The wiring to charge the chassis batteries id not from the inverter directly on my coach. I'm not an expert either but the way I understand it is that the the charge voltage goes to an echo charger that directs the charging voltage to the house batteries until they are charged then to the chassis batteries. My coach also has a solar charger that will charge the chassis batteries once the house batteries are charged. Again not an expert but I believe part of that system is the BIRD or "Bi-directional isolator relay delay" that directs or combines the charge. That is about the extent of my knowledge and I wouldn't count on it being correct!