Adding "house" batteries and isolator to diesel w/two starting batteries. . .

[Road]

I'd like to add 'house' batteries (add'l deep cycles to power accessories while the engine is off) and an isolator to my '08 GMC diesel van, which has two starting batteries; one under the hood and one underneath along the driver's side frame rail. The house batteries will be charged by the van's alternator while driving, then isolated and charged/topped off by solar panels or shore power when parked or camping.

The van's two starting batteries are wired in parallel, doubling the amps but staying at 12v. This is a typical set-up for diesel vehicles and is needed to spin the much higher compression engine. The house system will be 12v as well, whether I have one larger deep cycle or two in parallel.

I'm fine with how to set up the house batt system itself, Blue Sea fuse box, wiring to back-of-the-van items, but wonder if it matters where the house system is wired to the starting battery set-up, and if it matters where the isolator is placed.

I'd like to come up through the floor (near the 2nd starting battery on the frame rail) for my fuse box and battery monitor, but keep the house batts on the frame along side the 2nd starting battery. I may decide to put the house batts (AGM's most likely) inside along the driver's side, again, very near or directly above the 2nd starting battery underneath.

Is adding a house battery system to a dual starting battery system simply the same as adding to a single starting battery system, or does the power and isolator need to be tapped into the starting system in a specific place to prevent future problems and not mess with the parallel wiring of the starting system?

Been leaning towards CTEK products to help control and manage the charge from alternator, solar, or shore power, specifically the CTEK D250s Dual Charger and the CTEK Smart Pass Energy Management Unit.

I've received a mess of conflicting advice from those with experience wiring a house system only to a single starting battery, or who are considering doing the same themselves but have no actual experience.

If you have real experience adding deep cycle house batteries to a dual starting battery system on diesels and have advice to offer, I'd sure appreciate it. First round's on me when I'm in your area or meet you on the trail.

Sincerely appreciated,

Road

 

[87FoRunner]

Treat the batteries under the hood as a single battery and wire your “extra” battery as if it is a second battery.

Your factory batteries are wired and treated as a single unit of massive capacity.

 

[Road]

Treat the batteries under the hood as a single battery and wire your “extra” battery as if it is a second battery.

Your factory batteries are wired and treated as a single unit of massive capacity.

Well, thanks, yes, I understand that. One of my starting batteries though, is not under the hood, as I wrote, it's underneath on the driver's side frame rail. I'm not quite sure if it matters if I tap into the starting system at the second--on the frame rail--battery with an isolator and house system (much more convenient for what I want to do) or if it needs to be between the under-the-hood battery and the alternator.

That's what I keep getting conflicting advice about, that it should def be one way and that's tied in under the hood, then others say nah, doesn't matter. Not much consensus so far. Even the rep from Redarc I talked to at Overland Expo East said "Good question, I'll have to check into that and get back to you. . . "