WO2023044882A1

WO2023044882A1 - Method and apparatus for determining internal resistance of cell, and battery management system

Info

Publication number: WO2023044882A1
Application number: PCT/CN2021/120805
Authority: WO
Inventors: 王丹凤; 宋晋阳
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2021-09-26
Filing date: 2021-09-26
Publication date: 2023-03-30
Also published as: CN116648629A

Abstract

Provided in the present application are a method and apparatus for determining the internal resistance of a cell, and a battery management system. The method for determining the internal resistance of a cell comprises: collecting operating condition data of a cell in real time, wherein the operating condition data comprises a voltage, a current, a state of charge, and a temperature; and determining the internal resistance of the cell according to the voltage, the current, the state of charge, and the temperature. In this way, a relatively accurate internal resistance of a cell can be calculated.

Description

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

technical field

The present application relates to the field of battery technology, in particular to a method and device for determining the internal resistance of a battery cell, and a battery management system.

Background technique

With the increasingly severe energy and environmental problems, the country's strong support for new energy, and the increasingly mature power battery technology, electric vehicles have become a new direction for the future development of the automobile industry. The cruising range of electric vehicles has become an important factor affecting the popularity of electric vehicles. The battery pack as a key component is the main source of power for electric vehicles, and its product quality is stable and reliable.

For a battery pack, the internal resistance of the battery cell can well reflect the health status of the battery cell, thereby reflecting the health status of the battery pack, so the internal resistance of the battery cell is an important parameter in the characteristics of the battery pack.

In the prior art, the internal resistance of the cell is usually calculated by using half a year's data. However, this method ignores the fact that the internal resistance of the battery cell is constantly changing during the aging process, and the calculated internal resistance of the battery cell deviates greatly from the actual value.

Contents of the invention

The present application aims to provide a method and device for determining the internal resistance of a battery cell, and a battery management system, which can calculate and obtain a relatively accurate internal resistance of the battery cell.

To achieve the above purpose, in a first aspect, the present application provides a method for determining the internal resistance of a battery cell. The method includes collecting working condition data of the battery cell in real time, wherein the working condition data includes voltage, current, state of charge and temperature. According to the voltage, current, state of charge and temperature, determine the internal resistance of the cell.

Among them, the working condition data such as voltage, current, state of charge and temperature will change continuously with the use of the battery cell. That is to say, the above working condition data can more accurately reflect the change characteristics of the internal resistance of the battery cell. Then, the internal resistance of the battery cell calculated by combining the above working condition data can have a small deviation from the actual internal resistance of the battery cell, and a more accurate internal resistance of the battery cell can be obtained. Moreover, by detecting the working condition data of the battery cell in real time, the internal resistance of the battery cell can be determined in real time, so that the health status of the battery cell can be evaluated in real time, which is conducive to fully exerting the performance of the battery cell and prolonging the service life of the battery cell . At the same time, the method for determining the internal resistance of the battery cell is relatively simple, which can not only improve the practicability, but also reduce the workload of calculation, and is beneficial to improve the efficiency of determining the internal resistance of the battery cell.

In an optional manner, determining the internal resistance of the cell according to the voltage, current, state of charge, and temperature includes: if the state of charge is within the first state of charge interval, and the temperature is within the first temperature interval, The internal resistance of the cell is determined according to the voltage and current.

When the state of charge of the battery cell is in the first state of charge range and the temperature of the battery cell is in the first temperature range, the average state of the battery cell can be better reflected. In this case, the obtained working condition data can more accurately correspond to the actual condition of the battery cell, thus, the internal resistance of the battery cell determined according to the obtained working condition data is more accurate. Secondly, setting the data to be sampled in an interval can increase the probability of sampling data, which is conducive to improving work efficiency.

In an optional manner, determining the internal resistance of the cell according to the voltage and current includes: obtaining a continuous first time period and a second time period, wherein the moment when the second time period ends is the current moment. The first duration of the first time period is obtained, and the first rate of charge and discharge of the battery cell in the first time period is obtained according to the current. The second duration of the second time period is obtained, and the second rate of charge and discharge of the battery cell in the second time period is obtained according to the current, and the change trend of the current is obtained. According to the voltage, the first duration, the second duration, the first magnification, the second magnification and the change trend, determine the internal resistance of the cell.

With the current time as the end time, two consecutive time periods that meet the requirements are obtained, and according to the correspondence between actual parameters such as current and voltage in these two time periods and the internal resistance of the battery cell, the internal resistance of the battery cell can be calculated and determined in real time . Compared with the method of calculating the internal resistance of the battery cell using half-year data in the prior art, the internal resistance of the battery cell determined in the present application can be calculated in real time, so that the deviation from the actual value is smaller and the accuracy is higher.

In an optional manner, the internal resistance of the cell is determined according to the voltage, the first duration, the second duration, the first magnification, the second magnification and the change trend, including: if the current has a monotonic change trend, and/or, The current fluctuates within the first current interval, and the second duration is not less than the second duration threshold, and the second rate is not less than the second rate threshold, then the internal resistance of the cell is determined according to the voltage, the first period, and the first rate.

Wherein, the above-mentioned conditions are conditions that need to be satisfied in the second time period. That is, first determine whether the second time period meets the requirements, and then further judge whether the first time period meets the requirements on the premise that the second time period meets the above conditions. By gradually determining whether each time period meets the requirements, the workload of calculation can be reduced, which is conducive to improving the efficiency of determining the internal resistance of the battery cell.

In an optional manner, determining the internal resistance of the cell according to the voltage, the first duration, and the first magnification includes: if the first duration is not less than the first duration threshold, and the first magnification is not greater than the first magnification threshold, The internal resistance of the cell is then determined according to the voltage and the current in the second time period.

Wherein, the above-mentioned conditions are conditions that need to be satisfied in the first time period. By further determining that the first time period meets the requirements, the probability that the current voltage of the cell deviates from the steady-state voltage or the equilibrium potential can be reduced, so as to obtain a voltage with no polarization as much as possible. Therefore, relatively reliable voltage data can be obtained, which is conducive to improving the accuracy of calculating the internal resistance of the battery cell.

