Yeeco DC7-100V 0.56" Red Display Voltmeter Voltage Volt Panel Meter Gauge 3 Digit Two Wires Voltage Monitor Measurement Electric Car Tester with Reverse Polarity Protection 36V 48V 60V 72V 84V Digital voltmeter gauge voltage tester support 36V/48V/60V/72V/84V electric cars Can be used for measuring the car/battery car/motorcycle battery voltage, and other forms of voltage Can be used in all kinds of voltage measurement purposes; With reverse polarity protection Don't need additional power supply,Red line:Measure Voltage +(7-100V ) Black line:Measure Voltage - The voltmeter is not used to the electric motor which has reverse gear