Low battery alert

Mike Shellim 05 May 2018

Here's a simple but effective low battery alert which ignores short low voltage spikes. It can be used for receiver or flight batteries on a telemetry-enabled setup. It uses one logical switch and one special function.

In the example below, an alert is triggered when the voltage falls below 7V for 3 seconds, and repeats every 4 seconds until the voltage recovers.

L1: a>x, RxBatt, 7V, Delay(3s)

SF1: L1, Play Sound(Beep 1), repeat(4s)

The key is the use of the delay and repeat parameters.

For flight packs with sensors, use Cels as the first operand in L1.

Sound file for alerts

Instead of PlaySound, you could use Play Track with the lowbat or batlow file as provided on most sound packs. Beware however that they only say 'battery low', so it's not clear which battery is affected. To avoid confusion, use this custom sound file which plays "receiver battery low".

(There's no issue with the transmitter battery - the alert is 'transmitter battery low' and is handled natively by OpenTx, according to the threshold in the Radio Setup menu.)