I have a few wall wart type desulfators and have brought dozens of DEAD
lead-acid batteries back to life. I keep one on my bus batteries and on
my 20kw diesel generator for maintenance purposes. Batteries are over 5
years old and work just like new.
http://www.vdcelectronics.com/  are the commercial ones......
http://www.shaka.com/~kalepa/desulf.htm  if you want to roll your own....

Rick

Lee Jones wrote:

> >> - this isn't like trying to charge a dead, stone cold
> >> Lead-Acid cell ...
>
> > Aren't dead Pb batteries dead forever ? I've always been led to
> > believe that significant sulphate formation is irreversible, and
> > leaving Pb batteries discharged for any length of time is unwise
>
> People doing home power in the US (alternative energy, like solar)
> claim 4 out of 5 lead-acid batteries die because of sulfation of
> the plates and are recoverable.  Without minimum daily exercise,
> the plates will sulfate (gradual crystalization of electrolyte
> solution; reduces electrical potential and increases resistance).
>
> Historic technique to desulfate a battery was to force overcharge
> every so often.  This wastes energy (which solar/wind/etc people
> don't like).  And, when trying to revive a heavily desulfated
> battery can easily overheat it (damaging the battery, usually
> with a bulged case).
>
> There's a battery desulfator technique using "ringing" of the
> electrolyte & plates at the resonant frequency of the battery
> (circa 3.6MHz for 12V car battery).  Circuit to do so was
> published in Home Power magazine #77, June/July 2001, see:
>
>     www.humboldt1.com/~michael.welch/desulfator.pdf
>
> The "ringing" causes the crystalized sulfate to redisolve from
> the plates into the electrolyte solution.  This can take a few
> weeks to a couple months using the desulfator circuit and a
> trickle charger.
>
> I'm starting some experimentation now on reviving a couple of
> car batteries.
>
> Besides the home brew route, there are kits and commercial units.
>
> References include various patents which can be found via IBM's
> patent server.
>
>                                                 Lee Jones
>
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