Convoy S21A B35AM Flashlight Review

The Convoy S21A B35AM flashlight is my first Nichia B35AM emitter flashlight! This is the best way to get a B35AM, and you do need one!

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Official Specs and Features

Here’s a link to the Convoy S21A (B35AM) flashlight product page.

Versions

As with most Convoy flashlights, the Convoy S21A 21700 flashlight is available with many options. The specific listing is a 4500K Nichia B35AM emitter, but there are two CCTs available: 6500K and 5000K (seen here). Many other emitter options are available (and probably custom options if you ask).

There are also two user interface options: 12 groups (seen here) and 4 modes. Also available are many body colors, but not Convoy’s full range. Just Green, Orange (seen here), Purple, and Red (at the time of writing).

Price

When the S21A flashlight becomes available again (probably soon), it’ll be $22.35. Right now, Simon and the whole Convoy Store are on break forthe Chinese New Year. That should wrap up soon. So despite these saying “out of stock” or whatever, they’ll be ready soon! You can buy the Convoy S21A B35AM here!

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Short Review

There are a few reasons to buy this light (that is, instead of something like the S2+, which everyone should have anyway). The larger mass should deal with heat better, and give a higher output for at least a little longer. Most importantly, this is a great way to try out the Nichia B35AM emitter!

Long Review

The Big Table

Convoy S21A B35AM Flashlight
Emitter:	Nichia B35AM (4500K, High CRI)
Price in USD at publication time:	$22.35
Cell:	1×21700
100% Runtime Graph	100% Runtime Graph
LVP?	Warning, then off
Switch Type:	Mechanical
On-Board Charging?	No
Claimed Lumens (lm)	1500
Measured Lumens (at 30s)	1019 (67.9% of claim)^
Candela per Lumen	10
Claimed Throw (m)	–
Candela (Calculated) in cd (at 30s)	383lux @ 4.898m = 9188cd
Throw (Calculated) (m)	191.7
Claimed CCT	4500
Measured CCT Range (K)	4200-4500 Kelvin
Item provided for review by:	Convoy Store
All my Convoy reviews!

^ Measurement disclaimer: Testing flashlights is my hobby. I use hobbyist-level equipment for testing, including some I made myself. Try not to get buried in the details of manufacturer specifications versus measurements recorded here; A certain amount of difference (say, 10 or 15%) is perfectly reasonable.

What’s Included

• Convoy S21A 21700 Flashlight
• Lanyard

Package and Manual

The Convoy S21A 21700 Flashlight has the “old style” lower quality box. Newer S2+ lights, for example, have a harder side and are more crush-resistant.

There is no manual.

Build Quality and Disassembly

Convoy is very highly regarded by flashlight enthusiasts for having great build quality and low prices. At around $23, and available with tons of options, this is a very high-value flashlight.

Very minimal branding. The shorty does not have any branding at all.

The finish of this orange light is really spectacular. The knurling is right on point. Lights costing orders of magnitude more have had worse knurling!!

The cell tube is not reversible. One end is anodized, and one is unanodized. The anodized end is the tail end. Also, both ends have their own o-rings.

The tail end has a nice thick spring, while the head has only a brass button. You can see the retaining rings in both head and tail too. Parts inside are easily accessible. Note that this seems to be a design change from my other S21A, which had springs in both head and tail.

Size and Comps

Length / Diameter : 123mm / 26.6mm
Weight: 88g

If the flashlight will headstand, I’ll show it here (usually the third photo). If the flashlight 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 formats.

Retention and Carry

The main (and only included) means for carrying the Convoy S21A 21700 flashlight is the attached lanyard. It ships from Simon attached in this wrong way.

Easy to fix, though.

It’s a standard lanyard from Convoy and attaches through two holes in the tailcap. This setup allows tailstanding fairly easily, too.

No pocket clip is included. The diameter of the S21A is likely too much to fit a standard S2+ friction clip, but I believe the screw-in-type pocket clip would work fine.

Power and Runtime

The Convoy S21A 21700 flashlight is powered by a single lithium-ion cell. The default (and only) tube supports a single 21700 cell.

The cell goes into the light in the normal direction – positive end toward the head.

Here are a few runtimes for a couple of different mode groups.

Modes and Currents

These output levels are not all available in a single-mode group. But this represents all the steady output levels.