In an optional manner, determining the internal resistance of the cell according to the voltage and the current in the second time period includes: judging whether the current in the second time period is a constant current. If yes, determine the current in the second time period as the first current. If not, an equivalent current is obtained according to the current in the second time period, and the equivalent current is determined to be the first current. Determine the internal resistance of the cell according to the first current and voltage.

If the current in the second time period is a constant current, the current can be directly sampled for subsequent calculation. If the current in the second time period is not a constant current, the current needs to be converted into a corresponding constant current, that is, the current is equivalent to a constant current, which facilitates the process of calculating the internal resistance of the battery cell in the subsequent steps.

In an optional way, the equivalent current is:

Wherein, t is any moment in the second time period, I _eq is the equivalent current, w(t) is the weight function, I(t) is the current changing with time, and t _end is the end of the second time period , n is a positive integer and 2≤n≤6.

In the above formula, first calculate the weight of the current at each moment in the second time period, and then use each weight to multiply the current at the corresponding moment and then sum to obtain the equivalent current.

In an optional manner, before determining the internal resistance of the cell according to the first current and voltage, the method further includes: determining that the first current is within the second current range.

By limiting the first current to the second current range, the internal resistance of the cell obtained under different currents can be made similar, and the calculation accuracy can be improved.

In an optional manner, determining the internal resistance of the cell according to the first current and voltage includes: acquiring a 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. According to the first voltage difference and the first current, the internal resistance of the cell is determined.

If the current increases, the voltage difference will also increase under the same conditions. According to the change characteristics between the current and the voltage difference, it can be determined whether the currently obtained first voltage difference and the first current are credible.

In an optional manner, before determining the internal resistance of the cell according to the first voltage difference and the first current, the method further includes: recording the current first voltage difference as the Nth first voltage difference, and recording the current The first current of is recorded as the Nth first current, and according to the ratio of the Nth first voltage difference to the Nth first current, the Nth first internal resistance is obtained, where N is a positive integer greater than 1 . Obtain the N-1th first voltage difference and the N-1th first current, and obtain the N-1th first current according to the ratio of the N-1th first voltage difference to the N-1th first current One internal resistance. Calculate the first ratio of the absolute value of the difference between the Nth first internal resistance and the N-1th first internal resistance to the N-1th first internal resistance. If the absolute value of the N-1th first current is greater than the absolute value of the Nth first current, the absolute value of the N-1th first voltage difference is greater than the absolute value of the Nth first voltage difference, or When the absolute value of the N-1th first current is smaller than the absolute value of the Nth first current, the absolute value of the N-1th first voltage difference is smaller than the absolute value of the Nth first voltage difference, and, If the first ratio is less than or equal to the first ratio threshold, the internal resistance of the cell is determined according to the first voltage difference and the first current.

By acquiring two adjacent first voltage differences and first currents, if the variation characteristics between the currents and voltage differences meet the preset variation characteristics, the internal resistance of the cell can be further determined according to the first voltage difference and the first current. Therefore, the difference value caused by the sampling error can be eliminated, which is beneficial to further improving the accuracy of the subsequent calculated internal resistance of the battery cell.

In an optional manner, determining the internal resistance of the cell according to the first voltage difference and the first current includes: the internal resistance of the cell is: DCR=|ΔU|×K/|I|, where DCR is the The internal resistance of the cell, |ΔU| is the absolute value of the first voltage difference, |I| 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.

When obtaining the first current, the first current may be an equivalent current obtained by non-constant current conversion, and there may be errors in the conversion process. By setting the K value, the above error can be corrected according to the actual application situation, so as to improve the calculation accuracy.

In an optional manner, after determining the internal resistance of the battery cell, the method further includes: calculating a second ratio of the internal resistance of the battery cell to the initial internal resistance of the battery cell. Wherein, the second ratio is used to reflect the aging degree of the battery cell, and the initial internal resistance is the internal resistance of the unaged battery cell.

According to the second ratio, the dynamic evaluation of the internal resistance of the battery cell in the whole life cycle can be realized, which is beneficial to the battery management system to manage the battery cell more effectively, so that the performance of the battery cell can be fully utilized. At the same time, the growth mode of the internal resistance of the battery cell and the attenuation degree of the reflected battery cell can also be measured according to the second ratio, so as to be used for power attenuation calculation. Furthermore, the output power of the battery cell can be controlled according to the degree of attenuation, which can effectively reduce the risk of damage to the battery cell and help prolong the service life of the battery cell.

In a second aspect, the present application provides a device for determining the internal resistance of a cell, including: a data acquisition unit for collecting working condition data of the battery cell in real time, wherein the working condition data includes voltage, current, state of charge and temperature. The first determination unit is used to determine the internal resistance of the battery cell according to the voltage, current, state of charge and temperature.

In a third aspect, the present application provides a device for determining the internal resistance of a cell, including: a memory, and a processor coupled to the memory, the processor is configured to execute the method described in any one of the above based on instructions stored in the memory. Methods.

In a fourth aspect, the present application provides a battery management system, including: the device for determining the internal resistance of a battery cell as described above.

In a fifth aspect, the present application provides a battery pack, including: a battery module and the above-mentioned battery management system, the battery management system is electrically connected to the battery module, wherein the battery module includes at least one battery.

In a sixth aspect, the present application provides an electric device, including: a load and the above-mentioned battery pack, where the battery pack is used to supply power to the load.

In a seventh aspect, the present application provides a computer-readable storage medium, including: computer-executable instructions are stored, and the computer-executable instructions are configured as the method flow described in any one of the above items.

