A New Use For Your Sirocco II Fans!

Four Sirocco II fans. Four 6.5Ah portable batteries. How long will they last without charging input?


Late last year, we held our Offroad Challenge as part of the filming for our upcoming TV show. Trouble was, it was blistering hot and shade was hard to come by. Inside our gazebo, we had drinks, chairs, snacks… and four Sirocco II fans.

Yes, we realise that these fans are designed for permanent installation inside a caravan or motorhome. But I smelled an opportunity. Energy efficiency is, nowadays, a major selling point for any electronic appliance, and this topic is particularly important in an RV context. After all, when off-grid and completely reliant on your battery for power, it’s essential to ease the load on the battery wherever possible.

We had these brackets specially 3D-printed.

The Sirocco II fans have a reputation for energy efficiency. It’s one of the factors that sets them apart. With the summer sun expected to be brutal, we sourced four Sirocco II fans along with four 6.5Ah batteries. The idea: run each fan off one battery and note how long they ran before its battery gave up the ghost. We even had four brackets specially 3D-printed which would allow us to secure each fan to each post of the gazebo.

The Sirocco II draws 0.12A on its lowest setting while operating on 12V, and 0.35A while operating on its highest setting on 12V.

But rather than simply observing how long the fans ran on each battery, we could calculate in advance the expected run time, and the good news is, this formula works for all 12V appliances and batteries.


In order to calculate how long a 12V appliance, in ideal conditions, would run off a battery, we simply divide the battery’s capacity in amp hours by the current draw of the appliance.

In our case, it looks like this:

Fan on low setting: 6.5Ah/0.12A = 54 hours of run time.

Fan on high setting: 6.5Ah/0.35A = 18.5 hours of run time.

One of the portable 6.5Ah batteries we used to power each fan.

It must be said, however, that this is theoretical. Depending on factors such as the condition of the battery and its chemistry, it’s likely that in the real world, these run times would probably be reduced by about 10 per cent.

Did our real-world experience align with the theory? Put it this way: over two long days, we blasted each of the four Sirocco fans on a combination of their highest and lowest settings continuously, without pausing to charge them, and each fan was still confidently spinning by the time it was time to pack up. All in all, we were pretty happy.

But let’s extrapolate. After all, these fans are designed to be mounted inside a van which would have, at a minimum, a 100Ah battery on board. In this case, and assuming no other load on the battery, you’d achieve 833 hours of run time on the fan’s lowest setting, and 286 hours on its highest setting.

The Sirocco II Cool Down Station used a fan on each post.

You can absolutely apply this formula to other appliances, such as your caravan’s TV, too. For example, let’s say your van’s TV draws 10A. Well, dividing 100Ah (the van’s hypothetical battery capacity) by 10A gives us 10 hours of run time.

This would be a useful exercise for all caravanners. If nothing else, it would get you thinking about the power draw of your appliances which, in turn, would get you thinking about your options for charging your batteries, and indeed the efficacy of your 12V system as a whole.

Just remember, it’s a theoretical exercise that in the real-world would be affected by a host of variables, including the age and condition of the battery, and its true state of charge.

That said, the Sirocco II fans did a great job at providing some reprieve from the brutal sun. No, they’re not designed for this type of portable use, but running them off 6.5Ah batteries was a surprisingly effective way to provide a host of people reprieve from the heat.