Nitecore P20i UV

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Nitecore P20i UV Review: UV Flashlight

Nitecore P20i UV specifications

Brand/modelNitecore P20i UV
LED1* Luminus SST-40 + 4x 365nm UV
Lumens1,800 Lumens
Beam intensity28,500 cd
Battery config.1*21700i (Proprietary), 2*CR123
Review dateJune 2021


Nitecore is a big name in the flashlight space, particularly on the professional-use side of things. They’ve been producing robust, high-quality lights for at least 14 years. They have a very wide portfolio that they segment into different series: MH (Multi-task Hybrid), P (Precise), TM (Tiny Monster), T (products like the Tube, Tip, Tini, and Tiki), and so forth. My first ever high-output flashlight was Nitecore’s P12GT: a 1000 lumen throwy tube light. This first impression with Nitecore certainly didn’t disappoint.

Up for review is a brand new entry in Nitecore’s Precise lineup: the Nitecore P20i UV. For those trying to keep the numbers and letters straight, this is an upgrade to the P20 lights. The “i” indicates that this uses Nitecore’s unique i-Series battery (more on that later). The latter designation is fairly obvious – it indicates that this light has secondary UV LEDs built-in.

Package quality.

The Nitecore P20i UV arrived in a fairly standard package that would fit well in a store display. There was a form-fit plastic tray inside that kept all of the goodies arranged. Inside the box was:

  • Nitecore P20i UV
  • 4000 mAh 21700i battery (NL2140i)
  • Spare o-ring
  • Lanyard
  • Pocket clip
  • Tactical holster (NTH20)
  • USB-A to USB-C charging cable
  • 2*CR123 adapter
  • Manual

Flashlight in use

The more and more I use 21700-based flashlights, the more I’m convinced that it’s about the perfect size (at least for my hands) in terms of grip-ability. Most 18650 lights, while pocket friendly, can almost be too slender, while 26650 lights are generally pretty chunky. That is to say, I feel like the Nitecore P20i UV is a very comfortable size. The body is pretty smooth overall, but has plenty of rings and cutouts and such and provides good traction.

There are flat spots around the head in a hexagon pattern that keeps the light from rolling around. The power switch on the tailcap (a forward clicky) protrudes generously. This makes it easy to activate, but of course, means there’s no tail standing. There’s a second switch in the tailcap that sits flush, referred to as the STROBE READY mode select button.

The Nitecore NTH20 Tactical Holster is included. It’s designed to fit on various belt sizes between 1 ¼” to 2 ¼” as well as being compatible with the MOLLE system. The holster feels nice and sturdy and seems to function very well, allowing quick and easy removal of the flashlight. The other included accessories are a bit more lackluster. The clip holds on firmly enough, but the bend radius that clamps against the flashlight appears to be suitable for a considerably thinner light and so it doesn’t clip on cleanly. The included lanyard is pretty standard, but I can’t figure out where to put it unless you cinch it down to the pocket clip. This arrangement seems unusual to me, but installing the lanyard on the clip is exactly what Nitecore had in mind.

In addition to the included accessories, Nitecore offers several other products that are compatible with the P20i UV, such as the:

  • NTR10 Tactical Ring Pro
  • TSL10i Signal Light
  • RSW2i USB-C Remote Switch
  • Multiple gun mounts
  • Multiple diffusers

Build Quality, and Warranty

Nitecore is very consistent when it comes to design, materials, and overall build. Outside of a few exceptions, you know that you’re going to get top-notch HAIII anodized aluminum (in black, of course, is there anything else?) and a solid construction. The P20i UV falls right in line with this and feels very rugged. The finish is excellent, and installing and removing the pocket clip left no marks. The threads are nice and smooth. Even the USB-C port cover is designed to seal tightly and sits flush with the light, it doesn’t get in the way or get caught up or anything. Nitecore has given it an impact resistance rating of 2 meters. The attention to detail is great.

