What size power station for a 4WD fridge on a camping weekend

For a 45L compressor fridge over a two-night weekend, look for about 700Wh of usable battery. Three nights, or two with lights and phones on the same station, wants a 1kWh class unit. Plug the fridge into the station's 12V car port, not the AC outlet, and a 1kWh station will keep a single fridge going for close to three days of 32°C weather without any solar at all.

The fridge figure below is Dometic's published consumption for its CFX3 45, and the station specs come from the makers' Australian pages and manuals. The runtimes are our sums, with 15% allowed for conversion losses as our working assumption. Your own fridge's manual has its real number.

What a 4WD fridge actually uses

Don't size off the running current on the sticker. A compressor fridge cycles on and off, so what matters is its average use. Dometic rates the CFX3 45 at 1.03Ah per hour at 12V, with the fridge set to 4°C in 32°C heat. Its maximum draw is 8.2A, but it only pulls that while the compressor's running.

1.03Ah x 12V is about 12.4Wh an hour, or roughly 297Wh a day. That's for a fridge, not a freezer. Run it at minus 15°C and the figure climbs, and so does it in a tub that sits in the sun at 40°C. Dometic's flyer lists the 36L CFX3 at 0.98Ah an hour and the 55L at 1.10Ah, so the size of the fridge matters less than how hot it gets and how often the lid opens. ARB quotes its 60L fridge at an average of 0.89A an hour as a fridge, which is in the same ballpark.

Pre-cool the fridge and its contents on mains power at home the night before. Pulling a warm fridge full of warm drinks down to 4°C is the hardest work it does all weekend, and it's better done off the grid than off your battery.

Weekend sums

Take the CFX3 45's 297Wh a day as the base. For lights and phones we've allowed an LED strip at 10W for 4 hours (40Wh) and two phone charges (about 30Wh), so 70Wh a day.

Two nights, Friday afternoon to Sunday afternoon, is about 48 hours of fridge: 12.4 x 48 = 595Wh. Divide by 0.85 for losses and you need 700Wh of battery. Add two days of lights and phones (140Wh) and it's 735Wh of use, or about 865Wh of battery.

A long weekend of three nights is 72 hours: 12.4 x 72 = 893Wh, plus 210Wh of lights and phones, for 1,103Wh of use. Divided by 0.85 that's about 1,300Wh, which is a bit past a 1kWh station unless you top it up on the way.

Turn it around and a 1,024Wh station such as the EcoFlow DELTA 3 Plus or the Bluetti Elite 100 V2 gives about 1,024 x 0.85 = 870Wh. That's 870 / 12.4 = about 70 hours of the CFX3 45 on its own. The 1,070Wh Jackery Explorer 1000 v2 works out at about 73 hours. A small 300Wh station gives about 255Wh, which is 20 hours, so one night and not much more.

The drive helps. A station on the car's 12V socket puts back roughly 80W after losses, so a four-hour drive up adds about 320Wh, which is most of a day's fridge. Our guide to charging a power station from the car has the socket and alternator charger sums, and how much solar to recharge a power station covers a panel at camp.

Use the 12V car port, not the AC outlet

Most 4WD fridges run on 12V or 24V DC as well as 230V AC. Plugging into the station's AC outlet means the station turns 12V-ish battery power into 230V, then the fridge's own power supply turns it back into DC. That wastes energy twice and keeps the inverter running all weekend. Use the car-style 12V socket.

Check the socket's rating against the fridge. EcoFlow's manual rates the DELTA 3 Plus car port at 12.6V and 10A, Bluetti rates the Elite 100 V2's at 12V and 10A, and Anker lists the Anker SOLIX C1000 car outlet at 12V and 10A. The CFX3 45's 8.2A maximum fits under all three. One fridge per socket, though. A double adaptor with a second fridge or a 12V heater on it can trip the port.

Many 4WD fridges have a battery protection setting that switches them off when the voltage drops, meant to save a vehicle's starter battery. ARB suggests the low setting for a dual battery setup. On a power station the socket's voltage is set by the station, so in practice it's the station's own low battery shut-off that ends the run. Keep an eye on its percentage rather than relying on the fridge to warn you.

Weight and strapping it down

The makers list about 10.8kg for the Explorer 1000 v2, 25lb (about 11.3kg) for the Elite 100 V2, 12.5kg or less for the DELTA 3 Plus and 12.9kg for the SOLIX C1000. That's liftable, but it's also a heavy box in a crash. In Queensland the driver must make sure a load can't fall or be dislodged and is restrained by an appropriate method, and that covers what's in the back of a wagon as much as what's on a ute tray. The Queensland Government points to the National Transport Commission's load restraint guide for light vehicles for how to do it.

In practice that means strapping the station to the vehicle's tie-down points, behind a cargo barrier in a wagon, with the straps clear of its vents. Put it where you can reach the screen and the 12V socket without unloading the back. If it does take a hard knock, check it over before you use it again.

Heat in the back of a 4WD

Lithium batteries don't like heat. The Queensland Fire Department says to keep them out of direct sunlight and away from heat, and not to use or charge a battery that's hot, swollen or damaged. EcoFlow gives the DELTA 3 Plus a charging range of 0 to 45°C and Bluetti gives the Elite 100 V2 0 to 40°C. A closed 4WD parked at a beach in January goes past both quickly, and so does the tub of a ute under a black canopy.

At camp, put the station in the shade with air around it, and leave the vehicle's windows cracked or the station out under the awning if it's safe to. Don't leave it charging in a locked car in the sun while you're off on a walk. The fridge does better in the shade too, since a cooler tub means less compressor time and fewer watt-hours.

If you're building a bigger setup with a fan, a CPAP or a kettle, our caravan and camper sizing guide works through those loads, and the runtime calculator does the sums for your own fridge's figure.

Where to buy in Australia

Buying from the brand's Australian store means 230V AU outlets, the local warranty and local support. Prices move around a lot, so check on the day.

• EcoFlow DELTA 3 Plus (1,024Wh)EcoFlow AustraliaSee it at EcoFlow Australia
• Bluetti Elite 100 V2 (1,024Wh)Bluetti AustraliaSee it at Bluetti Australia
• Jackery Explorer 1000 v2 (1,070Wh)Jackery AustraliaSee it at Jackery Australia
• Anker SOLIX C1000 (1,056Wh)Anker SOLIX AustraliaSee it at Anker SOLIX Australia