An effective bicycle light



I made up a bike light a couple of years ago. It is quite simple and cost about $40 or so including a decent battery. I used a number of ideas found on the internet, modified to work with components I found locally. It uses a 12 volt 20 watt mr16 bulb and really lights up the night. When approaching cars dim their lights you know it is effective.

Along with the headlight I use two red led lights, one on the seat post and one on the back of my helmet (a tiny one). I usually set both to flashing mode. It wouldn’t be hard to attach a bigger red light to run off the headlight battery but I have never got around to it.


– charger – cheap wall wart, input 120 volts, output 14 volts, 360 mA – I have been told that this is a little weak but it does charge the battery – Princess Auto.

– wiring, switch and connectors – Princess Auto. 14 gauge lamp wire works.

– light and pvc fittings – Home Depot – mr16, 12 volt, 20 watts  – with a covered lens. These are not that easy to find locally at a decent price – Home depot seems to carry them sporadically.  I used a “spot” light rather than a “flood” and found the beam to be great for street riding and minor trails.  It projects to the side quite enough.
– battery – sealed lead acid 12 volt, 5 Amp Hr. – cannot recall where I bought it but they are carried at various battery and electronic stores and Princess Auto.

Notes on building:

– find a suitable mr11 or mr16 bulb and then look in your hardware store to find a pvc fitting that has an inside diameter a little bit smaller than the outside diameter of the light bulb. You will need a cap for the back of the light so look for this at the same time.

– I used a lathe to turn the inside of the pvc fitting to fit the light – turned it about 1/2 in. or so deep so that the light fit into the front against the lip created by the turning. Use a bit of gasket glue or high temperature silicon seal to hold the light into the housing.

– I had to turn the outside of the cap to fit into the back of the pvc tube, you may be able to find a cap that will press fit without modification. Mine isn’t glued together as it allows me to replace the light if need be.

– use small electrical connectors to connect to the back of the light or find a proper fitting for that light and connect the wires to it.

– add the switch to the rear of the light by mounting it in a hole or whatever is required for the particular switch.

– spray the back of the light (inside) with dark paint to keep it from reflecting back.

– The light has an aluminum bracket built with a hacksaw and drill press and a threading tap. It is held with a couple of screws from the inside of the housing and two more to lock it to the handle bars. You may be able to create something else using plumber’s pipe strapping (thin band of metal with several holes per inch) or something similar.

The 5 AH sealed lead acid battery will give at least 1 hour of decent light without harming the battery. I have never used it that long and could probably go with a smaller battery. I had planned to use another 10 watt head light in order to keep the battery drain down but couldn’t find a suitable one.

Note: I don’t have a fuse in the circuit and should have one. Princess Auto carries various types. Also note that I am not an electrician and that you make this light or any other based on this information at your own risk.

These bulbs put out a fair amount of heat. An aluminum housing would be better from the point of view of dissipating heat but the pvc doesn’t get too hot and I have not had problems. The pvc fittings are also easier than building an aluminum housing.



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