I think he gave the 12vdc batterys a 31vdc rapid charge. Normal would be 19vdc. The resistive load will drop to 14vdc. My experiance the shelf life afterward a high zap is very short. That is why nicad and nmhd batteries, last longer with slow chargers. IMO wonce the crystals grow they come back.
Im a tinker. I have tried zaping rechargeables. they didnt last and the internal damage was still there, after tear down inpection.