Victron smartshunt query

[Figaro]

I've changed my gel batteries to a Fogstar lithium recently.
All seems good except the smartshunt is showing the cab battery at 1.4v
It was a little low not having been used recently but not that low.
I put it on charge directly on the terminals and the v still shows 1.4v
Any suggestions ? The manual doesn't seem to offer much help
TIA

 

[MichaelT]

Have you got a common negative?

 

[Figaro]

Have you got a common negative?

Where from, yes I'd say so.
Shunt has - to leisure battery one side, and - to system on the other.
Cab battery - chassis of course

 

[Raul]

Can you describe how is the cab battery negative is connected to the shunt?

 

[Figaro]

Can you describe how is the cab battery negative connected to the shunt?

The shunt is on the lithium leisure battery negative so it's not directly connected to the cab negative although it also has a non isolated Victron B2B so I guess they are connected to the chassis

It previously showed the cab battery voltage accurately so I don't know what has changed
I've updated settings in the B2B, shunt and solar controller (Votronic 250 duo) to allow for the lithium change but can't see why thay would change anything to do with the cab battery

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[autorouter]

The shunt is on the lithium leisure battery negative so it's not directly connected to the cab negative although it also has a non isolated Victron B2B so I guess they are connected to the chassis

There should be a chassis connection to the shunt, which goes to the load side of the shunt, not the battery side. It's a common mistake to connect the chassis connection to the battery side of the shunt, or to the battery negative terminal.

 

[Figaro]

Thanks, it's not connected on the wrong side of the shunt, the battery side goes to the leisure battery negative and the load side goes to the load negative.
So if I read this correctly, I need another negative connection on the load side of the shunt going to the chassis ?
Do I need to actually run a cable direct to the cab battery negative / find another suitable earth / chassis connection or can I use the negative terminal on the B2B ?

autorouter

 

[Raul]

From load side to the chassis is all you need, at the moment the starter has no reference and reading a generic voltage.

 

[autorouter]

Originally, before the shunt was fitted, there should have been a connection from the leisure battery negative to the chassis. When the shunt was fitted, the chassis connection should have been moved so that it connects the load side of the shunt to the chassis. There should be no direct connection from the battery side of the shunt to the chassis. This is to ensure that the only path into and out of the battery near the negative terminal is through the shunt. The shunt can't account for all the amps going into and out of the battery if there is a path that bypasses the shunt.

There shouldn't be any need to run any new cables anywhere. You might need to crimp a new eyelet onto the chassis wire that was on the battery terminal, so that it fits onto the shunt.

 

[Googlebot]

On my shunt the fuse on the live between shunt and starter batter was playing up. I ended up replacing the holder and it’s been fine since.

Had the same, ridiculously low voltages I knew to be incorrect.

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[Figaro]

On my shunt the fuse on the live between shunt and starter batter was playing up. I ended up replacing the holder and it’s been fine since.

Had the same, ridiculously low voltages I knew to be incorrect.

I've been thinking about it overnight and I had to undo that inline fuse and I wondered if that might be the problem, I'll have a look today and also autoroute suggestions
Thanks guys

 

[Raul]

If that fuse is a 100mA, change it to 1A, Victron upgraded the fuse a while back and shunt comes with 1A if its been upgraded. If not just put an 1A in, and clean the terminals.

 

[Figaro]

The fault was indeed the inline fuse.
I'll upgrade it as suggested
Thanks Raul