Efficiency... Puzzling numbers?

Can someone explain this?... I have 2 lights, Fenix MC10 and Malkoff M60 hosted by a 6P. In BCs 10.5" sphere the malkoff does 220 and the MC10 on HI does 120... Lumens OTF.

With some simple tailcap measurements the MC10 is 32 Lumens per Watt and the Malkoff is 42 Lumens per Watt.

Why is this? Why does the XRE-Q5 Malkoff generate almost 2x the OTF Lumens AND have better efficiency than the MC10. Shouldn't the mildly driven MC10 and its XPE-Q5 dominate the ancient XRE-Q5 from an efficiency standpoint?

On a similar note my SF-E2L uses an XRE and emits 110 in the sphere of truth. It hums along at 79 Lumens/Watt. Why would the E2L-XRE smoke the XPE on a lumens/Watt basis... when the 2 emitters are driven to near-identical output levels?

The other thing I find puzzling is that the E2L runs ICE cold at 110Lumens, it generates no heat. The MC10 at 120 Lumens generates considerably more heat. Why is that? Shouldn't the temperatures be nearly identical at very similar output levels?

Is Lumens / Watt not a true measurement of efficiency?

:thinking:.. very puzzled.

kramer5150 said:

Shouldn't the mildly driven MC10 and its XPG-R4 dominate the ancient XRE from an efficiency standpoint?

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Unless they updated it, the Fenix isn't an XPG. Osram Golden Dragon Plus I think.

Edit, it looks as if it originally used the GDP, but switched to an XPE R2, I'm not finding anything saying XPG.

defloyd77 said:

Unless they updated it, the Fenix isn't an XPG. Osram Golden Dragon Plus I think.

Edit, it looks as if it originally used the GDP, but switched to an XPE R2, I'm not finding anything saying XPG.

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Oh DUH.. I'm an idiot... The MCE uses an XPE not an XPG. better update my first post.

But even still, in the case of the E2L why is its XRE more than 2x the efficiency of the XPE, when driven to nearly identical output levels? The E2L-XRE measured 110 and the MC10 did 120.

kramer5150 said:

Oh DUH.. I'm an idiot... its an XPE not an XPG.

But even still, in the case of the E2L why is its XRE more than 2x the efficiency?

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I would guess because the E2L is not really driven to hard, 60 lumens was it? Combine that with the electronics of the E2L being designed to run on 2 CR123A and not a wide voltage range like the Malkoff (3.8 - 9 volts?). So really it's not just the LED's efficiency that comes into play.

I saw that other thread with your numbers, I'm really intrigued by the MC10's numbers and the fact that medium has higher efficiency than low, actually the Zebra's numbers had this phenomenom on both high and low, that just goes to show lower doesn;t always equal efficiency.

The measurements on the OP don't take optical losses into account. This will have an effect on both tests.

I suspect the heat difference between the E2L and the MC10 is related to the relatively poor thermal connection between the MC10's head and body relative to the E2L and the high efficiency of SF's buck circuit relative to Fenix's boost circuit.

Kramer5150,

You might want to read our LED Fashlight White Paper. I think it will help you understand what controls the output of an LED flashlight.

Henry.

LukeA said:

...the high efficiency of SF's buck circuit relative to Fenix's boost circuit.

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Ding ding ding.

Boosting 1.5V nominal to drive a white LED will be much less efficient than a well designed buck circuit fed 6V nominal and driving a white LED.

Is the MC10's stated lumens emitter or OTF? If they are in fact OTF, the MC10 may have the E2L beat with efficiency on the medium level, E2L is 60 lumens with 79.7 Lu/W vs. the MC10 with 50 lumens and 97 Lu /W.

defloyd77 said:

Is the MC10's stated lumens emitter or OTF? If they are in fact OTF, the MC10 may have the E2L beat with efficiency on the medium level, E2L is 60 lumens with 79.7 Lu/W vs. the MC10 with 50 lumens and 97 Lu /W.

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My calculations are based on the following:
-My MC10 measured 120L OTF on HI. It draws 3A from a 1.2V NiMH.
-My E2L measured 110 OTF in HI. It draws .16A from a pair of RCR123 cells at 8.4V.

All lumen measurements were performed by bigchelis and myself in his 10.5" sphere.

Thanks for the info Henry... I'll read it tonight.

kramer5150 said:

My calculations are based on the following:
-My MC10 measured 120L OTF on HI. It draws 3A from a 1.2V NiMH.
-My E2L measured 110 OTF in HI. It draws .16A from a pair of RCR123 cells at 8.4V.

All lumen measurements were performed by bigchelis and myself in his 10.5" sphere.

Thanks for the info Henry... I'll read it tonight.

Click to expand...

110 OTF for the E2L? Wow, Surefire really sandbagged that rating.

The circuits are different.
The MC10 uses a 1.5V to 3.5V boost amplifier - terribly inefficient (maybe 60-70%).
The Malkoff uses the best 6V-3.5V buck regulator - highly efficient (maybe 90%).

kramer5150 said:

My calculations are based on the following:
-My MC10 measured 120L OTF on HI. It draws 3A from a 1.2V NiMH.
-My E2L measured 110 OTF in HI. It draws .16A from a pair of RCR123 cells at 8.4V.

All lumen measurements were performed by bigchelis and myself in his 10.5" sphere.

Thanks for the info Henry... I'll read it tonight.

Click to expand...

I just poked at some various cells to see voltage under load for this post.

what brand cells are you using? we then then accurately calculate wattage input.. the voltage under load is quite different for Liion cells.

defloyd77 said:

110 OTF for the E2L? Wow, Surefire really sandbagged that rating.

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Yeah this surprised me too.

LEDninja said:

The circuits are different.
The MC10 uses a 1.5V to 3.5V boost amplifier - terribly inefficient (maybe 60-70%).
The Malkoff uses the best 6V-3.5V buck regulator - highly efficient (maybe 90%).

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Aah OK, I didn't know boost circuits were so inefficient.

csshih said:

I just poked at some various cells to see voltage under load for this post.

what brand cells are you using? we then then accurately calculate wattage input.. the voltage under load is quite different for Liion cells.

Click to expand...

Just some non-IMR Ultrafire unprotecteds in the E2L and an Energizer 2450 in the MC10.

Thanks for all your replies!!