Method and apparatus for determining hysteresis coefficient of a battery

Abstract

The application provides a method for determining a hysteresis coefficient of a battery, comprising the following steps: S1, determining whether the battery is in a maintenance mode according to a charging operation and a discharging operation of the battery, and based on at least an entering condition for judging whether the battery enters the maintenance mode, wherein the entering condition for judging whether the battery enters the maintenance mode comprises that the battery has performed a specific charging operation after a specific discharging operation; and S2, in the case that the battery is in the maintenance mode, selecting one of a first corresponding relationship and a second corresponding relationship according to a current direction of the battery during a period from a previous state to a current state, to determine the hysteresis coefficient of the current state according to the hysteresis coefficient of the previous state. The application also provides a corresponding device for determining the hysteresis coefficient of the battery, a computer program product and a vehicle. The hysteresis coefficient determined in this way can have higher accuracy. This helps to more accurately estimate the state of the battery by using the hysteresis coefficient.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular to a method for determining the hysteresis coefficient of a battery, a computer program product, an apparatus for determining the hysteresis coefficient of a battery, and a vehicle. Background Technology

[0002] With the development of energy storage technology, batteries have been widely used in various fields in recent years. For example, lithium-ion batteries, with their advantages of high energy density and long cycle life, are widely used as power batteries in vehicles. During battery use, it is necessary to understand their state, which includes estimating key parameters such as the battery's state of charge, maximum usable capacity, and / or battery health. Accurate estimation of these parameters is of great significance for the safe and efficient operation of batteries, prediction of remaining driving range, and lifespan management.

[0003] In battery management systems, the open-circuit voltage (OCV)-state-of-charge (SOC) curve (which reflects the relationship between open-circuit voltage and state of charge) is typically used to determine the battery's state of charge. However, the accuracy of this method is affected by the inherent hysteresis effect of the battery. Hysteresis causes differences in OCV during charging and discharging at the same SOC. In practical applications, batteries experience complex and varied operating conditions, causing their actual OCV response to often deviate significantly from the static OCV-SOC curve under ideal calibration conditions, and the impact of hysteresis is difficult to accurately assess.

[0004] Existing technologies still have shortcomings in assessing the impact of hysteresis on batteries and battery status. Summary of the Invention

[0005] The purpose of this application is to provide an improved method for determining the hysteresis coefficient of a battery, as well as a corresponding computer program product, an apparatus for determining the hysteresis coefficient of a battery, and a vehicle, so as to at least partially overcome the shortcomings of the prior art.

[0006] According to a first aspect of this application, a method for determining the hysteresis coefficient of a battery is provided, wherein the hysteresis coefficient is used to represent the degree of deviation of the current OCV-SOC correspondence of the battery relative to a reference OCV-SOC correspondence caused by the hysteresis effect, and the method for determining the hysteresis coefficient of the battery includes the following steps: -S1, based on the battery's charging and discharging operations, determine whether the battery is in a sustaining mode, at least based on entry conditions for determining whether the battery has entered a sustaining mode, wherein the entry conditions for determining whether the battery has entered a sustaining mode include the battery undergoing a specific charging operation after a specific discharging operation; and -S2, When the battery is in maintenance mode, select one of the first correspondence and the second correspondence based on the current direction of the battery from the previous state to the current state to determine the hysteresis coefficient of the current state based on the hysteresis coefficient of the previous state.

[0007] By defining the battery's maintenance mode, a specific method can be used to determine the hysteresis coefficient when the battery is identified as being in maintenance mode. The hysteresis coefficient determined in this way can have higher accuracy. This helps to more accurately estimate the battery's state, such as estimating the battery's SOC and / or maximum capacity.

[0008] The concept of this application is based first on the inventors' discovery that, under specific battery operating modes, the hysteresis effect is significantly influenced by the mixed charging and discharging operations of the battery, causing the battery's hysteresis coefficient to exhibit a different variation pattern than that in continuous discharge and continuous charging modes. Based on this, the inventors have established entry conditions for determining whether the battery has entered a maintenance mode. The concept of this application is also based on the inventors' discovery that, in the maintenance mode, the battery's hysteresis coefficient is correlated with the battery's hysteresis coefficient in the previous state, and this correlation is related to the type of the last charging and discharging operation performed by the battery before the current state.

[0009] According to an optional embodiment of this application, in step S2, a first correspondence is selected when the current direction of the battery during the transition from the previous state to the current state is the direction of charging current, and a second correspondence is selected when the current direction of the battery during the transition from the previous state to the current state is the direction of discharging current. Based on the first and second correspondences, the rate of change of the hysteresis coefficient in the current state with respect to the hysteresis coefficient in the previous state is different.

[0010] According to an optional embodiment of this application, the first correspondence is: λ1=max(a1 λ0+b1,λ0), where λ1 represents the hysteresis coefficient in the current state, λ0 represents the hysteresis coefficient in the previous state, a1 and b1 represent predetermined parameters, and max() represents the operation of taking the larger value. Alternatively or additionally, the second correspondence is: λ1=min(a2) λ1 + b2, λ0), where λ1 represents the hysteresis coefficient in the current state, λ0 represents the hysteresis coefficient in the previous state, a2 and b2 represent predetermined parameters, and min() represents the operation of taking the smaller value. Using this first and second correspondence, the accuracy of the hysteresis coefficient can be improved. Furthermore, this helps to estimate the battery state more accurately. In addition, the first and second correspondences set in this way also help to broaden the applicability of the battery maintenance mode. It should be understood that the predetermined parameters a1, b1, a2, and b2 are determined at least before the hysteresis coefficient is determined accordingly using the first and / or second correspondences.

