Parallel adaptive equalization output method and control system for battery swapping mode lithium battery

Abstract

This invention discloses a method and control system for adaptive equalization output of parallel lithium batteries in a battery swapping mode. The method is applied to multi-cell / multi-cluster parallel lithium battery packs, with each cell / cluster configured with main and auxiliary discharge paths. Equalization is achieved through six steps: real-time sampling and monitoring, anomaly detection, main path disconnection, auxiliary path initiation, adaptive equalization, and main path reconnection. The control system includes a battery management system, a lithium battery pack, and main / auxiliary discharge path modules. This invention rapidly eliminates circulating current and balances voltage through multi-parameter linkage adjustment, adapting to the mixed parallel requirements of battery swapping scenarios, balancing equalization efficiency and discharge stability, and extending battery life.

Description

Technical Field

[0001] This invention relates to the field of lithium battery equalization control technology, and in particular to a method and control system for parallel adaptive equalization output of lithium batteries in a battery swapping mode. Background Technology

[0002] In battery swapping mode, when multiple lithium batteries are used in parallel, differences in batches, aging levels, and internal resistance can easily lead to problems such as circulating current in parallel branches and voltage imbalance, resulting in decreased battery discharge efficiency, shortened lifespan, and even safety hazards. Existing balancing methods mostly rely on dedicated balancing modules, which have drawbacks such as complex structure, high cost, and slow response. They also struggle to balance balancing performance and discharge stability under dynamic operating conditions, failing to meet the adaptive balancing requirements of multiple parallel lithium batteries in battery swapping scenarios. Therefore, there is an urgent need for an efficient, simple, and adaptive balancing output method and control system. Summary of the Invention

[0003] The purpose of this invention is to provide a method and control system for adaptive equalization output of lithium batteries in parallel in a battery swapping mode, so as to solve the problems of circulating current and voltage imbalance when multiple lithium batteries are connected in parallel in a battery swapping scenario.

[0004] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A battery swapping mode lithium battery parallel adaptive equalization output method is disclosed. The method is applied to multi-cell / multi-cluster parallel lithium battery packs, where each cell / cluster is configured with a main discharge path and an independent auxiliary discharge path. The method includes the following steps: Step 1: Real-time sampling and monitoring. The battery management system collects the individual cell voltage, output current, branch current and temperature parameters of each parallel battery in real time, calculates the voltage difference between each parallel battery in real time, and detects the magnitude and direction of the circulating current between parallel branches. Step 2: Circulating current / voltage difference abnormality determination. When the voltage difference between parallel batteries exceeds the set threshold, or when a significant bidirectional circulating current (i.e., battery mutual charging current) appears in the parallel branch, it is determined that there is a parallel unbalanced circulating current problem. Step 3: Cut off the main discharge path, shut down the main discharge path of the abnormal battery cell or all parallel battery cells, and disconnect the main path from the parallel bus. Step 4: Auxiliary discharge path is switched on, and all parallel batteries are switched to output through their own independent auxiliary discharge paths. Through the controllable current limiting and voltage regulation of the auxiliary discharge path, the batteries with high voltage are appropriately current limited and controlled to discharge to reduce their output equivalent voltage. For batteries with low voltage, reverse backflow is restricted, and only stable output is allowed. Step 5: Adaptive balancing and circulating current elimination. By dynamically adjusting the auxiliary discharge path, the static voltage difference and dynamic operating condition voltage difference between parallel batteries are smoothed out, and the internal circulating current that backflows between batteries is eliminated. Step 6: Switch back to main discharge path. When the voltage difference between each parallel battery returns to the set allowable range, the circulating current amplitude drops below the set threshold, and the current distribution of each branch is uniform, the main discharge path is closed again, the auxiliary discharge path is closed, and the main discharge path is switched back to perform high-power discharge.

[0005] In one alternative embodiment, the main discharge path is directly connected to the parallel bus using a MOS transistor or relay.

[0006] In one alternative embodiment, the sampling frequency of the battery management system is set to be no less than 10Hz.

[0007] In one alternative embodiment, when only a single battery cell experiences a voltage difference or abnormal circulating current, the main discharge path of the abnormal battery cell is cut off, while the main discharge path of the remaining normal battery cells remains open.

[0008] In one alternative embodiment, the auxiliary discharge path employs either linear voltage regulation or chopper voltage regulation.

