The Cyansky P20 is a dual switch 18650 flashlight, utilizing a Luminus SST-40 and claiming 1600 lumens!  It’s a nice package to offer so much!

Official Specs and Features

I can’t yet find this on any official channels, so no link to the official product page.


There’s just this one version.  You might note, however, that the P20 and P25 are extremely similar.  The main way they differ is that the P20 is an 18650 light, and the P25 is a (seemingly more current) 21700 light.  As such, much of the text will be similar.  You might like to see the Cyansky P25 review which can be found here.


Price is not public yet, as I can’t find it for sale.

Cyansky P20 18650 Flashlight Short Review

Depending on price, this could be a real winner.  Either way, it offers a nice package.  Cell is included, dual switch interface, good output…  If inexpensive, it’s a nice contender!

Long Review

The Big Table

Cyansky P20 18650 Flashlight
Emitter: Luminus SST-40
Price in USD at publication time: ?
Cell: 1×18650
Turbo Runtime Graph High Runtime Graph
Switch Type: Both
Quiescent Current (mA):
On-Board Charging? Yes
Charge Port Type: micro-USB
Charge Graph
Power off Charge Port
Claimed Lumens (lm) 1600
Measured Lumens (at 30s) 1550 (96.9% of claim)*
Candela per Lumen 11.8
Claimed Throw (m) 240
Candela (Calculated) in cd (at 30s) 1751lux @ 3.392m = 20146cd
Throw (Calculated) (m) 283.9 (118.3% of claim)*
All my Cyansky 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).

What’s Included

cyansky p20 18650 flashlight what's included

  • Cyansky P20 1600 Lumen Flashlight
  • Cyansky 2600mAh 18650
  • Charge cable (USB to micro-USB)
  • Nylon pouch
  • Lanyard (seen below)
  • Spare clicky cover (seen below)
  • Spare o-ring (seen below)
  • Manual and papers

Package and Manual

cyansky p20 18650 flashlight manual

Build Quality and Disassembly

cyansky p20 18650 flashlight

The finish – the anodizing, that is – feels great in hand.  Some mix of not quite matte, not quite glossy, that ends up being just right.

cyansky p20 18650 flashlight emitter

From the top down, you can see the light below.  First is the tailcap (because we’re headstanding here!).  Notice that the grip is exactly the opposite direction from what you’d want.  It doesn’t add any grip at all!

cyansky p20 18650 flashlight tailcap

Here’s the body, which has the brand name and model number.  This font is… not a font I’d pick for [basically anything].  The font looks a bit of an afterthought.

cyansky p20 18650 flashlight body

cyansky p20 18650 flashlight pocket clip

The head end has the same grip style as the tail, so at least the design language is transferred.

cyansky p20 18650 flashlight e-switch

cyansky p20 18650 flashlight head

When headstanding, no light escapes because the front is flat with no reliefs.

cyansky p20 18650 flashlight head

The tailcap, which again doesn’t have good grip for removal.  The threads here are very nice.  Square cut, very light lube, anodized, and not too long.

cyansky p20 18650 flashlight tailcap removed

A beefy spring is inside the tailcap.  The aluminum ring should provide good access if you need to use the spare switch boot.

cyansky p20 18650 flashlight tailcap spring

Here you can see into the cell tube, to the head.  There is no spring on the head, just a brass button.

cyansky p20 18650 flashlight inside tube

Surprisingly the bezel is easy to remove.  It’s threaded differently from the tailcap, so you won’t swap the two accidentally.

cyansky p20 18650 flashlight bezel removed

This provides easy access to the emitter.

cyansky p20 18650 flashlight bezel off showing emitter

Size and Comps

Officially the Cyansky P20 18650 flashlight is 25.6mm (head diameter), 24mm (body diameter), 133mm (length) and a weight of 74 grams (without cell).

If a light will headstand, I’ll show it here (usually the third photo).  If a light will tailstand, I’ll show that here, too (usually the fourth photo).

Here’s the test light with the venerable Convoy S2+.  Mine’s a custom “baked” edition Nichia 219b triple.  A very nice 18650 light.

And here’s the light beside my custom engraved TorchLAB BOSS 35, an 18350 light.  I reviewed the aluminum version of that light in both 35 and 70 format.

cyansky p20 18650 flashlight beside torchlab boss 35

Retention and Carry

Included, and attached from the factory, is a friction fit belt or pocket clip affording bezel down carry only.  This isn’t a deep carry clip, but due to the length of the light, it’s balanced fine.

