I drove a 1960 Chevy 48 pass school bus for several years. It had all the lights you expect to find on a bus, as well as 3 big heater motors and the flashing over head lights. It was a 261 6 with a generator system. I never had a problem with it not charging. Even driving with every light in and on the bus on in the winter with the heaters running. It was a route bus when I was driving it, so it idled a lot. But it would also start in the coldest weather when nothing else on the school grounds would go.