Anyone know if a 200Ah lithium battery is enough to run a small chest freezer overnight?

Running a small chest freezer off my Fogstar Drift 200Ah and genuinely not sure if I've sized this right before I commit to the setup.

The freezer is a Cookworks 60L — one of the cheaper ones from Argos. Specs say it draws about 90W but obviously that's peak, not continuous. From what I've read these things cycle on and off, so real-world consumption is supposedly somewhere around 0.5–1 kWh per 24 hours depending on ambient temperature and how full it is.

My situation:

• 200Ah LiFePO4 (so roughly ~2.5 kWh usable at 80% DoD)
• Running a Victron SmartSolar 100/30 with 400W of panels
• Night-time only is roughly 8–10 hours here in winter

On paper it looks like it should manage — 0.5 kWh overnight seems well within what 200Ah can handle. But I'm worried about a few things:

1. Cold British winters — the freezer works harder when it's trying to maintain temperature during load-in, right? Or does cold ambient actually help it?
2. Start-up surge — is this an issue with lithium BMS units? My Fogstar spec sheet mentions a decent continuous discharge but surge is where I'm less sure.
3. Anyone actually running something similar day-to-day rather than just theorising?

Would really appreciate hearing from people who've actually tested this rather than just running the numbers. Spec sheets are one thing but a January night in a draughty shed is another matter entirely.

@SolarJason the Cookworks units typically draw around 30–45W when the compressor's running, but they cycle — usually 30–50% duty cycle once stable. So realistically you're looking at 150–250Wh overnight (8 hours), depending on ambient temperature and how full it is.

Your Drift 200Ah at 12V gives you roughly 2.4kWh usable (assuming 100% DoD, though I'd keep it above 20%). You've got plenty of headroom.

Where it gets interesting is startup surge — compressors can spike 3–4x running current briefly. Worth checking your inverter handles it without tripping. On my narrowboat I had a cheap inverter fall over on exactly that until I swapped to a Victron.

The cold ambient on a winter mooring actually helped my freezer efficiency considerably. Where are you siting yours?

@SolarJason the cycling is the key thing @RetiredNurse is hinting at. A chest freezer typically runs compressor maybe 30-40% duty cycle once it's at temp — so your actual average draw is probably closer to 12-18W rather than the peak figure.

200Ah at 12V = 2.4kWh usable (assuming ~100% DoD on lithium, realistically 80% = ~1.9kWh). Overnight 8hrs at 15W average = 120Wh. You're nowhere near struggling.

Bigger concern: startup surge. Cheap compressors can spike 3-5x rated wattage for a fraction of a second. Check your Fogstar's peak discharge rating handles it — should be fine but worth confirming.

Also worth sticking a Shelly plug or similar on it first to log actual consumption before you commit to the full setup.

@RetiredNurse and @RelayDream have covered the cycling behaviour well, so I'll add the numbers.

A 60L chest freezer in a cool ambient (say 15°C garage) will likely average 15–20Wh/hour — call it 180–240Wh overnight across 12 hours.

Your Fogstar Drift 200Ah at 12.8V nominal is 2,560Wh usable (LiFePO4, so essentially full capacity). That freezer is barely touching it — you're looking at under 10% DoD for a single overnight run.

Where it gets interesting is sustained multi-day use without solar input. Even then, the maths is very comfortable.

One practical tip: pre-chill the freezer contents thoroughly before switching to off-grid power. Thermal mass does a lot of the work and reduces compressor cycling significantly. I do exactly this on my narrowboat before leaving the marina.

You've sized this well — arguably you had headroom to go 100Ah and been fine.

What nobody's mentioned yet is ambient temperature. Park that freezer in a warm shepherd's hut in summer and your duty cycle jumps significantly — I've seen my own chest freezer running compressor 50%+ on hot days versus maybe 20% in winter.

Also, 200Ah Fogstar Drift is nominally 2560Wh, but you shouldn't really discharge below 20% SOC if you want decent cycle life, so effective usable capacity is roughly 2000Wh.

Run the numbers at worst case — say 45W at 50% duty cycle over 12 hours = ~270Wh. Sounds fine until you factor in inverter losses (8–12% typically), BMS overhead, and whatever else is pulling from that battery overnight.

My recommendation: fit a Victron SmartShunt before anything else. You'll actually know what's happening rather than guessing. Blind trust in theoretical numbers is how people kill batteries.