"Modded" power cooling box for camping


A few years ago I went to the "Seenachtsfest" in Constance and therefore I bought one of these cheap, crappy cooling boxes available for 30 bucks in supermarkets; just like this one:

(Photo from internet)

It's the standard model using a 40 x 40 mm Peltier Thermo Electric Cooler (TEC) with approx. 50 Watts power consumption at 14 Volts.

There was just one problem: This thing wasn't really "cooling", it was only keeping inserted stuff at the temp. the stuff had when put into the box.
No chance for cooling a warm coke in this fridge!

So my first attempt to increase cooling power was to replace the original "cold side" fan (on the left of the lid in the photo above) by a better (and more quiet) one I found on my old heat sink of my former computer. The results were quite good; with enough time this thing was really able to cool stuff down!

After that, the box wasn't used for a longer time until some friends and me went to France last year.
Due to the fact that we stayed on a camp site, we needed a fridge. So I took this box and it worked great, but still I wasn't satisfied by the cooling power, although it was better than normal boxes.

For our vacancies this year I installed a 12cm "Papst" fan on the top heatsink which cools the warm side of the peltier element which resulted in 1-2 °C less.
At 30° ambient temperature I could reach about 12 to 15 °C less in the box.

But this still wasn't enough.
The main problem is that the "warm side" heat sink can't sink all the heat produced by the peltier. The area around the TEC is still getting more hot than the rest of the heat sink.
It seemed there was no suitable solution ......... until I found my old water cooling stuff from the time when a 1 GHz AMD Athlon processor was "state-of-the-art".
So why not replaye the warm side heat sink by a water cooler and use a radiator to keep the water at ambient temp?

First experiments with a water cooled TEC were very impressing:

click to enlarge
First try of water cooled TEC

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Ice on heat sink

I've used a cellular radiator made of aluminum (another part from my once planned and never realized PC water cooling) which cools the water which goes into the water cooler on top of the peltier.
The "exhaust" water (output of the cooler) goes into my old water reservoir and pump tank (... as you might guess also a part of my old system).
From here it's going back into the radiator and so on.

The ambient temp during this test was about 22°C and the "frozen" heat sink was partly exposed to the air flow of the radiator, but still the condensed water was freezing!
I've never got such a result with a normal heat sink and air cooling, independent from the size of the heat sink.

Next step was to integrate this into my cooling box ..... and this is what the prototype looks like:

click to enlarge

When I find some time I'll integrate the radiator and a smaller tank into the lid of the box.

(c) Thomas Gulden, 07. 09. 2008