[0009] In one alternative embodiment, in step 5, the current limiting amplitude of the auxiliary discharge path corresponding to the battery with a higher temperature is increased, and the output equivalent voltage is decreased; the current limiting amplitude of the auxiliary discharge path corresponding to the battery with a lower temperature is decreased, and the output equivalent voltage remains stable.

[0010] In one alternative embodiment, in step 6, the output equivalent voltage of each parallel battery auxiliary discharge path is first adjusted to be consistent with the bus voltage of the main discharge path, and the main discharge path is closed after a preset time delay. After closure, the main discharge path is turned on, and the current limiting amplitude of the auxiliary discharge path is gradually reduced to the point of being closed.

[0011] In one alternative embodiment, in step 1, the battery management system correlates the collected branch current changes with the individual cell voltage changes to obtain the dynamic internal resistance of each parallel battery, and uses the dynamic internal resistance as the basis for adjusting the auxiliary discharge path; the voltage adjustment range of the auxiliary discharge path corresponding to the battery with a larger dynamic internal resistance is lowered, and the voltage adjustment range of the auxiliary discharge path corresponding to the battery with a smaller dynamic internal resistance is increased.

[0012] In one alternative embodiment, after step 4 switches to the auxiliary discharge path, the output equivalent voltage of each parallel battery is compared with the preset equalization voltage in real time. When the difference is greater than the preset deviation value, the voltage regulation unit of the corresponding auxiliary discharge path is controlled to perform step-wise voltage regulation, and the voltage regulation amplitude does not exceed the preset voltage regulation step size each time. At the same time, the voltage regulation step size is dynamically adjusted according to the absolute value of the difference. The larger the absolute value of the difference, the larger the voltage regulation step size, and the smaller the absolute value of the difference, the smaller the voltage regulation step size, until the output equivalent voltage difference of each battery is less than the preset deviation value.

[0013] A parallel adaptive equalization output control system for lithium batteries in a battery swapping mode is provided to implement the aforementioned parallel adaptive equalization output method for lithium batteries in a battery swapping mode.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. Adopting a dual-path design, the battery achieves balance through the synergistic cooperation of existing paths. Its real-time sampling monitoring and differential pressure and circulating current detection technology can accurately capture the battery's operating status, promptly detect imbalances, and respond quickly. This avoids excessive circulating current and battery damage caused by untimely parameter monitoring, effectively improving the safety of battery operation. 2. Through the complete process of cutting off the main discharge path, switching in the auxiliary path, equalization adjustment, and switching back to the main path, the entire process of unbalanced state and normal discharge state is realized. It can not only ensure the high power discharge demand, but also achieve precise equalization, taking into account both discharge efficiency and equalization effect. 3. The design of “each cell / cluster of battery with an independent auxiliary discharge path” in this invention avoids the impact of a single path failure on the overall equalization effect. It can handle a single abnormal battery separately without stopping the overall discharge, thus improving the continuous operation capability in the battery swapping scenario. Attached Figure Description

[0015] Figure 1 This invention relates to a flowchart of a parallel adaptive equalization output method for lithium batteries in a battery swapping mode.

[0016] Figure 2 This invention relates to a simplified structural diagram of a parallel adaptive equalization output control system for lithium batteries in a battery swapping mode. In the picture

[0017] Battery Management System 1; Lithium Battery Pack 2; Main Discharge Path Module 3; Auxiliary Discharge Path Module 4. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings.

[0019] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

[0020] Reference Figure 1 and Figure 2 In battery swapping mode, when multiple lithium batteries are used in parallel, problems such as voltage imbalance and branch circulating current are likely to occur, affecting battery life and discharge safety. To address this, this embodiment details a lithium battery parallel adaptive equalization output method and corresponding control system adapted to this scenario. Its core logic is to achieve adaptive equalization adjustment through the coordinated work of the main and auxiliary dual discharge paths, taking into account both high-power discharge requirements and equalization stability, and adapting to the actual operation requirements of the battery swapping scenario.

