Batteries designed for renewable energy purposes serve the essential purpose of storing electricity generated from solar, wind, and hydro energy. They serve as a backup even when the power source is not available. The most commonly used type of battery is lithium – ion due to their efficiency and long life, but there are other types such as lead – acid and flow batteries which serve the same purpose. All of these enable the renewable sources of energy to be more effectively integrated into power grids while ensuring a reliable energy supply which leads to a sustainable future