Question about Flashlight LEDs

I was playing around with a flashlight that I'm pulling apart to turn into a laser host. It has 19 LEDs.

It normally takes 3x 1.5V batteries (and produced a hot white light), but just to see what happened I put in 2x 18650 batteries. The light turned bright blue with the exception of one single LED which turned orange and burned out.

Can anyone explain why this happened? I know that with overdriving you can get LEDs to change colour but to have 18 turn blue and one turn orange?

Needless to say it doesn't work anymore

Lase

If they're all in parallel (which I think they might be) then that one orange one probably hogged most of the current and thus died. It's because they don't have current balancing resistors, and if one starts to take too much, it'll eventually die as a result of overcurrent.

The color change is just because of heat, I think.

The orange you saw was PROBABLY just the LED overheating so much it glowed incandescent for a moment.

Le Quack said:

If they're all in parallel (which I think they might be) then that one orange one probably hogged most of the current and thus died. It's because they don't have current balancing resistors, and if one starts to take too much, it'll eventually die as a result of overcurrent.

The color change is just because of heat, I think.

The orange you saw was PROBABLY just the LED overheating so much it glowed incandescent for a moment.

Click to expand...

I figured that but why did the rest turn blue?

Lase

Wavelength shift from heating, most likely.

White LED's are just blue LED's with a phosphor coating on top of them. Good chance you simply overloaded the phosphor and got more blue light out the front than white.

That orange light was probably diode wires glowing orange hot. When I was kid and I started to play with LEDs, I burned many on them .. they always glowed orange (for a moment). Basically you are using the LED as light bulb :-D

I totally agree with Things's assessment...I actually had a flashlight with white LEDs that emitted this blue color which let me know that the LEDs were really pissed -- they were driven far beyond spec. in this case. The phosphor overheated and as a result, emitted far less light than normal, so the LEDs' native blue emission became dominant.