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francoisbrink asked

BMV 712 SOC % wrong

Good morning. I have a BMV 712 series. Trailer with 2x 105Ah Deep Cycle batteries. It is a new trailer and new equipment. The SOC% seems to be wrong. From Float (100% charge) when put to use the % goes down. The % goes to aroun 65% and then the batteries is 'flat' as the voltage has dropped too far. How do I ensure the SOC and state of charge is more true. I have already syncronized the SOC when in float. My current Setting

Battery Capacity - 210aH

Charged Voltage 13.2V

Dicahrge Floor 50%

Tail Current 4%

Charged Detection Time 3m

Peukert 1.25

Charged Efficiency Factor 95%

Currenth Threshold 0.10A

Time To go Averaging 3m

BMV Battery MonitorSOCvoltage
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seb71 avatar image seb71 commented ·
What is the usual discharge current?

Higher current means larger battery voltage drop.

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francoisbrink avatar image francoisbrink seb71 commented ·
Where do I see this
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seb71 avatar image seb71 francoisbrink commented ·

The current/power shown in your screeenshot are typical?

Or do you also have some big loads?

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francoisbrink avatar image francoisbrink seb71 commented ·
At that time I did have a big load as I was trying to see if SOC will go low...
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3 Answers
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francoisbrink answered ·

screenshot-20230624-222844-comvictronenergyvictron.jpg

This was 1hr before the batteries was 'flat' at 65% SOC


screenshot-20230624-222844-comvictronenergyvictron.jpg (334.3 KiB)
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francoisbrink avatar image
francoisbrink answered ·

Graph of SOC vs Voltagescreenshot-20230625-063622-comvictronenergyvictron.jpg


screenshot-20230625-063622-comvictronenergyvictron.jpg (263.1 KiB)
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pwfarnell answered ·

You may not actually be fully charging your ba as the the BMV may synchronise to 100% before the batteries are full. The charged voltage is too low at 13.2V, it should be set about 0.1 to 0.2V below your charging voltage, which is typically 14.4V or thereabouts. If you do charge at 14.4V then set the charged voltage to 14.2V. The tail current could also be set lower, perhaps 2% or even lower, mine is at 0.8% with AGM batteries.

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