To make this all-in-one wind turbine power bank, round up an old CPU fan, an old phone battery (or a 18650 cell), a small switch and a bike support element. Also, get some tools ready, including a soldering iron and a glue gun. The first step is to take off the propeller, find the three pins inside the fan, check which two give the best voltage and solder one wire to each one. Then you need to put the propeller back, create a diode bridge and connect it to the computer fan.
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If you want a voltage booster, connect a Joule Thief circuit to the DC output of the CPU fan. Then, all you need to do is to hook up your battery, connect it to the 5v step-up module and place a power switch in between (if you are using a Joule Thief connect that too). Then you need to glue everything on the CPU fan’s sides and make everything waterproof using some electrical tape. Your new device is ready to be used, so fix it to your bike and ride away while charging your phone with a gadget you have made!
You can check out the fully detailed DIY tutorial on Instructables.
Via Instructables Bicycle Cell Phone Charger
images from lmetomi
Very clever but I can't help believing that some company out there is already making such devices for bicycles, probably for not much more money as well.