Question about Fenix PD20 R5 output levels

poonchasta · Jun 20, 2011

I just got the PD20 R5 a couple weeks ago, and I love it to death. I'm just a little curious about the output levels, though. The low (9 lumens) mode seems a lot brighter than what 9 lumens should be. Also, when I go from low to medium (38 lumens), it seems like the light only gets a little bit brighter. I would expect a more pronounced difference when switching to a mode that has 4 times the lumens. But when I go from medium to high (90 lumens) I do notice that the light gets significantly brighter, even though the lumens are just a little over double of the medium mode. Is everyone else's PD20 R5 like this? Could I possibly have a defective unit? Will it really run for 66 hours in the low setting like that? Thank you all for answering these questions.

blah9 · Jun 20, 2011

Apparently all the LD20's have the glitch where the low modes are brighter than they should be if they are not running on alkaline batteries. I don't have one, but I think everyone has the same experience, and it sounds like the reason for this is that their output levels are only valid for alkaline battery use due to the difference in voltages between alkalines and eneloops/lithiums.

EnduringEagle · Jun 20, 2011

blah9 said:
Apparently all the LD20's have the glitch where the low modes are brighter than they should be if they are not running on alkaline batteries. I don't have one, but I think everyone has the same experience, and it sounds like the reason for this is that their output levels are only valid for alkaline battery use due to the difference in voltages between alkalines and eneloops/lithiums.

With all deference it is actually just the opposite. I have an LD20 and if you use alkaline batteries the flashlight will not step down due to voltage. If you email Fenix they will tell you to use NIMH batteries (not happening) and the flashlight will get the step down. This issue is well known.

blah9 · Jun 20, 2011

Ah, I stand corrected. Thank you! Whoops!

ScaryFatKidGT · Jun 21, 2011

So the LD10 and LD20 are made to run on NIMH?

EnduringEagle · Jun 21, 2011

ScaryFatKidGT said:
So the LD10 and LD20 are made to run on NIMH?

That is what Fenix will say if you contact them but it is clearly not indicated on their website. They indicate AA batteries which is standard. The problem is with the circuit that have used as it does not tolerate the variation in voltage. Other light manufactures are able to do it flawlessly. This is clearly a Fenix issue. I also can tell you that I have a Fenix TA20 (CR123a) that does not have this problem and a 4Sevens G5 that also does not have this problem or a Quark 123 that does not have this problem. Interestingly even my cheapo maglite does not have this issue either. You can contact them and see if you they are willing to fix the problem.

Outdoorsman5 · Jun 21, 2011

Yeah, this is a well known (on cpf) problem with the LD10 and LD20. I use eneloops, so it does not bother me, but here's what's happening. These two lights have a boost circuit only; there is no buck circuit like on other lights (quarks for instance.) By not having a buck circuit it makes these lights more efficient, but if a battery has more than 1.2 volts you lose the low mode until the battery runs down a little. Once the battery is below 1.2 volts the boost circuit kicks in boosting each output to where it was designed to be. At 1.2v the light is perfectly balanced for the low mode, so your light will produce the low mode. If the battery is above 1.2v the light cannot buck the voltage down, therefore, you lose the low mode until the battery drops to 1.2v or below. So, both of these lights work best on NiMH batteries since they were designed to work at 1.2v.

Worth mentioning, if you put a Li-ion 14500 (4.2v rechargeable battery which the light is NOT designed for) in the LD10 you lose all the modes. The light goes into direct drive which is way brighter than even the turbo mode. Kind of cool, but losing all the lower modes makes it not as useful plus you are risking the health of the LED. Since the light cannot buck the extra voltage of the Li-ion it just runs wide open and runs a lot brighter than the light was intended to run. It's probably not smart doing this very often or at least for very long.

EnduringEagle · Jun 21, 2011

Outdoorsman5 said:
Yeah, this is a well known (on cpf) problem with the LD10 and LD20. I use eneloops, so it does not bother me, but here's what's happening. These two lights have a boost circuit only; there is no buck circuit like on other lights (quarks for instance.) By not having a buck circuit it makes these lights more efficient, but if a battery has more than 1.2 volts you lose the low mode until the battery runs down a little. Once the battery is below 1.2 volts the boost circuit kicks in boosting each output to where it was designed to be. At 1.2v the light is perfectly balanced for the low mode, so your light will produce the low mode. If the battery is above 1.2v the light cannot buck the voltage down, therefore, you lose the low mode until the battery drops to 1.2v or below. So, both of these lights work best on NiMH batteries since they were designed to work at 1.2v.

