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Why Lithium Battery Management Systems Are So Important
With the increasing innovation of science and technology, lithium batteries stand out. From mobile devices to power equipment to energy storage equipment, people have overlooked the core battery management system of lithium batteries. BMS can ensure the performance, safety and life of the battery. A high-quality BMS can not only improve performance, but also avoid potential risks. This is the irreplaceable value of BMS.
Next, follow me to explore lithium-ion batteries and understand the role of battery management systems. I will reveal the secrets of BMS for you from the components of BMS, the architecture of BMS and the advanced derivative functions of BMS. At the same time, I will discuss how to choose a suitable battery management system according to user needs and provide authoritative guidance for you to save money. I can’t wait.
What is Lithium-ion Battery
Lithium-ion battery is inseparable from our life. As the hottest rechargeable battery at present, from mobile phones, laptops to electric vehicles to portable power banks and solar energy storage, this section will explore the advantages and characteristics of lithium batteries to fully understand this key technology.
Main features and advantages
1. Energy density: Compared with other battery components, lithium-ion batteries have a higher battery density, which means that more energy can be stored in a smaller storage space.
2. Lifespan: Lithium-ion batteries have a longer cycle life, 10 times that of lead-acid batteries. BSL lithium batteries can still maintain 80% of their remaining capacity after 3,500 charge and discharge cycles, and have stronger long-term value.
3. No maintenance required: No water or acid needs to be added, and no regular maintenance is required, which reduces the total cost of ownership compared to lead-acid batteries.
4. Fast charging and discharging: Lithium batteries support fast charging, charging 5 times faster than lead-acid batteries, less downtime, and high discharge is very suitable for applications that require explosive power. For example, 72V sightseeing cars or golf carts.
5. Lighter weight: Lithium batteries weigh only ¼ of lead-acid batteries, but have more energy and greater flexibility.
6. Temperature: Lithium batteries can also operate normally in extreme weather environments. BSL batteries can operate normally at temperatures from -30℃ (-22℉) to 55℃ (131℉) without performance degradation. Stronger temperature flexibility.
7. Discharge depth: Lithium batteries have a deeper discharge depth, with a healthy discharge rate of 90%, while lead-acid batteries only have 40-50%.
8. Environmental benefits: Lithium-ion batteries are zero-pollution, and more and more companies are beginning to abandon lead-acid batteries and switch to lithium batteries, making outstanding contributions to global sustainable green zero carbon emissions.
Lithium battery applications
1. Electric vehicles: electric cars, forklifts, golf carts, RVs.
2. Portable electronic devices: mobile phones, laptops, drones, etc.
3. Medical equipment: cardiac pacemakers and other medical equipment.
4. Renewable energy storage: solar cells. Photovoltaic systems.
5. Emergency power backup: UPS emergency power system
6. Remote monitoring system: Lithium-ion batteries have low self-discharge rates and long lifespans, making them more suitable for remote area monitoring and alarm systems.
7. Mobility assistive devices: electric bicycles and electric wheelchairs.
The role of the battery management system (BMS)
As the brain of the battery pack, BMS is a strong guarantee for the safety, performance and life of lithium batteries. It ensures that the battery operates within the optimal temperature, current and voltage range, monitors and protects the integrity of the battery in real time, and provides reliable guarantee for user safety.
Core functions
1. Monitoring
BMS continuously monitors the status of each battery throughout the day: voltage, current and temperature. This real-time data collection is essential for proactively managing the battery pack as it allows adjustments to be made at any time for optimal performance.
2. Protection
The battery management system plays an important role in protecting battery cells from damage and failure. Manage extreme temperature conditions and detect connections and short circuits.
Provide six major protections:
• Charging protection
• Discharging protection
• Overheat protection
• Short circuit protection
• Overcurrent protection
• Balance protection
Thanks to these protections, BMS can improve the safety of batteries and the overall reliability of power supply equipment.
3. State detection
The battery management system can detect the state of charge (SOC) and state of health (SOH) of the battery
For example, SOC can view the remaining battery power and estimate the remaining mileage or power supply time. SOH can detect battery health status and detect potential battery problems as early as possible, which helps to implement prevention and maintenance before any failure occurs.
4. Thermal management
BMS plays a vital role in detecting the thermal condition of the battery pack. By real-time monitoring and implementing cooling strategies, BMS can effectively avoid the risk of overheating. Overheating can significantly reduce battery life and, in severe cases, lead to thermal runaway. BMS can be used to cool down or automatically extinguish fires to prevent thermal runaway.
Thermal runaway is a catastrophic reaction in which the battery temperature continues to rise and cannot be controlled. It is usually caused by a battery short circuit. When a short circuit occurs, current flows unrestricted and generates heat.
