Originally Posted by jur
I use one of those same lights for my main light, but I use NiMH AAAs and recharge after 2 trips (I have 1.5 hour commute each way, back home in the dark). One thing that I like about them is they are focusable. Oh, and I also redid the terrible soldering job (dunno what they used for solder, sure wasn't anywhere close to eutectic) and insulated the bottom of the diode from the PCB. There is scope for a short circuit in their design!! The metal bottom actually can touch the PCB track which has plated thru holes on each polarity precisely under that metal bit, I don't know how the heck these things actually work at all except by accident. I also centered the diode nicely in the middle and modded the AlOx PCB so it seats nicely on the heasink and not on the contact which seems like an afterthought butchered in. And put thermal grease on it.
Yep, I had to do all that as well. Actually, I replaced the stock LED that was in there with a genuine Luxeon part, and let me tell you they make all the difference. When I bought a three-pack of those lights, each one was a different colour. But the Luxeons I bought are the exact same colours AND brightness, it's really quite amazing. I modified two as in the pictures, but the third I converted to a light for my wife's bike with three clamps and a few screws. That light still uses the original chinese LED and AAAs, though it definitely has a bluish tinge.