Vented flat battery

Cells or multicell batteries are provided with vents comprising fiber-filled plastic tubes. The plastic tube walls are formed of a hydrogen-permeable, liquid-impermeable, plastic material and the fibers which fill the interior of the tube serve to maintain an open gas diffusion passage through the tube. The vents extend through seals between battery components into electrochemically active regions of the battery, into gas permeable regions of the battery outside of the electrochemically active regions, or both. The fiber filled tube can terminate in the cell interior when the end positioned within the cell is sealed with a hydrogen-permeable, liquid-impermeable, plastic layer, or the tube can extend across the battery length or width. At least one end of the tube is open to the atmosphere.