On Feb 26, 7:42 pm, "Pilgrim" <
[email protected]> wrote:
> Has anyone ever seen a bike rigged with either a generator, or solar
> powered battery charger?
"I used to have a Dynohub on a tandem, and the bulb consumption was
unacceptable. I solved the problem (and some others) by running the
Dyno's output through a full-wave bridge rectifier and then hooking
the DC in parallel with a 6 volt (5 x 1.2v cell) nickel cadmium
battery. This not only provided light when I was stopped, the Dyno
would re-charge the nicads, and, when we went so fast that the voltage
rose above 6 volts, the low internal resistance of the nicads sucked
up the excess, gaining a bit of extra charge and saving the bulb.
The rectified output of the Dynohub was always connected to the
lights. There was no way to turn the light off while you were in
motion. It would have been easy enough to rig a switch for that
purpose, but I didn't see the need. The Dynohub has _very_ low drag.
I had a three way switch connecting the battery pack to the lights. In
the "night" position, the nicads were in parallel with the rectified
output of the Dynohub, as described above.
In the "day" position, the nicads were connected to the lights and
Dyno through a diode (rectifier). This would allow the Dyno to charge
the battery when it was going fast enough, but would not pass
electricity the other way, so that the battery would not drain running
the lights.
The "park" position completely disconnected the battery, because
diodes are not perfect, and there is a slight drain that would
discharge the nicads over a period of time.
Dynohubs are suitable for this type of set up because they do not use
the bicycle frame as a ground. If you use a full-wave rectifier, you
must keep the AC circuit seperated from the DC circuit. Since most
bicycle generator setups are made to use the frame as one of the wires
in the circuit, this is a problem. To use full-wave rectification,
either the generator or the lamps must be kept insulated from the
frame. Dynohubs are already insulated from the frame, that is why they
have two screw terminals and use twin-lead wiring."
>From http://www.sheldonbrown.com/dynohubs.html
- Frank Krygowski