The Walkman battery life is short even thought it is fully charged

Turn off the power when not using your Walkman.

The Walkman does not turn off automatically when playback is stopped. As a result, the battery will be depleted unless you turn off the power when you stop playback.
You can save the battery by turning off the Walkman whenever you are not using it.

Turning the Walkman on or off (NW-A30 Series):
 

1. Hold down the  power button [1] for 3 seconds while the screen is on.
   
2. Follow the onscreen instructions to turn off the Walkman.
3. Release the HOLD function if it is active.
   
   NOTE: The screen will turn off automatically if you do not operate the Walkman for a certain period of time.

Additionally, the usage time differs depending on the setting.
For example, you can reduce the battery consumption by using the Walkman under any of the following conditions.
NOTE: Depending on the model, some of the information listed below may not be available. For details, refer to the Help Guide of your Walkman.

• Set Auto Power Off to turn off the Walkman automatically.
• Set a shorter time for Screen Off Timer.
• Adjust the screen brightness.
• Set all sound quality settings to off.
• Disconnect the Bluetooth device when you are not using it.
• Turn off the NFC function when you are not using it.
• Turn off the Noise Canceling function.