DD from single Li+ 18650?

Crux

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Would it be safe to drive a 1W Q4H from a 18650 Li+?
Or, should I use a resistor?
How about a 3W SY0J?
Or should I try higher Vf devices?
Heat sinking is only moderate, copper pipe.

The particularly interesting thing here is that the Luxeon voltage drop pretty much limits the amount of discharge of the lithium cell. Kinda self-limiting.

Any thoughts are welcome.

Crux
 

paulr

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DD is probably safe, should be safe if you go to a higher Vf bin like L.
 

shiftd

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well, my 18650 drive my R2K at 470 mA. So i would say it prolly be safe. But it will be even safer to try and get higher binned lux. Well, you can always start with a couple ohm resistor and then go down from there. /ubbthreads/images/graemlins/smile.gif

good luck
 

AilSnail

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I use a LuxIII TWAK, works ok. I wouldn't use a higher Vf than this. There was a discussion of this recently. Try to measure current with a low ohm resistor like 0.1 ohm or less.
 

Justintoxicated

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Im running an SX1J Lux III but it is a J-bin and im running it off 3 C's direct drive...Maybe I'm nuts but it sure is bright off fresh cells.
 

Crux

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Ok, I did a check of current draw using a 0.1ohm resistor:
175mV / 0.1ohm = 1.75A !!! /ubbthreads/images/graemlins/eek.gif
I'd say a resistor is in order... /ubbthreads/images/graemlins/grin.gif
I chose two 0.3ohm in series (0.6ohm). This limits current to ~850mA fresh charge.

BTW, the Li+ cells are from allelectronics.com. I bought them with the charger.

Thanks for all the input, this place is a wonderful think tank! /ubbthreads/images/graemlins/bowdown.gif

Crux
 

AilSnail

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Ouch I might have done better suggesting a higher value resistor to begin with. How did you measure the current? Through the DMM or by monitoring the voltage over the resistor?
 

Crux

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Yes, I used a Fluke to measure the drop across a tenth ohm resistor. Its a nice value for figuring current. I only left it connected a few seconds (an eternity for the Lux), and the Lux was well heatsinked.
I don't think I hurt the Lux too badly, after this test I remeasured Vf @ 350mA and it was still where it was before the test. (A crude test but it lets you know if you wacked it out of spec.)

Crux
 
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