# Fenix E20 Mini-Review: OUTPUT, RUNTIME and BEAM Comparisons



## selfbuilt (Aug 18, 2008)

_*Reviewer's Note: *This is a "Mini-Review" of the new Fenix E20. I don't have time right now for a detailed photo comparison, but have included throw, output, runtime, and beamshot comparisons to some of the other 2AA lights available. Fenix E20 was purchased from fenix-store.com_







The E20 is Fenix's latest "budget" offering in the 2AA space. Up until now, Fenix "E" series lights denoted the entry-level 1AAA line of lights. These lights were single-stage only, and typically used less-expensive emitters and had lower build quality in keeping with their budget price. That is not to say they were cheaply made - in fact, the E series lights represent excellent value in their price range, IMO. The 2AA E20 carries that tradition on to the 2AA line with a simple single-stage light - but with a few nice features such as a focusable beam and forward clicky.






As you can see, the E20 length is within the range of available 2AA lights (from left to right: Fenix L2D, E20, JetBeam Jet-I PRO EX V2, and MiniMag LED). Note that unlike the others shown above, the E20 cannot tailstand (thanks to the forward clicky).

I haven't done detailed body shots, but construction of the E20 is relatively simple compared to the higher end lights. The knurling is more aggressive on the E20, which helps with "gripability" (if that's a word). Although still well made with good hand feel, overall build quality is not as high as the premium L2D/L2T line. It's hard to describe the difference, but the L2D just has a higher quality feel to me. 

All Fenix 2AA lights come with anodized tailcap threads, so tailcap lock-out is possible. Also, the E20 (like the recent L2Ds) offers reverse polarity protection in case you accidentally put the batteries in wrong. :thumbsup:

The obvious build difference between the lights is that the single-stage E20 has a wider head with a deeper and wider reflector. It also has a focusable beam feature similar to the infamous MiniMag.






From left to right: MiniMag LED, Fenix E20, L2D

As you can see, the E20 comes with a relatively deep smooth reflector. Although not quite as deep as the MiniMag LED, the reflector is well designed to give you a nice tight hotspot, as you can see below (pics taken ~0.5 m from a white wall, the L2D is on turbo).














As you see in the pics, the E20 (when focussed for maximum throw) gives a good medium-sized hotspot with sharply defined edges, and a relatively dim (but still very usable) spillbeam. In contrast, the OP reflector of the L2D gives you a much smoother transition from hotspot to spill.

So how well does the focusing feature work on the E20? Quite well actually - here are some pics are various levels of focus (taken at ~1 m):














User interface (UI) is quite simple - press the tailcap for on/off, and adjust the head for focus. Tailcap switch is a forward clicky, so you can lightly press for momentary on, and press further for it to lock-on (i.e. click on). You can unscrew the head a fair amount (with corresponding large center beam "donut" effect) before it falls off. Just off from maximally tight is pretty much the best throw, at least on my sample.

*Testing Method:* All my output numbers are relative for my home-made light box setup, a la Quickbeam's flashlightreviews.com method. You can directly compare all my relative output values from different reviews - i.e. an output value of "10" in one graph is the same as "10" in another. All runtimes are done under a cooling fan, except for the extended run Lo/Min modes which are done without cooling.

Throw values are the square-root of lux measurements taken at 1 meter from the lens, using a light meter.

*Throw/Output Summary Chart:*






As you can see, the E20 has less overall output than the L2D on Turbo (it's actually pretty close to the L2D on Hi). Surprisingly, it doesn't have that much additional throw, even when maximally focussed. When handling the two, the E20 certainly looks like it would throw further - but I realize now that this is largely an optical illusion brought upon by its more defined hotspot (and dimmer spillbeam). 

*Output/Runtime Comparison:*






As you can see, overall output of the single-stage E20 is actually pretty close to the Hi mode of the L2D, with expected excellent runtime.

I've thrown in runtimes for the older MiniMag LED (luxeon emitter), so you can see how the E20 compares. Basically, you get nearly three times the output for ~40% reduction in runtime. 

