The plates in a leadplatebattery are of very largearea per cell, and are placed close together. Sometimes, as in Planté's battery, largeflat plates are laid together with a separating insulator between them, and are then rolled into a spiral. Sometimes, the most usual arrangement, the plates are in sets, the positive and negative ones alternating, and each cell containing a number of plates.
To secure a goodquantity of active material, the plates are sometimes perforated, and the perforations are filled with oxide of lead. This gives a gooddepth of material for the charging current to act on, and avoids the necessity for a tedious "forming," q. v.
The electro-motive force of such a battery per cell is 2 volts. Its resistance may only be one or two-hundredths of an ohm. An intense current of many amperes can be supplied by it, but to avoid injuring the cell a current far less than the maximum is taken from it.
To charge it, a slightly greater electro-motive force, the excessbeing termed spurious voltage, is required.
Definitions of battery, secondary
