Fenix TK21

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muskyhunter

Newly Enlightened
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Jun 6, 2011
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Toronto, Canada
Any reviews on this flashlight? i want to get one.

Where is the best place to order one? I'm in Canada.

I've visited fenixtactical and they seem to sell what i want. The flight and recharge kit. How are their cs and pricing? any other dealers i should visit?

Thanks!
 
I bought a TK21 two months ago, and indeed, it doesn't run too well on a single 18650 battery. The XM-L is specified to run on 3 to 18 volts, so with a single 18650 you'll soon get below 3 volts, which causes the light to switch back to high very soon.

On 2 CR123a's it works very well, this thing is bright as hell, especially considering the size. ;)

There are TK21s out there with the green tint issue. I suggest testing it in store before you buy one. Or wait a bit longer until Fenix gets more better colored XM-L LEDs.

This is most likely an issue with the new XM-L LEDs, and should get better in a few months.
 
about the colour... what colour did ur tk21 U2 shows? mine is more to yellow... the spill is slightly whiter.. does this call natural white? or yellow??

yup i do find some post mentioning their xml having green tint...
 
The first TK21 I got had a horrible green colour, but the second one I got back from the store has a slight green tint on low, but on higher settings it's almost perfect white, with a touch of yellowish green in the corona around the hotspot.
 
hmmm on mine i did not notice any green now even on the lower mode... just yellow... everything yellow... yellow white i might say... at the corona mine is white... seem like not really much tk21 U2 user out there yet... feed back on this light is not much... but i really appreciate ur replies!!
 
I got a TK21 last night and it works great. I used regular 3v 1500mAh and 2900 mAh AW 18650 batteries. It's crazy to believe this light is 1/2 the price of my surefire and 6 times brighter. LOL!!

The bulb of mine is pure white with no yellow or green tint.
 
Richub said:
I bought a TK21 two months ago, and indeed, it doesn't run too well on a single 18650 battery. The XM-L is specified to run on 3 to 18 volts, so with a single 18650 you'll soon get below 3 volts, which causes the light to switch back to high very soon.
Click to expand...

Sorry, but that is complete nonsense. Typical voltage for XM-L LED is ~3,35V running at full power (3A). Everything else depends on the driver used in the flaslight. It also doesn't have 1300 lumens :D If you want valid XM-L specifications check the Cree datasheet.

Also with good quality 18650 battery, which can hold high voltage under load. You can get around 90 minutes of runtime before the light switches to lower level.
 
Hm, I stand corrected.

Well, after reading the page I linked to in my earlier post, I thought the low voltage of a single 18650 caused this dropback in brightness, that seemed logical to me.

I guess I gotta learn a bit more about the drivers in these high-end torches. ;)
 
I have emailed Fenix about the problem that some people have:

Thanks for your interest in Fenix TK21.​
​
The TK21 has the low volt protection function, at present, just this model has this function, it can stop the battery being over-discharged. Because of this function, if the battery power is not enough, the light will jump from higher output level to lower output level, so if his TK21 jump from turbo mode to high mode, it should be the case that the battery power get less, if he want to use turbo mode again, he can recharge the 18650 to 4.2v. ​
​
And we suggest the consumer use good quality 18650, the power can stand longer, or use CR123A due to higher volt, the rechargeable battery CR123A is OK to use in this model. ​
​
Best regards!"​

​
 
Today I received my TK21 U2. A nice light, but with the holster there is a negative side.
The holster which comes with the TK21 U2 is just like the holster that came with my TK11 R2, only the head from the
TK21 is much larger. This results in that the velcro of the holster is rubbing against the head of the light. So after time, that will leave a mark
on the head of the light. Solution for Fenix; make the holster-part that will go over the head of the light larger/longer.
 
I have the TK21 U2. I find it to be an amazing light which runs great on both cr123's or 18650's. All Fenix lights have a thermal step down from Turbo to High. I believe this to be for overheat protection and not a over discharge feature of the light.
This light, as all my Fenix lights, are fantastic product I feel. They run great on 18650's with really good run time, better than cr123's. A little bit green on low setting but that does not bother me. [Please feel free to forward any green tint flashlights to me if it bothers you. I will even pay the shipping costs! :]
One thing. Don't use poor quality 18650's. I use AW as they are one of the best out there. There are others as well, just do a search for the best 18650's. Cheap cells will do all sorts of funny [and not so funny] things.
 
loquutis79 said:
All Fenix lights have a thermal step down from Turbo to High. I believe this to be for overheat protection and not a over discharge feature of the light.
Click to expand...
No, they don't. And stepdown in TK21 has nothing to do with heat, it depends on battery voltage. So if you have good batteries TK21 can run on Turbo for half an hour (or more) but with others (not necessarily bad ones - high capacity Panasonic cells "like" low voltages) TK21 will switch to High after 5-10 minutes.
 
As phantom23 said, the step down from Turbo to High is voltage dependant. I have found 18650 performance unreliable. Some of my 18650s only last 30s on Turbo from fully charged. Some of the better performers have been Ultrafire 2600mAh Green unprotected cells which give about 45-50 mins on Turbo. The latest AW 3100mAh use a different chemistry and although have a great capacity to get it all requires a lower current draw. The TK21 is so fickle as one of the new AWs gave me 50mins on turbo with still about 50% capacity left (meaning a good runtime on High to go) but another exactly the same cell type gave 5 mins on Turbo. The green ultrafires are still the most reliable cells I have in this light.
 
I previously posted some TK21 test data I did, but it was lost in the 'great crash.' To summarize: I tested 5-10 TK21's, and discovered that the low battery cutoff voltage at which the turbo downshift occurred varied as much as .2-.3 volts. Therefore, I concluded that the issue is a combination of 18650 battery variability AND the TK21 variability in turbo downshift voltage.

If you have a higher voltage cutoff TK21 and a battery that doesn't hold it's voltage under load very well, the turbo downshift will occur way too soon...
 
Question; Does somebody know, if the XTAR protected 18650 (3100mAh) will fit in the TK21?
 
I don't have the 3100's but do have the 2600's which is slightly longer and wider (diam.) overall and it fits snugly.
 
turboBB said:
I don't have the 3100's but do have the 2600's which is slightly longer and wider (diam.) overall and it fits snugly.
Click to expand...

Thanks. Many protected batteries these days are to long to fit the light. For what I know, only AW keeps there 18650 relatively short. Hope that manufactures keep in mind that those new protected-batteries are (way)longer than they used to be.
Of course, you can make the light longer- but then CR123A batteries won't fit any-more. Hope they find a solution for this problem.
 
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