I use a Son 28 dynohub, paired with a Cycle2Charge unit on my handlebars, feeding an (external) battery pack.
I use the hub to either power a front light or charge the battery, never both at the same time.
I prefer not to charge electronics directly from the hub.
A day's riding will generally recharge my gps & phone with enough left over to top up my kindle or recharge some aa/aaa batteries.
I find that once I'm over 13 kph I'm generating power.
One factor to consider when considering a dynohub is wheelsize! I don't often see it mentioned in discussing the merits of 26 vs 700, but a 26 inch wheel produces more power than a larger wheel at the same speed, or produces power at a lower speed in comparison to a larger wheel, if you prefer.
I also carry a fold out solar panel on longer trips (from before I got the dynohub). Strapped on the back of the bike is not the most effective, but once still it does a reasonable job, excellent in direct sunshine. Since I like to stop often it supplements the dynohub nicely
Originally Posted by
CreakingCrank
Strongly suggest pass-through battery packs as they can charge devices while charging themselves.
What pass-through battery packs do you use?
Frank