Can you Desulfate an AGM battery

[FishbonzWV]

The workplace is throwing out 4 GNB 6v 195hr absolyte batteries and I told them I'd take them off their hands for free. Checked the voltage first and 3 were over 6v and one was 5.? or so. This is the second set I've got ahold of and the first set is currently at the camp with a 50w PV panel and a desulfater controller feeding them. They've been in use two years but the power usage is only about 300w when we use them and I thought they were vrla flooded batts when I put the controller on them.

Did I waste my $'s and time putting the desulfater on them?

Bonz

 

[whatsnext]

Actually, the best desulfator to use on AGMs is the electronic pulser type so you did the right thing assuming you had sulfation issues in the first place. Overcharging VRLA batts, rate or total, is bad because excess gas has nowhere to go except out the valve where it can't come back. I would probably just charge pairs at a low rate for a day or so and as long as you see something like 12.8VDC per pair I would put them into the bank and enjoy them.

John.........

[domwild]

Not wishing to detract from this excellent forum but to "catch more fish" you may wish

to add this question to the desulphator forum, which you probably know anyway. If not, here it is:

http://www.shaka.com/~kalepa/desulf.htm.

Regards,

[Ungrounded Lightning Rod]

AGM batteries do sulphate.

You'll want to desulphate them using a pulser rather than by feeding them an overcharge because of the problem with loss of electrolyte from gas generation due to excessive overcharging being permanent.

You'll want to check that your charge controller isn't feeding them a large number of big equalizing charges for the same reason.  Check on how to set the charge controller to match the batteries - with both the controller and battery manufacturers and/or their manuals.

[FishbonzWV]

Thanks for the info.

Put the low voltage battery on a trickle charger for about 4 hours and it came up to 6.4v.

When I can make it to the camp I'm going to pull the PV panel & controller to bring home where I can monitor this new set and hopefully revive them.

This latest set came from a powered pallet jack and I know they weren't taken care of like they should have been. Their lose is my gain. :-}

Bonz

P.S.  I also was able to 'dispose' of their dead APC 1400w ups. True sine wave. New batts took care of the dead condition.