I've already done that. I just put together an Amped rear gear motor with 20ah LiFePo4's. Been riding to work every day it's not raining.

http://www.bikeforums.net/showthread...ecommendations

This one is just for when the wife wants to ride along on the weekends. When these batteries go I'll check into better batteries, although the sla's seem to be doing pretty good.