Nitecore E4K Flashlight Review

Nitecore recently announced a pocket monster output light – a 21700 quad, which has a claimed output of a massive 4400 lumens.  Read on for some testing!

Official Specs and Features

Here’s a link to the official product page.


Just one version

Price and Coupon

Going price is $89.95 on (referral link).

Short Review

This light REALLY puts out some lumens, if briefly.  I like the big switch, too.  I don’t care for the UI one bit, but this one’s recycled from another light where I didn’t like the UI, too.

Long Review

The Big Table

Nitecore E4K
Emitter: Cree XP-L2 (x4)
Price in USD at publication time: $89.95
Buy it with this referral link!
Cell: 1×21700
Turbo Runtime High Runtime
LVP? Switch to Low
Switch Type: E-Switch
Quiescent Current (A): ?
On-Board Charging? Yes
Power off Charge Port with no Cell?
Claimed Lumens (lm) 4400
Measured Lumens (at 30s) 915 (20.8% of claim)*
Candela per Lumen 3.2
Claimed Throw (m) 211
Candela (Calculated) in cd (at 30s) 151lux @ 4.642m = 3254cd
Throw (Calculated) (m) 114.1 (54.1% of claim)*
All my Nitecore reviews!
  • Measurement disclaimer:  I am an amateur flashlight reviewer.  I don’t have $10,000 or even $1,000 worth of testing equipment.  I test output and such in PVC tubes!!  Please consider claims within 10% of what I measure to be perfectly reasonable (accurate, even).

  • This 915 measurement is just after the stepdown.  The light does hit the rated 4400 lumens and much higher, but not at 30 seconds, unfortunately.

What’s Included

  • Nitecore E4K Flashlight
  • Nitecore 5000mAh 21700
  • Nylon Pouch
  • Pocket Clip
  • Spare o-ring
  • Lanyard
  • Charge Cable (USB to USB-C, for the cell!)
  • 21700 to CR123Ax2 adapter
  • Manual

Package and Manual

Build Quality and Disassembly

Solid quality here.

There’s minimal finning in the head, but the light steps down quickly enough to prevent getting too hot.  I’d much rather some heat but 1 minute or more on the highest output.

Knurling on the body is good.

Knurling on the tailcap is even better.  The tailcap is what gets removed for swapping cells.  This knurling helps greatly.

The threads are square cut, anodized and lubed, but very long.  Lots of twisting required.  And the pocket clip makes this annoying.

Big beefy spring on the tailcap, but just a brass button on the positive contact.

Size and Comps



Basically the same length as a Convoy s2+, but a good bit thicker.

Retention and Carry

A standard nylon pouch is included.  The light will fit in either orientation.

Also included is a friction fit pocket clip.

It’s not reversible, allowing only bezel down carry.

Power and Runtime

The E4K runs on this included 5000mAh 21700, which has built-in USB-C charging.  An 18650 can be used, as well as CR123x2.

The cell is a customized Nitecore cell, with their name on the bottom, and a specialized hexagonal button.  It is not a proprietary cell.

Looks like in the photo below there’s a lot of wiggle room for the cell, but there isn’t.  When the tailcap is tightened down fully on a cell, the indicating switch shows the cell voltage.  It blinks the actual voltage.  Three blinks followed by pause, then 2 blinks = 3.2V.  If the light is off, and you wish to check the cell voltage range, click the switch.  It’ll indicate much more generically:

Three flashes: >50% power
Two flashes: <50% power
One flash: <10% power

Also included is this 21700 to CR123Ax2 adapter.

Here’s a runtime on Turbo.  Not that I want the light to cheat for specs, but I’d really like for the initial output to hold on just a little bit longer.  At startup, it’s practically 5000 lumens!  At… maybe 26 seconds, it’s around 4400 lumens.  Then it falls right off.

High doesn’t have this massive stepdown, though, and holds over 1200 lumens for just under 2 hours!

In both tests, the light just stepped down VERY low but didn’t shut off.

The included cell has built-in charging.  It’s a USB-C port.

Nitecore includes a cable – USB to USB-C.

Here’s a couple of charge cycles.  Charging looks fine.  USB-C to USB-C does not work.

Modes and Currents

Mode Mode Claimed Output (lm) Claimed Runtime Measured Lumens Tailcap Amps
Turbo 4400 30m 915* 12.50
High 1050 3h15m 1246 2.24
Mid 320 7h30m 362 0.55
Low 50 45h 74 0.13
UltraLow 2 700h 0.02
  • After the massive stepdown!

Pulse Width Modulation

No pwm.

For reference, here’s a baseline shot, with all the room lights off and almost nothing hitting the sensor.  And here’s the worst PWM light I have ever owned.  Also one of the very first lights I ordered directly from China!

User Interface and Operation

There’s a single switch, on the head.  It’s an indicating e-switch.  I like that it’s bigger than most switches like this.  There’s a silicone cover.

The indication can be seen below.

Here’s a UI table!  There are two mode groups.  They’re the same except where mentioned!  Switching between them is easy.  Turn the light off and loosen the tailcap.  While holding the switch, tighten the tailcap.  The light will flash once for Daily and twice for Tactical mode.

State Action Result
Off Hold On (Mode Memory), and mode advance through modes*
Off Double Click UltraLow
On Hold Turbo
On Triple Click Strobe
Strobe Hold Strobe Group Advance (Strobe>SOS>Beacon)
On Click Off
Off Triple Click Daily Mode: Turbo
Tactical Mode: Strobe
  • Advancing through the modes… must be done from a “light is off” state!  So you want medium, and High is the last used mode, you turn the light on to high (by holding) and keep holding through Turbo, the two lows, then medium.  There doesn’t seem to be another way.  You can double click to ultra low then advance from there…  It’ll still go to memory.

LED and Beam

There are four emitters in this light – a quad.  They’re Cree XP-L2, and they each have their own tiny smooth reflector.  My emitters aren’t all that well centered in the reflector, but I don’t think this affects the beam shape much if any.

These beamshots are always with the following settings:  f8, ISO100, 0.3s shutter, and manual 5000K exposure.

Tint vs BLF-348 (Killzone 219b version)

I compare everything to the Killzone 219b BLF-348 because it’s inexpensive and has the best tint!


What I like

  • Cell is included
  • Massive output for a short while
  • Nice big switch
  • Access to Ultralow from off
  • Respectable price from Nitecore

What I don’t like

  • Emitter Temperature and tint
  • Doesn’t stay at 4400 lumens for long
  • The UI is not a good UI


  • This light was provided by Nitecore for review. I was not paid to write this review.
  • This content originally appeared at  Please visit there for the best experience!
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