Fleetwood MHs do charge the chassis battery when on shore power. If you doubt this, measure the voltage on the chassis battery while shore is plugged in, then unplug and measure voltage again. You will see a drop in voltage with the shore unplugged. With a true 20 amp supply, we can run the ref, charger/converter and one AC unit without any problems. Anything other that what I have listed, does cause an overload. Depending on how much the overload is, will govern on how long it will take to trip the feed. If you use an extension cord, make sure it can carry the load you will put on it. We used a 20 amp supply for 3 TTs and our current MH, until 5 years ago when I install a 30 amp supply.
