power saver mode on facetime

I have the MacBook Pro with OS X Yosemite (version 10.10.3)

I was just on FaceTime for a few hours with plenty of battery and wifi bars on the Mac and out of nowhere the call failed and a message popped up saying "Power Saver Mode". I then went to the settings to try to turn it off but didn't find anything.

Anyone know how to turn this off?