updated 3/7/2010
Home- Made Ultra Bright Bicycle Headlight
(a.k.a. The "Face of God" Bicycle Light)
This easy to build home made ultra bright light will give you more respect from drivers and help you to see potholes and other road hazards while going full speed.
All truly bright bicycle lights currently on the market are very expensive. Don't be fooled by marketing claims of cheap lights. Typically, manufacturers avoid quantifying brightness in lumens and if they do the number is usually inflated. The only way to measure light output is a side by side test or independent measurements. Most designs try to get the most lumens (unit of light output) per gram. One of the brightest bicycle lights on the market is the Lupine Betty 12, which is $1,185 and puts out 1400 lumens or 1.69 lumens per gram (at 1.16 lumens per dollar!). My goal was to build an ultra bright light for a relatively low cost. My light is approximately 3000 lumens of white useable light. This translates into about 30 lumens per dollar which is about 30x more lumens per dollar than any bicycle light on the market. The way I did it was to use mass produced parts designed for cars and motorcycles. The main disadvantage of my system is weight. My system is about 12 pounds. Most of it is in the lead acid battery. It could easily be upgraded with a Lithium battery. Another "disadvantage" is there is no low power saver setting. There is only one power level: Bright. Of course, have you ever heard of brightness levels for car headlights? The brighter the better. Lastly, it takes a few minutes to get to full brightness. This is no big deal as this light starts out brighter than any other light and only gets better.
Many people have written to me asking why I didn't use LEDs or Lithium batteries. Here is the short answer:
LED's are getting better and better, but the very bright ones are the least efficient and need to be kept cool. HID (High Intensity Discharge) are still the best lights available for headlights. This is the same H4 bulb used on high performance cars such as BMW. LEDs are used for some car tail lights, but never headlights as they are not bright enough. There are a few exceptions to this like the new Prius, but those LED lights are very expensive.
Yes, I could save weight with Lithium and that is the reason all high-end bicycle lights use Lithium (as do exploding laptop computers). However, SLA (Sead Lead Acid) batteries have other benefits such as long life, the best self-discharge rate, very mature, easy to recharge, and very low cost. I am using a 12 volt 7 amp-hour battery that was only $16. It should last 500 cycles and is easily recycled. A lithium battery of the same capacity would be about $200 (over 2x the cost of my entire system). Lithium batteries can also be extremely dangerous so I wouldn't recommend them for a DIY project unless you use a standard battery pack with a compatible charger.
This Light is able to Break Through Trend Line of Lumens vs Dollars
A friend of mine (Steve B) made this tread-line this year in his quest to buy the light with the most lumens per dollar. He ended up buying the light at the $250 price point that jumps above the trend-line. I plotted this light on the same scale. He ended up buying the NiteFlux Enduro 8, which has a claimed output of 540 lumens and cost $250. Why is it possible to build a light that is off the charts compared to what is being sold in bike shops? The answer is not that I am a genius, but that I am very willing to carry around a light system that adds over 10 pounds to my bike. The graph I am not showing is Lumens per pound. However, this light is so bright it doesn't do as badly as you might think. For instance the Enduro 8 weighs about 2 pounds and puts out 540 lumens or 270 lumens per pound. My light puts out 3000 lumens and weighs about 12 pounds or about 250 lumens per pound. Very comparable.
You too can easily put together a similar system yourself....
Component #1: After- market motorcycle headlight-
I purchased this model new on Ebay for $36. Just search for "motorcycle headlight". The sellers name is "Tom" and he has sold quite a few. This light came with a Halogen bulb, which I removed and didn't use
This motorcycle housing is very heavy duty steal with chrome plating and too heavy to be mounted on a handle bar so front rack is required. You could try a plastic or aluminum housing if you want to save weight and attempt a handle bar mount. The nice thing about the large light is the optics are very good and the beam is broad. All bright bike lights on the market are tiny and lack the large optics to make a true low beam (a broad beam directed at the road and not in people's eyes). Because of the extremely high output there is still plenty of scattered light that makes it easy for drivers to notice you.
The Surly front rack I used is pretty expensive (about $140), but very nice and built to last. It comes with many bracket options and will fit a wide variety of bicycles. I bought it from JensonUSA (see link below):
Component #2: HID Conversion Kit-
The next step is to retrofit the above light housing with an automobile HID conversion kit (HID bulbs have 3 times the light, use less power, and last 10x longer than hologen). True HID lights need to be driven by a ballast. If someone tries to sell you an HID light without electronics it is probably not an HID light. There are many people selling "HID" lights on Ebay that are really only standard Halogen. The kit should include electronics and bulbs. I bought 2 sets for about $60 (right and left light). You only needed one so the cost is only $30. You can resell the extra on Ebay or share with a friend. The bulbs that came with my kit were H4 (low-beam). They are 5000K in color (bright white). Just search for "HID conversion kit" on Ebay. The seller on Ebay I bought from was "choi-q". I picked him because he shipped from California and most others shipped from Hong Kong. There are likely Goggle adds for HID kits that pop up on this page that you can also click on. It is amazing how Google is able to "read" webpages and find relevant ads. Just remember you need to specify: H4 and 5000K.
