Battery management system with modular design and variable mode function

Abstract

The invention provides a battery management system with a modular design and a variable mode function, and the system comprises a sensor module which comprises a voltage collection unit and a current and temperature sensor; the acquisition board is connected to each single battery in the battery pack, and the integrated voltage acquisition unit is used for acquiring the voltage of the single battery and is connected with an external current sensor and a temperature sensor; the acquisition board supports double-wire isoSPI or four-wire SPI communication and supports cascade connection of a plurality of acquisition boards; the control board receives and processes the battery state data transmitted by the acquisition board; and the equalization circuit adopts a passive equalization mode and is connected in parallel with each single battery, and the acquisition board automatically controls the on and off of the equalization circuit according to the detected voltage difference of the single batteries. According to the invention, at least one of the technical problems of poor adaptability and expansibility, low data acquisition precision, difficulty in adaptation to multiple scenes due to single communication mode, non-intelligent balance control and difficulty in integration and cooperation with external equipment in the existing battery management system due to non-modular design are solved.

Description

Technical Field

[0001] This invention relates to the technical field of battery management, and more particularly to a battery management system with modular design and variable mode functionality. Background Technology

[0002] With the rapid development of electric vehicles, energy storage systems, and other fields, the safety, reliability, and performance of battery packs have become crucial factors. Battery packs are typically composed of multiple individual cells connected in series or parallel. However, differences in manufacturing processes, materials, and operating environments can lead to variations in capacity, internal resistance, and self-discharge rate among individual cells, resulting in internal imbalances within the battery pack and directly impacting its overall performance and lifespan. Furthermore, in practical applications, different battery packs exhibit varying voltage ranges, current magnitudes, and temperature characteristics, requiring data acquisition boards to possess greater adaptability and flexibility.

[0003] However, current BMS data acquisition boards on the market have many limitations. Most adopt a non-modular design, with high hardware integration and fixed software functions. This structure makes it difficult for the acquisition boards to adapt to different types of battery packs, often requiring customized development. At the same time, it is impossible to flexibly adjust key parameters such as acquisition accuracy and sampling frequency according to specific application scenarios, resulting in extremely poor versatility and scalability, increasing R&D costs and maintenance difficulty.

[0004] Furthermore, existing BMS data acquisition boards also have shortcomings in core performance and collaborative capabilities. On the one hand, most solutions use acquisition chips with limited accuracy, and the acquisition accuracy of data such as voltage, current, and temperature cannot meet the needs of scenarios such as high-performance electric vehicles and large-scale energy storage systems. On the other hand, the communication mode is singular, making it difficult to achieve stable communication in complex electromagnetic environments and scenarios requiring high isolation, and integration and collaboration with external devices such as vehicle electronic control systems and charging piles are challenging. At the same time, the equalization control strategy lacks flexibility, failing to intelligently start or stop equalization based on the battery's charging and discharging state, making it difficult to effectively solve the problem of inconsistent voltage among individual batteries, thus affecting the battery pack's lifespan. Summary of the Invention

[0005] The purpose of this invention is to provide a battery management system with modular design and variable mode function, which solves at least one of the technical problems of existing battery management systems, including poor adaptability and scalability due to non-modular design, low data acquisition accuracy, single communication mode that is difficult to adapt to multiple scenarios, unintelligent equalization control, and difficulty in integration and collaboration with external devices.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: This invention provides a battery management system with modular design and variable mode functionality, comprising: a sensor module including a voltage acquisition unit, a current sensor, and a temperature sensor; an acquisition board connected to each individual cell in the battery pack, integrating the voltage acquisition unit for acquiring the voltage of each individual cell, and connecting the current sensor and the temperature sensor externally through its GPIO (input and output) ports to acquire current and temperature distribution data of the battery pack; the acquisition board supports communication with a control board via a two-wire isoSPI or four-wire SPI interface, and supports cascading of multiple acquisition boards via a daisy-chain communication method based on the two-wire isoSPI interface; a control board for receiving and processing battery status data transmitted by the acquisition boards, and interacting with external devices through its integrated communication interface; and an equalization circuit integrated into the acquisition board, employing a passive equalization method, connected in parallel with each individual cell, and automatically controlling the activation and deactivation of the equalization circuit by the acquisition board based on the detected voltage difference of the individual cells during charging or resting states.

