The exact reason “why” is pretty much a entire undergrad class in silicon junctions. Needless to say it involves quantum effects with the bandgap. I guess an ELI5 answer would be that the increased thermal energy can give lower voltage electrons a push across the bandgap? That is probably wrong on several levels though.
The effects of a falling Vf are huge though. It is why LEDs need current regulated supplies. Otherwise you get a thermal runaway and the LED destroys itself.
Anything with a negative temperature coefficient will need regulated current. Very few things have negative coefficients and voltage regulation is sufficient.
On a related note I’m always kind of amazed that direct drive FET lights work at all. The wires and contacts and the battery itself form a positive coefficient that magically balances out against the LED that is trying to self destruct.
The reason I thought forward voltage of an LED would go up is because of my experience in CPU and GPU over clocking.
See, when you up the voltage and frequency beyond its normal parameters, as you may already know, the additional power creates more resistance, and therefore more heat.
Then, what happens of this effect is that it accentuates electromigration since electrons have less incentive to stay inside of the silicon transistors, and if there is too much electromigration, boom! a crash even before speed ans temperature were a limit for the chip itself.
I had noticed this on my GPU, when I kept temperatures below 40°C, I could achieve massive frequencies and push voltage to its limit without any crashing.
Once I reached even 1°C above that threshold, it crashed. And observing the voltage and current behavior, I noticed that voltage slowly upped as the temperature went up, as well as current. Lowering the fan speed did this and if the voltage was not locked, this is what would happen.
Oh it is trial and error for sure. Many emitters get burned up before finding the limits. You have to get everything matched just right. The xhp50.2 has a tendency to burn up on a pair of weak 18350 cells while the 70.2 can handle a pair of the best 26650 cells. You can also help control things by emitter wire size and length to add that extra bit of resistance. Sometimes you want to bypass the battery springs and sometimes you don’t. Too hot of a combo can be tamed by using a weaker battery, etc…
Still testing it etc last i heard… they can take their sweet time too, not like anyone else have something at 40k lumens coming anytime soon unless Imalent pulls an 50k haha…
well yes but imalent has alot of quality issues imo its worse then olights x9 even tho more lumens the body cant handle that lumens from what ive seen. I wouldnt call that brand quality exactly acebeam and olight are on a whole different level.
You can get 2 DX80s for the price of one of these…Was expecting at least 50k at this price. I think they can push out more lumens but they’ll do it after a competitor releases something brighter.
Umm, that would be extremely hard to do even with 8 cells.
With with 8 30Qs, you would need to push above 500W! At a max of 70W per cell, that would mean a max of 560W! At 50k lumens, we are at the limits of 8 cell packs unless we go bigger.
Also, even with active cooling, how are you going to get rid of 500W in an LED flashlight? You would need to push an absolutely massive heatsink with a vapor chamber and some monster fans, or watercooling, which is not doable in a flashlight.
The DX80 can only do 7k lumen continous. The X70 should do much more. 20k, 30k, maybe even 40k continous. For those that need this massive continous output, there is nothing even close.
@hehaw77, first off, many reviews have noted that the light can’t actually output 32 000 lumens, but more like 28000 lumens. So less heat is produced there.
Second, can it hold that brightness for more than 3 min? Well, time it. See how long you can hold it before it either goes down to 7000 lumens because of the timer, or because it thermal throttles.
It has been noted that the DX80 under sustained load, gets very hot until the thermal sensor kicks it and thermal throttles it down.
I just finished telling you the quality issues with this light are pretty much fixed… your living in the past… if you buy the 2nd gen ones they are just fine…or by now 3rd or 4th gen…. if you owned one you would know… not just hearing whiners…
Well yes the Olight is a high quality light … their factory and their processes for making a light are quite impressive.
But again your “paying” for it….
Can’t speak for all of you but I’m grateful to Imalent for pushing the boundaries with their light. No one “to date” in a production environment has topped it yet.
While I’m waiting for the release of the Acebeam x70 its obvious they are having issues controlling the heat/ max output combo.
I just hope they don’t pull an “Olightened” moment and take 2 years to release the light similar to Olight announcing theirs 2 years ago but just releasing it now…
Putting pricing on your website which by the way is now 649 ; don’t think they received a good reception @ 749 lol…
Doesn’t mean anything till they release the light; otherwise its just hogwash….
Did any of you see Olights initial release of the x9r? With the fan you would slot it in on the side of the head etc…?
It’s obvious why they abandoned it…. easier to just restrict max lumen to 3min and have the user cycle in and out of it , than have a user stay in that mode say for 10-20 min….
Again I own one do you? Have you held one in your hand and used it? It does output 32K lumen and over time yes it will go down… as will all lights putting out that much power….
Now to set things right here… I’m not 100% sure of the time 20 min or something like that… one user took it up north in –20 weather and was able to keep max lumen for a long period of time can’t recall the exact time 15 min 20 min I can’t remember… obviously the weather played a role.
Now I’m not an Imalent fanboy but for people that don’t actually have one and just read old posts … that don’t carry a lot of weight now… its time to take a different look at the DX80 … still for the price… can’t go wrong….
lol…. spare me seery… I don’t know what DX you have but mine holds for quite a while… and to compare it to a grocery store flashlight is ridiculous and I own acebeams, Olights, etc… eagletec… and there isn’t that much of a disparity like your making it sound
hmm… ok sell me yours then… I’ll gladly take it from you since its only grocery quality say 20 bucks should cover it? Just send me your email and I”ll paypal you the money…