Introduction: 700-Lumen LED Bike Light

Equivalent light output of a 70-watt halogen bulb but only uses12-watts of power.
Beam shots show a building at night 100-ft away illuminated by this LED bike light.

Detailed Specs and Parts List are given at the end of Step 8.

Step 1: Building the Enclosure

Step 1: Enclosure
A. These are the parts needed for the enclosure and shown before cutting to size: Lexan MR10 plastic, 1/16-inch x 3/4-inch aluminum L-bracket, Hammond enclosure, heat sink.

B. Cut parts to size: 3/4-inch section from enclosure, aluminum back bezel, Lexan front bezel, heat sink slices.

Step 2: Attach the LEDs

Step 2: Attach LEDs and Heat Sinks

A. Trim LED stars to fit inside enclosure.

B. Position stars on back bezel with an extra piece of L-bracket which is same thickness as Hammond enclosure.

C. Rotate center star 180-degrees so the + and - tabs are next to each other on adjoining stars.

D. Glue stars with Arctic Silver thermal adhesive, then clamp until cured (five minutes).

E. Good thermal management is essential for LEDs. Glue heat sink slices to top and back of L-bracket using Arctic Silver thermal adhesive.

Step 3: Wiring the LEDs

Step 3: Wire the LEDs and glue on the lens holders

A. Wire stars together (two small red wires) between + and - tabs.

B. Drill another hole in back bezel for incoming power. Add shrink tubing for strain relief on each side of bezel.

C. Drill holes in base of lens holders to route black negative power wire.

D. Glue lens bases to stars, preferably with Loctite 460 superglue.

E. Solder incoming power wires to stars (white + and black -).

Step 4: Final Enclosure Steps

Step 4: Finish the Enclosure

A. Glue lenses onto lens holders with Loctite 460 superglue (regular superglue will frost the lenses with a white film caused by vapors as it dries). I used a flood lens in the center and spot lenses on each end.

B. Glue on a washer-nut to bottom of enclosure with JB-Weld epoxy to hold handlebar bracket.

C. Screw on aluminum back bezel and Lexan front bezel after lenses dry.

D. Attach a bracket such as the one pictured from old Vista Light, or any bracket that can fit the 3/4-inch enclosure base. I also used washers so the light can be adjusted right and left.

Step 5: Building the Power Supply

Step 5: Battery pack is made from four 18650 Li-ion cells.

Overview: LED driver and on/off switch will be placed inside water bottle with battery pack. Battery terminal leads use a Molex connector for charging and connecting to driver.

A. Parts Needed: 18650 battery pack from Battery Space with built-in poly-switch and PCB for protection, Molex wire connectors, on/off toggle switch, buck-puck LED driver with pot for dimming.

B. Assemble the wiring harness with solder and shrink tubing. Shown in the third photo is the wiring harness; clockwise from top: dimming pot, LED driver, blue and white wires to LEDs, on/off toggle switch, Molex connector to battery.

C. I used a two-pin connector between the power supply and LEDs, but any good connector will work and preferrably one that can keep out moisture and dirt.

Step 6: Final Assembly

Step 6: Add the finishing touches to the power supply

A. First photo shows the wiring harness bundled and zip-tied underneath the bottle cap. JB-Weld was added to dimming pot wires for strain relief.

B. Drill holes in bottle cap for on/off toggle switch and dimming pot as seen in second photo.

C. I padded the battery pack with pipe insulation for protection inside the bottle.
Shown in the third photo is the 2-pin connector that came with the charger. This was soldered onto the coiled wire coming through the bottle spout to connect to LEDs.

Step 7: The Completed System

A. Shown is the completed LED System: Li-ion charger from Battery Space - 3-hour charge time. Charger wire which had 2-pin connector was replaced with Molex connector to charge battery.

B. LEDs give a very bright white light. Bright portion of beam projects to a distance of about 100-ft and total throw is about 150-ft. These LEDs give 700-lumens of light or equivalent to a 70-watt halogen, but only use 12-watts of power including 1-volt for driver.

Step 8: Specs and Parts List

Three Cree XR-E R2 LEDs, 700-lumens, 3-hr run time on high using 14.8V 2.4Ah battery, dimmable with adjustable pot., light with mounting bracket weighs 0.22-lb (99-grams), 4 batteries weigh 0.40-lb (184 grams), 1.5-A Li-ion charger, LED parts cost $75, battery and charger $100.

PARTS (US Dollars)
Part - Price - Supplier

3 Cree XR-E R2 Lamps - $6 each - Deal Xtreme
3 Polymer Optic Lenses - $3 each - LED Lighting Supply part #170, 171
Hammond Enclosure - $8 - Newark Electronics part #1455B1202BK
Half brick heat sink - $4 - Newark mfr. part #241202B92200
Lexan MR10 12x12 inch sheet - $12 - Piedmont Plastics
36-inch Aluminum L-bracket - $4 - Home Depot
Buck Puck 1A driver w/pot. - $20 - LED Supply
Arctic Silver - $12 - LED Supply
On/off switch - $0 - Had one; only a few dollars at Battery Space

18650 Li-ion 14.8V 2.4Ah - $74 - Battery Space
Li-ion Charger - $27 - Battery Space
Molex connectors - $0 - Had some, only a dollar or two

Totals: $75 for light and $100 for power.

Final Note:
A month or two after I built this light which cost $175 in parts and was enjoyable to build, a company in China called 'Magic Shine' came out with a 900-lumen LED bike light for $80 including charger, battery pack, and a very nice enclosure. It has a three hour burn time on high and is slightly brighter than this light. It can be purchased from Deal Extreme in China or GeoManGear in the U.S.

"...a lamp to my feet and a light unto my path."