Sofirn C8F 21700 Teardown and Review

Store Sofirn kindly sent me a driver for C8F 21700
In my opinion it is different from the original version.



I’d kind of like to see a 26650 C8F or something even floodier.

Did you measure the output?

Sofirn Samsung is very kind. They had a brand new C8F 21700 shipped to me from Amazon for free. I was shocked to see the label titled to SKV89 and was wondering what the heck could be in the package. The output, unfortunately, measures the same as the output of the one I bought originally from Aliexpress and is also the same as the output after swapping in the free replacement driver into the Aliexpress C8F 21700.

Regardless, I sincerely appreciate Sofirn’s generosity and excellent customer service.

You should try the new Sofirn SP33 with xhp50.2. It has a little bit larger hotspot. Nice 26650 size. The boost driver kind of spoils me due to it’s consistent output and low heat production. It has replaced my C8F.

I think I actually have two of those coming to give to the inlaws as a Christmas gift. I also got a single C8F to play with.

Received my new order and it is disappointing to see no change in output. The plus side is the thermal sensor making it safer and more user friendly for my customers.

I get no higher than 2650 at 30 sec

It’s puzzling as to how they got 3500 lumens. Their ratings are usually not that far off. I see d_t_a mentions a wire gauge change boosts lumens a fare bit. I’m not going to bother as that would be a big hassle to perform on all of them

The manual states it steps down at 50C but I just ran a test and it kept on Turbo until I had to turn it off from the heat. It was too hot to touch on the head and top of battery tube. My 30Q was very hot. It was maybe 65C and still no step down

What’s everyone else’s experience with this?

I was in ramping and in Turbo. This one might have a fault?

EDIT: just tried another C8F with the same result but measured the temp and it was still climbing at 56C with no step down. The whole light was around the same temp and battery at 45C. Why don’t they step down at the specified 50C?

EDIT 2: Ran another test on my lumen tube and let it run slightly longer this time. Turns out it steps down at 58C to 800ish lumens. It felt scary hot though….I think I may have peed a little :smiley:

Yeah, they should have stuck with the same rating as the 18650 version which was about 2570 lumen or so.

FET drivers are greatly effected by resistance in the circuit which includes the battery, driver pcb, the FET, the LED, etc… There is just some extra resistance somewhere that’s reducing the drivers full potential.

Still, I don’t mind 2600 lumen. It’s bright for such a small light, plus you can run it longer at that level compared to if it was 3500 lumen. It’s ehh, whatever. Having a nice user interface is more important to me. I find the new Sofirn SP33 to be better than the 21700 C8F.

I should be receiving the SP33 later this week! looking forward to it.

It certainly is enough light for the C8F. The 18650 version at 3100+ lumens just got way too hot on Turbo for practical use. It’s quite nice having no step down timers as well.

I am currently trying to get a 22mm TA driver working in my C8F host. I am trying to figure out with trial and error which two wires of those four let the momentary switch work. Can anyone help me to solve that problem or do I need a new switch? Maybe I already killed the switch lights :person_facepalming: but they are not that important for me.

You’re not going to be able to get the lights working on the switch unless you cut pcb traces.

As far as the two wires to operate the switch, see below.

The black wire goes to the driver ground.

The white wire goes to the driver switch positive.

Thanks for telling me. I would have needed to try all combinations otherwise. Do you know where I would need to cut traces to get the switch leds working? In the mean time I will try to solder the black and white wires.

I show all the circuits a few posts above. You’ll need to replace the double leds with single units, cut a trace then solder a jumper wire - I think. I’ll have to look at it later tonight.

I’m already happy if the switch works. I already killed the green leds. Maybe I could fit a Q8 switch inside. Thanks for the nice helpful circuit drawings.

I managed to complete the TA driver with a working switch. But now there is another problem: Outside of the driver cavity the driver works perfectly when connecting a battery. But as soon as I screw it in with the retaining ring it stops working and shorts the battery! I have no idea where the unwanted contact is.

if your batt + spring is compressing too much or sideways it can touch a 7135 leg on the back side of the driver. I suppose you could test with an 18650 and the spacer to see if the shorter battery helps.

Is the retaining ring touching any of the components on the driver? You may have to increase the diameter of the retaining ring so that it doesn’t touch any components.

I tested the driver with a 18650 battery holder holding one cable to the spring and the other to the outer ring. I didn’t compress the spring. The driver retaining ring is touching the plastic part of the 7135. Shouldn’t be a problem?! So far I didn’t screw the battery tube on with a battery because I fear it would explode then (maybe not but who knows?).

I have a Utorch C8F which seems to have a timed ramp down to medium after being on Turbo for 5 minutes (+ a few seconds). Didn’t see any sign of temperature control during this time.

All the LEDs in the C8F are just wired in parallel, right?