Originally Posted by
gauvins
Yes (ForumSlader).
I'll ask and eventually report. For now, just saying that I'd never thought that USB out is proportional to dyno drag. My simplistic assumption being that increased output meant more efficient circuitry.
The drag caused by the alternator can be quantified in watts. If you can get more watts out of your charger than the drag caused by the hub, you have invented the perpetual motion machine that would have power to spare.
There used to be an article on the internet that unfortunately is no longer posted. Article title Shining Examples, December/January 2012-2013, Cycle, CTC.ORG.UK, Pg 58 to 64. They had graphs comparing different dynohubs for power output, drag with and without a headlamp, etc. Their drag graph was quantified in watts. I would attach a PDF here but that might be in violation of copyright rules, so I am hesitant to do so.
That article was one of the reasons I bought the SP hub in April 2013, at that time there were no distributors for that hub in USA, I had to order it from Asia.