A method and device for determining internal resistance of an electric cell, and a battery management system

Abstract

The application provides a kind of determination method and device of electric core resistance, battery management system, the determination method of electric core resistance, including the working condition data of electric core in real time acquisition, wherein, working condition data includes voltage, current, state of charge and temperature.According to voltage, current, state of charge and temperature, the electric core resistance is determined.Through the above-mentioned mode, the electric core resistance of more accurate can be calculated.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a method and apparatus for determining the internal resistance of a battery cell, and a battery management system. Background Technology

[0002] With increasingly severe energy and environmental problems, strong national support for new energy sources, and the growing maturity of power battery technology, electric vehicles have become a new direction for the future development of the automotive industry. The driving range of electric vehicles is a crucial factor influencing their widespread adoption. As a key component, the battery pack is the primary power source for electric vehicles, making its stable and reliable quality paramount.

[0003] For battery packs, the internal resistance of the cells can well reflect the health status of the cells, and thus the health status of the battery pack. Therefore, the internal resistance of the cells is a relatively important parameter among the characteristics of the battery pack.

[0004] In existing technologies, the internal resistance of a battery cell is typically calculated using six months of data. However, this method ignores the fact that the internal resistance changes continuously during the aging process of the battery cell, resulting in a significant deviation between the calculated internal resistance and the actual value. Summary of the Invention

[0005] This application aims to provide a method and apparatus for determining the internal resistance of a battery cell, and a battery management system, which can calculate the internal resistance of the battery cell more accurately.

[0006] To achieve the above objectives, in a first aspect, this application provides a method for determining the internal resistance of a battery cell. The method includes real-time acquisition of operating condition data of the battery cell, wherein the operating condition data includes voltage, current, state of charge, and temperature. The internal resistance of the battery cell is determined based on the voltage, current, state of charge, and temperature.

[0007] The operating conditions, such as voltage, current, state of charge, and temperature, change continuously during the battery cell's use. This means that the aforementioned operating condition data accurately reflects the changing characteristics of the battery cell's internal resistance. Therefore, the internal resistance calculated by combining this operating condition data has a small deviation from the actual internal resistance, resulting in a relatively accurate internal resistance. Furthermore, by monitoring the battery cell's operating condition data in real time, the internal resistance can be determined in real time, allowing for real-time assessment of the battery cell's health. This helps to fully utilize the battery cell's performance and extend its lifespan. Simultaneously, this method for determining the internal resistance is relatively simple, improving practicality and reducing computational workload, thus increasing the efficiency of determining the internal resistance.

[0008] In one alternative approach, the internal resistance of the battery cell is determined based on voltage, current, state of charge, and temperature, including: if the state of charge is within a first state of charge range and the temperature is within a first temperature range, then the internal resistance of the battery cell is determined based on voltage and current.

[0009] When the cell's state of charge (SOC) is within the first SOC range and its temperature is within the first temperature range, the average state of the cell can be better reflected. Under these conditions, the obtained operating data more accurately reflects the actual situation of the cell, thus leading to a more accurate determination of the cell's internal resistance based on this data. Furthermore, sampling data within a specific range increases the probability of successful data collection, which improves work efficiency.

[0010] In one optional approach, determining the cell's internal resistance based on voltage and current includes: acquiring a first time period and a second time period, wherein the end time of the second time period is the current time; acquiring a first duration of the first time period and acquiring a first charge / discharge rate of the cell during the first time period based on the current; acquiring a second duration of the second time period and acquiring a second charge / discharge rate of the cell during the second time period based on the current, and acquiring the current's trend; and determining the cell's internal resistance based on voltage, the first duration, the second duration, the first rate, the second rate, and the trend.

[0011] Using the current moment as the end moment, two consecutive time periods that meet the requirements are obtained. Based on the correspondence between actual parameters such as current and voltage and the internal resistance of the battery cell during these two time periods, the internal resistance of the battery cell can be calculated and determined in real time. Compared with the existing technology that uses six months of data to calculate the internal resistance of the battery cell, the internal resistance of the battery cell determined in this application can be calculated in real time, resulting in a smaller deviation from the actual value and higher accuracy.

[0012] In one alternative approach, the cell internal resistance is determined based on voltage, a first duration, a second duration, a first multiplier, a second multiplier, and a trend of change, including: if the current has a monotonic trend of change, and / or the current fluctuates within a first current range, and the second duration is not less than a second duration threshold, and the second multiplier is not less than a second multiplier threshold, then the cell internal resistance is determined based on voltage, the first duration, and the first multiplier.

[0013] The conditions mentioned above are the conditions that must be met in the second time period. That is, first determine whether the requirements are met in the second time period; if the conditions are met in the second time period, then further determine whether the requirements are met in the first time period. By progressively determining whether the requirements are met in each time period, the amount of calculation work can be reduced, which is beneficial to improving the efficiency of determining the cell's internal resistance.

[0014] In one alternative approach, the cell internal resistance is determined based on the voltage, a first duration, and a first multiplier, including: if the first duration is not less than a first duration threshold and the first multiplier is not greater than a first multiplier threshold, then the cell internal resistance is determined based on the voltage and the current during a second time period.

[0015] The conditions described above are the requirements to be met during the first time period. By further ensuring that the requirements are met during the first time period, the probability of the cell's current voltage deviating from its steady-state voltage or equilibrium potential can be reduced, thus obtaining a voltage with minimal polarization. This allows for more reliable voltage data, which is beneficial for improving the accuracy of calculating the cell's internal resistance.

[0016] In one alternative approach, determining the cell's internal resistance based on the voltage and the current during the second time period includes: determining whether the current during the second time period is a constant current. If so, the current during the second time period is determined as a first current. If not, an equivalent current is obtained based on the current during the second time period, and this equivalent current is determined as the first current. The cell's internal resistance is then determined based on the first current and the voltage.

[0017] If the current in the second time period is a constant current, it can be directly sampled for subsequent calculations. If the current in the second time period is not a constant current, it needs to be converted into a corresponding constant current, that is, the current is equivalent to a constant current, which makes the subsequent steps of calculating the cell internal resistance simpler.

