US Patent 7771865 Battery unit

A battery unit comprises a bypass structure. The bypass structure includes a bypass exit opening formed at one end of a second direction traversing a first direction at a first end of the battery case, the first direction being oriented from the first end to a second end at which an outlet is formed, a bypass entrance opening formed in a central part of the battery case along the first direction and in a central part along the second direction, a bypass duct by which the bypass exit opening communicates with the bypass entrance opening, and a flow path which guides a cooling gas downstream of the bypass entrance opening to both sides of the second direction.