Need a bit of Help Understanding VF and Amps

[Angler]

@AsylumSweep

1.) So for this particular LED (Nichia 219c) what would happen if you used a FET Driver with a fully charged 4.2V battery capable of 20amps to 1 LED? The chart doesn’t extend out to those voltages or amps. Does that LED just burn up? Does this chart represent an LED that cannot handle that sort of direct drive, while the XM-L2 can?

It would burn up for sure. However, 20 amps would never make it to the LED due to wire resistance. In this chart where Texas Ace tested it, he probably had it on a big heatsink. After 6 amps the lumens drop off, this is the point of diminishing return. The LED is producing absurd amounts of heat at this point.

[Lexel]

A battery capable of 20A continous discharge will drop to around 3.6V at 10A, if you got 0 resistance from wires, driver and body you will burn a Nichia 219

[Caleb]

This is a great thread. I’m learning too.

So… since V=IR; at a given current, does a led with lower Vf also mean lower resistance of the led and therefore greater efficiency? Or am I way off base?