I would guess ARB is providing the current draw at 120V despite saying they ran the test at 12V. Try and find a comparison in watts instead. 0.85 amps at 12v is only like 10 watts - no way it is that efficient.
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ARB and Dometic's ratings are talking about two different things, but both are measured in amps (the "/hour" beside "amps" in ARB's rating is important). The difference is one is referring to draw at 12v while running and one is referring to draw at 12v over an hour period. A 12V fridge will pull around 10 watts per hour from a portable battery (more on those below).
Rated input current (DC), [A]
8.9
This means that when the fridge is running, it draws 8.9 amps. If it drew this constantly you would need a battery rated to supply of 8.9 amp hours for every hour you wanted to run the fridge. However, the compressor cycles on and off, and will not draw nearly that much over an your. Over an hour period the dometic will likely draw about the same as the ARB:
Current Draw 0.85 amps/hour average power consumption
I've been running a 12v refrigerator with a portable battery for a couple years like
Rubeyu and
Artsifrtsi:
I have the Dometic CFX375DZ Dual Zone Fridge-Freezer. It works well but definitely put a drain on your battery.
I can’t go more than a few hours in hot weather until the low voltage protection system kicks in and shuts down the fridge. If you plan to use any 12V fridge for an extended time with your vehicle off your going to need an additional battery or power supply. Currently I run my fridge full time on a Jackery 1000 and recharge the Jackery through the inverter in my Ford Raptor. Future plans call for an installation of a lithium battery.
I have the same, but under a different name…
I run mine (when camping/traveling) always off of my Jackary 500, and connect the Jackary to the vehicle so it charges. When I get to camp, I’ll remove from vehicle, and connect my 120w solar panel. Doing this, I can keep food frozen for 3+ days in Florida summer… tested the cooler, and it ran 24 hours only connected to Jackary, and there was still 35% left.
in the TJ, I wired up a fused switch with a small panel volt meter to a 12v power port all in a project box… installed behind rear cage leg on drivers rear wheel well.
You don't want to use your vehicle's battery to run the fridge, it isn't designed for that type of draw. You're much better off getting a "portable power station" (sometimes called a "solar generator" as they are often used in conjunction with a portable solar panel). The ones with the newer Lithium Iron Phosphate (LiFePO4) batteries are ones to get. It will last 3x more cycles (~3000 vs ~1000) than lithium ion and is a "safer" battery tech. Jackery is one you see ads for, but they are only starting to use LiFePO4 batteries and there are other better value options. They are all advertised in watts, usually by AC inverter output such as "2000W" (with just the "W"), and then you'll see a separate rating for the battery capacity "1600Wh" (the "h" meaning hours). A device with those ratings would mean it can run an appliance that draws 2000 watts while in use, but it won't run it for an hour, as it only has 1600 watt hours of capacity. There are losses in the AC inverter as well so its not an exact conversion, but you won't be using the inverters for the fridge as you'll plug it into the 12V outlet on the power station. As a rough idea, you'll want 300-350 Wh of advertised capacity for every 24 hours you want to run the fridge without charging the battery, depending on the environmental temp you're working against. If you're running your vehicle every day for a several hours, and you pick one with a good charge speed, you might only need a 300Wh unit.
Ditching the cooler/ice when camping is simply amazing. The portable battery and fridge take up about the same space, so you don't need as large a fridge as you would a cooler (interior volume) as you don't need to leave room for ice. You also don't need to keep all the drinks cold for the weekend which cuts down on needed volume. Pull a cold drink out, put a warm one in, with a few as a "buffer".
What I think is the best part, when you get home you're not throwing away drowned food you had left swimming in the bottom of the cooler. Just put everything back in the fridge at home.
Dometic and ARB are big names and make good products. These fridges pretty much live and die by the refrigerant compressor, and there are other companies that use the same compressors as the big names for less dollars.
If you want to dive deep into the rabbit hole of 12v fridges, portable batteries, and the solar panels to charge them, check out this youtube channel:
https://www.youtube.com/@Jasonoid
