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Performance and maintenance of batteries
Initial charge
Wet-charged battery gradually decrease its capacity during storage. In order to provide sufficient
discharge capacity in the first discharge, the good initial charge is required. The conditions of
initial charging are seen as below at room temperature.
a
a
.
By modified constant voltage charger
Connect the battery to the charger and turn on the equalizing charge "ON". The battery will be
fully charged and terminated automatically.
b.
By constant voltage constant current charger
Connect the battery to the charger and turn on the equalizing charge "ON". The battery will be
fully charged and terminated automatically.
c.
By constant current charger
Connect the charger to the battery and charge the battery by 0.1C
capacity current for 24 hours or more. The charge shall be terminated when one of the following
condition is identified.
When a constant value is indicated for more than 1 hour after the battery voltage has reached
the maximum value.
When more than 1 hour of charge is continued after the electrolyte specific gravity has risen
fully and becomes constant.
D
D
ischarge and capacity
The capacity of batteries is indicated at 5 hour rate capacity which means the battery can be
discharged for 5 hours with the discharge current calculated by dividing the capacity value by 5
until the unit cell mean voltage reaches down to 1.7V at the electrolyte temperature of 30 C.
That is, the capacity is indicated by AH(ampere hour) being calculated as the product of
ampere(A) and time(H). However, even in the same type of batteries, the capacity varies with the
discharge conditions(discharge current, battery temperature and specific gravity of electrolyte)
Even if the batteries discharged its full capacity, if immediately charged to full, there will be no
harmful effects remained. Ideal charging amount(AH) is 110-125% of the amount of previous
discharge.
Specific gravity of electrolyte
Specific gravity of electrolyte drops at discharge and rises at charge. When the batteries are fully
charged, it becomes almost constant and shows no further rise. The specific gravity value varies
with the change in temperature. Therefore specific gravity measurement should be made with
temperature of electrolyte at the same so the measured specific gravity value could be corrected
to that at the standard temperature of 25 C by the following formula.
Where,
S
: Specific gravity at 25 C
25
S
: Actually measured specific gravity at t C
t
t
: Electrolyte temperature ( C)
The standard specific gravity for this type of battery is 1.280 0.01(25 C) at full charge condition.
If the electrolyte is decreased naturally while using, distilled water shall be replenished up to the
specified level. (Never refill sulfuric acid)
Only when large quantity of electrolyte is lost due to spillage, etc., dilute sulfuric acid specified in
gravity shall be added.
S
= S
+ 0.0007(t-25)
25
t
7-7
5 hour rate nominal
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