Thanks Todd and Barry for your suggestions.
Todd, I failed to mention that I have the kero start model and, if it needs a higher voltage, as Barry said, I don't think the 6.6v A123s will be sufficient.
Barry, How many amps does the kero start pull? Would this 10A BEC workrather than the 20A one you suggested:
http://www3.towerhobbies.com/cgi-bin...LXSWL3&P=7