F..Every Six Months

Record the voltages of every cell taken with the digital voltmeter on form POM-133C. Take the voltages while on float and compare with previous readings. 

6.7 TTEEMMPPEERRAATTUURREE  RREEAADDIINNGGSS

AA.. Quarterly

Check and record the electrolyte temperature of the pilot cell. Use only an alcohol thermometer reserved only for this battery. Mercury thermometers may break and cause sparking or an explosion. Never insert a thermometer or any tool ever used for other batteries into a ni-cad cell. 

6.8 VISUAL INSPECTION

Visual inspections are made to assess the general condition of the battery, battery room, and safety equipment. 

A. Monthly

Check for general cleanliness of the battery, mounting rack, and battery room. Check for electrolyte leaks and cracks in cells and take corrective action if found. Check for corrosion at terminals, connectors, racks, and cabinets. Check the ambient temperature and make sure ventilation devices (fans and vents) are operable. Check the charger for current and voltage output. 

Check for availability and condition of all safety equipment, gloves, face shields, aprons, etc. Check for a full gallon of labeled neutralizing solution (20 ounces of boric acid per gallon of distilled water) and operability of body wash/eyewash station or portable eyewash equipment. Check for availability of insulated tools so short circuits can be avoided (see section 8). 

6.9 BATTERY DISCHARGE TESTING

A. Acceptance Testing 

Acceptance testing may be done at the factory prior to shipping or at the service location after the battery comes to equilibrium in charge and temperature. The discharge rate should be constant at the full rated current for the duration of the test. See the manufacturer’s literature for this information. Most manufacturers recommend a test duration of 3 to 8 hours for this test. 

Note: Temperature affects battery capacity. Take electrolyte temperatures of individual cells and average them prior to the test. The test discharge current is equal to the rated discharge current divided by the temperature correction factor for electrolyte temperature. Contact the manufacturer or consult the instruction manual for correct data for the specific battery to be tested. 

1. Set up the instrumentation to measure time, test current, and the required voltages. 

2. Disconnect the charger, connect the test load, and maintain the constant current discharge for the duration of the test. Begin timing the test when the discharge current begins. 

3. Read and record individual cell voltages and the battery terminal voltage as soon as possible after the discharge begins. Repeat the readings at the required intervals and just before completion of the test with the rated discharge load connected. At least three sets of readings should be taken at rated discharge current flow. More readings are preferred. Individual cell voltages should be taken between like polarity posts of adjacent cells to include the voltage drops of intercell connections. 

4. Maintain the discharge and record the elapsed time at the point when terminal voltage decreases to the manufacturer’s specified minimum volts per cell, usually 1.00 volt times the number of cells. If one or more cells approach polarity reversal before the specified test time, continue the test for the originally planned test time. Ni-cad cells are not damaged as a result of polarity reversal, so bypassing weak cells is unnecessary. Contact the manufacturer if the battery fails the test, that is, if the specified terminal voltage (1.00 volt per cell) is reached prior to the specified test time. 

5. Battery capacity can then be calculated by dividing the actual time to reach specified terminal voltage by the rated time to specified terminal voltage and multiplying by 100. 

actual time Percent Capacity = x 100 rated time 

B. Five Year Capacity Discharge Testing

Perform this test every 5 years as in step A above. A battery capacity of 90 percent or less than rated capacity indicates that the battery is reaching the end of its service life. A battery that falls to 90-percent capacity must be tested annually as in step C below. 

C. Annual Capacity Discharge Testing

Perform capacity discharge tests annually after the capacity falls to 90 percent as revealed in the 5-year test in step B above. Replace the battery as soon as possible after the capacity falls to 75 percent. 

6.10 ELECTROLYTE

The electrolyte solution in nickel-cadmium batteries consists of purified caustic potash (KOH potassium hydroxide) and other salts in distilled water. Liquid electrolyte should be stored in a clean, glass, or porcelain container. The electrolyte will readily absorb carbon dioxide from air to form potassium carbonate. This process will temporarily lower battery capacity. Electrolyte must therefore be stored in airtight containers. The specific gravity of electrolyte does not change with state of charge but remains almost constant on charge and discharge. The average specific gravity of a normal cell will be about 1.190 at 72 EF;; however, in servicing a battery, always refer to the manufacturer's recommended specific gravity range. The specific gravity range for ni-cad cells has limits. Below 1.200, the resistivity begins to increase rapidly, making cells sluggish, and the lowest electrolyte density is usually set at 1.170. High concentrations are damaging because of the increased solubility of the iron electrodes, especially at higher temperatures. Concentrations much higher than 1.170 also result in increased resistivity. The proper density of the electrolyte is a compromise held within narrow limits. 

