strictly you DuraTrax Piranha Digital Peak Charger is not a lead acid (12v) charger. as it only does nimh and nicd cells.

however that being said you still can use it to charge.

just charge at 2amps, once the 12v cell reaches 14volts, then your 12v cell is prob around 90% full.

you then lower the amperage to around 1amp. once it reaches 14volts again it will be 95% full.

you will just have to watch the voltage manually, coz your piranah wont peak detect properly gell cells as they are charged differently to numh and nicd cells