It was a chilly December night in the run-up to Christmas 2014. Our Nissan Leaf electric car was crawling up a seemingly endless hill on the M2, somewhere in east Kent. My wife was driving, cajoling the last dregs of power from the battery, as we tried to make it to a service station with a charger that we hoped would actually be working. We were almost at the end of a six-hour journey from our home in the Peak District to Ramsgate, and the whole trip had been a nervous endeavour requiring the meshing of battery range with the...