Coleman 40qt Thermoelectric Cooler & Warmer, Keeps Contents Up to 40F Cooler or 140F Hotter, No Ice Required, Plugs into Vehicles & Trucks

Engineer here - These thermoelectric coolers work perfectly, AS LONG AS YOU KNOW A FEW IMPORTANT THINGS. Save yourself alot of money (and weight) and buy these over a compressor based unit if you're willing to follow some best practices.First - Prechill your cooler, and any food or drinks you may place in here for a few hours. Thermoelectrics are not great at removing heat quickly compared to compressor units, if you place a bunch of warm objects in here, you won't get the cooling you think you should. In order to pre-chill the unit, purchase the optional AC wall adaptor before you use it in your car.Second - This unit cools about 35-40 degrees F below AMBIENT temperature. If you place this in your trunk in the middle of the summer (where your trunk is 100+ degrees), this unit will only cool to 60F. If you bring an infrared thermometer with you, you can scope out placement for this unit and get the desired fridge (40F) or Freezer (10F) temps you're looking for. you also need to make sure the heat exchanger on the outside of the unit has some "breathing room". I've found in the summer time, that I can place it on my middle back seats, with the heat exchanger side sitting inbetween the driver and passenger front seats, and if I point my A/C vent directly at it, I can achieve temps as low as 15F inside the cooler. You can basically make small adjustments to your vents to raise or lower temps at that point (once again, having a cheap 15-20 dollar infrared thermometer makes this possible/easy).Third - Realize these units use about 3-4 more electricity than their equivalent compressor based counterparts. This means you can probably run one for about an hour or two off your car battery before it's dead, but that's it!!! If you plan on using something like this long term at home/office, or especially if you plan on using it off-grid a lot, you may be better off with a compressor based unit so you don't run out of/use too much electricity. This unit hooked up to the AC wall adaptor will pull 72 watts of power continuously, if you leave it running 24/7 at a standard rate of .12cents per kWh, it'll cost you 6 dollars a month to keep it plugged in. I only use this unit on trips where I'm in our car a lot.Alternatives - If you need something that uses less power for off-grid or long term use, and you don't mind the extra 10-15 lbs worth of weight, I recommend that you get a compressor based unit instead. They are pricey, but I did find a Massimo 50qt unit at costco for only 300 bucks (so only twice the price of this thing). Compressor based units also generally involve auto-shutoff battery saving features, and better temperature control that you don't need an infrared gun to monitor ;-).Bonus tip - Amazonbasics sells some Large rectangular ice packs that fit on the shelf mounts PERFECTLY. I purchased some of those to create a mini-freezer within this cooler. Worked great on a 12 hour long road trip. Frozen food only got up to 15F, and the refrigerated side stayed around 30-35F for the whole trip. Makes this unit quite versatile.Have fun!!

My old Coleman is ~20+ years old and still works after traveling 100,000+ miles in use plus many thousands of hours of use outside a vehicle, but seems to be aging, so I bought both a new Coleman and a K-Box (The K-Box looks like it's the same as the Knox.) The Coleman and K-Box (or Knox) look and measure about the same inside and out despite K-Box's (or Knox's) claim of "48" quarts and Coleman's "40" quarts.Plugged them in, empty, in my ~64 degree Fahrenheit basement overnight, and set a thermometer at the bottom, the Coleman fell to 19 F drawing 76 watts from an old 12V adapter (which dropped ~5 watts after running for hours); the K-Box cooled to 32 F using 72 watts on an old 12V adapter, which dropped to 59 watts after running for hours (the 12V adapter uses power that wouldn't be used if plugged into a vehicle)---(The K-Box started at 65 watts with its AC cord and dropped to ~50 watts after running for hours.) The K-box doesn't state that it stops cooling at 32 F---maybe it's a design feature---but it seemed not to have the strength to cool lower. (My ~20+ year old Coleman that cools noticeably less well than when new, still works, so I ran it: fell to 32 F empty in ~66 F air using 55 watts.)I stuck them, pre-cooled, outside in the shade in 70 F rising to 90+ F: temp rose to 53 F inside the K-Box after 4 hours plugged in; running next to it, the Coleman's inside was ~7 to ~11 F colder. (For example, 70 F outside, 50% humidity, 43 F in the K-Box, 32 F in the Coleman; in the evening, cooling to 65 F outside, 54% humidity, 36 F in the K-Box, 25 F in the Coleman.)Starting unplugged at air temperature, run side-by-side, the Coleman cools more. For example, morning, ~64 F, 62% humidity, (300' elevation) both cooled to ~45 F after the 1st hour, after 30 minutes more (air 66 F, 59%), K-Box = 40 F, Coleman = 39 F. 30 minutes later (air 70 F, 57%), K-Box = 37 F, Coleman = 35 F. 30 minutes later (air 78 F, 52%), K-Box 39 F, Coleman 34 F. 30 minutes later (air 81 F, 43%), K-Box = 43 F, Coleman = 35 F. 30 minutes later (air 84 F, 35%), K-Box = 45 F, Coleman = 38 F. 30 minutes later, (air 86 F, 33%), K-Box = 47 F, Coleman = 40 F. 30 minutes later, (air 87 F, 32%), K-Box = 49 F, Coleman = 42 F. 30 minutes later, (air 88 F, 31%), K-Box = 50 F, Coleman = 44 F. The heat exchange unit in the K-Box is too small for the heat gain of its compartment. I'd use the K-Box if it were 20% bigger and had a 30% bigger heat exchanger: as is, gets 3 stars. Coleman gets 5 stars.The lid of the K-Box/Knox is much heavier because its mechanism is there; the Coleman's is on the side and so you don't lift it every time you open the lid. Coleman's lid lifts with ~6 oz of force; K-Box needs ~1.5 lbs of force; the Coleman design is better.

I purchased this cooler just prior to going to visit my daughter in Houston Texas. I planned to drive from my home in New York state to Houston. Google Maps says that is about 1,750 miles each way. My car odometer agrees. I wanted something to keep some snacks and drinks cool along the way and did not want to worry about where I could get ice. Amazon, bless them, got it to me the Friday before I planed to leave on Monday.Since it is not a refrigeration unit I assumed it would take some time to get cold. I plugged it in Saturday morning (I also bought the power brick) and let it rum. Since I was not sure if it would really get cold I placed a thermometer inside so I could check. The temperature in the living room was about 74 degrees. By Sunday evening the cooler registered at 30 degrees.I packed the cooler with soda cans and water bottles chilled in the refrigerator. Also, some cut up veggies etc.. Other than the time the unit was unplugged during transport between the car and the hotel room it was running 24/7 for 7 days counting the two before I left. The unit gave no problems while running in the car and the power brick never got more than warm to the touch. Never hot.I used the cooler exactly the same way on the return trip. The only problem I ever had was that some of my cut up veggies froze in their plastic container box. They actually had visible frost on them and were stuck together. All-in-all, I found the unit very convenient to use. It will be in the back seat of the car on any future trips around the country.EDIT: One thing I should add. During my stay in Houston the unit ran 24/7 for 9 days using the power adapter.