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

Been through exactly this with my cabin setup, so whilst it's not a motorhome I reckon the principles translate directly.

The short answer is: one leisure battery almost certainly isn't enough. A decent compressor fridge — your Waeco, Dometic, or similar — will pull anywhere from 30–50Ah overnight depending on ambient temperature and how hard it's cycling. A standard 100Ah leisure battery, even a decent AGM, realistically gives you maybe 50Ah usable before you're damaging it with deep discharge. The maths just doesn't work.

What actually solved it for me:

• Upgraded to LiFePO4 — Fogstar Drift 100Ah gives you genuine 80–90Ah usable, which is a completely different proposition to lead-acid
• Added a second battery — two in parallel means overnight draw is barely touching your state of charge
• Checked fridge placement — mine was running far harder than necessary because of poor ventilation around the condenser

If you're determined to stick with a single battery, the only real mitigation is a quality DC-DC charger (Victron Orion-Tr Smart is the obvious choice) to ensure you're properly topping up from the vehicle alternator whilst driving, and keeping ambient temperatures down so the fridge doesn't cycle as aggressively.

What fridge are you running and what's your current battery chemistry? That'll narrow down whether this is a capacity problem, a charging problem, or both. Suspect it's both.

@WezWhite72 sounds like your post got cut off mid-sentence, but I'll pick up the thread anyway.

The maths rarely lies here. A decent compressor fridge — say an Alpicool or Dometic CFX — draws roughly 30–50Ah per 24 hours depending on ambient temperature and setpoint. A single 100Ah lead-acid leisure battery gives you maybe 50Ah usable before you're damaging it. That's your entire overnight budget gone with nothing left for lighting, phone charging, or the morning kettle.

The real fix is either:

• Two batteries minimum (or one good 100Ah LiFePO4 — Fogstar Drift is decent value)
• Adequate solar or mains hook-up to replenish during the day

I run a Victron SmartShunt which makes the actual consumption very obvious — worth every penny just for the diagnostic clarity alone.

Yep, both posts got chopped — forum's having a moment clearly.

To add something useful: it's not just capacity that bites you, it's the discharge curve. A single 100Ah AGM is basically done at 50Ah usable. My Fogstar 100Ah lithium in the motorhome runs the compressor fridge all night no problem — same physical size, double the usable capacity.

If you're stuck with AGM, two batteries minimum. If you're upgrading anyway, just go lithium and stop fighting it.

Good points from both above, and @DownsCruiser is right that capacity alone doesn't tell the whole story.

Worth adding: depth of discharge matters enormously here. A standard lead-acid leisure battery shouldn't really go below 50% — so that 100Ah battery is realistically only 50Ah usable. Run a compressor fridge pulling 3-5A average and you're doing the maths yourself.

On my narrowboat I made exactly this mistake early on. Swapped to a 200Ah lithium (Fogstar Drift) and the difference was night and day — genuine 80-90% DoD without hammering the cells.

If lithium's not in the budget yet, two decent AGMs in parallel is a reasonable stopgap. But honestly, the single-battery route is always going to be a compromise with a compressor fridge running overnight.

Swapped my single 110Ah for a pair of Fogstar 100Ah lithium last summer and my Waeco hasn't broken a sweat since — turns out doubling the usable capacity and halving the weight was the upgrade my motorhome and my back both needed.