Battery capacity determination method and device, and storage medium

Abstract

The present invention provides a method and apparatus for determining battery capacity, and a non-transitory computer-readable storage medium. The method for determining battery capacity includes the steps of: (S1) obtaining a first inflection point voltage and its corresponding first inflection point power amount of a battery, (S2) controlling the battery to be charged, and recording a first charging curve of the battery in real time, (S3) determining a target inflection point based on the first charging curve, (S4) detecting the power amount of the battery until charging is completed, and obtaining a first charging amount and a second charging amount, and (S5) calculating a current capacity of the battery based on the first inflection point power amount, the first charging amount and the second charging amount when the determined target inflection point includes the first inflection point.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to a Chinese patent application bearing application number 202210318139.5 and entitled "Battery capacity determination method and apparatus, storage medium, and battery," filed with the State Intellectual Property Office of the People's Republic of China on March 29, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to the technical field of batteries, and in particular to a battery capacity determination method and apparatus, and a non-transitory computer-readable storage medium. [Background technology]

[0003] With the rapid development of battery technology, lithium-ion batteries have been widely applied in fields such as electric vehicles and energy storage power plants. Lithium-ion batteries gradually deteriorate with continuous charge / discharge cycles, resulting in a gradual decline in performance, specifically, a decrease in capacity, an increase in internal resistance, and a decrease in power. The degree of battery deterioration is expressed as SOH (State of Health). SOH can be defined in several ways, including remaining capacity, internal resistance, and number of cycles. The most common and intuitive way is to define it as the remaining battery capacity, i.e., the percentage of the battery's capacity after deterioration compared to its initial capacity (also known as SOHC, State of Health Capacity).

[0004] Currently, the remaining battery capacity is mainly determined by fully charging and fully discharging the battery. Electrical charge Alternatively, charging and discharging are performed within a certain SOC (State of Charge) range, and the total battery capacity is calculated based on the charge or discharge amount and the corresponding SOC range.

[0005] However, all of the above methods for calculating remaining battery capacity have drawbacks. Specifically, fully charging and discharging a battery not only consumes more time and equipment resources, but can also lead to a series of safety issues, such as fire and even explosion due to overcharging. Furthermore, because users typically charge their batteries before they are fully discharged, the fully discharged battery state is unlikely to be triggered, and if triggered, it could affect the battery's service life. Therefore, calculating remaining battery capacity based on fully charging and discharging a battery is impractical in practical applications. Furthermore, when obtaining remaining battery capacity by charging or discharging within a specific SOC interval, a sufficiently long SOC interval must be selected, which also makes it difficult to trigger. Furthermore, there is a high requirement for accurate SOC estimation, and inaccurate SOC estimation can easily result in significant errors. Summary of the Invention [Means for solving the problem]

[0006] In order to solve the above technical problems, an object of the present invention is to provide a battery capacity determination method that can quickly calculate battery capacity and improve the accuracy of the battery capacity calculation.

[0007] A second object of the present invention is to provide a non-transitory computer-readable storage medium.

[0008] A third object of the present invention is to provide a battery capacity determination device.

[0009] To achieve the above object, in a first aspect, the present invention provides a method for determining a battery capacity, the method comprising: determining a first inflection point voltage of a battery and its corresponding first inflection point voltage; Electrical charge , the second inflection point voltage and its corresponding second inflection point Electrical charge a step of obtaining a voltage at the first inflection point, the first inflection point being greater than the second inflection point; a step of controlling the battery to charge and recording a first charging curve of the battery in real time; a step of determining a target inflection point based on the first charging curve; and a step of controlling the battery to charge until charging is completed. Electrical chargeand acquiring a first charge amount when the battery is charged to the first inflection point and a second charge amount when the battery is fully charged; and if the determined target inflection point includes the first inflection point, acquiring a second charge amount when the battery is fully charged. Electrical charge and calculating a current capacity of the battery based on the first charge amount and the second charge amount, and Electrical charge , the first charge amount, the second charge amount, 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 relational expression Qnow=Q_HVTP+Qch_End-Qch_HVTP.

[0010] Preferably, when the determined target inflection point further includes the second inflection point, a third charge amount when the battery is charged to the second inflection point is obtained, and the second inflection point is calculated. Electrical charge , the first inflection point based on the first charge amount and the third charge amount Electrical charge and further comprising the step of correcting the second inflection point Electrical charge When the third charge amount is defined as Q_LVTP and Qch_LVTP, respectively, Q_HVTP, Qch_HVTP, Q_LVTP and Qch_LVTP satisfy the relation Q_HVTP=Q_LVTP+Qch_HVTP-Qch_LVTP.

[0011] According to the battery capacity determination method of the embodiment of the present invention, a first charging curve is analyzed to determine a target inflection point. When it is detected that the battery is fully charged, i.e., charging is completed, a first charge amount when the battery is charged to the first inflection point and a second charge amount when the battery is fully charged are obtained. If the determined target inflection point includes the first inflection point, Electrical chargeThe current capacity of the battery can be calculated based on the first charge amount and the second charge amount. That is, the calculation method according to the embodiment of the present invention can accurately calculate the current capacity of the battery at any starting state before the target inflection point, and does not require deep discharging the battery before charging. This avoids the loss of the battery itself due to full charge or full discharge, extends the service life of the battery, and improves charging safety. Furthermore, when calculating the current capacity of the battery, it is only necessary to detect the first charge amount when the battery is charged to the first inflection point and the second charge amount when the battery is fully charged, which is advantageous for quickly calculating the battery capacity. Furthermore, it is not necessary to select an SOC range, and compared to calculating the battery capacity by selecting a specific SOC range and charging or discharging, this can avoid calculation errors of the battery state due to inaccurate SOC estimation, thereby improving the calculation accuracy of the battery capacity. Furthermore, when calculating the current capacity of the battery, it is necessary to detect the first charge amount when the battery is charged to the first inflection point and the second charge amount when the battery is fully charged. Electrical charge , based on the first charge amount and the third charge amount when the battery is charged to the second inflection point, Electrical charge It is also possible to correct the first inflection point of the battery in its current state of deterioration. Electrical charge It is possible to obtain the accurate value of , which allows us to determine the first inflection point due to battery degradation. Electrical charge Therefore, the inaccurate calculation of the current capacity of the battery caused by the change of the current capacity can be avoided, which is advantageous for improving the accuracy of the calculation of the battery capacity.

