BatterySpace has 3.7V smart chargers that put out 3A and 6A. I know the 64boy and most other portables (N64, at least) run off of 7.4V, but if you had one that instead used 3.7V batteries hooked up to a step-up regulator, wouldn't it be able to play and charge from one of those chargers? I've been planning a portable myself and this could be pertinent information.