Oswegatchie,
It doesn't matter if you are going to use the stock trailer/camper pin on the rig. But this set up doesn't really get the most out of your investment and if you haven't bought the BB already you might want to go the Fire Fly carbon foam route.
Let me explain these batteries love power. Power is current, or amperage, not voltage. The more current they see the faster they recharge. This is the primary advantage along with weight, and being able to draw down to 80% state of charge. That is draw out 80 percent and not fully recharge. Not fully refilling Lead chemistry battery is what kills them as fast as drawing them below 50%.
BB said 14.4 to provide a margin of error I am assuming. I hesitate to wade in with; this will work or that will work because of so many unknown factors. In an old van adding 1 gauge cable connections to your alternator and battery and upgrading your ground. Fusing and adding an ignition controlled isolator off the positive lead on your lead engine battery and running 2 gauge cable again fused correctly would be fine. No voltage regulation would be needed, you could add an alternator dump protector, (a unit that diverts the current if the alternator fails and sends a high voltage spike Usually because of a loose connection) and let the BB BMS handle the rest. But even this in a simple OLD VAN is not ideal.
With new vehicles you get regenerative braking voltage spikes and the lead engine sponge won't soak it.
With a high tech system you have to take a systematic approach.
I don't want to be discouraging. I myself went back and forth for over two years, and had the advantage of having an awesome boat electrical engineer as a good friend who installed this stuff weekly on boats with owners that just wrote the check. My problem is I need lots of power and have zero weight room. I can't get 500 useable amp/hours any other way. I had to go with Lithiums or cheat and put my power cube in the back seat of the 2500 Dodge quad cab and weigh the unit and then add the power cube. Kinda like how people go thru scales without water and then...Not ideal right. So out came the checkbook.
I am not an expert on the Balmor systems past that I know people use it. I don't want to advise you on something I am not an expert at. I use Sterling. They are a standard in the yacht industry. I would use this
http://www.sterling-power-usa.com/library/bbw12120manual.pdf. Get a meter and stick it on the positive terminal battery cable. Turn your headlights on for ten minutes or pull your starting battery down a bit. With the vehicle cold and the meter on the big cable start and read the amperage and sip a beer. You want to see the higest amp rating your alternator is putting out. Get a Sterling unit above that number. Then, using the wire guide found on the link I posted come off your positive post to a circuit breaker rated at 60 120 0r 180 (depending on the Sterling unit you bought) I like the JL units here
https://www.sonicelectronix.com/cat_i4_circuit-breakers.html They also sell handy battery teminal posts and saves you making terminals.
Then install the Sterling unit following the directions in the PDF. It is under the hood water proof. Run the cable back to the battery, again sized based on the PDF and add another circuit breaker, same size, as close to the house battery as you can. If you are pulling a trailer and the batteries are in the trailer it is going to be a thick cable. I am not sure what you have so hard to answer. If you are pulling a trailer a cheaper better way is a little honda genie and a ctek
http://smartercharger.com/battery-chargers/#CTEK LITHIUM US. Avoid all the fuss and muss of engine charging as a good solar array will charge just fine. The genie can be a whisper quiet smallest one you can find.
That is how it could be done. To do it is up to you. If you get a little carbon foam Firefly for a house battery as a stop gap fix for now and then when you want to take the systematic approach the Firefly becomes your engine battery and you install the solar, house system with the Battle Born then and based on the solar set up decide then if you need to add the expense of adding alternator charging to the system.
I am sorry this is long, and not as clear as it could be. I have to make assumptions and assumptions make an ass out of U and Me, or so the saying goes. Not that either of us are that just saying it is difficult. I hope you find this helpful. But the route you are going is not a simple easy brezzy cover squirrl option. It is a hell of a lot easier than it was years ago and Battle Born are great. One other option is to go see them and see if they have options and installers local in Nevada. They are trying to build a rep and are running around the country with a rig handing out discounts if you see the rig. Go plead your case and you might be surprised.
