This hack is for those that like night riding or want to get into it (it's great, never too many people and nice and cool) but think that those 300 lumen lights just don't cut it and don't have the cash for a 1000-2000 lumen lighting system (they can be like $500 - $1,000 dollars, yikes). Even with 1000 lumens, it's just not enough plus some of those systems out there can only last about 2 hours at max power.

There is hope though, with this slightly overdone bike light I built for my mountain bike. The light you see featured in these pictures I made myself and it has a max of 7,000 lumens on high with a battery life of 2.5 hours, while it can do 3000 lumen's on low power for over 6 hours. The light is made of 6 cree xml u2 LEDs mounted to a copper and aluminum heat-sink to keep its 60 watts nicely dissipated. To power this light I built a 150 watt-hours lithium polymer battery pack all in-closed in a extruded aluminum case. I built the case so it can easily attach to any standard water battle cage (you can see on my bike the water bottle cage just happens to be on the bottom of the frame, that's just how GT decided to do there full suspensions those years). The weight of the light and the battery and all the wires come out to just under 3.5 pounds (with the battery being the fatty at 2.9 pounds).  I also hooked up a few other cool things like rear red lights and a power level indicator so you know when you have to charge it.

The charging is done with a lithium polymer balance charger for rc cars and helis that I bought just for the light (cost me 30 bucks on ebay). I ended up building the whole thing for about $150 (would only have been $100 if i would have built a battery pack half the size). For those who know high power LEDs have to be run at constant voltage and current to make them last (these are guaranteed to last 50,000 hours). So I have 3 parallel dc-dc converters with a 93 percent efficiency regulating them to put out 20 watts, 40 watts or full power of 60 watts to make just over 7000 lumen's of light, but the lenses I used are 92 percent efficient and I am getting about 6600 usable lumens.

To put this in comparison a standard headlight of a car gives 1000lm while a D2S Xenon metal halide arc head light you can buy gives you about 3000lm (so double that and that is what I hit the trails with). I can't imagine much more power being useful or very easily created (running this amount of power gives you a problem with heat dissipation which made me do a lot of testing to get a good rough design) but I think I will keep trying.   I will give a detailed description on the parts i used and how to build the light.

Step 1:

Parts list:

18 li po 2200 mah batteries. I got them for 3.33 each on hobby king
random lenths of 18 gage wire.
3 2s lipo battery protection circuits found on ebay
1 aluminum case
2 automotive kill switches
3 dc-dc converters found on ebay
aluminum and copper pieces for heatsinks
assorted chip heatsinks for dc-dc converters
3 20 amp schottky diode for dc-dc modulation
2 push button switches for rear light and power indicator
1 6s power level indicator found on ebay for rc helis
2 high amperage rc power connectors
battery insulation tape
2 22 gauge 6 series lipo charging wire extenders (like 2 bucks each shipped on ebay)
Heat shrink tubing

Battery charger:
I-max B6 lipo charger bought on ebay for $35 shipped

6  cree xml u2 leds
6  75 in. copper end caps
1  75 watt heat sink for cpu ($8 at fry’s electronics)
Heat sink compound
Small brass screws found at hobby store
4x4 copper plate at least 0.060 in.
Some kinda mount for the light im going to use a bottle mount I found on ebay for 3 dollars
6 lenses for the leds (found on ebay, im using 2 9o, 2 45o and 2 60o lenses)

Rear light:
2 12 volt leds strips (meant for automotive purposes)
Vip ties to hold it down

Soldering iron
Hack saw
Something to consider is "night blindness" where the visual purple is "bleached" by light. When the illumination is removed the eye's ability to see in darkness is greatly reduced compared to eye's that have accommodated to the darkness. Subdued lighting shortens the adaptation time.
Very nice instructable! <br>Can you please share the link for the battery`s? Can`t find the right ones apparently :D
Yeah, I'll post the link when I get home.... I get them from hobbyking.com... They have the best prices(the best watt hour per dollar is the 2200 mah from tenergy, I trust there batteries since I have bought some othera that just sucked and did not have the energy they said they have), just make sure you use some lipo battery protection circuit
That is a killer light set up!!!! <br> <br>I've been into night DH in the Colorado rockies for about 6 years. People think there is too much risk (I have a 700 lumen Olight mounted to my helmet visor + a Fenix bar mount with 2nd cree flash light. It throws enough for me) <br> <br>With the Lumens you are capable of putting out, you could light the way for an entire group!!! <br> <br>I'm new to the building process, so please be patient with my questions: <br>*What is the best source for the Cree XML LED? <br>*Did you buy the Cree LED with the Reflectors? <br>*If not, what did you find to be the best source for LED &amp;/or reflectors? <br>*How did you confirm fitment? <br> <br>You have created a killer set up and have me excited for some PM DH!!! <br>My buddies will be thrilled as well. <br> <br>Great light!!! Any help for a newbe is appreciated. <br> <br>All the best my friend!!!
hey, yeah no problem.. I would love to help out in anyway i can. The best source for the cree xml I found was ebay. I was able to get them for 5 a piece with free shipping but I think buying the lens and driver separately was better. I also just bought the lens on ebay (10 lenses for like 8 dollars). I would suggest not to get the absolute cheapest lens. I first bought some 5 for 2 dollars pack of lenses and the sucked. I also used this dc-dc inverter (tried about 5-6 of them found this to be the best). <br>http://www.ebay.com/itm/DC-DC-Buck-Converter-Module-LM2596-Constant-Current-Voltage-Adjustable-Module-/221189132064?pt=LH_DefaultDomain_0&amp;hash=item337fe64f20 <br>(again ebay, you have to love it because of there buyers protection) also there is the one from china for 2 dollars less that I have bought a few of and work great. <br>I have bought a few lenses that were not meant for the cree xml, like the cree xr-e just make sure the aluminum star is the same dim. (they usually are) <br>hope that helped a little.... let me know if you have any other questions
As if you ride around with that thing on your bike hahaha
I am
Ok Ok...
I do... have you ever got mtb at night, from what I see there's no such thing as too much light...
No because I have a car and hate the environment. Props to you for still being able to ride it tho and get it up a hill.
Yeah I'm considering building a battery pack half this size to bring the lights weight down from 4.5 lb to 2.5 but I have a 30 lb bike anyway so, mhe...
Me like...
thanks for the thermal data. bit high even for my liking mate.
It does get pretty high in standing air but when biking it's not too bad. I did use another CPU heat sink that kept it's max temperature to 35 degrees c but it was an inch longer on both sides and heavier, being made of mostly copper. I ended up using this design because of it's size and while biking only for 10 degrees hotter. HD you want you can also under drive them all the time. I have a switch thatdrives them at 66 percent and then there is only a 9 degree temperature increase and it still makes at least 5500 lumens
Great Job mate. Can you measure the Heatsink temperature? I feel its kinda small for all 6 of those babies at full power!
i posted my heat testing data... hope its helpful
yeah temperature managment was one of the difficult parts and required a lot of testing but being that it is a big part of my studies I found that the copper plate really helped to evenly spread the heat for the cpu heat sink.... give me a day or two and ill post my data using a thermocouple

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