It is for an electrinic cigarette, the battery works at 3.3v - 4.2v. Im trying to work it without the battery, through a usb. I cant get my probes in to measure the current from the battery when its used but when its on 5v it draws 0.85A, which is weird because i thought you could only get 0.5A from a usb, is this info any good?
A single Silicon rectifier will have a forward voltage drop of about 0.8V at 0.8A. A 1N5817 Schottky rectifier will have a forward drop of about 0.4V. Add one of each in series and you will drop the 5V to about 3.8V