Patent ID: 8193777

Claim:
A charging method for charging a non-aqueous electrolyte secondary battery, the method comprising: a pulse charging step of performing pulse charge by applying a pulse to a secondary battery; a polarization detecting step of detecting a change amount of a cell voltage associated with a change in the concentration polarization of a non-aqueous electrolyte as a polarization voltage after the cell voltage is changed due to a voltage drop caused by an internal resistance of the secondary battery when a charge current flowing in the secondary battery changes as an applied state of the pulse changes; and a deterioration detecting step of terminating the pulse charge if the polarization voltage detected in the polarization detecting step increases to or above a predetermined first threshold value, wherein: the polarization detecting step includes a step of detecting a difference between a first cell voltage, which is the cell voltage of the secondary battery when the pulse application to the secondary battery is completed, and a second cell voltage, which is the cell voltage upon entering a steady state reached by a decrease of the cell voltage after the pulse application is completed as the polarization voltage associated with the elimination of the concentration polarization of the non-aqueous electrolyte, and a step of detecting the cell voltage after the lapse of a time equal to or longer than a polarization elimination time set beforehand as a time necessary to eliminate the concentration polarization after the detection of the first cell voltage as the second cell voltage, and the pulse charging step includes a step of extending a pulse interval to or longer than the polarization elimination time when the polarization voltage is detected in the polarization detecting step while performing the pulse charge by applying the pulse to the secondary battery in a specified cycle, the polarization elimination time being longer than a time period during which the pulse output is paused in the specified cycle.