Thanks to Saftwerk for finding this excellent presentation on Li-Ion battery life. It's long, but packed with information and is the closest we'll come to being inside Tesla's battery research lab. In fact, one of the grad students involved in this research project (Aaron Smith) is now running the Battery Lifetime Group at Tesla. It's a fascinating look at the science and technology behind the cells. Why do Li-ion Batteries die ? and how to improve the situation? - YouTube In general the research confirms many of the rules of thumb that have been discussed on the forum. Avoid spending long periods of time at high state of charge and keep the battery cool, and your pack should have a very long life.