When the battery dies in your smartphone, what do you do? You complain bitterly about its too-short lifespan, even as you shell out big bucks for a new device. 

Electric vehicles can’t work that way: Cars need batteries that last as long as the vehicles do. One way of getting to that goal is by keeping close tabs on every battery in every EV, both to extend a battery’s life and to learn how to design longer-lived successors.