The manual for my Winnebago says the converter is a 3-stage charger, but I don't have a 30A outlet to plug into. I think it would be fine plugged into a 15A extension cord, with nothing connected but the batteries I don't think it would draw much to keep them charged. But then I'd need a second cord to run a maintainer on the chassis battery.
So I ran one cord into the battery compartment and connected one tender to the house batteries and one to the chassis battery. Now I can leave both shut off and not worry about it. On my 5er I pulled the batteries and connected them to the tender in the garage, but that's not practical with the MH.
I have the extension cord plugged into a Kill-A-Watt and will see how much it actually draws over the next month or so. Maybe not the best approach but it works for me.