Battery idle problem! Flashing yellow light rapidly.

Unplugging the power cable immediately shuts down the laptop, meaning the battery is not working.

1. Battery Indicator Flashing Rapidly
   

1. Taskbar Showing Battery Information
   

1. System BIOS say “Battery Idle”
   

I disconnected the battery from the laptop and reconnected it but still nothing. This battery used to provide more than 3 hours of backup before the problem occurred. Laptop won't turn on without power cable, meaning the battery is not working. What can I do right now?