All batteries degrade over time. Based on current technology, there is no way around that. My understanding though is that Nissan batteries have been showing much higher degredation percentages than other manufacturers. Are there any studies that compare this? As far as I know, we have two other manufacturers with long enough data available, GM (Spark and Volt), and Tesla. For both of those manufacturers, I have heard that batteries have degraded very little. I have not heard about the Mitsubishi or VW evs. I am asking because I usually buy cars that are a few years old to save money. That is fine for most cars. My experience with an older Prius needing battery replacement kind of tempers my enthusiasm for cars with batteries. I bought a 2014 Leaf last year, and I'm worried about my bargain purchase not being so much of a bargain if I have to replace the battery in 4 years.