HobbyKing™ Lipoly Low Voltage Alarm (2s~4s)
Simple to use low voltage alarm that is small and light for on board use, plug's into balance lead for detecting low voltage on individual cells. A loud alarm will sound and LED will change from Green to Red if any individual cell drops to 3.3v or below.
Voltage Accuracy: 0.03v
Low Voltage Alarm Threshold: 3.3v (per cell)