A method for detecting an abnormal battery cell, the method comprising: detecting a voltage and a current of each of a plurality of battery cells electrically connected between first and second terminals and being in use so as to periodically generate a voltage value and a current value for each of the plurality of battery cells; updating, in real time by using an adaptive filter, a G parameter value and an H parameter value, which are numerical values of each of a G parameter and an H parameter indicting a current state of each of the battery cells, on the basis of the voltage value and the current value of each of the battery cells; the method being characterised by : calculating a representative G parameter value representing the G parameter value of the battery cells and calculating a representative H parameter value representing the H parameter value of the battery cells; and determining whether each of the battery cells is an abnormally deteriorated cell based on the G parameter value and the H parameter value of each of the battery cells, the representative G parameter value, and the representative H parameter value, wherein the G parameter is a parameter indicating sensitivity of voltage with respect to a change in a current of the battery cell, and the H parameter is a parameter indicating an effective potential determined by a local equilibrium distribution and a resistance distribution in the battery cell. detecting a voltage and a current of each of a plurality of battery cells electrically connected between first and second terminals and being in use so as to periodically generate a voltage value and a current value for each of the plurality of battery cells; updating, in real time by using an adaptive filter, a G parameter value and an H parameter value, which are numerical values of each of a G parameter and an H parameter indicting a current state of each of the battery cells, on the basis of the voltage value and the current value of each of the battery cells; the method being characterised by : calculating a representative G parameter value representing the G parameter value of the battery cells and calculating a representative H parameter value representing the H parameter value of the battery cells; and determining whether each of the battery cells is an abnormally deteriorated cell based on the G parameter value and the H parameter value of each of the battery cells, the representative G parameter value, and the representative H parameter value, wherein the G parameter is a parameter indicating sensitivity of voltage with respect to a change in a current of the battery cell, and the H parameter is a parameter indicating an effective potential determined by a local equilibrium distribution and a resistance distribution in the battery cell. calculating a representative G parameter value representing the G parameter value of the battery cells and calculating a representative H parameter value representing the H parameter value of the battery cells; and determining whether each of the battery cells is an abnormally deteriorated cell based on the G parameter value and the H parameter value of each of the battery cells, the representative G parameter value, and the representative H parameter value, wherein the G parameter is a parameter indicating sensitivity of voltage with respect to a change in a current of the battery cell, and the H parameter is a parameter indicating an effective potential determined by a local equilibrium distribution and a resistance distribution in the battery cell. <EOS>