OEM & Lieferant Ausgabe 2/2019 - OEM & Supplier 2/2019 by VEK Publishing

128 eMobility The Future of Battery Testing By Martin Schweiger, Senior Application Manager Battery Test Systems, AVL List, Graz A glance at future mobility concepts shows that they are all dominated to a greater or lesser degree by an electrified powertrain in which the high voltage battery plays a key role. Their characteristics determine the driving perfor- mance (for example range and overall vehicle performance) and their costs make a significant contribution to the success or otherwise of electromobility. For these reasons, we would like to take a thorough look at HV battery test procedures. The status today is that battery testing is a time-consuming and cost-intensive process. We asked ourselves the question, where could this part of the development process show po- tential for optimization? To answer the ques- tion, AVL has investigated the current test procedures with regard to efficiency, meth- odology and speed. AVL’s symbiosis of de- velopment services for the customer and the independent development of test equipment provides us with a holistic view of the chal- lenges faced in the domain of battery testing. What does battery testing focus on? The following factors play a decisive role in the development of an HV battery: lifetime, energy density, energy content, safety, inte- gration, driving experience and costs. Firstly, all of these factors must be clearly de- fined in order for the “ideal” energy storage device to be developed while considering all key factors. An HV battery constructed for use in a vehicle must pass several tests before reaching pro- duction maturity. These tests can be catego- rized into four basic classes: 1. Environmental tests (e.g. corrosion) 2. Safety tests (e.g. overcharging, short-circuit) 3. Misuse tests (e.g. crash tests, fire protection) 4. Lifetime tests (e.g. operational stability, electro-chemical ageing) This list shows that battery testing represents an enormous area of conflicting interests in the development process, since an optimal result requires that a compromise is reached between many factors. Which test characteristics should be considered during the analysis? We will concentrate on three key factors: 1. Test efficiency 2. Test quality (test methodology and process) 3. Test speed These three core elements have an immediate effect on a fourth factor: costs. If a battery manufacturer optimizes the first three areas, then this will automatically lead to a reduction in the total costs. Test efficiency Battery tests with superimposed thermal demands require uniform temperatures throughout the object and this leads to long test durations. The time required in large and hence expensive test beds as well as the high costs for battery prototypes result in high overall test costs. The availability of the unit under test is also critical for ageing tests. The application of the right test procedures and methods would significantly increase the test efficiency in this case. For example, thanks to new testing methods, instead of carrying out ageing tests on the complete battery, they could be carried out on the cell modules contained within it, which are available long before the complete battery is available. Furthermore, thermal load tests can be divided into different test levels by Images: © AVL