Picture of solar bicycle light
This is the lightest cheapest bicycle light I'm aware of. Furthermore, it does not take away pedalling energy and it´s quite aerodynamic.

I know that it is not very impressive, but I think it is really useful.

Remove these adsRemove these ads by Signing Up

Step 1: Materials:

Picture of Materials:
A pocket solar torch, avaliable in ebay for 2 €
A piece of inner tube or rubberband

Step 2:

Picture of
Fix the torch in the bike, for instance with a M3 screw.

Step 3:

Picture of
Make a knot on the piece of inner tube. This is needed because the torch only lights when the switch is pressed.

Step 4:

Picture of
When you put the inner tube piece with the knot on the switch, the lights are on.

Step 5:

Picture of
When you shift the position of the inner tube piece the lights are off and the battery is charged by the solar cell.