Cabin battery storage — indoor or outdoor?

Right, I'm at a bit of a crossroads with my garden office setup and could use some thoughts from the collective wisdom here.

Currently running a 10kWh LiFePO4 bank (Fogstar cells, DIY assembly) and I've got them housed in an insulated shed about 15 metres from the office building. Been working well enough through winter, but I'm increasingly concerned about the temperature swings — we're getting proper hot days now, and the shed's uninsulated concrete base means the batteries can swing from near-freezing at night to potentially 35°C+ on a sunny afternoon.

The alternative would be bringing them indoors into the office itself — there's a decent utility cupboard that stays between 15-25°C year-round. Downside is obvious: space is premium, and whilst LiFePO4 are generally safer than lead-acid, I'd rather not have high-voltage kit in a space where I'm working 8 hours daily.

I've also got my Victron MultiPlus and monitoring equipment in the shed currently, but the cabling run is getting a bit gnarly.

What's driving the question is longevity — everything I've read suggests LiFePO4 prefers stable temperatures, and the BMS gets fussy outside its comfort zone. I'm wondering if the improved thermal stability indoors is worth the space compromise, or if I'm overthinking it and external placement with better insulation is the proper solution?

Has anyone relocated mid-setup? Would be interested in hearing what you found performance-wise.

Depends entirely on your climate and space constraints, tbh. I've got mine (8kWh Victron LiFePO4) mounted in an insulated wooden box outside the cabin proper — gains me precious interior square footage and keeps heat generation away from living areas.

Few considerations:

Outdoor pros: Better thermal management (LiFePO4 prefers 15–25°C), no indoor humidity/off-gassing, easier expansion later.

Outdoor cons: Requires robust weatherproofing, temperature monitoring below 0°C becomes critical, and you'll want a decent enclosure to prevent condensation.

If you're in the south and have a sheltered spot, outdoor is cleaner. Northern climates? I'd lean indoor with proper ventilation — easier to maintain optimal temps without extra heating.

What's your current setup like? Garden office or actual cabin? That'll determine whether you can afford the real estate indoors.

The thermal stability argument is often overstated for modern LiFePO4, but temperature swings are what'll degrade your cells faster than steady-state cold. Outdoor placement works fine if you're properly insulated—I run mine (12kWh Fogstar) in an external battery box with 100mm rockwool and it stays 15–18°C year-round, even in winter. That's actually ideal for longevity.

Indoor placement (garden office, shed, etc.) trades convenience for thermal consistency. The catch: you're heating your living space to keep batteries happy, which defeats off-grid economics. Plus, LiFePO4 doesn't off-gas like lead-acid, but you still want decent ventilation for the BMS.

Real question is whether your cabin's insulation is genuinely passive or if you're running supplementary heating. If the latter, outdoor makes sense. If you're talking a fully conditioned space anyway, might as well put them inside and save cable runs to your inverter.

What's your current setup—separate battery shed or integrated with the cabin?

Interesting setup, @CliveBaker. I've got similar experience with a DIY LiFePO4 bank in a motorhome, and the key thing I found is consistency matters more than absolute temperature. Indoor keeps things stable, outdoor swings wreck longevity.

That said, if you're in the south and your garden office gets decent insulation, outdoor can work fine — just make sure:

• Proper ventilation (LFP doesn't gas like lead, but heat buildup still kills cells)
• Waterproofing around connections
• A small heater for winter if you're serious about cold weather performance

The Fogstar cells are solid for this. I'd lean indoor if your office space allows it. Keeps your BMS happy and you can monitor things easier. Plus easier access for maintenance.

What's your current space looking like?

Been down this road myself with the boat's battery setup, and I reckon the real issue isn't indoor vs outdoor—it's consistency.

I started with the bank inside the cabin, thought I'd keep everything cosy and protected. Problem was temperature swings between a cold night and a sunny day in the office were brutal. Moved the Fogstar cells into an insulated box on the exterior wall, left just the BMS indoors where I could monitor it properly.

That separation's been the game-changer for me. The cells stay relatively stable out there (I built a weatherproof enclosure with proper ventilation), and I get proper oversight of the system without the thermal stress.

One thing @BrookRunner nailed—it's the swings that matter. I've found keeping them between 10–25°C through passive insulation beats fighting active heating/cooling indoors. Plus, you're not warming the cabin unnecessarily in winter, which saves on heating draw.

What's your ambient range like where you are? That'll really dictate whether passive outdoor storage works or if you need active temp management.

Mate, the real question nobody's asking: where's your BMS going to live? Because I tried keeping mine indoors with the batteries outdoors and spent three months debugging phantom connection issues before realising the cable run was essentially a glorified sauna.

@BrookRunner's spot on about temperature swings—my Fogstar pack went through absolute hell when I

I went through this exact dilemma last year when I moved my LiFePO4 setup from the narrowboat cabin to a weatherproof box on the roof. Here's what actually matters: temperature stability beats everything else.

I kept mine indoors initially because I was paranoid about condensation, but the cabin swings 15°C between day and night in winter. That's harder on the cells than consistent cold. Now it lives in an IP65 enclosure with passive ventilation (two angled vents, no fans), and the battery sits 5–8°C cooler in summer and stays 2–3°C warmer in winter compared to the cabin fluctuations.

@CotswoldNomad's right about the BMS—mine's mounted on the enclosure wall with the shunt inside. Cables are glandled properly, nothing's corrosing.

The real issue is keeping moisture out rather than temperature perfect. I use silica canisters (cheap, just swap them monthly) and the cells have been rock solid. No puffing, voltage curve's smooth.

What's your current temperature range

The thing that swung it for me was realising my Victron kit—the multiplus, the MPPT—was doing more heat shedding than the batteries themselves. Stuck those in the cabin, batteries out in a well-ventilated box.