The beneficial effects of the embodiments of the present application are: the method for determining the internal resistance of the battery cell provided in the present application determines the internal resistance of the battery cell through the working condition data of the battery cell. Among them, the voltage, current, state of charge and temperature in the working condition data will change continuously with the use of the battery cell. That is to say, the working condition data can more accurately reflect the change characteristics of the internal resistance of the battery cell. Therefore, by combining the internal resistance of the battery cell determined by the above working condition data, the deviation from the actual internal resistance of the battery cell is small, so that a relatively accurate internal resistance of the battery cell can be obtained. At the same time, by detecting the working condition data of the battery cell in real time, the internal resistance of the battery cell can be determined in real time, so that the health status of the battery cell can be evaluated in real time, which is conducive to fully exerting the performance of the battery cell and prolonging the service life of the battery cell . In addition, the method for determining the internal resistance of the battery cell is relatively simple, which can not only improve the practicability, but also reduce the workload of calculation, and is beneficial to improve the efficiency of determining the internal resistance of the battery cell.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings that need to be used in the embodiments of the present application. Obviously, the accompanying drawings described below are only some embodiments of the present application. Those of ordinary skill in the art can also obtain other drawings based on the accompanying drawings on the premise of not paying creative efforts.

Fig. 1 is a schematic structural view of a vehicle disclosed in an embodiment of the present application;

Fig. 2 is a flowchart of a method for determining the internal resistance of a cell disclosed in an embodiment of the present application;

Fig. 3a is a schematic diagram of an implementation of step 22 shown in Fig. 2 disclosed in an embodiment of the present application;

Fig. 3b is a schematic diagram of another implementation of step 22 shown in Fig. 2 disclosed in an embodiment of the present application;

Fig. 4 is a schematic diagram of an implementation of step 33 shown in Fig. 3a or Fig. 3b disclosed in an embodiment of the present application;

FIG. 5 is a schematic diagram of an implementation of step 44 shown in FIG. 4 disclosed in an embodiment of the present application;

Fig. 6 is a schematic diagram of the current in the second time period disclosed by an embodiment of the present application;

FIG. 7 is a schematic diagram of an implementation of step 51 shown in FIG. 5 disclosed in an embodiment of the present application;

FIG. 8 is a schematic diagram of an implementation of step 71 shown in FIG. 7 disclosed in an embodiment of the present application;

FIG. 9 is a schematic diagram of an implementation of step 84 shown in FIG. 8 disclosed in an embodiment of the present application;

Fig. 10 is a schematic diagram of the current of the battery when the battery is set to work continuously in the first time period and the second time period disclosed in an embodiment of the present application;

Fig. 11 is a schematic structural diagram of a device for determining the internal resistance of a cell disclosed in an embodiment of the present application;

Fig. 12 is a schematic structural diagram of a device for determining the internal resistance of a cell disclosed in another embodiment of the present application.

In the drawings, the drawings are not drawn to scale.

Detailed ways

The implementation manner of the present application will be further described in detail below with reference to the drawings and embodiments. The detailed description and drawings of the following embodiments are used to illustrate the principles of the application, but not to limit the scope of the application, that is, the application is not limited to the described embodiments.

In the description of this application, it should be noted that, unless otherwise specified, the meaning of "plurality" is more than two; the terms "upper", "lower", "left", "right", "inner", " The orientation or positional relationship indicated by "outside" and so on are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a reference to this application. Application Restrictions. In addition, the terms "first", "second", "third", etc. are used for descriptive purposes only and should not be construed as indicating or implying relative importance. "Vertical" is not strictly vertical, but within the allowable range of error. "Parallel" is not strictly parallel, but within the allowable range of error.

The orientation words appearing in the following description are the directions shown in the figure, and do not limit the specific structure of the application. In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be interpreted in a broad sense, for example, it can be a fixed connection or a flexible connection. Disassembled connection, or integral connection; it can be directly connected or indirectly connected through an intermediary. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific situations.

In recent years, the new energy vehicle industry has ushered in explosive growth. The battery cell is the core of an electric vehicle, and it is also a comprehensive embodiment of automotive engineering and power engineering technology. The change of the internal resistance of the battery cell is a key indicator of whether the performance of the battery cell is deteriorating, and it is also an important basis for evaluating the monitoring status of the battery cell. Among them, if the internal resistance of the battery cell is too large, it will cause the battery cell to generate too much heat during use, which may pose a safety hazard. Therefore, it is particularly important to accurately calculate the internal resistance of the battery cell.

In the process of implementing this application, the inventors of the present application found that the current common way to calculate the internal resistance of the battery cell is to obtain the GB32960 data of a car for about half a year, and screen the data to obtain the data based on the screened data. Calculate the internal resistance of the cell from the data. Among them, GB32960 is the technical specification for electric vehicle remote service and management system, which is basically a specification that electric vehicles will implement. The internal resistance of the battery can be calculated according to the data of GB32960.

However, the internal resistance of the cell will continue to change during the aging process. The internal resistance of the battery cell calculated by the above method can be regarded as an average value of half a year, which will lead to a large deviation between the calculated internal resistance of the battery cell and the actual internal resistance of the battery cell. That is to say, the accuracy of the calculated internal resistance of the battery cell is poor, so that it cannot reflect the real situation of the internal resistance of the battery cell. In addition, the above method cannot obtain the internal resistance of the battery cell in real time, and the practicability is poor.

Based on this, the applicant has designed a method for determining the internal resistance of the battery cell, which determines the internal resistance of the battery cell through the working condition data of the battery cell. Among them, the voltage, current, state of charge and temperature in the working condition data can more accurately reflect the change characteristics of the internal resistance of the cell. Furthermore, by combining the internal resistance of the battery cell determined by the above working condition data, the deviation from the actual internal resistance of the battery cell is small, and a relatively accurate internal resistance of the battery cell can be obtained. At the same time, by detecting the working condition data of the battery cell in real time, the internal resistance of the battery cell can be determined in real time, so that the health status of the battery cell can be evaluated in real time, which is conducive to fully exerting the performance of the battery cell and prolonging the service life of the battery cell .

The battery pack including batteries disclosed in the embodiments of the present application can be used in electrical equipment such as vehicles, ships or aircrafts, but not limited to. The power supply system comprising the electrical equipment disclosed in this application, such as batteries and battery packs, can be used. In this way, the power output of the battery can be controlled according to the attenuation degree of the battery, which can effectively reduce the risk of damage to the battery, which is beneficial to Improve the stability of the battery performance and prolong the service life of the battery.

