Battery Heat Exchanger

A battery pack assembly comprising:

• a plurality of rectangular battery cells, each having two opposed major surfaces and arranged in a stacked configuration;
• a heat exchanger assembly comprising a fluid transfer layer comprising an elastomeric material and having opposed major surfaces;
• a first external layer comprised of flexible graphite and having an interior facing major surface and external facing major surface, said interior facing major surface secured to one of said fluid transfer layer major surfaces, said fluid transfer layer including at least one channel and configured to form a passage for receiving a thermal transfer fluid between said at least one channel and a portion of said interior facing major surface of said first external layer;
• and
• wherein said heat exchanger is folded in a repeating serpentine shape forming a plurality of U-shaped portions, said plurality of rectangular battery cells being received in said plurality of U-shaped portions.