A storage battery is a device that directly converts chemical energy into electrical energy. It is a rechargeable battery designed to be recharged through a reversible chemical reaction. It usually refers to a lead-acid battery, which is a kind of battery and belongs to two secondary battery. Its working principle: when charging, it uses external electrical energy to regenerate the internal active material, and stores the electrical energy as chemical energy.

It uses a lead substrate grid filled with spongy lead (also known as a lattice) as a negative electrode, a lead substrate grid filled with lead dioxide as a positive electrode, and dilute sulfuric acid with a density of 1.26--1.33g/mlg/ml is used as the electrolyte. When the battery is discharging, metal lead is the negative electrode, which undergoes an oxidation reaction to generate lead sulfate; lead dioxide is the positive electrode, which undergoes a reduction reaction to generate lead sulfate. When the battery is charged with direct current, elemental lead and lead dioxide are formed at the two poles, respectively. When the power source is removed, it returns to its pre-discharge state, forming a chemical battery.