[0007] Furthermore, the voltage acquisition unit employs a multi-cell battery pack monitor; the current sensor employs a Hall sensor; and the temperature sensor employs a negative temperature coefficient thermistor.

[0008] Furthermore, the acquisition board converts the four-wire SPI to a two-wire isoSPI through a bridging chip and achieves isolated output through an isolation transformer.

[0009] Furthermore, the control board controls external relays via a Darlington transistor array to control the battery charging and discharging circuit.

[0010] Furthermore, the control board is also extended with independent current and temperature acquisition circuits, which are used to continuously monitor current and temperature data when the acquisition board malfunctions, in order to facilitate fault diagnosis.

[0011] Furthermore, the equalization circuit includes a branch consisting of resistors and MOSFETs, which consumes overcharged energy through resistors to achieve voltage equalization.

[0012] Furthermore, the branch circuit is also connected to LED lights to visually display the on or off status of the equalization circuit, facilitating real-time observation of the equalization operation status.

[0013] Furthermore, the MOSFET is connected to the control output terminal of the acquisition board. The acquisition board monitors the voltage data of each individual battery in real time. When it detects that the voltage difference between individual batteries reaches a set threshold and the battery pack is in a charging or resting state, the acquisition board controls the MOSFET to turn on and starts the equalization process. When the acquisition board detects that the battery pack switches to a discharging state, the voltage difference between individual batteries is less than the set threshold, or the cell voltage difference protection mechanism is triggered, the acquisition board controls the MOSFET to turn off and stops the equalization process.

[0014] Furthermore, the system adopts a modular structure, with the acquisition board and the control board designed separately, supporting flexible configuration of working modes.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: This invention employs a modular structural design, separating the acquisition board and control board. It supports cascading of multiple acquisition boards via a daisy-chain communication method based on a dual-wire isoSPI interface, and allows for flexible configuration of operating modes, effectively solving the problems of poor adaptability and scalability in existing non-modular designs. This design eliminates the need for customized development for different battery packs, allowing for adjustments to acquisition requirements based on actual application scenarios. This significantly reduces R&D costs and maintenance complexity, meeting the usage requirements of battery packs with varying voltage ranges, current magnitudes, and temperature characteristics.

[0016] This invention offers significant advantages in data acquisition and communication. The voltage acquisition unit employs a high-precision multi-cell battery pack monitor (such as one based on the LTC6813 chip), the current sensor uses a Hall sensor, and the temperature sensor uses a negative temperature coefficient thermistor, greatly improving the acquisition accuracy of voltage, current, and temperature data. This meets the high data accuracy requirements of high-performance electric vehicles and large-scale energy storage systems. Furthermore, the acquisition board supports multiple communication modes, including two-wire isoSPI, four-wire SPI, and daisy-chain, enabling stable communication in complex electromagnetic environments and high-isolation scenarios, thus solving the problem of limited communication modes in existing systems.

