What is the Battery Status menu on Mac?
If you’re using a portable Mac, you can quickly see the status of your battery, and find out if an app is using a significant amount of energy.
If you don’t see the battery icon in the menu bar, you need to show the battery’s status.
To view the Battery Status menu, click the battery icon 
in the menu bar. To view your battery’s condition, press and hold the Option key and click the battery icon in the menu bar.
The first line of the menu says “Battery Is Charged” or shows the amount of time until the battery is full. This line only appears when your Mac is connected to a power supply.
The second line of the menu shows the current power source.
The third line of the menu provides information about energy usage. For example, if apps are using a lot of energy, it says “Using Significant Energy” and lists the apps. If an app is using significant energy, but you’re not using it, consider closing the app, particularly if your current power source is your Mac’s battery.
On some newer portable computers, you see
Display Brightness in the menu when the display’s brightness is set to a level that uses a significant amount of energy. If you click it, the display brightness reduces to approximately 75 percent, which helps to optimize battery use.