Off grid parallel mutliplus ii 48/15000 with 30kva generator

Running twin Multiplus II 48/15000s in parallel with a 30kVA genny is exactly the kind of overkill I aspire to whilst powering my garden office with a single kettle.

Serious question for the thread though — has anyone actually dialled in the generator assist settings properly on a parallel setup like this in the UK? I've been wrestling with my single unit and a much humbler Honda EU22i, and getting the AC input current limit playing nicely with the generator's output feels like negotiating with a particularly stubborn badger.

My concern with a 30kVA machine feeding two 48/15000s would be the PowerControl configuration — specifically making sure both inverters are reading the generator input correctly and sharing the charge current without one unit trying to hog all the fun. Victron's VE.Bus parallelism is generally solid, but I've seen a few threads on the Victron Community forum where people have had grief with unbalanced charging when the generator drops frequency slightly under load (common with cheaper diesel sets).

Worth double-checking:

• Are you using a VE.Bus BMS or external BMS, and has it been configured for parallel?
• Generator frequency stability at varying loads?
• ESS vs standalone off-grid assistant? The behaviour differs quite a bit.

Also — what's your battery bank? Fogstar Drift LiFePO4 cells, proprietary rack units, or something DIY? That'll massively affect how aggressive you want the bulk charge current set across both units.

Genuinely curious what generator you've gone with — 30kVA feels substantial unless the load profile genuinely demands it.

Ha @BayFrank, the classic off-grid paradox — spec everything to the moon "just in case" then spend six months boiling the kettle and wondering why you bothered! 😄

Genuinely though, have you considered what your actual peak demand might look like over the next 5-10 years? A garden office can creep up on you — air con, a decent workshop setup, EV charging point, who knows. The Multiplus II 48/15000 pair gives you serious headroom and that 30kVA genny pairing makes sense if you're also charging a decent battery bank simultaneously rather than relying on it for direct loads.

What's your battery situation looking like? That'll probably determine whether the generator sizing is genuinely overkill or actually quite sensible for bulk charging cycles.

@BayFrank genuinely though, have you actually sized the load properly first? Twin 48/15000s is ~30kW inverter capacity — your 30kVA genny will struggle on generator assist if you're not careful with the AC input current limit settings in VEConfig.

Done something similar (obviously far smaller scale) with a single Multiplus II 5000 at my cabin. Getting the generator interaction right took ages to dial in.

Few things worth checking before committing:

• AC input current limit — set conservatively to protect the genny
• PowerAssist settings — crucial in parallel configs
• Phase synchronisation — Victron parallel needs solid comms via VE.Bus

What's the actual load profile? Peak vs sustained matters massively here. Parallel Victrons are brilliant but they're not a substitute for proper load analysis.

@EmmaEdwards82 makes a fair point on load sizing. When I was planning my shepherd's hut setup I went down a similar rabbit hole — kept speccing "headroom" until I'd basically designed a small substation for what turned out to be lights, a laptop, and occasionally a kettle.

The 48/15000 parallel config does make sense if you're thinking long-term expandability, but that 30kVA genny needs to be able to handle the combined charge current plus load simultaneously or you'll get frustrating generator assist cycling.

Worth checking your AC input current limit settings in Victron's VRM — easy to overlook and it'll throttle the whole system in ways that aren't immediately obvious.

What's the actual anticipated peak load @BayFrank? That number changes everything.

@BayFrank twin 15000s and a 30kVA genny is basically buying a Ferrari to pop to Tesco — magnificent, but hard to justify to the accountant.

@EssexNomad not quite — a 30kVA genny pairs quite logically with twin 15000s actually. The Multiplus II 48/15000 draws up to ~16kVA per unit at full charge+invert load, so two units can genuinely stress a undersized genny. 30kVA gives you headroom without constantly running it at 80–90% which kills longevity.

That said, @BayFrank — what's your actual battery bank? Twin 15000s will demand serious current from a 48V bank. If you're not running something like 4–5 Fogstar Drift 48V batteries or equivalent LiFePO4 capacity, the inverters are the least of your worries.