[0011] According to an optional embodiment of this application, parameter a1 and parameter a2 are not equal.

[0012] According to an optional embodiment of this application, parameter b1 and parameter b2 are not equal.

[0013] According to an optional embodiment of this application, parameter a1 is less than 1 and greater than 0.

[0014] According to an optional embodiment of this application, parameter a2 is less than 1 and greater than 0.

[0015] According to an optional embodiment of this application, parameters a1 and / or a2 are set to decrease as the battery's health deteriorates. This helps to more accurately determine the battery's hysteresis coefficient throughout its entire lifespan and thus more accurately assess the battery's state.

[0016] According to an optional embodiment of this application, the first correspondence is: λ1=max(0.5 λ0+0.3,λ0); The second correspondence is: λ1=min(0.625) λ0-0.3,λ0).

[0017] According to an optional embodiment of this application, the specific discharge operation includes a discharge operation with a discharge amount exceeding a discharge amount threshold. The discharge amount threshold may optionally be greater than or equal to 8% SOC, and particularly greater than or equal to 10% SOC.

[0018] According to an optional embodiment of this application, the specific charging operation includes a charging operation in which the charging amount is above a charging amount threshold. The charging amount threshold may optionally be above 1% SOC.

[0019] According to an optional embodiment of this application, the specific charging operation does not include the charging operation of supplying power to the battery through an external charging device.

[0020] According to an optional embodiment of this application, in step S1, based on the battery's charging and discharging operations, and additionally based on exit conditions for determining whether the battery has exited the maintenance mode, it is determined whether the battery is in the maintenance mode.

[0021] Optionally, the exit condition for determining whether the battery has exited the maintenance mode includes: when the battery is in the maintenance mode, it performs a continuous discharge operation with a discharge amount exceeding the continuous discharge threshold.

[0022] Alternatively or additionally, the exit conditions for determining whether the battery has exited the maintenance mode include: the battery being electrically connected to an external charging device.

[0023] According to an optional embodiment of this application, when the battery enters the sustain mode and the amount of charge continuously applied is within a predetermined transition charge amount, the battery is in a first sustain phase. While in the first sustain phase, if the battery performs a continuous discharge operation exceeding a first continuous discharge threshold, the battery exits the sustain mode. The first continuous discharge threshold is positively correlated with the amount of charge continuously applied. In particular, the first continuous discharge threshold is equal to the amount of charge continuously applied.

[0024] When the battery enters the sustain mode and the continuous charge exceeds a predetermined transition charge, the battery enters the second sustain phase. While in the second sustain phase, if the battery performs a continuous discharge operation exceeding a second continuous discharge threshold, the battery exits the sustain mode. This second continuous discharge threshold is specifically greater than the transition charge.

[0025] Different exit conditions can be set for the first maintenance phase and the second maintenance phase to determine whether the battery has exited the maintenance mode. In particular, the exit conditions can be set such that, compared with the second phase, the battery is more likely to exit the maintenance mode and switch to the continuous charging mode due to a discharge operation in the first maintenance phase.

[0026] According to an optional embodiment of this application, the previous state of the battery is a state in which there is a predetermined SOC change relative to the current state of the battery, wherein the predetermined SOC change is in particular ±1% SOC change.

[0027] According to an alternative embodiment of this application, when the battery is in sustain mode, the hysteresis coefficient is determined independently of the battery current magnitude.

[0028] According to an optional embodiment of this application, the method for determining the hysteresis coefficient of the battery further includes: determining the hysteresis coefficient based at least on the current magnitude of the battery when the battery is not in sustain mode.

[0029] According to an alternative embodiment of this application, the battery includes an olivine-structured positive electrode lithium-ion battery, particularly a lithium iron phosphate battery.

[0030] According to an optional embodiment of this application, the battery is a vehicle's power battery.

[0031] According to a second aspect of this application, a computer program product is provided, comprising computer program instructions, wherein, when executed by one or more processors, the computer program instructions cause the one or more processors to perform a method for determining a hysteresis coefficient of a battery according to an exemplary embodiment of this application.

[0032] According to a third aspect of this application, an apparatus for determining the hysteresis coefficient of a battery is provided, wherein the apparatus for determining the hysteresis coefficient of a battery includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor is capable of performing a method for determining the hysteresis coefficient of a battery according to an exemplary embodiment of this application.

[0033] According to a fourth aspect of this application, a vehicle is provided, wherein the vehicle includes: a battery; and means for determining a hysteresis coefficient of the battery according to an exemplary embodiment of this application, configured to determine the hysteresis coefficient of the battery. Attached Figure Description

[0034] The principles, features, and advantages of this application will be better understood below with reference to the accompanying drawings. The drawings include: Figure 1 The OCV-SOC curve of a lithium iron phosphate battery as an example is schematically shown; Figure 2 A flowchart illustrating a method for determining the hysteresis coefficient of a battery according to an exemplary embodiment of this application is shown schematically. Figure 3 A flowchart illustrating a method for determining the hysteresis coefficient of a battery according to an exemplary embodiment of this application is shown schematically. Figure 4 , Figure 5 and Figure 6 The diagram schematically illustrates the data recorded while the sample battery was operating in sustain mode; Figure 7 The first and second correspondences employed in the maintenance mode according to an exemplary embodiment of this application are schematically illustrated. Figure 8 A flowchart illustrating step S1 of a method for determining the hysteresis coefficient of a battery according to an exemplary embodiment of this application is shown schematically. Figure 9 A flowchart illustrating step S1 of a method for determining the hysteresis coefficient of a battery according to an exemplary embodiment of this application is shown schematically; and Figure 10 A vehicle according to an exemplary embodiment of this application is illustrated schematically.