I did have to cut and solder wires as the connector wouldn't fit through the hole in the metal light housing. For me it was easier than making the hole bigger. The picture below is of the box and the extra set I didn't use. Each set consists of 2 electronics modules, 3 connectors and the HID bulb. You should follow the directions in your particular kit. However, the basics are you need to replace the halogen bulb in the motorcycle housing with this bulb. Since the connector is too big to fit through the hole, you need to either drill the hole bigger or to just cut the wires, pass them through, and splice them back together. The wires that feed into the electronics just connect up to the battery. You can add a simple switch in series with the wire if you want to be able to turn the light on and off. The switch should be in series with a wire that is in between the battery and the electronics and not between the electronics and the bulb. I used zip ties to hold down everything. The kit came with double sided tape to secure the electronics, but it is better to mount directly on the aluminum plate to better dissipate the waste heat and keep the electronics cool.
Component #3: Mounting plate
I mounted the light and HID parts to a custom aluminum plate (10" x 7" x 1/8") that I had custom cut. I drilled a 1/2 inch hole to bolt the light to as well as other holes to mount the electronics and to attach to my front rack. Aluminum is very easy to drill compared to stainless steel. I bought from www.speedymetals.com. They are fast and don't have a minimum order fee. The total cost was only $11.
Side view showing how I used Zip ties to secure the electronic modules to plate with holes I drilled. The plate is mounted to the rack with extra brackets and stainless steel hex bolts that came with my Surly rack. U-bolts could also be used. You can right click and "view" to enlarge any the pictures I took as they are high resolution.
Component #4: Sealed Lead Acid battery
The final purchase was a 12 volt Sealed Lead Acid battery for $16, which is carried in the front pannier to keep the weight as low as possible to improve handling your bicycle. I bought the battery from Ebay seller "battergallery" as he offered free 2 day shipping and a 2 year warranty. The battery is designed for motorized scooters. I connected the battery with an old used electrical cord I had laying around and and used recycled PC power supply connector so I could easily detach it. I initially used an existing battery charger, but later bought a trickle charger (see below). The 7 Amp-hr battery is optimal for a 30 minute run time. In a pinch it should last for well over an hour, but the battery will last for the most cycles if it is not allowed to run down. This is true for most types of batteries. The exception is NiCd batteries which do best if fully discharged on every cycle. SLA batteries are great for commuting because they can be plugged in every day and kept topped off. If you have a longer commute, you will need to add more batteries in parallel.
Component #5: 12v Automotive Battery Charger (and connectors!)
You may already have a automotive good battery charge, but if you don't this is a neat little unit. It is called "Deltran Battery Tender Junior" (Part#021-0123) and it has a computer controlled charging program that will gently charge and maintain the battery. I bought it from Ebay seller "buildorbust" for $27. I plug my battery into it after every use to keep it topped off. This unit comes with 2 very nice sets of connectors to enable you to use the included clamps or the terminals. I cut the wires to salvage the connectors and tossed out the clamps and terminals. There are also 2 in-line 7.5amp fuses. I end up soldering the wires directly to the battery and using both sets of connectors to optionally connect up to the charge or the battery. Just keep track of which wires are positive and negative when you are doing the soldering. Once you do it right once, you don't have to worry about it any more because the connectors only plug in one way. It is a very good idea to use the included inline fuse on the wire directly connected to the battery. If you don't want to cut off and use the connectors that come with the charger you can also use 1/4 speaker connectors. Make sure to insulate your soldered connections with heat shrink tube or electrical tape. If you use speaker connectors the "hot" (aka "red" or "positive") should be the female part of the connector leading to the battery, so you don't short your battery out by accident. You should also include a fuse.
Total cost: $36+$30+$11+$16+$27=$120 (with charger- $93 without)
Total labor: 2 hours to assemble and mount.
Front view showing the HID bulb (note the half cylinder reflector, which makes it "low beam"). You should be able to enlarge any of they pictures I took as they are at high resolution- Just right click on them and use "view".
The light exceeded my expectations in brightness. I was not able to take a picture that does it justice, but here is a picture comparing it to a 20W Halogen and a 10W Halogen. Both the 10W and 20W are mounted on the bike and the HID light is on a stand. The picture was taken at night with a very bright flash so that the reflectors on my bike are even brighter than the 20W Halogen. When my new light is mounted on the bicycle, you wouldn't be able to see the other lights. It is so bright that I don't use it on bicycle paths as even thought it is aimed down (low beam) as it will still blind on-coming cyclists (who have dim lights) on a dark path. Local cyclists have called it the "Face of God" light for good reason.
Click on the link to return to www.commuterbicycle.com, you can find my email at the end if you have questions
