Originally Posted by
CdCf
The Schmidt hub has no difficulty putting out 12 V, so that's not the problem. This is strange!
http://www.peterwhitecycles.com/schmidt.asp
Scroll down to the section labeled "12 V SON." The hub produces 6V at about 5 or 6 mph (you are spinning the wheel that fast when you test it, right?), and produces more than that when you go faster. However, the lights have a built-in 6V regulator that prevents them from blowing up when you go really fast. Theoretically you'll have to be going 10-12mph to light both lamps to full brightness, but I assume you've tried this already, right?
Again, try connecting the lights in parallel instead of in series.