Capacity correction method and system for power battery in low-temperature environment, terminal and medium

Abstract

The invention relates to the technical field of batteries, and discloses a capacity correction method and system for a power battery in a low-temperature environment, a terminal and a medium. The method comprises the following steps: acquiring a battery cell temperature in real time, and acquiring a capacity retention ratio corresponding to the battery cell temperature; and judging whether the environment temperature at the current moment is changed compared with that at the previous moment, if so, correcting the low-temperature available capacity at the current moment by adopting a formula, and otherwise, keeping the low-temperature available capacity unchanged. And calculating the low-temperature available SOC according to the low-temperature available capacity. On the basis of the measurement method, the current available SOC is introduced to serve as a new independent variable, the more reasonable low-temperature available capacity and the more accurate low-temperature SOC are obtained, the mileage of the electric vehicle at the low temperature is more accurate, and the problem that the electric vehicle cannot be started due to the fact that the SOC is set to be zero when the measurement method is powered on at the low temperature is solved; compared with the original measurement method, the method for activating the available capacity has the advantages that only the independent variable SOC is added, the calculation complexity is not obviously increased, but the low-temperature SOC precision is obviously improved.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a method for correcting the capacity of a power battery in a low-temperature environment, as well as a correction system, a computer terminal, and a computer-readable storage medium using the method. Background Art

[0002] Lithium iron phosphate batteries are widely used in the field of new energy vehicles due to their safety and long life. However, in low temperature environments, the available capacity of lithium iron phosphate batteries will drop significantly, causing challenges for the battery management system (BMS) in accurately calculating the battery's state of charge (SOC). Existing capacity correction strategies are mainly based on measurement methods, that is, measuring the battery's releasable capacity (Capacity) by discharging in low temperature environments. temp ) and the capacity at room temperature (Cap normal ) for comparison and calculate the capacity retention rate (η) at different temperatures. This method assumes that the capacity measured when the battery's SOC is 100% at low temperature represents the actual available capacity.

[0003] However, this measurement method has certain limitations, especially when the battery temperature fluctuates greatly. During the winter, as the electric vehicle is running, the battery temperature gradually rises, and the measurement method can more accurately reflect the actual available capacity. However, when the vehicle is parked overnight, the battery temperature drops, resulting in the measurement method causing the recorded frozen capacity (i.e., the available capacity at low temperature) to be greater than the capacity recorded by the BMS the previous night when the vehicle is started the next day, resulting in an error of 0% SOC, causing the vehicle to fail to start normally. This is because the measurement method does not take into account the actual SOC of the battery when it is parked, but only measures the capacity at low temperature when the SOC is 100%, resulting in deviations when it is used in a non-fully charged state. Therefore, how to more accurately correct the capacity measurement of the battery under low temperature conditions has become an urgent problem to be solved in the current battery field. Summary of the Invention

[0004] In order to solve the technical problem in the prior art that the capacity measurement of batteries under low temperature conditions is not accurate enough, the present invention provides a method, system, terminal and medium for correcting the capacity of power batteries under low temperature environments.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention discloses a method for correcting the capacity of a power battery in a low-temperature environment, comprising:

[0007] Obtain the battery cell temperature in real time and obtain the capacity retention rate corresponding to the battery cell temperature;

[0008] Determine whether the cell temperature at the current moment T has changed compared to the previous moment T0. If so, correct the low-temperature available capacity at the current moment T; otherwise, keep the low-temperature available capacity unchanged. The correction formula for the low-temperature available capacity is:

[0009] Cap F =Cap F0 (η1 / η0)

[0010] Where, Cap F is the low-temperature available capacity after correction at the current moment T, Cap F0 is the low-temperature available capacity at the previous moment T0, η1 is the capacity retention rate at the current moment T, and η0 is the capacity retention rate at the previous moment T0;

[0011] According to the low temperature available capacity Cap F Calculate the low temperature available SOC, that is, SOC temp , the calculation formula is:

[0012] SOC temp =SOC normal Cap F / Cap normal

[0013] Where, SOC normal Available SOC at room temperature, Cap normal This is the capacity available at room temperature.

[0014] As a further improvement to the above solution, the capacity retention rates corresponding to different battery cell temperatures are obtained by querying a pre-built battery cell capacity retention rate table. The process of constructing the battery cell capacity retention rate table is as follows:

[0015] Under a standard test environment, the available capacity of the battery cell is measured at multiple temperature nodes within a set temperature range, and the available capacity at one temperature is selected as the available capacity at room temperature. The available capacity at the remaining temperatures is divided by the available capacity at room temperature to obtain the capacity retention rate table of the battery cell.

[0016] As a further improvement of the above scheme, a current sensor is used to collect current at a preset period, and the real-time SOC is calculated by the ampere-hour integration method. The real-time SOC is then corrected by Kalman filtering and RLS-SOC online parameter identification processing, thereby obtaining the available SOC at room temperature without considering the influence of temperature, i.e., SOC normal .

[0017] As a further improvement to the above solution, multiple temperature sensors are arranged inside the battery pack to collect the battery cell temperature; wherein, the accuracy of each temperature sensor is not less than 0.1°C, and the temperature error collected by each temperature sensor does not exceed 3°C.

[0018] The present invention further discloses a capacity correction system for a power battery in a low-temperature environment, which applies the capacity correction method for a power battery in a low-temperature environment as described above; the system comprises:

[0019] Temperature acquisition module, which is used to obtain the battery cell temperature in real time;

[0020] The data processing module is used to obtain the capacity retention rate corresponding to the battery cell temperature, determine whether the ambient temperature at the current time T has changed compared to the previous time T0, and if so, correct the low-temperature available capacity at the current time T; otherwise, keep the low-temperature available capacity unchanged; wherein, the correction formula for the low-temperature available capacity is:

[0021] Cap F =Cap F0 (η1 / η0)

[0022] Where, Cap F is the low-temperature available capacity after correction at the current moment T, Cap F0 is the available capacity at the previous moment T0, η1 is the capacity retention rate at the current moment T, and η0 is the capacity retention rate at the previous moment T0;

[0023] According to the low temperature available capacity Cap F Calculate the low temperature available SOC, that is, SOC temp , the calculation formula is:

[0024] SOC temp =SOC normal Cap F / Cap normal

[0025] Where, SOC normal Available SOC at room temperature, Cap normal This is the capacity available at room temperature.

[0026] The present invention also discloses a computer terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. The terminal is characterized in that when the processor executes the computer program, the steps of the method for correcting the capacity of a power battery in a low temperature environment as described above are implemented.

[0027] The present invention also discloses a computer-readable storage medium having a computer program stored thereon, wherein when the program is executed by a processor, the steps of the method for correcting the capacity of a power battery in a low temperature environment as described above are implemented.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention introduces the current available SOC as a new independent variable on the basis of the measurement method, thereby obtaining a more reasonable low-temperature available capacity and a more accurate low-temperature SOC, making the mileage of electric vehicles at low temperatures more accurate, and solving the problem that the SOC is set to 0 when powered on at low temperatures in the measurement method, resulting in the electric vehicle being unable to start (breaking down); compared with the original measurement method, the activated available capacity method of the present invention only adds the SOC independent variable, and the calculation complexity is not significantly increased, but the low-temperature SOC accuracy is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a comparison chart of SOC freezing capacity at different starting freezing temperatures in Example 1 of the present invention.

[0031] Figure 2 This is a flow chart of a method for correcting the capacity of a power battery in a low-temperature environment in Example 1 of the present invention.

[0032] Figure 3 This is a comparison diagram of the SOC after capacity correction between the activation available capacity method of the present invention and the existing measurement method.

[0033] Figure 4 This is a structural block diagram of a capacity correction system for a power battery in a low-temperature environment in Example 2 of the present invention.

[0034] Figure 5 This is a schematic diagram of the structure of the computer terminal in Example 3 of the present invention. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] Example 1

[0037] For new energy electric vehicles equipped with lithium iron phosphate batteries, this invention incorporates the influence of current SOC into its measurement method, resulting in a novel low-temperature capacity correction method: the Activation Available Capacity Method. Through cell experiments, the variation pattern of low-temperature frozen capacity was determined, and the software was integrated into the BMS system. This method has been validated with real-world vehicle applications, demonstrating promising results.

[0038] First, the battery cell is verified: a 24AH lithium iron phosphate battery cell is used, and the test steps are as follows: at a normal temperature of 25°C, charge with a current of 1 / 3C to a full charge voltage of 3.65V; then change the ambient temperature to T°C to allow the battery cell to reach thermal equilibrium, then discharge the power of SOC0, and then cool it to -20°C to allow the battery cell to reach thermal equilibrium, and finally discharge the battery cell at 0.2C to a full discharge voltage of 2.0V, where T = 0°C, -10°C; SOC0 = 10%, 30%, 50%, 70%, 90%; organize the test data and calculate the total capacity of the battery cell frozen in each experiment. The results are as follows Figure 1 shown.

