Hmmmm, folks I'm talking to are putting a wire from the coach battery to the car battery (fused connection). When you are driving the coach it charges the coach batteries and the car battery.
It is Not the go through the taillight and drive with your lights on type.
I do have a Nav system but it is a third party that was installed from previous vehicle and not the Honda option. Don't know why the Nav system would pull on the battery when turned off.
Anyway having things installed Wed and hopefully all will go well.