I researched the new generation of LED flashlights for several weeks and was surprised to see people building their own lights with off the shelf components.
I also saw a discussion forum about building your own light.
They use L ION rechargeable batteries for high VA ratings and low internal resistance so they can really drive the LED hard for those dazzling lumen numbers.
Problem is I've come to distrust rechargeable batteries.
I've also come to distrust alkaline batteries.... what to do???
Another problem is those L ion batteries. A lot of vendors won't ship to HI.
So in the end I decided that a small, lightweight, pocket clip, inexpensive AA flashlight would be the choice.
When the AA battery leaks and destroys it, I'm only down $5.
if you want a quality starter kit i can help you pick one out.
-solarforce body is around $12-20 bucks depending on model.
-drop in led module is about $10-20 bucks depending on options. they can go wayy higher up to over $200 but i suggest a basic one to start with.
-3400mah li-ion panasonic battery with over/undercharge protection circuit $15
-nitecore charger $10
upgrades available too(anti reflective ucl glass, glow in the dark o-rings, stainless spikey bezel and tail cap, pocket clip, lantern conversion, red green blue filters etc etc. its standard surefire p6/fury size and it takes whatever accessories fit the surefire)
like a surefire, the body and led itself are completely modular. you can switch from reverse to tactical clicky switch or replace a worn switch, go from 1 cell to 2 cell for length and runtime, change to new glass if you break it, easily find right sized orings to replace any worn ones, upgrade the entire led drop in unit to a new one a few years down the road or to a different color temperature like neutral or warm white, get a new rubber boot for the switch, get a new body if it gets all gouged up from being run over etc.
parts are cheap too. glass lens is like 2 bucks, replacement switches are like 2 bucks