[0017] The equalization control of this invention is more intelligent. The equalization circuit is integrated into the acquisition board and adopts a passive equalization method. The acquisition board can automatically control the MOSFET to turn on or off to start or stop equalization based on the detected voltage difference of individual cells and the charging / discharging / resting state of the battery pack. It also displays the equalization status intuitively through LED lights, effectively solving the problem of inconsistent voltage of individual cells and extending the service life of the battery pack. In addition, the control board integrates multiple communication interfaces and expands independent current and temperature acquisition circuits, which not only facilitates integration and collaboration with external equipment such as vehicle electronic control systems and charging piles, but also allows for continuous data monitoring when the acquisition board fails, improving system reliability and fault diagnosis capabilities. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1This is a schematic diagram of the LF50K battery pack provided in this embodiment; Figure 2 This is a structural diagram of the battery management system provided in this embodiment; Figure 3 This is a pin diagram of the LTC6813 chip provided in this embodiment; Figure 4 This is a current acquisition circuit diagram provided in this embodiment; Figure 5 This is a temperature acquisition circuit diagram provided in this embodiment; Figure 6 This is a four-wire SPI circuit diagram provided in this embodiment; Figure 7 This is a circuit diagram of a two-wire isoSPI circuit provided in this embodiment; Figure 8 This is the isolated four-wire circuit diagram provided in this embodiment; Figure 9 This is a configuration diagram of the AT24C02 provided in this embodiment; Figure 10 This is a diagram of the ISOMD and DTEN modes provided in this embodiment; Figure 11 This is a configuration diagram of V+, VREG, and DRIVE provided in this embodiment; Figure 12 This is a configuration diagram of ICMP, IBIAS, and WDT provided in this embodiment; Figure 13 This is a front-end data acquisition circuit diagram provided in this embodiment; Figure 14 This is the PCB diagram of the LTC6813 acquisition board provided in this embodiment; Figure 15 The diagram of the STM32F103RCT6 microcontroller provided in this embodiment; Figure 16 The circuit diagram of the MP9486AGN-Z converter provided in this embodiment; Figure 17 The circuit diagram of the AMS1117-3.3V converter provided in this embodiment; Figure 18 This is a 5V power supply isolation diagram for CAN and RS485 provided in this embodiment; Figure 19 This is a CAN communication design diagram provided in this embodiment; Figure 20 This is the RS485 communication design diagram provided in this embodiment; Figure 21 This is a circuit diagram of a four-wire SPI to isoSPI converter provided in this embodiment; Figure 22The relay control circuit diagram provided in this embodiment; Figure 23 This is a circuit diagram of the control board temperature acquisition circuit provided in this embodiment; Figure 24 The LED lamp circuit diagram provided in this embodiment; Figure 25 This is the PCB diagram of the STM32F103RCT6 control board provided in this embodiment; Figure 26 This is a flowchart of the data acquisition board provided in this embodiment; Figure 27 This is a flowchart of the balancing process provided in this embodiment; Figure 28 The charging and discharging control flowchart provided in this embodiment. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This embodiment provides a battery management system with modular design and variable mode functionality, and the specific implementation details are as follows: I. Structural Composition (a) Battery pack The battery pack, as the core energy source of the entire system, consists of multiple individual battery cells connected in series. The individual battery cells are high-power lithium iron phosphate batteries, model LF50K. Figure 1 As shown, it boasts advantages such as long cycle life, high safety performance, and good thermal stability, meeting the high performance requirements of battery management systems. Each individual cell has a nominal voltage of 3.2V, a capacity of 50Ah, and an internal resistance of no more than 7 milliohms, ensuring efficient energy transfer and low energy loss during charging and discharging.

[0022] (ii) Sensors 1. Voltage sensor (voltage acquisition unit) Integrated into the acquisition board (based on the high-precision LTC6813 chip design, capable of measuring the voltage of up to 18 series-connected batteries with a small overall measurement error and a battery measurement range of 0V to 5V), it can acquire the voltage data of individual batteries in real time and accurately. Installed between the positive and negative terminals of each individual battery, it ensures comprehensive monitoring of battery voltage.

[0023] 2. Current sensor A Hall effect current sensor, model HEK016-100, with a range of ±100A and an accuracy of ±1%, is used to accurately measure the charging and discharging current of the battery pack. Installed in the main circuit of the battery pack, it monitors current changes in real time, providing a basis for charging and discharging control.

[0024] 3. Temperature sensor Negative temperature coefficient thermistors are selected, with a temperature measurement range of -55℃ to +125℃ and an accuracy of ±1℃. They are installed in key locations inside the battery pack, such as the surface of individual cells and the middle of the battery pack, to monitor the temperature distribution of the battery pack in real time and provide data support for battery thermal management.

[0025] (iii) Microprocessor (control board) The STM32F103RCT6 is selected, a 32-bit microcontroller based on the ARM Cortex-M3 core, with a maximum clock frequency of 72MHz. It features 256KB of Flash and 48KB of SRAM, providing ample storage capacity. For communication interfaces, it is equipped with three SPI (Serial Peripheral Interface) ports, two I2C ports, and five USART ports, meeting the communication needs of various peripherals.

[0026] (iv) Charge and discharge control circuit The ULN2003, a high-voltage, high-current Darlington transistor array, is used to control an external relay and the battery charging / discharging circuit. The ULN2003 consists of a Darlington array of seven NPN transistors, each individually controlled via an input pin. Internal clamping diodes are also integrated to protect the input from induced voltages from inductive loads, enabling the chip to provide high voltage and high current output to loads such as relays.

[0027] (v) Equalization circuit A passive balancing circuit is used to balance the voltage of each cell in the battery pack, improving battery pack performance and lifespan. It transfers energy through passive components such as resistors, featuring a simple structure, low cost, and high reliability, and is widely used in battery pack management. The balancing current is 90mA-160mA, and the balancing start-up voltage difference is ±50mV. This ensures that the voltage of each cell in the battery pack remains consistent, improving the overall performance and consistency of the battery pack.

