System comprising: an electric-powered device comprising: a charging unit configured to apply a charging current to a secondary battery; and a control unit configured to control the charging unit to supply a charging current to the secondary battery such that the charging current increases from zero to a predetermined peak value and then decreases to zero; and an apparatus for estimating a parameter of the secondary battery, comprising: a control means; a sensor means configured to measure a current-voltage data of the secondary battery in response to a measurement control signal from the control means and to provide the current-voltage data to the control means; and the control means being configured to provide the sensor means with a plurality of measurement control signals at a time interval while the charging current decreases from the predetermined peak to zero thus triggering measurement of a plurality of current-voltage data by the sensor means, receive an input of the plurality of current-voltage data from the sensor means, calculate a linear approximation equation representing a correlation between a current and a voltage from the plurality of current-voltage data, and estimate an open-circuit voltage of the secondary battery by reflecting a polarization voltage of the secondary battery based on a resistor-capacitor circuit model on a Y intercept of the linear approximation equation. an electric-powered device comprising: a charging unit configured to apply a charging current to a secondary battery; and a control unit configured to control the charging unit to supply a charging current to the secondary battery such that the charging current increases from zero to a predetermined peak value and then decreases to zero; and a charging unit configured to apply a charging current to a secondary battery; and a control unit configured to control the charging unit to supply a charging current to the secondary battery such that the charging current increases from zero to a predetermined peak value and then decreases to zero; and an apparatus for estimating a parameter of the secondary battery, comprising: a control means; a sensor means configured to measure a current-voltage data of the secondary battery in response to a measurement control signal from the control means and to provide the current-voltage data to the control means; and the control means being configured to provide the sensor means with a plurality of measurement control signals at a time interval while the charging current decreases from the predetermined peak to zero thus triggering measurement of a plurality of current-voltage data by the sensor means, receive an input of the plurality of current-voltage data from the sensor means, calculate a linear approximation equation representing a correlation between a current and a voltage from the plurality of current-voltage data, and estimate an open-circuit voltage of the secondary battery by reflecting a polarization voltage of the secondary battery based on a resistor-capacitor circuit model on a Y intercept of the linear approximation equation. a control means; a sensor means configured to measure a current-voltage data of the secondary battery in response to a measurement control signal from the control means and to provide the current-voltage data to the control means; and the control means being configured to provide the sensor means with a plurality of measurement control signals at a time interval while the charging current decreases from the predetermined peak to zero thus triggering measurement of a plurality of current-voltage data by the sensor means, receive an input of the plurality of current-voltage data from the sensor means, calculate a linear approximation equation representing a correlation between a current and a voltage from the plurality of current-voltage data, and estimate an open-circuit voltage of the secondary battery by reflecting a polarization voltage of the secondary battery based on a resistor-capacitor circuit model on a Y intercept of the linear approximation equation.