Thanks- and stupid Q on Cree Q5 bulb
Just wanted to thank everyone for recommending the Fenix L2D-Q5. I used it on my helmet as a backup last night while out running my 3 dogs on a sled, and it works SUPER. Always nice to see if that's a deer, elk, or a cougar ahead of us while out in the middle of absolute nowhere....
I've posted on a sled dog board about the flashlight and the bulb itself since this may be an item of interest to other mushers. Someone asked about heat sinking these Q5s: do they generate more heat than the Luxeon bulbs, less, or about the same? He was referencing the huge heat sink in the Princeton Tec Apex headlamp as comparison.
I had no idea about the relative heat generation between these bulbs so I volunteered to ask you fine mtbr experts and report back.
"...Some local fiend had built it with his own three hands..."
The short answer is that the better the LED, the less heat it generates. For a given amount of power that you put into it (say, 3 watts), more of that input power is turned into light, and less is wasted as inefficient heat.
Originally Posted by verslowrdr
So specifically for your examples, a Q5 Cree will generate less heat than a first generation Luxeon LED both consuming 3W (or whatever) of electricity. I don't know the real numbers, but ballpark would be that a luxeon might convert 10% of that 3W into light (~100 lumens), leaving 2.7W as heat, while the Q5 Cree might turn 20% of that 3W into light (~200 lumens), leaving 2.4W as heat. So you can see that twice as much light does not equal half the heat.
Having said that, you can run a bright LED really hard and obviously make it hotter that a poor quality LED run very easily.
I hope that made sense and helped...