Fenix LD20 r5 qestion

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z_Austin93906

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So a nice package came for me in the mail today, my new EDC light. My ICON rogue 2 dissappeared a few months ago so i figured why by another one, just get something better for 20 bucks more



My question is this, when im playing with the low, medium, high settings, low and medium have almost no noticeable difference at all. Honestly, low looks like its puttin out way more than 5 lumens. Is this normal? Could the circutry be faulty?
 

Danie24932

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I just purchased an ld20 r5 and I am having the same issue with mine also. Can anyone else with an ld20 chime in?
 

Thefo

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I've heard that can happen when you run them on alkalines...have you tried using NIMH like Eneloops? With my LD20 R5 on Eneloops the difference between low and medium is quite distinct.
 

Thefo

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Selfbuilt's excellent review explains this phenomenon about three quarters of the way down the page. I had it reversed though in that certain types of lithium L91 batteries cause this to happen and not alkaline. I would never recommend running alkaline batteries in your light though anyway as they can leak and ruin it.
 

LEDrock

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Not hijacking the thread here, but I was looking into getting a Fenix E21 and saw a review on youtube where the guy reviewing it said that the low (48 lumen) and high levels (150 lumen) also didn't have much of a difference.

Makes me wonder about all this multi-level stuff. Never had one, but was thinking of getting one. Now considering otherwise after so many people having the same problem.

Why should it not work right with alkalines? In a major power outage, alkalines would probably be what you'd use. Can you imagine wanting a low mode with something like an LD20 to make the batteries last longer only to have it run high? Kind of defeats the purpose, if that's one of your purposes for owning it.
 
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Phil828

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My LD20 R5 works fine on NiMH batteries. I think the regulatory circuit in Fenix's AA flashlights is tailored to the rechargeable batteries rather than to the alkalines. But that is just my unprofessional opinion.
I would recommend that you give rechargeables a try. When you consider that each battery can possibly do the work of $500 worth of alkalines it makes a lot of sense.
 

atbglenn

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My LD20 R4 does the same thing on Alkaline's, no difference between low and medium. Works perfectly fine on Eneloops though.
 

LEDrock

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My LD20 R4 does the same thing on Alkaline's, no difference between low and medium. Works perfectly fine on Eneloops though.

I have a question to ask regarding all this. In the review that Thefo makes reference to, the reviewer basically states that the higher voltage of alkalines is what causes the problem. Alkalines are 1.5v while NiMH are 1.2v. But I've also heard that Cree LEDs work more effeciently when running 3AAA batteries, which is even higher.

The reviewer also states that the problem may go away with alkalines once the batteries are run down some which reduces their voltage.

What about other flashlights with multi levels. Does anyone have the same experiences with them while using alkalines?
 

pinetree89

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I believe this problem stems from the fact that the LD20 has a boost circuit only, vs others like the 4Seven's Quark series that has a Boost and a Buck circuit. All things equal however, this does give the Fenix LD20 better run times over the 2AA Quark's. I think Selfbuilts reviews bear this out. Fenix has a great rep for building efficient circuits on their lights.

A quick glance at the Cree XP-G datasheet states that the forward voltage of the XP-G emitter at 350mA is 3v. This would probably equate somewhere close to a medium mode. Two fresh alkalines would easily give 3v. The circuit is only set up to boost voltage so when it sees 3v, it's just sends it straight on through to the emitter and is not able to regulate until the voltage drops down a bit. Or as stated, use NiMH's and this is no longer a problem.

From what I understand the Fenix LD20 and LD10 have the same head, thus the head should be able to take very low voltages (.9v maybe lower?). One thing I'd like to try to do with my LD20 is get/make a battery spacer and run it on a single Lithium AA. This should allow all the modes to be used and according to selfbuilt's review the lumen output is not all that different.

I have an LD20 and it's one of my favorite lights. Great ergos, great runtimes, efficient circuit, and tons of accessories.
 

LEDrock

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I believe this problem stems from the fact that the LD20 has a boost circuit only, vs others like the 4Seven's Quark series that has a Boost and a Buck circuit. All things equal however, this does give the Fenix LD20 better run times over the 2AA Quark's. I think Selfbuilts reviews bear this out. Fenix has a great rep for building efficient circuits on their lights.

A quick glance at the Cree XP-G datasheet states that the forward voltage of the XP-G emitter at 350mA is 3v. This would probably equate somewhere close to a medium mode. Two fresh alkalines would easily give 3v. The circuit is only set up to boost voltage so when it sees 3v, it's just sends it straight on through to the emitter and is not able to regulate until the voltage drops down a bit. Or as stated, use NiMH's and this is no longer a problem.

From what I understand the Fenix LD20 and LD10 have the same head, thus the head should be able to take very low voltages (.9v maybe lower?). One thing I'd like to try to do with my LD20 is get/make a battery spacer and run it on a single Lithium AA. This should allow all the modes to be used and according to selfbuilt's review the lumen output is not all that different.

I have an LD20 and it's one of my favorite lights. Great ergos, great runtimes, efficient circuit, and tons of accessories.

But I saw a review someone did on youtube about the Fenix E21, which is a completely different light, and it had the same problem. Is it something that all Fenix lights would have in common?
 

srfreddy

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Again, it probably is boost only, which is more efficient. Once that batteries run down a little, the modes will appear.
 

wingspar

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I have the LD20 Q5. Not sure of the difference between the Q5 and the R5, but the only time I've seen that is when the batteries are getting low. I use Duracell Alkaline batteries. I did a YouTube review on this light. The link to the video is in my signature. It's a newbie review, so nothing technical about the review.

Now that I think about it, I have seen that if I don't wait a second or two before going to the next mode.
 
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