A sodium-ion battery management system and method

Abstract

The application relates to a sodium-ion battery management system and method, the system comprising a cell layer, a management layer and a system layer; the cell layer comprising at least one battery basic unit, which is composed of multiple strings of sodium-ion cells connected in series; the management layer comprising a BMS slave control module corresponding to each battery basic unit and a master control module connected through an isolated communication bus; the MCU of the BMS slave control module sequentially executes a basic state estimation process, a health state evaluation process and an equalization control process; wherein the basic state estimation process calculates SOC according to an OCV-SOC curve characteristic region matching estimation strategy, the health state evaluation process evaluates SOH based on capacity attenuation and internal resistance growth, and the equalization control process selects an equalization strategy according to a characteristic region; the application solves the problems of poor SOC estimation accuracy in the platform region of the sodium-ion battery, invalid equalization strategy and insufficient adaptability in a wide temperature range, and realizes direct replacement of a 12V lead-acid storage battery.

Description

Technical Field

[0001] This invention relates to the field of fire emergency backup power technology, and more specifically, to a sodium-ion battery management system and method. Background Technology

[0002] Traditional 12V lead-acid batteries are widely used in the field of fire emergency backup power, but they have the following inherent defects: First, they have poor low-temperature performance, with their capacity dropping sharply below -20℃, making it difficult to meet the reliability requirements of fire-fighting equipment in cold regions; second, they have a short cycle life, usually only 300 to 500 cycles, and frequent replacements lead to high maintenance costs; third, they contain harmful substances such as lead and sulfuric acid, posing environmental pollution risks in the production, use, and recycling stages, and do not meet the increasingly stringent environmental protection regulations.

[0003] In recent years, with the implementation of relevant standards, higher requirements have been put forward for the batteries of self-powered fire emergency lighting fixtures. The standards clearly stipulate that the use of lithium cobalt oxide, ternary lithium and other lithium-ion batteries containing cobalt is prohibited. This regulation excludes the vast majority of commercial lithium-ion battery solutions on the market, making it urgent for the industry to find new alternative technology routes.

[0004] Sodium-ion batteries have attracted attention due to their unique material system advantages; sodium resources are abundant and inexpensive, and sodium-ion batteries possess characteristics such as a wide temperature range (-40℃ to 60℃), long cycle life (no less than 3000 cycles), and cobalt-free environmental friendliness, making them theoretically very suitable as energy storage components for fire emergency backup power. However, sodium-ion batteries face the following key technical bottlenecks at the BMS level, which restrict their application in practical products: First, the OCV-SOC curve of sodium-ion batteries has a flat voltage plateau region, within which the voltage changes extremely slowly with SOC. Traditional SOC estimation methods based on voltage lookup tables have extremely poor accuracy within this plateau region, with errors exceeding 20%, which cannot meet the accuracy requirements of fire-fighting equipment for power display. On the other hand, the single coulomb integration method suffers from accumulated errors and the inability to obtain the initial SOC.

[0005] Second, the voltage plateau region of sodium-ion batteries renders traditional equalization strategies based on voltage difference ineffective. Within this plateau region, the voltage difference between cells in each string is minimal, but the actual capacity may already show significant deviations. Traditional fixed voltage threshold equalization methods cannot effectively identify mismatched cells, leading to a deterioration in battery pack consistency.

[0006] Third, sodium-ion batteries operate over a wide temperature range of -40°C to 60°C, with significant differences in electrochemical characteristics at different temperatures. Especially at low temperatures, the sodium-ion diffusion rate decreases and the internal resistance increases. If a fixed charge-discharge strategy is used, sodium deposition or irreversible capacity decay is highly likely. Existing BMS solutions lack adaptive control mechanisms for a wide temperature range.

[0007] Fourth, existing BMS architectures are mostly customized for specific cell types, lacking modular and universal design; in application scenarios that require replacement of lead-acid batteries, large-scale transformation of the original power distribution system is often required, increasing deployment difficulty and cost.

[0008] In summary, the existing technology lacks a smart battery management system specifically designed for the characteristics of sodium-ion batteries that can directly replace 12V lead-acid batteries, and cannot simultaneously solve the comprehensive technical problems of sodium-ion batteries in terms of SOC estimation, equalization control, wide temperature range adaptive management and system compatibility. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a sodium-ion battery management system and a sodium-ion battery management method, in view of the above-mentioned defects of the prior art.

[0010] The technical solution adopted by this invention to solve its technical problem is: A sodium-ion battery management system is constructed, comprising a cell layer, a management layer, and a system layer; The cell layer includes at least one battery base unit, each of which is composed of multiple sodium-ion cells connected in series. The nominal voltage of the battery base unit is compatible with the voltage level of a 12V lead-acid battery system and can directly replace a 12V lead-acid battery. The management layer includes a BMS slave control module corresponding to each of the battery base units, and a master control module connected to all the BMS slave control modules via an isolated communication bus. The BMS slave control module includes an MCU and an AFE. The AFE is used to collect voltage, temperature, and current data of each cell in the corresponding battery basic unit. The MCU is used to sequentially execute the basic state estimation process, the health state assessment process, and the equalization control process. The basic state estimation process is configured to determine the characteristic region of the OCV-SOC curve based on the total voltage of the battery pack, and calculate the state of charge (SOC) using an estimation strategy that matches the characteristic region. The health status assessment process is configured to assess the battery health status (SOH) based on capacity decay and internal resistance growth, and detect cell consistency anomalies within the characteristic regions determined by the basic state estimation process. The equalization control process is configured to determine whether equalization operation needs to be initiated based on the voltage dynamic characteristics of each cell within the characteristic region determined by the basic state estimation process, and select the corresponding equalization strategy according to the region. The main control module is used to collect data reported by all BMS slave control modules, formulate system-level control strategies, and communicate with external devices. The system layer includes a DC bus that connects to the output terminals of the sodium battery packs of each BMS slave module, for supplying power to external loads.

