Since you are talking different voltages, it helps to think in terms of watts and not amperes.. The Honda is advertised to put out 1600 watts continuously. Watts = amperes X Volts.. so that is 13.3 amperes at 120 volts.. for a 12 volt battery, a bulk charging voltage from the charger might be 14.5 volts so 50 amperes would be 725 watts, easily within the capability of the Honda 2000. If the charger is 95% efficient that would mean 760 watts.. This is with NO other loads running except the charger, no refrigeration or electronics.. ultimately, the Honda should be able to power a good charger at a total output to the batteries of around 100 amperes... again, this is with no other loads... and assumes correctly sized wiring and good connections..