Here's a site I stumbled across a while back... It seems to be more in line with what you're trying to accomplish:
http://nordicgroup.us/s78/mr16LED.htm#Introduction_
If I were building a dyno system from scratch I would:
1. Pick the light(s) - this will determine the voltage and power requirements. Light are my top priority - yours may be different
2. Pick the dyno hub which will have ample power and the proper voltage for the lights & to charge accessories (iPhone, etc)
3. Find the USB adapter to charge my "stuff" - it too would have to be the same voltage as the lights and dyno.
4. Check the system cost.
3. Is the system still in my price range? If not go back to #1. Repeat as necessary...
From what I found on various sites, the Shimano and Sanyo dyno's are both well made and reliable.
The Shimano dyno is nearly as low resistance as the Son, but A LOT less expensive.
Some of the dyno reviewers mention vibration. "Better" dyno's produce less vibration. The larger, and most expensive, Son supposedly is the smoothest dyno. The amount of vibration is reported to be a function of the light. In other words, changing the light may affect the amount of vibration observed.
Few (none?) of the lights designed for use with dyno's offer a flash mode. I've read that this is due to European regulation which prohibits flashing lights.
But that's me... If cost is the most important aspect of the project, then go with the least expensive dyno and build the project from that point. From an engineering perspective, there is no compelling advantage to 6V versus 12V. There may be more lights and accessories available with one voltage or the other. You may also find that the budget gear is available in only one voltage.
Other criteria which may drive the decision process:
- Total power need (ie. how many watts are required)
- Lighting at slow speeds such as when mountain biking.
- Disc brakes will limit hub selection
- Spoke count will also limit the selection of dyno hubs.
Cheers,
Greg