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

Running a Fogstar Drift 200Ah in my van build at the moment and I'm weighing up whether to add a chest freezer to the setup.

The freezer I'm looking at is a Brass Monkey 30L — rated at roughly 45W running draw, though obviously the compressor cycles rather than running continuously. From what I can gather, duty cycle on a well-insulated chest freezer in moderate ambient temps is maybe 30-40%, so real-world consumption might be somewhere around 200-300Wh over 8 hours?

My 200Ah battery is a 12V unit, so roughly 2.4kWh usable (accounting for the recommended 80% DoD on LiFePO4). On paper that looks comfortable, but I've got a few variables I'm unsure about:

• Ambient temperature — parked in summer vs. winter will dramatically affect duty cycle, presumably?
• Pre-cooling the freezer contents before switching to battery overnight — does this make a meaningful difference?
• Van insulation — does the thermal environment of a poorly ventilated van at night push the compressor harder?

Also running a Victron SmartShunt so I can actually log consumption overnight and do proper testing, but before I spend £200+ on a freezer I'd rather get a sense of whether others have done this successfully on a similar capacity bank.

Has anyone got actual logged data from running a chest freezer overnight on a single 200Ah lithium? Particularly interested if you're also in the UK where overnight temps are obviously different to some of the Australian van life content that dominates search results.

@Lefty28 short answer: probably, but it's tight.

Chest freezers typically pull around 30-45W when running but cycle on/off — real-world draw ends up somewhere around 0.5-1kWh per 24hrs depending on ambient temp and how often you open it.

Your 200Ah at 12V is ~2.4kWh usable (assuming you're not hammering below 80% on a Fogstar). So overnight alone? Fine. Full 24hrs with everything else on? That's where it gets dicey.

Biggest variable nobody mentions — ambient temperature. A chest freezer in a van in August is working considerably harder than one sat in my garden office in January. It'll smash your duty cycle.

What's the rest of your load looking like? Lights, fridge, inverter standby etc all adds up fast. One 200Ah bank for van living plus a freezer feels lean to me.

@Lefty28 ran a little chest freezer off my van setup last summer and the real killer is those compressor startup spikes — my Victron BMV-712 was watching it like a disappointed parent every time it kicked in 😅

Key thing nobody mentions: ambient temperature absolutely destroys your runtime figures — parked in a sunny lay-by versus a shaded campsite is a completely different ballgame, especially in a metal van acting as a giant oven.

Also worth checking whether the Brass Monkey has an eco mode; mine dropped consumption dramatically once I stopped opening it every five minutes to check if my Magnums had melted.

@Lefty28 worth checking what ambient temperature you'll be running it in — a freezer in a hot van in summer will cycle far more frequently than one sat in a cool cabin or boat. I've noticed my 12V fridge works noticeably harder when the interior gets warm.

Also, what's your charge source? If you're relying solely on solar with no alternator or hook-up backup, a cloudy week could leave you in trouble even if the overnight draw is technically fine on paper. A 200Ah Fogstar is a decent bank but I'd want at least a 300Ah before I felt comfortable running a freezer full-time without a reliable daily recharge. Have you considered a Victron SmartShunt to actually measure what you're pulling rather than estimating?

Great question @Lefty28, and the others have covered the basics well.

One thing worth adding from my own experience running a BougeRV 30L off a Victron SmartShunt + 200Ah Fogstar setup — your usable capacity matters enormously here. The Fogstar Drift gives you roughly 160-170Ah usable before you're pushing the BMS hard.

A chest freezer pre-cooled properly before you sleep will cycle far less overnight when ambient drops. I'd strongly recommend getting a Victron Battery Protect or similar in the circuit so you're not accidentally draining below safe thresholds if the freezer runs harder than expected.

Also worth logging actual draw with a Bluetooth energy monitor for a few nights before committing — real-world numbers always surprise you compared to manufacturer specs. Your solar recharge capacity the following morning is equally important to factor in.

Got a Brass Monkey 35L running off my static caravan setup — similar situation. Rough rule of thumb I use is assume the freezer pulls maybe 30-40% of its rated wattage as an average draw over 24hrs once it's up to temp. So if it's rated ~45W, you're looking at maybe 15-18W average.

Over 12hrs that's roughly 22Ah at 12V — well within your 200Ah. Even being generous and doubling that estimate for a hot night, you've still got loads of headroom.

Main thing I'd watch: don't let the Fogstar drop below 20% if you can help it. Set your low voltage cutoff properly on your MPPT or inverter.

@AlexJones makes a solid point about ambient temp — that's honestly the biggest variable.