Schumacher BT-25 Automotive Power Alert LCD readout displays charging input voltage within 0.1V variance Detects car diode for any variance more than 0.8V Two LED warning lights alert you when your car's battery and charging system are running into problems Alerts in advance once the car battery drops down too low, which allows you about one hour to go to a repair center before you are completely stopped on the way. This product cannot be shipped to Oregon or California