Would anyone have more specifics on built in resistances and runaways? Recalling reading somewhere about a 4A value for this, what does it mean? Does this value change across models? Is there a way to measure the built in resistance on a given light?
The short answer for us commoners is no.
Stick to a Keeppower 18650 protected battery and you'll be good to go forever.
Order it from Malkoff or Illumn.com
Avoid high-drain batteries. High drain meaning 30-50amps.
Everything affects resistance....age, temperature, conditions, battery, literally every thing, QTC, distance from the battery to the LED, what all is between the battery and the LED, etc and it constantly changes....
As volts decrease the amps increase.
As heat increases so does amps.
The more amps you have the shorter the life of the LED.
Heat kills LEDs.
Heat = unused energy that is not converted into light