Battery capacity determination method and device, storage medium, and battery

Abstract

The present invention provides a battery capacity determination method and device, a non-temporary computer-readable storage medium, and a battery. The battery capacity determination method includes: obtaining a first inflection point voltage threshold of the battery and its corresponding first inflection point power, a second inflection point voltage threshold and its corresponding second inflection point power, the first inflection point voltage threshold being greater than the second inflection point voltage threshold; controlling the battery to charge, and recording the first charging curve of the battery in real time; determining a target inflection point according to the first charging curve; detecting the power of the battery until charging is completed, obtaining a first charge-in power when the battery is charged to the first inflection point and a second charge-in power when the battery is fully charged; when the determined target inflection point includes the first inflection point, calculating the current capacity of the battery according to the first inflection point power, the first charge-in power, and the second charge-in power. The battery capacity determination method according to the present invention can greatly improve the speed and accuracy of battery capacity calculation.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a method and device for determining battery capacity, a non-temporary computer-readable storage medium, and a battery. Background Art

[0002] With the rapid development of battery technology, lithium-ion batteries have been widely used in electric vehicles, energy storage power stations and other fields. Lithium-ion batteries will gradually age and their performance will gradually decay during continuous charge and discharge cycles, which is manifested in reduced capacity, increased internal resistance, and reduced power. The degree of battery aging is expressed as SOH (State of Health). SOH can be defined in many ways, such as remaining capacity, internal resistance, number of cycles, etc. Among them, the most commonly used and most intuitive way is to define it by the remaining capacity of the battery, that is, the percentage of the battery capacity after aging to the initial capacity of the battery, also known as SOHC (State of Health Capacity).

[0003] At present, the remaining capacity of a battery is mainly calculated by fully charging or discharging the battery to calculate the total power in the charging or discharging stage, or by charging and discharging the battery in a certain SOC (State of Charge) range and calculating the total battery capacity based on the charging or discharging power and the corresponding SOC range.

[0004] However, the above methods for calculating the remaining capacity of the battery all have shortcomings. Specifically, fully charging and discharging the battery not only takes more time and equipment resources, but may also cause a series of safety-related issues such as overcharging, fire, and even explosion. Furthermore, because users usually charge the battery before it is completely discharged, it is difficult to trigger the full discharge condition of the battery, and once triggered, it will also affect the life of the battery itself. Therefore, it is not realistic to calculate the remaining capacity of the battery by fully charging and discharging the battery in application; and charging or discharging in a specific SOC range to obtain the remaining capacity of the battery, the SOC range must be selected to be long enough, which also has the problem of being difficult to trigger, and the accuracy of the SOC estimation is required to be high. Inaccurate SOC estimation can easily cause large errors in the results. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide a battery capacity determination method, which can quickly calculate the battery capacity and improve the accuracy of the battery capacity calculation.

[0006] A second object of the present invention is to provide a non-transitory computer-readable storage medium.

[0007] A third object of the present invention is to provide a device for determining battery capacity.

[0008] A fourth object of the present invention is to provide a battery.

[0009] In order to achieve the above object, in a first aspect, the present invention provides a method for determining battery capacity, the method comprising:

[0010] Acquire a first inflection point voltage threshold and its corresponding first inflection point power, a second inflection point voltage threshold and its corresponding second inflection point power of the battery, wherein the first inflection point voltage threshold is greater than the second inflection point voltage threshold;

[0011] Controlling the battery to charge, and recording a first charging curve of the battery in real time;

[0012] determining a target inflection point according to the first charging curve;

[0013] detecting the power of the battery until charging is completed, obtaining a first charged power when the battery is charged to the first inflection point and a second charged power when charging of the battery is completed; and

[0014] When the determined target inflection point includes the first inflection point, calculating the current capacity of the battery according to the first inflection point power, the first charged power, and the second charged power;

[0015] The first inflection point power, the first charged power, the second charged power and the current capacity of the battery are defined as Q_HVTP, Qch_HVTP, Qch_End and Qnow, respectively, and Q_HVTP, Qch_HVTP, Qch_End and Qnow satisfy the relationship: Qnow=Q_HVTP+Qch_End-Qch_HVTP;

[0016] And, when the determined target inflection point also includes the second inflection point, obtaining a third charged power when the battery is charged to the second inflection point, and correcting the first inflection point power according to the second inflection point power, the first charged power and the third charged power;

[0017] The second inflection point power and the third charged power are defined as Q_LVTP and Qch_LVTP respectively.

[0018] Q_HVTP, Qch_HVTP, Q_LVTP and Qch_LVTP satisfy the relationship:

[0019] Q_HVTP=Q_LVTP+Qch_HVTP-Qch_LVTP.

