On my 10, with two EIs, I have two batteries and two master solenoids feeding the main buss. Have a switch for L/R/both. Also have two distinct 10 amp relays that feed my ignition buss. Also a switch for L/R/both. Same for the avionics buss, but 30 amp relay. SP3T switches can be wired such that the move from L or R to both does not "break" the connection during the movement.
In case of major problems, can kill both the master buss and the avionics buss without impacting ignition. Can also isolate one battery just for ignition. The 18 ah battery will run my ignition for over 3 hours.
I would never supply the ignition downstream of the master relay, as it can fail, if not redundant, and also needs to be shut off in case of an electrical fire. You want to be able to kill everything BUT the ignition in case of an elec fire. A pullable breaker, or the relay in my case, can kill the ignition power if it is determined that is where the fire is coming from and you choose that the fire is worse than no engine, though it is likely not working if it is on fire.
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
Last edited by lr172 : 11-02-2020 at 02:57 PM.