I believe there is a human aspect involved. I lack evidence for this, but I assume it may be a combination of the two. I have seen individuals discussing the practice of leaving their vehicles unlocked, or passing by their automobiles at home while carrying their phones or keys, and experiencing very low battery levels. These factors induce the automobile to reply or poll, therefore using the 12v power supply. I am not asserting this is the explanation; nonetheless, I believe there is a combination of factors including software and hardware, however the precise ratio of these elements remains the significant inquiry. Currently, I am predisposed to believe that the human aspect may be the more significant component. Should mine be succesful, I will amend that assertion 🙂
It seems that if the primary battery's charge falls below 20%, it will cease to charge the 12V battery.