US Patent 11609260 Method for inspecting insulation of a secondary battery

In a method for inspecting the insulation property of a secondary battery by connecting an external DC power supply to the secondary battery charged with an initial charge amount and evaluating the insulation property of the secondary battery based on a converging state of a power-supply current, when a charge amount at which an inclination of a tangent to a charge amount—battery voltage curve representing a relationship between the charge amount and a battery voltage of the secondary battery is smallest is assumed as a minimum-inclination charge amount, and the inclination of the tangent at the minimum-inclination charge amount is assumed as a minimum inclination (αL), the initial charge amount is selected from a range of the charge amount in which the inclination is two or more times the minimum inclination.