If batteries hadn’t had their limitations right from the start, diesel and gasoline combustion engines would never have become so pervasive. After all, the electric motor was already far more effective over a hundred years ago – apart from the problem of energy storage. Let’s compare: Diesel delivers around 12,000 watt hours per kilogram of fuel, while state-of-the-art rechargeable batteries can only just store 150 watt hours per kilogram. In other words, diesel stores around 80 times more energy than batteries of the same weight.
From a purely objective perspective, batteries put electric mobility on a short leash – but great progress has been made in rechargeable battery technology over the last 10 years. Above all, the lithium-ion battery has taken the consumer market by storm. Lithium is the lightest metal and has the highest negative potential in the electrochemical series, with lithium-ion batteries having a typical charging voltage of 3.6 V. Another option is the lithium polymer battery, which differs in that the lithium-salt electrolyte is not held in an organic solvent, but in an ion-permeable synthetic membrane.
Car batteries – which, due to the amount of energy needed, require dozens of lithium-ion cells to be connected in series to form a high-voltage system – must be stored between 25°C and 40°C. Unlike rechargeable batteries in notebooks or cell phones, batteries in electric cars can expect to have a lifespan of at least 10 years. This is because the price per kilowatt hour is still around €1,000 – which means a comparatively small battery with a capacity of 20 kilowatt hours would cost some €20,000.
Daimler’s smart fortwo electric drive has a range of 150 kilometers (93 miles) purely using battery power (31 kW). This small car will soon be equipped with the same 400-volt batteries as the Tesla – and Daimler plans to launch the new model before the end of this year. Trials took place in London with 100 vehicles that used the conventional smart chassis. The electric motor developed by British-based company Zytek with a 55 kW (75 hp) drivetrain weighs 60 kg and can easily accelerate to over 60 mph (100 kph), although the speed was limited to 60 mph in the city trial.
“Inductive charging” was one of the event’s biggest talking points, with energy giant E.ON planning to use this technology to charge the cars of tomorrow. With inductive charging, the car is driven onto a mat containing an induction coil. A second induction coil is attached to the undercarriage of the car. Instead of using a cable, the energy is transferred across a magnet field – flowing more or less through the air. Current applications for electric cars are still at the development stage.
By 2020, more than a million battery-powered cars are set to be in use in Germany. This is not only good news for the environment, but also for automobile manufacturers and their component suppliers, who are hoping to generate substantial sales. Furthermore, utility companies will be able to tap new markets – in the construction and production of the new vehicles, as well as in recharging their batteries.