Originally Posted by
njkayaker
You don't need the Magnic to take advantage of these. I'm skeptical that the LED's being used in the Magnic are any more efficient than what are being used in good generator lights.
I suspect that the energy obtainable from the eddy currents is very limited (much lower than what is available from a generator hub). One issue is whether you can get enough light from the energy that can be produced.
We don't have any idea whether ratio of usable energy to drag is better than a hub generator. (Ideally, we'd want 100% usable energy to drag.)
You don't need to suspect anything. Dirk has stated as much, which is why he puts such an emphasis on the efficiency of the LEDs he's using. That isn't to say another manufacturer can't (or isn't) using equally efficient LEDs, but that the Magnic Light is working with much lower wattage produced than a typical dynohub.
Here is some detail on the magnets and LEDs he's using:
http://www.magniclight.com/magniclig...rtseite/techno
Apparently something in the Cree Xb-D family.
Here is a chart about the LED efficiency, with accompanying text. Take from it what you will:
https://s3.amazonaws.com/ksr/assets/...jpg?1387147866
2.Leds with 160 lumen per watt
The Magnic Light generator is tailored to the LEDs used, which reach almost 50% of the theoretically possible values- while good old standard systems barely attain 10-25 %:
Theoretically, the maximum white light you can obtain from 1 watt is appr. 350 lumen.However, good-quality LEDs only deliver about 40 lumen per watt (as used in many bicycle lights), which represents only 11% of the maximum. Light bulbs, on the other hand, only put out 10-15 lumen per watt, while theoretical maximum light possible is 685 lumen per watt (for green light). .
With high power LEDs one can reach appr. 80 lm/W, while the Cree LEDs used in Magnic Light deliver ~160 lumen per watt. This is possible because we feed each LED with less than 1 watt, which results in the ability to operate at temperatures below 35° C. This way, we harvest roughly 46% of the theoretical maximum white light, and hence 4 times more than standard LEDs.