Most manufacturers will provide a warranty of eight to 10 years for their EV batteries, you get eight years/100,000 miles with a Nissan Leaf. It's also worth bearing in mind that they don't usually fail outright, so even after 10 years they're unlikely to suddenly stop working. And many manufacturers are finding that batteries are actually lasting better than expected, so we wouldn't be too concerned about the lifespan of a battery if purchasing an electric car. However, if it does need replacing - it can cost around £5000 for a new battery setup.