[0012] Preferably, in the battery capacity determination method, when the determined target inflection point includes only the first inflection point, Electrical charge If the time from the previous correction to the current time is greater than a predetermined time, the predetermined first inflection point Electrical charge Based on the empirical formula for the change over time, the first inflection point Electrical charge The method further includes the step of correcting

[0013] Preferably, the step of determining a target inflection point based on the first charging curve includes the steps of obtaining a voltage differential curve of the first charging curve, obtaining a peak voltage corresponding to a local maximum point of the voltage differential curve, and comparing the peak voltage with the first inflection point voltage and the second inflection point voltage to determine the target inflection point.

[0014] Preferably, the step of comparing the peak voltage with the first inflection point voltage and the second inflection point voltage to determine the target inflection point includes a step of setting the maximum point as the target inflection point and the target inflection point as the first inflection point when the peak voltage is greater than the first inflection point voltage, or a step of setting the maximum point as the target inflection point and the target inflection point as the second inflection point when the peak voltage is smaller than the second inflection point voltage.

[0015] Preferably, the step of comparing the peak voltage with the first inflection point voltage and the second inflection point voltage to determine the target inflection point further includes the step of continuing to charge the battery to search for the target inflection point when the peak voltage is equal to or less than the first inflection point voltage and equal to or greater than the second inflection point voltage.

[0016] Preferably, the first charging curve is a voltage-capacity characteristic curve established based on first voltage data during charging of the battery and its corresponding first capacity data. The step of obtaining a voltage derivative curve of the first charging curve includes the steps of performing a smoothing filter process on the first charging curve, first differentiating the first voltage data with respect to the first capacity data, obtaining a rate of change of the first voltage data with respect to the first capacity data, and establishing the voltage derivative curve of the first charging curve based on the rate of change and the first capacity data.

[0017] Preferably, the first inflection point voltage of the battery and its corresponding first inflection point Electrical charge , the second inflection point voltage and its corresponding second inflection point Electrical chargeThe step of acquiring includes the steps of acquiring a second charging curve of the battery, determining the first inflection point and the second inflection point based on the second charging curve, and determining the first inflection point voltage and the second inflection point voltage corresponding to the first inflection point. Electrical charge and the second inflection point voltage and the second inflection point corresponding to the second inflection point. Electrical charge and obtaining the

[0018] Preferably, the step of obtaining a second charging curve of the battery includes the steps of determining one or more reference batteries; fully discharging the reference batteries and then constant current charging them; recording second capacity data and corresponding second voltage data during the constant current charging; and establishing a voltage-capacity characteristic curve based on the second capacity data and the corresponding second voltage data to obtain the second charging curve.

[0019] Preferably, the battery capacity determination method further includes the steps of obtaining an initial capacity of the battery, and calculating a state of health (SOHC) of the battery based on the current capacity of the battery and the initial capacity of the battery.

[0020] Preferably, the step of recording the first charging curve of the battery in real time includes the steps of collecting and recording at least one parameter of the battery's voltage, current, temperature, current charging time, and charging amount using a battery management system (BMS); and obtaining the first charging curve according to a BMS charging algorithm.

[0021] Preferably, the second inflection point voltage and the second inflection point Electrical charge is the voltage and inflection point corresponding to the low voltage plateau inflection point in the second charging curve Electrical charge is.

[0022] Preferably, the battery capacity determination method further includes a step of obtaining the current capacity of the battery calculated the previous n times, and calculating the weighted current capacity of the battery based on the current capacity of the battery calculated the previous n times.

[0023] Preferably, a state of health (SOHC) of the battery is calculated based on the current capacity of the battery after the weighting and the initial capacity of the battery.

[0024] Preferably, the third charge when the battery is charged to the second inflection point Electrical charge The step of acquiring the third inflection point when the battery is charged to the second inflection point by a battery management system (BMS) is Electrical charge The method includes the step of obtaining:

[0025] Preferably, the battery capacity determination method is executed by a computer program. Preferably, the battery capacity determination method is performed by a computer program stored on a non-transitory computer-readable storage medium.

[0026] In a second aspect, the present invention provides a non-transitory computer-readable storage medium having stored thereon a computer program that, when executed, performs the battery capacity determination method described above.

[0027] According to the non-transitory computer-readable storage medium of the embodiment of the present invention, the speed and accuracy of calculating the battery capacity can be significantly improved by executing the stored computer program.

[0028] In a third aspect, the present invention provides a battery capacity determination apparatus including at least one processor and a memory communicatively coupled to the at least one processor, the memory storing commands processable by the at least one processor, the commands being processed by the at least one processor to execute the battery capacity determination method described above.

[0029] According to the battery capacity determination device of the embodiment of the present invention, the processor executes the battery capacity determination method, thereby significantly improving the speed and accuracy of calculating the battery capacity.

[0030] The present invention provides a battery, the capacity of which can be calculated by the above-mentioned method for determining battery capacity.

[0031] According to the battery of the embodiment of the present invention, the current capacity of the battery is calculated by the above-described battery capacity determination method, thereby significantly improving the speed and accuracy of calculating the battery capacity.

[0032] Additional aspects and advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. [Brief explanation of the drawings]

[0033] In order to more clearly explain the technical means of the embodiments of the present invention, the drawings necessary for the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative work.

[0034] [Figure 1] 3 is a comparative schematic diagram of first charging curves and charging voltage differential curves of batteries with different degrees of deterioration according to an embodiment of the present invention; FIG. [Figure 2] 2 is a flowchart of a battery capacity determination method according to an embodiment of the present invention. [Figure 3] 1 is a functional block diagram of a battery capacity determination device according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0035] In order to clarify the objectives, technical means, and advantages of the present application, exemplary embodiments of the present application will be described in detail below with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, and do not include all of the embodiments of the present application. It should be understood that the present application is not limited to the exemplary embodiments described herein. All other embodiments that can be obtained by a person skilled in the art based on the embodiments described herein without any creative work are also within the scope of protection of the present application.

