Nitecore NU25 UL

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Nitecore NU25 UL specifications

Brand & Model	Nitecore NU25UL
Flashlight category	Headlamp
LED	5500k dual LED + Red LED
Max. output	400 lumens
Max. beam distance	64meters
Max. beam intensity	1029cd
Battery config.	650mAh In-built Li-ion
Onboard charging	Yes
Modes	3 x 3 + 1 for primary LEDs + Red LED
Blinkies	Hidden
Waterproof	IP66
Review publication date	January 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

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.

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

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: 

Nitecore NU25 UL	Millimeters	Inches
Length	60.1mm	2.37in
Height	36.8 mm	1.45 in
Depth	25.5mm	1 in

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

Weight: 

Nitecore NU25 UL	Weight in grams	Weight in oz
With battery & headband	56 g	1.98oz

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

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 

Shortcuts:

To Low: Yes

To Strobe: Yes

Low voltage warning:

• Battery meter

Strobe/blinkies

• Yes

Lock-out mode: 

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

PWM

None that I can detect. Nitecore claims constant current.

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.

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

Mode	Amps at start	Specs	turn on	30 sec	10 minutes
High – Dual LED	Fully charged	400 lumens	370	356	138
High – Spot LED	Fully charged	200 lumens	173	172	69
High – Flood LED	Fully charged	200 lumens	231	230	92

Parasitic drain:

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

Battery Life: Runtime graphs

Mode	Specified runtime	Measured runtime ANSI	Time till shut off
High – Dual LED	2h 40 mins	2h 04 mins	3h 06 mins
High – Spot LED	4h 15 mins	5h 23 mins	5h 40 mins
High – Flood LED	4h 15 mins	4h 43 mins	5h 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

Mode	Specified	Candela measured	Meters	Yards
High	64m @ 1029cd	1225cd	70m	76.5yd

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.