TM-9-2330-356-14
SEMITRAILER, TANK: 5000 GALLON, BULK HAUL, SELF LOAD/UNLOAD M967 AND M967A1; SEMITRAILER, TANK: 5000 GALLON, FUEL DISPENSING, AUTOMOTIVE M969 AND M969A1; SEMITRAILER, TANK: 5000 GALLON, FUEL DISPENSING, UNDER/OVERWING AIRCRAFT M970 AND M970A1
TECHNICAL MANUAL; OPERATOR’S, UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL
OCTOBER 1990
TM-9-2330-356-14 - Page 194 of 528
TM 9-2330-356-14
NOTE
If water must be added to check specific
gravity, fast charge battery for 30 minutes or
false readings will be obtained.
d.
Checking Specific Gravity.
A hydrometer or an
antifreeze/battey tester is used to check the specific
gravity (weight) of the battery electrolyte. The specific
gravity of the electrolyte indicates the approximate state
of charge of the battery. Hydrometers are calibrated to
give the true reading when the electrolyte temperature is
80°F. Therefore, to obtain a correct specific gravity
reading, the temperature of the electrolyte must be
known. Some hydrometers contain a thermometer while
others do not. A separate thermometer is required to
check electrolyte temperature if the hydrometer is not so
equipped. Refer to figure 4-38 for hydrometer
temperature corrections. An antifreeze/battery tester is
already temperature corrected.
(1)
Test.
(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.
(b)
Note the electrolyte temperature. Refer
to figure
4-38
and add or subtract four (.004) specific
gravity points for each 10° above or below 80°F. The
corrected reading will be a true indication of cell
condition.
(c)
Repeat steps
(a)
and
(b)
for remaining
cells.
(2)
Interpretation of Hydrometer Readings.
(a) The
approximate state of charge can be
determined by comparing readings to specific gravity
(table 4-11).
(b)
If all cells read between 1.200 and 1.260,
and the variation between the high and low cell is less than
30 gravity points, the battery is good. It maybe necessary to
charge the battery before use.
(c)
If all cells read between 1.200 and 1.260,
and the variation between the high and low cell is 30
gravity points or more, fully charge battery and recheck
specific gravity. If the variation is still 30 gravity points or
more after charging, the battery is defective and must be
replaced.
(3) Testing with an antifreeze/battery tester is
done by following directions printed on the tester.
Table 4-11. Specific Gravity Table.
State of
Specific gravity
Electrolyte
Charge
at 80°F
Freezes approx.
1 00%
1.260
-75° F
75%
1.230
-38°F
50%
1.200
-17°F
25%
1.170
1°F
Discharged
1.110
19°F
TA099793
Figure
4-38.
Hydrometer Temperature Correction.
4-58
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