Sofirn SP40 Headlamp Review

Sofirn SP40 Headlamp Review

The Sofirn SP40 is a headlamp featuring 18650 and 18350 support, and an indicating e-switch. Read on for thoughts and testing.

Official Specs and Features

Here’s a link to the Sofirn SP40 Headlamp product page.


Just one body and emitter option, but there’s a kit that includes a cell (seen here) and an option that doesn’t include a cell.


These are around $22 – buy yours at BangGood!

Short Review

This is a nice headlamp, especially since it includes a 18350 cell tube.  That puts it in rarefied air (the only other being an Armytek light).  It’s a nice performer; I’d like to see one with better regulated modes.  Otherwise, this is a great offering, and certainly a buy-if-you-need-a-headlamp, at $20.

Long Review

The Big Table

Sofirn SP40
Emitter: Cree XP-L HD
Price in USD at publication time: $22.49
Cell: 1×18650
Turbo Runtime High Runtime
LVP? Yes
Switch Type: E-Switch
Quiescent Current (A): 0.00003
On-Board Charging? Yes
Power off Charge Port with no Cell? Yes (one mode). (also one mode while being charged)
Claimed Lumens (lm) 1200
Measured Lumens (at 30s) 1373 (114.4% of claim)^
Claimed Throw (m) 136
Candela (Calculated) in cd (at 30s) 334lux @ 4.379m = 6405cd
Throw (Calculated) (m) 160.1 (117.7% of claim)^
All my Sofirn reviews!

^ Standard 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

  • Sofirn SP40 Headlamp
  • 18650 cell tube
  • 18350 cell tube
  • Headband
  • Charge cable (USB to micro-USB)
  • Spare o-rings (2)
  • Pocket clip
  • Manual and paperwork

Package and Manual

This Sofirn is in a simple cardboard box with no adornments.

Here’s the manual:

Build Quality and Disassembly

The SP40 is well made.  There’s not much more to it than that.  Evaluating the build quality vs the price, the SP40 is excellently made.

I really appreciate that there are both 18650 and 18350 tubes included.  The cell tubes are even reversible.

Both the head and tail have large springs.

Of course, with two body tubes, the head removes easily (since you’ll likely be doing that often?)

The threads are thick square-cut, and quite long, too.  They’re anodized, which makes mechanical lockout easy.

The head has a bit of cooling fins, but not overly so.

The charge port is covered by a press in rubber cover.  The fit is very snug, but it’s not difficult to remove for use.

Both bodies have ample knurling, and the tailcap, in particular, is long, and with nearly full coverage knurling.  That makes for an easy-to-remove tailcap; another appreciated feature.

Size and Comps

Dimension: 108mm (length) * 25mm (head diameter)
Weight: 63 ± 1 gram (without batteries)

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.

The 18350 version is a cute little thing.

Retention and Carry

Being a headlamp, the primary carry for this light will be the headband.  The light slips into two silicone collars, which fit into specific non-knurled spots on the 18650 cell tube.  The fit is good, and the light rotates without damaging the holder.

The 18350 version fits easily as well, but the holder doesn’t line up ideally with any non-knurled areas.  I don’t think wear will be a big issue.

The other option is the included pocket clip.  One of my least favorite pocket clip styles, it does get the job done adequately.  It’s a friction fit clip, which fits on either end of the 18650 cell tube (and the tube is also reversible, so the clip can be reoriented that way, too).

The pocket clip also has a home on the 18350 body, but only one orientation makes good sense.  Bezel down… otherwise, the clip will hang off the body, and the light will stick much too far out of a pocket.  However, it will hold in this orientation, so as a downlight on a cap (etc), it could still be useful this way.

Power and Runtime

The Sofirn kit I have included an 18650.  Since the 18650 and 18350 outputs will be the same (differing only in runtime), I tested the light only with this Sofirn branded cell.  The cell is a button top 18650, and as a $2.5 add on, seems like a no-brainer.

Output is completely unregulated, tracking downward quickly as the cell voltage drains.  I’d love to see a better-regulated output.  At least there is LVP, though.

Output on High sees the same lack of regulation and a downward trend from essentially the start of the test.

The SP40 includes on-board charging and can charge either size cell just fine.  The charge port is micro-USB.


Sofirn includes the required cable, which is USB to micro-USB.

The charge proceeds at 0.9A, which could be a little high for an 18350, but still is around 1C charging, which most cells should be rated for.

Modes and Currents

Mode Mode Claimed Output (lm) Claimed Runtime Measured Lumens Tailcap Amps
Turbo 1200 1h50m 1347 3.11
High 450 4h10m 453 0.99
Medium 90 15h 87 0.16
Low 5 220h 12 0.02

Pulse Width Modulation

The light has PWM on all modes – a little surprising to see PWM sneaking in on Turbo.  I’m very PWM sensitive, and I don’t really notice this PWM during use, so I’d consider this a non-issue.

