Anyone else running Victron MPPT on a narrowboat with shading issues from bridges and trees?

Been living aboard for about two years now and solar has always been a bit of a headache. Currently running a Victron SmartSolar 100/30 with two 200W panels wired in series on the roof. Works brilliantly on open stretches of the canal, but the moment I moor up under trees or go through a long tunnel approach, output just dies completely.

I know series wiring is more vulnerable to partial shading than parallel — one shaded cell drags the whole string down. Thinking about rewiring to parallel to at least keep some output when one panel is shaded. The maths suggests I'd drop from ~40V open circuit down to ~20V, which still sits above my 12V bank's charging threshold, so should be fine.

Has anyone actually done this swap on a boat setup and noticed a real-world difference? Also wondering whether a Renogy Rover with its parallel input handling is any better than the Victron for this specific scenario, or whether I should just stick with what I've got and accept the limitations of canal life.

@VivaroProject series wiring on a narrowboat is always going to bite you — one bridge shadow kills the whole string. I ran the exact same setup on my 57-footer on the Kennet & Avon and it was maddening passing through wooded cuts in the afternoon.

Rewired to parallel last spring and the difference was night and day. Each panel fights its own corner when shaded.

Worth noting the 100/30 handles parallel 24V panels just fine within its voltage window — no need to upgrade the controller.

If you're moored under trees regularly rather than just transiting, you might also consider whether panel positioning is the real culprit. I shifted one panel forward to escape the cratch cover shadow and picked up a meaningful chunk of morning generation.

What's your battery bank — lithium or lead? Changes the conversation somewhat.

@VivaroProject worth noting you're actually in the wrong subforum here — this is Motorhome & Campervan, not Narrowboats 😄 mods might move it.

But yes, been there. Two panels in parallel made a massive difference on my boat. Partial shading only kills the affected panel rather than the whole string.

Also check your Victron app — the SmartSolar 100/30 handles parallel 12V panels brilliantly and you'll still be well within the input limits.

One other thing: panel placement matters more than people think on a narrowboat. Even staggering them slightly fore and aft means bridges rarely shade both simultaneously.

What voltage are your panels running at? That'd help narrow down the best rewiring approach for you.

@VivaroProject had exact same issue at my cabin before I sorted the wiring. Parallel is the way to go for shading — each panel works independently so one bridge doesn't wipe you out completely.

Your 100/30 can handle two 200W panels in parallel no bother, Voc stays lower too which is safer for that controller.

If you want to go further down the rabbit hole, look at panel-level optimisers — SolarEdge do them but they're pricey. Honestly for a narrowboat just rewiring parallel probably solves 80% of your grief for free.

@PanelGraham fair point on the subforum but the advice is solid either way 😄

Owen1991 replied:

@VivaroProject @CliveKnight is right about the series wiring being your main culprit. Worth looking into whether your panels support parallel wiring instead — you'd lose a bit of voltage headroom but partial shading from bridge shadows would only knock out one panel rather than strangling the whole string.

Also, have you checked whether your SmartSolar firmware is up to date? Victron pushed some improvements to the MPPT algorithm a while back that genuinely helped with patchy conditions. Pair that with enabling "Equalize" charging carefully and you might squeeze a bit more out of what you've got before rewiring anything.

If you do go parallel, make sure your cable runs can handle the higher current — it's a common oversight on boats where runs can get quite long. What gauge are you currently running from roof to controller?

@VivaroProject one thing nobody's mentioned yet — the Victron SmartSolar 100/30 has a relatively narrow MPPT tracking range. If you're going parallel with two 200W panels, double-check your Voc doesn't drop below the minimum input threshold under heavy shade, otherwise the controller won't even initiate tracking. Had this exact issue on my tiny house build before I understood the Victron datasheet properly.

Also worth enabling the Equalisation and tweaking the absorption voltage via the VictronConnect app — sometimes the default algorithm is too aggressive for partial-shade scenarios and you lose harvest chasing a voltage point the panels can't reach anyway.

If you're seeing dropout rather than reduced output, that's almost certainly a voltage floor issue rather than purely a wiring topology problem. Log a few days via VictronConnect's history graphs and look at your yield vs. peak irradiance — the pattern usually tells you everything.

TransitProject replied:

@VivaroProject Worth mentioning that narrowboat life adds a specific wrinkle here — you're not just dealing with random shading like a static install, you're getting rapid, repeated shade events every time you pass under a bridge. That's quite aggressive for any MPPT controller to track through efficiently.

Have you looked at the VictronConnect app to check your yield history? You can often see exactly where the dips are occurring throughout the day and get a clearer picture of how much you're actually losing.

Also, what's your battery bank situation? If you're on a decent LiFePO4 setup the controller recovers faster post-shade than with lead acid, simply because the absorption stage is shorter and it gets back to bulk sooner.

The canal orientation matters too — east-west stretches will catch you differently than north-south runs. Might be worth tracking that pattern.