circuit. When the connection takes place, this chemical energy is transformed back into the electrical energy used to start
the engine. It is very important to keep the battery properly charged at all times. The ability of the battery to power the
starting motor properly depends upon the strength of the battery charge. The degree of the battery charge is measured by
the specific gravity of the electrolyte. Table II shows how to determine battery condition from specific gravity readings
corrected to 800 F.
Table II. Battery Condition (Corrected to 80 F.)
Specific gravity
Battery condition
Specific gravity
Battery condition
1.280.................
Fully charged.
1.190 ................
25% charged.
1.250.................
75% charged.
1.160 ................
Almost discharged.
1.220.................
50% charged.
1.130 ................
Discharged.
b. Temperature influence. Cold weather has a considerable effect on electrochemical reactions, and battery capacity
is greatly reduced by cold temperatures. The battery will deliver its peak cranking power when the temperature of the
electrolyte is about 800 F. At 30 F., a fully charged battery will deliver only 65 percent of its cranking power. At 0 F. the
cranking power of the battery will be reduced to 40 percent. It is important to keep the battery fully charged when it is
operated in cold temperatures. The freezing point of the electrolyte depends on its specific gravity; the battery can be
protected from freezing by keeping it fully charged at all times. Table III lists freezing points and specific gravity of the
standard electrolyte commonly used in all batteries.
Table III. Electrolyte Freezing Points
Specific gravity
Temperature
Specific gravity
Temperature
+5 F.
1.280 ..........................
-900 F.
1.150 .........................
1.250 ..........................
-620 F.
1.100 .........................
+19 F.
1.200 ..........................
-16 F.
The specific gravity of the electrolyte varies with the temperature of the electrolyte. When checking the specific gravity of
the electrolyte in cold temperatures, the readings of the hydrometer must be corrected to 800 F. by referring to table IV.
At the top of table IV, find the column which indicates the temperature nearest to the temperature of the electrolyte. In this
column find the figure nearest to the specific gravity reading indicated on the hydrometer. Trace horizontally
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