On 4/12/2021 7:24 PM, sms wrote:
On 4/12/2021 1:59 PM, wrote:

snip

My bike had old halogen bulbs on PBP 2007.Â* I believe one of those two
lights was a special series light so the dyno would send power to one
of the lights first and then only send power to the second after
getting up to speed.Â* I think B&M or whoever made the lights
specifically made those second lights to use in that way.Â* But with my
newer B&M LED lights I just wired them parallel.Â* No one bothered to
make that special second light for LED because everyone thought LED
was good enough with just one bulb.Â* No need for two lights with LED
unlike with halogen where the second bulb in series was kind of
necessary.Â* Equal full power to both lights simultaneously.Â* Now at
lower speed both lights are weak.Â* But since LED lights up at fairly
low speeds, it only takes about 7-8 mph to get both LED lit up to full
brightness.Â* So no real downside because I never ride slow enough to
not get both lights going full brightness.


In honor of Frank I decided to stick my 12V tire-driven dynamo light set
on my beater bike. Very classic. But awful. At first I thought that I
had some kind of wiring problem because the output sucked so bad.

I hooked up a small 12V SLA battery and it brightened up considerably so
apparently the dynamo was not putting out enough current, though the
unloaded voltage exceeded 20 volts. The drag with the lights connected
was unbearable.

Going to give up on that experiment.

As I've said, I have two NOS 12V 6W bottle dynos in a drawer. I tried
one of them, briefly, on my mountain bike. It was terrible in many ways,
including the drag.

By contrast, for a while I used a 6V 3W roller dyno to power two halogen
bulbs plus a taillight. Output was thus about 12V, 6 W. The drag was
much less than that 12V bottle, and quite acceptable, indicating that
the big bottle was junk. However, with modern B&M LED lamps, I no longer
play around with such experiments. There's no need.

I suppose if I were competing in some ultra endurance event that
included lots of fast downhills, I might consider two B&M LED lamps
driven by one hub dyno. But my ultra days are long gone.

--
- Frank Krygowski