[0020] According to the battery capacity determination method of the embodiment of the present invention, the target inflection point is determined by analyzing the first charging curve, and when it is detected that the battery is fully charged, that is, the charging is completed, the first charge-in charge when the battery is charged to the first inflection point and the second charge-in charge when the battery is fully charged are obtained. When the determined target inflection point includes the first inflection point, the current capacity of the battery can be calculated according to the first inflection point charge, the first charge-in charge and the second charge-in charge of the battery. That is to say, the calculation method of the embodiment of the present invention can accurately calculate any starting state before the target inflection point, and there is no need to deeply discharge the battery before charging, so as to avoid the loss of the battery itself caused by full charging or full discharge, and improve the battery life and charging safety; furthermore, when calculating the current capacity of the battery, it is only necessary to detect the first charge-in charge when the battery is charged to the first inflection point and the second charge-in charge when the battery is fully charged, which is conducive to the rapid calculation of the battery capacity, and there is no need to select the SOC interval. Compared with selecting a specific SOC interval for charging or discharging to calculate the battery capacity, it can avoid the error caused by inaccurate SOC estimation in the battery state calculation, thereby improving the accuracy of the battery capacity calculation. In addition, when calculating the current capacity of the battery, the first inflection point capacity of the aged battery can be corrected according to the second inflection point capacity, the first charged capacity and the third charged capacity when the battery is charged to the second inflection point, so as to obtain the accurate value of the first inflection point capacity of the battery in the current aging state, thereby avoiding inaccurate calculation of the current capacity of the battery due to changes in the first inflection point capacity caused by battery aging, which is conducive to improving the accuracy of battery capacity calculation.

[0021] In a second aspect, the present invention provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein the computer program implements the battery capacity determination method as described above when executed.

[0022] The non-transitory computer-readable storage medium according to the embodiment of the present invention can greatly improve the speed and accuracy of battery capacity calculation by executing the computer program stored therein.

[0023] In a third aspect, the present invention provides a battery capacity determination device, the battery capacity determination device comprising:

[0024] at least one processor;

[0025] a memory communicatively coupled to the at least one processor;

[0026] The memory stores instructions that can be processed by the at least one processor, and the instructions implement the battery capacity determination method as described above when processed by the at least one processor.

[0027] According to the battery capacity determination device of the embodiment of the present invention, the speed and accuracy of battery capacity calculation can be greatly improved by executing the battery capacity determination method through a processor.

[0028] In a fourth aspect, the present invention provides a battery, the capacity of which is calculated using the battery capacity determination method as described above.

[0029] According to the battery of the embodiment of the present invention, the current capacity of the battery is calculated by using the above-mentioned battery capacity determination method, which can greatly improve the speed and accuracy of battery capacity calculation.

[0030] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description or learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings required for use in the implementation mode will be briefly introduced below. Obviously, the drawings described below are some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a schematic diagram comparing first charging curves and charging voltage difference curves of batteries with different aging degrees provided by one embodiment of the present invention.

[0033] Figure 2 It is a flow chart of a method for determining battery capacity provided by one embodiment of the present invention.

[0034] Figure 3 It is a functional block diagram of a battery capacity determination device provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0035] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0036] In view of the problems existing in the prior art, the battery capacity determination method proposed in the embodiment of the present invention can greatly improve the speed and accuracy of battery capacity calculation. The overall concept of the calculation method in the embodiment of the present invention is to detect the voltage-capacity curve of the battery to be tested in real time during the charging process, analyze the curve characteristics, and find the characteristic points of the curve. The battery capacity can be accurately calculated without deep discharge of the battery before charging and when the initial SOC state of the battery is unknown.

[0037] First, the curve characteristic points used in the embodiment of the present invention are explained and illustrated.

[0038] See also Figure 1 Generally speaking, the voltage-capacity characteristic curve (i.e., charging curve) of a battery (such as but not limited to a lithium-ion battery) has three intervals where the voltage changes slowly, which are called voltage platform areas. There is a region where the voltage changes rapidly between two voltage platform areas. The point where the voltage changes fastest in this region is called the voltage platform inflection point. The voltage is distinguished by the voltage level. The higher voltage is called the high voltage platform inflection point (referred to as HVTP), and the lower voltage is called the low voltage platform inflection point (referred to as LVTP). The voltage platform inflection point is shown as the maximum value point of the curve on the voltage differential curve. In practical applications, the high voltage platform inflection point and the low voltage platform inflection point can be distinguished according to the voltage value. Taking the power lithium-ion battery of an electric vehicle as an example, the SOC state at the beginning of charging is uncertain. If charging starts at a lower SOC segment (e.g., 5%), two platform inflection points, HVTP and LVTP, can be detected during charging; if charging starts at an intermediate SOC segment (i.e., the area between HVTP and LVTP), only one platform inflection point, HVTP, can be detected during charging. Figure 1 Shown are the charging curves and voltage difference curves of various batteries. Different curves represent batteries with different degrees of aging. It is not difficult to see that the curve of the battery with a lighter degree of aging will have two voltage platform inflection points, high and low.

