The cause of the Tesla fire in China clarified
01.07.2019
- Most common cause of fire in combustion engines
- Danger from extinguishing electric cars?
- Batteries in the crash test
- Problem with electric cars
- Conclusion
A white T esla Model S is in a parking garage in Shanghai. It doesn't seem to be connected to a charging station. Suddenly smoke rises sideways from the underbody of the electric car, seconds later it is on fire. The video clip spread in a flash, first through the Chinese online media, then worldwide. It even ensured that Tesla shares fell by four percent.
It was not clear for a long time whether the fire broke out in the battery - Tesla announced via the Chinese short message service Weibo that experts were on their way to Shanghai, to investigate the cause of the fire. This happened in April 2018 - the result of the fire investigation experts is now available.
Software update because not an isolated case
The fire should originate from a single battery module. This came out in the analysis of the battery, the vehicle history, the software and the manufacturing data. The module was located on the front of the Model S. As a countermeasure, Tesla has released a software update for the settings of the battery charge and the thermal management. The Californian electric car manufacturer announced this update in May after an Model S caught fire in Hong Kong. The Californian electric car manufacturer announced this update in May after a Model S caught fire in Hong Kong in March 2018. The fire in the Hong Kong Model S broke out after standing in its parking position next to a mall for half an hour. Surveillance cameras recorded three explosions.
Time and again, Tesla models have spectacular vehicle fires, which regularly triggers intense media coverage. It has not yet been clarified whether electric cars tend to burn more - according to the German fire department, older cars with internal combustion engines are currently responsible for most vehicle fires.
Investors reacted nervously to the fire, Tesla shares gave up at four percentafter.
This is what the experts say about electric car fires
The fire brigade, ADAC and Dekra all agree: It is extremely rare for cars to catch fire in an accident. Much more often, technical defects are the cause of the fire. The data is still too thin to make a definitive statement as to whether electric cars catch fire faster or less quickly than their burner brothers. According to Markus Egelhaaf, an expert in accident research at Dekra, hardly any conclusions can be drawn even from US road traffic, where significantly more electric cars and hybrids are on the road than in Germany. But there is a tendency: The experts are led to the very cautious assumption that electric cars may tend to burn a little less than vehicles with internal combustion engines. But it also seems clear: Burning electric cars are more difficult to put out. Brandweer Midden en West-Brabant also thought. The emergency services of this Dutch fire station have a BMW i8, which began to smoke in the showroom of a dealer for reasons that are still unexplained, put it in a container full of water as a precaution and leave the car there for 24 hours (see picture gallery). But first things first.
Cause of fire no. 1 in combustion engines: electrics
The main cause of vehicle fires in cars with internal combustion engines, the electronics are: frayed cables cause fires, for example when stationary. Extinguishing these is routine for the fire service. Very few firefighters have ever seen burning electric cars: 'We haven't had a single burning electric car yet,' says Friedhelm Bechtel, fire officer at the Augsburg fire department. As with conventional vehicles, the Augsburg fire brigade would also use compressed air foam to extinguish electric cars. 'Water also works very well for extinguishing electric cars.' says Bechtel. Markus Egelhaaf from Dekra adds: 'When a battery cell catches fire, it is very important to cool the cell. That works best with water - a lot of water.' According to Egelhaaf, extinguishing the individual, often difficult-to-access cell is almost impossible - after all, the cell also contains oxygen, which makes it impossible to suffocate the fire. The burning cell permanently heats up its neighboring cells until they also start to burn. The expert speaks here of a 'thermal runaway'. And this thermal runaway must be prevented with a lot of cooling water. That is why it takes longer to erase electric cars than combustion engine vehicles.
Electric shock when erasing electric cars?
Incidentally, the firefighters can use the tablet to check the vehicle's license plate number on site to see which type of drive is installed. In additionshows a schematic representation of where the vehicle can be cut open to rescue the injured without exposing the rescuers to the risk of electric shock. According to Egelhaaf, when extinguishing this danger, including by arcing, is almost impossible: 'In contrast to the domestic electricity network, the car's electricity network is not earthed. You would have to get between the two battery poles to get an electric shock.' And since there is no elementary lithium in lithium-ion batteries, contact with water is also unproblematic in this regard.
Fires in underground garages are fundamentally problematic because the heat that is generated cannot escape upwards, says Albert Kreutmayr , also a fire officer at the Augsburg fire brigade. One liter of water produces 1,700 liters of water vapor. This water vapor also prevents the heat from flowing away. 'It's like a sauna infusion,' says Kreutmayr. Since a particularly large amount of water is required to extinguish electric vehicles, fire fighters must take this into account in the event of fires in underground garages.
Batteries at E -Cars well crash-protected
The ADAC has already tested several electric vehicles in crash tests. 'We test at an impact speed of 64 km /h and so far a battery has never broken. Only a Mitsubishi i-MiEV has damaged the protective battery cover - but not the battery itself,' Melanie Mikulla tells us from ADAC. For a direct comparison, the ADAC crashed a VW e-Up and a VW Up with a petrol engine. The result: With the electric Up, the experts could not determine any loss of safety, despite the slightly higher weight. The world's largest automobile club has so far no evidence that electric cars are more likely to ignite in accidents than cars with a tank. And no electric car has gone up in flames in the Euro NCAP crashes either. Friedhelm Bechtel from the fire brigade says: 'When it came to cars with gas tanks, some initially thought that they could ignite quickly. That is why these vehicles were banned in many underground car parks. Today we know that gas vehicles do not tend to ignite more quickly this also applies to electric cars. ' Bechtel remembers cars with magnesium parts on the engine as difficult. 'Burning magnesium was very difficult to extinguish, but we got it under control with special extinguishing powder.'
Cars only explode in the film
On the one hand, Bechtel emphasizes that cars after accidents generally only burn extremely rarely, but the fact that a car explodes only exists in the film. Flames develop most violently when a plastic tank ruptures and the fuel spills out in large quantities. The resulting vapors are flammable, especially at high temperatures, whereby the diesel vapors are much more difficult to igniteas vaporized gasoline: 'Often not at all' says Bechtel.
