No any resistors. You are right, I have connected the +5v to positive battery terminal. To be honest after weeks of use my device seems to be too "strong"... It produces clouds of vapor and provides good throat hit

, but from time to time my laptop gives me a message saying that "unknown usb device is exceeding the power capacity of the usb port bla bla bla..."

. So I would like to reduce voltage to not hurt my pc, but do not know how