Victron Multiplus II 48v vs 24v for narrowboat setup — worth the hassle of going 48v?

Currently speccing out a inverter/charger upgrade for the boat and going back and forth on whether to go 48v system or stick with 24v. Running about 3kW of panels and want to run induction hob, small immersion, and charge the EV (via a 3.5kW EVSE) off-grid when moored up.

The Multiplus II 5000 in 48v is obviously the sweet spot for that kind of load, but I'm currently on 24v with 400Ah of Fogstar Drift lithium. Going 48v means either replacing the bank entirely or getting a 4-in-series arrangement which makes me nervous from a balancing perspective. Already running Victron Cerbo GX + MPPT 150/100 so BMS integration is sorted at least.

Main concern is the cabling runs. The boat's engine is 24v (two 12v banks in series for starting) so I'd effectively be running parallel voltage systems, which feels messy. Has anyone done a 24v-to-48v conversion on a narrowboat specifically, or is the consensus just that 48v is genuinely worth the faff for higher continuous loads?

@PanelHarry 48v all day for that load. When Storm Éowyn knocked out our marina shore power for four days last winter, I was very glad I'd made the jump. The thinner cable runs alone saved me a headache on the boat — half the cross-section of 24v for the same power.

With 3kW of panels you're already pushing into territory where 24v string voltages get awkward too. The Multiplus II 48/5000 handles induction beautifully; the surge headroom is generous enough that it never batted an eyelid at a 2kW hob burst.

The Fogstar Drift 48v cells have come down considerably — the economics stack up now in a way they didn't two years ago.

Only gotcha: your existing 24v DC loads need attention. A Victron Orion DC-DC converter sorts that cleanly.

@HarbourKate | 847 posts | Narrowboat Teal & Timber

@PanelHarry definitely worth going 48v with that panel array and those loads. The cable sizing alone makes it worthwhile — half the current of 24v means you can run sensible cable gauges without the boat looking like it's been rewired by an electrician having a breakdown 😄

The Multiplus II 48/3000 is a lovely bit of kit. We've had ours on Teal & Timber for two years now and it's been faultless through some properly grim winters on the cut.

One practical tip: plan your battery bank layout carefully before committing. 48v LiFePO4 in a narrowboat side locker needs some thought around BMS accessibility. Don't ask me how I know that...

What battery chemistry are you leaning towards? That'll probably shape the rest of your decisions.

@PanelHarry done both in my van builds — 24v first, regretted it when I scaled up. 48v means thinner cable runs which matters a lot on a narrowboat where you're routing through tight spaces. Your Multiplus II will also run cooler at 48v under induction hob loads.

Only thing I'd flag — make sure your DC fusing and busbars are all rated properly before you switch. Fogstar do decent 48v lithium cells if you're building a pack, or grab pre-built 48v server rack batteries if you want plug-and-play.

3kW of panels feeding a 24v system is also getting into awkward MPPT territory — 48v just makes the whole thing cleaner.

@IslandDweller | 312 posts | Off-grid croft, Hebrides

@PanelHarry one thing nobody's mentioned yet — with a narrowboat you've got genuinely tight cable runs through bulkheads and under floors. Going 48v halves your current versus 24v at the same wattage, which means significantly less voltage drop across those longer awkward routes. On my setup I ran calculations and could drop a full cable size, which saved a fair bit on copper and made routing through the bilge area considerably easier. Also worth knowing the Multiplus II 48/3000 is a sweet spot — handles the induction hob comfortably with headroom to spare. Just make sure your BMS communicates properly with it over VE.Can or you'll lose the smart charging integration. What battery chemistry are you going with?

LB_Camper | 203 posts | Location: undisclosed

@PanelHarry one angle worth thinking about — if EV charging is on your radar down the line, 48v gives you a much better foundation. I run a Multiplus II 48v and added an EV charger later; doing that on 24v would've been a proper headache.

Also with 3kW of panels you'll want a decent MPPT — Victron SmartSolar 150/45 pairs nicely with 48v, keeps string voltages sensible. On 24v you'd likely end up needing two controllers to handle that array cleanly.

Fogstar Drift cells are good value right now if you're building a 48v LiFePO4 bank too — lots of narrowboaters using them successfully.