[0028] The balancing current is typically around 90-160mA. Activation conditions: Generally, when the cell voltage difference is greater than or equal to 50mV, or greater than 25mV for equalization, equalization is activated during charging or resting.

[0029] Shutdown conditions: When the battery is in a discharge state, or the cell voltage difference is less than 50mV, or the cell voltage difference protection is triggered.

[0030] Resistor selection: The total resistance should be around 25Ω, and the resistor power rating should be high enough to withstand the heat generated during the balancing process. The resistance value determines the magnitude of the balancing current; a balance must be found between efficiency and balancing speed.

[0031] Thermal management: The heat generated by the equalization circuit is effectively dissipated, meeting the heat dissipation requirements.

[0032] (vi) Communication module The data acquisition board features a multi-channel communication design. The LTC6813 provides a standard 4-wire SPI interface, allowing direct connection and communication with an MCU microcontroller. SPI communication transmits data via four wires, offering advantages such as high communication speed and a simple protocol, meeting the data acquisition and control command transmission needs of typical battery management systems.

[0033] isoSPI communication is an isolated serial communication method of the LTC6813. It uses transformers or capacitors for isolation, effectively reducing noise interference during communication and improving reliability. In applications with high electrical isolation requirements, isoSPI communication can better ensure the safe and stable operation of the system. It typically requires the use of an LTC6820 bridge chip to convert the 4-wire SPI signal into a 2-wire isoSPI communication signal.

[0034] Daisy-chain communication: The LTC6813 supports daisy-chain communication, enabling the cascading of multiple chips, with a maximum of 18 chips in a daisy chain. In a daisy chain, data is transmitted from one chip to the next, reducing system complexity and making it suitable for monitoring multi-cell battery packs.

[0035] The control board has RS485, serial communication and CAN communication interfaces, which are used to communicate with external devices (such as charging piles, vehicle control systems, etc.) to realize remote monitoring and control of battery status.

[0036] (vii) Scheme Design A Battery Management System (BMS) must possess multiple functions, including battery state monitoring, charge / discharge control, battery equalization, thermal management, fault diagnosis and protection, and communication. The implementation of these functions requires consideration of key performance indicators such as system accuracy, stability, reliability, and real-time performance. Hardware circuit design must prioritize high reliability, while software algorithms need to be stable and fault-free to avoid crashes or freezes. Employing advanced technologies such as redundancy design, fault diagnosis, and fault-tolerant control can significantly improve the reliability of the BMS. Furthermore, a modular design strategy can effectively address the aforementioned issues; the structural block diagram of this solution is shown below. Figure 2 This ensures the system's flexibility and scalability.

[0037] II. Hardware Design 1. Design of a data acquisition board based on LTC6813 The hardware design uses EDA, and the acquisition board is mainly designed to acquire voltage, current, temperature, and communication signals, as well as configure the working mode and implement passive equalization functions.

[0038] Voltage data acquisition primarily utilizes the high-precision LTC6813 chip, such as... Figure 3 This multi-cell battery pack monitor from Analog Devices can measure the voltage of up to 18 series-connected batteries with a total measurement error of less than 2.2mV (less than 4.8mV for lithium iron phosphate batteries). The battery measurement range covers 0V to 5V and is suitable for most battery chemistry compositions.

[0039] The current acquisition uses a HEK016-100 Hall effect current sensor with a range of ±100A and an accuracy of ±1%. This sensor requires an input voltage of 5V, while its output voltage range is between 0.5V and 4.5V. By configuring the extended GPIO1 and GPIO2 of the LTC6813, accurate acquisition of currents within different ranges can be achieved, such as... Figure 4 .

[0040] Temperature acquisition utilizes a negative temperature coefficient thermistor, covering a measurement range of -55℃ to +125℃ with an accuracy of ±1℃. Its operating voltage requirement is 3V, and the output voltage range is 0-3V. By configuring the LTC6813's extended GPIO3, GPIO6, GPIO7, GPIO8, and GPIO9, up to five temperature acquisition channels can be achieved, such as... Figure 5 As shown.

