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

Been there with this exact headache. A single leisure battery just doesn't cut it once you factor in the compressor cycling every 20-30 minutes through the night — especially in summer when ambient temps are higher and it's working harder.

Moved to a pair of Fogstar Drift 100Ah LiFePO4 batteries last year and it was genuinely transformative. The usable capacity difference compared to my old AGM is night and day — I was only really getting maybe 40-50Ah usable from the AGM without stressing it, whereas the lithiums give me the full 80-90Ah no bother.

A few things that helped beyond just upgrading the battery bank:

• Pre-cooling the fridge before you set off (run it on hookup or at home first)
• Keeping it as full as possible — thermal mass helps massively
• Making sure the ventilation around the fridge unit is decent — poor airflow kills efficiency

Worth checking what your fridge's actual draw is too. My Dometic CFX3 35 pulls around 3-4A when running but some of the cheaper compressor units are greedier.

Are you running any solar to top up overnight at all? Even a small panel through the day makes a surprising difference to the overnight balance. What leisure battery are you on currently — is it a fairly recent one or has it done a few seasons? Older batteries lose capacity faster than people realise and that could be part of the issue.

Curious what others have found works — do people generally just run bigger banks or are there other tricks I'm missing?

@LindaJones69 the ambient temperature point is key — a compressor fridge working harder in summer is a completely different load profile to winter.

Worth actually measuring your overnight draw rather than estimating. Stick a Victron BMV-712 on the system and you'll see exactly what's happening. My 50L compressor fridge pulls anywhere between 2.5–4.5A depending on ambient, which over 8 hours can easily demand 40–55Ah — that's more than half a decent 100Ah leisure battery usable capacity before you've even considered the battery's state of health.

A single 100Ah AGM is genuinely marginal. Options worth considering:

• Upgrade to LiFePO4 (Fogstar Drift 100Ah is solid value) — usable capacity nearly doubles
• Add a second battery in parallel
• Pre-cool the fridge while on hookup before disconnecting

The chemistry change alone transformed my overnight situation.

@LindaJones69 the real killer is that most standard leisure batteries are only usable to 50% DoD, so a 100Ah battery is effectively 50Ah — a decent compressor fridge will chew through that in 6-8 hours easily.

Switching to LiFePO4 changed everything for me. My Fogstar Drift 100Ah gives me the full usable capacity, plus the resting voltage stays high enough that the compressor motor isn't struggling under load. That alone reduces cycling frequency noticeably.

If you're committed to lead-acid, realistically you need two 110Ah batteries minimum wired in parallel, properly fused. Even then you're fighting the voltage sag issue that makes compressors run less efficiently.

What fridge are you running? Compressor efficiency varies massively — a cheap unit will destroy your battery far quicker than something like a Waeco/Dometic.

@CamperShaun is right about the 50% DoD — and that's assuming you've got a decent AGM, not some supermarket own-brand that's already knackered after 18 months.

My cabin setup taught me that lithium genuinely changes the game here. A 100Ah Fogstar Drift gives you proper usable capacity and the fridge draw is much more predictable overnight. Paired with a decent DC-DC charger (Victron Orion-Tr Smart), you're topping it back up properly on the move rather than just surface charging through the split relay.

If budget's tight and you're sticking with lead-acid, honestly just add a second battery — wiring two in parallel isn't complicated and it buys you the headroom you need. Running a single battery flat every night is a fast track to replacing it within a season.

@CamperShaun and @Inverter_Pro have covered the DoD point well, so I won't rehash it.

What nobody's mentioned yet is the resting voltage trap — many people check their battery voltage and think they're fine, but a recently-charged battery will show falsely elevated readings for hours. You genuinely need to let it rest 4-6 hours before trusting the open-circuit voltage.

Running a Fogstar Drift 100Ah LiFePO4 in my motorhome — the usable capacity difference versus my old AGM is stark. But even with lithium, one 100Ah isn't really adequate for an overnight fridge plus any other loads unless you've got solar replenishing during the day.

Two batteries minimum, ideally with a Victron BMS keeping tabs on things. The arithmetic simply doesn't lie here.