A power supply system capable of providing electric power to an electronic device having a first battery includes a battery pack (100) and an attachment apparatus (300). The battery pack includes a body (110) having at least a first recess (221), a second battery inside the body, and at least one of a first circuit (500) capable of dynamically changing a charge current supplied to the second battery based on a power consumption level of the electronic device, and a second circuit (600) capable of dynamically switching the electronic device between a recharging state and a non-recharging state depending on a status of the battery pack. The attachment apparatus includes a frame (310), an extension (350) protruding from the frame, and attachment features (461) suitable for working with the recess to attach the battery pack and the attachment apparatus to each other and to the electronic device.