Generator for bicycle, and battery module attachable/detachable to/from generator

A rotating body, comprising:

• a rotation shaft provided through a center of the rotating body;
• eddy current induction magnets arranged around the rotation shaft;
• and
• an outer circumferential surface surrounding the eddy current induction magnets and being made of a synthetic resin,
• wherein the outer circumferential surface of the rotating body made of the synthetic resin is (i) located between the eddy current induction magnets and a moving object and (ii) configured to be adjacent to but spaced apart from the moving object,
• wherein the eddy current induction magnets are installed such that N and S poles alternate which face the moving object upon rotation of the rotating body, thereby inducing eddy current on a surface of the moving object,
• wherein, when the outer circumferential surface of the rotating body comes into contact with the moving object, the outer circumferential surface of the rotating body undergoes a rolling friction with the moving object such that a kinetic energy of the moving object can be delivered to the rotating body,
• wherein, when the outer circumferential surface of the rotating body located between the eddy current induction magnets and the moving object collides with the moving object, the outer circumferential surface of the rotating body prevents the eddy current induction magnets from directly colliding with the moving object and absorbs impact energy while being elastically deformed by an impact,
• wherein, the outer circumferential surface of the rotating body allows magnetic flux generated by the eddy current induction magnets to pass through the outer circumferential surface and to reach the moving object so that eddy current is induced on the surface of the moving object by the magnetic flux,
• wherein the eddy current applies magnetic force back to the eddy current induction magnets and pulls the eddy current induction magnets in a direction that the moving object moves so that the rotating body rotates without a contact with the moving object.