Modular test system puts battery safety devices through their paces

With its short-circuit tester for battery systems, the Stuttgart-based measurement and test system specialist SMART TESTSOLUTIONS remains true to its modular development approach: the test system is divided into two cabinets. One of them contains only the short-circuit switch and can be operated very close to the DUT, the other the measurement equipment. The first system of this kind was developed for umlaut, a full-service company specialising in consulting and engineering services.

umlaut uses the short-circuit tester to test the fuse elements of battery systems on behalf of a large car manufacturer. "In the event of an accident, the battery must be disconnected from the on-board power supply as quickly as possible so that the high electrical voltage is not conducted to the car body. On the other hand, faulty disconnections should of course be avoided", explains SMART-TESTSOLUTIONS Managing Director Wolfgang Neu. For this reason, comprehensive tests of the fuse elements are necessary.

The short-circuit switch in the smaller cabinet of the test system simulates the unintentional short-circuit. It is designed for very high currents; for a short time it can carry up to 45,000 amperes, even several times in succession. Placing it in a separate housing has the advantage that the connection paths to the test object, i.e. to the battery system, can be kept very short and thus higher contact resistances can be avoided. In addition, the switch is designed for an extended temperature range so that it can also be operated in a climatic chamber.

The measuring equipment, on the other hand, can be operated in a safe environment a few metres away from the short-circuit breaker and the battery system. „After all, there is always the residual risk that the battery will explode if the fuse elements do not respond quickly enough," says Neu. The measurement technology measures the voltage and current curves at various points in the battery system - and does so with high precision and very quickly. After all, measurements have to be taken at the speed at which the fuse trips, which is only a few milliseconds. The system has a total of 16 high-resolution analogue measuring channels.

"Another special feature of the system is that we measure the short-circuit currents both resistively and via a Rogowski coil, so that we can optimally record both the dynamic and static behaviour," adds Neu. For this purpose, a very powerful and very accurate measuring shunt was integrated into the short-circuit test system.

In the eMobility environment, SMART TESTSOLUTIONS is primarily known for its systems for cell voltage monitoring (CVM) on fuel cells. In addition, the Stuttgart-based company develops test systems for other eMobility applications - for example, the end-of-line test of complete battery systems. Depending on the customer's requirements, both the company's own high-voltage system modules for measured value acquisition, load and sensor simulation as well as third-party components are used.

Common to all test systems is usually a modular approach. This is also the case here, as the two-part design makes it possible to combine the short-circuit switch with less complex measuring equipment for other tests instead of the complete measuring technology for testing the fuse elements of a battery system.