[aiharkness]

To add to the above, batteries do wear out. The useful life depends in part how you use them and other stresses, like temperature. And they can begin to show failure in different ways. A bad battery may not charge. It may charge fully and then drain fast. A battery may indicate that it is charged but be able to deliver sufficient power under a load.

Your issue may be the battery. The best thing to do is try your battery in a known good device, and try a known good battery in your device. This way you can sort out whether the problem is the device is through battery or the device. Short of that, try a new battery in your device. If there is still a problem then odds are it's the device, but you won't be certain if you don't verify the new battery is good.

Good luck.