Thorfire VG15S Review

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Thorfire VG15S Review

This review covers the VG15S, which comes with a battery and a charger. The VG15S uses a single 18650 cell with anXM-L2 emitter. Thermal imager, o-scope, meter, and photo information is included.

The ordering and delivery process was the typical no problems Amazon experience. At the time I ordered the package price on Amazon was just under $30. This is worthy of note because it places the light in a price class normally found by shopping from far away sellers with long delivery times. Easy ordering, along with the complete package to get up and running, makes this an interesting starter set for those just entering the world of 18650 powered lights. Could I recommend this to friends who saw my lights but were put off by the investment in support equipment required? I put the light into my EDC rotation a few months to find out.

The light, battery, USB cable, spare O-rings, and charger arrived in a small tan cardboard box. Everything was packaged well and there was no shipping damage. This is typical packaging for lights of this type, but was above the bubble wrap in an envelope used by many inexpensive Amazon sellers. (Photo from the Thorfire web page.)

The Light
Manufacturer Specifications:

  • Upgraded version – VG15S LED flashlight is the upgraded version of ThorFire VG15 flashlight. VG15S is brighter and has 5 more reasonable brightness levels.
  • Ultra Bright Gives out 0.5LM-1000LM output with 200m beam distance.
  • 5 Modes – Firefly, Low, Mid, High, Turbo. Double tap quickly to activate Strobe Mode. Firefly mode gives out 0.5LM and Turbo mode 1000LM. (Test with ThorFire 18650 Battery)
  • Battery Usage – Runs on 1× 18650 battery ONLY. (3V CR123A batteries are banned)
  • Superior Quality – Made of Aircraft-grade Aluminum. Waterproof to IPX-8 standard.
  • Low Battery Alarm – Low battery warning flash

After unpacking, I put in a charged battery that I had on hand and turned on the light. The light has a very low firefly level and a very bright turbo mode. Mode changes are easy with a partial click on the tail switch, never skipping a level from an uncertain switch. The single frequency strobe is hidden but easy to enter if desired. Mode changes are slightly different from other lights with a moment of darkness between levels. It is so short that it does not affect the usefulness of the light and is not an issue, but it does show in some runtime graphs presented later in this review.

The textured reflector gives a smooth, even beam. I found it very well suited for indoor use, with the hotspot to spill transition very smooth and only visible when shining on a white wall. The color temperature is not specified but it is just cooler than neutral. I am not a huge fan of the yellowish tint of warm LEDS so this was very good for me. Outdoors the beam does well, with colors slightly shifted to the cool side of the range by the emitter color. This is mainly noticeable when looking at beam photos for color accuracy.

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 the ThorFire 18650. Firefly mode is so dim it does not show on the photos and is not included here. It is just enough light to navigate the house with eyes fully adjusted to the dark.





To make more sense of the turbo 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. Colors are close to true, but the cooler emitter does push the house siding and cement to appear more gray.

I used the Ceilingbounce app on an S5 cell phone, along with a white box, to get relative brightness measurements using the supplied 18650. The turbo mode specifies a 3-minute timed stepdown, and this is accurate. The light can be put back into turbo when it steps down. For this test, I let turbo step down, went back, and then ran through the modes in order.

Using the app again, I compared the VG15S with ThorFire cell to an Astrolux S1 with an HG2 18650. This light is generally considered to be 1200 lumens on its highest mode and 800 lumens when it steps down. The graph shows that the VG15S on turbo is between these two levels, supporting the advertised lumen rating.

I could not see any difference in the light’s performance between my high current HG2 18650 battery and the ThorFire cell, but I checked the two in the box. The measurements showed no real difference.

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 heat and then watch the warm area move toward the tail of the light. All temperatures are in degrees F. The emissivity (e=0.85) setting for anodized aluminum is not a good match for the wood desk, which shows 88.2F.

After a few weeks of carry and use, I took the light apart for photos. The finish showed minimal scratches even after bouncing around in my bag with other lights. After these photos, I finally managed to mark the black finish but it was an accidental 4 foot drop onto concrete that dented the aluminum of the tail slightly. Threads were well machined, turned smoothly, and arrived lightly lubricated. The o rings fit properly and did not pinch or move out of place when tightened down.

The only flaws I found were in the side recesses. They showed some machining marks and one area of thin anodizing. I believe this was atypical. (My usual luck.) Someone who saw my lights at a geocaching event ordered the VG15S set for himself and it had good machining and finish. I purchased a second VG15S set as a gift for a relative and it did not show any machining or anodizing defects. I’m sure I could have returned my light to Amazon but I am not bothered by such details. I would like to put glow in the dark material in the side recesses in the future.

