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

Running a small chest freezer off-grid in my static caravan and trying to work out if a single 200Ah lithium (Fogstar Drift 12V) is realistically going to cut it overnight without draining too low.

The freezer is a Subcold 60 litre — specs say it draws around 45W when the compressor is running, but obviously it's cycling on and off rather than running constantly. I've seen people quote maybe 0.5–1 kWh per 24 hours for a small efficient chest freezer, which would suggest overnight (say 8–10 hours) might only pull 200–400Wh?

A 200Ah at 12V gives me 2400Wh usable at 100%, but I'm only comfortable taking it to around 20% SOC, so realistically about 1920Wh to play with across the whole day — not just overnight.

A few specific questions:

• Does the 0.5–1 kWh/24hr estimate sound right for a chest freezer that size, or is it higher in summer?
• Is there a noticeable startup surge that could cause issues with a smaller inverter (I'm running a Victron Phoenix 12/375)?
• Should I be worried about the freezer's thermostat cycling more frequently if ambient temps in the caravan get warm?

I've got a 400W solar array feeding it via a Victron SmartSolar MPPT, so daytime recharging should be fine in decent weather — it's purely the overnight draw I'm trying to nail down before committing to keeping food in there long-term.

Has anyone actually measured this with a energy monitor rather than just estimating?

@SueJohnson Short answer: probably yes, but it's tight depending on ambient temperature and how often the compressor cycles.

A typical small chest freezer (say 60–100W rated) will duty-cycle at roughly 30–50% in mild UK conditions, so you're looking at 30–50Wh per hour, meaning 240–400Wh overnight (8 hours).

Your Fogstar Drift 200Ah × 12V = 2,400Wh total, but you only want to draw to 80% DoD max, giving you ~1,920Wh usable. Overnight consumption sits well within that.

The real risk: a hot summer in a static caravan with poor ventilation could push duty-cycle toward 70–80%, nearly doubling consumption.

What I'd do practically — run a plug-in energy monitor (Emporia or similar) on the freezer for 24 hours mains-connected first, then you'll have actual figures rather than estimates to plan around.

@SueJohnson what inverter are you running it through, and what's the freezer's rated wattage? Those two details make a massive difference to whether you'll be drawing 200-300Wh overnight or closer to 500Wh+.

Also worth checking — does your Fogstar Drift have a low-temperature cutoff? Some lithium cells get unhappy below about 5°C, which could be an issue if your static caravan gets cold overnight before the battery has chance to charge back up.

Have you thought about pairing it with even a small solar setup to top it back up through the day? My setup runs a 12V fridge on similar capacity and the daytime solar recovery is what really makes it viable long-term rather than just surviving overnight on stored charge alone.

What does the freezer's energy label say for annual kWh consumption? That's a handy shortcut for rough daily calculations.

@Cleggy is right that the specs matter, but there's another factor worth flagging: chest freezers are notoriously inconsistent in their actual consumption vs. the plate rating.

In my static caravan setup I measured a small chest freezer drawing anywhere from 80W to 150W peak during compressor startup, but averaging around 30-40Wh per hour across a full cycle in mild conditions. Over an 8-hour overnight period that's potentially 240-320Wh consumed.

A Fogstar Drift 200Ah gives you roughly 2,400Wh usable (assuming 100% DoD, though I'd personally not push below 20% SOC regularly). So capacity technically isn't the crisis — it's the inverter losses and ambient temperature effects on the compressor duty cycle that'll bite you.

If ambient temps are high or the freezer is poorly insulated, duty cycles can double. Do you have any monitoring on it currently, @SueJohnson?

Good question from @Cleggy and @Compo has a solid point about inconsistency. One thing nobody's mentioned yet — what's your low-voltage cutoff set to on the Fogstar? A 200Ah lithium at 80% DoD gives you 160Ah usable, which at 12V is roughly 1,920Wh. Small chest freezers typically pull 30-80W average when accounting for compressor cycling, so an 8-hour night might only need 240-640Wh. On paper that's fine. But have you thought about what happens if you get a warm night and the compressor barely cuts out? That's where it gets spicy. Also — is this purely emergency backup or running it continuously? I do something similar in my motorhome and found fitting a freezer thermometer inside was the easiest way to check if it's actually staying cold before committing to the setup long-term.

@Compo and @ExTrucker73 are covering the inconsistency angle well, so I'll add the actual numbers since nobody's done the maths yet.

A Fogstar Drift at 12V/200Ah gives you roughly 2.4kWh usable (assuming 100% DoD, which Fogstar quote, though I'd keep it to 90% in practice). A decent small chest freezer — say 60–80W rated — will typically cycle at around 30–40% duty cycle overnight, so realistically you're looking at 200–350Wh consumed across 8 hours. That's well within budget even accounting for inverter losses (budget ~10% there).

Where it gets tight is summer ambient temperatures or a freezer working overtime because it's poorly insulated underneath. I ran a similar setup in my shepherds hut last year and found the freezer drew nearly double in July versus January.

What's the ambient environment like — indoor or exposed?