SMAKN&reg; LED Tester Voltmeter Ammeter Digital Amp Volt Ampere Panel Meter DC Current 300V/300A Red/Blue 2-color Power Supply: DC 4.5-30V Measure Voltage: DC 0-300V Measure Current: 0-300A forward current (need an extra 300A shunt for measuring current ) Display: 0.28" LED, Dual Color, Red and Blue Operating Current: &lt; 20mA; with reverse polarity protection