REVIEW: ThorFire TK15 & TK15S Flashlights

Bdm82

Flashlight Enthusiast
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[Submitted as a REVIEW]


Introduction

The TK15 and TK15S are ThorFire's most recent introductions. They sport a compact 18650 design, XP-L2 emitters, and smooth reflectors. The TK15 uses a single electronic side switch while the TK15S uses a tail switch and side switch in concert. Both have the same 1050 lumen maximum output per specifications, though mode spacing and special modes are different.
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Here are the key details in one table for the those not included to read the full review:
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Skip to the commentary section at bottom to read my subjective notes.


These lights were provided free of charge by ThorFire and were 1st run or pre-production prototypes as they arrived ahead of the general release. I owe ThorFire a small apology as this review was not posted as quickly as expected.



Packaging

The TK15 and TK15S each shipped in a cardboard box with white product label. The same packaging is used throughout the ThorFire product line and is sufficient to keep the light protected in transit. Being pre-release samples, these were shipped from China rather than the usual ThorFireDirect Amazon warehouse. The boxes took a little extra wear in transit but maintained their integrity.

The labels feature the ThorFire logo, product name, image of the flashlight, registration and disposal information, website, and contact information.
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Opening the boxes, we find the lights in bubble wrap surrounded by foam.
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Spare o-rings, user manuals, and pocket clips (pre-attached to lights) are included.
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The manuals are in English and adequately cover modes, features, UI, and troubleshooting.
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Design

The TK15 and TK15S are very similar single 18650 slim head flashlights. On first glance, they appear to share most parts – but that isn't actually the case.
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The TK15 has a polished and crenulated bezel; the TK15S has a flat anodized head. The TK15's crenulated bezel would be adequate for breaking glass but is not sharp enough to cause discomfort in a pocket or to be used as a weapon.
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Both lights have smooth and visibly flawless reflectors of the same design.
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The same Cree XP-L2 LED is also found in both. Bin is not reported. Centering is good.
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The TK15's bezel can be unscrewed to access the LED and star. Wiring and soldering appears good quality.
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The lens has a gasket on the underside.
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The TK15 has a flat tail with single lanyard pass-through; the TK15S has a tail switch and dual lanyard attachment points. (No lanyards are included, yet I applaud the way both lights' lanyard attachment points are designed as tailstanding will be unaffected by lanyards.)
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The pocket clips are identical. Both are quite strong; if not for the upturned ends, installing and removing the pocket clip would be difficult. There is no space for the clips to be reversed so head-down carry is the only option.
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The side switches are also the same.
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Both the TK15 and TK15S disassemble into three pieces: head, body tube, and tail. All threads are square cut and well lubricated. All pieces are of different lengths between the TK15 and TK15S.
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The TK15S's head is longer than that on the TK15 – even with the TK15's crenulated bezel. The cooling fin design is also different between the two models.
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Head end springs are the same in both lights. Having springs at both head and tail qualifies the lights for use on bicycles, rifles, and in other scenarios where shock and vibration is expected. It also allows batteries of various lengths to fit; I had no problems with the longest 3500mAh protected cells I own fitting.
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Tail springs are not the same. Due to the retaining ring required for the TK15S's tail switch, the TK15S's spring is smaller diameter. Both are gold-colored.
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I measured the TK15 at 125 mm long, 24 mm at the head, and with a weight of 69 g.
The TK15S measured 132 mm long, 24 mm at the head, and having a weight of 75 g.

Both lights are slightly longer than ThorFire's VG-15S (which has a reverse clicky tail switch and no electronic side switches).
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Performance

The smooth reflector produces a defined hotspot and corona surrounded of course by the spill. The TK15's crenulated bezel produces some small artifacts at the edge of the spill; this is to be expected and not noticeable most of the time.
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The beams on both lights are slightly warm with a yellow-ish tint. The spill is a bit cooler. Overall it's a very nice tint/temperature.
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To demonstrate the relative color balance, here is the C1 flanked by lights with emitters of various tints and temperatures.
L to R: Convoy S2+ with cool XM-L U2 1B, ThorFire TK15S with XP-L2, ThorFire TK15 with XP-L2, Lumintop Tool with warm 219B, and BLF348 with neutral 219B.
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(Note: The TK15S has fewer modes and thus is on a slightly brighter mode than the TK15.)


