MultiPlus-II 48/3000 ESS grid-parallel: discharges 30s, relay clicks

Wondering if anyone else has hit this after the recent Venus OS update — I've seen a few mentions on the Victron community site but nothing definitive yet.

My setup is a narrowboat install: MultiPlus-II 48/3000 running ESS grid-parallel with shore power at the marina. After the update it's doing something odd:

• Discharges normally for about 30 seconds
• Internal relay audibly clicks
• Then drops into charge-only mode and refuses to discharge again until I restart

The Fogstar 48V lithium pack looks fine — BMS isn't throwing any faults, voltage is solid, and the same behaviour repeats every single time like clockwork.

What I've tried so far:

1. Rolled back to the previous Venus OS version — problem disappeared immediately
2. Re-updated — came back
3. Checked the ESS assistant config, nothing obvious changed
4. Confirmed grid code is set to G98 (UK)

That last point might be relevant. I wonder if the update tweaked something in the grid protection logic that's interacting oddly with the UK grid code settings. The 30-second window feels very deliberate rather than a random fault.

Has anyone with a similar single-phase shore power setup reproduced this? Particularly interested if it's happening to people on G99 as well, or whether it's specific to G98.

Also curious whether anyone has raised it with their Victron installer — I know the approved route is through a registered installer for ESS queries, but given this is clearly update-related it feels like a firmware bug rather than a config issue.

@HeathGazer interesting one — I haven't hit this exact issue but I'm running a similar MultiPlus-II 48/3000 on my boat and I'm always a bit nervous before hitting "update" on Venus OS for exactly this reason.

Quick question before others dig in — are you running a Pylontech bank or something DIY? I ask because I've seen relay-clicking behaviour on my shepherd's hut setup when the BMS was sending a slightly dodgy state-of-charge signal, which confused the ESS assistant into thinking the battery was full, then empty, then full again in a loop.

Also worth checking — did the 30-second discharge cycle coincide with anything on your AC input, like a shore power blip? On a narrowboat that connection can be flaky at the best of times.

What firmware version were you on before the update?

@HeathGazer classic Venus OS "gift" — had almost identical behaviour in my van build when the ESS assistant version mismatched the firmware; the relay cycling is the MultiPlus convincing itself the grid's failed the voltage window check, even when it hasn't.

Check your AC input current limit in VEConfigure — post-update it occasionally resets to a daft low value (seen 6A appear from nowhere), which triggers the handoff dance every 30s like clockwork.

Also worth pulling the VRM event log rather than guessing; if you see grid lost events firing repeatedly you've confirmed it's an AC sensing issue rather than the BMS pulling the plug.

What BMS are you running? If it's a JK or similar talking over CAN, there's a known timing quirk with the newer dbus-bms handling that can spook the assistant into the same loop.

@HeathGazer this is almost certainly the ESS assistant version mismatch that @BatteryAlan alluded to — but specifically, post-update Venus OS sometimes resets the Minimum SOC and Grid setpoint values silently, which triggers the relay cycling you're describing.

Check two things via VRM or local CCGX:

1. ESS → Minimum SOC — if it's dropped to 0% post-update, the system overshoots discharge before the BMS can intervene
2. Grid setpoint (W) — confirm it hasn't wandered to a negative value

On my narrowboat install I had near-identical behaviour after a Venus OS bump. Reflashing the ESS assistant via VE.Configure whilst the MultiPlus is offline from AC sorted it permanently. Don't just re-upload the same VEsmart config — pull a fresh assistant from the Victron website, versions do differ between minor releases.

Not a narrowboat setup but I've seen similar relay chatter on my static caravan install after a Venus OS bump — turned out the ESS assistant in VEConfigure wasn't aligned with what Venus expected, exactly as @LH_Marine describes.

One thing worth checking that nobody's mentioned: look at your ESS battery life minimum SOC setting. If Venus and the MultiPlus are briefly disagreeing on SOC during the handshake period, it can trigger a false low-SOC condition that causes the 30-second discharge-then-cutout cycle before the relay resets.

Pull the logs from Venus (Remote Console → System Overview → check the ESS reason codes) — the specific code will tell you whether it's an assistant mismatch or something else entirely. Don't just reflash the assistant blind without checking that first or you could mask a genuine comms issue between the BMS and the MPII.