You are right… The UI on the c8f 21700 is one I like.
Funny, you are describing the Sofirn SP33 UI exactly, I mean 100% exact. Just got mine today, and maybe even I might not mod this one.
I agree 100% as well - there's a few lights doing this UI now, wish they all did. Too many have clicks to next mode, and hold to turn OFF.
/\ . 
. I am really liking the SP33 UI too.
Emitters XHP. Compare your Sofirn C8F 18650 (mode group 3 - mode 990Lm) and Sofirn SP33 XHP50 in 1000Lm mode for 30 minutes and you will see a huge difference: Sofirn SP33 XHP50 more compact and much colder.
There are still factors that influence:
Bigger shelf (thick internal integrated emitter shelf)
Many cooling fins
Better drivers
Nobody should be complaining about short run time because it is normal. All small high powered lights have short turbo. If anyone knows of one that has a decent long turbo run time, please let us know so we can analyze how it works.
I am not so pleased by how fast my Astrolux S43S gets hot. It is small with a copper head so you would think it has a decent turbo run time. Unfortunately, it also draws 20A and the emitters and lens are not very efficient. It’s not that bright, yet it heats up super fast.
So small lights need good efficiency (light output to amperage draw), they need a limited amperage draw (nothing crazy high), then they need good control over the temperature (such as calibrated sensors combined with a smooth ramp down). All of this usually results in an expensive light.
I believe Zebralight is known to be really good at building small, yet high powered lights. They are very sophisticated and expensive, which is why I don’t own any.
Liquid cooling is not practical at all. It would be much larger than air cooling. So forget that idea.
I did a search and found your post with pics of this light. Wow that LuckySun F3X looks amazing. I like it alot more than the C8 series with those very functional cooling fins! I wish Sofirn can make one with fins like that and with USB-C recharge!
Love the optional extension tube
In general there are no silver bullets - small but super-bright will be very hot.
1. Liquid cooling - if you add a pump it’s going to work much worse than a fan and adds a lot of complexity as well. Passive liquid cooling, i.e. heat pipes may work, but there’s an easier improvement that I’d suggest trying first:
2. Unibody construction. Improving heat transfer across the light will improve both turbo and sustained performance.
3. For storing heat I suggest trying paraffin wax. It’s lightweight and as it melts it takes away a lot of heat. If you can make a sealed container and good thermal transfer into that container you’ll get much better turbo times.
If you heat 1g of aluminum from 20C to 60C, it can store ~54 Ws of heat.
If you heat 1g of paraffin wax from 20C to 60C, it can store ~360 Ws of heat.
Some lights released recently went with super-thick shelves to improve Turbo times. As you said - that made them large and heavy. I don’t think that using aluminium as heat storage is a good option….but it’s certainly a cheap one.
4. Consider thermally insulating the points where user touches the flashlight body. This way you make the LED hotter and a bit less efficient, so you harm sustained performance. But you can increase body temperature without burning user hands. This improves heat capacity and therefore - turbo times can be longer.
5. Also, I can join others in saying that the more efficient a light is the better. A 1000 lm light that does 50lm/W needs to dissipate or store roughly 17W of heat. A 1000 lm light that does 100 lm/W needs to dissipate or store 7W of heat. Double efficacy again, at 200 lm/W that’s just 2W.
So:
- efficient driver
- buck
- boost
- buck-boost
- many big LEDs (note: this can make the LED a flooder. If you don’t want a pure flooder consider flat LEDs, these are more efficint for throw)
- efficient optics
- multi-layer AR coating is better than single-layer which in turn is way better than uncoated optics
- some multi-layer AR coatings are better than others but they are more expensive as well
- review available reflector coatings - there’s a huge room for improvement though cost may be prohibitive
- TIR+glass lens is a bit less efficient than TIR alone
- some TIR lenses are better than others
- take care about your bezel design, every bezel reduces output but some are better than others
- multi-layer AR coating is better than single-layer which in turn is way better than uncoated optics
- low electrical losses
- quality springs, reasonably fat wires, e-switches…quite easy to do well and overkill doesn’t help much
Note that good cooling improves efficiency as well, but for a regular flashlight this is a small effect. As a practical example please consider Emisar D4 with Nichia 219C and XP-L HI. With the XP-L HI it has significantly longer turbo time even though it’s brighter.
6. I’d like to also add that compact designs are better…if you remove some features that use space you can re-invest that space for better cooling. Same with implementing features in a more compact way. Your light will have the same size and weight but it will perform better. What options to reduce size would I recommend?
- clicky switches are less compact than e-switches
- though quite a few users love the ergonomy of tail switch. Tail e-switch is an option then.
- Zebralight-style light engine
- DQG-style tail caps offer super-low electrical resistance and take less size than the more common spring-equipped ones
Storing heat through wax? Wrong objective.
Myself I tend to disregard turbo times, I tend to need only several seconds anyway. I’d much prefer manufacturers to focus on lm/g and lm/mm³ of their flashlights with lm being either turbo (disregarding turbo times) or sustained.
But I’m unusual in this regard and from what I’ve seen most users do care about turbo times. So it makes a lot of sense for manufacturer to optimise that.