[0035] List of reference numerals 1 vehicle 11 batteries 12. Apparatus for determining the hysteresis coefficient of a battery Detailed Implementation

[0036] To make the technical problems to be solved, the technical solutions, and the beneficial technical effects of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and several exemplary embodiments. It should be understood that the specific embodiments described herein are only for explaining this application and are not intended to limit the scope of protection of this application.

[0037] The following explanation uses a lithium iron phosphate battery as an example. However, it should be understood that hysteresis is widespread in various types of batteries. Therefore, this application is also applicable to other types of batteries, particularly lithium-ion batteries. The battery can, for example, be used as a power battery for vehicles. However, it should be understood that the concept of this application can also be applied to batteries for other applications. For example, the battery can also be used to power aircraft, ships, or robots.

[0038] To illustrate the concept of this application, we will first combine... Figure 1 The hysteresis coefficient is explained. Figure 1 The OCV-SOC curve of a lithium iron phosphate battery, as an example, is schematically shown. The OCV-SOC curve represents the relationship between the battery's open-circuit voltage and its state of charge. Specifically, in Figure 1 The diagram shows the charging OCV-SOC curve L11, the discharging OCV-SOC curve L12, and the average OCV-SOC curve L13. The charging OCV-SOC curve L11 represents the relationship between OCV and SOC during charging. The discharging OCV-SOC curve L12 represents the relationship between OCV and SOC during discharging. It can be seen that due to the battery's hysteresis effect, the OCV-SOC curves are not consistent during charging and discharging. This results in the same SOC corresponding to different OCV values.

[0039] The average OCV-SOC curve L13 is obtained by averaging the charging OCV-SOC curve L11 and the discharging OCV-SOC curve L12. Using the average OCV-SOC curve L13, the battery's SOC can be roughly determined based on its OCV. However, the SOC determined in this way is often not accurate enough, which in turn makes it difficult to accurately assess the battery's state.

[0040] In addition, the SOC can be determined based on either the charging OCV-SOC curve L11 or the discharging OCV-SOC curve L12, depending on the type of operation performed on the battery previously (charging operation or discharging operation).

[0041] Specifically, the baseline charge OCV-SOC correspondence and baseline discharge OCV-SOC correspondence of the battery can be pre-calibrated through experiments.

[0042] The reference charge OCV-SOC correspondence can be calibrated, for example, through the following experiment. At a preset temperature and reference charging current, the battery is charged from 0% to 100% state of charge. The reference charging current is particularly between 0.05C and 0.1C. For example, the reference charging current is 0.1C. During charging, whenever the battery's SOC increases by a preset SOC interval, the battery is allowed to rest for a period of time (e.g., 2-4 hours), and the battery's OCV is measured and recorded. The SOC interval is particularly less than 10%, especially less than or equal to 5%, and optionally set to 1%. Based on the measured OCV and the corresponding SOC, the reference charge OCV-SOC correspondence can be determined.

[0043] The reference discharge OCV-SOC correspondence can be calibrated, for example, through the following experiment. At a preset temperature and reference discharge current, the battery is discharged from 100% state of charge to 0% state of charge. The reference discharge current can be, in particular, between 0.05C and 0.1C. For example, the reference discharge current is 0.1C. During the discharge process, whenever the battery's SOC decreases by a preset SOC interval, the battery is allowed to rest for a period of time (e.g., 2-4 hours), and the battery's OCV is measured and recorded. The SOC interval can be, in particular, less than or equal to 5%, and optionally set to 1%. Based on the measured OCV and the corresponding SOC, the reference discharge OCV-SOC correspondence can be determined.

[0044] After a battery has been charged, its State of Charge (SOC) can be determined using the reference charging OCV-SOC correspondence. After a battery has been discharged, its SOC can be determined using the reference discharging OCV-SOC correspondence. The SOC determined in this way has relatively high accuracy, but still has a significant margin of error. In practice, batteries undergo complex and varied operating conditions. The theoretical charging OCV-SOC curve L11 and discharging OCV-SOC curve L12 do not match the actual conditions.

[0045] Therefore, a hysteresis coefficient can be used to improve accuracy. The hysteresis coefficient represents the degree of deviation of the battery's OCV-SOC correspondence from a reference OCV-SOC correspondence caused by the hysteresis effect. The impact of different operating conditions on the hysteresis coefficient can be determined in advance through experiments. The reference OCV-SOC correspondence may include a reference charge OCV-SOC correspondence, a reference discharge OCV-SOC correspondence, and / or a reference average OCV-SOC correspondence.

[0046] According to an exemplary embodiment of this application, the hysteresis coefficient is set to represent the degree of deviation of the actual OCV-SOC correspondence of the battery relative to a reference average OCV-SOC correspondence. The reference average OCV-SOC correspondence represents the correspondence between the state of charge and the average value of its open-circuit voltage, respectively, based on reference charging OCV-SOC correspondence and reference discharging OCV-SOC correspondence. The sign of the hysteresis coefficient is used to indicate the direction of deviation relative to the reference average OCV-SOC correspondence. The absolute value of the hysteresis coefficient is used to represent the degree of deviation relative to the reference average OCV-SOC correspondence.

