TÜV SÜD explores limits of lithium-ion batteries for cars
TÜV SÜD explores limits of lithium-ion batteries for cars
The world's first dynamic crash tests of lithium-ion batteries for passenger cars were completed successfully on the TÜV SÜD test ground in Munich Allach. "The results will be used to develop and define the urgently needed safety and installation standards for lithium-ion batteries in electric vehicles", TÜV SÜD Chief Executive Officer and President Dr Axel Stepken comments the test series.
For the crash-test series an impactor was crashed against a lithium-ion battery mounted on a block of concrete. The test series was conducted with a cylindrical impact body and a fork arm. | The crash tests were performed on the type of lithium-ion batteries used in the Mercedes S400 hybrid and the BMW 7 series and were aimed at determining the safety level of the installed batteries. Primarily, however, the test series were aimed at determining the load limits and the scenarios to be expected if a lithium-ion battery is damaged. The safety of lithium-ion batteries is regarded as critical for the success of electric mobility. Their high energy density compared to that of conventional batteries make lithium-ion packs the logical solution for increasing |
the range of electric cars. All major auto makers plan to use lithium-ion batteries in both hybrid vehicles and electric cars. The problem is that so far, the question of how lithium-ion batteries perform in a dynamic crash has been largely unsolved. Neither battery installation nor crash-test requirements have been established in the form of a standard. Standards, however, are critical for auto and battery manufacturers on the one hand and consumers, fire brigades and rescue services on the other.
Given this, the crash series carried out by TÜV SÜD are primarily aimed at gaining basic findings: "We explore limits, examine what is feasible and, on this basis, try to determine safety standards for lithium-ion batteries which permit the maximum level of safety", emphasizes Richard Richter, TÜV SÜD specialist in charge of the crash test series.
To determine these limits, a customized high-precision impactor system was developed for the world's first dynamic crash tests with lithium-ion batteries. For the test, the high-voltage battery was mounted on a 110-tonne block of concrete. With the help of an ECV carrier vehicle, an impactor with various impact bodies (cylinder, fork arm) and variable weight was then driven into the battery pack. The impactor consisted of a head piece and ballast weight and was guided on a carrier unit which in turn was fastened to a carrier vehicle. Shortly before impact, the impactor was decoupled from the carrier unit so that it crashed into the battery in free flight. This test arrangement allows speeds of over 55 km/h, weights of up to 500 kg and a resulting energy of almost 60 kJ. The first test series was performed at speeds of 18 to 29 kilometres per hour. The forces acting on the batteries thus roughly correspond to the level of a typical crash test but do not yet cover all possible accident scenarios. The result was positive: the serial-production batteries packed in a steel shell withstood the crash series. The deformation calculated on the basis of static tests proved almost identical to that determined in the actual dynamic tests. In the further course of the test series, crash tests were performed with the batteries packed into other materials than steel. In this case, the same test arrangement resulted in the expected differences. Another important finding: while a battery which had split in the crash leaked, leakage did not result in the feared explosion and/or fire. According to TÜV SÜD, the first tests demonstrated that lithium-ion batteries already offer a very high safety level but that further intensive efforts are needed to obtain proven results which can serve as a basis upon which to develop binding safety standards and must lead directly to crash-test procedures for hybrid and electric vehicles: "Our concern here as TÜV SÜD is to ensure the establishment of appropriate standards in a concerted effort with the manufacturers", underlines Dr Stepken.
Contact: Frank Volk
