Bus-powered battery internal resistance detection and active-passive composite equalization circuit and method

Abstract

The application belongs to the technical field of battery online monitoring and equalization management, and provides a bus-powered battery internal resistance detection and active-passive composite equalization circuit and method, which solves the problem of current hardware redundancy and low equalization effectiveness and battery pack late life, and improves the effectiveness of equalization and prolongs the life of the battery pack. The bus-powered battery internal resistance detection and active-passive composite equalization circuit comprises a master control unit and a plurality of single battery detection modules connected through a low-voltage communication power supply bus. Each single battery detection module comprises a microcontroller and a bus power supply and active equalization circuit and an internal resistance test and passive equalization multiplex discharge circuit in communication with the microcontroller. The master control unit is used to calculate the voltage average of the battery pack and the deviation of each single battery voltage, and according to the comparison result of the deviation and the equalization start adaptive threshold, generate an equalization instruction and issue it to the microcontroller to control the start and stop of the bus power supply and active equalization circuit or the internal resistance test and passive equalization multiplex discharge circuit.

Description

Technical Field

[0001] This invention belongs to the field of battery online monitoring and equalization management technology, and particularly relates to a bus-powered battery internal resistance detection and active-passive composite equalization circuit and method. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Due to differences in individual battery manufacturing processes, uneven operating temperatures, and varying charge / discharge histories, parameters such as voltage and internal resistance of the individual cells in a series-connected battery pack will gradually deviate. This can lead to battery failure, resulting in a lack of power supply at critical moments, and even severely impacting the battery pack's lifespan and power supply reliability. Detecting battery internal resistance and performing active / passive balancing are effective methods for predicting battery failure in advance and ensuring the reliability of the battery pack's power supply.

[0004] Traditional battery online monitoring systems typically employ distributed detection modules, which draw power from the battery under test to maintain their operation. This increases the battery's self-discharge burden and affects the accurate assessment of its state of charge (SOC). In the event of a depleted or faulty battery, the detection module may fail due to insufficient power, thus failing to complete the monitoring task. While centralized power supply online monitoring solutions address these issues, they require two power lines and two communication lines. In large-scale battery monitoring systems, the increased number of wires leads to increased costs and system risks. Furthermore, existing balancing circuits and battery online monitoring circuits suffer from hardware redundancy, supporting only passive or active balancing, and generally using fixed voltage deviation thresholds as the balancing initiation criteria. This results in increased voltage fluctuations and inconsistent battery performance at low temperatures, low SOC, or during later stages of battery aging. Fixed thresholds can lead to over-balancing (frequent false triggers, increasing energy consumption and heat generation) or under-balancing (true inconsistencies go undetected, accumulating bottlenecks), reducing the effectiveness of balancing and shortening the battery pack's lifespan. Summary of the Invention

[0005] To address the technical problems mentioned above, this invention provides a bus-powered battery internal resistance detection and active-passive composite equalization circuit and method, which can reduce hardware redundancy, improve the effectiveness of equalization, and extend battery pack life.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of the present invention provides a bus-powered battery internal resistance detection and active-passive composite equalization circuit.

[0007] A bus-powered battery internal resistance detection and active-passive composite equalization circuit includes: a main control unit and multiple single-cell battery detection modules. The main control unit and each single-cell battery detection module are connected via a low-voltage communication power supply bus. The low-voltage communication power supply bus simultaneously carries power supply and communication signal, and the communication signal and power supply are modulated and superimposed on the low-voltage communication power supply bus. Each single-cell battery detection module includes a microcontroller and a bus power supply and active balancing circuit, as well as an internal resistance testing and passive balancing multiplexing discharge circuit that communicate with it; the microcontroller is used to receive and respond to the polling requests of the main control unit and report the single-cell battery voltage and internal resistance data. The main control unit is used to calculate the average voltage of the battery pack and the voltage deviation of each individual cell. Based on the comparison result of the deviation and the equalization start adaptive threshold, it generates equalization instructions and sends them to the microcontroller to control the start and stop of the bus power supply and the active equalization circuit or the internal resistance test and passive equalization multiplexing discharge circuit. Among them, the dispersion base value is constructed by the standard deviation of the voltage and the standard deviation of the internal resistance within the pack, and the temperature correction factor, the state of charge correction factor, the individual cell internal resistance correction factor and the battery health state aging correction factor are introduced to calculate the equalization start adaptive threshold.

