I am pretty certain the ESC comes with the Lipo cutoff activated, this can end your fun early when running Nimh packs.

Another thing, if this is your first brushless system, you may want to use the settings to "tone it down" a bit. The 5700 is very powerful and you can tune it with the Castlelink to be more drivable. Plus its just plain fun to hook up your ESC to a computer.