Victron MultiPlus-II GX manual switch over from normal to Island mode

Been mulling over this one for a while and curious what others have done.

I've got a MultiPlus-II GX running in my shepherd's hut setup — currently grid-tied with a small PV array and a Fogstar Drift LiFePO4 bank. Works a treat 90% of the time. But I've been wondering about the practicality of manually switching over to island mode when grid quality is poor or during planned outages, rather than relying on automatic transfer.

The Victron documentation is decent but not exactly crystal clear on the cleanest way to trigger this manually without faffing about in VictronConnect every time. Ideally I'd want something like a physical switch or a simple Node-RED toggle on the Cerbo GX that puts the unit into island mode on demand — then switches back when I'm happy with the grid supply.

A few questions for anyone who's done this:

• Is it straightforward to configure via the assistants in VE.Configure, or does it get messy?
• Any risk of the MultiPlus getting confused when you switch back and trying to sync awkwardly with the grid?
• Has anyone used the generator input workaround to force island behaviour? Seen it mentioned a few times but I'm sceptical it's a clean solution.

My hut is a relatively simple single-phase 230V setup — nothing exotic — so I'd hope this isn't as complicated as it sometimes sounds online. But with Victron kit, I've learned there's often a "proper" way and a "bodge that technically works" way, and I'd rather know which is which before I start poking around.

Anyone been down this road?

On my narrowboat I rigged a simple AC input breaker on the panel — flick it off and the MultiPlus islands itself automatically via its internal transfer relay, no ESS faffing required. 🔌

Just make sure your grid code settings in VictronConnect are configured correctly first, otherwise it'll sit there confused like a golden retriever watching a magic trick.

Worth checking ESS → Grid setpoint and whether you've got "Prevent islanding" ticked — that one'll stop you dead in your tracks if left enabled.

@DevonNomad's breaker trick works, but if you want something a bit more deliberate about it, the MultiPlus-II GX has an Assistant you can program via VictronConnect — specifically the AC Input Control assistant lets you trigger island mode through a virtual switch in the Cerbo GX console without touching a single physical breaker.

Done exactly this on my shepherd's hut; mapped it to a button on the VRM dashboard so I can switch remotely when I'm not on-site and don't want the grid feeding back during a storm.

⚠️ Worth noting: you must comply with G98/G99 if you're export-enabled — manual islanding doesn't exempt you from DNO notification requirements.

Pedantic footnote nobody asked for: it's technically called "Inverter Only" mode in the Victron UI, not "Island mode" — same thing, just don't go hunting the wrong menu for twenty minutes like I did.

Good timing on this thread — I spent a winter on the cut working through exactly this scenario when shore power became unreliable at certain moorings.

What nobody's mentioned yet: if you're configuring this properly, look at VEConfigure (or VictronConnect for basic settings) and set your AC input current limit to something the grid genuinely cannot exceed. Combined with @DevonNomad's breaker approach, you get a clean, deliberate island transition rather than an emergency one.

Also worth noting — on the MultiPlus-II GX specifically, the Cerbo GX integration means you can trigger island mode via a digital input wired to a simple key-switch. My static caravan backup setup uses exactly this. One turn, logged in VRM, no ambiguity about what state you're in.

Your Fogstar Drift batteries should handle the transition seamlessly — mine never even blinked.

@FETFan is right that there's a more deliberate way — and "deliberate" is doing a lot of heavy lifting when you're fumbling around at midnight because the grid's gone wobbly again.

What I actually did for my garden office setup was create a virtual switch in VE.Configure with an assistant that responds to a physical momentary button w

Don't overlook the Victron Connect "switch" toggle on your phone either — nothing quite like manually islanding your shepherd's hut in your dressing gown at 2am because a storm took out the grid, all via Bluetooth from the sofa.