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] This application claims priority to a Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on March 29, 2022, bearing application number 202210318139.5 and title "Battery capacity determination method and apparatus, storage medium, and battery," 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 are very widely applied in fields such as electric vehicles and energy storage power stations. Lithium-ion batteries gradually deteriorate with continuous charge and discharge cycles, and their performance gradually declines, specifically, capacity reduction, internal resistance increase, and power reduction. The deterioration degree of a battery is expressed as SOH (State of Health). SOH can be defined in several ways, such as remaining capacity, internal resistance, and cycle count, among which the most common and intuitive way is to define it by the remaining capacity of the battery, that is, the percentage of the capacity after deterioration of the battery to the initial capacity of the battery (also called SOHC, State of Health Capacity).

[0004] Currently, the remaining battery capacity is mainly calculated by fully charging and fully discharging the battery to calculate the total power amount 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 amount and the corresponding SOC range.

[0005] However, all of the above methods for calculating the remaining battery capacity have drawbacks. Specifically, the full charge and full discharge of a battery not only consumes more time and equipment resources, but may also cause a series of safety-related problems, such as overcharging, fire, and even explosion. In addition, users usually charge the battery before it is fully discharged, so the full discharge situation of the battery is difficult to trigger, and if triggered, it will affect the service life of the battery itself, so the calculation of the remaining battery capacity by the full charge and full discharge of the battery is not practical in application. In addition, when charging or discharging in a specific SOC range to obtain the remaining battery capacity, it is necessary to select a sufficiently long SOC range, which also has the problem of being difficult to trigger. In addition, there is a high requirement for the accuracy of SOC estimation, and if the SOC estimation is inaccurate, it is easy to cause a large error in the result. 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] In order to achieve the above object, in a first aspect, the present invention provides a battery capacity determination method, the determination method including the steps of: acquiring a first inflection point voltage and its corresponding first inflection point power amount of a battery, and a second inflection point voltage and its corresponding second inflection point power amount, the first inflection point voltage being greater than the second inflection point voltage; 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; detecting the power amount of the battery until charging is completed, and determining a target inflection point power amount when the battery is charged to the first inflection point of the battery. acquiring a first charge amount and a second charge amount at the time of completion of charging of the battery; and if the determined target inflection point includes the first inflection point, calculating a current capacity of the battery based on the first inflection point power amount, the first charge amount, and the second charge amount, wherein when the first inflection point power amount, 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 satisfy the relational equation Qnow=Q_HVTP+Qch_End-Qch_HVTP.

[0010] Preferably, when the determined target inflection point further includes the second inflection point, the method further includes a step of acquiring a third charge amount when the battery is charged to the second inflection point, and correcting the first inflection point power amount based on the second inflection point power amount, the first charge amount, and the third charge amount, wherein when the second inflection point power amount and the third charge amount are defined as Q_LVTP and Qch_LVTP, respectively, Q_HVTP, Qch_HVTP, Q_LVTP, and Qch_LVTP satisfy the relational equation 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, and 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, and 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 amount, the first charge amount, and the second charge amount of the battery. That is, the calculation method of the embodiment of the present invention can accurately calculate the current capacity of the battery in any start state before the target inflection point, and does not require deep discharging the battery before charging, which avoids the loss of the battery itself due to full charging or full discharging, extends the service life of the battery, and improves 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 and the second charge amount when the battery is fully charged, which is advantageous for quickly calculating the battery capacity, and it is not necessary to select an SOC range, and compared to selecting a specific SOC range and charging or discharging to calculate the battery capacity, it is possible to avoid calculation errors of the battery state due to inaccurate SOC estimation, thereby improving the calculation accuracy of the battery capacity. In addition, when calculating the current capacity of the battery, it is also possible to correct the first inflection point power amount of the battery after deterioration based on the second inflection point power amount, the first charge amount, and the third charge amount when the battery is charged to the second inflection point of the battery, and it is possible to obtain an accurate value of the first inflection point power amount of the battery in the current deteriorated state, thereby avoiding inaccurate calculation of the current capacity of the battery caused by the change in the first inflection point power amount due to the deterioration of the battery, which is advantageous for improving the calculation accuracy of the battery capacity. In summary, according to the battery capacity determination method of the present invention, it is possible to significantly improve the calculation speed and accuracy of the battery capacity.

[0012] Preferably, the battery capacity determination method further includes a step of correcting the first inflection point power amount based on an empirical formula for a change over time of a predetermined first inflection point power amount if the determined target inflection point includes only the first inflection point and a time from a previous correction of the first inflection point power amount to a current time is greater than a predetermined time.

[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 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 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 if the peak voltage is less than or equal to the first inflection point voltage and greater than or equal to 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 differential 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 a voltage differential curve of the first charging curve based on the rate of change and the first capacity data.

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

[0018] Preferably, obtaining a second charging curve of the battery includes 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 obtaining the second charging curve by establishing a voltage-capacity characteristic curve based on the second capacity data and the corresponding second voltage data.

[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 by a battery management system (BMS); and obtaining the first charging curve according to a BMS charging algorithm.

[0021] Preferably, the first amount of power is smaller than the second amount of power.

[0022] Preferably, the first inflection point voltage and the first inflection point power are a voltage and an inflection point power corresponding to a high voltage plateau inflection point in the second charging curve.

[0023] Preferably, the second inflection point voltage and the second inflection point power are a voltage and an inflection point power corresponding to a low voltage plateau inflection point in the second charging curve.

[0024] Preferably, the battery capacity determination method further includes the steps of obtaining a current capacity of the battery calculated a previous n times, and calculating a weighted current capacity of the battery based on the current capacity of the battery calculated a previous n times.

[0025] Preferably, a State of Health of Capacity (SOHC) of the battery is calculated based on the current capacity of the battery after the weighting and the initial capacity of the battery.

