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

Running a small chest freezer off-grid and trying to work out if my battery bank is going to cut it overnight without the solar doing anything.

I've got a single 200Ah 12V lithium (Fogstar Drift) and a small chest freezer — it's a Klarstein 50 litre job, rated at about 60W but obviously it's not pulling that constantly, just cycling on and off.

From what I can gather, chest freezers are pretty efficient and might only run the compressor 30-40% of the time once they're up to temperature. So rough maths:

• 60W × 0.35 duty cycle = ~21W average draw
• Over 10 hours = ~210Wh
• 200Ah at 12V = 2400Wh usable (down to ~80% DoD that's ~1920Wh)

On paper that looks absolutely fine, but I'm wondering if I'm missing something. A few things I'm not sure about:

1. Does the compressor startup surge cause any issues with a 12V system/inverter?
2. Does ambient temperature massively affect the duty cycle? My setup is in a barn so it can get cold overnight in Wales — not sure if that helps or hinders
3. Is 200Ah actually enough headroom if I want to run other small loads too (a few USB charges, maybe a 12V fan)?

Anyone actually running a chest freezer overnight on a similar sized battery? Would love some real-world numbers rather than just theoretical. The Fogstar seems like a solid bit of kit but I don't want to find out the hard way that I've undersized things.

@Taffy62 chest freezers are the dark horse of off-grid life — mine runs about 40-45Ah per 24hrs once it's already cold, so a 200Ah Fogstar should handle overnight no bother, but don't forget you're only really playing with ~160Ah usable unless you fancy a warranty chat with Fogstar at 3am.

@Taffy62 the ambient temperature is the variable nobody talks about until it's too late. Had my chest freezer draw nearly double one August heatwave compared to a January night — same unit, wildly different consumption.

Worth grabbing a cheap energy monitor (Shelly EM or similar) and logging actual draw over 24 hours before committing to anything. My freezer sits around 35-42Ah daily in a cool shed, but in a warm van in summer that figure climbs fast.

With a Fogstar Drift you've got roughly 180Ah usable before you're pushing the limits — should be fine overnight if the freezer is pre-chilled and your ambient is reasonable. Where are you keeping it?

Really depends on the freezer itself — I went through exactly this when I set up my narrowboat. Spent a week logging my 12V chest freezer with a Victron BMV-712 and found the duty cycle was everything. Mine averaged 35Ah overnight in autumn but crept up to 55Ah on a warm night when I'd been opening it repeatedly during the day.

One thing worth doing before committing: run your freezer for a full 24 hours on shore power with a cheap plug-in energy monitor first. Gets you a solid baseline before you're anchored somewhere with no backup.

Your Fogstar Drift at 200Ah gives you roughly 160-170Ah usable at sensible depth of discharge. Tight but probably workable if the freezer's already cold when the sun goes down — pre-cooling during the day makes a massive difference.

@Taffy62 quick point nobody's nailed down yet — your usable capacity on that Fogstar Drift isn't actually 200Ah. Most lithium cells are rated to 80% DoD as a comfortable daily limit, so realistically you're working with ~160Ah before you're stressing the cells.

If the freezer pulls say 45Ah per night (as @DevonNomad suggests), you're fine on paper — but factor in any other loads. Lights, phone charging, whatever else is ticking away.

Also worth checking: is your 200Ah figure at 12V or does your BMS cut off before you reach it? Some cheaper units do. Fogstar's BMS is decent but still worth verifying with a proper battery monitor rather than guessing.

Get a Victron BMV or similar sorted first — you can't manage what you can't measure.