If the battery for the headphones is not keeping a charge, there may be a loose connection or a problem with the battery. Try doing the following steps to resolve this issue:
- Verify the power adapter for the transmitter is plugged into a working AC outlet.
- Make sure the other end of the AC power adapter is connected to the DC IN jack on the transmitter.
- Place the headphones on the transmitter so that the charging pins on the transmitter make contact with the connectors on the headphones.
- A green charge indicator will light when the battery is being charged.
- The required hours to fully charge an empty battery varies depending on the model. A charging time of 3.5 hours is required for an MDRRF985RK, while some models like MDRRF970/925RK will need up to 16 hours so when it's fully charged the green charge indicator should go out on the transmitter.
- If there is no charge indicator, try plugging the transmitter into a different AC outlet, just to make sure there is not a problem with the first outlet.
- Make sure the battery is fully charged .
- If applicable, test the battery performance.
- Depending on the age of the battery, try replacing the battery with a new one.
The troubleshooting steps listed above should resolve your issue. If you have completed all of the steps including trying a different battery or if you want to replace the built-in battery of a wireless headphones, the headphones may need service.  Go to Product Repair.