diy solar

diy solar

Shunt location on travel trailer with batteries in front

The chance of getting shocked is no more with the lead going to the chassis. This is fairly normal. My trailer went to the chassis before it went to anything else.
I’m going to try to trace the black wire connected to the negative bud bar in a day or two, but do I not understand how is the circuit completing if the negative wire from battery isn’t going to the negative bus bar? Is the trailer completing the circuit? Is this a stupid question? I thought the circuit had to be full circle.
 
So if I hav
It sounds there are two leads coming off the battery.
So if I have two leads coming off the battery (one to chassis ground and one to inverter) how do I put a shunt in a position to where I can capture the current going to both? They’re not even on the same battery currently. Wouldn’t I need to read current going to negative bus bar as well as to inverter?
 
For the shunt, I would get a piece of thick wire and place the shunt first, and then send that to a busbar that splits to the trailer ground and the inverter. At least that’s what I’m doing with mine.
 
So if I hav

So if I have two leads coming off the battery (one to chassis ground and one to inverter) how do I put a shunt in a position to where I can capture the current going to both? They’re not even on the same battery currently. Wouldn’t I need to read current going to negative bus bar as well as to inverter?

LOL! That's what I've been saying. The shunt has to be the first thing after the battery negative terminal.

Battery Negative Terminal -> Shunt -> Everything else

You need to remove both of the leads going to the negative posts. Those leads then go on the load side of the shunt.
 
LOL! That's what I've been saying. The shunt has to be the first thing after the battery negative terminal.

Battery Negative Terminal -> Shunt -> Everything else

You need to remove both of the leads going to the negative posts. Those leads then go on the load side of the shunt.

Thanks for hanging in there with me you guys. I took a quick video. Let me know what you think and thanks for being kind and patient.
 
Thanks for hanging in there with me you guys. I took a quick video. Let me know what you think and thanks for being kind and patient.
Should I just move all the negative wires to one side and it doesn’t matter which side? So one negative post will end up with only the wire from the other battery on it and other battery meg post will have the shunt then then off other end of shunt will be the the inverter wire and what? That’s it? Because the other wires aren’t loads they’re a chassis ground, solar charge controller, and the wire used to connect the batteries. So then only load is the inverter?
 
Been busy today with work :(, chasing down tools and teaching myself to "weld" aluminum.

The reason they likely have the dedicated cable from the battery negative to the inverter is because the inverter is the biggest amp-hog on your trailer. What I didn't see was a positive cable coming directly off the battery, going to the inverter. If they used a dedicated negative cable for the inverter, they should have also used a dedicated positive cable.

What I would do is this:
1. Figure out the gauge of the cables (both negative and positive) going to the inverter, chassis, solar charge controller and the main distribution panel (what you're calling the converter in the video - it's both a converter and a distribution panel for your lesser 12v items).
2. Remove ALL cables going to your negative battery terminals.
3. Get a new negative cable that is at least as big as the biggest cable from step 1. A cable at least one gauge larger is better. Get a cable long enough so you can run it into the trailer and out of the elements. The longer you have to run it, the bigger the gauge needs to be.
4. Run the new negative cable from the negative battery terminal (either one, it doesn't matter) to the battery side of your shunt.
5. Connect ALL the cables that were disconnected in step 2 to the load side of your shunt.

It's likely that your shunt can't hold all the ring terminals for all the cables. The bolt may not be that long, and the diameter of the shunt bolt may not be the same size as all the ring terminals. It looks like the stud on your battery is 5/16" (hard to tell). My shunt uses a 3/8" bolt. If that's the case then you may want to add a four post (or more) bus bar that uses 5/16" studs. Connect the load side of the shunt to the new bus bar. That's how I wired mine up.

Clipboard01.jpg
 
Connect the load side of the shunt to the new bus bar. That's how I wired mine up.
That picture looks awesome!
What I didn't see was a positive cable coming directly off the battery, going to the inverter. If they used a dedicated negative cable for the inverter, they should have also used a dedicated positive cable.
You are correct there is no positive directly to inverter. What they did was run a wire from battery positive to battery disconnect input, then disconnect output to 100A fuse, then to inverter.

Is there a simple way (or not simple way) to tell me how my negative side of the DC circuit is being completed? If I have one negative going to inverter, and one going to chassis ground, and that's it, how is the circuit making a "full circle?" Is the trailer chassis itself part of the circuit? Is that normal? In other words there is not a wire going from battery to negative bus bar. There is however a wire going from chassis ground to negative bus bar.
 
Instead of calling it ground call it chassis return.
If your camper was made of pure copper it would be awesome.
But its not so its just moderately ok for low amperage loads.
If you have chassis return your loads will have a positive wire from the battery and the negative wire going convenient points on the chassis.
So I suggest you trace the wire from a dc light or other small draw load to verify.
There may be a wire from the negative terminal to the chassis for "ground" reasons.
Either way the remedy is to move that connection to the downstream side of the shunt.
 
