THIS IS 2-1 BATTERY VOLTAGE CHECKER AND LOW VOLTAGE BUZZER.

It will warn you when it is time to land your helicopter
It will Buzz with very loud BB noise when any of the cells of your battery is under 3.3V, the volume is loud enough to alert you to land your helicopter immediately to avoid accident.

* Friendly remind:
The sound of the low voltage alarm is very big, so please be prepared when use it for the first time, and you can turn it OFF when use indoors.
 

• 1S test mode test range 3.7 to 30V, which means you can test the battery pack without balance connectors like RX battery pack etc., LiPb or other power source voltage. In other words, this very little devise can be used as a simple digital voltage meter.
  
• Loudly buzzer can be heard from distance, you can put this device on your plane and use it as on-board alarm, so you can hear the low voltage alarm during flight.
• 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.

• Use for 1-8S Lipo/LiMn/Li-Fe
  
• Voltage detection precision: ±0.03V
  
• Unit voltage display range 0.5-4.5V
  
• Total voltage display range: 0.5 - 36V
  
• 1S test mode voltage range: 3.7-30V
  
• Low voltage alarm mode for 2-8S
  
• Alarm set value range: OFF-2.7-3.8V
  
• Weight: 8.7g/ 0.31oz
  

• 1 x Li-Polymer Battery Voltage Tester / Low Voltage Buzzer Alarm (1-8 Cell)

** color of this device might be different (green or red electronic board) sometime but it is the same.