Vlad said:
I purchased this unit less then a year ago that comes with two set of
batteries.
One of the batteries failed (short circuit) .I open the unit that
consists of 10 Panasonic batteries and all of them are in short
circuit.
I wonder what makes ALL of them to short circuit.
Vlad
Does seem unlikely. Are you sure they're all shorted and not merely at
zero volts?
Problem is user misuse plus dumb fast charger.
You're drilling a hole. The drill starts to slow down. You finish the
hole. Maybe you're in a hurry and drill the last two holes too.
Result, one battery reversed. Next time the weakened cell reverses
sooner, but the others are still good and you keep drilling until it
slows down markedly. Result, one cell seriously damaged and
damage started on the next one. Eventually, one shorts. The charger is
dumb and charges the crap out of the others trying to get the n-1 pack
up to n volts. Cells overheat and vent.
Viscous cycle destroys the pack.
It is unusual for ALL to go shorted at the same time.
It is not unusual for overheated cells to self-discharge and all end up
at zero volts rather quickly.
The premeptive solution is to make sure the battery is fully charged
before you start and stop before it's fully discharged. This is
difficult. If you sense any sudden weakening in torque, stop
immediately and recharge the pack. If you start drilling with a battery
that's been fully charged then set on the self for two weeks, you're
asking for trouble.
mike
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