[0036] Hereinafter, the embodiments of the present invention will be described in detail, and examples of the embodiments are shown in the drawings, and the same or similar reference numerals indicate the same or similar parts or parts having the same or similar functions throughout. The embodiments described below with reference to the drawings are illustrative and are intended to interpret the present invention only, and should not be understood as limiting the present invention.

[0037] In contrast to the problems in the prior art, the battery capacity determination method according to the embodiment of the present invention can significantly improve the speed and accuracy of calculating battery capacity. The general concept of the calculation method according to the embodiment of the present invention is to detect the voltage-capacity curve of the target battery during charging in real time, analyze the curve characteristics, find the characteristic points of the curve, and accurately calculate the battery capacity without deep discharging the battery before charging, even when the initial SOC state of the battery is unknown.

[0038] First, the characteristic points of the curve used in the embodiment of the present invention will be described.

[0039] Referring to FIG. 1, the voltage-capacity characteristic curve (i.e., charging curve) of a battery (e.g., but not limited to, a lithium-ion battery) typically has three sections where voltage changes slowly, called voltage plateau regions. Between each pair of voltage plateau regions, there is a region where voltage changes rapidly. The points where voltage changes most rapidly within these regions are called voltage plateau inflection points. These are distinguished by voltage level: the higher voltage is called the high-voltage plateau inflection point (HVTP) and the lower voltage is called the low-voltage plateau inflection point (LVTP). Voltage plateau inflection points are expressed as the maximum points of the voltage differential curve. In practical applications, high-voltage plateau inflection points and low-voltage plateau inflection points can be distinguished based on the voltage value. Taking a lithium-ion power battery for an electric vehicle as an example, if the SOC state at the start of charging is uncertain and charging is initiated from a low SOC range (e.g., 5%), two plateau inflection points, HVTP and LVTP, can be detected during charging. If charging is initiated from an intermediate SOC range (i.e., a region between HVTP and LVTP), only one plateau inflection point, called the HVTP, can be detected during charging. Figure 1 shows the charge curves and voltage differential curves of several batteries, with different curves representing batteries with different degrees of degradation. It can be seen that the curve for a battery with a lower degree of degradation has two inflection points: a high-voltage plateau inflection point and a low-voltage plateau inflection point.

[0040] As is well known to those skilled in the art, as shown in FIG. 1, as the battery deteriorates, the voltage-capacity characteristic curve of the battery generally shifts toward a lower capacity, and during this shift, an inflection point corresponding to the LVTP is reached. Electrical charge Q_LVTP (also called low voltage plateau inflection point characteristic capacitance) is essentially unchanged, i.e., Electrical charge Q_LVTP is a fixed value, and the inflection point corresponds to HVTP. Electrical charge Although Q_HVTP (also called the high-voltage plateau inflection point characteristic capacitance) changes slightly within a certain degradation range, the voltages corresponding to HVTP and LVTP do not change with the parallel movement of the characteristic curve, so the detected plateau inflection points can be distinguished by voltage.

[0041] Based on the above description, a battery capacity determination method according to an embodiment of the present invention will be described below with reference to the drawings.

[0042] 2 is a flowchart of a battery capacity determination method according to an embodiment of the present invention, and as shown in FIG. 2, the battery capacity determination method according to the embodiment of the present invention includes at least steps S1 to S5. The specific process of each step is as follows:

[0043] In step S1, the first inflection point voltage of the battery and its corresponding first inflection point Electrical charge , the second inflection point voltage and its corresponding second inflection point Electrical charge and the first inflection point voltage is greater than the second inflection point voltage. Electrical charge is the voltage corresponding to the high voltage plateau inflection point and the inflection point Electrical charge and the second inflection point voltage and the second inflection point Electrical charge is the voltage corresponding to the low voltage plateau inflection point and the inflection point Electrical charge The first inflection point voltage and the first inflection point Electrical charge are characteristic parameters at the time of battery shipment and correspond to the first inflection point at the time of battery shipment. Similarly, the second inflection point voltage and the second inflection point Electrical charge are characteristic parameters at the time of shipping the battery, and correspond to the second inflection point at the time of shipping the battery. The first inflection point and the second inflection point are characteristic points of the battery, and change as the battery deteriorates. At the time of shipping, the first inflection point and the second inflection point correspond to the first inflection point voltage and the second inflection point voltage, respectively, or the first inflection point and the second inflection point correspond to the first inflection point voltage and the second inflection point voltage, respectively. Electrical charge , second inflection point Electrical charge However, as the battery is used, the battery capacity decreases and the voltage values ​​corresponding to the first and second inflection points may change. In some cases, the voltage value corresponding to the second inflection point is smaller than the second inflection point voltage, and the difference between the voltage value corresponding to the first inflection point and the first inflection point voltage is generally not large.

[0044] In the embodiment of the present invention, for a battery whose lot and specifications have been determined, the voltage and inflection point corresponding to the high voltage plateau inflection point or the low voltage plateau inflection point in the voltage-capacity characteristic curve are Electrical charge These characteristic values ​​can be obtained from only the voltage-capacity characteristic curves of a small number of batteries, and the specific method of obtaining these values ​​will be described in detail later.

[0045] In step S2, the battery is controlled to be charged, and a first charging curve of the battery is recorded in real time.

[0046] In an embodiment of the present invention, when charging a battery with an unknown SOC state, first capacity data and its corresponding first voltage data are recorded in real time during charging of the battery, and the first charging curve, which is a voltage-capacity characteristic curve, is established based on the first capacity data and the first voltage data. Specifically, taking a lithium-ion power battery as an example, in the prior art, when charging the lithium-ion power battery, parameters such as the voltage, current, temperature, current charging time, and charge amount of the lithium-ion power battery are collected and recorded by a BMS (Battery Management System), and the charging curve of the lithium-ion power battery can be obtained according to a BMS charging algorithm, and the description thereof will be omitted here.

[0047] In step S3, a target inflection point is determined based on the first charging curve.

