TM 11-6140-203-14-1TECHNICAL MANUAL

OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT,AND GENERAL SUPPORT MAINTENANCE MANUAL

AIRCRAFT AND NONAIRCRAFT NICKEL-CADMIUM BATTERIES(GENERAL)

H E A D Q U A R T E R S , D E P A R T M E N T O F T H E A R M Y14 OCTOBER 1980

WARNINGDANGEROUS CHEMICALS ARE USED IN

NICKEL-CADMIUM BATTERIESThe electrolyte used in nickel-cadmium batteries contains potassium hydroxide (KOH), which is a caustic chemical agent. Serious and deep burns of body tissue will result if the electrolyte comes in contact with the eyes or any partof the body. Use rubber gloves, rubber apron, and protective goggles when handling the electrolyte. If accidental.contact with the electrolyte is made, use ONLY clean water and immediately (seconds count) flush contaminatedareas. Continue flushing with large quantities of clean water. Seek medical attention without delay for the eyes.

EXPLOSIVE GASES ARE GENERATED BYNICKEL-CADMIUM BATTERIES

Hydrogen and oxygen gases are generated in explosive proportion while the nickel-cadmium battery is being.charged and discharged. Charge the nickel-cadmium battery in a well-ventilated area to reduce concentrations ofexplosive gases. Turn off the battery charger before connecting or disconnecting the nickel-cadmium battery to pre-vent arching. Do not use matches or an open flame in the charging area. Arcs, flames, or sparks in the charging area will ignite the gases and cause an explosion. The battery box cover must be removed and the battery case ventplug (if used) must be open when charging.

DO NOT MIX SULPHURIC ACID AND KOHThe electrolyte used in nickel-cadmium batteries reacts violently to the sulphuric acid used in the more commonlead-acid types of batteries. DO NOT add sulphuric acid electrolyte to the battery; the mixing of the acid and KOHelectrolytes will cause a violent reaction which could result in the splattering of the mixture into the eyes and ontothe skin. Every effort must be made to keep nickel-cadmium batteries as far away as possible from lead-acid bat-teries. Do not use the same tools and materials such as screwdrivers, wrenches, syringes, hydrometers, and glovesfor both types of batteries. Any trace of acid or acid fumes will permanently damage nickel-cadmium batteries oncontact.

BATTERY SHOP SAFETY PRACTICESNickel-cadmium battery maintenance personnel should be thoroughly trained in the use of charging, discharging,and test procedures. The employment of properly trained personnel in the maintenance of nickel-cadmium bat-teries cannot be overemphasized. The nickel-cadmium battery shop must be used ONLY to maintain nickel-cadmi-um batteries. Anything associated with lead-acid batteries should never come in contact with nickel-cadmium bat-teries, including acid fumes. In addition to the equipment required to maintain nickel-cadmium batteries; thenickel-cadmium battery shop should have adequate ventilation; deluge shower, eyewash fountain, and fire ex-tinguisher.

TIGHTENING TERMINAL SCREWSAND STUDS

Be extremely careful when tightening terminal screws and studs. Bodily injury and damage to the equipment mayresult if the torque wrench accidently causes a short circuit.

FIRE FIGHTING SAFETY PRACTICECO2 is an acceptable fire extinguishing agent once a fire has developed. In no case should CO2 be directed into a bat-tery compartment to effect cooling or displace explosive gases. The static electricity generated by the discharge ofthe extinguishers could explode hydrogen/oxygen gases trapped in the battery compartment.

*TM 11-6140-203-14-1

T E C H N I C A LM A N U A L HEADQUARTERSDEPARTMENT OF THE ARMY

No. 11-6140-203-14-1 W ASHINGTON , DC, 14 October 1980

OPERATOR’S ORGANIZATIONAL, DIRECT SUPPORT, ANDGENERAL SUPPORT MAINTENANCE MANUAL

AIRCRAFT AND NONAIRCRAFT NICKEL-CADMIUM BATTERIES(GENERAL)

REPORTING ERRORS AND RECOMMENDING IMPROVEMENTSYou can help improve this manual. If you find any mistakes or if you know of a way to improve

the procedures, please let us know. Mail your letter, DA Form 2028 (Recommended Changes to Pub-lications and Blank Forms), or DA Form 2028-2 located in back of this manual direct to: Com-mander, US Army Communications and Electronics Materiel Readiness Command, ATTN:DRSELME-MQ, Fort Monmouth, New Jersey 07703. In either case, a reply will be furnished direct toyou.

C HAPTER 1 .

CHAPTER 2.Section I.

II.

III.

Sec t ion IV.

CHAPTER 3.S e c t i o n I

II.

APPENDIX AGLOSSARY

INTRODUCTIONScope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Indexes of publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Maintenance forms, records, and reports. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .FUNCTIONING OF NICKEL-CADMIUM BATTERIESGeneralPurpose and use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Electrochemical action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Summsry of general information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Operating CharacteristicsElectrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Discharge chsracteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Charge characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Charge efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Gassing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Electrolyte level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Foaming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Summary of operating characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Factors Affecting ServiceabilityTemporary loss of capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Thermal runaway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Extreme temperature operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Summary of factors affecting serviceability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .General Servicing FeaturesCare of battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Determining state of charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Periodic maintenance cycling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Adjustment of electrolyte level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Summary of general servicing features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .SHIPMENT, STORAGE, AND DEMOLITION TO PREVENT ENEMY USEShipment and StorageRepacking for shipment or storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Demolition of Materiel to Prevent Enemy UseAuthority for demolition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Methods of destruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Para-graph

1-11-21-3

2-12-22-32-4

2-52-62-72-82-92-102-112-122-13

2-142-152-162-17

2-182-192-202-212-22

3-13-2

3-33-4A-1

Page

1- l1-11-1

2-12-12-22-3

2-32-32-52-62-72-82-82-92-9

2-102-102-112-12

2-122-142-142-142-16

3-13-1

3-13-1A-1

Glossary 1

i

*This manual supersedes TM 11-6140-203-15-1, 1 December 1969, including all changes.

