Sofirn C8F host. 21700 C8F Available

Wow John, that is amazing! You might want to consider selling a kit :wink: . Maybe make the spacer out of copper too. I think the C8F is a better host for a quad than the D4S because it has more mass for heat dissipation.

A kit sounds good :slight_smile:

Hey Sofirn C8F 21700 owners!
I am looking for floody single cell light with high capacity and good heat transfer.
I am not (so much) interested in maximum lumens, but I am interested in how much lumens C8F can pump out in continuous use without heat throttle and how many minutes its 4000mAh battery lasts in that mode.
Would 5000mAh 10A battery work with it in my use?
Do you know any similar lights around same price range that could be better for my use than the C8F?
Some other battery type flashlight maybe?

The Sofirn SP31A would be a good bet in the 18650 realm.

Since it uses a buck driver and an XPL2, it is a very efficient light, and still throws quite well, and can maintain its brightness for a long time. It also has a big heatsink, so you can hold the 1000 lumen turbo for quite a long time. It also uses a dual switch setup like the C8F 21700, which is very useful.

If you want something big and with a lot of runtime, I would recommend the SP33. 26650 light. You can get a 5500mAh 26650 for very long runtimes.

The C8F is a hotrod light mainly, so the lumens will go down if you use it above low brightness, and can get extremely hot.

Hey you! You did bring me here from reddit :slight_smile:
How long of a time are we speaking of with “quite a long time” as second highest mode on SP31A is 350 lumens which seems bit low maybe, would it stay on that mode untill battery goes out? Ofc I do not know what is realisticly possible on this size flashlight. Anyway that is more than C8F’s low which is 100 lumen. 700 and 500 lumen modes will eventually throttle down to 100 lumen with C8F yes?
SP33 looks quite nice too, but will it stop thermal throttling on 500, 250 or 45 lumen mode?

350 lumens should easily last 3hrs of constant brightness since it only pushes a bit less than 0,95A to the emitter on the SP31A.

It won’t probably thermal throttle on the 500 lumen mode, and it will step down on the timer, but you will be able to get the 500 lumen mode back up.

Is this about SP33 or C8F? If both can manage constant 500 lumen, then added max lumens on C8F feel tempting, even though I’d need to pay quite alot more for it than SP33 (damn taxes on 22€+ shipments)

The SP33. The C8F can’t actually manage more than 100 lumens of constant brightness, so the 500 lumen mode on the C8F will go down by quite a bit as the battery drains.

The SP31A would only be using Buck mode if 2 CR123A’s are installed. They have low capacity compared to a high capacity 18650 so using those half cell sized batteries would be sort of silly. Am I missing something?

No. The SP31A uses an XPL2, which has a very low forward voltage compared to the XPL, and especially XPL-HI.

On turbo at 1000 lumens, it’ll stay in regulation until the cell voltage reaches 3,7V using most buck drivers with a drop out voltage of 0,5V.

On the 350 lumen mode, it’ll basically stay in regulation down to 3,3V, where most of the useful energy of the cell would be used, about 2,5Ah out of a 30Q, so almost all of the capacity out of the cell before internal resistance goes up, so the 350 lumen mode will stay regulated up until the cell is almost empty.

That’s also the reason the XPL2 is such a monster: it can draw a ton of current from a cell since its forward voltage is very low.

Using a very low voltage LED like the XPL2, Nichia 219C 90CRI, LH351D 90CRI, and E21A array are probably the only LEDs in which using a buck driver is actually very useful with a single 18650.

Have used dozens of those emitters, haven’t noticed them having such a low Vf, probably because I don’t give em the chance… :wink:

Bottom line is:

The highest sustainable output plus the longest runtimes will always be with a bigger light. It can dissipate heat better and usually has bigger batteries.

Generally speaking, go with the biggest light you can.

So for those of you that are planning to buy a 21700 C8F host version and can’t figure out which driver to use. I can recommend Lexel’s narsilm driver. I had a 22mm driver that I grinded down until it fit. There’s plenty of room on the topside ring of the driver that it sits on the driver shelf without any of the driver components touching the shelf. On the bottomside of the driver, I added 3 solder blobs placed on the ring high enough that it just touches the retainer ring (I can post a picture later if people want to see it). Just remember to not put to much pressure when screwing in the driver retainer ring so that it cracks a 7135 chip (ask me how I know this).

Only problem with my light is that I accidentally ripped off one of the switch wires from the the soldering pad on the driver so now I need to try and fix it later. I emailed Lexel and he wrote me back how to get around it, so hopefully I can salvage the situation or if not I guess I’ll order another driver from Lexel.

The other problem I ran into was that I couldn’t figure out how to wire the stock switch to the driver. Luckily I had one of Lexel’s switch boards, it’s much easier to wire the switch when the solder pads are labeled. After putting the switchboard together, I realized that the leds weren’t bright enough for me (since the rubber boot is a dark color, anyone know if there are clear replacement boots that fit?). So I when I have more time I’ll go back adjust that as well.

I received mine, took nearly one month but Sofirn service was superb. Flashlight is a thing of beauty. Better than my former favorite, the original spec (3450 lumen) Jetbeam TH20. The 21700 battery combined with three deep-reflector well LED is so much better! :sunglasses:

I had a chance to go Turbo with the EFEST from Battery Junction. “Overwhelming force” is the thought that describes it. I have used the Jetbeam TH20 a lot with fully charged Sony VTC5A and Sanyo UR18650NSX. This Sofirn C8F 21700 with the EFEST is remarkably brighter. My dark, cavernous kitchen is lit up entirely, and into the backyard. It feels on par with the old Thrunite soda can lights from the year 2014 in terms of shock and awe feeling. Very bright. Perfect for pest control. Wish I had this over the Jetbeam TH20 when I was pest controlling food moths. This is just plain brighter, for longer, and covers a greater area. :+1:

What size is it?

Kaidomain carries a lot of boots.

Today answered :

Thank you friend
Yes, a driver for C8F-21700 is available, i will do a new link of it

Any news about the flat tail?…

Nothing yet. But I got my “thank you” C8F pack from Sofirn yesterday. It is a full pack 21700 version with battery, charger, 18650 tube. It has some issues but I contacted them and they are on it. Also as the low output problem of some lights. At first I also measured 2550 lumens with 18650 battery at first try but it was not completely full. Now with fully charged Sofirn 21700 it makes 3102 lumens. Temp regulation works fine. I measured 54°C on the head maximum and it stayed there while the light was adjusting output slowly down. My only negative now is the ramp characteristic. It maybe linear to current but not linear to the eye. The low side going up fast but the upper half barely changing. If they make an exponential curve to that like Narsil it will be a very good firmware.
Also like how they solved the two switch operation. It remembers the level and also if you leaved on or off with side switch. So when you press off and then On the tailcap it came back at any level you left or in a standby/off state.

So if have some issues. Don’t worry! It will be solved

I still haven’t got mine. It’s almost a month now. I hope it didn’t get lost. The last tracking date was Sept 2nd in China and then nothing.

Oh well, hopefully it will just show up. Lol

I used my 21700 C8 last night on my Thursday night walk, the Samsung LH351D in 5000K 80 CRI looked really good in the night and the power level was really good as well. Enjoyed it a lot, sure to be a favorite among my user group and will make it harder to decide which light to grab. :wink: