Inside a car battery, we have cells made up of lead plates submerged in an electrolyte solution (sulfuric acid). When the battery is connected to a circuit, a chemical reaction takes place. Lead sulfate forms on the plates, releasing electrons that flow as an electric current through the connected load. When charging the battery, an opposite reaction occurs, converting electrical energy back into chemical energy stored in the lead plates.
So, to summarize, a car battery contains chemical energy that can be transformed into electrical energy when needed to power various systems and components in a vehicle.
