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

Running a small chest freezer overnight is something I've been trying to figure out for my setup before committing to buying additional battery capacity.

Currently running a 200Ah LiFePO4 (Fogstar Drift 12V) with a 400W solar array, and I want to add a small chest freezer — probably something like a 100-litre unit — to run predominantly overnight when there's obviously no solar input.

From what I've read, a typical small chest freezer draws somewhere between 80–150W when the compressor is running, but the duty cycle is the critical variable here. In a cool environment (garage, around 10–15°C) I'd expect maybe 25–35% duty cycle, which works out to roughly 20–50Wh per hour, or 160–400Wh overnight across an 8-hour period.

A 200Ah 12V battery gives you 2,400Wh theoretical, but realistically you'd want to stay above 20% SoC, so usable capacity is closer to 1,920Wh. On paper that looks more than sufficient, but I'm uncertain about a few things:

• Does the compressor startup surge cause any issues with a standard 1,000W inverter?
• How much does ambient temperature actually shift the duty cycle in practice?
• Would I be better off running a 12V compressor-based fridge/freezer directly rather than through an inverter at all?

Has anyone actually done this and monitored the consumption with something like a Victron BMV or similar? Real-world figures would be genuinely useful rather than relying on manufacturer specs, which seem optimistic at best.

Also worth noting my solar recharge window in winter is pretty limited here in the north of England, so overnight draw

@QIH_Electric depends entirely on how often your compressor cycles, but a small chest freezer typically pulls 30-60W when running and cycles maybe 20-30% of the time, so you're looking at roughly 150-300Wh overnight — well within 200Ah LiFePO4 territory even keeping above 20% SOC.

Mine runs a freezer on the boat no bother, though I'd stick a smart plug with energy monitoring on it for a week first before assuming anything — real-world draw varies wildly depending on ambient temp, how full it is, and seal condition.

Fogstar cells are solid, just don't let your BMS cut out mid-night or you'll defrost your fish fingers.

@QIH_Electric I ran a similar experiment on my static caravan last summer with a Kill-A-Watt meter before committing to extra capacity. The ambient temperature is the sneaky variable nobody mentions — a freezer working hard in a 30°C July is a very different beast to the same unit in a 10°C October night.

Worth asking: what's the freezer actually set to? Many people run them unnecessarily cold, which hammers the compressor cycle rate.

Rough maths though — if you're averaging 40W draw with a 50% duty cycle, that's ~20W average = ~160Wh over 8 hours. Your 200Ah pack at 12V is 2400Wh theoretical, so even at 80% usable capacity you've got enormous headroom unless you've got other loads competing for that battery. What else is running overnight?

@QIH_Electric speaking from bitter experience here — ambient temperature is the variable everyone ignores until it bites them.

I ran a Lec CF100 on my narrowboat through a February freeze and consumption nearly doubled compared to summer figures, because the bilge air was damp-cold and the compressor struggled to maintain temperature differential. Conversely, a well-insulated chest freezer in a cool space is remarkably efficient.

Your 200Ah LiFePO4 holds roughly 2.56kWh usable at 80% DoD. A decent small chest freezer might average 40-50Wh/hour — so you're looking at 50-60 hours theoretical headroom, assuming nothing else is drawing.

That said, @WheresMeWires87 is right about compressor cycling being critical. If your freezer is elderly or partially loaded, all bets are off. Get a plug-in energy monitor on it for a week before deciding.

@QIH_Electric done exactly this on my static. Small chest freezer overnight on a 200Ah LiFePO4 is totally doable — mine typically uses 300-400Wh over 8 hours in decent temps. That's well within a 200Ah bank even staying above 20% SoC.

One thing nobody's mentioned yet — chest freezers are much more efficient than uprights for this. The cold air stays in when you open it. Makes a real difference to compressor cycles.

Worth logging actual consumption with a smart shunt (Victron BMV is good) for a week before committing. Seasonal variation matters too, @RetiredNurse is right about ambient temps affecting things massively in winter.

Great question and the replies so far are spot on. One thing worth adding — the freezer's duty cycle is massively affected by how full it is. A full freezer (even with water bottles if you're short on food) holds temperature far better and the compressor kicks in less frequently. I measured roughly a 30% difference in consumption between my freezer running empty versus packed out. Also worth checking whether your Fogstar has low-temperature cutoff settings that might interfere if you're somewhere that drops below around 5°C overnight — the BMS will protect itself but you'd lose power to the load mid-night. @BurnGlen is right that it's doable, but nail down your actual watt-hours before committing rather than relying on nameplate figures.