Number1-12-12-22-32-4

2-52-62-72-82-92-102-112-12

3-13-2

LIST OF ILLUSTRATIONSTitle

Typical Nickel-Cadmium Batteries, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Construction of a Typical Vented Sintered-Plate Nickel-Cadmium Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Electrochemical Action in a Nickel-Cadmium Storage Battery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Effects of Discharge Rates on Capacity of a 24-Volt, 30-Ampere-Hour Nickel-Cadmium Battery. . .Comparison of Typical Discharge Characteristics of a 19 Cell Nickel-Cadmium Battery at Normal and Low Tempera-

ture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Temperature-Capacity Relationship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Typical Constant Potential Charging Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Constant Current Charging Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .AN/USM-432 Charger/Analyzer-Front Panel Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Battery Discharge Equalization Fixture (Typical Setup). . . . . . . . . . . . . . . . . .Typical Nickel-Cadmium Battery Shop Equipment Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Typical Discharge Voltage Curve Under Moderate Load for Nickel-Cadmium Battery. . . . . . . . . . . . . . . . . . . . . . . . .Maintenance Flow (Every 100 Flight Hours or 120 Days for Aircraft Nickel-Cadmium Batteries; Quarterly or Every

100 Cycles for Nonaircraft Nickel-Cadmium Batteries . . . . . . . . . . . . . . . . . . . . .Typical Single Nickel-Cadmium Battery, Packaging Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Typical Multiple Nickel-Cadmium Batteries, Packaging Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page1-02-22-42-5

2-62-72-82-82-92-112-132-14

2-153-23-3

ii

TM

11-6140-203-14-1

Figure

1-1. T

ypical N

ickel C

admium

B

atteries

1-0

TM 11-6140-203-14-1

CHAPTER 1

INTRODUCTION

1-1. scopeThe full series of publications covering vented nickel-cadmium batteries is made up of four manuals: TM11-6140-203-14-1, TM 11-6140-203-14-2, TM11-6140-203-14-3, and DMWR 11-6140-203. Thismanual covers the description, functioning, opera-tional characteristics, serviceability and generalservicing information of aircraft and nonaircraft typevented nickel-cadmium batteries, Refer to TM11-6140-203-14-2 for specific data and maintenanceand repair instructions for each of the aircraft nickel-cadmium batteries. Refer to TM 11-6140-203-14-3for specific data and maintenance and repair instruc-tions for each of the nonaircraft nickel-cadmium bat-teries.

1-2. Indexes of Publicationsa. DA Pam 310-4. Refer to the latest issue of DA

Pam 310-4 to determine whether there are new edi-tions, changes, or additional publications pertaining tothis equipment.

b. DA Pam 310-7. Refer to DA Pam 310-7 to deter-mine whether there are modification work orders(MWO's) pertaining to this equipment.

1-3. Maintenance Forms, Records, andReports

a. Reports of Maintenance and UnsatisfactoryEquipment. Department of the Army forms and pro-cedures used for equipment maintenance will be thoseprescribed by TM 38-750, The Army MaintenanceManagement System.

b. Report of Packaging and Handling Deficiencies.Fill out and forward DD Form 6 (Packaging Improve-ment Report) as prescribed in AR 735-11-2(NAVSUPINST 4440.127E/AFR 400-54/MCO4430.3E/DSAR 4140.55)

c. Discrepancy in Shipment Report (DISREP) (SF361). Fill out and forward Discrepancy in ShipmentReport (DISREP) (SF 361) as prescribed in AR55-38/NAVSUPINST 4610.33B/AFR 75-18/MCOP4610.19C and DLAR 4500.15.

1-1

TM 11-6140-203-14-1

CHAPTER 2

FUNCTIONING OF NICKEL-CADMIUM BATTERIES

Section I. GENERAL

2-1. Purpose and UseVented nickel-cadmium (Ni-Cad) batteries derive theirname from the composition of their plates; nickeloxide on the positive and metallic cadmium on thenegative. They are “vented” in that gases generatedduring the charging process can be expelled from thecells in a controlled manner. They are used to provide asource of direct current (dc) power in both aircraft andnonaircraft applications. The following characteristicsprovide major advantages over other storage batteries.

a. Vented nickel-cadmium batteries will maintain arelatively steady voltage when being discharged athigh currents.

b. Vented nickel-cadmium batteries can be chargedand discharged at a high rate current without causingpermanent damage to the battery.

c. Vented nickel-cadmium batteries can stand idlein any state of charge (fully charged, partly charged ordischarged) without any damage.

d. Vented nickel-cadmium batteries can withstandextremely cold temperatures without damage.

e. Vented nickel-cadmium batteries can withstandhigh levels of vibration and shock without failure.

f. Vented nickel-cadmium batteries are composed ofindividually replaceable cells.

g. Vented nickel-cadmium batteries have a longservice life under severe conditions of use.

2-2. Constructiona. Batteries. The term “battery” is generally used to

describe a unit consisting of one or more cells. Cells arethe basic building blocks of a battery. A battery can bea single cell which has terminals and is insulated and isready for use; but usually a battery is a series combina-tion of individual cells assembled in a case containing aconnector and proper insulation. Each cell has a nomi-nal voltage of 1.20 volts; however, the actual operatingvoltage of a cell will range from 1.2 to 1.3 volts. Anominal 6-volt battery will contain 5 cells connected inseries and a nominal 24-volt battery will contain 19 or20 cells.

b. Principal Parts and Materials. The principalparts and materials used in the vented cells of thenickel-cadmium battery are shown in figure 2-1 andare described in paragraphs (1) through (5) below.

(1) Plates (electrodes). The sintered plates of nick-el-cadmium cells are made by a process in which carbo-nized nickel powder is sintered at high temperature to

a metal carrier. The welding together of the individualgrains of nickel powder onto the carrier, results in ahighly porous structure known as a plaque. Positive(nickel) electrodes are formed by soaking the plaque innickel salts and then subjecting the salt-impregnatedplaque to electric current. Negative (cadmium) elec-trodes are formed by the same processes except thatcadmium salts are used. Plates are formed by cuttingthe plaque to size and welding a nickel tab to a cornerfor connection purposes.

(2) Electrolyte. The electrolyte is normally, byweight, a 30 percent solution of potassium hydroxide(KOH) in distilled water. It provides a path for con-ducting the current that flows between the positiveand negative plates. The electrolyte does not take partin the chemical react on in nickel-cadmium batteries,but acts as an ion carrier. The specific gravity of theelectrolyte, which is approximately 1.300, remains thesame whether the battery is charged or discharged.Therefore, specific gravity measurements cannot beused to determine state-of-charge as is the case withlead-acid batteries.

(3) Separator. The separator is a continuous thinporous multiluminate of nylon and either cellophaneor plastic, that keeps the positive and negative platesfrom coming into contact with each other and causinga short. The layer of cellophane or plastic, also has theadded function of preventing oxygen generated onovercharge from coming into contact with the nega-tive electrode and lowering the end-of-charge voltage.Before 1979 (except for BB-433A/A, which is prior to1978) all aircraft and nonaircraft batteries containedcellophane separators. After 1979 (1978 for theBB-433A/A) most aircraft nicad batteries used plasticfilm separators such as “Permion” or “Celgard:” Theseplastic film separators have greater resistance to de-gradation and longer life than cellophane, greatlyreducing the possibility of “thermal runaway.”

(4) Cell assembly. The cell is assembled into itsfinal form by welding the tabs of the negative plates toone terminal post and the tabs of the positive plates toa second terminal post. Once assembled, it is insertedinto a plastic case (nylon for aircraft batteries and ny-lon on Acrylonitrile-Butadine-Styrene (ABS) for non-aircraft batteries) and fitted with a cover and ventassembly that permits the terminal posts to projectthrough the top of the case. After the cover is sealed tothe case, electrolyte is added.

2-1

TM11-6140-203-14-1

Figure 2-1. Construction of a Typical Vented Sintered-Plate-Nickel-Cadmium Cell.