Just for kicks, :devil: I thought I'd also show you the original incandescdent MiniMag most of us grew up on. Here, you can see roughly six times the output for a ~45% reduction in runtime.

*UPDATE 8/20/08:* Here are the runtimes on Duracell alkaline, with the L2T V2 (RB080) added into the mix:






As you can see, the relative performance of the E20 is quite good, with excellent regulation. But this is also true of the L2D-Q5, which is similarly very well regulated at its Hi setting. The L2T V2 RB080 doesn't stay as fully regulated for as long, but I'm not sure if that's because of the Rebel emitter or the fact that it is running at a higher drive current/output level than the other lights.

*Preliminary Observations*

The E20 certainly does a good job in besting the venerable MiniMag in the output department while providing a good focusing feature and forward clicky to boot. Regulation and runtime are excellent as always, and Fenix lights don't have the rapid drop-to-zero output the MiniMag LED 2AA suffered from on all cells. E20 Build quality is certainly acceptable for general use, even if doesn't seem quite as high as the L2D. 

So, that all sounds pretty good - makes this an easy recommendation for a "budget" quality light with a good mix of features, right? 

Well, yes and no. While all the above is true, I think its easy for us to forget just how bright LED lights have become. Frankly, I find this single-stage light way too bright for regular tasks around the house at night. I certainly wouldn't even consider it for up-close tasks like poking around inside a computer, looking under cupboards, etc - all tasks the original MiniMag became legendary for. Without a low mode, I'm afraid this light is relegated to mainly outdoor use. Simply put, it's more a replacement for 2- or 3-cell Mag than the MiniMag! oo:

Of course, YMMV, but I think most users would be better served by the slightly more expensive two-stage L2T series (which also comes with a forward clicky but no focusing feature). Personally, I can count on one hand the number of times I defocussed by old MiniMag back in the day. I think availability of a low mode (with corresponding increase in runtime) is worth far more in a general purpose light. And if you can afford it, the L2D is an incredibly versatile light at a great price. Although I haven't reviewed the current L2T Q2, you can see the earlier L2T RB080 and L2D Q2 in my Fenix 2AA comparison review - that should give you a pretty good idea what to expect.

Of course, if you are looking for a very bright "economical" single-stage 2AA light with a focussing feature and decent build quality, then the Fenix E20 is for you. It could make a great basic bike light, for example. The defocusing also means you can make it into a somewhat "floody" beam (although still with relatively narrow spill). But with so many options available (both from Fenix and all the other makers), just make sure you think carefully about how you plan to use the light first. As always, it's a question of the right tool for the right job.


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## werdnawee (Aug 19, 2008)

Another impressive "mini" review, Selfbuilt. :twothumbs

And interesting thought about the usefulness of a variable beam.
(I am probably in the same boat about the number of times it is actually used)

Makes me wonder :thinking: about my pre-ordered and paid for UA2 :green:

:laughing:


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## sol-leks (Aug 19, 2008)

Good review. I am very happy with my E20. I dont see myself using the focusability much but I really do love the light because I have seen very few other lights, especially ones that use AA's, that have such a nice floody beam. It is only slightly brighter thn my p4 rc-n3, but over short distances, 20-30 feet or so, it feels so much brighter. I rarely need to see things far away, so this is ideal for me. I wanted to stay away from p7's or multi q5 lights because most of those lights use rare batteries. I was thinking about a modded mag, but to do it right, costsmuch more money, is much larger, and often dont fit the light absolutely properly, have bad heat sinking or other problems. Basically, I just want to recommend this light to anyone who may be looking for a budget floodlight, which to me, seems to be quite rare right now.


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## Sharpy_swe (Aug 19, 2008)

Sweet review!

:twothumbs


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## StarHalo (Aug 19, 2008)

Ah, so the "focus" feature is just an adjustable head/reflector a la some of the JetBeams. Can the head/reflector be removed completely like the Jets, so you can "Mule"/bare emitter use the light?


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## DM51 (Aug 19, 2008)

Moving this to the Review section...


