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

Running a small chest freezer overnight in my garden office is something I've been trying to figure out before committing to a setup. Currently I've got a 200Ah Fogstar Drift LiFePO4 sitting in the office powering lights and a laptop, but I'm wondering if it can handle a chest freezer as well.

The freezer I'm looking at is a Lec 50 litre chest freezer, rated at around 85W but obviously it cycles on and off rather than drawing that constantly. From what I can work out, something like 0.5-0.8 kWh per day seems typical for a small unit, though I've seen wildly different figures online.

My concerns are:

• Whether a single 200Ah (roughly 2.56 kWh usable at 80% DoD) is actually enough headroom overnight if it's been partially depleted during the day
• Whether the compressor startup surge will cause any issues with my current 1000W inverter
• How ambient temperature in the office affects freezer efficiency — mine isn't insulated brilliantly

I'm charging via a small 400W solar array with a Victron SmartSolar MPPT, so overnight there's obviously no replenishment happening. Realistically I'd probably only be drawing from the battery from around 6pm to 8am in winter.

Has anyone actually run numbers on this or done it in practice? Would adding a second 100Ah battery make more sense than going straight to another 200Ah? Open to any advice from people who've done something similar.

@GeorgeJohnson83 depends heavily on the freezer. A decent chest freezer (say 60-80L) typically draws around 80-100Wh per day in moderate temps, so overnight you're probably looking at 40-60Wh if it's not working too hard. Your 200Ah Fogstar at 24V gives you a massive headroom — even at 12V that's 2400Wh usable (assuming 100% DoD, which you wouldn't want on LiFePO4 anyway, but still).

The real variables:

• Ambient temperature — garden offices can get cold, which actually helps
• How full the freezer is (thermal mass matters)
• Compressor type — inverter compressors are far more efficient

Realistically you'll be fine. Mine runs a chest freezer plus a small 12V fridge on a similar-sized setup without breaking a sweat. What's the wattage stated on your freezer's label?

@GeorgeJohnson83 good news — a 200Ah LiFePO4 at 12V gives you a usable ~2kWh (assuming 80% DoD on Fogstar's Drift). A small chest freezer running overnight (say 8 hours) in an insulated space will typically consume 200-400Wh total depending on ambient temperature and compressor duty cycle. So you're looking at comfortable headroom even on the pessimistic end.

Key thing to watch: startup surge current. Compressors can spike 3-5x running draw on startup, so make sure your inverter handles that — a 300W rated freezer might surge to 1,000W+ momentarily. Most decent pure sine inverters (Victron Phoenix etc.) handle this fine.

One practical tip from my motorhome setup — pre-chill the freezer thoroughly before switching to battery power. Dramatically reduces overnight consumption.

What inverter are you pairing it with?

@SimonKelly and @LindaJones69 have covered the headline numbers, but the devil's in the compressor start surge — cheap inverters will trip when that motor kicks in, so make sure your inverter's surge rating is at least 3x the freezer's running wattage.

Also worth noting: ambient temperature in a garden office swings wildly overnight in the UK (cheers, weather), which directly affects how hard the compressor cycles — a cold January night actually helps your runtime figures considerably.

One more pedantic point: the Fogstar Drift's 80% DoD spec assumes you're not hammering it with high discharge rates continuously — a freezer's intermittent cycling is actually quite gentle on the cells, so you're in good shape there.

Ran a similar setup myself last winter without drama — just don't forget a Victron SmartShunt so you actually know what's happening rather than guessing.

@OldSailor makes a fair point on the surge — worth adding that ambient temp matters loads too. My shepherd's hut setup runs a small Subcold chest freezer and it works fine off a similar capacity bank in summer, but in winter the compressor barely kicks in so consumption drops massively.

Garden office is probably better insulated than my hut tbh, so you're likely fine either way.

One thing nobody's mentioned — check the freezer's actual energy label, not forum guesstimates. The yearly kWh figure divided by 365 gives you a decent nightly ballpark. Some of the cheap chest freezers are surprisingly efficient.

200Ah Fogstar Drift is a solid bit of kit for this. You'll be grand.

Really good points all round. One thing worth adding from my boat setup — freezer cycling frequency matters as much as the raw wattage figures. A well-insulated chest freezer in a cool garden office might only run the compressor 30–40% of the time overnight, which dramatically changes your consumption vs. a warm summer night.

Also worth checking whether your Fogstar Drift is set up with a decent low-voltage cutoff — I run mine via a Victron SmartShunt so I can actually see what's being drawn in real time rather than guessing. Makes it much easier to validate the theory before you commit to anything permanent.

A 200Ah should be fine in most scenarios, but logging a few nights of actual data first would give you proper confidence.