[0008] As one implementation method, the temperature correction factor is: ;in, This refers to the temperature sensitivity coefficient. Current battery temperature; This is the reference temperature.

[0009] As one implementation method, the state of charge correction factor is segmented according to the state of charge of the battery pack.

[0010] As one implementation method, the monomer internal resistance correction factor is: ;in, The internal resistance sensitivity coefficient; This represents the current internal resistance of a single cell. This represents the average internal resistance of each monomer within the group.

[0011] As one implementation method, the battery health status aging correction factor is: Among them, SOH represents the battery health status, with 100% indicating brand new and decreasing as the battery ages.

[0012] As one implementation, in the main control unit, when the deviation is less than the equalization start adaptive threshold, the bus power supply and active equalization circuit or the internal resistance test and passive equalization multiplexing discharge circuit are not started. When the deviation is greater than the equalization start adaptive threshold and the voltage of a single cell is less than the average voltage of the battery pack, the internal resistance test and passive equalization multiplexing discharge circuit is activated to discharge the high-voltage battery. When the deviation is greater than the equalization start-up adaptive threshold and the voltage of a single cell is greater than the average voltage of the battery pack, the bus power supply and active equalization circuit is activated and the power supply operation from the low-voltage communication power supply bus is performed.

[0013] In one implementation, when the main control unit starts the bus power supply and active balancing circuit, it sends an active balancing constant current-constant voltage-cutoff mode switching command to each individual battery detection module through the balancing control frame in the communication signal.

[0014] As one implementation method, in the main control unit, the battery state of charge of each individual battery detection module is estimated based on the silent window period, and combined with the bus power supply capability, the active balancing time slot is dynamically allocated to achieve time-sharing collaborative balancing of the individual battery detection modules.

[0015] As one implementation method, the principle for dynamically allocating active balancing time slots in the main control unit is as follows: Calculate the number of modules that can be balanced simultaneously based on the maximum bus supply current, the bus base current, and the active balancing current of a single module. The single-cell battery detection modules that require active balancing are sorted from low to high battery state of charge, and time slots are allocated to the single-cell battery detection module with the lowest battery state of charge first. The corresponding single-cell battery detection module performs equalization within the allocated time slot, and automatically pauses when the time slot ends, waiting for the next round of instructions or stopping. When the state of charge of a single battery cell detection module reaches the target value or the time slot is exhausted, the time slot is released, and time slots are allocated to the next single battery cell detection module with the lowest state of charge.

[0016] A second aspect of the present invention provides a method for operating a bus-powered battery internal resistance detection and active-passive composite equalization circuit.

[0017] A method for operating a bus-powered battery internal resistance detection and active-passive composite equalization circuit includes: After power-on, the main control unit provides a preset low-voltage DC power supply to the low-voltage communication power supply bus, and each individual battery detection module draws power from the low-voltage communication power supply bus to complete self-test; the main control unit allocates addresses and establishes communication links for each individual battery detection module through the low-voltage communication power supply bus, and then configures the acquisition parameters of each individual battery detection module. The main control unit polls each individual battery detection module according to the configured acquisition parameters and performs operations such as voltage acquisition, internal resistance testing, temperature acquisition, battery state of charge acquisition, and battery health status acquisition. The main control unit calculates the average voltage of the battery pack and the voltage deviation of each individual cell. Based on the comparison between the deviation and the equalization start adaptive threshold, it generates an equalization command and sends it to the microcontroller to control the start and stop of the bus power supply and the active equalization circuit or the internal resistance test and passive equalization multiplexing discharge circuit. Among them, the dispersion base value is constructed by the standard deviation of the voltage and the standard deviation of the internal resistance within the pack, and the temperature correction factor, state of charge correction factor, single cell internal resistance correction factor and battery health state aging correction factor are introduced to calculate the equalization start adaptive threshold.

[0018] Compared with the prior art, the beneficial effects of the present invention are: The main control unit of this invention is connected to each individual battery detection module via a low-voltage communication power supply bus. Modulation technology is used to superimpose the communication signal and the power supply, achieving DC power supply and communication multiplexing. Furthermore, each individual battery detection module is equipped with an internal resistance test and passive equalization multiplexing discharge circuit, reducing hardware redundancy. Finally, a dispersion baseline is constructed using the standard deviation of the group's voltage and the standard deviation of the internal resistance. Temperature correction factors, state of charge correction factors, single-cell internal resistance correction factors, and battery health state aging correction factors are introduced to design an adaptive equalization start threshold. The average voltage of the battery pack and the deviation of the voltage of each individual battery are compared with the adaptive equalization start threshold to determine the equalization method. The impact of operating conditions such as temperature, state of charge (SOC), battery aging degree (SOH), and group dispersion on voltage consistency is considered, allowing the threshold to adaptively adjust with operating conditions and battery lifespan, improving the effectiveness of equalization and extending the battery pack's lifespan.

