A battery module includes a housing having an opening and a plurality of electrochemical cells disposed in the housing. The plurality of electrochemical cells have electrode terminals. The battery module also includes a carrier defined by an outside boundary and coupled to the plurality of electrochemical cells. The outside boundary of the carrier and the housing are in a nested arrangement. The battery module also includes a bus bar assembly disposed on the carrier, the bus bar assembly includes bus bars that electrically couple the electrode terminal of one of the plurality of electrochemical cells to a respective electrode terminal of another one of the plurality of electrochemical cells.