Usually a battery that died has an x on the icon. If not, got to Device Manager, go to the battery option, then uninstall the battery drivers. Shut down the computer, remove the battery pack, if your computer do not have a battery pack, disconnect it from the motherboard. Put the battery pack back in or connect it back to the motherboard after a few mins. Than see if you can power on the laptop without the cable. If not plug the cable in and look at your battery status.
The battery may need replacing since they have a limited lifespan, after which they can no longer hold a charge.
Actual lifespan can be affected by various factors, how well it's been looked after etc.