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From: cameronjames@snoc01.enet.dec.com (James Cameron)
Newsgroups: sci.electronics
Subject: Sick NiCd Cell Cure?
Message-ID: <22682@shlump.lkg.dec.com>
Date: 15 May 91 01:37:18 GMT
Sender: newsdaemon@shlump.lkg.dec.com
Reply-To: cameronjames@snoc01.enet.dec.com (James Cameron)
Organization: Digital Equipment Corporation (Australia)
Lines: 31

Wanted: documentation on curing nicad cells that are apparently dead.


I've got some nicad cells in sets that I use for assorted purposes.

When the series connected cells drop below their operating voltage, and the equipment
starts dying, I check the voltage of each cell.  Sometimes I find one cell is dead and the rest
are fine.  Sometimes the dead cell is at a reverse voltage.

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

            a) the terminal voltage, ensuring that it does not increase beyond 1.6VDC,
            b) the cell temperature, ensuring that it does not get "hot".

    2) following up with a three minute ten-times-normal charging current; again keeping to
        the limits above,

    3) charge up to normal level,

    4) discharge to zero volts and charge again.

I would like to know if this procedure, or one like it, is documented anywhere.
And if so where?  Feedback by mail welcome; if there is sufficient interest I will post
a summary.
--
James Cameron
Digital Equipment Corporation (Australia) P/L
(cameronjames@snoc01.enet.dec.com)