(5) Cell vent. Each cell is equipped with a ventplug and filler cap. These vents may be either a one-piece or a two-piece assembly. The cell vent can be re-moved for cleaning and adjustment of electrolytelevel. When excessive gases develop in a cell duringcharge, they escape through the vent hole. The vent re-lieves gas pressure by remaining closed until a pres-sure of at least 2 psi is reached and will open at a pres-sure below 10 psi. Except when releasing gas, the ventremains sealed to prevent electrolyte leakage, theentry of foreign material into the cell or contamina-tion of the electrolyte by exposure of air high in carbondioxide content. When a two-piece cell vent is used,the vent valve may be removed for shipping and re-placed by a shipping screw. Before putting the batteryinto service the slipping screw must be removed andreplaced by the vent valve.

2-2

2-3. Electrochemical ActionThe exact chemical reactions that occur within a cell ofthe nickel-cadmium battery during charge and dis-charge are open to question, particularly with regardto the reduced and oxidized states of the activematerials. However, the essential operation can be de-scribed. Figure 2-2 illustrates the essential electro-chemical actions.

a. Charge. When charging current is applied to thecell, the cadmium-oxide material of the negative platesgradually loses oxygen and becomes metallic cadmiumand the nickel-oxide active material of the positiveplates is brought to a higher state of oxidation. Thesechanges continue in both sets of plates as long as thecharging current is applied, or until the activemateriels at the plates have been completely con-verted. The cell emits gas toward the end of this proc-

ess because of the decomposition of the water compo-nent of the electrolyte as hydrogen at the negativeplates and oxygen at the positive plates. The electro-lyte conducts current between the plates of oppositepolarity and reacts to produce the electrochemicalchanges without producing any significant change inits own overall chemical composition. Thus, the mea-surement of specific gravity of the electrolyte gives noindication of the state of charge in a nickel-cadmiumcell. Because the charging of the nickel-oxide positiveelectrode is not 100 percent efficient, an overcharge of20 to 40 percent is usually required to bring the bat-tery to full capacity.

b. Discharge. During discharge, the chemical reac-tion is reversed. The positive plates gradually return toa state of lower oxidation, while the negative platessimultaneously regain lost oxygen. During the dis-charge process, the chemical energy is released as elec-trical current through the discharge load. The rate atwhich the chemical energy is converted is determinedprincipally by the resistance of the load to currentflow. A load with a very low resistance could causesuch a high current that the cell might be damaged ordestroyed.

TM11–6140–203–14–1

2–4. Summary of General Informationa. Individual nickel-cadmium cell nominal voltage is

1.2 volts while actual voltage is between 1.20 and 1.30volts.

b. Active materials of a nickel-cadmium cell arenickel oxide on the positive plate and metallic cad-mium on the negative plate.

c. Nickel-cadmium cell plates are separated by athin porous multilaminate of plastic materials.

d. Electrolyte used in the nickel-cadmium cell is a31 percent by weight solution of potassium hydroxidein distilled water.

e. Specific gravity of the electrolyte is the samewhether the nickel-cadmium cell is charged or dis-charged. However, the electrolyte level rises duringcharge and lowers during discharge.

f. The vent valve on the nickel-cadmium cell mustbe capable of venting excessive gases.

g. The value of charging voltage used depends onthe number of cells connected in series.

h. The value of charging current depends on theampere-hour rating of the storage battery.

Section Il. OPERATING CHARACTERISTICS

2–5. Electrical Characteristicsa. Voltage. Regardless of size or shape, the voltage

of a single nickel-cadmium cell is nominally 1.20 voltsbased on the plateau voltage at a 5-hour discharge ratebut a number of voltage levels other than this maybeencountered as the voltage varies depending on therate of charge or discharge, state of a charge, andtemperature. Battery voltages higher than this are ob-tained by connecting integral multiples of a suitablenumber of cells in series. Accordingly, a 6-volt nickel-cadmium battery consists of five cells connected inseries; a 12-volt battery contains 10 cells similarly con-nected, a 24-volt battery contains either 19 or 20 cellsserially connected. The quantity of cells a specific bat-tery contains is listed in chapter 2 of TM11-6140-203-14-2 or TM 11-6140-203-14-3 foraircraft and nonaircraft nickel-cadmium batteries re-spectively.

b. Open Circuit Voltage. Open circuit voltage is thevoltage of a cell without a load. At room temperature,this voltage is 1.25 to 1.35 volts for a fully chargedbattery, depending on how long the cell has beenstanding after charge. Elevated temperatures willlower the measure open circuit voltage.

c. Closed Circuit Voltage. Closed circuit voltage isthe voltage of a cell with a load applied. The value de-pends on the size of the load, the electrical capacity ofthe cell, the temperature, and the length of time ondischarge.

d. Plateau Voltage. Plateau voltage is the cellvoltage during the relatively flat portion of the dis-charge curve. This voltage depends on the dischargerate and, in most applications, is about 1.2 volts.

2–6. CapacitySintered-plate Ni-Cad cells are capable of delivering

almost full capacity over a wide range of dischargerates and temperatures. However, battery capacity canbe influenced by the primary factors of discharge rateand temperature and secondary factors such as stor-age, age, and previous charge history of the battery.

a. Rated Capacity. The capacity rating of a nickelcadmium battery is that capacity measured in ampere-hours at a specified rate of discharge, discharge tem-perature, and voltage end point.

(1) Aircraft batteries are normally rated at the 1-hour discharge rate; i.e., a 30-Ah battery is dischargedat 30 amperes, at 20°C (68°F) to an end point voltageof 0.9 volt/cell. However, in the past other rating sys-tems have also been employed. Thus, a battery whichis rated at 30 Ah at the 1-hour rate could also have arated capacity at 34 Ah at the 2-hour rate (17A) to anend-point of 1.0 volt/cell.

(2) Nonairaft batteries for communications useare normally rated at the 5 hour-discharge rate, i.e., a14 Ah battery is discharged at 2.8 amperes at 20°C(68°F) to an end point voltage of 1.0 volt.

b. Actual Capacity.

2–3

2-4 Figure 2-2. Electrochemical Action in a Nickel-Cadmium Storage Battery.

(1) Aircraft batteries. The actual capacity ob-tained from aircraft type batteries after a full chargenormally exceeds the rated capacity by 25 to 40 per-cent. When the actual capacity falls below ratedcapacity, the battery is considered unacceptable.

(2) Nonaircraft batteries. The actual capacity ob-tained from new communication type batteries after afull charge normally exceeds the rated capacity by 15to 30 percent. Actual capacity falls with cycling, andwhen it reaches 60 percent of rated capacity aftermany hundreds of cycles it is considered unacceptable.

