Method for under-voltage protection of a vehicle battery pack, battery management system, vehicle controller

Abstract

The present application belongs to the technical field of battery under-voltage protection, and particularly relates to an under-voltage protection method for a vehicle battery pack, a battery management system and a vehicle controller, the method comprising: obtaining the whole-pack voltage of the battery pack and the single-cell voltage of each internal cell of the battery pack during high-speed driving of the vehicle in a batch production stage; performing under-voltage grading diagnosis according to the whole-pack voltage and the single-cell voltage of all the cells to determine a target discharge limit strategy according to the under-voltage level after confirming that the battery pack has an under-voltage fault; and executing the target discharge limit strategy to achieve under-voltage protection of the battery pack. The present application can not only protect the battery pack well during the development stage of the vehicle to prevent immature data from causing under-voltage damage to the battery pack, but also can monitor the single-cell sampling voltage and the whole-pack voltage during driving to distinguish the severity of under-voltage and make a corresponding limited power level response, thereby protecting the battery pack and improving driving experience and driving safety.

Description

Technical Field

[0001] This invention belongs to the field of battery undervoltage protection technology, specifically relating to an undervoltage protection method for a vehicle battery pack, a battery management system, and a vehicle controller. Background Technology

[0002] With the rapid development and significant increase in the number of new energy vehicles, battery safety issues are occurring frequently, making the Battery Management System (BMS) increasingly important to the industry. Among these issues, undervoltage, overvoltage, and overtemperature of battery cells can cause irreversible damage to the battery pack. Therefore, it is necessary to design, optimize, and improve strategies and corresponding handling measures to prevent over-discharge and undervoltage of battery cells, minimizing battery pack damage as much as possible. Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a battery undervoltage protection strategy based on BMS control, which can cover most vehicle usage scenarios and take corresponding protective measures through diagnosis before and after the battery cell is undervoltage, so as to protect the battery safety as much as possible.

[0004] To achieve the above and other related objectives, the present invention provides an undervoltage protection method for a vehicle battery pack, comprising: acquiring the overall voltage of the battery pack and the individual cell voltage of each cell in the battery pack during high-speed driving of a vehicle in the mass production stage; performing undervoltage classification diagnosis based on the overall voltage and the individual cell voltages, so as to determine a target discharge limit strategy based on the undervoltage level after confirming that the battery pack has an undervoltage fault; and executing the target discharge limit strategy to achieve undervoltage protection for the battery pack.

[0005] According to a specific embodiment of the present invention, the step of performing undervoltage classification diagnosis based on the overall battery pack voltage and the individual cell voltages of all battery cells, so as to determine a target discharge limit strategy based on its undervoltage level after confirming that the battery pack has an undervoltage fault, includes: verifying the validity of the individual cell voltages of all battery cells; when the individual cell voltages of all battery cells are valid, performing a first undervoltage classification diagnosis based on the individual cell voltages of all battery cells to confirm whether the battery pack has an undervoltage fault and its corresponding first undervoltage level, and determining a target discharge limit strategy based on its first undervoltage level after the battery pack has an undervoltage fault.

[0006] According to a specific embodiment of the present invention, the step of performing a first undervoltage classification diagnosis based on the individual cell voltages of all battery cells to confirm whether the battery pack has experienced an undervoltage fault and its corresponding first undervoltage level includes: identifying the lowest individual cell voltage from all battery cells and comparing it with the threshold range of different first undervoltage levels to confirm whether the battery pack has experienced an undervoltage fault and its corresponding first undervoltage level; wherein the threshold range of different first undervoltage levels is related to the current temperature of the battery cell.

[0007] According to a specific embodiment of the present invention, the step of performing undervoltage classification diagnosis based on the overall battery pack voltage and the individual cell voltages of all battery cells, so as to determine the target discharge limit strategy based on its undervoltage level after confirming that the battery pack has an undervoltage fault, further includes: when there are one or more individual cell voltages that are invalid, performing a second undervoltage classification diagnosis based on the overall battery pack voltage to confirm whether the battery pack has an undervoltage fault and its corresponding second undervoltage level, and determining the target discharge limit strategy based on its second undervoltage level after the battery pack has an undervoltage fault.

[0008] According to a specific embodiment of the present invention, the step of performing a second undervoltage classification diagnosis based on the overall battery pack voltage to confirm whether the battery pack has experienced an undervoltage fault and its corresponding second undervoltage level includes: comparing the overall battery pack voltage with threshold ranges of different second undervoltage levels to confirm whether the battery pack has experienced an undervoltage fault and its corresponding second undervoltage level; wherein, the threshold ranges of different second undervoltage levels are related to the current temperature of the battery pack.