ThorFire rates maximum output of both lights at 1050 lumens (with a ThorFire 3000mAh battery). While that peak output is rated the same, the mode type and count varies between models.


The TK15 has 5 brightness modes plus strobe. The TK15S has 4 brightness modes, strobe, and a special bike mode that essentially operates at the mid output level output with 3 quick strobes added each second.
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Both require 18650 batteries. CR123A batteries are not allowed.


TK15
When I tested the TK15 on Turbo with a flat-top 3000mAh LG HG2 battery, I registered 933 lumens at turn on and 903 at 30 seconds. Tail-tested amperage draw was 2.7A.


Output slowly dropped until the 3 minute mark when output stepped down to about 375 lumens. It held close to that until the 33 minute mark when it stepped down again to about 100 lumens. 10% of initial output was reached at just over the 2 hour mark – exceeding ThorFire's 45 minute rating.
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It then dropped in a linear manner until the 18 hours when it powered off from 11 lumens.
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High tested at 409 lumens. At 30 minutes, the light stepped down to about 100 lumens.
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It then dropped in a linear manner with 10% being reached at 14 hours and 20 minutes. This significantly exceeds the rated 1 hour 25 minute runtime. The TK15 eventually shut off at 18 hours and 10 minutes.
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On Mid/medium, the TK15 is rated at 200 lumens. I tested a max of 117, with an average of 109 in tests. The output drop was pretty linear on this mode as well, with 50% being reached at 13 hours and 23 minutes and 10% reached at 19 hours and 43 minutes. Again, this dramatically exceeded ThorFire's 2 hour 45 minute rating.
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Low is rated at 50 lumens. I tested 13 – which is actually a more appropriate step between moonlight and mid modes than 50. Runtime was not tested. ThorFire rates it at 22 hours but I would expect real runtime to far exceed that given the performance on the other modes.


Moonlight/ultralow is rated for 0.5 lumens. I tested a slightly higher 1.3. Runtime was not tested but is reported by Thorfire to be 360 hours.
[TK15 all outputs – X]​


All tests were completed with an ambient temperature of 76-82F.



All outputs:
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All runtimes tested, first 35 minutes:
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All runtimes tested:
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The battery measured between 2.85 and 2.95V after all tests. The over-discharge protection is good as this is a safe termination voltage.


I tested throw distance at 1.46 meters and the resulting candela was 7,418 - equivalent to 172 meters of throw. ThorFire rates the TK15 at 11,200 candela and 120 meters of throw; these numbers are not correlated.


I did not detect PWM with my eyes on any modes using the "mirror test". A CMOS camera showed no PWM on Moonlight or Turbo, though Low and Med displayed very high frequency lines indicating high frequency PWM may be present.


I measured 210 microampere parasitic drain on standby due to the electronic switch. This is moderately high; I'd advise the flashlight be mechanically locked out (by unscrewing the tail cap slightly) when stored for long periods.



TK15S
When I tested the TK15S on High with a flat-top 3000mAh LG HG2 battery, I registered 880 lumens at turn on and 869 at 30 seconds. Tail-tested amperage draw was 2.6A.


Output slowly dropped until the 3 minute mark when output stepped down to about 375 lumens. It held about that amount until the 33 minute mark when it stepped down again to about 35 lumens – less than 10% of initial output. Thus, runtime of 33 minutes was noted. ThorFire rates runtime at 50 minutes.
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I let the test continue, until the 43 hour mark when I terminated the test due to personal time constraints. Output was 12 lumens and battery voltage was 3.17V at the time.
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Mid/Medium tested at 379 lumens. There was no stepdown, just a gradual decline until it turned off at 2 hours 30 minutes from 55 lumens. Runtime of 2 hours 30 minutes exceeds ThorFire's 1 hour 45 minute rating.
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On Low, the TK15S is rated at 100 lumens. I tested a max of 38. The output drop was pretty linear on this mode as well, with 10% output reached when the light turned off from 5 lumens at 58 hours and 42 minutes. Again, this dramatically exceeded ThorFire's 5 hour rating.
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Moonlight/ultralow is rated for 0.5 lumens. I tested a slightly higher 1.3. Runtime was not tested but is reported by Thorfire to be 360 hours.


