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

Running a small chest freezer off-grid overnight is something I'm currently trying to figure out for my cabin setup, so hoping someone with more hands-on experience can weigh in.

I've got a 200Ah 12V lithium (Fogstar Drift, so usable capacity is pretty much the full 200Ah) and I'm looking at picking up one of the smaller chest freezers — something around 60–80 litres. The ones I've been eyeing quote roughly 35–45W running power, but I know compressor startup draw and duty cycle complicate things massively depending on ambient temperature.

My rough maths:

• Assume 40W average draw with ~50% duty cycle = ~20W effective
• Over 10 hours = 200Wh consumed
• At 12V that's roughly 16–17Ah — which sounds almost too good?

But I suspect that's optimistic. In a poorly insulated cabin in winter the freezer might cycle more frequently, and in summer the ambient temps could push duty cycle up significantly. I've also read that some budget freezers have genuinely terrible efficiency once you factor in real-world conditions.

Questions:

1. Has anyone actually monitored their chest freezer draw overnight with a proper energy meter (Victron BMV or similar)?
2. Does a 200Ah bank feel comfortable for this, or would I want a second battery before committing?
3. Any specific freezer models people have had good results with off-grid?

Context: my cabin solar isn't massive — two 200W panels through a Victron SmartSolar — so I can't afford to arrive on a Friday evening to a flat bank because the freezer hammered it Thursday night.

@SolarCol depends heavily on the freezer's actual draw. My 45L chest freezer pulls about 30-35W when running but only cycles maybe 30-40% of the time overnight — so rough maths puts it around 3-4kWh per 24hrs in summer, less in winter when ambient is cooler.

200Ah at 12V = 2.4kWh usable (assuming 80% DoD on lithium). That's cutting it fine for a full 24hrs but overnight only? Should be fine.

Few things worth checking:

• Actual freezer wattage (not peak startup draw)
• Ambient temp where it's stored
• What else is on the battery

I run a Fogstar 200Ah on my boat with a similar freezer setup — works reliably overnight with solar topping it up each morning.

Really important question for static caravan setups too — I've been working through similar calculations for mine.

A few things worth pinning down before you can answer this properly:

• What's the ambient temperature where the freezer lives? Warmer conditions mean the compressor cycles more frequently
• What's your inverter efficiency? You'll lose 5-10% there if it's not a 12V native freezer
• What's your minimum DoD on that battery? Most lithium (Fogstar, Epoch, etc.) are fine to 80-90% but worth confirming

As a rough guide: a typical small chest freezer might average 20-40Wh per hour depending on duty cycle, so overnight (say 10 hours) could be 200-400Wh. A 200Ah/12V pack is 2.4kWh usable, so theoretically comfortable — but that assumes nothing else is drawing from the bank simultaneously.

What's the actual freezer model? Spec sheets usually list annual kWh which lets you back-calculate average draw.

Great question and one I worked through myself when setting up my motorhome's off-grid cold storage.

@SolarCol the key figure people miss is duty cycle — a chest freezer rarely runs 100% of the time. Most well-insulated units cycle around 25-40% depending on ambient temperature.

So rough numbers with a 200Ah (2,560Wh usable at 12.8V):

• 35W draw × 30% duty cycle = ~10.5W average
• Over 12 hours = roughly 126Wh consumed

You're looking at less than 5% of your battery capacity in ideal conditions. Even doubling that for a warm summer cabin, you're comfortably within limits.

Where it gets interesting is compressor start surge — worth checking your Victron BMS can handle the spike if you're running one. Fogstar batteries handle this brilliantly in my experience.

What's the freezer model? That'll pin down the real-world figures considerably.

Great points from @BatteryRay and @ExFirefighter42 already. One thing worth adding — ambient temperature makes a massive difference overnight. A chest freezer in an uninsulated cabin during a cold UK night will cycle far less frequently than the same unit in summer, so your actual consumption can vary quite a bit seasonally.

Also worth checking whether your 200Ah battery is quoted at 12V or 24V, as that changes the usable watt-hours significantly. A 12V 200Ah lithium gives you roughly 2,400Wh, and assuming 80% usable capacity that's around 1,920Wh to play with — which should comfortably cover most small chest freezers overnight, but you'd want a bit of solar or generator top-up during the day rather than relying on that bank alone long-term.