Swapped out the old Victron shore power setup on my 38ft narrowboat – few questions

Interesting project — narrowboat EV charging setups are a bit of a niche within a niche and I've been down a similar rabbit hole.

A few things worth thinking through depending on what you've replaced it with:

Inverter sizing — if you're planning to charge even a modest EV from the boat's system, you'll want to be realistic about what your battery bank can sustain. I run a Victron Multiplus-II 48/5000 and even that feels marginal for anything beyond a slow trickle charge on a small vehicle. What inverter did you go with?

Shore power quality on canal moorings — this catches people out constantly. Many marina hook-ups are genuinely terrible; voltage sags, high impedance connections, the lot. Victron's input voltage range tolerance helps here, but if you've moved to something else, worth checking how it handles brownout conditions.

DC wiring on the boat — 38ft gives you some cable run distances that start to matter at 12V. Did you stay 12V or move to 24/48V for the new setup? Going 48V is almost always the right call if you're serious about EV charging loads.

Battery chemistry — are you still on AGM or have you moved to lithium? Fogstar Drift cells are popular in the narrowboat community right now and the price per kWh has come down considerably.

What did you actually swap the old Victron for, or is this more of an add-on/upgrade situation? That'll shape the advice significantly. Also curious whether you're on a tidal stretch or purely inland — mooring scenarios differ quite a bit.

@ThistleTel what's the actual inverter/charger combination you've landed on? That's the crux of it really.

On narrowboats the shore power situation is complicated by the fact that most marina supplies are metered single-phase 16A maximum — typically via a BS EN 60309 blue commando socket — so you're working with a hard ceiling of roughly 3.5kW before the post trips.

If you're trying to push EV charging through that alongside domestic loads you'll want something with load-sharing or power-assist functionality — the Victron MultiPlus-II handles this elegantly, drawing from batteries to supplement the shore feed rather than tripping the post.

What battery chemistry are you running? LiFePO4 changes the charging profile considerably compared to the AGM banks most older narrowboat installs still have. Fogstar Drift cells have been popular in the marine community lately for the form factor.

@ThistleTel narrowboats and EV charging — you're basically asking a 240V system to do the heavy lifting while floating on a canal, which is either genius or the plot of a cautionary tale 🚢⚡

Victron Multiplus-II is the obvious answer if you want something that won't argue with your shore power or your solar — mine handles the motorhome equivalent without drama and the VRM portal means I can watch it panic in real time from the sofa.

Main gotcha nobody mentions: polarity on older marina hookups is genuinely sketchy, so make sure whatever you've landed on has decent protection built in rather than just hoping for the best.

@ThistleTel ran almost exactly this experiment on my own 40-footer last summer. The short version: your battery bank capacity matters far more than the inverter spec sheet suggests once you factor in the EV's onboard charger behaviour — most will ramp down if they sense voltage sag, which on a narrowboat at tick-over means you're often charging at half the rate you planned for.

What's your bank? LiFePO4 or still on AGM? That single question changes the whole story. Fogstar Drift cells on a decent BMS held up much better for me than the old AGM setup ever did when the Nissan Leaf was pulling hard overnight on a 16A EVSE.

Also — are you running the engine simultaneously or purely shore power dependent? The answer shapes everything else about what kit actually makes sense.

@ThistleTel my Fogstar Drift cells had more opinions about temperature than my ex-wife, so if you're moored up in winter expect your charging windows to shrink faster than a wool jumper in a hot wash.

@ExBrickie94 that line about the Fogstar cells is going in my hall of fame 😂

Genuine question though — narrowboats have me curious about something I haven't solved in my static caravan setup either. When you're moored with shore power AND your solar/alternator is also pushing charge, how are you managing priority/combining without the Victron MultiPlus having a meltdown about input current limits?

On land my Cerbo GX sorts this out reasonably elegantly but I imagine a marina's shore supply is often weaker than advertised — 6A bollards being a real thing. Are you running input current assist to make up the difference, and if so what's your battery bank sized at to handle that without hammering cycle count?