Dual Victron 24V MultiPlus-II 5kVA 120V Inverter backup

Bit of an unusual one seeing 120V spec in here — that's North American voltage, so not something you'd typically see on a UK forum. Worth flagging in case OP is in the wrong place or sourced units intended for a different market. The MultiPlus-II in 230V is what we'd be running this side of the pond.

That said, the dual inverter setup concept is solid and worth discussing regardless. I've got a single Victron MultiPlus-II 48V 3000VA running my garden office and it's been rock solid for two years. The idea of paralleling two 5kVA units for redundancy and surge capacity makes a lot of sense if you've got serious loads — workshop kit, heat pumps, that sort of thing.

A few things I'd be curious about if anyone's running a parallel Victron setup:

• How are you handling the battery bank sizing to feed dual inverters without voltage sag?
• Are you using Lynx Distributors for busbars or going DIY?
• What's your comms setup — VE.Bus or going full Cerbo GX?

The MultiPlus-II parallel capability is one of Victron's strongest selling points IMO. You can scale without ripping everything out. Fogstar or CATL cells in a decent 24V bank should handle it, though I'd probably go 48V at that power level personally — less copper needed.

Anyone here actually running paralleled Victrons? Curious what the real-world experience is like vs the theory.

@MidlandsSolar raises a fair point — the 120V split-phase spec is very much a North American configuration. Victron do produce those units but they're not what you'd typically source through UK distributors like Bimble Solar or Victron's standard UK channels.

Worth clarifying a few things for OP:

• Are you actually based in the UK or just posting here for the technical community?
• The 120V/240V split-phase topology is quite different from our 230V single-phase norm
• Parallel/stacking config for two MultiPlus-II units does work, but the setup via VEConfigure differs depending on regional firmware variants

I've only worked with the 48V 230V units on my narrowboat build so can't speak to the 120V config directly. If OP is stateside, the Victron Community forums will have far more relevant experience with that exact setup.

Dead giveaway was "120V" — my garden office runs on proper 230V like God and BS 7671 intended. 🇬🇧

Worth adding that Victron's own product catalogue separates these clearly — the MultiPlus-II you'd source through UK distributors like Bimble Solar or Victron's official UK channels will be the 230V/50Hz variant. The 120V split-phase units are specifically factory-configured for North American grids and aren't simply a setting you can toggle after purchase.

If @MidlandsSolar's hunch is right and the OP has sourced 120V units somehow, running them on UK mains would be a serious problem — your supply voltage would be double what the inverter's charger section expects. Not a "see what happens" situation.

There's also the small matter of G99/G98 compliance for any grid-tied element, which only applies to 230V/50Hz equipment approved for UK DNO connection. The 120V Victron units simply won't appear on that approved list.

Yeah @JackShaw nailed it really. If you're UK-based and bought 120V units — double-check your receipts, because those are genuinely the wrong spec for a 230V/50Hz grid-tied setup. You can't just "make it work" either, it's not like swapping a fuse.

My garden office runs a pair of Victron MultiPlus-II 48V/3000s on proper 230V and sourced them through Bimble Solar — all above board for BS 7671 compliance.

If you're actually stateside and just ended up here somehow, the 120V split-phase stacking setup is valid over there, but this forum won't be much help for regs etc.

Worth clarifying where you actually are and how the units were sourced — could be a grey import situation which brings its own headaches around warranty and DNO notification.