I build teardrop trailers as a hobby. In my electrical box where I supplied power to the trailer interior, I have a lithium iron battery, a 120V Power Converter /Charger, and a 12v to 120v Inverter to power 120 outlets. I want to power the outlets from grid power without back-feed powering the inverter because it burned up my last inverter. So when I switch to #1 position I am powering the outlets from grid, and on #2 position I am powering outlets from the battery and Inverter. I need to keep the inverter safe How can I wire this switch to accomplish this?