On more than one occasion, when I have gone in my garage at around 5 a.m., I hear a hum/buzz coming from the back end of my Prius. It has to come from the battery pack because the sound seems to come from under the back end of the car and is not as audible when I open the hatch. I just had the car serviced last week and everything should be good as new. I wish I had remembered to mention this to them, but I didn't. It's happened more than once. Can anyone enlighten me on what's happening? Last night's example: car was last driven at 7:30 p.m. the previous day and has been parked all night. At 5 a.m. this morning, it's humming. Is it just happy?