[0048] In an embodiment of the present invention, the first charging curve is analyzed to obtain its inflection point, and it is determined whether the inflection point of the first charging curve is a target inflection point based on the first inflection point voltage and the second inflection point voltage. As described above, for a battery with an unknown SOC state, at least a high-voltage plateau inflection point can be detected during charging, which means that the target inflection point includes at least a high-voltage plateau inflection point (defined as the first inflection point). A specific method for determining the target inflection point will be described in detail below.

[0049] In step S4, the battery is charged until charging is completed. Electrical charge and obtains a first charge amount when the battery is charged to the first inflection point and a second charge amount when the battery is fully charged. Note that the fully charged state of the battery is referred to as the fully charged state.

[0050] In an embodiment of the present invention, Electrical charge When it is detected that the battery reaches a full charge amount, the charge amount when the battery is charged from the start of charging to the first inflection point is set as the first charge amount, and the charge amount when the battery is charged from the start of charging to the completion of charging is set as the second charge amount, and the first charge amount is smaller than the second charge amount. The charge amount of the battery during charging can be obtained by the above-mentioned BMS, and a description thereof will be omitted here. For example, when the battery starts charging, Electrical charge is 10% of the battery capacity. After charging for a certain period of time, the battery is charged to the first inflection point. Electrical charge When the battery reaches 60% of its capacity, the first charge amount is calculated by subtracting 10% from the start of charging from 60% when the battery is charged to the first inflection point, i.e., the first charge amount is 50% of the battery capacity. Similarly, if the battery continues to be charged, it will reach 100% of its capacity when charging is complete. Since the second charge amount is the charge amount when charging is complete, in this case, the second charge amount is calculated by subtracting 10% from the start of charging from 100%, i.e., the second charge amount is 90% of the battery capacity. However, it should be noted that battery capacity decreases as the battery is used for an extended period of time due to factors such as battery degradation. In other words, the first and second charge amounts gradually decrease as the battery deteriorates.

[0051] In step S5, if the determined target inflection point includes the first inflection point, Electrical charge The current capacity of the battery is calculated based on the first charge amount and the second charge amount. The current capacity of the battery is calculated by calculating the total charge amount of the battery in the current state. Electrical charge is.

[0052] As can be understood, for a battery with an unknown SOC state, at least the high voltage plateau inflection point (i.e., the first inflection point) can be detected during charging, which means that the first inflection point is more easily triggered. Therefore, in an embodiment of the present invention, if the determined target inflection point includes the first inflection point (i.e., the high voltage plateau inflection point), the first inflection point Electrical charge , calculating the current capacity of the battery based on the first charge amount and the second charge amount, and determining the state of the battery based on the current capacity of the battery, which is advantageous for realizing timely updating of the battery state.

[0053] Specifically, in an embodiment of the present invention, the first inflection point Electrical charge , the first charge amount, the second charge amount, and the current capacity of the battery are defined as Q_HVTP, Qch_HVTP, Qch_End, and Qnow, respectively. Electrical charge Q_HVTP, the first charge level Qch_HVTP, the second charge level Qch_End, and the current capacity Qnow of the battery satisfy the relational expression Qnow=Q_HVTP+Qch_End-Qch_HVTP. Electrical charge Once Q_HVTP, the first charge amount Qch_HVTP, and the second charge amount Qch_End are determined, the current capacity Qnow of the battery can be quickly calculated based on the above-mentioned relational equation.

[0054] As described above, according to the battery capacity determination method of the embodiment of the present invention, when charging a battery with an unknown SOC state, a first charging curve of the battery is analyzed to determine a target inflection point. When it is detected that the battery is fully charged, i.e., charging is completed, a first charge amount when the battery is charged to the first inflection point (i.e., the high voltage plateau inflection point) and a second charge amount when the battery is fully charged are obtained. If the determined target inflection point includes the first inflection point, the obtained first inflection point of the battery is calculated. Electrical chargeThe current capacity of the battery can be calculated based on the first and second charge amounts. That is, the calculation method according to the embodiment of the present invention can accurately calculate the current capacity of the battery at any starting state before the target inflection point, eliminating the need to deep-discharge the battery before charging. This avoids the loss of the battery itself due to full charge or full discharge, extends the service life of the battery, and improves charging safety. Furthermore, when calculating the current capacity of the battery, it is only necessary to detect the first charge amount when the battery is charged to the first inflection point and the second charge amount when the battery is fully charged. This is advantageous for quickly calculating the battery capacity, and does not require selecting an SOC range. This avoids battery state calculation errors due to inaccurate SOC estimation compared to calculating the battery capacity by selecting a specific SOC range and charging or discharging, thereby improving the accuracy of the battery capacity calculation. In summary, the battery capacity determination method according to the present invention can significantly improve the speed and accuracy of battery capacity calculation.

[0055] In the embodiment of the present invention, the first inflection point voltage of the battery and its corresponding first inflection point Electrical charge , the second inflection point voltage and its corresponding second inflection point Electrical charge The step S1 of acquiring the first inflection point and the second inflection point specifically includes the steps of acquiring a second charging curve of the battery, determining the first inflection point and the second inflection point based on the second charging curve, and determining the first inflection point voltage and the second inflection point voltage corresponding to the first inflection point. Electrical charge and the second inflection point voltage and the second inflection point corresponding to the second inflection point. Electrical charge and obtaining the

[0056] Specifically, in the battery testing stage, a reference battery is selected from a plurality of batteries of the same lot and specifications, and is fully discharged and then constant-current charged, and second capacity data and corresponding second voltage data are recorded during the charging of the reference battery, and a voltage-capacity characteristic curve is established based on the second capacity data and the second voltage data during the charging of the reference battery, thereby obtaining the second charging curve. Furthermore, by analyzing the curve characteristics of the second charging curve, a first inflection point voltage corresponding to the first inflection point (i.e., high-voltage plateau inflection point) and its corresponding first inflection point are obtained. Electrical charge , and a second inflection point voltage corresponding to the second inflection point (i.e., the low voltage plateau inflection point) and its corresponding second inflection point Electrical charge The specific analysis process is the same as the process of analyzing the charging curve of the battery in the test stage in the prior art, and the description thereof will be omitted here.

