11,260. Tribelhorn, A. June 21. Secondary batteries.-Relates to bi-polar plates in which the opposite sides of the plates are of opposite polarity. Fig. 1 shows a vertical section of a plate, and Fig. 3 shows a front view of the same. The invention consists partly in providing a layer a of an impervious solution or material, such as caoutchouc, in the middle of the active material, to oppose the passage of the ions from p to n. The two surfaces p, n of the active material are in electrical contact by means of strips s of lead, and the whole is held in place by a light frame c of glass or ebonite provided with internal grooves of the shape shown. A rubber ring k serves to hold the plates in place in the cell. In the arrangement shown in Figs. 4 and 5, the frames c are dispensed with, and the active material is held in place both by strips s of lead which are preferably cemented into the cell h, and by threads x of glass which extend horizontally through the cell and through the electrodes.