Figure 4-38. Checking Battery Specific Gravity

Note

Do not add distilled water to electrolyte

immediately after charging the battery.

connections

battery

cable

d. Check

all

periodically to make sure they are clean and tight.

e. Remove any corrosion from battery terminals

by scrubbing with a solution of baking soda, or

ammonia, and water.

f. After cleaning, coat the exterior of the cable

terminals with a light film of Vaseline to retard

further corrosion.

4 - 3 3 . BATTERY TESTS.

4-34. LIGHT LOAD TEST. A defective battery or

Figure 4-38. Checking Battery Specific Gravity

a discharged battery may be found by performing

the following "Light Load Test."

a. Place an electrical load on the battery by

cranking the engine for three seconds. If it starts,

turn the ignition off immediately.

Never allow sparks or open flame in the

a r e a when checking the battery. Storage

b . Place a 10 ampere load across the battery

b a t t e r i e s produce hydrogen, an explosive

terminals for one minute. This will condition the

gas, as a normal by-product of operation.

battery so an accurate voltage comparison test can

be made between cells.

b. Hydrometer readings should be used to

d e t e r m i n e the battery state of charge. This is

c . After one minute, and with the 10 ampere

particularly true in cold weather, as a partially

load still on the battery, check the individual cells

discharged battery may freeze at temperatures up

with an expanded scale voltmeter.

t o 20F.

Note

c. Take readings on the hydrometer as shown in

figure 4-38. Battery will need charging if the

Checking individual cell voltage on newer

specific gravity reads 1.225 (or less) at 75F.

batteries with the completely enclosed

" h a r d - t o p " case is not possible. Use the

tests described in paragraph 4-35 to

determine battery condition.

Specific gravity should be 1.265 or greater

d. Place the positive voltmeter prod on the

battery is exposed to freezing

positive side of the cell and the other prod on the

t e m p e r a t u r e s . If machine is operated in

negative side. A good battery, sufficiently charged

tropical climates where no freezing weather

will read 1.95 volts or more on each cell with a

is encountered, the full charge specific

difference of less than 0.05 volt between highest

gravity may be lowered from 1.375 to

and lowest cell.

1.225 by diluting the electrolyte with

distilled water.

e. If cells read both above and below 1.95 volts

4-28