claudioita wrote:is it possible ot measure via software?
No, or at least not without additional circuitry, including a (calibrated) A/D converter. (A Pi doesn't have any "analogue" inputs). However it is possible to check whether a low-voltage trigger has happened (via the mechanism used to trigger the display of the low-voltage icon).
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, 2xB2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B+, P3B, B+, and a A+) but Buster on the P4B's. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm