Powering a small 12v fan directly with solar

Hi all,
I’m very new to all of this so excuses my lack of knowledge, but I’m after some advice on how to run a small 12V fan directly with solar.

The fan is only going to be used to help collect air particles and I don’t need it to run constantly or be at full power all the time for that matter but just come on ocationally and help pull air through a filter.

The fan specs are as follows:
Voltage: DC 12 volt
Current: 0.12A

I have a couple of questions

  1. What size panel or panels run in series might work best? I was thinking that two 0.6 watt 6v panels in series might work.

  2. At such low levels do I need some sort of regulator? And if so what might work best. Or will the fan survive being conected straight to the solar panels?

Thanks for your advice,

Hi Josh,

Welcome to the forum :slight_smile:

Typically the reason most solar setups will include a regulator is because solar panels by design have a pretty wide operating range so the voltage and current that comes out of them normally needs to be regulated to protect the device that is connected to it.
The other part of the issue is that relying on sunlight means the output is quite variable. The regulator also can help solve this problem simply by making the solar panel larger with a bigger output voltage, then letting the regulator continually output at a lower level.

Thanks for including some numbers about the fan you wanted to run. On paper that combination of two series panels should power the fan. In practice you might find that the panel only provides that rated output for 10-30% of the day and the rest of the day it drops to a fraction of that as the sun isn’t as direct and intense on the panels.

As for the survivability of the fan, the thing that usually harms motors is heating in the windings if the motor is energised but can’t turn. Most motors that are being driven but are mechanically stalled will burn out eventually. Having a motor that is being powered with not-quite enough power to start up is probably not ideal but depending on the motor you may get away with it without issue.
I think this would be less problematic than the worst case where the power is there to turn the motor but it physically restrained, in this case the power present is minimised so the heating should be less.

Ok thanks for that its a huge help! If I was to go for a regulator are there any that are small and light? the only ones I can find are large for big panels

Hey Josh, I did something similar. It’s an exhaust vent in a hay shed. It’s a 120mm PC cooling fan with low friction bearings, driven by a 20W 12VDC regulated solar panel. I used a buck:boost converter to lift the voltage from the solar panel to 12V on overcast days or first thing in the morning to get over the stall issue that Trent talks about.

It’s been running for 6 months now. Given the price of these fans on EBay, I can tolerate a short service life.

Hope that might help.


Hi Matt,

Thanks for the input, glad to hear you have a solution that can help others here.
We always love to see fellow makers helping each other on here, keep it up!

@Matt54566 I’m trying to do the exact same thing but for an even less glamorous purpose (I want to reduce moisture in the drop pans and help dry the quail poop in my quail shed - it stinks when wet).

The water pump and electric fence energizer in the shed are currently conventional solar solution (100w panel to a 50ah lifepo4 battery though a a Victron solar charge controller) but was thinking about just wiring two 12v 140mm pc fans directly to a spare solar panel to have them blowing at least some of the time when the sun was shining. The solar panel outputs a wide range of voltage(0-~19v)… is a regulator or buck/boost converted needed? or will it just help extend the life of the cheap fans? do you recall the part you used? thanks!

Hi @Joseph271411 - welcome to the forums :slight_smile: Sounds like a noble cause!

A wide-input DC-DC converter certainly won’t hurt. It will probably expand the usable range of the panel quite nicely while protecting the fans from over-voltage.

perhaps something like this? It’s good for up to 22Vin [ POLOLU-4984 ] 12V, 2.5A Step-Up/Step-Down Voltage Regulator S13V25F12

Else, there’s a whole buck-boost category for you to explore.

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Hi @Joseph271411, I’ve only ever used a buck:boost converter, so not sure how the system will perform or last without it. Mine was a cheapie off Ebay DC 9V-20V Converter To DC 12V 5A Boost Buck Power Module Voltage Regulator | eBay or just search for a 12V buck:boost voltage regulator.

Hope that helps.