Tethered to the wall? If your laptop dies the moment you unplug it, or your MacBook is showing a "Service Recommended" warning, it's time for a fresh battery.
If your trackpad is clicking strangely, your laptop case is bulging, or the screen won't close flush, you likely have a swollen lithium-ion battery.
This is a fire hazard. Stop charging the device immediately and bring it in for safe removal and disposal.