It can be used like the high beam when the main led light needs an extra boost.
But the fun is using it at night as a silent photon bell ...
On cycle paths just dab the switch at people with their back to you by the time the they look around the light will have faded and you can politely wave as they step aside.
( The photograph next to the main picture shows high beam that has been on my bike for about three years; I'm now making one for my other bike. )
Step 1: Paprika and parts.
Anything with a round opening makes things easy; I used a smoked paprika tin.
The bulb is a 12 volt, 50w halogen; I got two for a pound from the market.
A bracket of some sort is needed; the one I used is off an old rack but anything that makes a long "u" shape will do. In fact, the tin could be attached on one side only, although I have not tried this.
A strong battery ; I used an old drill battery. It is rated at 18volts . . .If I knew anything about electronics I would have hesitated to use it on a 12 volt bulb but it seems to work very well.
I must stress that I have only used this light for 30 second bursts, that's why it has a push and hold switch.
It may be fine to use it longer but maybe it will get too hot and burn out; I don't know but used as I say, just for a high beam when needed, it has lasted me years ( the first one that I made, that is).
So . . .
container, bulb, bracket, long bolt and nut , washers/spacers, wire, four self tapping screws, bit of inner tube, small length of pipe, drill battery.