[0018] In one alternative approach, the equivalent current is:

[0019] Where t is any moment within the second time interval. Let w(t) be the equivalent current, w(t) be the weighting function, and I(t) be the current that varies with time. Let n be the time when the second time period ends, where n is a positive integer and 2 ≤ n ≤ 6.

[0020] In the above formula, the weight of the current at each moment in the second time period is first calculated, and then each weight is multiplied by the current at the corresponding moment and summed to obtain the equivalent current.

[0021] In one alternative approach, before determining the cell internal resistance based on the first current and voltage, the method further includes: determining that the first current is within a second current range.

[0022] By limiting the first current to the second current range, the internal resistance of the battery cell obtained under different currents can be made similar, which can improve the accuracy of the calculation.

[0023] In one alternative approach, determining the cell internal resistance based on a first current and voltage includes: acquiring a first voltage difference between the voltage at the end of a first time period and the voltage at the end of a second time period; and determining the cell internal resistance based on the first voltage difference and the first current.

[0024] If the current increases, the voltage difference will also increase under the same conditions. By observing the characteristics of the change between the current and the voltage difference, it can be determined whether the currently obtained first voltage difference and first current are reliable.

[0025] In one alternative approach, before determining the cell internal resistance based on the first voltage difference and the first current, the method further includes: designating the current first voltage difference as the Nth first voltage difference, designating the current first current as the Nth first current, and obtaining the Nth first internal resistance based on the ratio of the Nth first voltage difference to the Nth first current, where N is a positive integer greater than 1. The method also involves obtaining the (N-1)th first voltage difference and the (N-1)th first current, and obtaining the (N-1)th first internal resistance based on the ratio of the (N-1)th first voltage difference to the (N-1)th first current. Finally, the method calculates the absolute value of the difference between the Nth and (N-1)th first internal resistances and the first ratio of the (N-1)th first internal resistance. If the absolute value of the (N-1)th first current is greater than the absolute value of the Nth first current, then the absolute value of the (N-1)th first voltage difference is greater than the absolute value of the Nth first voltage difference; or if the absolute value of the (N-1)th first current is less than the absolute value of the Nth first current, then the absolute value of the (N-1)th first voltage difference is less than the absolute value of the Nth first voltage difference, and the first ratio is less than or equal to the first ratio threshold, then the cell internal resistance is determined based on the first voltage difference and the first current.

[0026] By acquiring two adjacent first voltage differences and first currents, if the variation characteristics between the current and voltage differences conform to preset variation characteristics, the cell internal resistance can be further determined based on the first voltage difference and first current. This eliminates discrepancies caused by sampling errors, thus improving the accuracy of the subsequently calculated cell internal resistance.

[0027] In one alternative approach, the cell internal resistance is determined based on a first voltage difference and a first current, including: the cell internal resistance is: Wherein, DCR is the internal resistance of the battery cell. This is the absolute value of the first voltage difference. K is the absolute value of the first current, where K is greater than or equal to 0.8 and less than or equal to 1.2.

[0028] When obtaining the first current, it may be an equivalent current obtained through a non-constant current conversion, and errors may exist in the conversion process. By setting the value of K, these errors can be corrected according to the actual application, thereby improving the accuracy of the calculation.

[0029] In one alternative approach, after determining the cell's internal resistance, the method further includes: calculating a second ratio between the cell's internal resistance and its initial internal resistance. The second ratio reflects the degree of cell aging, and the initial internal resistance is the internal resistance of a cell before aging.

[0030] Based on the second ratio, dynamic assessment of the cell's internal resistance throughout its entire lifecycle can be achieved, enabling the battery management system to manage the cells more effectively and thus allowing the cell's performance to be fully utilized. Simultaneously, the second ratio can also be used to measure the growth pattern of the cell's internal resistance and reflect the degree of cell degradation, which can be used for power degradation calculations. Furthermore, based on the degree of degradation, the cell's output power can be controlled, effectively reducing the risk of cell damage and extending the cell's lifespan.

[0031] Secondly, this application provides a device for determining the internal resistance of a battery cell, comprising: a data acquisition unit for real-time acquisition of operating condition data of the battery cell, wherein the operating condition data includes voltage, current, state of charge, and temperature; and a first determination unit for determining the internal resistance of the battery cell based on the voltage, current, state of charge, and temperature.

[0032] Thirdly, this application provides an apparatus for determining the internal resistance of a battery cell, comprising: a memory, and a processor coupled to the memory, the processor being configured to execute the method described in any of the preceding claims based on instructions stored in the memory.

[0033] Fourthly, this application provides a battery management system, including: a cell internal resistance determination device as described above.

[0034] Fifthly, this application provides a battery pack, including: a cell module and a battery management system as described above, wherein the battery management system is electrically connected to the cell module, and the cell module includes at least one cell.

[0035] Sixthly, this application provides an electrical device, including: a load and a battery pack as described above, the battery pack being used to supply power to the load.

[0036] In a seventh aspect, this application provides a computer-readable storage medium, comprising: storing computer-executable instructions configured as described in any of the preceding claims.

[0037] The beneficial effects of this application's embodiments are as follows: The method for determining the internal resistance of a battery cell provided in this application determines the internal resistance of the battery cell through the cell's operating condition data. The voltage, current, state of charge, and temperature in the operating condition data all change continuously during the battery cell's use. That is, the operating condition data can accurately reflect the changing characteristics of the battery cell's internal resistance. Therefore, the internal resistance of the battery cell determined by combining the above operating condition data has a small deviation from the actual internal resistance of the battery cell, thus obtaining a relatively accurate internal resistance. Simultaneously, by real-time monitoring of the battery cell's operating condition data, the internal resistance of the battery cell can be determined in real time, thereby enabling real-time assessment of the battery cell's health status, which is beneficial for fully utilizing the battery cell's performance and extending its service life. Furthermore, this method for determining the internal resistance of the battery cell is relatively simple, which not only improves practicality but also reduces the computational workload, thus improving the efficiency of determining the internal resistance of the battery cell. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the structure of a vehicle disclosed in one embodiment of this application;

