[MBAtarga]

I've done the welder thing on some old Dewalt and Ryobi batteries. It's been a while - but I think I had somewhere around 50% success rate. I don't believe any of the "dead" batteries were revitalized back to as new and would take a full charge - but they definitely become usable again.

Another option besides a welder is an automotive battery charger that has the "start" capability.