Battery pack and manufacturing method therefor

1. A battery pack comprising:

a cell assembly comprising a plurality of secondary cells and a plurality of cartridges, the cartridges being configured to be stacked on one another and to accommodate the secondary cells while surrounding outer circumferential portions of the secondary cells from outsides of the secondary cells;

a lower housing having a bottom wall and a sidewall extending upwardly from the bottom wall to define an empty inner space to accommodate the cell assembly in the inner space, the lower housing being opened on an upper side thereof;

a lower end plate comprising a plate-shaped metallic material and placed in surface contact with a lower surface of the bottom wall of the lower housing; and

a lower cover placed on a lower surface of the lower end plate to cover the lower end plate, the lower cover being fixedly coupled to the lower housing and the lower end plate being between the lower housing and lower cover.

2. The battery pack of claim 1 , wherein the lower cover is fixedly coupled to the lower housing by a laser welding method.

3. The battery pack of claim 2 , wherein the lower cover and the lower housing comprise a same plastic material.

4. The battery pack of claim 1 , wherein the lower cover is fixedly coupled to the lower housing along and outside an edge of the lower end plate.

5. The battery pack of claim 1 , wherein at least one opening is formed in a center portion of the lower end plate, and

wherein the lower cover is fixedly coupled to the lower housing through the opening.

6. The battery pack of claim 1 , wherein the lower housing and the lower cover comprise concave and convex portions corresponding to each other.

7. A battery pack comprising:

a cell assembly comprising a plurality of secondary cells and a plurality of cartridges, the cartridges being configured to be stacked on one another and to accommodate the secondary cells while surrounding outer circumferential portions of the secondary cells from outsides of the secondary cells;

a lower housing having an empty inner space to accommodate the cell assembly in the inner space, the lower housing being opened on an upper side thereof;

a lower end plate comprising a plate-shaped metallic material and placed in surface contact with a lower surface of the lower housing; and

a lower cover placed on a lower portion of the lower end plate to cover the lower end plate, the lower cover being fixedly coupled to the lower housing,

wherein the lower end plate comprises at least one bolt protruding upward, and

wherein at least one through-hole is formed in the lower housing to pass the bolt through the through-hole.

8. The battery pack of claim 7 , wherein at least one insertion hole is formed in the cell assembly, and

wherein the bolt is inserted in the insertion hole.

9. The battery pack of claim 1 , wherein the secondary cells and the cartridges of the cell assembly are vertically stacked, and

a lowermost cartridge of the cell assembly is placed in the inner space of the lower housing in contact with a an upper surface of the bottom wall of the lower housing.

10. The battery pack of claim 1 , further comprising an upper end plate comprising a plate-shaped metallic material and provided on an upper portion of the cell assembly to cover the upper portion of the cell assembly.

11. The battery pack of claim 1 , further comprising an upper housing coupled to the opened upper side of the lower housing to seal the opened upper side.

12. An automobile comprising the battery pack of claim 1 .

13. A method of manufacturing a battery pack, the method comprising:

placing a lower end plate comprising a plate-shaped metallic material on a lower surface of a bottom wall of a lower housing comprising a sidewall extending upwardly from the bottom wall to define an empty inner space and an opened upper side such that the lower end plate makes surface contact with the lower surface of the bottom wall of the lower housing;

placing a lower cover on a lower surface of the lower end plate to cover the lower end plate;

fixedly coupling the lower cover and the lower housing to each other so that the lower end plate is between the lower cover and the lower housing; and

stacking secondary cells and cartridges in the inner space of the lower housing, the cartridges accommodating the secondary cells while surrounding outer circumferential portions of the secondary cells from outsides of the secondary cells.

14. The method of claim 13 , wherein, in the fixedly coupling of the lower cover and the lower housing to each other, the lower cover and the lower housing are fixedly coupled to each other by a laser welding method.

15. The method of claim 13 , wherein the lower end plate comprises at least one bolt protruding upward, and the lower housing comprises at least one through-hole, and

in the placing of the lower end plate, the bolt of the lower end plate is passed through the through-hole of the lower housing.

16. The method of claim 15 , wherein at least one insertion hole is formed in each of the cartridges, and in the stacking of the secondary cells and the cartridges, the bolt of the lower end plate is inserted into the insertion holes of the cartridges.

17. The battery pack of claim 1 , wherein the lower surface of the bottom wall of the lower housing has a concave portion, and

wherein a convex portion of the lower end plate extends into the concave portion.

18. The method of claim 13 , further comprising inserting a convex portion of the lower end plate into a concave portion in the lower surface of the bottom wall of the lower housing.