[0021] This adaptive equalization output method is applied to multi-cell / multi-cluster parallel lithium battery packs, where each cell / cluster is equipped with a main discharge path and an independent auxiliary discharge path. The entire equalization process follows a fixed closed-loop procedure, and the specific implementation steps are as follows: First, real-time sampling and monitoring are performed. The battery management system collects the individual cell voltage, output current, branch current, and temperature parameters of each parallel battery in real time, and simultaneously calculates the voltage difference between each parallel battery in real time. The magnitude and direction of the circulating current between parallel branches are accurately detected, providing comprehensive and accurate data support for subsequent equalization adjustment. Next, abnormality judgment of circulating current / voltage difference is performed. When the voltage difference between parallel batteries exceeds the set threshold, or when obvious bidirectional circulating current (i.e., battery mutual charging current) appears in the parallel branch, it is determined that there is a parallel unbalanced circulating current problem, and the equalization adjustment process needs to be initiated. Then, the main discharge path is cut off, the main discharge path of the abnormal battery cell or all parallel battery cells is closed, and the main path is disconnected from the parallel bus. The system connects the batteries to prevent abnormal current from further damaging them. Then, it switches to the auxiliary discharge path, switching all parallel batteries to output power through their own independent auxiliary discharge paths. Through the controllable current limiting and voltage regulation functions of the auxiliary discharge path, batteries with high voltage are appropriately current-limited and controllably discharged to lower their equivalent output voltage. Batteries with low voltage are restricted from reverse backflow, allowing only stable output. After entering the adaptive balancing and circulating current elimination stage, the static and dynamic operating voltage differences between the parallel batteries are gradually smoothed out through dynamic adjustment of the auxiliary discharge path, completely eliminating the internal circulating current that causes backflow between batteries. Finally, the main discharge path is switched back. When the voltage difference between the parallel batteries returns to the set allowable range, the circulating current amplitude drops below the set threshold, and the current distribution in each branch is uniform, the main discharge path is closed again, the auxiliary discharge path is shut down, and the system switches back to the main discharge path for high-power discharge, completing a full balancing and adjustment closed loop.

[0022] The core advantage of this equalization method lies in the scientific and practical nature of its closed-loop regulation logic, which can be reflected in two aspects: parameter preset and system control. First, the battery management system presets the allowable range of differential voltage, the threshold value of circulating current amplitude, and the deviation range of branch current distribution. The preset parameters are determined based on the rated voltage, capacity, and discharge power of the battery pack, ensuring that the parameters are adapted to the actual operating conditions of the battery. After the parameters are preset, the battery management system continuously collects core parameters such as the individual cell voltage and output current of each parallel battery, and compares the monitoring data with the preset thresholds in real time to form a closed-loop monitoring logic. When the monitoring data meets the equalization standard, the system automatically sends a command to close the main discharge path and simultaneously and gradually closes the auxiliary discharge path. The entire switching process relies on the automatic control of the system to achieve continuous operation. This design utilizes the functional differences between the main and auxiliary discharge paths. The main discharge path is responsible for meeting the high-power discharge requirements, while the auxiliary discharge path is responsible for equalization and adjustment. This eliminates the need for dedicated equalization hardware, reducing hardware costs and structural complexity from the outset. Furthermore, the equalization process does not require system shutdown, achieving synchronous connection between power supply and equalization. This effectively solves the problems of circulating current loss and voltage imbalance when lithium batteries are connected in parallel under battery swapping mode, reduces battery polarization caused by long-term imbalance, slows down battery capacity decay, and extends battery cycle life. Through dynamic monitoring and automatic adjustment, it ensures equalization accuracy and discharge stability, adapting to the core requirements of frequent start-stop and high-power output in battery swapping scenarios. Its adjustment logic is highly matched to battery operating characteristics, allowing direct adaptation to multi-cell / multi-cluster parallel lithium battery packs of different specifications.

