Today I noticed my 2015 latitude had a high voltage reading. Happened to look on the display screen when going to check my tire pressure and noticed that the voltage was reading 15.6v. Seemed odd because it’s normally at 14.8v. It has gotten colder and thought that it would go back to 14.8v. the only time I saw go back down to 14.8v while the engine was on was when I turned on the headlights. When the engine was off it read 12.4v. Is this an issue that I should take to the mechanic?