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## TONY M (Aug 19, 2008)

Nice review SB!


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## selfbuilt (Aug 19, 2008)

sol-leks said:


> Basically, I just want to recommend this light to anyone who may be looking for a budget floodlight, which to me, seems to be quite rare right now.


That's a good point - I debated whether or not to call this a "flood" light in my review, and decided not to because the overall beam width is a bit narrow for that. But you can certainly defocus it sufficiently to produce a "floodier" beam pattern. And that may indeed be one of its strong points for many - thanks for pointing it out.



StarHalo said:


> Ah, so the "focus" feature is just an adjustable head/reflector a la some of the JetBeams. Can the head/reflector be removed completely like the Jets, so you can "Mule"/bare emitter use the light?


Yes, the head/reflector comes right off and you can run the bare emitter (like the original Jet-II IBS). But just like the Jet-II, the protruding clicky means you can't tailstand.


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## selfbuilt (Aug 20, 2008)

After the discussion in the main LED forum thread, I thought I would compare alkaline performance of the 2AA lights:






As you can see, the relative performance of the E20 is quite good, with excellent regulation. But this is also true of the L2D-Q5, which is similarly very well regulated at its Hi setting. 

It's true the L2T V2 RB080 doesn't stay as fully regulated for as long, but I'm not sure if that's because of the Rebel emitter or the fact that it is running at a higher drive current/output level than the other lights. 

:wave:


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## TONY M (Aug 20, 2008)

Just over an hour of pan flat regulation on duracells, not too bad.

I'm very impressed with the L2D's regulation on high mode with alkalines! Is you're L2D Q5 the "new" one with polarity protection? (If that were to make any difference).
Its just going by memory I have seen L2D graphs that show runtime to be worse than yours when running on alkalines.

Both Fenixes are good on alkalines which is great!

Thanks.


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## selfbuilt (Aug 20, 2008)

TONY M said:


> I'm very impressed with the L2D's regulation on high mode with alkalines! Is you're L2D Q5 the "new" one with polarity protection? (If that were to make any difference). Its just going by memory I have seen L2D graphs that show runtime to be worse than yours when running on alkalines.


Actually, my results are quite consistent with what Chevro originally reported when the L2D first came out (if you take into account emitter differences - mine is a Q5 and the original was a P4 - plus there's always Vf variability, etc.). He found a curvilinear pattern for the L2D on Turbo similar to my L2T results, and rock-solid regulation of the L2D on Hi (and Med and Lo) modes on alkaline. The take home message is that the L2D is well regulated on alkalines - just not on Turbo mode.

FYI, my L2D is the original design with Q5 - I don't know if the new reverse-polarity protected versions have any different runtime.


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## adirondackdestroyer (Sep 12, 2008)

Great review Selfbuilt. 

Is this the best single stage forward clickie light on the market? I'm currently using the Coleman 2AA from Walmart, but I'm looking for something better. The light can't use AAA cells, but anything else is ok.


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## selfbuilt (Sep 13, 2008)

adirondackdestroyer said:


> Is this the best single stage forward clickie light on the market? I'm currently using the Coleman 2AA from Walmart, but I'm looking for something better. The light can't use AAA cells, but anything else is ok.


That's hard for me to say, since I don't have many modern single-stage 2AA lights (most everything now is multi-stage). The E20 certainly seems to outperform anything else I've seen, but some of the single-stage Romissen lights on the discount sites are quite good for the price. If you didn't need the focusing feature of the Fenix, you might want to look at some of those to save a few bucks. And for a few dollars more, I'm a big fan of the 2-stage L2T V2 for general use.


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## Desperad0s (Nov 20, 2008)

So... is it recommended for me? A 13 years old guy which wants to go out at night... through the forest...

I need it for like max. 50-75 metres, is it good for it? My budget is low (at the time) and I could buy one for max. 35€=43,58$. And... are eneloop batteries recommended? Or only some duracell batteries?

I'd like to get some help because when I was younger I just bought some Phillips flashlights which were good for me, but I wrecked them... xD I played with 'em -.- This were my last ones...

I think the size is good.

Kindly regards,
Marco


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## selfbuilt (Nov 21, 2008)

Desperad0s said:


> So... is it recommended for me? A 13 years old guy which wants to go out at night... through the forest...


:welcome:

Personally, I typically recommend the Fenix L2T v2 for a little more $, since it has a good low mode (but is maximally focused at all time). I think a low mode is far more useful than the focusing feature for most. But a good flashlight is not a subsitute for safe practices ... I wouldn't recommend walking through a forest alone at night.


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## Desperad0s (Nov 21, 2008)

Personally, I typically recommend the Fenix L2T v2 for a little more $, since it has a good low mode (but is maximally focused at all time). I think a low mode is far more useful than the focusing feature for most. But a good flashlight is not a subsitute for safe practices ... I wouldn't recommend walking through a forest alone at night.

Thank you! 
Hmm... I'm thinking now, too, to get a L2T...
But the price, I get a E20 for 30€ (37,7865$) and a L2T 2.0 for 50€ (62,9774$). That's a big thing for me, a little guy. But I think every home needs a flashlight, it's a good tool and also good for fun  so it might be OK, but I'd have to wait a bit longer. with d  :laughing:  Kidding...
And I'm thinking, too, how powerful is a LED? I will check some L2T reviews and compare those 2. Maybe I'll find a shop here, where I can see the differences... I also don't trust a LED light... I have experiences for LEDs, which weren't powerful enough, not powerful enough to reach a target in front of me like 3m :S

One thing are the batteries, too. Which can I use longer, I don't want to buy new batteries twice a week or more. Maybe I could use accus (sorry if you don't know what are accus, a rechargable battery)?

Regards!


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## adirondackdestroyer (Nov 21, 2008)

The L2T is $11.50 more than the E20. That isn't that much of a difference if the low mode is really important to you. 
I'm a little bit confused by your second paragraph. Are you asking if these lights can light up an object at 3 meters? You must have never seen a high power LED, because these things can light up an object at 50 meters easily! They are much brighter than any comparable Incandescent flashlight let alone any LED light that uses 5mm LEDS. 
The L2T and the E20 both have great regulation. I would recommend using rechargeable NIMH cells in both lights though. With NIMH cells regulation and runtime will be much better, and it will cost you nothing to run the light after you purchased the cells. 



Desperad0s said:


> Hmm... I'm thinking now, too, to get a L2T...
> But the price, I get a E20 for 30€ (37,7865$) and a L2T 2.0 for 50€ (62,9774$). That's a big thing for me, a little guy. But I think every home needs a flashlight, it's a good tool and also good for fun  so it might be OK, but I'd have to wait a bit longer. with d  :laughing:  Kidding...
> 
> And I'm thinking, too, how powerful is a LED? I will check some L2T reviews and compare those 2. Maybe I'll find a shop here, where I can see the differences... I also don't trust a LED light... I have experiences for LEDs, which weren't powerful enough, not powerful enough to reach a target in front of me like 3m :S
> ...


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## Desperad0s (Nov 21, 2008)

Yeah, sorry, I hope you understood what I mean... I'm from europe 

Thanks for the explanation!!!
10x!
I will now decide which one I choose, E20 or L2T 
Both good^^

10x

(and yes, I haven't seen any high-power LED... so this would be my first, too ... but I'm young, I will live long (I hope) )


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## phantom23 (Nov 22, 2008)

Just wondering...Can you make some focus shots of MinimagLED?


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## Blue72 (Nov 22, 2008)

any chance of outdoor beam shots, I would love to see how these all throw, especially with some of the optics and reflectors those lights have


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## Desperad0s (Nov 22, 2008)

dd61999 said:


> any chance of outdoor beam shots, I would love to see how these all throw, especially with some of the optics and reflectors those lights have


This would make my decision really much easier 

Like one from 5 metres, one from 15, 30, 50 and one from 80 or less if you want... your decision... I just hope to get some


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## selfbuilt (Nov 22, 2008)

I would definitely recommend low self-discharge (LSD) NiMH batteries - i.e. Sanyo Eneloop, Duracell pre-charged, etc. However, if you need to use regular alkalines, Fenix is generally a good choice.

