Any update to this? That LED should be warrantied. It’s like you only got a 88% working light xD
tactical_grizzly, sorry to hear about that. I hope you can get it resolved.
Having LEDs in parallel with no balancing (which is the recent trend) is unfortunately non-ideal.. Generally speaking, LEDs have a negative temperature coefficient whereby V_fwd typically drops when temperature rises. This leads to a feedback loop which can quickly cause unbalanced LEDs to go into thermal runaway. It's actually also a common problem with some kinds (especially older) of transistors as well (when used in parallel with no balancing, though many modern transistors actually have positive tempo which makes them perfect for parallel operation!)
You can imagine if in set of parallel LEDs, if one of them has a slightly lower V_fwd, current will preferentially flow through that LED more, causing it to heat up more than the other LEDs, causing V_fwd to drop even further, etc. In practical implementation, LEDs that flashlight manufacturers use typically are very tightly binned. The LEDs are then typically soldered fairly well to a MCPCB, which helps even-out the thermals somewhat. This generally mitigates the issue to an extent that it works out practically in real life. In fact, multi-die LEDs achieve this by using LEDs in various series and parallel configurations, but you can be sure that each of these dies are very tightly binned together and thermally coupled as well as possible (or at least that's what you'll hope for... I've seen some instances of off-brand multi-die LEDs which are definitely not well matched; very obvious at low input power).
But if you are in a situation where the LEDs have a completely different V_fwd (e.g. LEDs used were from different bins), and worse, use an unregulated source like a FET (which again, not ideal!), then you can imagine how the LEDs will get quite unhappy.. it's a small miracle that we don't see more magic smoke coming out of our hot-rod LEDs!
As a result, I'm all for advocating current controlled regulated drivers, especially in the boost configuration as contactcr pointed out, which eliminates these two problems... allowing for beautiful perfect sharing of current across the LEDs in series.
For Hank saying that different V_fwds leading to different brightness ' is a feature', it would be like calling the fundamental design flaw (having LEDs in parallel with no balancing), a feature.. That said, it looks like this is not quite the case here... it looks like your LED is in fact, physically damaged.
It almost looks like there is some phosphor burn on part of the LED itself, as opposed to being an LED which has higher V_fwd. Typically if the only issues is that the LED has a higher V_fwd, then entire LED phosphor may be dimmer, but it should look fairly even across the die. From your photos at least, it doesn't quite look like the case. This damage could have been just a bad LED from the factory, or could be some over temperature from the assembly / soldering process, or even exacerbated from different V_fwds. Hopefully you can get it replaced; otherwise it may make for a fun project to get into flashlight modding!
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