Air-conditioning in a Caravan while Off-Grid!?

Powering an Air-Conditioner while Off-Grid in an RV / Caravan

Running air conditioning in a caravan can be a challenge, especially if you're off the grid and don't have access to mains power. However, with the right equipment and setup, it is possible to power your air conditioning using solar energy.

The key to using solar energy to run your caravan's air conditioning is to have the right components in place. The first of these is a lithium battery, which provides a high-capacity, high-efficiency power source that can be recharged by your solar panels. Lithium batteries are ideal for this application as they are lightweight and have a long lifespan, making them perfect for use in a caravan.

Next, you'll need an inverter, which takes the DC (12V) power from your lithium battery and converts it into AC power (240V) that can be used by your air conditioning unit. This inverter should be sized to match the power requirements of your air conditioning unit, so it's important to do your research and get the right one for the job.

When the sun is not shining, it is wise to have a back-up power source, such as DC-DC charging and a mains charger. 

Finally, you'll need a solar panel or panels to provide the energy to recharge your lithium battery. The amount of solar panels you'll need will depend on the size of your air conditioning unit and how often you plan to use it. For example, if you have a large air conditioning unit and you plan to run it for several hours each day, you'll need a large solar panel setup to keep up with the demand.  Fortunately, the hotter the day, the more likely it is to have good solar performance.

Conversely, in the winter months when heating is required solar performs poorly, hence why electrically powered heating is not recommended off-grid.

Once you have all of these components in place, it's simply a matter of connecting everything up and turning it on. You should be able to run your air conditioning unit without any issues, and your lithium battery will keep your power supply topped up even when the sun isn't shining.

At Solar 4 RVs, our favourite inverter for this application is the MultiPlus 12/2000 or MultiPlus-II 12/3000. 

I Park in the Shade

The solar on the roof will still help, but output significantly drops off when shaded. In this case, portable panels are very helpful.  It is recommended to install the solar charge controller close to the battery, as the purpose of the solar charge controller is to maximise the power from the solar panels while providing the most efficient charging to the battery, in order to do that it needs to know the exact battery voltage.  The voltage of the solar panels is less important to the MPPT algorithm as most MPPTs these days will perform high speed tests to find the Maximum Power Point regardless of the voltage measured at the controller.

Lightweight portable panels can be good for this as they are easy to frequently manoeuvre, however lightweight panels can be easily damaged, so only use high quality brands such as Sunman / Merlin.  

Alternatively, the Exotronic glass portable panels use very high efficiency with a 17mm aluminium frame, with the small size and traditional glass format, this will provide a cost effective but highly reliable power source.

Crunching Some Quick Numbers

The MultiPlus 3000VA can run virtually any 10A appliance as 10A x 240V = 2400VA maximum allowable into a normal wall socket. 

Normally a good amount of solar for air-conditioning is 400-600W, towards the higher end if you have a large compressor fridge, other power hungry appliances and allowing for shading. Air-conditioners often use approximately 40A.  40A x 6 hours x 0.5 Duty Cycle = 120Ah per day.

Minimum Battery Size for a 3000VA inverter is 250Ah.  300Ah is the minimum we recommend.  Hence why you may need to upgrade your other chargers, i.e. 300Ah / 20A (many factory caravans are limited to 20-30A charge rate overall) = 15 hours from empty to full assuming no loads are being used, which is not a practical charge rate. 

400W of solar on a typical summer day -> 400W x 7 Sun Hours / 12V x 0.8 Efficiency Factor = 186Ah per day.

Envy of all Campers

If most of the infrastructure is there, it might be a cheap ordeal, however if you need to replace the power system, it can be costly.  But lets face it, it is cool to be in a perfectly air conditioned caravan quietly ticking away without the generator disrupting the neighbours!