An embodiment of the present application provides an electric device using a battery pack as a power source, wherein the battery pack includes at least one battery cell. Electrical equipment can be, but not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric vehicles, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric boat toys, electric airplane toys, etc., and spacecraft may include airplanes, rockets, space shuttles, spaceships, etc.

In the following embodiments, for the convenience of description, a vehicle 10 is taken as an example of an electric device in an embodiment of the present application.

Please refer to FIG. 1 , which is a schematic structural diagram of a vehicle provided by some embodiments of the present application. Vehicles can be fuel vehicles, gas vehicles or new energy vehicles, and new energy vehicles can be pure electric vehicles, hybrid vehicles or extended-range vehicles. A battery pack 10 is arranged inside the vehicle, and the battery pack 10 can be arranged at the bottom, head or tail of the vehicle. Wherein, the battery pack 10 includes at least one battery cell, which is used for charging or discharging, and can be recharged repeatedly in a rechargeable manner. The battery pack 10 can be used for power supply of the vehicle, for example, the battery pack 10 can be used as an operating power source of the vehicle. The vehicle may include a controller 20 and a motor 30 , and the controller 20 is used to control the battery pack 10 to provide power to the motor 30 , for example, for starting, navigating, and working power requirements of the vehicle.

In some embodiments of the present application, the battery pack 10 can be used not only as an operating power source for the vehicle, but also as a driving power source for the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

Please refer to FIG. 2 . FIG. 2 is a flow chart of a method for determining the internal resistance of a cell provided by an embodiment of the present application. The method for determining the internal resistance of the battery cell includes the following steps:

Step 21: Collect working condition data of the battery cell in real time, wherein the working condition data includes voltage, current, state of charge and temperature.

Working condition refers to the working state of the equipment under the conditions directly related to its action. Working condition data are parameters related to equipment in this working state. The working condition data of the battery mainly refers to the change data of the voltage or current of the battery during the charging or discharging process.

In the embodiment of the present application, the collected working condition data includes the voltage of the battery cell, the current when the battery cell is charging and discharging, the state of charge of the battery cell, and the temperature of the battery cell. Among them, the state of charge of the battery cell, also known as the SOC value (state of charge), which represents the ratio of the remaining capacity of the battery cell to the nominal capacity of the battery cell, usually expressed as a percentage. The SOC value can be obtained through the battery management system.

Wherein, in one embodiment, the sampling period for collecting the working condition data of the battery cell may be set to 0.1s, that is, the working condition data is collected every 0.1s.

Step 22: Determine the internal resistance of the cell according to the voltage, current, state of charge and temperature.

By combining the internal resistance of the battery cell determined by working condition data such as voltage, current, state of charge, and temperature, the deviation from the actual internal resistance of the battery cell is small, and a more accurate internal resistance of the battery cell can be obtained. At the same time, the internal resistance of the battery can be determined in real time by detecting the working condition data of the battery in real time, so that the health status of the battery can be evaluated in real time. In other words, by detecting the working condition data of the battery cell in real time, the dynamic evaluation of the internal resistance of the battery cell during the whole life cycle can be realized, which is beneficial to the battery management system to manage the battery cell more effectively. Therefore, the performance of the battery cell can be fully exerted, and the service life of the battery cell can be prolonged. In this embodiment, the full life cycle of a battery cell may include the entire interval from a brand new battery cell to a battery cell whose capacity has decayed by 70%. For example, batteries with a capacity of 50% Q1, 60% Q1 or 70% Q1, etc., where Q1 is the capacity of a new battery.

It is understandable that the battery life of a real vehicle is usually limited to before the capacity decays by 80%, that is, if the capacity of the battery decays by more than 80%, it can be considered that the life of the battery has expired. Therefore, it can be approximately considered that the internal resistance of the battery cell can be determined by the method provided in the embodiment of the present application during the whole process of using the battery cell. That is to say, the method provided by the embodiment of the present application can dynamically evaluate the internal resistance of the battery cell during the whole life cycle, so as to determine the internal resistance of the battery cell in real time.

In one embodiment, as shown in FIG. 3a, the process of determining the internal resistance of the cell according to the voltage, current, state of charge and temperature in step 22 includes the following steps:

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

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.

Wherein, step 31 and step 32 are two parallel steps, that is, the order between step 31 and step 32 can be exchanged. For example, as shown in FIG. 3b, step 31 may be performed after step 32 is performed.

It can be understood that both the first charge state interval and the first temperature interval can be set according to actual application conditions, which are not specifically limited in this embodiment of the present application. For example, in one embodiment, the first state of charge interval can be set to [53%, 57%], and the first temperature interval can be set to [29°C, 31°C]. 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°C, 46°C].

Step 33: If the state of charge is within the first state of charge interval and the temperature is within the first temperature interval, then determine the internal resistance of the cell according to the voltage and current.

In this embodiment, it is mainly determined whether the first state of charge and the temperature meet the target condition. The target condition is 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 condition is not met, return to step 21. If the target condition is met, the internal resistance of the cell is determined based on the voltage and current.

By setting to collect data in a set interval, the probability of collecting data can be increased, which is beneficial to improve work efficiency. At the same time, when the state of charge is within the first state of charge interval and the temperature is within the first temperature interval, the average state of the battery cell can be better reflected. In this case, the collected working condition data can more accurately correspond to the actual condition of the battery cell, so that the accuracy of the determined internal resistance of the battery cell can be higher.

In one embodiment, as shown in FIG. 4, the process of determining the internal resistance of the cell according to the voltage and current in step 33 includes the following steps:

Step 41: Obtain consecutive first time periods and second time periods.

The first time period and the second time period are two different continuous time periods, and the moment when the first time period ends is the moment when the second time period begins. The moment when the second time period ends is the current time, that is, the first time period and the second time period should be time periods that have already occurred.

Step 42: Obtain the first duration of the first time period, and obtain the first rate of charge and discharge of the battery cell in the first time period according to the current.

