RioRand 0.40" Waterproof Digital Voltmeter DC 2.5-30V Tester Red LED Display Car Auto Vehicle 12V 24V Battery Power Monitor; Little DVM Outdoor Gauge for Solar System; Two Wires mode, Self powered, Measuring Lithium Battery, 18650 Battery Voltage Directly; with Connecting Reverse Protection Powered by RioRand Advanced Technology Wide-range begin from DC 2.5V, low-power: Great convenience for measuring Lithium batteries, 18650 battery directly Accuracy Optimization: decimal point Automatically shift, 10V Below display as "x.xx", 10V or above display as "xx.x"; Two Wires mode, Self powered (5 to 20mA) monitor that can handle 2.5-30vdc and provides a perfect monitor for float charging SLA batteries; Waterproof design, outdoor Mounting, as a Power monitor/detection of solar power systems; Moisture-proof, anti-oil, anti-vibration ;Car Auto Vehicle Battery Power Monitor, Measure DC 5V 6V 12V 24V voltage directly