VARTA LCD Powerbank 18200mAhIt does not say on the Music Store website but this items needs to be charged with a USB port that is capeable of at least 500mAh. The first time iI connected it was to a unit with less than this capacity and it had not charged up at all after a few hours. I then read the instructions and switched to a more powerful USB charger and it charged up quickly. Unit seems to hold the charge well for several days so far with no drop and seems pretty robust with a nice clear display of the % charge remaining.