[0011] The sodium-ion battery management system of the present invention, wherein the basic state estimation process is a segmented adaptive SOC estimation process, including: The characteristic region of the sodium-ion battery OCV-SOC curve is determined based on the total voltage of the battery pack. The characteristic region includes a first region, a second region, and a third region. The first region corresponds to a total voltage below 11.2V, a single-cell voltage below 2.8V, and a SOC range of 0% to 25%. The second region corresponds to a total voltage between 11.2V and 12.0V, a single-cell voltage between 2.8V and 3.0V, and a state of charge (SOC) range of 25% to 85%. The third region corresponds to a total voltage higher than 12.0V, a single-cell voltage higher than 3.0V, and a SOC range of 85% to 100%. In the first and third regions, a SOC estimation strategy based primarily on voltage correction is adopted, with a voltage correction weight of no less than 70%. Within the second region, a SOC estimation strategy based primarily on the Coulomb integral method is adopted, with the Coulomb integral weight not less than 90%. During charging, when the battery pack voltage enters the third region, a reference capacity update is triggered, which does not depend on a complete full charge-full discharge cycle. When the battery is in a quiescent state and the current is below 50mA, the SOC estimate obtained from the open-circuit voltage lookup table is weighted and fused with the coulomb integral value, wherein the voltage correction weight in the second region is lower than the voltage correction weight in the first region and the third region. A nonlinear temperature compensation model for sodium-ion batteries, constructed within a temperature range of -40℃ to 60℃, is used to compensate for the SOC estimation results. The nonlinear temperature compensation model sets higher compensation weights when the temperature is below -10℃ and above 45℃.

[0012] The sodium-ion battery management system of the present invention includes a health status assessment process comprising: The first SOH factor is calculated based on capacity decay, and the first SOH factor is equal to the current maximum available capacity divided by the initial maximum available capacity. The second SOH factor is calculated based on the increase of DC internal resistance. The second SOH factor is equal to (RBL minus Rout) divided by (RBL minus ROL). The DC internal resistance is dynamically calculated at the beginning of each discharge based on the voltage and current changes before and after the load is applied. The fusion weight α is dynamically adjusted according to the current operating temperature of the battery. The total SOH is equal to α multiplied by the first SOH factor plus (1-α) multiplied by the second SOH factor. Among them, when the temperature is below 0℃, the value of α is reduced to increase the contribution weight of the second SOH factor, and when the temperature is between 20℃ and 30℃, the value of α is 0.5 to 0.6 to increase the contribution weight of the first SOH factor. Within the second region of the characteristic area, the rate of change of voltage of each string of cells over time is monitored. If the absolute value of the rate of change of voltage of a certain string of cells exceeds 2mV / min, the cell is marked as an abnormal cell, and a SOH degradation assessment is performed on the abnormal cell with a degradation factor of 0.9.

[0013] The sodium-ion battery management system of the present invention includes, wherein the equalization control process comprises: During the charging process, the rate of change of voltage of each cell in the series with respect to time is calculated in real time; Within the second region of the characteristic area, if the voltage change rate of a certain string of cells deviates from the median value of the voltage change rate of all cells by more than 2mV / min, then the cell is determined to be a mismatched cell, and a passive equalization operation is initiated for the mismatched cell. The required balancing time is automatically calculated based on the degree of deviation; the greater the deviation, the longer the balancing time. Within the third region of the characteristic area, a dynamic voltage threshold tracking method is used for rapid equalization, and the equalization target value rises synchronously with the voltage of the highest voltage cell.

[0014] The sodium-ion battery management system of the present invention, wherein the MCU is further configured to execute a temperature-adaptive charge-discharge control process, the temperature-adaptive charge-discharge control process being executed in parallel with the basic state estimation process, the health state assessment process, and the equalization control process, including: The operating temperature of sodium-ion batteries is divided into multiple ranges, and different charge and discharge control parameters are configured for different temperature ranges. When the temperature T satisfies -40℃ ≤ T < -20℃, the charging current limit is 0.1C, the single-cell charging voltage limit is 3.5V, and equalization is prohibited; When the temperature T satisfies -20℃ ≤ T < -10℃, the charging current limit is 0.2C, the single-cell charging voltage limit is 3.5V, and equalization is prohibited; When the temperature T satisfies -10°C ≤ T ≤ 10°C, the charging current limit is 0.5C, the single-cell charging voltage limit is 3.5V, and equalization is enabled only at the end of charging; When the temperature T satisfies 10°C<T ≤ 45°C, the charging current limit is 1.0C, the single-cell charging voltage limit is 3.5V, and equalization is normally enabled; When the temperature T satisfies 45°C<T ≤ 60°C, the charging current limit is 0.5C, the single-cell charging voltage limit is 3.4V, and equalization is prohibited; When the temperature T satisfies -40°C ≤ T<-30°C, the maximum continuous discharge current is 3.0C, and the single-cell discharge cut-off voltage is 1.8V; When the temperature T satisfies -30°C ≤ T<20°C, the maximum continuous discharge current is 6.0C, and the single-cell discharge cut-off voltage is 1.5V; When the temperature T satisfies 20°C ≤ T<45°C, the maximum continuous discharge current is 6.0C, and the single-cell discharge cut-off voltage is 1.5V; When the temperature T satisfies 45°C ≤ T ≤ 60°C, the maximum continuous discharge current is 2.0C, and the single-cell discharge cut-off voltage is 1.5V; On the basis of the above temperature interval division, the following supplementary control steps are also executed: When the temperature is lower than -10°C and the battery needs to be charged, the battery is preheated with a pulse current lower than the normal charging current, and after the battery temperature rises above -10°C, the normal charging mode is entered; When the temperature is higher than 45°C, the upper limit of the charging voltage is automatically reduced; When the temperature is lower than -30°C, the discharge cut-off voltage is automatically increased to avoid deep discharge damage.

[0015] In the sodium-ion battery management system according to the present invention, in the management layer: The AFE is integrated with a 16-bit VADC, a 16-bit CADC, an NTC interface, a hardware protection module and a balancing MOS drive module. The 16-bit VADC is used for collecting the voltage of each series-connected cell with an accuracy of ±1mV, and the 16-bit CADC is used for collecting the charging and discharging current with an accuracy of ±1mA. The BMS slave control module further includes a balancing management module, a charge-discharge control module and a DC / DC power supply unit. The balancing management module includes balancing MOSFETs corresponding to each series-connected cell, the charge-discharge control module includes a high-side NMOS switch tube, and the DC / DC power supply unit takes power from the battery pack and generates a working voltage through an internal LDO, with a standby power consumption not exceeding 100μA.

[0016] The isolated communication bus is an isolated SMBus bus or an isolated CAN bus. Signal isolation between the master control module and each of the BMS slave control modules is achieved through a digital isolation chip, and the isolation voltage is not less than 2500Vrms. The main control module also includes a data aggregation module, a decision control module, and an external communication module. The data aggregation module is used to poll all BMS slave control modules through the isolated communication bus and aggregate voltage, current, temperature, SOC, and fault status data of each group. The decision control module is used to make unified decisions on the start or stop of charging and discharging, the on or off of equalization, and fault handling strategies based on the aggregated data. The external communication module reserves a CAN interface for communication with a host computer or fire monitoring system.

[0017] The sodium-ion battery management system of the present invention, wherein the cell layer contains: The sodium-ion battery cell has a flat voltage plateau region and steep voltage change regions located on both sides of the voltage plateau region. The sodium-ion battery cell has an operating temperature range of -40℃ to 60℃, and its capacity retention rate is not less than 80% at the extreme low temperature of -40℃. The cycle life of the sodium-ion battery cell is no less than 3000 cycles @ 100% DOD; The sodium-ion battery cell does not contain cobalt and is not a cobalt-containing lithium-ion battery prohibited by GB 17945-2024.

[0018] The sodium-ion battery management system of the present invention comprises a battery base unit consisting of four sodium-ion cells connected in series. The nominal voltage of a single sodium-ion cell is 2.85V, the nominal voltage of the entire group is 11.4V, and the operating voltage range is 6.0V to 14.0V.

[0019] The sodium-ion battery management system of the present invention, wherein, in the system layer: The voltage range of the DC bus is from 11V to 48V. The system supports parallel expansion of multiple battery base units. Each parallel branch supports up to 4 battery base units in parallel. The capacity of a single unit is 15Ah, and the total capacity after 4 units are in parallel is 60Ah. The maximum installation distance is no more than 5 meters. The system supports multi-level fault detection and protection functions: Level 1 protection is software-configurable protection, including cell overvoltage protection, cell undervoltage protection, charging overcurrent protection, discharging overcurrent protection, and charging / discharging overtemperature protection; Level 2 protection is a hardware-based fast-response protection system, including charging short-circuit protection, discharging short-circuit protection, and discharging overload protection, with a response time in the microsecond range; Fault handling strategies include: automatic recovery for recoverable faults, automatic self-locking for severe faults requiring manual intervention for recovery, and permanent fault control by blowing external chemical fuses to achieve permanent physical disconnection; The system is used for backup power supply for fire emergency evacuation or for fire emergency lighting fixtures with self-contained power supply.

[0020] A sodium-ion battery management method applied to the above system, comprising: The sodium-ion battery cells in the battery cell layer provide energy storage and power output; The voltage, temperature, and current data of each battery cell are collected by the BMS slave control module of the management layer. The basic state estimation process, health status assessment process, and equilibrium control process are executed sequentially. Parallel execution of temperature-adaptive charge-discharge control process; The master control module of the management layer aggregates data from all BMS slave control modules to make unified decisions on starting or stopping charging and discharging, turning on or off balancing, and handling faults. External loads are powered via the DC bus of the system layer; The nominal voltage of the battery base unit is compatible with the voltage level of a 12V lead-acid battery system, and it can directly replace a 12V lead-acid battery.

[0021] The beneficial effects of this invention are as follows: The management layer adopts a hierarchical architecture of slave control + master control: each battery base unit is equipped with an independent BMS slave control module to realize local acquisition and fine control of the voltage, temperature and current of each string of cells; the master control module summarizes the data of all slave control modules through an isolated communication bus, formulates system-level control strategies and communicates with external devices, realizing comprehensive management from the cell level to the system level; in addition, the basic state estimation process overcomes the defect of poor accuracy of the traditional voltage lookup table method in the flat voltage plateau region of sodium-ion batteries, improving the accuracy of SOC estimation; the health status assessment process can promptly detect aging cells and abnormal cells, providing a basis for maintenance and replacement; the equalization control process solves the problem of the failure of traditional equalization strategies due to the extremely small voltage difference in the plateau region of sodium-ion batteries, effectively improving the consistency of the battery pack; the nominal voltage of the battery base unit is compatible with the voltage level of the 12V lead-acid battery system, and can directly replace the 12V lead-acid battery without modifying the original power distribution lines and equipment, reducing deployment costs and replacement threshold. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort: Figure 1 This is a schematic diagram of the sodium-ion battery management system according to a preferred embodiment of the present invention; Figure 2 This is a general architecture diagram of the sodium-ion battery management system according to a preferred embodiment of the present invention; Figure 3 This is a schematic block diagram of the BMS slave control module of the sodium-ion battery management system according to a preferred embodiment of the present invention. Figure 4 This is a flowchart of the sodium battery SOC segmented adaptive estimation process of the sodium-ion battery management system according to a preferred embodiment of the present invention; Figure 5 This is a flowchart of the sodium battery SOH comprehensive evaluation process of the sodium-ion battery management system according to a preferred embodiment of the present invention; Figure 6 This is a power and communication isolation architecture diagram of a sodium-ion battery management system according to a preferred embodiment of the present invention; Figure 7 This is a flowchart of a preferred embodiment of the sodium-ion battery management method of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, a clear and complete description will be provided below in conjunction with the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0024] The preferred embodiment of the sodium-ion battery management system of the present invention, such as Figure 1 As shown, see also Figures 2 to 6 It includes the cell layer 100, the management layer 200, and the system layer 300.

