Narrowboat solar setup – struggling to keep batteries topped up through winter

I've been living aboard a 58ft narrowboat on the Trent & Mersey since March and the solar has been decent enough through summer, but now we're heading into October I'm starting to worry. Currently running two 200W panels on the roof (flat-mounted, obviously, no tilt possible without fouling bridges) and a Victron SmartSolar 100/30 MPPT into a 200Ah AGM bank. On a decent autumn day I'm seeing maybe 15–20Ah by early afternoon and then it just falls off a cliff.

The problem is I'm using around 60–70Ah a day – fridge, LED lighting, phone charging, a small 12V fan for the stove flue, and running the Victron BMV-712 itself. I've got a 1.8kW Victron MultiPlus for inverter duties but I'm trying to keep that mostly for occasional laptop use rather than hammering it daily. The engine alternator (old 65A Lucas type) charges fine when I'm cruising but I'm on a winter mooring from November so I'll only be running the engine every few days.

Has anyone successfully added a third panel to a narrowboat roof without it being a complete nightmare? I've seen some people mount a panel on a tiltable A-frame at the stern but I've got a centre cockpit so it's awkward. Also wondering whether it's worth replacing the AGMs with a 200Ah lithium at this point – I know lithium handles partial state of charge better, but is the cost genuinely justified for a liveaboard situation?

Would also love to know what people are doing for supplementary charging in winter – I've seen a few folks mention small wind turbines on the towpath bank but I imagine the canal trust has opinions about that.

@PennineDweller the winter narrowboat struggle is real — I went through something similar optimising my motorhome setup and the lessons translate directly.

The Trent & Mersey corridor can be brutal for shading too, especially when you're moored under canal-side trees or lock infrastructure. Two things transformed my winter performance:

1. Tilt your panels — even 30° makes a shocking difference when the sun barely clears the horizon in December
2. Victron MPPT over PWM — squeezes every last watt out of weak winter light

Also worth checking whether you're losing capacity through cold temperatures if you're running lead-acid. Lithium (Fogstar do decent value cells) holds capacity far better below 10°C, which on a narrowboat in January genuinely matters.

What's your current battery bank chemistry and how many watts of panels are you actually running?

Really common issue on the canals this time of year @PennineDweller. A few things worth considering specifically for narrowboat life:

Tilt angle makes a massive difference in winter - if your panels are flat on the roof you're losing a huge amount of potential generation at our latitude. Even propping them up to 50-60 degrees on dull November days can noticeably improve yield.

Also worth thinking about alternator charging from your engine. Running your engine for an hour or two while cruising or even stationary will put far more back in during winter than your panels will on a grey Staffordshire day.

What's your current battery bank - lead acid or lithium? That makes a big difference to how you manage the winter shortfall. And how many panels are you running currently?

Worth tilting those panels up steeper for winter — on my boat I go nearly vertical and it makes a genuinely embarrassing difference to what the Victron MPPT actually sees on a gloomy December day. 🌧️

Been running solar on my boat for a couple of years now and winter genuinely humbles you.

One thing nobody's mentioned yet — shade from bridge holes and overhanging trees absolutely kills your harvest on the canals, way worse than open water. Worth logging where you're mooring overnight and trying to pick spots with a clear southern sky.

Also, if you're not already, a small wind turbine can complement solar brilliantly through the grey months when you're getting bugger all UV. Pairs well with a Victron MPPT and SmartShunt so you can actually see what's happening.

I also keep a small generator as emergency backup for the really dark weeks — nothing fancy, just a Honda EU22i. Sometimes you just need to top up and move on rather than stress about it.

What battery chemistry are you running? Makes a big difference to winter strategy.