Portable USB Essential oil diffuser for auto travel

This diffuser is suppose to be battery operated, but I couldn't get the fan to run with batteries.  The lights work with batteries but not the fan.  It does work fine when hooked up to a usb source, and since I have a usb in my car it isn't a problem.  I also carry it back and forth and plug it into my computer with a little Lavender oil when I'm laying in bed checking my FB before I go to sleep.  It helps relax me and I go right to sleep.