Battery pack

1. A battery pack comprising:

battery cells, each comprising end portions in a height direction thereof;

a case accommodating the battery cells and a cooling fluid to cool the battery cells; and

a first holder plate and a second holder plate which are coupled to the case to face each other along the case such that the end portions of the battery cells are insertable through the first and second holder plates, an accommodation space being defined between the first and second holder plates to accommodate the cooling fluid, the first and second holder plates comprising assembling protrusions protruding outward from the first and second holder plates away from the accommodation space to hold the end portions of the battery cells,

wherein the case, the battery cells, and the first and second holder plates have heights in the height direction of the battery cells that satisfy the following condition:

a height between outward-facing surfaces of the first and second holder plates <a height of the battery cells <a height of the case,

the outward-facing surfaces of the first and second holder plates facing away from each other in the height direction, and the height between the outward-facing surfaces of the first and second holder plates including thicknesses of the first and second holder plates and excluding heights of the assembling protrusions, and

the battery pack further comprises a potting resin on the outward-facing surfaces of the first and second holder plates and contacting an outer circumferential surface of each of the battery cells between the end portions.

2. The battery pack of claim 1 , wherein the potting resin on the first and second holder plates has a height in the height direction that satisfies the following condition:

the height of the battery cells <the height of the potting resin <the height of the case.

3. The battery pack of claim 2 , further comprising a bus bar electrically connecting the battery cells to each other,

wherein the potting resin covers coupling portions between the bus bar and the battery cells.

4. The battery pack of claim 3 , wherein the bus bar comprises a main body extending along neighboring rows of the battery cells, and branches branching from the main body toward the battery cells, and

the coupling portions comprise welded portions between the branches of the bus bar and the battery cells.

5. The battery pack of claim 4 , wherein the main body and the branches of the bus bar have a height difference in the height direction, and

the potting resin covers the branches of the bus bar together with the main body of the bus bar.

6. The battery pack of claim 4 , wherein the main body and the branches of the bus bar have a height difference in the height direction, and

the main body of the bus bar is exposed from the potting resin.

7. The battery pack of claim 1 , wherein the potting resin on the first and second holder plates has a height in the height direction that satisfies the following condition:

the height between the outward-facing surfaces of the first and second holder plates <the height of the potting resin <the height of the battery cells.

8. The battery pack of claim 7 , wherein the potting resin exposes vents located at the end portions of the battery cells.

9. The battery pack of claim 1 , wherein the case comprises a hollow member which is open in the height direction to accommodate the battery cells and the cooling fluid.

10. The battery pack of claim 9 , wherein the case comprises: the accommodation space in a center portion thereof; and outer walls and inner walls extending in parallel to each other along edges of the case around the accommodation space.

11. The battery pack of claim 10 , wherein the battery cells, the outer walls, and the inner walls have heights that satisfy the following condition:

a height of the inner walls <the height of the battery cells <a height of the outer walls.

12. The battery pack of claim 10 , wherein well spaces are defined between the outer walls and the inner walls along the edges of the case.

13. The battery pack of claim 12 , wherein the potting resin on the first and second holder plates is continuously arranged in the well spaces.

14. The battery pack of claim 12 , wherein skirt portions are bent inward from the first and second holder plates toward the well spaces and inserted into the well spaces.

15. The battery pack of claim 14 , wherein the skirt portions are bent and extend from the first and second holder plates and surround the inner walls.

16. The battery pack of claim 1 , wherein the first and second holder plates comprise cell holes, and the battery cells are inserted into the cell holes, and

the assembling protrusions are arranged along rows of the cell holes to hold the end portions of the battery cells neighboring each other in a state in which the assembling protrusions are at positions between the cell holes neighboring each other.

17. The battery pack of claim 1 , further comprising a bus bar electrically connecting the battery cells to each other,

wherein some of the assembling protrusions comprise first assembling protrusions which hold the end portions of the battery cells and do not physically interfere with the bus bar, and

others of the assembling protrusions comprise second assembling protrusions which hold the end portions of the battery cells and the bus bar.

18. The battery pack of claim 17 , wherein the first and second assembling protrusions comprise first protrusion portions protruding toward the end portions of the battery cells, and

the second assembling protrusions further comprise second protrusion portions protruding toward the bus bar.

19. The battery pack of claim 18 , wherein the first protrusion portions are arranged on opposite sides of the second assembling protrusions, and

the second protrusion portions are arranged on sides of the second assembling protrusions between the opposite sides.

20. The battery pack of claim 18 , wherein the first and second protrusion portions have a height difference in the height direction.

21. The battery pack of claim 1 , wherein cell ribs protrude inward from the first and second holder plates toward the accommodation space and surround the outer circumferential surfaces of the battery cells.

22. The battery pack of claim 21 , wherein gaps are defined between the outer circumferential surfaces of the battery cells and the cell ribs.