I bought one of these at O'Hare, when my cell phone gave me a low battery warning as I was waiting for my plane. No time to plug it in, and I didn't have a car charger cable that I could use in the airplane. So, I grabbed one of these just before I boarded the plane. I used it to make one last phone call, than threw the whole thing in my briefcase. My phone was fully charged an hour or so later. I keep it around now as a backup, in case I get a low battery warning at a time when I can't charge.