All tests were completed with an ambient temperature of 76-82F.



All outputs:
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All runtimes tested, first 35 minutes:
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Full runtimes tested:
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TK15 and TK15S together, first 35 minutes:
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The battery measured at or above 2.88V after all tests. The over-discharge protection is good as this is a safe termination voltage.


I tested throw distance at 1.46 meters and the resulting candela was 6,992 - equivalent to 167 meters of throw. ThorFire rates the TK15 at 11,200 candela and 120 meters of throw; these numbers are not correlated.


I did not detect PWM with my eyes on any modes using the "mirror test". A CMOS camera showed no PWM on Moonlight or High, though Low and Med displayed very high frequency lines indicating high frequency PWM may be present.


As the tail switch is a mechanical switch, the TK15S has no parasitic drain.




Outdoor Beamshots

All photos taken with a Canon SD4000IS camera. 1/4" exposure, ISO800, Daylight white balance, F2.0.
Approximate distances: White deck railing @ 15 ft., white fence in distance @ 75 ft., center of boat @ 100 ft.


Control shot:
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TK15

Low:
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Med:
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High:
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Turbo:
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TK15S
Low:
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Med:
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High:
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Interface

TK15
From off:
• Single press side switch to turn on.
• Press and hold for moonlight/ultralow.
From on:
• Single press to advance modes upwards L->M->H, resetting H->L to repeat. Moonlight/Ultralow is not in the rotation.
• Long press to turn off.
• Double press to activate strobe (single press to return).


TK15S
From off:
• Partial press tail switch for momentary on.
• Press tail switch fully to turn on.
From on:
• Single press side switch to advance modes upwards UL->L->M->H, then downwards H->M->L->UL. All modes are in the rotation.
• Double press to activate strobe. Double press again to activate bike mode. (Single press to return to normal modes.)
• Press tail switch to turn off.

Mode memory is present on both lights. Mechanical lockout is possible with 1/8 turn of the tail caps.


For those that prefer the TK15's modes but the TK15S's tail switch, the tail switch from the TK15S will function on the TK15. This is a one-way option; though; the TK15's tail switch on the TK15S leaves it unable to turn off.




Problems

The initial pre-release TK15S provided had an output issue and was replaced promptly by ThorFire with a post-release date sample. I do not consider this problem relevant as it was a pre-release sample and had an atypically long transit.




Commentary

ThorFire continues to build quality lights at budget prices, and I found nothing to fault with the overall feel of the lights or the build quality. Having two model options provides mode spacing, switch, and bezel options for the buyer to consider. Of course, both have the sharp looking, solid feel electronic side switches.

Lights at this affordable price point often times have cool blue tints; the TK15 and TK15S have a much more likeable slightly warm yellow tint. I imagine this will be another big selling point in addition to the price.

I must acknowledge that tested maximum outputs fell a bit short of specifications. The ThorFire VG-15S I tested previously (similar 18650 form factor but with tail switch only and XM-L2 instead of XP-L2) tested within 5% of specifications and pulled 0.3A more, so I don't believe it's a testing issue. It could be efficiency loss in the electronic switches or perhaps just these samples. I don't expect this will be a deal-breaker nonetheless.

As lights these size (of any brand) have to implement step-downs for thermal management, mode spacing and runtime is more important to me than absolute peak output anyway. I like the predictable output curves and that tested runtimes far exceeded specifications on all TK15 modes and most TK15S modes. Ultimately, the TK15 is my favorite of the two due to the additional mode and the general mode spacing being more to my preference. Those who need the bike strobe or are adverse to locking the light out at the tail (to prevent accidental activation and eliminate parasitic drain) should look to the TK15S.





Lux Meter: Dr. Meter LX1330B
Integrating "sphere": Homebuilt tube-style device calibrated on other known lights and test results. Numbers should be considered relative to each other and my other review figures but accuracy is in no way certified or guaranteed.
Camera: Canon SD4000IS
Multimeter: Craftsman 82170


 
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