Cell count vs LED count XM-LAWT

OldNick

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Sep 3, 2006
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I am organising some Cree XM-L LEDs, and also buying lipo batteries to drive them.

It _looks_ to me as if I can drive the LEDs on a one-to-one basis with the batteries, just using a buck current regulator. I want to run 3 in series, with a 3S pack. I can see an obvious safety factor there, but should I get that one extra cell to make better use of power-time?

Thanks for any advice
 

Aepoc

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I'm using three of AW's 17670's for my triple XM-L build. Everything is wired in series with the LEDs getting about 2.89A. I get about 15-20 minutes of run-time which is plenty for me because at that point, everything gets really hot.
 

OldNick

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Thanks for that. I had another look and realised my question is probably not needed :eek:. The XMLawts have a very low FV, and a cell per LED is plenty.

Sounds like a bit heavier stock or more heatsinking is in the pipeline!
 

Aepoc

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Mac finned the head of the mag that I'm using and it still gets hot... Be sure to heatsink the driver real well... I'm not sure what you are planning on using, but if you will be sending the LEDs ~3A then the board will get too hot without propper heat sinking. When I first got my light together, the current would drop by about half after around 30 seconds. After adding a thicker piece of copper, I had no more troubles.
 
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OldNick

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OK. Thanks. I will certainly take that on board. 3 of these guys at 3A will put out a LOT of light, so they will not always be at that current, but there will be times, and I also want them for permanent lighting, where coolth is paramount. Luckily there, size and weight do not matter much.
 
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