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tareq avatar image
tareq asked

BMV-712, Inaccurate SOC

Hello Everyone,


I have a question about the BMV 712, Why is the battery monitor giving 100% SOC while the voltage is low (49 - 50 V)?


I have 15 batteries (Lifepo4) connected to the BMV (1500 Ah) 100Ah/ each, and the electrical connection is correct. However, I feel the BMV is not giving the accurate SOC, so could you please advise how it can be as precise as possible?

Here are the current parameters set to the BMV:

1717151208942.png Note: the tail current was 4%, but I decreased it recently to 3%.


The loads are DC and they are being fed by Solar PV and a 5 kW Wind Turbine, and the float voltage of the solar and turbine chargers are (54.5 ~ 55V).


Kindly advise if there is anything that needs to be updated.

BMV Battery Monitor
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1 Answer
pwfarnell avatar image
pwfarnell answered ·

The SOC is synchronising to 100% before the battery is full. Increase the charged voltage to about 0.5V below your absorption voltage on the charger. If you use 57.6V then set to 57.0 or 57.1V. This means that it will not sync to 100% until you get to a nearly full voltage.

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kevgermany avatar image kevgermany ♦♦ commented ·
@tareq

Also look at charge detection time. With charge sources that are variable, like solar and wind, the drop off in charge current can trigger a false synch. Try increasing this. From memory I had to go to 15 minutes on solar.

You may need to drop the tail current further.

How balanced are the batteries? The BMS may be trying to balance things by reducing or cutting the charge current. Excessive voltage settings on the chargers will also cause this.

Beware of increasing charged voltage. On a 15S system, your existing charged voltage is already sufficient/high.

Adjust one parameter at a time and observe.



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