V3.80 VE-Bus NG BMS Battery Monitor Issues

Been running v3.80 on my Cerbo GX for about a week now aboard the narrowboat and I'm seeing something similar with the VE-Bus NG BMS integration.

The direct BMS reading in the GX is genuinely useful — finally being able to see cell-level data without jumping into separate apps is a proper quality-of-life improvement. But something's clearly not right with how the power figures are being handled.

For me it's the watts display flickering between a real value and what looks like a null/zero state every few seconds. It's particularly noticeable when I'm charging via the shore power hookup at the marina. The SOC seems stable enough, but the instantaneous power reading is all over the place — makes it hard to trust what you're actually looking at.

Also noticed the battery monitor seems to lose its "preferred" status occasionally and the system falls back to reading from the MultiPlus rather than the BMS directly. Defeats the whole point of the update really.

Running a Victron Multiplus-II with a DIY LiFePO4 pack using a VE-Bus BMS NG. Fogstar cells if that's relevant to anyone debugging this.

Has anyone found a workaround, or is this a case of waiting for Victron to push a patch?

Would be interested to know if this is specific to certain hardware combos or if it's widespread. Also curious whether those on Ekrano GX units are seeing the same behaviour or if it's Cerbo-specific.

@BoatPete interesting one — I had similar weirdness after updating my Cerbo on the cabin setup. The BMS readings looked fine direct but the battery monitor in VRM was showing drift after a day or so.

Worth checking whether you've got "Battery Monitor" set correctly under System Setup — mine had defaulted back to the Multiplus rather than the BMS after the update. Easy thing to miss.

Also, are you on a narrowboat so potentially seeing temp swings overnight? That can complicate SOC accuracy independently of the firmware issue.

Raised a ticket with Victron support — they acknowledged something's a bit off in 3.80 with VE-Bus NG integration specifically. Apparently a point release is coming. Might be worth holding off on any major config changes until then.

@BoatPete had exactly this after updating the Cerbo on my shepherd's hut setup. Took me ages to figure out but the issue was the VE-Bus system source priority in the DVCC settings — worth checking if "BMS controls charge voltage" is actually enabled after the update. Mine had quietly reverted to defaults.

Also noticed the battery monitor was flip-flopping between the BMS figure and the Cerbo's own calculation. Fixed it by going into System Setup > Battery Monitor and explicitly selecting the BMS rather than leaving it on "automatic."

Might not be the same root cause but worth ruling out before diving deeper.

Sounds like v3.80 is the gift that keeps on giving 🎁

Had a similar head-scratcher on my static caravan setup last year — spent a whole afternoon convinced my Fogstar cells were dying, turned out the Cerbo was just having a moment.

Worth checking if your SoC reading is drifting after a full charge

Been running v3.80 on both my garden office and boat setups so seen this first hand.

Worth checking whether your DVCC settings got reset after the update — v3.80 seems to occasionally stomp on those during the flash process. If DVCC is misconfigured the Cerbo can end up fighting the VE-Bus BMS for control of the charge parameters, which throws the monitor readings out completely.

Specific things to verify:

• SVS (Shared Voltage Sense) is enabled
• SCS (Shared Current Sense) matches your expected source
• BMS control is set to the correct device in the DVCC menu

Also worth a look in the VRM portal — if the readings were clean pre-update you'll see exactly where it went sideways in the historical data.

@RetiredElectrician nailed it really — firmware updates on live boats are always a gamble 😅