Abstract: A novel battery separator for a flat-pack or planar battery is disclosed wherein a nonwoven fabric is disposed on and across a plastic frame or grid, the outer edges of the fabric being disposed on said plastic frame are of extremely low fiber density and being oriented predominantly in a direction normal to each side of the frames so as to facilitate the more complete thermal pressurized bonding of a stack of separators and similarly electrodes by a sealing of the outer edges of the respective plastic frames. A more complete seal is thus formed insuring against the leaking or escaping of the liquid electrolyte contained therein.