Switch out the battery
Want to know why your MacBook can’t hold a charge the way it used to? Most modern models have a limited charge cycle of 1,000. Each cycle is measured when the machine uses all the battery’s power and then fully recharges it. Apple also claims "your battery is designed to retain up to 80 percent of its original capacity at 1,000 complete charge cycles." That’s not 100 percent.
You can check the condition of your battery by clicking the battery icon on the top right, where you’ll see one of four conditions: Normal, Replace, Replace Now, or Service Battery. Common sense suggests replacing the cell if prompted, but you can dig deeper into the issue by checking the cycle count on the back end. Hold down the Alt key and click the Apple icon at the top left, and choose System Report/Profiler. From there, select Power and check the battery’s current cycle run.