Abstract: A universal charging accessory for mobile devices. The accessory has a generally flat and thin body configured to lie flat against the flat rear side of the mobile device and includes an internal rechargeable battery, two charging plugs that are configured to be electronically coupled to the charging plug of the mobile device, with the charging plugs being retrievably stowed inside the body of the accessory and to be withdrawn as needed to charge the mobile device. The accessory has a window formed in the body of the charging accessory which receives, interchangeably, a plug-in module that can be inserted into an AC socket to charge the internal battery as well as the cellphone battery.