Sofirn C8F host. 21700 C8F Available

LH351D 4000K 90CRI at turn on:

2,803 at 14.xx amps (Samsung 25S 18650)
2,881 at ?? amps (rested 30T 21700)

This is using very long 20 gauge leads. Like 6” long or something in case I needed to re-flash or test. Numbers may not be exact since this is approximating shoe box.

@JasonWW, do you think it’s possible Sofirn to have changed the LEDs from XP-L W2s to a lower bin, which is perhaps why the average lumen numbers are about the same or down, even with an upgraded FET?

No, I’m looking at the amp draws. The 18650 driver is capable of pulling higher amps than the 21700 driver.

Yes, but the forward voltage of the XP-L W2s is lower on average than XP-L V6s, so they can be drawing more current than XP-L V6s. Therefore, the 18650 version, if they have W2s, can be quite a bit brighter as they are drawing quite a bit more current.

Heck, look at @contactr’s numbers. 2800 lumens with 4000k 90CRI LH351D with a 21700 stock C8F is very close to your numbers of the stock C8F with 5000k 70CRI XP-L HDs, which is really strange.

Wow, 14A.

Does the LH351D they have similar output to the xpl? Meaning similar lumens at the same amperage.

Not even close.

If I remember well, with the new FET, you got 3000 lumens at turn on with a 21700 C8F with 9,5A of current.

He is getting 2800 lumens with 14A of current, and he is using VERY long 20AWG leads, meaning current would be quite a bit higher in a real world situation, or using thicker wire leads.

That means my hypothesis of using lower-binned higher voltage LEDs in the 21700 C8F seems more plausible.

Just to be clear the driver i’m using is a MTN-20DDm (20mm FET+1) and driver spring (small “blue” spring) is through hole bypassed. LEDs are first batch from AEDe.

Okay, I see the point your making. I would not think that one output bin of difference would mean the forward voltage was noticable different. I know it can change with different color temps, like a NW may draw more amps than a CW, but I think there are a lot of other variables involved.

My stock driver C8F 21700 was drawing about 6.3A and 2300 lumen from a 30Q battery. With the FET swap, it draws 8.2A and 2600 lumen.

From the 18650 version reviews I found it seems everyone was getting between 8 and 9 amps from a high drain 18650. So it doesn’t seem like there is any big change in amp draws between the 2 drivers when using 18650 cells. This would indicate the xpl emitters are the same, right?

I don’t think I would look at contactr’s numbers as it’s a different driver and different emitters.

Both XPL2 and LH351D have relatively low fwd voltage so it seems more likely something else not allowing it to pull >10A. Seems more likely to me that it would be the driver. The difference between my long 20AWG wires and stock wires that are 22AWG and shorter is only like 0.05V drop isn’t it? Seemingly not enough to make such a big impact.

@contactr, I’m talking about XP-Ls W2, not XP-L2s.

The XP-L2s are a completely different beast.

Yes. 3050 lumens@10A at Turn On and 2900 lumens@9.5A at 30 seconds.
I think Sofirn should have officially rated it 3000 lumen instead of 3500. It is basically the same as the 18650 version (in theory), but with a bigger, higher drain battery. It doesn’t make sense that a bigger battery alone would add 1000 lumen.

Maybe if they also used some heavier 18ga led wires we would see more than a rough 1A and 300 lumen increase in output?

This could be misleading to some people. Thinner and longer wires decrease current, so I think you mean “he is using VERY long 20AWG leads, meaning the potential current is probably quite a bit higher (if he were to swap to shorter and thicker wires).”

I don’t want anyone getting confused.

Ah, I’m already having trouble remembering stuff with this light. I think I’ll try some 18 gauge wires and see what happens.

Yes. It would’ve been better to underrate the light most of the time.

Even overrating slightly a light will disappoint customers if they discover it.

You are right I should not comment on stock lights :person_facepalming: especially since they don’t exist at my house. I got confused because of various mods in this thread.

I think I figured out a small design flaw in the manufacturing that is causing reduced output.

It seems the new aluminum driver retaining ring is not able to fully tighten down on the driver (at least my driver). I thought it felt strange as it only tightened up to one point and then would go no further. I used some marker dots to confirm this. The ring seems to be squeezing the driver lightly instead of firmly.

The 2A difference I saw earlier with my battery tests and again a 1A difference after I swapped to 18 ga led wires. I can move the driver around when the retaining ring is about 1/16 of a turn from its “tightened” position.

So maybe the driver pcb is a bit thinner than it was supposed to be or maybe the threads are not cut far enough. Maybe they should have continued using a brass retaining ring. I’m not sure.

I will relay this information to Sofirn.

Add a tiny copper wire and see if it helps? They also anodized the driver side threads which im not a huge fan of. I think its better for heat transfer not to?

Lastly, my old 18650 sofirn bypassed tail switch broke and i probably havent changed that thing a dozen times. The wire was far too thin for how much solder they used.

Replaced the spring and bypass on that one and got 3,670lm at 0s with Samsung 25S. That one has LH351D 5000K 80CRI

Yeah, a simple copper washer should do the trick. That’s easier than my first thought of building up solder and filing down the high spots.

The inventory in amazon warehouse is still the old ones, but it has code to bring the price down to $32 for kit!

if you don’t mind the lower output or can replace new driver, just PM Sofirn for code.

Does anyone know is 42mm glass will fit into C8F? My host came with lens with no coatings so want to upgrade but I’m not sure if 42mm one from intl-outdoor.com will fit or should I just get 41,8mm.

The “42mm” one commonly marketed for the C8 fits fine, as does the stainless bezel if you fancy changing that too.

TBH I did order stainless bezel a while ago, just forgot about it, so the whole question was actually irrelevant :person_facepalming:
Thanks for the answer anyway :wink: