Replace the battery.
Batteries generally wear out after a while and they need to be replaced if you rely on it. For example, When my Lenovo IdeaPad Y470 was new back in 2011, the battery would last almost 4 hours on average use when not using wireless. When playing games like Crysis 2, the battery would last maybe 60 - 70 minutes.
Now the battery will only last for less than 2 hours based on average use. I did not even bother to check how long it would last when playing games. I don't need to carry the laptop around with me anymore so it is simply plugged into the A/C outlet at home.