Sofirn C8F 21700 Flashlight Review

Preface

Today I have in for review a light I’ve been looking forward to (and pestering Sofirn for) for a long while now: The C8F 21700.  I reviewed the original C8F (and that review didn’t go so well).  Sofirn responsively made some changes to the light, and now it uses a 21700 cell instead of a 18650, and I think generally has some build quality improvements.  Read on to see if that pans out!


Official Specs and Features

Versions

There is just one light option for the light, but it’s available as a kit or not a kit.  The kit is $46 and includes a 21700 cell and charger.  For $40, you get just the light.  (So for $6 more, it seems worthwhile to get a Sofirn branded cell and charger that works with that cell.)

The “21700” is an important part of the name, since there’s a previous “C8F” (which is 18650).

Price and Coupon

The kit is $46 and includes a 21700 cell and charger.  The $40 kit is just the light.  (So for $6 more, it seems worthwhile to get a Sofirn branded cell and charger that works with that cell.)


Short Review

I like this light quite a bit.  I like it better than the other C8F I had (which I’ve given away, to someone who could fix it).  I like it enough that I wish there was a dedicated thrower version of it.  I like the dual switch UI.  I like the included cell.  Overall, it’s just a great package!

Long Review

What’s Included

  • Sofirn C8F 21700
  • Sofirn 4000mAh 40A 21700 Li-ion cell
  • Single bay Charger (USB to micro-USB)
  • Lanyard
  • Charge cable
  • Spare o-rings (2)
  • 21700 to 18650 adapter sleeve
  • Manual and papers

Package and Manual

This light is shipped in a very generic flip top cardboard sleeve box, with a very non-descript bar code.  There’s no printing.

I know I’ve said it before but it’s still true.  On lights where the package isn’t… special…. (like the tactical hay of the original BOSS), I like packages that are easily recyclable.  I won’t want to keep this box – it’s nice that it has low impact.

The manual is a long sheet of paper with four languages total.  It’s a good manual, with illustrations and runtimes and all that.

Build Quality and Disassembly

As far as Sofirns go, this ranks among the best built that I’ve handled (and I’ve handled more than a few).  It’s rivaled only by the Q8 – I’d put them on the same level.  So if you’ve had a Q8 (and you should), consider the build quality about the same.

That’s a good thing.  This one is well built, and seems to have flashlight people in mind.  For example (as you’ll see later):  the head and tail springs are both already bypassed!  And in case you don’t know what that means, or why we’d want that:  A spring is one point of resistance in the electronics of a flashlight.  Bypassing the spring lowers that resistance.  Bypassing both springs gives even lower resistance in the circuit.  And since this light uses a “FET+1” driver, it’ll take all the current and make lumens.  So higher resistance directly means lower lumens.  Anyway it’s a great move by Sofirn!

This light is a 21700 light, so the body is a little thicker than a normal C8.  This suits me just fine; I love the 21700 size lights, and this is no exception.

There’s ample knurling on the body.

The threads on both ends are anodized, square cut, and the same length – the cell tube is reversible.  The cell tube does not have any indentions for a pocket clip.

Notice the spring bypass on the head.  The driver is held in place by an aluminum retaining ring.

The head has some crenelations, but not really “strike” crenelations (though with the right attitude, they would work just fine as weapons).

This is a well built light, and it’s a big step up from most other Sofirns, and certainly a huge step up from the original C8F.

Size and Comps

Officially:

  • Dimension: 149mm (length)*44.6mm (head diameter)
  • Weight: 200±2 gram (without battery)

Here are a couple other throwers.  Left is the BLF GT Mini.  Right is theSeeker Ns22.  Both of those are 18650 lights.

It’s thicker, but not that much thicker than the Convoy S2+.

Retention and Carry

There’s a lanyard included, which attaches only to the holes in the tailcap.  The holes are generously sized, and this is a very solid connection.

There is no other option.  The body is not made to accept a pocket clip, either.

Power and Runtime

Sofirn includes the best type cell for this light – a 21700.  The one included is an unprotected flat top, capable of a claimed 40A (though that specification is probably inflated).  The included cell is a flat top, too, but button tops should work just fine since there is a spring on the head and tail.

The wrapper doesn’t cover quite as much of the negative terminal as I’d like.

When installed in the light, the 21700 sticks out a few mm.

I performed two runtimes.  The first is on Turbo, which again, is FET driven.  (The driver is a FET+1 – the “+1” has to do with non-Turbo modes.)  Output is fairly stable for the first few minutes.  At 30s, I measure around 3000 lumens.  The claim is 3500, so my measure is significantly (~16%) under that.  Then there’s a pretty heavy stepdown, to around 850 lumens.  Unfortunately the output isn’t flat from there – the output basically tracks the cell voltage all the way down to … very low.  The light never shut off, but I stopped both runtimes when the output was very low, and both times the voltage was around 2.6.  That’s not “dangerously” low for the cell, but it’s bordering on it.

The output on High is essentially exactly like Turbo.  The output just doesn’t start as high, but otherwise – including the stepdown – the runtime is exactly the same.  (And sorry, I managed to miss the temp setting for this runtime.)

Sofirn also provides a sleeve to allow an 18650 to fit without rattle.  It’s just plastic, and doesn’t have any contacts or anything.  Thus, performance will be dependent fully on the 18650 you use.

The kit also includes a charger fit for a 21700 cell.  It’s a simple one-bay charger, which gets power from a micro-USB port.  A USB to micro-USB cable is included.

There’s a LED on the front – red if the cell is charging, green if charging is complete.

