RC-Thoughts Jeti Tools – Empty Battery Alarm

I know you. You once almost went out to fly with half-empty batteries, right? There is ways to prevent this, one of them being the a little cumbersome way with sequencers and a lot of dialing in the settings. (How-to for 14 and 16 series here)

Once again, LUA to rescue!

This can be made easier and more versatile. Let’s take an example, we have a really nice jet-fighter with two RX-batteries and one battery for turbine. Of course we get all the battery-voltages to transmitter as telemetry. Wouldn’t it be easy and nice to get a warning automatically if one of them is too low when we are going for yet another flight on the same day?

So, here it is.

Empty Battery Alarm is part of RC-Thoughts Jeti Tools available here. Always download current version from there.

RC-Thoughts Jeti Tools – Empty Battery Alarm


  • Possibility to define alarm for 3 different 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

Setting up and using “Empty Battery Alarm”

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


First 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.

Here’s an example with a heli and 14S flight-pack:


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!


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