The first duration is the total duration of the first time period. The first rate is the rate at which the battery is charged and discharged during the first time period. Among them, the charging and discharging rate of the battery refers to the current value required when the battery is charged into or discharged from its rated capacity within a specified time. It is equal to the multiple of the rated capacity of the battery in terms of data value, usually represented by the letter C. For example, in one embodiment, the first rate is 0.01C, and 0.01C means that at this rate of charge and discharge, it takes 100 hours for the charge of the battery cell to go from zero to fully charged.

Step 43: Obtain the second duration of the second time period, and obtain the second rate of charge and discharge of the battery cell in the second time period according to the current, and obtain the change trend of the current.

The second duration is the total duration of the second time period. The second rate is the charge and discharge rate of the battery cell in the second time period. The changing trend of the current may include a monotonically increasing trend, a monotonically decreasing trend, a trend of fluctuating up and down within a preset interval, a trend of monotonically increasing or monotonically decreasing first, and then fluctuating up and down within a preset interval, or a trend of fluctuating up and down within a preset interval first Fluctuates up and down within the preset interval, and there are many different trends such as monotonically increasing or monotonically decreasing trends.

Step 44: Determine the internal resistance of the cell according to the voltage, the first duration, the second duration, the first magnification, the second magnification and the variation trend.

The above-mentioned characteristics in the first time period and the second time period can be used to reflect the actual change of the internal resistance of the battery cell, and a relatively accurate internal resistance of the battery cell can be determined through the above-mentioned characteristics. At the same time, there is a corresponding relationship between parameters such as current or voltage in these two time periods and the internal resistance of the battery cell, and the internal resistance of the battery cell can be determined in real time through this corresponding relationship. It can be seen that compared with the internal resistance of the battery cell calculated by using half a year's data in the prior art, the internal resistance of the battery cell determined by the present application has a smaller deviation from the actual value, and the accuracy is higher, and it can be calculated in real time, and the practicability is also more powerful.

Specifically, in one embodiment, as shown in FIG. 5 , in step 44, according to the voltage, the first duration, the second duration, the first magnification, the second magnification and the change trend, the process of determining the internal resistance of the cell includes the following steps :

Step 51: If the change trend includes a monotonic change trend, and/or the current fluctuates within the first current interval, and the second duration is not less than the second duration threshold, and the second magnification is not less than the second magnification threshold, then according to The voltage, the first duration and the first magnification determine the internal resistance of the cell.

Wherein, the monotonous change trend includes a monotonically increasing trend and a monotonically decreasing trend. The first current range refers to the maximum range in which the current fluctuates up and down. Wherein, if the current fluctuates in the first current interval, it means that the maximum value of the current is not greater than the maximum value of the first current interval, and the minimum value of the current is not less than the minimum value of the first current interval. The second duration threshold and the second magnification threshold may be set according to actual application conditions, which are not specifically limited in this embodiment of the present application. For example, in an embodiment, the second duration threshold may be set to 2s, and the second magnification threshold may be set to 0.2C.

It can be understood that the first current interval defines the range of current fluctuations. For example, the first current interval can be [1A, 3A], [2A, 4A], or [10A, 12A], etc. It only needs to satisfy that the range (that is, the size) of the first current interval remains unchanged. In addition, if the current remains constant, it is a constant current, which also satisfies the trend of the current fluctuating in the first current range.

In this embodiment, the conditions in step 51 are the conditions to be met in the second time period. That is, first determine whether the second time period meets the requirements, and then further judge whether the first time period meets the requirements on the premise that the second time period meets the above conditions. By gradually determining whether each time period satisfies the conditions, the workload of calculation can be reduced, which is beneficial to improve the efficiency of determining the internal resistance of the battery cell.

Please also refer to FIG. 6 . FIG. 6 shows a schematic diagram of several currents that meet the conditions in step 51 that may be collected in the second time period. Wherein, the abscissa represents time, and the unit is second (s), and the ordinate represents current, and the unit is ampere (A). Curve L61 represents the first type of current that may be collected; curve L62 represents the second type of current that may be collected; curve L63 represents the third type of current that may be collected; curve L64 represents the fourth type of current that may be collected.

As shown in FIG. 6 , the variation trend of the current L61 includes both a monotonically decreasing trend part and a constant current part (that is, the trend of the current fluctuating in the first current interval). The changing trend of the current L62 only includes a monotonically decreasing trend. The current L63 is a constant current, that is, the variation trend of the current L63 only includes the trend of the current fluctuating in the first current range. The variation trend of the current L64 only includes the trend of the current fluctuating within the first current interval, wherein the first current interval is [I61, I62].

In one embodiment, as shown in FIG. 7 , in step 51, according to the voltage, the first duration and the first magnification, the specific implementation process of determining the internal resistance of the cell includes the following steps:

Step 71: If the first duration is not less than the first duration threshold and the first multiplier is not greater than the first ratio threshold, then determine the internal resistance of the cell according to the voltage and the current in the second time period.

The first duration threshold and the first magnification threshold may be set according to actual application conditions, which are not specifically limited in this embodiment of the present application. For example, in an embodiment, the first duration threshold may be set to 30s, and the first magnification threshold may be set to 0.05C.

After it is determined that the second time period meets the requirements, it is further determined whether the first time period meets the requirements. That is, the conditions in step 71 are the conditions to be met in the first time period. By further determining that the first time period meets the requirements, the probability that the current voltage of the cell deviates from the steady-state voltage or the equilibrium potential can be reduced, so as to obtain a voltage with no polarization as much as possible. Therefore, relatively reliable voltage data can be obtained, which is conducive to improving the accuracy of calculating the internal resistance of the battery cell.

When both the first time period and the second time period satisfy the preset condition, the internal resistance of the cell can be determined according to the collected voltage and the current in the second time period.

In one embodiment, as shown in FIG. 8 , in step 71, according to the voltage and the current in the second time period, the implementation process of determining the internal resistance of the cell includes the following steps:

Step 81: Judging whether the current in the second time period is a constant current.

Step 82: If yes, determine the current in the second time period as the first current.

Constant current means that the current remains constant at a constant value. When the current in the second time period is a constant current, the subsequent calculation of the internal resistance of the battery cell can be performed directly according to the obtained current. In this embodiment, the first current is the current in the second time period.

