Player only works on USB Cable

[gothsoul]

Hi it's my second iPod lookalike player.
This time the problem is when I slide the on button it doesn't tur itself on. It displays a black screen.
But if I plug the USB cable, it turns on and works fine.
The battery displays as full, so it shouldn't be a problem. But when I unplug the USB cable, the player turns off imediatly.

Any idea or suggestion?

[Th3_uN1Qu3]

Battery terminals probably broken, take it apart and re-solder them. Maybe put a larger capacity battery in as well.