[0009] According to a specific embodiment of the present invention, the step of performing undervoltage classification diagnosis based on the overall battery pack voltage and the individual cell voltages of all battery cells to determine a target discharge limit strategy based on its undervoltage level after confirming an undervoltage fault in the battery pack includes: verifying the validity of the individual cell voltages of all battery cells and the validity of the overall battery pack voltage; when the individual cell voltages of all battery cells are valid and the overall battery pack voltage is valid, performing a first undervoltage classification diagnosis based on the individual cell voltages of all battery cells to confirm whether the battery pack has experienced an undervoltage fault and its corresponding first undervoltage level, and determining a first discharge limit strategy based on its first undervoltage level after the battery pack has experienced an undervoltage fault; and performing a second undervoltage classification diagnosis based on the overall battery pack voltage to confirm whether the battery pack has experienced an undervoltage fault and its corresponding second undervoltage level, and determining a second discharge limit strategy based on its second undervoltage level after the battery pack has experienced an undervoltage fault; selecting the one with higher priority from the first discharge limit strategy and the second discharge limit strategy as the target discharge limit strategy.

[0010] According to a specific embodiment of the present invention, the method further includes: acquiring the individual cell voltage of each cell in the battery pack during the testing process of the vehicle in the development stage; performing undervoltage diagnosis based on the individual cell voltage of all cells, so as to control the battery pack to reduce the high voltage after confirming that an undervoltage fault has occurred in the battery pack; wherein, the vehicle is identified as being in the development stage or the mass production stage through the interface status.

[0011] According to a specific embodiment of the present invention, the step of performing undervoltage diagnosis based on the individual cell voltages of all battery cells includes: verifying the validity of the individual cell voltages of all battery cells; when the individual cell voltages of all battery cells are valid, identifying the lowest individual cell voltage among all battery cells and comparing it with a preset threshold to confirm whether the battery pack has experienced an undervoltage fault; wherein the threshold is higher than the threshold range set for undervoltage classification diagnosis.

[0012] A method for undervoltage protection of a vehicle battery pack includes: acquiring the total current, remaining charge, and individual cell voltage of the battery pack during parking or low-speed driving of a vehicle in the mass production stage; performing low-current over-discharge fault diagnosis based on the individual cell voltages, remaining charge, and total current of the battery pack; and limiting the battery pack from continuing to discharge and prohibiting it from being connected to high voltage when a low-current over-discharge fault occurs.

[0013] According to a specific embodiment of the present invention, the step of diagnosing a small current over-discharge fault based on the individual cell voltages of all battery cells, the remaining capacity of the battery pack, and the total current of the battery pack includes: verifying the validity of the individual cell voltages of all battery cells; if the individual cell voltages of all battery cells are valid, then diagnosing a small current over-discharge fault based on the minimum individual cell voltage, the remaining capacity of the battery pack, and the total current of the battery pack; wherein, when the minimum individual cell voltage is less than a preset threshold, the total current of the battery pack is within a preset small current range, and the remaining capacity of the battery pack is less than a preset capacity, it is determined that a small current over-discharge fault has occurred in the battery pack.

[0014] According to a specific embodiment of the present invention, after limiting the continued discharge of the battery pack and prohibiting it from being charged with high voltage, the method further includes: identifying the charging port status of the vehicle; allowing the battery pack to be charged with high voltage when the vehicle is in the charging port state; and monitoring abnormal discharge behavior of the battery pack during charging to control the battery pack to be charged with high voltage when charging fails and discharge continues.

[0015] According to a specific embodiment of the present invention, the step of monitoring abnormal discharge behavior of the battery pack during charging, so as to control the high voltage of the battery pack when charging fails and discharge continues, includes: calculating the ampere-hour integral of the battery pack discharge current to determine whether the battery pack has failed to charge and continues to discharge.

[0016] A battery management system is characterized by comprising a processor coupled to a memory, the memory storing program instructions, which, when executed by the processor, implement the method described above.

[0017] A vehicle controller includes the battery management system described above.

[0018] This invention provides an undervoltage protection method for vehicle battery packs. It monitors the voltage of individual cells and the overall battery pack during vehicle operation to differentiate the severity of undervoltage and respond with corresponding power limiting levels, preventing immediate power loss. This protects the battery pack and improves driving experience and safety. Furthermore, it effectively protects the battery pack during vehicle development, preventing undervoltage damage caused by immature data and saving on compensation costs for damaged battery packs.

