Gaston Planté, a French physicist working as a teaching assistant at the Conservatoire National des Arts et Métiers in Paris, develops in 1859 the first commercially viable rechargeable battery: two sheets of pure lead separated by a linen cloth, rolled into a spiral and immersed in a sulfuric acid solution. The following year he presents a nine-cell battery to the French Academy of Sciences. Unlike the voltaic pile or the Daniell cell, which are depleted as the electrode is consumed, Planté's battery can be recharged by applying a current in the reverse direction, thereby opening the category of secondary batteries or accumulators. The basic concept of a "secondary" current had, however, already been demonstrated by the German physicist Johann Wilhelm Ritter in 1802-1803, using copper and cardboard discs soaked in brine, although with no subsequent practical development; Planté's specific merit is not having conceived the idea of recharging, but having been the first to build a device capable of storing and releasing electrical energy practically and durably. The design, later improved by Camille Faure in 1881, would become the dominant technology for starting automobiles for more than a century.