Development of Smart Battery Cell Monitoring System and Characterization on a Small-Module Through In-Vehicle Power Line Communication

Current generation battery electric vehicles lack sufficient systems to monitor battery degradation and aging; consumers demand longer range, faster charging and longer vehicle lifetime. Smart cells, incorporating sensors (e.g. temperature, voltage, and current) offer manufacturers a means to develop longer lasting packs, enabling faster charging and extending range. In this work, instrumented cells (cylindrical, 21700) have been developed. Our novel data logging solution (using power line communication, PLC) permits a comprehensive range of sensors to be installed on each cell. Utilizing the cell bus bars, this reduces the necessary wiring harness size and complexity to instrument packs, which can enable higher density energy storage per volume and weight within the vehicle. In this initial feasibility study, a module (4S2P cells) was tested using two diverse cycles (stepped current, 200 mins $\times10$ cycles, and transient drive, 50 min) in a laboratory climate chamber. The interface system enables research-prototype or traditional sensors to be connected via the PLC network. Miniature sensors (6 temperature, 1 current, 1 voltage) were installed externally on each cell. Excellent performance was observed from the communication system; maximum 0.003% bit error rate, 50ms message receive time (compared to dedicated wired link). Variation in the measured parameters (originally identical cells, temperature 1.0 °C, voltage 5% state-of-charge, current $\sim 10$ %) support the need for improved cell instrumentation to understand cell manufacturing tolerances and aging. This work shows a proof-of-concept study using PLC with instrumented cells, and leads to future work to further reduce the cost and physical size of smart cells.