coach ? batteries
please clarify... do you mean engine /chassis or do you mean the house side
i usually assume coach means house, but that does not mean, that is what you are saying
chassis batteries will have drain from all the electronics, trasmission, radio, engine cpu etc..
house will have parasitic drains from control boards unless batteries are disconnected
even then the disconnect switch will not disconnect some circuits some inverters are hard wired and must be turned OFF at the inverter, some LP alarms and such safeties are hard wired and can only be "turned off" by disconnecting the battery cables