To see additional runtimes of various 2AA lights (including L2T Rebel and L2D Cree), check out my recent NiteCore D20 review.

Sorry, no plans for additional beamshots right now. But the summary table in the this review and the D20 should help you compare overall output and throw levels.
:wave:


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## Burgess (Nov 22, 2008)

Hello Desperad0s --


Welcome to CandlePowerForums !

:welcome:


Regardless of which flashlight you select,

using rechargeable, Low-Self-Discharge (LSD)

NiMH cells would be a *Great choice* for it. 


Recommend Sanyo Eneloops, or the Duracell equivalents --

(make sure those Duracells have a White Top, and package sez: "Made in Japan")



Please let us know which flashlight you select.


Bet you will be AMAZED at how BRIGHT an LED light is ! ! !


:wow:__


Good Luck in your quest for the perfect flashlight.

_


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## Desperad0s (Nov 26, 2008)

Thank y'all...!

And now here's my final question of L2T vs E20:
They reach 100m? Which reaches more metres?


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## lovefenix (Dec 6, 2008)

Hi all,i´m new in the forum.

I have a question.

In the E20 runtime chart on eneloops the output abruptly comes to 10 "overall light output" at 2 hours and 32 minutes. Does this mean that when it gets to that point it keeps running at 10 light output until shut-off?
Im new in the flashlight world so i am a little confused.


I bought the E20 and it´s an awsome light compared to the incan minimag and other crappy incan lights i used.The LED world of flashlights is like heaven to me compared to what i was used to.


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## jirik_cz (Dec 7, 2008)

lovefenix said:


> Does this mean that when it gets to that point it keeps running at 10 light output until shut-off?



It will continue to dimm slowly until it reaches zero. But don't do it with rechargeble cells or you will discharge them too deeply.


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## selfbuilt (Dec 7, 2008)

lovefenix said:


> In the E20 runtime chart on eneloops the output abruptly comes to 10 "overall light output" at 2 hours and 32 minutes. Does this mean that when it gets to that point it keeps running at 10 light output until shut-off?


As jirik_cz said, it will continue to run for longer before slowly dropping to zero output - but it is damaging to NiMH to run them until they are drained. Especially so for low-self-discharge cells like Eneloops (completely draining them increases their self-discharge rate, eventually turning them into more like traditional NiMH).

This is why I stop the runs on Eneloops on all my tests before it reaches that point (i.e. I typically manually stop the run ~10% max output). 

If I run a cell to zero output (as I do on Li-ion with protection circuits), you will see the graph actually drop to zero. You can see that on my reviews of lights that take Li-ions.


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## lovefenix (Dec 7, 2008)

Ok,i get it.So ,When do i know when to recharge the batteries before it reaches a very low voltage like 0,9V per cell?

When the light output reaches the bottom of the L.Won´t that be considered overdischarging and will hurt them?


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## selfbuilt (Dec 7, 2008)

lovefenix said:


> Ok,i get it.So ,When do i know when to recharge the batteries before it reaches a very low voltage like 0,9V per cell?
> 
> When the light output reaches the bottom of the L.Won´t that be considered overdischarging and will hurt them?


That sounds about right. To stop the cells before they drop below ~1V is a good idea, which would likely be somewhere shortly before the bottom part of the "L" on most lights (hard to know exactly, since I can't test the voltage under load very easily).

Basically, it's good to just periodically recharge the cells from time to time, before low output is reached (it doesn't hurt them). When the light begins to dim noticeably, that should be signal to definitely recharge now.


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## dealgrabber2002 (Jan 8, 2009)

I just received my E20 today and was quite eager to test out the beam pattern. I knew there will be donut hole when de-focusing the beam, but when I tighten the head for a tight beam, it still have a small black spot in the dead center of the hotspot (10-15 ft from wall). Is that normal for the Fenix E20?


