Another thing: The voltage range for (eg.) my LED at 700mA is:Min: 2.79 Typical: 3.55 Max:3.99Q: Given the above curves and the variance in voltage, what value resistor should you pick...? A: Don't even try.
This is also why you don't commit sin number (2) of the original list, ie. connect LEDs in parallel.Q: What happens if you pair a 2.79V LED with a 3.99V LED? A: The 2.79V LED doesn't last very long.
Well I think the OP has probably checked out and we are just all preaching to ourselves. Probably didn't get the answers he was hoping for.
to the 4.2V that a fresh li-ion is capable of sourcing...
I'm still confused though why my numbers aren't adding up on this setup I made. I have some 3w led's that say they are rated at 700ma max current.
Seems like a perfect fit, 4x 700 = 2800ma. I wired up the driver, and had 4 of these led's in parallel, and using a 18650 battery, which is a single cell lithium ion battery. However, at full power, this setup only seems to be drawing about 700ma for all 4 of them, not the 2800 I was expecting.
No two LEDs are exactly the same! One of the for LEDs you wired in parallel will start conducting at a slightly lower voltage than the others.