A surgical instrument system, comprising: a handle, comprising: a handle housing; a handle battery cell positioned in said handle housing; a handle electrical circuit, wherein said handle battery cell is configured to supply power to said handle electrical circuit; and a handle electrical connector in communication with said handle electrical circuit; and a supplemental battery selectively engageable with said handle, wherein said supplemental battery comprises: a battery housing engageable with said handle housing; a battery electrical circuit; a supplemental battery cell positioned in said battery housing, wherein said supplemental battery cell is configured to supply power to said battery electrical circuit; and a battery electrical connector in communication with said battery electrical circuit, wherein said battery electrical connector is engageable with said handle electrical connector when said supplemental battery is engaged with said handle to place said battery electrical circuit in communication with said handle electrical circuit, wherein said handle housing comprises a gripping portion and the handle battery cell is positioned in the gripping portion. a handle, comprising: a handle housing; a handle battery cell positioned in said handle housing; a handle electrical circuit, wherein said handle battery cell is configured to supply power to said handle electrical circuit; and a handle electrical connector in communication with said handle electrical circuit; and a handle housing; a handle battery cell positioned in said handle housing; a handle electrical circuit, wherein said handle battery cell is configured to supply power to said handle electrical circuit; and a handle electrical connector in communication with said handle electrical circuit; and a supplemental battery selectively engageable with said handle, wherein said supplemental battery comprises: a battery housing engageable with said handle housing; a battery electrical circuit; a supplemental battery cell positioned in said battery housing, wherein said supplemental battery cell is configured to supply power to said battery electrical circuit; and a battery electrical connector in communication with said battery electrical circuit, wherein said battery electrical connector is engageable with said handle electrical connector when said supplemental battery is engaged with said handle to place said battery electrical circuit in communication with said handle electrical circuit, a battery housing engageable with said handle housing; a battery electrical circuit; a supplemental battery cell positioned in said battery housing, wherein said supplemental battery cell is configured to supply power to said battery electrical circuit; and a battery electrical connector in communication with said battery electrical circuit, wherein said battery electrical connector is engageable with said handle electrical connector when said supplemental battery is engaged with said handle to place said battery electrical circuit in communication with said handle electrical circuit, wherein said handle housing comprises a gripping portion and the handle battery cell is positioned in the gripping portion.