For reference for you, this is my OEM battery grounding. The tray has the battery removed in the picture and has a short 1 or 2 foot 6 AWG cable directly to frame. To the same frame screw there is two other small wires I'm assuming power my leveling jacks and or my slide outs. Those are the two big amperage draws on my DC side.
If you're not lucky enough to be able to trace your negative cable, I know of no good way to trace the wiring for your inverter. If it's hard to get at, I can only recommend using a snake camera to trace the wiring. Honestly though, there's so few times my snake camera has shown me anything useful.
Trailer OEM grounding.jpg
You can always take a thick gauge wire and run it straight back to the battery or some other bus bar.
==========
Kind of seperate from the beginning of the post, but this is how I'm connecting the Solar DC power to the trailer.

To get my solar batteries to run my OEM DC, I am running from my main, large amperage positive and negative busbars with some 2 gauge wire, and I have two 4 stud 5/16" busbars to patch to RV DC needs. I'm going to hook the 2 gauge wire from the large main busbars with the solar batteries connected on one terminal, and on another terminal, I'm going to hook the battery cable to those busbars. This smaller distribution bar is going to be hosed in a 6X6X4 Junction box I got from home depot, which will be screwed onto a board, and them butyl tape to the metal floor.

My actual inverter is wired from the inverter to this large main, high amperage busbar, the same one the solar batteries are hooked to, and then the 2 gauge sends this to the smaller busbar.
 
If you're not lucky enough to be able to trace your negative cable, I know of no good way to trace the wiring for your inverter.
I am able to see my inverter negative (4ga) wire going directly from battery to inverter.
 
Right. The circuit is completed for everything - except the inverter - using the chassis
This is so crazy to me. But I guess is it a conductor so it works. So if I unscrewed chassis "return" or "ground" the 12v appliances that are connected in the distribution panel would stop working because that bus bar is also connected to the chassis.
Get a new negative cable that is at least as big as the biggest cable from step 1. A cable at least one gauge larger is better. Get a cable long enough so you can run it into the trailer and out of the elements. The longer you have to run it, the bigger the gauge needs to be.
I might get one of Will's larger wire crimpers so I can make this wire myself, and for future projects. I think I need a 2ga wire for this because my inverter wire is 4ga. He's got a hydraulic one and an a more simple one. Any recommendation? Or just buy premade wire? I probably need ~3-4' to get the shunt out of the elements while keeping the wire as short as possible. The only crimper I have is the one that Will says is for 10-22ga.
 
I don't like pre-made crimped cables. After you've made your own, its so much better to get the exact size you need without having to twist up the extra, or worst, finding out you're an inch short.

For my battery cables connecting four batteries, I was able to make cables four or five inches long that connects from terminal to terminal using normal lugs and 90° lugs. I had to cut them within 1/4" to fit into my tiny battery box, so they are pretty much the shortest route and about as perfect as a cable can be. No way I could have bought them that way.

I did crimp my cables with a hydraulic crimper off amazon. Depending on the larger crimper you get, mine is actually metric with SAE labels put over it. So if I'm crimping a wire, I may need to go one size down. Also look at the taps that come with it that if you're crimping a cable you can go one size down and they set doesn't skip a size. For example, my crimper for 4/0 wire was too big for it 4/0 lugs, and I did not have a 3/0 size included, so went down to a 2/0.

My next set of cables, I may crimp and solder. Since I built my cables I did read a white paper from trojan where they said the best way to build a cable is to crimp and solder. That is exactly opposite or what I learned. I learned the best way to build a cable is to crimp it because the proper crimp is so tight the metal gets fused together and its as if its a single piece of copper. This white paper showed thermal imagery of battery cables, and the crimped and soldered cable was cooler, so less resistance.
 
3. Get a new negative cable that is at least as big as the biggest cable from step 1. A cable at least one gauge larger is better. Get a cable long enough so you can run it into the trailer and out of the elements. The longer you have to run it, the bigger the gauge needs to be.
My current inverter cable is 4ga. My battery to shunt run will be about 3-4' I think. If I want to make it a little easier on myself I could run about 6'-8' but I was trying to keep it as short as possible while still putting inside the trailer to protect it. Do you think 2 ga will do it?
 
I agree with chrisski, make your own cables. I bought the TEMCo Hydraulic Crimper and it turned out excellent crimps. Zero failures, even though I was completely new to crimping lugs.

Yes, keep the cable run as short as possible. The thicker the cable, the longer it can run without losing significant voltage.

I've seen some very passionate discussions about soldering. My take is that you don't want to be soldering if the cables are used in a mobile environment. None of my connections are soldered. Crimps only.
 
I agree with chrisski, make your own cables. I bought the TEMCo Hydraulic Crimper and it turned out excellent crimps. Zero failures, even though I was completely new to crimping lugs.
So you have the exact one you linked to? The $94 one? There's also the $79 one that starts at 10awg instead of 12, and also doesn't go quite as big. Also there's a diff between 11ton vs 5ton for the cheaper one.
 
It's been a while since I bought the crimper. As I recall, my thought process at the time was that I absolutely needed 6 gauge through 2/0 for this project. Having 4/0 was good for the next project or in case I decided later to really beef up the wires.

My 10 gauge PV wires were going into circuit breakers and wouldn't have lugs/terminals. I ended up using ferrules on those.

I do have the TH0005, but mine starts at 6 awg. Maybe they upgraded that model to have 10 awg dies after I bought mine. The pictures and the description don't match. I noticed that the title of the product page says V2.0. I may see if they will sell me the 8 and 10 dies, they may come in handy someday.
 
Back
Top