DROK Small Digital DC Volt Panel Electronics Voltmeter Car Battery Monitor Voltage Tester 12/24V 0.36" 3~30V Blue LED 2 Wires Two-wires connection: simply connect the red and black wire to positive and negative pole respectively With reversed connection protection, meaning meter will not burn when connected reversely 0.36" LED digits visible display; it requires low voltage to start; if volt is less than 3.5V, the LED will dim but not affect measurement To acquire best accuracy, its decimal point can move according to different tested voltage(if &lt;10V, two digits show after decimal point; if&gt;10V, one digit shows after decimal point) It can test voltage of 18650 or lithium battery, NiMH battery pack, moto, auto, car, etc; screw potentiometer in back side for more accurate results