Plante Lead-Acid Cell

Every cell before 1859 ran one way. Discharge it and the zinc was gone; the only repair was new metal. In 1859 Gaston Plante rolled two lead foils separated by rubber strips into a spiral, stood them in dilute sulfuric acid, and found he could push the reaction backwards with a current and get the energy out again. He reported it to the French Academy of Sciences in 1860. The chemistry is unusually clean about it. Charged, the cell is lead dioxide against sponge lead in acid; discharged, both plates are the same substance, lead sulfate, and much of the acid has become water. That last part is the useful accident: the electrolyte is a REAGENT, not a bystander, so the density of the liquid tells you the state of charge. A float and a glass tube is a fuel gauge, and no other common cell offers one. What it cost Plante was time. He made no plates - he made lead foil and then MADE the plates out of it, by charging and discharging over and over until the surface had converted deep enough to hold a useful charge. Formation took weeks to months, which is why lead-acid existed for twenty-two years before anyone could sell it. That single problem is the whole subject of the next blueprint in this chain. He never patented it. The cell that starts almost every car on earth entered the world as a paper read to an academy.