The freezing point of electrolyte with a specific gravity of 1.190 is about -10 °F, at which the solution forms a slush but will not freeze solid. If the battery will encounter temperatures colder than -10 EF, specific gravity is usually raised to 1.230 for protection to -40 EF. Always consult the manufacturer before attempting to change the specific gravity of electrolyte. 

6.11 ELECTROLYTE LEVEL

Cells lose water through natural evaporation and when gassing on equalizing charge. Always keep the plates covered with electrolyte. Serious damage will occur if the plate tops are exposed to air. 

A. Monthly

Check the electrolyte level in every cell during the visual inspection. The level can be observed by looking closely at the cell. Cell cases are typically translucent, and the electrolyte level can be seen through the cell case. When electrolyte level is low, add distilled water to the proper height but do not overfill. If cells are overfilled, the electrolyte may be forced out of vents on charge. This condition can cause electrolysis between the cells, corrosion of the cell containers, and grounds in the electrical circuit. The maximum maximum level of the electrolyte is halfway halfway between the tops of the plates and the inside of the cell covers. 

To retard natural evaporation, pure mineral oil should be floated on the electrolyte in each cell. All cells should be checked annually for adequate oil depth, (about 1/4 inch). See manufacturer's instructions for the recommended oil type and depth. 

6.12 SPECIFIC GRAVITY READINGS

Specific gravity readings are only needed every 5 years to determine if the electrolyte needs to be replaced (see 6.9 above). When taking a hydrometer reading, squeeze the bulb before inserting, insert the nozzle to the top of the plates, then release the bulb. This procedure will avoid introducing air bubbles and prevent floating oil from being drawn into the barrel. The sample should always be returned to the cell from which it was taken. Wash out the hydrometer thoroughly with distilled water. Electrolyte remaining in the hydrometer absorbs carbon dioxide from the air, forms a coating, and causes false readings. Specific gravity changes with temperature, and if the electrolyte temperature is different from 77 EF, add 0.001 to the reading for every 4 EF above 77 EF. Subtract 0.001 for every 4 EF below 77 EF. 

Do not take specific gravity readings when gas bubbles are visible in the electrolyte. False readings will result unless the bubbles are allowed to dissipate. Specific gravity readings cannot be taken on cells just after adding water; the readings should be delayed until mixing has occurred. 

Do not try to maintain a single supply of distilled water for serving both ni­ cad and lead-acid batteries. Water will become contaminated with traces of sulfuric acid from the filler bulb by the transfer between lead-acid cells and the water container. A separate supply of distilled or approved mineral water, used only for nickel-cadmium batteries, is necessary. Provide a separate hydrometer that is used exclusively for testing nickel-cadmium cells. 

6.13 ELECTROLYTE RENEWAL

Traces of potassium hydroxide are lost with the gas while the battery is on charge, resulting in gradual lowering of specific gravity over the years. Performance deteriorates as the battery ages, and cannot be restored by normal charges. When this condition occurs, check the electrolyte color by inserting a clear glass draw tube to the top of the plates. Place a thumb over the top end and partially withdraw the tube; do not totally remove the tube. This procedure avoids spills on the tops of the cells. After observing the color, release the electrolyte back into the same cell. Clear electrolyte is in good condition. Electrolyte that has absorbed small quantities of carbon dioxide from the air will appear cloudy. Impurities accidentally introduced in cells during manufacture or by addition of contaminated water may also color the electrolyte. Electrolyte that becomes colored or cloudy is contaminated with impurities and should be changed. 

