Battery drains despite seemingly being charged
When your battery is losing charge despite the fact that you have plugged in A/C power (and you have not inhibited charging via Tp smapi etc.), then check whether the A/C adapter is to blame. Shut down, unplug the battery, and try to power up the laptop by only running on A/C power. If this doesn't work, it's likely that the A/C adapter is broken.
Note: even if the A/C adapter is broken it may appear as if it is running fine (i.e., the screen turns brighter and the battery LED is red)!