The Sony WF-1000XM5 Charging Case in Black contains built-in lithium-ion rechargeable batteries. Before using the earphones, you may charge them using the USB Type-C connection. If you charge the charging case in advance, you can use it to charge the WF-1000XM5 earbuds when you go out without a power supply. The required time for fully charging the charging case is about 2 hours when the battery is fully empty.
