Summarize the following:
To find out the condition of your battery, hold the ⌥ Option key as you click the battery icon in the menu bar. This displays the Battery Status menu, which will display one of the following status indicators: Normal: The battery is working properly. Replace soon: The battery is working normally, but is no longer at full capacity. This is not time to panic, but you should definitely check the status frequently to make sure it doesn't get worse. Replace now: The battery works normally but its capacity is significantly lower than it was when brand new. You can still use the laptop, just make sure you always have a power cable handy until you can replace the battery. Service Battery: The battery is not working properly. You should still be able to use the computer with a power cord connected, but the battery will likely not work on its own. Bring the computer to the Apple-authorized service provider as soon as possible. If your computer is turning off unexpectedly, it may be related to incorrectly-set power settings. In the Apple menu, click System Preferences, select Energy Saver, and then click Power Adapter to see check out what your computer's set to do when plugged in. Make sure the "Turn display off after" slider is not set to sleep after a brief period of inactive time. If you're still having trouble, the remaining steps will help you reset the System Management Controller (SMC), which can help resolve power problems. Begin by making sure the computer is turned off and not plugged into a power source. Don't turn the computer on, just plug it in for now. After holding the buttons down for about 4 seconds, lift your fingers from the keyboard. This will power your Mac back on. Once it comes back up, the SMC will be reset, hopefully clearing up any residual power issues.

Summary:
View your battery health status. Check your Energy Saver settings. Shut down your Mac. Plug the power adapter into the Mac. Press and hold Control+⇧ Shift+⌥ Option and the Power button. Press the Power button once.