Battery Management System (BMS), commonly known as a battery nanny or battery manager, is mainly used for intelligent management and maintenance of each battery cell, preventing overcharging and over-discharging, extending battery life, and monitoring battery status.
A BMS (Battery Management System) mainly consists of various sensors, actuators, controllers, and signal lines. To ensure the safe operation of new energy vehicles on the road and compliance with relevant standards and specifications, a BMS should have the following functions:
Battery parameter detection
This includes total voltage, total current, individual cell voltage detection (to prevent overcharging, over-discharging, or even reverse polarity), temperature detection (ideally, each battery string and key cable connector should have a temperature sensor), smoke detection (to monitor electrolyte leakage, etc.), insulation detection (to monitor leakage current), and impact detection.
Battery state estimation
These include state of charge (SOC) or depth of discharge (DOD), state of health (SOH), state of function (SOF), state of energy (SOE), and state of fault and safety (SOS).
Online fault diagnosis
This includes fault detection, fault type identification, fault location, and fault information output. Fault detection refers to using diagnostic algorithms to diagnose fault types and provide early warnings based on collected sensor signals. Battery faults refer to sensor faults, actuator faults (such as contactors, fans, pumps, heaters, etc.) in various subsystems such as the battery pack, high-voltage circuit, and thermal management, as well as network faults and various controller hardware and software faults. Battery pack faults refer to overvoltage (overcharge), undervoltage (over-discharge), overcurrent, overheating, internal short circuit faults, loose connections, electrolyte leakage, and reduced insulation.
Battery safety control and alarm
This includes thermal system control and high-voltage electrical safety control. After the BMS diagnoses a fault, it notifies the vehicle controller via the network and requests the vehicle controller to take effective action (the BMS can also cut off the main circuit power supply if a certain threshold is exceeded) to prevent damage to the battery and personnel caused by high temperature, low temperature, overcharge, over-discharge, overcurrent, leakage, etc.
Charging control
The BMS has a charging management module that can control the charger to safely charge the battery based on the battery's characteristics, temperature, and the charger's power level.
Battery balancing
Inconsistencies cause the battery pack's capacity to be smaller than that of the smallest individual cell in the pack. Battery balancing involves using active or passive, dissipative or non-dissipative balancing methods, based on information from individual cells, to bring the battery pack's capacity as close as possible to the capacity of the smallest individual cell.
Thermal Management
Based on the temperature distribution information within the battery pack and the charging and discharging requirements, the intensity of active heating/cooling is determined to ensure that the battery operates at the most suitable temperature and fully utilizes its performance.
Network communication
BMS needs to communicate with network nodes such as the vehicle controller; at the same time, BMS is inconvenient to disassemble on the vehicle, and needs to be calibrated, monitored, automatically generated, and downloaded online (program updates without disassembling the product) without removing the casing. General vehicle networks use CAN bus technology.
Information storage
Used to store critical data such as SOC, SOH, SOF, SOE, cumulative charge/discharge Ah, fault codes, and consistency. A true BMS in a vehicle may only contain some of the hardware and software mentioned above. Each battery cell should have at least one battery voltage sensor and one temperature sensor. For a battery system with dozens of cells, there may be only one BMS controller, or even the BMS functionality may be integrated into the vehicle's main controller. For a battery system with hundreds of cells, there may be one main controller and multiple slave controllers managing only one battery module at a time. For each battery module with dozens of cells, there may be some module circuit contactors and balancing modules, and the controllers manage the battery modules like measuring voltage and current, controlling contactors, balancing battery cells, and communicating with the main controller. Based on the reported data, the main controller will perform battery state estimation, fault diagnosis, thermal management, etc.
Electromagnetic compatibility
Because electric vehicles operate in harsh environments, the BMS (Battery Management System) is required to have good electromagnetic interference resistance and low external radiation.
As the monitoring and management center of the power battery pack for new energy vehicles, the BMS management system must monitor the relevant parameters of the battery pack, such as temperature, voltage, and charging and discharging current, in real time. When necessary, it should take proactive emergency measures to protect each individual battery cell and prevent safety issues such as overcharging, over-discharging, overheating, and short circuits in the battery pack.
In addition, the BMS management system must accurately estimate the battery's SOC throughout the entire battery pack's lifespan and promptly feed back key information such as remaining charge, driving range, and faults to the driver in an appropriate manner. At the same time, it must complete the data exchange function between the system and the vehicle's ECU or host computer in an appropriate way.