[0019] In addition, this invention takes into account the situation of small current over-discharge and the failure of plug-in charging, covering the vast majority of vehicle usage scenarios, and can play a protective role before the battery cell becomes undervoltage. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of a specific embodiment of an undervoltage protection method for a vehicle battery pack provided by the present invention.

[0021] Figure 2 This is a flowchart illustrating a specific embodiment of an undervoltage protection method for a vehicle battery pack provided by the present invention.

[0022] Figure 3 This is a schematic flowchart of another specific embodiment of the undervoltage protection method for a vehicle battery pack provided by the present invention;

[0023] Figure 4 This is a flowchart illustrating another specific embodiment of the undervoltage protection method for a vehicle battery pack provided by the present invention.

[0024] Figure 5 This is a structural block diagram of a specific embodiment of a battery management system provided by the present invention. Detailed Implementation

[0025] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0026] Unless otherwise defined, 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 application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0028] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0029] Example 1

[0030] Please see Figure 1 As shown, this application mainly provides an undervoltage protection method for vehicle battery packs, which consists of three parts. First, an undervoltage diagnostic strategy is added to the vehicle's BMS development stage. This strategy can disconnect the relay on the high-voltage circuit when the battery pack is about to be damaged, thus protecting the battery by reducing the high voltage. This function can be disabled during mass production, reducing the frequency of fault reports and avoiding impacting the user experience. Second, the undervoltage diagnosis and protection response are divided into multiple levels based on the undervoltage level of the vehicle's battery pack. Different levels correspond to different power level limits, protecting the battery without causing the vehicle to completely lose power, thereby ensuring driving safety. Third, a small-current over-discharge diagnostic strategy is added, taking into account conditions such as SOC, current, voltage, vehicle speed, and successful connection of the charging port, providing comprehensive over-discharge protection before the battery pack becomes truly undervoltage. Based on the above, the software protection strategy of the BMS can be improved across all scenarios to achieve undervoltage protection for the vehicle battery pack.

[0031] Firstly, during the vehicle development phase, logic design can be used to enable the software program within the BMS to recognize this stage and activate the corresponding undervoltage protection function. In practical applications, the development of the BMS, whether at the software or hardware level, requires continuous testing of its performance, necessitating the establishment of connections through its software or hardware interfaces. However, when the vehicle enters actual production, these testing interfaces will be closed to prevent interference with the normal operation of the BMS or to prevent other manufacturers from cracking its core technologies.

[0032] Therefore, relevant software programs for identifying interface status can be pre-written in the BMS, enabling the BMS to correctly identify the current status and thus enable the undervoltage protection function of the battery pack during the development phase to avoid irreversible damage to the battery pack during testing.

[0033] Furthermore, this function is only enabled during the development phase. Once the BMS detects a change in the interface status, or fails to detect the corresponding interface status (i.e., the vehicle has entered production (mass production phase), this function will be disabled to avoid redundancy with other undervoltage protection strategies. This also serves as a preventative measure; even if the data settings for this function are incorrect, it will not affect the undervoltage protection strategy during mass production.

[0034] Specific steps are as follows Figure 2 As shown, it includes:

[0035] Step S100: Obtain the individual cell voltage of each cell in the battery pack during the testing process of the vehicle in the development phase.

[0036] Step S120: Perform undervoltage diagnosis based on the individual cell voltage of all cells, so as to control the battery pack to reduce the voltage after confirming that an undervoltage fault has occurred.

[0037] Therefore, for undervoltage fault identification during vehicle development, the system collects the individual cell voltages within the battery pack in real time. If the minimum cell voltage, Umin (the lowest of all cell voltages), is less than or equal to a preset threshold, Uprotect (slightly higher or roughly equal to the initial undervoltage risk threshold provided by the cell manufacturer), and remains in this state after a certain delay (e.g., 2 seconds), it indicates an undervoltage fault in the battery pack. The BMS will then report the undervoltage fault and send a request to reduce the high voltage. The actuator will then disconnect the relays in the high-voltage circuit to reduce the high voltage, preventing further discharge of the battery pack. It can be understood that responding by directly reducing the high voltage, rather than simply limiting the power, can protect the battery in a timely manner to a large extent.

[0038] Furthermore, the aforementioned undervoltage fault identification can also simultaneously monitor other factors such as the battery pack's current parameters and SOC parameters, thereby improving the reliability of undervoltage diagnosis. No further limitations are imposed on this aspect. Modifications and refinements made by those skilled in the art to the embodiments of the present invention without departing from the spirit of the present invention still fall within the scope of the invention application patent of the present invention.

