Hi. I purchased a Victron isolated DC to DC charger (not sure why I chose isolated, but too late to return). The wiring diagram shows to connect input pos and neg to starter battery. However, I have read online that the neg input should not be connected to the neg on the starter battery (mostly due to the battery disconnect on the sprinter and this being a potential bypass). But if this is an isolated charger, surely the negative cannot bypass as the in and out are isolated.. what am I missing here? If I cannot connect it, could I just make it non isolated by connected the in and out negs together via a splitter or just wire them both to my house negative busbar (which has it’s own chassis ground I created). Help 
Yeah, i guess that’s the best way to do it, and place the XS near the house battery, losses on the way to starter will compensate by themselves.