The box hangs off the chassis and the word came directly from Airstream's warranty honcho. The other reason it would seem plausible is that the original battery was a Mopar branded unit. Need to run this by someone from MB to see what they say. I have an additional year warranty on both the RV and the chassis, not really concerned. Kind of more like a whodunnit mystery at this point.That statement is suspect. At least on the T1Ns. On those, Mercedes might have installed a house battery under the passenger seat but not, I think in a box in the rear.
Live and learn. There is an easy way to remove the seat cushion, allowing the battery below to be easily removed.I replaced the house battery in my 2007 Interstate with an Exide Orbital battery after a cell in the original went bad. There was very little room under the passenger seat to wiggle the old out or the new in. However, there is a way to accomplish this task.
The passenger seat rides on two runners when you adjust the seat for and aft. At the far forward end of the runner track are tabs that prevent the seat from moving too far forward and sliding off the track. If you remove the tabs (hack saw) you'll be able to slide the seat forward enough to remove the battery easily provided you raise the seat using the two lifters on the right side of the seat. Be careful not to let the seat rail run off the track. There are small delrin bearings that may come out.
When you're through with the battery installation, you can insert screws into the tracks where the tabs were to act as a slider stop to prevent the seat from coming too far forward.