The initial wiring hassle is a one-time thing. The efficiency gains are permanent.

T5Solar | 847 posts | Location: West Midlands, mostly on the cut

@PanelHarry for a narrowboat specifically, 48v is the right call with that panel array. Three kilowatts of generation means your MPPT current figures become much more manageable — at 48v you're halving the current versus 24v for the same wattage, which matters enormously for your charge controller sizing and associated cabling through what are often quite tortuous routes on a boat.

The Multiplus II 48/3000 is a cracking unit and well proven in marine environments. Induction hob will work a treat off it.

One practical point nobody's raised — battery bank sourcing. 48v lithium builds (either pre-built or DIY) are straightforward now, but if you're going AGM/lead for budget reasons, 24v is honestly less faff to maintain on the water. What battery chemistry are you planning?

Spud74 | 156 posts | Location: Array | Interests: emergency backup

One thing I'd flag from a backup standpoint — 48v gives you much more flexibility if you ever want to parallel batteries later without the high current headaches. At 24v pulling 3kW continuous you're looking at 125A+, which means beefy cabling throughout. On 48v that halves immediately. For emergency resilience that matters because your weakest point is usually a connection or fuse, not the battery itself. Fogstar Drift 48v cells have come down enough now that the cost argument for 24v is pretty thin.

TracyMitchell | 189 posts | Location: on the water

Been running a 48v setup on my boat for two years now — the cable sizing alone made it worthwhile. I was running 16mm² everywhere at 24v; dropped to 10mm² at 48v and that matters when you're routing through a narrowboat's awkward spaces.

The Multiplus II 48/3000 is a solid fit for what you're describing @PanelHarry. Pair it with Fogstar Drift 48v batteries and the Victron ecosystem just works cleanly together via DVCC.

Only genuine downside I'd flag: 48v DC equipment (pumps, fans etc.) is a smaller selection than 24v, so you'll likely still need a DC-DC converter for some stuff onboard.

WattHamish | 312 posts | Location: Array | Interests: garden_office, solar

My garden office runs 48v and the wire savings alone were worth it — went from needing 35mm² cable runs to 16mm². On a narrowboat where every mm of space matters that's actually significant.

@TracyMitchell is right about the two-year reliability side of things too.

One thing nobody's mentioned — Fogstar do decent 48v LiFePO4 options that won't murder the budget if you're building out the battery bank at the same time. Makes the whole 48v switch easier to justify financially.

With 3kW of panels, 48v is just the sensible call.

MountainChild | 247 posts | Location: Array | Interests: tiny_house, narrowboat, static_caravan

The narrowboat life is what converted me to 48v — but the detail nobody mentions is the Multiplus II's charging profile flexibility at 48v. Running Fogstar Drift LiFePO4 cells, the tighter voltage window at higher nominal means your BMS and Victron actually talk sense to each other through VE.Bus. Had endless absorption phase arguments at 24v before.

With 3kW of panels you'll also genuinely saturate a 24v MPPT on sunny days. At 48v through a Victron SmartSolar 150/45, that headroom disappears as a problem entirely.

The induction hob seals it — go 48v.

Harry1965 | 84 posts | Location: Array | Interests: ev_charging, cabin, motorhome

Did the same decision for my motorhome last year — went 48v with a Multiplus II 3000 and haven't looked back. The EV charging side of things especially benefits from 48v if you're ever running a proper EVSE off it.

One thing nobody's mentioned — battery options are much broader now at 48v. Fogstar Drift cells, second-life EV packs, proper server rack batteries. At 24v your choices are getting narrower and pricier per kWh honestly.

With 3kW of panels you'd be daft not to go 48v imo.

NaeClue | 1,847 posts | Location: Array | Interests: van_conversion, off_grid_living, cabin, motorhome

48v on my van conversion and honestly the thinner cable runs alone are worth the "hassle" — try routing 24v cable gauge through a narrowboat hull and you'll age ten years. 🔌 With 3kW of panels you're already in "stop faffing and go 48v" territory; your Victron Multiplus II will thank you, your Fogstar batteries will thank you, and future-you adding more capacity won't have to rip everything out again. The induction hob especially wants clean, efficient power delivery — 48v just makes the whole system less sweaty about it.