Why my Lenovo ThinkPad L560 battery pack cannot be fully charged?

It may happens to you when Lenovo ThinkPad L560 battery pack cannot be fully charged in the standard charge time when the computer is powered off. You may check the suggestion below to fix it, this information is from official manual.

Solution: The Lenovo ThinkPad L560 battery pack might be over-discharged. Do the following:
1. Turn off the computer.
2. Make sure that the over-discharged battery pack is in the computer.
3. Connect the ac power adapter to the computer and let it charge.If a quick charger is available, use it to charge the over-discharged battery pack.If the battery pack cannot be fully charged in 24 hours, use a new battery pack.

Brand new LENOVO ThinkPad L560 10.8V 4400mAh laptop batteries
Voltage: 10.8V
Capacity: 4400mAh (48Wh)
Battery cells: 6-cell
Chemical: Li-ion
Battery Color: Black
Condition: new original battery
Warranty: 9 months