[0025] The cell layer 100 includes at least one battery base unit (sodium battery pack), each battery base unit consisting of multiple series of sodium-ion cells connected in series; the nominal voltage of the battery base unit is compatible with the voltage level of a 12V lead-acid battery system, so that it can directly replace a 12V lead-acid battery.

[0026] Instead of the traditional 12V lead-acid battery (which consists of six 2V cells connected in series), a wide-temperature-range sodium-ion battery is used as the energy storage medium. Sodium-ion batteries have the following key characteristics: With a nominal voltage of 2.85V, the total nominal voltage of the four connected in series is 11.4V. Its voltage plateau range (approximately 11.2V~12.0V) and normal power supply voltage range (6.0V~14.0V) are compatible with the voltage level of a 12V lead-acid battery system (operating voltage approximately 10.5V~14.4V), and it can directly replace a 12V lead-acid battery without modifying the downstream load equipment. Operating voltage range: 1.5V~3.5V (single unit); Capacity retention rate is ≥80% at extreme low temperatures of -40℃, fundamentally solving the problem of low-temperature failure; Cycle life ≥3000 cycles @100% DOD, far exceeding lead-acid batteries; Internal resistance ≤0.5mΩ (1kHz), supports high current charging and discharging; Ensure safety; non-flammable and non-explosive. It contains no cobalt and complies with the compliance requirements of Clause 5.3.11.1 of GB 17945-2024.

[0027] The management layer 200 includes a BMS slave control module 210 corresponding to each battery basic unit, and a master control module 220 connected to all BMS slave control modules 210 via an isolated communication bus.

[0028] A distributed BMS architecture of "1 master + N slaves" is adopted, with each battery basic unit (4 strings) equipped with a BMS slave control module based on MCU + AFE architecture; the AFE chip is responsible for hardware-level sampling and protection of voltage, current, and temperature, and the MCU runs the core algorithm of this invention; unlike traditional lithium battery BMS, this invention has made the following special designs for the electrochemical characteristics of sodium-ion batteries: Optimization of SOC estimation for sodium battery voltage plateau: The charge and discharge curve of sodium-ion battery has unique plateau characteristics (the voltage change is gradual in the 2.8V-3.0V range). This invention adopts a segmented SOC-OCV correction strategy, which mainly uses software coulomb integration and supplements voltage correction in the voltage plateau region, and enhances the voltage correction weight in the steep voltage change region. This solves the problem of large SOC estimation deviation when traditional lithium battery BMS is directly used for sodium batteries. Adaptive protection for the wide temperature range characteristics of sodium batteries: Sodium batteries can operate in a wide temperature range of -40℃ to 60℃. This invention dynamically adjusts the charging and discharging cutoff voltage and current according to different temperature ranges. In the low temperature range (<-10℃), it automatically reduces the charging current and appropriately adjusts the protection threshold. In the high temperature range (>45℃), it automatically reduces the charging voltage, which is different from the single temperature threshold protection strategy of lithium battery BMS. Optimization of balancing strategy for long cycle characteristics of sodium batteries: Sodium batteries have a long cycle life but a flat voltage plateau. This invention adopts a balancing start judgment based on the slope of the charging curve, rather than relying solely on the voltage difference. Even if the voltage difference is small during the voltage plateau period, it can identify mismatched cells and start balancing through slope anomalies.

[0029] The system layer 300 includes a DC bus 310, which connects to the output terminals of the sodium battery packs of each BMS slave control module 210 for powering external loads.

[0030] System layer 300 adopts a plug-and-play backup power system: Voltage compatibility: The voltage platform of the 4-cell sodium battery (nominal voltage 4×2.85V=11.4V, fully charged voltage 4×3.5V=14.0V) is compatible with the operating voltage range (10.5V~14.4V) of the 12V lead-acid battery system; Charging compatibility: It adopts the CC-CV charging strategy with a charging voltage of 13.6V~14.0V and sets a dedicated voltage threshold according to the characteristics of sodium battery cells (overvoltage protection 3.5V / series, over-discharge protection 1.5V / series). It can be directly adapted to the original 12V lead-acid battery charging system (charging parameters need to be adjusted). Interface compatibility: The output interface is the same as that of a 12V lead-acid battery, requiring no modification to the existing power distribution line; Compliance assurance: Sodium batteries do not contain cobalt and do not fall under the category of cobalt-containing lithium-ion batteries such as lithium cobalt oxide and ternary lithium batteries that are prohibited by standards, thus complying with the requirements of Clause 5.3.11.1 of GB 17945-2024; Intelligent management: Real-time battery status monitoring, SOC / SOH estimation, fault self-diagnosis and early warning, and remote data uploading are achieved through the BMS.

