Foaming

TM 116140203141

ing 2 hours. The correct level of electrolyte is ¼-inch

plates. These changes in electrolyte level should only

above the top of the plates of a fully charged cell that

be made if absolutely necessary and only in cells con-

has been at rest for the prescribed period of time. Re-

taining adequate head space over the plates.

fer to TM 11-6140-203-14-2 and TM 11-6140-

212. Foaming

203-14-3 respectively for rest time limitations for

specific aircraft and nonaircraft nickel-cadmium bat-

Foam may sometimes be noticed in cells during

teries. Observing the rest time limitations before

charge. It normally does not indicate a defect and is

checking the electrolyte level is an absolute must to in-

harmful only if it results in excessive overflow. Foam-

sure that the cell is not overfilled or underfilled. How-

ing is more likely to occur after adding water and

ever, some modification in electrolyte level height or

should disappear after a few cycles of operation. Con-

rest time after charging may be required depending on

tinued foaming indicates contaminated electrolyte and

the equipment used for charging and the environment

the cell should not be used until thoroughly checked

the battery will see in use (voltage regulator setting

for damage. When electrolyte is lost due to foaming in

and temperature). In general, the constant current

new cells, add 31 percent KOH electrolyte to the cell

(CC) chargers used in the battery shop will produce a

rather than water. After the first two charge cycles,

higher apparent level of electrolyte than a constant po-

only distilled water should be added.

tential (CP) charger, since the CC charger normally

213. Summary of Operation Character-

charges to a higher end-of-charge voltage. If this is the

istics

case, then it maybe necessary to increase the rest time

after charge from 30 minutes to up to 2 hours and/or

a. Cell capacity decreases when discharged at high

increase the electrolyte to

-inch above the top of the

currents.

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