Home made cheap bright bike light.
Pictures of the light.
Story of the light.
Here I will detail my experience making a 20W 12V 20 degree headlight for my bicycle commute. Since it is getting darker due to shortened days & daylight savings time. Of course, as you know, good bright bike lights are expensive. Lowest price I've seen is 60 bucks (US) for a five watt set up. Compared to 5 bucks for my 2 watt set up, I couldn't justify the price. The next price was 100 bucks for 10 watts. Again, not impressed. It seems if you want to have 20 Watts of power, you need to be ready to drop $150. To put it in perspective, my bike, purchased from Grandpa's Bike Shop 7 years ago, was $300. That, of course, included my dear friend's employee discount...
Anyway, I'm thinking of using a combination of the following designs, with a little of my own thrown in. I 'll try to get some pictures when I'm done. I'm predicting that the whole thing, including battery & charger will be under $50, but we'll see. It is a 12V 20W light($5), with 3.3 AH battery($15). I think that I should get a 2 hour run time, but even 1 hour would be enough for my daily commute. I've purchased the basic light & housing already for around $9 US. Just need switch, fuse, wire, battery, charger, & connectors etc. :-)
1) http://tim.paton.net/bikes/light/tr.htm
2) http://www.nas.com/~petes/bikelite.htm
I'm planning on using PVC components, similar to 1), above. I'm also planning on incorporating a quick release, like 2) above, eventually. For now, I'm using the 2 hose clamp method.
Here are some preliminary shots of the light "head"... The bright shiny thing is a U.S. Quarter dollar.
For the battery, I have cut open a water bottle & placed the battery inside. I have the fuse inside of the water bottle. The bottle has a nice wide lid, so I can unscrew it & replace the fuse if necessary. To connect the battery to the light head, I have wired up a DC female connector & used silicone around the connector to seal it in the hopes of weather proofing the bottle & keeping the battery dry.
For the charger, I'm using an old 9V 300 mAH transformer that I had lying around. It works nicely because the transformers DC male plug is made for the female connector that I use on my bottle/battery. I'm using this as a "trickle" charger. Below are some shots of the battery & charger. My apologies for the quality, I took the pictures at work with a different camera :
Here is a summary of my parts, costs & where I found the part.
| Part | Location | Price (US) |
| MR 11 lamp w/ Glass. 12V 20W 20 degree Beam | Interstate Lighting | $4.95 |
| L-47 25V 100W lamp socket & ponytail wire | Interstate Lighting | $1.50 |
| PVC 1 1/2 " x 1/14" converter | Menards Hardware | $0.62 |
| PVC 1 1/2 end cap | Menards Hardware | $0.49 |
| 5/2.1 coax plug | Radio Shack | $1.99 |
| spst submini switch | Radio Shack | $2.89 |
| PK2 Rubber Cover | Radio Shack | $1.49 |
| Coax PWR JKs5/2.1 | Radio Shack | $1.69 |
| Inline Fuse Holder | Radio Shack | $1.59 |
| PK4 AGC 2.5 AMP fuse | Radio Shack | $1.29 |
| 3.3AH 12V SLA battery | Batteries Plus | $21.95 |
| 9V 300mA transformer | existing | $0.00 |
| Waterbottle | existing | $0.00 |
| Black Electrical Tape | existing | $0.00 |
| silicone | existing | $0.00 |
| epoxy | existing | $0.00 |
| hose clamps | existing | $0.00 |
| $40.45 |
Summary: I assembled the unit, charged the battery for 16 hours & rode to work today (11/06/00) in the rain. The light was solidly mounted & bright during the 1/2 hour ride. I then took the battery in to work. I'm pretty pleased with the performance. For a period of time, the battery "sizzled" around the DC connection & produced a smell like silicone curing. I don't know if this was due to moisture & silicone around the contacts, or if it was my crappy job of sealing it with silicone, or if using silicone was a "bad idea", or what that was. It has stopped sizzling now, so we'll see what happens tomorrow.
11/07/00 Well, actually, it didn't last through the whole ride on the way home. I had put about 45 minutes on it in the morning & then brought the battery inside. Then I rode about 10 minutes to my polling place--at the top of a hill--and left the battery outside for 20 minutes. Then, it seemed to "dim out" after about 5 minutes of riding. So, I only got about a little over an hour of "use", although I suspect that the cold had a little to do with it. Talking to my dad (an engineer), he said I have too wimpy of a charger by using the 9V, 300mA transformer. He suggested getting a 12V 300-400mA transformer. This makes sense, but I just happened to have the other one laying around. I will upgrade soon. Maybe I'll use the slower one here at work to boost it for the ride home. Other than that, I'm pretty pleased with it and I think that the new charger will help. As will having a charger here at work.
11/09/00 Purchased a 12V 300mA transformer. Neglected to note whether or not it is regulated or unregulated. Will test it soon. In order for the battery to charge, the voltage must be slightly higher than the batteries.
11/10/00 put up pics of completed unit on the bike.
12/27/00 Just another update to say that I believe this design is good. The "sizzling" that I mentioned before hasn't happened at all since the first day--I still don't know what that was, but it seems to be fine. I would recommend using the 12V 300mA transformer rather than the 9V. Due to the cold conditions, I am not sure if the PVC will melt if it gets too hot in the summer with the light on. We shall see... I think if I had to do it again, I would get more of a "spot" light. I chose the 20 degree over the 10 degree angle because I thought that would be sort of a happy medium between a spot light & a wide angle. It is really more of a wide angle--I think I would be happier with the 10 degree spot. I can change this easily for about 5 bucks, though. The advantage of a spot would be that you would have a brighter light to see what is farther & directly in front of you, as opposed to a wide angle where you would "be seen" & be able to see a wide angle, but you would not be able to see as far.
All in all, I'm pretty happy with it. It is bright, cheap, easy to make, easy to recharge, seems to be weather resistant.
Here are what some other people have come up with for DIY bike lights :
http://www.cam.net.uk/home/hembrow/light/index.html
http://aaronandleah.dutton.net/bicycling/experience/headlight.html
Here is a good page on lights, batteries & chargers.
http://bikezone.org/brian/bicycling/homebrew.htm
A page on Iowa Biking!
Last updated 9/12/2002.
