Battery for replacing the factory one Galaxy S21 5GSamsung Galaxy S21 5G G991. If your mobile phone battery lasts very little, drains suddenly after a call, is swollen, or no longer charges, it is time to replace it. Modern smartphones do not make this process easy, as they can only be opened with special tools, and it is recommended to consult a specialized technician as any mistakes may result in the malfunction of your device. See full description