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From: agodwin@acorn.co.uk (Adrian Godwin)
Newsgroups: sci.electronics
Subject: Re: Sick NiCd Cell Cure?
Message-ID: <7137@acorn.co.uk>
Date: 17 May 91 13:15:47 GMT
References: <22682@shlump.lkg.dec.com>
Organization: Acorn Computers Ltd, Cambridge, UK
Lines: 29

In article <22682@shlump.lkg.dec.com> cameronjames@snoc01.enet.dec.com (James Cameron) writes:

>
>My father told me of a way to cure these sick cells, it involves
>
>    1) giving them half second bursts of 12VDC from a car battery or 5A power supply, until
>        they keep a 1.2VDC level, monitoring


I've used this procedure successfully in the past - I used a large electrolytic
capacitor rather than a continuous source. I think it was documented in 'Wireless
World' around 1975 - that's when I started doing it, anyway.

The theory was that some sort of crystals grew in the electrolyte and shorted out
the cell (though this won't be tha case if a cell is reverse-charged). The high 
currents supposedly melted the crystals, removing the short. 

Given the amount of rubbish that seems to be talked about NiCd failure modes this
may well be totally untrue - I'd certainly be interested to know !
However I can confirm that the procedure works : but not in every case, and the
repaired cells don't seem to stay repaired forever.

I haven't blown my limbs off trying this ..... yet (!)

-adrian

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Adrian Godwin                                        (agodwin@acorn.co.uk)