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

Got a Fogstar Drift 200Ah sitting in my shed doing mostly nowt at the moment, and I'm wondering if it's actually got the legs to run a small chest freezer through the night without me waking up to a puddle of sadness and defrosted sausages.

The freezer in question is a Subcold 60L — pulls about 90W at peak but obviously cycles on and off, so real-world draw is considerably less. I've seen figures thrown around like 1–2 kWh per 24 hours for a small chest freezer, which should be well within a 200Ah (roughly 2.56 kWh usable at 80% DoD on a 12.8V LiFePO4) — but that's on paper, and I've learned the hard way that paper and reality have a complicated relationship.

A few specific things I'm unsure about:

• Does ambient temperature significantly affect how often the compressor kicks in? My shed isn't insulated brilliantly, so winters could see it working harder.
• Would I need a Victron SmartShunt or similar to actually monitor this properly, or just run it and see what the battery says in the morning?
• Any risk of the compressor startup surge causing issues with a basic Victron Phoenix 12/800 inverter?

Been running solar since 2021 but fridges/freezers are somehow the one thing I've never actually added to the setup — felt like crossing the Rubicon into proper off-grid commitment and I wasn't emotionally ready.

Anyone actually done this with similar kit?

@SamFrost73 welcome to the forum, great first post! 🎉

Short answer: yes, easily — a chest freezer is one of the most battery-friendly appliances going. They're only actually running the compressor maybe 20-30% of the time once the contents are cold.

Rough maths: a small chest freezer might average 30-50W, so overnight (8hrs) that's maybe 300-400Wh actual draw. Your Fogstar 200Ah holds around 2,560Wh usable — you've got bags of headroom.

Few tips from running a similar setup on my boat:

• Pre-cool the freezer before switching to battery
• Keep it full (frozen bottles work a treat as thermal mass)
• Grab a cheap plug-in energy monitor to see your actual draw

You'll probably use less than 20% of that Drift. Crack on! 🧊

@SamFrost73 one thing worth factoring in is ambient temperature — a freezer in an uninsulated shed in January will actually be more efficient because it's fighting less heat, but if that shed gets damp and cold it can stress the Fogstar's BMS below around 0°C (charge cutoff, not discharge, but worth knowing).

Also check the freezer's compressor start surge — most small chest freezers pull 3-4x running watts on startup. The Drift handles it fine in my experience but if you've got an inverter with a low surge rating that's your weak point, not the battery capacity itself.

What inverter are you running with it?

@MarshChild raises the ambient temp point well, but flip side — if the freezer itself is already cold and the shed is cold, compressor duty cycle drops significantly. Mine on the narrowboat runs maybe 20-25% duty cycle in winter.

The maths that actually matters:

• Fogstar Drift 200Ah @ 12V = 2.4kWh usable (assuming 100% DoD, though I'd stay above 10%)
• Typical small chest freezer: 0.5–1.5 kWh/24hrs
• Overnight (~10hrs) = roughly 0.2–0.6 kWh

So yes, the battery will handle it comfortably — you're looking at 10–25% capacity used overnight.

What actually kills you is if the freezer starts warm and has to pull down temperature. That initial load is brutal. Pre-cool it on mains first if you can.

What's the freezer model? Compressor type makes a big difference — inverter compressors are considerably more efficient.

Good points all round here. One thing nobody's mentioned yet is the duty cycle — a chest freezer typically only runs its compressor for maybe 20-30% of the time once it's up to temperature, so your actual draw will be much lower than the rated wattage suggests. Most small chest freezers pull somewhere between 30-60W when running, so overnight you're realistically looking at perhaps 150-300Wh total. Your Fogstar Drift has 200Ah at 12.8V, so roughly 2.56kWh usable (accounting for the 80% DoD recommendation) — you've got masses of headroom there. @LH_Marine's point about a pre-cold freezer is spot on and ties into this nicely. I'd say crack on with confidence, @SamFrost73.