If you click on that battery icon, a menu will drop down. That will likely tell you that the battery status is "failing", or something similar to that.
Click on the Apple menu, choose About This Mac. Then, click on System Report.
System Information will open.
Click on the Power tab.
What is reported there for Full Charge Capacity?
What is listed under Health Information?
You may even see that "Battery Installed" says "No"
[doublepost=1565704281][/doublepost]"A1398" is the model number of any 15-inch Retina MBPro from 2012 to 2015.
Which year model do you have?