Sofirn C8F 21700 Teardown and Review

The FET they used in the early drivers did have a little more resistance in it which reduced output. The details are in post #17

I actually don’t know what a triple xpl can do amperage wise. Right now each emitter is doing about 3.2A and about 1000 lumen.

Should we be expecting 15A and 4000 lumen?

Is there too much resistance in the led wires?

A completely new driver might tell us if there is something in the Sofirn driver that is creating a bottle neck.

Frankly, I was okay with the stock driver that only drew 7.25A and 2600 lumen. I tend to set it at about 500 lumen for walking around and do the occasional blast of turbo. It’s a big jump in output and it doesn’t get too hot or run the battery down too fast. It is a good general purpose light.

Using the 30T and 4000mah battery gets the light hot so fast it’s not that practical anymore. If I put a Lexel driver in it and got even more output, I’d probably remove the spring bypasses to try and reduce output on turbo to make the light practical again.

I know, it’s not the BLF way to reduce output, but I use this light at work where it needs to be a bit more practical.

The latest versions already have the updated FET so you don’t need to do anything.

What do you mean by beefing up connections? Both springs are factory bypassed. There is nothing to do there either.

Do you mean replacing the led wires with bigger ones? How big are the wires in the 18650 version? Bigger or the same? I don’t know.

How many amps does the 18650 version pull? I don’t have one so I don’t know.

I looked up reviews for the 18650 xpl version to find amp draws. (This is usually more accurate than lumens)

Bilakos10 measured 8.33A with a Samsung 25R cell, but that is not a very good battery.

Robo819 measured 8.4A with the Sofirn 18650 and 8.9 with an LG HE4 cell.

ImA4Wheelr measured 8.8A with the Sofirn 18650.

Barkuti measured 9.7A with a Samsung 30Q. He used a shunt as apposed to a clamp meter.

DB Custom drew 13.57 amps with a very high drain VTC5A 2600mah and with slightly lesser batteries, like a 30Q, he got between 10A and 11A. This was with 18ga led wires and an upgraded MOSFET though. So it doesn’t really count as stock.

Since the 18650 version is supposed to be about 2500 lumen and the 21700 version is supposed to be 3500 lumen I’m guessing there is some kind of bottleneck with this 21700 driver. The 21700 light should probably be drawing at least 12A to 13A stock to get 3500 lumen. Sofirn may have over rated this 21700 version. It might be a true 3000 lumen light.

Referencing this post;

Dale shows the following;

Sofirn ……………………………30Q…………………………Sony VTC4

  1. 0.552 Lumens…………………0.552 Lumens………………0.587 Lumens
  2. 37.50 Lumens…………………22.29 Lumens………………22.81 Lumens
  3. 83.15 Lumens……………………82.8 Lumens………………84.53 Lumens
  4. 890 Lumens………………….872.85 Lumens………………931.5 Lumens
  5. 1338.6 Lumens……………1314.45 Lumens…………….1400.7 Lumens
  6. 3015.3 Lumens……………3018.75 Lumens…………….3125.7 Lumens
    ……2756.66 at 30 sec…………….2691 at 30 sec

This is stock from what is described.
Amp draw do not know.

After 18 gauge wires and new mosfet went well over 4000

Bottom line, If I can’t see the difference I do not need to be buying a new battery form just to be “like the new kids”
Like the New Version just can not justify another version at this time.
Thanks!

Keith

His lumen tube reads way higher than mine. This is why I don’t use his lumen numbers. The amp draw is more accurate.

The best thing about the 21700 version is the new ramping mode UI with one click on/off. This is why I never bought the 18650 version.

OK, that’s cool
Good info.

I just spent some time to dig up my post with my own lumen numbers and seems like Dale’s measurements are spot on

I grabbed a few 40T to try them out in my light.

I’ve got the SIRa800 and 18 gauge from the driver to mcpcb installed.

Turn on with sofirn battery gave me 3,904 and 3,504 at 30s
Turn on with 40T gave me 4,024 and 3,764 at 30s

3% difference, negligible IMHO

Both tests, batteries fresh off the charger. Measured in a maukka light calibrated sphere.

Mtn. D4-v2 driver in mine, I got 3890lm on the Sofirn battery 4430-4400lm on 2 of my 30T batteries.

This does not invalidate my statement. It still holds true.

I’m guessing there is some kind of bottleneck with this 21700 driver.

The 18650 version light seems to be capable of higher output then the 21700 version which is the opposite of what it should be.

Did you measure the stock driver output in lumens and tail amps?

How many tail amps are you drawing with the new driver?

I’m curious what effect a straight driver swap can do.

D4v2 driver with 20awg leads,18awg TC bypass 30T off the charger at 4.21v….4460lm.

No doubt 18awg leads will get you a bit more… I don’t have the patience for it on this light. :smiley:

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.

Thanks for the review and also the analysis on why the Sofirn C8F 21700 may sometimes be underperforming… Hope Sofirn will solve the “underperforming” issue soon.

They already know the old FET is not the best, so it hurts performance a little. They have already switched to a better FET.

I don’t know if all the lights have a weak contact on the driver retaining ring. Some may.

I also recommended they swap the led wires to 18ga. It’s a cheap way for them to boost the output even higher.

Here’s an update. I swapped out the factory wires (I think 22ga) with some heavier 18ga. I ended up shortening them about an inch, but that’s barely long enough. I recommend 1/2” shorter at most.

Once I got a decent connection with the driver retaining ring, output jumped up quite a bit. Look at the bottom of the page. I was in a rush so I only did Turn On and 15 seconds for both tail amps and lumens with each battery.

The Sofirn battery gained about 2 amps and 400 lumen. 3,450 lumen, wow!

The 30T battery gained about 1.5 amps and 300 lumen.

The 50E battery gained about 1.4 amps and 300 lumen.

The little Samsung 30Q gained about 1 amp and 300 lumen.

So some pretty nice gains just by swapping to 18ga wire. :beer:

But I thought your lumen sphere is calibrated with Maukka lights so it should be reading about the same as mine. So if Dale’s measurements are similar to mine, then shouldn’t it be similar to yours?

Very nice info. So the 30T measured 3,400 lumens, which is less than the Sofirn 4000mah because of bad connection? Also the performance of the Sofirn 4000mah is very impressive. Seems like a rewrapped Samsung 40T.

I don’t know why, but my lumen tube seems to read a bit lower than others. Not so much with other TA Tubes, but with some other different designed measuring tubes.

Like when it comes to the xhp70.2. Dale can measure lights with that emitter at 6000-7500 lumen.

With my L6 I can only get 5300 lumen at turn on. This is with 2 different color temp leds and Liitokala cells drawing 17.6A. Even with Aspire 4300 cells drawing 19.6A, I only see 5500 lumen at turn on.

Keep in mind that Dale does not use a TA lumen tube. He uses a lumen tube design with no diffusers and calibrated by a wide variety of factory lights. (Unless he has recently bought a Maukka calibrated light). I think he always uses turn on numbers and never anything lower.

So I always take his, and everyones, lumen results with a grain of salt. People should not take my lumen numbers as exact, but just in general.

I am really surprised your lumen numbers and Dale’s are really close. Have you compared the output of several factory or modded lights between him and you or just a few?