Fenix's circuits seem pretty good...

I was looking at runtime graphs from Chevrofreak (great work and a very big thanks!) and it appears as though the new Fenix models have more efficient circuits that most of the competitors. I am really impressed with the runtimes for the P3D and P2D.

In order to make a fair comparison, you need to see the brightness and runtimes compared between lights - and Chevrofreak has many good comparisons. I don't care for a light that is made to be really bright but has poor runtime do to an inefficient circuit.

I think some of the cheaper "clone" lights out there can be misleading because they appear to be equal in brightness to the better quality lights. Its when you look at efficiency and regulation that you see what you are paying more for besides better construction.

Fenix seems to have more efficent circuits then other lights. Their P1D-CE has a longer run time then the Lumapower D-Mini with about the same output. Their L series seems to run pretty well regulated even on alkalines. Fenixes are a great bang for the buck.

Yup, I love the efficiency of the new circuits.

Thanks again Chevrofreak. I appreciate the great amount of time and effort you put into those graphs.

The graph you just posted was the one that really suprised me. I just got the Pila G2 and the Fenix P3D at almost the same time. I was really suprised to see how much longer the P3D runs on 2 CR123's compared to the Pila with Cree module on 2 CR123's - and its brighter too! I primarily use the 18650 cell in the Pila for LONG runtime with a large amount of light and really love that light. Its built very well.

I think that someone needs to get your page posted in the Review/Runtime section so it can easily be found. I had to do a search to find it. It has great information.

good one

LEDs don't maintain a linear relationship between input power and output. 25% increase in actual output would be perceived as 11.8% increase in brightness (square law), but if the LED is running at relatively high level already, the power consumption goes up way more than 25%.

Also, unlike incandescent and fluorescent lamps, LEDs at current state have a major disparity in output between units even for same input power within the same part number.

The only way to know the efficiency is to simultaneously measure the input and output power over the full range of voltage expected to be present under battery use. I feel it's too soon to conclude it's efficient from your observations.

chevrofreak said:

Yup, I love the efficiency of the new circuits.

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:thinking: What's the significance of that green blob? Is the circuit really going up & down madly like that, or are you trying to show some area of efficiency. I'm confused.

I believe the green blob represents the low battery warning blink.

I'm also impressed with fenix's efficiency which is why I carry a P1Dce in my backpack where weight is always a concern. One thing I am curious about - how consistent is the fenix circuit for lumens output from light to light.

Visually comparing the 12 lumens low output of my P1d to the 9 lumens low output of my P3d, the P1d looks 3 to 4 times brighter. Also the 40 lumens medium output of the P3d is significantly dimmer than the P1D's low of 12 lumens. The P3d's high (80 lumens) seems right - just a hair brighter than the P1D's 72 lumens. Has anyone else noticed this kind of discrepancy from fenix to fenix?

Most of their $40+ lights seem to have very good circuits. Their mid to upper end lights are all high quality, and it shows in the price. They do have some weaknesses though. They haven't updated their reflectors for the new Cree LEDs. Their build quality is very decent, but not even close to say Inovas. Finally, they do seem to suffer sometimes from manufacturing QC issues, with occasional poorly machined threads, loose fiting heads, dirty contacts, etc.

shakeylegs said:

I believe the green blob represents the low battery warning blink.

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Thank you, I was unaware of that feature; it makes sense now.

Second tech question, why is it that some circuits get that "spike" before going off regulation?

I have tested several L1T/L2T heads. When the voltage decreased
(3V --> 2V), the current decreased too. No current regulation.

Energie said:

I have tested several L1T/L2T heads. When the voltage decreased
(3V --> 2V), the current decreased too. No current regulation.

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Their one light that had really excellent regulation on two AAs was the now discontinued L2P. With regular Alkalines, the L2T output drops linearly to about 75% before dropping fast. Alot fo the flat output curves out there are for NiMH or lithium batteries. Of course, all their CR123 lights have very flat outputs, but they better do with such batteries

But I must say that I haven't seen any other 2AA light with such good regulation on two AA alkalines, unless flashlightreviews.com made a mistake.

