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Dynamo Powered Bicycle Lights

Posted by Big Boo on October 27th, 2010

Dynamo Powered Bicycle LightsOne of the most important things about riding a bicycle at night is to get yourself seen, and one of the best ways of doing that is to make sure you’ve got front and rear lights on your bike. Whilst most people opt for battery powered lights because they’re cheap and easy to install, there is another option – a dynamo powered system.

I used to ride my bicycle to school, so my parents got me a set of dynamo powered lights for my bike, as they figured in the long run it would be a cheaper option than buying batteries all the time, and it also meant you never had to worry about batteries failing you when you needed the lights most. They worked by having a little bottle shaped dynamo mounted on the back frame of your bike. The end of the dynamo rotated, and when active this rotating part was in contact with your back tyre, so when your wheels went round, the dynamo turned and electricity was generated.

Another advantage was that dynamo powered lights, once you got going at least, always ran at a good brightness level – whereas battery lights tended to only keep full brightness for a short while after fresh batteries had been inserted.

However, dynamo lights did have some drawbacks. One was that with the dynamo engaged you found it was actually harder to pedal your bicycle, which was surprising given how small the dynamo was, you wouldn’t think it would make much difference. Another problem was that where the dynamo rubbed against your back tyre it had a tendency to wear the rubber of the tyre away.

The final issue, which was probably the biggest problem with them, was that when you stopped the dynamo obviously stopped as well, and so the lights on your bike stopped glowing. Not exactly the best idea if you were stopped at a junction. Some modern dynamo systems get round this by storing up some of the generated electricity in a capacitor, and using this to power the lights when you aren’t moving.

I also had one final problem with my set of dynamo lights, although this was one of my own making really where I failed to keep them maintained properly. One of the wires that went to the back light came loose, and was touching against the frame of my bike and passing a small but detectable electric current through the bike frame. I never noticed it whilst riding normally, but every time I applied the brakes I would get a little tingle of an electric shock in my fingers!

Finally, many thanks to Rich, one of the readers of this site, for suggesting dynamo lights as a good topic for me to write about.