bluemagic98, yes 7.4v Li-XX is a good plan. As far as I understand 6 volts is the minimum and a 5 cell pack is not to be used with this ignition. Use 6 cells or 7.4v Li-XX.

wttiger42, try removing the regulator - you don't need it as the ignition accepts 7.4v without the regulator. Again 6v is minimum and should be read as the engine will accept a 7.4v Li-XX pack that has been dischanged down to 6.00000001v. With 6.00000000v you get low voltage warning.