Originally Posted by
Tourist in MSN
This data is over a decade old. Screen print below:
Above screen print from this article. Article describes testing apparatus, and includes some discussion on difference between LEDs and resistors.
https://www.cyclinguk.org/sites/defa...ub-dynamos.pdf
Reading this article was one of the pieces of info out there that convinced me to buy my first dynohub. So, although it is over a decade old, I remember the article for that reason.
That is a great article! Olaf and Andreas are great guys, and Chris Juden has been a wonderful cycling journalist.
Looking through the text, their testing was done with a 12 ohm load on the dynamo under test. That's a very reasonable way to do it.
The results show power increasing up to a certain speed, and then increasing at a much slower rate. I see this in my own data.
For instance, this is the data for a 10 ohm load....
We usually think of dynamos as being current limited, which would suggest that the output power would reach a limit once the dynamo was putting out its rated current. If you assume a half amp limit, then the output power is 3 watts into a 12 ohm load. In truth, the current isn't strictly limited, but does increase slightly with speed.
I should point out that my first graph showed the peak power as speed varied, and that assumes that the load resistance is adjusted in order to obtain the peak power. At most speeds, a load resistance of something other than 12 ohms will allow you to get more power out of the dynamo.
Steve in Peoria