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Electric cars in the crash test: Danger from burning batteries

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Electric car crash test in video
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E times a year more than 80 tons of metal and concrete are used carted in the form of crash barriers and other barriers to the airfield in Dübendorf. Then it's crash test time again. The lead AXA insurance company always focuses on other safety aspects for automobiles. This time, the contemplative place near Zurich was about electric cars.

The acceleration of electric cars plays a role

Although electric cars are generally as safe as those with combustion engines, says Bettina Zahnd, Head of Accident Research and Prevention at AXA Insurance. 'But we are seeing the first tendencies in which areas the damage scenarios differ.' Statistically, this is not yet completely reliable, but especially with SUVs and luxury cars with electric drive, between 2014 and 2018 in Switzerland, the damage frequency increased by 40 percent Compared to models with petrol and diesel engines.

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Strong acceleration, heavy impact, large debris field: Renault Zoe vs. Volvo V70.

Zahnd sees one of the reasons in the strong and sudden power delivery of the cars from the Tesla class, which are often blessed with a lot of power. In an AXA survey, 52 percent of e-car drivers said that they had to adapt their driving behavior due to the changed acceleration ability. 'We can see that the power and acceleration are a challenge,' says Zahnd.

Violent clatter, widespread rubble

This is what the first crash test scenario aimed at. A Renault Zoe and an old Volvo V70 with a conventional drive approached each other at 68.5 km /h. To a violent oneCrashed on impact was followed by a widespread field of rubble, which only gave an idea of ​​the strong forces at work. The consequences for the dummies on board the two cars involved in the accident were correspondingly great. The passenger cell of the Volvo was no longer intact, 'I expect major injuries,' says Zahnd. Although the more modern Zoe was hit a little less badly in the impact, the injuries to the occupants would have been serious - possibly even fatal.

The impact is only part of an accident. The real challenge then comes with electric cars, and that has to do with the battery in particular. This can be deformed in such a violent collision and catch fire due to excessive heat generation. Not necessarily directly, it can still happen after 48 hours. Because of this danger, the cars that crashed in Dübendorf no longer had their actual battery on board. In order to simulate their contribution to the rigidity of e-mobiles and to reproduce everything else as accurately as possible, the AXA team installed battery dummies weighing around 300 kilograms in the cars instead.

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If there is a fire, then please in the container: the Zoe comes in the hermetically sealed box.

Accident cars are put in the container

In real accidents, the high-voltage energy storage systems present the rescuers with new problems for which creative solutions have to be found. In Switzerland, for example, there are six specially developed containers in which a crashed electric car can be transported from the scene of the accident. If it starts to burn after a while and nobody notices, it does not threaten the environment in the hermetically sealed box. Even more: the container has a fire extinguishing system that can stifle the flames and an outlet for the smoke.

So far, such measures have been individual initiatives, they are not yet in use across the board . But the rescuers generally want simpler technical solutions and further improvements in electric cars in order to be able to help effectively: “For example, it would be important to have extinguishing openings in the battery packs so that we can flood the batteries immediatelyas soon as a fire develops, ”says Michael Derungs, specialist trainer for alternative drives at the Zurich Fire Brigade. But he, too, sees electric cars 'not per se' as more dangerous than conventional vehicles.

Manufacturers favor other solutions

On the manufacturer side, the wishes of the rescuers are ambivalent. Especially since you would need several extinguishing openings so that the fire brigade can actually reach them from all sides depending on the accident scenario. 'This would create a kind of predetermined breaking point that could have a negative impact on the life of the car,' says a high-ranking Audi developer. For example, condensation could get into the batteries through the openings and cause short circuits.

This is why the Ingolstadt-based company opted for hermetically sealing the battery in their E-Tron models. Because the cooling runs around the battery housing, the battery pack is in a watertight environment that you don't want to break open. In addition, the safety concept is designed to prevent battery fires from occurring in the first place; the previous crash tests would show that this does not happen either. If a battery does catch fire, it can be easily extinguished using the extinguishing lance, which is part of the standard equipment of the fire service.

E-cars are too quiet

A safety problem of the first E-car generation is the lack of engine noise when starting and driving. US studies already show that accidents between electric cars and pedestrians and cyclists at low speeds increase. Due to their low distribution, this cannot yet be reproduced in other countries, but similar trends can be seen there. That is why AXA insurance collided an electric car that was reversing out of parking space with a pedestrian in the second crash test.

AXA
Unspectacular accident, far-reaching effect: E-car hits dummy when pulling out of a parking space.

Result: Although the collision of the car with the pedestrian - the primary impact - was not bad, the secondary impact (on the ground) can still be severe. 'It depends primarily on the victim's constitutionhow it survives this situation ”, says Bettina Zahnd. In order to minimize the risk of such accidents, artificial driving noises at low speeds have been mandatory for newly type-approved electric cars in the EU since July 2019. These will be mandatory for all e-cars from 2021. So far, however, no such regulation has been prescribed for existing cars. A mistake from AXA's point of view. 'We recommend drivers who own an electric car to retrofit such a noise in any case,' says Zahnd.

Don't rely too heavily on driver assistants

And she has one more point in particular to those e-car drivers who drive premium vehicles with extensive assistance systems. Zahnd believes that they shouldn't rely too much on technology. Another crash test showed what she meant. The scenario: At a point where the lane divides, the driver assistants do not know which route to follow. So the car hits the barrier exactly in the middle - at 94.7 km /h and accompanied by a correspondingly loud bang.

Of course, the crashed Mitsubishi i-MiEV did not have modern assistance systems. And his passenger cell remained intact despite the force of the impact, which is why a person instead of the dummy would have had a good chance of getting out of the car largely harmless. This was mainly due to the effectiveness of the guardrails and the impact absorbers they contain. Nevertheless, the car and the road infrastructure were scrap metal afterwards, with the correspondingly large (financial) consequences for drivers and insurers. This is another reason why Zahnd says: “If you can drive a car, you cannot necessarily drive every car.”

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