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When reading the manual, I noticed an option to change the voltage supplied to the led, does this mean the board will always supply the same voltage (3.7) or is it just whatever the battery supplies. I know 18650 batteries can go up to 4.1 volts and am wondering if I should use 3.7 volts or 4.1 volts for resistor calculatios
Use 3.7v for your calculations.
The option does not change the voltage supplied to the LEDs. It changes the amount of current that is given to the LED on average over a given amount of time using PWM.
when using a nb v3 do you need to use a resistor for the led module or will it be ok with using 3.7 volt batteries
You need a resistor.
Have someone measured out the LED forward voltage from the NB v3.0?
Is it the same voltage as the battery or handle the NB to 3.7? I think this should be importand to the resistor we use.
It's the same as the battery. The NB does not have a LED driver on board.
So i have to calculate with 4.2v to be safe? Or why @CET recommend 3.7v for calculation?
3.7 is safe for calculation. The battery doesn't stay at 4.2v for very long, and the LEDs are robust enough to not blow if they're a little bit over their rated Vf. Just be sure the LED is mounted on the heatsink before you turn it on. Heat is the real enemy of LEDs, not voltage.
Thanks for the answers :)