What is CAN bus communication?
CAN bus communication
Controller Area Network (CAN) is a serial communication protocol bus used in real-time applications. It can transmit signals using twisted-pair cable, coaxial cable, or fiber optic cable. Due to its high performance, high reliability, and high real-time performance, it has become one of the most widely used fieldbuses in the world. CAN communication is currently the mainstream communication method in battery management systems (BMS). It is widely adopted in numerous industrialized electric vehicle BMS systems both domestically and internationally, as well as in domestic and international BMS data communication standards. RS232 and RS485 buses are also used in some internal communication within BMS systems.
Figure 8-26 shows a battery management system for a pure electric bus. Among them, RS232 mainly realizes the communication between the main control board and the host computer or handheld device, and completes the setting of various parameters of the main control board and the detection board; RS485 mainly realizes the communication between the main control board and the detection board, and completes the transmission of battery data and detection board parameters between the master and slave boards; CAN communication is divided into two channels, CAN1 and CAN2. CAN1 mainly communicates with the vehicle main controller to complete the transmission of battery-related data required by the whole vehicle; CAN2 mainly communicates with the vehicle instrument and the non-vehicle charger to realize the sharing of battery data and provide data basis for charging control.
The structure of the battery management system (BMS) in vehicle operation mode is shown in Figure 8-27. The central control module of the BMS communicates real-time and necessary battery status information to the vehicle controller and motor controller via the CAN1 bus, enabling the adoption of more rational control strategies to effectively complete operational tasks and extend battery life. Simultaneously, the BMS (central control module) communicates detailed battery pack information to the onboard monitoring system via the high-speed CAN2 bus, displaying battery status data and providing fault alarms, thus providing a basis for battery maintenance and replacement.
The structure of the BMS in emergency charging mode is shown in Figure 8-28. The charger is physically connected to the electric vehicle. At this time, the onboard high-speed CAN2 bus connects to the charger node, while other aspects remain unchanged. The charger uses the high-speed CAN2 bus to understand the real-time battery status and adjust the charging strategy to achieve safe charging.