[0041] For the LTC6813's communication method, it is equipped with a 4-wire SPI interface, such as... Figure 6 It can directly connect and communicate with a microcontroller (MCU). Furthermore, it provides an isoSPI 2-wire interface, which needs to be converted to an SPI interface via an LTC6820 bridge chip for connection to the MCU. This 2-wire interface allows multiple acquisition boards to be cascaded, enabling one control MCU to manage multiple LTC6813s, and consequently, multiple battery packs.

[0042] In this design, the two-wire communication uses an HM2102NLT transformer for isolated output, such as... Figure 7 The four-wire SPI design employs both direct connection and isolation schemes, such as... Figure 8 The direct-connect solution connects directly to an external MCU, while the isolated solution uses the ADUM5401ARWZ-RL for isolation. In the direct-connect solution, it's necessary to expand the external MCU's ground (GND) and various standard voltage interfaces to facilitate a unified GND voltage.

[0043] To ensure the LTC6813 functions correctly, external circuitry must be configured. First, GPIO4 and GPIO5 for auxiliary measurements must be designed, such as... Figure 9 And use AT24C02 to store the detected data.

[0044] Then, configure ISOMD and DTEN, as follows: Figure 10 This allows you to select different working modes and configure V+, VREG, and DRIVE, such as... Figure 11 This ensures that the LTC6813 can operate at standard voltage.

[0045] In addition, ICMP, IBIAS, and WDT also need to be configured, such as Figure 12 Finally, in addition to the battery voltage input, an external power supply input to V+ should also be designed to ensure that the input voltage meets the requirements.

[0046] In battery packs, due to differences in manufacturing processes and aging levels, individual cells may overcharge during charging. Passive balancing technology is designed to address this issue. It uses a bypass balancing circuit to dissipate energy, reducing the voltage of overcharged cells to the same level as other cells, thereby extending the lifespan of the entire battery pack. In practice, a resistor, an LED, and a MOSFET are connected in parallel across each individual cell. The resistor converts electrical energy into heat. The balancing current is typically maintained between 90-160mA. Normally, the balancing process is initiated during charging or resting when the battery voltage difference is greater than or equal to 50mV, or when the battery voltage exceeds the average value by 25mV.

[0047] In the front-end acquisition circuit, RC filtering technology is used to optimize signal processing. Switch S controls the connection state of the equalization resistor, thus affecting the circuit balance. Whether the equalization state is on or off can be visually indicated by an LED. Pin C is responsible for acquiring the voltage information of cells 1 to 18, while CELL0 to CELL18 are connected to external terminals, such as... Figure 13 As shown.

[0048] After drawing the circuit diagram of the acquisition board in EDA software, the next step is to design its printed circuit board (PCB) and assemble it into a PCBA after completing surface mount technology (SMT) to facilitate subsequent experimental analysis, such as... Figure 14 As shown.

[0049] 2. Control board design based on STM32F103RCT6 Regarding the control board, its design mainly involves power supply, communication, charge and discharge control, download port, extended current acquisition, LED display, and peripheral circuits.

[0050] The core of the main control board uses an STM32F103RCT6 microcontroller, such as Figure 15 This 32-bit processor, based on the ARM Cortex-M3 core, can reach a maximum clock speed of 72MHz. It is equipped with 256KB of Flash and 48KB of SRAM, providing ample storage space. This configuration ensures the microprocessor has sufficient computing power to quickly respond to changes in battery state and execute necessary control instructions. Furthermore, it features a low-power mode, operates over a voltage range of 2V to 3.6V, and can operate stably in ambient temperatures ranging from -40℃ to 85℃.

[0051] The power supply configuration uses the vehicle's power supply, with an input voltage of 24V. The 24V voltage is then stepped down to 5V via an MP9486AGN-Z converter. Figure 16 As shown.

[0052] For MCUs requiring a 3.3V input voltage, we further use an AMS1117-3.3V converter to step down the 5V voltage to 3.3V, such as... Figure 17 As shown.

[0053] In this STM32 communication design, the solution adopts CAN, RS485, SPI, and serial communication interfaces. To ensure the stability of CAN and RS485 communication, power isolation is an essential step. We use a CFB0505XT-1WR3 module to convert a 5V voltage to an isolated 5V voltage to power the CAN and RS485 interfaces, such as... Figure 18 .

[0054] In CAN communication design, in addition to power isolation, digital isolation is also required. The ADUM1201AR chip is used for digital isolation, while the TJA1050T-JSM model is selected as the CAN transceiver. Figure 19 .

[0055] RS485 communication, after power isolation, also requires digital isolation; here we use the same digital isolation chip as CAN. In addition, the PC817C is used to control RS485 communication, such as... Figure 20 As shown. SPI communication uses a four-wire direct connection method, directly connecting to the four-wire interface of the LTC6813.

[0056] For isoSPI communication, we use the LTC6820HMS#3ZZTRPBF chip to convert the four-wire SPI to a two-wire SPI, then isolate the output using an HM2102NLT transformer, and finally connect it to the isoSPI interface of the LTC6813. For serial communication, the interface needs to be brought out to transmit data to the host, such as... Figure 21 .

[0057] The charge / discharge control circuit integrates the ULN2003 Darlington transistor array chip, a high-performance chip capable of withstanding high voltage and high current. It contains seven independent Darlington transistor pairs, each channel equipped with independent input and output pins. This chip is designed to operate stably over a temperature range of -40°C to 85°C. Connecting to an external port via a current-limiting pin allows control of an external charge / discharge relay, thereby managing the charge / discharge process. The relay circuit's on / off status is indicated by LED indicators, such as... Figure 22 The download port is SWD, so that code written in the KEIL environment can run on the hardware.

[0058] The purpose of the extended current and temperature acquisition circuitry is to continuously monitor current and temperature data even when the LTC6813 malfunctions, facilitating fault diagnosis. The current sensing function is brought out via an interface for easy connection to an external current sensing module or the use of a Hall effect current sensor. Temperature acquisition utilizes a negative temperature coefficient thermistor, with a measurement range covering -55℃ to +125℃ and an accuracy of ±1℃. This circuit requires a 3.3V operating voltage and provides a 0-3.3V output voltage to meet the acquisition requirements of the analog-to-digital converter (ADC), such as... Figure 23 As shown.

[0059] LED displays, acting as indicators of SOC (State of Charge), visually reflect the remaining battery capacity during normal operation. Furthermore, in software development, they serve as tools for verifying code validity. Figure 24 .

[0060] To ensure the proper operation of the STM32 microcontroller, peripheral circuit design is crucial. This includes proper chip configuration and designing necessary decoupling and reset circuits. Additionally, 8MHz and 32.768kHz crystal oscillator circuits and a boot circuit must be designed. For ease of subsequent development, excess pins should be brought out and extended with pin headers to provide GND, 3.3V, and 5V voltage interfaces for various tests.

[0061] After drawing the circuit diagram of the acquisition board in EDA software, the next step is to design its printed circuit board (PCB) and assemble it into a PCBA after completing surface mount technology (SMT) to facilitate subsequent experimental analysis, such as... Figure 25 As shown.

[0062] III. Software Design 1. Software code writing based on Keil Please download and install the Keil development tools for your chosen microcontroller from the Keil official website. Depending on your microcontroller model, install the corresponding hardware support package to ensure Keil can recognize and configure the chip's peripherals and registers. After completing the environment configuration, be sure to configure the necessary firmware library files when creating your project to ensure your programming environment meets your requirements.

[0063] Write the code required for the LTC6813 acquisition board, including initializing the LTC6813. After initialization, a series of commands need to be configured to achieve the acquisition target. Specifically, this involves mapping the global ADC control to various ADC commands, initiating battery voltage conversion, and initiating GPIO and second reference voltage conversion. After completing these configurations, parameters are stored in the corresponding registers by sending broadcast commands.

[0064] By reading the corresponding registers and parsing the raw data from the LTC6813 battery voltage register and LTC6813 auxiliary registers, we can obtain the basic voltage, temperature, and current values. This requires writing commands for configuring and clearing the registers, such as... Figure 26 As shown, it can also read out disconnection information.

[0065] Write code to control the equalization process. The MCU will send the channel activation command using a 16-bit mask. When the difference between the maximum and minimum voltage in the battery pack reaches 50mV, equalization will automatically begin and continue until the maximum voltage drops to the average voltage, at which point equalization will end. Equalization will only be activated during charging and when the battery is stationary. Figure 27 .

[0066] After completing the LTC6813 acquisition code, the next step is to write the control board code. First, configure the SOCLED code to display the SOC status through level inversion; this will facilitate code writing. Then, continue configuring the code for the buttons, watchdog timer (WDG), real-time clock (RTC), clock, and timer.