2–7. Discharge Characteristicsa. Discharge Rate. The nickel-cadmium battery is

capable of delivering very high discharge currentsrelative to its size. Figure 2-2 shows the capacity andvoltage obtained during discharges of a 30 ampere-hour aircraft type cell over a wide range of dischargerates at normal temperature. The lowest usable volt-age for proper cell operation in noncranking applica-tions is considered to be approximately 1.0 volt(equivalent to 19 volts for a 19-cell battery). Thecurves in figure 2-3 show that an increase in currentdemand from 8 amperes to 100 amperes will onlyslightly decrease the capacity output of the storagebattery. However, the individual cells are still capableof delivering current in excess of their rated ampere-hour capacity. As the current demand is increased to300 amperes, the cells are degraded until their capac-

TM 11–6140–203–14–1

ity has dropped to approximately 24 ampere-hours,which is approximately a 20 percent reduction overthe rated capacity of 30 ampere-hours. As the currentdemand is increased to 500 amperes, the cell can nolonger deliver usable current for noncranking load be-cause the cell voltage has dropped below the minimumacceptable level. However, for engine cranking loads,cell voltages as low as 0.6V are acceptable. The curvesof figure 2-3 show that the aircraft type cells are capa-ble of sustained current drains up to 10 times their rat-ed capacity before the voltage level drops below 1.0volt. Nonaircraft type cells are usually designed forlower rate applications and therefore will be limited toapproximately one-half the current levels of the high-rate aircraft type cells. Curve A of figure 2-3 is a typi-cal discharge curve for a 19-cell aircraft battery dis-charged at the one and two hour rates.

b. Discharge Temperature. Nickel-cadmium cellsare capable of sustaining high current drains and goodperformance at temperatures as low as 0°F. However,sustained high current at temperatures below 0°F willresult in a reduced cell performance because the in-creased internal resistance of the cell lowers the closedcircuit voltage. The effective capacity of a cell will de-crease when it is subjected to high current demandsand extreme temperatures. This is shown in figure 2-4where battery capacity and voltage is compared at the5-minute rate at 80°F and –22°F. The preferred oper-ating temperature for typical vented nickel-cadmium

Figure 2-3. Effects of Discharge Rates on Capacity of a 24-Volt, 30-Ampere-Hour Nickel-Cadmium Battery.

2–5

TM 11–6140–203–14–1

cells is the range from 0°F to 100°F, with the opti-mum temperature range being 50°F to 90°F. An in-crease or decrease in temperature from the optimumrange causes a corresponding reduction in cell capac-ity. Vented nickel-cadmium batteries, however, maybe discharged at temperatures as low as – 65°F if dis-charge rates are limited. Figure 2-5 indicates availablebattery capacity as a function of temperature. The in-formation given in figure 2-5 should be consideredonly a guide because cell design and battery size willaffect low temperature discharge performance consid-erably. Discharging at high rates for sustained periodswill cause large increases in battery temperature. Bat-teries should be allowed to cool to approximately roomtemperature after high rate discharge before startingto recharge.

2–8. Charge Characteristics

A nickel-cadmium battery is capable of acceptingcharge at rates many times its rated capacity for ashort period. However, once the battery is fullycharged the rate of current input must be limited toprevent excessive loss of water, spewage of electrolyteand overheating. Control of charging current or volt-

Figure 2-4. Comparison of Typical Discharge Characteristics of a19-Cell Nickel-Cadmium Battery at Normal and Low Temperature.

2–6

age and tone is necessary to prevent excessive over-charge while still providing full capacity. The charac-teristics of the various charging methods follow. Ingeneral, the constant potential charge provided by theaircraft bus does not provide a full charge.

a. Constant Potential. Constant-potential (CP)charging applies a fixed voltage to the cell. The result-ing charge current is determined by the applied volt-age level, the state-of-charge of the cell and its temper-ature. Figure 2-6 shows a typical constant potentialcharging curve of a partially discharged battery in anaircraft. As shown by the figure, very large amounts ofcurrent are input for a short period of time until theback voltage of the battery rises as it nears full charge.Adjustment of the constant potential setting of theaircraft bus with temperature is required to match thecharacteristics of the battery.

b. Modified Constant Potential. Frequently, batterycharging equipment used for charging nickel-cadmiumbatteries cannot tolerate the very high currents whichwould be drawn in the initial stages of charging at con-stant potential. In such cases, current-limiting devicesor electrical resistances are commonly connected be-tween the battery and its charging source. Becausethese practices supply a fixed voltage when the batteryis fully charged, but reduced voltage in the initialstage of charging, they are called modified constantpotential charges. The limitation of charging currentduring initial stages of charging current lengthens thetime required to completely charge the battery. Cur-rent can also be limited by manually reducing the volt-age for the first few minutes of charge. For constantpotential charging rates for aircraft nickel-cadmiumbatteries, refer to chapter 5, TM 11-6140-203-14-2.For constant potential charging rates for nonaircraftnickel-cadmium batteries, refer to chapter 5, TM11-6140-203-14-3. A typical modified constant po-tential charging curve is shown in figure 2-6.

c. Constant Current. The constant current methodof charge is not limited by the back voltage of the bat-tery and as such will provide a full charge irrespectiveof battery temperature. A typical constant currentcharging curve is shown in figure 2-7. The figure indi-cates that the battery voltage rises sharply as a 100percent state-of-charge is reached. Charging current isstill applied, however, to achieve the desired 20 to 40percent overcharge. When automatic equipment is em-ployed, charging can be done at high rates; i.e., the 1-hour rate, until the voltage rise takes place. At thispoint the constant current value can be reduced to the3- to 5-hour rate in order to provide the required over-charge at a low enough rate to prevent spewage of elec-trolyte. The length of the overcharge period is normal-ly timed. If automatic equipment is not accessible, theentire charge must be run at a rate which will be safefor overcharge. These charging rates are provided witheach specific battery.

TM 11–6140–203–14–1

Figure 2-5. Temperature-Capacity Relationship

d. Pulse Charging. Several types of automaticcharging equipment are available which provide thecharging current in the form of high current pulses in-terspersed with periods of no current or discharge. Ingeneral, these charges function in the same manner asautomatic constant current types, in that the currentlevel is reduced when the battery voltage rises to pro-vide a controlled overcharge. Because of the nature ofthe pulse charge and the automatic controls employed,it is usually possible to charge at very high rates.Charge time of 1 hour is typical. One type of chargeanalyzer that can charge 24-volt batteries in 1 hour isthe AN/USM-432. Figure 2-8 gives its front panellayout.

e. Charging of New or Unformed Batteries. Bat-teries which have never been cycled have a differentcharge voltage characteristic than used batteries. Thisoccurs because the cadmium electrode in a new batterymay have a large excess of uncharged cadmium oxidewhich must be formed by overcharging. Thus, thesharp voltage rise seen in figure 2-7 does not occurduring the first cycle. Up to 150 percent overchargemay be required to reach full charge. Because of thiscondition, care must be taken when charging at very

high rates with automatic pulse or constant currentcharging equipment, since the voltage level requiredto reduce the charging current is not reached. This canresult in overheating of the batteries and spewage ofelectrolyte out of the cell vents. It is recommendedthat new batteries be charged at a current no higherthan the 2-hour rate for the first cycle and the chargeshould be continued until the voltage reaches at least1.50 volts per cell. When charging a new battery, thevoltages of all the individual cells should be checkedperiodically for either very high or low values.

f. Standby or Trickle Charging. Because the self-dis-charge of a nickel-cadmium battery is approximately1.2 percent per day at normal temperatures, standbycharging is required to maintain its full rated capacity.For standby charging in the temperature range of60°F to 90°F, use a current equal to 3 ma per ampere-hour rated capacity or a constant potential of1.35V/cell. Batteries on standby charge must be regu-larly checked to ensure adequate electrolyte level.

