A battery coolant jacket for use with a plurality of cells is provided, the jacket comprised of a hollow enclosure configured to permit a liquid coolant to flow through the enclosure, entering via a coolant inlet and exiting via a coolant outlet; a plurality of cell apertures that extend completely through the hollow enclosure, where each cell aperture is sized to fit a cell; and a plurality of coolant segregation walls that are integrated into the hollow enclosure and separate the cells into groups of cells, and where each coolant segregation wall forms a barrier between the cell group contained within that coolant segregation wall and the liquid coolant flowing through the hollow enclosure. The coolant jacket may include at least one flow control wall integrated within the hollow enclosure that controls the coolant flow pathway between the enclosure's coolant inlet and outlet, for example causing the coolant flow pathway to alternate directions between adjacent cell groups.