When the heat hits, we look for desperate solutions. Let them tell the Parisians by installing aluminum foil and thermal bags on the windows to try to mitigate the heat. At home, we turn on the air or the fanbut on the street it is suffocating and something I have been seeing a lot these last few days is people with portable fans.
These devices are interesting because, although little, the air flow allows us to cool our faces a little. I’ve also seen passersby with more ‘pro’ solutions like neck fans (We have tried some, by the way.). A few days ago I was in London and I was looking at the tools that people were carrying, and among all the heat patches, I saw several using fans connected to their cell phones.
And if I am writing this it is so that, if you use one of these USB-C fans connected to the port of your mobile, think a couple of times if you want to risk the integrity of the smartphone because it is something that can free you from the heat for a while, yes, but also It is more than likely that it will end up frying your phone.
And no, it is not an exaggeration.
The USB-C fan that fries your phone
Although the USB-C port is great for connecting all kinds of accessories to your mobile, it is one thing if we can do it and another if we should. Not to mince words, plugging a USB-C fan directly into your phone works to power the fan, but it can damage the port, battery, or even the motherboard of your device.
The reason is that these mini fans generate voltage spikes because they have cheap components and, above all, a motor that does not have a filter, so it “takes” what it needs without taking into account anything else because it does not have any filtering circuit. And that “nothing more” is the integrity of the device to which we connect it, which can be the mobile phone, but also the USB of a laptop.
This video is tremendously revealing:
The one of LeftyMaker It is a spectacular channel to dabble in electronics at home, but in recent years it has published several videos on battery and powerbank technology with ridiculous sizes, but great power and capacity. He usually gets to the point and the fan couldn’t be more direct.
“Don’t buy this dangerous USB fan for your cell phone” is the title of a video in which, in less than three minutes, he demonstrates the reason why it should not occur to us to plug in the accessory. In it, he states that, with the help of an oscilloscope, he has observed voltage peaks above 20 or 40 V, depending on the fan. The mobile phone is not designed for that.
According to the youtuber, it is due to the nature of the DC motor, since the current switches many times per second through the coils, generating those peaks when the current is interrupted even by a thousandth. Basically, the motor is continuously switching current between coils. Each short interruption acts as a small “disconnect” of an inductive load, and this generates momentary overvoltages.
He explains that, although they are very brief peaks, because they are so constant they can reach the energy management chips, regulators and other components of the smartphone that are designed for 5 V, not for dozens of them, with the associated risk of permanent failure.
Fan measurement | Screenshot of LeftyMaker video
Measurement with the capacitor. He says there are still mini-peaks, but the decrease in voltage is evident | Screenshot of LeftyMaker video
Can it be fixed? Yes, with a capacitor placed in parallel with the motor, something that costs a few cents, but not all of us know how to install nor do we have to know that we need it. And, although he does not show it on camera, he claims that he tested it on a real phone and the screen began to show lines that flickered as soon as he turned on the fan.
His conclusion is clear: don’t buy it or give it only to someone you don’t likeand if you are hot, use a fan that is not powered directly by the USB port of a mobile phone, but by a powerbank that is more prepared for those peaks (it is not ideal either, but it is better to “kill” a 40 euro powerbank than a 500 euro mobile phone) or, directly, use fans that have their own battery.
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