Yesterday Marko Mäkelä sent me some interesting information about a charging solution for bicycles. He's not on the list and wants me to forward his mail:
-------- Original-Nachricht -------- Betreff: Re: Freerunner-powered bike ride Datum: Sat, 2 Aug 2008 22:56:15 +0300 An: André Gaul <[EMAIL PROTECTED]> CC: community@lists.openmoko.org I'm not subscribed to the list, but I've been following the development of the OpenMoko since the Neo1973 was announced. André, I think I can answer your question: > The next step would be a dynamo-powered charger for the Freerunner. I read an > article in the german computer magazine ct [2] about creating a converter for > charging USB devices while riding your bike with a hub-dynamo. The c't article features a step-up/down converter that outputs 5 volts and a battery charger for 4 Ni-MH cells. I suppose that you'd be only using the 5-volt supply. However, I have designed a much simpler and cheaper solution that I believe should work at 500 mA. I don't know if you can convince the Freerunner to input 500 mA instead of 100 or 1000 mA, or if you can tell the Freerunner to adjust its charge current according to the voltage, as per the USB battery charging specification that the Freerunner does not comply with. My solution consists of a MOSFET rectifier bridge and a low-dropout linear voltage regulator that outputs 5 volts: http://www.iki.fi/~msmakela/electronics/dynamo5v/ The SMD version is about 14mm*22 mm, so it can be fitted inside the head tube, for example. I know of two switch-mode regulators: the c't one (which is available as a kit from segor.de) and a commercial product, the JaWeTec BikeCharger. I don't think that they're significantly better than my cheap and simple circuit. Fully charging an old Nokia DCT-3 series phone (about 1 Ah) takes about 50 km when riding at an average speed of 20 km/h. I'm going to build a small series (5 or 10 or so) of the circuit and sell it to fellow hobbyists at about 10 EUR. It'd be nice to see this being sold as a commercial product (for a similar price, I guess). Best regards, Marko Mäkelä
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