Electrolyte renewal may also become necessary because of overcharging and overflow of electrolyte, causing cell specific gravity to fall below manufacturer's specified minimums. A rapid reduction in the life of the battery will follow with continued operation. The electrolyte should be changed when the specific gravity falls below 1.170 (see 6.8 above). Renewal electrolyte, which is purified potassium hydroxide plus additives, is available from the battery manufacturer in dry form. The dry renewal electrolyte is mixed with distilled water in accordance with manufacturer's instructions and allowed to cool for 24 hours. Do not substitute commercial grade potassium hydroxide. After the renewal electrolyte solution of proper specific gravity has been prepared and cooled, the change of electrolyte is made in steps as follows: 

1. Discharge the battery to a voltage of 0.8 volt per cell or lower. 

2. Pour the electrolyte out of the cells and rinse cells with clear distilled water. 

3. Fill the cells with renewal electrolyte to the proper level. Leave about 1/4 inch of space for mineral oil (see step 4 below). 

4. To retard evaporation and contamination by CO2, add pure mineral oil to cells as instructed by the manufacturer (about 1/4 inch) and mentioned in step 6.7 above. Do not overfill cells above the high level mark. Add oil as needed until about 1/4-inch deep. 5. Charge the battery at the equalizing charge rate until fully charged. 66..1144 GGEENNEERRAALL  CCAARREE

A salt formation called potassium carbonate may form on the top of the cells. This formation is non-corrosive and does not damage the battery but should be removed. Excessive salt formation indicates that charging may be excessive. Top hardware should be coated with no-ox grease after cleaning to keep the carbonate salts in a soft condition for easy removal. Any excess grease should be removed with a clean, soft cloth. 

Cells and trays must be kept clean and dry at all times. Moisture and dirt on top of and between cells permits stray inter-cell currents, resulting in corrosion through electrolysis. For this reason, water or electrolyte spilled on the cells or the trays must be wiped off all surfaces. Never place or drop metal objects, such as nuts, bolts, or tools, on or between the cells. These objects may cause heavy short circuits and damage containers and cells. 

Small traces of sulfuric acid will ruin a nickel-cadmium battery by corroding the steel plates and cell containers. To prevent contamination, never use any tools, such as hydrometers, funnels, rubber hoses, battery fillers, etc., that have ever been used for serving lead-acid batteries. 

Keep all vent caps closed. To prevent air from entering the cells, raise the caps only for checking the electrolyte, never for charging.. Always check and service only one cell at a time. 

Never allow sparking near any storage battery or remove connections with current flowing. Keep all connections tight and in good repair. Never approach any storage battery with an open flame. The gas given off by all storage batteries on charge is an explosive mixture of hydrogen and oxygen..

6.15 BATTERY RECORDS

A manufacturer's warranty provided with each battery extends from the date of purchase. Battery records are kept to show the care provided during the service period as well as to facilitate routine battery maintenance. Monthly report form POM-133C should be filled out each month for each battery and filed for future reference. 

66.16 WALL CARD RECORDS

To facilitate proper battery operation, maintenance, and care, post a battery data card (POM-159) in a conspicuous place near the battery to provide the attendant with service information and data. 

7. BATTERIES FOR MICROWAVE AND VHF RADIO EQUIPMENT

7.1 LEAD-ACID BATTERY

See section 1 for detailed information. 

A. Engine-Generator Starting Battery

Keep the engine-generator starting batteries clean and installed in the trays provided. The cell tops should be wiped with a solution of 1 pound of bicarbonate of soda to 1 gallon of water two or three times a year. 

Keep the electrical connections tight and free of corrosion. A coating of no- oxide anti-corrosive grease on terminals will usually prevent corrosion. Dry sand should be kept in trays on which batteries are placed. 

Adjust the charge rate to keep batteries fully charged. Open-cell voltage should be maintained at the manufacturer’s recommended level. Open circuit voltage on a 12-volt battery should be approximately 12.9 to 13.2 volts d.c., based on the manufacturer’s data. Care should be taken not to overcharge the battery in order to avoid the excessive use of water. Use only distilled water 

When replacing starting batteries, use batteries of equal or greater capacity than originally installed. The battery should be of sufficient capacity to hold starting voltage after 30 seconds cranking (10.5 volts d.c. or higher on 12­ volt systems). 

If the difference in specific gravity between the highest and lowest cell is 0.050 (50 points) or more, the battery is nearing the end of its useful life and should be replaced. However, if the highest cell reads less than 1.190, the results are questionable. Recharge the battery and make the test again. 

B. Load Batteries

Refer to section 1 of this bulletin for instructions on the maintenance and care of lead-acid load batteries. 

7.2 NICKEL CADMIUM BATTERY

See section 6 for detailed discussion of nickel-cadmium batteries.