Generator stalls & main 12 volt circuit breaker trips

When operating the 12v just on the convertor (batteries switched off to avoid overcharging by the old style fixed rate charger) I can try starting the generator and it tries to crank but there isn't enough power to start it. That may be the condition causing your rig to trip the breaker. If I switch the fully charged batteries on, I can crank the generator with no problem even when it takes awhile to start.