[0023] To further optimize the equalization effect and improve the practicality of the method, this equalization method also includes several targeted optimization designs. Each optimization step revolves around the core closed-loop process and is integrated with the overall technical solution. In the design of the main discharge path, a MOSFET or relay is directly connected to the parallel bus. The logic is to connect the MOSFET or relay in series to the main discharge branch of each cell / cluster of battery, with one end directly connected to the battery output and the other end seamlessly connected to the parallel bus, without any intermediate conversion components, thus reducing energy loss during path connection. The selection of the MOSFET or relay is determined based on the rated discharge power of the battery pack, ensuring that the rated current and withstand voltage of the component match the battery discharge parameters to avoid component overload damage. MOSFETs have the characteristics of low on-resistance and fast switching response, while relays have the advantages of strong anti-interference capability and high conduction reliability. Both components can achieve rapid switching on and off of the main discharge path. When the battery management system detects an imbalance anomaly, it can cut off the main discharge path in a very short time, blocking the abnormal current conduction and preventing internal damage to the battery caused by excessive circulating current and voltage imbalance. This direct connection method can minimize the conduction loss of the main discharge path, ensure the energy conversion efficiency during high-power discharge, and simplify the path structure, reducing the construction and maintenance costs. Its design logic fits the high-power, fast-response discharge requirements of the battery swapping mode. Through the synergy of component characteristics and path structure, it realizes the dual functions of high-power discharge and abnormal protection, ensuring the stable operation of the battery pack under high load conditions.

[0024] In the parameter acquisition phase, the battery management system (BMS) is set to a sampling frequency of no less than 10Hz, meaning that it completes parameter acquisition for the entire branch at least once every 0.1 seconds. This frequency is determined based on the parameter change characteristics of lithium batteries operating in parallel—the circulating current and voltage difference change rapidly when lithium batteries are connected in parallel. A sampling frequency below 10Hz will cause parameter acquisition lag, making it impossible to capture subtle imbalances in time, thus leading to delays in equalization adjustment and exacerbating battery damage. After setting this sampling frequency, the BMS can acquire the individual cell voltage, output current, branch current, and temperature parameters of each parallel battery in real time, simultaneously performing voltage difference calculations and circulating current detection between batteries. The acquired data is transmitted to the control unit in real time, providing accurate data support for voltage regulation and current limiting adjustment of the auxiliary discharge path. High-frequency sampling can effectively avoid missed or false judgments of imbalance anomalies, ensure the timeliness of equalization adjustment commands, enable the auxiliary discharge path to respond quickly to parameter changes, adjust the adjustment strategy in real time, reduce the voltage difference between batteries, eliminate circulating current, and thus improve the accuracy and efficiency of equalization adjustment. Its frequency setting logic is highly compatible with the dynamic characteristics of parallel operation of lithium batteries, ensuring the authenticity and real-time nature of monitoring data, and providing data support for the reliable operation of the entire equalization method.

[0025] To address the specificity of anomaly handling, this method employs a differentiated main discharge path control strategy. When only a single battery cell experiences a voltage differential or circulating current anomaly, only the main discharge path of that abnormal battery cell is disconnected, while the main discharge paths of the remaining normal battery cells remain open. Specifically, the battery management system can accurately locate a single abnormal battery cell through comparative analysis of real-time sampled data. Its location logic is based on the differential comparison of current and voltage parameters in each branch. The voltage and current parameters of the abnormal battery cell will deviate from the normal range, and the system can complete the location by comparing parameter thresholds, without the need for an additional location module. After location is completed, the system only sends a disconnect command to the main discharge branch of the abnormal battery cell, controlling its switching element to disconnect, while the main discharge branches of the remaining normal battery cells remain open, continuing to achieve high-power discharge through the main discharge path. The core logic of this design lies in the differentiated handling of abnormal and normal battery cells, avoiding the shutdown of the entire battery pack due to the abnormality of a single battery, maximizing the continuity of power supply, and reducing work interruptions and energy waste in battery swapping scenarios. At the same time, by only cutting off the main discharge path of abnormal batteries, targeted equalization adjustment can be performed on them, while normal batteries maintain normal discharge, reducing energy loss during the equalization adjustment process. Moreover, the abnormal handling process does not affect the overall system's operational stability. Its logical design fits the efficient and continuous power supply requirements of battery swapping scenarios, achieving the coordinated advancement of abnormal handling and normal discharge.

