I have a coleman version that works well
In my recent work in the oil field, I have been spending the night in a motel with a mini-fridge in the motel. The mini fridge will freeze water, so I bought some one-liter bottles and froze two of them. I would keep a one-liter bottle in the Coleman fridge and keep it plugged in all day long. The nature of my work in the oil field required me to leave the engine idling most of the day, if I wasn't driving from lease to lease. Therefore, the unit was powered all day long.
My observations were that the unit, while powered and running in an air-conditioned cab (maybe internal cab temperature of 65-70F) would barely allow any thaw in the iced bottle of water. I noticed that the grape juice I had in the Coleman would actually approach freezing, such that when I poured it out, it would go from liquid to slushy. That was awesome, too! It kept my lunchmeat, condiments, yogurt, iced tea, and everything else barely above freezing.
When I bought it, the box or instructions said it kept things about 30-35 degrees cooler than outside ambient temperature. I don't recall whether it was 30 or 35.
I cannot opine to how much power draw it makes, as I had the truck running most of the time because I needed the electric power for a centrifuge I had mounted in the bed. If I ever finished using the centrifuge for an extended period of time, I would turn the engine off with only the fridge and the laptop power supply running. The longest I left it alone was about an hour and it never killed my batteries.
Early on with this project, I did make the mistake once of using the centrifuge for a couple of hours without the engine running, and learned quickly that it isn't a good idea, even for dual batteries. LOL
I hope this helps.
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