Victron Smart Shunt and 3 BMS amperage consumption reading discrepancy

Q&A and troubleshooting
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1

Hi,

I noticed an amperage discrepancy reading between my

  • Victron Smart Shunt IP65 500A/50mv (Software version V4.19)
    and
  • 3 x Daly BMS Smart BMS Lifepo4 4S 12V Li-ion. (Software version 32_231109_001T, hardware version BMS-GD230-303E). Each BMS manages a pack of 4 310Ah prismatic cells.

Every couple of week I have to lower the Smart Shunt State Of Charge by 10%.

smart_shunt_configuration
smart_shunt_configuration1125Ă—2436 234 KB

Is there a setting I can tweak on the Smart Shunt to have the same amperage reading?

Thanks
Simon

2

Why do you think the SmartShunt is incorrect? Most people find it to be the only SoC truth in a system.

In my experience, BMSes are terrible at counting coulombs properly.
They are made to be inexpensive, not accurate.
And their main function is to protect the batteries, not give an accurate SoC measurement.
See if you can look at the actual cell voltages (preferably at rest) to determine why the SoC is dropping 10% per week.

Also, the smarthsunt must see all of the current coming into and leaving the batteries.
If you are powering anything off to the side the shunt will not be accurate.

3

I do not think the Smart Shunt is incorrect, I just want it to show, over time, the same State Of Charge (SOC) as the BMSs. The 100% full charge seems to be the only way to keep the SOC in sync.

The wiring makes the Smart Shunt the electron gate keeper but I will double check.

Thanks

4

ok, I also recommend you read this post on diysolarforum about the Victron shunt settings for LiFePO4 batteries.

5

Thanks for the reference!

The “Tail Current” settings seems to be difficult to set. I found these recommendations :

  1. General Range: 2% to 4% of your battery’s Ah capacity (e.g., 2-4 amps for a 100Ah battery).
  2. Starting Point: A default of 4% is often fine, especially with solar, as current naturally drops.
  3. Lower Setting: Try 2% or 3% if your system charges well, but be aware of false triggers.
  4. Disable/Use Fixed Time: Some suggest using a fixed absorption time (e.g., 30 mins) or relying on voltage for LiFePO4, as tail current can be tricky with varying solar.

Having solar, I will keep the 4% setting.

Cheers

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