Padlock with removable or interchangeable shackle

A padlock comprising:

• a lock body;
• a shackle having a long leg and a short leg receivable in corresponding first and second shackle recesses in the lock body, the shackle being movable in an axial direction between a locked position and an unlocked position, the short leg being withdrawn from the lock body in the unlocked position;
• a retaining shaft receivable within a corresponding bore of the lock body, wherein the long leg includes a longitudinal recess for providing a travel path for the movement of the shackle from a locked position defined by the retaining shaft engaging a first end of the longitudinal recess to an unlocked position defined by the retaining shaft engaging a second end of the longitudinal recess to prevent the shackle from being removed from the lock body when the shackle is in the unlocked position;
• wherein the lock body further comprises a rear cover for replacing a battery, and the cover further including a torx cap, wherein the torx cap includes a projection for engagement with an elongated device for receiving the projection, wherein when the lock body is in the unlocked position, and when the elongated device is engaged with the projection, a rotation of the elongated device in a predetermined direction and predetermined amount of rotation allows the rear cover to be capable of being removed from the lock body.