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The innovative AVL Battery Cell TS ACORA test system saves time and money
Sales of electric vehicles are reaching new heights with each passing year. The demand from manufacturers for efficient, safe batteries is growing accordingly. Before these batteries can be mass produced, they require extensive testing – including examination of how the battery cells react to a range of climatic conditions and operational states.
To accomplish this complex task as efficiently as possible, AVL has launched the AVL Battery Cell TS ACORA (Active Cooling Rack). The highly efficient and space-saving battery cell test system uses direct cooling and enables full automation of the test series. The innovative solution will be presented at Automotive Testing Expo Europe 2023 in Stuttgart, Germany.
Large-scale testing of battery cells poses a wide range of challenges for OEMs and suppliers of batteries and cells. In particular, the test procedures and methodology demand a very high level of flexibility. For this purpose, climate chambers with indirect air cooling of the cells are generally used in test facilities. The units under test are normally placed in the racks by hand. Depending on the scope and operational strategy, this type of climate chamber test can require a significant amount of time, energy and space. The accuracy and reproducibility of the test results are also not ideal. AVL, one of the world’s leading mobility technology companies for development, simulation and testing in the automotive industry, presents a completely new solution: ACORA.
Direct cell conditioning
ACORA provides an extremely dynamic and precise method for controlling the temperature of cells in a test environment. Unlike conventional test environments with climate chambers, the new AVL test system applies direct thermal conditioning to the battery cells. The key element of ACORA is a cell mounting system with attached conditioning plates. These are in direct contact with the cell body and are supplied with a permanent flow of coolant (water/glycol). This saves a large amount of energy, compared to air cooling.
“Direct conditioning of the cells leads to significantly faster thermal stabilization. Waiting times due to the intended temperature changes are reduced considerably, enabling us to shorten the duration of testing by up to 60%,” says Urs Gerspach, executive VP, AVL List.
In addition to time and energy savings, direct cell conditioning also improves the accuracy and reliability of test results. This is because air-cooled climate chambers do not assure homogeneous air distribution, leading to potential temperature deviations of up to 10k (kelvin) within a chamber. Conversely, the ACORA system provides a significantly higher level of temperature homogeneity during testing. Deviations remain within a range of +/-0.5K in idle and steady state conditions.
Flexible system design
In the ACORA test system, the battery cells can be arranged similar to a battery pack in a vehicle, where the water cooling usually also affects the cells from below. This allows very realistic thermal modeling of the thermal gradients. The standardized mounting platform of the ACORA system can hold all common cell sizes and permits numerous configurations. Depending on the test requirements, the plates can be inserted vertically – for testing prismatic cells – or horizontally – for testing pouch cells. The modular design of the new ACORA system makes it fully scalable: multiple racks can be combined to form an AVL ACORA Lab. Depending on the design verification plan (DVP), different operating strategies can be applied – either with changing temperatures within the racks or with consistent temperature zones (between -40°C and 80°C) for each individual rack.
To perform the test, the platform unit carrying the UUT is inserted into the ACORA rack, where it docks directly with the power supply and the other systems. These include the cell tester on the rear and the automation system, as well as other measurement units. The conditioning module is also integrated into the rack and brings the cooling fluid to the desired temperature. The ACORA system has a total of eight separate test channels, or 16 in the double module, which can all be tested simultaneously. Each test channel provides space for one UUT.
Optional automation and use of space
The automation of test sequences plays a crucial role in efficient operation. The ACORA system can be extended with an optional robot solution, which guarantees smooth, round the-clock operation. An autonomous conveyor system is responsible for transporting the cells between the racks, as well as for the fully automatic processes for connecting and disconnecting in the designated drawers.
“It is not uncommon to have 25 to 30 test cycles per hour in the test lab. A robot solution can really pay off here – and it saves space as well. In a fully automated ACORA Lab, you can operate double the amount of test channels per test system that would be possible in a test lab with climate chambers, and it uses the same amount of space,” says Gerspach.
As the AVL ACORA system has no side or overhead access, the racks can be arranged directly next to one another or placed in stacks. When combined with robot automation, this allows optimal use of the spatial volume in the hall. ACORA towers can reach a height of up to 3.80m, which significantly reduces the required floor space. This optimized use of space is a particularly important cost factor for major users with upwards of 500 cell test channels, but smaller labs can also benefit from reducing the space required, which also keeps maintenance costs down.
Key benefits of ACORA at a glance:
• Duration of tests reduced by up to 60%;
• High temperature accuracy of <1k;
• Less space required than conventional testing systems;
• Full automation leads to cost and time savings;
• High potential for saving energy with central cooling.
ACORA at Automotive Testing Expo Europe
The AVL Battery Cell TS ACORA has been designed for maximum efficiency in its standard configuration, but individual customization is possible. Visitors can see ACORA live at the show, which takes place on June 13, 14 and 15 in Stuttgart, Germany. AVL will be represented with two stands at the leading exhibition for testing, development and validation in the automotive industry. The ACORA system will be on show at booth 1430. For more information or to arrange an appointment during the show, please contact testsystems@avl.com.