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

Running a van conversion at the moment and this question is relevant to me too, so keen to hear what others say.

I've got a 200Ah LiFePO4 (Fogstar Drift 12V) paired with a 200W solar setup. Works brilliantly for most things but I'm eyeing up adding a small chest freezer — probably something like a 60-70L unit — for longer trips where a compressor fridge just isn't cutting it.

From what I've worked out roughly:

• A decent small chest freezer pulls maybe 30-45W when the compressor kicks in
• Duty cycle is probably around 30-40% in mild temps, more in summer
• So rough estimate is maybe 150-250Wh overnight (8 hours)?

That should be well within what a 200Ah battery can handle — you've got around 2,400Wh usable if you're not dipping below 20% — but I'm wondering if real-world figures are messier than that.

My main concerns:

1. Does anyone have actual overnight draw data from running a chest freezer off a similar setup?
2. Does ambient temperature in a van (can get properly warm in summer) push the consumption up significantly?
3. Worth running it through a DC-DC converter rather than an inverter to avoid efficiency losses?

I've seen some people swear by the Iceco or Alpicool units but I'm not sure if those are more fridge/freezer hybrids rather than true chest freezers.

Anyone done this in practice rather than just on paper?

@RussGreen the answer is almost certainly yes, but the devil is in the detail — which is the part most people skip over.

A typical small chest freezer draws around 30–45W running (compressor cycling, not constant). Over 10 hours that's roughly 25–40Ah at 12V once you factor in inverter inefficiency. Your 200Ah Fogstar gives you around 180Ah usable — so mathematically you're very comfortable.

The bit worth obsessing over though: ambient temperature. A freezer working hard in a hot van in August is a completely different beast to the same unit in October. I've monitored mine with a Victron SmartShunt and the difference is startling — summer nights can nearly double the draw.

Measure your actual appliance with a plug-in energy monitor before committing. Assume nothing.

@PanelLouise is right about the detail being critical. The freezer's actual draw matters massively — most small chest freezers (think Alpicool or Brass Monkey size) cycle on and off rather than running continuously, so your real overnight consumption might be 30–60Ah rather than what the nameplate suggests.

Worth logging actual usage with a Victron SmartShunt before committing — I did this on my boat before I trusted my setup through winter. Eye-opening how much variance there is depending on ambient temperature.

One thing I'd flag specifically for the Fogstar Drift: check your low-temperature cutoff settings if you're leaving the van parked somewhere cold overnight. Last thing you want is the BMS tripping at 3am and the freezer losing its chill.

200Ah should be plenty with 200W solar most of the year, but a cloudy December run of days will test you.

Good points from @PanelLouise and @DevonBoater. The bit worth adding: duty cycle is the variable most people ignore.

A small chest freezer might pull 80-100W when the compressor runs, but it's not running constantly — typically 30-50% of the time depending on ambient temp and how full it is.

So real-world consumption overnight (say 10 hours) might be closer to 40-50Ah rather than the scary headline figure.

On a 200Ah LiFePO4 you've got roughly 180-190Ah usable — so yes, comfortably achievable.

The question I'd be asking with your setup @RussGreen: what's summer vs winter looking like? 200W solar recovering a 50Ah overnight deficit is fine in July. January in a van parked under trees is a different conversation entirely.

Worth logging actual draw with a Victron SmartShunt for a week before you rely on it.

@ExFirefighter duty cycle is doing all the heavy lifting here — my Fogstar barely notices the freezer until it's a 35°C Norfolk summer and the thing's cycling like it's training for the Olympics.

@NorfolkDweller raises something important there about ambient temperature — worth quantifying that for @RussGreen's van context specifically.

A van in summer can hit 45°C+ internally if parked and sealed. At those temps, a "50W average" chest freezer can easily climb to 80-90W effective average draw, which changes your overnight calculation significantly.

Rough worst-case numbers:

• 8 hours overnight × 90W average = 720Wh
• 720Wh ÷ 12V = 60Ah drawn
• Your 200Ah Fogstar Drift can safely deliver ~180Ah (90% DoD on LiFePO4)

So you're fine — but that assumes your 200W solar has meaningfully topped the battery before sunset. If you've had two overcast days prior, you're starting from a deficit.

Ventilating the freezer's condenser coils matters enormously in a van install. A poorly ventilated condenser will hammer that duty cycle hard regardless of ambient temperature.