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File description: Reviving old batteries Your name: (optional) Randall
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Is the battery pack nickel-cadmium ? If so, you can try an old trick (if
you've got the equipment) : find a fairly big capacitor (several hundred
microfarads at 50 volts or more), charge it up to 50v (or whatever it will
stand and you have handy), then zap the battery pack with it (being careful
to observe polarity). Yes, there will be a sizeable spark, just keep calm.
Repeat several times, then try the battery in your charger again. You may
also have to charge the pack just a little using an external power supply,
as I believe some chargers won't recognize the presence of a battery pack
unless it's still putting out some voltage. If you've removed the short by
zapping, it should take only a few seconds of charge to bring the voltage
up.
This won't bring back a shorted NiCd to full capacity, but you might get
70-80% of what it was before it got shorted. Running a NiCd pack down to
zero will almost always cause at least one cell to short, since the
individual cells are very sensitive to reverse voltage, and the weak cells
get reversed while the stronger ones are still putting out current.