[0019] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0021] Figure 1 This is a schematic diagram of the battery internal resistance detection and active-passive composite equalization circuit powered by bus according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the line power supply and active balancing circuit according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the internal resistance testing and passive equalization multiplexing discharge circuit according to an embodiment of the present invention. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] according to Figure 1 The battery internal resistance detection and active-passive composite equalization circuit powered by the bus in this embodiment of the invention includes: a main control unit and multiple single-cell battery detection modules. The main control unit and each single-cell battery detection module are connected through a low-voltage communication power supply bus. The low-voltage communication power supply bus carries both power supply and communication signal. The communication signal and power supply are modulated and superimposed on the low-voltage communication power supply bus.

[0026] In this embodiment, the low-voltage communication power supply bus is the infrastructure, and its electrical characteristics are as follows: Power supply voltage range: preset range, such as 15~24VDC, compatible with standard secondary power supply output of communication base stations; Communication protocol: Standard protocol, such as standard Modbus RTU, configurable baud rate 9600 / 2400bps; Communication method: Modulate the communication waveform of a preset standard protocol (such as Modbus RTU) onto the power supply line; Bus topology: Bus type, with the master control unit as the master station and each individual battery detection module as the slave station; Slave addressing: Each individual battery detection module has a unique slave address, ranging from 1 to 254; Bus signal superposition principle: The communication signal sent by the main control unit is converted into a voltage modulation signal by the modulation circuit in the main control unit, and superimposed on the DC power supply line through the coupling circuit; the single battery detection module extracts the modulation signal from the low-voltage communication power supply bus through the coupling circuit, and then restores it to the communication signal through the demodulation circuit. The signal modulation adopts the method of downlink voltage loop and uplink current loop.

[0027] Waveform synchronization time base: The low-voltage communication power supply bus provides three levels of time base: frame synchronization, baud rate synchronization, and polling cycle synchronization. These can be extended for silent measurement window triggering and equalization control frame timing alignment.

[0028] In this embodiment, the single-cell battery detection module draws power from the low-voltage communication power supply bus, without consuming the power of the battery under test. This eliminates the interference of the detection module's self-discharge on the battery's SOC assessment. Furthermore, the single-cell battery detection module can still operate normally even when the battery is low on power or in a faulty state, ensuring the reliability and availability of the overall circuit.

[0029] This embodiment modulates the communication signal onto the power supply line, enabling power supply and communication to share a single bus. This eliminates the need for separate communication and power cables, significantly reducing wiring complexity and installation costs. In large-scale battery pack applications, wiring simplification is substantial.

[0030] Each single-cell battery detection module includes a microcontroller and a bus power supply and active balancing circuit, as well as an internal resistance testing and passive balancing multiplexing discharge circuit that communicate with it. The microcontroller is used to receive and respond to the polling requests from the main control unit and report the single-cell battery voltage and internal resistance data.

[0031] Figure 2 The bus power supply and active balancing circuit are presented. It draws power from the 15-24V low-voltage communication power supply bus and generates the required 3.3V / 5V operating power for the module internally via a DC-DC buck converter. The power supply circuit is equipped with overvoltage and reverse connection protection at the front end to ensure module safety during bus voltage fluctuations. The core circuit for active balancing charging is implemented using chip U3, employing a BUCK-type active balancing charging circuit to step down the bus voltage (15-24V) to the charging voltage of a single battery cell, thus transferring energy from the bus to the battery. A switching transistor Q1 and a resistor R1 are also placed between the BUCK-type active balancing charging circuit and the single battery cell BAT. The DC-DC buck converter achieves a conversion efficiency of over 90%. Compared to passive balancing, which dissipates energy entirely as heat, active balancing charging exhibits minimal heat dissipation, which is beneficial for the thermal management of the sealed battery cabinet. Figure 2 In this circuit, the DC-DC buck converter is implemented using a buck chip U1. A Zener diode D1 and a diode D2 are connected to the input circuit of chip U1. After the linear regulator chip U2 regulates the voltage, it supplies the internal circuit load.

