Battery packs are among the most crucial components of electric vehicles (EVs). Not only does EV performance rely upon the ability to charge and discharge them, but battery packs are also classified as Automotive Safety Integrity Level D (ASIL D) — the highest classification of injury risk defined within ISO 26262, requiring them to adhere to the standard’s most stringent level of safety measures.
Power HIL testbeds like the 8610, above, can play a key role in the BMS-to-battery pack design process. Source: Chroma ATE Inc.As test and measurement instrument supplier Chroma explained, today’s EV battery packs incorporate ingenious mechanical designs, extensive battery cell monitoring and management strategies, multiple switch and fuse safety mechanisms, thermal management systems integrated with the vehicle’s heat sources, as well as intricate battery state estimation and safety strategies. That sort of complexity means that the smallest design flaws could result in sizeable correction costs further down the line, underscoring the critical nature of rigorous testing prior to entering automated production.
Chroma’s answer to this challenge leverages hardware-in-the-loop (HIL) simulation via power testbeds to two key areas of battery testing: the battery management system, or BMS, and the complete battery pack that combines battery cells with other components.
Battery management systems
Chroma said a battery management system may encounter compound failure scenarios within a short period of time, including overheating and communication line failure. As a result, the BMS must be able to detect and respond to faults quickly and effectively, such as by issuing power limitation instructions to other power-consuming devices in the system.
Chroma’s 8630 BMS Power HIL Testbed can use battery and microcontroller unit (MCU) models to simulate the actual discharge behavior of the battery pack. The testbed also generates actual current to the current sensor, which can further correct the impact of the current sensor measurement signal on the state-of-charge (SoC) calculation algorithm under instantaneous current changes.
Complete battery packs
While a battery cycler can only replay specific current records to test the known limits of a battery pack, Chroma’s 8610 Battery Pack Power HIL Testbed can import a vehicle model to dynamically simulate the current under real driving conditions.
This allows further testing of driving cycles and evaluation of the battery pack with actual power equivalent to a real vehicle road test — including, for instance, battery pack temperature control and SoC correction under conditions such as rapid acceleration and deceleration. The 8610 also offers on-board electrical safety testing equipment to test the insulation of the battery pack before and after high-power testing.
Because the same real-time control system can be used for both the 8630 and the 8610, it’s possible to cover the entire BMS-to-battery pack design process with a comprehensive power HIL test platform combination. According to Chroma, this reduces hardware and software costs, along with shortening user learning curves.