[0039] It can be seen from the experimental results that as the remaining discharge capacity decreases, the frozen capacity of the battery cell also decreases; at the same time, the frozen capacity does not change significantly with the starting freezing temperature of 0℃ and -10℃, but is mainly related to the final temperature of -20℃.

[0040] See also Figure 1 This embodiment provides a method for correcting the capacity of a power battery in a low-temperature environment, comprising the following steps:

[0041] S1. Obtain the battery cell temperature in real time and obtain the capacity retention rate corresponding to the battery cell temperature.

[0042] S2. Determine whether the cell temperature at the current time T has changed compared to the previous time T0. If so, correct the low-temperature available capacity at the current time T; otherwise, keep the low-temperature available capacity unchanged. The correction formula for the low-temperature available capacity is:

[0043] Cap F =Cap F0 (η1 / η0)

[0044] Where, Cap F is the low-temperature available capacity after correction at the current moment T, Cap F0 It is the low-temperature available capacity at the previous moment T0. The initial value of the low-temperature available capacity = available capacity * capacity retention rate of the temperature at the time of BMS power-on; η1 is the capacity retention rate at the current moment T, and η0 is the capacity retention rate at the previous moment T0.

[0045] S3. Based on the low temperature available capacity Cap F Calculate the low temperature available SOC, that is, SOC temp , the calculation formula is:

[0046] SOC temp =SOC normal Cap F / Cap normal

[0047] Where, SOC normalAvailable SOC at room temperature, Cap normal This is the capacity available at room temperature.

[0048] In step S1, the capacity retention rates corresponding to different battery cell temperatures are obtained by querying a pre-constructed battery cell capacity retention rate table.

[0049] The process of constructing the cell capacity retention rate table is as follows:

[0050] Under standard test conditions, the battery cells are measured to obtain the available capacity at different temperatures such as -20℃, 0℃, 25℃, and 40℃. The available capacity at 25℃ is selected as the available capacity at room temperature. The available capacity at other temperatures is divided by the available capacity at room temperature to obtain the battery cell capacity retention rate table.

[0051] As a further improvement of the above scheme, a current sensor is used to collect current at a preset period (10ms), and the real-time SOC is calculated by the ampere-hour integration method. At the same time, various correction methods such as Kalman filtering and RLS-SOC online parameter identification are used to eliminate the error caused by insufficient current collection accuracy. Finally, the available SOC at room temperature without considering the influence of temperature is obtained, that is, SOC normal .

[0052] In some embodiments, multiple temperature sensors may be arranged inside the battery pack to collect the cell temperature; wherein the accuracy of each temperature sensor is not less than 0.1°C, and the temperature error collected by each temperature sensor does not exceed 3°C.

[0053] This embodiment uses a test vehicle equipped with a 104AH lithium iron phosphate battery for experiments, and its capacity retention rate table is as follows:

[0054] Table 1. Capacity retention of the test vehicle at different temperatures

[0055] -20℃ -10℃ 0℃ 10℃ 25℃ 30℃ 45℃ 56.00％ 74.00％ 83.00％ 92.00％ 100.00％ 100.00％ 100.00％

[0056] The vehicle was driven in urban conditions and discharged to the actual SOC = 17.6%. It was then left to stand overnight in a low-temperature environment and started the next morning. The battery cell temperature was detected to be -6°C. The vehicle was then started and driven in urban conditions, discharging to the end.

[0057] As shown in Table 2, the measurement method and the activation available capacity method are compared at power-on startup; for the activation available capacity method of the present invention, the true SOC at room temperature is 17.6%, and the true SOC at low temperature after capacity correction is 14.3%, and the vehicle can start normally; for the measurement method, the true SOC at room temperature is 17.6%, and the true SOC at low temperature after capacity correction is 0%, and the vehicle cannot start.

[0058] Table 2. Low temperature power-up comparison results

[0059]

[0060]

[0061] See also Figure 3 , where the horizontal axis is time (t) and the vertical axis is SOC (%). As shown in Table 3, in the subsequent discharge condition, the actual SOC discharge amount = 17.6% - 4.8% = 12.8%; after capacity correction, the actual low-temperature SOC discharge amount = 14.3 - 2.7 = 11.6%. After using the activated available capacity method, the SOC error value is 1.2%, proving that this method can accurately determine the actual low-temperature SOC in low-temperature environments.