[0032] Figure 3A discharge circuit combining internal resistance testing and passive equalization is presented. It measures the battery's internal resistance using a DC discharge method, and simultaneously serves as the discharge path for passive equalization. By controlling the conduction of a discharge switch (such as a MOSFET), the battery generates a known discharge current through a precision discharge resistor. Simultaneously, the voltage change before and after discharge is collected, and the battery's internal resistance is calculated based on the ratio of the voltage change to the current change. This discharge path is reused for passive equalization, allowing continuous discharge with a small current. In this embodiment, the discharge switch Q3 and discharge resistor R4 are shared by the internal resistance testing and equalization functions. Mode switching is achieved by controlling the connection / short-circuit of switch Q3 via bypass switch Q2, eliminating hardware redundancy in the independent equalization circuit and reducing circuit area and component cost.

[0033] Figure 3 The microcontroller (MCU) in the system is implemented using the U5 chip: it is responsible for all logic control, including voltage acquisition, internal resistance testing, passive equalization discharge control, active equalization charging control, and communication. The MCU receives polling requests from the main control unit, reports voltage and internal resistance data, and receives equalization commands to control the start and stop of the corresponding switching transistors. Figure 3 In the diagram, D3 is a diode, and R2 to R7 are all resistors.

[0034] In this embodiment, the main control unit is used to calculate the average voltage of the battery pack and the voltage deviation of each individual cell. Based on the comparison result between the deviation and the equalization start adaptive threshold, an equalization command is generated and sent to the microcontroller to control the start and stop of the bus power supply and the active equalization circuit or the internal resistance test and passive equalization multiplexing discharge circuit. Among them, the dispersion base value is constructed by the standard deviation of the voltage and the standard deviation of the internal resistance within the pack, and the temperature correction factor, the state of charge correction factor, the individual cell internal resistance correction factor and the battery health state aging correction factor are introduced to calculate the equalization start adaptive threshold.

[0035] In this embodiment, the main control unit is responsible for the power supply management, communication scheduling and equalization decision of the low-voltage communication power supply bus, runs the set protocol (such as Modbus RTU protocol), periodically polls the data of each individual battery detection module, and executes the corresponding equalization strategy according to the voltage deviation.

[0036] The main control unit is equipped with bidirectional equalization control logic. Specifically, when the deviation is less than the equalization start adaptive threshold, the bus power supply and active equalization circuit or the internal resistance test and passive equalization multiplexing discharge circuit will not be activated. When the deviation is greater than the equalization start adaptive threshold and the voltage of a single cell is less than the average voltage of the battery pack, the internal resistance test and passive equalization multiplexing discharge circuit will be activated to discharge the high-voltage battery. When the deviation is greater than the equalization start adaptive threshold and the voltage of a single cell is greater than the average voltage of the battery pack, the bus power supply and active equalization circuit will be activated and power will be drawn from the low-voltage communication power supply bus.

[0037] This embodiment automatically selects passive equalization discharge or active equalization charging based on the direction of voltage deviation, discharging high-voltage batteries to release energy and charging low-voltage batteries to replenish energy, thus improving battery pack consistency in both directions simultaneously. Compared with a unidirectional equalization scheme, bidirectional equalization can converge the battery pack voltage to a uniform state more quickly within the same time frame.

[0038] Within the main control unit, the balanced startup adaptive threshold is set to... Its formula is: ; in, The discreteness base value, This is a temperature correction factor; This is a correction factor for the state of charge; This is a correction factor for the internal resistance of the monomer. This is a battery health status aging correction factor.

[0039] Within the main control unit, the discrete base value The standard deviation of the voltage of each individual cell in the group is the weighted sum of the standard deviations of the internal resistance of each individual cell in the group. The formula is as follows: ; in, The standard deviation (mV) of the voltage of each individual unit within the group reflects voltage consistency. The standard deviation (mΩ) of the internal resistance of each individual unit within the group reflects the consistency of internal resistance; This is the voltage dispersion weight, typically 1.5, with an selectable range of 1.0 to 2.0; This is the equivalent weight for the internal resistance dispersion (including the equivalent conversion of internal resistance to voltage dimensions), with a typical value of 1.0 and an selectable range of 0.5 to 1.5.

