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From: John De Armond
Subject: Re: desulphate AGM ?
Date: Mon, 05 Jun 2006 23:32:37 -0400
Message-ID: <>

On Sun, 4 Jun 2006 15:24:10 -0400, "soundhaspriority"
<> wrote:

>A brand new AGM battery was discharged deader than dead by a defective
>starter switch that pulled in the fuel solenoid.
>I have a Vector computer controlled charger that has a desulphate function.
>Are there any prospects for getting a battery into reasonable shape, ie. 80%
>back, from this?
>It was a brand new Yuasa YIG30L. Set me back $80.

The prospects are dim but give it a shot.  If an AGM sits discharged
for any length of time, generally the very thin plate material becomes
sufficiently corroded that large portions of each cell become
disconnected from the interconnects.  Still it's worth a try.

Your Vector won't come up from zero volts.  It'll throw either an F2
or F3 code.  You'll be better off with a dirt-simple low current
trickle charger.  One of those 1/2 amp or 1 amp battery maintainers is
a good choice.  Leave it in place for several days.

If there has been plate corrosion as I mentioned above then the
battery will charge and have normal rest voltage but will have little
to no capacity.  If only a couple of cells have corroded then the
voltage will quickly drop to whatever the string is without those
cells and stay there until the ones in better condition discharge.

If, after the trickle charger has been connected for a couple of
hours, the battery still isn't taking a charge, try shocking it.  This
involves connecting it to a source of DC reverse polarity.  Another
storage battery is a good source.  Hook the bad battery up backwards
and monitor the current (with light gauge wiring, this can involve
little more than holding the wire and noting when it starts getting
warm.)  Disconnect when the current starts sharply rising.

This technique will sometimes break through the hard insulating
sulfate crystal coating that forms on the plates after sitting
discharged for a long time.

I give you maybe 20-30% odds on it working but what the heck?  It's
only time :-)


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