Mode	Mode Claimed Output (lm)	Claimed Runtime	Measured Lumens	Tailcap Amps
100%	–	–	1019	4.72
35%	–	–	472	1.48
10%	–	–	145	0.40
1%	–	–	10	0.04
0.1%	–	–	–	0.01

Pulse Width Modulation

These PWM graphs are representative – this is mode group 2 (0.1%, 1%, 10%, 35%, 100%).

Here you can see a “baseline” – a chart with almost no light hitting the sensor.

Then there’s the Ultrafire WF-602C flashlight, which has some of the worst PWM I’ve seen. It’s so bad that I used a post about it to explain PWM! Here are multiple timescales (10ms, 5ms, 2ms, 1ms, 0.5ms, 0.2ms) to make comparing this “worst” PWM light to the test light easier. That post also explains why I didn’t test the WF-602C at the usual 50us scale.

User Interface and Operation

There’s a single switch on the Convoy S21A flashlight. This is a reverse mechanical clicky. A reverse clicky has the benefit of allowing mode changes while the light is on.  But this also means that the switch does nothing until it is on – no momentary action whatsoever.

This is the same user interface that I covered in my Convoy C8+ and S2+ reviews. And for that matter, the other Convoy S21A before this one!

This driver is known as “Biscotti” and has a bunch of mode groups (or faux-Biscotti – I’m not sure Simon runs an official version of Biscotti). The two big differences are the number of taps required to enter programming (20+ instead of 10+) and that this firmware has thermal protection (with the max temperature being 55 degrees C, per Convoy.)

Mode memory can be turned on or off (yay!), and programming is easy! But there are simply too many possibilities for me to list the user interface in a table as I usually do. Here is Simon’s flow chart for the UI.

Here’s the official guide for the Biscotti firmware:

From the mode group selection above, the light ships in mode group 1. You’ll want to switch it to mode group 2 quickly of course.   And I always turn off memory if possible (and it’s possible here!). I made a first pass at my own flow chart, which you can see below.

If something’s wrong (or even just “unclear”) in there, please let me know!

LED and Beam

The whole point of this review and of me even being interested in another copy of this light is the emitter. It’s a Nichia B35AM, and my copy is 4500K.

Why is this important, or awesome? Well let me copy text from Clemence (source link here)

Near gapless configuration of 4x E21A die size on a ceramic package with phosphors deposited in between the seams. This 3,65mm x 3,65mm LED is a miniaturization of the bigger 144A (5mm x 5mm) but with color quality and CCT range of E series. Although the max output and current capabilities are less than normal 4x E21A setup, the tighter uniform “donut free” beam and robust ceramic package makes this LED easier to implement where tight beam control is required. The white reflector “fence” make sure most of the light directed upwards and reduce the color shift over angle.

The point is that it should be awesome.

You can see that there’s an AR coating on the lens, which is a nice feature.

LED Color Report (CRI and CCT)

Here’s the most important part of this whole review! How does the Nichia B35AM fare! Well, it’s very good. Even without clicking the images below, you can see how tight that red circle is to the black circle – that’s good, that’s the goal. The CRI is around 100, which means this is not just “High CRI” but “very high CRI.” In fact, a CRI of 100 is perfect. The scale does not go higher!

There are two points other than CRI here. First, the CCT is also fantastic. “Fantastic” is a matter of perspective – I happen to like 4000K-5000K just fine. The Convoy S21A B35AM 4500K clocks in just under 4500K even on the highest level. This is great! If that’s too warm for you, grab the cooler option. Here’s a reminder though: Just because you get a cooler (or warmer) CCT doesn’t mean the CRI will suffer! The CRI can still be just as good as this sample even over different CCTs.

The next point (other than CRI and CCT) is the dUV. If I were picking a downside (and also stating why this 4500K doesn’t match my 219b reference light almost exactly), it’d be that the dUV is only negative on the highest output. There will be a slight pinkness on 100%, but all other modes, since they have positive dUV, will not be pink at all. I think you can see this clearly in the beamshots below.

Beamshots

These beamshots always have the following settings: f8, ISO100, 0.3s shutter, and manual 5000K exposure. These photos are taken at floor level, and the beam hits the ceiling around 9 feet away.  These beamshots are representative – this is mode group 2 (0.1%, 1%, 10%, 35%, 100%).

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

I keep the test flashlight on the left and the BLF-348 reference flashlight on the right.

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

Conclusion

What I like

• Great way to get into a Nichia B35Am emitter option
• Low price
• Build quality is great, especially for such a low-cost light
• No PWM
• Can run 18650/20700/21700 easily

What I don’t like

• No pocket clip
• Positive Duv on all but highest output

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Notes

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