Anyone know if a 200Ah lithium battery is enough to run a small chest freezer overnight?

Got a 200Ah LiFePO4 (Fogstar Drift) sitting in the garage that I mainly keep topped up for emergency backup. Been thinking about putting it to proper use running a small chest freezer overnight when the grid goes down.

The freezer is a 60L unit, rated at about 85W but obviously it cycles on and off rather than running flat out. From what I've read it might average somewhere around 30-40W depending on ambient temp and how full it is.

Rough maths puts that at maybe 30-40Ah over 12 hours at 12V, which sounds well within the 200Ah capacity — even with the usual 80% usable limit on LiFePO4. But I'm not confident I'm calculating this right, especially when you factor in inverter losses.

Running it through a Victron Phoenix 375VA inverter if that matters.

Few specific questions:

• Is my consumption estimate realistic for a small chest freezer?
• Any gotchas with the startup surge tripping things or stressing the battery?
• Would ambient temperature in an unheated garage through winter significantly affect either the battery performance or the freezer consumption?

The setup is purely for emergency use so it won't be running 24/7, just need confidence it'll hold food safely through a typical overnight outage. Real world experience would be more useful than datasheets here — anyone actually done something similar?

@LDVSolar ran almost exactly this scenario in my shepherd's hut last summer. The chest freezer is the sneaky one — the average draw sounds fine on paper, but watch the compressor startup surge and how often it cycles in warm weather.

Key thing I learned: a 200Ah LiFePO4 gives you roughly 2kWh usable (keeping above 20% SOC). A decent small chest freezer pulls maybe 80-150Wh per 24 hours when ambient is cool — so overnight alone you're laughing.

But in a warm garage? That cycle frequency doubles or trebles. Log the actual consumption for a day with a basic energy monitor before committing.

Also worth checking your Fogstar's continuous discharge rating against the compressor startup spike — usually 3-5x running watts for a fraction of a second. Most LiFePO4 handle it fine, but worth confirming.

Depends entirely on the freezer. A decent small chest freezer (50-100L) typically draws 100-150W when the compressor kicks in but only runs maybe 20-30% duty cycle overnight if ambient is cool. You're looking at 30-50Wh actual consumption over 8 hours — nowhere near your 200Ah.

BUT. Cold garage in winter? Compressor barely runs. Hot summer night? Could be 2-3x that draw.

Main thing people miss: the compressor startup surge. Make sure your Fogstar's BMS can handle it — most LiFePO4 can, but worth checking the discharge specs.

I run a chest freezer off 100Ah in my cabin without issue. The 200Ah will cope fine assuming you haven't got a knackered old fridge-freezer masquerading as "efficient." Check the actual wattage on the label first.

@LDVSolar done this exact thing in my static van — 200Ah Fogstar is fine for overnight but your killer is ambient temperature; freezer works twice as hard in a warm garage versus outside in January. Run a Victron SmartShunt and actually log the draw before committing, because "small chest freezer" covers everything from a miserly 0.1kWh/day unit to a power-hungry 0.4kWh/day disaster depending on age and make. Don't forget usable capacity on LiFePO4 is roughly 80-90%, so you've got ~170Ah realistically — plenty of headroom if your freezer isn't ancient.

@GrumpyBuilder is right on the numbers but nobody's mentioned the inverter yet — that thing's eating 10-20W just sitting there idling all night even when the compressor's off, which on a 200Ah pack adds up to roughly 10% of your usable capacity gone before the freezer's done a single cycle. Run the freezer directly on 12V DC if your model supports it, or grab a decent pure sine inverter with a low no-load draw (Victron Phoenix is embarrassingly good at this). Also worth noting your Fogstar Drift's usable capacity depends heavily on your BMS cutoff settings — I've seen people lose 20Ah arguing with their own battery's protection circuit at 3am in a motorhome layby. Don't ask how I know.