a device would be useful, as far as im aware sabertooths are the only escs with low vloltage cut outs, although a telematary system could also be used, http://www.hobbyking.com/hobbyking/stor ... metry.html
would give you a warning when your running out of power, and need to go easy? although i sopose that relies on the roboteers to stop, which could be hard in the heat of battle.