Batteries in quarantine

Before a crash test, the vehicle is fitted with the sensors with the HV system switched off. In addition, voltage and temperature are measured at the battery. The next step is the commissioning of the software, which is particularly complex because of the new wiring system architectures. “All the components have to work because everything is connected to everything else,” says Florian Mayr from IAV Fahrzeugsicherheit GmbH. “Even the exterior mirror has to work, otherwise nothing works.” Once the software is updated, the e-vehicle is metrologically prepared. After this, itmrolls onto the crash track, always accompanied by a specially trained electrician. Now the crash can take place.

Not only the preparation, but also the phase after the crash differs significantly from tests with conventional cars. “We have to quarantine the vehicle for at least ten minutes, because a battery fire does not happen suddenly,” says Scholz. “During this process, there are always two firefighters in protective suits standing by. They are equipped with thermal imaging cameras and gas detectors.”In an emergency, they use a forklift truck with insulated tines to tow the car to a pool of water, where it only poses little danger still to its surroundings in the event of a fire. “Burning battery modules cannot be extinguished. However, the waste heat causes other modules to be destroyed,” Mayr explains. “In the past, this has led to complete vehicles burning down.”

After the quarantine, an electrician checks whether the HV voltage is switched off and the body is voltage-free. Only after this are the test results documented. However, this is not the end of the complex procedure: A second quarantine may follow for 24 hours in a special garage. “Because problems with the battery can still occur,” Mayr explains. “This is why, depending on the situation, we use battery monitoring to measure whether the temperature or voltage is behaving conspicuously.” If this is the case, the battery monitoring system sends a message to the emergency call system, leaving enough time for countermeasures. Should the car be used for further tests – up to five crashes per vehicle are possible – the next tests are prepared. To do this, the IAV experts will have to get the cooling system going so that the battery can be charged, among others.

“E-vehicles pose a manageable safety risk during testing,” Scholz sums up. “But as with all new topics, we have to take a lot of precautions with the procedures and train our personnel intensively.” The qualification takes place internally and externally at TÜV and is oriented to the qualification levels stipulated by the German Statutory Accident Insurance .

In Ingolstadt alone, IAV runs ten tests a week and around 400 a year – and the trend is rising. The company operates one of the most modern crash facilities in Europe there and can support customers in any crash phase with e-mobility. “We have trained employees at all levels,” Scholz emphasizes. “Thanks in no small part to our employees and our modern infrastructure and measurement technology, there has never been a major accident to date.”

The article appeared in automotion 02/2021, IAV’s automotive engineering trade magazine. Here you can order the automotion free of charge.