Anyone else struggling to keep the compressor fridge running overnight on a 100Ah lithium?

Ran the numbers on my van build last summer and the maths doesn't lie — a halfway decent compressor fridge like a BougeRV or Alpicool will chew through 30–45Ah overnight on a warm night, which is already nearly half your usable capacity before you've even thought about lighting, phone charging, or that one mate who insists on running a hairdryer off your inverter (yes, Dave from Bristol, I mean you).

The brutal truth is 100Ah lithium is fine for a weekend overnighter if you're disciplined, but you're basically living on the edge with no solar input after sundown. My garden office setup runs a similar fridge on a 200Ah Fogstar Drift bank and even that gets sweaty in August.

Few things worth checking before you bin the battery and upgrade:

• Fridge thermostat setting — people routinely run these far colder than needed, dial it back a degree or two
• Ambient temperature — compressor works harder when the van is hot, park in shade where you can
• State of charge going into the night — are you actually hitting 100% before sunset?
• Victron SmartShunt — if you haven't got one, you're basically guessing your consumption in the dark

Also worth checking your Victron MPPT settings if you've got solar — some folks have low-voltage disconnect set too conservatively and wonder why the fridge cuts out at 2am.

What fridge are you running and what's your setup? Curious whether this is a consumption problem or a capacity expectation problem — they're different beasts and the fixes are completely different.

@DuctTapeDave different use case here — I've got a static caravan setup rather than a van — but I ran into exactly the same issue before I upgraded to a 200Ah Fogstar Drift.

Worth noting that ambient temp makes a massive difference to compressor duty cycle. Have you looked at where the fridge is actually positioned in the van? Mine was next to the cooker originally and the consumption was noticeably higher.

Also curious what your overnight voltage drop looks like — are you seeing the BMS throttle anything? On my setup I noticed the fridge compressor didn't love starting up when the battery was already below about 12.4V.

Would a second 100Ah be feasible in your build, or are you weight/space limited? That feels like the obvious solution before messing with the fridge itself.

Interesting thread. I've been wrestling with exactly this in my motorhome setup.

One thing I haven't seen mentioned — what's your fridge placement like? I moved mine away from the cab-side wall (gets roasting in summer sun) and saw a noticeable drop in duty cycle. Not a battery fix, but it reduced my overnight draw from roughly 38Ah down to around 28Ah on warm nights.

Also worth asking:

• What's your ambient overnight temp typically?
• Are you monitoring actual draw or just estimating?

I've got a Victron SmartShunt on my Fogstar Drift 100Ah and the data logging has been genuinely eye-opening — the fridge spikes are much shorter than I expected but more frequent than I'd assumed.

Has anyone tried pairing a dedicated small solar panel purely to offset the fridge load overnight via battery top-up during daylight?

@DuctTapeDave 100Ah was always going to be marginal for overnight fridge use — that's not really a van build problem, that's just physics.

I've got a Fogstar Drift 200Ah in my motorhome and even that feels tight on a hot August night if I've not had decent solar during the day. Bumped it to two in parallel last year and haven't thought about it since.

Worth also looking at fridge placement and insulation — my Alpicool was working twice as hard because I had it wedged next to the engine bay bulkhead. Moved it, pre-chill before you set off, keep it topped up with food mass — knocked a good 20% off the draw overnight.

If you're committed to 100Ah, a DC-DC charger from your alternator while driving is probably your best friend.

@DuctTapeDave this is basically why I went 200Ah minimum when I spec'd out my van build. Even then, a hot August night with the fridge working overtime nearly caught me out.

One thing worth checking — what's your fridge thermostat set to? I dropped mine from 4°C to 6°C and the duty cycle dropped noticeably. Not always practical if you're storing dairy long-term but for a weekend away it makes a difference.

Also, are you running Victron's battery protect or similar? Some fridges draw a nasty little phantom load even when the compressor's off. Found that out the hard way with my Fogstar 200Ah — woke up to lower SOC than expected and traced it back to the fridge controller sitting there sipping away all night.

What solar input are you actually getting? That's the real question here.