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IV. Initial charge
The initial charge is very important for the battery life.
It is most important that the battery is fully charged before putting into service so charging must be conti-
nued until the specific gravity of electrolyte for all cells is nominal at level indicated page 8.
Methods of charging
Charging time
The charge must be stopped
during the charging
When can charge
start again ?
Notice
End of charge
Very important
Is it possible
to have after the charge :
- voltage heterogeneity ?
- specific gravity
heterogeneity ?
Notice
VERY IMPORTANT
Constant current
I = 0.053 C10
Example for a battery of 500 Ah
500 x 0.053 = 26.5 A
Basically 6 to 15 hours.
It depends on how battery was stored.
After a long or bad storage, the time of charge will be longer
If the temperature of electrolyte reaches :
- temperate climate : 40° C or 104° F
- tropical climate :
50° C or 122° F
55° C or 131° F (maxi case)
When the temperature of electrolyte is below :
- temperate climate : 30° C or 86° F
- tropical climate :
40° C or 104° F
Charging must be stopped 2 or 3 times depending on the ambiant temperature.
In the case of charging at a constant current, it is better reduce the intensity and to
increase the time of charge.
Until all cell voltages and electrolyte specific gravities (corrected to 20° C) cease to rise for
three consecutive hourly readings.
After a long or bad storage, the time of charge will be longer. So it is necessary to rechar-
ge the battery at constant current to obtain more quickly the homogeneity of the electro-
lyte.
YES in the following cases :
- after storage for a very long time
- after storage without protection against humidity, etc...
example : charging at constant voltage of a battery which has been stored in bad conditions,
24 cells in which only 6 cells have been kept in good storage conditions.
- charge at constant current
- maxi voltage supplied by the charger
- the voltage of the best 6 cells rises quickly to
- 18 cells will be in average at 2.26 Volts per cell
when the battery voltage will reach 56.4 Volts :
- at 56.4 Volts, the current falls off to a very small value. With this very low float current, the charging
time will be longer for the 18 cells at 2.26 Volts.
So continue charging until the specific gravity of electrolyte for all cells rise to nominal specific gra-
vity at level indicated page 8.
If the temperature of electrolyte is below 40 °C, it is better to overcharge the battery rather
than to keep the battery undercharged.
initial current limited to 0.1 C10
12
Constant voltage
2.35 Volts per cell
: 2.35 Volts per cell
: 2.35 x 24 = 56.4 Volts
: 2.60 x 6
= 15.6 Volts
: 2.26 x 18 = 40.8 Volts
56.4 Volts
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