question

chadwick-torp avatar image

BMV-712 resets to 100%

I have a Bmv-712 batter monitor that is resetting to 100% when the battery is not fully charged. Looked at the level around 8am and it was at 89% checked it 15 minutes later and it was at 100%. Nothing else was plugged up and I was checking to see what my solar panels were charging to determine if they needed clean. Now I am not sure what my battery is at to reset. Is it possible the BMV would reset itself?

BMV Battery Monitor
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2 Answers
sportswagoneer avatar image
sportswagoneer answered ·

(Response to Victron comment:)
Have seen similar responses elsewhere on the forum.

It appears to me that:

1. For most users, monitoring the SOC is the primary utility of having the BMV.

2. The combination of large Lithium banks and modest solar (like a LOT of RVs and boats are getting) will reset prematurely “every morning” with default settings. As the sun rises, a little current nowhere near 4% of the large bank will start dripping in - and 13.2V is not very high when charging even a little.
(Mine have jumped from around 70% to 100% within one VRM logging point several mornings now.)

If this this understanding is correct, I suggest you publish an amended default recommendation for LiFePo banks with solar as this combination must be becoming vastly more popular now. If I have misunderstood I‘m happy to be corrected!

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Thank you! This perfectly explains why my Victron 700 was resetting to 100% every morning and then showing 100% all day as it continues to charge.

Happens whenever the (lithium) batteries get fully charged (or close) one day, then they are still over 13.2 the next morning as the sun rises. Changed the charged voltage to 13.4 and the tail current to 1%.

Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @Chadwick Torp,

This is normal, and intended.

It is covered under the "Synchronisation" section of the manual for the BMV.

"For a reliable readout, the state of charge as displayed by the battery monitor has to be synchronized regularly with the true state of charge of the battery. This is accomplished by fully charging the battery. In case of a 12V battery, the BMV resets to ‘fully charged’ when the following ‘charged parameters’ are met: the voltage exceeds 13.2V and simultaneously the (tail-) charge current is less than 4.0% of the total battery capacity (e.g. 8A for a 200Ah battery) during 3 minutes."

If you do not believe that your battery is actually fully charged, and the BMV is synchronising prematurely (or too late/not at all), you can adjust those settings, voltage and tail current, to be more accurate to your specific installation, battery type, and usage profile.

Try first to reduce the tail current value. Though the default settings are usually quite good enough for most installations.

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