# Cree XM-L T6 bin resistor recommendations for direct drive on one 18650



## mattlite (Apr 5, 2011)

Is anyone here driving an XM-L T6 bin really hard while VERY well-heatsinked for extended periods...like 30-40 minutes continuous runtime?...and what is the minimum resistor to achieve really bright output without smoking the LED.

Just looking for some electrical expertise.


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## LEDninja (Apr 6, 2011)

This is what Elektrolumens did.
http://www.cpfmarketplace.com/mp/showthread.php?248030-EDC-XML-1000-Lumens-Narrow-Beam

Quote:
According to specs at 3A brightness is 910 lumens for a T6 bin. On my bench power supply I'm getting 4A at 4.2V with .1 ohms 20 watt resistor. I do add in a tiny bit of resistance because the Vf of the LED is so low. I am using the solid copper heat sink, there is no sign of turning blue or overheating that I can see. I can use more resistance for those who want longer run time as opposed to higher brightness.


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## mattlite (Apr 13, 2011)

LEDninja said:


> This is what Elektrolumens did.
> http://www.cpfmarketplace.com/mp/showthread.php?248030-EDC-XML-1000-Lumens-Narrow-Beam
> 
> Quote:
> According to specs at 3A brightness is 910 lumens for a T6 bin. On my bench power supply I'm getting 4A at 4.2V with .1 ohms 20 watt resistor. I do add in a tiny bit of resistance because the Vf of the LED is so low. I am using the solid copper heat sink, there is no sign of turning blue or overheating that I can see. I can use more resistance for those who want longer run time as opposed to higher brightness.



For convenience I would like to put such a device in the tailcap, and recommendations on brand/make etc. Brightlumens sells a resistor that looks like a FET...assume some heat might be generated...there are also other "silicon" ones. Anyone have any good experiences with different resistor types? Specific recommendations for sourcing certain ones from Digikey or similar joint?


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## degarb (Oct 28, 2016)

It seems like a dumbest question for me. . But its been since the 300 ma days. . I am calculating I need a .3 ohm to .4 behind my variable pot. Which will be parallel to my amc7135

But cannot find such animal. . Yes, could use 3 1 ohm in parallel. . But this is space consuming. 

Also, shipping of electronic components is insane if you only need one part under $50. . Read digikey had mail in check free shipping. Do they still? . And what is up with their broken search pulling irrelevant results?


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