Pilou,
I belive, flashlightreviews.com tested the light-output and not the current during the runtime. There is no great output-difference between 500 and 800 mA (current from the battery).

Handlobraesing said:

The only way to know the efficiency is to simultaneously measure the input and output power over the full range of voltage expected to be present under battery use. I feel it's too soon to conclude it's efficient from your observations.

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Well, it is definately more efficient as far as lumens vs runtime. As far as circuit efficiency, it is probably more efficient there too.

chevrofreak said:

Well, it is definately more efficient as far as lumens vs runtime. As far as circuit efficiency, it is probably more efficient there too.

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Until real measurements are taken, it remains purely a speculation.

Handlobraesing said:

Until real measurements are taken, it remains purely a speculation.

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I don't understand how you can say this. Isn't the only thing that really matters is the output/runtime. In that regard the P3DCE is quite a bit ahead of the competition.

runtime does tell a good story!

The runtimes do tell a true story. Given the same power source - you can determine if one light is making better use (efficiency) of the power by looking at the output over time. If the lights have equal brightness and one runs longer using the same cells - it is more efficient - nuff said.
If one light is brighter - and runs longer - it is very easy to determine. Now, there are also variances in same models of lights and batteries that can complicate the issues. But for a "general" rule - the runtime plots tell a lot about how well a light makes use of its power source. Of course several light samples would have to be compared to make an official claim.

It would be very difficult to make a comparison between two lights if their outputs were very different. But again, you can make a pretty good conclusion of how efficient a light is by the amount of light put out over time.

Until real measurements are taken, it remains purely a speculation.

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Let's try rocket science ...

Brighter light, longer runtime. If it makes you feel better, don't call it more efficient. Just call it superb

Batteries can vary in their true capacity by +/- 10% so that gives a margin of error of +/-20% in measured runtime between samples. If several people carry out tests idependently and achieve similar results, then it can reasonably be assumed that the results are representative for that model of flashlight ...

Re: runtime does tell a good story!

precisionworks said:

Let's try rocket science ...


Brighter light, longer runtime. If it makes you feel better, don't call it more efficient. Just call it superb

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It is quite possible that the efficiency credit goes to the LED, just as it's possible the circuit is more efficient than the competitor. The thread title gave an apparent praise to the Fenix circuit, but without knowing for sure that the circuit is responsible for superior efficacy over the competitor's, it's unwarranted to give it a praise

regulator said:

The runtimes do tell a true story. Given the same power source - you can determine if one light is making better use (efficiency) of the power by looking at the output over time. If the lights have equal brightness and one runs longer using the same cells - it is more efficient - nuff said.

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Let's consider that the original discussion topic was regarding the LED driver, found in Fenix brand flashlights. Comparing to something many of us are familiar with,

If the criteria are mpg (litre/100km) and thermal efficiency in %, the two represent a very different thing. If a two stroke 49cc scooter gets 80mpg while a small car gets 30mpg the argument "the scooter's engine is more efficient" is not correct. Even though the overall efficacy(capacity to produce desired effect per input) of the scooter is far superior, it doesn't mean the conversation efficiency of the scooter's engine is superior(mechanical energy produced over fuel energy consumed).

Therefore, until the conversion efficiency of the circuit over the full range of usable voltage is measured, the Fenix circuit shouldn't be given a credit for being more efficient than those of competitors.

If one light is brighter - and runs longer - it is very easy to determine. Now, there are also variances in same models of lights and batteries that can complicate the issues. But for a "general" rule - the runtime plots tell a lot about how well a light makes use of its power source. Of course several light samples would have to be compared to make an official claim.

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The LED itself makes a very big difference in the overall output. Also the efficacy of the LED drops considerably at higher drive current.

It would be very difficult to make a comparison between two lights if their outputs were very different. But again, you can make a pretty good conclusion of how efficient a light is by the amount of light put out over time.

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Calculating the area under curve of lumen vs hour gets you the true lumen-hr, the total quantity of light produced but under same conditions, lights that drives the LED at lower current would always have an advantage.