My bicycle lights

Dynamo light
The first bike I owned was a Peugeot UE8, bought second hand in 1981. This came with mudguards, pack rack and dynamo lights. These were original, not retrofitted. Front globe is 6V 2.4W, rear globe is 6V 0.6W. Later I replaced the original bottle dynamo with a Sanyo dynapower roller, and added a Vistalite rear LED flasher. Front light output is estimated to be 12 lumens.
20W Halogen
My first battery powered bike light was a 20W 12V halogen (MR16 downlight) with narrow 12 degree beam. This was powered by a 12V 3.5AH NiMH battery pack in a drink bottle. This worked well on a 7.5km commute of less than 25 minutes. Run time was 2 hours. Light output is estimated to be 300 lumens.
LED module
To get a longer run time for a longer commute I needed a lower power light. I used a 3W LED MR16 module from Jaycar for the 2006 winter. It looks like this module has been discontinued (ZD0342). Although the light was supposed to have a narrow width beam, it actually had a medium width beam and only provided enough light if there were no street lights and your eyes adjusted to the darkness. Run time was 10 hours. Light output is unknown.
Single Luxeon III
Next came the 4W home made bike light known as Version 1. This one looks smart compared with earlier lights. Light output is 80 lumens. Run time is 8 hours from the 12V 3.5AH battery, or 4 hours from a smaller 9.6V 2.4AH battery.
Single Cree XR-E
The previous light was upgraded by replacing the LED with a newer and more efficient device, and using better optics. This became Version 1.5 Light output is 170 lumens. Run time is 6 hours from a 12V 2.4AH battery, or 40 hours on low power.
Triple Cree XR-E
A new 8W bike light with 3 LEDs is also planned as Version 2. Light output will be about 400 lumens.

Beam photos

The comparison photos of the different light beams were taken by placing the light on a table, pointing at the ceiling 1.7m above. The beam pattern on the ceiling was photographed using a Canon 300D digital SLR camera placed on the table next to the light, using manual settings (ISO100, 1/15s, f/5.6, 18mm) The resultant images were then cropped from 3072x2048 pixels down to 1527 pixels square, then rescaled to the 128 pixel square images shown above. The width of each image corresponds to about 33 degrees. If I was doing the beam shots again, it would be worthwhile putting some marks on the ceiling (or whatever target is used) to more accurately determine the scale and hence beam width.

Battery packs and chargers

The easiest way to get a 12V battery pack made from NiMH cells is to buy individual cells and stuff them in a plastic holder. This is actually a bad idea. First problem is that they fall out when you ride over a bump. Solution to that is to put a strap around the battery pack. Second problem is the terminal resistance, particularly at high discharge currents. Instead of getting 12V under load, you might only get 9V. The cells need to be soldered or welded together to form a battery pack. It is difficult to solder onto the end of a cell, so the better solution is to buy cells with tabs welded onto their ends, then solder these tabs together to make a pack, which you then hold together with duct tape. My current battery pack is made of 10 x AA NiMH cells with 2400mAH capacity. This has a flying lead with a DC plug on the end to suit my bicycle light. Currently this is carried in a Topeak Tri-bag on the top tube, but I plan to make a smaller bag and hang it from the head stem.

The image below shows a NiMH cell with solder tabs, the 10xAA 2400mAH battery pack wrapped in duct tape, and the old tweety battery with 10x3500mAH cells.

The next problem is one of charging. With individual cells you can pull them out and charge them in a commonly available charger. With a sealed up battery pack you need a different charger. To charge NiMH battery packs I use the Master Instruments MW7168. If I was buying a charger now, I'd probably buy the Swallow Advance, which can charge NiCd, NiMH, Sealed Lead Acid and Lithium Ion. Both these are designed for charging radio contolled model vehicle batteries in the field, from a car battery. In a fixed environment, you need to provide a 12V power supply which can supply at least twice the charge current. So if you plan to charge a 3500mAH 12V pack at 0.25C or about 1A, then your power supply needs to be rated for at least 2A.

Why build a bike light?

Because I could.

It is cheaper ($200 vs $500 commercial), but only if you already have the necessary tools. Otherwise it could be more expensive.

At the time I couldn't buy a commercial light that was as good.

To show what commercial lights will be like in 1-2 years.

Other bicycle lights

Suzy's 3W Luxeon Bike Light.

Ian Howson's High-power LED mountain bike light

Mart's Twin 5 Watt Luxeon bicycle lights MK4

The fat hippy's home made lights

Allen Chapman's Triple Cree XR-E light

Mozbike: DIY 12V Bike Lights

Halogen-Bulb High-Powered Bike Lights and other tips

Dynamo-Powered LED Headlight and Tail Light for your Bicycle

Fenix L2D CE from TorchWorld, attached to the handlebar with Lite Ride, or some hardware from a ship's chandler.

KtroniK LED light housings made using computer controlled machines (CNC).

Original 2006-12-20, updated 2007-06-25