don't know much electronics like some here above, but I know this one :-) ,the xml2 has a variable resistance, at say 4A it should be 3.8V/4A=0.95ohm
All led’s present a rather steep equivalent resistance curve.
It’s the forward voltage vs current curve.
So say you have 3.3 volts at 3amps like a normal XM-L, equal to about .9 ohms. But current goes up much faster than forward voltage. So So applying 4 volts to the led which is what my IMR 18650’s will put into an XM-L you’d think oh no problem that’s only 4.44 amps. Nope I measured about 11 amps at the LED for about 1/4 of a second before it flashed and burned. It probably was higher but my multimeter couldn’t get as fast an instantaneous reading. So in that case it was less than .36 ohms likely a lot less since I couldn’t get a good reading, likely since the exponential voltage curve of the XM-L seems to hit a vertical wall above about 3.8 volts the equivalent resistance pretty much goes to nothing. This is why with LED’s you need a true constant current regulator.
The difference with resistive loads is that it’s fairly constant with the nitinol wire as long as you’re not burning them red hot which wouldn’t be good for smoking.
But the drivers being buck drivers, it’s why most people run 2 ohms or less when running single cell. If you want to look like a firebreathing dragon you’re not doing it with a 3 ohm coil and a boost circuit and single cell. Everyone who builds them use 2 CR123 IMR cells an a buck circuit and 3 ohm wires or they use really low resistance 1 ohm wire or less and high discharge IMR 18650’s. The last option works but the problem is you get less and less smoke as the battery drains. The first option is the best as it’s perfectly regulated just like our flashlights.
It's called a kick, for vaping, you drop this in a 18650 mod on top of an 18500/18490 battery and it let's you adjust the amount of power to the coil to make the vapor
Yeah I am a vapor, I own 3 kicks, and about 4 other mods for vaping...but they are not for Cree flashlights...they have a PWM of 33.3hz in em
They are cheap clones of more expensive versions, and they don't have any anti-short protection like the originals...I did conformal coat mine with clear nail polish though
Bum kick due to soldering | E-Cigarette Forum
If it wasn't for the Cree driver technology...vaping with these "regulated" devices would be a whole lot different
20 year smoker...ain't touched one in over 5 months and I feel AWESOME!
The difference between what we do and what you do...our ohm law (E/IxR) runs thru a coiled up wire the work done is a vapor we inhale to get nicotine, your ohms law (E/IxR) runs thru an LED emitter and the work done is alot of light so you don't stump your toe on the couch 
It's still ohms law...
Here is a chart we go by that helps us pick the voltage and coil resistance to give us the power for vaping (and just like with light levels and shades of LED's it's all subjective to the user)
I will say this...it won't work in a LED flashlight though...mainly because unlike the drivers in our flashlights...the kick is designed to "dummy proof" vaping (provide protection for those running low resistance and/or not the best batteries)...it auto shuts off after 10 seconds so if someone held down the button it wouldn't keep firing and drying out the wick and burning the juice or overheat the battery causing a thermal runaway causing it to vent, it does short/high current protection, won't fire on anything under 1.3Ω and has low power protection shutoff
And I beg to differ on the not electronically inclined (2841 in the Marines 92-98)...ohms law to us (especially the guys sub ohming and blowing clouds like a dragon) they are VERY in tune with ohms law...they push 20-30 watts thru those coils and buy the BEST batteries (the flashlights direct competition for those REAAAALY good batteries) in fact many of our folks use the 20-30 amp high current AW's, Efest, and MNKE batteries in their rigs, you would be surprised on just how much they know about batteries and what they can and can't do
http://www.e-cigarette-forum.com/forum/blogs/baditude/4848-9-battery-basics-mods-imr-protected-icr.html
http://www.e-cigarette-forum.com/forum/blogs/baditude/5163-12-deeper-understanding-mod-batteries-part-i.html
http://www.e-cigarette-forum.com/forum/blogs/baditude/5162-11-deeper-understanding-mod-batteries-part-ii.html
In fact if you want to know the latest and greatest on high capacity high current batteries...go ask a vaper
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