A battery module that includes a cell stack and a battery module housing that receives and supports electrochemical cells arranged in the cell stack, each cell disposed in a cell housing, comprising a positive electrode, a negative electrode and a separator, where the separator is sandwiched between the positive electrode and the negative electrode and prevents physical contact between the positive electrode and the negative electrode, the battery module housing comprising: a rigid frame formed of an electrically non-conductive plastic or metal, that is rigid to physically support the cell stack, retain the cell stack in a desired position and orientation during use, and prevent deformation of the cells within the cell stack due to impacts in the course of normal handling and use, and surrounds a circumference of the cell stack, the frame having an inner surface that faces the cell stack, an outer surface that is opposed to the inner surface, a first edge that joins the inner surface to the outer surface at one end of the cell stack and includes a flat surface, and a second edge that joins the inner surface to the outer surface at an other end of the cell stack and includes a flat surface, wherein a first cover element formed of a flexible metal foil laminate sheet, the first cover element that overlies the one end of the cell stack and a peripheral edge of the first cover element being joined to the frame along the entirety of the peripheral edge of the first cover element, and a second cover element formed of a flexible metal foil laminate sheet, the second cover element that overlies the other end of the cell stack, a peripheral edge of the second cover element being joined to the frame along the entirety of the peripheral edge of the second cover element, wherein the first and second cover elements (260, 280) are dimensioned so as to extend beyond the first and second edges (10, 12) of the frame, whereby the peripheral edges (266, 286) of the first and second cover elements (260, 280) overlie and are sealed to the outer surface of the frame, the first and second cover elements (260, 280) are joined to the frame along seal lines (268, 288) that extend about the circumference of the frame so as to form a closed loop, the flexible metal foil laminate sheet is a multi-layer sheet that includes a central layer of metal foil that is sandwiched between a layer of polyamide and a layer of polypropylene, or the flexible metal foil laminate sheet has three layers of oriented nylon/aluminum foil/polypropylene or four layers of polyethylene terephthalate/oriented nylon/aluminum foil/polypropylene, that are joined by a thin adhesive between adjacent layers, the first cover element is heat sealed to the frame along the entirety of the peripheral edge of the first cover element, and the second cover element is heat sealed to the frame along the entirety of the peripheral edge of the second cover element, whereby the first cover element, the second cover element and the frame cooperate to form a heat sealed module housing for containing the cell stack. a rigid frame formed of an electrically non-conductive plastic or metal, that is rigid to physically support the cell stack, retain the cell stack in a desired position and orientation during use, and prevent deformation of the cells within the cell stack due to impacts in the course of normal handling and use, and surrounds a circumference of the cell stack, the frame having an inner surface that faces the cell stack, an outer surface that is opposed to the inner surface, a first edge that joins the inner surface to the outer surface at one end of the cell stack and includes a flat surface, and a second edge that joins the inner surface to the outer surface at an other end of the cell stack and includes a flat surface, wherein a first cover element formed of a flexible metal foil laminate sheet, the first cover element that overlies the one end of the cell stack and a peripheral edge of the first cover element being joined to the frame along the entirety of the peripheral edge of the first cover element, and a second cover element formed of a flexible metal foil laminate sheet, the second cover element that overlies the other end of the cell stack, a peripheral edge of the second cover element being joined to the frame along the entirety of the peripheral edge of the second cover element, wherein the first and second cover elements (260, 280) are dimensioned so as to extend beyond the first and second edges (10, 12) of the frame, whereby the peripheral edges (266, 286) of the first and second cover elements (260, 280) overlie and are sealed to the outer surface of the frame, the first and second cover elements (260, 280) are joined to the frame along seal lines (268, 288) that extend about the circumference of the frame so as to form a closed loop, the flexible metal foil laminate sheet is a multi-layer sheet that includes a central layer of metal foil that is sandwiched between a layer of polyamide and a layer of polypropylene, or the flexible metal foil laminate sheet has three layers of oriented nylon/aluminum foil/polypropylene or four layers of polyethylene terephthalate/oriented nylon/aluminum foil/polypropylene, that are joined by a thin adhesive between adjacent layers, the first cover element is heat sealed to the frame along the entirety of the peripheral edge of the first cover element, and the second cover element is heat sealed to the frame along the entirety of the peripheral edge of the second cover element, whereby the first cover element, the second cover element and the frame cooperate to form a heat sealed module housing for containing the cell stack.