ThruNite TN42 LED Searchlight

ThruNite TN42 LED Searchlight

*Disclaimer: TN42 provided for review courtesy of Thrunite.

This is it, folks… the reigning King of Throw in LED flashlights!

Manufacturer’s Description:


  • One of the most powerful throw LED lights on the market.
  • Uses one advanced CREE XHP35 HI LEDs with a lifespan of 20 years
  • The high output reaches 2000 lumens and an ultra-long distance of 1550 meters.
  • ThruNite ITC technology to prevents possible damage from overheating.
  • Reversed polarity protection system prevents damage to the light.
  • Intelligent and ergonomic user-friendly interface.
  • Only applicable for 18650 batteries to use.


  • LED: 1xCREE XHP35 HI LED with a lifespan of 20+ years of run time.
  • Runs on: 4 x 18650 (ThruNite 18650 3200Mah).
  • Working voltage: 5.5V-8.4V.
  • Output & Runtime (Tested with four pieces ThruNite Li-ion 18650 batteries (3.6V/3400mAh) and for CW. NW parameters is 10% off):
    • Strobe(680 lumens /10.8hrs),
    • Turbo(2000 lumens/1.5hrs),
    • High(780 lumens /5.3hrs),
    • Medium(256 lumens /17.8hrs),
    • Low(38 lumens /4.3days),
    • Firefly (0.8 lumens /58days).
  • Peak beam intensity: 600750cd.
  • Max beam distance: 1550m.
  • Waterproof to IPX-8 Standard (2 meters).
  • Impact resistant: 1.0 meter.
  • Working Temperature: -40℃-40℃.
  • Dimensions: 206mm (length) x 100mm x 52mm.
  • Weight: 666g (including battery carrier).
  • Accessories: Shoulder strap*1, Strap ring*1, A, Spare O-ring*2, Side switch Cap*1, Battery Carrier x1 (inside the flashlight).


There you go.  3000 words in 6 seconds. $199 USD gets you over 700kcd.  You like throw? BUY IT!


What?  That wasn’t enough to convince you how awesome the new LED king of throw is?  OK…fair enough.  Read on.  I thought about making everything above this paragraph my entire review but I took a lot of pictures and spent too much time testing, editing, uploading, and writing to just throw away all the effort.  So here are the particulars, starting with what everyone really wants to know, how bright is it and how far will it throw?


Here are the particulars.  I take my OTF lumen measurements using a calibrated Integrating Sphere.  Lux is measured at 8.9m distance and 30 seconds of “on” time and converted back to 1m.  Throw distance is calculated as distance until output reaches to 0.25 lumens (ANSI standard).  Batteries used in testing are Samsung 30Q INR 18650 high drain 20A cells.  Cells at full charge of 4.2V.

To measure a light like this it is imperative that lux be measured from more than 7m away due to the convergence point of the beam which is several meters away.  Taking measurements any closer than that will definitely result in inaccurate readings since the beam won’t even be focused at closer ranges.  This is why I measure at 8.9m distance and almost feel I should go back further for this crazy light but I’m confident that my readings, for my sample, are accurate.

You can see the insane numbers this light returns (728kcd!!!), especially for throw (1.7km!!!).  How does it look in the real world?  Let’s take a look and see.  With claims of 1550m of throw, I needed a place to take beam shots that was as close to 1.5km as I could find.  The best I could do is 1.2km and this worked out great because it is far enough to show how insanely brilliant this light is as well as one or two other lights to have a chance to show their reach.  I don’t have as many dedicated throwers as some other flashlight collectors but I’m working on it. The only lights I have that I know for a fact that could reach 1.2km are my TN40 (quad XP-L HI) and the TN42 (XHP35 HI).  I also brought along my Fenix TK61 and ThruNite TN32 to see if they even stood a chance of hitting that far.

