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In preparation for the 2006 Sydney 24 Hour, I wanted new mountain bike lights. Last year's light was a 20W halogen globe and two packs of ten AA cells. This was nice and bright, but the battery packs got rather hot and only lasted about 40 minutes each.

This year, I raced solo. Recharging two battery packs per lap wouldn't cut it. My plan was to spend about an hour per lap - each lap was 10km - and sleep for an hour or two when I charged the batteries. So I was aiming for 3-4 hours battery life at about the same brightness as a the 20W halogen.

The new system weighs 715 grams and lasts for about four hours at 9 watts of output. Charging the batteries takes under two hours.

So after my recent set of mountain bike lights, I decided that I was ready to build what would be my be-all, end-all set of bike lights. These would be it. The Ultimate.

After the mountain bike lights, I wanted lighter, brighter, and longer battery life. I wanted to be able to use them for long road rides - so they can't use a bottle cage. I wanted to be able to commute without having to charge the battery every night. I wanted even more power for mountain bike riding and scaring pedestrians. I wanted lighter weight, so I could use them for fast group rides.

This is a simple bike light which can be contructed with a minimum of tools. It is bright enough to be useful as a headlight, is fairly robust, and cheap to construct. It's perfect for commuting and does a surprisingly good job for mountain biking too.

The whole thing, including rechargeable batteries, weighs about 200g and will run for over two hours.