A battery control unit comprising: a plurality of switching units (4a, 4b, 4c); a control unit; a charger configured to charge batteries (2a, 2b, 2c) in series; and a charging control unit, wherein the plurality of switching units (4a, 4b, 4c) are respectively provided for a plurality of batteries (2a, 2b, 2c) connected in series, and are configured to switch between a connected state and a non-connected state, wherein the connected state is a state that a corresponding battery (2a, 2b, 2c) is connected in series with other batteries (2a, 2b, 2c) and the non-connected state is a state that the corresponding battery (2a, 2b, 2c) is disconnected from a series connection with the other batteries (2a, 2b, 2c), wherein the control unit is configured to determine whether each voltage of the plurality of batteries (2a, 2b, 2c) reaches a charge end voltage during charging, and to control the switching unit (4a, 4b, 4c) corresponding to the battery (2a, 2b, 2c) which is determined to reach the charge end voltage to switch to the non-connected state, and wherein the charging control unit is configured to perform constant current charging of the batteries; characterized in that: the charging control unit is configured to determine whether remaining chargeable capacity reaches a predetermined charge switching capacity during the constant current charging, wherein the remaining chargeable capacity indicates an amount of electricity that can be charged to the batteries (2a, 2b, 2c), to control the switching unit (4a, 4b, 4c) corresponding to the battery (2a, 2b, 2c) which is determined to reach the charge switching capacity to switch to the non-connected state to bypass the battery (2a, 2b, 2c) which is determined to reach the charge switching capacity, to control all the batteries (2a, 2b, 2c) to switch to the connected state and switch the charger to constant voltage charging when the remaining chargeable capacity of all the batteries (2a, 2b, 2c) reaches the charge switching capacity, and to perform the constant voltage charging of the batteries (2a, 2b, 2c) in series. a plurality of switching units (4a, 4b, 4c); a control unit; a charger configured to charge batteries (2a, 2b, 2c) in series; and a charging control unit, wherein the plurality of switching units (4a, 4b, 4c) are respectively provided for a plurality of batteries (2a, 2b, 2c) connected in series, and are configured to switch between a connected state and a non-connected state, wherein the connected state is a state that a corresponding battery (2a, 2b, 2c) is connected in series with other batteries (2a, 2b, 2c) and the non-connected state is a state that the corresponding battery (2a, 2b, 2c) is disconnected from a series connection with the other batteries (2a, 2b, 2c), wherein the control unit is configured to determine whether each voltage of the plurality of batteries (2a, 2b, 2c) reaches a charge end voltage during charging, and to control the switching unit (4a, 4b, 4c) corresponding to the battery (2a, 2b, 2c) which is determined to reach the charge end voltage to switch to the non-connected state, and wherein the charging control unit is configured to perform constant current charging of the batteries; characterized in that: the charging control unit is configured to determine whether remaining chargeable capacity reaches a predetermined charge switching capacity during the constant current charging, wherein the remaining chargeable capacity indicates an amount of electricity that can be charged to the batteries (2a, 2b, 2c), to control the switching unit (4a, 4b, 4c) corresponding to the battery (2a, 2b, 2c) which is determined to reach the charge switching capacity to switch to the non-connected state to bypass the battery (2a, 2b, 2c) which is determined to reach the charge switching capacity, to control all the batteries (2a, 2b, 2c) to switch to the connected state and switch the charger to constant voltage charging when the remaining chargeable capacity of all the batteries (2a, 2b, 2c) reaches the charge switching capacity, and to perform the constant voltage charging of the batteries (2a, 2b, 2c) in series. is configured to determine whether remaining chargeable capacity reaches a predetermined charge switching capacity during the constant current charging, wherein the remaining chargeable capacity indicates an amount of electricity that can be charged to the batteries (2a, 2b, 2c), to control the switching unit (4a, 4b, 4c) corresponding to the battery (2a, 2b, 2c) which is determined to reach the charge switching capacity to switch to the non-connected state to bypass the battery (2a, 2b, 2c) which is determined to reach the charge switching capacity, to control all the batteries (2a, 2b, 2c) to switch to the connected state and switch the charger to constant voltage charging when the remaining chargeable capacity of all the batteries (2a, 2b, 2c) reaches the charge switching capacity, and to perform the constant voltage charging of the batteries (2a, 2b, 2c) in series.