2–9. Charge EfficencyCharge efficiency is the ratio of ampere-hours avail-able on discharge to ampere-hours returned to a bat-

2–7

TM 11–6140–203–14–1

Figure 2-6. Typical Constant Potential Charging Curve.

tery during charge. This ratio is always less than 1;therefore, excess charge must always be returned tothe battery after discharge to restore rated capacity.The total charge necessary may be as low as 110 per-cent, or much greater, depending on the temperatureand cell characteristics. It is generally recommendedthat the nickel-cadmium battery be charged (constantcurrent) for a time that will give at least 125 percentof the previously discharged ampere hours. For exam-

Figure 2-7. Constant Current Charging Curve.

2–8

ple, a 20-ampere-hour battery that is fully dischargedshould be recharged at constant current until at least1.25 times 20 ampere-hours are restored, or at least 25ampere-hours are returned. In general, a 40 percentovercharge is recommended, particularly when cell im-balance has occurred, charge rates are at the 5-hourrate or lower, and the temperature is above 90°F.

2–10. GassingDuring charge, the tendency of nickel-cadmium cellsto gas increases with temperature rise and the chargestate. Cell gassing characteristics will also vary some-what among manufacturers, cell types and for variousother reasons. A certain amount of gassing is neces-sary for a battery to become fully charged. The dangeris in excessive or violent gassing, leading to possibleexplosion, loss of electrolyte, or damage to the battery.Monitor the charging procedure to insure that exces-sive or violent gassing is controlled by reducing charg-ing current or charging voltage.

2–11. Electrolyte LevelAn inherent characteristic of nickel-cadmium batterycells is that the electrolyte is absorbed within theplates and separators to a point where it is not visiblefrom the top of the cells when at a low state of chargeor in a discharged condition. When the battery is re-charged, the electrolyte level rises and reaches its max-imum height at full charge. Ideally, the electrolytelevel should be checked on a fully charged battery thathas been at rest for at least 30 minutes and not exceed-

TM 11–6140–203–14–1

ing 2 hours. The correct level of electrolyte is ¼-inchabove the top of the plates of a fully charged cell thathas been at rest for the prescribed period of time. Re-fer to TM 11-6140-203-14-2 and TM 11-6140-203-14-3 respectively for rest time limitations forspecific aircraft and nonaircraft nickel-cadmium bat-teries. Observing the rest time limitations beforechecking the electrolyte level is an absolute must to in-sure that the cell is not overfilled or underfilled. How-ever, some modification in electrolyte level height orrest time after charging may be required depending onthe equipment used for charging and the environmentthe battery will see in use (voltage regulator settingand temperature). In general, the constant current(CC) chargers used in the battery shop will produce ahigher apparent level of electrolyte than a constant po-tential (CP) charger, since the CC charger normallycharges to a higher end-of-charge voltage. If this is thecase, then it maybe necessary to increase the rest timeafter charge from 30 minutes to up to 2 hours and/orincrease the electrolyte to -inch above the top of the

plates. These changes in electrolyte level should onlybe made if absolutely necessary and only in cells con-taining adequate head space over the plates.

2–12. FoamingFoam may sometimes be noticed in cells duringcharge. It normally does not indicate a defect and isharmful only if it results in excessive overflow. Foam-ing is more likely to occur after adding water andshould disappear after a few cycles of operation. Con-tinued foaming indicates contaminated electrolyte andthe cell should not be used until thoroughly checkedfor damage. When electrolyte is lost due to foaming innew cells, add 31 percent KOH electrolyte to the cellrather than water. After the first two charge cycles,only distilled water should be added.

2–13. Summary of Operation Character-istics

a. Cell capacity decreases when discharged at highcurrents.

Figure 2-8. AN/USM-432, Charger/Analyzer, Front Panel Layout.

2–9

TM 11–6140–203–14–1

b. Cell capacity decreases at temperatures lowerthan 20°F or higher than 100°F.

c. Voltage level of nickel-cadmium batteries re-mains essentially constant until approximately 90 per-cent of its capacity has been delivered.

d. Nickel-cadmium batteries should be charged forat least 125 percent of previously discharged ampere-hours to be at approximately full charge state.

e. Electrolyte is not visible from the top of the cellswhen the cell is at a low state of charge. When chargedproperly and rested for a minimum of 30 minutes and

a maximum of 2 hours, the electrolyte level should be¼-inch above the top of the plates.

f. The electrolyte level should be checked when thenickel-cadmium battery is fully charged and has beenat rest for a minimum of 30 minutes and a maximumof 2 hours.

g. Refer to TM 11-6140-203-14-2 and TM11-6140-203-14-3, respectively, for rest time limita-tions for aircraft nickel-cadmium and nonaircraftnickel-cadmium batteries.

Section Ill. FACTORS AFFECTING SERVICEABILITY2–14. Temporary Loss of CapacityAn important characteristic observed in nickel-cad-mium batteries is temporary loss of capacity or “sleep-iness” (also referred to as the “memory effect”). Whenthis temporary loss occurs, the battery is unable to de-liver the designed capacity. The loss of capacity is a re-sult of shallow discharge cycles. For instance, when abattery is continually discharged, as for example, to adepth of only 20 percent of full charge, its voltage-time curve begins to drop abnormally near the 20-per-cent discharge point. The effect is that 80 percent ofthe capacity has become temporarily inactive.

a. Causes. The loss-of-capacity effect is more com-mon when recharging a battery across a constant po-tential bus, such as in aircraft, than when chargingwith constant current. The loss of capacity is usuallyan indication of an imbalance between the cells be-cause of differences between individual cells in tem-perature, charge efficiency, and self-discharge rate.Imbalance can be verified by a periodic check of indi-vidual cell voltages after the battery has shown asharp rise in voltage while being charged by the con-stant current method, or after current has droppedand essentially stabilized during constant potentialmethod. The individual voltage of each cell under fullcharge should be 1.5 volts or more when the cell is atroom temperature (about 70° F). A variation of morethan 0.10 volt between cells after completion of chargeis an indication of imbalance and that the lower volt-age cells need to be additionally charged to reachequalization. Usually, a deep cycle discharge at the 10-hour rate of 0 volt followed by a recharge of the bat-tery is sufficient to equalize the cells. Figure 2-9shows a battery discharge equalization fixture and alist of available fixtures. Another cause of capacityloss is a growth of the grain size of the active materialwithin the battery plates. This type of effect is nor-mally associated with very low rates of discharge par-ticularly at high temperatures.

b. Consequences. The temporary loss-of-capacity ef-fect should not be taken lightly. Even though a batterymay appear to be giving satisfactory performance, itmay deliver only a portion of its rated capacity if re-

2–10

quired during an emergency. For example, during atest being conducted on 19-cell, 34-ampere-hour, 24-volt nickel-cadmium batteries, 30 were given a capac-ity test. The average capacity measured on 30 bat-teries was less than 15-ampere-hours, or less than halfof the rated capacity; two of the batteries deliveredonly 2-ampere-hours each. It is clear that the conditionof the batteries would not be ideal under emergencyconditions. To minimize the loss-of-capacity problem,nickel-cadmium batteries should be serviced period-ically and given a deep cycle discharge to 0 volt.

