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TK15S Flashlight - My first review

tk15s flashlight 18650 light

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#1 Ed



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Posted 10 January 2018 - 09:55 PM

While I have been playing with and modifying flashlights for a long time, I am new to reviewing lights.  Constructive feedback is welcome.


Most of my lights cost $50 or less.  The TK15S sells for $25 on Amazon as of the date of this review.  The typical light in this price range is ordered from a vendor on the other side of the globe and can have huge variations in quality.  I was interested to see how the TK15S would perform.  The light with spare O rings arrived in a small tan cardboard box.  Everything was packaged well and there was no shipping damage. 



The Light

Manufacturer Specifications (from the ThorFire literature):

Super Bright:

Latest XPL-2 V6 CREE Led delivers Max 1050 Lumens, covers a long throwing of 150 yards.

Multiple 6 Modes:

Moonlight(1LM)/Low(100LM)/Mid(500LM)/High(1050LM)/Hidden Strobe(1050LM)/ Hidden Bike Blink(200LM) with memory for daily different usage; Hidden Strobe for emergency, self-defense; bicycle blink for cycling.


Made from aviation aluminum material with premium type III hard -anodized tough for extreme condition; IPX8 Waterproof standard for use in heavy rain.

Smart Design:

TK15S flashlight has reverse polarity protection, high voltage protection and low voltage indication; Pocket size with a removable clip for EDC; Tail stand as an emergency lamp.

What you get:

1* ThorFire TK15S flashlight with clip, 2 spare O-rings, 1*user manual; ThorFire provide customer 18-month warranty and helpful customer service.

Low Battery Alarm

Low battery warning flash


The user interface (UI) is different than most lights.  The tail switch controls on and off, offering both latched and momentary operation.  The side switch controls the modes.  Each press cycles one level, with the light ramping up and down rather than in a circle.  Moon, low, mid, high, mid, low, moon, etc.  While different than most lights it works well in practice.  Strobe and bike mode are available via the side switch.  With the light on in any of the regular modes, double-tap the side switch to access the dual pattern strobe.  The emergency strobe is interesting, using two different strobe frequencies which change a few times per minute.  With the light on in any of the regular modes, hold the side switch down to access the bike mode.  The bike mode keeps the light on and pulses it brighter to create the strobe.  This is better than other lights I’ve seen that allow brief moments of darkness in the bike light mode.  


The TK15S has a smooth reflector, providing a noticeable central hotspot but keeping good spill especially at a distance.  The XP-L2 does show some of the expected tint-shift from the emitter when indoor, closeup, white wall hunting.  But really, how often do you shine your light against a plain white wall just to look for minor variations in the beam?  This slight difference in color across the beam pattern is a product of the CREE LED used.  No one who borrowed the light ever noted the issue, even during more than an hour of closeup use while geocaching.  The light is well suited for outdoor use with its good color rendition.  If you do not like LED flashlights because the blue/white light washes out colors you will like this light.


Li-Ion powered lights can cause problems if the batteries are allowed to discharge too far.  This light can use both protected and unprotected 18650 cells.  It has a low voltage warning, blinking the light when the battery is low.  I ran the light to its warning point and then measured the battery voltage.  When removed the ThorFire battery measured 3.0V.  The light offers mechanical lockout by slightly unscrewing the tailcap.


I set up my tripod mounted camera using fixed exposure settings for outdoor beam photos.  I chose settings that gave the image that best matched what I saw in person.  The light is mounted above the camera.  All beam photos use an HG2 18650.  Moonlight mode is so low it does not show in these photos.  Moonlight's tiny amount of light does work well for navigating a dark house without disturbing night vision.  Outdoors the hotspot and slight tint shift are not an issue.  Especially on high note the true color reproduction of the tans, grays, and greens in the photo.  The cement foundation and siding on the house show true to life color.  To make more sense of the highest level photo, I’ve added distances to the objects.  There are trees at 150 and 200 feet, and a house at 440 feet.  To verify the claimed throw distance the light illuminated a house 520 feet away.  There are no photos of this test as it was done quickly to avoid annoying the neighbors.








