Due to the precise nature of the step down voltage points, it’s clear Sofirn chose these in the software. 3.70v and 3.40v. They probably based their decision on what works best.
Bwrf… My DQG 26650 never steps down and has a similar output.
I mean, what’s the fuss when we’re talking about 20+ Watts / 2500 Lumen lights on a fat battery?
Still under 10 Amperes even when only 3 Volts.
Strange decision.
The amp limit Sofirn has chosen to use is 5.8A.
I don’t think anyone has seen this new SP33 driver design so we are all guessing about how it works.
A stupid choice i.m.h.o.
I’ll post pics when i get the driver.
Not sure if it’s the V1.0 or V2.0 version though.
I think there may be another limiting factor.
The springs are the same found in the original SP33. While steel springs are fine at 3A for the XP-L version, they aren’t at 4A, as they start to heat up a lot faster than at 3A, and at 5A, this becomes even worse, resulting in an even high Vdroop.
Dual springs would have helped in this case like in the Q8 and a brass button on the driver.
So Sofirn chose to limit the current not based on the driver design, but on the spring design.
I’ve actually tried that trick with my Haikelite MT01. Trying to run on 1 cell is fine, but the spring gets stupid hot, and the problem becomes worse at lower voltage levels.
Yep, the springs are wide so it’s a long thin wire, made of iron… 
So is it ok to do spring bypass or too much current?
YES. It’s always much better to do spring bypasses with buck/boost drivers. Power is regulated, so less voltage loss in the springs means more runtime at high brightneses.
In fact, unless you are running 2+ cells, good springs/spring bypasses are needed for optimal power/runtime.
Thanks, wasn’t sure if they were using the low quality springs to limit current.
It is okay to do, but it may not change anything in this particular driver design.
It seems the driver looks at resting battery voltage to determine whether to have Turbo or not. Voltage sag seems to not effect it. Quite strange.
Maybe a bypass will squeeze out a little more Turbo run time? I’m not sure. On other boost drivers, where the current goes up as voltage goes down, I always recommend bypasses. They make a bigger difference there. With this light, I’m not so sure.
Nice write up Jason, have you thought about slicing and dicing the 50.2 to get rid of the weird aura and tighten the beam?
With ANY current regulated driver it is better.
You lose less voltage when your electrical path is optimized.
No, I prefer the beam as is. The hotspot is already pretty small for my needs (walking around at night). I don’t want to go smaller. I’m not bothered by the corona. I think I’ve gotten used to it.
Well, it’s not as bad as the smaller Cree flip chip LEDs like the XP-G3 and the XP-L2, but i still don’t like it.
I’m gonna try a Nichia 144A in it, which is probably just as bad, but i found a suitable frosted TIR that will blend everything to perfection, or so i hope…
Gonna have to shorten the head though, because TIRs are short…
First i have to tidy the huge mess that has grown in the shed, though…
My v2 has a different tailspring than my original SP33. The old one was the full diameter of the tube. The new one is ~1/2 that. The length of the current path is shorter, as a result.
The point still stands about voltage drop, though.
Thank you all for answers. This is what i like about this forum, you ask something and you get a decent answer in no time! Thanks guys! That 26mm mcpcb would be great but i have never reflowed a led. Maybe i will try with 20mm XHP50.2.
The DQG 7x emitter 26650 definitely steps down. It’s actually very noticeable. Just try it. I wish Sofirn will get rid of the timed step downs on their newer lights that already have advance temperature regulation. I don’t want timed step downs especially when used in outdoor cold temperatures.
Driver pics are added to post 1.
Thanks for the driver photos!
It looks like it is using the TI TPS61088 boost converter.
Edit: And it looks like this is how an switch current limit is set.
There are other ways to do current limiting though, using an op-amp and the voltage feedback pin.