[0039] It is well known to those skilled in the art that Figure 1 As shown in the figure, as the battery ages, the voltage-capacity characteristic curve of the battery will move toward the low capacity direction as a whole. During the movement, the inflection point charge Q_LVTP corresponding to LVTP (or the low voltage platform inflection point characteristic capacity) remains basically unchanged, that is, the inflection point charge Q_LVTP is fixed to, and the inflection point charge Q_HVTP corresponding to HVTP (or the high voltage platform inflection point characteristic capacity) changes little within a certain aging range, but the voltage thresholds corresponding to HVTP and LVTP will not change with the shift of the characteristic curve, so the voltage threshold can be used to distinguish the detected platform inflection points.

[0040] Based on the above explanations, a method for determining battery capacity according to an embodiment of the present invention is described below with reference to the accompanying drawings.

[0041] Figure 2 is a flow chart of a method for determining battery capacity according to one embodiment of the present invention. Figure 2 As shown, the battery capacity determination method of the embodiment of the present invention at least includes steps S1 to S5. The specific process of each step is as follows:

[0042] Step S1, obtaining a first inflection point voltage threshold and a first inflection point power corresponding to the battery, a second inflection point voltage threshold and a second inflection point power corresponding to the battery, wherein the first inflection point voltage threshold is greater than the second inflection point voltage threshold. It can be understood by those skilled in the art that the first inflection point voltage threshold and the first inflection point power are the voltage threshold and inflection point power corresponding to the inflection point of the high voltage platform, and the second inflection point voltage threshold and the second inflection point power are the voltage threshold and inflection point power corresponding to the inflection point of the low voltage platform.

[0043] In an embodiment of the present invention, for batteries of a certain batch and specification, the voltage threshold and inflection point power corresponding to the high voltage platform inflection point or the low voltage platform inflection point in its voltage-capacity characteristic curve can be determined. The values ​​of these characteristic quantities can be obtained through the voltage-capacity characteristic curve of a small number of batteries. The specific acquisition method will be described in detail in the subsequent content.

[0044] Step S2, controlling the battery to charge, and recording a first charging curve of the battery in real time.

[0045] In an embodiment of the present invention, when charging a battery with an unknown SOC state, the first capacity data of the battery during the charging process and its corresponding first voltage data are recorded in real time, and the voltage-capacity characteristic curve established according to the first capacity data and the first voltage data is the first charging curve. Specifically, taking a lithium-ion power battery as an example, in the prior art, when charging the lithium-ion power battery, the voltage, current, temperature, current charging time, charged power and other parameters of the lithium-ion power battery can be collected and recorded through a BMS (Battery Management System), and the charging curve of the lithium-ion power battery can be obtained according to the BMS charging algorithm, which will not be described in detail.

[0046] Step S3: determining a target inflection point according to the first charging curve.

[0047] In an embodiment of the present invention, the first charging curve is analyzed to obtain its inflection point, and whether the inflection point of the first charging curve is a target inflection point is determined according to the first inflection point voltage threshold and the second inflection point voltage threshold. As mentioned above, for a battery with an unknown SOC state, at least a high voltage platform inflection point can be detected during its charging process, which means that the target inflection point at least includes a high voltage platform inflection point (defined as the first inflection point), and the specific determination method of the target inflection point will be described in detail in the subsequent content.

[0048] Step S4, detecting the power of the battery until charging is completed, obtaining a first charge when the battery is charged to the first inflection point and a second charge when the battery is fully charged. It should be noted that charging completion means that the battery is fully charged.

[0049] In an embodiment of the present invention, when it is detected that the power of the battery reaches the full charge, the power charged to the battery from the start of charging to the time when the battery is charged to the first inflection point is taken as the first charge power, and the power charged to the battery from the start of charging to the time when the battery charging is completed is taken as the second charge power, and the first charge power is less than the second charge power. The charge power of the battery during the charging process can be obtained through the aforementioned BMS, which is not described in detail here.

[0050] Step S5, when the determined target inflection point includes the first inflection point, the current capacity of the battery is calculated according to the first inflection point power, the first charged power and the second charged power, wherein the current capacity of the battery is the total power of the battery in the current state.

[0051] It is understandable that for a battery with an unknown SOC state, at least a high voltage platform inflection point (i.e., the first inflection point) can be detected during its charging process, which means that the first inflection point is relatively easy to trigger. Therefore, in an embodiment of the present invention, when the determined target inflection point includes the first inflection point (i.e., the high voltage platform inflection point), the current capacity of the battery is calculated based on the first inflection point power, the first charged power, and the second charged power, and the battery state is judged by the current capacity of the battery, which is conducive to timely updating of the battery state.

[0052] Specifically, in an embodiment of the present invention, the first inflection point power, the first charged power, the second charged power and the current capacity of the battery are defined as Q_HVTP, Qch_HVTP, Qch_End and Qnow, respectively, and the first inflection point power Q_HVTP, the first charged power Qch_HVTP, the second charged power Qch_End and the current capacity Qnow of the battery satisfy the relationship: Qnow = Q_HVTP + Qch_End - Qch_HVTP. In other words, in the battery capacity determination method of the embodiment of the present invention, as long as the first inflection point power Q_HVTP, the first charged power Qch_HVTP and the second charged power Qch_End are determined, the current capacity Qnow of the battery can be quickly calculated according to the aforementioned relationship.

