We were running the unit on shore power with the inverter on. I had a number of devices (computer, iphone, electric blanket and heater) plugged in and the unit was working fine, but when I plugged in the kettle, an E03 alarm occurred. We then realized the car battery was dead and went through the steps of flipping all the breakers and GFIs we can find (located under the bed). We then tried to charge the battery with both the generator and then with a battery charger power source, to no avail. We can't get the engine to start and although some electrical is working (the fridge, unit lights and we see 13.3V from shore power on the volt meter), we cannot get the microwave or outlets to work. Is there something we are missing as to how we can get the outlets working again? The inverter sill reads E03. Any advice would be greatly appreciated.