[Review] Sofirn SP35 - SST40 21700 Buck Driver

Same here, I’d love it if this light would come in 5000k (or maybe even 4000k but probably not, that seems to be my sweet spot though) and with Anduril… Maybe some day!

My thoughts:

  • With the ATR, I think it’s only necessary if you plan on keeping your light on Turbo for extended periods and want to make sure you don’t get burnt. Otherwise, I think this no-ATR batch is great.
  • I understand the CCT preference. 6000K isn’t exactly my favorite. I may eventually try to swap it out.
  • As for the beam, like I said… I’m either not sensitive to it or mine has the newer reflector. Here’s a couple beamshots on my white ceiling.

Note: if there is any coloration in the beam, take it with a grain of salt. I’m colorblind and can’t confirm if the tint matches reality.

Beamshot 1: ~18 inches away (~46cm) using Low mode, ISO 80, 1/200 second exposure, 6000K white balance

Beamshot 2: ~8 feet away (~244cm) using Low mode, ISO 80, 1/50 second exposure, 5000K white balance

ATR is fine in my book if it doesn’t throttle down too soon. My wife picks up a light to go to the garden or lend one to someone, etc. Turbo could burn down my house with some lights. It has to be done well though. It’s like a gun without a safety which I do own but they have to be treated with special care.

Ok, and now for the modding crowd out there:

  • After running the light on turbo for a few minutes, the glue was easy to break loose. Using channel-locks and leather gloves for protection and it came open without any damage. I might not have even needed the channel-locks, it opened so easy after running on turbo.
  • Reflector is screwed in
  • The LED is on a copper 16mm MCPCB
  • Centering gasket is 1.15mm thick
  • Including threads, the reflector outer diameter is 25.8mm
  • The business-end of the reflector reduces in diameter after the threads a bit. Where it’s seated in the bezel (the top 2.5mm or so of the reflector), the diameter is 24.0 mm.
  • Reflector height: 16.0mm
  • Reflector (LED) opening: 7.2mm

This thing may end up with a 5000K LH351D or maybe a 3V XHP50.2 or something like that :smiley:



How easy is it to get to the driver-PCB/microcontroller? Perhaps Anduril can be flashed onto it? This seems like a very interesting light for me to do a first mod on. LH351D 4000k 90CRI (with Anduril?) in a 21700 package with type C charging and CC regulation would be pretty awesome!

I haven’t removed the driver. Like most Sofirn’s, it’s held in with a little glue but could be tapped out through the holes for the LED wires. On the couple Sofirns with buck drivers that I have dissembled (I’m thinking SP31 V2.0, maybe others) they used a 10-pin PIC-style chip. If that’s true with the SP35, there’s nothing that swaps in very easily. I dunno if I’ll be ripping the driver out of this one - too many irons in the fire right now.

Nice review, thanks. It’s sort of refreshing to see a light without thermal stepdown.

It looks like a nice performing light. And with the low Vf of the SST40 the regulation should be decent in the turbo mode. Did you measure the cell current?

Yeah the UI is fine as-is for me I suppose, the only thing I’ll miss is battery voltage readout. Is the SST40 voltage and current wise compatible with the LH351D? And how about the beam profile? Is the reflector fine for both so it could be as simple as a drop-in replacement? If so, I guess I’ll pick up one soon with some LH351D LED’s from sofirnlight.com :smiley:

Lastly, is the LED-carrier board glued down as well with some sort of thermal glue or can it easily be removed you think?

Just tested it. With the battery fresh off the charger at 4.20 volts, it was pull 4.75 amps (and creeping up) using a clamp meter and short, heavy wire. And that’s when I noticed my shirt was starting to smoke. Oops, you’d think I’d have learned that lesson by now, right?

The SST40 has a lower vF so the LH351D won’t be as bright or efficient. But if you’d prefer a warmer CCT and higher CRI, it might be a worthy swap for you. If you just want a warmer CCT and don’t care about CRI, grab a 5000K SST40. The SST40 is a 5050 footprint, while the LH351D is a 3535 footprint, so you might want a different centering gasket; not required but probably preferred. The LH351D beam would probably look just fine, both of these are fairly floody LEDs.

No thermal glue, just the usual white thermal paste.

Thank you so much for the info! 4000k LH351D 90 CRI would be ideal for me… Sounds like I’ll get myself a SP35 with some other components in a few days :laughing:

So the ED’s PCB is held in place by the reflector pushing it down?

Yes. That screw keeps it from spinning. Pressure from the reflector holds it down. This is very common: many Sofirn’s, Convoy’s, etc all employ this design.


Thx for measurements.

Now i need to find OP refelector...

That looks much better than this one, from this review.

I like Sofirn, and have a few of their lights, but TBH these kinds of things are frustrating, and can be avoided. If the light isn’t done, then don’t start to produce and then ship them, instead of laying traps for customers who have to wonder whether their will unit fall within the batch with the bad reflector, the buggy driver, or whatever.

SP35 without stepdown version is availble on amazon.com now!

Grap a 10% off coupon to save money!

LINK

Any idea if the new version of SP35 with ATR is out yet?

I was wondering the same thing.

Hope I find out soon, ’cause I can’t wait!

Yeah, if only we could get an official announcement on its status.
Maybe even a few times, since I’m worried about missing it!

I know that Der Enderman was looking for one, so I hope he could find out some information, too.

I pre-ordered mine direct from Sofirn last month, received ship notification on 3/8, and according to tracking, should have it by Friday.