Classification of BMS.
From the perspective of topology, BMS is divided into two types: Centralized and Distributed according to different project requirements.
Centralized BMS has the advantages of low cost, compact structure, and high reliability. It is generally common in scenarios with low capacity, low total pressure, and small battery system, such as power tools, robots (handling robots, booster robots), IOT smart homes ( Sweeping robots, electric vacuum cleaners), electric forklifts, electric low-speed vehicles (electric bicycles, electric motorcycles, electric sightseeing cars, electric patrol cars, electric golf carts, etc.), light hybrid vehicles.
The BMS hardware of the centralized architecture can be divided into high pressure area and low pressure area. The high-voltage area is responsible for collecting the voltage of single cells, collecting the total voltage of the system, and monitoring the insulation resistance. The low-voltage area includes power supply circuit, CPU circuit, CAN communication circuit, control circuit, etc. As the power battery system of passenger cars continues to develop towards high capacity, high total pressure, and large volume, the BMS with distributed architecture is mainly used for plug-in hybrid and pure electric vehicles.
The distributed BMS architecture can better realize the hierarchical management of module level (Module) and system level (Pack). The slave control unit CSC is responsible for voltage detection, temperature detection, equalization management of the cells in the Module (some will independently output the CSU unit) and the corresponding diagnosis; the high voltage management unit (HVU) is responsible for the total battery voltage of the Pack , Bus total voltage, insulation resistance and other status monitoring (bus current can be collected by Hall sensors or shunts); and CSC and HVU send the analyzed data to the main control unit BMU (Battery Manangement Unit), and the BMU performs the battery System BSE (Battery State Estimate) evaluation, electrical system state detection, contactor management, thermal management, operation management, charging management, diagnosis management, and implementation of internal and external communication network management.
At present, mainstream mass-produced electric vehicles generally adopt a distributed BMS architecture, such as BMW i3/i8/X1, Tesla Model S/X, GM Volt/Bolt, BYD Qin/Tang, Roewe e550/e950/eRX5 and so on. The advantage of the distributed BMS architecture is that it can be configured efficiently according to the series and parallel designs of different battery systems. The harness distance between the BMS and the battery is shorter, more uniform, and more reliable, and it can also support larger batteries. System design (such as MW-level energy storage system).
Another reason why distributed BMS has become a mainstream application is that it better meets the trend of power battery system module design. With the widespread application of power battery systems in the automotive field and the increase in production scale, unified standard battery modules are gradually on the agenda in the industry. If there is no standard Module as the support for industrialization, the old electric models will encounter the embarrassment of replacement of batteryless spare parts after several years of use, and the power batteries that have been retired from the automotive field will face the situation where they cannot be effectively used in cascades. . The standardized Module needs to highly integrate part of the functions of the battery management system (cell state acquisition and management) with the battery, so as to achieve the requirements of high space utilization, high reliability, and strong versatility. Therefore, the slave control unit CSC has gradually become one of the indispensable key components in the standard module.