Battery pack case having nonuniform thickness

1 . A battery pack case configured to receive a battery cell stack constituted by a plurality of battery cells stacked therein, the battery pack case comprising:

a first case configured to allow the battery cell stack to be mounted therein; and

a second case coupled to the first case, the second case being configured to cover the battery cell stack,

wherein the first case comprises a first flat panel portion and a first side portion,

wherein the second case comprises a second flat panel portion extending in a first direction and a second side portion extending in a second direction,

wherein a thickness of the second flat panel portion of the second case is less than a thickness of the second side portion of the second case, and

wherein a thickness of the second case in the first direction is greatest at an end portion of the second side portion contacting the first side portion.

2 . The battery pack case according to claim 1 , wherein the first case comprises two first side portions extending, in a direction perpendicular to the first flat panel portion, and from opposite outer peripheries of the first flat panel portion in a longitudinal direction thereof, and

wherein the second case comprises two second side portions extending, in a direction perpendicular to the second flat panel portion, and from opposite outer peripheries of the second flat panel portion in a longitudinal direction thereof.

3 . The battery pack case according to claim 2 , wherein the second case comprises a flange portion being an end of each of the second side portions extending from the second flat panel portion and bent in a direction toward an outside of the second case, and

wherein the flange portion is coupled to an end of a corresponding one of the first side portions of the first case.

4 . The battery pack case according to claim 2 , wherein a height of each of the second side portions is greater than a height of a corresponding one of the first side portions.

5 . The battery pack case according to claim 1 , wherein a thickness of the first flat panel portion of the first case is less than a thickness of each of first side portions of the first case.

6 . The battery pack case according to claim 3 , wherein the first case comprises a flange portion formed as a result of the end of each of the first side portions extending from the first flat panel portion being bent in a direction toward an outside of the first case,

wherein a thickness of the first flat panel portion of the first case is less than a thickness of each of the first side portions of the first case, and

wherein a screw hole is formed through the flange portion of the first case and the flange portion of the second case.

7 . The battery pack case according to claim 1 , wherein the second case includes a thermoplastic resin.

8 . A battery pack comprising:

the battery pack case according to claim 1 ,

wherein the plurality of battery cells are received in the battery pack case, and

wherein electrode plates of the plurality of battery cells are disposed so as to face first side portions and second side portions.

9 . A battery pack case configured to receive a battery cell stack constituted by a plurality of battery cells stacked therein, the battery pack case comprising:

a first case configured to allow the battery cell stack to be mounted therein; and

a second case coupled to the first case, the second case being configured to cover the battery cell stack,

wherein the first case comprises a first flat panel portion and a first side portion,

wherein the second case comprises a second flat panel portion and a second side portion, portion,

wherein a thickness of the second flat panel portion of the second case is less than a thickness of the second side portion of the second case, and

wherein an outer second side portion protrudes further away from the plurality of battery cells than an outer surface of the first side portion.

10 . The battery pack case according to claim 9 , wherein the first case comprises two first side portions extending, in a direction perpendicular to the first flat panel portion, and from opposite outer peripheries of the first flat panel portion in a longitudinal direction thereof, and

wherein the second case comprises two second side portions extending, in a direction perpendicular to the second flat panel portion, and from opposite outer peripheries of the second flat panel portion in a longitudinal direction thereof,

wherein each of the second side portions is configured to have a structure including a step at an outer surface of the second side portion such that a thickness of an end thereof is reduced, and

wherein the end of each of the second side portions is inserted into an inside of a corresponding one of the first side portions and a stepped portion of each of the second side portions having a large thickness is seated on an end of a corresponding one of the first side portions so as to be coupled thereto.

11 . The battery pack case according to claim 10 , wherein the stepped portion of each of the second side portions includes a vertical hole formed therethrough in a height direction thereof.

12 . The battery pack case according to claim 11 , wherein a screw hole is located under the vertical hole, the screw hole being configured such that an inner diameter of the screw hole is less than an inner diameter of the vertical hole and a height of the screw hole is less than a height of the vertical hole.

13 . The battery pack case according to claim 10 , wherein the stepped portion of each of the second side portions includes a horizontal hole formed therethrough in a horizontal direction thereof.

14 . The battery pack case according to claim 9 , wherein the second side portion includes a flange portion located at a lower portion of the second side portion, and

wherein the flange portion contacts the first side portion on a first surface and a stepped portion of the second side portion located below the flange portion contacts the first side portion on a second side surface.

15 . The battery pack case according to claim 1 , wherein an end portion of the first side portion is a flat surface that contacts the flat surface of the second side portion.

16 . The battery pack case according to claim 1 , wherein a thickness of the second side portion above the end portion of the second side portion is approximately equal to a thickness of the first side portion contacting the end portion of the second side portion.