i did a battery swap just for the hell of it. used a 3800 mAH chinese battery with solder tabs. i agree with mr krinkle, don't try it unless you know what your doing. it's really easy to lose stuff and ruining the o-rings is almost unavoidable. i got some longer running time, not much, but the indicator doesn't work right. it goes from really long green, to long yellow, to flashing red shutoff, there is no red warning period. no biggie since my pax is usually on a charger (car or home) when im not using it.