[0039] It is important to add that the validity of the collected individual cell voltages needs to be verified. That is, all data collected by the relevant acquisition devices needs to be verified to avoid data abnormalities caused by acquisition device failure, which would affect the accuracy of battery pack undervoltage diagnosis. Of course, this is not limited to verifying the validity of individual cell voltages. If other parameters, such as current parameters and SOC parameters, are used for comprehensive diagnosis, they also need to be verified. Undervoltage diagnosis of the battery pack can only be performed if all data are valid. For example, if the individual cell voltages of all collected cells are valid, the minimum value can be used to diagnose whether the battery pack has an undervoltage fault. Otherwise, an alarm should be triggered to remind the developers.

[0040] Secondly, for the mass production stage of vehicles, the undervoltage protection function configured by the BMS can also be enabled by identifying the interface status, but it is not limited to this method, and there are no restrictions on how the undervoltage protection function is enabled. It is understood that the undervoltage protection function configured in the mass production stage is different from the undervoltage protection function configured in the development stage. Considering that the battery pack cannot be directly subjected to high voltage during vehicle operation, different levels of undervoltage faults can be defined to limit the output power of the battery pack. This further protects the safety of the vehicle's battery pack while ensuring the safety of the driver and the vehicle. For example, a high-level undervoltage fault will limit higher output power, while a low-level undervoltage fault will limit lower output power, which will not affect the vehicle's operation and will also maintain battery safety.

[0041] Specific steps are as follows Figure 3 As shown, it includes:

[0042] Step S210: Obtain the overall battery pack voltage and the individual cell voltage of each cell in the battery pack during high-speed driving of the vehicle in the mass production stage.

[0043] Step S220: Perform undervoltage classification diagnosis based on the overall pack voltage and the individual cell voltage of all cells, so as to determine the target discharge limit strategy according to its undervoltage level after confirming that the battery pack has an undervoltage fault.

[0044] Step S230: Execute the target discharge limit strategy to achieve undervoltage protection for the battery pack.

[0045] It should be noted that in this embodiment, four levels of undervoltage faults are defined. By collecting the individual cell voltages of each cell in the battery pack in real time, the system can diagnose whether the battery pack has experienced an undervoltage fault and its corresponding undervoltage level.

[0046] In the case of the least severe undervoltage, an additional level of undervoltage fault diagnosis is added. That is, when the minimum value Umin of the cell voltage is less than or equal to the preset threshold Uwarn, and this state persists after a delay time (e.g., 5s), it indicates that an undervoltage fault has occurred in the battery pack. In this case, the BMS will first report the undervoltage fault. Moreover, since the undervoltage situation is relatively mild, a message can be sent to reduce the discharge power to 80% of the maximum power, and a response to limit the output power to 80% of the maximum power is executed.

[0047] For a more severe undervoltage situation, an additional level of undervoltage fault diagnosis is added. That is, when the minimum value Umin of the cell voltage is less than or equal to the preset threshold Ualarm (Ualarm < Uwarn), and this state persists after a 5s delay time, it indicates that the undervoltage situation in the battery pack has worsened. Similarly, the BMS will first report the undervoltage fault, and then send a message to reduce the discharge power to 50% of the maximum power to execute a more stringent response of limiting the output power to 50% of the maximum power.

[0048] If the undervoltage continues to deteriorate, an additional level of undervoltage fault diagnosis is added. That is, when the minimum value Umin of the cell voltage is less than or equal to the preset threshold Uerror (Uerror < Ualarm < Uwarn), and this state persists after a 5s delay time, it indicates that the undervoltage in the battery pack continues to deteriorate. The BMS will continue to first report the undervoltage fault, and then send a message to reduce the discharge power to 20% of the maximum power to further limit the discharge power of the battery pack.

[0049] If the undervoltage still does not improve, an additional level of undervoltage fault diagnosis is added. That is, when the minimum value Umin of the cell voltage is less than or equal to the preset threshold Uerrftal (Uerrftal < Uerror < Ualarm < Uwarn), and this state persists after a 2s delay time, the BMS reports the undervoltage fault and then sends a message to reduce the discharge power to 0, no longer allowing the battery pack to discharge. It can also achieve lowering the high voltage at a lower vehicle speed through the VCU (Vehicle Control Unit) and cut off the relay on the high-voltage circuit to fundamentally protect the battery pack.

