TM 9-2330-356-14
NOTE
(2) Interpretation of Hydrometer Readings.
If water must be added to check specific
(a) The approximate state of charge can be
gravity, fast charge battery for 30 minutes or
determined by comparing readings to specific gravity
false readings will be obtained.
d.
Checking Specific Gravity. A hydrometer or an
antifreeze/battey tester is used to check the specific
(b) If all cells read between 1.200 and 1.260,
gravity (weight) of the battery electrolyte. The specific
and the variation between the high and low cell is less than
gravity of the electrolyte indicates the approximate state
30 gravity points, the battery is good. It maybe necessary to
of charge of the battery. Hydrometers are calibrated to
charge the battery before use.
give the true reading when the electrolyte temperature is
80F. Therefore, to obtain a correct specific gravity
(c) If all cells read between 1.200 and 1.260,
reading, the temperature of the electrolyte must be
and the variation between the high and low cell is 30
gravity points or more, fully charge battery and recheck
others do not. A separate thermometer is required to
specific gravity. If the variation is still 30 gravity points or
check electrolyte temperature if the hydrometer is not so
more after charging, the battery is defective and must be
replaced.
temperature corrections. An antifreeze/battery tester is
already temperature corrected.
(3) Testing with an antifreeze/battery tester is
(1) Test.
done by following directions printed on the tester.
(a) Remove electrolyte from one cell at a
time with the hydrometer. Observe and record the
hydrometer reading. Be sure to hold the hydrometer
vertical, check that the float is free, and take reading at
eye level.
State of
Specific gravity
Electrolyte
(b) Note the electrolyte temperature. Refer
Charge
at 80F
Freezes approx.
to figure 4-38 and add or subtract four (.004) specific
1 00%
1.260
-75 F
gravity points for each 10 above or below 80F. The
-38F
75%
1.230
corrected reading will be a true indication of cell
condition.
50%
1.200
-17F
25%
1.170
1F
(c) Repeat steps (a) and (b) for remaining
Discharged
1.110
19F
cells.
TA099793