CJ wrote:Thanks for the link, which shows that although you can connect two LED lights in parallel, you hardly get any more light out of them that way. Sharing the power is right. Each lamp gets half as much power and produces only slightly more than half as much light.
Check out the graphs and you'll see that in order to get a worthwhile amount of extra light you still have to connect the lamps in series. Only that way, by increasing the resistance of the load, can you get appreciably more power out of an alternator that's designed to produce a constant current.
Connection in parallel works, but connection in series works a whole lot better.
True, but if you add the 330uF capacitor in series then the parallel connection is useful at some speeds. The capacitor boosts the output as it forms an AC resonant circuit with the inductance of the hub dynamo. This explains the peak in the output vs speed. I believe the Schmidt E6-Z light designed for the 'two lights in series' connection has a capacitor built in.
Andreas Oehler of Schmidt who did these measurements doesn't recommend using the series capacitor trick with a single IQ fly as he reckons it will push too much current through the LED.
A word of caution - standard electrolytic capacitors will be designed for DC and should only be used one way round, use non-polarised electrolytic capacitors.