Mostly likely you have AC adapter plugged in all the time and that will eventually kill the battery. Happened to me. Battery are not supposed to be charged all the time. It needs to be discharged fully and charged. If using AC adapter plugged in all the time, you need to remove the battery. Use battery only on the go.
To fix you problem you need to replace the battery. It is not covered by warranty since it is considered as consumable item.