[0031] Through a three-layer architecture design consisting of cell layer 100, management layer 200, and system layer 300, comprehensive management from the cell level to the system level is achieved. The nominal voltage of the battery base unit is compatible with 12V lead-acid battery systems, allowing direct replacement of existing lead-acid batteries without modification of the original power distribution lines. The management layer 200 adopts a hierarchical architecture of "slave control + master control." The BMS slave control module 210 achieves local fine control of each string of sodium-ion cells, while the master control module 220 achieves system-level coordination through an isolated communication bus, balancing control accuracy and system efficiency. The basic state estimation process uses an estimation strategy matching the characteristic region of the OCV-SOC curve, solving the problem of poor SOC estimation accuracy in the flat voltage plateau region of sodium-ion batteries. The health status assessment process evaluates SOH from both capacity and internal resistance dimensions and detects consistency anomalies within the characteristic region. The equalization control process selects appropriate strategies based on the characteristic region, overcoming the problem of traditional equalization strategies failing in the plateau region.

[0032] like Figure 3As shown in the table below, the functional components of the BMS slave control module are as follows:

[0033] The functional components of the main control module are shown in the table below:

[0034] The core algorithm is explained below: like Figure 4 As shown, the basic state estimation process is a piecewise adaptive SOC estimation process, which specifically includes: The characteristic region of the sodium-ion battery OCV-SOC curve is determined based on the total voltage of the battery pack. The characteristic regions include the first region, the second region, and the third region, as shown in the table below:

[0035] The first region corresponds to a total voltage below 11.2V, a single-cell voltage below 2.8V, and a State of Charge (SOC) range of 0% to 25%. The second region corresponds to a total voltage between 11.2V and 12.0V, a single-cell voltage between 2.8V and 3.0V, and an SOC range of 25% to 85%. The third region corresponds to a total voltage above 12.0V, a single-cell voltage above 3.0V, and an SOC range of 85% to 100%.

[0036] In the first and third regions, a SOC estimation strategy based primarily on voltage correction is adopted, with a voltage correction weight of no less than 70%; in the second region, a SOC estimation strategy based primarily on coulomb integration is adopted, with a coulomb integration weight of no less than 90%.

[0037] During charging, when the battery pack voltage enters the third region, a baseline capacity update is triggered. This update does not depend on a complete full charge-discharge cycle and uses the following formula: Formula 1; t1 is the start time of entering Region III (the voltage of a single cell crosses 3.0V, that is, the voltage of the entire group crosses 12.0V), and t2 is the end time of charging. By capturing the complete charging segment in advance, the limitation of the traditional method relying on the complete cycle of "full charge-full discharge" is eliminated, making the reference capacity update more frequent and adapting to the slow decay characteristics of sodium batteries under long cycle life.

[0038] When the battery is in a quiescent state and the current is below 50mA, and the duration exceeds a predetermined time (e.g., 30 minutes), the algorithm performs voltage correction: Obtain the OCV value of each cell.

[0039] The SOC estimate based on OCV is obtained by looking up the table. OCV(Based on the sodium battery OCV-SOC mapping table determined in advance by this invention).

[0040] The fusion weight w is determined based on the work area: Region I and Region III: Weight w = 0.7 (high weight for voltage correction); Region II: Weight w = 0.1 (low weight for voltage correction).

[0041] Calculate the final SOC final : Formula 2; The self-discharge rate of sodium-ion batteries is significantly affected by temperature. This invention introduces a temperature compensation coefficient k(T) in the SOC estimation: ; Among them, I self (T) represents the self-discharge equivalent current at different temperatures as determined by experiments, and k(T) is the temperature compensation coefficient. Unlike the linear temperature compensation of lithium battery BMS, the k(T) of this invention is based on the measured data of sodium battery in a wide temperature range of -40℃ to 60℃ to establish a nonlinear compensation model, and sets higher compensation weights in the low temperature region (<-10℃) and the high temperature region (>45℃).

[0042] like Figure 5 As shown, the health status assessment process includes: Based on capacity decay-based SOH estimation, the classic definition of SOH is: ; Wherein, Qmax_current is the current maximum available capacity; the present invention updates Qmax_current in each effective charging segment through the aforementioned baseline capacity update strategy (Equation 1), rather than only after the full charge-full discharge cycle, which greatly improves the timeliness of SOH estimation.

[0043] SOH-assisted evaluation based on DC internal resistance (DCIR) growth: The aging of sodium-ion batteries is manifested not only in capacity decay but also in increased internal resistance; this invention dynamically calculates the DC internal resistance at predetermined time intervals (e.g., at the start of each discharge): ; Where V1 and I1 are the voltage and current before the load is applied, and V2 and I2 are the voltage and current after the load is applied and stabilized.

[0044] This invention uses DCIR growth as an auxiliary criterion for SOH and defines an internal resistance health factor: ; The final SOH is the combined value of the capacitance factor and resistivity factor: ; Wherein, α is a configurable weight. Unlike the practice in lithium battery BMS where α is usually fixed at 0.8-0.9, this invention dynamically adjusts α according to the actual operating conditions of sodium batteries: in low temperature environment (T<0℃), the contribution weight of resistance growth to SOH increases (α decreases), and in normal temperature environment (20℃≤T≤30℃), the contribution weight of capacity decay increases (α increases).

[0045] Anomaly identification based on voltage plateau characteristics: This invention also utilizes the unique voltage plateau characteristics of sodium batteries for abnormal cell identification: In region II (voltage plateau region, overall voltage 11.2V~12.0V), the voltage change rate dV / dt of a normal cell should approach zero. If a cell in a string exceeds a predetermined threshold (e.g., 2mV / min) in region II, the cell is marked as "plateau abnormal," triggering a reduction in SOH assessment (degradation coefficient 0.9), and prioritizing the initiation of equalization for that cell.

[0046] This anomaly identification method based on voltage platform characteristics is a unique technical feature that distinguishes this invention from all other lithium battery BMS solutions, because the OCV-SOC curves of lithium batteries have different slope characteristics in the same SOC range, and the same judgment criteria cannot be applied.