2–15. Thermal RunawayThermal runaway is a condition in which the currentfor a fully charged nickel-cadmium battery rises out ofall proportion to the impressed voltage.

a. Cause. Since runaway occurs in an overchargedstate after the battery is fully charged, the excesscharging energy is dissipated as heat and electrolysisof water. Continued overcharging under certain condi-tions has the effect of reducing the internal battery re-sistance so that it draws a higher current from the im-pressed voltage. As the temperature of the battery in-creases, the effective internal resistance continues todecrease and the current becomes progressivelygreater. This process continues and eventually de-stroys the battery unless it is properly protected by acutout device.

b. Effect of Temperature and Voltage. Thermalrunaway primarily depends on temperature and charg-ing voltage; therefore, the higher the charging voltage,the less the temperature required to effect the run-away condition, or the higher the temperature, the lesscharging voltage required. Battery temperatureshould never exceed 120°F.

c. Effect of Battery Separator Material. Most ther-mal runaways in the past have been caused by thebreakdown of the cellophane, film separator, so thatoxygen generated on overcharge could reach the cad-mium electrode, thereby lowering its voltage and in-creasing the current from a constant potential source.Plastic film separators such as “Permion” or “Celgard”used in many Army nickel-cadmium batteries since

TM 11–6140–203–14–1

Figure 2-9. Battery Discharge Equalization Fixture (Typical Setup).

1979 will not break down in the alkaline environmentof the cell as did cellophane, and therefore thermalrunaway is much less likely with these materials. How-ever, even with these new improved plastic materials,overheating and spewing of electrolyte can occur if ex-cessively high potentials and temperatures are en-countered.

d. Detecting Thermal Runaway. Thermal runaway

at the end of charge (approximately 130°F).(2) When the constant potential charging method

is used, the current gradually increases rather thangradually decreases.

(3) If the constant current charging method isused, runaway will be indicated by a decrease of bat-tery voltage with time rather than an increase as isusual.

may occur if the batteries are charged for long periodsat high charging voltages or high temperatures. 2–16. Extreme Temperature Operation

Thermal runaway may be detected by the following The nickel-cadmium battery displays a much greatersigns low temperature operation capability than the lead-

(1) Battery temperature shows a significant rise acid battery. Usually, design specifications list the

2–11

TM 11-6140-203-14-1

operating temperature range as – 65°F to + 165°F. Itsoutput capacity will be considerably degraded at bothextremes.

a. Charging. Charging at low temperatures requiresmore time and higher charging voltages than at nor-mal temperatures. In general, the lower the batterytemperature, the longer the time required for charg-ing. Conversely, charging at high temperatures re-quires lower charging voltages.

b. Discharge Voltage. The voltage decreases with anincrease in discharge rate and a decrease in tempera-ture.

2-17. Summary of Factors Affecting Serv-iceability

a. Shallow discharge cycles result in temporary loss

of capacity and an imbalance of cells within a nickel-cadmium battery.

b. Slow deep cycle discharge to 0 volt followed bycharge is necessary to equalize cells within a nickel-cadmium battery.

c. Cells containing plastic film separators are moreresistant to thermal runaway than cellophane sep-arated ones.

d. Nickel-cadmium battery temperature rise above130°F may cause thermal runaway.

e. Charging at low temperature requires more timeand/or higher charging voltage.

Section IV. GENERAL SERVICING FEATURES2-18. Care of BatteryNickel-cadmium batteries are rugged and provide longlife. However, they require proper handling and main-tenance if they are to deliver designed output and areto have a maximum useful life. Certain general han-dling techniques and precautions must be observed.

a. The electrolyte in nickel-cadmium batteries con-tains potassium hydroxide and distilled water. Chem-ically, this is the exact opposite of an acid. Lead-acidbatteries use sulphuric acid. Take every step possibleto keep the nickel-cadmium batteries as far away aspossible from the lead-acid type batteries. Do not usethe same tools and materials (screwdrivers, wrenches,syringes, hydrometers, gloves, apron, etc.) for bothbatteries. Anything associated with the lead-acid typebattery (even air) must never come in contact with thenickel-cadmium battery or the electrolyte. Even atrace of sulphuric acid fumes from a lead-acid batterymixing with the electrolyte for the nickel-cadmiumbattery may result in damage to the nickel-cadmiumbattery.

b. If separate battery shops are not possible, setupbench facilities at opposite ends of the battery shop.Mark each area of the battery shop clearly. Keep toolsand materials separate. The nickel-cadmium areashould be free of all contamination. Markings thatidentify the tools and materials for use with nickel-cadmium batteries will insure that contamination willnot occur. Painting the color blue is recommended onthe tools and materials used with nickel-cadmium bat-teries. Painting the color pink is recommended on thetools and materials used with lead-acid batteries. Theuse of properly trained personnel in the maintenanceof nickel-cadmium batteries is most important. In ad-dition, strict adherence to the maintenance proceduresprescribed for nickel-cadmium batteries is equally im-portant. The authority responsible for battery mainte-nance must insure that all battery maintenance per-

sonnel are qualified and fully aware of proper safetyprecautions. Figure 2-10 illustrates the equipmentlayout of a typical nickel-cadmium battery shop.

c. If a shortage of tools exists and it becomes neces-sary to use the same tools for both types of batteries,be absolutely sure to wash and rinse the tools withplenty of clean, hot water after they are used on eithertype. Use plenty of strong soap. Potassium hydroxidewill give the tools a very slippery, soapy feeling. Tospeed up the cleaning, if available, use a mild solutionof vinegar to wash the tools. Dip the tools in thevinegar solution, rinse in warm tap water, and thenrinse in distilled water.

d. When working around batteries, use the apron,gloves, and goggles or face-shield provided. If you spillany potassium hydroxide on your skin, immediatelyflood the area with cold water and seek medical aid.