The internal construction is good, with thermal paste under the star and no dirt inside the light. The driver is held in with a brass ring, as are the tail components. The star is held in place by the pressure of the metal reflector. I did not disassemble the light further, but it should allow easy modifications. The dome of the XM-L2 was clean and unmarked.

With the light apart, it was time for measurements. The removable reflector allowed measurements at the driver with the light running. This simplified the measurement process.

Using my DMM for low current levels and a DC clamp meter on a short wire shunt for the higher levels shows that the ThorFire cell performs well, but does not allow the tail current of the HG2. The ThorFire is a protected cell so this may not be a fair fight. I compared to an older unprotected cell for another data point. Remember that the slightly higher current of the HG2 did not give a significant difference in brightness.

Measuring DC voltage across the LED while running lets us estimate the current out of the driver and then the lumens emitted using the CREE datasheet.

By eye I could not detect evidence of PWM, and user reports on the internet supported this. I checked voltage at the LED with an oscilloscope and found something puzzling. Firefly and turbo showed DC voltage as expected, but the levels in between showed a nearly 1V 21kHz signal riding on the DC voltage. Is this PWM that does not turn off the light? I sent a note to ThorFire but have not yet received a response.






The Battery
The ThorFire protected 18650 performs well, but what is it? ThorFire calls out a Samsung cell, and through the orange areas of the wrapper I could see most of the OEM numbers on the battery. ICR18650-30___. Under the wrapper the cell’s OEM color is light green. This sounds like ICR18650-30B but I have not unwrapped it to be sure. Checking a second ThorFire cell, I could see __________-30B under the wrapping. This supports the Samsung -30B identification. Testing on my Opus BT-C3400 charger using the charge/discharge capacity test showed 2700mAh when the cell was new. My HG2 also read just under its rated 3000mAh so I was happy with the ThorFire cell. There are many stories of exaggerated battery ratings on mail-order cells. I am glad to see that does not apply to the ThorFire cell I received.

The supplied cell is protected – it has a protection circuit added to prevent over or under discharge. This is an important safety to prevent battery failure via “significant thermal event” and helps make this set good for those new to lithium ion battery powered lights. The VG15S has low voltage indication but not shutdown, so this protected cell is a good match.

The Charger
The supplied charger achieves its small size by running on a 5V USB power supply (not included). This makes it good for both home and mobile use, and the small size is easy to pack. I used a high current USB supply for my testing. The charger was simple – connect a USB power supply capable of 1A, insert the battery, and watch for the LED to change color. The charger initially did not work, which I traced to a faulty USB cable supplied with the unit. Note than the other lights I saw or purchased did not have this problem. I’m just lucky. . . Using a known good cable allowed charging without issues. Multiple measurements charging with the ThorFire charger and measuring capacity via discharge on the Opus showed the ThorFire charged their cell to approximately 2300mAh. I keep the ThorFire charger in my work bag, but I use desktop chargers whenever possible. The charge info shown in the images is from the ThorFire site. The back of the charger says 750mA charge current. The charger is specified for 18650, 26650, 16340, 14500, and 10440 cells. (Photo from the ThorFire web page.)

Summary and Opinion


  • Light and battery perform as advertised
  • Good construction
  • Easy disassembly for modification
  • Inexpensive
  • Good color
  • Good beam
  • Charger is a good size for travel
  • Good user interface
  • Protected battery for safety
  • Light has a low voltage warning


  • My sample light had some finish issues, not seen on other lights
  • Charger seems to cut off a little early
  • Defective USB cable on my charger, not seen on other lights
  • Light does not have low voltage shutdown

I did not know what to expect from a low-cost light with an unknown battery. I am pleased with the performance of the light especially at this price point and quick availability. The light went to Boy Scout meetings and camping, geocaching, and to work in an industrial setting and always impressed those who saw it. The rest of the time it bounced around in my work bag with other lights. Through all that abuse it held up well. While not a lumen monster, the good turbo runtime, useful high setting, and smooth beam make a very good light especially for indoor or other close work. I prefer the just cooler than neutral emitter used in this light, along with the textured reflector for a smooth even beam.

I feel the VG15S is a very good intro light for someone who does not already have many batteries and chargers and who desires simple operation. A light with low voltage warning using a protected cell makes for a reasonably safe setup. Two of my friends have purchased the light for their use and I was so pleased with the light that I bought another one to give as a gift to a family member getting started with 18650 lights. I find myself carrying this light more often than I expected (more often than some more expensive lights) because it performs so well for typical EDC tasks and I can lend it to someone without the 5 minutes of instructions and warnings often required for custom “enthusiast” lights.

Test Equipment

  • BT-C3400 Opus charger
  • Ideal 61-768 clamp meter
  • Protek 506 DMM
  • Fluke Ti32 thermal imager (e=0.85)
  • Fluke 199C scope meter
  • Zeiss Stemi 1000 microscope
  • Pentax K50 camera