HID Bicycle Light

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Bring light to darkness...

Ever since I had a bike, I wanted it to have a headlight. Here's my latest abomination of a headlight.

I wanted something that is bright enough and lasts enough for a few trips around town. And here's what I came up with.

Power source: 18pcs of used Sony US18650GR Lithium Ion cells from Ebay wired in a 3S6P configuration, 11.1V nominal, 14.4Ah total.

Ballast: 35Watt output, 12V nominal HID ballast from a Chinese HID retrofit set.

Bulb: 35W 6000K 9006/HB4 D2S, also from a Chinese retrofit set.

Both bulb and ballast are extras from my car. So this is an ultimate cheapskate project.

The reflector assembly I bought from a car accessories store for about US$4.

The housing originally uses an H3 type Bulb. My spare bulb is a 9006/HB4 type. A bit of elbow grease and some metal work, I was able to fit it into the assembly with the right bulb position for focus.

Burn time is a total of 2.5 Hours from full to totally flat.

Above is the DIY battery charger (black thing with lights) which is a CC/CV automatic version with built in Balancer. (all discrete and analog. No microprocessors of any kind) Takes about 6-8 Hours to charge.

My old but faithful bike. I think this is already about 10 years old.

Here's the entire abomination attached to the bike with reusable zip ties (I don't usually use that much zip ties...)

Beam Photos. The spill light just at the front wheel isn't actually that bad. It's just a camera artifact.

In an empty soccer field at night...

On a street...

My view when riding...

So far, I've done several trips around town and in all cases, this light catches everyone's attention.

Next in line: A six LED 555 Timer based brake/Tail light for added safety.

06 Feb 2011:

I hated the bluish light of the blue tinted glass cover. Remember that this is a cheapskate project so buying another housing is not an option. (besides, I couldn't find another one with the right size and shape)

Here the housing is on my makeshift turntable with a hot air tool on the side to soften the adhesive:

It actually didn't work. A knife inserted between the glass and reflector and slowly prying it open did the trick but left the glass edge full of small cracks. The reflector didn't have any damage. I won't be using the glass anymore so it's not a problem.

I made a ring of acrylic by heating and bending an acrylic strip around to form the ring. Using a cutting disk held on a drill press, I was able to trim the acrylic ring so the ends are flat and true.

Gluing a flat piece on the front, a little work with the band saw and belt sander then sealing with silicone to the reflector and the new cover is done!

Here are the results of the new cover:

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After:

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After:

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After:

I'm not sure if it is obvious in the pictures, but in actual use, I like the brighter, pure white output. I used the same settings on my phone cam (night mode).

I actually had issues with the acrylic lens softening due to heat but nothing major. It softens only when the bike is standing still for more than 10 minutes. When running, there is no problem.