Casing for battery pack and battery pack

A casing for a battery pack, wherein the casing has a receiving space and an opening in communication with the receiving space, the receiving space is enclosed by a wall portion of the casing, and the wall portion is formed by pressing two or more stacked metal base plates, between which a plurality of cavities are formed, wherein an island is disposed within the cavity, wherein

• the wall portion comprises a bottom wall and side walls surrounding the bottom wall on a peripheral side of the bottom wall, and the bottom wall and the side walls are integrally formed by said pressing and are each formed by the two or more stacked metal base plates as the wall portion,
• the plurality of cavities are in communication with each other to form a flow passage, and the island is disposed within the flow passage,
• the two or more stacked metal base plates comprises a first base plate and a second base plate, the cavity is formed by an outwardly projecting convex wall of the second base plate and a flat wall of the first base plate corresponding to the convex wall,
• a portion of the island attached to the flat wall is formed in a shape of a strip or an ellipse, and a long side of the strip or a major axis of the ellipse is parallel to the length direction of the flow passage,
• a ratio of a height h of the cavity to a width W of the cavity is in a range of h/W≤1, and
• a ratio of a length L of the island to a width W1 of the island is in a range of 2≤L/W1≤5, and the length L is in a range of 5 mm≤L≤15 mm, and
• a ratio between a wall thickness t1 of the flat wall and a wall thickness t2 of the convex wall is in a range of 0.5≤t2/t1≤1.