Hi All, As you may know a weak 12 V battery has been traced to poor mileage in the 2nd Gen Prius. Recently, I read how the 3 rd Gen Navi diagnostics are accessed, and found the 12 V battery volt meter. My car is less than a year old, and it read 11.7 V. Hmmm... Maybe some others with the Navi can read their battery voltages and post on here? Sit in the car, do not press the brake pedal. Press the power button once. Wait for the screen to come on. Then press and hold the INFO button on the right side of the Navigation screen, and while holding it cycle the head lights on and off three times. Then find the soft key on the screen which takes you to the screen which shows the voltmeter display. Let me know what you get. Then press the gas pedal and hit the button again. My reading rose to 13.5 V as the car became ready, as it should.