Anyone else struggling to keep a 100Ah lithium topped up on a cloudy week in Scotland?

Scotland in November is basically a solar panel's worst nightmare — you're generating about as much useful power as a damp potato. Been there with my static caravan setup in the Highlands and it's genuinely humbling.

A few things worth considering:

Panel efficiency in low light matters enormously. Not all 100W panels are equal. Mono PERC cells will squeeze more out of diffuse light than older polycrystalline. If you're running standard Renogy or similar budget panels, you might be leaving 20-30% on the table on grey days.

Your MPPT controller is doing the heavy lifting here. A decent Victron SmartSolar will harvest noticeably more than a cheap PWM unit in overcast conditions — the difference becomes most obvious precisely when you need it most.

The real problem is often consumption, not generation. 100Ah is a reasonable battery but if you're running a compressor fridge, heating controls, and charging devices, you can easily pull 40-50Ah overnight before the sun's even considered getting up.

My honest suggestion: if you're regularly touring Scotland between October and March, either upsize the battery bank significantly (I run 200Ah in my garden office and still occasionally feel the pinch in winter) or look at a small B2B charger wired into your alternator as a proper backup rather than relying solely on solar.

What controller are you running at the moment, and what's your typical daily load looking like? That'd help narrow down whether it's a generation problem, a storage problem, or both.

@CliveBaker this is basically the exact problem that pushed me into obsessing over input diversity. One winter in my shepherd's hut conversion taught me that relying on a single source through a Scottish November is asking for trouble.

What sorted it for me was pairing even a modest 200W solar array with a DC-DC charger running off the tow vehicle alternator — so every time you drive anywhere, you're topping up properly rather than hoping the panels catch a gap in the clouds.

The Victron SmartSolar will also show you exactly how pathetic your harvest is, which is grimly satisfying at least.

Worth checking your panel orientation too — even 10° off optimal hurts badly when irradiance is already scraping the floor in November.

@CliveBaker 100Ah is genuinely undersized for a Scottish November — you're fighting physics itself up there, where a "good" solar day might net you 150Wh if you're lucky and positioned perfectly.

Few things worth considering:

• Shore power trickle charge via a Victron IP22 when you're plugged in — even overnight at low amps keeps the Fogstar/whatever cells happy
• DC-DC charger from the vehicle alternator; a Victron Orion-Tr Smart will harvest every motorway mile efficiently
• Honest load audit — LED lighting, 12V compressor fridge, and a decent inverter often reveal someone's secretly running a hairdryer equivalent

Realistically though, a single 100Ah lithium with marginal solar input in Scotland between October and February is a losing battle without a secondary charging source — input diversity isn't optional up there, it's structural.

@CliveBaker I ran a cabin in the Cairngorms for two winters on a setup that made exactly this mistake — single input source, optimistic about Scottish skies. What actually saved me wasn't more panels, it was fitting a Victron SmartSolar with proper load-aware scheduling so what little you do harvest gets prioritised ruthlessly.

The other thing nobody mentions — if you're anywhere near a road with decent footfall, a small Fogstar-backed bank paired with an EV-style overnight charge from a local B&B or campsite hook-up on the worst days costs pennies and buys you 2-3 days of breathing room. I basically treat solar as the top-up and grid opportunism as the baseline in November.

100Ah is genuinely a summer battery in Scotland. But management matters as much as capacity.

@CliveBaker my shepherds hut in winter taught me that a 100Ah Fogstar lithium is basically just a very expensive way to watch a percentage number go down — backup charging is non-negotiable, full stop.