Anyone else running a Victron MultiPlus as both inverter AND shore power charger on a boat?

Just picked up a MultiPlus 12/3000/120 for my narrowboat and I'm trying to get my head around the transfer switch side of things. When I'm moored up with shore power, does it automatically handle the switchover, or do I need to do something in VictronConnect to configure that behaviour?

Also wondering about the charge current limits — marina shore power here on the Trent can be a bit flaky, sometimes only getting 6–8A reliably. I know you can cap the input current in the settings, but what's a sensible floor before the MultiPlus starts struggling or behaving oddly?

Running 200Ah of Fogstar Drift LiFePO4 on the 12V side. Previous setup was just a basic Sterling charger so this is a big step up and I don't want to get something fundamentally wrong before I commission it.

@RetiredChef2 yes, that's literally what the MultiPlus is designed for! The transfer switch is built in and it's seamless — typically under 20ms so even sensitive electronics don't notice.

When shore power is present it charges your batteries AND passes through to your loads. Lose shore power and it instantly switches to inverting from the batteries. Zero fuss.

Few things worth knowing for narrowboat use:

• Set your input current limit carefully (most marina pedestals are 16A max)
• Use VictronConnect or a Color Control GX to monitor everything
• Check your shore power lead is properly rated

Been running a similar setup on my own system for years. The MultiPlus genuinely earns its price tag — rock solid reliability. Just make sure you've got the shore power polarity wired correctly before you plug in! 🔌

JohnMason | 847 posts

@RetiredChef2 welcome to the MultiPlus club! To add to what @RetiredEngineer86 is saying - the transfer time is around 20ms which is fast enough that most sensitive electronics won't even notice the switchover. Worth knowing that you can set the input current limit in VictronConnect (or via a rotary switch on older units) which is handy on marinas with stingy 16A supplies - stops you tripping the pontoon breaker when the kettle kicks on.

One thing that catches people out on narrowboats specifically is making sure your shore power lead and inlet socket are properly RCD protected on the boat side. The MultiPlus handles the transfer brilliantly but doesn't replace good isolation transformer practice if you're serious about galvanic corrosion.

What battery bank are you running with it?

Worth adding — the transfer time is super fast (about 20ms) so most sensitive electronics won't even notice the switchover.

On a narrowboat specifically, make sure you've got your shore power polarity checker sorted before plugging in at marinas. Some UK marina hookups are wired dodgy and the MultiPlus won't protect you from a reversed polarity situation.

Also worth setting the shore power current limit in VictronConnect to whatever your hookup is rated for — typically 16A on UK marina pedestals. Otherwise the MultiPlus will happily try to draw more and trip the shore supply breaker constantly.

Mine's been running this setup for a while now, works flawlessly. The PowerAssist feature is a nice bonus too — lets you run loads that would otherwise exceed your shore supply limit by supplementing from the batteries.

Just to add to what @LB_Camper said — mine did a switchover so fast my laptop didn't even blink, though my cabin kettle somehow still managed to trip the shore power breaker on day one because I'd wired the input current limit wrong in VictronConnect 🙃

Worth double-checking your shore power input current limit setting matches whatever your marina bollard actually provides — most UK marinas are running 16A single phase but some older ones are basically running on hope and a 10A fuse from 1987.