I just went through this and ended up with three busses and three switches. A master bus, an avionics bus and an ignition bus. In case of a fire or problem, the master goes off, leaving me avionics and ignition. If not solved, the avionics bus goes off, leaving only the ignition with power. In my case, each bus can be separately switched from Left, Right or both batteries: I am using relays/contactors.
I would not want to be without a way to kill everything except the ignition, being ignition dependant. &$*^ happens and you need a way to isolate things if you want to keep the fan spinning with dual EI.
RV-6A / IO-320, Flying as of 8/2015
RV-10 in progress
Last edited by lr172 : 01-11-2019 at 12:42 PM.