I bought this as a backup power source for a family vacation to Colorado. I charged it at home, using included suction cups to attach it to a sunny window. When fully charged, it will charge a dead mobile device to about 50%, not spectacular by any means, but enough to make a few phone calls, especially in an emergency, or to get you to a place where you can use a traditional charger. The suction cups also mean you could recharge it in your car by sticking it to a window. It's a well-designed product.