It worked well enough to get a month or so per zap, and I always had a spare battery pack on hand to swap out for it. Yes the dendrites always grow back, but for daily cycling it was worth it, as new cells would do the same in a few months anyway, as the Panasonic charge circuit was bound up in the microcontroller on the board, and simply did a sort of constant current charge while monitoring current to light a LED, and disabling the phone side when charging. No room to add anything inside, and a PITA to get to those boards inside, as they were well hidden by other boards soldered over them, along with all the soldered on paper and foil shields.