Just got the d4 with XP-L HI yet, it is unbelievably hot. My first insanely powerful rocket. I tried to find any mods on cooling but can’t seem to find any. Thinking along the lines of some non-conductive fluid permanently inside, or some copper that transfers heat from head to body while finned, but that sounds like it would need to be precisely / costly fabricated…
sounds like my first S2+ triple with DD driver I had. Nice result and lumens… but literally untouchable after 30 seconds.
rc boat motors have special “vest” with water circulating inside. If youll found one with suitable ID, add water pump, external water cooling heatsing with fan (and extra battery to power this stuff), you will be able to run turbo untill cell is empty.
I originally was thinking not adding any bulk, but I think this may be the most practical and viable idea. I would really prefer no pump and extra battery tho. Perhaps a finned reservoir that’s part of a small handle attached to the d4.
Just back it off one. Like you do in a car on a hill climb.
Even we get hot when exerting.
That “wow” factor. is to impress those that don’t know.
They not realistically designed to run at that temp for more than 30 seconds or more.
Try my Copper S41. Quad. Or Imalent DN35, same thing. Magic.
But not for long hey.
Basically, those torches are a novelty. To play with.
THAT’s why we have the bigger torches.
They all work well one/two steps down. Just flash the max
Occasionally to see.
I dont think there is anything practical u can do, i mean it would be very costly and not very comfort to hold, the light is not mean to use the max output for very long either its more the wow factor if u want that much lumens longer u need bigger light with more heatsinks, there is no shortcuts. even if u dont run on highest its still a fun light to have and u get enough brightness i think. Not even the s41 with the small copper heatsink helps much, heats up like crazy to in less then 30 seconds.
Must be fun to use it in winter tho, i think u can get longer runtimes then 
I set the temp level below (52º) the max limit (70º) so that it wouldn’t get so much hot! Not the same thing as adding something to transfer heat, but helps a bit :+1:
The heat transfer is already very good, because the LED’s are on a metal cored circuit board to give good transfer of heat to the body. The circuit board sits on a fairly thick metal shelf, which transfers that heat to the outside of the body.
I suppose it could be filled with a non-conducting fluid like those designed for passive computer cooling. However, I don’t think the light is sealed between the head and the battery, so you’d have to be careful not to spill the fluid when removing the battery to charge.
This might slightly improve the heat transfer away from the LED’s, but that just means the head gets even closer to the temperature of the sensor on the driver that throttles back the output to keep it cool.
What you really need is more thermal mass or a way to remove heat from the body faster. Some users set fans blowing on their lights or actually submerge their light in water when they want to test driver behavior when heat is less of an issue. That’s not convenient, but it’s pretty straightforward.
Not at all. Even at much lower outputs, the D4 is a very useful light. I bought mine with the expectation I’d seldom, if ever use it above 500 lumens, based on the high CRI option, and reviews praising the user interface.
Yet the higher outputs are not without their uses. I’ve used mine on max a couple times so far to see something further in the distance without having to walk closer. 10 seconds can be fine for that. I could also simply have used a throwier light, but prefer a floody beam if the main task I’m using the light for a the moment is up close.
Get a bigger light (26650 version available I think), or turn it down. 20A of current in a pocket device is bound to generate heat, especially with something as inefficient as lighting.
As mentioned above, there is no practical way to deal with 4000 lumens in such a small light - unless it is some kind of water cooled frankenlight project. It is not meant to be used above 600 lumen for any extended period of time. But it’s nice to have such power just a double click away… be it for a few seconds.
The coming 26650 D4S will have a little more mass, but not nearly enough to sustain turbo very long either - especially with so few and short fins.
Turn it on, put it in the Freezer. Problem solved … 
Don’t think its possible, sorry.
Maybe wear an oven glove.
Peltier cooler?
How about a hydration bladder filled with ice water?
Put it in a backpack, run the tube down your shirt sleeve, and leave it on a slow drip right onto the D4 head.
Would totally work for night hiking. Kinda messy for indoor use.
OK IAMLUCKY.
Ammendments.
Those torches “on max” are for wow factor.
My A41 I use a lot round house.garden and walking. On 4 or 5 from 7 settings.
Imalent DN35 the same (450 fine, 1500 for scanning. NEVER used the 2200).
Outside walks I use along with a XM-L2 headlight .
Serious light. It’s the BLF L6 for my requirements. (Can’t SEE any further chuckle)
The max on those tiny torches is. realistically a novelty though,
S2 or late model C8 do 90% of what’s required. Or more exxy ones.
No argument from me on the second part. I’ll go even further. An S2 will cover 99% of my actual use, and 100% of my flashlight requirements.
But I’ve found that, even though I also initially scoffed at such briefly sustainable outputs, I do from time to time appreciate having the feature.
As a result, I no longer think of it as a novelty.
I haven’t checked out the Imalent DN35. I’ll have to look it up.
Any tube light with more than 3A of drain can’t realistically be used for long period.
It’s physics. There’s nothing more to say that was not discussed for years here.
Add some mass to make the Turbo timer a bit longer…
Add some fins? Nope, that doesn’t make a huge difference.
Add some magic cooling fluid ? Well you’ve got to cool that fluid with a radiator and some air flow now…
Peltier ? Even hardkor gamerz don’t use them…
Add some copper ? Now your light weights more than you like and isn’t cooler anyway…
1000 lumens in a tube light for 1h is already an impressive performance IMHO 
3000 lumens is what an Olight SR mini II can sustain for 1h, but again it gets scorching hot and weights 300g… Not really a pocket light :person_facepalming:
I don’t use my D4 as much as I would like, I might try to flash Anduril so I’m not tempted to use the turbo mode
Most realistical and doable thing from an industrial point of view is maybe design the flashlight body with a slot to carry a tiny fan somewhere. With a dust air filter, it would be usable.
Cheers :-)
How about not using a high amp battery