[sonium]

Hi, I made myself a voltage sensor using two resistors as described in the librepilot manual.
I only connected the voltage lead of the PWR port of the of the CC3D since the ground seems to be connected anyways.
I calibrated the voltage factor by matching the fully charged battery voltage which I meassured using a multimeter. However the empty battery voltage is still significantly off, and I infact destroyed a battery pack by undercharging it.

Does the ground of the PWR port also need to be connected?

[f5soh]

You say Revo in title and next CC3D, what board do you use ?

Are you sure you choose / use the right input pin ?
adc0 is pin3
adc1 is pin4

Better connect also the ground from PWR port to the ground from voltage divider and avoid issues.

[sonium]

I use a Revolution thinking that this is what people call 'Revo'. I connected Pin4 to the voltage divider, so adc1. I'll go forward with Pin1 connected to ground in addition.

[f5soh]

That a Revolution board and Chinese sellers call it "Revolution" for marketing purposes.
CC3D and Revolution boards are two different boards.

[sonium]

Ok, thanks for the clarification. So it's called just 'Revolution' without the 'CC3D'.

Just for sake of completeness, i fixed the sensor problem. Turned out I had used a 1kOhm resistor instead of 2.2kOhm. By means of destructive testing the ADC1 port was able to tolarate a voltage of ~ 9V with however beeing out of the measurement range.

Furthermore after using appropriate values for resistors it is not necessary to connect Pin1 of the PWR port to anything.

One last thing: Is it possible to have a low voltage alarm in the GCS?

[f5soh]

The full size Revo has ESD protections in inputs so looks like it works well...

There is already low voltage alarm, values are displayed in orange and red.
Look FlightBatterySettings > CellVoltageThresholds

You can also add a voice talking using the notification plugin with something like that: