Anyone know if a 200Ah lithium battery will run a small chest freezer overnight?

Running a small chest freezer off-grid is something I've been trying to work out the maths on before committing to a purchase. My setup currently uses a 200Ah Fogstar Drift LiFePO4, and I'm trying to figure out whether it can realistically handle overnight freezer duty without wiping out the battery.

The freezer I'm looking at is a 60-litre chest unit rated at around 45W, but I know compressor-based appliances cycle rather than run continuously, so real-world consumption is obviously lower.

A few specific questions:

• What's a reasonable duty cycle to assume for a small chest freezer in a cool environment (garage, UK climate)? I've seen figures suggesting 20–35% but that seems like a wide range.
• Is 200Ah genuinely sufficient for an 8–10 hour overnight period, assuming I want to stay above 20% state of charge to protect the cells?
• Does ambient temperature significantly affect compressor cycling in a way that would make winter use notably more efficient?

My solar array isn't producing much this time of year, so realistically the battery would be going into the night at maybe 80–90% and relying entirely on stored capacity until morning. I'm using a Victron SmartShunt so I can monitor consumption accurately once I get the freezer running, but I'd rather not just plug it in and hope for the best.

Has anyone actually logged overnight consumption on a similar setup? Real-world data from a Victron BMV or similar would be genuinely useful rather than theoretical calculations, which I can do myself.

@ZoeGrant ran this exact scenario at my cabin last summer. Small chest freezer (Currys own-brand, around 90L) pulled roughly 30–35Ah per 24 hours once the ambient temperature settled — so overnight you're looking at maybe 12–15Ah. Your 200Ah Fogstar will barely notice it.

The caveat nobody mentions: startup surge. Every time the compressor kicks on it draws 3–4x the running wattage for a second or two. Worth checking your inverter's surge rating handles that comfortably.

Also factor in what else you're running overnight. The freezer alone? No bother whatsoever. Add lighting, a fan, phone charging — still fine, but start mapping your actual loads. A Victron BMV-712 transformed how I understood my consumption; stopped guessing entirely.

Really depends on the freezer's duty cycle and ambient temperature, @ZoeGrant. A typical 90-100L chest freezer might draw 80-150W when running, but only cycles maybe 25-35% of the time overnight — so realistic consumption is often 150-250Wh across 8 hours.

Your 200Ah Fogstar Drift gives you roughly 2,000Wh usable (keeping above 20% SOC), so overnight running is very achievable — you'd barely dent it.

Worth checking:

• Compressor start surge — most inverters handle this fine but worth confirming yours does
• Ambient temperature — a cold garage means the freezer works less
• Inverter efficiency losses — budget around 10% overhead

I ran a similar setup in my motorhome last winter using a Victron MultiPlus, and the freezer was genuinely the least of my worries consumption-wise. The kettle causes far more damage! 😄

Good question to stress-test before committing. One thing worth adding to what @SimonKelly mentioned — the depth of discharge matters as much as the raw capacity figure.

A 200Ah Fogstar Drift gives you roughly 2.56kWh usable (assuming 12.8V nominal). A small chest freezer in a cool location might average 30–50W, so overnight (say 10 hours) you're looking at 300–500Wh consumed — well within range if the battery is fully charged going in.

Key variables I'd check:

• Where is the freezer located? Ambient temp massively affects duty cycle
• Are you recharging via solar or generator the following morning?
• What inverter are you running? Startup surge can catch people out

I'm working through similar calculations for my static caravan setup with EV charging in the mix, so headroom matters — I'd want at least 150Ah spare before feeling comfortable.

Good points from @SimonKelly and @BlownFuse already. One thing I'd add, @ZoeGrant — location matters more than people realise. If your freezer's sitting in an uninsulated shed in winter, it'll actually use less power because the ambient temp is doing some of the work. Shove it in a sunny outbuilding in July though and duty cycle rockets. I ran a similar setup last year and found a decent programmable plug (something like a Tapo P115) brilliant for monitoring actual consumption over a few days before you commit. Real-world data beats any spec sheet. Also worth checking your Fogstar's low-temp discharge rating if it's going somewhere cold overnight — LiFePO4 can get a bit grumpy below about 5°C. 🙂