[0047] In an exemplary embodiment according to this application, a positive (greater than 0) hysteresis coefficient indicates a deviation in direction from the reference average OCV-SOC correspondence toward the reference charging OCV-SOC correspondence; a negative (less than 0) hysteresis coefficient indicates a deviation in direction from the reference average OCV-SOC correspondence toward the reference discharging OCV-SOC correspondence. The larger the absolute value of the hysteresis coefficient, the greater the degree of deviation from the reference average OCV-SOC correspondence.

[0048] The hysteresis coefficient for the reference charge OCV-SOC correspondence is +1. The hysteresis coefficient for the reference discharge OCV-SOC correspondence is -1.

[0049] Figure 2 A flowchart illustrating a method for determining the hysteresis coefficient of a battery according to an exemplary embodiment of this application is shown schematically. The method for determining the hysteresis coefficient of a battery may, for example, be performed by a controller of a battery management system (BMS).

[0050] like Figure 2 As shown, the method for determining the hysteresis coefficient of a battery includes at least steps S1 and S2.

[0051] In step S1, based on the battery's charging and discharging operations, it is determined whether the battery is in sustain mode, at least according to entry conditions for determining whether the battery has entered sustain mode. Entry conditions for determining whether the battery has entered sustain mode include the battery performing a specific charging operation after a specific discharging operation. If the battery is not in sustain mode, and it is detected that the battery performed the specific charging operation after the specific discharging operation, then the battery meets the entry conditions. Based on this, it can be determined that the battery has entered sustain mode.

[0052] If it is determined in step S1 that the battery is in sustain mode, then step S2 can be executed.

[0053] In step S2, when the battery is in sustain mode, one of the first and second correspondences is selected from the current direction of the battery from the previous state to the current state to determine the hysteresis coefficient of the current state based on the hysteresis coefficient of the previous state.

[0054] By defining the battery's sustain mode, the hysteresis coefficient can be determined in a specific way when the battery is identified as being in sustain mode. The hysteresis coefficient determined in this way can have higher accuracy.

[0055] The inventors discovered that, under specific battery operating modes, the hysteresis effect is significantly influenced by the mixed charging and discharging operations of the battery, causing the battery's hysteresis coefficient to exhibit a different variation pattern than in continuous discharge and continuous charging modes. Based on this, the inventors established entry conditions for determining whether the battery has entered a maintenance mode. This application's concept is also based on the inventors' discovery that, in maintenance mode, the battery's hysteresis coefficient is correlated with the battery's hysteresis coefficient in the previous state, and this correlation is related to the type of the last charge / discharge operation performed by the battery before the current state.

[0056] According to an embodiment of this application, in step S2, a first correspondence is selected when the current direction of the battery during the transition from the previous state to the current state is the direction of charging current, and a second correspondence is selected when the current direction of the battery during the transition from the previous state to the current state is the direction of discharging current. The difference between the first and second correspondences is not merely that the hysteresis coefficient changes in opposite directions (increases or decreases) due to the type of charging or discharging operation performed by the battery in the last instance. According to the first and second correspondences, the rate of change of the hysteresis coefficient in the current state with respect to the hysteresis coefficient in the previous state is different.

[0057] According to embodiments of this application, the method for determining the hysteresis coefficient when the battery is in sustain mode differs from the method used when the battery is not in sustain mode (e.g., continuous discharge mode). Figure 2 As shown, the method for determining the hysteresis coefficient of a battery may include step S3. If it is determined in step S1 that the battery is not in sustain mode, then step S3 may be performed. In step S3, the hysteresis coefficient is determined in a manner different from that in step S2.

[0058] In particular, when the battery is in sustain mode, the hysteresis coefficient can be determined independently of the battery current magnitude.

[0059] Optionally, in step S3, the hysteresis coefficient is determined at least based on the current magnitude of the battery.

[0060] In an exemplary embodiment according to this application, step S1 may include determining whether the battery is in a sustain mode, a continuous charging mode, or a continuous discharging mode based on the battery's charging and discharging operations. In step S3, the hysteresis coefficient may be determined using different methods depending on whether the battery is in a continuous charging mode or a continuous discharging mode. In particular, in the method for determining the hysteresis coefficient of a battery according to an exemplary embodiment of this application, different methods are used to determine the hysteresis coefficient for sustain mode, continuous charging mode, and continuous discharging mode, respectively.

[0061] For example, if the battery is in continuous discharge mode, the hysteresis coefficient can be determined in step S3 based on the current magnitude during the discharge process. Specifically, if the battery is in continuous discharge mode, the average discharge current during the discharge process can be obtained in step S3, and the hysteresis coefficient corresponding to the average discharge current can be determined using a pre-established correspondence between discharge current and hysteresis coefficient. The correspondence between discharge current and hysteresis coefficient can be stored, for example, as a functional expression, so that it can be used to determine the hysteresis coefficient corresponding to the battery's discharge current during battery use. The correspondence between discharge current and hysteresis coefficient can also be stored in the form of a lookup table.

[0062] The relationship between discharge current and hysteresis coefficient can include, in particular, the negative correlation between the absolute values ​​of discharge current and hysteresis coefficient.

[0063] As an example, the relationship between discharge current and hysteresis coefficient can be expressed as: λ=a ln(I_D)+b Where λ represents the hysteresis coefficient, I_D represents the discharge current, and a and b are predetermined parameters.

[0064] Figure 3 A flowchart illustrating a method for determining the hysteresis coefficient of a battery according to an exemplary embodiment of this application is shown schematically.

