Cerbo GX intermittent VRM data sync issue with off-grid solar setup

Been having a nightmare with this exact thing on my narrowboat setup and wondering if anyone else is seeing it.

Running a Cerbo GX alongside a pair of Victron SmartSolar MPPTs and a MultiPlus-II 24/3000. Most of the time VRM is brilliant — proper peace of mind when I'm away from the boat. But every few days the data just... stops. The dashboard shows the last known state and then nothing for hours, sometimes longer.

A few things I've ruled out already:

• It's not a SIM signal issue (I'm on a 4G dongle and the signal strength looks fine)
• The Cerbo itself is still running — I can access it locally via the GX Touch
• Rebooting the Cerbo seems to kick it back into life, but that's not really a fix is it

What's puzzling me is that it seems worse overnight when solar input drops right down and the system is running primarily off the battery bank. Makes me wonder if it's somehow linked to low-voltage conditions, though I'm not dipping below 24.5V or anything alarming.

Has anyone had issues with VRM sync dropping on firmware versions past 3.10? I updated a few weeks back and think that's roughly when it started, but I can't be certain.

Also — is there a recommended logging interval that's less likely to cause sync issues? Currently set to 60 seconds which feels like it should be fine.

Would love to know if this is a known gremlin or if I should be raising it with Victron directly. Any Cerbo veterans in here got any pointers? 🛥️

Hey @CopperRoamer, classic narrowboat headache this one! A few things worth checking that often get overlooked:

First, have a look at your VRM Portal ID under the Remote Console — occasionally after a firmware update the device can lose its heartbeat interval setting. Try setting it manually to 60 seconds rather than leaving it on auto.

Also worth checking whether you're on WiFi or the built-in GSM — narrowboats obviously move around, and if the Cerbo is bouncing between mobile cells it can cause those sync gaps you're seeing in VRM.

Finally, make sure your two MPPTs are both properly networked via VE.Direct or VE.Can rather than just Bluetooth — Bluetooth devices can sometimes confuse the data logging.

What firmware version are you running on the Cerbo? That'll help narrow it down considerably.

@CopperRoamer – worth adding to what @QuietSparky mentioned: have you checked your VE.Direct cable connections at both ends? On a narrowboat the constant vibration and movement can work these loose over time, and a slightly dodgy connection will cause exactly the kind of intermittent dropout you're describing rather than a clean failure.

Also, what firmware version is your Cerbo running? There were some known VRM sync issues in earlier builds that Victron patched. You can check and update directly through the Remote Console. I'd make sure you're on the latest stable release before diving too deep into troubleshooting elsewhere.

Finally, is your boat connected to a marina WiFi when syncing, or relying on a mobile data dongle? Signal dropouts on a moving vessel can mimic what looks like a Cerbo fault.

Something that bit me badly last winter in the van — check your Cerbo GX firmware version first before chasing cables and connections.

Mine was dropping VRM sync intermittently for weeks. Turned out the unit was sat on an older firmware build that had a known timing bug with multiple VE.Direct devices polling simultaneously. Updated through the remote console, problem vanished overnight.

@QuietSparky and @SilverWarden are right to check the physical stuff, but firmware gets overlooked constantly. Victron pushed several stability patches through 2023-2024 specifically around multi-device polling behaviour.

SSH into the unit if you're comfortable, or just use the local console. Check Settings > Firmware > Online Updates. Worth thirty seconds before you start unplugging anything.

@CopperRoamer – one thing nobody's mentioned yet: check whether your WiFi signal strength is consistent along your mooring. Narrowboats are notorious for this because you're constantly shifting position slightly, and the Cerbo can drop VRM sync if it's hovering on the edge of a weak signal.

I had almost identical gremlins on my static setup until I realised the router was just far enough away to cause intermittent dropouts rather than a clean disconnect – those are the worst to diagnose because VRM looks like it's connected.

Worth logging into the Cerbo's local interface directly and checking the signal strength reading. If it's below about -70 dBm you're in dodgy territory. A cheap WiFi extender sorted mine completely. Also consider the cellular dongle route if you're moving berths regularly – far more reliable for a liveaboard situation. 🚢