"VE.Bus Error: VE.Bus Error 11: Relay test fault" when applying grid codes for the ESS mode

Been wrestling with something similar on my shepherd's hut setup and wanted to see if others have hit this wall.

Running a MultiPlus-II 48|3000|35 with a Cerbo GX, pair of Fogstar Drift 48V batteries, and a couple of SmartSolar MPPTs. When I tried enabling ESS mode and applied a grid code (G98 in my case, as required for any UK grid-tied configuration), the system threw a VE.Bus Error 11 — Relay Test Fault and refused to come up properly.

From what I've dug into so far:

• Error 11 is essentially the MultiPlus performing its internal relay self-test before connecting to the grid, and something in that sequence is failing
• It seems particularly sensitive to grid code selection — choosing the wrong regional standard (or having firmware mismatches between the Cerbo and the Multi) can cause the relay test to abort
• Some reports suggest the AC wiring configuration matters enormously here — neutral-PE bonding, earth loop resistance, all of it

My situation is slightly unusual because this is primarily an off-grid/emergency backup arrangement, so I'm not actually exporting to the grid. I only applied the grid code because VEConfigure was pushing me toward it for ESS functionality. Now I'm questioning whether ESS is even the right mode for a standalone shepherd's hut that occasionally sees a generator input.

Has anyone navigated this on a similar UK off-grid setup? Wondering whether:

1. Dropping back to a non-ESS configuration avoids this entirely
2. There's a specific G98/G99 firmware version known to behave with the 48|3000 unit

Keen to hear from anyone who's sorted this — particularly if

@JYT_Solar what firmware version are you running on the MultiPlus-II? I had something similar crop up on my setup and it turned out the VE.Bus Error 11 was being triggered during the relay self-test because the grid code settings were conflicting with the transfer switch timing.

Worth checking in VEConfigure whether your grid code is actually set correctly for UK (EN 50549-1) rather than defaulting to something generic. Also — are your Fogstar Drift batteries communicating via DVCC? I wonder if the relay test is running at the wrong point in the startup sequence when ESS tries to initialise.

Have you tried temporarily disabling the grid code to see if the error disappears? Would at least help narrow down whether it's definitely the relay test itself or something upstream causing it.

@JYT_Solar classic VE.Bus Error 11 — the MultiPlus is basically throwing its toys out because the internal relay self-test is failing during the grid code application, usually because ESS assistant grid code settings don't match your actual AC input wiring or the relay physically can't complete its cycle cleanly.

Check these in VEConfigure:

• Grid code set to UK G98/G99 (not a random European standard)
• AC input voltage/frequency tolerances matching your supply
• ESS assistant reinstalled fresh after any firmware change

Also worth confirming your Fogstar Drifts are communicating battery state properly — a BMS cutoff mid-relay-test will trigger this too.

@Mike1980 makes a fair point on firmware; stick to the latest stable release via VictronConnect rather than bleeding-edge on a live install — learnt that the hard way on my narrowboat when I updated mid-season! 🚢

@RetiredChef already covered the relay tantrum angle, so I'll add: nine times out of ten with Error 11 on ESS grid code application it's the AC input wiring not meeting the relay test's voltage expectations — had this exact saga with my garden office MultiPlus-II when I'd bodged the N-PE link incorrectly.

Check your neutral-earth bonding arrangement is correct for UK G98/G99 compliance before anything else. VEConfigure's grid code settings are extremely fussy about seeing a proper 230V L-N relationship during that relay self-test.

Also worth pulling the VRM portal logs rather than just the Cerbo screen — the error timestamps often reveal whether it's triggering on AC input connect or during the ESS mode switch, which narrows it down considerably.

Worth adding from my narrowboat experience — when I first set up ESS on my MultiPlus-II 48|3000 I wasted two days chasing hardware before realising the grid code selection itself was the culprit. The UK G98/G99 codes are stricter about that relay test sequence than the "no grid code" option.

If you haven't already, try switching to VEConfigure rather than just the Cerbo interface to apply the grid code — there's a specific order of operations that matters. Set the grid code before enabling ESS assistant, not after. Doing it the wrong way round seems to confuse the relay test timing completely.

Also double-check your AC input voltage tolerance is within spec for UK grid — 230V ±10% — because the relay test will fail if those thresholds look wrong to the unit.