My neighborhood has a one mile walking trail, which is where I like to walk my dogs before bed at night. Pitch dark. So I rigged together a 12 volt, 20 watt MR16 halogen bulb (narrow spot, 9 degree) (with various mounting hardware) to an old ball cap. Then I power it with my 18 volt Ryobi tool battery (which fits well into my back pocket). That's right, I am overvolting it a full 50%, or maybe even more with a fresh charge. But it is incredibly bright! Probably somewhere around 800 to 1,000 lumens sitting on top of my head.
The bulbs are $3 each when bought in a 3 pack at Lowes. I rotate thru them, and have never (yet) had a bulb failure, despite convention wisdom that they should only last 20-30 hours each.
So, the battery weighs about a pound, and it all looks really ghetto, but since I already own the batteries and the charger, my total cost for my headlight is probably under $10. I kid you not, I can light up the side of houses 400 feet away with it. It could probably be mounted to a bike helmet, or to the bars, if you have a little bit of time to figure it all out. I get about 40 minutes run time with the 20 watt bulb. A 10 watt bulb is still way more than enough, and I get an hour and 15 minutes on one charge with it.
Just tossing the idea out there for people that can't afford $400 bike lights
