@Ritar Hylon:
in order to have a stand light for the tail, do this:
Get a German-standard 6V dynamo LED tail light with stand light feature, like the
B&M Toplight Flat plus. Connect this across the 2 lowest LEDs of the LED string. Polarity doesn't matter, as the tail light has a rectifier inside.
When you do this, be aware that short circuit of the tail light will shunt a part of the LED string, so that the smoothing capacitor of the circuit will drive a rather high current through the remaining LED(s) of the string. This will probably do damage to the LEDs.
You can eliminate this risk by splitting the smoothing capacitor into two, one connected across the LED(s) that has/have the tail light in parallel, one connected across the remaining LED(s) of the string. The capacitance of these parts has to be twice the capacitance of the previously-used smoothing capacitor while their voltage can be reduced (a minimum of 4V per LED).
The cable to the tail light must be electrically isolated from the frame of the bike, which may be connected to the dynamo.
If you'd like to have the stand light feature for both head- and tail light, be patient (and use a flashlight for the time being). I have a concept that I'm not perfectly happy with so I'm not motivated to start on a PCB for this right now...
The main issue is, that charging the reservoir eats some of the dynamo's energy and charging the reservoir QUICKLY costs a very noticeable amount of light. To reduce the impact from this, I need to have a switch that selects trickle-charge & light (rural riding with a lot of light output), fast-charge & light (city riding with frequent traffic lights), fastest charge without light (topping up the battery during short daytime hops), off (bike parked). So much complexity and less light output.. Need a better idea.
