APM 2.52 Battery Low Buzzer not working

Hi Guys

I’m hoping you will be able to help with this issue.

I’m running Arducopter 3.1.4 on the APM2.52. The buzzer is connected correctly and I get the two beeps when I arm the craft and the single beep when I disarm the craft.

I am not running the APM from a power module but power it directly from a BEC via the input rail.
Before I continue, I have not been able to source a power module for the APM in South Africa yet but I’m hoping that a contact I receive today will be able to assist me with this.
Do I need to have the power module connected for the low battery buzzer to work?

The problem I’m facing is that low battery buzzer never sound when I hit the low voltage I set. When I arm the craft and the failsafe is enabled, the buzzer just constantly beeps. I also have not been able to figure out if the “Low buttery buzzer” and the “Battery Failsafe” are actually related configurations. As far as I understand it, the Low battery buzzer should work without the Failsafe being configured, since the failsafe tells the craft what to do when the battery is low. The buzzer should just warm me when the power gets low.

Anyhow. As soon as the craft is armed, the buzzer beeps continuously. I have tried every setting for the LED_Mode i could fine (7 / 11/ 127 / 170) and it still does not work.

Can someone please explain to me who these to things relate, if at all, and please give me some advice on how I can be notified of a low battery.

I’m quite desperate for answers since I have just got new Lipo’s and I have no Idea (apart from a timer on my DX8) when they run low and I don’t want to damage them but running them too low.

Thank you for your help in advance.

Kind regards


Ehm, how is your APM supposed to know that the battery voltage is low if you don’t have a power module or another voltage sensor connected? Do you have any other sensor, like Attopilot or FrSky?

Well … Stefan

You are correct, I don’t have any external sensors… but

Under the battery Monitor, If you set the APM Version to APM2-2.5 Non3DR (I have the RC-Timer version) the “Sensor” section is disabled. Under Calibration it gives me a measured voltage, etc…

I was assuming since the APM shows me what the voltage is, and the “Sensor” item is disabled, the APM had a built in sensor (although probably with some restrictions) which will allow it to know when the voltage is low.

There is also under APM version, the AMP2.5+ - 3DR Power Module - Which I assumed would be used when you have the power Module.

Therefor, I wanted to find out what the story is and how it works…

Apologies for asking a stupid question … and wasting your time…

I can’t speak to the code bit but one of these [youtube]https://www.youtube.com/watch?v=a4gv3FFoTpY[/youtube] is a belt and braces way of doing things.

Not sure where you are in RSA but if you are in a hot and high bit you can total a battery quick!



Ah, ok. That’s because, the APM is measuring something :slight_smile:. The sensor which you would connect, is a voltage divider, which proportionally reduces the battery voltage to a range of 0-3.3V or 0-5V, depending on the sensor. If I remember correctly, the ATMEGA chip used in the APM has internal pull-up resistors which means, if nothing is connected, the chip measures 5V at the input, which the APM:Copter software then translates into a battery voltage according to the sensor configuration.
I can see how that can fool somebody who is not familiar with the system :slight_smile:, so not really a stupid question.

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