Is 300 Lumens OTF from 1x18650 real?

jsr

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I've been away from flashlights for a couple of years due to new job, new baby, and a few other things. My current light arsenal has served me well. However, I made the mistake this weekend of revisiting a few of the vendors I once frequented and may have caught the bug again. I've already bought another light (there goes my wallet!).

I'm amazed at current LED technology and capabilities. As I browse CPF and the web with the little time I have, I find some claims difficult to believe, even when they're substantiated by 3rd party tests. I went through some review sites and found some test results difficult to believe. Most of these involve P60-sized drop-ins and Mag upgrades that seem to exceed the mfr rated capabilities of the LEDs. I browsed through those quickly though, but one caught my eye the most...the EagleTac lights (because I can remember the brand and because I like their lights).

The most accurate generalization relating LED lumens to OTF (Out-The-Front) or Torch Lumens has been OTF = LED * 0.65. Or, only 65% of the LEDs generated light comes out of the flashlight. This has always held true in the past and still holds true now when I look at test results vs. light and LED mfr claims. It holds true for all except those upgrades I mentioned above (which I can't remember the details of) and the EagleTac products.
EagleTac claims to only lose 20% of the light created at the LED, instead of the 35% loss. Their 1000 lumen light says 800 OTF. Their T20C2 claims 380 lumens LED and 300 lumens OTF, again only 20% loss. 3rd party reviews/testing seems to confirm the 300 lumens OTF for the T20C2 XP-G. However, this doesn't add up correctly. I doubt EagleTac has the magic reflector and lens combo that retains 15% more light than every other brand. Yet it's still 300 lumens OTF. So if it's really 35% loss (like it should be), that would mean the T20C2 makes 460 lumens LED. And EagleTac claims the LED is only driven at 1.2A. But according to Cree XP-G specs, the max possible output is just under 400 lumens LED at a drive of 1.5A. Nowhere near 460 lumens at 1.2A.

So how is 300 lumens OTF possible? Magic super-low-loss optics?...LEDs driven beyond the 1.5A rating to achieve higher than 400 lumens LED? Inaccurate test results?
As I mentioned, I like EagleTac's lights, but I like to understand what I'm buying if I decide to pick some up. This is important to me so I can understand whether EagleTacs (and the others with physics-defying performance) are truly better than their competition or if the claims, and the 3rd party testing, are inaccurate. So far, my brief time I can spend on CPF has shown no one questioning this inconsistency. So your fellow CPFers help and knowledge is greatly appreciated to help shed some light on this.

BTW, has anyone noticed the EagleTac T20C2 has near the exact same body as the Olight M20? The shape is exactly identical with the only differences being surface treatment (knurling, flat, etc.). I'm guessing the same contractor machine house makes the bodies for both and it's cheaper to buy an existing design with some minor surface changes than it is to have them make something completely new. That's how it is for all contract mfg I've been involved in.

Thanks.
 

Search

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You got an 18650 to make 300 lumens?!

..pictures or it didn't happen :ironic:
 

FlashKat

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Are we talking about a specific LED, or any in general? SST-50, P7, MC-E LEDS put out more than 300 OTF lumens on a 18650 battery.
 

jsr

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Per my original post, the specific numbers I refer to are about the EagleTac T20C2. It's a 2x123 or 1x18650 light. EagleTac claims 300 Lumens OTF, 380 Lumens LED (doesn't add up), with a XP-G R5 driven at 1.2A. These numbers don't add up correctly, but some review sites confirm about 300 Lumens OTF.
 

dhouseng

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I don't think the T20C2 is doing 300 lumens OTF continuously. It is driven at 1.2A and stabilizes at around 285 lumens OTF.

380 LED lumens at 1.2A is not exactly accurate. They tend to underrate their LED lumens.
 

bigchelis

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I think the real question should be:

Is 2000 Lumens OTF from 18650 real?


So, far we have just 1260ish real OTF lumens from Moddoo's Tripple XP-G R5 Direct Drive P60 drop-in.


There is a Quad P60 drop-in due to be tested soon, but I think if we can find 5 or 6 XP-G R5's in a P60 drop-in then absolute yes (well if Moddoo makes it).
 

jirik_cz

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The most accurate generalization relating LED lumens to OTF (Out-The-Front) or Torch Lumens has been OTF = LED * 0.65. Or, only 65% of the LEDs generated light comes out of the flashlight. This has always held true in the past and still holds true now when I look at test results vs. light and LED mfr claims.

LED lights usually lose only around 15% on the reflector+AR glass. There are also some losses due to the heating of the LED (it is less efficient when it heats up). So you can add another 5-10% losses due to heat. So OTF = LED lumens * 0.75 is a good formula for a LED light. (If manufacturers don't exaggerate LED lumens :))

And EagleTac claims the LED is only driven at 1.2A. But according to Cree XP-G specs, the max possible output is just under 400 lumens LED at a drive of 1.5A. Nowhere near 460 lumens at 1.2A.

XP-G R5 has 398.6 lumens when driven with 1.2A. (source: Cree product characterization tool)

BTW, has anyone noticed the EagleTac T20C2 has near the exact same body as the Olight M20? The shape is exactly identical with the only differences being surface treatment (knurling, flat, etc.). I'm guessing the same contractor machine house makes the bodies for both
Thanks.

Yes, T20C2 looks pretty similar to Olight M20. My personal guess is that they just inspired by M20 when designing T20C2. I wouldn't expect that they use the same machine contractor.
 

Beamer4D

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mmm agreed. 300 lumens from one 18650 battery seems to be old news no?

