Reboot when starting engines



I have a brand new GW with twin NavNet 14's.When I go to start engines after turning off at way point to fish, The Nav Net shuts down..I have to turn on again. I assume its because of the voltage drop when starting the engines. What is the requirement for min voltage. None of my other equipment does this (another brand GPS and sounder and AP). I have 4 batteries 2 per bank. My old Nav Net 2 never had this issue either. Is there some filter or anything to prevent this. Only solution we have found is either running engines all day..(not good) or combining both banks then after starting engines put back to individual bank settings. We even have chargers going with generator running.