On Sunday, May 6, 2018 at 11:11:14 PM UTC-5, Frank Krygowski wrote:
On 5/6/2018 11:46 PM, bob prohaska wrote:
Joerg wrote:
Why should bicycle lighting be inferior to car lighting?


Does anybody make a bicycle dynamo that produces more than 3 watts
at 10 mph?

The power produced by many (most?) dynamos depends on the load, in a
counterintuitive way. Most dynamos are approximately constant current
(about 0.5 Amp) sources, in the same way that batteries are
approximately constant voltage sources. So if you present more
resistance to the dynamo, its output voltage will rise so as to pump
that same 0.5 Amp through the higher resistance. The result is more
power. Putting two lamps in series does this.

I did this for quite a while as an experiment back in the halogen lamp
days. With my Soubitez roller dyno of the day, I needed something like
14 mph to get both lights brightly lit, so I suppose that was putting
out about six Watts. (A bottle dyno would slip doing that.)

I wouldn't bother with it today, though. What you need for night riding
is not a certain number of Watts, nor a certain number of lumens. You
need sufficient illumination of the road. The better B&M lamps certainly
give that, in spades. Those are so good there's no need to play around
with two lamps or other homebrew tricks, IMO.

--
- Frank Krygowski

I might disagree with you. I have two B&M Cyo LED lights mounted either side of my front hub, driven by a Shimano hub generator. I think they are better than just one Cyo light. You can aim one of them close and one of them far. Good coverage. Its not like one of the Cyo is a spotlight that blinds you. Its OK and usable. But more light at night is good.