Clip hug!

cyansky p20 18650 flashlight pocket clip hug

Included with the P20 is a nylon pouch.  The light will go into the pouch head up or down, but can’t be used while in the pouch.

There is a lanyard which I seem to have failed to photograph.  Here’s the (same) one from the P25.

Cyansky P25 Flashlight lanyard and stuff

There are two holes in the tailcap for receiving the lanyard.  One hole here would have sufficed – the light will not tailstand anyway.

cyansky p20 18650 flashlight

Power and Runtime

The Cyansky P20 is powered by a single lithium ion cell.  Cyansky includes an appropriate cell – a 2600mAh 18650, the BL1826U.

cyansky p20 18650 flashlight 18650

As far as usage goes, this is a standard button top 18650.  It has some additional features, which I’ll cover below.


The cell fits into the P20 in the usual way – positive terminal toward the head.

cyansky p20 18650 flashlight 18650 installed

Here are a few runtimes.  Performance is not at all dissimilar to all the other Cyansky lights I’ve reviewed.  I think these may share a driver.

cyansky p20 18650 flashlight runtime graph turbo cyansky p20 18650 flashlight runtime graph high

cyansky p20 18650 flashlight runtime graph medium

I did not observe low voltage protection.  The light does shift down to a very low output, though, at around 20 lumens.


As stated, the cell has some other features too.  There’s built-in micro-USB charging, by way of a micro-USB port on the positive terminal end.

cyansky p20 18650 flashlight charge port on cell

Another feature is a little indicating LED right in the positive terminal of the 18650.  When charging, this indicator is red.  When charging is complete, the indicator is green.  Otherwise, the indicator is not on at all.

An appropriate cable is included – USB to micro-USB.

Charging proceeds at a fairly slow 1A or so, which is well under 0.5C for this 2600mAh cell.  Time required is around 3.5 hours, and the terminal voltage seems to be around 4.18-4.19V.

cyansky p20 18650 flashlight charge graph

Modes and Currents

Mode Mode Claimed Output (lm) Claimed Runtime Measured Lumens Tailcap Amps
Turbo 1600 1.5h 1550 4.61
High 650 3h 647 1.25
Medium 200 8h 208 0.34
Low 10 150h 0.01

Pulse Width Modulation

No modes utilizes pulse width modulation.

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

Two switches are used for control of the Cyansky P20.  First is the mechanical tail clicky.  It’s a forward clicky, which allows momentary actuation.  This switch also serves as a mechanical lockout to prevent any parasitic drain on the cell.

cyansky p20 18650 flashlight tailcap switch

The switch cover is big but the switch itself is normal sized.  It’s not terribly thick, so you can feel the actual switch underneath.  The clicky is very clicky and the action is low.

The switch is also very proud.  It completely prohibits tailstanding.

cyansky p20 18650 flashlight tailcap switch profile

The second option for operation is the e-switch on the side near the head. This switch is metal(ish?) and very proud.  Also it doesn’t compete with anything else, so it’s very easy to find without looking.

cyansky p20 18650 flashlight e-switch

cyansky p20 18650 flashlight e-switch

The user interface is not complicated.

Here’s a UI table!

State Action Result
Off Click Tail Switch On (last used mode, except strobe)
Off Tap Tail Switch Momentary (last used mode, except strobe)
On Click Tail Switch Off
Off Click Side Switch No action
On Click Side Switch Mode advance L>M>H>T
On Hold Side Switch Strobe (the manual doesn’t cover this!)
Strobe Click Side Switch Return to previous mode

LED and Beam

Cyansky ha sopeted to put a Luminus SST-40.  A color temperature is not stated, but based simply on the image below, you can probably guess it’s cool white.

cyansky p20 18650 flashlight emitter

The emitter is accessible after removing the bezel, too.

cyansky p20 18650 flashlight emitter revealed

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

Tint vs BLF-348 ( 219b version) (affiliate link)

Test light is on the left!

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


What I like

  • Complete package light
  • Good (and simple) dual switch interface
  • Included cell with micro-USB charging
  • Fairly flat output of nearly 900 lumens for around an hour and a half (!!)

What I don’t like

  • Cool emitter
  • No tailstanding
  • Charging is micro-USB instead of USB-C


  • This light was provided by Cyansky for review. I was not paid to write this review.
  • This content originally appeared at  Please visit there for the best experience!
  • For flashlight related patches, stickers, and gear, head over to PhotonPhreaks, another site where I write!
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