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

Running a Fogstar Drift 200Ah on my narrowboat and debating whether to plug in a small chest freezer (looking at the Inventor CF110, roughly 110L) overnight instead of relying on the boat's tiny icebox that's about as useful as a chocolate teapot.

From what I've worked out, a decent chest freezer at that size pulls maybe 30–45W running average once it's properly cold, so over say 10 hours that's potentially 300–450Wh — which on paper sounds fine for a 200Ah (roughly 2,400Wh usable at 12V, less if you're keeping above 80% DoD like a sensible person).

My concerns though:

• Compressor startup surge — anyone know if the Fogstar handles that without the BMS throwing a wobble?
• I'm on solar with a Victron SmartSolar 100/30, but overnight obviously means zero input, so it's pure battery draw
• Ambient temp on the boat in autumn can be properly grim, which I assume makes the freezer work harder

Has anyone actually done this rather than just done the maths on a napkin? Particularly interested if you're running it off a single 200Ah rather than a bank, because everything I read assumes people have four batteries and a wind turbine the size of a small aircraft.

Also worth noting my inverter is only a 350W pure sine so if the startup surge goes above that we've got a whole other problem to solve before we even get to the battery question.

@OffGridJulie the CF110 draws around 30-45W average once settled (compressor cycles), so overnight — call it 10 hours — you're looking at roughly 300-450Wh consumed. Your 200Ah Fogstar at 12V is 2400Wh nominal, but you want to stay above 20% on lithium, so usable is ~1920Wh. Purely on paper, yes, it'll cope comfortably.

The catch on narrowboats is ambient temperature. Chest freezers work harder when the engine bay or cabin gets warm in summer — I've seen a CF110-type unit spike to 60W+ average in a poorly ventilated space. Worth logging actual consumption with a Victron BMV or similar before committing.

Also check your BMS discharge rating — the Fogstar Drift handles surge well, but compressor start draw can hit 3-4x running wattage momentarily.

@LutonCamper has covered the watt-hour maths reasonably well, but there's a critical nuance being glossed over here.

The Fogstar Drift 200Ah is a 12V unit, giving you ~2400Wh nominal — but Fogstar rate it to 80% DoD comfortably, so realistically 1920Wh usable. Overnight freezer draw won't trouble that in isolation.

The problem on a narrowboat is cumulative loads. Bilge pump, lighting, phone charging, fridge if you have one separately — these stack up silently. I run a CF82 aboard and found the compressor starting current briefly spikes to 3-4x running draw, which matters less for lithium than lead-acid but still worth noting if your inverter is undersized.

More importantly: what's your morning recharge situation? Solar, alternator, shore power? A freezer held overnight needs replacing those watt-hours before the next cycle, otherwise you're in a slow discharge spiral within a few days.

@DefenderAdventure stop teasing and finish the point.

@OffGridJulie the maths is fine but your usable capacity is the real constraint. The Fogstar Drift is rated to 100% DoD but I'd personally never push lithium that hard routinely — stick to 80% usable, so ~160Ah practical = roughly 1,920Wh.

Overnight at 40W average that's ~400Wh. Fine on paper. But:

• Startup surge from the compressor — the CF110 will spike briefly. Check your BMS can handle it.
• Ambient temperature matters. Colder bilge = compressor works less. Warmer = more draw.
• Is that your only load? Nav electronics, lighting, bilge pump — it all stacks up.

Run it for one night with a decent energy monitor (Victron BMV-712 is worth every penny) and log actual consumption before committing. Don't guess on a narrowboat — you've got no quick escape route if the bank dies.

Great points from @LutonCamper and @DefenderAdventure already. One thing worth adding specifically for the Fogstar Drift — it's a LiFePO4, so you've got a pretty flat discharge curve which is good news, but do check your BMS low-voltage cutoff settings. Some are configured conservatively from the factory and will trip earlier than you'd expect.

Also worth factoring in: overnight ambient temps on a narrowboat can be quite cool, which actually helps the freezer work less hard. That'll nudge your real-world consumption towards the lower end of @LutonCamper's 30-45W estimate.

Short answer: you should be absolutely fine for a single overnight run, but I wouldn't make it a nightly habit without either a decent solar input or a secondary battery to lean on. What's your charging setup looking like?