[0026] For the voltage regulation method of the auxiliary discharge path, either linear voltage regulation or chopper voltage regulation is adopted. The two methods can be flexibly selected according to the actual needs of the battery swapping scenario, without the need for an additional dedicated equalization module. Among them, the linear voltage regulation method is implemented by series adjustable resistors and other voltage regulating components. Its voltage regulation logic is to gradually adjust the output equivalent voltage of the auxiliary discharge path by changing the resistance value. The voltage regulation process is stable, without voltage abrupt changes, and the voltage regulation accuracy can be controlled within ±5mV. It is suitable for battery swapping scenarios with moderate discharge power and high voltage stability requirements, and can effectively avoid the impact of voltage fluctuations on the battery and electrical equipment. The chopper voltage regulation method is implemented based on pulse width modulation (PWM) technology. By adjusting the pulse duty cycle, the output voltage of the auxiliary discharge path is dynamically adjusted. Its response speed is fast (millisecond level) and energy loss is low. It is suitable for high-power discharge scenarios and can meet the high-power equalization adjustment requirements while ensuring voltage regulation accuracy. Both voltage regulation methods are integrated into the auxiliary discharge path. The structural design and the current limiting function of the auxiliary discharge path work together to achieve synchronous control of voltage regulation and current limiting. This adapts to the discharge power and voltage regulation accuracy requirements of different battery swapping scenarios. Its voltage regulation logic is highly matched with the core requirements of battery balancing. It can quickly smooth out voltage differences and ensure the stability of the regulation process, avoiding performance damage to the battery caused by improper voltage regulation.

[0027] To achieve synergy between equalization accuracy and battery protection, this method introduces temperature parameters and dynamic internal resistance parameters for coordinated adjustment during the adaptive equalization adjustment phase. Regarding temperature-linked adjustment, for batteries with excessively high temperatures, the current limiting amplitude of the corresponding auxiliary discharge path is increased, and the output equivalent voltage is decreased; for batteries with excessively low temperatures, the current limiting amplitude of the corresponding auxiliary discharge path is decreased, and the output equivalent voltage remains stable. In principle, batteries with excessively high temperatures exhibit accelerated internal chemical reaction rates. Over-discharge can lead to increased battery polarization, accelerated capacity decay, and even thermal runaway. Therefore, by increasing the current limiting amplitude of the auxiliary discharge path, the discharge current is reduced, and the output equivalent voltage is lowered, thereby reducing the battery's discharge power and internal heat generation. This achieves coordinated control of temperature and discharge power, preventing damage to high-temperature batteries due to over-discharge. For batteries with excessively low temperatures, the internal chemical reaction rate is slower, and the discharge capacity is reduced. In this case, maintaining the normal current limiting amplitude of the auxiliary discharge path and keeping the output equivalent voltage stable ensures stable external output, preventing insufficient discharge due to excessive current limiting, and ensuring voltage equalization with other batteries. This regulation logic is designed based on the temperature characteristics of lithium batteries. The linkage regulation of temperature, discharge power, and output voltage can achieve synergy between equalization accuracy and battery protection. It ensures that the voltage difference between batteries is quickly smoothed out and circulating current is eliminated. It can also optimize discharge parameters according to the battery temperature state and extend battery life. Its regulation logic is in line with the thermodynamic characteristics of lithium batteries and can effectively avoid equalization failure or battery damage caused by abnormal temperature.

[0028] In terms of dynamic internal resistance linkage adjustment, the battery management system correlates the collected branch current changes with the individual cell voltage changes to calculate the dynamic internal resistance of each parallel battery. This dynamic internal resistance is then used as the basis for adjusting the auxiliary discharge path. Batteries with higher dynamic internal resistance have their auxiliary discharge path voltage adjustment reduced, while batteries with lower dynamic internal resistance have their auxiliary discharge path voltage adjustment increased. Specifically, the dynamic internal resistance is calculated using the ratio of the branch current change ΔI to the individual cell voltage change ΔU (R=ΔU / ΔI). This calculation logic is based on Ohm's law and accurately reflects the real-time discharge performance of the battery. Batteries with higher dynamic internal resistance have higher internal polarization and weaker discharge capacity; excessive voltage adjustment can lead to over-discharge, exacerbating polarization and capacity decay. Batteries with lower dynamic internal resistance have stronger discharge capacity; appropriately increasing the voltage adjustment can quickly reduce their output equivalent voltage, ensuring voltage matching with other batteries. Using dynamic internal resistance as the basis for adjusting the auxiliary discharge path enables personalized adaptation of equalization adjustment, avoiding the problems of over-discharge of some batteries and incomplete equalization of others caused by uniform voltage regulation. By calculating the dynamic internal resistance in real time, the auxiliary discharge path can dynamically adjust the voltage regulation parameters to make the output equivalent voltage of each battery more consistent, while protecting batteries with weaker discharge capabilities and extending the overall battery pack's lifespan. Its adjustment logic combines the dynamic characteristics of the battery with Ohm's law to ensure the accuracy and rationality of equalization adjustment, improving the adaptability and reliability of the entire equalization method.

