I’ve got a new project in the works for a randonneur with a Garmin gps and an iPhone. He wants a USB charger that will be powered by his SON Dynamo hub. There are a couple of products that do this on the market. The one I’ve heard of is the E-WERK, “The Mobile Energy Supply Marvel”. Looking at its spec’s, it looks like a very powerful, impressive and versatile charger. It has both variable voltage and current limiters, capable of 2.8v to 13.3v and up to 1.5A. This device would be perfect for charging that plethora of electronic devices that we all haul around on our bikes. Coffee makers, toasters, fax machines, radios, fans. If you can’t leave the comforts of home at home, and don’t want to haul batteries. (it’s also a little spendy, in the $200+ range)
All jokes aside, it looks like a great product, but not everyone needs the ability to power any small electronic device ever made with your bicycle dyno-hub. What I’m building is simpler and less versatile, but just perfect for its application.
I’m modifying the Adafruit industries “minty-boost” kit, originally designed to provide battery back-up/mobile charge for usb devices. I’m going to replace the battery with a dynamo driver that will masquerade as one. I’ll be taking the power from the hub, running it through a diode rectifier w/ some smoothing capacitors, putting it through a 5v voltage regulator to charge a 5v, 5F Supercapacitor. The storage Cap’s will be hooked up to the positive and negative leads of the Adafruit Board. The Adafruit board has a 5v Boost converter and will output 5v 350mA with an input of anything from 5v down to 0.7v. I’m choosing capacitors instead of batteries as a power storage medium because of their long life cycle, robustness, and because they don’t need special treatment while charging. They will not explode, catch fire, or up and die unless you brutally overcharge them.
I am also going to try to build a tutorial to go along with this project to A: up my readership, and B: give a step by step guide for others to build it as well.
The parts are on their way,