Ok..here is a link to the Victron specs in case Scalf77 shows up..he'll need it
This is a very sweet
battery separator that acts as a smart 3 stage charger for your house battery while your engine is running. It's bluetooth-able to your phone and very configurable.
Reading the specs I don't see anything about it being bi-directional i.e. allowing the house connected solar to be able to also charge your starting battery. It also appears that you can't use the house battery to start the van in the event that you kill the starting battery....but being a smart charger overrides the above limitations in my booklet.....
So presently you have your solar connected to your house battery?
I think you can move the solar to your starting battery and get the Victron to charge the house battery...it's certainly worth a try..can't see any downside...not going to harm anything..unless your solar controller is putting out 44V..which it shouldn't be....