[0047] Adaptive protection strategy for sodium batteries over a wide temperature range: Unlike traditional lithium battery BMS which uses a simple protection strategy with a single temperature threshold (e.g., 0℃~45℃), this invention designs a segmented adaptive protection parameter table for sodium batteries operating over an ultra-wide temperature range of -40℃ to 60℃. Charging parameter temperature segment table:

[0048] Discharge parameter temperature segmentation table:

[0049] C is the unit of charge / discharge rate for a battery cell. For a 15Ah battery cell, 1C corresponds to 15A. Implementation mechanism of adaptive protection: Unlike the passive approach of lithium battery BMS that only reports temperature alarms, this invention actively adjusts the charging strategy in low-temperature and high-temperature regions. Low-temperature charging preheating judgment: When the ambient temperature is below -10℃ and the battery needs to be charged, the BMS first performs pulse preheating on the battery with an extremely low current (0.05C, i.e. 0.75A). By monitoring the temperature rise rate, it judges whether the battery has recovered to the safe charging temperature range. Only after the temperature rise rate reaches the set threshold will it switch to normal CC-CV charging mode.

[0050] High-temperature charging derating strategy: When the ambient temperature is higher than 45℃, the BMS automatically reduces the upper limit of the charging voltage from 3.5V per cell (14.0V for the whole group) to 3.4V per cell (13.6V for the whole group) to prevent the risk of sodium deposition on the negative electrode caused by overcharging at high temperatures.

[0051] Low-Temperature Discharge Cut-off Voltage Correction: In ultra-low temperature environments of -40℃, the internal resistance of sodium batteries increases significantly, and reaching the 1.5V cut-off voltage too early will result in a large amount of remaining capacity not being discharged. This invention increases the discharge cut-off voltage in the low-temperature region (<-30℃) from 1.5V for a single cell to 1.8V (from 6.0V to 7.2V for the entire battery pack), sacrificing very little usable capacity in exchange for effective battery protection, avoiding irreversible damage caused by deep discharge.

[0052] The equilibrium control process includes: Slope calculation: During the charging process, the rate of change of voltage of each cell string with respect to time is calculated in real time. ; Slope anomaly identification: In region II (voltage plateau region, overall voltage 11.2V~12.0V), the normal cell ki(t)≈0 (voltage remains almost unchanged).

[0053] If the ki(t) of a certain cell deviates significantly from the median value (deviation > predetermined threshold, such as 2mV / min), the cell is considered to have "abnormal platform voltage". Even if the voltage difference between the cell and the maximum voltage difference in the group is less than the traditional voltage difference threshold, equalization startup will be triggered.

[0054] Equilibrium duration calculation: This invention automatically calculates the equilibrium duration based on the degree of slope deviation. The greater the deviation, the longer the equilibrium time required, thus avoiding the problems of under-equilibrium or over-equilibrium caused by the fixed equilibrium duration in traditional methods.

[0055] Rapid equalization at the end of charging: When the battery pack enters Region III (SOC > 85%, single cell voltage > 3.0V, overall pack voltage > 12.0V), the voltage difference between the individual cells increases rapidly. At this time, the present invention activates the rapid equalization mode: The MCU increases the equalization current to the maximum allowable value (100-200mA) through the AFE. Dynamic voltage threshold tracking is adopted: the equalization target value rises synchronously with the voltage of the highest voltage cell, rather than being fixed at a certain absolute voltage value, thus avoiding equalization oscillations caused by the continuous change of the target value during the equalization process; Once the differential pressure drops to a predetermined value (e.g., 10mV), the MCU immediately stops equalization to prevent over-equalization.

[0056] The BMS system of this invention has a comprehensive multi-level protection function built in: Level 1 protection (configurable by software): Cell overvoltage protection (OVP): Triggered when the voltage of a single string is >3.55V (total voltage of the group is >14.2V).

[0057] Cell undervoltage protection (UVP): Triggered when the voltage of a single string is <1.5V (total group <6.0V) (1.8V for a single string / 7.2V for the entire group in the low temperature range).

[0058] Overcurrent protection (OCC): Triggered when charging current > 1C.

[0059] Overcurrent discharge protection (OCD): Triggered when discharge current > 3C.

[0060] Over-temperature protection (OTP): dynamically adjusted according to the temperature segmentation table of the present invention.

[0061] Level 2 protection (hardware fast response): Charging Short Circuit Protection (SCC): Microsecond-level response; Short-circuit discharge protection (SCD): microsecond-level response; Overload Discharge Protection (OLD): Fast Response.

[0062] Troubleshooting strategies: Recoverable faults (such as transient overcurrent): Automatic recovery; Serious faults (such as overvoltage, overtemperature, short circuit): trigger fault self-locking, requiring manual intervention to recover; Permanent faults (such as cell open circuit or AFE failure): The MCU controls the external chemical fuse to blow, achieving a permanent physical disconnection.

[0063] Isolation communication function like Figure 6 As shown, the communication bus between the master controller and the slave controller is electrically isolated through a magnetic isolation chip (isolation voltage ≥2500Vrms), blocking common-mode interference and circulating current paths caused by ground potential difference.

[0064] Isolation design: The communication bus uses a magnetic isolation chip (such as ADuM1201) with an isolation voltage ≥2500Vrms, which completely blocks common-mode interference and circulating current paths caused by ground potential difference.

[0065] Independent power supply: The slave side (secondary side) of the isolated communication is powered by an independent isolated power supply module (such as B0505S-1WR3) to ensure electrical isolation of the communication.

[0066] A sodium-ion battery management method applied to the above system, comprising: Step S1: Energy storage and power output are provided by sodium-ion cells in the cell layer.

[0067] Step S2: Collect voltage, temperature and current data of each sodium-ion battery cell from the BMS control module of the management layer.

[0068] Step S3: Execute the basic state estimation process, health status assessment process, and equilibrium control process in sequence.

