How to make Mac shut down when fully charged? Since I have heard that keeping on the charger plugged while the battery is at 100% will degrade battery life, I would like to find a way to make the Mac switch off by itself when it reaches 100%. This is mainly for when I want to charge the laptop overnight.

Is the first claim true? Also, if it is, how can I get the Mac to shut down by itself when it reaches 100% charge?
The claim is not true.

The only thing that has been proven to degrade battery life is heat, which also means overnight charging with your Mac sleeping is better than charging it while in use.

Switching it off doesn't make a difference.