Remove and reset the battery to make sure it is properly connected.
Swap batteries with another similar system, if available. If another similar system is available, then verify that the battery pack works in the other system and that the other system battery pack works in this system.
Verify the battery status indicator. The battery status indicator is normally illuminated whenever the battery is installed and the computer is on, or the AC adapter is connected and the battery is charging. This indicator may be blinking or solid in either orange or green color depending on the status of the battery.
Verify the condition of the battery by attaching AC adapter, booting into Windows, and checking battery status in Power Manager. If not installed, Power Manager can be downloaded from here: