Replacing the battery on your Sony earbuds by yourself might not be possible as technical knowledge is required to replace the built-in rechargeable battery. Also, if it has been modified by a non-Sony technician, it might void the warranty of earbuds. For that matter, if you want to replace the battery, it is better to go to the nearest service center in your location. The Sony technician will need to disassemble the earbuds to replace the built-in battery.