I purchased a 12/24 volt compressor fridge/freezer a few months back. It’s a 55 litre FridgeMate (FM55) by EvaKool, an Australian company. Reading discussions on Aussie four-wheel drive and fishing forums, EvaKool has a good reputation but can you believe patriotic piss-heads? I’ve experienced difficulties with power consumption and cooling performance from my FM55. Maybe I was expecting too much. I have done some testing to better understand the performance of the FM55.
The FridgeMate 55 is simply a polyethylene ice box (IceMate) with a refrigeration unit bolted on one side. The evaporator plate covers the left half of the ice box and an insulated divider separates the freezer from the fridge section. The divider can be removed to allow operation as a single compartment freezer or refrigerator.
I filled my FM55 with a mixture of block and cubed ice and recorded temperature and melt water depth over several days. The ice box was opened only once per day and in the morning. Ice box temperature was measured in air and not in the melt water.
EvaKool claimed their larger IceMate boxes can hold ice for up to 10 days. My FM55 held ice for 6 days in warm weather. Air temperature inside the ice box was cold and stable, averaging 1.5 °C. Frozen goods will slowly thaw at this temperature.
EvaKool’s marketing claims for insulation performance are somewhat irrelevant. I expect that 10 days holding duration is only possible if the ice box is filled with block ice and the lid never opened. An ice-box that is full of ice is practically useless.
Most Australians like cold beer. I packed 30 warm cans of lager beer in my FM55, set the compressor speed to high, turned the thermostat up to maximum position 9 and ran the fridge/freezer all day without opening the lid. Thermostat settings were read at the 12 o’clock position on the white dial face, where there is a black dot.
After 10 hours continuous cooling, I removed and consumed one beer which measured 6.7 °C. I consumed another beer from the kitchen fridge for comparison, it measured 7 °C. Cooling performance from the FM55 was disappointing – it took a full day to get 30 cans cold. Faster cooling is possible with fewer cans inside the fridge/freezer or by adding ice.
I bought the FM55 mainly for freezing dead birds (generally road kill, which I donate to natural history museums). Other users might be wanting to freeze bush meat or fish.
I placed 4 tubs of water (total 8 litres) in my FM55, set the compressor speed to high, turned the thermostat up to position 9 and ran the fridge/freezer until the water was frozen. Then I reduced the thermostat and checked for melting.
The water froze in about 28 hours at thermostat setting 9. The ice remained frozen at settings above 4. The ice was melting at thermostat setting 1 and then refrozen at setting 5.
Instructions supplied with my FM55 recommend settings 1 to 3 for fridge applications, 4 to 6 for fridge/freezer and 7 to maximum when using as a freezer. My results are consistent with these recommendations. Even at setting 5, it is possible to maintain contents frozen. I have noticed, however, that the top of the fridge/freezer is warmer than the bottom (because warm air is lighter than cold air). Secondly, the evaporator plate only covers half of the ice box and the fridge end is warmer.
Do not expect outstanding performance from 12/24 volt compressor fridge/freezers. Care is required to achieve a satisfactory balance of cooling performance and power consumption. Here are some tips:
- The fridge/freezer should be on 24 hours/7 days, like your domestic fridge/freezer at home.
- Pre-chill and pre-freeze contents. If you must freeze warm stuff, run the fridge/freezer at maximum.
- If the freezer is not full, add ice packs to increase the thermal capacity of the system. A full fridge/freezer is easier to keep cool than an empty fridge/freezer.
- Use fridge baskets to improve air circulation. The coldest part of the fridge/freezer is on the bottom and next to the evaporator plate.
- Avoid opening the fridge frequently, which allows cold air to escape and warm air to go inside.
I have not made any comparisons with other fridge/freezers. It would be interesting to compare the performance of the 12/24 volt fridge/freezer to a 240 V domestic fridge/freezer. I would expect similar cooling performance under similar conditions. Secondly, I do not know how Engel and other fridge/freezers would perform in standardised comparisons. I suspect that most 12/24 volt compressor fridge/freezers have mediocre cooling performance.