Ive been here a bit, but I don't have a good grasp on this.

Say you have an itp A1 with a CR123. On its maximum, it outputs around 200 lumens.

How much wattage is this? My guess was about 3 or 4 watts, but I honestly don't know.

My thought is that a power LED's brightness depends on how much current runs through it. Many lights are current-controlled. So, my itp A1 probably runs about 1 Amp through it to get the 200 lumens.

The big question is: How much voltage does it take to push 1A through the LED?

I know that the CR123 produces around 3 volts. An RCR123 can go from 2.8 to 4.2 varying. The current regulator should adjust the input voltage (within input specs) so that the current stays regulated. That means it transforms up or down to the right voltage, which would then pull more current from the battery.

Do most current LEDs have about the same resistance? For example, a MC-E is fully driven at 2.5 Amps. P7 at 2.8. Do they vary widely?

How much voltage would one need to drive the MC-E at 2.5 amps? Do the power LEDs have a certain resistance or do you put them in series with a resistor like the 5mm ones?

Once you know that, then Wattage is simply the current times Voltage.

For the itp A6 Polestar, I could say: 6xAA eneloop = 7.2 input voltage at 2000 mAh = 14.4 Watt*hours.

Given a runtime of a bit more than 1 hour, I could say that the Wattage is probably around 13 Watts. Assuming 2.5 amps driven, that means around 5.2 Volts are used to drive it.

Anyone have any insight into understanding this a bit better? Thanks!