Click for larger 1024px image

The TK61 and TN32 don’t really hit it at all to my eye.  I believe the TN32 may barely touch it but not enough to say it does.  The TN40, with it’s huge 100mm head and quad XP-L HI emitters hammers the entire building with a huge swath of light.  In my testing the big quad can hit over 1300m so it’s no surprise to me that it hits at 1.2km.  The TN42 lights just a small section of the big building even more with it’s focused beam.  I thought the TN40 was king of throw, or at least equal to other renowned competitors such as the Acebeam K70, until I got the TN42.  This baby THROWS!  Imagine… Over 728kcd and 1.7km of throw!  Based on how well it lights the tower at over 1200 meters, I have no doubt that it can truly reach 1.7km.  With custom modders getting around 3000 lumens form the Cree XHP35 HI emitter, there should be room for modders to increase the output even more and get even better throw.  This light is stunning.  Bravo, ThruNite!

^ You can see in the gif above just how focused this beam is.


The TN42 uses the same UI as all the newer models they make that have electronic switching.  The only oddity in the mode switching that is different from other brands with similar UI is that whenever you press and hold to change modes starting in Medium mode, the light will switch to Low, then Medium, then high, then loop back to Low.  If you change modes while starting in High mode nothing will seem odd.  If you are in Low mode to start it will switch to Medium then High – nothing odd here either.  It’s only odd if you start in Medium: the light will drop to Low, then back to medium and then to High.

This is different from pretty much every other light where modes cycle starting with the mode above the one you are in., For example, if you are in Medium and press and hold to change modes, most other lights will go to High, then loop to Low, then go to medium, and so on.  On the ThruNites, if you are in Medium and press and hold to change modes, the light will always shift to Low, then to Medium, then to High.

If you aren’t used to this it feels very odd but there is a bright side to it and I now believe I understand the thinking behind it, at least why it makes sense in my opinion – it protects your night vision.  If you start from Low it goes to medium an up no issue, as one would expect. What if you are in Medium and want to back down to Low?  Instead of having to cycle past High before getting to Low, like in most every other light with press and hold UI, it drops back into Low first, thereby preventing you from damaging your night vision.  If you wanted to get to high from medium, there is only a brief amount of extra time needed to cycle through and reach High.  To me, I would rather take an extra second to reach high than flash my eyes when I don’t want High but want Low instead.  Personally I would like it best if every light, including this one, utilized short, medium, and long presses to navigate both forward and backwards through the modes.  Click to go up in modes, medium press to go backwards in modes, and long presses, double-clicks and triple-clicks for special functions.

Either way, the TN42 UI functions perfectly well, it’s just that it may throw you off the first few times you change modes from Medium and it drops to Low before going to Medium then High instead of going directly to High mode.

  • Turn On/Off
    • Press the side switch to turn the light on/off.
  • Change Mode
    • When the light is on, long press the side switch to cycle through low, medium and high.
    • Shortcut to firefly: When the light is off, long press the side switch to get firefly mode.
    • Double click to turn to turbo from any mode. Another double click to get strobe.
  • ITC Technology
    • The light will automatically lower the current when temperature in LED or driver rises to 80 degrees centigrade to protect the flashlight from overheating. Thus to extend its lifespan.
  • Memory Function
    • The light will turn on in the last mode accessed, except firefly, turbo and strobe.
  • Low Voltage Indication
    • When the indicating light on the side switch turns from blue to red, it means the battery package should be replaced or charged.
  • Battery Replacement:
    • Take off the tail cap, insert four 18650 batteries into the battery carrier, put the carrier into the flashlight and screw on the tail cap. With either end of the battery carrier towards the light head is OK. But make sure the batteries are correctly inserted into the carrier with polarities matched (springs on the carrier should connect with the cathodes of batteries).


Onto what is actually my favorite part of a review – seeing close-up details you won’t ever see unless it’s in your hands, or by reading my reviews.  Smile

^ The TN42 and TN42C are shipped in the same sturdy cardboard box

^ Inside the box is a fitted foam liner holding the light, Accessory bag, User Manual, shoulder strap, and “Thank You” card.  The large cutout in the back-right corner is where the charger for the TN42C (rechargeable version) would be.

^ Nice, simple User Manual tells you everything you need to know about the operation of the light.