To optimise turbo times without lowering output there are only 3 options:
- improve efficiency
- improve heat shedding
- store the heat
The first option doesn’t get you very far. The second is pretty much meaningless for improving turbo times of powerful lights. The last one? I don’t like that objective but I think it makes a lot of sense for manufacturers.
Heat is indeed an issue for small lights. Playing with my D4 made me aware of that.
Still, with the popularity of smaller 18650 lights (DQG, Emisar FW3A, Zebralight and others) I think that if you could find a way to make a light in this size range, you would find a good deal of customers.
I wonder if the tailcaps could be reduced in size. The one on my SC31 is a good deal smaller and lighter than my other 18650 Sofirn lights. A shallower reflector, no charging circuit, shorter springs (to be used with unprotected flattops only) and perhaps using a triple carcio optic could reduce the length in a measurable way. You could also use a driver that doesn’t allow the highest levels for safety and longer turbo runtimes if you choose.
A light that is shorter in length (using some of these ideas) but larger in diameter like the SP33 might have enough mass to handle the increased heat too.
I realize that it’s easier said than done, but with the solid reputation Sofirn has established I don’t see how a more compact design like this wouldn’t be a success. Thanks for your consideration.
@JasonWW, Agro is talking about phase change materials.
The advantage of using aluminium is mostly good heat dissapation, but can’t handle heat too well.
Using a material that changes of phase can handle a lot of heat.
It goes from solid to a viscous liquid. It can be very useful to hold heat then release it.
Our goal is not to hold on to heat. It’s to get it away from the led and driver as quickly as possible.
Trying to store heat inside the flashlight would be like having a pill inside an 18650 tube flashlight holding the led and driver. Then we isolate that pill so the heat doesn’t reach the outer body of the flashlight. We might think it’s a miracle. The light gets super bright and doesn’t even get warm. Great, right? Unfortunately, the led and driver are frying themselves inside because all the heat is stored up in the pill.
Technically it works, but it’s short term. If the pill, led and driver get too hot they will destroy themselves. The advantage here is that they can handle higher temps than our hand can. So we can extend turbo run time maybe 50% or something. But that is the only advantage (at the expense of stressing the internals more)
Storing the heat inside is a disadvantage when it comes to sustained output. That heat has to get out somehow. It needs to be exposed to the air and our hand to cool the light. Otherwise we have a light that can do a longer Turbo run, but then needs to be reduced to maybe 50 lumen or maybe shut down completely for 10 minutes or so to let the heat slowly go down inside.
There is a good reason nobody builds flashlights like that. Instead, everyone builds lights that try to get the heat out to the exterior as quickly as possible. It heats up fast, but also cools down fast and can actually sustain maybe 400-500 lumen (still talking about an 18650 tube light)
A light designed to store the heat could not run 400-500 lumen continous. It would fry itself internally and might only do 100 lumen continous due to the poor heat path.
My above example might be kind of extreme because I wanted to show both the advantages and disadvantages of storing heat inside. Maybe there is a way to build something in between. Like a hybrid. I don’t know. To me it seems like any type of design that tries to store heat instead if get rid of it just has too many disadvantages.
One way to view this differently is using a phase change material with a vapor chamber heatsink.
The material would store a lot of heat without rising in temperature much, and the vapor chamber would be directly connected to the fins.
That’s the advantage of using phase change materials: the temperature doesn’t actually change until it changes of phase. That’s the magic that makes it so amazing.
This would not work well at all with small lights.
However, with lights like the BLF Q8, SP70, and BLF GT sized lights, this would work extremely well since there’s a lot of surface area to dissipate the heat outside of the light, even at 50-100W+ and 200W+ power levels.
The design of these lights allow for very efficient heat dissipation. They don’t have enough thermal mass to sustain that, since they aren’t being actively cooled.
Phase change material change that.
Heck, even some eBike battery packs using this design with aluminium heatsink. They use phase change materials to cool down very high performance packs, and aluminium heatsinks to get rid of the heat quickly.
Maybe I should do an experiment related to this…
I’m serious on this, but I’m actually going to buy some paraffin wax, and fill the BLF Q8 driver cavity with paraffin wax to not only waterproof the driver completely, but to also see if it helps with sustained thermals.
Chances are you’ll bust the Q8 wide open. Paraffin wax expands a lot with increasing temperature. That’s how the thermostat in your car works.
And anyone who ever tried pouring hot wax into containers for making candles is familiar with the “sinkhole” that forms when it cools.
I… wouldn’t do that.
BUT…… if you decide to do it, we want pictures & report; success or failure. . :innocent:
Do the fins really help a lot for heat dissapation? I found Surefire lights don’t have fins, streamlight lights have but not many and not that deep. Maybe I’m wrong.
Anyone do the experiment to compare with mass fins and without fins?
Yes, but you need a bit of airflow
I wouldn’t rely heavily on the cooling fins. their efficiency strongly depends on external conditions - air movement.
As an example “no air movement” ~24°C- there is not much difference between Olight X7 (~47°C) and Haikelite mt03(~45°C) in the ~2000Lm mode, while Haikelite has noticeably more area cooling fins.
But it is better to conduct an additional experiment, without wind and with blowing and compare. for example, if anyone has old Convoy C8 and new updated C8+(add fins) in the same configuration, or Sofirn C8F 18650 and C8F 21700.