VRM and remote CERBO GX

Right, so I've been wrestling with VRM connectivity on my garden office setup for months now and I reckon this deserves a proper thread. Got my Cerbo GX talking to a Fogstar 4G router out here in the sticks, and the data sync is about as reliable as English summer weather.

The problem: Intermittent VRM drops mean I'm flying blind on battery state half the time. Usually it's the router dropping connection to the mobile network, but sometimes the Cerbo itself goes quiet and needs a reboot to sort it.

What I've tried:

• Switched from Three to Vodafone (marginally better signal here, but your mileage will vary depending on postcode)
• Added a second antenna to the router
• Set the Cerbo to auto-reboot weekly (bit hacky, but works)
• Wired ethernet where possible instead of WiFi

My current theory: The 4G router loses its DHCP lease and doesn't recover gracefully. Anyone else seen this with Victron's remote monitoring, or is it more of a router firmware issue?

Curious whether others managing off-grid systems remotely have found a bulletproof solution, or if we're all just accepting that rural UK connectivity is a bit temperamental. What's your setup looking like?

The Fogstar 4G route is solid, but I'd flag a couple of things from my own setup out here. First, make sure your Cerbo's getting stable power — I had intermittent VRM drops that turned out to be voltage sag during inverter transitions, not connectivity.

Second, the Cerbo needs a clean DNS path to Victron's servers. If your 4G router's doing NAT or has dodgy DNS forwarding, you'll see "connected but not updating" nonsense on VRM. Worth checking your router logs and forcing Google DNS (8.8.8.8) if you're not already.

Latency matters less than people think, but packet loss will kill you. Run a ping test to your gateway over a full charging cycle — that'll show whether it's the link or your load profile.

What's your current uptime looking like? That'll help diagnose whether it's a connection drop or something else entirely.

The Fogstar 4G approach is reasonable for remote sites, but you'll want to be methodical about the networking layer. I've got my Cerbo GX on a narrowboat with intermittent 4G, and the key is understanding that VRM connectivity is separate from your local LAN functionality — the Cerbo will continue logging data locally even if cloud sync drops.

A few practical points:

• Ensure your 4G router has a static IP for the Cerbo (DHCP reservation, not assignment)
• Check your Fogstar's firewall rules — port 443 outbound must be open for VRM
• Monitor the Cerbo's signal strength; below -110dBm and you'll see intermittent drops that cause sync lag
• Consider implementing a secondary path if critical — USB tethering from a phone as failover isn't elegant but it works

What's your current signal strength reading on the Fogstar? That'll determine whether this is a configuration issue or a site limitation.

Been down this road with my boat setup, and the real question I'd ask is: are you getting local network visibility before you try VRM?

With the Fogstar 4G, make sure the Cerbo can actually see the router on the same subnet first. I spent weeks chasing VRM connection issues only to realise my DHCP wasn't handing out addresses properly on the 4G side.

Also worth checking: what's your latency like? The Cerbo can be finicky with high-latency connections. If you're getting 100ms+ from the 4G link, it sometimes drops VRM sessions even if the connection itself is solid.

Have you got the Cerbo firmware up to date? There were some stability improvements in the last few releases around cellular connectivity.

What's the actual error you're seeing when it disconnects?

Right, good thread this. One thing worth checking that doesn't always get mentioned – make sure your Cerbo's time and date are actually synced before you start troubleshooting VRM connectivity. Sounds daft, but I've spent hours chasing phantom issues that sorted themselves once NTP kicked in properly.

Also, if you're relying on 4G, give some thought to your DNS settings. The Cerbo can be finicky about which nameservers it uses, and sometimes the router's defaults aren't ideal. Worth manually setting it to something like 8.8.8.8 as a fallback.

What upload speeds are you actually seeing on that Fogstar? VRM doesn't need much bandwidth, but if your connection's dropping regularly, that'll manifest as gaps in your data that look like connectivity problems rather than signal issues.

Ah, the VRM remote access dance—I've been there with my narrowboat setup. Here's the thing nobody tells you: your Cerbo will connect to VRM just fine, but you'll go mad waiting for the data to actually appear on the dashboard if your 4G connection's dodgy.

What worked for me was setting the VRM update interval down to something sensible (not the default 15 mins) and ensuring the Fogstar's got proper signal strength before you blame Victron. Also, if you're getting intermittent connectivity, check whether your router's dropping the LAN connection to the Cerbo itself—happened to me when the power management kicked in.

The local network visibility point @GrumpyWarden mentions is gold. Can you ping the Cerbo's IP before expecting VRM to work? If not, everything else is just noise.