[0040] Figure 2 This is a flowchart of a method for determining the internal resistance of a battery cell disclosed in an embodiment of this application;

[0041] Figure 3a This is an embodiment disclosed in this application. Figure 2 A schematic diagram of one embodiment of step 22 is shown in the figure;

[0042] Figure 3b This is an embodiment disclosed in this application. Figure 2 A schematic diagram of another embodiment of step 22 is shown in the figure;

[0043] Figure 4 This is an embodiment disclosed in this application. Figure 3a or Figure 3b A schematic diagram of one embodiment of step 33 is shown in the figure;

[0044] Figure 5 This is an embodiment disclosed in this application. Figure 4 A schematic diagram of one embodiment of step 44 is shown in the figure;

[0045] Figure 6 This is a schematic diagram of the current during the second time period disclosed in an embodiment of this application;

[0046] Figure 7 This is an embodiment disclosed in this application. Figure 5 A schematic diagram of one embodiment of step 51 is shown in the figure;

[0047] Figure 8 This is an embodiment disclosed in this application. Figure 7 A schematic diagram of one embodiment of step 71 is shown in the figure;

[0048] Figure 9 This is an embodiment disclosed in this application. Figure 8 A schematic diagram of one embodiment of step 84 is shown in the figure;

[0049] Figure 10 This is a schematic diagram of the cell current when the cell is set to operate continuously during a first time period and a second time period, as disclosed in an embodiment of this application.

[0050] Figure 11 This is a schematic diagram of the structure of a device for determining the internal resistance of a battery cell disclosed in an embodiment of this application;

[0051] Figure 12 This is a schematic diagram of the structure of a device for determining the internal resistance of a battery cell disclosed in another embodiment of this application.

[0052] The accompanying drawings are not drawn to scale. Detailed Implementation

[0053] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0054] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," and "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. "Vertical" is not vertical in the strict sense, but within the allowable tolerance range. "Parallel" is not parallel in the strict sense, but within the allowable tolerance range.

[0055] The directional terms used in the following description refer to the directions shown in the figures and are not intended to limit the specific structure of this application. It should also be noted in the description of this application that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0056] In recent years, the new energy vehicle industry has experienced explosive growth. Battery cells are the core of electric vehicles and a comprehensive embodiment of automotive and electrical engineering technologies. Changes in the internal resistance of a battery cell are a key indicator of whether its performance has deteriorated and an important basis for assessing its monitoring status. If the internal resistance of a battery cell is too high, it will lead to excessive heat generation during use, potentially posing a safety hazard. Therefore, accurately calculating the internal resistance of a battery cell is of paramount importance.

[0057] In the process of developing this application, the inventors discovered that the common method for calculating the internal resistance of a battery cell is to obtain approximately six months of GB32960 data from a car, filter and process this data, and then calculate the internal resistance of the battery cell based on the filtered data. GB32960 is a technical specification for the remote service and management system of electric vehicles, a specification that is generally implemented in electric vehicles, and the battery internal resistance can be calculated based on the data from GB32960.

[0058] However, the internal resistance of a battery cell changes continuously during the aging process. The internal resistance calculated using the above method can be considered a six-month average, leading to a significant deviation between the calculated and actual internal resistance. In other words, the accuracy of the calculated internal resistance is poor, failing to reflect the true state of the cell's internal resistance. Furthermore, this method cannot provide real-time information on the internal resistance, making it impractical.

[0059] Based on this, the applicant designed a method for determining the internal resistance of a battery cell. This method determines the internal resistance of the battery cell through its operating condition data. The voltage, current, state of charge, and temperature in the operating condition data can accurately reflect the changing characteristics of the internal resistance of the battery cell. Furthermore, the internal resistance determined by combining the above operating condition data has a small deviation from the actual internal resistance of the battery cell, thus obtaining a relatively accurate internal resistance. Simultaneously, by monitoring the operating condition data of the battery cell in real time, the internal resistance can be determined in real time, thereby enabling real-time assessment of the battery cell's health status. This is beneficial for maximizing the performance of the battery cell while extending its service life.

[0060] The battery packs including battery cells disclosed in this application can be used, but are not limited to, in electrical equipment such as vehicles, ships, or aircraft. A power system for such electrical equipment can be constructed using the battery cells and battery packs disclosed in this application. This allows for control of the power output of the battery cells based on their degradation level, effectively reducing the risk of cell damage and improving the stability and lifespan of the battery cells.

[0061] This application provides an electrical device that uses a battery pack as a power source, wherein the battery pack includes at least one battery cell. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0062] For ease of explanation, the following embodiments will be described using a vehicle 10 as an example of an electrical device according to an embodiment of this application.

[0063] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle provided in some embodiments of this application. The vehicle can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery pack 10 is installed inside the vehicle, and the battery pack 10 can be located at the bottom, front, or rear of the vehicle. The battery pack 10 includes at least one battery cell, which is used for charging or discharging and can be repeatedly charged using a rechargeable method. The battery pack 10 can be used to power the vehicle; for example, the battery pack 10 can serve as the vehicle's operating power source. The vehicle may include a controller 20 and a motor 30. The controller 20 is used to control the battery pack 10 to supply power to the motor 30, for example, to meet the power needs of the vehicle during starting, navigation, and driving.

[0064] In some embodiments of this application, the battery pack 10 can not only serve as the operating power source for the vehicle, but also as the driving power source for the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0065] Please see Figure 2 , Figure 2 A flowchart illustrating a method for determining the internal resistance of a battery cell provided in this application embodiment. The method for determining the internal resistance of a battery cell includes the following steps:

[0066] Step 21: Collect real-time operating data of the battery cell, including voltage, current, state of charge and temperature.

[0067] Operating condition refers to the working state of equipment under conditions directly related to its operation. Operating condition data refers to the parameters related to the equipment under this operating state. For battery cells, operating condition data mainly refers to the changes in voltage or current during charging or discharging.

[0068] In the embodiments of this application, the collected operating condition data includes the cell voltage, the cell charging and discharging current, the cell state of charge (SOC), and the cell temperature. The SOC, also known as the cell's state of charge, represents the ratio of the cell's remaining capacity to its nominal capacity, usually expressed as a percentage. The SOC value can be obtained through the battery management system.

