Fashionclubs Lipo Battery Monitor Alarm Tester Checker Low Voltage Buzzer Alarm with LED Indicator for 1S-8S Lipo LiFe LiMn Li-ion Battery 2 pcs Protect the battery from overcharging or overdischarging. Compatibility: 1-8s Lipo/Li-ion/LiMn/Li-Fe battery Test the working state of lithium battery. Push key which can change the voltage settings and save When the voltage is below the set value,it will buzzer with red LED light,pre-set value 3.3V