State of Charge

ELECTRICAL

Clamps on battery posts and tighten firmly, then coat

c. If the specific gravity readings are 1,215-

posts and clamps with petroleum Jelly to help retard

1.270 at 800F., and variation between

corrosion.

cells is less than 25 gravity points (.025)

the battery presumably is at least 3/4

charged and in good condition for further

use.

d. If the specific gravity readings are below

1.215 and the variation between cells is

less than 25 gravity points, the battery

presumably is in sound condition, but its

state of charge is too low for further use or

testing electrical circuits.

e. If the specific gravity readings show a

variation between cells of more than 25

gravity points, an unsatisfactory battery

condition is indicated, which may be

caused by shorted cells, acid loss, or a

worn out battery.

2. Voltage Test

a. Connect the voltmeter from the positive

Figure 2.

post to the negative post of the battery,

Be sure the clips make a positive

B. TESTS Before making any battery condition test,

connection with a cleanportion of the

make sure the battery terminal poets are free of

battery posts, Under a no-load condition a

corrosion, dirt and oxidation, This is necessary to

fully charged battery should read at least

insure the lowest possible resistance for all electrical

12.0 volts. (2.0 volts per cell).

connections.

b. If the reading is low, connect the

voltmeter across each individual cell. If

1. State of Charge

all cells are low but have equal readings,

the battery is low and should be charged.

a. The hydrometer test is merely a means of

c. If some cell readings are 2.0 volts and

determining the state of charge of the

another cell is discharged more than .5

battery. This test will not necessarily

volt, it indicates a short or the electrolyte

indicate whether the battery is able to

is low in that cell.

perform its normal functions, such as

starting.

C. CHARGING

b. Measure specific gravity of electrolyte in

each battery cell. The hydrometer tube

1. Batteries removed from the vehicle for charging

must be held vertically. Do not draw too

should be charged continuously

much electrolyte into the hydrometer.

The float must be freely suspended in the

electrolyte and the reading taken at eye

level. If water has been recently added to

the cells or battery fast charged, the

hydrometer reading will be false.

B-56