DETECTION SYSTEM AND DETECTION METHOD

A detection system detects connection quality of a connection part where a plurality of electrode tabs and external electrodes are connected in a wound battery A, and includes a power feed unit that supplies a current between a positive electrode tab B of the wound battery A and a negative electrode tab C of the wound battery A, a detection unit that detects a magnetic field resulting from current supply to the wound battery A, and a processing unit that determines connection quality of the connection part based on a magnitude of the magnetic field.