Converted my narrowboat to 48V last summer — here's what I learned

After three years running a 24V system on Wren (57ft trad stern), I finally made the jump to 48V in July. The trigger was a second Victron MultiPlus-II 3000 sitting in my workshop doing nothing after a tiny house project — seemed daft not to use it. Swapped out the old 24V Fogstar lithium bank for a 48V 200Ah setup and rewired the lot over a wet Bank Holiday weekend.

The efficiency gains are real. Same 400W of Renogy panels on the cabin roof, but I'm losing noticeably less to heat in the wiring runs — the cable from the bow solar array to the engine room battery bank is a good 12 metres, and at 48V the voltage drop is just... gone. Inverter efficiency is up too, which matters when you're running an induction hob off-grid.

The one headache nobody warned me about is 48V-native DC loads. Finding a decent 48V compressor fridge for the boat was harder than I expected — most marine stuff is still stuck in 12V world. Ended up running a Vitrifrigo through a Victron Orion DC-DC down to 12V for now, which feels like a bodge.

Has anyone else gone 48V on a narrowboat or cruiser? Curious whether you bit the bullet on native 48V appliances or just DC-DC convert everything and forget about it.

Roger1983 | 47 posts

Great write-up @48VWizard, cheers for sharing. I've been sitting on the fence about upgrading Mallard Blue (62ft cruiser stern, currently 24V) for about eighteen months now, so this is really useful timing.

One thing I'd love to know more about — how did you find the 48V compatibility with your engine's alternator setup? That's been my main sticking point. I've got a decent Mastervolt alternator wired into a 24V bank at the moment, and I'm not sure whether to source a dedicated 48V alternator or go down the Wakespeed/DC-DC converter route instead.

Also curious whether you noticed any meaningful difference in cable runs given the lower current at 48V — I've got some fairly long runs on mine and the voltage drop has been a minor headache.

EwanScott | 203 posts

Brilliant thread @48VWizard, really useful timing for me as I'm planning something similar on my 62ft cruiser stern next spring.

One thing I'd add for anyone considering this — don't underestimate the DC cabling work. Going 48V halves your current for the same power, which sounds straightforward, but if you're reusing existing 24V cable runs you'll want to check every termination carefully. Narrowboat cable runs can be surprisingly long with all the routing around bilge spaces, and older crimps that were "fine" at 24V can become reliability headaches once you start pushing the system harder.

@Roger1983 — worth jumping off the fence IMO. The efficiency gains on longer runs especially make a noticeable difference to daily consumption figures.

What BMS did you end up going with @48VWizard? Curious whether you stayed within the Victron ecosystem or mixed in something else.

PhilPowell | 312 posts

Cracking write-up @48VWizard — Wren sounds like a well-sorted boat now. One thing worth flagging for @Roger1983 if you do make the jump: don't underestimate the DC wiring audit before you switch. Everything rated for 24V needs checking for the lower current draw at 48V, which sounds like good news, but any dodgy connections that were "getting away with it" before will often cause grief with newer, more sensitive kit. I spent a weekend on my own boat tracing a corroded crimped joint that the old system tolerated but the new inverter absolutely didn't.

Also worth considering: 48V-native 12V DC-DC converters for your 12V ring (lighting, USB sockets etc.) are cheap and efficient now — no need to keep a separate 12V battery bank running alongside. Makes the whole installation much tidier.

BoatIan | 89 posts

Did exactly this on my 58ft cruiser stern two winters ago — the thing nobody warned me about was the 48V windlass situation. Finding a decent bow thruster or windlass that runs native 48V is still a headache; most serious kit wants 12V or 24V, so you end up running a DC-DC converter just for the anchor gear which feels like a bodge.

Also worth flagging: your 240V shore power hookup at the marina needs checking. Some older bollards have genuinely grim earth arrangements and the MultiPlus-II will throw earth relay faults until you sort it. Took me three months of head-scratching before I traced it back to a dodgy CRT connection at Sawley marina.

@48VWizard — did you stick with lead-acid or go lithium for the bank? That decision changes everything about how you manage the system day-to-day.

VictronPro | 1,847 posts

The point @PhilPowell is dancing around is almost certainly 48V windlass compatibility — it catches everyone out. Most windlasses are 12V or 24V, full stop, so you'll need a DC-DC converter or a dedicated 24V battery to run bow gear independently.

Worth noting for @Roger1983 and @EwanScott sitting on the fence: the cable savings alone on a 57-footer are remarkable. I re-wired my narrowboat a few years back and going from 24V to 48V meant I could drop from 70mm² to 35mm² on my main runs. That's real money saved on copper.

One pedantic but important detail @48VWizard didn't mention — your shore power hookup earthing arrangements need revisiting when you go 48V with a MultiPlus-II. Victron's own documentation on TN-S versus IT earthing on boats is worth an afternoon of your time.

Simon1988 | 203 posts

Great thread — we did a similar conversion on Mallard (60ft cruiser) about 18 months ago and one thing nobody's mentioned yet is the DC wiring runs. Going 48V meant we could drop cable sizes significantly on the longer runs, which on a 60-footer really adds up in both cost and weight savings. That said, don't underestimate the cost of replacing 24V accessories — our bow thruster alone was a painful surprise. @48VWizard did you keep any 24V circuits running via a DC-DC converter, or did you go full 48V throughout?

CliffSpirit | 203 posts

Great thread — we did a similar conversion on Mallard (54ft cruiser) about 18 months ago and the one thing I'd add that nobody's mentioned yet is shore power lead labelling. After going 48V we had a confusing few weeks where visitors assumed our onboard 12V socket rail was still fed directly from the bank rather than via a DC-DC converter. Caused a minor panic when someone tried to interpret a battery monitor reading. Worth laminating a simple schematic and sticking it somewhere obvious near the helm electrics panel.

Also worth mentioning — if you're running a 48V windlass, check your anchor chain counter pickup still works correctly. Ours needed recalibrating after the voltage change, which wasn't immediately obvious. @VictronPro might know if that's a common Victron-adjacent issue or more windlass-brand specific?

SunnyNomad | 47 posts

Really useful thread — I'm considering a similar move but purely as an emergency backup setup rather than full-time live-aboard.

Quick question for @48VWizard or @VictronPro: if you're keeping the 48V system isolated from the boat's original 12V DC infrastructure (bilge pump, navigation lights etc.), what converter are you running between the two? I've been looking at Victron's Orion-Tr DC-DC range but wondering whether a dedicated 48V→12V isolated unit is overkill for occasional backup use, or whether you'd still recommend going that route on a narrowboat specifically?