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

Got a Fogstar Drift 200Ah sitting in my cabin and wondering if it'll cope with running a small chest freezer overnight without completely tanking the battery.

The freezer is a Subcold Pro 35 — it's rated at about 35W but obviously it cycles on and off rather than drawing that continuously. Not sure what the actual average consumption works out to be in practice.

Setup is pretty basic:

• Fogstar Drift 200Ah LiFePO4
• 200W of solar (two Renogy 100W panels)
• Victron MPPT 75/15 controller

The cabin is in Scotland so overnight temps can drop quite a bit, which I imagine helps the freezer run less frequently? Or maybe not, not sure how that works.

Main concern is whether I'll have enough capacity left by morning for the battery to recover reasonably well through the day. Don't want to be hammering it down to 10-20% SOC every single night — defeats the point of having lithium really.

Has anyone actually run something similar and can share rough figures on what a small chest freezer pulls overnight? I've seen wildly different numbers online and half of them are for American setups with 120V so doesn't really translate.

@Fogstar_Fan the Subcold Pro 35 pulls around 45W when the compressor's running but it's cycling, not constant — typically 30-40% duty cycle in a cool ambient, so realistically 15-18Wh per hour average.

Over 8 hours that's roughly 120-145Wh, which on your 200Ah (2560Wh) is barely a dent even accounting for BMS overhead and inverter losses if you're running it on AC.

Running it direct 12V DC would be more efficient though — worth checking if the Subcold has a DC input option.

The Fogstar Drift handles continuous draws like this brilliantly in my experience on the narrowboat. Just make sure your BMS low-voltage cutoff is sensibly set — I run mine at 20% SOC as a floor.

Overnight should be absolutely fine. More concerned about ambient temperature — hot cabin will dramatically increase compressor runtime.

Hey @Fogstar_Fan, good news really — you should be absolutely fine for an overnight run. The Subcold Pro 35 is pretty efficient and as @MrBodge65 says it's cycling, so your actual consumption over 8 hours will likely be somewhere in the region of 150-250Wh depending on ambient temperature in the cabin. Your Fogstar Drift is a cracking battery — 200Ah at 12V gives you 2400Wh theoretical, and even keeping to the recommended 80% DoD you've got 1920Wh to play with. That freezer overnight is barely touching it. Worth keeping an eye on cabin temperature though — if it's warm, the compressor runs longer cycles and draws more. Cold nights actually work in your favour here!

Has anyone actually measured the real-world draw on that freezer with a meter rather than going off the spec sheet? In my motorhome I've found compressor fridges can pull noticeably more than quoted during startup spikes, especially in warmer ambient temps.

Also worth considering what your Fogstar Drift's usable capacity actually is overnight — are you running anything else alongside the freezer? Even a phone charger or LED lights adds up across 8+ hours.

I'd be curious whether you have any way to monitor consumption — something like a Victron SmartShunt would tell you exactly what's happening rather than guessing. Made a massive difference to how I manage my motorhome setup, stopped me being caught out.

What's the lowest you're comfortable letting the battery drop to? That changes the maths quite a bit.

@Moorey44 raises a valid point — spec sheets are optimistic. I've got a Victron SmartShunt on my narrowboat and the actual cycling behaviour varies quite a bit depending on ambient temperature and how full the freezer is. A fuller freezer holds temperature better, meaning the compressor runs less.

Worth noting that the Fogstar Drift has a 100A BMS limit, so a cold-start compressor surge shouldn't be an issue, but do check the freezer's startup current if you're stacking other loads.

Rough estimate: if the freezer averages ~20Wh actual consumption per hour over 8 hours, that's 160Wh — well within what a 200Ah (at 12V, so ~2400Wh usable at 80% DoD) can handle.

Grab a Jackery or Owl energy monitor and run it for 24 hours before committing to a permanent setup.