[0069] In one embodiment, the sampling period for collecting the operating condition data of the battery cell can be set to 0.1s, that is, the operating condition data is collected once every 0.1s.

[0070] Step 22: Determine the internal resistance of the battery cell based on voltage, current, state of charge, and temperature.

[0071] The internal resistance of the battery cell, determined by combining operating condition data such as voltage, current, state of charge, and temperature, has a small deviation from the actual internal resistance, thus obtaining a relatively accurate internal resistance. Furthermore, the internal resistance can be determined in real-time by monitoring the cell's operating condition data, enabling real-time assessment of the cell's health status. In other words, by monitoring the cell's operating condition data in real-time, dynamic assessment of the cell's internal resistance throughout its entire lifecycle can be achieved, facilitating more effective cell management by the battery management system. This allows the cell's performance to be fully utilized while extending its lifespan. In this embodiment, the entire lifecycle of the cell can include the range from a brand-new cell to a cell with 70% capacity degradation. For example, cells with capacities of 50%Q1, 60%Q1, or 70%Q1, where Q1 represents the capacity of a brand-new cell.

[0072] It is understandable that the lifespan of battery cells in current vehicles is typically limited to before 80% capacity decay. That is, if the capacity decays by more than 80%, the battery cell's lifespan is considered over. Therefore, it can be approximated that the internal resistance of the battery cell can be determined throughout its entire lifespan using the method provided in this application. In other words, the method provided in this application can dynamically evaluate the internal resistance of the battery cell throughout its entire lifespan to determine the internal resistance in real time.

[0073] In one embodiment, such as Figure 3a As shown, step 22, which involves determining the internal resistance of the battery cell based on voltage, current, state of charge, and temperature, includes the following steps:

[0074] Step 31: Determine whether the state of charge is within the first state of charge interval.

[0075] Step 32: If the state of charge is within the first state of charge range, then determine whether the temperature is within the first temperature range.

[0076] Steps 31 and 32 are two parallel steps, meaning their order can be interchanged. For example, ... Figure 3b As shown, step 31 can be executed after step 32.

[0077] It is understood that both the first charge state range and the first temperature range can be set according to the actual application, and the embodiments of this application do not specifically limit them. For example, in one embodiment, the first charge state range can be set to [53%, 57%], and the first temperature range can be set to [29℃, 31℃]. As another example, in another embodiment, the first charge state range can be set to [63%, 67%], and the first temperature range can be set to [44℃, 46℃].

[0078] Step 33: If the state of charge is within the first state of charge range and the temperature is within the first temperature range, then determine the internal resistance of the cell based on the voltage and current.

[0079] In this embodiment, the main step is to determine whether the first state of charge and temperature meet the target conditions. The target conditions are that the state of charge is within the first state of charge range, and the temperature is within the first temperature range. If the target conditions are not met, the process returns to step 21. If the target conditions are met, the cell internal resistance is determined based on the voltage and current.

[0080] By setting data collection within a defined range, the probability of data acquisition increases, which is beneficial for improving work efficiency. Furthermore, when the state of charge and temperature are both within the first charge state range, the average state of the battery cell can be better reflected. Under these conditions, the collected operating data more accurately reflects the actual situation of the battery cell, thereby increasing the accuracy of the determined internal resistance.

[0081] In one embodiment, such as Figure 4 As shown, step 33, which involves determining the internal resistance of the battery cell based on voltage and current, includes the following steps:

[0082] Step 41: Obtain the first and second consecutive time periods.

[0083] The first and second time periods are two consecutive but distinct time periods. The end of the first time period coincides with the start of the second time period. The end of the second time period is the current moment, meaning that the first and second time periods should be considered as time periods that have already occurred.

[0084] Step 42: Obtain the first duration of the first time period, and obtain the first charge / discharge rate of the battery cell in the first time period based on the current.

[0085] The first duration refers to the total duration of the first time period. The first multiplier is the charging and discharging rate of the battery cell during the first time period. The charging and discharging rate refers to the current required for the battery cell to charge or discharge its rated capacity within a specified time. It is equal to a multiple of the battery cell's rated capacity and is usually represented by the letter C. For example, in one embodiment, the first multiplier is 0.01C, which means that at this charging and discharging rate, it takes 100 hours for the battery cell to be fully charged from zero.

[0086] Step 43: Obtain the second duration of the second time period, and obtain the second charge / discharge rate of the battery cell in the second time period based on the current, as well as the trend of current change.

[0087] The second duration is the total duration of the second time period. The second multiplier is the charging and discharging multiplier of the battery cell during the second time period. The trend of current change can include a monotonically increasing trend, a monotonically decreasing trend, a trend fluctuating within a preset range, a trend that first increases or decreases monotonically and then fluctuates within a preset range, or a trend that first fluctuates within a preset range and then increases or decreases monotonically, etc.

[0088] Step 44: Determine the cell internal resistance based on the voltage, first duration, second duration, first multiplier, second multiplier, and the trend of change.

[0089] The aforementioned characteristics in the first and second time periods can be used to reflect the actual changes in the cell's internal resistance, thus allowing for a more accurate determination of the cell's internal resistance. Furthermore, parameters such as current or voltage in these two time periods correspond to the cell's internal resistance, enabling real-time determination of the cell's internal resistance. Therefore, compared to existing technologies that use six months of data to calculate the cell's internal resistance, the internal resistance determined in this application deviates less from the actual value, has higher accuracy, can be calculated in real-time, and is more practical.

[0090] Specifically, in one embodiment, such as Figure 5 As shown, step 44, which determines the cell's internal resistance based on voltage, first duration, second duration, first multiplier, second multiplier, and the trend of change, includes the following steps:

[0091] Step 51: If the trend of change includes a monotonic trend and / or a trend of current fluctuation within the first current range, and the second duration is not less than the second duration threshold and the second multiplier is not less than the second multiplier threshold, then determine the cell internal resistance based on the voltage, the first duration and the first multiplier.

