General Motors Ultium battery pack with wireless battery management system
Back in March when General Motors held its EV day, it revealed a number of interesting design details about its new Ultium. Among these was the decision to integrate the battery management system (BMS) into each module of the pack. GM has now revealed additional information that the BMS in each module will have wireless communication capabilities.
The module-integrated BMS provides several advantages over the traditional method of managing everything at the pack level. Most importantly, it allows GM to manage the output of each module independently. In the traditional approach, each module would be populated with the same type and number of cells and have the same output.
The individual module management allows GM to mix and match modules with different types of cells in the same pack. Over the life of a vehicle, if a battery needs to have a module serviced, it can be replaced with one that has newer cells with a different configuration or chemistry. The module can be reprogrammed to match the output of the rest of the pack. In this way, GM won’t have to stock service parts for every type of cell they use for different applications or change over time as technology improves.
This method will also make it easier to repurpose modules for second-life applications such as stationary storage when they no longer have enough capacity for use in a vehicle. A rack of modules can have any combination of cells that are balanced via software.
The so-called wBMS makes it easier to handle this management by eliminating individual physical connections to each BMS. GM has reduced the overall wiring content in the Ultium battery packs by up to 90%. In addition to reducing cost, this also makes the pack lighter which in turn leads to greater energy efficiency for the vehicle and longer range from the same battery capacity.
Through the wireless communication system which was developed with supplier Analog Devices, modules can communicate with each other and with the vehicle systems run real-time health checks and continuously balance the output. This can contribute to improved battery life as well, a crucial factor to the life cycle cost of the vehicle when the battery remains the single most expensive component.
The wBMS system also makes it easier to scale the battery architecture to a range of vehicle types and sizes. At the EV day event, GM said the Ultium battery system would range from 50-kWh for smaller vehicles up to 200-kWh for larger trucks and SUVs.
Adding this wireless capability does introduce potential security vulnerabilities if an attacker were able to remotely reprogram the modules. This could allow the vehicle to be disabled or to create safety issues. However, in the course of developing its new Vehicle Intelligence Platform electrical and electronic architecture, over the past several years, GM designed for security and resilience from the beginning. This focus on cybersecurity and resilience extends to the wBMS. GM has not revealed specific details about its approach to security, but the automaker established a dedicated product cybersecurity team back in 2015.