As far as warranty goes, Nitecore has your back with three levels of guarantee:

  • Exchange and DOA/defective products locally within 15 days of purchase
  • Defective/malfunctioning products will be repaired free of charge for 60 months
  • Beyond 60 months, Nitecore will cover the cost of the labor and the end user is responsible for the cost of the parts

LED, Lens, Bezel, and Reflector

The business-end of the Nitecore P20i UV is pretty unique looking. There’s a single reflector with supposedly an advanced design thanks to Nitecore’s “Precision Digital Optics Technology (PDOT)”. In the center is the primary emitter. But what makes the P20i UV unusual is the inclusion of four UV LEDs recessed around the outside of the reflector. The UV LEDs appear to be somewhat standard 5mm LEDs with a total power output of 320mW and a wavelength of 365nm.

For the primary LED, Nitecore went with the Luminus SST-40. In my book, that’s a great choice. The SST-40 is efficient, one of the brightest single-die 3 volt LEDs, and has no noticeable tint shift (unlike recent Cree emitters). Nitecore hasn’t stated a particular CCT for this light, but unless otherwise specified they generally use 6000K – 6500K LEDs. While that may not be everyone’s favorite CCT, it lines up with the general consensus for preferred temperature of their target market: law enforcement, patrol workers, search and rescue, etc.

The LEDs and reflector are protected by a sheet of AR-coated glass. That arrangement is housed beneath a strike bezel, which is a bit unique. Instead of relying on highly aggressive crenulations to form the strike bezel, Nitecore has embedded beads of high-strength silicon nitride ceramics in a mildly crenulated bezel. The result of that is you’ve got a business-end that should have no trouble safely breaking glass, but is also smooth enough that it’s not going to tear up your pocket.

Dimensions and size comparison

  • Length: 150.5 mm / 5.93 in
  • Head diameter:  31.8 mm / 1.25 in
  • Body diameter:  25.4 mm / 1.00 in


  • With cells:  200 g / 7.0 oz
  • Without cells:  124 g / 4.37 oz

Flashlight size comparison

Image 1+2 Nitecore brothers, from left to right: Nitecore P20i UV, Nitecore P20iX

Image 3+4 UV lights, from left to right: Olight i3UV EOS, Nitecore P20i UV, Wuben E19UV

Image 5+6 Common 21700 lights, from left to right: Amutorch E3, Sofirn IF25A, Nitecore P20i UV, Wuben TO50R, Sofirn SP35

Driver & User Interface:

I feel like Nitecore made a great decision with the UI. There are two distinct UIs that you can choose from: Daily-Mode and Tactical-Mode. Switching between them is also very easy, while not being something you’d accidentally do. So how do you do it? Glad you asked. Just unscrew the tailcap a little bit when holding down the Mode button. The light will blink at you, confirming the change. Then just tighten the tailcap back down.  

Daily Mode cycles from low to high and has memory. In contrast, Tactical Mode has cycles from high to low and does not use memory; the light always comes back on in High (or Strobe via the Strobe Ready button).

Modes: UV, Low, Medium, High, Strobe

Daily Mode, From OFF:

  • Power button, Half press: momentary on
  • Power button, Single click: on in last used mode
  • Mode button, Press and Hold: momentary Strobe

Daily Mode, From ON:

  • Power button, Single click: turns off
  • Mode button, Single click: go to next (higher) mode
  • Mode button, Long press: Strobe mode

Tactical Mode, From OFF:

  • Power button, Half press: momentary High
  • Power button, Single click: on in High (no memory)
  • Mode button, Press and Hold: momentary Strobe

Tactical Mode, From ON:

  • Power button, Single click: turns off
  • Mode button, Single click: go to next (lower) mode
  • Mode button, Long press: Strobe mode

Mode memory:

  • Daily Mode uses memory, Tactical Mode does not

Short cuts:

  • To High: In Tactical mode (only), the Power button goes right to High
  • To Strobe: from Off, the Mode button activates Momentary Strobe
  • No other real shortcuts

Low voltage warning:

  • There is a power indicator LED on the side of the head that remains lit while the flashlight is on to read out the voltage range


  •  Strobe mode only

Lock-out mode: 

  •  No documented lockout besides physical lockout


  •  PWM is not present in any mode.  I used a photodiode circuit and my DMM’s Hz setting to verify.

