jcb JS300 Service Manual page 576

Specific Gravity Testing
The specific gravity of the electrolyte gives an idea of the
state of charge of the battery. Readings should be taken
using a hydrometer, when the electrolyte temperature is
15°C (60°F). If the battery has recently been on charge,
wait approximately one hour (or slightly discharge the
battery) to dissipate the surface charge before testing.
Ambient temperature up to 27°C (80°F)
Ambient temperature above 27°C (80°F)
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Readings should be as tabulated and should not vary
between cells by more than 0.04. A greater variation
indicates an internal fault on that particular cell.
If the electrolyte temperature is other than 15°C (60°F) a
'correction factor' must be applied to the reading obtained.
Add 0.07 per 10°C (18°F) if the temperature is higher than
15°C (60°F) and subtract the same if the temperature is
lower.
Table 3. Specific Gravity at 15°C (60°F)
Fully Charged
1.270 - 1.290
1.240 - 1.260
9813/5100-1
Section C - Electrics
Charging System
Test Procedures
Half Discharged Fully Discharged
1.190 - 1.210 1.110 - 1.130
1.170 - 1.190 1.090 - 1.110
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