Plugged into 50 amp. It's the inverter. You can feel the Bump when your hand is on it. Does sound like a transfer attempt to float charge, initialized, or what? No idea about electrical, but not the ATS. Inverter green lite showing on charge . 13.9 volt showing on house batteries while plugged in. Turn off 50 amp power, turned inverter on and Batteries showing 12.0 volts only? Batteries four years old. Surprised how much water I had to add, while trouble shooting, as I normally just need to add a little on the monthly checks wondering if batteries need to be replaced? No noise on inverter only. Green light blinking on charge cell1.