Step 83: If not, obtain an equivalent current according to the current in the second time period, and determine that the equivalent current is the first current.

When the current in the second time period is not a constant current, such as current L61 , current L62 or current L64 shown in FIG. 6 , an equivalent current can be obtained according to the current in the second time period. This equivalent current helps to simplify the subsequent process of calculating the internal resistance of the cell to improve calculation efficiency. In this embodiment, the first current is the obtained equivalent current. Wherein, the voltage difference caused by the converted current (that is, the equivalent current) and the corresponding pre-converted current should be equal.

In one embodiment, the equivalent current may be a constant current, that is, the current in the second period of time may be converted into a corresponding constant current. Among them, the equivalent current can be obtained by the following formula:

Among them, t is any moment in the second time period, I _eq is the equivalent current, w(t) is the weight function, I(t) is the current changing with time, and t _end is the moment when the second time period ends , n is a positive integer and 2≤n≤6. In the formula (1), first calculate the weight of the current at each moment in the second time period, and then use each weight to multiply the current at the corresponding moment and then sum to obtain the equivalent current.

Step 84: Determine the internal resistance of the cell according to the first current and voltage.

In an embodiment, before step 84 is performed, that is, after determining the first current, it is further determined whether the first current is within the second current interval. If the first current is not within the second current range, it may go back to step 21 in the above embodiment.

Wherein, the second current interval may be set according to actual application conditions, which is not limited in this embodiment of the present application. For example, in one embodiment, the second current interval can be set to [0.05Imax, 0.8Imax], where Imax can be set to the temperature of the battery core is 25 ° C, and the state of charge is 50%, no aging (ie Brand new) the maximum charge and discharge current of the cell. Moreover, Imax is related to the performance of the cell, that is, different Imax can be obtained based on different cell types or materials. For example, for a ternary cell, its Imax charged in 10s is 926A, and its Imax discharged in 10s is 940A.

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

Furthermore, in one embodiment, as shown in FIG. 9 , in step 84, according to the first current and voltage, the implementation process of determining the internal resistance of the cell includes the following steps:

Step 91: Obtain a 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 first voltage difference is the difference between the voltage of the battery cell at the end of the first time period and the voltage of the battery cell at the end of the second time period.

Step 92: Determine the internal resistance of the cell according to the first voltage difference and the first current.

In an embodiment, it may first be determined whether the currently obtained first voltage difference and the first current are credible. If it is authentic, execute step 92; if not, execute step 21 in the above embodiment. Calculating the internal resistance of the battery cell according to the credible first voltage difference and the first current is beneficial to improve the accuracy of the calculation.

In one embodiment, whether the first voltage difference and the first current are credible is determined in the following manner. First, record the current first voltage difference as the Nth first voltage difference ΔU, and record the current first current as the Nth first current I, and according to the Nth first voltage difference and the Nth A ratio of current to obtain the Nth first internal resistance R=ΔU/I, where N is a positive integer greater than 1.

Next, obtain the N-1 first voltage difference ΔU ₁ and the N-1 first current I ₁ , and obtain the N-1 first current I 1 according to the ratio of the N-1 first voltage difference to the N-1 first current. N-1 first internal resistances R ₁ =ΔU ₁ /I ₁ .

Then calculate the first ratio of the absolute value of the difference between the Nth first internal resistance R and the N-1th first internal resistance _R1 to the N-1th first internal resistance, that is, the first ratio is: | RR ₁ |/R ₁ .

Furthermore, if the absolute value |I ₁ | of the N-1th first current I ₁ is greater than the absolute value |I| of the N-th first current _I , the absolute When the value is greater than the absolute value of the Nth first voltage difference ΔU, or the absolute value | _I1 | of the N-1th first current _I1 is smaller than the absolute value |I| of the Nth first current I, the The absolute value of the N-1 first voltage differences ΔU ₁ is less than the absolute value ΔU of the Nth first voltage difference, and the first ratio is less than or equal to the first ratio threshold, then it is judged that the first voltage difference and the first current can be letter, step 92 can be performed. In other words, the reliability of the first voltage difference and the first current can be determined by the following preset criteria (2), (3) and (4):

If |I ₁ |>|I|, then |ΔU ₁ |>|ΔU|. (2)

If |I ₁ |<|I|, then |ΔU ₁ |<|ΔU|. (3)

|RR ₁ |/R ₁ ≤ first ratio threshold. (4)

Wherein, the first ratio threshold may be set according to actual application conditions, which is not limited in this embodiment of the present application. For example, in one embodiment, the first ratio threshold may be set to 20%.

It can be understood that if the current increases, the voltage difference will also increase under the same conditions. According to the change characteristics between the current and the voltage difference, it can be determined whether the currently obtained first voltage difference and the first current are credible. Therefore, by obtaining two adjacent first voltage differences and first currents, if the change characteristics between the current and voltage differences conform to the preset change characteristics, the cell can be further determined according to the first voltage difference and the first current. internal resistance. Through the above method, the difference value caused by the sampling error can be eliminated, which is beneficial to further improve the accuracy of the subsequent calculated internal resistance of the battery cell.

In an embodiment, after determining that the first voltage difference and the first current are credible, the internal resistance of the cell can be calculated as:

DCR=|ΔU|×K/|I|. (5)

Wherein, DCR is the internal resistance of the cell, |ΔU| is the absolute value of the first voltage difference, |I| is the absolute value of the first current, and K is greater than or equal to 0.8 and less than or equal to 1.2.

The internal resistance of the cell can be obtained by calculating the ratio of the voltage variation in the second time period to the current in the second time period. However, since the first current may be an equivalent current obtained by non-constant current conversion when obtaining the first current, there may be errors in the conversion process. Then, by setting the K value, the error can be corrected according to the actual application situation, so as to improve the calculation accuracy.

In one embodiment, after the internal resistance of the cell is determined by the method provided in the embodiment of the present application, the second ratio of the internal resistance DCR of the cell to the initial internal resistance R0 of the cell is further calculated, that is, the second ratio is: DCR /R0. Wherein, the second ratio is used to reflect the aging degree of the battery cell, and the initial internal resistance is the internal resistance of the unaged battery cell.