The heat damages the internal battery, causing the current to increase and continue to generate heat. This feedback loop can seriously damage the battery and even catch fire or explode.
BMS can comprehensively protect the battery by monitoring the temperature of the battery cells and taking action based on the built-in fire extinguishing system to prevent the probability of thermal runaway.
5. Performance Optimization
BMS ensures the balance of cells within the battery pack through electrical and thermal management. When this balance is achieved, the battery capacity and performance will be maximized.
6. Reporting:
BMS provides important information about the operation of the battery to external devices. Thanks to this timely information, the battery can be used and maintained effectively.
Key Components of a BMS
1.Sensing element
• Voltage sensor
Voltage monitoring devices are an integral part of monitoring the voltage of each battery cell. Battery safety and efficiency depend on maintaining compliant voltage levels. Voltage devices measure the voltage difference of each battery cell. The battery management system (BMS) performs cell balancing procedures by closely monitoring the battery voltages, ensuring that all the cells in the battery are charged and discharged evenly. In addition, it calculates the state of charge (SOC) and protects the battery from overcharging or deep discharge, which can damage the battery.
• Current sensor
Current monitoring is important for many reasons. First, it calculates the SOC by integrating the current over time, a technique called coulomb counting. In addition, it helps identify abnormal conditions such as overcurrent or short circuits, so that protective measures can be implemented. Available current sensors include Hall effect sensors, shunt resistors, and current transformers. In BMS settings, Hall effect sensors are widely used because they have the flexibility to measure both AC and DC currents and provide electrical isolation between the sensor and the current-carrying conductor.
• Temperature sensor
Thermal sensors are used to monitor battery temperature conditions. Batteries generate heat when they operate, and their thermal environment can greatly affect their efficiency. In addition, overheating can lead to a dangerous condition called thermal runaway, which can cause battery failure or even fire. These issues can be addressed by strategically placing temperature sensors, including thermocouples and thermistors, within the battery pack. Essentially, they measure the temperature of individual cells and the ambient temperature surrounding the battery pack. By collecting data from these sensors, the battery management system (BMS) is able to make intelligent decisions. These decisions may involve activating cooling systems or adjusting charge and discharge rates in order to maintain safe thermal conditions.
2.Battery Controller
Batteries are a key component of the BMS framework. Coordinates multiple battery operations as a central processing unit and decision-making center. Based on predefined control algorithms, this component process the data collected from various sensors and takes actions to ensure that the battery maintains optimal performance and safety. Microcontrollers or digital signal processors (DSPs) are typically used in battery controller units along with battery monitors and protectors.
• Battery Monitor and Protector
The battery monitor continuously monitors the voltage, current, and temperature of the battery. Using this information, you can determine the battery’s state of charge, state of health, and overall health. When an anomaly is detected by the battery monitor, the battery protector responds. To prevent damage, the protector prevents the battery from overcharging or overdischarging by taking appropriate measures, such as disconnecting the battery or changing the charge/discharge rate.
• Control Algorithm
An algorithm is a set of rules and mathematical models that assist the battery management system (BMS) in making intelligent decisions. A battery chemistry, intended use, and desired performance characteristics must all be taken into account when designing these algorithms. They can be very complex and are carefully designed to take all factors into account. For example, a control algorithm may determine how the charge current needs to be dynamically adjusted as the battery nears full charge to prevent overcharging. To determine the state of charge (SOC), another algorithm might use data from voltage and current sensors. In order for batteries to operate efficiently and safely, these algorithms must be effective.
• Microcontroller or Digital Signal Processor (DSP)
Microcontrollers or digital signal processors (DSPs) are the heart of a battery controller. The control algorithm is executed by this component. The versatility and ease of integration of microcontrollers make them an extremely popular general-purpose processor. As well as acquiring data, communicating, and executing control algorithms, they have the capability of handling many other tasks. A DSP, on the other hand, is a specialized processor that excels at numerical processing. DSPs may be preferred for certain applications, especially those requiring high-speed data processing. Microcontrollers and DSPs are ultimately chosen based on the specific needs of the BMS and its application.
3.Communication Interfaces
Communication interfaces are key components of a BMS, allowing information to be exchanged with devices or other systems. Communication interfaces include data logging, reporting, and communication protocols.
Communication Protocols
The format and exchange of data between devices in a BMS is controlled by communication protocols. These protocols are required to ensure that devices can understand each other and communicate successfully. Typical BMS practices include:
• Controller Area Network (CAN): It is often used in automotive applications. It supports real-time communication and has good reliability and durability.
• Inter-Integrated Circuit (I2C): In embedded systems, I2C is often used to connect low-speed peripherals. It is usually used for single devices communicating over short distances.