[0053] In summary, according to the battery capacity determination method of an embodiment of the present invention, when a battery with an unknown SOC state is charged, the target inflection point is determined by analyzing the first charging curve of the battery, and when it is detected that the battery is fully charged, that is, the charging is completed, the first charged power when the battery is charged to the first inflection point (that is, the high voltage platform inflection point) and the second charged power when the battery is charged are obtained. When the determined target inflection point includes the first inflection point, the current capacity of the battery can be calculated based on the first inflection point power, the first charged power and the second charged power of the battery that have been obtained. That is to say, the calculation method of the embodiment of the present invention can accurately calculate any starting state before the target inflection point, and there is no need to deeply discharge the battery before charging, thereby avoiding damage to the battery itself due to full charging or full discharging, and improving battery life and charging safety; furthermore, when calculating the current capacity of the battery, it is only necessary to detect the first charging amount when the battery is charged to the first inflection point and the second charging amount when the battery is fully charged, which is conducive to quickly calculating the capacity of the battery, and there is no need to select the SOC interval. Compared with selecting a specific SOC interval for charging or discharging to calculate the battery capacity, it can avoid the error in the battery state calculation caused by inaccurate SOC estimation, thereby improving the accuracy of the battery capacity calculation.

[0054] It should be noted that, in an embodiment of the present invention, step S1 of obtaining the first inflection point voltage threshold of the battery and its corresponding first inflection point power, the second inflection point voltage threshold and its corresponding second inflection point power, specifically includes: obtaining the second charging curve of the battery; determining the first inflection point and the second inflection point according to the second charging curve; obtaining the first inflection point voltage threshold and the first inflection point power corresponding to the first inflection point, as well as the second inflection point voltage threshold and the second inflection point power corresponding to the second inflection point.

[0055] Specifically, during the test phase of the battery, some reference batteries can be extracted from several batteries of the same batch and the same specification, and then discharged and charged at a constant current, and the second capacity data and the corresponding second voltage data of the reference battery during the charging process can be recorded, and a voltage-capacity characteristic curve can be established based on the second capacity data and the second voltage data during the charging process of the reference battery, so as to obtain the second charging curve. Further, by analyzing the curve characteristics of the second charging curve, the first inflection point voltage threshold corresponding to the first inflection point (i.e., the high voltage platform inflection point) and the corresponding first inflection point power, as well as the second inflection point voltage threshold corresponding to the second inflection point (i.e., the low voltage platform inflection point) and the corresponding second inflection point power can be determined. The specific analysis process is the same as the process of analyzing the charging curve of the battery in the test phase in the prior art, and will not be described in detail.

[0056] Among them, it can be understood that, since the inflection point power Q_HVTP, Q_LVTP and the corresponding voltage threshold corresponding to the high and low voltage platform inflection points of a certain batch of batteries are determined, only a small number of battery characteristic curves are needed to determine the values ​​of these characteristic quantities, so the reference battery in the embodiment of the present invention can be the battery to be tested itself, or one or more batteries from the same batch as the battery to be tested can be extracted. In addition, the second charging curve, the first inflection point voltage threshold and its corresponding first inflection point power, and the second inflection point voltage threshold and its corresponding second inflection point power can be pre-stored in a non-temporary computer-readable storage medium, such as NVM (non-volatile memory) or other software contained in the BMS.

[0057] It should also be noted that, in an embodiment of the present invention, step S3 of determining the target inflection point based on the first charging curve specifically includes: obtaining the voltage differential curve of the first charging curve; obtaining the peak voltage corresponding to the maximum point of the voltage differential curve; comparing the peak voltage with the first inflection point voltage threshold and the second inflection point voltage threshold to determine the target inflection point.

[0058] In some embodiments, obtaining the voltage differential curve of the first charging curve includes: performing smoothing filtering on the first charging curve, and performing a first-order derivative of the first voltage data with respect to the first capacity data to obtain a change rate of the first voltage data with respect to the first capacity data, and establishing the voltage differential curve of the first charging curve according to the change rate and the first capacity data, see Figure 1 shown.

[0059] In some embodiments, the comparison of the peak voltage with the first inflection point voltage threshold and the second inflection point voltage threshold to determine the target inflection point specifically includes: if the peak voltage is greater than the first inflection point voltage threshold, the maximum point is the target inflection point, and the target inflection point power is the first inflection point; or, if the peak voltage is less than the second inflection point voltage threshold, the maximum point is the target inflection point, and the target inflection point is the second inflection point. It can be understood by those skilled in the art that in the embodiments of the present invention, if the peak voltage does not satisfy any of the above relationships with the first inflection point voltage threshold or the second inflection point voltage threshold, then continue to look for the next peak voltage to compare with the first voltage threshold or the second voltage threshold.