[0092] The monotonic change trend includes both monotonically increasing and monotonically decreasing trends. The first current interval refers to the range of maximum fluctuation in current. If the current fluctuates within the first current interval, it means that the maximum current value is not greater than the maximum value of the first current interval, and the minimum current value is not less than the minimum value of the first current interval. The second duration threshold and the second multiplier threshold can be set according to the actual application, and this application embodiment does not specifically limit them. For example, in one embodiment, the second duration threshold can be set to 2s, and the second multiplier threshold can be set to 0.2C.

[0093] Understandably, the first current range defines the range of current fluctuation. For example, the first current range can be [1A, 3A], [2A, 4A], or [10A, 12A], etc., as long as the range (i.e., size) of the first current range remains unchanged. Furthermore, if the current remains constant, i.e., it is a constant current, it also satisfies the trend of current fluctuation within the first current range.

[0094] In this embodiment, the condition in step 51 is the condition that the second time period needs to meet. That is, first it is determined whether the second time period meets the requirements, and then, provided that the second time period meets the above conditions, it is further determined whether the first time period meets the requirements. By determining whether each time period meets the conditions step by step, the amount of calculation can be reduced, which is beneficial to improving the efficiency of determining the internal resistance of the battery cell.

[0095] Please refer to the following: Figure 6 , Figure 6 This diagram illustrates several possible currents that satisfy the conditions in step 51, which may be collected during the second time period. The horizontal axis represents time in seconds (s), and the vertical axis represents current in amperes (A). Curve L61 represents the first possible current; curve L62 represents the second possible current; curve L63 represents the third possible current; and curve L64 represents the fourth possible current.

[0096] like Figure 6 As shown, the trend of current L61 includes both a monotonically decreasing trend and a constant current trend (i.e., the current fluctuates within the first current interval). The trend of current L62 only includes a monotonically decreasing trend. Current L63 is a constant current, meaning that the trend of current L63 only includes the current fluctuating within the first current interval. The trend of current L64 only includes the current fluctuating within the first current interval, where the first current interval is [I61, I62].

[0097] In one embodiment, such as Figure 7 As shown, the specific implementation process of determining the cell internal resistance based on voltage, first duration, and first multiplier in step 51 includes the following steps:

[0098] Step 71: If the first duration is not less than the first duration threshold and the first multiplier is not greater than the first multiplier threshold, then determine the cell internal resistance based on the voltage and the current in the second time period.

[0099] The first duration threshold and the first magnification threshold can be set according to the actual application, and the embodiments of this application do not impose specific limitations on them. For example, in one embodiment, the first duration threshold can be set to 30s, and the first magnification threshold can be set to 0.05C.

[0100] After confirming that the second time period meets the requirements, it is necessary to further determine whether the first time period meets the requirements. That is, the conditions in step 71 are the conditions that the first time period needs to meet. By further confirming that the first time period meets the requirements, the probability of the cell's current voltage deviating from the steady-state voltage or equilibrium potential can be reduced, thus obtaining a voltage with as little polarization as possible. Therefore, more reliable voltage data can be obtained, which is beneficial to improving the accuracy of calculating the cell's internal resistance.

[0101] When both the first and second time periods meet the preset conditions, the internal resistance of the battery cell can be determined based on the collected voltage and the current in the second time period.

[0102] In one embodiment, such as Figure 8 As shown, the process of determining the cell internal resistance based on the voltage and the current during the second time period in step 71 includes the following steps:

[0103] Step 81: Determine whether the current in the second time period is constant.

[0104] Step 82: If so, then determine the current in the second time period as the first current.

[0105] Constant current means that the current remains at a constant value. When the current in the second time period is constant, the subsequent calculation of the cell's internal resistance can be directly performed based on the obtained current. In this embodiment, the first current is the current in the second time period.

[0106] Step 83: If not, obtain the equivalent current based on the current in the second time period, and determine the equivalent current as the first current.

[0107] When the current in the second time period is not constant, for example... Figure 6 The currents L61, L62, or L64 shown can be used to obtain an equivalent current based on the current in the second time period. This equivalent current helps simplify the subsequent calculation of the cell's internal resistance, thereby improving calculation efficiency. In this embodiment, the first current is the obtained equivalent current. The voltage difference caused by the converted current (i.e., the equivalent current) should be equal to the voltage difference caused by the corresponding current before conversion.

[0108] In one embodiment, the equivalent current can be a constant current, that is, the current in the second time period is converted into a corresponding constant current. The equivalent current can be obtained using the following formula:

[0109] (1)

[0110] Where t represents any moment within the second time period. Let w(t) be the equivalent current, w(t) be the weighting function, and I(t) be the current that varies with time. Let n be the end time of the second time period, where n is a positive integer and 2≤n≤6. In formula (1), the weight of the current at each moment in the second time period is first calculated, and then the equivalent current is obtained by multiplying each weight by the current at the corresponding moment and summing the results.

[0111] Step 84: Determine the internal resistance of the battery cell based on the first current and voltage.

[0112] In one embodiment, before performing step 84, i.e. after determining the first current, it is further determined whether the first current is within the second current range. If the first current is not within the second current range, the process can return to performing step 21 in the above embodiment.

[0113] The second current range can be set according to the actual application, and this application embodiment does not limit this. For example, in one embodiment, the second current range can be set to [0.05Imax, 0.8Imax], where Imax can be set as the maximum charge and discharge current of a non-aged (i.e., brand new) battery cell when the cell temperature is 25°C and the state of charge is 50%. Furthermore, Imax is related to the performance of the battery cell, that is, different Imaxes can be obtained based on different cell types or materials. For example, for a ternary lithium battery cell, its Imax during 10s charging is 926A, and its Imax during 10s discharging is 940A.

[0114] When the first current is within the second current range, step 84 is further executed. In this embodiment, by limiting the first current to the second current range, the cell internal resistance obtained under different currents can be made similar, which is beneficial to improving the accuracy of the calculation.

[0115] Furthermore, in one embodiment, such as Figure 9 As shown, step 84, which determines the internal resistance of the battery cell based on the first current and voltage, includes the following steps:

[0116] Step 91: Obtain the first voltage difference between the voltage at the end of the first time period and the voltage at the end of the second time period.

