Secondary Battery

—One in which electrical energy may be stored. It consists e entially of a number of leaden plates, immersed in dilute sulphurie acid within a ve el of gla , vuleanite or other insulating material. The plates are made in the form of grids, their interstices being filled with a paste composed of lead oxides such as minium and litharge, the former for the positive plates, the latter in the negative. The action of the batteries is as follows: the sulphuric acid appears to attack the lead oxide and convert it into sulphate; on supplying the charging current the acidulated water decomposes, the hydrogen going to the cathode or negative plate and converting the lead sulphate into metallic lead, the oxygen converting that on the anode, or positive grid, to peroxide This is shown by the blue color of one ana the reddish brown of ‘the other. When the chemical action is completed, the gases bubble up through the liquid, showing that the battery is charged. The elements are in a state of tension, and the work done by the battery is the attempt to restore the equilibrium. An accumulator will restore about 80 per cent of the power spent in charging it; the current discharge at about 2 1 volts for each cell being reduced to 1.8 volts as the cell is exhausted. A secondary battery is commonly known as a storage battery or acèumulator.