I use the JetCat 1250 mah Nicad, 6 cell, 7.4 volt battery and swap it out with another for three additional flights. I've got as many as 4 on one with a P-120. I have another spare, which is a 3800 mah NiMH 7.4V that weighs 15oz that I got from Tower. Works well so long as you charge it slow the first few times.

I also use 2X, 5 cell 2700 mah NiMH batteries for the receiver. Each go direct to a charge switch, then y-harnessed together direct to the receiver. I can get minimum 6-7 flights without charge.