Suzuki 2000 Grand Vitara SQ625 Service Manual page 700

HYDROMETER TEST
The direct method of checking the battery for state of charge is to
carry out a high rate discharge test, which involves a special pre-
cise voltmeter and an expensive instrument used in the service
shops, but not recommendable to the user of the vehicle.
At 20 _C of battery temperature (electrolyte temperature):
– The battery is in FULLY CHARGED STATE if the electrolyte S.G.
is 1.280.
– The battery is in HALF CHARGED STATE if the S.G. is 1.220.
– The battery is in NEARLY DISCHARGED STATE if the S.G. is
1.150 and is in danger of freezing.
As the S.G. varies with the temperature, if battery temperature is
not at 20_C (68_F), you have to correct your S.G. reading (taken
with your hydrometer) to the value at 20_C (68_F) and apply the
corrected S.G. value to the three-point guide stated value.
For the manner of correction, refer to the graph showing the relation
between S.G. value and temperature at the left.
How to use the temperature-corrected state-of-charge
graph
Suppose your S.G. reading is 1.28 and the battery temperature is
–5 _C (23_F). Locate the intersection of the –5 _C line and the 1.28
S.G. line.
The intersection is within the "A" zone (shaded area in the graph)
and that means CHARGED STATE.
To know how much the battery is charged, draw a line parallel to the
zone demarcation line and extend it to the right till it meets with the
percentage scale. In the present example, the line meets at about
85% point on the percentage scale. Therefore, the battery is
charged up to the 85% level.
CHARGING SYSTEM 6H-7