A plate assembly for a heat exchanger includes a first plate, a second plate, and an intermediate plate arranged between the first and second plates. The intermediate plate is joined to the first and second plates at peripheral edges to create a sealed periphery of the plate assembly. Corrugations of the intermediate plate provide crests and troughs that are in contact with inwardly facing surfaces of the first and second plates. The plate assembly can be configured as a battery cooling plate heat exchanger to transfer heat from a battery to fluid flowing through the plate assembly.