A battery management system , comprising: a plurality of diodes which are configured to be connected in parallel to a plurality of battery cells , the plurality of battery cells , being connected in series; a switch unit which includes a plurality of switches respectively configured to be connected to the plurality of battery cells ; a control unit which is configured to detect voltages of the plurality of battery cells and is configured to perform cell balancing; and a plurality of sensing lines which are configured to connect the plurality of battery cells and the control unit , wherein the control unit is further configured to: measure a first upper voltage difference between each battery cell and an adjacent upper battery cell in a state in which the switches are turned off, measure a second upper voltage difference between each battery cell and the adjacent upper battery cell after turning on the switches for a predetermined time, when the second upper voltage difference is greater than the first upper voltage difference, determine that a sensing line of a corresponding battery cell is a disconnected sensing line, characterised in that the control unit is further configured to: measure a first lower voltage difference between each battery cell and an adjacent lower battery cell in a state in which the switches are turned off, measure a second lower voltage difference between each battery cell and the adjacent lower battery cell after turning on the switches for a predetermined time, and when the second lower voltage difference is smaller than the first lower voltage difference, determine that the sensing line of the corresponding battery cell is disconnected. a plurality of diodes which are configured to be connected in parallel to a plurality of battery cells , the plurality of battery cells , being connected in series; a switch unit which includes a plurality of switches respectively configured to be connected to the plurality of battery cells ; a control unit which is configured to detect voltages of the plurality of battery cells and is configured to perform cell balancing; and a plurality of sensing lines which are configured to connect the plurality of battery cells and the control unit , wherein the control unit is further configured to: measure a first upper voltage difference between each battery cell and an adjacent upper battery cell in a state in which the switches are turned off, measure a second upper voltage difference between each battery cell and the adjacent upper battery cell after turning on the switches for a predetermined time, when the second upper voltage difference is greater than the first upper voltage difference, determine that a sensing line of a corresponding battery cell is a disconnected sensing line, measure a first upper voltage difference between each battery cell and an adjacent upper battery cell in a state in which the switches are turned off, measure a second upper voltage difference between each battery cell and the adjacent upper battery cell after turning on the switches for a predetermined time, when the second upper voltage difference is greater than the first upper voltage difference, determine that a sensing line of a corresponding battery cell is a disconnected sensing line, measure a first lower voltage difference between each battery cell and an adjacent lower battery cell in a state in which the switches are turned off, measure a second lower voltage difference between each battery cell and the adjacent lower battery cell after turning on the switches for a predetermined time, and when the second lower voltage difference is smaller than the first lower voltage difference, determine that the sensing line of the corresponding battery cell is disconnected. <EOS>