[0057] As can be seen, for a given batch of batteries, the inflection points corresponding to the high and low voltage plateau inflection points are Electrical charge Since Q_HVTP, Q_LVTP and their corresponding voltages are all determined and the values ​​of these characteristic quantities can be determined only from a small amount of battery characteristic curves, the reference battery in the embodiment of the present invention may be the battery itself to be detected, or may be one or more batteries selected from the same lot of batteries as the battery to be detected. Electrical charge and the second inflection point voltage and its corresponding second inflection point Electrical charge may be pre-stored in a non-transitory computer-readable storage medium such as a non-volatile memory (NVM) or other software included in the BMS.

[0058] In this embodiment of the present invention, step S3 of determining a target inflection point based on the first charging curve specifically includes the steps of obtaining a voltage differential curve of the first charging curve, obtaining a peak voltage corresponding to a local maximum point of the voltage differential curve, and comparing the peak voltage with the first inflection point voltage and the second inflection point voltage to determine the target inflection point.

[0059] In some embodiments, the step of obtaining a voltage derivative curve of the first charging curve includes the steps of performing a smoothing filter process on the first charging curve, first differentiating the first voltage data with respect to the first capacity data, obtaining a rate of change of the first voltage data with respect to the first capacity data, and establishing the voltage derivative curve of the first charging curve shown in FIG. 1 based on the rate of change and the first capacity data.

[0060] In some embodiments, the step of comparing the peak voltage with the first inflection point voltage and the second inflection point voltage to determine the target inflection point specifically includes the steps of: if the peak voltage is greater than the first inflection point voltage, setting the local maximum point as the target inflection point and setting the target inflection point as the first inflection point; or if the peak voltage is less than the second inflection point voltage, setting the local maximum point as the target inflection point and setting the target inflection point as the second inflection point. As can be understood by those skilled in the art, in embodiments of the present invention, if the peak voltage and the first inflection point voltage threshold or the second inflection point voltage do not satisfy any of the above relationships, the system continues to search for a next peak voltage to be compared with the first voltage or the second voltage.

[0061] 1, for a battery at any degradation level, the first inflection point (HVTP) and the second inflection point (LVTP) can be determined according to the corresponding voltage differential curve in combination with the voltage values ​​of the first inflection point voltage and the second inflection point voltage. More specifically, a maximum point is selected within the section of the voltage differential curve, and it is determined whether the point is a local maximum of the voltage differential curve. If it is not a local maximum, the battery continues to be charged, and the first voltage data and the first capacity data are recorded in real time during charging to find the local maximum of the curve. If it is a local maximum, the peak voltage corresponding to the local maximum of the voltage differential curve is obtained based on the local maximum, and the peak voltage is compared with the first inflection point voltage of the second charging curve. If the peak voltage is greater than the first inflection point voltage, the peak voltage is the target inflection point. Electrical charge is the first inflection point Electrical charge The peak voltage is compared with the second inflection point voltage in the second charging curve. If the peak voltage is smaller than the second inflection point voltage, the peak voltage is the target inflection point. Electrical charge is the second inflection point Electrical charge If the peak voltage is equal to or less than the first inflection point voltage and equal to or greater than the second inflection point threshold, charging continues to search for the target inflection point. Therefore, in this embodiment of the present invention, by increasing the voltage value limit condition, it is possible to determine whether the detected target inflection point is the first inflection point or the second inflection point, and it is also possible to filter out erroneous judgments caused by abnormal data in the intermediate section in special cases, thereby improving the accuracy of battery state calculation.

[0062] As mentioned above, as the battery deteriorates, the voltage-capacity characteristic curve of the battery generally shifts toward a lower capacity, and during this shift, the first inflection point (HVTP) Electrical charge Q_HVTP changes within a certain degradation range and reaches the second inflection point (LVTP) Electrical charge Q_LVTP is basically unchanged. Electrical charge Since Q_HVTP changes due to battery deterioration, the first inflection point Electrical chargeThe accuracy of the current capacity Qnow of the battery calculated based on Q_HVTP is affected. In order to improve the accuracy of the calculation of the battery capacity, the battery capacity determination method according to the embodiment of the present invention includes: Electrical charge The method further includes the step of correcting Q_HVTP.

[0063] Specifically, as shown in FIG. 2 , in some embodiments, the battery capacity determination method includes: If the determined target inflection point further includes the second inflection point, a third charge amount when the battery is charged to the second inflection point is obtained, and the second inflection point is Electrical charge , the first inflection point based on the first charge amount and the third charge amount Electrical charge The method further includes a step S6 of correcting

[0064] The third charge amount is smaller than the first charge amount, and the third charge amount when the battery is charged to the second inflection point during charging can be obtained by the BMS described above, and its description will be omitted here.

[0065] In the embodiment of the present invention, when the third charge amount is defined as Qch_LVTP, the first inflection point Electrical charge Q_HVTP, the second inflection point Electrical charge Q_LVTP, the first charge amount Qch_HVTP, and the third charge amount Qch_LVTP satisfy the relational expression Q_HVTP=Q_LVTP+Qch_HVTP-Qch_LVTP. Electrical charge After determining Q_LVTP and obtaining the third charge amount Qch_LVTP and the first charge amount Qch_HVTP, Electrical charge Q_HVTP can be corrected.

[0066] As can be understood, for a battery whose lot and specifications have been determined, the second inflection point Electrical charge Q_LVTP is a fixed value that does not change with deterioration, and the third charge amount Qch_LVTP and the first charge amount Qch_HVTP in any deterioration state of the battery are determined values ​​acquired in real time while the battery is being charged. Electrical chargeQ_LVTP, the first charge amount Qch_HVTP, and the third charge amount Qch_LVTP, a first inflection point of the battery after deterioration is calculated. Electrical charge By correcting Q_HVTP, the first inflection point of the battery in its current state of deterioration is Electrical charge The accurate value of Q_HVTP can be obtained, which allows the first inflection point due to battery degradation to be detected. Electrical charge This can avoid inaccurate calculation of the current capacity Qnow of the battery caused by changes in Q_HVTP, which is advantageous in improving the accuracy of calculation of the battery capacity.

