Parece que a bateria do seu notebook não foi calibrada há algum tempo. Siga este guia para calibrar a bateria do seu notebook.
Instruções de calibração da bateria (da HowToGeek):
Charge your laptop’s battery to full — that’s 100%.
Let the battery rest for at least two hours, leaving the computer plugged in. This will ensure that the battery is cool and not still hot from the charging process. You’re free to use your computer normally while it’s plugged in.
Go into your computer’s power management settings and set it to automatically sleep or hibernate at 5% battery.
Pull the power plug and leave your computer discharging until it automatically sleeps or hibernates. You can keep using your computer normally while this happens.
(Note: If you want to calibrate the battery while you aren’t using the computer, be sure your computer isn’t set to automatically sleep, hibernate, or turn its display off while idle. If your computer automatically enters power-saving mode while you’re away, it will save power and won’t discharge properly.)
Allow your computer to sit for five hours or so after it automatically shuts down.
Plug your computer back into the outlet and charge it back up to 100%. You can keep using your computer normally.
Ensure any power management settings are set to their normal values. For example, you probably want your computer to automatically power off the display and then go to sleep when you’re not using it to save battery power.