Originally Posted by bsedor
Can anyone tell me if my 2016 Grand Tour has a battery tender to keep the chassis battery charged while the van is plugged in?
Interstates have a relay called a Battery Isolation Module (BIM). The purpose of the BIM is to isolate the house batteries from the chassis battery when there is a drain on one side but not the other, and to connect the house and chassis batteries together when there is a source of charging voltage from (almost) any source— shore power, generator, engine alternator, but usually not solar because the stock solar panel doesn't produce enough charging current to activate the relay.
So, if you have the van plugged into shore power— and the inverter/charger is turned on so that it can charge the batteries— then the chassis battery will be charged as well. Which is the gist of your question, even if a BIM isn't exactly a "battery tender."
Note however that the house batteries are Group 24s, and the chassis battery is a Group 49, so charging will be less efficient when the house and chassis batteries are connected. The two battery sizes have different amp-hours and cold cranking amps and may be at different charge states when charging begins, so when the house batteries are fully charged, the chassis battery may end up over-charged or under-charged (a Magnum inverter/charger only measures the charge state of the house batteries, not the chassis battery). But it's still better than not being able to charge the chassis battery from shore power.