[0060] Specifically, please combine Figure 1For any battery of any aging degree, the first inflection point (HVTP) and the second inflection point (LVTP) can be determined according to the corresponding voltage differential curve and the voltage values ​​of the first inflection point voltage threshold and the second inflection point voltage threshold. More specifically, a maximum value point is selected within the interval of the voltage differential curve to determine whether the point is a maximum value point of the voltage differential curve. If it is not a maximum value point, the battery continues to be charged, and the maximum value point of the curve is found by recording the first voltage data and the first capacity data in the charging process in real time; if it is a maximum value point, the peak voltage corresponding to the maximum value point of the voltage differential curve is obtained according to the maximum value point, and the peak voltage is compared with the first inflection point voltage threshold in the second charging curve. If the peak voltage is greater than the first inflection point voltage threshold, it means that the peak voltage is the target inflection point, and the target inflection point power is the first inflection point power; the peak voltage is compared with the second inflection point voltage threshold in the second charging curve. If the peak voltage is less than the second inflection point voltage threshold, it means that the peak voltage is the target inflection point, and the target inflection point power is the second inflection point power. If the peak voltage is neither greater than the first inflection point voltage threshold nor less than the second inflection point threshold, charging continues and the target inflection point is sought. Therefore, in the embodiment of the present invention, by adding a voltage value restriction, it can be determined whether the detected target inflection point is the first inflection point or the second inflection point, and the misjudgment caused by abnormal data in the middle interval of special cases can also be filtered out, thereby improving the accuracy of battery status calculation.

[0061] As mentioned above, as the battery ages, the voltage-capacity characteristic curve of the battery will move toward the low capacity direction as a whole. During the movement, the first inflection point power Q_HVTP corresponding to the first inflection point (HVTP) will change within a certain aging range, while the second inflection point power Q_LVTP corresponding to the second inflection point (LVTP) remains basically unchanged. The first inflection point power Q_HVTP will change due to the aging of the battery, so the accuracy of the current capacity Qnow of the battery calculated based on the first inflection point power Q_HVTP will be affected. In order to improve the accuracy of the battery capacity calculation, the battery capacity determination method of the embodiment of the present invention also includes the step of correcting the first inflection point power Q_HVTP.

[0062] Specifically, Figure 2 As shown, in some embodiments, the battery capacity determination method further includes step S6:

[0063] When the determined target inflection point also includes the second inflection point, a third charged power when the battery is charged to the second inflection point is obtained, and the first inflection point power is corrected according to the second inflection point power, the first charged power and the third charged power.

[0064] Among them, the third charged capacity is less than the first charged capacity, and the third charged capacity when the battery is charged to the second inflection point during the charging process can be obtained through the aforementioned BMS, which is not repeated here.

[0065] In an embodiment of the present invention, the third charged power is defined as Qch_LVTP, and the first inflection point power Q_HVTP, the second inflection point power Q_LVTP, the first charged power Qch_HVTP and the third charged power Qch_LVTP will satisfy the relationship: Q_HVTP = Q_LVTP + Qch_HVTP - Qch_LVTP. In other words, after determining the second inflection point power Q_LVTP and obtaining the third charged power defined as Qch_LVTP and the first charged power Qch_HVTP, the first inflection point power Q_HVTP can be corrected.

[0066] It can be understood that, for batteries of a certain batch and specification, the second inflection point power Q_LVTP is a fixed value that does not change due to aging, and the third charging power Qch_LVTP and the first charging power Qch_HVTP of the battery in any aging state are determined values ​​obtained in real time during the battery charging process. Therefore, by correcting the first inflection point power Q_HVTP of the aged battery according to the second inflection point power Q_LVTP, the first charging power Qch_HVTP and the third charging power Qch_LVTP, the accurate value of the first inflection point power Q_HVTP of the battery in the current aging state can be obtained, thereby avoiding the inaccurate calculation of the current capacity Qnow of the battery due to the change of the first inflection point power Q_HVTP caused by battery aging, which is beneficial to improving the accuracy of the battery capacity calculation.

[0067] In addition, it can also be understood that different users have different usage habits for battery charging and discharging. Some users are accustomed to charging the battery after the battery is discharged to a lower SOC segment, or occasionally charging the battery after the battery is discharged to a lower SOC segment. In this way, the second inflection point of the battery can be triggered frequently or occasionally during the charging process. Based on the correction method of the first inflection point power Q_HVTP in the above embodiment, the first inflection point power Q_HVTP of the battery can be timely corrected according to the second inflection point power Q_LVTP, the first charge-in power Qch_HVTP and the third charge-in power Qch_LVTP. However, some users are accustomed to charging the battery before the battery is discharged to a lower SOC segment, so that the second inflection point of the battery may not be triggered for a long time during the charging process, and thus the first inflection point power Q_HVTP will not be able to be timely corrected according to the second inflection point power Q_LVTP, the first charge-in power Qch_HVTP and the third charge-in power Qch_LVTP.

