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

Running a small chest freezer overnight is something I've been trying to figure out for my Transit build. Currently have a 200Ah Fogstar Drift lithium (so realistically about 180Ah usable if I'm being cautious), and I want to add a chest freezer rather than a compressor fridge.

Looking at a Subcold 30L chest freezer which claims around 0.65 kWh per 24 hours — so roughly 27Ah per 24 hours at 12V in theory. That sounds almost too manageable, but I'm suspicious that real-world draw will be higher, especially in summer when the ambient temperature in the van shoots up.

Few things I'm unsure about:

• Does the compressor startup surge cause any issues with a standard inverter setup?
• Anyone running one of these through a Victron MultiPlus or similar? Curious whether the inverter efficiency losses significantly change the maths
• What's the ambient temperature threshold where power consumption starts getting silly?

My current setup has 200W of solar (two Renogy 100W panels) which clearly won't cover everything on a cloudy UK winter night, but I'm wondering if the 200Ah bank is at least a reasonable starting point or whether I should be looking at upgrading to 300Ah before committing to the freezer.

Real-world experience massively preferred over spec sheet maths here — those manufacturer figures seem optimistic at best.

@TransitCamper a few things worth factoring in that get overlooked:

Chest freezers cycle on/off rather than run continuously, so your actual draw depends heavily on ambient temperature and how full the freezer is — a full freezer holds temperature far more efficiently than an empty one.

My rough numbers from logging a Shoreline 35L chest freezer in my garden office setup: averaging around 30–40Wh per hour at 20°C ambient, so roughly 300–400Wh overnight (10hrs). Your 180Ah usable at 12V gives you ~2,160Wh theoretical headroom, which looks comfortable on paper.

The real risk is summer temps pushing that consumption up significantly, plus any other loads running simultaneously.

I'd strongly recommend fitting a Victron SmartShunt so you can actually log overnight consumption rather than estimate — the real data will tell you far more than any calculation.

Great question to kick off with, @TransitCamper — chest freezers are actually one of the more forgiving loads once they're up to temperature.

One thing worth adding: ambient temperature matters enormously. A freezer sitting in a warm van in summer will cycle far more frequently than one in a cold British winter. I've seen my own setup pull nearly double the watts in July versus January.

Also consider the startup surge — small chest freezers can spike 3-4x their running wattage on compressor startup. Worth checking your Fogstar's continuous and peak discharge ratings handle that comfortably (it will, but good habit to verify).

200Ah should genuinely be fine for most overnight scenarios with a decent-sized freezer, provided you're not also running loads of other kit simultaneously. What are your other overnight consumers looking like?

Had a chest freezer in my static for two summers running off a 200Ah LiFePO4. Short answer: yes, comfortably.

The ambient temperature is the sneaky variable nobody mentions. Same freezer used maybe 30% more power during last July's heatwave than it did in April. Worth keeping that in mind if your van turns into an

Good to see you asking this before buying rather than after! @RetiredElectrician and @CarlBaker have covered the main points well.

One thing worth adding from my narrowboat experience — insulation matters enormously with chest freezers. I swapped to a second-hand Tefcold unit with thicker walls and my overnight draw dropped noticeably compared to a cheaper chest freezer of similar capacity. Worth checking the specs if you're still deciding on a model.

Also, pre-cooling the freezer before your battery has to carry it solo (while you're still hooked up or the engine's running) makes a real difference to overnight consumption figures.

Your 200Ah Fogstar should handle it fine in most UK conditions — just factor in winter ambient temperatures helping you out, summer working against you.