How do lithium-ion batteries for electric vehicles react to heat, cold and rapidly fluctuating temperatures? This is tested repeatedly during their development and production in order to guarantee the safety of the energy storage systems. Weiss Technik has provided 22 test chambers for the VW Battery Competence Centre in Braunschweig. These feature safety equipment in accordance with Hazard Level 6 and, thanks to a new chamber concept, have an especially small footprint.
Impressive testing capacity created
With over nine million registered vehicles in 2023, the Volkswagen Group is one of the world’s leading automotive manufacturers. Volkswagen has now consolidated the development and pre-series production of high voltage battery systems in its Battery Competence Centre in Braunschweig. For this, comprehensive testing capacity for temperature and climate testing with a total of 22 test chambers was required. These test chambers had to offer sufficient space for complete lithium-ion packs on the one hand, while having as small a footprint as possible on the other. Since the tests were to be carried out on energised specimens, the chambers also had to have suitable safety equipment.
Safety first: the Hazard Level equipment
Lithium-ion battery packs, modules and cells have a high energy density. When testing specimens that are energised and stressed by temperature and climate, overloads and malfunctions can occur due to the increase in energy density, which can lead to the destruction of the batteries. In order to ensure the safety of the personnel and test chambers in the best possible way by means of technical measures, the test chambers were equipped with protective devices for Hazard Level 6 in accordance with the hazard assessment pursuant to the EUCAR Hazard Level Standards. These include, steam-tight welded test spaces and insulation made of non-combustible material, purge air equipment, gas warning systems for CO and HC, nitrogen inerting in case of fire, overpressure-protected test spaces and fire detection by means of temperature measurement.
Basic equipment and special variants
The test chamber can be used to meet common test standards such as the VW norm VW PV1200. 18 of the test chambers are suitable for temperature tests from -40°C to 90°C with a change rate of 3 K. Three more chambers were designed with an extended temperature range of -40°C to 150°C. One of the test chambers was equipped with an increased change rate of up to 10 K to enable special temperature cycling tests to be conducted. In addition to the aforementioned test chambers, Weiss Technik also supplied a special climate test chamber with a multi-axis shaker table (MAST) as part of the project, as well as two identical systems for corrosion tests with a common machine room.
Concept with a small footprint
In order to ensure the smallest possible footprint, as was required, and the space-saving installation of the test chambers, Weiss Technik first reworked the tried-and-tested chamber design and developed a new chamber concept. This involved elevating the test chamber on a base frame so that the machine part that would usually be on the side could be positioned under the test chamber. The test chambers were installed individually and protected by floor-to-ceiling housings in order to prevent any possible incidents in one chamber impacting the other test facilities in the hall.
Basic equipment and special features
All test chambers are equipped with a multi-glazed, heated viewing window and a double-wing door for easy loading. Half of the chambers have a two-level testing frame so that two smaller specimens can be tested at the same time instead of one larger one. The test chambers are operated via the tried-and-tested SIMPAC digital measurement and regulation system and the WEBSeason software. The operation, programming and monitoring unit with its web-panel is mounted on the test space door.
With its 22 test chambers, the VW Battery Competence Centre has state-of-the-art and space-saving testing technology with safety equipment according to the highest standards and thus the optimal basis for the testing and further development of lithium-ion batteries.