A battery pack assembly has a plurality of interconnected battery cells and is suitable for use in an electric vehicle or a hybrid electric vehicle. The assembly includes a first battery cell having a first terminal and a second battery cell having a second terminal electrically interconnected by a bus bar formed of a conductive material and attached to the first terminal and the second terminal. A bus bar retainer formed of a dielectric material is configured to contain the bus bar within the bus bar retainer. The bus bar has a greater freedom of movement within the bus bar retainer along a first, e.g. vertical, axis than along a second, e.g. longitudinal, axis and a third, e.g. lateral axis, wherein both the second and third axes are substantially perpendicular to the first axis and to each other. The assembly may also include individually removable temperature sensing devices.