[0065] exist Figure 3 In the illustrated embodiment, the method for determining the hysteresis coefficient of the battery also includes steps S1, S2, and S3. Steps S1, S2, and S3 are as described above and will not be repeated here.

[0066] Step S2 may include steps S21, S22 and S23.

[0067] In step S21, the direction of the current in the battery during the transition from the previous state to the current state can be identified. The direction of the current may include the direction of the charging current (represented here, for example, by "+") and the direction of the discharging current (represented here, for example, by "-").

[0068] According to an exemplary embodiment of this application, the previous state of the battery is a state in which there is a predetermined change in SOC relative to the current state of the battery. The predetermined change in SOC is specifically a change of ±1%. Accordingly, the battery's hysteresis coefficient can be updated whenever the battery's SOC changes by 1%.

[0069] Optionally, the previous state of the battery can also be set to a state in which there is a predetermined change in charge or power input / output relative to the current state of the battery.

[0070] If, in step S21, the current direction of the battery from the previous state to the current state is identified as the charging current direction, then step S22 can be executed. If, in step S21, the current direction of the battery from the previous state to the current state is identified as the discharging current direction, then step S23 can be executed.

[0071] In step S22, the first correspondence is selected from the first correspondence and the second correspondence, and the hysteresis coefficient of the current state is determined based on the hysteresis coefficient of the previous state according to the first correspondence.

[0072] According to an exemplary embodiment of this application, the first correspondence is as follows: λ1=max(a1 λ0+b1,λ0) Where λ1 represents the hysteresis coefficient in the current state, λ0 represents the hysteresis coefficient in the previous state, a1 and b1 represent predetermined parameters, and max() represents the operation of taking the larger value. Parameter a1 is specifically less than 1 and greater than 0.

[0073] In step S23, a second correspondence is selected from the first correspondence and the second correspondence, and the hysteresis coefficient of the current state is determined based on the hysteresis coefficient of the previous state according to the second correspondence.

[0074] According to an exemplary embodiment of this application, the second correspondence is as follows: λ1=min(a2 λ0+b2,λ0) Where λ1 represents the hysteresis coefficient in the current state, λ0 represents the hysteresis coefficient in the previous state, a2 and b2 represent predetermined parameters, and min() represents the operation of taking the smaller value. Parameter a2 is specifically less than 1 and greater than 0.

[0075] By utilizing the first and second correspondences set up in this way, the accuracy of the hysteresis coefficient can be improved. This, in turn, helps to estimate the battery state more accurately.

[0076] Furthermore, the first and second correspondences established in this way help to broaden the applicability of the battery's maintenance mode. For example, when the battery is in maintenance mode, the first correspondence can still be applied even if the battery has undergone continuous charging operations with a large amount of charge.

[0077] Parameters a1 and a2 are specifically unequal, i.e., a1 ≠ a2. Alternatively or additionally, parameters b1 and b2 are unequal, i.e., b1 ≠ b2. These distinctions in parameter settings further clarify and effectively differentiate the mapping rules between the first and second correspondences.

[0078] Figure 3 The method for determining the hysteresis coefficient of a battery, as illustrated in an exemplary embodiment of this application, may include step S4. In step S4, the state of charge and / or maximum capacity of the battery may be determined using the hysteresis coefficient determined in step S2 (or step S3) and the reference OCV-SOC correspondence. For example, the state of charge of the battery may be determined based on the actual open-circuit voltage of the battery, according to the hysteresis coefficient and the reference OCV-SOC correspondence.

[0079] The first and second correspondences can be pre-calibrated experimentally using sample batteries. The functions or lookup tables used to describe the first and second correspondences can be stored in the BMS's memory.

[0080] The first and second correspondences used in the maintenance mode are further described below with examples.

[0081] Figure 4 The diagram schematically illustrates the data recorded while the sample battery was operating in sustain mode. Figure 4 In the diagram, the horizontal axis represents the hysteresis coefficient λ0 of the battery in the previous state, where the battery in the previous state has a SOC change of ±1% relative to the battery in the current state; the vertical axis represents the rate of change of the battery's hysteresis coefficient with respect to SOC Δλ / ΔSOC.

[0082] In maintenance mode, the rate of change of the battery's hysteresis coefficient is correlated with the battery's hysteresis coefficient in the previous state. From Figure 4 Observation suggests that this correlation may not be obvious. However, by filtering through this data to identify data points where the battery's current direction from the previous state to the current state is the direction of the charging current, we can obtain... Figure 5 The data points shown are used to select data points from which the current direction of the battery from the previous state to the current state is the direction of the discharge current. This yields the following results. Figure 6 The data points shown are filtered according to the current direction, making it clearer that the hysteresis coefficient of the battery in maintenance mode follows different changing patterns after charging and discharging.

[0083] Through the Figure 5 Analyzing the data points shown, we can obtain the correlation between the rate of change of the battery's hysteresis coefficient after a charging operation in maintenance mode and the hysteresis coefficient in the previous state. As an example, this correlation can be expressed as: Δλ = max(-0.5) λ0+0.3,0).

[0084] Similarly, through the Figure 6 Analyzing the data points shown, we can obtain the correlation between the rate of change of the hysteresis coefficient after a discharge operation in maintenance mode and the hysteresis coefficient in the previous state. As an example, this correlation can be expressed as: Δλ=min(-0.385λ0-0.3,0).

[0085] Based on the analysis of experimental data from the sample batteries, the first correspondence can be set as: λ1=max(0.5 λ0+0.3,λ0), the second correspondence is λ1=min(0.625). (λ0-0.3, λ0). The first and second correspondences established therefrom are applicable to determining the hysteresis coefficient when batteries of the same type and / or batch as the sample battery are in maintenance mode.