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## selfbuilt (Jan 8, 2009)

dealgrabber2002 said:


> I knew there will be donut hole when de-focusing the beam, but when I tighten the head for a tight beam, it still have a small black spot in the dead center of the hotspot (10-15 ft from wall). Is that normal for the Fenix E20?


No, it should focus to a tight spot with no the hole in the center. See the beam pics at the top of this review - if it doesn't look like that, then there is something wrong.

Either it is not screwing down all the way, or maybe there's a problem with the actual emitter? Take a close look to make sure there is no damage or debris stuck to the emitter dome.


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## dealgrabber2002 (Jan 8, 2009)

I tighten the head all the way down, it still have the dark spot.

that's odd, two other cpfers said they have the same dark spot in the center of the hot spot...

But I cannot see it when I am 1m away from the wall... I can see it when I am about 10-15 ft off the wall... can you check for me to confirm?... Thanks Selfbuilt.


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## selfbuilt (Jan 8, 2009)

dealgrabber2002 said:


> that's odd, two other cpfers said they have the same dark spot in the center of the hot spot... But I cannot see it when I am 1m away from the wall... I can see it when I am about 10-15 ft off the wall... can you check for me to confirm?... Thanks Selfbuilt.


Sorry, I no longer have the E20 to confirm. But I don't recall seeing a void in the center of my beam during testing (and I was looking at things 10-15 ft away with it). :shrug: Does loosening the head help any?


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## dealgrabber2002 (Jan 8, 2009)

Yea, when I loosen it 1/2 a turn, the dark void is gone, but then I will not have max throw.


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## tracker870 (Jan 12, 2009)

This review is very good, and offers some good reasons why the E20 is not in great demand.


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## recDNA (Jun 14, 2009)

Do you know if I can use Li-Ion AA's in my E20?

I find that if my E20 is left on wide focus it is dim enough for any indoor task.

Well, yes and no. While all the above is true, I think its easy for us to forget just how bright LED lights have become. Frankly, I find this single-stage light way too bright for regular tasks around the house at night. I certainly wouldn't even consider it for up-close tasks like poking around inside a computer, looking under cupboards, etc - all tasks the original MiniMag became legendary for. Without a low mode, I'm afraid this light is relegated to mainly outdoor use. Simply put, it's more a replacement for 2- or 3-cell Mag than the MiniMag! oo:


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## recDNA (Jun 14, 2009)

Do you know if I can use Li-Ion AA's in my E20?




dealgrabber2002 said:


> I tighten the head all the way down, it still have the dark spot.
> 
> that's odd, two other cpfers said they have the same dark spot in the center of the hot spot...
> 
> But I cannot see it when I am 1m away from the wall... I can see it when I am about 10-15 ft off the wall... can you check for me to confirm?... Thanks Selfbuilt.


 
No dark spot unless I focus to flood rather than spot. The Spot is very nice.


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## selfbuilt (Jun 14, 2009)

recDNA said:


> Do you know if I can use Li-Ion AA's in my E20?


If you mean lithium AAs (i.e. energizer e2 lithium), then I see no reason why not. They should work fine and give your longer runtime.

If you mean rechargeable Li-ions (i.e. 14500) then the answer is no. None of the 2xAA lights can handle 2xLi-ion, and most of them (including the E20 to my knowledge) could not even handle 1xLi-ion.


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## recDNA (Jun 14, 2009)

selfbuilt said:


> If you mean lithium AAs (i.e. energizer e2 lithium), then I see no reason why not. They should work fine and give your longer runtime.
> 
> If you mean rechargeable Li-ions (i.e. 14500) then the answer is no. None of the 2xAA lights can handle 2xLi-ion, and most of them (including the E20 to my knowledge) could not even handle 1xLi-ion.


 
I did mean the 14500. I assumed since I could use the 10440 in my LD01 I could use the 14500 in my E20 to boost output. Good thing I asked!

Thanks!