CAUTIONDo not use a wire brush. Do not attempt toclean the battery shops with solvents, acids,or any chemical solvents because the bat-teries are constructed with plastic cellswhich would be damaged by contact withsuch chemicals. Keep open flames and metalobjects, such as tools, etc., away from the ex-posed parts of the battery. If objects are acci-dentally dropped across the terminals, ashort circuit could cause damage to one ormore cells.

e. The white powder found on top of the cells andcell connectors is potassium carbonate and is formedwhen the potassium hydroxide reacts with the carbondioxide in the air. Potassium carbonate deposits in thedry state are nonconductive and when in contact withnickel or nickel-plated material is noncorrosive. Whenmoisture is added to the powder, which occurs withdrastic humidity changes, an electrical leakage path isestablished. Also, if the potassium carbonate comes in

2-12

Figure

2-13Figure 2-10. Typical Nickel Cadmium Battery Shop Equipment Layout TM 11-6140-263-14-1

TM 11-6140-203-14-1

contact with copper, which could occur if the nickel-plating is scratched, corrosion will set in. For thesereasons, the battery must be carefully cleaned andkept free of potassium carbonate deposits.

f. The potassium carbonate deposits, when dry, maybe removed with a nylon brush. Be sure that the fillercaps are secured before brushing. Any foreign mattercan contaminate the battery. If necessary, the tops ofthe batteries may be flushed with water. Be sure thatthe filler caps are tightly closed before flushing withwater. Batteries must be thoroughly dry before use.

g. Do not attempt to determine the state of chargeof a nickel-cadmium battery by a voltage check or by aspecific gravity check of the electrolyte. The electro-lyte is not Changed by the chemical reaction whichtakes place in the battery; the specific gravity is thesame whether the battery is charged or discharged. Anindication of the approximate state of charge is theamount of current the battery draws when it is con-nected to a constant potential charger. The higher thestate of charge, the less current the battery will draw.

2-19. Determining State of ChargeThe actual state of charge of a nickel-cadmium batteryis difficult to determine. It cannot be determined bythe specific gravity of the electrolyte since it does notchange during battery charge and discharge. Themethods described in a and b below may be used for ageneral determination of charge condition. Howeverthe most accurate method is to fully recharge the bat-tery before use if it has been charged and is on standbyfor any length of time.

a. Battery Current Drawn From Constant PotentialSource. A common method of checking the state ofcharge is to connect the battery across a constant po-tential charging source and observe the charging cur-rent drawn by the battery as indicated by an ammeterin series with the battery. The charging-source voltagewould normally be 1.5 volt times the number of cells;for example, 28.5 volts for a 19-cell, 24-volt battery at70ºF. If the current drops to 1 or 2 amperes or lesswithin 5 minutes, the battery can be assumed to be in anear state of full charge.

b. Voltmeter Reading With Battery Under Load.Since the discharge voltage of a nickel-cadmium bat-tery is essentially constant until the battery is approx-imately 90 percent discharged, voltmeter readingsacross the terminals while the battery is under load arenot too reliable. Figure 2-11 shows a typical voltagedischarge curve under moderate load, and illustratesthe problem associated with voltmeter readings. Areading of approximately 24 volts may mean that thebattery is almost fully charged (point 1 on the curve)or almost totally discharged (point 2 on curve).

E L 4 G R O 0 7

Figure 2-11. Typical Discharge Voltage Curve Under ModerateLoad for Nickel-C!admium Battery.

2-20. Periodic Maintenance CyclingFigure 2-12 shows the maintenance sequence thatshould be performed at direct support or general sup-port categories. For aircraft nickel-cadmium batteries,maintenance shown in flow chart is required every 100flight hours or every 120 days (whichever shall occurfirst). For nonaircraft nickel-cadmium batteries, main-tenance shown in flow chart is required quarterly orevery 100 cycles (whichever shall occur first). The pe-riodic maintenance cycle should result in the rebalanc-ing of all cells in the battery, the reactivation of in-active plate material, and the replacement of defectivecells. In addition, the battery as returned to the usercontains the proper electrolyte level and a full charge.

2-21. Adjustment of Electrolyte LevelThe proper height and method for adjusting the elec-trolyte level has caused considerable confusion in thepast. This has been because of the wide variety ofcharging methods, conditions of use, and availablehead space within each size and type of nickel-cad-mium cell. Refer to TM 11-6140-203-14-2 or TM11-6140-203-14-3 for detailed procedures coveringthe battery being serviced.

a. Checking Electrolyte Level. Because a nickel-cad-mium cell contains large amounts of electrolyte belowthe top of the plates, the fact that electrolyte is notvisible in the partially discharged state is not neces-sarily cause for alarm. When a battery has beencharged on an aircraft bus, the electrolyte should bevisible above the cell plates immediately after thecharge is ended. If not, the electrolyte level in the cell

2-14

TM 11-6140-203-14-1

Figure 2-12. Maintenance Flow Chart (Every 100 Flight Hoursor120 Days for Aircaft Nickel-Cadmium

Batteries; Quarterly or Every 100 Cycles forNonaircraft Nickel-Cadmium Batteries).

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TM 11-6140-203-14-1

is low and must be adjusted using distilled water fol-lowing the procedure given in c below. Adjustment ofelectrolyte level is not authorized at the organizational(AVUM) level.

NOTEA low setting of the aircraft voltage regula-tor will result in the battery being only par-tially charged and therefore an apparent lowlevel of electrolytes.

b. Adjusting Electrolyte Level. The electrolyte levelof cells in a nickel-cadmium battery should not be ad-justed when the state of charge is unknown. The levelof the electrolyte should be adjusted after the batteryhas been completely charged and allowed to rest for atleast 30 minutes. The procedure is exactly the oppositeof that for lead-acid batteries in which the electrolytelevel is adjusted by adding water before placing thebattery on charge, or whenever the electrolyte level islow. An inherent characteristic of nickel-cadmiumcells is that when they are in a low or discharged condi-tion, the electrolyte is absorbed within the plates andseparators to a point where it is not visible from thetop of the cells. When the battery is recharged, theelectrolyte level rises. At full charge, the electrolytelevel is at its maximum.

c. Adding Distilled Water or Electrolyte (KOH). Ifdistilled water or electrolyte (KOH) is added to nickel-cadmium cells while the battery is in the aircraft or ve-hicle and the state of charge is unknown, electrolytemay boil or spew through the filler caps as the batteryreceives its charge from the power bus. The potassiumhydroxide contained in the electrolyte may eventuallyplug the vent valve of the filler caps. If the vent valvesbecome plugged, pressure builds up in the cells and gas

accumulates. If sufficient pressure builds up, the cellwill rupture. The electrolyte may then flow over thetop of the cells and down into the case bottom betweenthe cells. The overflow of electrolyte eventually startscorrosion and may cause a short circuit between thecell connectors. This chain of events, particularly theaccumulation of hydrogen, can lead to an explosion.An igniting spark could be caused by a loose cell con-nection or a short circuit between the cell connectorsresulting from the spewed electrolyte. Electrolyte(KOH) should only be added to a new cell on its initialcharge or if large amounts of electrolyte have spewedout of a cell.

d. Check State of Charge. Before adjusting a sus-pected low electrolyte level, cycle the battery in theshop to assure that it is fully charged. Conversely,never allow electrolyte to fall below the cell level indi-cators (if used) when the battery is in a charged condi-tion. Low electrolyte levels in the charged conditionwill cause the cells to heat up, resulting in their ulti-mate destruction.

2-22. Summary of General Servicing Fea-tures

a. Nickel-cadmium batteries must be kept awayfrom lead-acid batteries to avoid contamination.

b. State of charge cannot be determined with a spe-cific gravity check of electrolyte in nickel-cadmiumbatteries.

c. Adjust electrolyte level only when the nickel-cad-mium battery is fully charged and allowed to rest forat least 30 minutes. If level is low, use only distilledwater.

