Anyone else struggling to keep a 12v compressor fridge running overnight on a single leisure battery?

Familiar problem, and one I sorted out for my shepherd's hut build last year — though the principles are identical for a van setup.

The short answer is that a single leisure battery almost certainly isn't enough. A compressor fridge typically draws 3–5A when the compressor is running, and depending on ambient temperature and how often you open it, you're realistically looking at 30–50Ah overnight. A standard 100Ah lead-acid leisure battery only gives you access to maybe 50Ah before you're doing real damage to it, so you're already cutting it fine before you account for anything else running.

A few things that genuinely helped me:

• Switch to lithium if you haven't already. A 100Ah Fogstar Drift gives you ~95Ah usable. Game changer.
• Check your fridge placement. Compressor works harder if it's in a warm spot or the ventilation is restricted.
• Pre-cool the fridge before a trip so it's not working from ambient temperature when you're relying on stored power.
• Victron BMV-712 — knowing your actual state of charge rather than guessing transforms how you manage overnight draw.

What fridge are you running? Some of the cheaper units are genuinely inefficient compared to something like a Dometic or Indel B. There's a massive difference in real-world draw between brands even at the same quoted capacity.

Also worth asking — are you getting any solar top-up during the day? Even a modest 200W panel on a van can comfortably cover a fridge's daily consumption in reasonable UK weather from April through September.

What's your current battery setup? That'll help narrow down where the problem actually sits.

@WattEd knows what he's talking about. Been there myself on my old Hymer — one 100Ah AGM battery and a Waeco compressor fridge, and by 3am the battery voltage was already crying for mercy.

The game-changer for me was switching to a pair of Fogstar Drift 100Ah lithium batteries. Same physical footprint as my old setup, but suddenly I had usable capacity rather than the 50% cutoff AGMs punish you with.

Compressor fridges are deceptive — they don't pull much continuously, but those startup spikes and overnight cycling add up fast. I was genuinely surprised how much I'd been underestimating my actual consumption until I fitted a Victron SmartShunt and watched the data properly.

One battery for overnight fridge duty alone is really only viable if you're hooked up or have serious solar input doing the heavy lifting.

A single 100Ah AGM is roughly 50Ah usable — a typical compressor fridge pulls 3-5Ah average depending on ambient temp, so you're doing the maths on a bad night before you've even factored in your phone charger and LED strips.

Swap to a 100Ah Fogstar Drift LiFePO4 and suddenly you've got ~95Ah usable for about the same footprint — transformed my van setup overnight, literally.

If budget's tight, at minimum run two AGMs in parallel before you start blaming the fridge.

Worth adding that ambient temperature makes a massive difference that people often underestimate. @WattEd and @BatteryAlan have covered the capacity maths well, but I've seen setups that work fine in April completely fall over in August when the van's been baking in a car park all day. The fridge compressor runs almost continuously trying to maintain temp, and your draw suddenly doubles or more.

One practical tip — pre-chill everything before loading the fridge, and throw a small blanket over it if it's in direct sunlight. Sounds daft but it genuinely reduces runtime significantly. Also worth checking your fridge's thermostat setting; many people leave them unnecessarily cold.

If you're serious about overnight reliability, either add a second battery or look at a small solar panel even just 100W to top things up during the day.

Great points all round. What nobody's mentioned yet is the duty cycle trap — I spent an embarrassing amount of time scratching my head in a Tesco car park last summer wondering why my Dometic was cutting out, convinced the fridge was faulty. Turned out the battery was sagging under load and the fridge's low voltage cutoff was kicking in around 11.8v, even though my battery monitor claimed 40% remaining.

Moved to a 100Ah Fogstar Drift LiFePO4 and genuinely never looked back — usable capacity is night and day compared to AGM, and it holds voltage flat right until the end. @BatteryAlan's maths checks out but those AGM numbers are generous in real-world conditions, especially once the battery's a couple of seasons old.

Worth checking your low-voltage cutoff setting too before throwing hardware at the problem.