A battery pack (1) includes a housing (2) and an array (40) of electrochemical cells (80) disposed in the housing (2). The housing (2) includes a container (3) and a lid (30) that closes an open end of the container (3). The container (3) has a base (4), a sidewall (8) that surrounds the base (4), and a spring plate (110) disposed inside the side wall (8) between the cells (80) and the sidewall (8). The spring plate (110) is free standing within the container (3) and applies a spring force to the cell array (40) that restrains the cells (80) along an axis normal to the surface of the spring plates (110). The lid (30) includes inwardly-protruding pins (50, 60) that further restrain the cells (80) within the housing (2).