Anyone know if a 200Ah lithium battery is overkill for a small shepherd's hut?

So I've been going back and forth on this for weeks and could do with some outside perspective.

I'm fitting out a small shepherd's hut — about 14ft — primarily for weekend use, occasionally a week at a stretch during summer. The loads are pretty modest:

• 12V LED lighting (maybe 50W total across the hut)
• A small 12V compressor fridge (roughly 40Ah/day from what I've read)
• Phone/laptop charging
• Possibly a small 12V fan in summer

I've been looking at a Fogstar Drift 200Ah because the price is genuinely hard to argue with right now, but I'm second-guessing whether 200Ah is sensible or whether I'm massively overspeccing for what's essentially a weekend retreat.

My rough back-of-envelope maths puts me at maybe 60-70Ah per day under normal use, which would mean a 100Ah battery only gets drawn down to around 50% daily — fine for lithium, obviously. The 200Ah would barely break a sweat.

The counterargument I keep coming back to: lithium likes being cycled shallowly, a larger bank means less stress on the cells long-term, and the price difference between 100Ah and 200Ah isn't enormous these days.

But then — is there a point where too much capacity becomes a problem? I'm planning a modest solar input (maybe 200W of panels), so I'm wondering whether I'd even be able to fully recharge a 200Ah bank on a typical British summer day, let alone autumn.

Has anyone been through similar sizing decisions for a small static setup? Would you go 100Ah and keep it simple, or is the 200Ah genu

@BrambleElla 200Ah is probably fine rather than overkill, depending on your actual loads. The critical question is what you're running — a small 12V compressor fridge alone will chew through 40-50Ah per day in summer. Add lighting, phone charging, maybe a 12V fan, and you're realistically at 60-80Ah daily.

With lithium (assuming Fogstar or similar), you've got ~180Ah usable at 90% DoD. That gives you roughly 2-2.5 days of autonomy without solar input, which matters enormously for UK weather where you might see three overcast days consecutively.

I'd argue 200Ah is the minimum sensible starting point for a habitable off-grid space here. Going smaller to save money often means compromising comfort or buying again in 18 months. What's your planned solar input — that calculation changes everything.

@BrambleElla 14ft weekend hut, 200Ah lithium is fine tbh. Not overkill at all once you factor in that you shouldn't really drain lithium below 20% anyway — so you're working with closer to 160Ah usable.

What's actually running off it? That's the bit nobody's mentioned yet. LED lighting and phone charging barely touches it. Throw in a 12v compressor fridge and suddenly you're actually using that capacity.

Had a similar debate with my static — ended up wishing I'd gone bigger first time round. Cheaper to size right once than upgrade later.

If budget's tight, Fogstar do decent cells. Victron if you want proper monitoring and don't mind spending more. Worth it for the BMS peace of mind alone imo.

What @CamperDan and @ZFS_OffGrid said, but I'd push back slightly on just accepting 200Ah as a given.

The real question is your solar input. A 200Ah LiFePO4 sitting in a shaded spot with a single 100W panel is going to cause you grief in winter — you'll be cycling it hard and never fully recovering.

For a 14ft weekend hut I'd honestly consider:

• 100Ah battery + decent solar (200W+) = often better than 200Ah + poor harvest
• Fogstar Drift cells if you're going DIY, solid quality for the money

I've got a garden office setup on 200Ah and two 200W panels, and even that gets marginal December through February in the UK. A shepherd's hut is presumably more exposed to shading risk depending on your site.

What's your solar situation looking like?

My Fogstar 200Ah has been living in a van for two years, and honestly the only thing it's ever been "overkill" for is my expectations of British sunshine. ☀️