Battery pack

1. A battery pack comprising:

a battery cell group comprising a plurality of battery cells disposed parallel to each other;

a holder holding the battery cell group, the holder comprising a first surface provided with insertion holes in which the battery cells are inserted, a second surface perpendicular to the first surface, and a plurality of fastener-receiving portions each having a fastener-receiving surface formed at the first surface;

a terminal board disposed facing the first surface of the holder and electrically connecting terminals of the battery cells to each other;

a bus bar electrically connected to the terminal board; and

a plurality of fasteners fastening both the terminal board and the bus bar to the holder and electrically connecting the terminal board to the bus bar, wherein

the terminal board is thinner than the bus bar and welded to the terminals of the battery cells,

the terminal board comprises an elongated portion extending in a direction in which the battery cells are arranged and a plurality of fixation portions arranged at intervals on a long side of the elongated portion,

the bus bar comprises a plurality of fixation portions respectively placed in face-to-face contact with the fixation portions of the terminal board, and

the fasteners fasten the fixation portions of the terminal board and the fixation portions of the bus bar to the fastener-receiving portions.

2. The battery pack according to claim 1 , wherein

each fastener-receiving portion is shaped to bulge on the second surface,

the bus bar comprises: a first bar portion disposed facing the first surface, extending along the long side of the elongated portion, and comprising the fixation portions of the bas bar; a second bar portion disposed facing the second surface; and a plurality of coupling bar portions connecting the first bar portion to the second bar portion, each coupling bar portion being formed in a bent shape,

the fixation portions of the terminal board project from the elongated portion in a width direction of the elongated portion,

the coupling bar portions are arranged at intervals in a length direction of the first bar portion and situated at different locations than the fastener-receiving portions in the length direction of the first bar portion,

the second bar portion and the coupling bar portions are shaped to bypass the fastener-receiving portions, and

the second bar portion and the coupling bar portions are located at the same level as at least a part of each fastener-receiving portion in a direction of a normal to the second surface.

3. The battery pack according to claim 2 , wherein

the terminal board has an edge located in proximity to the first bar portion, the edge comprising concave portions recessed in a direction away from the first bar portion,

the first bar portion comprises offset portions projecting toward the concave portions, and

the coupling bar portions are connected to the offset portions.

4. The battery pack according to claim 3 , wherein

each of the fastener-receiving portions and the concave portions is disposed between two adjacent battery cells of the plurality of battery cells in the direction in which the battery cells are arranged, and

the fastener-receiving portions and the concave portions alternate with one another in the direction in which the battery cells are arranged.

5. The battery pack according to claim 1 , wherein

the first surface comprises a terminal board mounting surface on which the terminal board is mounted and a bus bar mounting surface on which the bus bar is mounted, and

the bus bar mounting surface is recessed relative to the terminal board mounting surface.

6. The battery pack according to claim 5 , wherein

the first surface comprises a major surface other than the terminal board mounting surface and the bus bar mounting surface, and

the terminal board mounting surface is recessed relative to the major surface.

7. The battery pack according to claim 1 , wherein the terminal board has a thickness of 0.05 to 0.25 mm.