Introduction: Portable USB Battery Pack Bike Light (with a Luxeon III Conversion)

You've probably seen how handy it can be to have a portable USB power supply for charging iPods, PSP, cellphones etc. I decided to make one but it needed to be multipurpose to justify carrying around the extra weight.

I wanted to make it as simple a possible so I decided to use 4 AA sized NiMH batteries rated at 1.2v (or 1.25v) Which can provide the needed 5v without regulation. This also makes it possible to more quickly charge PSP's which can draw almost 1A when charging.

To extend the functionality I decided it should also be a flashlight. But a quick search of the local stores showed that most AA flashlights are generally 1 or 3 cells. Fortunately for me I decided to check the bike aisle at Wal-Mart and found that many of the bicycle headlights are 4AA cell!

So using a bicycle headlight we'll end up having a:

1. portable USB power
2. flashlight
3. bicycle headlight

Not only that but I happened to have a Luxeon III star and optics laying around the house so, why not improve this project by switching out the bulb for the Luxeon?

Expandable Capacity Bicycle Headlight
The most interesting part for me is that if you decide to make a second battery pack and connect them together via USB you'll double the burn time of the flashlight! How cool is that when being used as a bicycle headlight?!?

How about connecting it to a USB power generator such as the Hand Crank Lego USB charger set up so it's turned by a tire?

Multipurpose enough? I think so.

Step 1: Parts

You'll need:

-1 Bicycle headlight (4xAA type)
-4 rechargable NiMH AA batteries
-1 Luxeon III star
-1 Luxeon Optics
-1 Heatsink for Luxeon (I used a copper pipe cap)
-1 Resistor ( Luxeon resistor calculator )
-1 USB motherboard adapter

Where to find parts

I didn't have to buy a headlight but they can be had at the bicycle section of most stores.

NiMH batteries. Again I had these as well as a charger. I got them from Walmart. They are 2500mAH generic, $5 at in the electronics section. I think they had it also availible with a wall charger for a bit over $10. Either way they're half the price of the brand names.

I don't remember where I got the Luxeon III, somewhere online with the optics and resistor. I believe everything cost about $10 shipped. I would suggest using either 5 or 10 degree lens.

The USB motherboard adapter I got from ebay for $2 plus $2 shipping

Step 2: Add the USB Port

I didn't take many pictures of this step. It basically consists of stripping one of the male USB ports down to the bare essentials -leaving just the red and black power wires attached.

Once that's done you need to decide on the best placement for the usb port withing the light housing. I chose to place the port on the bottom in the space left by removing the original reflector.

Just mark the location you can fit the USB port in and use a drill several holes to make the rough opening. A small file is then used to make the opening the right size and shape. I used the original USB adapter hardware for mounting, with a little hot glue to serve as strain relief.

In the final picture you can see how it's attached to the battery pack.

Step 3: Make the Light Assembly

The steps for this are pretty well explained by the pictures.

Attach the heatsink and Luxeon III using thermal compound and screws. Since the Luxeon came from a different project this was already done.

Then attach the optics to the Luxeon, with glue, hot glue, etc. Just be aware that if the hot glue is touching the heatsink it may get hot enough to melt and cause the optics to seperate from the LED. For this reason I usually apply some hot glue to the inside of the optics secure it to the star board.

Due to some clearance issues some cuts had to be made to the bottom of the flashlight lens, the heatsink, and the original lens face. Once that was done everything was glued together and the relay was soldered in.

Step 4: Replacing the Switch

This whole circuit board is just a complex switch. We don't know the tolerances so it'll have to go. In order to avoid a future failure it is best to just replace it with a simple switch.

Step 5: Putting It Together.

Pretty simple here, just solder everything together.

-The usb is connected directly to the batteries. red (+) black (-)

-The Luxeon III is connected (+) to the switch and then the battery; (-) directly to the battery.

Test with a multimeter before using shows 5.2v @ the USB port and 3.4v @ the light. Yay!


Voltage regulation can be added to the USB port if you desire

A buckpuck or other type of led driver can be added

More heatsinking for the Luxeon III

An additional battery pack such as this one can be connected via the USB port in order to double the burn time of the LED. Quite easy to do since the USB motherboard adapter comes with 2 USB ports.

Thank you for reading, hope you enjoyed my first instructable!