[0062] Table 3. Terminal discharge conditions

[0063] BMRealSoc(%) 17.6 15.2 10 4.8 RealSOC(%) 14.3 11.8 7.1 2.7 Temperature (℃) -6 -5 -1 2

[0064] In summary, the present invention introduces the current available SOC as a new independent variable on the basis of the measurement method, thereby obtaining a more reasonable low-temperature available capacity and a more accurate low-temperature SOC, making the mileage of electric vehicles at low temperatures more accurate, and solving the problem that the SOC is set to 0 when the measurement method is powered on at low temperatures, resulting in the electric vehicle being unable to start; compared with the original measurement method, the activation available capacity method of the present invention only adds the SOC independent variable, and the calculation complexity is not significantly increased, but the low-temperature SOC accuracy is significantly improved.

[0065] Example 2

[0066] This embodiment provides a capacity correction system 10 for a power battery in a low-temperature environment, which applies the capacity correction method for a power battery in a low-temperature environment described in Example 1. The system includes:

[0067] A temperature acquisition module 11 is used to obtain the battery cell temperature in real time;

[0068] The data processing module 12 is used to obtain the capacity retention rate corresponding to the battery cell temperature, determine whether the ambient temperature at the current time T has changed compared to the previous time T0, and if so, correct the low-temperature available capacity at the current time T; otherwise, keep the low-temperature available capacity unchanged; wherein, the correction formula for the low-temperature available capacity is:

[0069] Cap F =Cap F0 (η1 / η0)

[0070] Where, Cap F is the low-temperature available capacity after correction at the current moment T, Cap F0is the available capacity at the previous moment T0, η1 is the capacity retention rate at the current moment T, and η0 is the capacity retention rate at the previous moment T0;

[0071] According to the low temperature available capacity Cap F Calculate the low temperature available SOC, that is, SOC temp , the calculation formula is:

[0072] SOC temp =SOC normal Cap F / Cap normal

[0073] Where, SOC normal Available SOC at room temperature, Cap normal This is the capacity available at room temperature.

[0074] Example 3

[0075] This embodiment provides a computer terminal, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method for correcting the capacity of a power battery in a low-temperature environment as described in Example 1 are implemented.

[0076] like Figure 5 As shown, the computer terminal provided in this embodiment includes: at least one processor 101, and a memory 102 connected to the at least one processor 101. The specific connection medium between the processor 101 and the memory 102 is not limited in this embodiment. Figure 5 In the example, the processor 101 and the memory 102 are connected via the bus 100. Figure 5 The bus 100 can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 5 The bus is represented by only one thick line, but it does not mean that there is only one bus or one type of bus. Alternatively, the processor 101 can also be called a controller, and there is no limitation on the name.

[0077] In this embodiment, the memory 102 stores instructions that can be executed by at least one processor 101 , and the at least one processor 101 can perform the aforementioned method by executing the instructions stored in the memory 102 .

[0078] Among them, the processor 101 is the control center of the device, which can use various interfaces and lines to connect the various parts of the entire control device, and monitor the device as a whole by running or executing instructions stored in the memory 102 and calling data stored in the memory 102, the various functions of the device and processing data.

[0079] In one possible design, processor 101 may include one or more processing units. Processor 101 may integrate an application processor and a modem processor. The application processor primarily processes the operating system, user interface, and application programs, while the modem processor primarily handles wireless communications. It is understood that the modem processor may not be integrated into processor 101. In some embodiments, processor 101 and memory 102 may be implemented on the same chip. In some embodiments, they may also be implemented on separate chips.

[0080] The processor 101 can be a general-purpose processor, such as a central processing unit (CPU), a digital signal processor, an application-specific integrated circuit, a field programmable gate array or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component, and can implement or execute the various methods, steps, and logic block diagrams disclosed in the embodiments. A general-purpose processor can be a microprocessor or any conventional processor. The steps of the method for correcting the capacity of a power battery in a low-temperature environment disclosed in Example 1 can be directly embodied as being executed by a hardware processor, or can be executed by a combination of hardware and software modules in the processor 101.

[0081] The memory 102 is a non-volatile computer-readable storage medium that can be used to store non-volatile software programs, non-volatile computer executable programs and modules. The memory 102 may include at least one type of storage medium, such as a flash memory, a hard disk, a multimedia card, a card-type memory, a random access memory (RAM), a static random access memory (SRAM), a programmable read-only memory (PROM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a magnetic memory, a magnetic disk, an optical disk, etc. The memory 102 is any other medium that can be used to carry or store desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto. The memory 102 in this embodiment can also be a circuit or any other device that can implement a storage function, for storing program instructions and / or data.

[0082] By programming the processor 101, the code corresponding to the security verification method described in the above embodiment can be fixed into the chip, so that the chip can execute the security verification method when it is running. Figure 2 The steps of the method for correcting the capacity of a power battery in a low temperature environment are shown. How to design and program the processor 101 is a technique well known to those skilled in the art and will not be described in detail here.

