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Battery problems in electric cars: burning, charging, weak

Hans-Dieter Seufert
Battery problems in electric cars
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I yeah, sure, some electric cars will definitely be -Skeptics thought when a Chevrolet Volt burned down after a crash test by the American traffic safety authority NHTSA. Such high-energy lithium-ion batteries are considered dangerous and sometimes even get hotter in our smartphones than our hands or ears can handle. After all, there are already air freight transport restrictions for charged lithium-ion batteries, and their spontaneous flammability has often been reported.

Chevrolet Volt -Battery not safely discharged after crash test

But viewed soberly, there is currently no evidence that the fire risk of a cleanly designed electric car is higher than that of a normal combustion vehicle. Some flare up every year without it becoming a major scandal. In the case of the Chevrolet Volt, there was a fire in the parked car weeks after the crash, and only because the battery was not safely discharged by the NHTSA as prescribed. GM reacted anyway and made the battery structures more stable.

Last winter showed us very clearly where the real battery problems lie. In principle, it is the same as at the end of the 19th century, when the electric car learned to drive: insufficient energy density (range), too long charging time and too high costs. Electrochemistry is a stubborn field in which the performance cannot be doubled by building a new chip exposure system.

Low energy density of lithium-ion batteries

Problem number one is the low energy density. Together with the electrical infrastructure, it is currently no higher than 100 Wh /kg in series cars (petrol has around 12,000 Wh /kg). Since a typical e-mobile consumes around 20 kWh /100 km, 200 kilograms of battery are required for this distance. If other components such as complex transmissions are omitted and clever lightweight construction is used, the electric car does not have to be heavier than a conventional car.

However, the range that can be achieved with it will also depend heavily on the outside temperature in the future. Not only because the electrolyte becomes more viscous in winter, but also because heating and air conditioning demand their contribution. Everyone knows how uneconomical electricity is for heatingHave operated an electric radiator at home. The manufacturers must therefore relativize the utopian factory specifications and state worst case ranges. The energy density of car-compatible batteries can be expected to double by the end of this decade.

Hope lithium-air variant

Some people dream of extremely energy-dense batteries such as the lithium-air version (2,500 Wh /kg), but here, too, the physics cannot be outwitted. This exotic type of battery is slow to give and take up electricity. The larger the battery, the longer its charging time. A battery for a range of 500 kilometers at 230 volts and 16 amps would take a day and a half before it would be full again.

Charging time is not yet suitable for everyday use

And that brings us to problem number two: the Charging time. Energy cannot flow nearly as quickly through charging stations that can be used by the driver as it does with liquid or gaseous energy carriers, because otherwise the required currents would be much too high. High currents also mean major charging losses and stress for the battery and its electronics. It is quite conceivable, however, that we can recharge a 100-kilometer range once in just under fifteen minutes. With the DC-based fast charging principle Chademo (as in the Nissan Leaf) it is currently already half an hour - if not, as in our test drive, the charging station freezes.

Large batteries are very expensive, however. If you want to drive 200 kilometers and more electrically, you have to calculate in five-digit cost dimensions for the battery. This is uneconomical because, statistically, there are only very few journeys above 100 kilometers. However, the costs for the necessary battery capacity continue to rise almost linearly. The last kilowatt hour costs the same as the first, although it is needed much less often. By the end of the decade, many manufacturers expect the prices per kilowatt hour to halve.


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