Why does this 180Lm last the same amount of time as the 120Lm?

Looking at the specs on my next flashlight(Fenix LD20), and my current flashlight(Neutron 2A) I noticed that the Neutron 2A is tested at 120LM for 2.1hrs and the Fenix LD20 is tested at 180LM for 2.1 hours.

Why are they the same? What technology in the Fenix makes it last as long as the light with 60 less lumen? Both take 2 AA batteries.

The only difference I can see is the LED

• Neutron 2A LED Emitter: Premium Cree XM-L T6
• Fenix LD20 Cree XP-G LED (R5)

Is that the sole reason for the difference? Does anyone know of any good links that talk about the technology in somewhat simple terms? Or am I way off on my assumption that the type of LED is the difference here?

The Cree XM-L and XP-G are very different. That will be the main reason, though Fenix are known for making very efficient circuits. I suggest going to the Cree website and reading up on their technical PDFs.

its important to remember that all manufacturers use different ways to determine runtime. would guess the neutron prob does 120 lms for 2 hrs but the fenix starts at 180 but looses some before it gets to the 2 hrs, some quote max to 50% and the like.

You also have to take into account the efficiency of the drive circuits an the method use to determine the lumens figures.
Norm

zs&tas said:

its important to remember that all manufacturers use different ways to determine runtime. would guess the neutron prob does 120 lms for 2 hrs but the fenix starts at 180 but looses some before it gets to the 2 hrs, some quote max to 50% and the like.

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When I get mine in a few weeks I will post the results of each. I'm sure I can at least eyeball which one is brighter after 2 hours.

Thanks for the website recommendations.

Lightingman said:

Both take 2 AA batteries.

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zs&tas said:

its important to remember that all manufacturers use different ways to determine runtime.

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These differences may also include the types of batteries used (e.g. alkaline, NiMH, lithium), which can make a huge difference.

Rather than purely speculate, let's look at some independent test results for both here:

http://www.candlepowerforums.com/vb/showthread.php?311559

According to the graphs, the R4 edition of the LD20 (pretty close to the R5) does indeed deliver approximately 180 lumens on Turbo mode, and runs for about 1h 27m on Eneloops and 2h 43m on L91s. Perhaps it (or the R5 edition) could achieve the advertised 2h 16m using higher-capacity NiMH cells (the standard Eneloop is only 2000 mAh), so the LD20, all things considered, seems to live up to its billing.

Now if we look at the Neutron 2A's results, we can see that it actually outputs approximately 160 lumens on its second-highest mode rather than the advertised 120 lumens. :thinking: And it does so for about 2.3 hours on Eneloops, exceeding the published specs with a relatively low-capacity battery.

So to sum up, things aren't always what they appear to be. When the same type of battery is used, the 2A at 160 lumens will run significantly longer than the LD20 will at 180 lumens, which makes sense (although the 2A seems a bit more impressive overall here). It's just that the 2A's specs are understated in comparison to those of the LD20 (which should be accurate with one type of battery, in all fairness to Fenix).

Yeah, I believe the manufacturer may have goofed. It must be there (260) for 2.1 hours. Well regardless I will do an independent test of them. I was really disappointed with the so called water proofing that my Neutron 2A claimed to have( IPX-8 Standard). I do 2 testes in a freakin bowl of stagnant water a few inches deep. It could take 15minutes without the chamber getting lots of water.

Lightingman said:

Yeah, I believe the manufacturer may have goofed. It must be there (260) for 2.1 hours.

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According to selfbuilt's tests (referenced above) their 260 lumens mode actually outputs nearly 300 lumens (calculated according to this formula), but only for 1.2 hours on Eneloops and a little less than 2 hours on L91s (although that is quite impressive, I think).

Somebody goofed somewhere, but the result is that according to independent tests the 2A is more impressive than its published specs indicate, while the LD20 meets its specs. This explains the discrepancy that you noticed between them, and in reality it does not appear that the LD20 is more efficient.

Lightingman said:

Well regardless I will do an independent test of them.

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Be sure to let the rest of us know how it goes and whether your results are in line with or different from the results that selfbuilt got (one or maybe both flashlights have been updated since that time).

Lightingman said:

I was really disappointed with the so called water proofing that my Neutron 2A claimed to have( IPX-8 Standard). I do 2 testes in a freakin bowl of stagnant water a few inches deep. It could take 15minutes without the chamber getting lots of water.

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That's too bad. :shakehead What I've found is that water resistance can vary greatly between individual flashlights, whatever the claimed specs are for the model.