A modular battery pack and method of making a battery pack. Prismatic can battery cells are interspersed with cooling frames along a stacking axis within a housing such that numerous a cell-frame assemblies, each with a cooling path, are formed. Resiliently-biased sealing members on the frames are arranged such that they remain out of the way of a footprint defined by the joined cells and frames to promote ease of high-speed cell-to-frame assembly. Upon formation of the cell-frame assembly and subsequent placement into the housing with inner walls that press against the protruding ends of the sealing member, the sealing member is forced by the housing to come into contact engagement with a corresponding surface of the edge of the battery cell. The generally linear, planar contact surface formed by the contact engagement promotes the formation of a sealing surface that makes it harder for introduced cooling air to escape. By this sealing member construction, cell-frame assemblies may be produced with high-speed automated assembly techniques that may have both large manufacturing tolerances prior to assembly and substantially gap-free cell-to-cooling frame contacting surfaces after assembly.