Specifications: Two wires digital voltmeter, mini size, with reversal protection, and connect easily. According to the different measuring voltage, automatically moving the position of the decimal point. LED display, so it is visible even at night. 2 wires design, simple wiring and convenient to install. With polarity protection function for meter power supply. Wiring: Red Wire: Measure Voltage Connected to the Positive (2.50-30V DC) Black Wire: Measure Voltage Connected to the Negative Measure Voltage Range: DC2.50-30V (When the voltage lower than 3.5V, the brightness of the LED display is dimmed, but does not affect the correct measurement.) Some Applications: Measure 18650 Batteries Measure Cell-phone Lithium Batteries Measure Nickel-hydride Battery Pack Measure Cars Motorcycles Battery Voltage etc. Item Name: Digital Voltmeter Min Input Voltage: DC2.50V Max Input Voltage: DC30V Measurement Accuracy: 1% (+ / - 1 Digit) Display: Three Digit 0.36" LED Display Color: Red, Blue, Green Refresh Rate: About 200mS/Times Operating Temperature: Minus 10 Degree Celsius- 65 Degree Celsius Features: LED Display, 2 Wires, Polarity Protection Function, Reversal Protection Size: 48cm x 29cm x 22cm/18.99" x 11.42" x 8.76" (Approx.) Hole Size: 46mm x 27mm/1.81" x 1.16" (Approx.) Leading Wire: 20cm/0.39" (Approx.) Thickness: 10mm/7.97" (Approx.) Mounting Hole Center Distance: 28mm/1.10" (Approx.) Screw Size: M2.0 x 12 (NOT Included) Wire Length: About 15cm/0.69" (Approx.) Notes: Due to the light and screen setting difference, the items color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Package Includes: 1 x Digital Voltmeter