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