How long would you estimate an XM-L2 could survive Direct Drive on a cheap aluminum star?

…because I’d say a little under 30 seconds.

:person_facepalming:

:smiley:

pics or it didnt happen? lol

without heat sink 7 seconds

:smiley: 5-7 seconds…Poof! :smiley: It is pretty cool though, the last seconds, when it turns blue, then Fitzzzzz! :+1: Don’t blink or you will miss it! :person_facepalming:

well, wait a minute…

what if its being “fed” by a sh!tfire battery? might last forever like that, lmFao…

we would advertise it as “great moon mode!… but… not much more, though…”

the way you guys talk about sh!tfire batteries? i would do better to hook lemons and potatoes up in series, ha ha

DD on mine lasted a good 1 minute before it turns blue>green>purple>firefly blue on my P60 setup.

If you are direct driving an LED directly from a Li-ion battery, with no resistance, the current is only limited by whatever resistances are in the path, like the wires, etc. So, if current through the LED (and or voltage) could be high enough to kill the LED.

Depends on the battery quality and voltage, If you use 8000mAh UltraFire battery that is at 3.8V you could probably run that thing DD for hours….

:person_facepalming:

So do you want to know the point at which it goes from “facepalm” to actually embarassing?

That would be the point at which I installed the SECOND one and promptly fried it, too.

Because of course it was a faulty LED the first time, I didn’t wire up anything wrong so I’ll just put a new one in… hey, WTF? Ohhh… (moment of realization of what I just did)

That’s nothing, you haven’t boner-ed till you put a 4S battery carrier loaded with VTC5A’s into a 2S2P XHP70 light! :smiley: Magic smoke my ass! :person_facepalming:

That's not true unless etc includes the LED. The current through the LED is a function of the voltage applied to it. While it's not a linear resistor it does have a resistance, one that depends on voltage and temperature, and it does limit its own current. From what I can tell the currents that are normally drawn at 4.2V are right on the edge of what these LED's can survive and it is true that any extra resistance at all may help them survive, but I guess the main effect here is that the heat is both directly damaging and heat also increases current at a given voltage (often referred to as lowering the Vf). I don't know the exact threshold, but I guess at 4.0V or something a bit lower maybe, even with a battery capable of delivering 30A, the LED would desolder itself before it would burn out.

There is the concept of thermal runaway, where the heat continues to increase the current drawn at a given voltage, generating more heat, and more current etc, but I don't think that's truly a runaway process. It should reach some equilibrium in situations where nothing breaks first.