Hello,
Please recommend me an EDC flashlight that is quite bright and cheap.
- around 400 lumens
- prefer floody light
- less than $20
- any cell formats
I currently have a convoy s2+. I’m impressed by its brightness but it just gets too hot.
So I’m looking for something with less heat and less brightness.
Thanks!
OK this is just too obvious but why don’t you just use the S2+ in medium mode??
If you get a smaller light that has 400 lumens on high or will also get hot… Laws of physics…
K.
the S2+ Is also with 1.4A driver availiable or new firmware with max. 50%
https://www.aliexpress.com/item/7135x3-7135x4-7135x6-7135x8-with-new-firmware/32734523412.html?spm=2114.13010608.0.0.Yf1keW
You could pick up an AR glass as well
https://www.aliexpress.com/store/product/20-5-1-6mm-ar-coated-glass-suitable-for-Convoy-S2-S2-S3-S6-S8-flashlight/330416_32679292741.html
Even on medium mode, it’s still quite hot. (Or maybe it’s just an excuse to buy more lights 
So I wonder if all the small edc lights with 400+ lumens gets hot even the much more expensive ones?
Lexel, thanks for your suggestion. however, I have zero mod knowledge. But I will sure look at the X2R.
Short answer, Yes.
Given the same LED emitter and same power level,
the same heat will be produced regardless of the price of the light.
There are effeciancy differences between emitters in the same class. Example XPL V2 puts out less lumens than the XPl V6 at the same current. That also stands between models XPL vs XML2. So at 3 amps the emmiter with the best effeciency will theoretically run cooler. The real issue lies with thermal transfer. The smaller the light the smaller the surface area used to sink and radiate the heat. Running identical emmiters at 3amps, one in a small 14500 and the other in a 26650 body will result in the same thermal signature, the difference is that the bigger body can regulate the heat dissipation better, hence a cooler light.(Dependent also on design but thats another can of worms). Ive never taken the time to check the temperature or runtime on any of my small 300-400 lumen lights, just know they all get hot. Goodluck
As Kusie says, you’re pretty much stuck with the laws of physics on this one. The only real way to make it run cool is to choose a larger light with more surface area to dissipate the heat from.
If you’re determined to stay with the same size of light, you could mitigate the issue a bit by:
1. Looking for a light made from copper rather than aluminium. The higher thermal conductivity of copper allows the heat to spread faster into the rest of the light body, so it then has more surface area to dissipate from. Copper lights are more expensive, though.
2. Opting for a higher LED bin. At the extremes, an XML2 T4-7A produces 400lm OTF at 1.4A, but an XML2 U2-1A can do it at 1.1A - a 20% reduction in heat to dissipate. However, that generally means accepting a cooler tint, if that matters to you.
I don’t think its possible with todays emitters. 400 OTF lumens is going to generate some degree of heat.
Question to the forum… Wouldn’t a multi-emitter design run cooler? 400 Lumens from one LED versus 100 Lumens from 4 LEDs. The latter would run cooler, for the simple reason that the LEDs are severely under driven… correct?
Yes, LEDs are considerably more efficient at lower current. If you modded for all the possible heat-reducing upgrades, the changes would add up. So, that would mean changing to a quad, which would help in two ways - the copper pill that goes in helps dissipate the heat and you get higher lm/w efficiency. You would also use the latest, highest bin, highest efficiency emitters in the quad so less of the power is converted to heat and more into light. Then you turn down the current by removing a chip or two from the driver. According to Cree PCT, the XP-L2 W2 will give you a raw output of 389.1 lumens at 700ma of current. The PCT doesn’t show any results for lower than 350ma for the XP-L2, but with the increased efficiency, you’re probably still going to be over 400lm OTF at 700ma divided into a quad.
At 1.5A the light of the size of the S2+ doesnt get too hot, its warm but never too hot to touch it
I ran the S2+ 7135*4 and X2R on highest mode till the battery depleted a couple times without a problem
The Convoy C8 doesnt get too hot at 2.8A but its bigger
Ditto the rest, any light producing a real 400 OTF lumens will produce about the same amount of heat. Money can’t fix that.
If you go with a larger light it will stay cooler.
Or simply use a lower mode. I find I rarely need more then ~150 lumens for most tasks and that hardly produces any noticeable heat in the S2+.
…except that’s not exactly true. Some lights take 1.5A to make 400lm, but it can be done with only 0.7A which would produce less than half the heat. What is true is that any LED lights that use the same wattage will produce about the same amount of heat.
Well, that’s not exactly true either. 
I have a few 2xAA lights, and while they use the same LED and brightness bin, they differ dramatically on how efficient they are when above 200 lumens. My 4sevens Quarks are horribly inefficient on max(350 lumens or so), while my Armytek Prime uses less power when producing 500 lumens.
The Quarks have very inefficient drivers on their maximum output. I estimate the driver is only about 50% efficient, the rest going into waste heat. They’re quite efficient on levels below max, though.
So, it doesn’t just depend on the LED. It also depends on the driver.
Yeah, I think you might be confused about what I said, which is that - basically - LED lights using the same wattage will produce about the same amount of heat. I agree with you that a more efficient light can produce more lumens with less heat. 
There is another option no one has mentioned for reducing heat (beyond temperature regulated lights), which is waiting 10 years for more efficient emitters, by then the efficiency should have doubled meaning half the heat
Good to see a place where these things are understood. Watts = rate of energy input. The energy goes almost entirely to heat (except for a little that goes to light) so watts is heat flow. Only the surface of the light removes heat, and the rate it does that depends directly on the temperature that the surface comes to. To dissipate a given input power, the surface MUST reach a certain temperature, regardless of DTP, efficiency or anything (wind and environmental temperature obviously do matter but that's different). Yes, even DTP does NOT help dissipate electrical power from the light in the long run. What it does do is keep the led itself cooler which helps use less electrical power for the same light output.
The thing to look for as others have said, is just lumens per watt... so long as the color of the lumens is suitable to you. Of course if you just care about case temperature, a larger case will reduce that.
Lol, I didn’t see it mentioned, which S2+ driver do you have now?
I thought leading LEDs are about 50% efficient at converting energy into light, with the other 50% going to heat. If so, that’s more than just a little.
Electrical power input - light power output = heat.
All the components (battery, driver, circuit resistance, etc.) except the LED go into heat. The LED about 50% into heat. So if your other components are efficient, the efficiency of the LED can have a big impact on the amount of heat produced. And for a fixed lumen output, a more efficient LED not only generates less heat, but you can drive it with less power so even less heat is produced.
you either lose heat in the led in PWM or lose heat in the linear driver. There's really not a driver that works much better, or probably few that even work much worse than any others in middle modes. Even if there are contact and trace resistances, that's just less resistance for the linear regulator to produce. You're blowing off the extra voltage with resistance anyway, so it doesn't matter where you do it. You're still limited by physics, P=dV^2/R for the amount of V you need to reduce, and there's probably not much difference at all from one driver to the next in these modes. You can in principle get around the physics with a buck, but reality isn't as pretty as principle, especially for 1-cell lights.