Additional info, UV Mode: 

  • The UV mode is in the normal cycle of modes. Daily Mode rotation goes UV > Low > Medium > High and Tactical Mode goes High > Medium > Low > UV.
  • The P20i UV employs Nitecore’s ATR (advanced temperature regulation) control scheme. In testing, I never actually saw this play out. High mode appeared to ramp down at a set time (1 ½ minute) and then output stayed flat, with no sign of thermal regulation.

Batteries & Charging

The Nitecore P20i UV takes a 21700i battery. Note that little “i” there? That’s important. The P20i UV won’t take just any 21700. It needs to be Nitecore’s i-Series 21700 cell. While some proprietary cells I’ve seen recently have Neg ring around the Pos terminal, Nitecore takes it a step further: they do this at both ends of the cell. Kinda slick. But also very unique, very proprietary

Some people invariably dislike proprietary batteries, but I feel like Nitecore has a good business case for using one here. That dual-ended design serves multiple purposes:

  • Having both positive and ground at the tail enables helpful accessories like the TSL10i Signal Light and RSW2i USB-C Remote Switch without needing to rely on a dual-tube body design that have been known to cause reliability problems.

That said, if you’re in a pinch, Nitecore included a 2*CR123 adapter that you can use instead. Just know that you’re going to lose out on some output: High mode drops to 1100 lumens instead of the usual 1800 lumens.

The P20i UV has built-in USB-C charging. It’s great to see USB-C finally taking over on charging ports. And while the P20i UV ships with a USB-A to USB-C cable, it is compatible with USB Power Delivery (USB-C to USB-C) chargers. In testing, I observed a charge rate around 1.4A at 5.0V for 7.1 watts. Charging took 4 hours and 3 minutes.

I was able to carefully orient the Nitecore battery in my Vapcell S4+ charger. It fit just fine and charged as expected. If you try this, make sure you don’t short out the battery contacts on the charger contacts.

There’s a power indicator LED on the side of the head. While the flashlight is on, it’ll shine steady when the battery is above 50%. It’ll flash slowly below 50% and flash rapidly below 10%. But wait, there’s more! When you insert the battery or remove the charging cable, the power indicator LED will blink out the actual voltage just like what you’d see with Anduril. For a 4.2V battery, it’ll blink 4 times, pause, and blink 2 times. Nice!


Lux was measured by a UNI-T UT383 BT at 10 meters. Lumens were measured in a homemade lumen tube using a TSL2591 sensor, calibrated with a Maukka calibration light. Testing was performed with the included battery.

Runtime graph

High mode started out at 1785 lumens and was still at 1699 lumens by 30 seconds. Between 1 ½ minutes and 3 ½ minutes there was what appeared to be a timed ramp-down to 603 lumens. After the ramp-down, the temperature hovered around 46°C (later topping out at 49°C). While Nitecore says the P20i UV has ATR, I saw no sign of it in this test: while the light didn’t get very hot, it seemed to be operating on a timed control basis rather than a thermal basis. The runtime to 10% of output was measured at 2 hours and 45 minutes, a full hour longer than spec.

The Medium mode was fairly uneventful. It started out at 193 lumens and stayed there until low voltage protection started kicking in. The light never got hot, staying around 29°C. It took 11 hours and 23 minutes to reach 10%, nearly 3 hours longer than spec.