[0117] The first voltage difference is the difference between the cell voltage at the end of the first time period and the cell voltage at the end of the second time period.

[0118] Step 92: Determine the internal resistance of the battery cell based on the first voltage difference and the first current.

[0119] In one embodiment, it can be first determined whether the currently obtained first voltage difference and first current are reliable. If reliable, step 92 is executed; if not reliable, step 21 in the above embodiment is executed. Calculating the cell internal resistance based on reliable first voltage difference and first current helps improve the accuracy of the calculation.

[0120] In one embodiment, the reliability of the first voltage difference and the first current is determined as follows: First, the current first voltage difference is denoted as the Nth first voltage difference ΔU, and the current first current is denoted as the Nth first current I. Then, based on the ratio of the Nth first voltage difference to the Nth first current, the Nth first internal resistance R = ΔU / I is obtained, where N is a positive integer greater than 1.

[0121] Next, the (N-1)th first voltage difference ΔU1 and the (N-1)th first current I1 are obtained. Based on the ratio of the (N-1)th first voltage difference to the (N-1)th first current, the (N-1)th first internal resistance R1 = ΔU1 / I1 is obtained.

[0122] Next, calculate the absolute value of the difference between the Nth first internal resistance R and the (N-1)th first internal resistance R1, and the first ratio of the (N-1)th first internal resistance, i.e., the first ratio is: .

[0123] Furthermore, if the absolute value of the first current I1 in the (N-1)th time... Greater than the absolute value of the Nth first current I At that time, the absolute value of the (N-1)th first voltage difference ΔU1 is greater than the absolute value of the Nth first voltage difference ΔU, or the absolute value of the (N-1)th first current I1 is greater than the absolute value of the (N-1)th first voltage difference ΔU. Less than the absolute value of the Nth first current I When the absolute value of the (N-1)th first voltage difference ΔU1 is less than the absolute value of the Nth first voltage difference ΔU, and the first ratio is less than or equal to the first ratio threshold, then the first voltage difference and the first current are deemed reliable, and step 92 can be executed. In other words, the reliability of the first voltage difference and the first current can be determined by the following pre-set standards (2), (3), and (4):

[0124] like ,but (2)

[0125] like ,but (3)

[0126] ≤ First ratio threshold. (4)

[0127] The first ratio threshold can be set according to the actual application, and this application embodiment does not limit it. For example, in one embodiment, the first ratio threshold can be set to 20%.

[0128] Understandably, if the current increases, the voltage difference will also increase under the same conditions. By observing the variation characteristics between the current and the voltage difference, the reliability of the currently obtained first voltage difference and first current can be determined. Therefore, by acquiring two adjacent first voltage differences and first currents, if the variation characteristics between the current and voltage difference conform to preset variation characteristics, the cell internal resistance can be further determined based on the first voltage difference and first current. This method eliminates differences caused by sampling errors, which helps to further improve the accuracy of the subsequently calculated cell internal resistance.

[0129] In one embodiment, after determining that the first voltage difference and the first current are reliable, the cell internal resistance can be calculated as follows:

[0130] (5)

[0131] Wherein, DCR is the internal resistance of the battery cell. This is the absolute value of the first voltage difference. K is the absolute value of the first current, where K is greater than or equal to 0.8 and less than or equal to 1.2.

[0132] The internal resistance of the battery cell can be obtained by calculating the ratio of the voltage change to the current during the second time period. However, since the first current may be an equivalent current obtained through a non-constant current conversion, there may be errors in the conversion process. Therefore, by setting a value of K, the errors can be corrected according to the actual application, thereby improving the accuracy of the calculation.

[0133] In one embodiment, after determining the cell internal resistance using the method provided in this application, a second ratio of the cell internal resistance DCR to the cell's initial internal resistance R0 is further calculated, i.e., the second ratio is DCR / R0. The second ratio reflects the degree of cell aging, and the initial internal resistance is the internal resistance of an unaged cell.

[0134] In one embodiment, the initial internal resistance R0 of the battery cell can be determined by pre-detecting the battery cell and setting it in the battery management system.

[0135] Specifically, please refer to Figure 10 , Figure 10 A schematic diagram of the cell current is shown when the cell is set to operate continuously during a first time period and a second time period. (See diagram below.) Figure 10As shown, the horizontal axis represents time in seconds (s), and the vertical axis represents current in amperes (A). The current in the first time period is represented by curve L91, and the current in the second time period is represented by curve L92. Both the first and second time periods are set as constant current segments.

[0136] In this embodiment, the first time period and the second time period are time periods that meet preset conditions. Then, based on the voltage and current of the second time period and the method for determining the internal resistance of the battery cell provided in this application embodiment, the initial internal resistance R0 of the battery cell can be calculated.

[0137] The aging degree of a battery cell characterizes the extent of its capacity degradation. For example, a cell with a 50% capacity degradation is more severely aged than one with a 20% capacity degradation. Therefore, based on the second ratio, dynamic assessment of the cell's internal resistance throughout its entire lifespan can be achieved. This allows the battery management system to manage the cells more effectively, ensuring their performance is fully utilized. Simultaneously, the second ratio can also measure the growth pattern of the cell's internal resistance and reflect its degradation degree, which can be used for power degradation calculations. Furthermore, by controlling the cell's output power based on the degree of degradation, the risk of cell damage can be effectively reduced, thus extending the cell's lifespan.

[0138] In the method for determining the internal resistance of a battery cell provided in this application embodiment, the operating condition data of the battery cell is first collected. Then, it is determined whether the temperature and state of charge in the operating condition data meet the target conditions. If the target conditions are not met, the process waits for the next operating condition data collection; if the target conditions are met, it is further determined whether there are a first time period and a second time period that meet the requirements. If there are no first time period and a second time period that meet the requirements, the process waits for the next operating condition data collection; if there are first time period and a second time period that meet the requirements, it is further determined whether the current in the second time period is a constant current. If the current in the second time period is not a constant current, the current is converted to calculate an equivalent constant current. Then, it is determined whether the constant current or equivalent constant current in the second time period is within a set current range. If the constant current or equivalent constant current in the second time period is not within the set current range, the process waits for the next operating condition data collection; if the constant current or equivalent constant current in the second time period is within the set current range, the reliability of the obtained current or voltage parameters is determined according to the set standards. If the data is unreliable, wait for the next data collection under operating conditions; if it is reliable, calculate and determine the cell internal resistance based on the current and voltage data from the second time period.