[0029] In the voltage regulation control of the auxiliary discharge path, a stepped voltage regulation strategy is adopted, and the voltage regulation step size can be dynamically adjusted according to the voltage difference and temperature parameters to further improve the balancing accuracy and safety. Specifically, after entering the auxiliary discharge path, the system compares the difference between the output equivalent voltage of each parallel battery and the preset balancing voltage in real time. When the difference is greater than the preset deviation value, the voltage regulation unit of the corresponding auxiliary discharge path is controlled to perform stepped voltage regulation, and the voltage regulation amplitude does not exceed the preset voltage regulation step size each time. At the same time, the voltage regulation step size is dynamically adjusted according to the magnitude of the absolute value of the difference. The larger the absolute value of the difference, the larger the voltage regulation step size, and the smaller the absolute value of the difference, the smaller the voltage regulation step size, until the difference in the output equivalent voltage of each battery is less than the preset deviation value. The preset equalization voltage is determined based on the battery's rated output voltage, and the preset deviation value (10mV-50mV) is set based on the equalization accuracy requirements. The core logic of the stepped voltage regulation is to avoid voltage fluctuations caused by excessive voltage adjustment amplitude. Each voltage adjustment amplitude does not exceed the preset step size (5mV-20mV), ensuring a smooth voltage regulation process and avoiding impact on the battery. The step size is dynamically adjusted according to the absolute value of the voltage difference, based on the synergistic requirements of equalization efficiency and accuracy. When the absolute value of the difference is large, a larger step size can quickly reduce the voltage difference and improve equalization efficiency. When the absolute value of the difference is small, a smaller step size can precisely fine-tune the voltage, ensuring equalization accuracy and avoiding voltage overshoot caused by excessive step size. The entire voltage regulation process forms a closed-loop regulation through real-time feedback of the voltage difference, requiring no manual intervention and automatically achieving equalization of the equivalent output voltage of each battery. Its logic design takes into account both equalization efficiency and voltage regulation stability, solving the circulating current problem caused by excessive voltage difference and avoiding damage to the battery during voltage regulation, ensuring accurate and efficient equalization adjustment.

[0030] During the dynamic adjustment of the voltage regulation step size, temperature parameters are introduced simultaneously for constraint, further improving the safety of the equalization adjustment. When the battery temperature is higher than the preset temperature threshold, the voltage regulation step size is forcibly adjusted to the preset minimum step size; when the battery temperature is lower than the preset temperature threshold, the dynamic adjustment logic of the voltage regulation step size with the absolute value of the voltage difference is maintained. The preset temperature threshold (45℃-55℃) is determined based on the safe operating temperature range of the lithium battery. Above this threshold, the battery's thermal stability decreases. If the voltage regulation step size is too large, it will cause fluctuations in the battery's discharge power, generating additional heat, exacerbating the rise in battery temperature, and even triggering the risk of thermal runaway. Therefore, when the temperature is higher than the threshold, the minimum voltage regulation step size (not greater than 5mV) is forcibly adopted, which can slow down the voltage regulation speed, reduce discharge power fluctuations, reduce heat generation, and achieve linkage constraint between temperature and voltage regulation step size to protect the safety of high-temperature batteries. When the temperature is lower than the threshold, the battery's thermal stability is good, and the original dynamic adjustment logic of the step size is maintained, which can balance equalization efficiency and accuracy, ensuring that the voltage difference is reduced rapidly. This constraint logic is designed based on the thermal characteristics of lithium batteries. It deeply integrates temperature parameters with voltage regulation step size, which avoids damage to the battery caused by voltage regulation operation at high temperatures, and does not affect the equalization efficiency at normal temperatures. This further improves the safety and reliability of equalization regulation and perfects the closed-loop control of equalization regulation.

