Thanks for your answer to both of you.

I don't want to get into a fight Suicideneil, but I must correct you by sasying that a123 does sfit tight in the e-revo. I've made a 4s1p pack == style that barely fit in but then transformed it into a 2s1p + 3s1p to get more voltage. I only have 7 working cell out of that salvaged dewalt battery I got from a friend. Still, I think lipo would be a better option, in that I agree with you. Think I'll stick with 5000 3s battery then. I only need to find one that put out enough amp.

Mikey, have you used the 5000mah 20c with a neu 1515 1y ? I'm affraid the voltage will drop when I try to push the motor to it's limits. I might be wrong, and would love it seeing the low price on those!