[0067] After completing the initial condition code for the control board, the next step is to implement the communication code between the acquisition board and the control board. This includes configuring the SPI protocol to ensure that the data collected by the acquisition board can be successfully transmitted to the control board, and that the control board can send broadcast commands to the acquisition board. Furthermore, data parsing code needs to be developed to convert voltage readings into 8-bit data format and to convert the voltage values ​​acquired through GPIO1 and GPIO2 into corresponding actual current values. Temperature data is converted from the voltage values ​​measured by GPIO to actual temperature values ​​using a lookup table. Simultaneously, disconnection information also needs to be converted into 8-bit data format for transmission. Currently, the State of Charge (SOC) estimation uses a lookup table method based on SOC-Open Circuit Voltage (OCV), but to improve accuracy, future improvements should consider using an Extended Kalman Filter (EKF) algorithm with parameter identification.

[0068] When writing the communication code for the control board, we used different headers and trailers for CAN communication to ensure reliable data transmission. For serial communication, we specified the use of fixed-length headers and trailers for data transmission.

[0069] Regarding the writing of charge / discharge control code, the host computer is equipped with control buttons. When the microcontroller (MCU) receives a message of a specific format, it will activate or deactivate charge / discharge control functions to meet different requirements, such as... Figure 28 .

[0070] IV. Experimental Examples (I) Test Example 1: Performance Monitoring of Electric Vehicle Battery Packs 1. Test Methods Battery pack setup: Select a set of 18 lithium-ion battery packs for electric vehicles and connect them to the battery management system equipped with the designed BMS acquisition board.

[0071] Data Acquisition and Recording: During the normal temperature charge-discharge cycle of the battery pack, the voltage, current and temperature of the battery pack are collected by the BMS acquisition board. The data acquisition frequency is set to once per second and the acquisition time is 1 hour.

[0072] Data analysis: The collected data is transmitted to the host computer for data analysis, including voltage change trend analysis, current change law analysis, temperature distribution analysis, etc., to evaluate the performance status of the battery pack.

[0073] 2. Test Results Product structure assessment data: The modules of the BMS acquisition board are tightly connected and rationally laid out. They are stable and reliable when installed in the battery pack, meeting the requirements for use in electric vehicles.

[0074] Performance Data: Data analysis revealed that the acquisition board can accurately collect voltage, current, and temperature data of the battery pack. Regarding voltage acquisition and analysis, the error between the actual voltage value and the acquired value is small, meeting the accuracy requirements for voltage acquisition. The average error is only 2mV, with an error accuracy of ±0.06%, as shown in Table 2. As for current acquisition and conversion, the error remains generally between 0.2-0.3A for different current magnitudes, with an error accuracy of ±0.7%.

[0075] Table 2 Voltage Data Analysis

[0076] Regarding temperature acquisition and conversion, the error for different temperature detections is ±0.5%, as shown in Table 3, which presents the data analysis for temperature and current. Therefore, it can be concluded that the acquisition accuracy for voltage, temperature, and current is high, and the data also reveals differences between different individual units.

[0077] Table 3 Analysis of Temperature and Current Data

[0078] (II) Experimental Example 2: Balanced Management of Battery Packs in Energy Storage Systems 1. Test Methods Battery pack setup: Select a set of lithium iron phosphate battery packs for energy storage and connect them to a battery management system equipped with the designed BMS acquisition board.

[0079] Balanced control strategy implementation: During the battery pack charging process, the BMS acquisition board collects the voltage data of each battery cell in real time. When the voltage difference of a single battery cell exceeds the set threshold, the balanced control strategy is activated. The balanced circuit is used to regulate the charging and discharging of the battery cells so that the voltage of each battery cell tends to be consistent.

[0080] Equalization effect evaluation: During trickle charging, the voltage value of each battery cell is recorded every 30 minutes for 2 hours. The difference in individual battery voltage before and after equalization control is compared to evaluate the equalization control effect.

[0081] 2. Test Results Product structure assessment data: The interface between the BMS acquisition board and the energy storage battery pack is well-matched and easy to install. Signal transmission between modules is normal, and there are no problems such as communication interruption or data loss.

[0082] Performance data: Before the implementation of the equalization control strategy, the maximum voltage difference between individual cells in the battery pack was 166mV. After the implementation of equalization control, the maximum voltage difference between individual cells was reduced to within 69mV. Over a long period of time, this effectively improved the voltage consistency of the battery pack, extended the battery pack's lifespan, and enhanced the overall performance of the energy storage system. See Table 4.