[0050] Among them, the values of the above thresholds Uerrftal, Uerror, Ualarm, and Uwarn are all related to the current temperature of the battery cell. For example, in this embodiment, the smallest one among the cell voltages is selected for judgment, and the temperature of the battery cell corresponding to the minimum value of the cell voltage can be detected accordingly, so as to select the thresholds Uerrftal, Uerror, Ualarm, and Uwarn within the corresponding temperature range. In this regard, for each of Uerrftal, Uerror, Ualarm, and Uwarn, the values in different temperature ranges can be preset in advance and stored in the database for direct call, so as to ensure the reliability of the undervoltage fault diagnosis.

[0051] Therefore, by using the minimum value of the individual cell voltage to determine whether the battery pack has experienced an undervoltage fault and the corresponding undervoltage level, the appropriate discharge limit strategy can be implemented to protect the safety of the battery pack.

[0052] Similarly, before performing undervoltage diagnosis based on the minimum value of a single cell voltage, it is also necessary to verify the validity of the single cell voltage. That is, only when the single cell voltage of all cells is valid will the minimum value of the single cell voltage be compared with the preset threshold range.

[0053] Furthermore, to avoid the inability to perform undervoltage diagnosis due to invalid individual cell voltages, a redundant system is set up to diagnose whether the battery pack has an undervoltage fault and its corresponding undervoltage level by real-time acquisition of the overall battery pack voltage.

[0054] Specifically, multiple fault levels can be pre-defined, and corresponding fault diagnoses can be set accordingly. When the collected total battery pack voltage BattPrs_u is less than or equal to the threshold Upack set for different fault levels, and remains in this state after a 5-second delay, it indicates that the battery pack has an undervoltage fault. The BMS first reports the undervoltage fault, and then sends a signal to reduce the discharge power to a preset value, such as 0. The VCU then sends a slow high voltage reduction signal. That is, after receiving this fault signal, the VCU will slowly reduce the power to 0 within 60 seconds, and finally reduce the high voltage to protect the battery pack and give the driver enough time to park. The specific graded diagnosis will not be detailed here, but it is basically the same as the undervoltage graded diagnosis using the individual cell voltages mentioned above. The total battery pack voltage is compared with different preset thresholds to determine the undervoltage fault level, thereby responding to the corresponding discharge limit strategy. The value of the preset threshold for different fault levels is also related to the current temperature of the battery pack. For any undervoltage fault level, the value of the preset threshold for the current undervoltage fault level needs to be determined based on the current temperature of the battery pack to adapt to temperature changes in the battery pack.

[0055] Based on the above, when the voltage of a single cell is valid, that is, when all single cell voltages are verified to be valid, the single cell voltage can be used for undervoltage classification diagnosis. When the voltage of a single cell is invalid, that is, when one or more single cell voltages are invalid, the voltage of the entire battery pack can be used for undervoltage classification diagnosis, thereby achieving dual protection function.

[0056] Therefore, the validity of the overall battery pack voltage also needs to be verified. If both the individual cell voltage and the overall battery pack voltage are valid, a first undervoltage classification diagnosis can be performed based on the individual cell voltage to confirm whether the battery pack has an undervoltage fault and its corresponding first undervoltage level. Based on the first undervoltage level, a corresponding first discharge limit strategy can be determined. A second undervoltage classification diagnosis can also be performed based on the overall battery pack voltage to confirm whether the battery pack has an undervoltage fault and its corresponding second undervoltage level. Based on the second undervoltage level, a corresponding second discharge limit strategy can be determined.

[0057] It is understandable that the first and second undervoltage classification diagnoses can be consistent or inconsistent. That is, the fault levels can be the same or different, and the discharge limit strategies can be the same or different. Accordingly, the results of undervoltage classification diagnoses of the battery pack using the individual cell voltage and the overall battery pack voltage may differ, and the corresponding discharge limit strategies may also conflict.

[0058] Therefore, when it is necessary to respond to both the first and second discharge limit strategies simultaneously, the target discharge limit strategy needs to be identified. Specifically, the strategy with higher priority is selected from the first and second discharge limit strategies for response. For example, if the first discharge limit strategy requires limiting the battery pack's discharge power to 30%, while the second discharge limit strategy requires limiting the battery pack's discharge power to 40%, then the former is selected as the target discharge limit strategy and the response is executed accordingly.

[0059] In addition, if either the overall voltage of the battery pack or the individual cell voltage is invalid, the valid voltage can be used for undervoltage classification diagnosis. If both voltages are invalid, an alarm will be triggered to alert the user.

[0060] Therefore, differentiating undervoltage conditions to limit power output response and classifying undervoltage into multiple fault levels based on individual cell undervoltage severity or overall pack undervoltage conditions can improve protection coverage. Even if there is a problem with individual cell voltage sampling, undervoltage protection can still be performed by sampling the overall pack voltage. Conversely, even if there is a problem with overall pack voltage sampling, undervoltage protection can still be performed by sampling individual cell voltages, thereby improving the reliability of battery pack undervoltage diagnosis.

[0061] It should also be added that the voltage threshold set for diagnosing undervoltage faults using the single-cell voltage of the battery cell during the development stage needs to be higher than the voltage threshold set during mass production, that is, Uerrftal < Uerror < Ualarm < Uwarn < Uprotect. It can be understood that since the capabilities of the BMS need to be continuously adjusted and tested during the development stage, in order to avoid damage to the battery pack during this process, the upper limit of the threshold is raised to fully protect the safety of the battery pack. During mass production, the BMS state has stabilized, and relatively dangerous situations are unlikely to occur again, so the corresponding threshold can be set according to the actual capabilities of the battery pack.

[0062] The above undervoltage diagnosis is specifically applied when the vehicle is traveling at high speed. When the vehicle is parked or traveling at low speed, the following method can be used to尽可能地 avoid the occurrence of undervoltage faults in the battery pack.

[0063] The specific steps are as Figure 4 shown, including:

[0064] Step S310, obtain the total current of the battery pack, the remaining power, and the single-cell voltage of each internal battery cell during the parking process or low-speed driving process of the vehicle during mass production.

[0065] Step S320, perform small-current over-discharge fault diagnosis based on the single-cell voltage of all battery cells, the remaining power of the battery pack, and the total current of the battery pack.

[0066] Step S330, when a small-current over-discharge fault occurs in the battery pack, limit the battery pack from continuing to discharge and prohibit it from going on high voltage.

[0067] Identify the abnormal discharge behavior of the battery pack through small-current over-discharge fault diagnosis, and then stop it in time to avoid the occurrence of undervoltage faults in the battery pack. Specifically, by continuously collecting the single-cell voltage of each battery cell in the battery pack and the total current of the battery pack (incoming current), when the minimum value of the single-cell voltage Umin < Ulowsoc (usually set Ulowsoc > Uwarn), and the total current i is in the small-current range of [-2A, 2A], and this state remains after 三分钟, the BMS reports a fault. It should be noted here that the validity of the single-cell voltage of the battery cell also needs to be verified first, and after confirming that they are all valid, the minimum value Umin is identified from the single-cell voltages of all battery cells.

[0068] It should be noted that the text you provided contains some Chinese characters that seem to be incorrect or incomplete in the English translation part (such as "尽可能地" in and "三分钟" in ). If you can correct these parts, the translation will be more accurate. Also, the " " etc. are likely some kind of specific identifiers in a system and are left unchanged as required.Furthermore, this fault diagnosis can also consider the battery pack's SOC condition. When the SOC is less than 3% and the above conditions are met, the BMS will then report a fault. Finally, the BMS can send a message indicating that the feedback power and discharge power have decreased to 0, and execute a response, thereby preventing the battery pack from continuing to discharge with a low current under high voltage conditions, thus protecting the battery pack before an undervoltage situation actually occurs. It can also be understood that if the vehicle is traveling at low speed, the system can control the battery pack's discharge power to gradually decrease to 0; if the vehicle is parked, the system can directly control the battery pack to reduce its high voltage.

[0069] Furthermore, high voltage is generally prohibited for this fault to prevent continued discharge after high voltage is applied. However, when this fault occurs, users may plug in the charging gun to charge the battery pack at high voltage. Considering this situation, the function of applying high voltage to the battery pack under plug-in conditions can be allowed, and the fault will be cleared when Umin > Ulowsoc. To prevent the battery pack from continuing to discharge under high voltage after plug-in charging failure, the discharge current of the battery pack can be integrated in ampere-hours to monitor abnormal discharge behavior. When the integrated value reaches a certain threshold, such as 150As, a fault is reported. The corresponding BMS sends a feedback power and a message indicating that the discharge power has dropped to 0, limiting the output power of the battery pack to 0, requesting the disconnection of the relay on the high voltage circuit to reduce the high voltage, and re-prohibiting high voltage application. Alternatively, when the BMS receives a battery pack charging failure report from other functional modules, it can also directly control the battery pack to reduce the high voltage, thereby protecting the battery pack from further damage caused by continued discharge after the small current over-discharge fault is cleared by plug-in charging.

[0070] It should be noted that the steps of the various methods described above are only for clarity. In practice, they can be combined into one step or some steps can be split into multiple steps. As long as they contain the same logical relationship, they are all within the scope of protection of this application. Adding insignificant modifications or introducing insignificant designs to the algorithm or process, but without changing the core design of the algorithm and process, are also within the scope of protection of this application.

[0071] Example 2

[0072] Please see Figure 5 As shown, embodiments of this application also provide a battery management system, including a memory 2, a processor 1, and a program stored in the memory and executable on the processor, wherein the processor executes the steps of any of the methods described above.

[0073] The memory includes at least one type of readable storage medium, such as flash memory, portable hard drive, multimedia card, card-type memory (e.g., SD or DX memory), magnetic memory, magnetic disk, optical disk, etc. In some embodiments, the memory can be a portable hard drive; in other embodiments, it can be an external storage device, such as a plug-in portable hard drive, smart media card (SMC), secure digital (SD) card, flash card, etc. The memory can be used not only to store application software and various types of data installed in the battery management system, but also to temporarily store data that has been output or will be output.

[0074] In some embodiments, the processor can be composed of integrated circuits, such as a single packaged integrated circuit or multiple integrated circuits packaged with the same or different functions. This includes combinations of one or more central processing units (CPUs), microprocessors, digital processing chips, graphics processors, and various control chips. The processor is the control unit, connecting to various components of the entire battery management system via various interfaces and lines. It executes programs or modules stored in the memory and calls data stored in the memory to perform various functions and process data within the battery management system.

[0075] The processor executes the operating system of the battery management system and various installed applications. The processor executes the applications to implement the steps in the above method embodiments.

[0076] For example, the program can be divided into one or more modules, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules can be a series of program instruction segments capable of performing specific functions, which describe the execution process of the program in the battery management system.

[0077] Example 3

[0078] Embodiments of this application also provide a vehicle controller, including the battery management system described above.

[0079] In summary, this invention provides an undervoltage protection method for vehicle battery packs. This method effectively protects the battery pack during the vehicle development phase, preventing undervoltage damage caused by immature data and saving on compensation costs for damaged battery packs. Furthermore, when actual cell undervoltage occurs during driving, monitoring can be performed not only based on individual cell sampling voltages but also on the collected overall pack voltage. This allows for differentiation of the severity of the undervoltage and appropriate power limiting responses, preventing immediate power loss. This approach protects the battery pack and improves driving experience and safety.

[0080] In addition, this invention takes into account the situation of small current over-discharge and the failure of plug-in charging, covering the vast majority of vehicle usage scenarios, and can play a protective role before the battery cell becomes undervoltage.

[0081] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

[0082] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

Claims

1. A method of under-voltage protection for a vehicle battery pack, the method comprising: The method comprises: obtaining the whole-pack voltage of the battery pack and the single-cell voltage of each cell in the battery pack of the vehicle in the batch production stage during high-speed driving; performing under-voltage grading diagnosis according to the whole-pack voltage and the single-cell voltage of all cells to determine a target discharge limit strategy according to the under-voltage level of the battery pack after confirming that the battery pack has an under-voltage fault, and the step comprises: checking the validity of the single-cell voltage of all cells; when the single-cell voltage of all cells is valid, performing first under-voltage grading diagnosis according to the single-cell voltage of all cells to confirm whether the battery pack has an under-voltage fault and its corresponding first under-voltage level, and determining a target discharge limit strategy according to the first under-voltage level of the battery pack after the battery pack has an under-voltage fault; when the single-cell voltage of one or more cells is invalid, performing second under-voltage grading diagnosis according to the whole-pack voltage to confirm whether the battery pack has an under-voltage fault and its corresponding second under-voltage level, and determining a target discharge limit strategy according to the second under-voltage level of the battery pack after the battery pack has an under-voltage fault; performing the target discharge limit strategy to achieve under-voltage protection of the battery pack.

2. The method of under-voltage protection of a vehicle battery pack of claim 1, wherein, The step of performing first under-voltage grading diagnosis according to the single-cell voltage of all cells to confirm whether the battery pack has an under-voltage fault and its corresponding first under-voltage level comprises: identifying the minimum single-cell voltage from the single-cell voltage of all cells, and comparing it with the threshold range of different first under-voltage levels respectively to confirm whether the battery pack has an under-voltage fault and its corresponding first under-voltage level; wherein the threshold range of different first under-voltage levels is related to the current temperature of the cell.

