What is the voltage of a battery?

lead storage battery is a kind of storage battery, which uses a lead plate filled with sponge lead as a negative electrode, a lead plate filled with lead dioxide as a positive electrode, and 22-28% dilute sulfuric acid as an electrolyte. When charging, electrical energy is converted into chemical energy, and when discharging, chemical energy is converted into electrical energy. When the battery is discharged, metal lead is the negative electrode, which undergoes oxidation reaction and is oxidized into lead sulfate; Lead dioxide is the positive electrode, which undergoes a reduction reaction and is reduced to lead sulfate. When the battery is charged by direct current, lead and lead dioxide are generated at the two poles respectively. After the power supply was removed, it returned to the state before discharge to form a chemical battery. Lead storage battery is a battery that can be repeatedly charged and discharged, and it is called secondary battery. Its voltage is 2V, usually three lead-acid batteries are connected in series, and the voltage is 6V. Cars use 6 lead-acid batteries in series to form a 12V battery pack. After a period of use, lead-acid batteries should be supplemented with sulfuric acid to keep the electrolyte containing 22-28% dilute sulfuric acid.