I don’t think I have a feed to my caravan battery or fridge from my bmw. So my caravan battery was completely flat. But on the caravan control panel if I select the car battery on the right of the panel when the engine is on I can turn all the 12v things in the caravan including the fridge. But there was a red flashing light in the fridge. Could I use this way to keep my fridge going when driving. Bit unsure what is going on.