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  • Stephen Knight

Flashlight Review: Convoy S21E 519A

Updated: Jul 4, 2023

The Convoy S2+ has been one of the most popular flashlights/torches for nearly a decade. Many people have asked for a version with USB charging and side e-switch. Convoy have answered this with the 21700 format S21E.


The Convoy S21E was purchased with my own funds. This review is written from the perspective of a light painting / night photographer and flashlight enthusiast.

The Convoy S21E is a 21700 tube light with side switch.
The Convoy S21E is a 21700 tube light with side switch.


The Convoy S21E is a compact 21700 battery sized tube light, with a side e-switch and USB-C charging port near the head. The diameter is 3mm wider than the popular Convoy S2+ at 27.3mm, and the length is marginally shorter than the S2+ at 116.4mm. Both the head and tail sections can unscrew, and there are springs at both ends of the battery tube. Waterproof rating is IPX4, so it should be splash proof. At the time of writing, the price was US$20.50 without battery, and US$24.80 with battery.

The light arrived in the usual Convoy minimalist packaging - soft cardboard and bubblewrap. For a light that comes with an optional 21700 battery (inside the light), and has USB charging circuits, etc, this is inadequate, and may have contributed to the dented battery. I would pay a few $ more for more protective packaging. A side clip and lanyard are included.

The light has options for Nichia 519A (tested), and Luminus SST-40 and SFT-40 emitters, with a 6A LED driver. These provide choice a between a floody high-CRI beam with good output, or low-CRI floody/throwy combination beam with even more output. The 519A version uses an orange peel reflector, and the others a smooth reflector.

The S21E includes USB-C charging input and internal charging at up to 2A, something that has generally been lacking on compact Convoy flashlights. The rubber charging port flap fits well, and is easy to press back in place. The S21E's charging worked with both USB-A to USB-C and USB-C to USB-C cables. During charging the side switch glows red, and once charging has terminated it glows green. The light is off during normal flashlight use. Charging terminated at 4.18V which is acceptable. Personally I prefer to use dedicated analysing Li-ion chargers such as the Vapcell S4 Plus, but internal charging is very useful when traveling.

The S21E optionally comes with an Liitokala 5000mAh 21700 unprotected Li-ion battery, which costs just $4 extra, and can easily handle the 6A max current. I am not sure of the OEM manufacturer of this battery. Unfortunately, the battery that arrived with my sample had a dented positive pole. I don't know if this was damaged in transit (as per packaging concerns), or whether it was poor QC by Liitokala? Speaking with other flashlight enthusiasts, it seems that this dent should be acceptable, and Convoy did offer a refund if I deemed the battery to not be acceptable. If I order more S21E, I will most likely purchase without the 21700 battery and buy a 5000mAh 21700 (such as a Samsung 50E) closer to home.

For light painting / night photographers - whilst this light fits in most light painting connectors, the side switch is not accessible. This light is however very useful for the illumination genre of light painting (i.e. lighting things up), where it excels. The light fits in U-shaped tripod mounts, and has compatibility with the Convoy S21A/B diffuser. The light is not suitable for use with backlight scanners - check out the Convoy S21D for that!

Update 22/03/2023 - the Convoy S21E is now available in 5 different body colours - black, blue, orange, green, red.

The Convoy S21E uses 21700 Li-ion batteries.
The Convoy S21E uses 21700 Li-ion batteries.

Size comparison L to R - Emisar D4V2, Convoy S2+, Convoy S21E, Convoy S21D.
Size comparison L to R - Emisar D4V2, Convoy S2+, Convoy S21E, Convoy S21D.

The Convoy S21E with head and tail unscrewed.
The Convoy S21E with head and tail unscrewed.

LED Driver Board (battery side)
LED Driver Board (battery side)

The Convoy S21E has USB-C charging.
The Convoy S21E has USB-C charging.

Dented positive pole of Liitokala 5000mAh 21700 battery.
Dented positive pole of Liitokala 5000mAh 21700 battery.

User Interface

The S21E uses a side e-switch. This is my preferred switch location for lights used for illumination purposes as it is more ergonomic, and there is less chance of water ingress if the light is tail standing in shallow water, puddles, or damp ground.

The S21E uses Convoy's e-switch user interface (as seen on the M3-C and M21D/E/F), which has a good compromise between functionality and ease of use. Instructions are provided on the product page. It is possible to use ramping brightness, or change to stepped brightness (1%, 10%, 40%, 100%) with last mode memory. These brightness levels are well spaced. Moonlight mode (0.2%) is available, as is 100% only Tactical mode, and Lockout. As night photography requires consistency, I prefer to use the stepped brightness mode. The ramping is a bit too fast at lower brightness levels in my opinion. There is a 10Hz strobe, accessed with a triple click. The clicking required to change settings, such as 6 clicks from ramping to stepped brightness needs to be done very quickly.

As well as electronic lockout to prevent accidental activation, the light can be mechanically locked out by slightly unscrewing the tail cap. It should be noted that last mode memory resets to low mode when the light is mechanically locked out.

The Convoy S21 uses a side e-switch.
The Convoy S21E uses a side e-switch.

