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Fixing dead NiCd batteries

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HowardP

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There are funny videos of people over-volting dead Nickel Cadmium (NiCd) batteries to fix them. I haven't tried this yet .. safety understood as a given ... They claim that this changes the chemistry back enough that a dead cell might work again. Basically you set pos to pos, neg to neg, but just do a few quick tap / zaps at over voltage. One guy set his arc welder to DC, then zapp zapp zaap to a dead 18volt power tool battery. It worked. :eek: (DC, buzz-box welders put out about 30 - 45 volts on DC setting, if I recall correctly.)

Before I zap my DeWalt batteries, was wondering what you all think ?

thanks
- H
 
Doesn't work in the long run. You are fusing a "dendrite" that shorts the cell due to a pin-hole in the di-electric layer. It only fixes the cell for a day or two before the dendrite grows back.
 
interesting ... how many times can those dendrites be zapped ? Or rather, about how many times can the fix be repeated before it's futile ?
 
Since the fix is unreliable (doesn't work every time you try it), and even if it does, it only lasts a day or two (unpredictable), I think it is futile to try. Just buy new batteries; you will be much happier in the long run...;)
 
If you are zapping a full pack, I have had good luck only when I zap across the individual cells.

I would not re-use them in a critical situation, such as for an in-flight battery pack. I have done it for starters, ground test equipment, and an old drill years ago. Be sure they are NiCd. I am not sure it works with, nor have I tried it with other battery types.

John
 
There are some very expensive battery reconditioners out there but they cost far too much for the little in return from trying to rejuvenate a NiCad or Lead Acid type. I'm talking chargers that are well beyond $1000 US. I had on at my work place and while it did prolong some useful service life from a battery, it wasn't anything worth crowing about and it 's just more economical to buy a new replacement battery than fuss with an expensive charger.
 
Fixing a NiCd pack by using a large cap carged to 40 VDC or so oes work. It can work for quite a while too. Te earlier the short is found, the better success.

I do tend to look at age and when I replace a battery pack, I always write the date on it. If, say it's a cordless phone pack and it's 6 years old, I won;t try to resurrect it.

You have to zap individual cells. NiCd's can and will, reverse their polarity especially in a pack.
 
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