[0040] The dispersion baseline value integrates two consistency indicators: voltage and internal resistance. Voltage dispersion reflects apparent consistency, while internal resistance dispersion reflects deep consistency (internal resistance differences often appear before voltage differences, allowing potential inconsistencies to be detected earlier). The combination of the two enables the baseline value to more comprehensively characterize the true degree of inconsistency of the battery pack.

[0041] Temperature correction factor is ;in, This is the temperature sensitivity coefficient, with a typical value of 0.4 and an selectable range of 0.3 to 0.5. Current battery temperature (°C); The reference temperature is 25℃, with an optional range of 20~30℃.

[0042] When the battery temperature deviates from the reference temperature, the electrochemical reaction rate, internal resistance, and polarization characteristics change, leading to increased voltage fluctuations. The temperature correction factor widens its threshold as the deviation increases to prevent frequent false triggering of equalization due to voltage instability at extreme temperatures.

[0043] The state-of-charge (SOC) correction factor is segmented according to the SOC of the battery pack. This adapts to the steepness / gradation characteristics of the open-circuit voltage-SOC (OCV-SOC) curve in different segments of the lead-acid battery, as shown in Table 1.

[0044] Table 1. Values ​​of the state of charge correction factor;

[0045] The monomer internal resistance correction factor is ;in, This is the internal resistance sensitivity coefficient, with a typical value of 0.3 and an selectable range of 0.2 to 0.5; The current internal resistance of a single cell (mΩ); The average internal resistance of each individual cell in the group (mΩ); The internal resistance correction factor is applied at the individual cell level: when the internal resistance of a cell deviates significantly from the group average (e.g., due to loose connection or early failure), the reliability of its voltage reading decreases. In this case, the equalization threshold of the cell is appropriately relaxed to avoid misjudgment of voltage deviation caused by abnormal internal resistance.

[0046] Internal resistance plays a dual role in this algorithm: firstly, it participates in the construction of the dispersion baseline in the form of within-group standard deviation, characterizing the overall consistency within the group (group level); secondly, it represents individual bias. Form serves as a correction factor for individual internal resistance, characterizing individual reliability (at the individual level). Both form and form work together to correct the threshold at both the group and individual levels, fully utilizing internal resistance information to improve the accuracy of threshold determination.

[0047] Battery health status aging correction factor is Among them, SOH represents the battery health status, with 100% indicating brand new and decreasing as the battery ages.

[0048] As batteries age, internal resistance increases, capacity decreases, and the voltage plateau shifts, naturally leading to poorer consistency between individual cells. If the tight threshold used for new batteries is applied, it will result in frequent equalization triggers and excessive equalization losses in the later stages of aging. The aging correction factor increases as SOH decreases (η=1.0 at SOH=100%; η=1.2 at SOH=80%; η=1.4 at SOH=60%), automatically relaxing the threshold to achieve soft correction throughout the battery's lifespan and avoid over-equalization in the later stages of aging.

[0049] In this embodiment, the passive equalization discharge current can be adjusted by connecting multiple sets of current-limiting resistors in parallel; the active equalization charging current can be adjusted by adjusting the current sampling resistor. Active equalization charging directly replenishes the low-voltage battery, which is a more indirect improvement compared to the discharge-type solution, resulting in faster response and better performance; high-voltage discharge + low-voltage charging improve battery pack consistency in both directions simultaneously; the fusion of five-dimensional parameters enables the threshold to be dynamically adjusted according to temperature, SOC, internal resistance, SOH, and intra-group dispersion, avoiding over-equalization / under-equalization under varying operating conditions with a fixed threshold, and achieving self-adaptation throughout the battery's entire life cycle.

[0050] In the main control unit, when the bus power supply and active balancing circuit are started, the constant current-constant voltage-cutoff mode switching command for active balancing is uniformly sent to each individual battery detection module through the balancing control frame in the communication signal.

[0051] The equalization control frame extends the function code on the basis of the standard communication frame, and includes information such as the target module address, mode word, target parameters (target current / target voltage), switching conditions, time slot number, and time slot length.

[0052] Each individual battery detection module precisely executes the active balancing mode switching according to the balancing control frame timing, rather than making local autonomous judgments. The switching from constant current to constant voltage is determined by the main controller based on the quasi-open circuit voltage collected in the silent window and the real-time reported charging parameters, and then a switching command is issued through the balancing control frame to avoid improper switching timing caused by local measurement errors of individual cells.

