There are bike lights, and then there are bike LIGHTS. My rides are mostly urban and I can get by with a lower level light because of all of the ambient light I have access to. Reader Jesse on the other hand wanted to bike in conditions devoid of ambient light and he came up with a bad ass DIY solution. Take it away Jesse . . .
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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 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. Next I am thinking to go over 9000 lumens (for those dragon ball Z fans out there).