Installing battery shunt

[Bigeddie58]

Not 100% sure where the negative connection for shunt should attach? any help much appreciated.

[BayouBiker]

In order to accurately monitor 100% of the load, the shunt must be installed between the the negative battery post(s) and all negative returns from all connected devices. AS typically wires the tongue jack and the inverter using separate positive and negative leads. So the best setup is to re-wire in the battery box a bit. You most likely will have to use an increased wire size from the battery post to the shunt and the size would depend on your inverter size and the combined main fuse sizes for all other loads. You do not need to increase the size of the wire connecting any batteries in parallel.

If you have your heart set on placing your shunt in the area pictured rewiring become just a bit more extensive. You will have to extend your jack negative and all other negatives (solar charger, external charger leads, added aftermarket stuff, inverter, etc.) into the area pictured. then up-size the black negative battery lead connected to the white "neutral/ground bus" to a #2 (or larger) connect it to the battery side of the shunt and connect all other device negatives to the pictured ground bus (if it has room, if not get a larger bus bar) then connect another #2 (or larger) between the ground bus bar and the load side of the shunt. Easy as that....

good luck

[ROBERT CROSS]

I used this....
Running all grounds to the negative buss bar.👍

Bob
🇺🇸

[EGinMV]

Thank you for all your posts, I’ve been finding them very helpful.

I’m installing a BMV 712 shunt and monitor on my 2017 Airstream, 25 feet. I have two negatives coming into the front of my airstream. And I understand they should both be going to the shunt. Do I combine the two 4 gauge wires together and put one O ring on them? Or do I just put two wires on the shunt? Two negatives going in and two negatives going out?

Do I just splice them together and put an O ring on it?

Thank you for any input and advice!

Eric

[BayouBiker]

Two in and one (a 2 gauge) out just as Bob's diagram shows. Then another 4 or 2 gauge negative to negative to parallel the dual batteries.

[EGinMV]

Thank you. Is that different from the attached diagram where both negatives coming from both batteries go in the shunt?

[EGinMV]

Here’s the current configuration of my solar wiring. If I do 2 in and one out, does the one out go to the inverter, or the negative bus bar?

Thanks again for your input. I’ve never done any electrical work, but I’m so glad to be getting rid of the Atkinson controller.

Eric

[ROBERT CROSS]

^
That looks correct if we assume that the "fuse panel" includes the negative buss bar that is illustrated.

POI... our neg buss is not integrated into the fuse panel.

Bob
🇺🇸

My shunt is mounted on the floor downstream of the combined ground wire from the two batteries,(arrow)

[EGinMV]

Great. But if it’s only one negative out of the shunt to negative bus bar, then were does the inverter negative connect to? Should I connect the inverter to the negative bus bar?

It seems like there should be two negatives coming out of the shunt, one to the negative bus bar and one to the converter? What am I not getting?

Thanks again!!!!

[EGinMV]

How about if I use this coming out of my shunt and connecting both the inverter and the negative bus bar to this?

Thanks again, trying to make sure I have all the parts before I start this.

Eric

[Malia20]

Originally Posted by EGinMV

Great. But if it’s only one negative out of the shunt to negative bus bar, then were does the inverter negative connect to? Should I connect the inverter to the negative bus bar?

It seems like there should be two negatives coming out of the shunt, one to the negative bus bar and one to the converter? What am I not getting?

Thanks again!!!!

No, you are getting it. Just put neg wire from neg buss to house side of shunt and also neg wire from inverter to same bolt on shunt. Then you only need one 2 guage wire from battery side of shunt to battery negative. One 2 ga. is about equivalent to the 4 and 6 that are on the house side of shunt. You will also need to bring the negative wire from the Zamp solar feed (if you have one mounted on A-frame) into the house side of the shunt. On my 20' the jack is grounded through the frame (and the frame to the neg. buss bar) so that, for me, was not an issue.
you're getting there.
Fred

[EGinMV]

Thanks again, learning a lot!!

So the battery side of the shunt, the 2 gauge wire, is connected to both of the negative of my my two batteries?

I have two 6V AGM in series.

