“YOU NEVER KNOW WHAT RANGE YOU’VE GOT LEFT”

Dashboards on electric cars usually have a prominent ‘range’ readout: how many miles you have left. It’s meant to reassure you, so you can plan your trip and avoid premature flat battery misery. But these things are almost all pathological liars. You set off, and before you’ve driven five miles the gauge has fallen by 10. It’s anything but reassuring and always spooks newbie EV drivers.

Well, once I’ve driven any electric car through a couple of battery cycles, I can do better myself and never bother with the range meter. I look only at the percentage.

It’s easy. Drive for a bit to get the temperatures stabilised. Then zero the trip, and note the battery percentage. Keep driving and when the battery percentage has dropped by 10, read the trip. Divide the trip mileage by 10. This is how far you can drive for every one per cent of battery. Then at any stage you can multiply the remaining percentage by your miles per one per cent figure, and that’s your remaining range. On that day, in that temperature, at that speed, on those roads. Why can’t the car just do that?

Manufacturers say their range meter reading takes account of previous driving style. I don’t believe it does because they’re still always optimistic. But in any case what good is previous style? Your brain contains a far more valuable piece of information: future driving style. You know whether a bit of fast motorway’s coming up (it’ll knock your miles per one per cent), or if you’re coming into a town (improving it). You also know that if the range you’ve calculated isn’t enough, you can start hypermiling right now in order to squeak it home.