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

Been there with this exact headache. Single leisure battery just doesn't cut it for a compressor fridge overnight — you're looking at roughly 30-50Ah consumed depending on ambient temp, and most leisure batteries shouldn't really be drained below 50% if you want them to last.

Moved to a 100Ah Fogstar Drift lithium last year and it's transformed things. You can actually use the full capacity rather than tiptoeing around the 50% cutoff like you do with AGM. Fridge runs no problem through the night and there's still juice left in the morning.

Few things worth checking though:

• What's your fridge set to? Every degree warmer saves noticeable power
• Is the van well ventilated around the fridge? Compressor works harder in a hot cupboard
• Any solar on the roof topping it up during the day?

Without solar I'd honestly say a single battery is always going to be marginal. Even a small 100W Renogy panel makes a surprising difference in summer — on a decent day you're putting back more than the fridge takes overnight.

If you're not ready to go lithium yet, running two AGM batteries in parallel buys you some breathing room, but it's not a long-term fix really.

What fridge are you running and what battery capacity have you got at the moment? Might be able to give more specific thoughts.

@LutonNomad aye, and that's before you factor in that your "100Ah" leisure battery is actually 50Ah usable unless you've gone lithium — AGM doesn't like being taken below 50% without sulphating itself into an early grave.

Fogstar Drift 100Ah LiFePO4 sorted my van conversion overnight; fridge barely notices the night shift now. Pair it with even a modest Victron BMV to actually see what's happening rather than guessing from a cheap voltage meter that lies to you constantly.

Honestly, running a compressor fridge on a single AGM is like trying to fill a bath with the plug half out — thermodynamics always wins.

@DuctTapeDave hit the nail on the head there.

When I first converted my van, I made exactly this mistake — one 100Ah AGM, a shiny new compressor fridge, and the romantic notion I'd wake up to cold milk. Instead I woke up to a flat battery and warm beer.

The turning point was switching to a proper 200Ah lithium from Fogstar and adding two 175W panels feeding through a Victron SmartSolar. Night sorted completely.

The maths is actually pretty simple once you accept it:

• Fridge: ~40Ah overnight minimum
• Fridge needs 2x that capacity available
• Lithium gives you 80%+ usable vs AGM's 50%

You essentially need at least 100Ah lithium dedicated to that fridge alone before touching anything else in the van. One leisure battery was never going to cut it, regardless of the brand.

Great thread this. One thing worth adding that nobody's mentioned yet — ambient temperature makes a massive difference to how hard your compressor's working. I've seen my Waeco pull nearly double the current on a hot summer night compared to a cool autumn one. So your 30-50Ah estimate from @LutonNomad could creep even higher in July.

If you're not already, stick a cheap thermometer inside the fridge and make sure it's not overcrowded — restricted airflow inside means the compressor cycles more frequently. Also keep the fridge out of direct sun during the day if at all possible.

None of this replaces the need for more battery capacity obviously, but it'll squeeze more efficiency out of what you've already got while you're saving up for a second battery! 😄