Wiring problem Victron b2b and Shunt (1 Viewer)

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Apr 7, 2018
118
71
Funster No
53,229
The supplier of my Victron b2b charger very kindly sent me the attached schematic showing how to fit it with my 2 batteries AND the Victron Shunt, which I already had.
It is now fitted. The b2b charger does seem to work fine, but as things stand the battery is ALWAYS shown as being at 100%, and probably other readings are therefore incorrect.
Can someone please have a look at the diagram and advise just where it has gone wrong?

B673146C-1175-48EC-9815-627643CFB6CD.jpeg
 
Sep 17, 2017
5,971
11,307
Birmingham, UK
Funster No
50,575
MH
A-Class
Exp
2017
It's probably settings for the shunt rather than a wiring issue. First use it has to be fully charged so it knows 100% point before it'll start correctly counting the electrons out of the battery.
 
OP
OP
D
Apr 7, 2018
118
71
Funster No
53,229
So the wiring looks correct to you?
I did fully charge the batteries. I used the b2b to charge them fully (with the shunt wired in) and it was 100% from the get go.
 
Apr 14, 2022
292
530
Carvoeiro, Portugal
Funster No
88,080
MH
Bavaria T71LP
Exp
50 years of boating, just one on motorhomes.
I think the standard setting on the shunt is to always reset to 100% after a disconnect. This needs changing to remember the last setting. You then need to charge the battery to 100% and it should work from there. I got in a complete mess with mine before I worked that out

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Feb 27, 2011
15,042
79,356
UK
Funster No
15,452
MH
Self Build
Exp
Since 2005
That looks correct as far as it goes. But I suspect based on your description that you have left the outgoing from the battery connected.

By this I mean you have the B2B on the right side of the shunt so you can see incoming charge. But there will be a wire going from the battery to the fuse panel. If this is connected to the battery still then the shunt will not see any outgoing current and it will display 100% forever.

You need to have only 1 thing connected to the negative terminal of the battery and that is the shunt. everything else should be connected to the other side of the shunt to the battery or to the chassis.

Literally one connection on the negative terminal. anything more and you have a problem.
 
Last edited:
Aug 6, 2018
251
564
Dorset
Funster No
55,424
MH
GLOBECAR CAMPSCOUT
Exp
Since 2019
The supplier of my Victron b2b charger very kindly sent me the attached schematic showing how to fit it with my 2 batteries AND the Victron Shunt, which I already had.
It is now fitted. The b2b charger does seem to work fine, but as things stand the battery is ALWAYS shown as being at 100%, and probably other readings are therefore incorrect.
Can someone please have a look at the diagram and advise just where it has gone wrong?

View attachment 742159
We have the same set up and it's working fine. W have no solar involvement, but I don't think you've mentioned any either. I suspect it's your app settings as others have said
 
Feb 27, 2011
15,042
79,356
UK
Funster No
15,452
MH
Self Build
Exp
Since 2005
We have the same set up and it's working fine. W have no solar involvement, but I don't think you've mentioned any either. I suspect it's your app settings as others have said
Sorry, should have said B2B not solar. I just saw the Victron box and jumped to a conclusion without reading. I was mainly looking at the wiring. Same thing applies though.
 
OP
OP
D
Apr 7, 2018
118
71
Funster No
53,229
We have the same set up and it's working fine. W have no solar involvement, but I don't think you've mentioned any either. I suspect it's your app settings as others have said
Pulling my hair out with this. And I’m just about to add 4 x 100 solar. I’m absolutely useless with electrics, what settings should I have. A screen shot of yours would be most appreciated. Please don’t forward the too complicated youtube video!
 
Jan 22, 2017
523
2,040
Bristol
Funster No
47,006
MH
DAF LF Conversion
Exp
Since 2013
Could you please check what Gromett has said about the battery negative? The only connection on the battery should be a wire to the shunt, no other connections on either end of this wire, except the link to the other battery, which should also have no other connections.

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Feb 27, 2011
15,042
79,356
UK
Funster No
15,452
MH
Self Build
Exp
Since 2005
Pulling my hair out with this. And I’m just about to add 4 x 100 solar. I’m absolutely useless with electrics, what settings should I have. A screen shot of yours would be most appreciated. Please don’t forward the too complicated youtube video!
Please take a photo of the battery and what is connected to it. That will help a lot in assisting you.
 
Sep 29, 2007
833
1,289
Wantage, UK
Funster No
475
MH
C Class
Exp
Motorhoming since 2006, 30 years tent camping in Africa
You want nothing between the shunt and the battery. And the diagram shows this.
I’m trying to remember which side is which on the shunt.
Can you post a pic of the actual shunt. I’d like to make sure you have it connected the right way.
 
