GENEVA - An executive for the German car maker Mercedes says a central concept behind Shai Agassi's Better Place electric cars may be dangerous.

Better Place has been working with Renault-Nissan to build recharging stations for electric-powered cars, which the French-Japanese auto maker expects to have on the market by 2011. To extend the distance the car can travel, Agassi's firm suggests intercity battery replacement stations to complement the more time-consuming option of recharging. But Thomas Weber, Mercedes' director of group research and car development, told TheMarker that such battery replacement stations could pose safety hazards.

Weber, also a director at Daimler-Benz, says Mercedes explored a similar plan in the 1970s, and found that changing a battery on the road could cause electrocution or fire.

The industry has not even resolved matters as basic as the optimum location for an electric car's battery or the battery type, he says.

Without such battery replacement stations, electric cars would be confined to city use, with a range of only 150 to 200 kilometers.

Better Place says highway battery replacement stations would not only extend the cars' range, but would also save the time of recharging.

Weber says that from conversations with Agassi, he believes Mercedes does not share Better Place's vision. The Mercedes exec thinks that at least initially, electric cars should have a permanent lithium ion battery with a 200-kilometer range, and said Mercedes is already working to produce such a product.

He also discounts the prospect of a totally non-polluting car in the near future, and thinks that for the next 10 to 20 years, almost all cars on the road will still have gasoline- or diesel-powered internal combustion engines.

Even achieving a 10% market share for electric cars would require hefty government subsidies, which would be difficult to come by, he says.

In Germany, where the average car is at least nine years old, it will be years before the current models are replaced by more environmentally friendly ones, Weber predicts.

Weber says there have been baby steps in advancing the electric car, noting that Mercedes has a fleet of 100 electric test cars. He concedes that the distant future belongs to the electric engine, which will be powered by rechargeable batteries or fuel cells. Mercedes, he says, is also looking to develop infrastructure for an electric car and has inked letters of understanding with governments around the world.

The world economic crisis has actually accelerated the push for fuel-efficient environmentally friendly cars, but there is consumer resistance, Weber says. In deliberating whether to buy now or wait, many people choose to put off a purchase, believing that technology is constantly improving, he adds. The same dynamic exists in the computer market, he notes. The thinking goes that for the same price, in a few years the consumer can buy a much more advanced model.

So what does he advise potential car buyers? Don't wait.

Better Place commented that its product is designed to enable the mass use of electric cars. The model is based on daily recharging at charging points, and replacing the battery during long journeys. The element of battery replacement is being developed with Renault, the company said.