BMV-712 incorrectly shows 100%; what do I do???

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Brian Knapp asked Feb 14, '21

BMV-712 incorrectly shows 100%; what do I do???

I updated the firmware whole the batteries were arou d 16-20% charged. It then read 100% after it updated.

I have two 200AH Lithium Ion batteries connected.

I am afraid of overcharging the batteries by manually choosing an estimated SOC, but I'm also afraid of over-discharging by NOT manually changing the SOC and them not charging above their current SOC because the system thinks they are at 100.

I guessed the SOC had charged to around 30%, so I manually changed it to that. Will a wrong guess damage my batteries as the system charges and then discharges???

What should I do???

BMV Battery Monitor Lithium Battery

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Answer 1 · 2021-02-14T07:40:20Z

klim8skeptic answered · Feb 14, 2021 at 07:40 AM

You should fully charge your batteries, with a quality charger that has been programmed with your lithium batteries' voltages.

Once your batteries are full, your BMV will synchronize back to 100%.

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Brian Knapp commented · Feb 14, 2021 at 03:50 PM

Can I leave the charger manually set to 30% (my best guess about its SOC) before I charge to 100%? Or should I manually click the "Synchronize SOC TO 100%" button in the app before I try to charge to 100%?

I am very concerned about overcharging or over-discharging the batteries. If the SOC is set to 100%, but the batteries are really at 30%, will they continut to charge all the way up to 100%?

My BMV-712 and LiFPO4 batteries were set up by a company, so I assume they are calibrated correctly.

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Brian Knapp commented · Feb 14, 2021 at 03:53 PM

OP here. For context, this is how the batteries are set up in the Victron App under the BMV-712:

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81b358f1-57cf-4a1e-b12f-e82593f4ba1c.png (182.8 KiB)

Answer 2 · 2021-02-14T16:16:04Z

Matthias Lange - DE answered · Feb 14, 2021 at 04:16 PM

The BMV is just a monitor it doesn't "tell" the charger to stop because it thinks the battery is full.

The battery charger is working with a voltage based charging algorithm and doesn't care about the SOC measured by the BMV.

And as long as you don't have some cheap no-name china batteries they should have some kind of BMS that is stopping the charging if there is a problem.

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