Last edited:
Apr 26, 2015
3,029
7,464
Ottershaw
Funster No
36,067
MH
Hymer S820
Exp
First motorhome May 2021
I’m trying to remember which side is which on the shunt
One side is marked battery minus and the other side is marked system minus, or load minus if it's old stock (it changed in 2020 I think). There should be nothing connected to the battery negative other then the battery minus on the shunt and nothing else connected to the battery minus on the shunt, every other negative cable including the chassis earth should be connected to system minus on the shunt either directly or via a bus bar.
 
Aug 6, 2018
251
564
Dorset
Funster No
55,424
MH
GLOBECAR CAMPSCOUT
Exp
Since 2019
Pulling my hair out with this. And I’m just about to add 4 x 100 solar. I’m absolutely useless with electrics, what settings should I have. A screen shot of yours would be most appreciated. Please don’t forward the too complicated youtube video!
I can take a screenshot a bit later on but the settings depend upon what battery type you have. We have 200Ah of lithium. Is this what you have? The full instructions for the shunt can be found on the Victron Website.
 
Sep 29, 2007
833
1,289
Wantage, UK
Funster No
475
MH
C Class
Exp
Motorhoming since 2006, 30 years tent camping in Africa
One side is marked battery minus and the other side is marked system minus, or load minus if it's old stock (it changed in 2020 I think). There should be nothing connected to the battery negative other then the battery minus on the shunt and nothing else connected to the battery minus on the shunt, every other negative cable including the chassis earth should be connected to system minus on the shunt either directly or via a bus bar.
I worded my question rather badly. I couldn’t remember offhand whether system was on the left facing the blue face or the other side. I guess I could have googled a standard pic, just that a pic of his setup might tell us if it’s wired the right way round. But you are correct.

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OP
OP
D
Apr 7, 2018
118
71
Funster No
53,229
I’m going to need yo go back to the motorhome today and I’ll take a photo, as requested, and post here.
 
OP
OP
D
Apr 7, 2018
118
71
Funster No
53,229
That looks correct as far as it goes. But I suspect based on your description that you have left the outgoing from the battery connected.

By this I mean you have the B2B on the right side of the shunt so you can see incoming charge. But there will be a wire going from the battery to the fuse panel. If this is connected to the battery still then the shunt will not see any outgoing current and it will display 100% forever.

You need to have only 1 thing connected to the negative terminal of the battery and that is the shunt. everything else should be connected to the other side of the shunt to the battery or to the chassis.

Literally one connection on the negative terminal. anything more and you have a problem.
But isn’t that how it is in the scematic?
 
Sep 13, 2022
1
0
Ireland
Funster No
91,303
MH
Weinsberg CaraBus
I have the Victron 12V non-isolated B2B and your wiring is similar to mine (mine is 1 battery and I use a bus bar though).

I do not know how you are doing your test to measure the drop in state of charge (SoC). Does the shunt indicate that there is a significant consumed Ah following the test?

State of charged is inferred from the measured voltage (and possibly the measured current to compensate for a voltage drop due to current draw). Could there be an issue with one of the batteries (e.g. model, design or fault)? Have you tried disconnecting one of the batteries, running your tests and then repeating for the other battery?

EDIT: I started reading the manual and the Victron shunt actually tries to track SoC using power in and power out calculations unlike the display that came with the van. Check the 100% charged voltage value as well per 7.2.2 in the manual: https://www.victronenergy.com/upload/documents/SmartShunt/9172-Manual_BMV_and_SmartShunt-pdf-en.pdf
 
Last edited:
Feb 27, 2011
15,042
79,356
UK
Funster No
15,452
MH
Self Build
Exp
Since 2005
But isn’t that how it is in the scematic?
The schematic does not cover all the wiring in your motorhome only the addition.

I will try and clarify for you.

There should be NOTHING attached to the negative terminal of the battery except for the shunt.

The side of the shunt connected to the battery should also have nothing else connected to it. There should be a single wire on that terminal of the shunt going to the batteries negative terminal.

ALL negative connections should go to the other side of the shunt opposite the side that is connected to the battery.

I hesitate to say this, but if this is not clear it is probably not a great idea for you to be DIY'ing electrics.
 
Apr 27, 2016
7,132
8,404
Manchester
Funster No
42,762
MH
A class Hymer
Exp
Since the 80s
There should be NOTHING attached to the negative terminal of the battery except for the shunt.
True, apart from one minor detail. If there's more than one battery, the link to the other batteries should be on the battery terminal side of the shunt, ie from the negative terminal on one battery to the negative terminal on the other battery. Apart from that, NOTHING else. Even the chassis connection should be moved to the load side of the shunt. And certainly the wire from the battery to the fuse panel should be moved.

