Converted an old shepherd's hut last summer — still can't get the battery bank right

Did something very similar about 18 months ago — converted a 1970s hut that had been rotting in a field corner for years. Took longer than expected (don't they all) and the battery sizing is genuinely the hardest part to get right when you can't predict your actual usage until you're living with it.

My first mistake was undersizing. Went in with two 100Ah Fogstar lithiums thinking it'd be plenty for lighting, a small fridge, and occasional phone charging. Worked fine through summer but the moment October arrived and the solar dropped off, I was constantly nursing the state of charge.

Eventually landed on four 200Ah cells in a 24V configuration with a Victron SmartSolar doing the management, and that's transformed things. The Victron app alone is worth the premium — being able to actually see what's happening rather than guessing changed everything.

The thing nobody really warns you about is how much small loads add up. That little fridge cycling every few minutes is surprisingly hungry over 24 hours.

What's your current setup — panels, battery chemistry, inverter? And are you grid-tied at all or fully island? Makes a big difference to the conversation. I've also been tinkering with adding a small EV charging capability for when the bank is full and solar is throwing away excess, which throws its own complications into the mix.

Would love to hear where others have landed on this — feels like every hut has its own personality when it comes to power demands.

Barry1965 | 847 posts | West Yorkshire

@Davo49 Ha, the eternal struggle! I went through three different configurations before I got mine settled. One thing that really helped me was logging actual usage over a fortnight rather than relying on calculated estimates — the difference was eye-opening. Shepherd's huts are tricky because the thermal mass is so poor compared to a brick building, so heating loads in winter absolutely hammer the bank in ways your summer figures won't predict.

What's your current setup — lithium or lead-acid? And are you on solar only or have you got a backup charger? Makes a big difference to the sizing conversation. Also worth knowing whether it's occasional weekend use or longer stays, because that changes the whole approach entirely.

Don't give up on it — once you crack the sizing it's genuinely satisfying. Mine's been running sweet for two years now.

MoorLee | 312 posts | Array

@Davo49 Battery sizing a shepherd's hut is basically the universe's way of teaching you humility 😄 I reckon the hut's original shepherd had it easier — just a candle and existential dread.

On the actual problem though — what's your current setup? Because "

LazyFisher | 634 posts | Array

My narrowboat taught me that whatever size battery bank you think you need, double it, then add another 20% for the things you'll plug in at 11pm when you've had a couple of tins. 🔋

Trigger | 1,247 posts | Array

The hut conversion is where I learned to actually log consumption rather than estimate it. Ran a Victron BMV-712 for a full fortnight before touching the battery sizing question — the data was genuinely humbling compared to my spreadsheet assumptions.

Worth noting that shepherd's huts have unusual thermal mass behaviour too. My heating draw in shoulder seasons (March/October) was far more variable than peak winter, which threw my worst-case calculations completely.

Currently running 400Ah of Fogstar Drift LiFePO4 in mine and it's about right for year-round use with a small wood burner taking the heating edge off. The critical metric isn't total capacity — it's your overnight load during consecutive low-solar days. Run those numbers specifically before committing.

@Davo49 what's your current panel array and typical overnight load looking like?

LochChild | 89 posts | Array

Had the same headache with mine. Ended up going Fogstar Drift 200Ah LiFePO4 — thought it'd be plenty, then realised I'd completely forgotten to account for the inverter standby draw overnight. Classic mistake.

Worth actually metering everything for a week before you commit to a bank size. Plug-in energy monitors from Amazon, couple of quid. Stick one on anything with a transformer or standby mode.

@Trigger is right about logging — gut feel is useless for this stuff. My gut was wrong by about 40%.