Running a caravan aircon from a battery system

Since getting our 340aH of lithium batteries, a 3000W inverter and 600W of solar installed, we’ve been running an induction cooktop and various other appliances every day, and thoroughly enjoying the experience. I always wanted to give running a caravan aircon from our battery system, and on a stinking hot day after returning from some rock pools near Point Labatt, the opportunity presented itself.

My folks have been travelling with us on and off for a while now, and their Kokoda Digger Caravan has a Dometic (Inverter style) aircon, but they don’t have an inverter capable (and maybe some battery limitations too, with the iTech Lithium Batteries) to run the aircon, so I thought we’d give it a whirl. 

We ran two leads from my inverter outlet, to the 15 amp inlet of the caravan, and Dad powered it up. I watched a tiny blip of 93 amps from the Victron Battery monitor, and then the amps dropped off to about 4 or 5, and then slowly started increasing.

I reckon it took about 5 minutes to hit 60 amps, and then I watched it go up and down gently over the next hour or so, up to a maximum of 80 odd amps. Now, we would have had a tiny amount of solar going in (maybe 15 amps) which would affect the reading, but it certainly didn’t draw as much power as I thought it would.

How long could you run the aircon for?

Off our 340aH of batteries, I reckon you’d get somewhere between 4 and 6 hours of run time before they were pretty flat, with no solar. If you were running it in the middle of the day though, when our 600W of solar is putting in 35 – 40 amps you could run it for a lot longer, and that’s where the tipping point comes in.

Ambient temperature would play a huge roll though, as the aircon uses a lot less power when it hits the setpoint you give it, and the hotter the outside temperature, the harder it will have to work to keep the van cool.

Can you run a caravan aircon overnight off a battery system?

Yes, you absolutely can, with a system that is big enough. That means enough battery capacity, and enough solar to recharge the batteries during the day. With 1000 – 1600W of solar on the roof of many big caravan builds, you can comfortably run an aircon during the day and still charge your batteries up with the left over power.

Once a caravan gets to the temperature you set it at, the aircon’s power draw will reduce considerably, and that means even less power drawn. I would suggest if you wanted to run one overnight though, you’d be looking at a minimum of 500Ah of lithium, and probably 800 – 1000W of solar.

Why doesn’t everyone have this?

If you can run an aircon from your own battery system, why doesn’t every van come with a setup to do it? There’s a heap of reasons, but lets cover the most common

Cost

This is primarily the limitation on a caravan build, as lithium batteries, solar panels and inverters cost a fair chunk of money. To get a system capable of running an aircon for an extended period of time, you are going to be looking at somewhere from 5 – 20k, and possibly more depending on who does it, and what products you use. Our lithium battery and solar upgrade was about 4k in total, but you can spend a lot more!

Weight

There’s no beating physics. Solar panels, electronics and a 12V lithium battery (despite them being light) add a lot of weight, and most vans simply don’t have the payload to take a system so big.

Space

To run a system like this, you need lots of roof space (and a suitable roof rating), and then enough room inside the van, or underneath it to install the batteries, inverter, chargers and everything else that goes with it.

Caravan Aircons don’t work that well

Before you go and spend a huge amount of money on a big battery system and solar array, have a good test of your current aircon, and make sure you are actually happy with it. Most Caravan aircons work OK, but they aren’t amazing, and in really warm weather they won’t get your van icy cold.

There are other alternatives

There’s a reason so many people run decent 12V fans in their Caravans; they are heaps cheaper, use almost no power and are quite effective at keeping you cool.

This was just a bit of fun

I like to learn, and the only reason we gave this a crack was to see how much power it would draw, and if you could feasibly run an aircon. The answer is yes, with a system that isn’t that amazing, but only for a short period of time.

Do you run a caravan aircon off a caravan battery setup? Are you happy with it?

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