You should have one battery box with room for two batteries. These batteries supply power to the camper and the breakaway switch.
Page 25 of your owners manual states: The auxiliary battery powers many interior 12-volt components including the lighting fixtures, water pump, 12-volt motors, 12-volt appliances, slide room, etc. It also powers the breakaway switch.
Of course, when you are plugged into shore power, all your 12-volt needs are supplied by the converter.
If you don't have one, a 100 page owner's manual is available for download at: http://www.jayco.com/files/downloads...lename_154.pdf