[0068] In order to meet the battery charging and discharging habits of different users, in other embodiments, the battery capacity determination method also includes: when the time from the first inflection point power to the last calibration is greater than a preset time, and the determined target inflection point only includes the first inflection point, correcting the first inflection point power according to a preset empirical formula for the change of the first inflection point power over time.

[0069] Among them, the preset time can be set according to the aging speed of the battery. For example, for a battery with a slower aging speed, the preset time can be 8 months, 10 months or 1 year, and for a battery with a faster aging speed, the preset time can be 4 months, 5 months or 6 months. The preset time can be set according to the specific aging speed of the battery, and there is no limitation on this.

[0070] Specifically, in an embodiment of the present invention, the time from the last calibration of the first inflection point power Q_HVTP is defined as ΔT, the empirical formula of the first inflection point power Q_HVTP changing with time is defined as f(ΔT), the corrected first inflection point power is defined as Q_HVTP_ΔT, the first inflection point power Q_HVTP, the empirical formula f(ΔT) and the corrected first inflection point power are defined as Q_HVTP_ΔT satisfying the relationship:

[0071] Q_HVTP_ΔT=Q_HVTP-f(ΔT).

[0072] Among them, it is well known to ordinary technicians in this field that for batteries of different batches and different specifications, the empirical formula for the variation of the first inflection point charge Q_HVTP over time is defined as f(ΔT) is different, and for batteries of certain batches and specifications, the empirical formula for the variation of the first inflection point charge Q_HVTP over time is defined as f(ΔT), which can be obtained through multiple tests and will not be elaborated here.

[0073] As described above, for a battery in which the second inflection point is not triggered for a long time during the charging process, the first inflection point power Q_HVTP can be corrected based on the first inflection point power Q_HVTP calibrated last time and the empirical formula for the change of the first inflection point power Q_HVTP with time obtained by test, which is defined as f(ΔT). In this way, it can also avoid the inaccurate calculation of the current capacity Qnow of the battery caused by the change of the first inflection point power Q_HVTP due to battery aging and the failure of the first inflection point power Q_HVTP to be promptly corrected based on the second inflection point power Q_LVTP corresponding to the triggered second inflection point, thereby improving the accuracy of the battery status calculation.

[0074] Based on the above two methods for correcting the first inflection point power Q_HVTP, the battery capacity determination method of the embodiment of the present invention can meet the different usage habits of different users for battery charging and discharging. It can be understood that no matter which correction method is used, the corrected first inflection point power Q_HVTP and the correction time of the first inflection point power Q_HVTP can be stored in a readable storage medium, such as the NVM or other software included in the aforementioned BMS, so as to calculate the state of the battery next time.

[0075] Furthermore, in an embodiment of the present invention, the battery capacity determination method further includes: obtaining the initial capacity of the battery; and calculating the SOHC of the battery according to the current capacity of the battery and the initial capacity of the battery. Specifically, the initial capacity of the battery is defined as Qnew, and the SOHC of the battery, the current capacity of the battery Qnow, and the initial capacity of the battery Qnew satisfy the relationship: SOHC = Qnow / Qnew*100%.

[0076] Among them, optionally, in order to eliminate random errors, that is, calculation errors of the current capacity of the battery caused by random reasons such as temperature, current or system algorithm errors, the current capacity of the battery calculated for the previous n times can be obtained, and the weighted current capacity Qnow of the battery calculated according to the current capacity of the battery calculated for n times can be calculated, and the SOHC of the battery can be calculated according to the weighted current capacity Qnow of the battery. Specifically, the weighted current capacity Qnow of the battery can be calculated according to the following formula:

[0077] Qnow=n1Qnow1+n2Qnow2+…+n n Qnow n .

[0078] Among them, Qnow is the weighted current capacity of the battery, Qnow1 to Qnow n The current capacity of the battery calculated n times, n1-n n is the weight parameter corresponding to the current capacity of the battery n times, n1+n2+…n n =1,n1-n n The specific value of can be set in combination with the historical data and current operating conditions of the battery, and is not limited to this.

[0079] After calculating the weighted current capacity Qnow of the battery, the SOHC of the battery is calculated according to the aforementioned SOHC calculation formula, and the calculation result is more accurate.

[0080] The following takes the power battery of an electric vehicle as an example to illustrate the battery capacity determination method in the embodiment of the present invention. When the battery capacity determination method is executed, it mainly includes the following steps:

[0081] In the first step, after the battery leaves the factory, a part of the battery to be tested of the same specification is extracted as a reference battery, the reference battery is discharged and then charged to a full charge state at a constant current, and the voltage-capacity curve of the reference battery during the charging process (i.e., the aforementioned second charging curve) is recorded. By analyzing the characteristics of the charging voltage curve, the first inflection point voltage threshold and the first inflection point power Q_HVTP corresponding to the high voltage platform inflection point (i.e., the first inflection point) of the battery, and the second inflection point voltage threshold and the second inflection point power Q_LVTP corresponding to the low voltage platform inflection point (i.e., the second inflection point) of the battery are obtained, wherein the first inflection point Q_HVTP will be stored in the NVM of the BMS, and the second inflection point power Q_LVTP is a fixed value written into the corresponding software of the BMS for quick call to realize subsequent calculations.

