User Manual

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Because of this initial small charge current, in an over
discharged battery, as described above, unless due
consideration is given to this fact then if the charging
regime uses current monitoring for determining either
the state of charge and/or for signalling that the switching
point has been reached for reducing the voltage to a
float/standby value (as is the normal case in a multi-stage
charger), the charger could be ‘tricked’ into entering
further stages before completing earlier ones. In other
words the charger may give a false “full charge”
indication, or may initiate charge at the float voltage
figure, instead of at a higher voltage level.
Recovery Charge After Deep Discharge
When a battery has been subjected to deep discharge
(commonly referred to as over discharge), the amount of
electrical energy which has been discharged can be 1.5
to 2.0 times greater than the rated capacity of the battery.
Consequently, a battery which has been over discharged
requires a longer charging period than normal. Please
note from Figure 28 that as a result of increased internal
resistance, the charging current accepted by an over
discharged NP battery during the initial stage of charging
will be quite small, but will increase rapidly over
approximately the first 30 minutes until the internal
resistance has been overcome, then normal, full recovery
charging characteristics resume.
Top Charging
Since any battery loses capacity through self discharge,
it is recommended that, prior to putting the battery into
service, a process called “top charging” be applied to any
battery which has been stored for a long period of time.
Excluding conditions in which storage temperatures have
been abnormally high, top charging is recommended
within the following parameters:
In order to successfully top charge a battery stored for
more than 12 months, the open circuit voltage must be
checked to ensure that it is higher than 2.0 volts per cell.
Therefore ALWAYS check the open circuit voltage FIRST.
If the open circuit voltage of the battery is 2.0 vpc or lower,
please refer to us prior to attempting to “Top Charge”.
Battery Age Top Charging Recommendations
Within 6 months 4 to 6 hours at constant current of 0.1C Amps or 15 to 20 hours
after manufacture at constant voltage of 2.40 vpc
Within 12 months 8 - 10 hours at constant current of 0.1C Amps or 20 to 24 hours
after manufacture at constant voltage of 2.40 vpc