[12V & 24V Car Battery Tester]: AUTDER AD-808 car battery tester works with all 12 volt and 24 volt batteries for vehicles, cars, motorcycles, trucks, mobile homes, off-road vehicles, SUVs, boats, yachts, mowers, and golf carts. The accuracy of the car battery voltmeter is close to 0.01V, such as 12.29V. [Generator Charging System Analyzer]: In addition to providing a quick read to determine if a vehicle battery needs repair or replacement, it can also test the output status of the generator to prevent battery damage due to overcharging or undercharging. [Ease of Use]: Features three testing modes for alternator, 12V battery, and 24V battery. When the selector is in the middle position, the LCD screen displays real-time voltage while LEDs indicate generator status. When switched to 12V or 24V mode, the LCD shows real-time voltage and LEDs indicate battery status. [Reverse Connection and Overvoltage Protection]: If connected in reverse, the LCD displays "ERR" and the built-in buzzer sounds. The digital voltage test range is 4 to 20V DC. If voltage is out of range, LO (30V) will appear on the screen.