I've seen my fair share of much higher output lights with one 18650
 

LEDninja

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Maybe you should look at the whole test:
EagleTac T20C2___________XP-G R5_________1 AW 2600mAh___________318.5______1 sec
_______________________________________________________________ 287.7______30 sec
________________________________________________________________283.8______1 min
________________________________________________________________280.0______2 min
________________________________________________________________277.7______3 min
You are not likely to recharge your battery after only 1 sec of use. Even at 30 sec the lumens had dropped below 300 lumens. Some torches drop 20%, others 10% in those 3 minutes.
Now I only look at the last line in the tests (usually 3 minutes) to get a better feel for what I see in real life extended usage.
From this thread: https://www.candlepowerforums.com/threads/260659

EagleTac T20C2_XP-G R5_1 AW 2600mAh_318.5_1 sec_____626______15,650

So that's 318.5 lumens, I think.

Which is slightly more than the 300 lumens from a quark Mini AA running on a 14550 :devil:

I am surprised this question is asked today. I bought an MTE P7 on 4/6/2008. My worst case calculations show 350+ lumens based on:
700 lumens at 2.8 A vs advertised 900 lumens;
2.1A measured instead of 2.8A;
low reflector/lens efficiency of only 65%.
Tests of the very few 'DX' P7/MCE lights/modules show 400-450 lumens actual.
So we have had over 300 lumens on 1 18650 for over 2 years now.
mmm agreed. 300 lumens from one 18650 battery seems to be old news no?

I've seen my fair share of much higher output lights with one 18650
 

jsr

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LED lights usually lose only around 15% on the reflector+AR glass. There are also some losses due to the heating of the LED (it is less efficient when it heats up). So you can add another 5-10% losses due to heat. So OTF = LED lumens * 0.75 is a good formula for a LED light. (If manufacturers don't exaggerate LED lumens :))

There was testing done several years ago (by some longtime CPFers) with a true integrating sphere (not a homemade light box) that verified the 65% loss from emitter lumens to OTF lumens. 75% is far too low of a loss estimate and if that's what people are using these days, they're not getting what they think they are.

Yes, T20C2 looks pretty similar to Olight M20. My personal guess is that they just inspired by M20 when designing T20C2. I wouldn't expect that they use the same machine contractor.

EagleTac's factory is in China and they're a small company so I doubt they have their own mfg house out there. ALL the light mfrs contract for virtually all the mfg, except for end-product assembly. I'm almost positive they use the same contract mfr, which isn't a bad thing. Just something I noticed when comparing the lights.

Maybe you should look at the whole test:
EagleTac T20C2___________XP-G R5_________1 AW 2600mAh___________318.5______1 sec
_______________________________________________________________ 287.7______30 sec
________________________________________________________________283.8______1 min
________________________________________________________________280.0______2 min
________________________________________________________________277.7______3 min
You are not likely to recharge your battery after only 1 sec of use. Even at 30 sec the lumens had dropped below 300 lumens. Some torches drop 20%, others 10% in those 3 minutes.
Now I only look at the last line in the tests (usually 3 minutes) to get a better feel for what I see in real life extended usage.

Thanks for the rest of the data. The reviews I was looking at didn't have extended time data, only a single discrete data point. The 3min figure seems much more realistic based on the specs of the XP-G LED.


I am surprised this question is asked today. I bought an MTE P7 on 4/6/2008....So we have had over 300 lumens on 1 18650 for over 2 years now.

I should've phrased my question better (and made my post shorter it seems since I don't think anyone read through all of it). I meant to say "is 300 Lumens OTF from single XP-G with 18650 real?" In the body of my original post, I specifically state the EagleTac T20C2 as the source of my figures, which is a single XP-G R5. At 400 LED lumens and 35% loss, that's only 260 OTF lumens. The ~280 OTF lumens number at 3min is in line with the predicted OTF numbers with test inaccuracies taken into account.
The other lights I mentioned (which wasn't meant to say those weren't capable of 300 OTF lumens, but that the test results are inaccurate or inappropriately reported (i.e. instantenous max numbers only)) were Mag drop-ins and the like that I briefly viewed the test data for on a site. The numbers, like the EagleTac, did not abide by the 35% loss rule based on the ratings from the LED mfrs.

As for what's been around for the last couple of years, as mentioned in my OP, I've been away from lights for the last couple of years.

Thanks all for the insight.
 

Bullzeyebill

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I have been around here since 2003, and have read and re-read thousands of posts and the only references to the 65% figure I recall concern incandescent figures for OTF lumens vs bulb lumens. We are finding that the figure is really about 80%, and sometimes better, for LED OTF output. There are of course variables that can tweek this figure, such as poorly heatsinked LED lights, or other factors that can reduce the effeciency of LED output shortly after being turned on, but these are becoming the exception, and not the norm, more and more.

Bill
 

jirik_cz

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I have been around here since 2003, and have read and re-read thousands of posts and the only references to the 65% figure I recall concern incandescent figures for OTF lumens vs bulb lumens.

Exactly. LEDs are different from incandescents. They emit light only in forward direction so usually only ~50% of light hits the reflector, rest of the light goes directly to the spill. That is the reason why overall luminous losses on the reflector are lower compared to incandescent lights.

So please, do not use incan formulas for LEDs!

EagleTac's factory is in China and they're a small company so I doubt they have their own mfg house out there. ALL the light mfrs contract for virtually all the mfg, except for end-product assembly. I'm almost positive they use the same contract mfr, which isn't a bad thing. Just something I noticed when comparing the lights.

I agree that they must use some contract mfr. But I doubt that it is the same as Olight's, because Olight was pretty unhappy about the T20C2 shape.
 
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