The Ford alternator on our 2005 Itasca (built by Winnebago) is supposed to automatically be connected to the coach batteries and charging them whenever the engine is running. Your Winnebago Minnie is probably set up the same way.
However after owning our Class C for only a couple of years, the solenoid that does this hookup started to become erradic so that our batteries would sometimes be getting charged when underway and sometimes not. I changed out the stock solenoid with a much more heavy duty one that has never let us down since.
When drycamped, we can periodically charge our coach batteries three ways: Using the built-in generator, using a small portable generator we carry along, or using the engine alternator with the main engine very quietly idling. Whenever using one of the generators to charge the coach batteries, the main engine battery is not automatically getting charged. (We have never went to solar battery charging in our Class C for a variety of reasons.)
