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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
 

MikeMl

Well-Known Member
Most Helpful Member
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.
 

HowardP

New Member
interesting ... how many times can those dendrites be zapped ? Or rather, about how many times can the fix be repeated before it's futile ?
 

MikeMl

Well-Known Member
Most Helpful Member
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...;)
 

jpanhalt

Well-Known Member
Most Helpful Member
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
 

HiTech

Well-Known Member
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.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
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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