Cree Q5 lumens confusion.

I am confused with the output of the Cree Q5 at the following output levels:

350mA
700mA
1000mA


I was on www.dealextreme.com and they say at 1A is 228lm but I forgot where I saw this before but somewhere else said it's 273lm at 1A. If the Q5 is 228lm at 1A then that makes the SSC P4 a better buy (cheaper as well) because it putsout 240lm @ 1A.

DX claims the following for thier Cree Q5.

350mA: 107~114lm
700mA: 171.2~182.4lm
1000mA: 214 ~ 228lm

Click to expand...

So what are the lumens for this LED at 350/700/1000?? Is DX right or wrong?

Thanks in advance.

Here is what i found about cree7090xre binq 5



can not remember where it comes from

http://www.cree.com/products/pdf/XLamp7090XR-E.pdf

I think DX numbers are consistent with the spec sheet from CREE.

Seoul buys Cree die, so their brightness multipliers at a given current are spec'd the same. They have different optical, thermal, and phosphor designs, so their efficiency, even with the same die bin, can and does vary. It is also worthwhile to note that Seoul specs their brightness at typical values for the bin, but Cree specs minimum.

Cree XR-E Q5: minimum 228 lumens @ 1A
SSC Z-LED P4 U: minimum 220 lumens @ 1A
the often publicized 240 lumens are the maximum specs for the U bin, so they won't be reached, or there would exist a higher bin already

I don't think you're using a high enough multiplier on the Q5 there - my calcs would suggest min 235lm based on 1000mA lumens being 2.2 times 350mA lumens (looking at page 7 of the datasheet). Meanwhile the SSC P4 is min 200lm based on the same multiplier (given that the bottom of the bin is 91lm, not 100lm - a Q2 bin XR-E could be brighter than a U bin P4!)

p.s. DX numbers are also not consistent with the data sheet, since they only allow for a multiplier of 2 from 350mA to 1000mA.

fa__ said:

... can not remember where it comes from

Click to expand...

It is from member jtr1962's very interesting thread White LED lumen testing.


tl

Thanks, i found the picture somewhere but i had never seen the whole thread

I measured the current draw from a freshly charged Eneloop AA in a Cree Q5 light that is sold as 300 lumens and 7 watts. Initial draw on the high setting was 2.0 amps. I measured the current draw from a freshly charged Eneloop AA in a Chinese Cree Q5 light that is sold as 300 lumens and 7 watts. Initial draw on the high setting was 2.0 amps from the battery. At 1.5 volts max. battery cell voltage that is 1.5V x 2.0 amps = 3.0 watts.

Has anyone measured the current draw from a 14500 (3.6v) cell? The current from this cell would need to be at least 1.9 amps to get 7 watts.

Send in your numbers - maybe this budget thrower really does do 300 lumens and 7 watts!

this type of led can't reasonably take a continuous 7 watt anyway unless you had the most extensive heatsinking. There would be no significant lumens gain.

A 14500 probably won't reach 7W either because the XR-E LED has a pretty high forward voltage compared to nowadays' new and cool emitters. A higher Vf directly results in a lower current when direct driven by a single Li-Ion battery.

BTW under a 2A draw the eneloop's voltage will be at 1.2V or less, no way it's staying at 1.5.

Ergolator said:

I measured the current draw from a freshly charged Eneloop AA ...

Click to expand...

Are you measuring at the battery (before the driver), or at the LED (after the driver)?