Nitecore NU25 UL

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Nitecore NU25 UL review: lightweight headlamp

Nitecore NU25 UL specifications

Brand & ModelNitecore NU25UL
Flashlight categoryHeadlamp
LED5500k dual LED + Red LED
Max. output400 lumens
Max. beam distance64meters
Max. beam intensity1029cd
Battery config.650mAh In-built Li-ion
Onboard chargingYes
Modes3 x 3 + 1 for primary LEDs + Red LED
Review publication dateJanuary 2023


Note: most of the following review was copied from the Nitecore NU25 review, which is the same headlamp except for the head strap.

The Nitecore NU25 UL is part of Nitecores dual beam lightweight headlight series. Its sister light the NU25 which uses the same main components with a slightly different headband and slightly different bracket to cater for the different headband.

The NU25 UL, the UL I presume stands for Ultra Lightweight, is part of a new breed of in-built Li-ion battery powered headlamps. Some will always prefer user replaceable batteries, but you can’t deny the packaging benefits of in-built battery setups.

The NU25 UL is a feature packed, very compact and lightweight headlight that is sure to find many happy users. I know of a number of tasks I will happily put this headlight to the test.

Package quality.

The NU25 UL comes in full retail packaging with lots of info and a very professional premium look and feel to the packaging.

In the box you get:

  • The headlamp
  • Headband
  • Comprehensive user manual
  • USB charging cable

Flashlight in use

The Nitecore NU25 UL has a large and comprehensive set of modes and options. This is a dual beam headlamp, which means it has 2 x LEDs. But it is more than just two outputs. One LED is coupled to a floody TIR optic while the other TIR optic is designed more for throw.

This means you not only have multiple output levels, you can also have three different types of beam:

  • Flood
  • Spot
  • Combo

You can either have one LED or the other in use or both together. In all modes you also have differing output modes. This makes the headlight very versatile and gives the user easy ways to extend runtimes. Although maybe at the sacrifice of introducing a fairly complex and confusing user interface.

There is also a dual red LED mode too as well as some hidden blinky modes using either the red LEDs or the white ones.

One thing I really like about the NU25 UL is the shape and lightweight. It really is very little weight to have on your head and the shape of the unit is comfortable to wear. The main light is permanently fixed into a carrier holder that also allows you to tilt the light forward and down. It all feels very natural and easy to use.

The headband itself is very minimal, using a double elastic cord. This does keep the weight down, although I did find that on my hair (which is fairly long), that it did want to slip a bit.

The NU25 UL has two buttons, both located on the top of the unit. They are rubber switches and easy to locate and use. The larger switch is labeled with the universal power symbol and the small button says ‘Mode’. Both buttons are multi-function with single, multiple and click and hold actions.

Build Quality, and Warranty

There are no metal parts on the Nitecore NU25 UL, this is deliberate to keep the weight down. It appears to be mostly made of some kind of ABS plastic. It feels both durable and high quality. I have no concerns over the build quality, fit and finish appears to be superb.

The switches are rubber covered and there is a rubber cover that covers the USB port. Although I must admit, having opened the USB cover I have since been unable to get it to fully reseat again. The USB port is a type C and the cover is designed to go inside the socket as well as around it. Try as I might, I just can’t seem to get the rubber to align correctly. A minor annoyance and I doubt one that would cause any real issues.

Warranty wise, Nitecore offer a 15 day from purchase replacement service via an authorised dealer/distributor backed by a 24 month warranty beyond this

LED, Lens, Bezel, Beam, and Reflector

Nitecore doesn’t disclose much about the LEDs used in the NU25 UL. Their website does confirm they should be of 5500k which is a very nice kelvin level in my opinion. The beam is a nice crisp white with a nice neutral white tint.

Sadly there is no mention of CRI nor much info on the optics. The flood is claimed to be 100 degrees but I couldn’t find info on the spot beam. However, visually one can clearly see a difference between the two beam profiles.

The Red LEDs are also not specified on what brand they are, however they also have their own smaller optics and appear to be modern LEDs rather than the old 5mm style ones.The red beam is bright enough to be highly useful too.

My Opple light meter confirms the dual white LEDs have a CCT (k) value of 5409 and an Ra of 70.2, while the red LEDs have a 5002 CCT(k).

Overall the beam quality on any of the modes is superb. Being a headlamp close up illumination is likely a key requirement for many. The flood, combo modes and red LED all work really well for this with nice even illumination. If you are outside or needing more light at distance, it is nice to have the ability to use the spot beam also for extra beam distance. For me, the real key is being able to use these LEDs in isolation. While both will offer more lumens, they’ll also use more power. Switching to just a single LED should be an easy way to massively extend the runtimes.

Dimensions and size comparison


Nitecore NU25 ULMillimetersInches
Height36.8 mm1.45 in
Depth25.5mm1 in

Dimensions are rounded to the nearest millimeter, and to the nearest tenth of an Inch.


Nitecore NU25 ULWeight in gramsWeight in oz
With battery & headband56 g1.98oz

Weight is rounded to the nearest gram, and to the nearest tenth of an Oz.

Flashlight size comparison with its competition:

Group 1: Nitecore headlamps: Nitecore NU25 UL and Nitecore NU25 boxed

Group 2: Nitecore NU25 UL and Nitecore NU25

Driver & User Interface:

If I have any complaints with the NU25 UL it is the User Interface. You have two buttons to interact with, both located on top of the unit. One says Power, the other Mode. Which in principle sounds completely rational.

