TM 9-6140-200-14
3. Electrolyte Temperature Correction. When the temperature of the battery
electrolyte is above or below 80 degree F, the reading taken from the
hydrometer must be adjusted to get a correct battery cell specific gravity,
correct for temperature as follows:
(b) Check tester thermometer. If thermometer reads above or below 80
degree Fahrenheit adjust electrolyte specific gravity reading as follows:
(1) For every 10 degrees Fahrenheit below 80 degrees Fahrenheit,
subtract four (4) specific gravity units from electrolyte reading taken.
(2) For every 10 degrees above 80 degrees Fahrenheit, add four (4)
specific gravity units from electrolyte reading taken (see examples
below).
EXAMPLE 1
Battery electrolyte temperature reading is 60 degrees Fahrenheit and the hydrometer
shows a specific gravity of 1.240. Since 60 degrees is two 10's below 80 degrees
Fahrenheit, you must subtract two 4's or eight (8) specific gravity units from hydrometer
reading. This leaves a corrected specific gravity reading of 1.232 (See Figure 3-6).
EXAMPLE 2
Battery electrolyte temperature is down to 20 degrees Fahrenheit and the hydrometer
shows a specific gravity of 1.256. Subtract 20 from 80 to get 6 10's difference and 6 4's
(24) subtract from 1.256 gives a corrected specific gravity of 1.232. (See Figure 3-6).
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