My usual charger testing would fit in this charger with the cell in place.  There’s just not much extra room.  So this data is recorded from the USB source.  Still interestingly proves that the cell is much higher capacity than the claimed 4000mAh (because remember, the shown 4+Ah is recorded at 5V).  The charger performs well, charging with over 0.8A in the CC, and having a short CV phase.

User Interface and Operation

The C8F 21700 utilizes two switches.  The first is a mechanical forward clicky tail switch.  It’s very clicky, quite proud, and doesn’t protrude over the edges fo the tailcap.  Tailstanding is possible.

The other switch is an indicating e-switch on the side of the head.

This switch is flat, but since the only other feature on the head is the fins for cooling, it’s easy to find without looking.

There is a lot going on with this UI.  There are four groups, each with different modes, and one of them being a ramping UI!  Switching between the groups requires the light to be on and the user to click quickly 4x.  The mode group change will be signaled by two quick flashes.  It’s a little hard to tell into which group you’ve landed.  A hint will be what output you land in after the two flashes:  a higher output (but not Turbo) will be either Group 1 or 4.  A lower output (but not low) will be Group 2 or 3.   Also the Groups advance logically, 1>2>3>4.  So you might have to do a bit of hunting but it can be figured easily enough.

Also noteworthy:  Group 1 can be seen as a “1 Mode Light” even though there are other modes available through certain click actions.  That’s fairly unusual.

Here’s a UI table!  Generally this is for only Groups 1-3, though there is some carryover to Group 4, too.

Also I’ll try to explain up front since it is confusing in a table form.
“Off” means there is no complete electrical circuit.  Ie “mechanical lockout.”
“Active” means the circuit is complete, but there is no light coming out.
“On” means there is light coming out the front.

State Action Result
Off Click Tail Switch (TS) On (Mode Memory, including Standby).  Switch indicates battery level for 5s*
Off Click Side Switch (SS) No action
Active Click TS Off (Electrically off)
Off Half Press TS Momentary memorized mode, and Battery check
All following actions require Tail Switch to be in the “On” state (where “on” means electrically on, but not necessarily with output)
Active Click SS On
On Click Mode Advance (Except Group 1)
Active (or On) Double Click SS Turbo
Active (or On) Triple Click SS Strobe
Active Hold SS Moonlight **
Moonlight Click SS Standby
On Hold SS Standby
On Quad Click SS Mode group Advance
Turbo Or Strobe Click SS Previous mode (including Standby and Moonlight)

* Battery indication:
Solid Green: Cell is 3.4V to 4.2V
Flashing Red: Cell is 3.0V to 3.4V
Rapid Red Flash: Cell is between 2.8V and 3V
Below 2.8V, light will turn off (Claimed – this was not my experience!)

** As far as I can tell, it’s not possible to advance to other (non special) modes from Moonlight.

Modes and Currents

This table too, will be a little convoluted, because each Group doesn’t have the same lumen outputs.  But since that isn’t a concern for this specific table, I’m just going to cover that generally.  To see which mode works is available in which group, refer to the manual scan above.  I’ll try to indicate in which group the mode is available in parenthesis.

Mode Mode Claimed Output (lm) Claimed Runtime Measured Lumens Tailcap Amps
Turbo (1,2,3,4) 3500 45m ~4.50
High (2,3) 1800 1h30m 1.71
Medium (2) 700 4h15m 0.39
Medium (1,3) 500 5h15m 0.24
Low (2,3) 100 30h 0.03
ECO (3) 10 210h 0.00
Moonlight (1,2,3,4) 1 550h 0.00

Regarding LVP:  At 3.10V, the switch blinks red slow.
At 2.90V, red fast.
And at 2.5V, the light is electrically off.  So there is LVP, but it’s quite low LVP.

LED and Beam

The emitters used in the C8F 21700 are three Cree XP-L HD’s.  There’s a three-up smooth reflector.  The beam has a lot of throw and little spill.  The triple doesn’t really show up in the beam.

I can detect some PWM on at least moonlight.

 

Tint vs BLF-348 (Killzone 219b version)

The Big Table

Sofirn C8F
Emitter: Cree XP-L
Cell: 21700
Runtime Chargetime
LVP? Yes, but very low.
Power off Charge Port with no Cell?
Claimed Lumens (lm) 3500
Measured Lumens (at 30s) 2969 (84.8% of claim)*
Claimed Throw (m) 299
Throw (Calculated) (m) 360.1 (120.4% of claim)
Candela (Calculated) in cd (at 30s) 952lux @ 5.836m = 32424cd
All my Sofirn reviews!

Random Comparisons and Competitive Options….

There’s really not a lot just like this light out there – being that it’s a 21700 light.  But without that stipulation, there are a number of lights with similar features.  Every other option is much more expensive, and many of those aren’t complete packages and don’t offer charging.

Conclusion

What I like

  • Full package light
  • 21700 makes a nice sized light in this format
  • Build quality is great for a $46 light
  • Dual switch interface is quite versatile
  • Four mode groups, with good options
  • Moonlight available in all mode groups
  • Ramping UI is available
  • Indicating switch, with battery indicator

What I don’t like

  • Seems like XP-L HI might have been a better choice
  • Moonlight has visible PWM

Up Next

Up next we have a new year!!  Happy New Year!!

Notes

  • This light was provided by Sofirn for review. I was not paid to write this review.
  • This content originally appeared at zeroair.org.  Please visit there for the best experience!
  • Whether or not I have a coupon for this light, I do have a bunch of coupons!!  Have a look at my spreadsheet for those coupons. It’s possible to subscribe and get notifications when the sheet is edited!!

Author: zeroair

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