A surgical instrument system is disclosed which comprises a handle and a battery positioned in the handle. The system can further include a power adapter which can be exchanged for the battery and can supply power from an alternate power source. In other instances, the system can include a power adapter which is engageable with the battery to supply power from an alternate power source. The power adapter can be placed in series with the battery. Alternatively, the engagement of the power adapter with the handle can electrically decouple the battery from the handle. Also disclosed herein is a supplemental battery which can be attached to the handle to provide additional power to the handle.