I have installed two shunts on two separate batteries on my boat (Interstate 24M-AGM-A). The shunts work, however the battery State of Charge is inaccurate. It always shows 100% regardless of the actual state of charge. I cannot fix this. The SoC settings are confusing and manual is little help. I have charged them to 100% and pressed the Synchronize button to no avail. Screenshots of my installation are attached. Help, please. [IMG_9077] [IMG_9080] [IMG_9079] [IMG_9078] Without an accurate state of charge reading, these shunts are next to useless to me.

Take a look at this: [image] Battery monitor jumping to 100% or reporting a high SOC with low Volts / the BMS shuts down DIY This topic covers the reported SOC being out of sync with the actual battery voltage or state. It covers 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 and is often linked to mobile applications with small solar systems. The SOC jum… [image] Shunt / battery monitor not reading the correct SOC/ Amps, missing solar, decreasing daily or other misreading problems DIY 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…

I am reviewing these, thanks. Followup: The battery specs for my Interstate 24M-AGM-A battery lists its capacity as “N/A”. However, on the side of the battery is printed “70AH/140 RC”. So what do I set for Battery settings > Battery capacity? 70?

Please note that the setting “Battery starts synchronized” referred to in these FAQs is not present in the latest edition of the control software on my phone. That setting has been replaced by “Battery SoC on reset”. It is this setting for which I need a better explanation and a recommendation.

The displayed voltage is 14.56v this is way above the Charged Voltage so if Tail Current and Detection Time are also met then the shunt will think the battery are at 100%. With a current of 0.22A and the voltage being 14.56V if it’s been running for more than 3mins it will register 100% Try 14.4v as the charged voltage, 2% as the tail current and see how you get on. It’s a delicate balancing game to get these 3 values right.

If the battery says 70Ah you should enter that. The name of that setting might be different but it still does the same. If the shunt gets disconnected from power it will set the SOC to 100%, to unknown (recommended) or saves the SOC.

I tried applying your advice: I set the Charged Voltage to 14.4, set the Tail Current to 2%, then charged the batteries up to 100%. Unfortunately this did not make a difference. This is what I see now on the battery (I have two identical batteries, each with its own shunt). One battery shows “99.8 %” , the other “100%”. [IMG_9083]

What are you seeing after a period of discharge Do they stay at 100% ? Or drop as you would expect. Also how do you know they are charged to 100%? If it’s using a charger that is going into float there is no guarantee that it is 100% especially if using adaptive charging.

Peukert exponent for AGM is typically 1.12-1.15. This is only a minor accuracy setting so should not affect synchronisation to 100%.

Thank you. Based on your articles and responses, I am going to try the following settings: Set Tail Current to 2.5% Set Battery SoC to Keep SOC Set Peukert to 1.12 Set Charged Detection Time to 5 minutes As for Charged Voltage, 14.4 did not work. I am not sure what value to try next.

Regarding your questions: I have cheap bluetooth monitor connected to each battery. These have been accurate since I installed them. The Victron shunts are intended to replace these monitors. After a period of discharge, these monitors indicate a drop in SoC from fully charged. Typically up to 20% (one of the reasons I have installed the shunts Is to find current leaks.) My charger is a Pro Mariner ProNauticP. I believe it was working properly before I installed the shunts. But I see your point regarding the possibility of it generating a less-than-full charge. I will look at its settings again.

New shunt installation: State of Charge does not work

Q&A and troubleshooting

M_Lange (Matthias Lange - DE) 2 October 2025 03:50 2

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New shunt installation: State of Charge does not work

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