If you want full speed (and risk the internals) get one of these 11.1 volts lipo's.
Turnigy nano-tech 1800mah 11.1v 3S 20~40C - Ready to go Lipo
Turnigy 2200mAh 11.1v 3S 20C - Needs a new plug (Get the T-Plugs below!)
If you want to play it save get one of these 7.4 volts (Gives same speed as regular 9.6v types).
ZIPPY Flightmax 2200mAh 7.4v 2S1P 20C
Turnigy nano-tech 1800mah 7.4v 2S 20~40C
To increase amps to the motor change plugs on your gun (and battery) with this cheap set.
Mini T-Connector (Pair)
Low Voltage Alarms
On Board Lipoly Low Voltage Alarm (2s~4s) - Small voltage alarm
2-8S Cell Checker with Low Voltage Alarm - With voltage adjustment, and display.
B3AC Compact Charger - All you need charger for lipo's.
Turnigy Multi-Blade Micro Tachometer - Measure RPM's of your motor with this tool.
Register Here - Good Asian site (Remember your local Import tax)