Hi guys! I have a problem to find the right resistor for a led. http://forums.thecustomsabershop.com...e-to-Ohm-s-Law I have already read this post, but, I don't know where I can find the voltage of the led. In the shop, the description of the led for example is, typical voltage and maximum voltage. So, witch voltage i have to use for a seoul p4 or a cree xp-e2 or a luxeon? I wanna try with a 18650 3.7 volt battery. I hope you can help me guys, is my first building.