Fenix L2D Q5 users-question

[BJKct]

Hi, this is my first post, so hope I do it right...

I just received my Fenix L2D Q5 premium, and have noticed something a little odd with the brightness functions:

When I click from the low to medium setting, there is almost no discernable difference in the brightness level. Also, on low, the light seems like it is much brighter than the 12 lumen stated level. I compare the low setting to my other Dorcy LED that I have which is about 45 lumens (http://www.dorcy.com/products.aspx?p=414260). I am not using any light meters, but my eyes are pretty good and cannot see much of a difference between low and medium (maybe a slight increase to medium, at best).

I should note that I am using Energizer ultimate lithium batteries and when I put some cheapy half-used Duracell alkalines in, I do see an obvious difference from low to medium. With the alkalines, the low is much lower (still seems brighter than 12 lumens). Does anyone else have the same result with these batteries?

I'm not complaining about a bright light, but sometimes it's nice to have a low setting for midnight runs to the Can or checking on my kids without waking them up.

Thanks!

 

[jenskh]

As far as I know, the L2D is not designed to be used with lithium batteries. I think that is the reason for your problem.

 

[primox1]

:welcome:


The l2d loses its lower modes when running on lithium batteries. It is designed to run best on Ni-MH, but alkalines are fine also.

 

[Nake]

Not having used lithiums in my L2D Q5, I just went and tried it. It is just as you say, low and med are the same. This I confirmed with the lux numbers in my lightbox.

The voltage of the lithiums was 1.8V. The NiMH start out at 1.4V off the charger, but quickly drop to 1.2V upon usage.

 

[Zatoichi]

I'm so glad you asked. I've just realised it's the same with the Olight T-25. I noticed the low and medium sometimes looked the same, but didn't make the connection with the fact I've had both rechargables and lithiums in it. :thumbsup:

 

[BJKct]

Thanks everyone, I think I'll pick up some Nimh batteries to use.

I did also find some other info on my problem (kinda answered my own question) which verifies that low and medium with lithiums are almost the same. The first chart shows the light level is close...

http://www.cpfreviews.com/Fenix-L2DCE-Premium-Q5.php

 

[burf151]

I had the same thing going on with lithium primaries, switched to alkalines and it worked great.

 

[TONY M]

I did also find some other info on my problem (kinda answered my own question) which verifies that low and medium with lithiums are almost the same. The first chart shows the light level is close...

http://www.cpfreviews.com/Fenix-L2DCE-Premium-Q5.php

:welcome:
Yes interestingly the original L2D did not seem to have the same issue.
This is further evidence to suggest so http://www.flashlightreviews.com/reviews/fenix_l1dce-l2dce.htm

 

[Jarl]

It does to a certain extent- see the slight elevation at the start of the plots. Maybe that sample had an exceptionally high Vf?

 

[Hooked on Fenix]

Mine does this as well. Low and medium will be at the same brightness until the voltage drops some. Then you get the normal low and medium on lithium batteries. Lithiums won't damage the light and you still get a brighter high and turbo, but you just don't have low. In mine, the low actually starts off a little brighter than medium until the voltage drops.

 

[upriver]

:welcome:
Yes interestingly the original L2D did not seem to have the same issue.
This is further evidence to suggest so http://www.flashlightreviews.com/reviews/fenix_l1dce-l2dce.htm

This is definitely pretty annoying...Before and after I bought the L2D Q5, I have used flashlightreviews for info, and assumed that the operation of the Q5 would be the same as the earlier CE, just with more efficiency. I had been counting on a super long runtime on low with lithiums, but now I guess it's unknown how long the low runtime will be since it starts on a medium level until a voltage drop.

I recently bought my sister an LD01 for Christmas, it's a Q5, and has no problem with low-medium-high modes using a lithium. I wonder why this is (thought it was a Q5 issue maybe...).

Anybody know if the L1D Q5 has the same issue with a lithium battery?

 

[HKJ]

The L2D has a boost converter, i.e. it can only increase battery voltage, not reduce it.
A led will have max brightness around 3.6/3.7 volt, but it will light up from below 3 volt. When the battery voltage is above 3 volt, the low levels may disappear. This depends on led Vf (That has some variation between individual leds) and exactly what low levels Fenix has defines.

I have a suspicion that the reason Fenix does not have a really low low is because then they would have to design another circuit, or only make models for a single 1.5 volt battery, not 2*1.5 V or 1*3V battery in the same head.

To get around this problem with low levels, some lights uses pwm regulation, but this has other issues.

 

[LightObsession]

The LD20 also losed it's low with fresh Energizer lithiums.

 

[Jarl]

Anybody know if the L1D Q5 has the same issue with a lithium battery?

The L1D would be fine with an energizer E2 lithium, but would lose the low modes with a rechargeable lithium based cell.

 

[clbnc]

I recently ordered a LD10 and I would like to know if I understand this right. Because my light (and the L1D) are single cell AA, I would have normal low/med/high modes using an energizer L91 lithium primary right from the start. But, the two cell AA ones (LD20, L2D) would lose those lower modes using the energizer L91 lithium primary. Is this right?

 

[HKJ]

I recently ordered a LD10 and I would like to know if I understand this right. Because my light (and the L1D) are single cell AA, I would have normal low/med/high modes using an energizer L91 lithium primary right from the start. But, the two cell AA ones (LD20, L2D) would lose those lower modes using the energizer L91 lithium primary. Is this right?

Yes, with two cells the voltage gets above 3 volt and interferes with the low mode.

 

[Wiggle]

Yes, with two cells the voltage gets above 3 volt and interferes with the low mode.

I though the low mode was achieved using PWM though? Shouldn't the only difference between medium and low be the duty cycle of the pulse-wave used to drive it?

 

[Jarl]

Nope, the L2D uses constant current for drive levels. It only uses PWM for strobe/SOS

 

[clbnc]

Thanks for the response. I had no idea that this was the case. Looks like I kinda lucked out on buying the 1 AA model.

 

[pustefix8965]

Wrong information.