^ With the non-rechargeable TN42 this is all you get, but all you need.  A couple of spare O-rings, a sturdy, flat split-ring for attaching the shoulder strap to the tail of the light, a replacement inner switch seal, and the shoulder strap in lieu of a holster.

^ With the TN42 out of it’s box the first thing that strikes you is the humongous head with that smooth, deep reflector.

^ Way down in the reflector well is a Cree XHP35 HI emitter.

^ The emitter is perfectly focused for long range throw.  The LED is perfectly centered.

^ Here is a little shot with the LED in Moon low.  You can see the double-sided AR coating on the inside in this photograph.  I usually like to get a photo taken head on with throwers (and most of my reflectored lights) where the reflection of the LED makes the entire reflector appear yellow like the LED itself.  I couldn’t do that with this light because the focus point for the beam is so far out that to get it all yellow I would be too far from the light to really see anything.  I certainly was unable to get the shot in my kitchen due to limited space.  This is the first time I’ve ever had this happen.  3 or 4 feet is usually all one needs to get a full LED reflection.

^ The beam from the TN42 is almost artwork in my opinion.  This shot was taken with the TN42 perfectly level with the surface it was on and the beam is so tight and focused that the center of the beam isn’t even touching the surface it was on.  This creates a beam profile that looks to be the smoothest, creamiest spill I’ve ever seen on any light.  Usually I take this pic and it allows me to overlay a protractor image to get the beam angles in degrees.  Not even possible with this light as it is so damned focused and tight.  Amazing to me!

^ When the TN42 is powered on, the LED in the center of the switch glows blue (looks turquoise in this photo).  As the cells drain the LED charge indicator changes to red when it’s time to charge or swap the four 18650 cells.

^ The head of the TN42 is so big that there is tons of surface area for heat dissipation.  Around the driver and emitter section of the light, where the switch is, there are a few deep, wide fins cut into it for further heat management.  The flat, raised shelf the switch is located on makes it really easy to find the switch in the dark just by feel.  No mistaking or doubt when locating by feel.

The knurling behind the switch allows great grip of the head while unscrewing the battery tube to swap or charge cells.

^ The knurling, like every other big ThruNite light I have, is exceptional.  Tons of grip for a secure, comfortable hold.

^ The tail itself is just like that of the TN40.  The 3 wide crenellations offer a stabile platform on uneven surfaces (think tripod) and the large, chamfered lanyard holes easily accommodate 550 Paracord with absolutely no sharp edges to cut your lanyard.

^ Here is where you would install the included split-ring for the shoulder strap but you can also clip the end of the shoulder strap directly into one of the holes without using the split-ring.

^ To swap cells, the battery tube unscrews from behind the 3-piece head.  The TN42 uses a cartridge style battery holder.

^ On the head of the TN42, the anode contact is a huge, stiffly sprung, brass button.

^ Threads where the battery tube join the head are perfectly machined and square.  The thick O-ring is perfectly sized for a real tight seal.  O-ring and threads came perfectly prelubed from the factory.

^ With the battery cartridge removed, this is what the inside of the battery tube looks like.  The inner surface is perfectly smooth just like the exterior of the light.  No shortcuts in machining were taken to save time.  Anodizing on the TN42 is also exceptional with no missed or thin spots and no uneven coloring.  Just beautiful throughout.

^ The battery cartridge is well made and very sturdy.  It allows for insertion into the light in either direction.  Batteries, however, must be inserted into the cartridge in the correct directions.  Raised contacts allow the use of flat or button topped cells.  Very stiff and thick cathode springs are just long enough to use about any cells you want to use although I feel you will want to use only high-drain cells.  Cells are arranged in a 2S2P format for 8.4v output.

^ I used Samsung 30Q flat-topped cells.  There is just enough tension with these 65mm long cells and plenty of room for longer cells.


Time to take a look at the internals as far as I can without unsoldering things.

^ The contact/retaining plate for the driver is a very thick slab of anodized aluminum with a broad, machined contact ring for negative current.  A plastic isolator ring is pressed snugly into the center of the contact plate to insulate the positive current from the thick brass anode contact button in the center.  Removing the three screws in the plate allow access to the driver itself.

