Answer

Please check the battery capacity before connecting the AC adapter and check if your unit has the Battery Master in Dragon Center / Creator Center.

These mechanisms are used to avoid the loss of battery life span from constantly charged and uncharged, it's a normal battery-charging behavior.

Normally, the value of setting capacity (%) to start charging the battery is usually located between 90 – 95%(the actual number may differ by models); if the battery capacity is higher than 90%, the system won't start charging the battery. 

*Under one condition the battery will still be charged even when the capacity is over 90%: Connecting the AC power when the battery capacity is lower than 90% to start the battery charging, however, before the battery gets fully charged, the AC power is removed and interrupt charging; when connecting the AC power the next time, the battery will continue charging from the last state where the charging was interrupted until it gets fully charged (100%); Once the battery is fully charged, the next charging will start when the battery capacity is lower than 90% again.

For units which support the Battery Master in Dragon Center or Creator Center, users get to set the different battery charging point.

a. At 90% (Best for Mobility)

    If the battery capacity is higher than 90%, the system won't start charging the battery.

b. At 70% (Balanced)

    If the battery capacity is higher than 70%, the system won't start charging the battery.

c. At 50% (Best for Battery)

    If the battery capacity is higher than 50%, the system won't start charging the battery.

*Note: Dragon Center's Lucky setup assistant dialog might lead to make changes on the Battery Master settings.