Lead acid batteries are the most commonly used rechargeable batteries today. They also represent the oldest design with one of the worst energy-to-weight ratios, they are cheap and can supply the high surge currents needed in started motors.
Increasing the surface area of the plates in a cell increases its current capacity, but not its nominal voltage. Cells connected in series make a battery. The number of cells determines its nominal voltage.
During discharge, the chemical energy of the plates is transformed into electrical energy, then used to perform work. The plates develop the same composition, which reduces the potential of the cell.
