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I charged my phone with a bicycle dynamo

Long, long ago, when you weren't born yet, I created a post on my old blog about a phone charger I made that worked on a bicycle dynamo. And I found that old post back, so I'm posting it here again.

Well, ok, you may actually have been born back then. It was in 2009, so by the time I write this it was a bit over 13 years ago.  Still, it's been a long time since, and although I did have my first smartphone back then already, phones have since gotten smarter and require more electricity nowadays. So I'm reposting this article in case it's of any use to you, but do keep in mind that I haven't tested it with modern phones so there's no guarantee that it'll work still. And also that the language used is from 2009, when most people didn't have a smartphone yet, or even a (decent) camera on their phones. People called and sent text messages, that's pretty much it. And the prices are outdated, shops have since closed, etcetera... You get the idea. Welcome back to the late 2000s!

Having said that, I do have to say I look back at this project as a very fun thing to do. And as proof that I've always been a tech girl and probably always will be. 😊

Anyone who goes cycling long distances will be without power for a long time. And that's annoying if you want your phone to keep working. And I am such a person. Not that I was planning to call the home front during the entire trip, but I have such a far too modern phone that I will use to take all the pictures along the way and send those pictures to my weblog immediately and if I get lost, I can use my phone as a GPS device. But that takes a lot of power, so I needed a way to charge my phone without a power outlet.

The most obvious way is solar energy. For less than twenty euros you will find a solar-powered phone charger at the Kijkshop, BCC or electronics store that works for most phones, including mine. But what if the sun doesn't shine? In the Netherlands we complain that it always rains here and that the sun never shines here, but that is of course not too bad. It is different in parts of Asia. When it rains there, it can rain continuously for a few days to many weeks. So much for the use of your solar panel...

Luckily I still had a wind-up flashlight with a built-in phone charger. Plug in your phone and crank! One drawback: you can't really keep that up long enough to actually get your phone charged. One minute of cranking should be enough for three minutes of talk time, but after half a minute of cranking your arm gets really tired. So I need an easier way of doing this.

After opening up the flashlight I found out that the dynamo that was built into it supplies 6 volts. That is also what a bicycle dynamo produces, so I got the idea of replacing the built-in dynamo, which was much too small for a bicycle, with a bicycle dynamo and mounting the whole thing in my headlight (after all, it had a light attached to it , and so I could still use it). The disadvantage of my folding bike was that it was built for dynamos on the right hand side, instead of the left hand side which is common with bicycles. It took me some effort to find a suitable dynamo, but in the end I succeeded. Solder a longer wire to the phone charger that goes to the dynamo, and you're done. After removing the old content from my headlight, the whole system was ready to be tested.

And it worked. As soon as I started cycling with my dynamo against my tire and connected my phone to the whole thing, my phone reported that it was being charged. Which gave me a new challenge, because now my headlight couldn't be closed anymore, because the cable to my phone was in the way. I solved that by poking a hole at the bottom of the cover of my headlight, through which the plug of the cable fits. I attached the lights to the lid with sealant, so the whole thing could be closed.

And just cycle. Unfortunately I haven't had time to try longer distances yet, and just like with a mains charger, a phone has to hang on the charger a bit longer before it really pays off. But I turned my phone off for a second and then plugged it into the charger, which caused my phone to jump on and start charging. That is a good sign! I'll let you know if I've cycled a longer distance with my phone on the charger!

Last modified: 17 November 2022 13:22:11.
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