[0031] To ensure the smooth implementation of the above-mentioned equalization method, a parallel adaptive equalization output control system for lithium batteries under battery swapping mode was designed. This system is compatible with the equalization method and can perform various equalization operations to ensure stable and reliable equalization results. The control system mainly includes a battery management system 1, a multi-cell / multi-cluster parallel lithium battery pack 2, a main discharge path module 3, and an auxiliary discharge path module 4. The modules are rationally structured and work together to form a complete closed-loop control system. The battery management system 1, as the core control unit, is electrically connected to the main discharge path module 3, the auxiliary discharge path module 4, and the lithium battery pack 2. It is primarily responsible for collecting battery parameters, detecting circulating current and differential voltage, and sending path switching and adjustment commands, serving as the "brain" of the entire system. The main discharge path module 3 includes a main discharge branch corresponding to each cell / cluster of batteries. Each main discharge branch is connected in series with a switching element (MOSFET or relay) to control the on / off state of the main discharge path, ensuring rapid response and stable operation. The auxiliary discharge path module 4 includes an independent auxiliary discharge branch corresponding to each cell / cluster of batteries. Each auxiliary discharge branch integrates a current limiting unit, a voltage regulating unit, and an impedance matching unit, enabling current limiting, voltage regulation, and circulating current elimination functions, providing hardware support for equalization adjustment. Each cell / cluster of batteries in the lithium battery pack 2 is electrically connected to its corresponding main discharge branch and auxiliary discharge branch. The output terminals of each main discharge branch and auxiliary discharge branch are connected to a parallel bus, achieving centralized current transmission and stable output.

[0032] The control system is logically designed to meet the core requirements of the equalization method. Multiple cells / clusters of lithium batteries are connected in parallel to form a lithium battery pack 2. Each cell / cluster corresponds to a main discharge branch and an auxiliary discharge branch, forming an independent discharge and equalization unit. This ensures that abnormal handling of a single cell / cluster does not affect the overall system. The switching element connected in series in the main discharge branch is electrically connected to the control terminal of the battery management system 1. It receives system commands to control the on / off state, ensuring a rapid response of the main discharge path. The auxiliary discharge branch integrates a current limiting unit (current limiting resistor), a voltage regulating unit (voltage regulating chip), and an impedance matching unit (impedance matching resistor), which work together to achieve current limiting, voltage regulation, and circulating current elimination. The impedance matching unit ensures impedance matching between the auxiliary discharge path and the main discharge path, preventing reflected current during path switching. The output terminals of all main and auxiliary discharge branches are connected to the same parallel bus to achieve centralized current transmission. The battery management system 1 collects parameters of each battery and branch through sampling lines and sends control commands through control lines, forming a closed-loop system of "acquisition-detection-adjustment-control". This structural design eliminates the need for a dedicated balancing module, simplifying the system structure and reducing costs. Simultaneously, the collaborative operation of each module allows for precise execution of the aforementioned balancing method, automating parameter acquisition, anomaly detection, path switching, and balancing adjustment. It is compatible with parallel use of lithium batteries from different batches and with varying aging levels under battery swapping conditions. Its structural logic and balancing method are highly compatible, ensuring system stability, reliability, and efficiency. It can directly achieve adaptive balancing output for parallel lithium battery connections through conventional circuit assembly and parameter presets, providing strong support for the safe and stable use of lithium batteries under battery swapping conditions.

[0033] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Unless otherwise specified, an element defined by the phrase "comprising..." or "including..." does not exclude the presence of additional elements in the process, method, article, or terminal device that includes said element. Additionally, in this document, "greater than," "less than," "exceeding," etc., are understood to exclude the stated number; "above," "below," "within," etc., are understood to include the stated number.

