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

So I'm in the middle of converting a long-wheelbase Transit (she's a beauty, chaos incarnate, and currently missing a ceiling) and I'm trying to plan the electrical system before I do something catastrophic and irreversible.

The big question: can a single 200Ah lithium battery realistically run a small chest freezer overnight without solar input?

My thinking is I'd be using one of those compact 30–40 litre chest freezers — the kind marketed at campers. Not a massive chest freezer nicked from a corner shop. I've seen figures suggesting they draw somewhere between 30–60Ah per 24 hours depending on ambient temperature and how often you're raiding it for ice lollies.

If that's roughly accurate, a 200Ah lithium (so realistically ~180Ah usable if I'm being kind to it) should cover an overnight stretch of say 8–10 hours without sweating too much. But I'm factoring in a UK summer, which let's be honest could mean anything from 12°C to an absolutely sweltering 19°C.

I'm planning around a Fogstar Drift 200Ah paired with a Victron SmartShunt so I can actually monitor what's happening rather than just vibing and hoping.

Has anyone run a similar setup? Specifically:

• Did the freezer cycle frequently in cooler UK overnight temps, or did it barely bother?
• Any particular chest freezer brands that play nicely with inverters?
• Would you bother with a 12V compressor freezer instead, skipping the inverter entirely?

Genuinely trying to avoid buying the wrong thing twice, which is already my signature move on this build. 😅

WattRoger | 847 posts | ⚡ Solar Obsessive

@KangooDream Wise move planning this first — I've seen too many builds where the electrics were an afterthought!

Short answer: probably yes, but it depends heavily on the freezer. A decent modern chest freezer (think 60-80 litre range) typically draws 30-60W when running but only cycles on maybe 30-40% of the time, so overnight you're looking at roughly 150-300Wh — well within a 200Ah (roughly 2,000Wh usable from a quality LiFePO4) battery.

However, ambient temperature matters enormously. If you're parked somewhere warm, that compressor runs much harder and more frequently.

What freezer model are you considering? Check the energy label — annual kWh figure divided by 8,760 gives you average wattage. That'll tell you everything.

Also factor in what else you're running overnight. Lights, phone charging, ventilation fan all nibble away quietly.

WillowWalker | 312 posts | 🌿 Solar & Wind Hybrid

@KangooDream Great that you're planning ahead! The short answer is maybe, but it depends heavily on which freezer you're looking at. Chest freezers vary massively in efficiency — a decent 12V compressor unit like a Brass Monkey or Dometic will use far less than a repurposed household AC chest freezer running through an inverter (which I'd steer well clear of for van life, personally).

Worth checking the freezer's actual duty cycle too. A well-insulated chest freezer in a cool environment might only run the compressor 30-40% of the time overnight, which changes your calculations considerably.

What's your solar setup looking like? A 200Ah lithium in isolation tells half the story — you'll want to know you can reliably replenish it during the day. Happy to help crunch some numbers if you share more details! 🔋

WattAMess25 | 203 posts | 🔋 Battery Nerd

Something nobody's mentioned yet — the type of freezer matters enormously here. I ran a cheap compressor chest freezer on my narrowboat for two seasons, pulling roughly 30–45Ah per 24 hours once it settled to ambient. A 200Ah lithium (realistically 180Ah usable) handles that comfortably overnight with headroom to spare.

The nasty surprise is startup surge. My Fogstar 200Ah handled it fine, but pair it with an undersized inverter and you'll be troubleshooting at 2am in a lay-by somewhere near Stoke.

Worth knowing: well-insulated chest freezers are dramatically more efficient than uprights. If you're still sourcing one, that choice alone could halve your daily draw.

What inverter are you planning?

Rob1963 | 2,341 posts | 🔧 Reluctant Expert

@WattAMess25 is right about freezer type, but the number everyone keeps ignoring is ambient temperature — a chest freezer in a black Transit in summer is working three times harder than one sitting in a cool garage, which'll absolutely murder your runtime calculations.

Real-world: my static caravan setup runs a 60L chest freezer off a 200Ah Fogstar Drift LiFePO4 with no issues overnight in autumn. July was a different story entirely.

Get the actual watt-hour draw from a plug-in energy monitor (£12 on Amazon) before you trust any spec sheet — manufacturers test these things in a 25°C lab, not a tin box in a Tesco car park. Then add 20% buffer minimum.

And fit a Victron BMV battery monitor or you're just guessing in the dark, which is basically how I built my first van.

FrostyTrekker | 847 posts | ❄️ Van Life Veteran

@KangooDream One thing worth adding to what @Rob1963 and @WattAMess25 have covered — ambient temperature makes a massive difference overnight. A freezer working hard in a warm van in summer will cycle far more frequently than one sitting in a cold British November. I'd also factor in your battery's usable capacity; with lithium you're typically working with around 80-100% DoD, which is brilliant, but don't forget inverter losses if you're running a mains-voltage freezer. A 12V compressor unit (Alpicool, Brass Monkey etc.) cuts that inefficiency out entirely and I've found them far more van-friendly overall. Might be worth considering if you're still sourcing a freezer. 🙂