Have you even tried charging off your generator? I was running mine earlier this week to test it out and just for kicks tried to charge my car off the 5/20 plug and when I plugged in my UMC the green light flashed a few times then went out. I was not able to charge at all. I have a high quality Honda EU6500 generator that actually powers my house with 1 AC unit running so it's not a matter of not enough power. I didn't try the 220v outlet as I don't have the correct adaptor. I think that the UMC sees the power as "dirty" and turns off as a safeguard.