[0034] The above description of the embodiments is provided to facilitate understanding and use of the present invention by those skilled in the art. It is obvious to those skilled in the art that various modifications can be easily made to the embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A method for adaptive equalization output of parallel lithium batteries in a battery swapping mode, characterized in that, The method is applied to multi-cell / multi-cluster parallel lithium battery packs, wherein each cell / cluster in the lithium battery pack is configured with a main discharge path and an independent auxiliary discharge path, and the method includes the following steps: Step 1: Real-time sampling and monitoring. The battery management system collects the individual cell voltage, output current, branch current and temperature parameters of each parallel battery in real time, calculates the voltage difference between each parallel battery in real time, and detects the magnitude and direction of the circulating current between parallel branches. Step 2: Circulating current / voltage difference abnormality determination. When the voltage difference between parallel batteries exceeds the set threshold, or when a significant bidirectional circulating current (i.e., battery mutual charging current) appears in the parallel branch, it is determined that there is a parallel unbalanced circulating current problem. Step 3: Cut off the main discharge path, shut down the main discharge path of the abnormal battery cell or all parallel battery cells, and disconnect the main path from the parallel bus. Step 4: Auxiliary discharge path is switched on, and all parallel batteries are switched to output through their own independent auxiliary discharge paths. Through the controllable current limiting and voltage regulation of the auxiliary discharge path, the batteries with high voltage are appropriately current limited and controlled to discharge to reduce their output equivalent voltage. For batteries with low voltage, reverse backflow is restricted, and only stable output is allowed. Step 5: Adaptive balancing and circulating current elimination. By dynamically adjusting the auxiliary discharge path, the static voltage difference and dynamic operating condition voltage difference between parallel batteries are smoothed out, and the internal circulating current that backflows between batteries is eliminated. Step 6: Switch back to main discharge path. When the voltage difference between each parallel battery returns to the set allowable range, the circulating current amplitude drops below the set threshold, and the current distribution of each branch is uniform, the main discharge path is closed again, the auxiliary discharge path is closed, and the main discharge path is switched back to perform high-power discharge.

2. The parallel adaptive equalization output method for lithium batteries in battery swapping mode according to claim 1, characterized in that, The main discharge path is directly connected to the parallel bus using a MOS transistor or relay.

3. The parallel adaptive equalization output method for lithium batteries in battery swapping mode according to claim 1, characterized in that, The sampling frequency of the battery management system is set to no less than 10Hz.

4. The parallel adaptive equalization output method for lithium batteries in battery swapping mode according to claim 1, characterized in that, When only a single battery cell experiences a voltage difference or abnormal circulating current, the main discharge path of that abnormal battery cell is cut off, while the main discharge path of the remaining normal battery cells remains open.

5. The parallel adaptive equalization output method for lithium batteries in battery swapping mode according to claim 1, characterized in that, The auxiliary discharge path adopts either linear voltage regulation or chopper voltage regulation.

6. The parallel adaptive equalization output method for lithium batteries in battery swapping mode according to claim 1, characterized in that, In step 5, the current limiting amplitude of the auxiliary discharge path for batteries with higher temperatures is increased, and the output equivalent voltage is reduced; the current limiting amplitude of the auxiliary discharge path for batteries with lower temperatures is decreased, and the output equivalent voltage remains stable.

7. The parallel adaptive equalization output method for lithium batteries in battery swapping mode according to claim 1, characterized in that, In step 6, the output equivalent voltage of each parallel battery auxiliary discharge path is first adjusted to be consistent with the bus voltage of the main discharge path. After a preset time delay, the main discharge path is closed. After closure, the main discharge path is turned on, and the current limiting amplitude of the auxiliary discharge path is gradually reduced to the point of being closed.

8. The parallel adaptive equalization output method for lithium batteries in battery swapping mode according to claim 1, characterized in that, In step 1, the battery management system correlates the collected branch current changes with the individual cell voltage changes to obtain the dynamic internal resistance of each parallel battery. This dynamic internal resistance is used as the basis for adjusting the auxiliary discharge path. The voltage adjustment range of the auxiliary discharge path corresponding to the battery with a larger dynamic internal resistance is lowered, and the voltage adjustment range of the auxiliary discharge path corresponding to the battery with a smaller dynamic internal resistance is increased.

9. The parallel adaptive equalization output method for lithium batteries in battery swapping mode according to claim 1, characterized in that, After step 4 switches to the auxiliary discharge path, the output equivalent voltage of each parallel battery is compared with the preset equalization voltage in real time. When the difference is greater than the preset deviation value, the voltage regulation unit of the corresponding auxiliary discharge path is controlled to perform step-by-step voltage regulation. Each voltage regulation amplitude does not exceed the preset voltage regulation step size. At the same time, the voltage regulation step size is dynamically adjusted according to the absolute value of the difference. The larger the absolute value of the difference, the larger the voltage regulation step size, and the smaller the absolute value of the difference, the smaller the voltage regulation step size, until the output equivalent voltage difference of each battery is less than the preset deviation value.

10. A parallel adaptive equalization output control system for lithium batteries in a battery swapping mode, characterized in that, This method is used to implement the parallel adaptive equalization output method for lithium batteries in the battery swapping mode as described in any one of claims 1-9.

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