triple leds

LED Flashlights – General Info
1

someone refresh me

what is the reason for triple vs single leds?

say in an 18650 light?

is it that you distribute the heat from high current levels?

or is it that the LED/s is less efficient if driven to the max of one 18650, compared to 3?

or something else?

seems like the minuses would be cost, head size, driver complication <?>, larger optics…

wle

2
  • Easier to scale output through parallelism than driving a single LED harder; conveniently LEDs are more efficient at low currents than high currents
  • Standard off the shelf triple/quad optics produce decent beam patterns … so long as you’re not trying to maximize throw

Of course, there’s a common compromise with high-performance triples and quads in an EDC formfactor - their peak output is often a multiple of their sustained output. The Emisar D4 is the prototypical example - briefly capable of some ~4000 lumens before protective thermal throttling kicks in, after which it’s more like a ~400 lumen sustained output.

3

that’s mostly because of the small size though and lack of fins or other thermal dissipators

4

so it sounds like having 1 led, would have about the same sustained output…?

i still consider it nice to have a peak output that exceeds the sustained…

5

In a compact EDC formfactor there’s no volume left for additional mass and more surface area (ala fins) are apt to provide marginal improvement.

Ultimately a given design will have a limit on its ability to sink heat that can be simplified as X watts for an acceptable maximum temperature rise vs ambient. And since a single LED would need to be driven harder its sustained output would likely be lower than the same X watts distributed across three or four LEDs.

I consider this to be a desirable feature since in usage I only need the nominal ~400 lumens >95% of the time, with turbo or boost modes being used for seconds out of every ~five minutes of runtime. Or to put it simpler - this capability while limited doesn’t really cost anything against the normal utility of the light.

6

interesting

i would guess extra mass would not help either, without some kind of extra dissipation

i mean it would but it would also reach a too-high temp, unless there is also more dissipation

extra mass would delay the high temp but not forever

7

Exactly. Copper lights hold turbo slightly longer due to more thermal mass, but sustain a lower level than alu because they are less efficient at actually transferring the heat to air. Why a lot of high performance heatsinks etc. use Cu for heat transfer to Al fins for the actual surface.

2 Thanks
8

One other reason that I don’t see directly called out: some LEDs have petty low max current. By themselves they aren’t very impressive but a triple or quad can solve that problem.

E.g. I’m really liking the XPP 3000k 90 CRI right now. The tint is great and it has a punchy beam profile. One downside is its max current/output is pretty low, but it works great in a triple.

9

From flashlight body to air heat is transfered via convection. Hotter the outer surface compared to air->more heat is transfered to air also. So copper allows higher sustained output given the surface area is the same.

10

I really like my triple 18650 flashlights (18 so far), much better than single LED flashlights.

The Carclo 10511 frosted narrow spot optic is my favorite and does have some throw. The beam is great and doesn’t have the artifacts that a single LED flashlight can have.

And for some LEDs, like the Optisolis, a triple is needed to get some decent output. Or with the 219B, a triple is nice to not have to drive the LED too hard.