[0086] Figure 7 The first and second correspondences employed in the maintenance mode according to an exemplary embodiment of this application are schematically illustrated. Figure 7 In the diagram, L71 schematically illustrates the first correspondence used in the maintenance mode when the current direction of the battery during the period from the previous state to the current state is the charging current direction, and L72 schematically illustrates the second correspondence used in the maintenance mode when the current direction of the battery during the period from the previous state to the current state is the discharging current direction.

[0087] In an exemplary embodiment according to this application, parameters a1, a2, b1, and b2 may be pre-calibrated to fixed values ​​and stored in the memory of the BMS.

[0088] In an exemplary embodiment according to this application, parameters a1, a2, b1, and b2 can be configured to change with variations in the battery's health state. Specifically, parameters a1 and / or a2 can be configured to decrease as the battery's health state declines, according to a predetermined pattern. This helps to more accurately determine the battery's hysteresis coefficient throughout its entire lifespan and, consequently, to more accurately assess the battery's state.

[0089] As an example, the first correspondence can be set as: λ1=max(a1_0 SOH (λ0+b1,λ0). Similar to the above, λ1 represents the hysteresis coefficient in the current state, λ0 represents the hysteresis coefficient in the previous state, b1 represents the predetermined parameter, and max() represents the operation of taking the larger value. Here, a1_0 represents the baseline parameter value set for parameter a1, and SOH represents the health state of the battery.

[0090] Alternatively or additionally, the second correspondence can be set as: λ1=min(a2_0 SOH (λ0+b2,λ0). Similar to the above, λ1 represents the hysteresis coefficient in the current state, λ0 represents the hysteresis coefficient in the previous state, b2 represents the predetermined parameter, and min() represents the operation of taking the smaller value. Here, a2_0 represents the baseline parameter value set for parameter a2, and SOH represents the health state of the battery.

[0091] Figure 8 A flowchart illustrating step S1 of a method for determining the hysteresis coefficient of a battery according to an exemplary embodiment of this application is shown schematically.

[0092] As described above, in step S1, based on the battery's charging and discharging operations, it is determined whether the battery is in sustain mode, at least based on entry conditions used to determine whether the battery has entered sustain mode. Entry conditions used to determine whether the battery has entered sustain mode include the battery undergoing a specific charging operation after a specific discharging operation.

[0093] The specific discharge operation may include a discharge operation with a discharge amount exceeding a discharge amount threshold. The discharge amount threshold may optionally be greater than or equal to 8% SOC, particularly greater than or equal to 10% SOC. Alternatively or additionally, the specific charging operation includes a charging operation with a charging amount exceeding a charging amount threshold. The charging amount threshold may optionally be greater than 1% SOC.

[0094] The specific charging operation refers in particular to charging operations achieved through the vehicle's regenerative braking. Optionally, the specific charging operation does not include charging operations that supply power to the battery via an external charging device.

[0095] In an exemplary embodiment according to this application, if it is identified that the battery has performed a discharge operation with a discharge amount of 10% or more SOC and then a charging operation with a charge amount of 1% or more SOC based on the battery's charging and discharging operations, then it can be determined that the conditions for the battery to enter the maintenance mode are met.

[0096] like Figure 8 As shown, step S1 may include steps S11, S12, S13 and S14.

[0097] In step S11, if the battery is not in sustain mode, it is determined whether the entry condition is met. If the battery is found to meet the entry condition in step S11, step S12 can be executed; otherwise, step S13 can be executed.

[0098] In step S12, it can be determined that the battery is in maintenance mode. When the battery is in maintenance mode, step S14 can be executed. In step S14, it can be determined whether the battery meets the exit conditions for exiting maintenance mode. The exit conditions for determining whether the battery exits the maintenance mode may optionally include: when the battery is in maintenance mode, the continuous discharge amount exceeds a continuous discharge threshold. The continuous discharge threshold may optionally be greater than or equal to 5% SOC. Alternatively or additionally, the continuous discharge threshold may be less than or equal to 10% SOC.

[0099] Alternatively or additionally, the exit condition for determining whether the battery has exited the sustain mode may include: the battery being electrically connected to an external charging device. An external charging device refers to a charging device independent of the battery and the devices (e.g., vehicles) on which the battery is mounted. External charging devices may include, for example, home charging stations, public charging stations, fast-charging stations, etc.

[0100] If it is determined in step S14 that the exit condition is not met, the process can return to step S12. This means that the battery remains in sustain mode.

[0101] If it is determined in step S14 that the exit condition is met, then step S13 can be executed.

[0102] In step S13, it can be determined that the battery is not in sustain mode. Optionally, in step S13, it can be further determined whether the battery is in continuous discharge mode and / or continuous charging mode. For example, if the battery is in sustain mode and the continuous discharge exceeds the continuous discharge threshold, it can be determined that the battery exits sustain mode and switches to continuous discharge mode. Alternatively, if it is detected that the battery is electrically connected to an external charging device, it can be determined that the battery switches to continuous charging mode.

[0103] After performing step S13, you can return to step S11.

[0104] Figure 9 A flowchart illustrating step S1 of a method for determining the hysteresis coefficient of a battery according to an exemplary embodiment of this application is shown schematically.

[0105] like Figure 9 As shown, in step S1, step S11 can be executed first. In step S11, if the battery is not in sustain mode, it is determined whether the entry condition is met. If the battery is found to meet the entry condition in step S11, step S12 can be executed; otherwise, step S13 can be executed.

