Hello all,
I am installing a Smart Shunt in my RV, and I seem to be getting some strange readings. It is showing the amps out that are being drawn at the moment, not the charge amps in. See different readings in pic. And it is not showing an increase in the SOC as it is actually increasing. Any help much appreciated!
Dean
What loads do you have on?
The SmartShunt shows a net value, so I look at the numbers shown and it looks to me like you have a load of ~60A running; the solar controller is producing ~37A, which leaves ~22A still coming out of your battery to power the load.
Editing to add: that’s assuming that all of your system -ves are correctly running through the shunt to be able to measure them, of course, which I can’t verify from the photos. I see what looks to be a large inverter/charger on the “loads” side of the SmartShunt, but you have an awful lot of wiring in there and I don’t see that all of your system -ves are also run to the “loads” side of the shunt. If they aren’t, then the shunt can’t see them and won’t measure them, whjether they’re loads or chargers.
Thanks for the reply Justin,
The load out is roughly what is shown on the Smart Shunt..around 20 amps. At the moment I also have about 65 amps going into the battery bank from one Victron 100/50 and one Midnight 150 CC. I can see this charging rate through the built in BMS readout of the battery bank.
I may be overlooking something obvious as I am not experienced at this.
If I am installing the Smart Shunt between the battery and inverter on the negative 2/0 cable going into the inverter, wouldn’t everything connected in the system (like the Midnight 150 CC) by necessity be going through the Smart Shunt?
And I just noticed that the SOC reading with the Smart Shunt is going down, not up, even though the battery bank is being charged.
Dean
I don’t know how Midnight runs their systems, but in general probably not.
The SmartShunt must be the only thing connected to the battery bank negative, period full stop. Every other system negative, with zero exceptions, must run to the “loads” side of the shunt.
So for instance, the shunt can’t see the current produced by your Victron solar controller because the Victron solar controller’s output -ve is not running through the shunt; therefore your SOC calculation keeps going down even though, presumably, the bank’s voltage reading is going up.
Hi Justin,
Okay now I am confused. From the diagrams I have seen, there should be no other negative connections to the load side of the Smart Shunt before it enters the inverter/charger. So I don’t understand how both charge controllers can not be going through the Smart Shunt. Both the Midnight and the Victron charge controllers go to the positive and negative terminal blocks seen in the pic. From that negative terminal, the negative 2/0 wire goes to the inverter/charger, and goes through the Smart Shunt on the way.
How could/should I have wired it differently that what I did? In my confusion, I just don’t see an alternative. Thanks for your help!
Dean
I think you may have misunderstood whatever diagrams you may have seen; please thoroughly review the full user and installation manual for more information. As stated, the “Battery” side of the SmartShunt must be the only thing connected to the battery bank negative, period full stop. Every other system negative, with zero exceptions, must run to the “loads” side of the shunt. Any deviation from this will result in incorrect readings from the SmartShunt.
The user and installation manual can be found here: Manual - SmartShunt IP65
If it helps, you can draw a diagram of how everything’s currently wired in your system; I see an awful lot of wires running around, so can’t tell how things are actually set up.
What’s important for the SmartShunt is: is anything and I mean anything at all, connected to the battery bank -ve other than a hopefully large cable between the battery bank -ve and the “battery” side of the SmartShunt?
Hi Justin,
Okay I think I might see my mistake.
In the second pic below, I am pointing to the terminal for all 3 negative wires from the batteries. From that point, a 2/0 wire goes to the inverter/charger, and it is on this wire that I installed the Smart Shunt.
In the first pic below, is this where I maybe should have installed the Smart Shunt? On any of the three negative battery wires, BEFORE they go to be joined at the negative terminal shown in the other pic? This seems to be the only way to put any other negative connections from CC, etc, on the correct side of the Smart Shunt.
Dean
If you have 3 batteries, and all 3 negatives are joined at a power post, then one wire from that power post should go to the battery side of the smartshunt, and then all other system negatives should go on the other side of the shunt. In your first pic it kind of looks like you’re holding only a negative wire from a single battery, which won’t work. You have 3 batteries in parallel, which means that all 3 battery negatives must go to the battery side of the shunt, and then every other system negative must go to the other side of the shunt.
Below are the 4 acceptable ways of paralleling batteries, and I’ve pointed in the location of where the shunt must go in each scenario:
Hi Justin,
Ok I think I understand the issue now. My setup looks like the first pic, only using terminals instaed of bus bars. But I have both CCs grounded at the same negative terminal as the three batteries. See pic. My fingers point to the negative wires coming from both the Midnight and the Victron CCs. If I understand correctly, these two charge controllers need to be removed from this negative terminal, and connected to the “load” terminal at the Smart Shunt. Is that correct?
Dean
Correct! The shunt is a gateway to the battery, measuring everything going in or out of the battery bank, but if you have things that bypass it, it can’t see them. Moving the two solar controller -ves to the load side will allow the shunt to see their contributions, and the displayed SOC will start rising as the shunt is now able to add the charger’s contributiuons to its SOC calculation.
Hi Justin,
Ok thanks for your explanations. Now I have to decide where or not to drive 20 miles into town to get the correct wires and lugs today, or in two weeks when I leave my boondocking site in the Arizona desert.
