What happens if the battery actually drains completely? For example the car sits for months at a dealership? Or driving across country, only driving in sport mode?
The car will not allow the battery to go below 15% SOC when it is running, so driving it across the country, or running in Sport mode only would not cause that. The only time you would worry about this is the long-term storage scenario.
I experienced something like this first hand when I picked up my car. The dealership's L2 charger was not working correctly and the car had been on ships and trucks and had not been charged since it left Finland.
I had to pull over and shut the car down for unrelated reasons. When I tried to start the car up again, I get a very serious "Out of Energy" warning and all sorts of red lights come on and the car refused to start. I think the SOC must have been just below 15% because when I did a hard reset, the computer allowed me to get the ICE going, which then charged the battery up to the required minimum as I drove the car.
But normally, you would find someplace to plug the car in just long enough to get it up to 15% (3 KWH).