Wherein, in one embodiment, the initial internal resistance R0 of the battery cell can be detected by the battery cell in advance and set in the battery management system.

Specifically, please refer to FIG. 10 , which shows a schematic diagram of the current of the battery cell when the battery cell is set to work continuously in the first time period and the second time period. As shown in FIG. 10 , the abscissa represents time in seconds (s), and the ordinate represents current in ampere (A). Wherein, the current in the first time period is a curve L91, the current in the second time period is a curve L92, and both the first time period and the second time period are set as constant current periods.

In this embodiment, the first time period and the second time period are the time periods that meet the preset conditions, and then, according to the voltage and current of the second time period, and through the internal resistance of the battery cell provided by the embodiment of the present application By determining the method, the initial internal resistance R0 of the cell can be calculated.

The aging degree of the battery cell can represent the attenuation degree of the capacity of the battery cell. For example, the aging degree of the battery cell with a capacity attenuation of 50% is more serious than that of the cell with a capacity attenuation of 20%. Therefore, according to the second ratio, the dynamic evaluation of the internal resistance of the battery cell during the whole life cycle can be realized, which is beneficial to the battery management system to manage the battery cell more effectively, so that the performance of the battery cell can be fully utilized. At the same time, the growth mode of the internal resistance of the battery cell and the attenuation degree of the reflected battery cell can also be measured according to the second ratio, so as to be used for power attenuation calculation. Furthermore, the output power of the battery cell can be controlled according to the degree of attenuation, which can effectively reduce the risk of damage to the battery cell and help prolong the service life of the battery cell.

In the method for determining the internal resistance of the battery cell provided in the embodiment of the present application, the working condition data of the battery cell is firstly collected. Then judge whether the temperature and state of charge in the working condition data meet the target conditions. If the target condition is not met, wait for the next working condition data collection; if the target condition is met, further judge whether there is a first time period and a second time period that meet the requirements. If there is no first time period and second time period that meet the requirements, wait for the next working condition data collection; if there are first time period and second time period that meet the requirements, then further judge whether the current in the second time period is For 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 judged whether the constant current in the second time period or the equivalent constant current is within the set current range. If the constant current or equivalent constant current in the second time period is not within the set current range, wait for the next working condition data collection; if the constant current or equivalent constant current in the second time period is within the set current range In the interval, according to the set standard, it is judged whether the obtained parameters such as current or voltage are credible. If it is unreliable, wait for the next working condition data collection; if it is credible, calculate and determine the internal resistance of the battery cell according to the current and voltage in the second time period.

In this embodiment, in the whole life cycle, the actual internal resistance of the battery during use (for example, during driving) can be obtained according to the real-time working condition of the battery. Therefore, it can effectively guide the performance of the battery cell to be more fully exerted, and is beneficial to prolong the service life of the battery cell. At the same time, if the battery cell is used as a power source for an electric vehicle, it can improve driving safety and power of the electric vehicle.

Please refer to FIG. 11 , which shows a schematic structural diagram of a device for determining the internal resistance of a cell provided by an embodiment of the present application. The device 1100 for determining the internal resistance of a cell includes: a data acquisition unit 1101 and a first determination unit 1102 .

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

The first determining unit 1102 is used for determining the internal resistance of the cell according to voltage, current, state of charge and temperature.

The above-mentioned product can execute the method provided by the embodiment of the present application shown in Fig. 2, and has corresponding functional modules and beneficial effects for executing the method. For technical details not described in detail in this embodiment, refer to the method provided in the embodiment of this application.

Please refer to FIG. 12 , which shows a schematic structural diagram of a device for determining the internal resistance of a cell provided by an embodiment of the present application. As shown in FIG. 12 , the device 1200 for determining the internal resistance of a cell includes one or more processors 1201 and a memory 1202 . Wherein, one processor 1201 is taken as an example in FIG. 12 .

The processor 1201 and the memory 1202 may be connected through a bus or in other ways. In FIG. 12 , connection through a bus is taken as an example.

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 method for determining the internal resistance of a cell in the embodiment of the present application Corresponding program instructions/modules (for example, each unit described in FIG. 11 ). The processor 1201 runs the non-volatile software programs, instructions and modules stored in the memory 1202 to execute various functional applications and data processing of the device for determining the internal resistance of the battery cell, that is, to realize the battery cell in the above method embodiment. The method for determining the internal resistance and the functions of each unit of the above-mentioned device embodiment.

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

The program instructions/modules are stored in the memory 1202, and when executed by the one or more processors 1201, perform the method for determining the internal resistance of the cell in any of the above method embodiments, for example, perform the above-described Each step shown in Fig. 2, Fig. 3a, Fig. 3b, Fig. 4, Fig. 5, Fig. 7, Fig. 8 and Fig. 9; the function of each unit described in Fig. 11 can also be realized.

An embodiment of the present application further provides a battery management system, including the device for determining the internal resistance of a battery cell in any of the above embodiments.

An embodiment of the present application also provides a battery pack, including a battery module and the battery management system in any of the above embodiments, the battery management system is electrically connected to the battery module, wherein the battery module includes at least one battery .

The internal resistance of each battery cell in the battery pack can be determined by using the method provided in the embodiment of the present application, so that the internal resistance of the battery pack can be obtained.

In an embodiment, the internal resistance of the cell with the smallest capacity and the internal resistance of 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 through the internal resistance of the two battery cells, which is beneficial to better management of the battery pack to better exert the performance of the battery pack and prolong the service life of the battery pack.

An embodiment of the present application further provides an electric device, including a load and the battery pack in any one of the above embodiments, where the battery pack is used to supply power to the load.

The embodiment of the present application also provides a non-volatile computer storage medium, the computer storage medium stores computer-executable instructions, and the computer-executable instructions are executed by one or more processors, which can make the above-mentioned one or more processors The method for determining the temperature in any of the above method embodiments, and/or the method for determining the current threshold may be implemented. For example, execute the steps shown in Fig. 2, Fig. 3a, Fig. 3b, Fig. 4, Fig. 5, Fig. 7, Fig. 8 and Fig. 9 described above; the functions of each unit described in Fig. 11 can also be realized.

