effects of Sulphuric Acid. — Sulphuric acid produces very painful burns when it comes in contact with the skin, and the following precautions should be observed when handling this acid : (a) Wear rubber gloves, apron, boots or shoes. (b) Wear goggles to j)rotect the eyes. (c) Woolen clothes should be worn in preference to cotton clothes for the reason that cotton is easily attacked and eaten away by the acid. If cotton iclothes are worn, it will be found that it is a good plan to soak them in a strong solution of bicarbonate of soda and then allowed to dry, as this process will tend to neutralize the effect of any acid which may come in contact with the clothes. It will also prove a good plan to have at hand a bottle of strong ammonia solution for applying to the clothes to neutralize any acid spilled on them. (d) In order to protect the hands from acid have at hand a bucket or 'other vessel filled with a solution of bicarbonate of soda for rinsing off the hands or other partsi of the body from time to time while handling the acid. (e) In case acid should be splashed in the eyes they should be immediately washed out thoroughly with warm, fresh water, after which apply warm vaseline, Albany grease, olive oil, or ordinary lubricating oil to and around the eyes. (f) Additional precautions for handling and mixing acid will be found in Chapter IX. Protection Ag^ainst Lead Poisoning. — In working around storage batteries or handling storage battery parts always bear in mind that the major por- tions of such parts are composed of lead in some form, and that if lead be allowed to enter the human system serious injury from lead poisoning may result. The following precautions are therefore given as a guide in pre- venting injury to the health from this cause : (a) In order to prevent as much as possible any lead from entering the system through the mouth, do not eat and do not chew tobacco while handling such parts. 25 384 Storage Batteky Manual (b) Keep hands out of the mouth while handling such parts. (e) When knocking-off work, the face and hands should be trhoroughly washed clean with soap, being careful to also clear out the nostrils and clean the finger nails. Clothes should also be changed before leaving the work- shop. Bathe frequently. (d) Use a mild purgative if necessary to prevent constipation. (e) Good fresh milk is especially effective in preventing lead poisoning. Drink plenty of it. (f) The characteristic symptoms of lead poisoning are loss of appetite, constipation, indigestion, muscular pains developing into weakness, and in advanced cases, paralysis. In some cases the gums become abnormally dark or blue. Notes on lead Oxides for Storage Battery Plates. The quality and characteristics of storage battery plates of the paste type depend largely upon the quality and grade of the lead oxides of which the Fig. 141. — Miorophotograpli of Fig. 142. — Microphotograph of Lead Oxide of Rugged Molecular Lead Oxide of Light, Smooth Mole- Structure. Produces High Capacity, cular Structure. Produces Low Ca- Long Life Plates. pacity. Short Life Plates. paste is composed. A considerable amount of research work has been done in the past, and is still going on, in improving the quality and characteristics of the plates through improving the quality of the lead oxides used for this purpose. Prom present research data available it would seem that a definite rela- tion exists between the capacity of a plate and the molecular structure of the oxides used in the paste composing the active material. Moreover, it appears to be an established principle that the grade and quality of the oxide pro- duced and its suitability for storage battery use depend upon the specia nature of the process of converting the virgin lead into the oxides. Miscellaneous Notes 385 As illustrating that feature of the relation existing between capacity and the molecular structure of the oxide of which the active material of the plate is composed, attention is invited to the microphotographs shown in Figs. 141 and 142. These photographs represent specimens of lead oxides which are magnified by approximately 400 diameters. The specimen shown in Pig. 141 is of large, rugged molecular structure and it may be said that it is characteristic of this grade of oxide to produce a relatively heavy and rugged crystaline formation when mixed in the paste and subjected to the electro-chemical action which takes place in the storage battery cell. Furthermore, it may be said that on account of these properties, this grade of oxide will in general produce a plate of high capacity, and one Fie. 143. — Testing Lead Oxide to Deter- mine Ratio of Volume to the Weight o£ the Sample. Known as the " Volumeter Test." which is possessed of a high factor of cohesion between the particles of active material, and, since this factor is a function of the life of a plate, it follows that the plates composed of this grade of oxide should be of comparatively long life. The photograph shown in Fig. 143 represents a specimen of oxide the particles of which are of light, smooth molecular structure and have a rela- tively low factor of cohesion. Plates composed of this grade of oxide may in general be said to be of low capacity and short life. Eigid specifications covering the grade and quality of storage battery oxides have therefore been developed as a result of the extensive amount of research work which has been performed by electro-chemists and battery engineers. All leading storage battery manufacturers accordingly subject the oxides going into the fabrication of their plates to a rigid series of specification tests before using such oxides. Fig. 143 contains an illustra- 386 Storage Battery Manual tion of one of the tests being conducted on a lot of oxides intended for storage battery use; this particular test is known as the volumeter test, and is designed to determine the ratio of volume to the weight of the sample, and constitutes one of the most important tests in this line of work. Gun-Firing Battery. The gun-firing battery is given special mention in the text of this volume by reason of the unique position which it occupies in being the pioneer in the field of general application of storage batteries to the naval service, and in view of the fact that many people in the service received their first experi- ence in the care and operation of storage batteries with this type of cell. It is therefore considered eminently fitting that this type of battery should receive special mention in this volume. Fig. 144 contains an assembled view of a type of battery used for this purpose, while Fig. 145 contains a disassembled view of the same battery and from which a clear idea of the details of its construction may be obtained. Paraffin Impregnation of Wood Parts Used in Storage Battery Installations. Where it is necessary to use wood parts around storage battery installations, it has been found that the life of the wood is materially increased througn impregnating it with paraffin. This operation is designed to thoroughly saturate the wood with the paraffin, thereby preserving it against the corro- si\e action of the sulphuric acid of the electrolyte, and also adding to its insulating qualities. This method of treating the wood has also proved more effective for this purpose than the use of acid-resisting paints and other like coatings. For wood parts such as cell-wedges, battery tank liners, etc., as used in submarine battery installations, this method of treating the wood has proven very effective in preserving these parts. Due to its capacity for absorbing a relatively large amount of molten paraffin, maple-wood has been found especially adapted for such parts used around storage battery installations. The process of impregnating wood by this method will be described in detail. Paraffin Impregnation Process on "Wood. — This process is based upon the principle of immersing wood in a bath of boiling paraffin, the temperature of which is sufficient to drive out the moisture and other free organic matter contained in the wood, and to replace this matter with molten paraffin. The length of time required to complete this process depends upon the temper- ature of the molten paraffin bath, which is a function of its power of pene- tration, the higher the temperature the shorter the time required. Miscellaneous Notes 387 Fig. 144. — Assembled View of Gun Firing Battery. UNIT JAR POSCONN STRAP ■» P n NEG COHN VENT PLUS VENT PLUG STRAP WASHER n WOOD SEPARATOR PERFORATED RUBBER SHEET SCABLE TERM P0$> NEG Li_li-J THUMB HUT «''^' CONN TERMINAL CABLE TERMINAL TOP CONNECTOR POSiNEG StrapIiandle ^^^^^amm POSITIVE PLATE END NEGATIVE PUTE POSITIVE GROUP NEGATIVE GROUP Fig. 145. — Disassembled View of Gun Firing Battery. 388 Storage Battery Manual Fig. 146 contains a diagram indicating, the apparatus required to impreg- nate wood with paraffin by this process. Referring to this diagram, tanks T-1 and T-3 are approximately two-thirds to three-fourths filled with paraffin, WATER SUPPLY O -" ■-