So it looks like I need to buy some lugs to fit the M10 bolts on the Smart Shunt, and that also match the negative wires (#2?), from each of the two CCs so they can be directly connected to the “loads” bolt at the Smart Shunt.
I also need to somehow reconnected the 2/0 negative cable that I mistakenly cut to install the Smart Shunt in the wrong location. I assume I can buy some kind of block to connect them back together, since they already have the lugs installed? I’d rather do that than replace the entire wire if possible.
And it looks like there might be some kind of fuse installed protecting the CCs? See pic of where I am pointing. If I connect the negative wire from the Midnight CC to the “load” terminal of the Smart Shunt, am I bypassing this protection? The Victron has it’s own inline fuse so I am not concerned with it.
And I also have a negative wire going from that same negative terminal to the “solar in” breaker right above the terminal. See the other pic. Can I assume that is not a problem, since the breaker neither adds or subtracts current?
Dean
A busbar would do that pretty well, since there would likely be some gap between them. Honestly investing in a few busbars would be a good thing, as I see stacked connections that far exceed the general recommendations; usually 3-4 stacked connections on a single post is considered the absolute maximum and I see at least 7 on one of the powerposts; ideally that should be changed out to a 2- or 3-post busbar at least so you can spread those connections out.
As for the rest, I wouldn’t offer conjecture as to the suitability of the installation, as I’m not there to inspect the full installation myself. There’s a lot to proper electrical installations, required fusing locations, proper fusing/breakering to meet the wire gauge, sizing wire gauge according to current and also circuit length, and so on and so forth. Victron’s free “Wiring Unlimited” book is a great place to start learning about all of it if you’re into going over the system yourself: Wiring Unlimited
Ok I may be in over my head. I might take it into Quartzsite to have an installer there do it correctly. I didn’t do the installation myself. It was done by a reputable installer about 8 years ago.
I do have one more question that would help me decide whether to give up at this point.
If you look at the attached pic, my fingers are near the negative post. From the right is the fused(?) wire that connects to the other post with the three negative battery wires. At the top of the left post is the big lug for the 2/0 wire going to the inverter. The other three wires on that post are the negative wires of the 2 charge controllers, and the DC wire that goes to the DC fuse block. I assume it has to be moved to the “load” side of the Smart Shunt too.
So what it looks like to me is that I can perhaps put the Smart Shunt right where the left post is now - splitting up the lugs on the post between the “load” and the “battery” terminals.
Can I just remove the post on the left completely, and install the Smart Shunt in the very same location? I can then attach the fused line coming from the 3 batteries to the “battery” side of the Smart Shunt, and the 3 negative wires from the two CCs and the DC fuse block to the “load” side of the Smart Shunt? That would seem to me to solve all the issues. The only wire attached to the “battery” side of the Smart Shunt would be the (fused?) wire going directly to the post with the three battery negative wires. And the other three wires (2 CCs and the DC block wire) that are on that post at the moment would all go onto the “load” side of the Smart Shunt, along with the 2/0 wire going to the inverter. This would allow me to put the Smart Shunt in a location where I don’t think I would even need any new wires made up. I think replacing that post with the Smart Shunt would work. Am I overlooking something? Thanks!
Dean
I know I am late here, but have a look at this FAQ. rV installs often get the chassis ground wrong, this must also be on the system side of the shunt.
The fusing is odd, usually a fuse is on a +ve side rather than the -ve side, but in theory this will work as long as you’re tracing the wires correctly. One issue I see though is that you may well not be able to get all the connections onto the SmartShunt, the bolts on each side can hold 2 connections, not sure they could hold 3 or more and still have enough thread to be able to get proper torque on them.
Thanks for the reply.
From what I can see the problem is number three. I have negative loads on the “battery” side of the Smart Shunt rather than on the “load” side. My two charge controllers are working fine and charging, and the Bluetooth battery app is showing charging as normal. But the Smart Shunt app shows only the drain on the batteries and not the charge coming from the two charge controllers.
Dean
Hi Justin,
I was also worried about the lugs on the other 3 wires being too small for the M10 bolts on the Smart Shunt. Would it work to use a bus bar to attach the three smaller wires from the two CCs and the DC fuse block, then make up a wire to go from the bus bar to the M10 bolt of the Smart Shunt?
Dean
Absolutely, that’s the way most installs will do it; depending on the system, there will usually be a busbar on the “battery” side where the battery -ves connect, and one wire from that busbar to the “battery” side of the shunt, then one wire from the “loads” side of the shunt to a second busbar where all the system load, charger, and chassis -ves connect.
Hi Justin,
Okay on this installation it looks like they used a post for the negative wires rather than a bus bar. So I should be able to just attach the fused wire from that post to the “battery” side of the Smart Shunt.
Now the question I have to figure out is are there bus bars that can accomodate the smaller wires from the two CCs and the DC fuse block and still let me attach the bus bar to the bigger M10 bolts of the Smart Shunt?
I just talked to an installer in Quartzsite on the phone, and may head into town tomorrow to buy what I need to make the changes. I might do the work just around the corner so I can go back for help if needed. 
Thanks again for your time!
Dean
edit: It just occurred to me that I can use the existing negative post on the left in the pics by just moving it 6 inches to the left to make room for the Smart Shunt, and then making up an appropriate wire to connect that post to the “load” side of the Smart Shunt, along with the 2/0 wire to the inverter.