question

mark-moussa avatar image
mark-moussa asked

SoC Graph and charge cycles on BMV 702

Hi,

I am using BMV 702 to monitor a battery bank (48V - 1200Ah).

The device is really great. I need to undertsand the read-outs more

1- Usually every day, while charging, the SoC graph goes up suddenly from some 92-93% to 100% .On one day, I even observed that sudden rise from 76% to 100% (photo attached). What could be the reason?

2- How are the charge cycles counted on BMV ? As far as I know, the cycle is counted a full charge followed by one discharge (not necessarily a full discharge). Even though our application is an off-grid system where this charge-discharge cycle happens every day, the charge cycles value is only "12" after one month or more from the start of the BMV monitoring. Kindly advise

BMV Battery Monitor
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charge-cycles.jpg (26.5 KiB)
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1 Answer
JohnC avatar image
JohnC answered ·

Hi Mark.

It's likely that 'sudden rise' in SOC is the BMV syncing. It needs to do that sometimes to correct accumulated drift. You can set it to do that at whatever stage you want. Related to a few things, but perhaps your 'Tail' current is set a little too high, so it's happening prematurely.

From memory, I think a charge cycle is counted when cycled between 65% and 90%. One of those things that may/may-not have meaning to you. For many, no. Perhaps the Ah cumulative or average would get more attention from serious peeps.

The manual may look formidable, but likely the only way to bring your 'understanding' up to full speed.

https://www.victronenergy.com/upload/documents/Manual-BMV-700-700H-702-712-EN-NL-FR-DE-ES-SE-PT-IT.pdf

We're all guilty of 'not reading the manual'. Dodge this one at your peril.. :)


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mark-moussa avatar image mark-moussa commented ·

Thank you John for your time.

- I set The tail current setting at the default 4% with 3 minutes charged detection time and charged voltage of 54.9 V (set 0.3V below the absorption voltage 55.2) - as recommended by Victron for solar applications. Can this cause error in readings on the long run or the automatic syncs compensate for it ?

- If charged cycles are counted in the range 65%-90% , I think that would make sense now. however, I guess it does not match the real cycles that batteries experience.

Thanks

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