@Vanholio
I don't know about how the Victon B2B works, but did the research on the Kisea, Sterling and Renogy(w/solar). They all have an available input for an ignition signal (which is available from under the drivers seat) that when fed a voltage will reduce the cut in/cut out voltage shat the B2B needs to sense from the vehicle to start /stop charging. This is how they can effectively charge the house batteries in vehicle with the potentially lower voltages that smart charging relies on.
There is a common misconception that this signal turns the B2B on and off. That is wrong. (wrong misconception

) When the signal is removed it merely raises the the disconnect voltage to the standard alternator value setting. This may in fact shut the charging off in many situations, but not necessarily. If the vehicle is above the standard disconnect voltage the B2B will still keep charging the house batteries until it drops to the disconnect voltage. In those cases the cut out voltage is still above the lowest voltage smart charge algorithm is programmed to let the vehicle reach. The only exception to that is the Sterling (newer ones?) where the ignition signal can be used as a hard on off switch for the charger.
Bottom line with these three brands, is hook up the ignition signal and charge away. Just don't call me if you batteries won't charge or your van won't start. 😈
I would encourage you to go to the prime source documentation The manuals are all on line. They are painful to read, especially multiple times. I didn't know squat about any of this stuff. I got the general gist of it from all of the folks on this site that are generous with their experience and knowledge, but have needed to go to the manuals to be fully confident in my understanding.