A heat exchanger for thermal management of battery units made-up of plurality of battery cells or battery cell containers is disclosed. The heat exchanger has a main body portion defining at least one primary heat transfer surface for surface-to-surface contact with a corresponding surface of at least one of the battery cells or containers. A plurality of alternating first and second fluid flow passages are formed within the main body portion each defining a flow direction, the flow direction through the first fluid flow passages being generally opposite to the flow direction through the second fluid flow passages providing a counter-flow heat exchanger. In some embodiments the heat exchanger has a two pairs of inlet and outlet manifolds, the heat exchanger providing a single-pass, counter-flow arrangement. In other embodiments the first and second fluid flow passages are interconnected by turn portions forming a U-flow, counter-flow heat exchanger.