[0053] In the main control unit, the battery state of charge of each individual battery detection module is estimated based on the silent window period, and the active balancing time slot is dynamically allocated in combination with the bus power supply capability to achieve time-sharing collaborative balancing of individual battery detection modules.

[0054] The master control unit defines a silent window during the bus communication polling cycle. Within the silent window: The main control unit suspends downlink voltage loop modulation, and the bus maintains only pure DC power supply (no communication waveform). All individual battery detection modules simultaneously stop active equalization charging; All single-cell battery detection modules pause internal resistance test discharge pulses; Each individual battery detection module synchronously samples the battery terminal voltage within the window to obtain the quasi-open circuit voltage; The main control unit collects the quasi-open circuit voltage of each individual battery detection module and performs SOC fusion estimation by combining the ampere-hour integration method.

[0055] The main control unit obtains the SOC corresponding to the open-circuit voltage of each module based on the quasi-open-circuit voltage collected during the silent window, and then weights and fuses it with the ampere-hour integrated SOC. Since all batteries enter the quasi-quiet state synchronously within the silent window, the disturbances of bus modulation and equalization current on the open-circuit voltage measurement are eliminated, and synchronous sampling ensures the time consistency of SOC estimation for each battery, providing reliable input for equalization decision-making.

[0056] This embodiment combines bus waveform synchronization with SOC estimation, and utilizes the controllability of the bus waveform to create a silent window within the communication cycle, thereby improving the accuracy of SOC estimation using the open-circuit voltage method.

[0057] Specifically, in the main control unit, the principle for dynamically allocating active balancing time slots is as follows: Calculate the number of modules M that can be balanced simultaneously based on the maximum bus supply current, the bus base current, and the active balancing current of a single module; M = floor((I bus_max -I base ) / I eq ), where I bus_max I is the maximum supply current of the bus. base For the bus base current, I eq is the active balancing current for a single module; floor is the floor function.

[0058] The single-cell battery detection modules that require active balancing are sorted from low to high battery state of charge, and time slots are allocated to the single-cell battery detection module with the lowest battery state of charge first (the most power-depleted module is replenished first). The corresponding single-cell battery detection module performs equalization within the allocated time slot, and automatically pauses when the time slot ends, waiting for the next round of instructions or stopping. When the state of charge (SOC) of a single-cell battery detection module reaches the target value (e.g., SOC ≥ average SOC within the group) or the time slot is exhausted, the time slot is released, and time slots are allocated to the next single-cell battery detection module with the lowest SOC.

[0059] This embodiment utilizes time-sharing collaborative scheduling to ensure that the number of modules simultaneously balanced does not exceed the bus capacity, the bus current remains stable, and voltage drops and modulation signal distortion caused by multiple modules drawing power simultaneously are avoided.

[0060] The working principle of the battery internal resistance detection and active-passive composite equalization circuit based on the above-mentioned bus power supply is as follows: After power-on, the main control unit provides a preset low-voltage DC power supply (such as 15~24V DC power) to the low-voltage communication power supply bus. Each individual battery detection module draws power from the low-voltage communication power supply bus to complete self-test. The main control unit assigns addresses and establishes communication links for each individual battery detection module through the low-voltage communication power supply bus, and then configures the acquisition parameters of each individual battery detection module (voltage acquisition cycle, internal resistance test cycle, equalization threshold, etc.). The main control unit polls each individual battery detection module according to the configured acquisition parameters and performs operations such as voltage acquisition, internal resistance testing, temperature acquisition, battery state of charge acquisition, and battery health status acquisition. Among them, voltage acquisition: the ADC of the single-cell battery detection module samples the battery terminal voltage in real time, and the main control unit reads the voltage register to obtain the current voltage value; Internal resistance test: The main control unit sends an internal resistance test command to the designated single-cell battery detection module. The single-cell battery detection module performs an internal resistance test using the DC discharge method (short-time pulse discharge, lasting 10~100ms). After the test is completed, the internal resistance value is written to the register for the main control unit to read. Temperature acquisition: Read the temperature data of the battery's negative electrode; SOC acquisition: The main control unit estimates the SOC of each cell by integrating the battery open-circuit voltage and the charge / discharge current; SOH Acquisition: The main control unit estimates the SOH based on the relative change trend of the internal resistance of each unit during the initial installation period.

