1 . A battery pack case, comprising: a battery cell housing assembly, the battery cell housing assembly being made of metal, the battery cell housing assembly being configured to accommodate, from one side in a second direction, a battery cell in a state in which a plurality of the battery cells are stacked in a first direction perpendicularly intersecting the second direction and are compressed in the first direction, and the battery cell housing assembly being configured to support a restoring force of the battery cell; and a flow path forming member, the flow path forming member being made of resin, the flow path forming member being provided integrally with the battery cell housing assembly, the flow path forming member being disposed at another side, in the second direction, of the battery cell, and the flow path forming member configuring a part of a cooling air flow path through which battery cell cooling air flows; wherein the battery cell housing assembly comprises: a first component, including: a pair of first side wall parts that extend in the first direction and that are configured to support the battery cell in a third direction perpendicularly intersecting the first direction and the second direction, and a support wall part that supports the battery cell from the other side in the second direction; and a pair of second components, including: a second side wall part configured to support the battery cell in the first direction, and a pair of third side wall parts that are provided continuously with the second side wall part at one side and another side, in the third direction, of the second side wall part, and that are joined to the respective first side wall parts.
2 . The battery pack case according to claim 1 , wherein: a main flow path part is provided integrally with the support wall part at the other side, in the second direction, of the support wall part, the main flow path part configuring a part of the cooling air flow path, extending in the first direction, and being configured to supply the cooling air to the battery cell; and the flow path forming member includes: an end part structural part provided integrally with a portion of the first component at one side thereof in the first direction and with the one side, in the first direction, of the second component, and configuring an end of the cooling air flow path, and an air vent part provided integrally with a portion of the first component at another side thereof in the first direction and with the other side, in the first direction, of the second component, and configured to connect to a blower part configured to supply the cooling air to the cooling air flow path.
3 . The battery pack case according to claim 1 , wherein a plurality of the battery cell housing assemblies is disposed in a consecutive manner in the third direction, and the battery cell housing assembly further comprises: a first connection member, the first connection member being made of metal, the first connection member connecting together the second side wall parts at the one end in the first direction; and a second connection member, the second connection member being made of metal, the second connection member connecting together the second side wall parts at the other end in the first direction.