[0069] Step S4: Execute the temperature-adaptive charge and discharge control process in parallel.

[0070] Step S5: The master control module of the management layer aggregates the data of all BMS slave control modules to make unified decisions on the start or stop of charging and discharging, the activation or deactivation of equalization, and the fault handling strategy.

[0071] Step S6: Power the external load through the DC bus of the system layer.

[0072] The nominal voltage of the battery base unit is compatible with the voltage level of the 12V lead-acid battery system, and it can directly replace the 12V lead-acid battery.

[0073] This method fully realizes end-to-end management from energy storage, data acquisition, core algorithm execution to system-level decision-making and power output. The three processes of basic state estimation, health status assessment, and equalization control are executed sequentially. The data dependency relationship of providing characteristic region information for SOH assessment and equalization control based on the SOC estimation results ensures the logical correctness and execution efficiency of the algorithm. The temperature adaptive charge and discharge control process is executed in parallel with the above three processes, ensuring that the real-time performance of temperature protection is not affected by the delay of other processes. The unified decision-making mechanism of the master control module 220 avoids conflicts that may arise from independent decision-making by each slave control module. The battery base unit managed by this method is compatible with 12V lead-acid battery systems and can be directly replaced, reducing the user's replacement cost and technical threshold.

[0074] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A sodium-ion battery management system, characterized in that, Including the cell layer, management layer, and system layer; The cell layer includes at least one battery base unit, each of which is composed of multiple sodium-ion cells connected in series. The nominal voltage of the battery base unit is compatible with the voltage level of a 12V lead-acid battery system and can directly replace a 12V lead-acid battery. The management layer includes a BMS slave control module corresponding to each of the battery base units, and a master control module connected to all the BMS slave control modules via an isolated communication bus. The BMS slave control module includes an MCU and an AFE. The AFE is used to collect voltage, temperature, and current data of each cell in the corresponding battery basic unit. The MCU is used to sequentially execute the basic state estimation process, the health state assessment process, and the equalization control process. The basic state estimation process is configured to determine the characteristic region of the OCV-SOC curve based on the total voltage of the battery pack, and calculate the state of charge (SOC) using an estimation strategy that matches the characteristic region. The health status assessment process is configured to assess the battery health status (SOH) based on capacity decay and internal resistance growth, and detect cell consistency anomalies within the characteristic regions determined by the basic state estimation process. The equalization control process is configured to determine whether equalization operation needs to be initiated based on the voltage dynamic characteristics of each cell within the characteristic region determined by the basic state estimation process, and select the corresponding equalization strategy according to the region. The main control module is used to collect data reported by all BMS slave control modules, formulate system-level control strategies, and communicate with external devices. The system layer includes a DC bus that connects to the output terminals of the sodium battery packs of each BMS slave module, for supplying power to external loads.

2. The sodium-ion battery management system according to claim 1, characterized in that, The basic state estimation process is a piecewise adaptive SOC estimation process, including: The characteristic region of the sodium-ion battery OCV-SOC curve is determined based on the total voltage of the battery pack. The characteristic region includes a first region, a second region, and a third region. The first region corresponds to a total voltage below 11.2V, a single-cell voltage below 2.8V, and a SOC range of 0% to 25%. The second region corresponds to a total voltage between 11.2V and 12.0V, a single-cell voltage between 2.8V and 3.0V, and a state of charge (SOC) range of 25% to 85%. The third region corresponds to a total voltage higher than 12.0V, a single-cell voltage higher than 3.0V, and a SOC range of 85% to 100%. In the first and third regions, a SOC estimation strategy based primarily on voltage correction is adopted, with a voltage correction weight of no less than 70%. Within the second region, a SOC estimation strategy based primarily on the Coulomb integral method is adopted, with the Coulomb integral weight not less than 90%. During charging, when the battery pack voltage enters the third region, a reference capacity update is triggered, which does not depend on a complete full charge-full discharge cycle. When the battery is in a quiescent state and the current is below 50mA, the SOC estimate obtained from the open-circuit voltage lookup table is weighted and fused with the coulomb integral value, wherein the voltage correction weight in the second region is lower than the voltage correction weight in the first region and the third region. A nonlinear temperature compensation model for sodium-ion batteries, constructed within a temperature range of -40℃ to 60℃, is used to compensate for the SOC estimation results. The nonlinear temperature compensation model sets higher compensation weights when the temperature is below -10℃ and above 45℃.

3. The sodium-ion battery management system according to claim 2, characterized in that, The health status assessment process includes: The first SOH factor is calculated based on capacity decay, and the first SOH factor is equal to the current maximum available capacity divided by the initial maximum available capacity. The second SOH factor is calculated based on the increase of DC internal resistance. The second SOH factor is equal to (RBL minus Rout) divided by (RBL minus ROL). The DC internal resistance is dynamically calculated at the beginning of each discharge based on the voltage and current changes before and after the load is applied. The fusion weight α is dynamically adjusted according to the current operating temperature of the battery. The total SOH is equal to α multiplied by the first SOH factor plus (1-α) multiplied by the second SOH factor. Among them, when the temperature is below 0℃, the value of α is reduced to increase the contribution weight of the second SOH factor, and when the temperature is between 20℃ and 30℃, the value of α is 0.5 to 0.6 to increase the contribution weight of the first SOH factor. Within the second region of the characteristic area, the rate of change of voltage of each string of cells over time is monitored. If the absolute value of the rate of change of voltage of a certain string of cells exceeds 2mV / min, the cell is marked as an abnormal cell, and a SOH degradation assessment is performed on the abnormal cell with a degradation factor of 0.

9.

