Low Thermal Expansion Battery Module

A battery pack (20) assembly having a casing (32) enclosing stacks (22, 24) of cells (26). The casing (32) defines a plurality of air intake chambers for receiving a flow of air and a plurality of slots (44, 46) diametrically opposite of the air intake chambers for dispensing the flow of air, and the air flows circumferentially through a gap (37) around the cell walls (34) to cool the cells (26). A plurality of circumferentially and radially spaced flow interrupters (60) arc disposed on at lest one of the cell wall (34) and the casing (32) for disrupting the flow of air to increase the heat transfer coefficient of that air.