I wanted a good rechargeable LED flashlight, that would combine long battery life, and a very bright output. I could have bought one, but where is the fun in that?
UPDATE! Most Store bought LED Flashlights do not work well with rechargeable batteries, as the typical rechargeable (NiCd / NiMH) is 1.2v instead of 1.5v, causing dim lighting even when fully charged. This Project uses a constant brightness bulb, so no dimming. When battery voltage drops too low, light goes out.
I started with a $3 lantern flashlight from Walmart, installed a 1 watt replacement LED, a 4 D cell carrier, and 4 NiMH 10ah batteries. I have gone a full year of regular use, and just swapped the batteries for another charged set, and put the old batteries in the charger for next year.
Here is the original post - http://www.green-trust.org/wordpress/?s=lantern
Lantern Flashlight - $7
1 Watt LED replacement bulb (constant brightness) - $16 (never have to change this)
4 D Cell Adapter - $3.50 (Walmart - http://goo.gl/dmjw4R)