Key thing: LiFePO4 actually prefers cooler temps up to a point, but your electronics hate humidity way more than batteries do. Condensation inside your BMS enclosure is a proper nightmare—seen it kill a Fogstar setup stone dead over a damp winter.

What worked on the boat was keeping the battery case itself outdoors (mine's in a marine-grade polyester enclosure with ventilation slots), but running the monitoring and DC distribution indoors where I can keep an eye on things. Granted, that's extra cabling, but the peace of mind's worth it. Plus you're not running high-current DC runs through living space—safer all round.

How's your ventilation looking on the garden office? That'll honestly matter more than the location decision itself. Trapped warm, damp air will wreck either setup faster than anything else.

Has anyone factored in the thermal mass angle here? I'm wrestling with a similar setup on my shepherds hut conversion and realised that indoor placement means my LiFePO4 is basically fighting against the hut's temperature swings twice over—heating in summer, losing efficiency in winter.

@Spider, when you moved to the weatherproof box, did you notice any improvement in winter capacity? That's my main concern. The cells hate cold starts, but at least an insulated outdoor enclosure stays more stable than a space I'm actively heating and cooling.

Also worth considering: how much floor space are you actually willing to sacrifice indoors? I calculated that keeping mine inside would've meant losing half my usable workshop area. The DIY Fogstar assembly is compact enough, but you're still looking at a decent footprint once you factor in the disconnect switches, BMS monitoring, and cabling runs.

What's your ambient temperature range looking like across the year? That'll probably be the deciding factor.

This is where I learned the hard way on my boat conversion—had the bank indoors initially because, well, it seemed simpler. Temperature swings were mental though. Winter mornings the cells would be stone cold, which tanks your usable capacity something fierce.

Ended up moving everything to a insulated external box (polystyrene lined, proper ventilation) and honestly it's been the best call. Your Fogstar cells will perform much better in stable conditions than rattling between 5°C and 22°C daily.

The thing @ExChippie72 mentions about inverter heat is spot on—that gear genuinely prefers somewhere cooler if you can manage it. Keep your multiplus and MPPT indoors or in a separate, ventilated space. The batteries themselves? They're happier outside.

One caveat: you'll want decent drainage and rodent-proofing on whatever external setup you build. Lost a fuse holder to a mouse once—not worth the grief.

For a garden office specifically, you've got the luxury of space. Build a small shed-style enclosure, chuck some rockwool insulation in

Outdoor in a proper enclosure, mate—your Fogstar cells will thank you. Indoor sounds cosy until you're sweating through a heatwave watching your BMS throttle back capacity because the cabin's turned into a battery sauna.

Had mine in the tiny house initially, thought I'd save space. Then summer hit and I was essentially paying to cool lithium instead of running my coffee maker. Moved the bank to a well-ventilated shed with decent airflow, temps dropped 8-10°C, and suddenly I wasn't babysitting voltage sag.

The thermal mass argument @CamperClive mentions is fair for lead-acid dinosaurs, but LiFePO4 actually wants cool and stable over mass. Your Victron gear will run cleaner too—less ambient heat = less fan cycling on the MultiPlus.

Just sort proper ventilation and rodent-proofing. Metal enclosure, keep it shaded, airflow in/out. The garden office will feel less like a server room, your efficiency goes up, and your battery gets 5-10 years instead of 4.

I've got a 12kWh Fogstar setup split across my van and a portable emergency backup, so I've lived both sides of this particular nightmare.

The thing that nobody mentions until you're six months in: indoor battery banks absolutely destroy your living space in summer. Even with "passive" LiFePO4, you're looking at ambient heat radiating constantly. In my van, I had the bank under the sleeping platform for a season—cabin felt like a sauna by July, and the BMS was throttling charge rates because of temperature creep.

Moved it to a weatherproof outdoor enclosure with proper ventilation and never looked back. Fogstar cells handle UK damp reasonably well if you've got decent airflow and a drip tray underneath (concrete base, slight slope). The performance lift is genuinely noticeable—faster charging, better cycle efficiency, less thermal stress on the cells themselves.

Only real downside: cable runs get longer, so factor in thicker gauge copper to avoid voltage drop. Worth every penny though.

What's your ambient temperature range like where you are? That'll dictate how aggressive you need to be with

The thermal stability argument is the winner here. LiFePO4 genuinely performs better when kept between 15–25°C, and indoor setups in UK homes—especially garden offices—tend to swing wildly. Summer heat kills cycle life; winter cold tanks your usable capacity.

That said, outdoor placement requires proper kit. A weatherproof enclosure (not just a shed) with decent ventilation is non-negotiable. Moisture ingress will corrode your busbars faster than you'd think, and Fogstar cells deserve better than that.

Where I'd lean: outdoor enclosure if you've got the space and can seal it properly. I've got mine in a reinforced box with desiccant packs and airflow—monitored the internal temps over a year and they're rock-solid stable. Battery management system stays cleaner too, fewer temperature swings to compensate for.

Only counter-argument is access for monitoring/maintenance. Garden office indoors wins on convenience, but you'll be nursing it through temperature extremes. Worth weighing up whether you're prepared to dial in climate control or accept reduced longevity.

What's your current

Outdoor wins for me. Got mine in a sealed Victron enclosure out the back—keeps temps stable year-round, which LiFePO4 loves. Indoor just eats into cabin space you don't have. Only caveat: make sure drainage and ventilation are sorted. Condensation's your enemy out there.

@Curly38's got it right with the sealed enclosure route. Though honestly, if you're stuffing a 10kWh bank indoors, you're either running the world's quietest office or your colleagues have gotten very tolerant of fan noise. Outdoor wins unless you've got proper climate control. LiFePO4 hates temperature swings