revival of Ni-cd Batteries

[Darrell O'Neill]

Anyone heard of this before?

Zapping dead ni-cd batts with a Mig welder to revive them?

Just out of interest, i have serverval dead 18v and 24v batts, might give it a go..

[Hammy]

sounds a bit dangerous . Nicad can often be recoverd by careful cycling  ( charge/discharge cycles). Don't discharge below 1v per cell.

[dhutch]

I guess ulitmatly if the cells are totaly knackered, then we some saftly glasses, i might be game to give it a go.

- However that said, for the cost of them, i would be tempted to sling in a set of replacment NiMH's into existing drill case and do the job proberbly!

Daniel

[david.c]

Not something I would try .................but then I have never been that keen to wear exploded battery all over my face      

David

[Matt Seabrook]

Dont know it could catch on

[RICHARD+PHILIP]

I know you can zap ni-cad cells we used to do it with radio control car batteries to get that little extra out of them.

I used to use a specific bit of kit so I'm not sure if a mig welder would work. but I suppose the theorys good just wouldn't want to try.

and it's probably cheaper to buy a new nicad pack anyway.

Of course Nicad packs are very much so last year most people use Ni-Mh which you certainly CAN'T Zap as they go pop

I think the Phrase DON'T TRY THIS AT HOME is Adpt

[Man On The Clapham Omnibus]

I am sure there's a lot of misinformation about NiCds. I used to make alarm equipment warning devices (for buildings, not vehicles) and we used thousands of NiCd and NiMh batteries. The supplier's technical manager (GP) said that the decay of these cells is due to the growth of things he called dendrites between the plates which eventually cross the electrolyte and short the plates together. If they are kept charged then the dendrite's first contact point is blown away by a high current discharge. It grows again and again and eventually there are too many bridging the plates to be removed by internal shorts. Many years ago I was advised by Every Ready to run a NiCd (specifically - NiMh wasn't around) down to zero volts and to put a G clamp across it for a fortnight before recharging from scratch. Strangely it didn't seem to work. On the basis of the dendrite theory, it is credible that a welder might blow them away, but it'll be temporary I imagine. Two really disappointing things in life (among others of course) are rechargable batteries and adhesives. They never seem to do what they are supposed to quite as well as they should.

[dhutch]

Interesting to hear what GP say about it.

- Ive also dabbled in the RC car gear, and at the time i left every one was on GP NiMH.

- Used to discharge them down to 0.9v per cell, then charge at 6amps to cycle them before race night.

When on NiCd's im fairly sure it was common practice to take them down to 0v before recharging.

Daniel

[Man On The Clapham Omnibus]

There was the so-called 'memory' effect with NiCds and to avoid this the drill was to do as you say and discharge totally before charging. The GP man, can't recall his name unfortunately, reckoned that this effect did exist but was very application specific - he cited space satellites using NiCd cells charged from solar cells in which the cycle was precisely the same day after day after day. On the odd occasion that more was asked of a cell than the daily cycle, it was found to have become set into the required capacity rather than its design value. The inference was that unless the charge-discharge cycle was indentical every time, the memory effect was largely a myth.