Empty Battery Alarm


Featured functions

  • Possibility to define alarm for 3 different batteries
  • Possibility to name the batteries
  • Free choice of voice-announcement-file per battery, own announcement for each alarm
  • Start-time of announcement adjustable so all alarms do not sound on top of each other
  • Warning displayed also as system message on main screen
  • Warning is checked only after a new battery is connected (model powered)
  • Voltage-check starts 3 seconds after telemetry is available (Time for voltage to settle)
  • Fully automatic, set settings and forget


  • Heli: Flight-pack and RX-voltage
  • Park-flyer: Main battery
  • Jet: 2 x RX-battery and Turbine-battery


In short: Copy the .lua file from github here to your transmitters Apps-folder, if there is a translation file copy the .jsn file to Apps/Lang-folder on your transmitter. Head on to “Applications” -> “User applications” and add the app. Guide on installation of Lua-apps available here if you need some more in-depth guide.

Setting up and using “Empty Battery Alarm”

After installing the application to your transmitter go to “Applications” -> “Empty Battery Alarm” and open the application:

If you want you can give battery a name, for example “RX-Battery” or “Turbine Battery”. Then select the voltage-sensor you want to use for each battery. If you are using different announcements already you can adjust the announcement-time. The value means “how many seconds after alarm the voice announcement is made”. Alarm value is the voltage limit. For example for 2S battery this could be put to 8.2 volts (4.1V per cell), after connecting a 2S battery with 8.2 volts or under is then considered as not fully charged and creates an alarm. After selecting the audiofile to be played on alarm you can choose to have the announcement repeated 3 times.

After this your all done. It really is that easy.

Operation is as follows:

  • Look for sensor to be active
  • Look for sensor to give a value (voltage)
  • Wait 3 seconds for values to settle
  • If voltage is same or under the alarm-voltage then activate the alarm
  • After 60 seconds disable the alarm if user decides to not care (Unless user disconnects battery)

If you start your model with a battery of too low voltage the alarm-message of your choice will play either once or three times and you will see a system-warning on your main-screen:


Finally a really easy way to do a complicated task!

Version history

  • 1.0 Original version – Languages available EN, DE
  • 1.1 Added Spanish translation from César Casado
  • 1.2 Added Italian translation from Fabrizio Zaini
  • 1.3 Memory improvements
  • 1.4 Bugfix on alarm-thershold
  • 1.5 Big rework “under the hood”, added battery-naming


Some rules do of course apply!

  • Never use Lua to control a function that would take the model down if misbehaving!
  • Always, always test the function thoroughly!
  • If you do not know, then don’t!
  • RC-Thoughts or myself is NOT responsible for anything this application does
  • Applications are free to use (MIT-license) and linking to this page is encouraged!