Does anyone know if a 200Ah lithium battery can run a small chest freezer overnight?

Got a Fogstar Drift 200Ah sat in my garage that I'm putting together as an emergency backup system, mainly paired with a small rooftop solar setup. Been wondering whether it'd actually be capable of running a small chest freezer through the night if we had a grid outage.

The freezer I'm looking at is a 60L chest freezer — one of those compact ones. Specs say it draws around 90W but obviously it's not running constantly, more of a duty cycle situation.

My rough maths:

• Say it runs 30-40% of the time overnight (~8 hours)
• That's roughly 2.5–3 hours of actual runtime
• Around 225–270Wh consumed

The 200Ah Fogstar at 12V gives me 2400Wh usable (assuming I don't go below 20% SoC), so on paper it looks more than fine?

But I'm second-guessing myself because:

1. Compressor startup surge — does this cause issues with a standard inverter?
2. Ambient temp in the garage drops quite low in winter — does that affect lithium discharge capacity noticeably?
3. Is 200Ah overkill, or sensible headroom for this use case?

Haven't sized the inverter yet, leaning toward a Victron Phoenix 12/800 but open to suggestions if something else handles compressor loads better.

Anyone actually done this or something similar? Real-world numbers would be really useful rather than just spec sheet stuff — always seems to work out differently in practice.

@Hamish1975 running a small chest freezer from a 200Ah Fogstar is exactly what I did when I first set up power for my shepherd's hut. A decent chest freezer draws somewhere around 30-60W average (they cycle, they don't run constantly), so overnight — call it 10 hours — you're looking at maybe 300-600Wh consumed. Your 200Ah at 12V gives you roughly 2.4kWh usable, so yes, comfortably done.

The gotcha nobody mentions is the startup surge. Make sure your inverter can handle 3-4x the running wattage on startup or the freezer compressor will stall it.

With your solar topping it back up through the day, you should have no drama at all. Just keep an eye on your State of Charge over a few cycles to see how your actual unit performs — every freezer varies.

@Hamish1975 mine runs a small chest freezer all night on a 200Ah no bother — the freezer's only cycling maybe 30-40% of the time once it's already cold, so you're not actually pulling as much as you'd think! 🧊

Something to factor in that hasn't been mentioned — starting surge. Freezer compressors can pull 3-5x their running wattage on startup, so make sure whatever inverter you're running between the Fogstar and the freezer can handle that spike.

A decent pure sine inverter (Victron Phoenix or similar) will manage it without issue, but a cheap modified sine unit might struggle or cause the compressor to run inefficiently, which ironically increases your overnight draw.

Also worth checking the freezer's ambient temperature rating — a chest freezer sitting in an unheated garage in winter will actually run more efficiently, which'll help your overnight figures considerably compared to summer.

@VoltBarry's 30-40% duty cycle sounds about right in cooler conditions, but I've seen that climb to 60%+ in a warm space.

Good points all round, especially @Mark1978 on the surge — worth checking your battery's BMS can handle it. Most decent lithiums including the Fogstar Drift are fine, but worth confirming the spec sheet.

One thing nobody's flagged yet: ambient temperature matters enormously. A freezer in a cold garage in February works much harder to maintain temperature than you'd expect — counterintuitively, freezers struggle in very cold environments because the thermostat logic gets confused. Mine in the van taught me that the hard way.

Also factor in your solar replenishment window. In a UK winter you might only get 2-3 usable hours of decent generation, so overnight discharge needs to be genuinely modest to avoid running the battery too low before it can recover.

A 200Ah Fogstar is absolutely capable of doing this job — just run the numbers carefully for your specific freezer's wattage.

@Mark1978 makes a fair point on surge, but honestly the Fogstar Drift's BMS handles that fine in my experience — it's one of the better budget units for short-duration peaks.

What nobody's mentioned is ambient temperature. If that battery's sitting in a garage over winter, you're losing usable capacity. LiFePO4 starts getting grumpy below ~5°C, and the Drift doesn't have self-heating. Could realistically knock 10-15% off what you're expecting.

Also worth knowing your actual freezer draw rather than guessing. Clip-on energy monitor for a week tells you far more than any spec sheet. I was convinced my boat's freezer was modest until I actually measured it — turned out to be pulling nearly double what the label suggested.

200Ah should be enough, but I'd want data before relying on it as emergency backup.