Nitefox UT20 - USB Rechargeable Single 18650 Light

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Nitefox UT20 - USB Rechargeable Single 18650 Light

Presented with the opportunity to review the USB rechargeable UT20 from Nitefox, I agreed with the caveat that I would report whatever I found. I ordered it from Amazon at a discounted price, meaning I received a light without any special preparation. Preferring reviews with real life experience using the light to see its durability in actual EDC use I carried the UT20 from January to March before writing this review.

The UT20 arrived in a typical small, tan box. The light and accessories were secure inside the box and there was no shipping damage. The light comes with a pocket clip, a tactical ring (more on that later), lanyard, USB cable, O-rings, a spare button cover, and a holster. The holster is not shown in the Nitefox photo.

The tactical ring is plastic and fits on the back of the light. This prevents the UT20 from rolling and allows easy one-handed use of the rear switch. The photos later in this review show the ring in place. With the tactical ring installed the light must go into the holster lens down.
The holster is black woven material with a hook and loop fastener to close the flap. The flap holds the light securely. Shaking it upside down can’t dislodge the light. The back has two straps. One is sewn in place for a belt loop and over that is another strap with Velcro for a removable attachment. While smaller than a standard molle strap this second strap allows placement on molle webbing or backpack straps.

The Light
The UT20 is the usual size for a single 18650 powered flashlight. The first photo from Nitefox shows the manufacturer specifications and dimensions. The other three are my photos after nearly 2 months of EDC use.

The UT20 has a unique user interface with two different operating modes – Outdoor and Tactical – using both a tail and a side switch. The tail switch is a forward clicky. This means that with the light off, a partial press of the switch will turn on the light but not latch it on. This is useful to briefly shine the light if the button is held but have the light turn off when the switch is released.


  • Tail switch = power on/off
  • Side switch = change modes (moon, low, medium, high) – hold side switch for strobe.


  • Tail switch – power on/off and mode control (high, strobe, low)
  • Side switch – disabled

The side switch has an indicator light to show the light’s status when running or charging. It is illuminated at turn on and at each mode change.

  • Green = more than 20% battery charge
  • Red = 10-20%
  • Blink red = Under 20%
    Testing with a battery discharged to 3.0V I verified the low voltage indication:
  • Moon and low – the indicator LED turned on green, changed to red, and went out. The UT20 operated normally on these low modes.
  • Medium – the indicator LED turned on green, changed to red, and then continued to blink red.
  • High – this mode could not be selected, the light remained on medium.

USB charging is through a port on the side of the light, shown here in the open position.

The supplied USB cable can handle the charging current with no problems and can charge other devices at over 1A. There is a specific process for charging called out in the manual and in a printed note with the light. With the USB cable plugged in the main LED goes out. (Nitefox photo)

A discharged battery reading 3.0V took almost 4 hours and 15 minutes to charge in the UT20. Charge current into the light is 0.83A until gradually reducing at the end of charge. Discharge testing for capacity on my BT-C3400 showed that the UT20 charger gets full capacity out of the included battery.

On a white wall the beam has a neutral white center with a slightly yellowish ring all surrounded by spill that tends to purple. The purple edges of the spill are only noticeable when very close (a foot or two) to a white wall. In real world use this is not noticeable, as shown in the outdoor beam photos.

The beam photos are all from a tripod mounted camera with fixed settings and daylight white balance to accurately show what I saw during the test. The UT20 is mounted above the camera. Moon mode is too low to show in the photos using these settings, but it is useful for navigating a dark room without disturbing others. PWM is not visible by eye or by a digital camera.

Control – UT20 Off




The fence is 200 feet away (red mark) and the white house is 535 feet away (yellow mark).

An animated GIF showing the modes

I used the Ceilingbounce app on an S5 cell phone along with a white box to get relative brightness measurements of the UT20. The four brightness levels with the Nitefox battery are:

To determine the brightness of the different levels I tested the UT20 with the Nitefox battery and my HG2 against the Astrolux S1. The S1 is 1200 lumens on turbo and then drops back to 800 lumens. The graph shows that the Nitefox battery runs the UT20 as well as a high drain unprotected cell, and that the claimed 1080 lumens on high is correct.