The idea is that every last bit of current flow into and out of the battery is forced to pass through the shunt, so it can be measured and accounted for by the monitoring software.

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Last edited:
Feb 27, 2011
15,042
79,356
UK
Funster No
15,452
MH
Self Build
Exp
Since 2005
True, apart from one minor detail. If there's more than one battery, the link to the other batteries should be on the battery terminal side of the shunt. Apart from that, NOTHING else. Even the chassis connection should be moved to the load side of the shunt. And certainly the wire from the battery to the fuse panel should be moved.
Agreed important caveat.
 
OP
OP
D
Apr 7, 2018
118
71
Funster No
53,229
I can take a screenshot a bit later on but the settings depend upon what battery type you have. We have 200Ah of lithium. Is this what you have? The full instructions for the shunt can be found on the Victron Website.
I have 2 x70ah “wet” batteries
 

PeterCarole29

LIFE MEMBER
Jul 23, 2013
1,314
1,410
Colchester
Funster No
27,084
MH
Renault Master Fleetwood
Exp
20 years
Pulling my hair out with this. And I’m just about to add 4 x 100 solar. I’m absolutely useless with electrics, what settings should I have. A screen shot of yours would be most appreciated. Please don’t forward the too complicated youtube video!
Just an observation as you said you are hopeless with electrics.
Having a B2B is great and the 4 x 100 solar. I see you said only 2 x 70amp hr batteries thats a tiny amount of useable i.e 50% .
Someone more technical could advise but they will be bubbling away mind you it depends on your draw.
 
Apr 26, 2015
3,029
7,464
Ottershaw
Funster No
36,067
MH
Hymer S820
Exp
First motorhome May 2021
Just an observation as you said you are hopeless with electrics.
Having a B2B is great and the 4 x 100 solar. I see you said only 2 x 70amp hr batteries thats a tiny amount of useable i.e 50% .
Someone more technical could advise but they will be bubbling away mind you it depends on your draw.
They shouldn't be bubbling if the batteries are sound because both the b2b and the solar controller will only supply the amount of current the batteries can cope with, I believe they work this out on the batteries internal resistance, as the batteries charge the internal resistance increases, old fashioned non smart mains chargers on the other hand might over charge them.

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OP
OP
D
Apr 7, 2018
118
71
Funster No
53,229
Just an observation as you said you are hopeless with electrics.
Having a B2B is great and the 4 x 100 solar. I see you said only 2 x 70amp hr batteries thats a tiny amount of useable i.e 50% .
Someone more technical could advise but they will be bubbling away mind you it depends on your draw.
I have got another 2. But that would mean “new electric layout”. Any ideas how I’d link up four?
 
OP
OP
D
Apr 7, 2018
118
71
Funster No
53,229
True, apart from one minor detail. If there's more than one battery, the link to the other batteries should be on the battery terminal side of the shunt, ie from the negative terminal on one battery to the negative terminal on the other battery. Apart from that, NOTHING else. Even the chassis connection should be moved to the load side of the shunt. And certainly the wire from the battery to the fuse panel should be moved.

The idea is that every last bit of current flow into and out of the battery is forced to pass through the shunt, so it can be measured and accounted for by the monitoring software.
So my wiring is wrong as it stands? If so, please show me how to correct it
 
OP
OP
D
Apr 7, 2018
118
71
Funster No
53,229
The schematic does not cover all the wiring in your motorhome only the addition.

I will try and clarify for you.

There should be NOTHING attached to the negative terminal of the battery except for the shunt.

The side of the shunt connected to the battery should also have nothing else connected to it. There should be a single wire on that terminal of the shunt going to the batteries negative terminal.

ALL negative connections should go to the other side of the shunt opposite the side that is connected to the battery.

I hesitate to say this, but if this is not clear it is probably not a great idea for you to be DIY'ing electrics.
But to me it looks like that is how i’ve done it. Where the bloody hell has it gone wrong?
 
Apr 26, 2015
3,029
7,464
Ottershaw
Funster No
36,067
MH
Hymer S820
Exp
First motorhome May 2021
What I would do is put the van on hook up for a day to make sure the batteries are fully charged and then go into the app tap settings then battery then tap synchronise this should tell the app your batteries are full and then you can check if your actually using power from the batteries or if the solar panels are covering the current being drawn by the van. Bare in mind that if you are not using much electricity the batteries may become fully charged again by late morning.

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