LED Reciprocal Lifespan?

[7741]

Here's a naïve question about increasing voltage and LED lifespan.
An LED's lifespan is rated in the tens of thousands of hours. Let's say we have a flashlight with an LED & circuit board that's rated for 3.7 ~ 12v. If you doubled the voltage to 24v, would it cut the LED/board lifespan in half? Is there some kind of a chart or guide that can predict the lifespan with voltage increases? Or is this issue just a matter of an overheating problem?

 

[DIWdiver]

Until you get into the extremely short (minutes) timeframe, the lifetime of an LED is primarily determined by temperature. For a lot of things, every 10 degrees C increase cuts the life in half. Something like this might well apply to LEDs, but I've never seen a well-researched discussion of it. Also, there comes a point where this rule breaks down and lifetime begins to drop even more precipitously.

As far as changing voltage, unlike a regular incandescent light, the battery voltage isn't applied directly to the LED (in most cases). There's often a layer of electronics between the battery and the LED. The nature of these electronic 'drivers' varies widely, and there's no single rule that would be a good answer to your question. But in many cases exceeding the max recommended voltage by more than a little can result in swift and catastrophic failure. Also, for lights with a well-made driver, increasing the battery voltage will not increase the light output. In poorly made drivers it often has a minimal effect.

There are lights where the battery is directly connected to the LED. We call this 'direct drive', and these are mostly the super cheap throw-away ones. Increasing the number of batteries by even one in a direct drive light will normally destroy the LED rapidly. There are also high-end and custom made direct drive lights which are made for absolute max output. These would follow that same rule, but are by no means cheap or throw-away!

 

[7741]

Great, thanks-----that really does clear it up. I just have to do much more reading on this forum to understand the mechanics of LED flashlights.