Welcome to CPF mikewgordon!
Lets see if I can answer some of these questions.
Do we have an FAQ on LED flashlights here? If not, maybe we can put one together for the newbies (like me). Here are some suggestions for topics:
Definitions and comparisons:
LED types: Cree, Seoul, Luxeon, etc
Luxeon I, III, V, and K2 LEDs were the great LEDs of a year or two ago(they are still good but not great). Basically, the newer Cree(P4-Q5), Seoul P4, Rebel 80-100 and many of the "new" generation LED have twice the efficiency of the older Luxeon LEDs. Or for the same power, the newer LEDs will produce twice the amount of light and also less heat.
The myth of LEDs not producing heat is false. Some LED lights will be too hot to handle in 10-15 minutes to to the heat produced by the LED, but that's mainly with Luxeon V and K2 LEDs. A high power LED requires a good heat sink in order to not burn itself out.
These two of my posts might help.
This thread might help comparing the newer LEDs.
Basically, the Cree XR-E P4(3W is just the current it might be running at in a light) have double the efficiency of a Luxeon I, III, V, and K2 LED. The Q2-Q5 bins are even more efficient. A single Cree P4 should output about 180 lumen at 1 amp and around 3.4-3.8v, a single Q5 should output around 230 lumen at the same current. The Cree Q5 should be the brightest consumer single die LED available at this time(there are brighter ones but they aren't for sale). The Cree has a narrower emitting pattern then the Luxeon. Could be hard to solder and requires clipping the corners or removing the surface mount parts to prevent shorting if you are using the bare emitter.
The Seoul P4 uses that same die as the Cree and has similar efficiency. It has a similar emitting pattern to the Luxeon and is used by some to replace their Luxeon LEDs. It has around 200 lumen at 1 amp and 3.5-3.8v. The Seoul has phosphor problems with temperature and it also has a positive slug which might require isolation to prevent shorts with the bare emitter..
The Edison Opto is another LED that uses the same die as the Cree and has similar performance. IIRC, it has the exact emitting pattern of a Luxeon but will leave a yellow ring around the hotspot if used with a reflector.
The Luxeon Rebel is a surface mounted LED 1/4 the size of the Cree, though it has the same die size. There are many different bins of Rebels with the Rebel 100 being the brightest. If the Rebel 100 die and phosphor was used in a 4 die LED like the Luxeon V, you should easily get 800 lumen out of the LED at 1 amp.
I hope that I made sense.
Usually, the bin of the LED refers to the efficiency of the LED. Here is
a explanation of Luxeon's bin code. A Cree P4(probably the most common Cree XR-E LED) should be equivalent to a higher end W bin, similar to a W bin Luxeon V but at about half the voltage and a smaller die size. A Cree Q2-Q5 should easily be in the X bin if they were using Luxeon's bin codes.
The
Cree Q4 evaluation might be a good read if you want to understand how some of the newer LEDs react to different currents.
The
White LED Lumen testing thread tests LEDs and their Vf, amperage and lumens at a current.
The links Derek Dean(
Data SheetBinning and Labeling) posted are also helpful with understanding Cree's bin code.
What are these numbered battery types? voltage vs size vs chemistry, etc
You mean Lithium Ion batteries? They are mostly 3.7v and 4.2v when fully charged. The first two numbers represent the battery diameter in mm, the second two represent length in mm, and the last one means shape. I'll use a 18650 as an example, it would be 18 mm in diameter, 65mm long and tube shaped.
Protected vs unprotected cells
A protected cell has a circuitry that prevents overcharge, overdischarge and excess drain. The circuitry will shut down the cell if any of those thing happen. Any one of those thing will damage the cell and your will risk an explosion if you tried to charge a damaged cell. Unprotected batteries do not have this circuitry and can be overcharge, overdischarge and drained excessively. In short, protected batteries are safer.
Regulated vs non-regulated circuits
A regulated light has a circuitry to keep the light output stable for the entire life of the batteries. How stable depends on the regulator and it's application. Unregulated light will dim constantly as the batteries drain. Unregulated lights have less to break but regulated lights have a constant output.
A drop-in is a replacement of the original bulb of a flashlight. For example, the amazing
Malkoffdevices Maglite Drop-in is designed to replace the Maglite bulb with a brighter LED.
smooth vs orange peel vs ? reflectors
A smooth reflector will provide the most throw, or projection ability, but will also contain artifacts and the beam pattern might look ugly on a white wall. A orange-peel(OP) reflector has bumps on the reflector to smooth out the beam and make it look better, it reduces throw but if you need a good beam(No rings or holes), OP reflector is for you.
light quality: throw, halo, spread, hotspots
Throw is how far a light would project a beam. On here, it is usually measured in LUX(Lumens per square meter). The halo is the lighter spot of light around the concentrated center spot of a beam(also known as the hot-spot). The Spread/spill of a light is the area around the hot-spot and halo that allows you too see what is on the ground ahead of you.
throw vs output, lux measurements
Throw is how far a beam would project(usually measured in Lux and Candlepower) and output(usually measured in lumens) is how much light something is putting out. Something, like a laser could have a very high throw but a very low overall output. Something like a lantern might have a very high output but much less throw.
comparisons (brightness, run time, etc) to a common light (2AA Maglight?)
list of good beginner LED lights, what makes them good beginner lights
Decent LED lights in national stores (Target, Walmart, Gander Mnt, REI etc.)
How is this for figures, a typical 2D celled light(the cheap kind,
something like this) is about 15-20 lumens max and has a throw of around 800-900 lux. The 2AA Maglite(
review) is similar in throw and has less output, around 10-15 lumen max. A Fenix L2D-CE(
review) has 100+ lumens on Turbo and almost 3000 lux throw. The Medium mode has a longer total runtime(as full, flat regualtion) compared to the Maglite and still puts out about 30 lumens and 870 lux throw.
A good place to start seeing the "new" LEDs for cheap is Dealextreme,
Cree section,
Seoul section,
Rebel section. I'd recommend the
MTE Seoul,
Ultrafire C3, or a
HF2 Cree light as a good reasonably priced starter. These light don't drive the LEDs anywhere close to their limits but the light that do require 18650 batteries but the whole kit, batteries, light and charger, should cost less the $45.
Feel free to point out my mistakes.
The whole point of a FAQ is to have a shallow overview that can be read in 5 to 10 minutes, so you *don't have to* spend 10 hours searching every topic, until you know which subject you need to see in depth. 
