This is a Princeton Tec product, basically a somewhat waterproof headlamp that takes 2 alkaline AA batteries and has a "1W Luxeon white side-emitter" as the light source.
The problem with this product is that either there is no feedback system in place for the driver circuitry: the lamp must be run off of 3V (2 alkaline batteries) and will not work off of 2.4V (2 rechargable batteries). The upgrade replaces the driver circuitry and allows the lamp to be run on anywhere from 1.2V to 3.3V. Unfortunatly, due to the unpleasantness of running a boost converter at 90 duty cycle, it's more efficient to run the lamp at 2.4V (90% efficient) than 3.0V (70% efficient)
This project is not fun, it's rather difficult and shouldn't be done unless you are:
- Skilled at smt soldering (TSSOP-8, 0603, etc)
- Have time to kill
This project is not profitable. Depending on how cheap you can get the PCB, it is about $10 to upgrade. You might also break your bulb.