Loudhailer Lipo Battery Voltage Alarm Indicator Checker 2-4S LED Display for RC Helicopter Quadcopter Car Battery Lipo Battery Voltage Alarm Indicator Checker 2-4S LED Display for RC Quadcopter Functions: Tested battery cell voltage (> 3.6V) 2S LiPo battery: 2 green LED lights on Tested battery cell voltage (> 3.6V) 3S LiPo battery: 3 green LED lights on Tested battery cell voltage (> 3.6V) 4S LiPo battery: 4 green LED lights on Cell voltage < 3.3V, corresponding red light will on and alarm will be sounded Specifications: Used for: 2S-4S lipo battery Package size: 4 * 2 * 1cm / 1.6 * 0.8 * 0.4in Package weight: 5g / 0.2oz Package list: 1 * Loudhailer Lipo Battery Voltage Alarm Indicator Checker