Noob! Smart Shunt Set up on Sailboat - Incorrect SOC Showing

[brooksiej24 (JB)]

Hello All,

I am new to this and have my Victron Smart shunt hooked up to my system and I can see all the flow out of the bank but when I am charging or running the engine with alternator, it shows that the battery Voltage is at a voltage charge but I do not see positive into the bank. This is throwing off my SOC as for a weekend trip I need to see what is in and out etc. Before a trip gets going, I will plug in to shore power and charge batteries while also running the fridge to chill it down and the shunt thinks I am just burning amp hours on a 30A charge controller. Fridge draws about 6.5a

My set up is this:

Starter Batter - Lead Acid 800CCA in Position 1 on the switch
2 Lead Acid House batteries wired in parallel for 200 AH (100AH Usable)

I have the Shunt placed and the panel wires to left side of shunt and then the battery terminal on the shunt is located on the starter (which may be an issue).

My system has 2 bus bars located in the boat and flows through the ground to the engine.

Any ideas? Thank you all for any assistance for me.

[pwfarnell]

There is a FAQ in the DIY section that covers this which a bit of searching would have found. The manual also covers it. Simply, you have not wired it up correctly.

Shunt / battery monitor not reading the correct SOC/ Amps, missing solar, decreasing daily or other misreading problems

This topic covers the SOC / Amps reported by BMV battery monitors, SmartShunts, Lynx BMSs and Lynx Shunts and will just be called shunt below. It is also assumed that the shunt is monitoring the domestic / house / cabin battery bank and not engine start / bow thruster / winch / caravan mover battery banks. The problems may be one or more of the following The SOC decreases daily despite the solar charger or other charger(s) working. The SOC increasing when discharging and falling when charging…

[brooksiej24 (JB)]

Thanks for the intel. I am also trying to figure out the wiring on this older boat and gathering all the wires and tracing them to know where they come to.

I noticed on the post you sent the diagram makes sense however I have 2 house batteries in parallel to increase ah and then there is a negative cable that goes over to starter negative then back to a bus bar which complete the circuit to the ground.

I plan to move the cable to house negative to shunt but I still think something is off.

Thanks again for insight.

[pwfarnell]

Answered in the shunt wiring thread. The simple rule is the only thing you can connect to the battery side of the shunt are the house battery negatives and the only thing connected to the house battery negatives is the shunt. Everything else goes to the load side of the shunt.

[brooksiej24 (JB)]

Ok thanks. I did not realize I could put multiple cables on to the shunt so I am drawing up a diagram I think to help me make this change.

Appreciate you helping this rookie here!

[brooksiej24 (JB)]

Also what is throwing me off is the multiple bus bars that are all seem to be tied together and grounded on engine block.

So when you say load side that is everything off the panel correct? And the battery side is where I connect to battery minus on the shunt?

[pwfarnell]

@brooksiej24

So when you say load side that is everything off the panel correct? And the battery side is where I connect to battery minus on the shunt?

The above is correct, load side includes loads, chargers and grounding cables.

[brooksiej24 (JB)]

Ok, thank you. I am trying to follow the loop though on how the circuit completes itself back to the bus bar which goes to main ground on engine. Am I overthinking or missing something on how it connects to the main ground line?