Battery management chip increases range, reliability of electric cars
Forecasts indicate that by the end of this decade, e-cars will cost the same as conventional vehicles and will exceed their sales figures by 2038. To help automakers to achieve these goals, the chip manufacturer has developed an advanced Battery Management System (BMS) controller that provides the industry’s best voltage measurement accuracy, increasing range and battery life, while additional temperature monitoring inputs improve safety.
The L9963 controller represents the latest generation of ST’s BMS program, which has already produced semiconductor devices for joint projects with traction battery manufacturers. These include the cooperation with LG Chem, which began in 2008, and the collaboration with the Chinese R&D institute IMECAS and EPOCH, a technology company active in the field of electric vehicle batteries, which was announced in 2007.
The L9963 can monitor up to 14 chained battery cells and monitor voltages ranging from 1.7 V to 4.7 V with an accuracy of better than 2 mV to ensure optimal cell condition. The simultaneous digitization of all acquired values, which is probably the first time this has been realized in a battery management product, avoids delays in cell synchronization. The device can also monitor up to seven external temperature sensors, improving the system’s ability to detect fluctuations and maintain stability.
The L9963 meets the requirements of ISO 26262, ASIL-D by integrating a redundant cell measurement path that improves functional safety and supports an emergency mode. Additionally, error detection and reporting functions are built in to meet automotive safety requirements.
In addition to a Serial Peripheral Interface (SPI), the L9963 features a 2.66 Mbps vertical communication interface for fast communication between multiple L9963 ICs to monitor the entire battery stack. This allows eight chips to convert and read the values of 96 cells in less than 4 ms, and can be used with any combination of transformer-based or capacitive isolation solutions.
The L9963’s design allows plugging and unplugging during operation without the external Z-diodes that are otherwise required to protect the BMS because the battery cannot be de-energized. Designers can eliminate these components from the L9963, further reducing costs.
Typical BMS applications use multiple L9963 devices to monitor the different cell groups in the battery stack. Management is handled by a host microcontroller, for example from ST’s SPC5 series, which consists of high-performance, automotive-qualified MCUs for safety-critical applications.
More information: www.st.com/automotive-bms
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