​ ​Checking the Macbook battery performance are easy to find out. First  if its on charging for many hours to consumed and once its been fully charge, it's easy to drained. The signed is taking time to fully charge and easy to drained. The macbook will work only thru adapter thats on charging.

To see the exact model of a macbook battery and so ever spare parts may need to change or replace. It will be base on the Model number  will seen at the back of macbook.  Example of the image above.

The image was shown is the battery percentage after its been charging for 4 hours. 

Here is the percentage after been stop to charge it and make shut down the macbook. After an hour passed and do open the macbook. Its get drained half way . So the solution is to replace a new battery and get the work without hussle for charging it always.