[0067] It is also understood that different users have different habits when charging and discharging a battery. Some users are accustomed to discharging a battery to a low SOC range and then charging it, while other users sometimes discharge a battery to a low SOC range and then charge it. In this way, the second inflection point is frequently or occasionally triggered during charging of the battery, and the first inflection point in the above embodiment is not triggered. Electrical charge Based on the Q_HVTP correction method, the first inflection point of the battery Electrical charge Q_HVTP is the second inflection point Electrical charge The battery can be corrected in a timely manner based on Q_LVTP, the first charge amount Qch_HVTP, and the third charge amount Qch_LVTP. However, some users are accustomed to charging the battery before discharging it to a low SOC range. In this way, the second inflection point may not be triggered for a long time during charging, and the first inflection point may not be triggered for a long time during charging. Electrical charge Q_HVTP is the second inflection point Electrical charge It is not possible to perform timely correction based on Q_LVTP, the first charge amount Qch_HVTP, and the third charge amount Qch_LVTP.

[0068] In order to accommodate different user habits for charging and discharging the battery, in some other embodiments, the battery capacity determination method further comprises: Electrical charge If the time from the previous correction to the current time is greater than a predetermined time and the determined target inflection point includes only the first inflection point, Electrical chargeBased on the empirical formula for the change over time, the first inflection point Electrical charge The method further includes the step of correcting

[0069] The predetermined time can be set based on the deterioration rate of the battery. For example, for a battery with a slow deterioration rate, the predetermined time can be 8 months, 10 months, or 1 year. For a battery with a fast deterioration rate, the predetermined time can be 4 months, 5 months, or 6 months. The predetermined time can be set based on the specific deterioration rate of the battery, and is not limited thereto.

[0070] Specifically, in an embodiment of the present invention, the first inflection point Electrical charge The time from the previous correction of Q_HVTP to the current time is defined as ΔT, and the first inflection point Electrical charge The empirical formula for the time-dependent change in Q_HVTP is defined as f(ΔT), and the first inflection point after correction is Electrical charge When Q_HVTP_ΔT is defined as the first inflection point, Electrical charge Q_HVTP, the empirical formula f(ΔT) and the first inflection point after correction Electrical charge Q_HVTP_ΔT satisfies the relation Q_HVTP_ΔT=Q_HVTP-f(ΔT).

[0071] As is well known to those skilled in the art, the first inflection point may vary for different lots and different specifications of batteries. Electrical charge Although the empirical formula f(ΔT) for the change in Q_HVTP over time is different, for batteries whose lot and specifications have been determined, Electrical charge The empirical formula f(ΔT) for the time-dependent change of Q_HVTP can be obtained through multiple tests, and its explanation is omitted here.

[0072] As described above, for a battery in which the second inflection point is not triggered for a long period of time during charging, the previously corrected first inflection point Electrical charge Q_HVTP and the first inflection point obtained by the test Electrical charge Based on the empirical formula f(ΔT) for the time-dependent change of Q_HVTP, Electrical charge Q_HVTP can be corrected, and the first inflection point due to battery degradation can be corrected. Electrical charge Change in Q_HVTP and the first inflection point Electrical charge The second inflection point corresponding to the second inflection point that triggered Q_HVTP Electrical charge This avoids inaccurate calculation of the current capacity Qnow of the battery caused by not correcting it in time based on Q_LVTP, and improves the accuracy of the calculation of the battery state.

[0073] The first inflection point Electrical charge Based on the two above-mentioned methods for correcting Q_HVTP, the battery capacity determination method according to the embodiment of the present invention can accommodate different user habits for charging and discharging the battery. It can be understood that, regardless of the correction method, the first inflection point after correction Electrical charge Q_HVTP and the first inflection point Electrical charge The Q_HVTP correction time may be stored in a readable storage medium such as NVM or other software, both of which may be included in the BMS described above, to facilitate the next calculation of the battery's state.

[0074] In addition, in an embodiment of the present invention, the battery capacity determination method further includes: obtaining an initial capacity of the battery; and calculating an SOHC of the battery based on the current capacity of the battery and the initial capacity of the battery. Specifically, when the initial capacity of the battery is defined as Qnew, the SOHC of the battery, the current capacity Qnow of the battery, and the initial capacity Qnew of the battery satisfy the relationship SOHC=Qnow / Qnew*100%.

[0075] Preferably, in order to eliminate random errors, i.e., calculation errors of the current capacity of the battery due to random reasons such as temperature, current, or system algorithm errors, the previous n calculated current capacities of the battery are obtained, and the weighted current capacity Q of the battery is calculated based on the previous n calculated current capacities of the battery, and the SOHC of the battery is calculated based on the weighted current capacity Q of the battery. Specifically, the weighted current capacity Q of the battery can be calculated according to the following formula:

[0076] Qnow=n1Qnow1+n2Qnow2+…+n n Qnow n .

[0077] where Qnow is the current capacity of the battery after weighting, and Qnow1 to Qnow n is the current capacity of the battery calculated n times, and n1 to n n is a weight parameter corresponding to the current capacity of the battery at n times, where n1+n2+...n n =1, and n1~n n The specific value of can be set according to the history data and current operating conditions of the battery, and is not limited thereto.

[0078] After calculating the weighted current capacity Qnow of the battery, the SOHC of the battery is calculated based on the above SOHC calculation formula, so that the calculation result is more accurate.

[0079] Hereinafter, the battery capacity determination method according to the embodiment of the present invention will be described using a power battery of an electric vehicle as an example, and the battery capacity determination method mainly includes the following steps 1 to 4 when executed.

[0080] In step 1, after the battery is shipped, some of the batteries to be tested with the same specifications are selected as reference batteries, and the reference batteries are fully discharged and then charged to a full charge state at a constant current. The voltage-capacity curve during charging of the reference battery (i.e., the second charging curve) is recorded, and the charging voltage curve characteristics are analyzed to determine the first inflection point voltage and the first inflection point Vc corresponding to the high voltage plateau inflection point (i.e., the first inflection point) of the battery. Electrical charge Q_HVTP, and a second inflection point voltage and a second inflection point corresponding to the low voltage plateau inflection point of the battery (i.e., the second inflection point). Electrical charge The first inflection point Q_HVTP is acquired, and the second inflection point Q_HVTP is stored in the NVM of the BMS. Electrical charge Q_LVTP is written into the corresponding software of BMS with a fixed value, so that it can be quickly called to realize subsequent calculations.

