Today, let's talk about the battery management system (BMS), which is inseparable from the battery.
1) What is BMS
The full name of BMS is Battery Management System. It is a device for monitoring the status of energy storage batteries. It is mainly to intelligently manage and maintain each battery unit, monitor the status of the battery, prevent the battery from overcharging and overdischarging, and prolong the service life of the battery.
Generally, the performance state of the BMS is a circuit board or a hard-disk cartridge.
BMS is one of the core subsystems of the battery energy storage system. It is responsible for monitoring the operation status of each battery in the battery energy storage unit to ensure the safe and reliable operation of the energy storage unit. The BMS can monitor and collect the state parameters of the energy storage battery in real time (including but not limited to the voltage of the single cell, the terminal voltage of the battery pack, the insulation resistance of the battery system, etc.). Necessary analysis of relevant state parameters is carried out to obtain more system state evaluation parameters, and effective management and control of the energy storage battery body is realized according to a specific protection control strategy to ensure the safe and reliable operation of the entire battery energy storage unit.
From the perspective of topology architecture, BMS is divided into two categories: Centralized and Distributed according to different project requirements.
Simply put, the integrated BMS collects all cells with one BMS hardware.
Centralized BMS has the advantages of compact structure, high reliability and low cost, and is generally used in scenarios with low capacity, low total voltage, and small battery system volume, such as power tools, robots, IOT smart homes, electric forklifts, electric low-speed vehicles (electric bicycles, electric sightseeing cars, electric golf carts, etc.)
The BMS hardware of the centralized architecture can be divided into high-voltage area and low-voltage area. The high-voltage area is responsible for the collection of single battery voltage, the collection of total system voltage, and the monitoring of insulation resistance. The low-voltage area includes power supply circuit, CPU circuit, CAN communication circuit, control circuit, etc.
With the continuous development of passenger car power battery systems to high capacity, high total pressure and large volume, distributed architecture BMS is mainly used in plug-in hybrid and pure electric vehicles.
At present, there are various terms for distributed BMS in the industry, and different companies have different names.
Most power battery BMSs have a master-slave two-layer structure: energy storage BMSs are mostly three-layer structures because of the large scale of the battery pack. On top of the slave control and the master control, there is also a layer of master control.
Just like batteries form battery clusters, and battery clusters form stacks; the three-layer BMS also follows this layer-by-layer rule:
① Slave control: battery cell management unit
BMU (battery module unit, most of them are called BMU, and some are called CSC/CSU)
- Collect single battery information.
- Monitor battery cell voltage and temperature
- In-pack battery equalization
- information upload
- thermal management
- Abnormal alarm
② Main control: battery cluster management unit
BCU (battery cluster unit, also high voltage management unit HVU, BCMU, etc.) is responsible for collecting BMU information and battery cluster information.
- Battery cluster current acquisition
- Total voltage acquisition
- Leakage detection
- Power-off protection when battery status is abnormal
- Under the management of BMS, capacity calibration and SOC calibration can be completed independently, as the basis for subsequent charge and discharge management
③ Master control: battery array management unit
BAU (battery array unit, also called BAMS, MBMS, etc.) centrally manages the batteries of the entire energy storage battery stack. Connect each battery cluster management unit downward, interact with other device information upward, and feed back the operating status information of the battery array.
- Charge and discharge management of battery array
- BMS system self-check and fault diagnosis alarm
- Battery pack fault diagnosis alarm
- Safety protection for various abnormal and fault conditions in the battery array
- Communicate with other devices such as PCS, EMS, etc.
- Data storage, transmission and processing
The main purpose of this blog is to give everyone a basic understanding of the framework of BMS.
In the next blog, we will focus on what BMS does to give you a deeper understanding of BMS functions.