[writchie]

Al's comments are well worth heeding!

It is certainly possible to engineer systems that can operate while charging but this requires a lot of extra effort and extensive testing, especially with lithium ion batteries where the changes in voltage and current into the battery (and temperature) need to be closely monitored to determine when to change charge modes. The current draw from the operating device can mess this up unless fully accounted for.

While lead acid chemistry is much more tolerant, as Al pointed out most chargers today operate in switch mode and while the battery does a good job at filtering them at it's end, the high frequency pulses from the charger can find their way into the power supply of the PDU causing catastrophic problems. You don't want this kind of headache. Stick with powering from the battery and re-charge it when it drops below 11 volts. Learn to manage your batteries now - not during competition.

While we're at it - don't let your underclassman carry batteries by the wires. They can't resist this for some reason. This of course weakens the connections at the terminal and the damage can be hidden by the required insulating tape. The problem will show up as a voltage drop during heavy loads and you don't want to find this out on the competition floor. Remember, we're dealing with 100 amp loads.