While at BMW in Munich, I received an insight into why we should not hold our breath for pure electric cars to replace those with internal combustion engines.

It came from Hans Rathgeber, a BMW executive in charge of developing fuel-efficient technology for the BMW and Mini brands. Mr Rathgeber’s latest project is a BMW concept sports car, unveiled at the Frankfurt motor show, which accelerates to 100 km per hour in 4.8 seconds but is extremely fuel efficient.

BMW has produced the Mini E, an experimental electric car which is being tested by selected drivers (about 450 in the US, for example). It is powered by a lithium ion battery and has a maximum range of about 170 km in normal driving conditions.

However, Mr Rathgeber had doubts about whether battery technology will advance rapidly enough in the next two decades to enable pure electric cars to have sufficient range to challenge hybrids that have both internal combustion engines and electric ones.

The problem of the battery is that it is not an electronic part, it is chemical. In chemistry what you don’t know today you won’t know in 20 years,” he told me.

BMW has been working on improving the fuel efficiency of its entire fleet of cars under a programme known as Efficient Dynamics. Its new cars registered in 2008 had lower carbon dioxide emissions that competitors such as Audi and Volvo.