The same thing happened to my 2009 CPO one month after I purchased it in 2012. I had it jumped, drove to the dealership, and they replaced it under CPO warranty. However, they were quick to point out that this was the only time a battery would be replaced under warranty and that I needed to drive it at least 500 miles per month to keep the battery charged. Since I do not drive that much per month I invested in a trickle charger and so far so good with the new battery.

 

Once I heard my car begin to crank a little slower than normal I looked at the battery to confirm it was the original battery. It was and it was now 5 years old. I bought a new Porsche battery for about $200 (friend at dealership) and installed it myself. Much easier for me to do that than hassle getting it to the dealer, fighting the SA and dealing with the warranty. Not worth the BS for $200.