Alright, I think I will look into lipo a bit more, but I haven't given up on LIFE yet. The cylinder cells look to be good, and can be had for about $10 each. Apparently they can do 75 amp constant discharge, which is good enough for my needs. The only problem is soldering them together, because lots of them don't have tabs. If I made a 5 cell pack, that would be about the equivalnt voltage of a 4s lipo.

Thanks for all the input.