What's everyone using for emergency backup when the solar goes down in winter?

Had a rough few weeks in the shepherd's hut — three days of solid cloud and the 200Ah Fogstar lithium was properly struggling. Running a small diesel heater and 12v lighting kept draining it faster than the two 200W Renogy panels could recover in that grey January light.

Ended up relying on a little Honda EU22i petrol genny to top up via a Victron IP22 charger, which did the job but feels like a faff. Wondering if there's a slicker solution — maybe a wind turbine addition or a larger battery bank.

What are others doing as a proper backup plan when solar just isn't cutting it for days at a time? Anyone running a hybrid setup that actually works through a UK winter without constant babysitting?

@Fiona1974 know that feeling well. My go-to is a Honda EU22i generator — stupid quiet and surprisingly fuel-efficient for what it is. I only run it for a couple of hours to top up the Victron batteries rather than running it continuously, which stretches a full jerry can out considerably longer.

One thing worth adding to your setup — a decent Victron BMV battery monitor if you haven't already. Knowing exactly where your state of charge sits means you can intervene earlier rather than letting the bank get hammered.

Also worth checking whether your diesel heater is pulling more than you think on startup — some of those Chinese units spike quite hard on the glow plug cycle. Caught me out first winter.

Really feel for you @Fiona1974 — shepherd's huts can be brutal in a proper grey January.

I've been running a small propane genset as my backup but honestly the game-changer for me was adding a wind turbine alongside the solar. Even on those horrible overcast days you often get decent wind, so the two complement each other brilliantly rather than both failing at the same time.

Worth considering if your location gets reasonable exposure — mine's a Rutland 914i and it's kept the batteries topped up through some genuinely grim winter stretches when the panels were practically useless.

The other thing I'd suggest is keeping a small 20L spare diesel can specifically for the heating circuit so at least that's decoupled from your battery concerns during extended low-generation periods. Reduces the pressure on the bank considerably.

Really feel for you @Fiona1974 — three days of solid overcast in a shepherd's hut sounds grim.

I've been running a 100Ah AGM as a dedicated emergency buffer alongside my main lithium bank for exactly this sort of situation. The AGM takes the overnight load when the lithium's low, which buys me a day or two of headroom.

That said, my proper belt-and-braces solution is a small propane genset rather than diesel — easier cold starting in January when temperatures drop, and I can share the same bottles I use for cooking. Keeps the fuel logistics simpler.

One thing worth checking — are you running any passive loads overnight? A cheap energy monitor like a Victron BMV really opened my eyes to what was quietly nibbling away at my batteries when I thought everything was off.

Good timing on this thread — just came through a similar stretch in Yorkshire.

One thing nobody's mentioned yet: a small wind turbine as a complement to solar works brilliantly for exactly these situations. Grey, overcast days in winter often come with decent wind, so the two sources almost naturally offset each other. I've got a 400W unit alongside my panels and it genuinely saved me during last month's low-pressure system.

Also worth considering a decent battery monitor if you haven't got one — knowing your actual state of charge rather than guessing means you can manage loads much more intelligently before things get critical. Victron BMV-712 changed how I manage my whole system.

@Fiona1974 what's your charge controller situation? Sometimes there's headroom to squeeze a bit more from marginal winter sun that people aren't capturing.

Same setup as you @Fiona1974 — shepherd's hut here too so I get it completely.

My backup is a small Jackery 500 I keep topped up via a separate 100w panel on a south-facing wall. Means even on grim days it's trickling in something. Not enough to run everything but it buys me another day or two before I'd need to fire up a genny.

Also switched to a Webasto diesel heater which draws way less than some of the cheaper units — made a noticeable difference to overnight drain.

Worth checking your Fogstar BMS settings too if you haven't — mine was set conservatively from factory and I managed to squeeze out a bit more usable capacity once I'd adjusted the low voltage cutoff.

On the narrowboat I learned pretty quickly that winter backup isn't optional — it's just part of the setup.

What sorted me out was a small Honda EU22i tucked in the engine room. Quiet enough, efficient enough, and a Victron IP22 charger means it's pushing proper amps into the bank rather than dribbling. Two hours running and I'm back to a comfortable state of charge.

The key thing I'd add that nobody's mentioned — pre-empt the forecast. When I see three overcast days coming on Windy or Yr.no, I top everything off the night before. Battery management is half anticipation.

@Fiona1974 your shepherd's hut situation sounds like the 200Ah just isn't quite enough headroom for winter loads. Worth calculating your actual daily consumption versus what the Fogstar can realistically deliver at low temperatures — lithium capacity drops more than people realise in the cold.

Great thread, really timely for this time of year.

@Fiona1974 one thing worth considering alongside whatever backup gen you settle on is a small wind turbine — even a 400W unit makes a surprising difference during those grey winter weeks because you're usually getting decent wind exactly when the solar is useless. I added a Rutland 914i last autumn and it genuinely transformed my winter resilience.

The other thing I'd suggest is reviewing your loads before reaching for more generation capacity. I swapped my diesel heater's control board fan for a lower-draw alternative and saved nearly 8Ah a day — not massive but it adds up over three cloudy days.

@Gill1983 the Jackery 500 is a decent stopgap but it'll disappear fast if you're running heating overnight. Worth keeping it strictly for lights and phone charging in a real pinch.

Really relevant thread for me — living on a boat means I've had to think hard about this too.

Been looking seriously at a small inverter generator as a shore-power alternative when moored somewhere without hookup. The Honda EU22i keeps coming up as a solid option, though the price is brutal. Anyone tried the cheaper Chinese alternatives like the Hyundai units for occasional topping up rather than continuous run?

Also curious whether anyone's rigged a shore power input with automatic transfer switch so the backup kicks in without manual intervention — seemed like overkill at first but after a few flat battery mornings I'm reconsidering.