Worth mentioning, if you put a Li-ion 14500 (4.2v rechargeable battery which the light is NOT designed for) in the LD10 you lose all the modes. The light goes into direct drive which is way brighter than even the turbo mode. Kind of cool, but losing all the lower modes makes it not as useful plus you are risking the health of the LED. Since the light cannot buck the extra voltage of the Li-ion it just runs wide open and runs a lot brighter than the light was intended to run. It's probably not smart doing this very often or at least for very long.

Terrific Explanation!!

ebow86 · Jun 21, 2011

poonchasta said:
I just got the PD20 R5 a couple weeks ago, and I love it to death. I'm just a little curious about the output levels, though. The low (9 lumens) mode seems a lot brighter than what 9 lumens should be. Also, when I go from low to medium (38 lumens), it seems like the light only gets a little bit brighter. I would expect a more pronounced difference when switching to a mode that has 4 times the lumens. But when I go from medium to high (90 lumens) I do notice that the light gets significantly brighter, even though the lumens are just a little over double of the medium mode. Is everyone else's PD20 R5 like this? Could I possibly have a defective unit? Will it really run for 66 hours in the low setting like that? Thank you all for answering these questions.

The OP is asking about the PD20, not the LD20. Poonchasta, I own the Fenix PD20+R5. My light operates EXACTLY the way you describe and is perfectly normal. The way you describe the way your light functions indicates to me a normal operating PD20. Yes the low mode is actually quite high which is unfournate but overall it is a wonderful light. I have not tested the runtime in low mode but I would take an educated guess and say 66hrs on low is probably a stretch.

Outdoorsman5 · Jun 21, 2011

ebow86 said:
The OP is asking about the PD20, not the LD20.

My bad; looks like a few of us went down the wrong road here. I have the LD10 and LD20 that uses AA batteries. My discription above is for those two lights not the PD20.

MichaelW · Jun 21, 2011

The change from xp-e to xp-g really highlights the limitations of a buck only circuit design.
Fenix should have kept the xp-e in the PD20, and LD10 (the xp-e is up to R3 output)
A buck/boost circuit should be in the LD20-with xp-g

poonchasta · Jun 22, 2011

Thanks to everyone for trying to answer my questions! I've come to terms with my PD20 low mode being brighter than advertised by ordering a Quark MiNi 123. It'll be my back-up keychain flashlight that has a nice low mode of 3 lumens that will last for 150 hours. And I thought I was done buying flashlights for the time being.

poonchasta · Jun 22, 2011

Thanks to everyone for trying to answer my questions! I've come to terms with my PD20 low mode being brighter than advertised by ordering a Quark MiNi 123. It'll be my back-up keychain flashlight that has a nice low mode of 3 lumens that will last for 150 hours. And I thought I was done buying flashlights for the time being.

ebow86 · Jun 23, 2011

poonchasta said:
Thanks to everyone for trying to answer my questions! I've come to terms with my PD20 low mode being brighter than advertised by ordering a Quark MiNi 123. It'll be my back-up keychain flashlight that has a nice low mode of 3 lumens that will last for 150 hours. And I thought I was done buying flashlights for the time being.

Fenix's lumens rating on their lights has been mostly inaccurate on most models in the past, but now they use the ANSI system to rate output and runtime, so you can be a little more sure now of what you're getting. I too was disappointed on how bright the low mode was, but I don't think that takes away how how good of a light it really is.

TadpolePilot · Jan 15, 2012

Never Done Purchaseing Flashlights!
Just
received my 3rd which is a Fenix PD-20 with a CR123 cell and now looking for another. On order is an attachment to install one of the three at a time on my bicycle.:naughty:

Question about Fenix PD20 R5 output levels

poonchasta

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blah9

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EnduringEagle

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blah9

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EnduringEagle

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