[0139] In this embodiment, the actual internal resistance of the battery cell during use (e.g., during driving) can be monitored throughout its entire lifecycle based on real-time operating data. This allows for more effective guidance to ensure the battery cell's performance is fully utilized, thus extending its lifespan. Furthermore, if this battery cell is used as a power source for an electric vehicle, it can improve driving safety and enhance the vehicle's power performance.

[0140] Please see Figure 11 The diagram shows a structural schematic of a battery cell internal resistance determination device provided in an embodiment of this application. The battery cell internal resistance determination device 1100 includes: a data acquisition unit 1101 and a first determination unit 1102.

[0141] The data acquisition unit 1101 is used to collect the operating condition data of the battery cell in real time, wherein the operating condition data includes voltage, current, state of charge and temperature.

[0142] The first determining unit 1102 is used to determine the internal resistance of the battery cell based on voltage, current, state of charge, and temperature.

[0143] The above products can be executed Figure 2 The method provided in the embodiments of this application shown has corresponding functional modules and beneficial effects for performing the method. Technical details not described in detail in this embodiment can be found in the method provided in the embodiments of this application.

[0144] Please see Figure 12 This illustration shows a structural schematic diagram of a device for determining the internal resistance of a battery cell, as provided in an embodiment of this application. Figure 12 As shown, the cell internal resistance determination device 1200 includes one or more processors 1201 and a memory 1202. Wherein, Figure 12 Take a processor 1201 as an example.

[0145] Processor 1201 and memory 1202 can be connected via a bus or other means. Figure 12 Taking the example of a connection between China and Israel via a bus.

[0146] The memory 1202, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs, non-volatile computer-executable programs, and modules, such as the program instructions / modules corresponding to the method for determining the internal resistance of the battery cell in the embodiments of this application (e.g., attached...). Figure 11 (The aforementioned units). The processor 1201 executes various functional applications and data processing of the cell internal resistance determination device by running non-volatile software programs, instructions, and modules stored in the memory 1202, thereby realizing the cell internal resistance determination method in the above method embodiment and the functions of the various units in the above device embodiment.

[0147] Memory 1202 may include high-speed random access memory, and may also include non-volatile memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In some embodiments, memory 1202 may optionally include memory remotely located relative to processor 1201, and these remote memories may be connected to processor 1201 via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0148] The program instructions / modules are stored in the memory 1202. When executed by one or more processors 1201, they execute the method for determining the cell internal resistance in any of the above method embodiments, for example, executing the method described above. Figure 2 , Figure 3a , Figure 3b , Figure 4 , Figure 5 , Figure 7 , Figure 8 and Figure 9 The steps shown can also be implemented in the appendix. Figure 11 The functions of each of the aforementioned units.

[0149] This application also provides a battery management system, including the cell internal resistance determination device in any of the above embodiments.

[0150] This application also provides a battery pack, including a cell module and a battery management system as described in any of the above embodiments. The battery management system is electrically connected to the cell module, wherein the cell module includes at least one cell.

[0151] The internal resistance of each cell in the battery pack can be determined by using the method provided in the embodiments of this application, thereby obtaining the internal resistance of the battery pack.

[0152] In one embodiment, the internal resistance of the cell with the smallest capacity and the cell with the smallest voltage in the battery pack can also be obtained. Furthermore, the performance of the battery pack can be reflected in real time using the internal resistances of these two cells, which facilitates better management of the battery pack, allowing for better utilization of its performance and extending its lifespan.

[0153] This application also provides an electrical device, including a load and a battery pack as described in any of the above embodiments, the battery pack being used to supply power to the load.

[0154] This application also provides a non-volatile computer storage medium storing computer-executable instructions that are executed by one or more processors, enabling the processors to perform the temperature determination method and / or the current threshold determination method described above. For example, performing the above-described... Figure 2 , Figure 3a , Figure 3b , Figure 4 , Figure 5 , Figure 7 , Figure 8 and Figure 9 The steps shown can also be implemented in the appendix. Figure 11 The functions of each of the aforementioned units.

[0155] The device or equipment embodiments described above are merely illustrative. The unit modules described as separate components may or may not be physically separate. The components shown as module units may or may not be physical units; that is, they may be located in one place or distributed across multiple network module units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0156] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented using software plus a general-purpose hardware platform, or of course, using hardware. Based on this understanding, the above technical solutions, in essence or the parts that contribute to the related technology, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0157] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for determining the internal resistance of a battery cell, comprising: Real-time acquisition of battery cell operating condition data, including voltage, current, state of charge, and temperature; The internal resistance of the battery cell is determined based on the voltage, the current, the state of charge, and the temperature. The step of determining the cell internal resistance based on the voltage, the current, the state of charge, and the temperature includes: acquiring a continuous first time period and a second time period; determining whether the current in the second time period is a constant current, wherein the end time of the second time period is the current time; the first duration of the first time period is not less than a first duration threshold, and during the first time period, the first charge / discharge rate of the cell is not greater than a first rate threshold; the second duration of the second time period is not less than a second duration threshold, and during the second time period, the second charge / discharge rate of the cell is not less than a second rate threshold; the first duration is the total duration of the first time period, and the second duration is the total duration of the second time period; if yes, then the current in the second time period is determined to be the first current; if no, then an equivalent current is obtained based on the current in the second time period, and the equivalent current is determined to be the first current; the cell internal resistance is determined based on the first current and the voltage; the equivalent current is: Where t is any moment within the second time period, Let w(t) be the equivalent current, w(t) be the weighting function, and I(t) be the current that varies with time. Let n be the time when the second time period ends, where n is a positive integer and 2 ≤ n ≤ 6; The internal resistance of the battery cell is: Wherein, DCR is the internal resistance of the battery cell. This is the absolute value of the first voltage difference. K is the absolute value of the first current, K is greater than or equal to 0.8 and less than or equal to 1.2, and the first voltage difference is the voltage difference between the voltage at the end of the first time period and the voltage at the end of the second time period.

