Appliable for: RC Quadcopter, helicopter, multicopter,car,boat and airplane,1S-8S / Lipo / Li-ion / Li Mn / Li-Fe battery. Features: -This product is using for detecting 1S-8S lithium battery -Detect the voltage of each battery core automatically, support reverse connection protection. -To know the working state of your battery anytime, protect the battery from overcharge and over discharge. -The red LED will flash,the buzzer will beeping when the voltage is below the set point. -The factory default setting is 3.3V, press the button to change the voltage setting, and it will save your current setting automatically. Package Included: 1 x Voltage Buzzer Alarm