Optics, Output, and Runtime

The tested Convoy S21E uses the Nichia 519A LED, which I recently reviewed in the S2+. This LED is very impressive as it has excellent colour rendering at >95CRI / R9080, a neutral tint (no significant green or magenta shift), and decent output for a high-CRI LED. The 519A emitter is available in an amazing 7 different CCTs from Convoy from warm to cool white - 2700k, 3000k, 3500k, 4000k, 4500k, 5000k, and 5700k. Whilst >95CRI LEDs are common on LED panel lights, most flashlights manufacturers well behind the times. At the time of writing, only Convoy, Noctigon, Emisar, Fireflies, and Acebeam offer multiple EDC flashlights with 95CRI emitters. The likes of Nitecore, Fenix, Olight, and Klarus are still stuck in the dark ages when it comes to CRI, with "horrible" washed out <70CRI cool white beams.

This light is also available with the high output, but <70CRI SST-40 emitter in 5000k or 6500k, and the more throwy <70CRI SFT-40 emitter in 6500k. There is no lack of competing low-CRI flashlights, though Convoys are generally excellent value for money compared to alternatives.

The S21E uses a single 519A LED emitter in an orange peel reflector. There is a diffuse hotspot, and the spill beam angle is 95 degrees. I prefer this wider spill beam compared to than the S2+'s narrower spill beam. Since March 2023 - a 60 degree TIR optic version with a much floodier beam is also available. The default lens is purple anti-reflection (AR) coated, which slightly changes the tint towards green. I prefer the green AR coated lens option to be standard as slightly changes the tint towards magenta. However, the tint is still impressively neutral compared to the Samsung LH351D 5700k, and even that isn't excessively green (nowhere near the SST-20/40 "wall-o-green"). Below are the results on testing 3 versions of the Convoy S21E for CCT/colour temperature, CRI Ra, and tint DUV with an Opple Lightmaster 3 Pro. Hotspot measurement on 40% mode.

  • 2700k green AR lens - 2681k 97.9Ra +0.0010 DUV

  • 5700k green AR lens - 5147k 98.1Ra -0.0013 DUV

  • 5700k purple AR lens - 5157k 98.3Ra +0.0018 DUV

Convoy S21E 519A 5700k with Green AR Glass
Convoy S21E 519A 5700k with Green AR Glass

The LED driver is a 6A driver, which is 20% more max current than the 5A driver in the S2+. With the 519A emitter, this would in theory only provide around 10-15% more max lumens, as lumens/watt is starting to level off at this current, and my testing generally accepts that theory.

Tested brightness levels (+/- 10% margin of error) at 30 seconds, with the 519A 5700k emitter:

  • 100% - 1,150lm

  • 40% - 530lm

  • 10% - 210lm

  • 1% - 20lm

On 100% mode, maximum brightness was sustained for 35 seconds, followed by a gradual decrease to 590 lumens by 150 seconds, where output stabilised, with only a small reduction in brightness during the rest of the runtime. With a 4000mAh Samsung 40T 21700 battery, low voltage warning (red flashing switch and brightness stepdown) kicked in at 97 minutes. With a 5000mAh battery I would expect an approximate 120 minute useable runtime, that's 40 more minutes than the S2+ with a 3500mAh 18650. As is traditional with Convoy S series lights, this light runs very hot (thermal throttling is generally set to 55C). I hope the battery charging electronics can handle this!

No PWM was visible during testing, though my phone camera detected some waveform rippling.

The Convoy S21E 519A has a shallow orange peel reflector.
The Convoy S21E 519A has a shallow orange peel reflector.

Beam comparison L to R (Nichia 519A 5700k) - Convoy S21E, Convoy S2+, Convoy S21D (60 degree).
Beam comparison L to R (Nichia 519A 5700k) - Convoy S21E, Convoy S2+, Convoy S21D (60 degree optic).

Outdoor beam shot - 100% brightness - f/5.6, 1.6secs, ISO400.
Outdoor beam shot - 100% brightness - f/5.6, 1.6secs, ISO400.

Photographed using three Convoy S21E flashlights with diffusers - 2x 2700k, 1x 5700k.
Photographed using three Convoy S21E flashlights with diffusers - 2x 2700k, 1x 5700k.



  • Excellent value for money.

  • Excellent colour rendering 95CRI/R9080 and neutral tint.

  • Good sustained output and runtime.

  • Excellent range of 7 CCT options from warm to cool white.

  • USB-C charging and (optional) included battery.

  • Side e-switch with stepped or ramping brightness, with last mode memory (note: unscrewing the tail cap resets last mode memory).

  • Diffuser and tripod mounting options.

  • Mechanical or electronic lockout for safety.


  • Ramping brightness is too fast at lower brightness levels.

  • Included battery had a dented positive pole.

  • Packaging is inadequate.

Various iterations of the excellent Convoy S2+ have been my "go to" light for low to medium brightness night photography illumination for the last 7 years. The Convoy S21E with the 519A emitter has finally knocked the S2+ off its perch! It is slightly larger, heavier, and pricier than the S2+, but the small increases in max and sustained brightness, longer runtime, ergonomic side switch, flexible user interface, optional included battery, and USB-C charging make up for this.

Can it be improved? I would like to see a green anti-reflective lens to slightly lower the DUV/tint towards magenta - note: this is now an option at Convoy Flashlight Store on Aliexpress, add an "order comment" during purchase. I would also like to see better packaging, that hopefully prevents more instances of dented batteries. I would purchase 21700 batteries separately.

If you need a big step up in maximum and sustained high-CRI lumens, in a slightly larger flashlight, also consider the excellent Convoy S21D 8A CC with 519A emitters (noting it has a tail switch and no USB charging).


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