Abstract: A battery management system includes: a battery which includes battery cells connected in series; diodes which are connected in parallel to the battery cells; a switch unit which includes switches respectively connected to the battery cells; a control unit which detects voltages of the battery cells and performs cell balancing; and sensing lines which connect the battery cells and the control unit, wherein the control unit measures 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, measures a second upper voltage difference between each battery cell and an adjacent upper battery cell after turning on the switches for a predetermined time, and, when the second upper voltage difference is greater than the first upper voltage difference, determines that the sensing line of the corresponding battery cell is disconnected.