Not a practical question but interesting anyway.
Century batteries reckon modern vehicle charging systems (smart charge?) might be to blame, with CO2 emmissions causing the problem:
Q. Why has my battery gone flat?
Undercharging - This is the most common cause of a flat battery. Modern vehicle charging systems are designed to reduce CO2 emissions and improve fuel economy by increasing battery usage, while at the same time not providing sufficient charge to fully recharge the battery.
https://www.centurybatteries.com.au/...sked-questions
I wonder how true it is, and how much CO2 is needed to make a new battery.