[0081] In step 2, in a real-world vehicle application, charging of a target battery whose SOC state is unknown is initiated, and a voltage-capacity curve (i.e., the first charging curve) after charging of the battery is initiated is recorded in real time. A target inflection point for the battery is determined based on the first charging curve and the first and second inflection point voltages obtained in step 1. During charging of the battery, the charge amounts when the battery is charged to each node are obtained in real time, including a first charge amount Qch_HVTP when the battery is charged to the first inflection point, a second charge amount Qch_End when the battery is fully charged, and a third charge amount Qch_LVTP when the battery is charged to the second inflection point.

[0082] In step 4, after the charging is completed, the first inflection point is determined based on the determined target inflection point and the charge amount corresponding to the target inflection point. Electrical charge The Q_HVTP is corrected and updated, and the specific correction method includes the following: 1. When the first inflection point (HVTP) and the second inflection point (LVTP) are detected simultaneously, Electrical charge Q_LVTP, the first charge amount Qch_HVTP, and the third charge amount Qch_LVTP. Electrical charge The Q_HVTP is corrected and the updated time is stored in the NVM for use in subsequent calculations. 2. If the second inflection point (LVTP) is not detected and the first inflection point Electrical charge If the time until the last update of Q_HVTP exceeds a predetermined time, the first inflection point is Electrical charge The Q_HVTP is corrected and the update time is stored in the NVM for subsequent calculations. For more details about the two correction methods, please refer to the related content above, and the description will be omitted here.

[0083] In step 4, after the battery is fully charged, the current capacity Q of the battery is calculated, and after the current capacity Q of the battery is calculated, the SOHC of the battery is further calculated based on the current capacity of the battery. For detailed calculation methods of the current capacity Q and the SOHC of the battery, please refer to the above related content, and the description will be omitted here.

[0084] As can be seen, batteries for electric vehicles generally need to be replaced when their capacity fade exceeds 20%, and therefore, for batteries for electric vehicles, it is possible to detect at least a high voltage plateau inflection point (first inflection point) located in a high SOC range. Therefore, the battery capacity determination method according to the embodiment of the present invention is particularly suitable for power batteries of electric vehicles.

[0085] In summary, when calculating the battery state using the battery capacity determination method according to the embodiment of the present invention, there is no need to deep discharge the battery before charging, which avoids the loss of the battery itself due to full charge or full discharge, and is advantageous in extending the service life of the battery and improving the safety of charging. In addition, when calculating the current capacity of the battery, it is only necessary to detect the first charge amount when the battery is charged to the first inflection point (i.e., the high voltage plateau inflection point) of the battery and the second charge amount when the battery is fully charged. Electrical charge The battery capacity can be quickly calculated based on the characteristic capacity of the high-voltage plateau inflection point (i.e., the characteristic capacity of the high-voltage plateau inflection point), and there is no need to select an SOC range. This avoids an error in the calculation of the battery state due to an inaccurate SOC estimation, compared to calculating the battery capacity by selecting a specific SOC range and charging or discharging, thereby improving the accuracy of the calculation of the battery capacity. In addition, when the determined target inflection point includes the first inflection point and the second inflection point (i.e., the characteristic capacity of the low-voltage plateau inflection point), the second inflection point can be calculated based on the characteristic capacity of the low-voltage plateau inflection point. Electrical charge (i.e., low voltage plateau inflection point characteristic capacity), the first charge amount, and the third charge amount when the battery is charged to the second inflection point. Electrical charge It is also possible to correct the first inflection point, and the determined target inflection point includes only the first inflection point. Electrical charge If the time since the previous correction is greater than the specified time, the first inflection point is Electrical charge The first inflection point is determined based on the empirical formula for the time course of Electrical charge In this way, the first inflection point Electrical charge By correcting this in a timely manner, the first inflection point due to battery deterioration can be prevented. Electrical charge This avoids inaccurate calculation of the current capacity of the battery caused by changes in Electrical charge Since there are two correction methods for , the battery capacity determination method according to the embodiment of the present invention can accommodate different user usage habits for charging and discharging the battery.

[0086] A non-transitory computer-readable storage medium according to an embodiment of the second aspect of the present invention stores a computer program, which, when executed, performs the battery capacity determination method according to any of the above embodiments.

[0087] According to the non-transitory computer-readable storage medium of the embodiment of the present invention, the speed and accuracy of calculating the battery capacity can be significantly improved by executing the stored computer program.

[0088] FIG. 3 is a functional block diagram of a battery capacity determination device 1 according to an embodiment of the third aspect of the present invention. As shown in FIG. 3, the battery capacity determination device 1 according to the present invention includes at least one processor 10 and a memory 20 communicatively connected to the at least one processor 10. Commands that can be processed by the at least one processor 10 are stored in the memory 20. When the commands are processed by the at least one processor 10, the battery capacity determination method according to any of the above embodiments is executed.

[0089] According to the battery capacity determination device 1 of the embodiment of the present invention, the processor 10 executes the battery capacity determination method of any of the above embodiments, thereby making it possible to significantly improve the speed and accuracy of calculating the battery capacity.

[0090] The present invention also provides a battery, the capacity of which can be calculated by any of the battery capacity determination methods according to the above embodiments. According to the battery of the present invention, the current capacity of the battery can be calculated by the battery capacity determination method, thereby significantly improving the speed and accuracy of calculating the battery capacity.

[0091] In describing the present invention, a description that refers to the terms "embodiment," "specific embodiment," "example," etc. means that the specific features, structures, materials, or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, exemplary expressions of the terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples, as appropriate.

[0092] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and purpose of the present invention, and that the scope of the present invention is limited by the claims and their equivalents.

