Originally Posted by amirm
FYI, I have two chassis batteries in my 2016. According to the schematic and looking at the system, there is yet another battery isolator between those two (located under the driver's seat where the primary battery is). Does yours have two batteries there too and still got discharged?
For those Interstates that have both a starting battery under the driver's footwell and an auxiliary battery under the hood (not all do; mine doesn't), only the one under the driver's footwell is used to start the engine. The one under the hood is always isolated when the engine isn't running, and only connected when the engine is
running. It's meant as a house battery for non-RV conversions such as ambulances and news vans that have electrical requirements when the engine is turned off.
way to use the under-hood battery for starting the engine is to hook up jumper cables from the auxiliary battery to the remote jumper posts under the hood. Which is possible in extremis
, but may confuse the relay when the jumper cables are disconnected. Or you might be able to remove the relay so the two batteries are permanently connected…