There are a few steps that need to be done to troubleshoot this.
Firstly, does your laptop run fine on battery power? Have you charged it long enough as usual and let it run on the battery? And if so, does it last as long as it should?
If it doesn't run long on battery power after charging it for a while, this may mean your battery is faulty and needs replacing.
Secondly, if your battery does work fine, if maybe a software glitch. Go the Device Manger, (Start key and X then click on Device Manger, or type it in at Start) double click on Battery and right click on Microsoft ACPI-Compliant Control Method Battery, and hit Uninstall. Then click on Action, and hit Scan for hardware changes and the driver will reinstall itself.
If this solves it, then it's a software glitch. This is sometimes common, but in all of my experiences with battery related issues and charging, it's ALWAYS been the battery or some type of hardware issue. My gut feeling is that since your laptop is probably four to six years old, you probably do need a new battery.
Solutions to common battery problems
Some additional battery resources.
A tip I'll don off, I always clean the contact fins on the motherboard of the laptop with about 90 percent rubbing alcohol. This cleans the contacts and can help the battery in some cases and prevents weirdness in general.