Jeep 1987 Wrangler Workshop Manual page 547

ELECTRICAL
BATTERIES
Keep the hydrometer in a vertical position while
raising the electrolyte into the hydrometer and
observing the specific gravity.
CAUTION: Exercise care when inserting the tip
of the hydrometer into a cell to avoid damage to
the separators. Damaged separators can cause
premature battery failure.
Hydrometer floats are generally calibrated to
indicate the specific gravity correctly only at one
fixed temperature, 2 6 . 6 ° C (80°F). When testing
the specific gravity at any other temperature, a
correction factor is required.
each 5.5°C below 2 6 . 6 ° C ( 1 0 ° F below 8 0 ° F ) ,
subtract four points. Always correct the specific
gravity for the temperature variation.
Test the specific gravity of the electrolyte in each
battery cell.
Example: A battery is tested at - 1 2 . 2 ° G (10°F)
and has a specific gravity of 1.240. The actual
specific gravity is determined according to the
following example:
• number of degrees above or below 2 6 . 6 ° C
(SOT) equals 3 8 . 8 ° C (70°F) 26.6 minus -12.2
(80 minus 10)
• 3 8 . 8 ° C divided by 5 . 5 ° C ( 7 0 ° F divided by
10°F), each 5.5°C (10°F) difference equals 7
• 7 multiplied by 0.004 (temperature correction
factor) equals 0.028
• temperature is below 2 6 . 6 ° C (SOT), therefore,
the temperature correction is subtracted
• temperature corrected specific gravity is 1.212
(1.240 minus 0.028)
• a fully charged battery should have a
temperature corrected specific gravity of
1.250 - 1.265
NOTE: The correction factor is approximately a
specific gravity value of 0.004, referred to as four
points of specific gravity. For each 5.5°C above
2 6 . 6 ° C ( 1 0 T above 8 0 T ) , add four points. For
5-0