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

Been there with my boat setup, ended up going down a bit of a rabbit hole honestly.

Single leisure battery just doesn't cut it for a compressor fridge overnight in my experience — even a decent 100Ah AGM is pretty much done by morning if the fridge is cycling regularly. Ambient temp makes a massive difference too, warmer it is the harder it works.

Couple of things that helped me:

• Switched to a Fogstar Drift 100Ah LiFePO4 — usable capacity is just so much better than AGM, night and day difference
• Added a second battery in parallel
• Made sure the fridge was actually shaded properly and not sitting next to something warm

The fridge brand matters as well. Some of the cheaper compressor units are really inefficient. Dometic and Engel tend to draw less over 24hrs than some no-name alternatives even if the spec sheet looks similar.

What battery are you currently running and what fridge? Might be worth checking actual draw with a meter rather than going off the fridge manufacturer figures — those are usually optimistic.

Also — are you getting any solar charge during the day? Even a small panel through a Victron SmartSolar makes a surprising difference to overnight reserves.

Curious what others are doing in similar setups, motorhomes must have the same headache especially in summer.

YorkshireExplorer | 847 posts | ⚡ Solar Enthusiast

@Fogstar_Fan Spot on mate. The maths just doesn't stack up when you think about it properly — a decent compressor fridge like a Dometic or Engel pulls anywhere from 3-5 amps average depending on ambient temperature and how full it is. Over 12 hours that's potentially 60Ah, and you shouldn't really be dipping below 50% on a standard lead-acid leisure battery anyway, so your usable capacity from a 100Ah battery is only around 50Ah realistically.

I run two 110Ah batteries in parallel on my van and even then I'm glad I've got a decent solar setup topping them up through the day. If you're on lithium it's a different story entirely — full 100% depth of discharge available changes everything. Worth considering if you're doing regular overnight trips.

IslandWanderer | 1,203 posts | 🏝️ Off-Grid Liveaboard

@Fogstar_Fan @YorkshireExplorer — worth adding that ambient temperature plays a massive role here too. Same fridge, same battery, but stick it in a warm van in summer versus a cool night and you'll see wildly different consumption figures. I've logged mine pulling anywhere from 2.5Ah to 6Ah per hour depending on conditions.

Also worth checking how full the fridge is — a well-stocked fridge holds temperature far better than a half-empty one. Chuck a couple of frozen water bottles in there if you've got spare space.

Realistically though, you're looking at needing either a second battery or a decent solar top-up during the day to make it comfortable overnight without anxiety about waking up to flat batteries!

GlenSimon | 412 posts | 🚐 Van Dweller

My Fogstar 100Ah lithium laughed at my optimism exactly once before I wired up a second one — the fridge doesn't care about your feelings or your budget.

BenJackson | 234 posts | ☀️ Solar & Motorhome

@GlenSimon two Fogstar 100Ah lithiums later and my fridge still runs like it pays rent — the secret is telling yourself it's "just one more battery" until your motorhome's suspension quietly weeps.

GoldenMechanic | 89 posts | 🔧 Van & Garden Office Builds

@GlenSimon @BenJackson — same boat here (well, van). Running a Waeco CFX35 in my conversion and the real issue nobody mentions is duty cycle in warm weather. That fridge can hit 60-70% duty cycle on a hot day, which absolutely destroys your overnight figures.

What actually solved it for me wasn't just adding capacity — it was fitting a Victron BMV-712 so I could finally see exactly what the fridge was pulling in real time. Turns out mine was spiking higher than spec on startup.

Has anyone actually measured their compressor's actual draw vs the rated figures? Mine was noticeably worse than the datasheet claimed, especially when the ambient temp inside the van crept up.

Worth logging it over 24 hours before throwing more batteries at the problem.