Battery pack

1. A battery pack comprising:

a plurality of battery modules each including a plurality of cells aligned and accommodated in a case, wherein

each battery module includes a plurality of battery assemblies accommodated in the case, each battery assembly including a plurality of cells,

the plurality of cells are aligned in a same direction and are electrically connected in parallel with each other,

the battery modules include a first battery module and a second battery module,

the case of the first battery module is a rectangular parallelepiped,

the case of the second battery module is a rectangular parallelepiped,

at least one side of the case of the first battery module is different from each of sides of the case of the second battery module,

the first battery module includes a plurality of first battery assemblies,

the second battery module includes a plurality of second battery assemblies,

the number of the cells in each first battery assembly is equal to the number of the cells in each second battery assembly,

the first battery module and the second battery module are combined with each other such that directions in which cells are aligned in the first and second battery modules are perpendicular to each other to form the battery pack,

each cell has an opening portion through which gas generated in the cell is exhausted to the outside,

each battery assembly further includes an exhaust duct in communication with the opening portion of each cell,

the exhaust duct includes a flat plate disposed at one side of the plurality of cells,

the opening portions of the cells are in communication with the exhaust duct via through holes formed in the flat plate, and

on the flat plate, interconnects connected to a positive electrode terminal and a negative electrode terminal of the respective cells and to a signal terminal via which a signal for controlling charge and discharge of the cells is input and output are formed.

2. The battery pack of claim 1 , wherein

each battery assembly includes an electrode terminal as a positive electrode, and an electrode terminal as a negative electrode, and

a signal terminal via which a signal for controlling charge and discharge of the cells is input and output.

3. The battery pack of claim 2 , wherein

in the first battery module, the electrode tenninals as the positive electrodes and the negative electrodes of the battery assemblies are electrically connected to each other in series, and

in the second battery module, the electrode terminals as the positive electrodes and the negative electrodes of the battery assemblies are electrically connected to each other in series.

4. The battery pack of claim 1 , wherein

the flat plate is arranged in close contact with an end section of each cell, and

the exhaust duct is partitioned in a sealed state with respect to the plurality of cells.

5. The battery pack of claim 1 , wherein

the flat plate is formed as a circuit board,

interconnects are formed on the circuit board, and

the interconnects are connected to the electrode terminals as the positive electrodes and the negative electrodes, and the signal terminal of each battery assembly.

6. The battery pack of claim 1 , wherein

the cells are cylindrical batteries,

the cells included in each battery assembly are arranged in a single row,

in the first battery module, the battery assemblies are aligned in a direction perpendicular to a row direction of the plurality of cells aligned in the single row, and

in the second battery module, the battery assemblies are aligned in a direction parallel to the row direction of the cells arranged in the single row or in a direction parallel to an axial direction of the cells which are the cylindrical batteries.

7. The battery pack of claim 6 , wherein

the axial direction of the cells in the battery assemblies included in the first battery module is orthogonal to the axial direction of the cells in the battery assemblies in the second battery module.

8. The battery pack of claim 1 , wherein

the number of the battery assemblies included in the first battery module is greater than a number of the battery assemblies included in the second battery module.