I started getting frequent battery discharging notices on the display when starting the car. Figured out it was the 12V AGM battery. I called my BMW Center for a price on the replacement battery for my barely over 4 year old i3. They quoted me $365 parts and labor, and confirmed it was out of warranty. Car was ready a few hours later, including a SW update for a minor safety recall. I am very happy to report that BMW warrantied the new battery completely since the car was only six weeks out of warranty. Thank you BMW!