3. The method of under-voltage protection of a vehicle battery pack of claim 1, wherein, The step of performing second under-voltage grading diagnosis according to the whole-pack voltage to confirm whether the battery pack has an under-voltage fault and its corresponding second under-voltage level comprises: comparing the whole-pack voltage with the threshold range of different second under-voltage levels to confirm whether the battery pack has an under-voltage fault and its corresponding second under-voltage level; wherein the threshold range of different second under-voltage levels is related to the current temperature of the battery pack.

4. The method of under-voltage protection of a vehicle battery pack of claim 1, wherein, The step of performing under-voltage grading diagnosis according to the whole-pack voltage and the single-cell voltage of all cells to determine a target discharge limit strategy according to the under-voltage level of the battery pack after confirming that the battery pack has an under-voltage fault comprises: checking the validity of the single-cell voltage of all cells and the validity of the whole-pack voltage; when the single-cell voltage of all cells is valid and the whole-pack voltage is valid, performing first under-voltage grading diagnosis according to the single-cell voltage of all cells to confirm whether the battery pack has an under-voltage fault and its corresponding first under-voltage level, and determining a first discharge limit strategy according to the first under-voltage level of the battery pack after the battery pack has an under-voltage fault; and performing second under-voltage grading diagnosis according to the whole-pack voltage to confirm whether the battery pack has an under-voltage fault and its corresponding second under-voltage level, and determining a second discharge limit strategy according to the second under-voltage level of the battery pack after the battery pack has an under-voltage fault; selecting the one with higher priority from the first discharge limit strategy and the second discharge limit strategy as the target discharge limit strategy.

5. The method of under-voltage protection of a vehicle battery pack of claim 1, wherein, The method further comprises: obtaining the single-cell voltage of each cell in the battery pack of the vehicle in the development stage during testing; The under-voltage diagnosis is performed according to the single voltages of all the battery cells, so as to control the battery pack to be under high voltage after confirming that the battery pack has an under-voltage fault. The interface state is used to identify whether the vehicle is in a development stage or a batch production stage.

6. The method of under-voltage protection of a vehicle battery pack of claim 5, wherein, The under-voltage diagnosis according to the single voltages of all the battery cells comprises: checking the validity of the single voltages of all the battery cells; when the single voltages of all the battery cells are valid, identifying the minimum single voltage from the single voltages of all the battery cells, and comparing the minimum single voltage with a preset threshold value, so as to confirm whether the battery pack has an under-voltage fault; The threshold value is higher than the threshold value range set by the under-voltage grading diagnosis.

7. A method of under-voltage protection for a vehicle battery pack, the method comprising: It comprises: obtaining the whole-pack current, the remaining capacity of the battery pack, and the single voltages of the battery cells in the vehicle in the batch production stage during parking or low-speed driving; The small-current over-discharge fault diagnosis is performed according to the single voltages of all the battery cells, and the remaining capacity and the whole-pack current of the battery pack, and the steps comprise: checking the validity of the single voltages of all the battery cells; when the single voltages of all the battery cells are valid, performing the small-current over-discharge fault diagnosis according to the minimum single voltage, and the remaining capacity and the whole-pack current of the battery pack; wherein, when the minimum single voltage is less than a preset threshold value, the whole-pack current of the battery pack is in a preset small-current range interval, and the remaining capacity of the battery pack is less than a preset capacity, it is determined that the battery pack has a small-current over-discharge fault; 8. The method of under-voltage protection of a vehicle battery pack of claim 7, wherein, When the battery pack has a small-current over-discharge fault, the battery pack is limited to continue discharging, and is prohibited to be under high voltage. After the battery pack is limited to continue discharging, and is prohibited to be under high voltage, it further comprises: identifying the plug-in state of the vehicle; when the vehicle is in the plug-in charging state, the battery pack is allowed to be under high voltage; 9. The method of under-voltage protection of a vehicle battery pack of claim 8, wherein, monitoring the abnormal discharging behavior of the battery pack during charging, so as to control the battery pack to be under high voltage when the charging fails and the discharging continues. The step of monitoring the abnormal discharging behavior of the battery pack during charging, so as to control the battery pack to be under high voltage when the charging fails and the discharging continues, comprises:

10. A battery management system, characterized by, calculating the ampere-hour integral of the discharging current of the battery pack, so as to determine whether the battery pack has a charging failure and continues to discharge.

11. A vehicle controller characterized by comprising: The battery management system comprises a processor and a memory coupled to the processor, and the memory stores program instructions, which, when executed by the processor, implement the method of any one of claims 1 to 9. The battery management system comprises the battery management system of claim 10.

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