[0106] In step S12, it can be determined that the battery is in sustain mode. Then, step S141 can be executed.

[0107] In step S141, it can be determined whether the amount of charge continuously applied to the battery after entering the maintenance mode is within a predetermined transitional charge amount. If the amount of charge continuously applied to the battery after entering the maintenance mode is within the predetermined transitional charge amount, step S142 can be executed. If the amount of charge continuously applied to the battery after entering the maintenance mode exceeds the predetermined transitional charge amount, step S143 can be executed. The transitional charge amount is, for example, less than 2% SOC, and can optionally be set to 1% SOC.

[0108] In step S142, it can be determined that the battery is in the first maintenance phase. Then, step S144 can be executed. In step S144, it is determined whether the battery has performed a continuous discharge operation with a discharge amount exceeding the first continuous discharge threshold. If so, step S13 is executed, that is, the battery exits the maintenance mode. If not, it returns to step S12, that is, the battery is still in the maintenance mode.

[0109] The first continuous discharge threshold can be set to be positively correlated with the continuously charged amount. Alternatively or additionally, the first continuous discharge threshold can be less than the overcharge amount. In particular, the first continuous discharge threshold can be equal to the continuously charged amount.

[0110] In step S143, it can be determined that the battery is in the second maintenance phase. Then, step S145 can be executed. In step S145, it is determined whether the battery has performed a continuous discharge operation with a discharge amount exceeding the second continuous discharge threshold. If so, step S13 is executed, that is, the battery exits the maintenance mode. If not, it returns to step S12, that is, the battery is still in the maintenance mode.

[0111] The first continuous discharge threshold and the second continuous discharge threshold are different values. The second continuous discharge threshold can be set to be greater than the overcharge amount. The second continuous discharge threshold may optionally be greater than or equal to 5% SOC. Alternatively or additionally, the second continuous discharge threshold may be less than or equal to 10% SOC.

[0112] exist Figure 9 In the illustrated embodiment, when the amount of charge continuously applied after the battery enters the sustain mode is within a predetermined transition charge amount, the battery is in a first sustain phase; when the amount of charge continuously applied after the battery enters the sustain mode exceeds the predetermined transition charge amount, the battery is in a second sustain phase. Different exit conditions can be set for determining whether the battery should exit the sustain mode in the first and second sustain phases. Specifically, the exit conditions can be set such that, compared to the second phase, in the first sustain phase, the battery is more likely to exit the sustain mode and switch to continuous charging mode due to a discharge operation.

[0113] Figure 10 A vehicle 1 according to an exemplary embodiment of this application is schematically illustrated. The vehicle 1 includes a battery 11, which serves as a power battery for providing driving force to propel the vehicle 1. The vehicle 1 also includes a device 12 for determining the hysteresis coefficient of the battery.

[0114] The apparatus 12 for determining the hysteresis coefficient of a battery may include a memory and a processor, wherein the memory stores a computer program that, when executed by the processor, enables the processor to perform a method for determining the hysteresis coefficient of a battery according to exemplary embodiments of this application. The computer program instructions may be stored in a computer-readable storage medium. The computer-readable storage medium may include, for example, high-speed random access memory, and may also include non-volatile memory or volatile solid-state storage devices. The processor may be a central processing unit, or other general-purpose processors, digital signal processors, application-specific integrated circuits, off-the-shelf programmable gate arrays, or other programmable logic devices. It should be understood that the features and advantages described herein with respect to the method for determining the hysteresis coefficient of a battery also apply to the apparatus 12 for determining the hysteresis coefficient of a battery, and vice versa.

[0115] The device 12 for determining the hysteresis coefficient of the battery can be implemented as part of the battery management system (BMS). For example, the device 12 for determining the hysteresis coefficient of the battery can be implemented as the main control unit (MCU) of the battery management system or integrated into the main control unit.

[0116] It should be understood that, in describing exemplary embodiments, the specification may describe the method for determining the hysteresis coefficient of a battery in a specific order of steps, or the flowchart may present the method for determining the hysteresis coefficient of a battery in a specific order of steps. However, where the method for determining the hysteresis coefficient of a battery does not depend on the specific order of steps described herein, the method for determining the hysteresis coefficient of a battery should not be limited to the steps in that specific order. As will be understood by those skilled in the art, other orders of steps are also possible. For example, step S2 may be performed after and / or at least partially concurrent with step S1. Therefore, the specific order of steps set forth in the specification should not be construed as a limitation of the claims. Furthermore, the claims for the method for determining the hysteresis coefficient of a battery should not be limited to the steps performed in the order they are written, and those skilled in the art will readily understand that these orders may be varied and still fall within the scope of this application.

[0117] Although specific embodiments of this application are described in detail herein, they are given for illustrative purposes only and should not be construed as limiting the scope of this application. Various substitutions, modifications, and alterations can be conceived without departing from the spirit and scope of this application.

Claims

1. A method for determining the hysteresis coefficient of a battery, wherein, The hysteresis coefficient is used to represent the degree of deviation of the current OCV-SOC correspondence of the battery from the reference OCV-SOC correspondence caused by the hysteresis effect. The method for determining the hysteresis coefficient of the battery includes the following steps: -S1, based on the battery's charging and discharging operations, determine whether the battery is in a sustaining mode, at least based on entry conditions for determining whether the battery has entered a sustaining mode, wherein the entry conditions for determining whether the battery has entered a sustaining mode include the battery undergoing a specific charging operation after a specific discharging operation; and -S2, When the battery is in maintenance mode, select one of the first correspondence and the second correspondence based on the current direction of the battery from the previous state to the current state to determine the hysteresis coefficient of the current state based on the hysteresis coefficient of the previous state.

