Ingress playing (game with augmented reality geotagging) I needed to seriously boost the autonomy of my smartphone. It's done. This external battery gives me 5 and 7 times more autonomy. The rather compact size allows me to take with me almost all the time (even when I do not play), it is convenient to make additional energy during a long day without charger. And with 3 usb ports I can help my friends.