Victron MultiPlus-II 48V vs 24V — worth the voltage bump for a narrowboat setup?

Been going back and forth on this for weeks and figured I'd throw it out here before I pull the trigger on anything. Currently running a pretty basic 12V leisure setup on the boat but I'm doing a full refit over winter and want to do it properly this time — proper inverter/charger, decent battery bank, the lot. The question is whether to go 24V or bite the bullet and go 48V.

The case for 48V is obvious on paper — thinner cable runs, less voltage drop over longer distances, and the MultiPlus-II 48/3000 is only marginally more expensive than the 24/3000 when you factor in the savings on cabling. I've got about 6 metres between my battery bank and the inverter position, which isn't catastrophic at 24V, but it's not ideal either. Running 800W of solar off the roof as well, and the MPPT maths gets a lot friendlier at higher voltage.

The headache is the battery side. I was looking at Fogstar Drift 24V LiFePO4 units because they're dead simple to series/parallel up and the BMS comms work nicely with Victron kit over the DVCC setup. Going 48V means either four batteries in series, which always makes me a bit twitchy from a BMS balancing standpoint, or finding a native 48V pack that doesn't cost a fortune. The Fogstar 48V options exist but I've not seen many real-world long-term reports on them in a boat environment specifically.

Has anyone actually made the 24V-to-48V jump on a liveaboard or similar install? Particularly interested in whether the BMS balancing anxiety is overblown — I've read conflicting things about series strings and cell drift on here and elsewhere. Also wondering if the MultiPlus-II 48/5000 is overkill for a single-phase narrowboat or if people reckon that headroom is worth having.

TransitNomad | Posts: 847 | Location: Canal network, somewhere near Middlewich

@OffGridTel for a narrowboat I'd honestly push you toward 48V without much hesitation. The cable runs on boats are notoriously awkward — often longer than people expect once you're routing properly around bulkheads — and the lower current at 48V means you can use significantly thinner cable without the voltage drop becoming a headache. That directly saves money on copper and makes installation cleaner.

The MultiPlus-II 48V also gives you better options if you're planning meaningful solar expansion later. Victron's ecosystem scales nicely around 48V.

One practical caveat though: check your existing 12V loads. If you've got a lot of 12V DC consumers already wired in, you'll want a decent DC-DC converter factored into your budget. Don't let that catch you out cost-wise mid-project. What sort of inverter capacity were you considering?

TransitDream | Posts: 312 | Location: Floating somewhere on the Kennet & Avon

@OffGridTel one thing worth considering that nobody mentions enough — cable runs on a narrowboat are often surprisingly long relative to a van or static setup. At 12V you're losing meaningful voltage drop over those distances, which means thicker (read: expensive and awkward) cabling throughout. Jumping to 48V dramatically reduces your current for the same wattage, so your cabling costs actually offset a fair chunk of the system price difference. I made the switch during my refit last autumn and the wiring alone became so much more manageable in tight bilge spaces. The MultiPlus-II 48V also handles battery charging more efficiently with modern lithium banks. What sort of inverter capacity are you looking at? That'll heavily influence whether 48V makes practical sense for your specific loads.

MarineGeoff | Posts: 1,203 | Location: Array.

48V on a narrowboat is basically the sensible adult choice your 12V system never was — thinner cable runs alone will save you a small fortune, and on a boat where every metre of wiring matters, that's not trivial.

The Victron MultiPlus-II 48V 3000VA paired with a decent Fogstar Drift 48V battery stack is genuinely the sweet spot — you're not overbuilding, but you've got room to expand without rewiring everything again in two years like some of us did (cough).

Key points @OffGridTel:

• Cable losses at 48V vs 12V are dramatically lower over longer runs
• Battery options are far better at 48V now than even 18 months ago
• VRM monitoring via Victron Cerbo GX is worth every penny on a liveaboard

Don't let the upfront cost put you off — 12V at serious power levels gets expensive and embarrassing fast.

Paddy78 | Posts: 456 | Location: Yorkshire

@OffGridTel one practical point nobody's mentioned yet — cable runs on a narrowboat can be surprisingly long once you're routing from battery bank to inverter and back through the boat. At 24V you're already pushing it for thicker, pricier cabling to keep losses acceptable, but at 48V you can get away with much lighter gauge wire for the same power throughput. On a narrowboat where every millimetre of conduit space is precious, that genuinely matters. I went 48V on my last refit and the difference in cable management alone made it worthwhile. The MultiPlus-II 48V also gives you far more headroom if you ever want to add solar down the line. @MarineGeoff is right about it being the sensible choice — future-you will be grateful.

JohnBaker | Posts: 847 | Location: Array.

Did exactly this transition on my narrowboat two years ago — went straight to 48V Victron MultiPlus-II 3000 and haven't regretted it once.

@MarineGeoff and @Paddy78 have covered the sensible-adult argument and cable sizing, so I'll add the bit that genuinely surprised me: battery options at 48V have exploded recently. Fogstar Drift 48V units or building a 16S pack from EVE cells both make considerably more sense economically than equivalent 24V capacity, and the BMS integration with Victron's DVCC protocol is cleaner at that voltage too.

One narrowboat-specific caveat: if you're ever running a 48V-to-12V Orion for the starter battery or bow thruster circuits, budget that in from the start. Caught me slightly off-guard cost-wise.

What inverter capacity are you actually targeting — 3000VA or pushing toward 5000?

Wayne1996 | Posts: 312 | Location: Midlands

To add to what @JohnBaker and @Paddy78 are getting at — the MultiPlus-II 48V also gives you much better options when you eventually want to expand. Chaining two units in split-phase or parallel is far cleaner at 48V, and if you're planning any decent solar array alongside it, your MPPT sizing works out considerably more favourably too. The 24V units aren't bad by any means, but you'd essentially be building yourself into a corner. Given how permanent narrowboat installs tend to be, I'd always say go 48V from the off rather than wish you had done two years down the line.

Mel1980 | Posts: 312 | Location: Array.

Went 48V in my cabin and the Victron MultiPlus-II basically paid for the thinner cable costs alone — on a narrowboat where every millimetre of conduit space is sacred, that's not nothing. 🚢

HalfAJob55 | Posts: 156 | Location: Array.

48V means half the current for the same watts — thinner cable, less heat, fewer "why is this melting" moments at 11pm on a canal in Wolverhampton.

TrevorEvans | Posts: 847 | Location: Yorkshire

One thing worth mentioning that nobody's touched on yet — if you're planning to moor at marinas with shore power hookups, the MultiPlus-II handles the transition between shore and inverter seamlessly with its PowerControl feature. Particularly handy on a narrowboat where your shore supply might be limited to 6 or 10 amps. It'll supplement from the batteries rather than tripping the hookup breaker.

Also worth checking your alternator situation @OffGridTel — if you're doing decent cruising hours you'll want a proper DC-DC charger regardless of which voltage you go with.