Ebay repair for NiCad batteries - Snake Oil ?

on 21/04/2010, robgraham supposed :

They repair information is freely available of the Internet, why pay for it?

Basically NiCads can grow whiskers, which short out the cells.

You just charge a large capacitor up and connect it to discharge across a cell. The heavy current flow explodes the whiskers and (hopefully) the cell will then take a normal charge again. I have recovered lots of old cells this way. No voltage at all across a cell, probably means it is whiskered up.

I'd imagine it's going to describe the memory effect or something, and explain how to discharge the battery using some fairly high power resistors, then to keep charging/discharging.

JW

Thats obviously a simple thing for you to do Harry, but could you explain it so a numpty could do it?

How large would a large capacitor be? Where would you buy one? How would you connect it?

Unfortunately once a cell has shorted from one whisker, the next whisker is just round the corner. So they don't last.

NT

The ebay Cd is for numptys lol

Bob

Worked for me with an identical but charged working cell. Mind you this was back in the early '70's so I have yet to try it on modern *c* cells:-)

The symptoms then were caused by a steady overnight discharge of a series battery pack. I believe current continued to flow after the weakest cell had fully discharged. This current was in the *wrong* direction leading to the growth of whiskers.

There has been much sensible comment in here on the inadvisability of over discharging portable tool batteries.

One day, should I be spared, I fully intend to open up some of my spare battery packs in an effort to sort out *good* from *bad* cells and create a sound set:-)

regards

Google Nicad ZAPPING.

Nothing critical about it... Large, pretty well what ever you can find

- say 20,000 MFD rated 25v or higher. Charge it up by putting it + to

If I were doing it (and I'm not suggesting anyone else does this), I would spark a cell directly and very briefly across a 12v battery.

Not sure that's all it is... the seller has very good feedback (3989,

If you look at the few negative/neutral feedbacks he's received here:

there doesn't appear to be anything dodgy about it.

Personally - along with TMH I suspect! - I (a) know nothing about NiCad whiskers, and (b) don't have the wherewithall or ability simply to "charge a large capacitor up and connect it to discharge across a cell", and I doubt very much that that's the sort of procedure being mooted, given the apparently very high level of satisfaction. Could be wrong, of course...

David