Farmunion 4 in 1 Cigarette Lighter Digital LED Voltage/ Current/ Temperature Monitor 12v 24v+3.1a Dual Port USB Car Charger (red) 3.1 amps; 10W; uses smart technology to ensure each device pulls the right amperage. Charger is powered by the vehicle's cigarette lighter. Automatically displays the current temperature (inside the car), current and voltage, Rotate every 20 seconds After inserting the cigarette lighter (Note: When Charging the Temperature display will rise) OVER-CHARGE PROTECTION - auto power off when input/output is greater than safety current, protects against over-heat, over-current and over-charging Constantly monitor battery voltage, extend and protect the battery and engine life Stylish, Compact design(2.9*1.6*1 inchs 0.9oz), Easy to use, easy to carry.