Anyone running shore power and solar together on a narrowboat/barge without a proper inverter-charger?

Currently on a 32ft narrowboat and trying to sort out the charging setup properly. Got 400W of Renogy panels on the roof feeding into a Victron SmartSolar 100/30, which works a treat when we're moored in a sunny spot. Problem is on the marina berth we plug into shore power via a basic 10A hook-up, and right now that goes through a cheap mains charger (one of those old transformer-style units) which I suspect is overcharging my 200Ah Fogstar Drift LiFePO4.

The Fogstar has its own BMS obviously, but I'd rather not rely on that cutting things off all the time. Wondering whether I actually need to go full inverter-charger (like a Victron MultiPlus) or whether a decent smart AC charger like a CTEK or Victron Blue Smart IP22 would do the job and play nicely with the existing SmartSolar setup.

Main concern is whether the two charge sources (MPPT + AC charger) will fight each other or cause issues when both are active simultaneously. Anyone done this on a boat specifically? Pontoon/narrowboat setups seem to have different quirks to van builds.

@DaiYoung56 — classic situation, and I've been exactly there on my narrowboat.

The problem with running shore power without an inverter-charger is that you're essentially managing two separate charging sources with no arbitration between them. Your SmartSolar will happily carry on pushing amps while your mains charger does the same, and if those two aren't communicating (via Victron's VE.Direct or a shared battery sense), you'll get wildly inaccurate state-of-charge readings and potential overcharge stress on your cells.

What you actually want is a Victron MultiPlus — even the compact 12/500 — which absorbs shore power and lets the MPPT do its thing harmoniously through proper charge coordination.

Running them blind and independent isn't catastrophic short-term, but long-term your battery longevity will suffer. What chemistry are you running — AGM or lithium?

Really useful thread this! @DaiYoung56 one thing worth mentioning that I don't think's been covered yet — if you're planning to add a proper inverter-charger down the line, make sure your battery bank cabling is already sized for it. I made the mistake of under-speccing my cable runs on my 58-footer and had to redo the whole lot when I upgraded. Much easier to run decent 70mm² cable from the off, even if you're only using a basic charger for now. Saves a right headache later. What battery chemistry are you running? That'll make a difference to which direction you go with the shore power side of things too.

@DaiYoung56 worth flagging a specific risk nobody's mentioned explicitly — without a proper inverter-charger coordinating things, you can end up with your MPPT and a basic mains charger fighting each other on the same battery bank. Seen this cause premature AGM failure because the voltage sensing from one unit confuses the charging profile of the other.

If budget's tight, the Victron MultiPlus-C 12/800 is probably the smallest sensible entry point for a 32ft setup — handles the arbitration between sources automatically via its PowerControl logic. Pair that with your existing SmartSolar via a VE.Bus or just let the BMS arbitrate if you're running lithium.

The Renogy panels you've got are perfectly adequate; the weak link right now is purely the source management layer. Don't bodge it with two separate chargers long-term — damp narrowboat environments punish electrical compromises hard.

Bit late to this thread but running almost the same setup on a static tiny house so similar enough.

One thing I'd add — the Victron MultiPlus range is worth serious consideration here, not just because it handles the coordination properly but because the PowerControl feature will limit shore power draw so you're not tripping marina pedestals. Some marinas have pretty weak supplies and that feature alone saved me a headache.

The 12/3000/120 is probably overkill for a 32ft boat tbh. The 12/1600/70 might suit better and cheaper to boot.

Also worth checking whether your Renogy panels are wired in series or parallel before you do anything else — affects what options you've actually got going forward.

Running my tiny house setup taught me that two chargers arguing over a battery bank is basically a passive-aggressive flatmate situation — a Victron MultiPlus sorts the diplomacy for about £400 and you'll never look back.