Anyone else running a compressor fridge off a single 100Ah lithium? What's your real-world draw?

Picked up a Alpicool C15 compressor fridge a few months back and I'm trying to get a proper handle on the actual power draw over a full day. On paper the specs say around 40–45W when running, but obviously it's not running constantly. I've got a basic watt meter on the feed and I'm seeing somewhere between 25–35Ah per 24 hours depending on ambient temp — more like 40Ah+ when it's been warm lately, which is a bit concerning.

I'm running it off a single 100Ah lithium (Fogstar Drift if anyone's wondering) charged via a 175W panel on the roof and a Renogy 40A MPPT controller. On decent sunny days it's absolutely fine, the panel easily keeps up. It's the overcast days and overnight that I'm worrying about — I don't want to be hammering the battery below 20% regularly.

Has anyone found any good tricks to reduce the draw? I've seen people mention pre-cooling at home before setting off, keeping it out of direct sunlight, and not opening it constantly — all obvious stuff really. But I'm also wondering whether a second 100Ah battery would just solve the headache entirely, or whether I'm overthinking it and my setup is actually fine for most trips.

@Tommo10 specs are written by the same people who calculate MPG figures — technically true, practically fiction.

My Alpicool on the narrowboat averages 3–5Ah per hour in real life, so roughly 72–120Ah over 24hrs depending on ambient temp and how many times you crack it open for another biscuit.

One 100Ah lithium is technically survivable but you're living dangerously — you'd be cycling that battery into the floor every single day.

Minimum I'd want behind it is 200Ah, preferably with decent solar on top. Fogstar do solid affordable cells if you're looking to expand without crying at the price.

@StormyNomad

Running a C15 off a single 100Ah lithium here — been doing it for about eight months across various trips. Real-world draw in mild UK weather sits around 18-22Ah per day for me, but that climbs noticeably once you're parked in direct sun or the ambient temp creeps up. Shading the fridge makes a genuine difference, honestly worth the faff.

@Tommo10 the duty cycle is the thing people underestimate. That 40-45W figure is only when the compressor's actually running — factor in maybe 30-40% duty cycle in reasonable conditions and your daily consumption starts making more sense.

One 100Ah lithium is workable but tight if you're wild camping without solar input. I wouldn't want to rely on it beyond a night or two without some recharge source, even with disciplined usage.

On a boat so my ambient temps are all over the place — that makes a massive difference to duty cycle. Same fridge in a hot van vs a cool morning will draw completely differently.

Rough rule of thumb I've found: assume ~20Ah per 24hrs in mild conditions, double it if it's roasting or the fridge is stuffed full. My Victron BMV-712 logs it all so I can actually see the difference day to day rather than guessing.

Single 100Ah should cope fine as long as you're not trying to also run lights, charging laptops etc without some solar topping things up.

@Rachel1995

@Tommo10 I've got a C15 running off a 100Ah lithium in my Transit conversion — tracked it pretty carefully with a Victron SmartShunt over a few weeks. My real-world average sits around 18–22Ah per day in mild UK weather, but that crept up to nearly 30Ah during last summer's hotter stretches. The big thing nobody mentions is how full you keep it — a packed fridge holds temperature far better than a half-empty one, so I try to keep mine reasonably stocked or use a few frozen water bottles as thermal mass. At that draw you're absolutely fine on a single 100Ah lithium provided you're getting some solar or engine charging in. Just don't let your ambient van temperature get silly high — parking in shade makes a noticeable difference to duty cycle.

@FrostyTrekker

Worth mentioning ambient temp inside the van rather than just outside — I found mine draws noticeably more when parked in direct sun even with decent insulation. Also, pre-cooling the fridge contents before loading makes a surprising difference to that initial spike @Tommo10 mentioned in the specs. I run a C20 off a single 100Ah and honestly the biggest game-changer was adding a small 12V fan to improve air circulation around the compressor — dropped my daily consumption by roughly 8-10Ah once the heat wasn't building up behind the unit. @MandyGrant makes a fair point about ambient conditions being everything. If you're wild camping and parking sensibly in shade, a single 100Ah should serve you fine through a UK summer night at least.

My setup's a bit different — static caravan rather than a van — but I ran a similar compressor fridge through last summer as part of testing the electrics before committing to a full Victron/Fogstar build for my garden office.

What surprised me most wasn't the running wattage but the startup spike. Caught it properly on a Victron BMV-712 — brief but sharp, and it matters if your BMS is twitchy.

Also worth logging overnight specifically. Ambient drops, duty cycle drops with it, and your 24-hour average can look deceptively healthy until a hot August afternoon hits and suddenly everything's working twice as hard.

@Rachel1995 's point about tracking carefully is spot on — gut feel lies to you with compressor fridges. The variance between a cool night and a sunny afternoon is genuinely dramatic.

Not a van setup but running an Alpicool off a 100Ah Fogstar Drift in my shepherd's hut — similar ballpark. Found it pulls roughly 15–20Ah per 24hrs in mild weather, but that crept up noticeably once ambient inside the hut got above 25°C in summer.

One thing nobody's mentioned — lid discipline matters more than you'd think. Every time you rummage around you're losing cold and the compressor kicks back in harder.

@FrostyTrekker makes a good point about ambient. I started logging mine with a Victron BMV and it made a real difference seeing the actual patterns rather than guessing.

@BodgeItAndScarper92

Running a C20 off a 100Ah Fogstar Drift here, so close enough to be useful. My real-world average works out around 18-22Ah per 24 hours in mild weather — but that's with the fridge maybe a third full and set to 4°C. Pack it properly and pre-cool your contents before loading and you'll shift that down noticeably. The duty cycle is everything really — mine's running about 30-35% of the time once it's up to temp. Keep an eye on your battery's state of charge overnight; I wouldn't let a 100Ah drop below 20% regularly. Should be manageable though!

Good news is the duty cycle's where the real variance hides. Mine sits around 30–40% in a reasonably cool van, but stick it in direct sun or pack it with warm food and watch that climb sharply. Worth logging a full 24hrs with a proper meter — I use a Victron BMV-712 and the historical data is genuinely eye-opening.

@AnneWatson shepherd's hut must help with ambient temps vs a metal box baking in a carpark though — you're probably getting a friendlier duty cycle than most van dwellers.

100Ah is doable but tight if you're not getting solar input during the day.

Good thread this. I'd add from an electrical background — watch your actual cycle frequency more than just the wattage figure. In summer with the van sitting in sun, that compressor kicks in far more often and your daily draw can creep up surprisingly. I've seen setups chew through nearly double the "average" figures people quote once ambient temps push past 25°C inside the van.

Worth sticking a simple energy monitor inline if you haven't already — the Victron BMV series shows you exactly what's happening over 24 hours rather than guessing. Proper data makes a real difference when you're trying to size your system accurately. 🔌

@JoeFisher

Great timing on this thread — I ran a very similar setup last summer with a C15 on a 100Ah lithium. The figure that surprised me most was how dramatically ambient temp inside the van affected things. Parked in direct sun, my daily consumption nearly doubled compared to an overcast day. @CamperSam's point on duty cycle is spot on — shade your fridge from direct sunlight and leave a gap behind it for airflow, and you'll genuinely claw back meaningful amp-hours over a full day. Small thing, big difference.