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

Running a small chest freezer off a 200Ah lithium in my garden office setup and not sure if I've got enough capacity to get through the night comfortably.

The freezer is a Subcold 60L — pulls around 80W when the compressor kicks in but obviously it's cycling on and off rather than running flat out. Seen some figures suggesting maybe 0.3–0.5kWh per 24hrs for a small unit like this, but that feels optimistic depending on ambient temps.

My battery is a Fogstar Drift 200Ah 12V (so roughly 2.4kWh usable if I keep it above 20% SOC). Solar input overnight is zero obviously, just relying on what's stored from the day.

Few things I'm unsure about:

• Does ambient temp in the office massively affect draw? It can get down to 5°C out there in winter
• Is there a meaningful efficiency hit running the compressor through a 12V inverter vs mains?
• Should I be worried about the battery dropping too low if there's a cold snap and the compressor runs longer cycles?

Instinct says 200Ah should be enough but I don't want to risk food spoilage finding out the hard way. Anyone actually done this or got monitoring data from a similar setup? Running a Victron SmartShunt so I can track consumption properly once I get it going, just want a rough sense before I commit to putting anything valuable in there.

@Rodney running a similar setup in my garden office — what's your inverter efficiency looking like? That'll eat into your usable capacity more than people realise.

Also worth checking whether you're running a Victron BMV or similar to see actual consumption vs the rated draw. Freezers cycle on and off so the average is often much lower than the peak figure.

The other thing I'd flag — are you accounting for depth of discharge limits? If it's a lithium like a Fogstar Drift you've typically got 80-100% usable, but if it's an older LiFePO4 with a more conservative BMS you might only be pulling 160Ah realistically.

What's your overnight ambient temperature in the office? Colder = compressor runs less = less draw. Might actually be fine.

A 60L chest freezer typically draws around 60–90W but only runs ~30–40% of the time, so your overnight load is probably 15–25Ah realistically — your 200Ah Fogstar or similar should laugh at that, assuming you're not draining below the recommended 20% floor.

The sneaky killers are:

• Ambient temperature (garden office in a British winter = compressor barely cycles; summer = runs constantly)
• What else is sharing that battery

Worth chucking a Victron SmartShunt on it so you're watching actual consumption rather than guessing — genuinely the best £80 you'll spend on a setup like this.

@MarineGeoff has the duty cycle bang on — so you're looking at roughly 20–30Wh per hour of actual consumption, meaning an 8-hour night costs you maybe 160–240Wh total.

Your 200Ah (assuming 12V = 2400Wh usable at ~80% DoD = ~1920Wh) has that comfortably covered, even accounting for @ExJoiner19's valid point about inverter losses — budget another 10–15% for a typical pure sine unit.

The real enemy isn't overnight capacity, it's ambient temperature — a poorly insulated garden office in a British January means that compressor cycles far more frequently than the manufacturer's figures suggest.

If you're running a Fogstar or similar quality cell, you'll be fine; just keep an eye on your state of charge via a Victron BMV and don't let it drop below 20% repeatedly or you'll be buying new cells sooner than planned.

@OldSailor's numbers stack up well. Worth adding — ambient temperature makes a massive difference to duty cycle. My shepherd's hut setup sees the freezer working noticeably harder in summer, easily pushing toward that 40% end.

On a 200Ah lithium (assuming a decent 100Ah usable if you're cautious, though most quality cells like Fogstar give you more like 80% DoD comfortably) you should be absolutely fine overnight. Probably using 150-200Wh across 8 hours.

Main thing I'd watch is your inverter quiescent draw — if it's sitting idle between compressor cycles pulling 10-15W, that adds up. Some people run the freezer direct on 12V if their model supports it, cuts that loss out entirely. Worth checking the Subcold spec sheet.

Great thread — I ran almost this exact scenario when I first set up my garden office.

One thing nobody's mentioned yet: what's the battery's usable capacity? A 200Ah lithium (LiFePO4, presumably) gives you around 180–190Ah usable, but if yours is an older or budget cell, check whether the BMS cuts off earlier than you'd expect.

I've got a Fogstar Drift 200Ah paired with a Victron SmartShunt, and the shunt's historical data genuinely transformed how I understood overnight loads. Stopped me guessing completely.

Also worth checking: does your freezer have a fast-freeze mode that kicks in on startup? Mine spiked to nearly 200W on compressor start — fine for the battery, but worth knowing your inverter handles the inrush without tripping.

Short answer though — 200Ah should be very comfortable for a 60L freezer overnight.