In practice however, both buttons seem to be able to turn the light on and off and both can change modes. But each button does different things from the other. This means you need to have a very good memory on which button to press at which time. I’ve found I have had to refer to the instruction manual many times and then still end up forgetting. This means each time you use the NU25UL it does feel a bit like trial and error.

A minor annoyance as you just end up clicking a few times to get what you want or end up just saying “whatever” and end up using a mode you might not have meant to have selected.

Available modes: 

In essence you have 3 output modes:

  • Low
  • Mid
  • High

Which the light cycles through. Although there is also a hidden Ultralow mode. Where it then gets a bit confusing is, you can also select One LED or the other or both and then have L-M-H for each of these. So your 3 modes have suddenly become 9, plus a hidden Ultralow. On top of this you also have hidden blinky modes and a lockout. But it doesn’t end there, you also have a dual Red LEDs too, which also have a blinky mode, although I’m not 100% sure how I have accessed this as it isn’t on the provided mode diagram in the instruction manual.

Ultimately I don’t think this is a deal breaker, but I’d defy anyone to be able to consistently turn it on to the mode & output you desire without getting it to do something you didn’t mean too.

Available blinky modes:

  • Yes, semi hidden.

Mode memory:

  • No 


To Low: Yes

To Strobe: Yes

Low voltage warning:

  • Battery meter


  • Yes

Lock-out mode: 

  • Yes – Click and hold both buttons for approx 2 secs to activate/deactivate lockout.


None that I can detect. Nitecore claims constant current.

Batteries & Charging

The battery is 650mAh in-built Li-ion, broadly equivalent to the power/runtime of a 14500 Li-ion cell. But being in-built the battery can be of a different shape, allowing the NU25 UL to be much smaller than it would be if it had used a 14500.

Personally I’m all for this. I know in the unlikely event of battery failing you probably can do little to restore the headlamp to working order. But the reality is, Li-ion batteries rarely fail. The weight saving and packaging benefits the in built battery brings cannot be dismissed.

The NU25 UL has a battery meter on the top of the unit by means of 4 blue LEDs, these will give you an indication of current battery level, which can be easily checked by pressing the Power button.

Charging is by means of a USB C cable. Once plugged in the blue lights will flash until all 4 are fully illuminated, indicated fully charged.

Performance test

As there are so many different LED and output combos on the Nitecore NU25 UL, I decided to simply measure the highest output using the combo beam.

I cannot guarantee my lightbox produces the same lumen numbers as the integrated spheres used at a commercial level. However the lumens I recorded are close enough for me to believe this light puts out the claimed figures.

Lumen measurements

ModeAmps at startSpecsturn on30 sec10 minutes
High – Dual LEDFully charged400 lumens370356138
High – Spot LEDFully charged200 lumens17317269
High – Flood LEDFully charged200 lumens23123092

Parasitic drain:

  • Due to the in-built battery, it is not possible to measure this.

Battery Life: Runtime graphs

ModeSpecified runtimeMeasured runtime ANSITime till shut off
High – Dual LED2h 40 mins2h 04 mins3h 06 mins
High – Spot LED4h 15 mins5h 23 mins5h 40 mins
High – Flood LED4h 15 mins4h 43 mins5h 35 mins

ANSI FL1 standards: The runtime is measured until the light drops to 10% of its initial output (30 seconds after turning on). This does not mean that the flashlight is not usable anymore. The last column shows how long the light actually works till it shuts off. If there is a + symbol, it means that the test was stopped at that particular point, but the light was actually still running. This happens on certain occasions, with certain drivers, firmware, or batteries.

Peak beam intensity and beam distance measurements

ModeSpecifiedCandela measured MetersYards
High64m @ 1029cd1225cd70m76.5yd

Extra info: Peak beam distance according to ANSI FL1 standards: The calculated value of distance in meters at which the flashlight produces a light intensity of 0.25 lux. (0.25 lux is about the brightness of a full moon shining on an object). The columns ‘Meters’ and ‘Yards’ use rounded numbers.


Camera settings and distance: Canon EOS 200D – Canon 18-55mm EFS IS – 2”/F6.3/ISO 400/WB 5200k “Daylight”

As the NU25 UL is quite floody overall, even including the spot beam. I decided to do some fairly close up beam shots to show the beam profile options. The subject is approx 2 metres away from the light source.

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. Lightweight design
  2. Compact dimensions
  3. Multiple beam types
  4. Battery meter


  1. Slightly complex UI
  2. Headband a little slippery at times

Explanation on star ratings:

1: Avoid: a match would be a better choice – 2: Poor: significant defect or issues; almost unusable – 3: Average: some defects or issues; but still usable 4: Good: recommended (minor issues) – 5: Great: highly recommended

Author: Matthew

4 stars: ★★★★

The NU25 UL is a really compact and lightweight headtorch. For me this is ideal, as the times I want a headtorch are when I’m crawling under the car or maybe when in the loft (attic) going up and down a ladder. Having something that you hardly notice on your head, but that offers a nice beam and tint is very handy in my book. As for the in-built battery, I have no problems with this at all and I suspect it is the future of lights like this.

The only things I didn’t love about the NU25 UL are the User Interface, it is perfectly usable, just a little frustrating at times. And the headband did tend to slip on my hair a bit, but not to the point that I wouldn’t use it.

Nitecore NU25 UL discount code

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