Need your guidance. Hooked up my eu2000i with a power cord adapter and fired up the generator. Reset the ground fault switch. Had every breaker on the AC panel off. First switched on the Hot Water heater and that worked just fine. Switched off the Hot Water tank, and turned on the Microwave breaker. Worked just fine. Switched off the Microwave and then switched on the battery charger. For the first time the reverse polarity light came on. Can you explain why that would happen, and what if anything I need to do. Thank you.