Shunt Wiring a Victron 712 Battery Monitor

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Shunt Wiring a Victron 712 Battery Monitor

November 27, 2019, 05:45:15 pm

Hello,
I'm getting ready to show you how much I don't know about the workings of batteries. We have 26.5MB 2008. We're originals. I'm getting ready to replace our 2008 Trojan 105s with new 105's. They have served us well so no upgrade. The Profill makes it easy. No solar. Since I'll be pulling the batteries I think it is time to install a battery monitor. I have been doing my research, and if we do make the move, I'll put in a Victron 712. Now my problem that will show my ignorance. My understanding is that I only mount cables from the NEG posts from both batteries-battery side and load side to the shunt. On the left battery I have 2 grounds on the NEG post. Do I just add another cable to this post and run it to the battery side of the shunt? On the second battery, the series cable is all that is connected to this NEG. This cable is split for the disconnect. Do I add another cable from this post and take it to the NEG load on the shunt? Hope this rambling has not been too hard to follow. I told you I would show you what I don't know. I am always willing to tackle projects but sometimes I just don't see it. Thanks for any help. Bill

Re: Help needed Shunt Wiring Victron 712

Reply #1 – November 27, 2019, 06:08:53 pm

First, think of your two T-105s connected in series to be essentially one 12V battery with loads connect to the positive end and the negative end connected to ground. Next, think of the battery as being part of a loop. Current flows out of the positive end, through whatever devices are currently on and using power and then back to the negative end of the battery (often using the chassis as part of the electrical circuit). You want all of that returning current to pass through the shunt to completely measure the current flow. So the only thing you want connected to the battery negative is a single cable to the shunt. The other end of the shunt needs to be connected to the chassis as the main ground return. If any other ground wires are attached directly to the battery negative, they need to be moved to the side of the shunt that is connected to the chassis. This insures that the return current from that wire also goes through the shunt and is properly measured.

Hope this helps,
Art

Re: Help needed Shunt Wiring Victron 712

Reply #2 – November 27, 2019, 06:38:55 pm

Art, Thanks so much. So you're saying that I take off the two ground wires ( one of which is the chassis ground) that are connected to the NEG of the left battery and just set them aside and run just a single cable from that post to the battery side of the shunt. I connect another cable to the load side of the shut and where do I connect it? Is the second battery not connected to the shunt? Art, sorry about being more than a little slow on the uptake. Bill

Re: Help needed Shunt Wiring Victron 712

Reply #3 – November 27, 2019, 07:07:07 pm

I'm kind of thinking about the same monitor and the way I understood it , you would connect the large new negative cable to the negative on the battery and the other end to the battery lug on the shunt and then connect the two smaller ground wires to the load side of the shunt. I haven't studied a wiring diagram yet but I think i'm close.

Jon

Re: Help needed Shunt Wiring Victron 712

Reply #4 – November 27, 2019, 08:16:00 pm

Hi Jon,
The ground wires that you mentioned that come off the NEG post and then attached to the load side of the shunt sounds like that is what Al said in the post above. So we end up with a new lone cable from the NEG on the left side battery to the battery side of the shunt. The two ground wires that were pulled-one is the ground to chassis and the other is the ground to the converter-these two wires are then connected to the other side, or load side, of the shunt. More checking to be done. Thanks for helping me out. Bill

Re: Help needed Shunt Wiring Victron 712

Reply #5 – November 27, 2019, 08:17:46 pm

Quote from: coho17 - November 27, 2019, 06:38:55 pm

Art, Thanks so much. So you're saying that I take off the two ground wires ( one of which is the chassis ground) that are connected to the NEG of the left battery and just set them aside and run just a single cable from that post to the battery side of the shunt. I connect another cable to the load side of the shut and where do I connect it? Is the second battery not connected to the shunt? Art, sorry about being more than a little slow on the uptake. Bill

The battery monitor measures current into and out of the batteries, and since they are in series, the current through one battery passes through the other one too, so you only have to measure it in one place. So, when you remove the two black wires from the battery terminal, they don't get set aside - they connect to one side of the shunt. The other side of the shunt has a new cable connected from there to the battery negative where you had removed the two black cables.

Steve

Re: Help needed Shunt Wiring Victron 712

Reply #6 – November 27, 2019, 08:34:27 pm

Maybe this quick diagram hack will help. You just need to pick up a short battery cable long enough to reach the shunt. My batteries on our LD were on a tray, so I mounted the shunt on the left side of the battery box and got a battery cable long enough to allow the battery tray to slide in and out. Most auto parts stores have battery cables and often can make them up.

Art

Re: Help needed Shunt Wiring Victron 712

Reply #7 – November 27, 2019, 08:47:08 pm

Steve and Art,
Thank you so much for setting me straight on the shunt. Now I understand! Art, thanks for going above and beyond with the illustrations. You guys are the best! Bill

Re: Help needed Shunt Wiring Victron 712

Reply #8 – November 27, 2019, 10:27:20 pm

Bill,

In case you haven’t seen AM Solars video on the Victron Battery Monitor and Shunt Installation, here it is.

https://youtu.be/tV055vmZgvY

Kent

Re: Help needed Shunt Wiring Victron 712

Reply #9 – November 27, 2019, 10:56:16 pm

Thanks, Kent. I have this video memorized. I appreciate your taking the time. Bill

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