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Low Powered Air Conditioner Answered

I live in a converted bus made into a mobile home in Outback Australia. I'm currently building a 'Solar System'  so I can go anywhere without relying on hooking up to mains power.

The biggest problem I'm having is finding an 'Inverter' that will handle power consumption to run my 'Fridge' and ''Air Conditioner', I have a 2500w Inverter but this can only run an 'Aircon' up to 300w, so tell me where you can get one that runs at this power level !!

I have an idea that may get over both problems (Fridge and Aircon). I was looking through 'ebay' and found a 80L Fridge/Freezer that runs on 12v, mainly used for 4WDs and RVs.
I'm just wondering if I could somehow carefully drill a hole into the freezer cabinet and coil copper or aluminum small bore pipe around the internal walls of this, then have a small 12v DC Pump circulating 'Antifreeze' or similar through a external radiator with fan blowing through this into my living area.

I know this will be a drain on batteries as the freezer will be constantly running due to the warmer return fluid circling around inside the cabinet, but I'm not really worried about this as I will have 4 Solar Panels totaling around 500w production at 7-8amps and  4 Deep Cycle Batteries rated at 100ah each, total 400ah.

Will this setup be efficient as a air cooling system without effecting the frozen food in my freezer too much.

Would love to here any comments on this and also any suggestions will be gratefully accepted.




5 years ago

Hi Guys
Many thanks for taking the time to answer my concerns, there is certainly some very good comments and ideas I can look at here.

It appears there's no way I'm going to set this up as I planned, as I don't want to burn out the compressor !

I do like the idea which 'Vyger' wrote using a mechanical type converter, I'm not familiar with this and would be grateful if you could maybe supply a sketch showing how I can do this.

My Bus is painted white which does reduce the temperature a bit, I'm not always mobile so using the "Hold-over Plates" is a good option when the engine is running, can you please tell me what "PEG" solutions are ?

Kind Regards

Here's a link to the specialist components you need.

Thanks for your link Steve, these are worth looking at for a optional setup :)

There's nothing to them really. You could get them fabricated at any decent metal shop - just make sure you get a lot of pipe into them


5 years ago

You might think of making a mechanical type converter. Use your 12 volts to power a 12 volt motor and then gear it up and connect it into a generator replacing the gas engine with the 12 volt motor. It is a method of converting from one type of power to the other that has been in use for a long time. Of course your going to loose some in the conversion process, it goes into heat, but you will get what you need in the end, which would be stable AC that can run an Air Conditioner. The neat thing is that it could be set up to only run when needed. When the thermostat kicks on it would start the 12 volt motor which would then power up the generator and finally give you AC. Mount the "converter" on the roof so it radiates the heat away and you are all set.

Very interested in this, is there any plans for setup or pics of an installed system ?

In the Aussie climate, you might get away with a swamp cooler, evaporative air cooler.

Otherwise, there's nothing else: you need power, and lots of it. Your fridge/freezer is unlikely to be more than 300W.

Thanks for your info, I have downloaded plans for a "Swamp Cooler", looks interesting !

You CAN do your own cooling system, but remember a portable fridge motor is designed to have the compressor turn off at a given duty cycle - if you use the fridge as an air conditioner, you run the strong risk of burning the fridge out.

In addition to finding a suitable AC solution,
you may want to consider other details for keeping
heat out of the bus. For example, painting the bus
white or silver will help to reflect the heat.
Also, insulating the bus will probably help.

If your inverter can only handle a single 300W AC unit and you still want to run a couple of other heavy powered units then get another inverter. Just be sure you have a large enough battery bank that can support everything for the length of time you need on a full day's charge.

Trying to tap into a fridge or freezers compressor to use as a makeshift AC probably isn't a good idea. Freezer and fridge units are not meant to cool large spaces and there compressors are not designed to run for long periods of time. You wouldn't get much cooling effect from that kind of system anyway unless you forced the compressor to run longer which would wear it out quite fast.

Ever heard of "Hold-over plates" ? Thin tanks filled with PEG solutions, and chilled by the refrigerator compressor running cold gas through internal pipes. They're cooled down when you're on the road by the engine compressor, and then provide some cool-th when you're not.