Dc-dc Install As A Battery Isolator- Questions

I'm finally getting around to putting in the Renogy 30A DC-DC charger. I have the unit location and wiring runs figured out (right side bin into the foot of the mattress and a hidden loop back in to the battery compartment).

The Renogy has a number of other wired connections such as temperature probe, Bluetooth, Voltage Sensor and ignition wire. None of those are causing me (yet) to scratch my head as much as the main connections. (PDF below)

This unit, like the CTEK, can also function as a battery isolator. Presumably, if it is installed correctly in its proper place in the proper electrical "chain".

I've determined that the alternator/charge wire is the thick black wire attached to the bottom of the +BAT post in the jpg.

View attachment upload_2024-4-16_13-42-31.jpeg

My question is: in order to maintain the unit's function as a battery isolator, must I remove the alternator wire from the post, fix it to a 40A fuse, and from there, run it to the DC-DC, and back to the +BAT post? i.e. make the DC-DC the first and only thing the car alternator "sees" when sending a current to the trailer?

The only other configuration for the main wiring that I can even conceive involves coming directly off the +BAT post, to the DC-DC, and back to the + terminal of the trailer battery. I'm pretty sure that would still allow the DC-DC to fully charge the battery, but at the expense of not isolating it. And maybe messing something else up.

How close am I?

Of course the manufacture install notes don't touch on where to put this in the "system", nor speak of its relationship with power disconnect switches, AC-DC chargers, and the like. The PDF diagram is "simple" to say the least. Too simple.

I'm not worrying about the solar connects at the moment. I want to see how this operates first.

(And yes... the scorched wires in the photo are from a long-ago mishap.)

Thanks in advance for any insight.

 

Are you replaicng the ctek? It seems redundant, and you could just install it in place of the ctek. Or am I misreading this?

 

No CTEK previously installed. Starting from scratch, DC-DC-wise. And I have no isolator either.

The Renogy seemed like an affordable alternative to the CTEK, with some extra features, I believe. Don't quote me on that though; it certainly wasn't giving up any functionality to the CTEK.

Its relative size, however, demands placement in the bin. Right side cupboard, was possible, but seemed like too much work. Especially if it needed tweaking. And there's zero room above the battery, unlike some older CIs.

 

OK...suddenly makes more sense...I though you had the CTEK already. It looks like the install is the same electronically.

I need to look at the wiring diagram to be sure. But you should be able to simply bring the wire from the tow vehicle up to the converter, then take the output from the converter to the existing stud. Its needs to be serial not parallel connection.

OLD:
7 pin -------> Battery/Stud

NEW:
7 pin ---- > [DC Converter in put]/[DC Converter output] ---> Battery/Stud

You're basically just putting this "inline" -- just like putting a water valve in to a piece of wire pipe.

The ground can just to to the grounding point in the battery box.

Theoretically, a simple cut and splice. Do not use the "vampire" type connectors (These are the little blue things you see car stereos hacked in with) --- you'll want to use a good solid crimp butt connectors. I buy name branded ones from the home store, the cheap things that come from China are questionable at best.

If you want guidance on those, I'd be happy to expound, a good crimper is worth its price ... they "weld" the connections together if you do it right -- they aren't coming off unless you REALLY work at it...


EDIT: This is my crime of choice: Ratcheting Crimper, 10-22 AWG - Insulated Terminals - 3005CR | Klein Tools. The simple plier things, I've never had a really good solid crimp.

 

Thanks Sweeney. I was pretty sure the placement in the chain would be identical to the CTEK since they do pretty much the same thing. I bought a dedicated quality crimper in anticipation of the install back in the fall. The needle-nose pliers and ball peen hammer stay in the drawer.

I was 95% convinced that was way to do it, and when I explained the "problem" to others who have some limited experience in these areas, the process itself brought me up to 99%. I was making sense to myself. Go figure.

I have a new C-I owner in Toronto (down-payment paid) coming for a tour, primarily to get a handle on what options are useful and advisable, so he can tell Cary before production begins. I wanted the trailer put together, and up and fully running when he showed.

 

Have you tried the waterproof low heat solder butt connectors?
Visit the Wirefy Store
4.5 4.5 out of 5 stars 2,426
Wirefy 110 PCS Solder Seal Wire Connectors Kit - Heat Shrink Solder Butt Connectors - Waterproof Solder Sleeves - Self Soldering Wire Connectors - Set 26-10 AWG

 

Thanks. I do have some of those. First attempt (on another project) at getting the right right amount of heat in the right place left lots to be desired. (Did you know that plastic melts?)

Subsequently, I picked up a better heat gun with more precise attachments. Hopefully the operator has also been upgraded in the meantime.

 

Wait, heat gun?
I thought its wooden matches...
no wonder my DIY electric wires are all smoky and melty looking...
J/k

 

Very similar product...If you have any questions, PM me we can talk through it....

I enjoy those tours, the curious onlookers I dont' care so much for -- but when they are truly interested in the little details, it makes it a lot of fun.

 

I got it in and working. (pics to follow, with my usual verbose descriptions, for those who might be putting in the same Renogy).

