BATTERY CONTROL UNIT

The invention is directed to provide a battery pack in which a current sensor is eliminated and the whole size is reduced. In order to solve the problem described above, a battery pack of the invention includes a battery group in which a plurality of battery cells (lithium ion battery ) are connected in series, a resistor (bus bar ) connected in series to the battery group, cell voltage detection lines (cell voltage detection lines to ) arranged at both ends of the battery cells (lithium ion battery ) and the resistor (bus bar ), and a battery controller connected to the cell voltage detection lines (cell voltage detection lines to ), in which one cell voltage detection line (cell voltage detection lines to ) adjacent to the battery cell (lithium ion battery ) includes a terminal which is branched and connected to the battery controller.