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## pulstar (Feb 20, 2010)

I don't know how the runtimes with rechargeables are always so much longer. I mean, let's say that capacity of rechargeable AA cell is around 1.9-2.1 mAh (eneloops), but duracell plus alkaline should be in the 2.3-2.8 mAh range. Why is runtime in this Fenix (or any other AA powered flashlight) longer with ni-mh cells?


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## selfbuilt (Feb 20, 2010)

pulstar said:


> I don't know how the runtimes with rechargeables are always so much longer. I mean, let's say that capacity of rechargeable AA cell is around 1.9-2.1 mAh (eneloops), but duracell plus alkaline should be in the 2.3-2.8 mAh range. Why is runtime in this Fenix (or any other AA powered flashlight) longer with ni-mh cells?


Because it's not just a question of total capacity - it's how different batteries respond to different types of sustained loads (which is a reflection of their internal chemistry). Alkaline cells are very good in low-drain applications (i.e. analog clocks, remote controls, etc.). NiMH is much better for sustained moderate drains. Each doesn't do as well in the other areas (i.e. NiMH self-discharges relatively rapidly over time, alkaline can't handle sustained loads). As an aside, lithium and lithium-ion cells are much better for high drain applications.

A flashlight at high output is drawing a very high load from the cells (e.g. the boost circuit required to raise the voltage needed by the LED has a heavy impact, not to mention the attempt to maintain constant output regulation from a rapidly failing power source). In this situation, AA-based batteries will not last long. 

But if you were to do really low output mode tests in lights that had this option, you will find AA alkaline often does at least as well as NiMH. I've noticed that by the time we are talking several days of runtime, alkaline and NiMH are basically equivalent (i.e. total capacity is a good indicator). At really low moonlight levels that last weeks to months, alkaline could possibly even exceed NiMH.

This is all part of the reason why I don't like single-output lights like the E20 - they remove the flexibility in output/runtime/power sources. I also find it's sole level to be too bright for everyday tasks around the house.


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## pulstar (Feb 20, 2010)

So, while boost circuit requiers constant power to maintain LED's brightness, and voltage of the alkaline cell drops pretty quickly (and dramatically) current flow becomes higher? P=U*I and regulator tries to make P constant during entire discharge time. If P is constant, regulator "sees" no other way than pulling out more current from the cell if voltage drops, right?

Thanks for reply


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## selfbuilt (Feb 20, 2010)

pulstar said:


> So, while boost circuit requiers constant power to maintain LED's brightness, and voltage of the alkaline cell drops pretty quickly (and dramatically) current flow becomes higher? P=U*I and regulator tries to make P constant during entire discharge time. If P is constant, regulator "sees" no other way than pulling out more current from the cell if voltage drops, right?


In general terms yes - but in practice, I believe it is more complicated (i.e. battery chemistry responds differently as a function of current, temperature, etc.). The battery experts in the "flashlight electronics - batteries included" forum should be able to shed some further light on the subject ... I just measure flashlight output and runtime.


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## RemcoM (Mar 14, 2013)

selfbuilt said:


> In general terms yes - but in practice, I believe it is more complicated (i.e. battery chemistry responds differently as a function of current, temperature, etc.). The battery experts in the "flashlight electronics - batteries included" forum should be able to shed some further light on the subject ... I just measure flashlight output and runtime.



I want know, can a fenix E20 light up my entire area /street? at night?

Is it a carheadlightkiller? 

Remco


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## kj2 (Mar 14, 2013)

RemcoM said:


> I want know, can a fenix E20 light up my entire area /street? at night?
> 
> Is it a carheadlightkiller?
> 
> Remco



No , it has a pretty bright hot-spot for such a "old"-light, but won't light up a whole street.


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## RemcoM (Mar 14, 2013)

kj2 said:


> No , it has a pretty bright hot-spot for such a "old"-light, but won't light up a whole street.



Hi, thank you for your reply,

The E21 (i have) looks like the E20, but the E21 is much brighter. Great light the E21 for all day use.

Remco


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