I just found a 3s 1500Mah LiFePo4 pack for TX's 5C discharge and 2C charge rated, I'll use them for the same experiment, unless I'm not setup to do it until they get here in which case I'll test them. =) Only $9.99 + S&H but I think its going to ship from China so it may be awhile. Under $20 total for an experiment I can't complain
S&H is a killer though...