Battery module and battery module assembly

A battery module assembly, comprising:

• a first battery module including a first module case having an interior housing a plurality of battery cells therein, the first module case having an outermost periphery in a horizontal direction, and the first battery module including a first input/output terminal and a second input/output terminal positioned at one side of the first module case;
• and
• a second battery module including a second module case housing a plurality of battery cells, the second battery module including a first input/output terminal and a second input/output terminal positioned at one side of the second module case,
• wherein the first input/output terminal of the first battery module includes a first module bus bar extending from within the interior of the first module case to an exterior of the first module case, the first module bus bar comprising a first portion and a second portion integrally connected together at a connecting region, the first portion extending within the interior of the first module case such that the first portion is connected to at least one of the plurality of battery cells in the interior of the first module case, and the second portion extending from the connecting region to a terminal end opposed to the connecting region and positioned exteriorly to the first module case, the terminal end being spaced away from the first module case such that the terminal end is located beyond the outermost periphery of the first module case in the horizontal direction, the terminal end comprising a recess portion defined therein, such that, when the second battery module is disposed next to the first battery module in the horizontal direction, the second input/output terminal of the second battery module can be received in the recess portion of the terminal end of the first input/output terminal of the first battery module.