TI’s Wireless Approach to EV Battery Management

January 26, 2021

Steve Macaulay

TI illustrations of the conventional wired (at left) and the newly developed wireless BMS. (Texas Instruments)

The battery pack of a typical electric vehicle (EV) contains a daisy-chain of wiring. Miles of copper cabling interlinked by hundreds of connectors. Even the battery management systems (BMS) that monitor individual cells are hard wired. The approach is safe; it does the job.

But wiring harnesses and connectors “are a common source of failure,” acknowledged Karl-Heinz Steinmetz, general manager, Powertrain in Automotive Systems, at Texas Instruments (TI). The nature of the assembly is such that if a system fault occurs, it isn’t particularly simple to find the point of failure, which could lead to a costly battery replacement.

There also is the issue of weight – up to 75 to 200 lb (34 to 92 kg) in pack wiring alone, according to Ram Vedantham, TI’s 2.4 GHz business line manager, connectivity. And as larger batteries are used to achieve increased range, there are increased packaging considerations, as well as an increase in the number of connections – and more mass. Steinmetz also notes the manufacturing cost and complexity of connecting modules to modules within the battery pack. It’s largely a manual operation involving wires, isolation components, wiring harnesses and connectors.

With OEMs seeking lighter, less complex and more cost-efficient battery packs, TI has developed a wireless BMS that is based on the company’s CC266C2R-Q1 system-on-a-chip. It’s an AEC-Q 100 compliant, Arm Cortex M4 wireless microcontroller (MCU) that works in conjunction with the BQ79616-Q1 battery monitor and balancer. The combination forms a cell supervisor unit (CSU); the CSU then wirelessly communicates with the overall battery control unit. Each CSU is capable of managing up to 24 cells.

Because this technology approach – using microchips to replace copper cables – is new and unconventional, TI contracted with TÜV SÜD to test the system to assure that it would meet the required error-detection performance. This step, in turn, will assure automakers using the system can obtain Automotive Safety Integrity Level (ASIL) D. According to TI, the BMS setup has a network availability of more than 99.999% and a network restart of 300-ms maximum availability. TI has a suite of countermeasures that can be deployed to provide security for the BMS.