Claims

1. A step (S1) of acquiring a first inflection point voltage and a corresponding first inflection point electrical quantity of a battery, and a second inflection point voltage and a corresponding second inflection point electrical quantity of a battery, wherein the first inflection point voltage is greater than the second inflection point voltage; (S2) controlling the battery to be charged and recording a first charging curve of the battery in real time; determining a target inflection point based on the first charging curve (S3); detecting the amount of electricity of the battery until charging is completed, and acquiring a first charge amount when the battery is charged to a first inflection point and a second charge amount when charging is completed; If the determined target inflection point includes the first inflection point, calculating a current capacity of the battery based on the first inflection point electrical quantity, the first charge amount, and the second charge amount (S5); When the first inflection point electrical quantity, the first charge amount, the second charge amount, and the current capacity of the battery are defined as Q_HVTP, Qch_HVTP, Qch_End, and Qnow, respectively, Q_HVTP, Qch_HVTP, Qch_End, and Qnow are expressed by the following relational expressions: Qnow=Q_HVTP+Qch_End−Qch_HVTP A battery capacity determination method, characterized in that:

2. If the determined target inflection point further includes a second inflection point, a third charge amount when the battery is charged to the second inflection point is obtained, and the first inflection point quantity of electricity is corrected based on the second inflection point quantity of electricity, the first charge amount, and the third charge amount (S6). When the second inflection point electrical quantity and the third charge quantity are defined as Q_LVTP and Qch_LVTP, respectively, Q_HVTP, Qch_HVTP, Q_LVTP, and Qch_LVTP are expressed by the following relational expressions: Q_HVTP=Q_LVTP+Qch_HVTP−Qch_LVTP 2. The method for determining battery capacity according to claim 1, wherein the following is satisfied:

3. 2. The battery capacity determination method according to claim 1, further comprising: correcting the first inflection point electrical quantity based on an empirical formula for a change over time of a predetermined first inflection point electrical quantity if the determined target inflection point includes only the first inflection point and if a time from a previous correction of the first inflection point electrical quantity to a current time is greater than a predetermined time.

4. determining a target inflection point based on the first charging curve, obtaining a curve obtained by differentiating the voltage of the first charging curve with respect to the capacity; obtaining a peak voltage corresponding to a maximum point of a curve obtained by differentiating the voltage with respect to capacitance; 2. The method of claim 1, further comprising: comparing the peak voltage with the first inflection point voltage and the second inflection point voltage to determine the target inflection point.

5. The step of comparing the peak voltage with the first inflection point voltage and the second inflection point voltage to determine the target inflection point includes:

5. The battery capacity determination method according to claim 4, further comprising: when the peak voltage is greater than the first inflection point voltage, setting the local maximum point as a target inflection point and setting the target inflection point as the first inflection point; or when the peak voltage is less than the second inflection point voltage, setting the local maximum point as a target inflection point and setting the target inflection point as the second inflection point.

6. The step of comparing the peak voltage with the first inflection point voltage and the second inflection point voltage to determine the target inflection point includes:

6. The method of claim 5, further comprising: if the peak voltage is equal to or less than a first inflection point voltage and equal to or greater than a second inflection point voltage, continuing to charge the battery to search for a target inflection point.

7. The first charging curve is a voltage-capacity characteristic curve established based on first voltage data during charging of the battery and its corresponding first capacity data, and the step of obtaining a curve obtained by differentiating the voltage of the first charging curve with respect to the capacity includes:

5. The method of claim 4, further comprising the steps of: performing a smoothing filter process on the first charging curve; first differentiating the first voltage data with respect to the first capacity data; obtaining a rate of change of the first voltage data with respect to the first capacity data; and establishing a curve obtained by differentiating the voltage of the first charging curve with respect to the capacity based on the rate of change and the first capacity data.

8. The step of acquiring a first inflection point voltage and a corresponding first inflection point electrical quantity, and a second inflection point voltage and a corresponding second inflection point electrical quantity of the battery includes: determining one or more reference cells; obtaining a second charging curve of the reference battery; determining a first inflection point and a second inflection point based on the second charging curve; acquiring the first inflection point voltage and the first inflection point electrical quantity corresponding to the first inflection point, and the second inflection point voltage and the second inflection point electrical quantity corresponding to the second inflection point.

9. The step of obtaining a second charging curve of the reference battery includes: fully discharging the reference battery and then charging it at a constant current; recording second capacity data and corresponding second voltage data during the constant current charging; and obtaining the second charging curve by establishing a voltage-capacity characteristic curve based on the second capacity data and the corresponding second voltage data.

10. obtaining an initial capacity of the battery; 2. The method of claim 1, further comprising: calculating a state of health (SOHC) of the battery based on a current capacity of the battery and an initial capacity of the battery.

11. The step of recording a first charging curve of the battery in real time includes: collecting and recording at least one parameter of the battery's voltage, current, temperature, current charging time, and charge amount by a battery management system (BMS); and obtaining the first charging curve according to a BMS charging algorithm.

12. 9. The method of claim 8, wherein the first inflection point voltage and the first inflection point electrical quantity are a voltage and an inflection point electrical quantity corresponding to a high-voltage plateau inflection point on the second charging curve.

13. 9. The method of claim 8, wherein the second inflection point voltage and the second inflection point electrical quantity are a voltage and an inflection point electrical quantity corresponding to a low-voltage plateau inflection point on the second charging curve.

14. The step of acquiring a third electrical quantity when the battery is charged to a second inflection point includes:

3. The method for determining battery capacity according to claim 2, further comprising the step of acquiring a third electrical quantity when the battery is charged to the second inflection point by a battery management system (BMS).

15. A non-transitory computer-readable storage medium having a computer program stored thereon, the non-transitory computer-readable storage medium being configured to, when executed by a processor, perform the battery capacity determination method of any one of claims 1 to 14.

16. A computer program that, when executed by a computer, executes the battery capacity determination method according to any one of claims 1 to 14.

17. At least one processor (10); a memory (20) communicatively connected to the at least one processor (10), wherein commands processable by the at least one processor (10) are stored in the memory (20), and when the commands are processed by the at least one processor (10), the battery capacity determination device (1) executes the battery capacity determination method according to any one of claims 1 to 14.

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