Thanks for the offer. The Bluetooth-phone app is a little (lot) confusing. I may not have a true handle on the whole ball of wax until I do a deep deplete of the battery and watch what the DC-DC does. Though, I expect: Its Job.

Tour went well and he's likely sticking with his long list of options, as his travel style, non-camping spouse and (very) young family dynamics demand a few more of the niceties than what we take with us.

 

Renogy 30A DC-DC Install Complete.

Given it's relative size to other DC-DC chargers, this could (practically) only go in the bin. There would be room in the right side cabinet, but at the cost of disassembly. As it was, I have plenty of room for ventilation, storing the cookware, the under-counter tray, and getting the battery in and out is no problem.

Basic Steps as a recap:

1) I took the alternator charge wire off the +BAT post. The 40A fuse that came with the Renogy has enough real estate on the board to be mounted here (YMMV):

View attachment upload_2024-4-22_8-58-33.jpeg

2) The Red Out goes from the fuse to the Renogy.

3) The "Out" on the Renogy goes back to the +Bat post:

View attachment upload_2024-4-22_9-2-2.jpeg

... also with a 10 gauge 40A flex fuse.

4) The Renogy "Neg" terminal is grounded to the "Body" ground post. (there was another ground post that C-I had labeled "Chasis" but the Body post had more going to it so I went with that.)

5) The Renogy "Ignition" wire (thin red) goes the the "Lights" post with many of the green wires. This post is energized when the TV's headlights (and subsequently) the trailer's taillights and running lights are on. This is what "turns on" the Renogy, and is the easiest way to do so, rather than trying to run a wire all the way back to the TV's ignition switch. You just have to remember to drive to with your headlights on (I always do) if you want the alternator to charge, or top up, the battery.

The other wires from the Renogy were a voltage monitor, which goes to the + and - terminals of the battery and allows it to optimize it's charge profile, and a temperature probe which is taped to the top of the battery, and does the same thing. All wires come up the "other" side of the battery, and there is plenty of slack to pull the battery and/or drop the fuse panel:

View attachment upload_2024-4-22_9-14-22.jpeg

(The other green wires in the back of the battery compartment are from my solar and third brake like installations.)

I kept the Renogy mounted slightly below the top of the bin divider, to provide some ventilation, the wires went into the foot of the bed and back in the battery compartment:

View attachment upload_2024-4-22_9-19-49.jpeg
View attachment upload_2024-4-22_9-18-56.jpeg

The Froli and mattress conceal any extra bundled wiring that I couldn't shorten. The BT has decent range, so it didn't really matter where I put the module.

In the bin, there is plenty of room for the Renogy, ventilation, Dutch oven, Magma cook set, 2 kettles, additional pot and frying pan, the under-counter tray, and to get both the battery and battery panel in and out. I have the cookware stored with foam dividers, so they don't move and/or impact the Renogy or the shore charger.

View attachment upload_2024-4-22_9-43-21.jpeg

All-in-all, very do-able and inexpensive (The Renody was $210 CDN). But given a choice in the beginning, and knowing what I know now, it would have been a factory CTEK installation.

Still need to test it out with a half empty battery to get an idea how warm it gets going full-tilt, and whether I need to give it more breathing space

 

Nice work! Very clean looking install.
I appreciate the extra words in explanation, btw.

 

Bluetooth Update:

Despite some cautions from those on the interwebs, the BT module works as it should and is simple to understand. I can even monitor both batteries SOC and (dis)charging condition from inside the car. The module has good range, so it doesn't have to be displayed any place conspicuous. Under the bed is good. It also monitors both of the the trailer battery temperature, and the charger's temperature. Which is also good, as my one concern was proper ventilation of the unit inside the bin, surrounded by packed-in cookware. There's not much I need the app to do beyond that. Default settings are for an AGM/Sealed, and don't have to be messed with.

I haven't hooked up the solar panel to it, as I already have a good separate charger for that. The only benefit it would give me, if I ran the solar through the Renogy, would be the ability to trickle charge the TV battery. Or... gaining shared charging between the alternator and the solar panel while mobile on the road. Both functions are rather dubious in their usefulness, and aren't worth the hassle of unwiring, rewiring, adding complexity, and losing some system redundancy.

 

Nice work. I like the fact the exposed connectors are under a cover. Way too easy to short out a battery and that could be disastrous if it happened while driving down the road.

Bluetooth is sorely disappointing in its range --- My smart shunt, I can see it but only get very minimal data if I am any distance away from the galley. I am not sure if it is just that the data packets are larger and prone to transmission error, where the simple voltage, and current screen is sending a small packet?

But it works...just not quite up to my fastidious nature.

 

To your point... the build of the unit is rather robust. I wouldn't have felt comfortable with it in this position, next to cast iron, pots and pans, if it wasn't. Or if I had to build an extra protective cover around it to mitigate the possibility of shorts or damage.

Wire routing can be taken all out the bottom, on either side, and grouped, even though there are "exits" provided on all four corners.

 

I wouldn't worry bout it, when I saw the picture initially I saw open screws. With the plastic encasement, you're in better shape, especially if you travel as the photo depicts. I know my bay hasn't changed much in 3 years, the way things went in there the first time is pretty how much I travel...and with the cast iron in the storage slot, its not a factor...