A battery pack includes at least one serpentine fluid circulation tube that extends around part of the periphery of a plurality of electric cells. First and second segments of the tube are disposed adjacent a first and a second edge of a first set of the plurality of electric cells. The sets of electric cells are disposed in an alternating arrangement. A first fin and a second fin are provided between each of the electric cells. The fins have a reverse turn wrapped around the segments of the tube. The fins have internal ends that are disposed between the electric cells and the tube segments. The battery pack may be assembled by folding the fins around the electric cells and the tube or by preforming folded sheets that define thermal fins and assembling the folded sheets over segments of the tube from opposite sides of the electric cells.