I have had a Victron BMV 712 monitoring a Victron Lithium Smart battery. This has been working fine for about 6 years. Recently the SOC only gets as high as 95% when the battery is full, (14.2V all MPPT’s in float, little or no current going into the battery). No settings have changed on the BMV. It’s not causing any issues but why does it now only get to 95%?
Loss of capacity possibly. They do degrade.
Or a cell imbalance.
Do you have another charge source?
Definitely no cell imbalance. Will charge with a Multiplus but will be some months before I next see a shore power supply.
And it hasn’t done this before when you have been away from shore power for extended times?
Maybe a firmware update changed something? Or did you add or remove a smart network?
No hasn’t done this before normally it will creep up to to either 99 or 100% by the end of the afternoon. It’s quite feasible that a firmware upgrade could have affected it.
What do you charge to in absorption on the mppt? Does the mppt reach that voltage?
The Victron Lithium Smart battery reports as “balanced” via Victron Connect in the last 30 days?
Drop the “Charged Voltage” to 14.1v in the BMV.
Absorption voltage on the MPPT is set to 14.2v, this is the preset Victron profile for their batteries.
Will try this but doesn’t really explain why it happens now but didn’t happen before.
The charged voltage should be set 0.1 to 0.2V below absorption voltage to give a bit of margin for the BMV to auto synchronise to 100% when the batteries are full. The tail current is also a bit low, 4% I believe is better for lithium. The BMV should be set to auto synchronise to 100% just as the batteries are nearly full to remove any small discrepancies or cumulative errors in the Ah counting. With your current BMV settings they were probably right on the cusp of perfect accuracy and your synchronisation settings (charged voltage and tail current) were too restrictive, so the battery did not synchronise but counted up to 100%. As the battery aged the charge efficiency may be slightly lower now so it does not reach 100% and the effect is cumulative. You could reduce charge efficiency to say 98% and monitor.
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Good advice. Thank you.