I own a 2009 Lexus Isf and yesterday I noticed it started to lose battery voltage while at a red light. The voltage only drops while in drive and not moving it does not drop if the car is in neutral or in park. Spoke with a mechanic and he said it wasn’t something he had seen before. Has anyone else had this problem before?

 

This has not been mentioned here before. Sounds like you're due for a new alternator.