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TM 11-6140-203-14-1

CHAPTER 3

SHIPMENT, STORAGE, AND DEMOLITION

TO PREVENT ENEMY USE

Section I. SHIPMENT AND STORAGE

3-1. Repacking for Shipment or Storage in figures 3-1 and 3-2. If the original packaginga. Battery Discharging. The battery should be fully materials are not available, use sturdy cartons and

discharged prior to packing for shipment or storage. barrier material to protect the batteries.Discharge the battery as specified in paragraph 5-7,TM 11-6140-203-14-3. 3-2. Storage

b. Material Requirements. For material require- Nickel-cadmium batteries can be stored for indefinitements, use the original packing material, or equal. periods of time without deterioration. After storage,

c. Packaging. The exact procedure for packaging the battery should be prepared for service as specifiedbatteries for shipment and storage depends on materi- in paragraph 5-5, TM 11-6140-203-14-2 for aircraftals available and conditions under which the batteries nickel-cadmium batteries or paragraph 5-5, TMare to be shipped or stored. If the original packaging 11-6140-203-14-3 for nonaircraft nickel-cadmiummaterials are available, package the batteries as shown batteries.

Section Ill. DEMOLITION OF MATERIEL TO PREVENT ENEMY USE

3-3. Authority for Demolition. trolyte comes in contact with any part of the

Demolition of the equipment will be accomplished only skin. Before destroying cells, empty all

upon the order of the commander. The destruction pro- electrolyte to prevent spattering when

cedures outlined in paragraph 3-4 will be used to pre- smashing.

vent further use of the equipment. a. Smash. Smash the battery case, battery boxes,and cells.

3-4. Methods of Destruction. b. Burn. Burn the battery box liners, the gaskets,

Use any or all of the following methods to destroy the and the technical manuals.

battery: c. Dispose. Bury or scatter the destroyed parts inslit trenches or foxholes, or throw them into streams.

WARNING Scatter the connectors, cells, wire harnesses, andThe electrolyte used in the nickel-cadmium boxes.batterySerious

contains a caustic chemical agent. d. Other. Use anything immediately available forflesh burns will result if the elec- destruction of this equipment.

3-1

TM 11-6140-203-14-1

Figure 3-1. Typical Single Nickel-Cadmium Battery,Packaging Diagmm.

3-2

TM 11-6140-203-14-1

Figure 3-2. Typical Multiple Nickel-Cadium Batteries, Packaging Diagram.

3-3

TM 11-6140-203-14-1

APPENDIX A

REFERENCES

DA Pam 310-4

DA Pam 310-7SB 11-573

TB 43-0118

TM 11-6130-413-12

TM 11-6140-203-14-2

TM 11-6140-203-14-3

TM 38-750TM 740-90-1TM 750-244-2

Index of Technical Publications: Technical Manuals, Technical Bulletins, SupplyManuals (Types 7, 8, and 9), Supply Bulletins, and Lubrication Orders.

US Army Index of Modification Work Orders.Painting and Preservation Supplies Available for Field Use for Electronics Com-

mand Equipment.Field Instructions for Painting and Preserving Electronics Command Equipment

Including Camouflage Pattern Painting of Electrical Equipment Shelters.Operator’s and Organizational Maintenance Manual for Battery Charger-Analyzer

AN/USM-432.Operator’s, Organizational, Direct Support, and General Support Maintenance

Manual for Aircraft Nickel-Cadmium Batteries.Operator’s, Organizational, Direct Support, and General Support Maintenance

Manual for Nonaircraft Nickel-Cadmium Batteries.The Army Maintenance Management System (TAMMS).Administrative Storage of Equipment.Procedures for Destruction of Electronics Materiel to Prevent Enemy Use

(Electronics Command).

A-1

TM 11-6140-203-14-1

GLOSSARY

Ampere-hour–An ampere-hour is a unit of measurefor battery capacity obtained by multiplying the cur-rent flow in amperes by the time in hours duringwhich the current flows.

Charge–Charge is an electrochemical process bywhich electrical energy in the form of direct current(forced through the battery in a direction opposed tothe discharge current) is converted to chemicalenergy.

Cycle–A cycle is one charge period followed by onedischarge period.

Discharge-Discharge is an electrochemical process inwhich chemical energy is converted into electricalenergy in the form of direct current flowing out ofthe battery into an external circuit.

Discharged battery—A discharged battery is one inwhich continued passage of charging current pro-duces no further appreciable conversion of electricalenergy into chemical energy.

Fully charged battery—A fully charged battery is onein which continued passage of charging current pro-duces no further appreciable conversion of electrical

energy into chemical energy.Normal discharge rate–Normal discharge rate is the

steady amount of current which a battery will pro-vide over a given time before the voltage drops to apredetermined point (1.0 volt per cell). The normalrate is expressed in the length of time this currentcan be provided by the battery. Nickel-cadmium bat-teries are generally rated at the 2-hour rate for air-craft type or at the 5-hour rate for nonaircraft type.

Rated capacity—Rated capacity is the capacity in am-pere-hours which a charged battery will deliver con-tinuously at its normal (2-hour for aircraft type or 5-hour for nonaircraft type) rate. The capacity of abattery or the total amount of electrical energy a cellcan deliver depends entirely on the amount of activematerial it contains. (To increase the capacity of abattery, therefore, a greater number of plates ; orlarger or thicker plates must be used in each cell,with enough electrolyte to provide a conductingpath for the current flowing between the positiveand negative plates.)

✩ us. GOVERNMENT PRINTING OFFICE: 1995 - 388-421/41047

Glossary 1

By Order of the Secretary of the Army:

Official:

E. C. MEYERGeneral, United States Army

Chief of Staff

J. C. PENNINGTONMajor General, United States Army

The Adjutant General

DISTRIBUTION:To be distributed in accordance with DA Form 12-36A Section IV requirements for Aircraft and NonAircraft

Nickel Cadmium Batteries.

‘PUBLICATION NUMBER

TM 11-6140 -203-14-1BE EXACT PIN-POINT WHERE IT IS

P A G EN o

PARA-GRAPH

FIGUREN o

TABLEN o

PUBLICATION DATE PUBLICATION TITLE Aircraft and Non-

a i r c r a f t N i c k e l - C a d m i u m B a t t e r i e s

IN THIS SPACE TELL WHAT IS WRONGAND WHAT SHOULD BE DONE ABOUT IT:

PRINTED NAME GRADE OR TITLE AND TELEPHONE NUMBER SIGN HERE

DA 2028-2 P R E V I O U S E D I T I O N S P S --IF YOUR OUTFIT WANTS TO KNOW ABOUT YOURA R E O B S O L E T E R E C O M M E N D A T I O N M A K E A C A R B O N C O P Y O F T H I SA N D G l V E I T T O Y O U R H E A D Q U A R T E R S

THE METRIC SYSTEM AND EQUIVALENTS

PIN: 047121-000

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