A battery pack includes: a plurality of battery cells arranged in a line in one arrangement direction; a pair of end plates disposed at opposite ends of the plurality of battery cells in the arrangement direction; a pair of binding bars disposed on opposite sides of the plurality of battery cells in a direction perpendicular to the arrangement direction; and an insulator disposed in a gap between each of the binding bars and the battery cells. The insulator having an initial thickness larger than a thickness of the gap before insertion of the insulator into the gap in a compressed state. The end plates sandwich the battery cells therebetween in the arrangement direction, and the binding bars sandwich the battery cells therebetween in the direction perpendicular to the arrangement direction.
1. A battery pack comprising:
a plurality of battery cells arranged in a line in one direction as an arrangement direction, wherein adjacent battery cells of the plurality of battery cells are connected to each other via a bus bar on upper surfaces of the plurality of the battery cells;
a pair of end plates configured to sandwich the plurality of battery cells from both ends of the plurality of battery cells in the arrangement direction of the plurality of battery cells;
a pair of binding bars configured to sandwich the plurality of battery cells from a direction perpendicular to the arrangement direction and to fasten the pair of end plates at both ends in the arrangement direction; and
an insulator sandwiched in a gap between each of the binding bars and the plurality of battery cells,
the insulator having an initial thickness larger than a thickness of the gap before insertion into the gap in a compressed state,
each of the binding bars being in contact with a first surface of the insulator,
side surfaces of the battery cells being in contact with a second surface of the insulator, which is an opposite surface relative to the first surface of the insulator, and
each of the binding bars has first and second bent ends that confront and are in direct contact with upper surfaces and lower surfaces of the battery cells, respectively.
2. The battery pack according to claim 1 , wherein
assuming that a friction coefficient between the battery cells and a corresponding one of the binding bars, and the insulator is μ, and a compressibility ratio of the insulator is ΔL, a following relationship is satisfied,
if 0.2<μ<0.4, then ΔL>13μ 2 −11.55μ+2.63, and
if 0.4≤μ, then ΔL>0.125μ 2 −0.275μ+0.18.
3. The battery pack according to claim 1 , wherein the insulator is adhered to at least one of a corresponding one of the binding bars and the battery cells.
4. The battery pack according to claim 1 , wherein when a mounting surface of an electrode of the battery cells is set to be an upper side, the initial thickness of the insulator becomes larger toward the upper side.
5. The battery pack according to claim 1 , wherein the insulator is provided on an entire side surface of the battery cells.
6. The battery pack according to claim 1 , wherein the insulator is provided on an entire side surface of the battery cells, and the first and second bent ends of each of the binding bars are bent at a right angle at each end thereof.
7. The battery pack according claim 2 , wherein the insulator is provided on an entire side surface of the battery cells, and the first and second bent ends of each of the binding bars are bent at a right angle at each end thereof.
8. The battery pack according to claim 1 , wherein each of the binding bars is formed of a metal material, and a surface of each of the binding bars, which faces the insulator, is roughened.