4. The sodium-ion battery management system according to claim 2, characterized in that, The equilibrium control process includes: During the charging process, the rate of change of voltage of each cell in the series with respect to time is calculated in real time; Within the second region of the characteristic area, if the voltage change rate of a certain string of cells deviates from the median value of the voltage change rate of all cells by more than 2mV / min, then the cell is determined to be a mismatched cell, and a passive equalization operation is initiated for the mismatched cell. The required balancing time is automatically calculated based on the degree of deviation; the greater the deviation, the longer the balancing time. Within the third region of the characteristic area, a dynamic voltage threshold tracking method is used for rapid equalization, and the equalization target value rises synchronously with the voltage of the highest voltage cell.

5. The sodium-ion battery management system according to claim 1, characterized in that, The MCU is also used to execute a temperature-adaptive charge-discharge control process, which is executed in parallel with the basic state estimation process, the health state assessment process, and the equalization control process, including: The operating temperature of sodium-ion batteries is divided into multiple ranges, and different charge and discharge control parameters are configured for different temperature ranges. When the temperature T satisfies -40℃ ≤ T < -20℃, the charging current limit is 0.1C, the single-cell charging voltage limit is 3.5V, and equalization is prohibited; When the temperature T satisfies -20℃ ≤ T < -10℃, the charging current limit is 0.2C, the single-cell charging voltage limit is 3.5V, and equalization is prohibited; When the temperature T satisfies -10°C ≤ T ≤ 10°C, the charging current limit is 0.5C, the single-cell charging voltage limit is 3.5V, and equalization is enabled only at the end of charging; When the temperature T satisfies 10°C<T ≤ 45°C, the charging current limit is 1.0C, the single-cell charging voltage limit is 3.5V, and equalization is enabled normally; When the temperature T satisfies 45°C<T ≤ 60°C, the charging current limit is 0.5C, the single-cell charging voltage limit is 3.4V, and equalization is prohibited; When the temperature T satisfies -40°C ≤ T<-30°C, the maximum continuous discharge current is 3.0C, and the single-cell discharge cut-off voltage is 1.8V; When the temperature T satisfies -30°C ≤ T<20°C, the maximum continuous discharge current is 6.0C, and the single-cell discharge cut-off voltage is 1.5V; When the temperature T satisfies 20°C ≤ T<45°C, the maximum continuous discharge current is 6.0C, and the single-cell discharge cut-off voltage is 1.5V; When the temperature T satisfies 45°C ≤ T ≤ 60°C, the maximum continuous discharge current is 2.0C, and the single-cell discharge cut-off voltage is 1.5V; On the basis of the above temperature interval division, the following supplementary control steps are also executed: When the temperature is lower than -10°C and the battery needs to be charged, the battery is preheated first with a pulse current lower than the normal charging current, and after the battery temperature rises to above -10°C, the normal charging mode is entered; When the temperature is higher than 45°C, the upper limit of the charging voltage is automatically reduced; When the temperature is lower than -30°C, the discharge cut-off voltage is automatically increased to avoid deep discharge damage.

6. The sodium-ion battery management system according to claim 1, characterized in that, In the management layer: The AFE integrates a 16-bit VADC, a 16-bit CADC, an NTC interface, a hardware protection module and an equalization MOS drive module; the BMS slave control module further includes an equalization management module, a charge and discharge control module and a DC / DC power supply unit; The isolated communication bus is an isolated SMBus bus or an isolated CAN bus, and signal isolation between the master control module and each of the BMS slave control modules is realized through a digital isolation chip, with an isolation voltage of not less than 2500Vrms; The master control module further includes a data aggregation module, a decision control module and an external communication module, wherein the data aggregation module is configured to poll all BMS slave control modules through the isolated communication bus and aggregate the voltage, current, temperature, SOC and fault state data of each group; the decision control module is configured to uniformly decide the start or stop of charging and discharging, the turn-on or turn-off of equalization, and the fault handling strategy according to the aggregated data; the external communication module is reserved with a CAN interface for communicating with an upper computer or a fire monitoring system.

7. The sodium-ion battery management system according to claim 1, characterized in that, In the cell layer: The OCV-SOC curve of the sodium-ion cell has a gentle voltage plateau region and steep voltage change regions located on both sides of the voltage plateau region.

8. The sodium-ion battery management system according to claim 1, characterized in that, The basic battery unit is composed of 4 sodium-ion cells connected in series, the nominal voltage of a single sodium-ion cell is 2.85V, the nominal voltage of the entire group is 11.4V, and the operating voltage range is 6.0V to 14.0V.

9. The sodium-ion battery management system according to claim 1, characterized in that, In the system layer: The system supports multi-level fault detection and protection functions: Level 1 protection is software-configurable protection, including cell overvoltage protection, cell undervoltage protection, charging overcurrent protection, discharging overcurrent protection, and charging / discharging overtemperature protection; Level 2 protection is a hardware-based fast-response protection system, including charging short-circuit protection, discharging short-circuit protection, and discharging overload protection, with a response time in the microsecond range; Fault handling strategies include: automatic recovery for recoverable faults, self-locking of severe faults requiring manual intervention for recovery, and permanent fault control by blowing external chemical fuses to achieve permanent physical disconnection.

10. A sodium-ion battery management method applied to the system according to any one of claims 1 to 9, characterized in that, include: The sodium-ion battery cells in the battery cell layer provide energy storage and power output; The voltage, temperature, and current data of each battery cell are collected by the BMS slave control module of the management layer. The basic state estimation process, health status assessment process, and equilibrium control process are executed sequentially. Parallel execution of temperature-adaptive charge-discharge control process; The master control module of the management layer aggregates data from all BMS slave control modules to make unified decisions on starting or stopping charging and discharging, turning on or off balancing, and handling faults. External loads are powered via the DC bus of the system layer; The nominal voltage of the battery base unit is compatible with the voltage level of a 12V lead-acid battery system, and it can directly replace a 12V lead-acid battery.

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