An expansion system for portable electronic devices is provided. A portable electronic device includes a main logic board and a battery component. The device includes a package for enclosing components of the device that is sealed to prevent ingress of foreign material from the surrounding environment. A mounting interface is provided that extends into the internal space of the package. The mounting interface mounts an expansion component that expands functionality of the device so that it is physically and mechanically spaced from the main logic board. The device may include an expansion interface mounted on the main logic board for logical communication between the main logic board and the expansion component.