[0061] The main control unit calculates the average voltage of the battery pack and the voltage deviation of each individual cell. Based on the comparison between the deviation and the equalization start adaptive threshold, it generates an equalization command and sends it to the microcontroller to control the start and stop of the bus power supply and the active equalization circuit or the internal resistance test and passive equalization multiplexing discharge circuit. Among them, the dispersion base value is constructed by the standard deviation of the voltage and the standard deviation of the internal resistance within the pack, and the temperature correction factor, state of charge correction factor, single cell internal resistance correction factor and battery health state aging correction factor are introduced to calculate the equalization start adaptive threshold.

[0062] Specifically, the passive equalization discharge execution process is as follows: The main control unit sends a passive equalization discharge command to the target detection module; The MCU of the single-cell battery detection module turns off the bypass switch Q2, thereby turning on the switch Q3 to continue discharging; The battery continuously discharges at a current of approximately 2A through the diode D3-switch Q3-resistor R4 path; The MCU continuously monitors the battery voltage, and when VV avg When the voltage ≤ ΔV1 / 2 (hysteresis threshold) or the discharge time reaches the upper limit, switch Q2 turns on and switch Q3 turns off; where V is the monitored battery voltage; V avg This represents the average battery voltage. To achieve a balanced start-up adaptive threshold.

[0063] Specifically, the active equalization discharge execution process is as follows: Based on SOC sorting and bus power supply capacity constraints, the main control unit determines the active balancing scheduling scheme for this round and allocates time slots to the detection modules of each target single battery cell. The main control unit sends a balancing control frame start command (constant current mode, target current 2A, target voltage 14.4V, time slot number, time slot length) to the target single-cell battery detection module. The MCU of the single-cell battery detection module turns on the switching transistor Q1 to perform constant current charging; Bus energy is delivered via step-down chip U1 - charging circuit chip U3 - switching transistor Q1 - resistor R1 - battery to charge the low-voltage battery; The active equalization charging circuit controls the charging process by feeding back the output voltage and sampling the charging current in real time.

[0064] In practice, the main control unit comprehensively judges the switching timing based on the quasi-open circuit voltage collected during the silent window period and real-time feedback: When the quasi-open circuit voltage reaches 14.4V, the main controller sends an equalization control frame (constant voltage mode) to switch to constant voltage mode. During the constant voltage phase, when the charging current drops to the cutoff current (typically 0.5A), the main controller sends an equalization control frame (cutoff mode) to stop charging; or when V avg When -V≤ΔV1 / 2 (hysteresis threshold) or the charging time reaches the upper limit, the MCU outputs a control to turn off Q1 and stop charging; When the SOC of a single-cell battery detection module reaches the target value or the time slot is exhausted, the time slot is released, and the main controller replenishes the next single-cell battery detection module with the lowest SOC from the candidate queue.

[0065] The constant current-constant voltage-cutoff mode switching of the entire active equalization charging process is controlled by the main control unit through the unified distribution of equalization control frames via bus waveform timing. The detection module only executes according to the instructions, realizing the timing coordination of the active equalization process of multiple modules, avoiding bus disturbances caused by simultaneous power draw and improper timing of local autonomous switching.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A bus-powered battery internal resistance detection and active-passive composite equalization circuit, characterized in that, include: The system includes a main control unit and multiple individual battery detection modules, with the main control unit connected to each individual battery detection module via a low-voltage communication power supply bus. The low-voltage communication power supply bus carries both power supply and communication signal, and the communication signal and power supply are modulated and superimposed on the low-voltage communication power supply bus. Each single-cell battery detection module includes a microcontroller and a bus power supply and active balancing circuit, as well as an internal resistance testing and passive balancing multiplexing discharge circuit that communicate with it; the microcontroller is used to receive and respond to the polling requests of the main control unit and report the single-cell battery voltage and internal resistance data. The main control unit is used to calculate the average voltage of the battery pack and the voltage deviation of each individual cell. Based on the comparison result of the deviation and the equalization start adaptive threshold, it generates equalization instructions and sends them to the microcontroller to control the start and stop of the bus power supply and the active equalization circuit or the internal resistance test and passive equalization multiplexing discharge circuit. Among them, the dispersion base value is constructed by the standard deviation of the voltage and the standard deviation of the internal resistance within the pack, and the temperature correction factor, the state of charge correction factor, the individual cell internal resistance correction factor and the battery health state aging correction factor are introduced to calculate the equalization start adaptive threshold.

