Inspection method and manufacturing method for electric power storage device

An inspection method for an electric power storage device, the inspection method comprising:

• current measuring of i) connecting an external electric power supply to a charged electric power storage device in a reverse voltage direction to form a circuit, ii) adjusting a voltage of the external electric power supply such that a current does not flow in the circuit immediately after the connection, and iii) then, acquiring a converged current value of the current flowing in the circuit;
• quality deciding of deciding a quality of the electric power storage device based on the converged current value acquired in the current measuring;
• and
• grouping a target electric power storage device based on a rule that the converged current value of when the target electric power storage device is a normal product is constant in a group, the grouping being performed before the quality deciding,
• wherein the quality deciding includes
• variation calculating of calculating a degree of variation in the converged current value for each group, and
• determining, in a case where the calculated degree of variation of a group is equal to or lower than a predetermined level, any electric power storage device belonging to the group as a normal product, and determining, in a case where the degree of variation of a group exceeds the predetermined level, at least one electric power storage device having the highest converged current value in the group as a defective product.