*face palm* You can only use 30 nicad cells in series max. This results in 36v (1.2v per cell)

Don't even think about mixing battery types either to get more voltage!!!! A bunch of used nicads will get hammered if put in series with lipo.

You can't get 72v using the cell numbers you are allowed to use

Easy with the optipower discount to get lipo at that cost. I wouldn't bother with the turnigy nano tech. They can't deliver what they promise (as ever)