> Does anyone know what the "procedure" is? I have lots of batteries that I
> could at least try this on.
Just a WAG, but I'd guess it's a variation of the old electro-shock
treatment.
What happens with NiCad batteries in a pack is that one (or more) of the
cells in the pack ages faster than the others and won't take as much charge
during normal charging. Then when you run the pack down, current continues
flowing through the pack even when that one cell goes to zero; reversing the
voltage on the cell. As soon as that happens, NiCad cells will grow
tendrils of metal that short the plates together. Applying a relatively
high current, high voltage pulse in the forward direction will sometimes
burn away the tendrils without burning away all of the plates; leaving a
cell that is still weak but functioning at perhaps 80% of where it was
before.
I supply the pulse by charging a relatively beefy capacitor up as high as my
bench supply will go, about 50 volts, and then discharging it through the
pack. Repeat that a few times, then try charging the battery normally a bit
and see if the voltage comes up and stays where it should under a light
discharge. If it's still 1.2v low, you can try the shock treatment again.
Works better if you can disassemble the pack and test/treat each cell
separately.
First round success rate is fairly good; but of course that one cell is
still weak and hence still quite prone to being reversed again. Overall,
it's a stop-gap measure at best.
Randall
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