NOVELTY - The portable electrical energy storage device, has first and second electrical energy storage cells. An electrical energy storage cell barrier comprises a thermal insulating material and an elastic material. The electrical energy storage cell barrier located between the electrical energy storage cells. The first electrical energy storage cell comprises nickel-metal hydride chemistry or lithium-ion chemistry and the second electrical energy storage cell comprises a same chemistry as the first electrical energy storage cell.    USE - Portable electrical energy storage device.    ADVANTAGE - The oxygen available to support combustion to the oxygen generated in situ minimizes the length of time combustion within the electrical energy storage device occurs, thus reducing the temperature within the device is elevated to a level where failure and subsequent bursting and combustion of gases from other cells occurs. The electrically nonconductive materials of the electrical isolation layer prevent electrical isolation layer from adversely affecting the terminals or conductive features electrically connected to the electrical energy storage cells. The electrically nonconductive material making up electrical isolation layer is noncombustible or flame retardant, thus allowing electrical isolation layer to impede or prevent propagation of combustion from one side of electrical isolation layer to an opposite side of electrical isolation layer. The biased vents impedes or prevents gases that impinge on the biased vents from coming in direct contact with an electrical energy storage cell making up an electrical energy storage cell module that is on a side of the biased vents opposite from the side upon which the gases impinge.    DESCRIPTION OF DRAWING(S) - The drawing shows an exploded view of the portable electrical energy storage device.    Electrical energy storage cell module (12)    Housing (16)    Shell (18)    Cover (20)    Limiting examples thermal insulating material (26)