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

Running a small chest freezer overnight is something I've been trying to figure out for my van build and I can't seem to land on a definitive answer anywhere.

I've got a 200Ah lithium (Fogstar Drift 12V) wired up with a 200W solar setup, but obviously overnight there's no input so I'm working purely off stored capacity. Realistically I'd say I've got around 160Ah usable before I'd want to push it.

The freezer I'm looking at is the Alpicool C15 — draws roughly 45W when compressing but obviously it's not running constantly. I've seen people quote duty cycles anywhere from 20% to 50% depending on ambient temperature, which makes planning this properly really difficult.

So my rough maths goes something like:

• 8 hours overnight
• Say 35% duty cycle on a warm-ish night
• ~45W draw = roughly 13Ah per hour when running
• So maybe 36Ah total?

That seems almost too comfortable on a 200Ah bank, which makes me think I'm missing something. Are these compressor freezers actually that efficient, or am I underestimating the duty cycle in a poorly insulated van?

Also worth mentioning — the van isn't insulated to any serious standard yet, so summer temperatures could push that duty cycle up considerably I'd imagine.

Has anyone actually run something similar and tracked the real-world draw overnight? Would be good to see some actual figures rather than spec sheet estimates. A Victron SmartShunt is on my list so I can start logging properly, but I haven't fitted it yet.

@VanLee done exactly this in my shepherd's hut last summer — Fogstar Drift 200Ah running a small Liebherr chest freezer overnight.

Short answer: yes, but it's tight.

Chest freezers are sneaky because the compressor duty cycle matters massively. Mine was pulling maybe 2-3A average overnight once it reached temperature, so roughly 20-25Ah across 8 hours. Totally manageable.

The killer is:

• Ambient temperature (hot nights = compressor works harder)
• How full it is (fuller = more thermal mass = better)
• Initial cool-down — if it's warm when you start, that first few hours will hammer the battery

I'd say you've got comfortable headroom if your freezer is already cold going into the evening. Where are you parking mostly — hot spots or shaded?

@VanLee worth thinking about this differently — it's not just the battery capacity, it's the duty cycle of the compressor that'll make or break you.

My garden office runs a small chest freezer year-round off a Victron system, and I've noticed the compressor runs far less frequently in winter versus July. Peak summer I was seeing it pull maybe 30-40Ah overnight; mid-winter barely half that.

The 200Ah Fogstar should have plenty of headroom on paper, but factor in:

• Ambient temperature — warmer air = compressor runs longer
• How full the freezer is — thermal mass matters enormously
• Lid seal condition — old seals bleed cold air constantly

Pack it full of water bottles if it's half empty. Genuinely makes a measurable difference on the draw. A cheap plug-in energy monitor before you commit will tell you your actual numbers within a couple of nights.

Really useful thread for me too — I've got a shepherd's hut build in the planning stages and a chest freezer is on my wishlist.

Genuine question though: does ambient temperature make a dramatic difference to how hard the compressor works? I'm imagining a hot July night vs a chilly October one being quite different stories for that duty cycle @WattNick mentioned.

Also wondering whether the chest format specifically helps — presumably less cold air escapes when you open it compared to an upright, so the compressor isn't fighting as hard to recover? Or am I overthinking it and the overnight standby draw is roughly the same either way?

@VivaroNomad did you notice your Fogstar dropping significantly by morning, or were you still sitting comfortable on SOC?

What freezer are you actually running though?

Because "small chest freezer" is doing a lot of heavy lifting in that sentence 😅

I've got a 200Ah Fogstar Drift in my motorhome and the difference between my little 30L camping compressor box versus a proper domestic chest freezer is enormous — we're talking maybe

@Slim — relevant to your shepherd's hut planning: insulation quality matters enormously here. My hut sits in a field in the Cairngorms and the ambient swing between summer and winter nights is brutal. A poorly-insulated chest freezer works its compressor much harder than the specs suggest.

In practice, I'm running a 60-litre chest freezer off a 200Ah Fogstar Drift in my hut. Overnight draw (roughly 10 hours) lands between 25–40Ah depending on ambient temperature. That's well within 200Ah even respecting the recommended 80% DoD limit on lithium.

The real killer is your solar recharge window the following day — if you're in a shaded or winter scenario, that's where the maths gets uncomfortable. A 200Ah bank is survivable for one night; it's the cumulative deficit over several cloudy days that catches people out.