2. The method according to claim 1, wherein, Determining the cell internal resistance based on the voltage, the current, the state of charge, and the temperature includes: If the state of charge is within the first state of charge range and the temperature is within the first temperature range, then the internal resistance of the battery cell is determined based on the voltage and the current.

3. The method according to claim 2, wherein, Determining the cell internal resistance based on the voltage and the current includes: Obtain the first duration of the first time period, and obtain the first charge / discharge rate of the battery cell during the first time period based on the current; The second duration of the second time period is obtained, and the second charge / discharge rate of the battery cell during the second time period is obtained based on the current, as well as the trend of the current change; The internal resistance of the battery cell is determined based on the voltage, the first duration, the second duration, the first multiplier, the second multiplier, and the trend of change.

4. The method according to claim 3, wherein, Determining the cell internal resistance based on the voltage, the first duration, the second duration, the first multiplier, the second multiplier, and the changing trend includes: If the trend of change includes a monotonic trend and / or a trend of fluctuation of the current within a first current range, then the internal resistance of the cell is determined based on the voltage, the first duration, and the first multiplier; wherein, the first current range is the range of maximum fluctuation of the current.

5. The method according to claim 4, wherein, Determining the cell internal resistance based on the voltage, the first duration, and the first multiplier includes: If the first duration is not less than the first duration threshold and the first multiplier is not greater than the first multiplier threshold, then the internal resistance of the battery cell is determined based on the voltage and the current during the second time period.

6. The method according to claim 5, wherein, Before determining the cell internal resistance based on the first current and the voltage, the method further includes: The first current is determined to be within a preset second current range.

7. The method according to any one of claims 5 or 6, wherein, Determining the internal resistance of the battery cell based on the first current and the voltage includes: Obtain the first voltage difference between the voltage at the end of the first time period and the voltage at the end of the second time period; The internal resistance of the battery cell is determined based on the first voltage difference and the first current.

8. The method according to claim 7, wherein, Before determining the cell internal resistance based on the first voltage difference and the first current, the method further includes: The current first voltage difference is denoted as the Nth first voltage difference, the current first current is denoted as the Nth first current, and the Nth first internal resistance is obtained according to the ratio of the Nth first voltage difference to the Nth first current, where N is a positive integer greater than 1. Obtain the (N-1)th first voltage difference and the (N-1)th first current, and obtain the (N-1)th first internal resistance based on the ratio of the (N-1)th first voltage difference to the (N-1)th first current; Calculate the absolute value of the difference between the Nth first internal resistance and the (N-1)th first internal resistance, and the first ratio of the (N-1)th first internal resistance; If the absolute value of the (N-1)th first current is greater than the absolute value of the Nth first current, then the absolute value of the (N-1)th first voltage difference is greater than the absolute value of the Nth first voltage difference; or if the absolute value of the (N-1)th first current is less than the absolute value of the Nth first current, then the absolute value of the (N-1)th first voltage difference is less than the absolute value of the Nth first voltage difference, and the first ratio is less than or equal to a first ratio threshold, then the determination of the cell internal resistance based on the first voltage difference and the first current is performed.

9. The method according to claim 1, wherein, After determining the internal resistance of the battery cell, the method further includes: Calculate the second ratio of the cell's internal resistance to its initial internal resistance; The second ratio is used to reflect the degree of cell aging, and the initial internal resistance is the internal resistance of the unaged cell.

10. A device for determining the internal resistance of a battery cell, comprising: The data acquisition unit is used to collect the operating condition data of the battery cell in real time, wherein the operating condition data includes voltage, current, state of charge and temperature; The first determining unit is configured to determine the internal resistance of the battery cell based on the voltage, the current, the state of charge, and the temperature. The step of determining the cell internal resistance based on the voltage, the current, the state of charge, and the temperature includes: acquiring a continuous first time period and a second time period; determining whether the current in the second time period is a constant current, wherein the end time of the second time period is the current time; the first duration of the first time period is not less than a first duration threshold, and during the first time period, the first charge / discharge rate of the cell is not greater than a first rate threshold; the second duration of the second time period is not less than a second duration threshold, and during the second time period, the second charge / discharge rate of the cell is not less than a second rate threshold; the first duration is the total duration of the first time period, and the second duration is the total duration of the second time period; if yes, then the current in the second time period is determined to be the first current; if no, then an equivalent current is obtained based on the current in the second time period, and the equivalent current is determined to be the first current; the cell internal resistance is determined based on the first current and the voltage; the equivalent current is: Where t is any moment within the second time period, Let w(t) be the equivalent current, w(t) be the weighting function, and I(t) be the current that varies with time. Let n be the time when the second time period ends, where n is a positive integer and 2 ≤ n ≤ 6; The internal resistance of the battery cell is: Wherein, DCR is the internal resistance of the battery cell. This is the absolute value of the first voltage difference. K is the absolute value of the first current, K is greater than or equal to 0.8 and less than or equal to 1.2, and the first voltage difference is the voltage difference between the voltage at the end of the first time period and the voltage at the end of the second time period.

11. A device for determining the internal resistance of a battery cell, comprising: Memory; And a processor coupled to the memory, the processor being configured to perform the method as described in any one of claims 1 to 9 based on instructions stored in the memory.

12. A battery management system, comprising: The device for determining the internal resistance of a battery cell as described in claim 10 or 11.

13. A battery pack, comprising: The battery cell module and the battery management system as described in claim 12, wherein the battery management system is electrically connected to the battery cell module, and the battery cell module includes at least one battery cell.

14. An electrical appliance, comprising: The load and the battery pack as described in claim 13, wherein the battery pack is used to power the load.

15. A computer-readable storage medium comprising: The device stores computer-executable instructions configured as a method flow as described in any one of claims 1 to 9.

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