Most Efficient 12 Volt Refrigeration

Most Efficient 12 Volt Refrigeration

We recently came across an A'vanner with problems getting his Electrolux fridge to run cold enough when on the move. On closer inspection we found he was running his fridge from the 12 volt accessory socket in the back of his 4WD. His auto electrician suggested this and made up the lead! We were horrified! It is absolutely essential to wire fridges in separately using 6 mm wires with fuse/self reset overload to another outlet straight from the battery, both positive and negative. This is to prevent voltage drop. If the standard wiring is too small, instead of getting a full 12.8–13.2 V or more to the outlet, you may only get 11–11.5 V. In Engel 12 volt motor driven type fridges this causes them to run inefficiently and even burn out from running under voltage. Voltage drop is probably the biggest cause of portable fridge problems followed closely by outback caravan parks running their own diesel generators, sometimes causing voltage spikes.

Photographic proof that the Electrolux works really well on the move on 12 volts! This shows Minus 3 degrees!

Just having the Electrolux in your van severely limits how long you can be away from the shops. We currently use a portable Chescold 3 way, to carry all our frozen food - it works really well. Running this plus the van fridge is in our opinion too greater load for our vehicle. We have done a lot of research and have come to the conclusion that the Quirk Auto Fridge is the way to go as you do not need auxiliary batteries. Unlike anything else on the market in Australia this unique 12 V Fridge/Freezer only has to run 5 hours out of every 24 hours to maintain temperature - say 2 hours in the morning and 3 hours in the afternoon. This is because it uses a rather unique way of cooling. Instead of having insulation it has a liquid running between the walls - Eutectic. This liquid gets frozen by the compressor, so it loses very little temperature when opening the lid. You can turn it off for hours without it losing temperature as the contents are virtually encased in ice. It uses the well tried Danfoss 12 volt compressor.

We were also attracted to the unit because of its robustness and reliability - looking at the 4WD magazines you see most of the hire firms using the Auto Fridge. The only negative is it costs around $200 more than the Engel and as you all know they are already pretty hexie! Hopefully it will be well worth it in the long run. The 240 volt adaptor is also an extra. You could get away without this though, if when at home you only plugged it into the Chalet or A'van's 12 volt socket. On the plus side however it has two extra features built in for which most manufacturers charge extra - an electric cut-out to prevent battery damage and a rubber mounted compressor to handle corrugated roads. Engel for instance charge extra for a spring-loaded base plate. The pull down temperature takes a little longer than Engel being eutectic. You just treat it the same as your Electrolux and turn it on the day before you depart and everything will be quite cold for the following day. At present you can't get a model to put in as a replacement for your Electrolux in the van, BUT of course Engel have exact size replacements. Life is so hard for a caravanner and nothing is ever clear cut!

Quirks have a fantastic Internet site, and you will find yourself on there for hours, as it is just about all relevant to caravanners. The main reason for reproducing it here, is that it gives lots of info on using it with solar and how to calculate how long you can stay in a spot before draining your battery. The information below is directly from their site as being in frames we can't give you a direct link. http://www.quirks.com.au

Why choose an AUTOFRIDGE?

The AUTOFRIDGE has been designed and manufactured in Australia to suit Australian conditions.

Ideally suited to work with the SOLAR-PORT* power supply.
The interior cabinet and the exterior construction of the AUTOFRIDGE are white fibreglass the COLOUR is the best for hot climates and the integral strength of FIBREGLASS for use in rough conditions has been proven by the long-term popularity of fibreglass for boat manufacture.
The compressor chosen for use in the AUTOFRIDGE is the latest Danfoss BD35F unit and controller. This compressor has been selected because of its remarkable efficiency, and it is supplied as a spring-housed unit - suitable for use in any off-road conditions.
The EUTECTIC operation of the refrigeration system allows you, the user, the luxury of knowing that in ambient temperatures of up to 32 degrees Celsius, the MAXIMUM DAILY POWER CONSUMPTION of your fridge is on average only 20AH/12Volt. This of course means that you can easily determine how long you can remain stationary without flattening your battery.

The AUTOFRIDGE comprises a compressor driven system combined with the power-saving advantages of the eutectic refrigeration system - the 'eutectics' act as a cold storage compound for the refrigeration contents. The eutectic fluid surrounds the outside of the four walls of the interior cabinet acting as an 'ice bank', and, in an ambient temperature of up to 32 degrees Celsius, having initially pre-chilled the AUTOFRIDGE, it need only be run on its maximum setting for a total of 5-6 hours per day (preferably 2 hours in the morning and ~3 hours in the afternoon), and during this run-time, the fluid is frozen and the cabinet contents are thoroughly chilled. The AUTOFRIDGE can be turned OFF in between the run-times, and the eutectic fluid acts as a thermal phase change (cold storage) compound and provides the continuous refrigeration hold-over for NIL power consumption. Figures quoted assume normal usage of your refrigerator, e.g. opening/shutting the lid to use or replace contents.

The AUTOFRIDGE can be operated in any one of the following ways :-

As a EUTECTIC refrigeration system – the AUTOFRIDGE is run for a total of 5-6 hours per day – split into two separate running periods of 2 hours in the morning and ~3 hours in the afternoon. The AUTOFRIDGE is turned "OFF" in the interim. Average daily power consumption for this mode of operation is ~20Ah/day @ 12V.
As a CYCLIC refrigeration system – the AUTOFRIDGE is set on a refrigeration setting (e.g. '2') on the thermostat and left to cycle 'on' and 'off' throughout the day. Average daily power consumption for this mode of operation is ~24Ah/day @ 12V.
As a CYCLIC freezer – the AUTOFRIDGE is set on one of its sub-zero settings ('5', '6' or '7') on the thermostat – the higher the setting, the colder the AUTOFRIDGE will cycle – and left to cycle 'on' and 'off' throughout the day. Average daily power consumption for this mode of operation is ~40Ah/day @ 12V.

As you probably are aware, the efficiency of your vehicle or marine electrical system can greatly affect the operation of any low voltage refrigerator. Whether to install an auxiliary battery can usually be determined by how you intend to use your AUTOFRIDGE or any other D.C. lights or appliances

If you require any information regarding auxiliary batteries and/or vehicle electrics, please let us know.

Also available for operation of the AUTOFRIDGE from 240VAC power supply is the AUTOFRIDGE POWER PACK (AFPP10F).

For more information on the Autofridge you might like to research the excellent website at http://www.quirks.com.au/. Unfortunately as mentioned above it is a "frames" site so we can't give you exact page addresses, however it is a very well laid out site so to find the above info and more click on the Auto Fridge icon at the top left. The 39 litre model costs $1564 and the optional power supply is $208. A nifty accessory that could be worthwhile is a voltmeter, thermometer and LED fitted into the lid at the factory for an extra $120.