A battery control unit comprising: a plurality of switching units (41a to 41c, 42a); a first controller; and a plurality of bidirectional voltage converters (61, 62) including a ground terminal (T GND), a first (T 1), and a second input-output terminal (T 2), wherein each of a plurality of battery packs (21, 22) connected in parallel to each other includes a plurality of batteries (21a to 21c, 22a to 22c) connected in series with each other, wherein the plurality of switching units (41a to 41c, 42a) are disposed corresponding to the plurality of batteries (21a to 21c, 22a to 22c) respectively, and are configured to switch between a connected state where a corresponding battery among the plurality of batteries (21a to 21c, 22a to 22c) is connected in series with non-corresponding battery among the plurality of batteries (21a to 21c, 22a to 22c) and a non-connected state where the corresponding battery is disconnected from series connection with the non-corresponding battery, wherein the first controller is configured to control the plurality of switching units (41a to 41c, 42a) corresponding to the battery, which is determined to reach a termination voltage during charge or discharge, to the non-connected state, wherein the plurality of bidirectional voltage converters (61, 62) are configured to convert a first input voltage input between the first input-output terminal (T 1) and the ground terminal (T GND) and output a first converted voltage from between the second input-output terminal (T 2) and the ground terminal (T GND), and convert a second input voltage input between the second input-output terminal (T 2) and the ground terminal (T GND) and output a second converted voltage from between the first input-output terminal (T 1) and the ground terminal (T GND), wherein the plurality of bidirectional voltage converters (61, 62) are disposed corresponding to the plurality of battery packs (21, 22), and the first input-output terminals (T 1) are connected to one end of a corresponding battery pack and the ground terminals (T GND) are connected to another end of the corresponding battery pack, respectively, and wherein the one ends of the plurality of battery packs (21, 22) are connected to each other via the first input-output terminals (T 1) and the second input-output terminals (T 2) wherein the battery control unit further comprises a second controller configured to control output voltages (V DC11, V DC12) from the first input-output terminals (T 1) of the plurality of bidirectional voltage converters, and wherein the second controller is configured to control the output voltages (V DC11, V DC12) from the first input-output terminals (T 1) such that charge currents in a predetermined range flow through the plurality of battery packs (21, 22) during the charge. a plurality of switching units (41a to 41c, 42a); a first controller; and a plurality of bidirectional voltage converters (61, 62) including a ground terminal (T GND), a first (T 1), and a second input-output terminal (T 2), wherein each of a plurality of battery packs (21, 22) connected in parallel to each other includes a plurality of batteries (21a to 21c, 22a to 22c) connected in series with each other, wherein the plurality of switching units (41a to 41c, 42a) are disposed corresponding to the plurality of batteries (21a to 21c, 22a to 22c) respectively, and are configured to switch between a connected state where a corresponding battery among the plurality of batteries (21a to 21c, 22a to 22c) is connected in series with non-corresponding battery among the plurality of batteries (21a to 21c, 22a to 22c) and a non-connected state where the corresponding battery is disconnected from series connection with the non-corresponding battery, wherein the first controller is configured to control the plurality of switching units (41a to 41c, 42a) corresponding to the battery, which is determined to reach a termination voltage during charge or discharge, to the non-connected state, wherein the plurality of bidirectional voltage converters (61, 62) are configured to convert a first input voltage input between the first input-output terminal (T 1) and the ground terminal (T GND) and output a first converted voltage from between the second input-output terminal (T 2) and the ground terminal (T GND), and convert a second input voltage input between the second input-output terminal (T 2) and the ground terminal (T GND) and output a second converted voltage from between the first input-output terminal (T 1) and the ground terminal (T GND), wherein the plurality of bidirectional voltage converters (61, 62) are disposed corresponding to the plurality of battery packs (21, 22), and the first input-output terminals (T 1) are connected to one end of a corresponding battery pack and the ground terminals (T GND) are connected to another end of the corresponding battery pack, respectively, and wherein the one ends of the plurality of battery packs (21, 22) are connected to each other via the first input-output terminals (T 1) and the second input-output terminals (T 2) wherein the battery control unit further comprises a second controller configured to control output voltages (V DC11, V DC12) from the first input-output terminals (T 1) of the plurality of bidirectional voltage converters, and wherein the second controller is configured to control the output voltages (V DC11, V DC12) from the first input-output terminals (T 1) such that charge currents in a predetermined range flow through the plurality of battery packs (21, 22) during the charge.