If my batteries are in my front box, what’s the best way to bring it inside? Do I need to pull out the seal under the Airstream and snake it through?

[Malia20]

Originally Posted by EGinMV

Thanks again, learning a lot!!

So the battery side of the shunt, the 2 gauge wire, is connected to both of the negative of my my two batteries?

I have two 6V AGM in series.

If my batteries are in my front box, what’s the best way to bring it inside? Do I need to pull out the seal under the Airstream and snake it through?

NO! The shunt is not connected to BOTH battery negatives. You said you have 2 6V batteries, so they must be connected in series, so the positive of one is connected to the negative of the other. This pair is now considered a single "12V battery". the one positive post and one negative post not used in the series connection are now the positive and negative posts of "12V battery". Connect the battery side of the shunt with a 2Ga wire to the negative post of the "12V battery".

To put the shunt inside the trailer (not the battery box), pull the negative 4 ga and negative 6 ga wires from the battery box back into the trailer. You could use one of those as a "snake" to pull your new 2Ga wire from the battery box into the trailer through the same hole those 4 & 6 vacated. If you're real ambitious, you'll shorten the 4 & 6 that you pulled into the trailer, put new lugs on (the inverter 4ga could be trimmed at the converter-no lug required, at least not on mine), and then attach them to the house side of the shunt. The new 2ga pulled in goes to battery side of shunt in the trailer and the negative post of the "12V battery".
The red positive 4ga and 6ga wires can remain attached to the positive post of the "12V battery".
Good luck!
Fred

[Malia20]

Originally Posted by Malia20

(the inverter 4ga could be trimmed at the converter-no lug required, at least not on mine),

That should be (the inverter 4ga could be trimmed at the inverter-no lug required, at least not on mine)
Sorry.
Fred

[wulfraat]

Originally Posted by EGinMV;

Thank you. Is that different from the attached diagram where both negatives coming from both batteries go in the shunt?

Glad to see my diagrams are making the rounds and are helpful....

The first is how airstream wire from the factory:



The second is how you would use * existing * negative leads (one going to bus bar / one going to inverter) and re-route / pass through the shunt...



All negative leads to the battery must pass through the shunt, oterwhise it cannot measure all currents and hence will not provide accurate battery SOC information.

Alternatively, you can combine these 2 negative factory installed leads by replacing with a single 1/0 or 2/0.... this simply makes for a cleaner install but is not necessary.

Just make sure all negative (aside from the tongue jack perhaps, because that would be a serious PITA) go through your shunt...

[gator.bigfoot]

https://marinehowto.com/installing-a-battery-monitor/

[nvestysly]

I am not an expert so take anything I say with the proverbial grain of salt...

The picture shown in post #3 may not provide the best results and may even cause erroneous results. I think all the negative battery connections need to be on the same side of the shunt. The only thing connected to the other side of the shunt is the chassis ground. Otherwise, it seems current from the second battery (shown in dashed lines) doesn't really go "through" the shunt.

[ROBERT CROSS]

This better illustrates our connections...also a Victron diagram.

Bob
🇺🇸

My bad...I just took a better look at the OP's picture.
I installed it on this wire...arrow.

[EGinMV]

Wow! Thanks everyone for they’re input.

Fred, when I said both negatives I was referring to the 2 negative leads coming off the battery, the 4 ga and 6 ga.

So it sounds like it’s ok to use the existing two battery leads, the 4 ga and 6 ga, already inside the trailer, and connect them both to the battery side of the shunt. All other loads are connected to the other side of the shunt, either directly to the converter, or to the neg bus bar.

It’s would be so much easier to have to pull 2 ga wire from the battery box.

Thanks again everyone!!

Eric

[EGinMV]

So something is not working.

I installed the shunt, see photos. Both negative leads of my batter to the shunt, inverter and negative bus coming off of it.

My Mttps controller shows everything is good. Solar, battery, current, voltage reading as I expect.

However, there is no power to the display of the BMV-712. The screen is off. It connected to the RJ12 that came with the unit. See pictures below.

Any suggestions?

Thank you everyone for your input.