Fwiw, A household freezer is set in the 0F (-17C) to 10F (-12C) range on standard operating setup, thus the same type of temperatures should be expected for your portable versions as well, even more so when you figure lack of circulating fan and often much higher ambient temps. Thus if you are taking ice-cream with you, 30F isn't going to cut it, real world losses prevent 100% heat transfer (through air in most situations within a portable unit) thus its pretty expected imo for your fridge to be set at least 10 degrees (F) lower than freezing to actually obtain freezing items in your cooler, likewise for refrigerator duty, 10 degrees below your target temp, just like your house fridge... thermal losses. Different brand units may vary widely on similar situations, but that is 100% arbitrary imo and shouldn't be used to judge one unit from the next, rather it should be used as a baseline for the owner of said unit to decide what temperatures they use for various loading conditions. Your results may vary.
(re-posted my reply from a similar thread on the subject, again x 3
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