BMW will unveil its i3 electric supermini concept at the Frankfurt motor show in September, but it's not going to be available until 2013.

It's powered by a 125kW electric motor driving through a single-speed gearbox and the company claims a range of between 80 and 100 miles.

It also claims an excellent 0-62mph acceleration time of just 7.9 seconds and a top speed of 93mph.

A full charge takes a very good six hours but like most electric cars, an 80% charge takes just an hour.

The four-seater is designed for the city with a tight turning circle and is about the same size as a VW Polo.

The company says that a range-extender version will also be available, using a one litre two-cylinder petrol engine to recharge the car's batteries, doubling the range.

It is crammed with new technology, including a sophisticated brake-energy recuperation system and a traffic assistant that maintains the distance from the vehicle in front.

Rear-hinged doors and no central pillar make access easy apparently and, of course, there's no transmission tunnel so the cabin should be a good size.

At 200 litres, the boot is a little bigger than that in a Fiat 500 and owners can operate the doors, headlights and horn from a smartphone, as well as check the battery charge and range.