Weiss Umwelttechnik has planned and realised a very special test bench for lithium-ion batteries with high energy density at the EU research centre (JRC). For the first time computer tomographic (CT) images are possible during battery operation, thus making the test system the first of its kind.
Heat, cold and humidity are the major environmental influences on batteries in electric cars, e-bikes or solar power systems. Now, the changes in these batteries under a wide range of different environmental influences – during operation – can be investigated using the test system. The scientists at the JRC expect test results that improve safety, durability and performance of the batteries. Another objective is the development of EU-standards.
The researchers also intend to use CT images to find internal weak-spots. Thus chemical processes inside the battery can be followed dynamically under stress conditions, for example. In addition, the entire external test space can be moved on a linear guide in order to focus the CT images. In combination with a rotary table, a 360° view of the DUTs during the tests is also possible. The batteries are subjected to stress beyond the usual load limits under extreme environmental conditions and current load during the computer tomographic recording.
Safety equipment guarantees safe stress tests
Safety is top priority: To protect personnel from CT radiation, the external test space was realised in an installation room clad with lead on the outside. During stress tests on the battery, there is a risk of overheating, fire or even explosion. To prevent explosions happening, the external test space is build with protective measures for ATEX Zone 1 classification.
In addition, Weiss Umwelttechnik has equipped the entire system with protective measures which comply with a classification up to EUCAR hazard level 6. The conditioning device is outside the installation room unprotected from the beams. To ensure no openings occur for radiation emission, the supply pipes for climate control and the pipes for gas discharge via a pipe labyrinth must be routed out of the lead-clad room. Permanent oxygen-controlled inerting is realised as a protective measure, for example. Through this, just enough nitrogen (N2) is introduced as is necessary from a safety point of view. Four different gas sensors monitor the test space, two more the lead-clad installation room, in order to detect leaks in the battery DUT.
The Fraunhofer company was commissioned to build the battery test bench in Petten, Holland. This company also researched the suitable material which allowed the CT radiation to penetrate while ensuring the gas tightness of the test space at the same time. Together with partner diondo, specialist for industrial computer tomography, Weiss Umwelttechnik planned and realised the climate-related part of the test system including all safety equipment.