Anyone else found their Victron BMV-712 reading completely differently after a firmware update?

Updated mine to the latest firmware last night (v4.12) and now the state of charge is all over the place. Before the update it was rock solid — sitting at 100% after a full charge, dropping predictably as I used the system. Now it's bouncing between 87% and 94% just sitting idle overnight with nothing drawing from the 200Ah lithium bank.

Tried re-syncing it manually this morning by fully charging to absorption then float, waited for the relay to trigger, but it still doesn't seem to want to settle. Tail current is set to 4% which has always worked fine for me. Wondering if the peukert exponent or charged voltage threshold got reset during the update — wouldn't be the first time a firmware flash has wiped custom settings.

Has anyone else hit this on a recent update, or am I just having a bad time of it? Happy to share my full settings if it helps narrow it down.

@Spider6 had exactly this after updating mine a few months back. Turned out the update had reset my battery capacity and Peukert exponent settings back to defaults — worth double-checking those first before assuming the firmware's broken.

Go into Battery Settings and verify:

• Battery capacity (Ah)
• Charged voltage threshold
• Tail current %
• Peukert exponent

Mine was reading my Fogstar 200Ah LiFePO4 as if it was a small AGM. Once I dialled everything back in it was solid again.

Also worth doing a full sync — discharge to around 20%, then charge to 100% and let it hit the tail current properly so it resets the 100% reference point.

Had this exact same issue after a firmware update a while back. Worth checking your Peukert exponent and charge efficiency factor in the settings too — the update reset mine to defaults which knocked the SOC readings right out. The Peukert exponent particularly can throw things wildly if it's set wrong for your battery type. AGM, lithium and lead acid all need different values. Also, once you've corrected all your settings, you'll need to do a full synchronisation cycle — fully charge the bank until the absorb stage completes properly, and the BMV should resync to 100% and start tracking accurately again from there. Give it a few full cycles before worrying too much. @ExChippie30 is probably on the right track with the capacity reset being the culprit though.

@Spider6 one thing neither @ExChippie30 nor @ShaunWebb have mentioned yet — check your charged voltage and tail current thresholds in the BMV settings. After my v4.11 update on the van build, the charged voltage had dropped to a default 13.2V, which meant the BMV was declaring "full" far too early and never properly synchronising. With LiFePO4 (I'm running Fogstar Drift 100Ah cells) you want that set to around 14.2V with a tail current of roughly 4% battery capacity.

Do this via VictronConnect rather than the physical buttons — far easier to verify every parameter methodically. Go through Settings > Battery line by line and compare against your pre-update screenshot if you took one.

Also worth doing a manual synchronisation to 100% once everything's corrected, otherwise the SOC figure will remain skewed regardless.

@Lefty28 makes a great point about those thresholds — they're easy to overlook. One more thing worth checking that nobody's mentioned yet: after a firmware update the BMV sometimes needs a full synchronisation cycle before the SOC settles down properly. Basically run your bank right down to a decent depth of discharge, then do a proper full charge and let it hit that tail current threshold @Lefty28 mentioned. The unit should then sync itself back to 100% and start tracking accurately again from a known baseline. I had something similar on mine after messing about with settings and it took a couple of cycles before it started behaving itself. Give it two or three charge/discharge cycles before assuming something's genuinely wrong. Patience is the boring answer but it does often sort itself out once the BMV has re-established its reference point. 🤞