Emergency Handling Considerations in Wireless BMS

Abstract

In current BMS (Battery Management System) in xEV (electric vehicles including hybrid, plugin, and fuel cell), wired communication between cell monitoring ICs and a main controller has been the most commonly used method to connect battery balancing ICs and MCUs. Nowadays, many of global car OEMs are considering wireless communication in BMS for expansion of battery size and design flexibility. In a wireless Battery Management System where wireless communication is mostly formed in Bluetooth, each battery balancing IC is coupled with a local BLEMCU. Then, all local BLE MCUs communicate with the master MCU. This structure provides a significant difference between wired and wireless BMS. In the most common wired BMS, one MCU controls multiple balancing ICs mostly in serial. Although wired connection is normally faster than wireless, individual control is not possible in wired BMS. In comparison, each local BLE MCU has control over a balancing IC in wireless BMS (wBMS). wBMS can mostly cover the functionality of wired BMS. However, wireless solution is working based on pre-defined connection interval thus the delay could vary depends on the timing of error occurrence. Wired system can send emergency signal to master immediately once error occurred. Therefore, this paper will clarify the differences between wired and wireless BMS in emergency condition, and what should be considered to overcome the delay of BLE communication