When I originally designed the RV9A electrical system, I used the Vertical Power VP100 Subaru schematic as a reference. This was mainly based upon my original intent to use a EJ25 Subaru engine for the power plant. This design incorporated dual batteries which could be selected to feed aircraft loads independently or in parallel. Once I decided to use a conventional aircraft engine verses an automobile conversion, I evaluated my needs and found that I had more batteries on board than I really wanted. The Precision Eagle Fuel and Ignition system has its own backup battery which can easily provide up to 6 hours of backup power in the event of a primary power failure. The Skyview system also has its own backup battery, providing primary flight data and engine monitoring data for up to an hour after the loss of primary power. The boost fuel pump is only required during startup, takeoff and on final. The engine’s mechanical pump keeps fuel flowing as long as the engine is running. I keep a handheld radio in the aircraft for backup communications, so I figure with the exception of the position transponder and auto-pilot servos I should be able to safely find my way to an airport as soon as I detect an alternator fault.

I removed the extra battery contactor, fuse, cables and terminals from my cabin power panel. I retained the “B” battery selector switch in my switch panel lineup. For now it will be known as “Spare”. It may become something else in the future.