I have a GLP 120-12 AGM battery, this thing to be exact:
It's a 120 amps battery, and it is about 26 months old. All of a sudden, I noticed that the battery is holding only about 10-15% of it's designed capacity. The voltage drops from 12.8 to 10.5 within half an hour when I'm draining about 100 W of power out of it, and after that, it also rises back quickly to 12.8 V, it looks more or less like this:
Draining (100 W): Start => 12.8 V 5 minutes => 12.5 V (and it stays that way for another 20 minutes or so) 25 minutes => 12.4 ... 12.2 ... 11.9 all down to 10.5 in a minute or two Charging (10 Amps): Start => 11.5 V (after my inverter disconnects at 10.5 V, the battery gets back to about 11.5 V, with no load) 30 minutes => The charger stops, and it reads 12.8 V (or slightly more)
Right now, I measured the voltage (fully charged a week ago and disconnected from the inverter,)) and it reads 12.8 V as if fully charged.
I'm wondering if I could somehow revive it? Are there any chargers or other devices that could somehow restore at least part of the missing capacity? Or is it a lost cause?
Just to let those that may be reading this know...
I was able to recover some of the lost juice (20-30%) by using a Novitec 'Megapulse' desulfator (cost ~ 70 euro). It made the battery somewhat usable again after about three weeks.