For reference, here’s a baseline shot, with all the room lights off and almost nothing hitting the sensor.  Also, here’s the light with the worst PWM I could find.  I’m adding multiple timescales, so it’ll be easier to compare to the test light.  Unfortunately, the PWM on this light is so bad that it doesn’t even work with my normal scale, with is 50 microseconds (50us).  10ms5ms2ms1ms0.5ms0.2ms.  In a display faster than 0.2ms or so, the on/off cycle is more than one screen, so it’d just (very incorrectly) look like a flat line.  I wrote more about this Ultrafire WF-602C flashlight and explained a little about PWM too.

User Interface and Operation

There’s a single switch on the SP40.  It’s an indicating e-switch on the head.  There are red and green indicators.  During use, the switch indicates the cell’s power level.

Power Indicator: the LED indicator on side switch flashes in green for 5 seconds if remaining battery is over 30%. When the indicator turns red, battery juice is under 30%. Flashing red light indicates low power-replacing or recharge ASAP battery.

Here’s a UI table!

State Action Result
Off Click On (Mode Memory, LMH)
On Click Off
Any Click 2x Turbo
On Hold Mode Advance (LMH)
Any Click 4x Lockout
Lockout Click Double flash
Lockout Click 4x Unlock (Low)
Turbo Click Previous Mode
Off Hold No Action
Any Click 3x No Action

This UI is very simple, and not too hard to learn.  Note the lack of strobe.

LED and Beam

The emitter used here is a Cree XP-L HD.  The reflector is shallow and orange peel.

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)

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

Random Comparisons and Competitive Options….

Here’s a link to a relevantly filtered page on  I use that site a lot!  A bunch of what you’ll see on that link is an Armytek light, but also interesting is a headlamp by Wowtac, which is available in NW and CW both.


What I like

  • Low price!
  • Kit including cell is also low price!
  • LVP
  • 18350 body in a headlamp

What I don’t like

  • Unregulated output


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13 thoughts on “Sofirn SP40 Headlamp Review”

  1. Hi and congratulation for your reviews. This SOFIRN SP40 seems to be very good. I’m french and i don’t understand all your review.
    Can you tell me what headlamp around 1000 lumen, with rechargeable USB not proprietary and waterproof is the best in your opinion ? If it’s possible for you to tell a answer because there is a lot of items…
    Thank you in advance,
    Best regards.

    1. Yes, for the price the SP40 is a great option. I’m a big fan of the Skilhunt H03, and there are rechargeable options there. Thrunite makes very nice headlamps, some of which offer non-proprietary charging, too.


  2. Hello, i have a SP40 and like it, especially with the 18350 tube. One thing i dislike is that mine has a really long pause after pressing the switch before it actually turns on. Does yours have this same pause or is mine just acting strange? Thank you

    1. Mine has a slight pause, but I wouldn’t call it “really long.” Probably normal e-switch delay?

      A mechanical switch light might suit you better – on the other hand I don’t know what headlamp uses a mechanical switch.

      1. Thanks, the pause is not “really long”, as i previously said. Sorry for that. More like a short pause for on and off. Watching video reviews of this light it is normal. Still a good deal for this light and i like it.

  3. DO NOT BUY! This flashlight just destroyed my NCR18650B. The flashlight turned off, and after measuring the voltage it was 2,4V!!!!! So the cell is destroyed. Also, the RED/GREEN indicator is STUPID. The flaslight is on your head, you can not see it!!!!

    1. Mine shut off in tests at around 2.9V to 3V. So maybe you got one with some issue?

      Anyway, 2.4V isn’t really “destroying” a cell – 2.4V is not the worst voltage for a li-ion cell. Yes you wouldn’t want to do that often, but once won’t be that bad.

      1. Renan Santana Pelícia

        2.9V to 3V LVP é for HIGH and TURBO respectively. For MEDIUM I measured below 2.8V and manually turned it off. I wander whats is the LOW voltage protection.

      2. Ok, but if it measured 2,46V (that was ~3 minutes after it shutoff) the cell already regained some voltage. After 2 additional minutes (so 3+2 minutes) until I find my mobile to take the photo for proof, it was around 2,6-2,7V). So, the cell must have been somewhere in around ~2,3V after shutdown, and that is with no load and with load the voltage for sure was under 2,3V, probably lower.
        This is unacceptable. Do you really want to wear on your head a flashlight (a pipe bomb in case if vents) driven by a cell, which you know has been damaged?
        I send an email to their contact email and will post here what they say.
        Also, when I have time, I will make my own test and sacrifice one more cell.

        1. Also forgot to mention. I noticed that it was under discarged because initially it didn’t want to start charging on my XTAR VC4 charger. That was the first thing i did (didnt suspected anything), and because it did not start charging i tool a multimeter and measured it.

  4. I have contacted the Sofirn. We exchanged several emails as I have made some more tests and send the results back. They were quite responsive. Here are the conclusions if you don’t want to read the whole message:
    -I was unable to replicate the problematic scenario, where cell is drained below 2,5V
    -LVP kicked in between 2,64V and 2,746V. The range is quite big; also seems to be heat and current dependent. In my opinion 2,64V is too low for LVP. Many cells should not go lower than 2,85V.
    -Sofirn claims that this is ok and LVP works fine based on my testing. However, they said, they will talk to engineer, if there is a need to increase the LVP trigger voltage from 2,8V to 3,0V.
    -I suggested to them to increase LVP to over 3,00V, even better to 3,3V

    Full conclusion here:

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