This could be the sh!p. I have a 24 volt combined system.
http://www.ebay.com/itm/Blue-Sea-M-ACR-Automatic-Boat-Marine-Battery-Charging-Relay-12-24-V-7601-/291241620046?pt=Boat_Parts_Accessories_Gear&hash=item43cf5a724e&vxp=mtr
http://www.ebay.com/itm/Blue-Sea-M-ACR-Automatic-Boat-Marine-Battery-Charging-Relay-12-24-V-7601-/291241620046?pt=Boat_Parts_Accessories_Gear&hash=item43cf5a724e&vxp=mtr
