Luxeon Limits?

lumileds says that at beyond 300mA a luxeon will burn out...
with proper heatsinking (O-sinks, copper slugs, homemade aluminum heatsinks) just how far can you push them without doing damage??

second: i've been searching for a circuit design and have not been able to find one that will limit the current flowing to a luxeon 3; in testing my LED pulls around 2A (while heatsunk) and i want to know if driving in this manner would be safe....
:help:
UX1L
headsink aprox. 2.1cm Diameter, 1.8cm height, solid aluminum with a hole drilled for the positive lead
2xcr123 in series, no resistors

the heatsink can conduct heat out to the body and head, and i have never driven the led for more than just long enough to take measurements

my budget is nonexistant, though i have acess to all kinds of resistors, transistors, and dead electronics(power supplies, amps, etc.) to salvage parts from

If I were you, I wouldn't run that light too much at that level--2amps is a bit much. The 300mA level you quote might have been for the Lux I, but people here run them with 400 mA drivers often it seems.

The Lux III is more robust, and --someone will correct me--spec'd at around 700 or 750 mA. I've done three mods so far, and used resistors to set my initial current (on brand new batteries) at a little over an amp. I've gone through a few sets of batteries, and run the lights for sometimes an entire 8 hour shift continuously, and have never had a failure at this level.

Regarding the drivers--check out the sandwich shop. They have buck regulators (and also boosting ones) that will limit the current to your led to a safe level. The downboy series, for example, comes in several different current cinfigurations like 1000, 917, 750, 500, and 400mA. I'm just using this model because I looked at it today, but if you want to buy a different one or make your own---there are lots of other options. You'll need to search the posts of people a lot more experienced than me, but I'm sure you can come up with a number of different options to safely run the light with the brightness and runtime you want. Just please --take good care of that U***.

Rover is pretty much dead on. You can also purchase drivers from taskled.com and leddynamics.

2 x 123 with 2 ohms is a great setup for a Lux III - about 700ma. I have done similar things with a Lux I and would not really worry about it.

2 amps - maybe you would like to do that on a bit lower grade Lux III - one you do not care very much about.

Just a bit of nomenclature - your Al cylinder is a "heat spreader" , not really a "heat sink". The heat needs to be transferred either to your hand or to the air. In order to transfer the heat to the air, the rule of thumb is at least 1 in square per watt, and ideally more like 3 inches square per watt.

At 700ma, nominally 3 watts, that is 9 square inches. At 2 amps, that is around 27 square inches. Most portable lights of course rely on pushing the heat into your hand, which has a practical limit of around 5 watts continuous, more if you are drinking ice cold lemonaid.

a lux3 at over 1amp you really just make more heat and not much light. At 2.5amps I belive is when the bond wires melt and fuse open.

700 is spec for luxIII, with an optional drive of 1amp. Make sure it's well heatsinked.

gahr! $58 invested in my 113 lumen beast, i guess ill have to toss another 22 in there....:-/