A battery unit includes a battery housing, a module assembly, electrode portions, fins and a blower. The module assembly includes battery modules having positive terminals and negative terminals. The electrode portions are disposed to connect the positive and negative terminals of the battery modules. The fins are disposed along the electrode portions. The module assembly defines a first surface and a second surface along a stacking direction of the battery modules. The blower is disposed to supply air toward the fins over a range substantially equal to a dimension of the module assembly in the stacking direction. A rotation shaft of the blower is located between a first plane that includes the first surface of the module assembly and a second plane that includes the second surface of the module assembly. The fins have surface areas that increase toward a downstream location with respect to a flow of the air.