[0083] Example 4

[0084] This embodiment provides a computer-readable storage medium having a computer program stored thereon. When the program is executed by a processor, the steps of the method for correcting the capacity of a power battery in a low-temperature environment as described in Example 1 are implemented.

[0085] The computer-readable storage medium may include flash memory, a hard disk, a multimedia card, a card-type memory (e.g., SD or DX memory), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic memory, a magnetic disk, an optical disk, etc. In some embodiments, the storage medium may be an internal storage unit of a computer device, such as the hard disk or memory of the computer device. In other embodiments, the storage medium may also be an external storage device of the computer device, such as a plug-in hard disk equipped on the computer device, a smart media card (SMC), a secure digital (SD) card, a flash memory card, etc. Of course, the storage medium may also include both the internal storage unit of the computer device and its external storage device. In this embodiment, the memory is generally used to store the operating system and various application software installed on the computer device. In addition, the memory may also be used to temporarily store various types of data that have been output or are about to be output.

[0086] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for correcting the capacity of a power battery in a low temperature environment, characterized in that: include: Obtain the battery cell temperature in real time and obtain the capacity retention rate corresponding to the battery cell temperature; Determine whether the cell temperature at the current moment T has changed compared to the previous moment T0. If so, correct the low-temperature available capacity at the current moment T; otherwise, keep the low-temperature available capacity unchanged. The correction formula for the low-temperature available capacity is: Cap F =Cap F0 ·(η1 / η0) Where, Cap F is the low-temperature available capacity after correction at the current moment T, Cap F0 is the low-temperature available capacity at the previous moment T0, η1 is the capacity retention rate at the current moment T, and η0 is the capacity retention rate at the previous moment T0; According to the low temperature available capacity Cap F Calculate the low temperature available SOC, that is, SOC temp , the calculation formula is: SOC temp =SOC normal ·Cap F / Cap normal Where, SOC normal Available SOC at room temperature, Cap normal This is the capacity available at room temperature.

2. The method for correcting the capacity of a power battery in a low temperature environment according to claim 1, characterized in that: The capacity retention rates corresponding to different battery cell temperatures are obtained by querying a pre-built battery cell capacity retention rate table. The process of constructing the battery cell capacity retention rate table is as follows: Under a standard test environment, the available capacity of the battery cell is measured at multiple temperature nodes within a set temperature range, and the available capacity at one temperature is selected as the available capacity at room temperature. The available capacity at the remaining temperatures is divided by the available capacity at room temperature to obtain the capacity retention rate table of the battery cell.

3. The method for correcting the capacity of a power battery in a low temperature environment according to claim 1, characterized in that: The current sensor is used to collect current at a preset period, and the real-time SOC is calculated by the ampere-hour integration method. The real-time SOC is then corrected by Kalman filtering and RLS-SOC online parameter identification processing to obtain the available SOC at room temperature without considering the influence of temperature. normal .

4. The method for correcting the capacity of a power battery in a low temperature environment according to claim 1, characterized in that: Multiple temperature sensors are arranged inside the battery pack to collect the battery cell temperature; the accuracy of each temperature sensor is not less than 0.1°C, and the temperature error collected by each temperature sensor does not exceed 3°C.

5. The capacity correction system of the power battery in low temperature environment is characterized by: The method for correcting the capacity of a power battery in a low temperature environment according to any one of claims 1 to 4 is applied; the system comprises: Temperature acquisition module, which is used to obtain the battery cell temperature in real time; The data processing module is used to obtain the capacity retention rate corresponding to the battery cell temperature, determine whether the ambient temperature at the current time T has changed compared to the previous time T0, and if so, correct the low-temperature available capacity at the current time T; otherwise, keep the low-temperature available capacity unchanged; wherein, the correction formula for the low-temperature available capacity is: Cap F =Cap F0 ·(η1 / η0) Where, Cap F is the low-temperature available capacity after correction at the current moment T, Cap F0 is the available capacity at the previous moment T0, η1 is the capacity retention rate at the current moment T, and η0 is the capacity retention rate at the previous moment T0; According to the low temperature available capacity Cap F Calculate the low temperature available SOC, that is, SOC temp , the calculation formula is: SOC temp =SOC normal ·Cap F / Cap normal Where, SOC normal Available SOC at room temperature, Cap normal This is the capacity available at room temperature.

6. A computer terminal comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method for correcting the capacity of a power battery in a low temperature environment according to any one of claims 1 to 5 are implemented.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method for correcting the capacity of a power battery in a low temperature environment as claimed in any one of claims 1 to 5 are implemented.

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