[0082] In the second step, charging of the battery to be tested with an unknown SOC state in the actual vehicle application is started, and the voltage-capacity curve (i.e., the aforementioned first charging curve) after the battery charging starts is recorded in real time, and the target inflection point of the battery is determined according to the first charging curve and the first inflection point voltage threshold and the second inflection point voltage threshold obtained in the first step; wherein, during the charging process of the battery, the charged power of the battery when charging to each node is obtained in real time, including the first charged power Qch_HVTP when the battery is charged to the first inflection point, the second charged power Qch_End when the battery charging is completed, and the third charged power Qch_LVTP when the battery is charged to the second inflection point.

[0083] The third step, after charging is completed, the first inflection point power Q_HVTP is corrected and updated according to the determined target inflection point and the charged power corresponding to the target inflection point. The specific correction method is: 1. If the first inflection point (HVTP) and the second inflection point (LVTP) are detected at the same time, the first inflection point power Q_HVTP is corrected according to the second inflection point power Q_LVTP, the first charged power Qch_HVTP and the third charged power Qch_LVTP, and its update time is stored in NVM for subsequent calculations; 2. If the second inflection point (LVTP) is not detected and the time from the last update of the first inflection point power Q_HVTP exceeds the preset time, the first inflection point power Q_HVTP is corrected according to the empirical formula f(ΔT) and its update time is stored in NVM for subsequent calculations; wherein, the more detailed contents of the above two correction methods can be found in the aforementioned related contents, which will not be repeated here.

[0084] In the fourth step, after the battery is fully charged, the current capacity Qnow of the battery is calculated. After the current capacity Qnow of the battery is calculated, the battery SOHC is further calculated according to the current capacity of the battery. It should be noted that the detailed calculation method of the current capacity Qnow of the battery and the SOHC of the battery can be referred to the above-mentioned related content, which will not be repeated here.

[0085] It is understandable that batteries generally used in electric vehicles need to be replaced when their capacity decay is greater than 20%. Therefore, the batteries used in electric vehicles can at least detect the inflection point of the high-voltage platform (the first inflection point) located in the higher SOC segment, making the battery capacity determination method of the embodiment of the present invention particularly suitable for the power battery of electric vehicles.

[0086] In summary, when calculating the state of the battery according to the battery capacity determination method of the embodiment of the present invention, there is no need to deeply discharge the battery before charging, thereby avoiding damage to the battery itself caused by full charging or full discharging, which is beneficial to improving the battery life and charging safety; furthermore, when calculating the current capacity of the battery, it is only necessary to detect the first charging amount when the battery is charged to the first inflection point (i.e., the high voltage platform inflection point) and the second charging amount when the battery charging is completed, and the battery capacity can be quickly calculated in combination with the first inflection point amount of the battery (i.e., the high voltage platform inflection point characteristic capacity), and there is no need to select the SOC interval. Compared with selecting a specific SOC interval for charging or discharging to calculate the battery capacity, it can avoid the error in the battery state calculation caused by inaccurate SOC estimation, thereby improving the accuracy of the battery capacity calculation. In addition, when the determined target inflection point includes the first inflection point and the second inflection point (i.e., the low voltage platform inflection point), the first inflection point charge can also be corrected according to the second inflection point charge (i.e., the low voltage platform inflection point characteristic capacity), the first charged charge and the third charged charge when the battery is charged to the second inflection point. When the determined target inflection point only includes the first inflection point and the time from the last correction of the first inflection point charge to the last correction is greater than a preset time, the first inflection point charge can be corrected according to a preset empirical formula for the change of the first inflection point charge over time. In this way, by timely correcting the first inflection point charge, inaccurate calculation of the current capacity of the battery due to changes in the first inflection point charge caused by battery aging can be avoided, which is beneficial to improving the accuracy of the battery status calculation. Moreover, the first inflection point charge has two correction methods, which can enable the battery capacity determination method of the embodiment of the present invention to meet the different usage habits of different users for battery charging and discharging.

[0087] The non-temporary computer-readable storage medium of the second aspect of the present invention stores a computer program thereon, and when the computer program is executed, the battery capacity determination method mentioned in any of the above embodiments is implemented.

[0088] The non-transitory computer-readable storage medium according to the embodiment of the present invention can greatly improve the speed and accuracy of battery capacity calculation by executing the computer program stored therein.

