All you need to know right here.
www.hangtimes.com I switched to the A123 cells and what a difference. Set it and forget it. Charge today and fly next week still just as good. I had 2 hydramax packs go bad on me and when I ripped of the shrink wrap I found a piece of foil thin metal connecting the cells and it was broken in two. Good thing I was using them for ignition and not the radio.