How Many Lumens for a Cree XP-L V4 at 275mA?

LEDAdd1ct

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One of my future lights is going to be based off an IMR 16340 or a li-co 16340, AW in either flavor.

I will be using the Cree XP-L V4 5D2, which should be great for a nice floody pocket light.

I would like to get two hours runtime out of one IMR or lithium cobalt 16340 cell.

550mAH nominal capacity of an AW 16340 divided by two hours = 275mA.

The lowest I can compute is 183 lumens at 350mA.

Can someone please help me figure out approximately how many lumens I would be looking at if I went lower,
to the ballpark of 275mA drive current?

Thank you!

Source:

350m_A_XP_L_5_D2.png
 

mattheww50

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At low currents (relative to ratings), the current-lumen relationship is essentially linear.
So 275/350=x/183 so you should get about 144 lumens,

You may get an extra lumen or two more because the efficiency of the device increases with decreasing drive current.
 

LEDAdd1ct

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Excellent!

I was guessing 150 lumens, plus/minus a few.

Thank you for your lightning fast reply!

144 lumens is plenty for making sure you don't stumble over your own two feet, a sudden blackout, navigating a path, etc.
without making one feel wanting for more lumens.

I suppose we could drop the current even lower for three or even four hours runtime, but I know I would probably never need it.

Two hours feels like a nice round number, as does 144 lumens.
 
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