This object perfectly fulfills its function charger for my phone and troubleshoots good when I'm traveling, without access to a computer USB port. The principle is simple: it is simply a portable battery which once charged, in turn, allows to recharge any device requiring 5V (with a charging current of less than 2000 mA anyway) in other words everything that can typically be recharged on a computer USB port. I myself have not tested the ability to charge two devices at the same time but with a full battery recharge I twice my mobile (Samsung Galaxy S +, an antique). The battery charge is done on a computer USB port and is fairly fast (one to two hours depending on the level of discharge). Attention to the fact that no charger is supplied, so you will not be able to recharge the battery to a wall outlet, but only to a USB port. Probably a phone charger would do for this use (micro USB connector for charging port), but I did not do the test. Remains to be seen holding in the life of this battery but until then I am perfectly happy!