I'm really good at building and modding but I'm not a theory guy... so I need someone educated to answer this.
I was told since time began that a device will only draw the current that it needs, IOW, say a device is specd out at a 2A draw at a given voltage. Let's say 3.7V for example. This device will only draw what it needs for its maximum whether your 3.7v is from a 2A or 100A supply.
So I was reading the review thread on the 8X7135 driver here and guys talk about removing a couple chips to downrate it t0 ~1.5A... as an experiment once I took a single XP-G, hooked up a 8X7135 to it, and it still only drew ~1.4A from that LED. So it wouldn't matter if there were 4 or a dozen chips on the board since the LED is only gonna draw ~1.5A, right?
So how can you overdrive LED's at a given voltage when it will draw a certain amount of amperage maximum unless you go direct drive? The only thing that's gonna fry it is overvoltage as opposed to overamperage as far as I can see.
You'd think I'd know this stuff, so be easy... feeling kinda dumb!
It just depends on all the variables .. Battery - driver - LED
Anyhow , I have a XP-G [ more than one ] , but this one in anyway , pulled over 2A and put out over 400+Lumen OTF , unfortunately , it also started to turn blue and emitting smoke ...
If run for more than 5 to 10 seconds .
On a RCR123A it pulls about 1.6 to 1.7A and is able to handle it ... and does 320OTF with a fresh cell .. [ My first Pocket rocket XP-G ] and now recides in a 501A , it just cant handle a 18650 .
So some folks just want to play it safe , in case the LED is capable of thermal overload .
And if you want , you can remove some 7135 chips to lower output . I havent used these with XP-G , but I have used the 1.4A version with 4x7135 .
I think KD sells them now [ Very nice ] as well .
Generally speaking , smaller cells cant supply the same current as larger cells , if we could run 26650 in a light [ XM-L ] then you would most likely see more current than with a 18650 .
As to how much voltage sag affects things , that would be interesting , very interesting . But a fully charged 16340 should not sag much more than a 18650 , especially in the first 10 seconds . [ Im guessing here ] , I wonder how one would test that ?