[0083] Table 4 Voltage Data Analysis

[0084] (III) Test Example 3: Performance Testing of Battery Packs under High and Low Temperature Environments 1. Test Methods Battery pack setup: Place a battery pack in a high-temperature environment chamber (30℃) and a low-temperature environment chamber (-20℃) respectively, and connect the battery pack to a battery management system equipped with the designed BMS acquisition board.

[0085] Data Acquisition and Recording: Under high and low temperature environments, voltage tests are conducted on the battery pack at the same capacity, and the voltage and temperature data of the battery pack are collected through the BMS acquisition board.

[0086] Data analysis: The collected data is transmitted to the host computer to analyze the performance changes of the battery pack under high and low temperature environments.

[0087] 2. Test Results Product structure assessment data: The BMS acquisition board can work normally in both high and low temperature environments without any component damage or circuit failure. The temperature acquisition module can accurately measure the temperature changes inside the battery pack, providing reliable data support for the battery pack's thermal management system.

[0088] Performance data: Under high-temperature conditions, the battery voltage is high, meeting battery characteristics, and the temperature difference between the battery pack and the test temperature is small. Under low-temperature conditions, the battery voltage is low, meeting battery characteristics, and the temperature difference between the battery pack and the test temperature is small. See Tables 5 and 6.

[0089] Table 5 Voltage Data Analysis

[0090] Table 6 Temperature Data Analysis

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A battery management system with modular design and variable mode functionality, characterized by, The system comprises: a sensor module comprising a voltage acquisition unit, a current sensor and a temperature sensor; an acquisition board connected to each single battery in a battery pack, integrating the voltage acquisition unit for acquiring single battery voltage, and connecting external current sensor and temperature sensor through its GPIO port to acquire battery pack current and temperature distribution data; the acquisition board supports communication with the control board through a two-wire isoSPI or four-wire SPI interface, and supports cascading of multiple acquisition boards through a daisy chain communication mode based on the two-wire isoSPI interface; a control board for receiving and processing battery state data transmitted by the acquisition board, and interacting with external devices through its integrated communication interface; an equalization circuit integrated in the acquisition board, which is connected in parallel with each single battery and automatically controls the opening and closing of the equalization circuit according to the detected single battery voltage difference in the charging or resting state.

2. The battery management system with modular design and variable mode functionality of claim 1, wherein, The voltage acquisition unit adopts a multi-battery pack monitor; the current sensor adopts a Hall sensor; and the temperature sensor adopts a negative temperature coefficient thermistor.

3. The battery management system with modular design and variable mode functionality of claim 1, wherein, The acquisition board converts four-wire SPI to two-wire isoSPI through a bridge chip, and realizes isolated output through an isolation transformer.

4. The battery management system with modular design and variable mode functionality of claim 1, wherein, The control board controls external relays through a Darlington transistor array to realize control over the battery charging and discharging circuit.

5. The battery management system with modular design and variable mode functionality of claim 1, wherein, The control board is also extended with independent current and temperature acquisition circuits for continuously monitoring current and temperature data when the acquisition board has an error, so as to facilitate fault diagnosis.

6. The battery management system with modular design and variable mode functionality of claim 1, wherein, The equalization circuit comprises a branch connected by a resistor and a MOSFET, which realizes voltage equalization by consuming overcharged energy through the resistor.

7. The battery management system with modular design and variable mode functionality of claim 6, wherein, The branch is also connected with an LED lamp for directly displaying the opening or closing state of the equalization circuit, so as to facilitate real-time observation of the equalization working state.

8. The battery management system with modular design and variable mode functionality of claim 6 or 7, wherein, The MOSFET is connected to the control output end of the acquisition board, and the acquisition board monitors the voltage data of each single battery in real time. When the acquisition board detects that the voltage difference between single batteries reaches a set threshold and the battery pack is in a charging or resting state, the acquisition board controls the MOSFET to be turned on to start the equalization process; when the acquisition board detects that the battery pack switches to a discharging state, the voltage difference between single batteries is less than the set threshold, or a cell voltage difference protection mechanism is triggered, the acquisition board controls the MOSFET to be turned off to stop the equalization process.

9. The battery management system with modular design and variable mode functionality of claim 1, wherein, The system adopts a modular structure, and the acquisition board and the control board are designed separately to support flexible configuration of working modes.

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