Hi Pieter, after much head scratching and throwing things about, I've found out how to make the Aux port work. There are three settings, battery SOC to make the port live, battery SOC to turn it off, and the minimum solar input for it to happen. (I had the solar setting to match my maximum solar input so the bl***y thing never switched on unless the 'Grid on always on' box was ticked and it stayed on permanently). I use my Aux to put spare solar into my car, and I want the inverter batteries to be as highly charged as possible when the sun goes down, so I have set the minimum solar input to 1500W, the SOC to switch on at 95%, and SOC to switch off at 90%. Once solar output drops to 1499W, the port switches off, and the inverter battery has at least 90%, and I still have 1500W coming in from the sun.