2. The method for determining the hysteresis coefficient of a battery according to claim 1, wherein, In step S2, a first correspondence is selected when the current direction of the battery during the period from the previous state to the current state is the direction of charging current, and a second correspondence is selected when the current direction of the battery during the period from the previous state to the current state is the direction of discharging current. According to the first and second correspondences, the rate of change of the hysteresis coefficient of the current state with respect to the hysteresis coefficient of the previous state is different.

3. The method for determining the hysteresis coefficient of a battery according to claim 2, wherein, The first correspondence is: λ1=max(a1) λ0+b1,λ0), where λ1 represents the hysteresis coefficient in the current state, λ0 represents the hysteresis coefficient in the previous state, a1 and b1 represent predetermined parameters, and max() represents the operation of taking the larger value; and / or The second correspondence is: λ1=min(a2) λ0+b2,λ0), where λ1 represents the hysteresis coefficient in the current state, λ0 represents the hysteresis coefficient in the previous state, a2 and b2 represent predetermined parameters, and min() represents the operation of taking the smaller value.

4. The method for determining the hysteresis coefficient of a battery according to claim 3, wherein, Parameters a1 and a2 are not equal; and / or Parameters b1 and b2 are not equal; and / or Parameter a1 is less than 1 and greater than 0; and / or The parameter a2 is less than 1 and greater than 0.

5. The method for determining the hysteresis coefficient of a battery according to claim 3 or 4, wherein, Parameters a1 and / or a2 are set to decrease as the battery's health deteriorates.

6. The method for determining the hysteresis coefficient of a battery according to any one of claims 3-5, wherein, The first correspondence is: λ1=max(0.5) λ0 +0.3, λ0); The second correspondence is: λ1=min(0.625) λ0 -0.3, λ0).

7. The method for determining the hysteresis coefficient of a battery according to any one of claims 1-6, wherein, The specific discharge operation includes discharge operations with a discharge quantity above a discharge quantity threshold, wherein the discharge quantity threshold is optionally greater than or equal to 8% SOC, particularly greater than or equal to 10% SOC; and / or The specific charging operation includes charging operations where the charging amount is above a charging amount threshold, wherein the charging amount threshold may optionally be above 1% SOC; and / or The specific charging operation does not include charging operations that supply power to the battery through an external charging device.

8. The method for determining the hysteresis coefficient of a battery according to any one of claims 1-7, wherein, In step S1, based on the battery's charging and discharging operations, and additionally based on the exit conditions used to determine whether the battery has exited the sustain mode, it is determined whether the battery is in sustain mode, wherein... The exit conditions for determining whether the battery has exited the sustain mode include: the battery, while in sustain mode, undergoing a continuous discharge operation with a discharge amount exceeding the continuous discharge threshold; and / or The exit conditions for determining whether the battery has exited the maintenance mode include: the battery being electrically connected to an external charging device.

9. The method for determining the hysteresis coefficient of a battery according to any one of claims 1-8, wherein, When the battery enters the maintenance mode and the amount of charge continuously supplied is within the predetermined transition charge amount, the battery is in the first maintenance phase. When the battery is in the first maintenance phase, if the battery performs a continuous discharge operation with a discharge amount exceeding a first continuous discharge threshold, the battery exits the maintenance mode. The first continuous discharge threshold is positively correlated with the amount of charge continuously supplied, and the first continuous discharge threshold is in particular equal to the amount of charge continuously supplied. When the battery enters the maintenance mode and the amount of charge continuously applied exceeds the predetermined transition charge amount, the battery enters the second maintenance phase. When the battery is in the second maintenance phase, if the battery performs a continuous discharge operation with a discharge amount exceeding a second continuous discharge threshold, the battery exits the maintenance mode. The second continuous discharge threshold is greater than the transition charge amount.

10. The method for determining the hysteresis coefficient of a battery according to any one of claims 1-9, wherein, The previous state of the battery is a state in which there is a predetermined change in SOC relative to the current state of the battery, and the predetermined change in SOC is specifically a change in SOC of ±1%.

11. The method for determining the hysteresis coefficient of a battery according to any one of claims 1-10, wherein, When the battery is in sustain mode, the hysteresis coefficient is determined independently of the battery current magnitude; and / or The method for determining the hysteresis coefficient of a battery further includes determining the hysteresis coefficient based at least on the battery current magnitude when the battery is not in sustain mode.

12. The method for determining the hysteresis coefficient of a battery according to any one of claims 1-11, wherein, The battery includes olivine-structured positive electrode lithium-ion batteries, particularly lithium iron phosphate batteries; and / or The battery in question is the vehicle's power battery.

13. A computer program product comprising computer program instructions, wherein, When executed by one or more processors, the computer program instructions enable the one or more processors to perform the method for determining the hysteresis coefficient of a battery according to any one of claims 1-12.

14. An apparatus for determining the hysteresis coefficient of a battery, wherein, The apparatus for determining the hysteresis coefficient of a battery includes a memory and a processor, wherein the memory stores a computer program that, when executed by the processor, enables the processor to perform a method for determining the hysteresis coefficient of a battery according to any one of claims 1-12.

15. A vehicle, wherein, The vehicles include: Batteries; and The apparatus for determining the hysteresis coefficient of a battery according to claim 14 is configured to determine the hysteresis coefficient of the battery.

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