1.Reliable Car Battery Tester: BT172 automotive battery tester is engineered to test 12V batteries across a variety of vehicles, such as cars, motorcycles, trucks, RVs, ATV, SUV, boats, yachts, mowers, and even golf carts.The accuracy of this car battery voltmeter is approximately 0.01V, ensuring dependable results. 2.Alternator Charging System Analysis: Besides assessing if a vehicle's battery needs replacement or a jump start, BT172 can also evaluate the alternator's output status to prevent battery damage from overcharging or insufficient charging. 3.: BT172 three modes for testing the alternator, 12V battery tester, In the middle mode, the LCD screen shows real-time voltage while LEDs indicate the alternator status. Switching to the 12V mode displays the real-time voltage on the LCD screen, with LEDs indicating the battery status.Note:Properly connect the meter battery clamps to the battery terminals: attach the red alligator clip to the positive terminal and the black alligator clip to the negative terminal. 4.Protection Features: BT172 is equipped with reverse connection protection to prevent damage in case of incorrect hook-up.The voltage test range is 4-30V DC, and if the voltage is out of range, the screen will display 'LO' (4V) or 'HI' (30V), providing protection against over-voltage.