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

Got a bit of a dilemma and hoping someone here has done the math already.

Running a small chest freezer (Cookworks 60L from Argos, pulls about 80W when the compressor kicks in) in my static caravan. Currently got a single 200Ah lithium on a Victron SmartShunt and it's managing daily loads fine, but I'm nervous about leaving the freezer running overnight without solar topping things up.

From what I can work out:

• Compressor cycles roughly 30-40% of the time
• So maybe 80W × ~35% duty cycle = ~28W average draw
• Over 8 hours that's roughly 224Wh
• 200Ah at 12V = 2400Wh, so even at 80% usable that's 1920Wh

On paper it looks dead comfortable, but I've heard chest freezers can behave weirdly when it's warm — compressor running longer cycles, etc. Mine's sat inside the van so ambient temps are fairly stable.

Has anyone actually monitored a similar setup overnight with a SmartShunt or similar? Curious whether real-world figures match the theory or if there's something I'm missing. Also wondering if the startup surge is worth worrying about — Victron MPPT into a Fogstar Drift 200Ah here.

Really depends on your duty cycle more than anything. A chest freezer like that typically runs the compressor maybe 30-40% of the time once it's at temperature, so you're looking at roughly 25-35Wh actual draw per hour rather than the full 80W.

Overnight say 8 hours = roughly 200-280Wh consumed.

On a 200Ah lithium (assuming 12V, so ~2400Wh usable at 100% DoD, though I'd keep it above 20% personally), you've got loads of headroom for just the freezer.

Main question is what else you're running alongside it? My 200Ah Fogstar setup handles my fridge overnight no problem but once I start adding lighting and phone charging it all adds up faster than you'd expect.

What's your charging source for the battery? That'll affect whether you can sustain it longer term more than the overnight capacity question.

Good question — I've been wondering the same thing for my emergency backup setup.

@Mike1980 makes a good point about duty cycle. One thing I'd add: what's your battery's usable capacity? A 200Ah lithium (say a Fogstar Drift or similar) at 100% DoD gives you the full 200Ah, but if you're running a Victron SmartShunt you'll see real-world figures quickly enough.

Quick rough calc:

• 80W compressor at ~35% duty cycle ≈ 28W average draw
• Over 8 hours = 224Wh
• At 12V that's roughly 19Ah — well within 200Ah

That looks comfortable on paper, but has anyone actually logged their freezer's duty cycle in winter vs summer? I'd imagine a cold caravan overnight means the compressor barely kicks in. Does ambient temperature make a meaningful difference to real consumption figures?

@Mike1980's cut off but he's absolutely right about duty cycle being the key variable.

Here's my experience from my motorhome setup: a chest freezer like that typically runs the compressor 30–40% of the time once it's pre-cooled. So your 80W becomes roughly 25–32W average draw.

Over 8 hours overnight that's around 200–256Wh.

A 200Ah LiFePO4 (Fogstar Drift, for example) gives you roughly 2,000Wh usable at 100% DoD — but sensibly you'd use 80%, so 1,600Wh.

You're looking at ~12–16% of your capacity for one night. Totally manageable.

The catch: ambient temperature matters massively. A warm static caravan in summer means the compressor works harder. And if the freezer is warm when you start — forget those numbers, it'll run flat out for hours.

Pre-cool on mains before switching to battery. Every time.

@LiFePO4Nerd is right that duty cycle is the crux of it, but worth adding the usable capacity angle too.

A 200Ah LiFePO4 (Fogstar Drift or similar) at 12V gives you ~2.4kWh. Your Cookworks at ~30-35% duty cycle averages roughly 25-28W, so an 8-hour overnight is around 200-225Wh — well within limits even accounting for inverter losses (assume 10-15% overhead).

Practical caveat: how full the freezer is matters enormously. A near-empty chest freezer cycles far more aggressively because there's minimal thermal mass to hold temperature. Pack it with water bottles and your duty cycle drops noticeably.

I run a similar setup in my shepherd's hut and the freezer is genuinely one of the least problematic loads — far more predictable than EV charging. The battery will handle it comfortably; just ensure your inverter is rated well above 80W surge.

Done this exact calc for my garden office setup.

@PaulCross and @LiFePO4Nerd have covered the theory well. Real-world number to add: chest freezers typically run compressor about 30-40% of the time once stable temperature is reached (less if it's well-packed and the ambient isn't roasting).

So your 80W × ~35% duty cycle = roughly 28W average draw. Over 8 hours that's ~224Wh, which a 200Ah LiFePO4 barely breaks sweat over — you're talking maybe 10-12% depth of discharge.

Where it gets trickier:

• Startup surge (compressor kick) — shouldn't be an issue for any decent LiFePO4 BMS
• How full/insulated the freezer is
• Ambient temp in the caravan overnight

Something like a Fogstar Drift 200Ah would handle this no problem. Just make sure your inverter is rated for the startup surge.