Battery pack

1. A battery pack comprising:

a battery casing section having an upper surface;

a plurality of battery cells accommodated in the battery casing section and stacked in a predetermined stacking direction, each of the plurality of battery cells having an upper end surface and a pair of positive and negative electrode terminals projecting from the upper end surface of the corresponding one of the plurality of battery cells;

a conductive-member casing section mounted to face the upper surface of the battery casing section;

a plurality of conductive members disposed in the conductive-member casing section, each of the plurality of conducive members being configured to electrically connect between the positive electrode terminal of a selected one of the battery cells and the negative electrode terminal of a selected other one of the battery cells so that the battery cells are electrically connected in series; and

a cover member arranged to face the conductive members to thereby form a cooling fluid passage between the cover member and the conductive members, the cooling fluid passage enabling cooling fluid to flow, wherein:

the conductive-member casing section has opposing first and second walls in a flow direction of the cooling fluid passage, the flow direction of the cooling fluid passage being perpendicular to the predetermined stacking direction of the plurality of battery cells,

the cover member has opposing first and second ends in the flow direction of the cooling fluid passage,

the first end of the cover member is arranged to project toward the first wall of the conductive-member casing section to form an inlet opening between the first end of the cover member and the first wall of the conductive-member casing section, the inlet opening constituting an inlet of the cooling fluid passage,

the second end of the cover member is arranged to project toward the second wall of the conductive-member casing section to form an outlet opening between the second end of the cover member and the second wall of the conductive-member casing section, the outlet opening constituting an outlet of the cooling fluid passage, and

each of the first and second walls of the conductive-member casing section is located to be closer to the battery cells than an upper surface of the conductive members is.

2. The battery pack according to claim 1 , wherein:

each of the inlet opening and the outlet opening has a cross sectional area,

one of the inlet opening and the outlet opening is located to be closer to the battery cells than the other of the inlet opening and the outlet opening is, and

the cross sectional area of the one of the inlet opening and the outlet opening is smaller than the cross sectional area of the other of the inlet opening and the outlet opening.

3. The battery pack according to claim 1 , wherein:

at least one of the plurality of conductive members includes radiation fins located to be closer to one of the inlet opening and the outlet opening than to the other of the inlet opening and the outlet opening;

each of the inlet opening and the outlet opening has a cross sectional area; and

the cross sectional area of the one of the inlet opening and the outlet opening is smaller than the cross sectional area of the other of the inlet opening and the outlet opening.

4. The battery pack according to claim 1 , wherein:

the cooling fluid passage comprises:

an upstream side passage;

an intermediate communication passage; and

a downstream side passage;

the upstream side passage is communicated with the downstream side passage through the intermediate communication passage,

the intermediate communication passage is comprised of wall surfaces of the cover member, and

at least a part of the wall surfaces of the cover member is located to be closer to the battery cells than the upper surface of the conductive members is.

5. The battery pack according to claim 4 , wherein:

each of the plurality of battery cells comprises a safety valve,

the cover member comprises a duct part that constitutes a gas discharge passage that is communicated with the safety valve of each of the battery cells, and

the intermediate communication passage is arranged crossing the gas discharge passage, and located to be closer to the battery cell sides than the gas discharge passage is.

6. The battery pack according to claim 5 , wherein:

the inlet opening of the cooling fluid passage comprises inlet opening parts, each of the inlet opening parts being located to face a center of a corresponding one of the conductive members in a cell thickness direction perpendicular to the stacking direction, and

the outlet opening of the cooling fluid passage comprises outlet opening parts, each of the outlet opening parts being located to face a center of a corresponding one of the conductive members in the cell thickness direction.

7. The battery pack according to claim 4 , wherein:

the inlet opening of the cooling fluid passage comprises inlet opening parts, each of the inlet opening parts being located to face a center of a corresponding one of the battery cells in a cell thickness direction perpendicular to the stacking direction,

the outlet opening of the cooling fluid passage comprises outlet opening parts, each of the outlet opening parts being located to face a center of a corresponding one of the battery cells in the cell thickness direction, and

the intermediate communication passage is arranged to face both sides of the battery cells in the cell stacking direction.

8. The battery pack according to claim 1 , wherein:

each of the plurality of conductive members comprises:

a contact part arranged to contact the positive electrode terminal of a selected one of the battery cells and the negative electrode terminal a selected another one of the battery cells; and

a bent part shaped to be farther from the battery cells than the contact part is,

wherein the bent part of each of the conductive members and the battery cells define a passage therebetween through which the cooling fluid flows.