I did confirm my coach does not use the generator input on the BIRD controller as was suggested. I also confirmed the BigBoy relay on my coach is closed when running either on shore or generator with engine running. So I think as Eric described, the alternator and inverter are designed so there's no "fight" issue when both are attempting to charge both batteries (but could be problematic if coach batteries severely discharged). That said, as part of my Lithium install I really feel I don't want (or really need) the engine alternator charging my large lithium bank due to large potential alternator current and alternator voltage higher than lithium likes, so I jumpered the 12V IGNITION to the GENERATOR input on the BIRD controller and confirmed it operates as expected. I attempted to contact BIRD manufacturer but no response so just did it and tested. Now, anytime ignition is ON the BigBoy is open separating chassis and coach batteries. I have a big generator to charge my coach batteries (engine running or not) and the system still works to charge chassis from generator or shore when engine is off. They sell after market BIM that "sort of" manages lithium but they control current by duty cycling the connection or detecting overload (voltage collapse) on the alternator. That does reduce "average" heat load on alternator but still pushes it to max during the ON period- especially if you have large capacity coach bank. One popular BIM is ON 15min, OFF 20min. Also really just wanted to avoid expense and hassle of swapping out BigBoy and controller.