[0089] Figure 3 : is a functional block diagram of a battery capacity determination device 1 according to a third aspect of the present invention, as shown in FIG. Figure 3 As shown, the battery capacity determination device 1 provided by the present invention includes at least one processor 10 and a memory 20 that is communicatively connected to the at least one processor 10, wherein the memory 20 stores instructions that can be processed by the at least one processor 10, and when the instructions are processed by the at least one processor 10, the battery capacity determination method mentioned in any of the above embodiments is implemented.

[0090] According to the battery capacity determination device 1 of the embodiment of the present invention, the speed and accuracy of battery capacity calculation can be greatly improved by executing the battery capacity determination method mentioned in any of the above embodiments through its processor 10.

[0091] It should be noted that the fourth aspect of the present invention provides a battery, and the capacity of the battery can be calculated using the battery capacity determination method mentioned in any of the above embodiments. According to the battery of the embodiment of the present invention, the current capacity is calculated by the above battery capacity determination method, which can greatly improve the speed and accuracy of battery capacity calculation.

[0092] In the description of the present invention, the description with reference to the terms "embodiment", "specific embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0093] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for determining battery capacity, characterized in that: include: Obtaining a second charging curve of the battery, where the second charging curve refers to: a charging curve established according to second capacity data and corresponding second voltage data of the battery during the charging process in the test phase, or a voltage-capacity curve of a reference battery with the same specifications as the battery during a charging process in which the battery is discharged and then charged at a constant current to a fully charged state; Determine a first inflection point and a second inflection point according to the second charging curve, and obtain a first inflection point voltage threshold and a first inflection point charge corresponding to the first inflection point, and a second inflection point voltage threshold and a second inflection point charge corresponding to the second inflection point; Controlling the battery to charge, and recording in real time first capacity data and corresponding first voltage data of the battery during the charging process, and establishing a first charging curve according to the first capacity data and the first voltage data; Acquiring a voltage difference curve of the first charging curve; Obtaining a peak voltage corresponding to a maximum point of the voltage difference curve; Comparing the peak voltage with the first inflection point voltage threshold and the second inflection point voltage threshold to determine the target inflection point; Detecting the power of the battery until charging is completed, obtaining a first charged power when the battery is charged to the first inflection point and a second charged power when charging of the battery is completed; When the determined target inflection point includes the first inflection point, calculating the current capacity of the battery according to the first inflection point power, the first charged power, and the second charged power; The first inflection point power, the first charged power, the second charged power and the current capacity of the battery are defined as Q_HVTP, Qch_HVTP, Qch_End and Qnow, respectively, and Q_HVTP, Qch_HVTP, Qch_End and Qnow satisfy the relationship: Qnow=Q_HVTP+Qch_End-Qch_HVTP; And, when the determined target inflection point also includes the second inflection point, obtaining a third charged power when the battery is charged to the second inflection point, and correcting the first inflection point power according to the second inflection point power, the first charged power and the third charged power; The second inflection point power and the third charged power are defined as Q_LVTP and Qch_LVTP respectively. Q_HVTP, Qch_HVTP, Q_LVTP and Qch_LVTP satisfy the relationship: Q_HVTP=Q_LVTP+Qch_HVTP-Qch_LVTP.

2. The method for determining battery capacity according to claim 1, wherein: The battery capacity determination method further includes: When the time from the last calibration of the first inflection point power is greater than a preset time, and the determined target inflection point only includes the first inflection point, the first inflection point power is corrected according to a preset empirical formula of the change of the first inflection point power over time.

3. The method for determining battery capacity according to claim 1, wherein: The comparing the peak voltage with the first inflection point voltage threshold and the second inflection point voltage threshold to determine the target inflection point specifically includes: If the peak voltage is greater than the first inflection point voltage threshold, the maximum point is the target inflection point, and the target inflection point power is the first inflection point; or, if the peak voltage is less than the second inflection point voltage threshold, the maximum point is the target inflection point, and the target inflection point is the second inflection point.

4. The method for determining battery capacity according to claim 1, wherein: The first charging curve is a voltage-capacity characteristic curve established according to first voltage data of the battery during the charging process and its corresponding first capacity data. The step of obtaining a voltage differential curve of the first charging curve specifically includes: The first charging curve is smoothed and filtered, and the first voltage data is first-order derived with respect to the first capacity data to obtain a change rate of the first voltage data with respect to the first capacity data, and a voltage difference curve of the first charging curve is established according to the change rate and the first capacity data.

5. The method for determining battery capacity according to claim 1, wherein: The battery capacity determination method further includes: Obtaining the initial capacity of the battery; The SOHC of the battery is calculated based on the current capacity of the battery and the initial capacity of the battery.

6. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the battery capacity determination method according to any one of claims 1 to 5 is implemented.

7. A battery capacity determination device, characterized in that: include: at least one processor; a memory communicatively coupled to the at least one processor; The memory stores instructions that can be processed by the at least one processor, and when the instructions are processed by the at least one processor, the battery capacity determination method according to any one of claims 1 to 5 is implemented.

8. A battery, characterized in that: The capacity of the battery is calculated using the battery capacity determination method according to any one of claims 1 to 5.

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