• Serial Peripheral Interface (SPI): SPI is suitable for embedded systems and is used for short-distance communication. It is faster than the I2C protocol and is therefore used in applications with high-speed requirements.
• Modbus: It is often used in industrial environments. The advantage is that it can communicate between multiple devices connected to the same network.
• RS-485: RS-485 is a serial communication protocol that began to appear in the mid-1980s and was originally developed for industrial applications. Jointly published by the Telecommunications Industry Association and the Electronic Industries Alliance.
• Bluetooth: A wireless communication technology that transmits data to personal devices, such as smartphones and mobile devices.
Data Logging and Reporting
BMS records data on voltage, current, temperature, and SOC over a specific period of time. This facilitates performance analysis and troubleshooting of potential risks.
By sending this data to other systems and devices, the reporting process is externalized. For example, the SOC can be displayed on the dashboard of an electric vehicle through a BMS so that the driver can view the power level and estimated mileage at any time. In industrial applications, the BMS can provide data to a centralized control system for monitoring and control.
4.Protection Circuits
In order to ensure the safety and reliability of the battery system, the protection circuit is a crucial part of the BMS. To prevent potentially harmful or dangerous situations, it continuously monitors the battery condition and adjusts or intervenes in real time.
There are four main safety features in the BMS:
• Overcharge protection
• Overdischarge protection
• Short circuit protection
• Thermal protection
5.Balancing Circuits
The balancing circuit is a fundamental component of the BMS framework. In a battery pack with multiple cells, cell balancing is essential to ensure that all cells within the battery pack have the same state of charge (SOC). Besides ensuring optimal performance, this also enhances battery pack durability and reliability.
• Passive Balancing:
Passive balancing involves dispersing excess energy from cells with higher SOC in the form of heat to cells with lower charge at higher SOC.
• Active Balancing:
As opposed to passive balancing, active balancing redistributes charge between cells instead of letting it go. DC-DC converters, inductors, and capacitors are all used in active balancing. Energy is transferred from cells with higher SOC to cells with lower SOC during active balancing.
Types of Battery Management Systems
1.Centralized BMS Architecture
There is only one central BMS in the battery assembly, and all battery packs are directly connected to the central one.
Advantages:
Compact and cheap.
Disadvantages:
Because the batteries are all connected to the BMS, a large number of port connections are required, so there are a lot of wiring harness cables, which is inconvenient for later maintenance.
2.Modular BMS Topology
Similar to a centralized BMS, a modular BMS is divided into multiple repeating modules, each with its own bundle of wires for connecting to adjacent battery packs. These BMS submodules may be monitored by a master BMS module, which is responsible for monitoring the status of the submodules and communicating with peripheral devices.
Advantages:
Modularity is more conducive to troubleshooting and maintenance, and it is also convenient to expand the battery pack.
Disadvantages:
Higher total cost, and there may be unused duplicate functions due to different applications.
3.Master/Slave BMS
Similar to the modular topology, slave devices are limited to relaying measurement information, while the master device is responsible for computation, control, and external communications. Although similar to the modular type, slave devices tend to have simpler functionality, potentially less overhead, and fewer unused features.
4.Distributed BMS Architecture
In a distributed BMS, all electronic hardware is integrated on a control board on the placed battery or module. It simplifies most of the wiring to a few sensor lines and communication lines between adjacent BMS modules.
Advantages:
Each BMS is independent and can handle calculations and communications on its own.
Disadvantages:
This form of integration is deep inside the shielded module assembly, so troubleshooting and maintenance can be difficult. Costs also tend to be higher due to the presence of more BMSs in the overall battery pack structure.
Application of BSLBATT in Li-ion BMS Systems.
New cloud platform technology can view basic information through BMS
Basic information
Includes the project information of the vehicle, BMS software and hardware information, operation statistics, etc.
Real-time status
You can browse the real-time operation information of the vehicle, including battery cell voltage, temperature, etc., whether the vehicle is running.
Location information
You can browse the real-time location information of the vehicle, and support viewing the vehicle movement trajectory by time
BMS configuration
Display the current calibration values of various BMS parameters, which is conducive to BMS status tracing and fault analysis
Operation history
Record each charge and discharge trajectory of the vehicle
Fault history
Record each fault data of the vehicle, support sorting by time, fault type/level, etc.
Upgrade history
Whether it is an air 0TA upgrade or an on-site CAN upgrade, every update of the BMS software will be recorded and support online query, realizing full life cycle software traceability
Equipment change
For the distributed structure BMS system, each slave replacement will be detected and recorded in real time
Data export
The BMS terminal sends operation data to the cloud platform periodically during operation
