Surefire vs Fenix runtimes

SO for this post I am going to be specific and use the P2X Fury and the TK20R.

The Fury low mode is 15 lumens (Yes I know Surefire underrates their lights but at the most I would guess it's 30 lumens) And the Fenix has a 10 lumen mode. The difference is that the Surefire says it lasts 46 hours at 15lm and the Fenix says it lasts over 150 hours at 10lm... Why such a big difference?

BugoutBoys said:

SO for this post I am going to be specific and use the P2X Fury and the TK20R.

The Fury low mode is 15 lumens (Yes I know Surefire underrates their lights but at the most I would guess it's 30 lumens) And the Fenix has a 10 lumen mode. The difference is that the Surefire says it lasts 46 hours at 15lm and the Fenix says it lasts over 150 hours at 10lm... Why such a big difference?

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Runtimes based on different cells. Moreover, Fenix's circuit likely more efficient in the first place.

scs said:

Runtimes based on different cells. Moreover, Fenix's circuit likely more efficient in the first place.

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The mAh is the same between the two specs. Somehow the Fenix is supposedly 3 times longer though. I mean I love SF and swear by them but why would the runtimes be so low? Do they underrate their runtimes too?

BugoutBoys said:

The mAh is the same between the two specs. Somehow the Fenix is supposedly 3 times longer though. I mean I love SF and swear by them but why would the runtimes be so low? Do they underrate their runtimes too?

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Isn't the P2x rated on cr123s and the Fenix on an 18650?

scs said:

Isn't the P2x rated on cr123s and the Fenix on an 18650?

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Yes, but Surefire 123a's have been tested around 1500 mAh. Even the best 18650 is only 600 mAh more than two SF 123a's

Mah is not a measure of capacity, watt-hours is. 2xCR123 is only 70% 1x3500mah 18650. Likely the biggest difference will be how the two companies rate their products.

other things to consider, the p2x is an older product with a more inefficient buck driver, less efficient LED, and is rated at a different output in the first place.

staticx57 said:

Mah is not a measure of capacity, watt-hours is. 2xCR123 is only 70% 1x3500mah 18650. Likely the biggest difference will be how the two companies rate their products.

other things to consider, the p2x is an older product with a more inefficient buck driver, less efficient LED, and is rated at a different output in the first place.

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The newer Fury was released just last year I believe. It has an XM-L2

also, the difference between 15 lumens and 10 lumens isn't THAT substantial, is it?

BugoutBoys said:

The newer Fury was released just last year I believe. It has an XM-L2

also, the difference between 15 lumens and 10 lumens isn't THAT substantial, is it?

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Disregard the age part, surefire list no specs so all the reviews were all years old. You can't cross reference to a newer version.

anyways,

http://www.candlepowerforums.com/vb...ot-review-quot-(mostly-lumen-and-CCT-testing)

it it would be likely that at 15 lumens you would use 50% more power

staticx57 said:

Disregard the age part, surefire list no specs so all the reviews were all years old. You can't cross reference to a newer version.

anyways,

http://www.candlepowerforums.com/vb...ot-review-quot-(mostly-lumen-and-CCT-testing)

it it would be likely that at 15 lumens you would use 50% more power

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Wow, that makes a lot more sense. Especially if the P2X is, in reality, 30ish OTF lumens.

BugoutBoys said:

Wow, that makes a lot more sense. Especially if the P2X is, in reality, 30ish OTF lumens.

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Yup. It would be nice to compare both low modes in a sphere.
I have a LX2 rated for 15 lumens on low, no way that's 15. More like 40.
Or my G2X LE also rated 15 on low, no doubt it's more than 20.

BugoutBoys said:

Yes, but Surefire 123a's have been tested around 1500 mAh. Even the best 18650 is only 600 mAh more than two SF 123a's

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I find in actual field use it seems like a 18650 runs longer than 2XCR123 and more so than the extra mAh might imply. Not sure why but that's been my observation from the woods. There are other differences beyond pure mAh between these battery types such as voltage, ability to deal with higher draw etc etc. Comparing both lights might be harder than on the surface it might seem. What is the real output? Not just what is stated. How are they regulated? Are the LEDs the same? Probably would be best to use the exact same battery type as well if they both can take it. I am no expert on this smack. Just thinking out load as sometimes have the same questions comparing two lights in terms of efficiency.

I'm by no means an electrical engineer so don't ask for a deep dive on these things but here's what I've learned.

LEDs have a forward voltage of a hair over 3 volts. You can direct drive on a single cr123a but as it gets drained you have to boost the voltage, this is inefficient.

With adequate heat sinking you can direct drive on a lithium ion cell as well. Want to limit the brightness then you will need to limit the current and the voltage, this is bucking and it is inefficient as well. But bucking is more efficient than boosting.

1 3500mah 18559 has 12.95 watt hours of capacity where as 2xcr123a has 9 amp hours of capacity. So right off the bat a single 18650 has 44% more capacity. Not to mention an 18650 at 4.2v is closer than 6v to the forward voltage of the LED so the driver will also be more efficient.

Makes sense to me.

US vs Chinese ANSI lumen scale (eg, ti-force vs Selfbuilt scale), combine with the W-h battery differential - as mentioned by the folks above. So, on common Fenix lumen scale, you're probably really looking at 10lms/160hr/3500mah 18650 vs 20lms/46hr/1500mah 2CR123. So adjust 10 > 20 lms and you got 20lms/80hrs/18650. Then adjust the W-h differential of 9/13 (or 69%) and you got 20lms/55hrs/2CR123 equiv. So now it's down to 55hrs vs 46hrs (and I notice a few of Selfbuilt's runtime test of Fenix not quite living up to spec).