I'm new to airplanes but I have been flying for a while with Electric and Nitro Helicopters.

I moved away from NiMh batteries because they are heavy and hard to keep charged. I now have Lipo batteries in all my helicopters. I even put a Lipo battery in my new plane (which I will maden this Thursday). For all my stuff I'm using a 3s 11.1v 1050mAh Lipo battery. It is very small and very light weight. I get about 4 flights and that brings the charge to about 70% usage. Thats on my helicopters with High Torque - High Speed servo's. So far I've been happy with the Castle Creations CC BEC 10A - which brings the 11.1 volts to 5.1 volts.

Lipo batteries have gotten really cheap - I buy my batteries from HobbyKing.com for $12 bucks a piece.