Power control arrangements for surgical instruments and batteries

A surgical system comprising:

• a surgical device comprising a battery dock;
• and
• a battery unit comprising at least one battery cell, a first electrode, a second electrode and a battery drain comprising a first and second contact wherein, in a first position, the battery drain is not in electrical communication with the at least one battery cell, wherein, when the battery drain is in a second position within the battery unit the first and second contacts are in electrical communication with the first and second electrodes to electrically couple the battery drain to the at least one battery cell to discharge the at least one battery cell and wherein the battery drain transitions from the first position to the second position upon attachment of the battery unit to the battery dock.