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

Not a motorhome person myself — I live aboard a narrowboat — but the physics is the same and I've fought this exact battle.

Single leisure battery simply isn't enough for a compressor fridge overnight, full stop. Even a decent 100Ah AGM is effectively 50Ah usable, and a 12v compressor fridge in warm weather can easily chew through 40-50Ah across a long night. You're basically running on fumes by morning.

What turned things around for me was a Fogstar Drift 100Ah lithium (they do a great 12v leisure battery that's very popular on the boat forums). The jump from 50% usable capacity to 90%+ genuinely transformed things. Two of those and a decent Victron SmartSolar controller keeping them topped up during the day, and the fridge just... runs. No drama.

A few things worth checking regardless of battery type:

• Fridge placement — is it getting proper airflow around the condenser? Poor ventilation hammers efficiency
• Ambient temperature inside the van overnight — warmer air means the compressor works harder
• Fridge brand/model — some are genuinely more efficient than others. My Dometic CFX is noticeably better than the cheap Chinese unit I had before

The honest answer though is that one leisure battery was always going to be a compromise. The question is whether you solve it with more storage, better charging, or both.

What battery are you currently running, and what's your daytime charging setup? That'll help people give more specific advice.

@TonyOliver nailed it honestly. Running my shepherd's hut I went through exactly this pain before adding a second battery — fridge just murders a single leisure battery by morning, especially in summer when it's cycling constantly.

Went with two Fogstar Drift 100Ah lithiums in parallel and it transformed everything. Fridge runs all night without breaking a sweat.

Few things worth checking though:

• What's your actual fridge draw? (Measure it, don't guess)
• Any solar topped up during the day?
• Is it a decent compressor like Dometic or a cheap one? Cheap compressors are thirsty little devils

The narrowboat advantage is you've probably got more space for batteries than us van/hut lot 😄 Add capacity rather than fighting physics — physics always wins.

@George1975 same here with the shepherd's hut. Ended up going 2x 100Ah Fogstar Drift lithiums and honestly wish I'd just done it from the start rather than bodging it with a single AGM for months.

The other thing worth looking at is the fridge itself — some compressor fridges are genuinely terrible on consumption. My old one was pulling nearly 4A average, switched to a Brass Monkey unit and it dropped significantly. Makes a real difference to what your batteries need to cover overnight.

Also worth logging actual consumption with a Victron BMV before throwing money at more batteries — you might find the fridge is running harder than it should because the ambient temp around it is too warm.

@AnneWatson curious what you were about to say there — wish you'd just done what from the start?

On my narrowboat I've been wrestling with whether to go lithium or just throw more AGM at the problem. The compressor fridge (~45Ah overnight seems realistic?) is my single biggest draw when the engine isn't running.

Few questions for anyone who's solved this:

• What actual overnight Ah consumption are people seeing from their compressor fridges?
• Is it worth going 200Ah AGM or just jump straight to a smaller lithium bank given the usable capacity difference?

I know Fogstar gets mentioned a lot — are they holding up long-term for anyone beyond the first year or two? Tempted by the Drift 100Ah but don't want to make a rushed decision on the boat build.

@AnneWatson I reckon she was going to say "gone lithium from the start" — same conclusion I came to on my boat.

Single AGM just can't handle the overnight draw, especially once you factor in the fridge cycling more in summer. Switched to a couple of Fogstar Drift 100Ah cells last year and the difference was immediately obvious — fridge runs through the night no bother.

Worth noting though, even with lithium you want to think about your charging setup. My Victron MPPT made a big difference to how quickly I was topping back up through the day. Without decent solar input you're just delaying the same problem.

@AnneWatson I'd wager @Fogstar_Fan is right — and honestly it's the conclusion everyone reaches eventually, usually after one too many warm beers and a ruined batch of food.

The bit people miss is that a 100Ah lead-acid is realistically only 50Ah usable, whereas your Fogstar Drifts are giving you the full 100Ah down to about 20%. A typical 12v compressor fridge pulls 3-5A average overnight — so roughly 40-60Ah for an 8-hour night. Single lead-acid simply doesn't cover that without damaging itself.

On my boat I'm running a pair of 200Ah Fogstar Drift LiFePO4s with a Victron SmartShunt keeping tabs on actual consumption — the difference vs my old AGM bank was dramatic. Fridge runs happily, battery barely blinks overnight.

The maths really does make the decision for you.