^ The driver is sandwiched between the pill section and retaining plate.

^ The center anode spring is very thick and stiff.  ThruNite performs a factory spring bypass for as little resistance possible and maximum current throughput.

^ All the larger components on the back of the driver are potted for extra impact resistance.  This driver boosts the voltage from the battery pack to power the XHP35 HI emitter which is a 12V emitter.  Modders will be happy to see what look to me to be a bank of four sense resistors that could probably be changed to increase output beyond the factory 2000 lumens.  It goes without saying but doing so will definitely void your warranty.  Some folks I know won’t be deterred from seeing how much they can wring from the boost driver.

^ With the driver lifted out of the way we see the one-piece pill and emitter shelf.  Very thick leads provide current to the LED itself and a ribbon cable leads to the electronic switch.

^ The head of the light consists of 4 main pieces: main light engine section, upper head section, bezel (with lens and O-ring), and reflector.

^ Fine, square threads in the bezel are very smooth.  All components of the head thread super smoothly and seal very tightly.

^ A close look at the square threads of the upper head section where the bezel attaches.  Everything came prelubed and the O-ring is perfectly sized for snug, tight fit.

^ The upper head section attaches to the main driver section here with more perfectly machined, square threads.  Again, everything is prelubed and the O-ring seals perfectly.

^ Looking into the light engine, we see a square, copper, DTP emitter board (MCPCB) that is mounted to the main emitter shelf with screws.  The MCPCB has thermal grease under it for better heat dissipation. A large, nylon centering ring/insulator fits over the XHP35 HI emitter and centers the big reflector perfectly.

^ Leads to the LED are fairly thick and soldered perfectly.  The big reflector is so deep that the switch sits inside the reflector cup area in the head.

^ A shot of the undomed LED in Moon low.

^ The aluminum reflector in the TN42 is gorgeous.  The depth of the emitter is 84mm to the broad, flat opening.  This broad opening allows the LED to sit deep into the reflector for perfect focus.

^ Inside diameter of the reflector well is roughly 90mm.

^ Outer diameter of the reflector is just under 93mm.

^ The double-sided AR coated lens is 94.24mm*2.5mm

^ Outer diameter of the head itself is a beefy 100mm.


Here is the TN42 shown next to a couple of other ThruNite mega-throwers.  On the far left is the TN42 with quad XP-L HI emitters that throw a broad swath of light easily past 1300m.  Farther than most dedicated single LED throwers.  In the middle is the TN42.  The TN40 and TN42 share the same head diameter and the same battery tube.  On the far right is the TN32.  ThruNite’s classic mega-thrower that may be aging but still holds up against many of today’s throwers.


^ Even though the TN40 and TN42 have the same head O.D., the TN40 with it’s big quad reflector looks larger in this pic.  The TN32 with it’s big 79mm head looks absolutely diminutive next to the big TN42.

^ From this angle you can get an idea of the different reflector depths.

^ The odd shoulder strap clip makes instant sense once you see how it hooks into the head of the light with a solid, secure connection.  The lobster claw clip on the other end of the strap can be attached directly into one of the lanyard holes in the tail cap if you don’t feel like attaching the stiff split-ring between the two.

^ The TN42 is a big light, no doubt, but it doesn’t feel that big in the hand.  The huge head does not create a front heavy feel like one might expect.  The majority of mass is in the battery tube which sits behind my index finger.


As you can readily see, this is a superbly built machine.  It’s the flashlight equivalent of a .50cal sniper rifle.  If you need a light to reach out and touch something far, far away, this is the one to have.  At $199.95 for the TN42 (as I have here) and $259.95 for the TN42C with rechargeable battery pack and charger, it’s competitively priced for a light of this class and capability.  I LOVE it!  I recommend it without any reservations.  Need another reminder of just what a light it is?  Here you go:

One thought on “ThruNite TN42 LED Searchlight

  1. Pingback: King of Throw! ThruNite TN42 | Johnny Mac Reviews

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