The device or device embodiments described above are only illustrative, and the unit modules described as separate components may or may not be physically separated, and the components shown as modular units may or may not be physical units , which can be located in one place, or can be distributed to multiple network module units. Part or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a general hardware platform, and of course also by hardware. Based on this understanding, the essence of the above technical solutions or the part that contributes to related technologies can be embodied in the form of software products, and the computer software products can be stored in computer-readable storage media, such as ROM/RAM, disk , optical disc, etc., including several instructions for a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments.

While the application has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the application. In particular, as long as there is no structural conflict, the technical features mentioned in the various embodiments can be combined in any manner. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

A method for determining the internal resistance of a battery cell, comprising:

Real-time collection of working condition data of the battery cell, wherein the working condition data includes voltage, current, state of charge and temperature;

The internal resistance of the cell is determined according to the voltage, the current, the state of charge and the temperature.
The method according to claim 1, wherein the determining the internal resistance of the cell according to the voltage, the current, the state of charge, and the temperature comprises:

If the state of charge is within the first state of charge interval and the temperature is within the first temperature interval, then determine the internal resistance of the cell according to the voltage and the current.
The method according to claim 2, wherein the determining the internal resistance of the cell according to the voltage and the current comprises:

Obtaining a continuous first time period and a second time period, wherein the moment when the second time period ends is the current moment;

Obtain a first duration of the first time period, and obtain a first rate of charge and discharge of the battery cell in the first time period according to the current;

Acquiring a second duration of the second time period, and obtaining a second rate of charge and discharge of the battery cell in the second time period according to the current, and obtaining a change trend of the current;

The internal resistance of the cell is determined according to the voltage, the first duration, the second duration, the first rate, the second rate, and the variation trend.
The method according to claim 3, wherein said determining said Cell internal resistance, including:

If the change trend includes a monotonic change trend, and/or the current fluctuates within the first current interval, and the second duration is not less than the second duration threshold, and the second magnification is not less than the second The rate threshold value is to determine the internal resistance of the cell according to the voltage, the first duration, and the first rate.
The method according to claim 4, wherein the determining the internal resistance of the cell according to the voltage, the first duration, and the first multiplier includes:

If the first duration is not less than a first duration threshold and the first multiplier is not greater than a first ratio threshold, then determine the internal resistance of the cell according to the voltage and the current in the second time period.
The method according to claim 5, wherein the determining the internal resistance of the cell according to the voltage and the current in the second time period comprises:

judging whether the current in the second time period is a constant current;

If so, then determine that the current in the second time period is the first current;

If not, obtaining an equivalent current according to the current in the second time period, and determining that the equivalent current is the first current;

Determine the internal resistance of the cell according to the first current and the voltage.
The method of claim 6, wherein,

The equivalent current is:
Wherein, t is any moment in the second time period, I eq is an equivalent current, w(t) is a weight function, I(t) is a current changing with time, and t end is the second time The moment when the segment ends, n is a positive integer and 2≤n≤6.
The method according to claim 6, wherein, before determining the internal resistance of the cell according to the first current and the voltage, the method further comprises:

It is determined that the first current is within a second current interval.
The method according to any one of claims 6-8, wherein the determining the internal resistance of the cell according to the first current and the voltage includes:

acquiring a 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 cell is determined according to the first voltage difference and the first current.
The method according to claim 9, wherein, before determining the internal resistance of the cell according to the first voltage difference and the first current, the method further comprises:

The current first voltage difference is recorded as the Nth first voltage difference, and the current first current is recorded as the Nth first current, and according to the Nth first voltage difference and the Nth A current ratio to obtain the Nth first internal resistance, where N is a positive integer greater than 1;

Obtain the N-1th first voltage difference and the N-1th first current, and obtain the N-1th first current according to the ratio of the N-1th first voltage difference to the N-1th first current an internal resistance;

calculating the first ratio of the absolute value of the difference between the Nth first internal resistance and the N-1th first internal resistance to the N-1th first internal resistance;

If the absolute value of the N-1th first current is greater than the absolute value of the Nth first current, the absolute value of the N-1th first voltage difference is greater than the Nth An absolute value of a voltage difference, or when the absolute value of the N-1th first current is smaller than the absolute value of the Nth first current, the absolute value of the N-1th 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 perform determining the battery cell according to the first voltage difference and the first current internal resistance.
The method according to claim 10, wherein the determining the internal resistance of the cell according to the first voltage difference and the first current comprises:

The internal resistance of the cell is: DCR=|ΔU|×K/|I|, wherein, DCR is the internal resistance of the cell, |ΔU| is the absolute value of the first voltage difference, and |I| The absolute value of the first current, K is greater than or equal to 0.8 and less than or equal to 1.2.
The method according to claim 1, wherein, after determining the internal resistance of the battery cell, the method further comprises:

calculating a second ratio of the internal resistance of the cell to the initial internal resistance of the cell;

Wherein, the second ratio is used to reflect the aging degree of the battery cell, and the initial internal resistance is the internal resistance of an unaged battery cell.
A device for determining the internal resistance of a battery cell, comprising:

The data acquisition unit is used to collect the working condition data of the electric core in real time, wherein the working condition data includes voltage, current, state of charge and temperature;

A first determining unit, configured to determine the internal resistance of the cell according to the voltage, the current, the state of charge and the temperature.
A device for determining the internal resistance of a battery cell, comprising:

a memory; and a processor coupled to the memory, the processor configured to perform the method of any one of claims 1 to 12 based on instructions stored in the memory.
A battery management system, comprising: the device for determining the internal resistance of the battery cell according to claim 13 or 14.
A battery pack, comprising: a battery module and the battery management system according to claim 15, the battery management system is electrically connected to the battery module, wherein the battery module includes at least one battery core.
An electrical device, comprising: a load and the battery pack according to claim 16, the battery pack being used to supply power to the load.
A computer-readable storage medium, comprising: storing computer-executable instructions, the computer-executable instructions being configured as the method procedure according to any one of claims 1 to 12.