There is no mention of stepdown in the manual, but it appears that there is throttling taking place. I ended this test after 22 minutes. This test used the Nitefox battery.

Extended runtime in high mode makes the light warm but not too hot to hold. This series of thermal imager photos shows the heat moving through the head into the body tube. The upper left image was after running on high for 2.5 minutes and continued with the image times shown in the bottom right of each image. All temperatures are in degrees F with emissivity set to 0.85. The light is on an insulating pad in a 70F room.

I carried this light for nearly two months, using it at work and other activities. After this EDC 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 color is smooth and even. Most of my two-month test had the UT20 bouncing around in a work bag pocket with another flashlight. My photos in this review show minimal scratches after this EDC use. I carried the light with the tactical ring in place and did not use the pocket clip. The body texture allows a good grip without being sharp.

The threads were well machined, turned smoothly, and arrived lightly lubricated.

The head has a gold spring but no visible retaining ring for the driver. I was not able to disassemble the head without risking damage to the light. It appears the front bezel is glued in place. The four squares appear to be two circuit boards that extend into the head at a right angle to the board shown. One should be for USB charging and one for the side switch.

The tail uses a retaining ring and a gold spring. Note that the tail ring is reverse threaded.

The XM-L2 emitter was clean and well centered.

With the light apart, it was time for measurements. The head does not readily come apart, so I did not take measurements at the emitter.

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 the Nitefox 18650. The supplied 18650 allows the light to operate at its full potential as shown in both light and current readings.

The Battery
The Nitefox provided protected battery is rated at 2600mAh. Using a 1A charge/discharge/charge test cycle confirmed the rated capacity on my BT-C3400 charger. The 18650 can supply more than enough current for this light but with protection circuitry it may not run high power direct drive lights to their full potential. I compared the Nitefox battery to my HG2 in a different light that uses direct drive circuitry with multiple emitters. This pushes the batteries to deliver their maximum current. The HG2 supplied 7.6A and the Nitefox initially provided 5.6A and then stabilized at 5.1A. Remember that the Nitefox is a protected cell and direct drive lights aren’t typically used with protected cells. The battery wrap is sturdy, and thick enough that I can’t see any trace of the battery color or markings on the cell inside.

Summary and Opinion
• Light performs as advertised
• Battery performs as advertised
• Good construction, fit, and tough finish
• Good value with included battery
• Selectable user interface
• Low voltage warning
• Battery level indication with the side switch LED
• No need to purchase a charger
• Side and rear switches for control (if you like side switches)
• Responsive customer service.

• Not easily disassembled
• Side and rear switches for control (if you don’t like side switches)
• No low voltage shutdown
• Problem with the light I received, which was quickly resolved by Nitefox.

Many thanks to Nitefox for allowing me to do this review. My testing shows a light that performs well and meets its advertised specifications. The price is good for all that is included in the kit. The side switch may take some getting used to, but it adds battery level indication and the switch can always be disabled if you prefer. The USB powered built in charger makes it easy to recharge in the car, from a computer, or any other USB port. I initially had a problem with my light but Nitefox customer service responded quickly and resolved the issue. In the real-world things don’t always go smoothly, and that’s when we can see how well a company stands behind its products. Recommended.

Test Equipment
• Ideal 61-768 clamp meter
• Protek 506 DMM
• Fluke Ti32 thermal imager (E=0.85)
• Zeiss Stemi 1000 microscope
• Pentax K50 camera
• BT-C3400 Opus charger
• UM2C USB voltage/current test unit with PC software

Lightbringer's picture
Last seen: 11 min 33 sec ago
Joined: 08/30/2016 - 14:12
Posts: 12860
Location: nyc

Wow, another review of the UT20 with zero replies. Mine got no love, either.

Quite a nice light, though. I really like (and still use) mine.

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Relampago's picture
Last seen: 3 months 2 weeks ago
Joined: 04/14/2019 - 11:44
Posts: 549

Seems muggle friendly, any coupons?

“Electricity is really just organized lightning”
― George Carlin