2. The bus-powered battery internal resistance detection and active-passive composite equalization circuit as described in claim 1, characterized in that, Temperature correction factor is ;in, This refers to the temperature sensitivity coefficient. Current battery temperature; This is the reference temperature.

3. The bus-powered battery internal resistance detection and active-passive composite equalization circuit as described in claim 1, characterized in that, The state of charge correction factor is segmented according to the state of charge of the battery pack.

4. The bus-powered battery internal resistance detection and active-passive composite equalization circuit as described in claim 1, characterized in that, The monomer internal resistance correction factor is ;in, The internal resistance sensitivity coefficient; This represents the current internal resistance of a single cell. This represents the average internal resistance of each monomer within the group.

5. The bus-powered battery internal resistance detection and active-passive composite equalization circuit as described in claim 1, characterized in that, Battery health status aging correction factor is Among them, SOH represents the battery health status, with 100% indicating brand new and decreasing as the battery ages.

6. The bus-powered battery internal resistance detection and active-passive composite equalization circuit as described in claim 1, characterized in that, In the main control unit, when the deviation is less than the equalization start adaptive threshold, the bus power supply and active equalization circuit or the internal resistance test and passive equalization multiplexing discharge circuit will not be started. When the deviation is greater than the equalization start adaptive threshold and the voltage of a single cell is less than the average voltage of the battery pack, the internal resistance test and passive equalization multiplexing discharge circuit is activated to discharge the high-voltage battery. When the deviation is greater than the equalization start-up adaptive threshold and the voltage of a single cell is greater than the average voltage of the battery pack, the bus power supply and active equalization circuit is activated and the power supply operation from the low-voltage communication power supply bus is performed.

7. The bus-powered battery internal resistance detection and active-passive composite equalization circuit as described in claim 1, characterized in that, In the main control unit, when the bus power supply and active balancing circuit are started, the constant current-constant voltage-cutoff mode switching command for active balancing is uniformly sent to each individual battery detection module through the balancing control frame in the communication signal.

8. The bus-powered battery internal resistance detection and active-passive composite equalization circuit as described in claim 1, characterized in that, In the main control unit, the battery state of charge of each individual battery detection module is estimated based on the silent window period, and the active balancing time slot is dynamically allocated in combination with the bus power supply capability to achieve time-sharing collaborative balancing of individual battery detection modules.

9. The bus-powered battery internal resistance detection and active-passive composite equalization circuit as described in claim 8, characterized in that, In the main control unit, the principle for dynamically allocating active equalization time slots is as follows: Calculate the number of modules that can be balanced simultaneously based on the maximum bus supply current, the bus base current, and the active balancing current of a single module. The single-cell battery detection modules that require active balancing are sorted from low to high battery state of charge, and time slots are allocated to the single-cell battery detection module with the lowest battery state of charge first. The corresponding single-cell battery detection module performs equalization within the allocated time slot, and automatically pauses when the time slot ends, waiting for the next round of instructions or stopping. When the state of charge of a single battery cell detection module reaches the target value or the time slot is exhausted, the time slot is released, and time slots are allocated to the next single battery cell detection module with the lowest state of charge.

10. A method for operating a battery internal resistance detection and active-passive composite equalization circuit based on bus power supply as described in any one of claims 1-9, characterized in that, include: After power-on, the main control unit provides a preset low-voltage DC power supply to the low-voltage communication power supply bus, and each individual battery detection module draws power from the low-voltage communication power supply bus to complete the self-test; The main control unit assigns addresses and establishes communication links for each individual battery detection module through a low-voltage communication power supply bus, and then configures the acquisition parameters of each individual battery detection module. The main control unit polls each individual battery detection module according to the configured acquisition parameters and performs operations such as voltage acquisition, internal resistance testing, temperature acquisition, battery state of charge acquisition, and battery health status acquisition. The main control unit calculates the average voltage of the battery pack and the voltage deviation of each individual cell. Based on the comparison between the deviation and the equalization start adaptive threshold, it generates an equalization command and sends it to the microcontroller to control the start and stop of the bus power supply and the active equalization circuit or the internal resistance test and passive equalization multiplexing discharge circuit. Among them, the dispersion base value is constructed by the standard deviation of the voltage and the standard deviation of the internal resistance within the pack, and the temperature correction factor, state of charge correction factor, single cell internal resistance correction factor and battery health state aging correction factor are introduced to calculate the equalization start adaptive threshold.

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