Hi I have a 1998 patriot coach does the hart inverter charge the engine battery's ? My unit has been sitting for 2 1/2 months with the unit plug into 110 ac  the inverter has been on the house battery's are ok but the engine battery are down to 5volts  if the inverter is not set up to charge the engine battery's how much of a draw should I see with the coach not in use?    The inverter is a freedom combi inverter/charger model20