Lumen measurements (for each mode)

  • Low: 32 lm
  • Medium: 193 lm
  • High @ 0 sec: 1785 lm
  • High @ 30 sec: 1699 lm
  • High @ 10 min: 603 lm 

Throw numbers: 

  • High: 29,400 cd = 343 m / 375 yd


  • Beam shots of the building are taken at 15 m (16 yd) using a Pixel 3 set to ISO 200 with 1/10 second exposure time
  • Beam shots of the playset are taken at 30 m (33 yd) using a Pixel 3 set to ISO 200 with 1/2 second exposure time. The trees in the background are around 65 m away.
  • Nitecore P20i UV
  • Sofirn SP35 (SST-40 6500K)
  • Astrolux EC01 (SST-40 5000K)

UV Testing

Of course the big selling point of the P20i UV over the regular P20i is the addition of UV capabilities. Nitecore went with 365nm, which is typically a good choice for UV fluorescence. To see just how good the UV performance is, I lined up a few US $20 bills and used 3 different UV lights to get the security strips to fluoresce. About each light (in order of appearance, top to bottom):

  • Wuben E19UV: uses a single SMD LED with 365nm wavelength and filter/bandpass lens, total output of 850mW
  • Nitecore P20i UV: uses four 5mm LEDs with 365nm wavelength, total output of 320mW
  • Olight i3UV EOS: uses a single SMD LED with 395nm wavelength, total output of 350mW

So what can be seen in comparing the UV performance?

  • The Wuben E19UV performs amazingly well. The 365nm high output filtered light brightly fluoresces the security strip and little else.
  • The Nitecore P20i UV does a fair job of causing the security strip to glow, thanks to its use of 365nm. The lack of a UV bandpass filter allows visible light to be emitted in addition to UV, thus lighting up the entire $20 bill. Part of this is because the UV LEDs actually excite the phosphor of the primary LED and cause it to emit white light.
  • The Olight i3UV EOS didn’t fare as well. Its 395nm UV did a poor job of revealing the security strip.

Disclaimer: This flashlight was sent to me for review at no cost by Nitecore. I have not been paid to review, nor have I been holding back on problems or defects.

Final Verdict


  1. Solidly built
  2. Very bright
  3. Good beam
  4. Two UI choices
  5. USB-C charging
  6. Great kit and available accessories
  7. 365nm UV light


  1. Timed ramp-down
  2. UV in normal mode rotation
  3. Questionable clip and lanyard
  4. Proprietary battery
  5. No shortcut to low

Explanation on star ratings:

1: Avoid: my phone flashlight would be a better choice – 2: Poor: significant defect or issues, much better options available at the same price – 3: Average: some defects or issues – 4: Good: recommended (minor issues) – 5: Great: highly recommended

Reviewer Gabriel
Author: Gabriel

4.5 stars: ★★★★⋆

When put up against other tactical / mixed use lights, the P20i UV holds its ground. It has Nitecore’s proven build quality. With all of the included items and available accessories, it’s very versatile. I like the nice clean beam from the Luminus SST-40 LED. Choice of UI (Daily/Tactical) and USB-C charging are great inclusions. The driver has excellent regulation and good mode spacing. Runtimes even greatly exceeded Nitecore’s specifications.

There’s something I’m just not sure about, though, and it’s what is supposed to make the P20i UV special. The addition of UV LEDs can be pretty handy. But without a filter, these ones emit enough white light to be distracting. They are useful if you want to check some currency or casually look around for substances that would fluoresce under UV light. And for the $10 premium over the normal P20i, I think they’re probably worth it. If you routinely rely on clean and clear UV, you might still want a dedicated light. In short, I think they’re handy, but not a replacement for a high-quality UV light.

When it comes down to it, the Nitecore P20i UV takes an already great light (the P20i) and adds on even more features for barely any more money and that’s certainly nothing to complain about!

Nitecore P20i UV discount coupon code

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1lumen selects and reviews products personally. We may earn affiliate commissions through our links, which help support our testing.