It is important that you get the information on your specific coach and how it is wired. On my Monaco coach, when you start the generator, it supplies power to the inverter/charger, which actually charges the batteries. If the inverter/charger is turned off, your batteries will not be charged by the generator. The same goes for when you are hooked to shore power for the night. With the inverter/charger turned off, your batteries will not get charged.
Other coaches may be wired differently which is why you need to get the specific information on your rig.