DCDC charger install for camper

I built a 12’ camper with a heat pump for heating and AC. It has 5kwh of battery storage, and is a 24v system for the sake of efficiency and cost savings. We tend to camp in places that don't have available shore power. I do have solar panels, but most of our travels are from the midwest to the maritime Canadian provinces where cloudy days are plentiful. So I needed a backup charging system. I had this in my 2nd gen, and just transferred it into the Terra, and it works beautifully. Better in fact than in the 2nd gen, either because of the alternator’s age, or different charging parameters it had compared to the 4th gen.

The charger is a Sterling Power BB1224120. It has a maximum charging capacity of 1440w (120a@12v/60a@24v) which is more than I found with any other product, and as a plus it can reverse current direction and jump a dead starter battery in the truck. Instructions call for 2g wire which I used. Maybe could have gotten away with 4g, but didn't feel like taking chances.

Taking apart the face piece around the back seat was remarkably easy. Just pop up the little plastic connectors. There's a bundle of wires already coming through the floor where I passed the wires coming from the rear connector.





This is the dry run wiring connected to the charger. It will be cleaned up, notably with anderson SB120 plugs so I can easily connect and disconnect the charger when needed. There is an ignition wire I ran (12g red) which may or may not be necessary. Likely not. The little black wire coming out of the left side of the charger is for the remote control that runs to the dash.


Wires from the truck battery run under the foot sills and up to the hole through the firewall that already exists. Again, all trim pieces were very easy to get off.



Wires after they come through the firewall, positive is fused with a waterproof ANC fuse holder (lower left), to the battery. Yes, I'll lengthen the positive cable so it's not rubbing non the battery. Had this one left over from prior install so I could test the system.


To install the fuse holder, there are already a few pre-threaded bolt holes in that area. I used one of those and one hole without threads that needed a nut behind the wall. To get to that, I pulled back just a small portion of the felt fender lining. I futzed around with this taking off way too many screws and almost breaking some plastic connectors before figuring out I could just snip the felt next to the plastic of the two connectors closest to the place I needed access to and slide it off, then bend it down, and then slip it back behind the plastic connectors afterwards.



Behind the felt liner. Bolt I added is the one with the nut.


And for the wires running to the camper side, I used SB120 anderson plugs with waterproof harnesses over them. There's a small hole just above the license plate I ran it out. The other one pictured here is from the camper.



Finally, the remote control mounted to the dash with some 3M double sided tape.


The remote control allows you to set the charging rate, which is important. While it has the capacity to take 120a at 12v (1440w), you're unlikely to get that much power consistently diverted from the alternator. But the big plus with this installation over the 2nd gen is that even at idle sitting still I can charge at 65% of total (38a @ 24v), and while driving I can charge at 85% of total (49a @24v) pictured here. Haven't actually tried it at 100% while driving in this install, but might play with it. In the 2nd gen I could only get consistently 65% while driving without it cutting out due to low voltage, and at idle nothing at all. I think it cuts out at less than 13.5v. The alternative is to connect the ignition wire and it just turns on and off with the ignition. I prefer the voltage cutoff so I'm not stealing from the starter battery.

Super happy with this install. It worked well before, but is much more efficient in the Terra.

Here are vendors and parts I used. I have no affiliation with them, and I paid full price for everything.

BB1224120 charger from https://sterling-power.us/
Tinned marine cables and connectors from https://www.batterycablesusa.com/ They pre-assemble custom cut lengths with connectors and high quality shrink wrap.
Blue Sea Systems 7721 waterproof ANC fuse block
Anderson SB120 plugs and SBSX75A waterproof housings from https://www.peigenesis.com/ Other online vendors can be found at Where to Buy

One last plug for Sterling. Their niche is the marine market, which gave me confidence about quality and durability. I found them exceptionally helpful, and eager to make sure the application I was using their product in was appropriate to the product. Both pre- and post-purchase support was spot on. They're UK based but have a warehouse States-side. Make sure to order from their US website, or you may suffer from tariffs.

 

Good post

Is that hole you ran the power out for the tool to lower the spare tire?

 

Ha! You are correct. In my haste I didn't stop to consider why the hole was there, just felt fortunate it was, since in the last install the cable went under the bumper, and that seemed vulnerable. A smart person would have realized this already, having had a 2nd gen with the same damned hole.......

I just went out and dropped the spare. No problem at all. The visibility is very good, and the little hook tool still has room to pass. And the cables pass over the whole spare hoist assembly, with no interference at all.

Thanks for that.

 

That's a shitload of current to run through the alternator. The alternator is horribly inefficient, so for every watt out, it generates about 1 watt of heat in the alternator itself. Are you absolutely certain the stock alternator is up to task?

 

Considering our trips are infrequent, and at the 65% setting I'd charge at 900w, then even from near flat it would take 5h to fully charge the battery, and so far I've charged from closer to 30-50% requiring much less time, it's not much total time in its life to stress the alternator, and I do tend to turn off other things while charging the camper. But reasonable point, and time will tell. I'd be happy to get a high output alternator once available. If ever we go mobile full time, I'll certainly look into upgrading. But that's years off for sure.