^ The Sterling and Victron seem to differ in this regard. The priority with the Sterling is always the starting/house battery/batteries (2-starting batteries on my HD2500). Once the starting battery's voltage reaches 13.2v (not sure how it knows if the alternator is sending higher voltage than 13.2v...but this is how Sterling explains it in their op manual) it allows the BB1260 (ditto for their BB1230, et al) to then send up to 70A of current to the auxiliary battery.