KWE 3.4A 2-Port USB Rapid LED Car Charger - Display Out / Input Voltage and Car's battery, Travel Charger for iPhone and All Other USB Plugs FAST DUAL USB CHARGING PORTS - Combined 3.4 amps; 5V; ensure each device pulls the right amperage. Charger is powered by the vehicle's cigarette lighter. OVER-CHARGE PROTECTION - auto power off when input/output is greater than safety current, protects against over-heat, over-current and over-charging LED DISPLAY - LED digital luminescence tubes; Display cycles between internal temperature (Fahrenheit), device's charging current, and the voltage of the vehicle's car battery. (Note: When using the device to charge, it display the charger's temperature instead of the internal temperature of your car. ) The LEDs are bright enough to read the display without being a distraction while driving. LOWER VOLTADE WARNING - when the voltage us below 11.8V or between 18V and 23.8V, the buzzer alarm will automatic ringing. SPECIFICATIONS - Input: DC 12V - 24V, Output: DC 5V/3.4 A, 15 W, Conversion efficiency 95%, Measuring range: Voltage 5V-25V, Current 0 - 3.1A, Temperature -4 to 176 F