LEVEL 4 - HIGH wc3e8Dx.jpg


I used the Ceilingbounce app on an S5 cell phone, along with a white box, to get relative brightness measurements using my HG2 battery.  The light's highest mode specifies a 3-minute timed stepdown, and this is accurate.  The light can be put back into high when it steps down.  For this test I let high step down, set it back to high with a single quick press of the side switch, then ran through the modes in order.  Low and mid are bright enough for close tasks, while high mode illuminates a good distance.




Using the app again, I compared the TK15S to an Astrolux S1 with both lights using the HG2 18650.  The S1 is generally considered to be 1200 lumens on its highest mode and 800 lumens when it steps down.  The graph shows that the TK15S on high is between these two levels, supporting the advertised lumen rating.




After multiple 3-minute runs on turbo the light became warm but not too hot to hold.  The heat was transferred through the head into the body tube.  Here is the light after this test, on an insulating pad in a 70F room.  During the test I could see the head getting hotter with the warm area moving toward the tail of the light.  All temperatures are in degrees F.  The emissivity setting for anodized aluminum is not a good match for the wood desk, which shows 86.7F.  (I found differing recommended emissivity settings for anodized aluminum in my research, the photo used e=.85.)




After a few weeks of carry and use, I took the light apart for photos.  The O rings fit properly and did not pinch or move out of place when tightened down.  The black finish is smooth and even and it is highly resistant to scratches.  The finish showed minimal scratches even after weeks of use and bouncing around in a work bag pocket with another flashlight. 


The threads were smoothly machined and arrived lightly lubricated.  The side switch is flush with the side of the light.  It is not easy to accidentally press the switch when handling the light.  The knurling is well machined and gives a good grip without feeling sharp.



The emitter is clean and everything is centered.  Note the smooth reflector.



With the light apart, it was time for measurements.  I did not try to disassemble the head, as the inner retaining ring appears to release the entire inside of the head.  I don’t think the light would safely operate that way for emitter voltage measurements.  (I like the light too much to risk damaging it.)


Using my DMM for low current levels and a DC clamp meter on a short wire shunt for the higher levels I recorded tailcap currents for both my HG2 cell and a ThorFire 18650 (which I believe to be a protected ICR18650-30B but I have not removed the wrapper to verify).  The TK15S can pull reasonable currents if the battery allows.



Summary and Opinion


  • Light performs as advertised
  • Good construction, fit, and tough finish
  • Inexpensive
  • Very good color rendition in real world use, good for those who don't like cold white light
  • Simple user interface
  • Uses both protected and unprotected cells
  • Low voltage warning



  • Tint shift noticeable on a flat white surface
  • Side button could be easier to find by feel in the dark
  • Not good for those who like cold, white light
  • No low voltage shutoff


This was my first experience with a ThorFire 18650 light.  The light went to Boy Scout meetings and camping, geocaching, got banged around during a home remodeling project, and was used at work in an industrial setting.  The rest of the time the TK15S bounced around in my work bag.  After loaning it to someone for a night geocache hunt he called the TK15S "a game changer” for night caching and wanted his own good light.  A bright light that I can loan to others without a 5-minute list of special instructions to navigate a strange user interface or prevent light damage or injury is good.  I always enjoy spreading the flashlight hobby to people who are only used to cheap department store lights.  Through all that abuse the TK15S held up well, showing barely a mark on the finish and no dents or scratches.  This is a well-made, true to spec light.


Test Equipment

  • Ideal 61-768 clamp meter
  • Protek 506 DMM
  • Fluke Ti32 thermal imager (e=0.85)
  • Zeiss Stemi 1000 microscope
  • Pentax K50 camera


  • Mikey Bautista likes this

#2 Mikey Bautista

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Posted 11 January 2018 - 06:05 AM

Just wanted to congratulate and commend you on your first review, because damn, that's pretty comprehensive. Looking forward to more!

#3 Ed



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Posted 11 January 2018 - 09:46 PM

Just wanted to congratulate and commend you on your first review, because damn, that's pretty comprehensive. Looking forward to more!

I'm glad the review fit your site.  I have another ThorFire review, and then if we ever get warm weather again I will do some other lights.

#4 Syluxguy



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Posted 20 January 2018 - 03:38 PM

Good review, I look forward to your next one!

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