[0026] Preferably, the step of acquiring a third amount of power when the battery is charged to the second inflection point includes a step of acquiring the third amount of power when the battery is charged to the second inflection point by a battery management system (BMS).

[0027] Preferably, the battery capacity determination method is performed by a computer program stored on a non-transitory computer readable storage medium.

[0028] In a second aspect, the present invention provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed, performs the battery capacity determination method described above.

[0029] According to the non-transitory computer-readable storage medium according to the embodiment of the present invention, by executing the stored computer program, the speed and accuracy of calculating the battery capacity can be significantly improved.

[0030] In a third aspect, the present invention provides a battery capacity determination device comprising at least one processor and a memory communicatively connected to said at least one processor, wherein said memory stores commands processable by said at least one processor, and wherein said commands, when processed by said at least one processor, execute the battery capacity determination method as described above.

[0031] According to the battery capacity determination device of the embodiment of the present invention, the processor executes the battery capacity determination method, thereby making it possible to significantly improve the speed and accuracy of calculating the battery capacity.

[0032] The present invention provides a battery, the capacity of which can be calculated by the above-mentioned method for determining battery capacity.

[0033] According to the battery of the embodiment of the present invention, the current capacity of the battery is calculated by the above-mentioned battery capacity determination method, so that the speed and accuracy of calculating the battery capacity can be greatly improved.

[0034] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. [Brief description of the drawings]

[0035] In order to more clearly describe the technical means of the embodiments of the present invention, the drawings necessary for the embodiments are 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.

[0036] [Figure 1] FIG. 2 is a comparative schematic diagram of a first charging curve and a charging voltage differential curve of batteries with different deterioration levels according to an embodiment of the present invention. [Diagram 2] 4 is a flowchart of a battery capacity determination method according to an embodiment of the present invention. [Diagram 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 PREFERRED EMBODIMENTS

[0037] In order to make the objectives, technical means and advantages of the present application clearer, 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, but not 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. Based on the embodiments described herein, all other embodiments that a person skilled in the art can obtain without creative labor are all within the scope of protection of the present application.

[0038] 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 throughout indicate the same or similar parts or parts having the same or similar functions. The embodiments described below with reference to the drawings are illustrative and are only intended to interpret the present invention, and should not be understood as limiting the present invention.

[0039] In contrast to the problems existing in the prior art, the method for determining battery capacity according to the embodiment of the present invention can greatly 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 the need to deep-discharge the battery before charging, even if the initial SOC state of the battery is unknown.

[0040] First, characteristic points of the curve used in the embodiment of the present invention will be described.

[0041] Referring to FIG. 1, in general, the voltage-capacity characteristic curve (i.e., charging curve) of a battery (e.g., lithium ion battery, but not limited thereto) has three sections in which the voltage changes slowly, called voltage plateau regions. Between each two voltage plateau regions, there is a region in which the voltage changes rapidly, and the point in these regions where the voltage changes most rapidly is called a voltage plateau inflection point, and they are distinguished by voltage level, the one with a high voltage is called a high voltage plateau inflection point (HVTP), and the one with a low voltage is called a low voltage plateau inflection point (LVTP). The voltage plateau inflection point is expressed as a maximum point of the curve in a voltage differential curve, and in practical applications, the high voltage plateau inflection point and the low voltage plateau inflection point can be distinguished based on the voltage value. Taking the lithium ion power battery of an electric vehicle as an example, when the SOC state at the start of charging is uncertain and charging is started from a low SOC section (e.g., 5%), two plateau inflection points, HVTP and LVTP, can be detected during charging. If charging is started from an intermediate SOC section (i.e., a region between HVTP and LVTP), only one plateau inflection point, HVTP, can be detected during charging. Figure 1 shows the charging curves and voltage differential curve diagrams of multiple batteries, where different curves represent batteries with different degrees of degradation, and it can be seen that the curve of a battery with a smaller degree of degradation has two inflection points, a high voltage plateau inflection point and a low voltage plateau inflection point.

[0042] As is well known to those skilled in the art, as shown in FIG. 1, as a battery deteriorates, the voltage-capacity characteristic curve of the battery generally shifts in the direction of lower capacity, and during the shifting process, the inflection point energy Q_LVTP (or called the characteristic capacity of the low-voltage plateau inflection point) corresponding to the LVTP basically does not change, that is, the inflection point energy Q_LVTP is a fixed value, and the inflection point energy Q_HVTP (or called the characteristic capacity of the high-voltage plateau inflection point) corresponding to the HVTP changes slightly within a certain deterioration range, but the voltages corresponding to the HVTP and LVTP do not change with the parallel shift of the characteristic curve, so the detected plateau inflection points can be distinguished by voltage.

[0043] 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.

[0044] 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:

[0045] In step S1, a first inflection point voltage and its corresponding first inflection point power amount, and a second inflection point voltage and its corresponding second inflection point power amount of a battery are obtained, and the first inflection point voltage is greater than the second inflection point voltage. As can be understood by those skilled in the art, the first inflection point voltage and the first inflection point power amount are a voltage and an inflection point power amount corresponding to a high voltage plateau inflection point, and the second inflection point voltage and the second inflection point power amount are a voltage and an inflection point power amount corresponding to a low voltage plateau inflection point. The first inflection point voltage and the first inflection point power amount are both characteristic parameters at the time of shipment of the battery and correspond to the first inflection point at the time of shipment of the battery. Similarly, the second inflection point voltage and the second inflection point power amount are both characteristic parameters at the time of shipment of the battery and correspond to the second inflection point at the time of shipment of the battery. The first inflection point and the second inflection point are one characteristic point of the battery and change with the deterioration of the battery. At the time of shipment, 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 power amount and the second inflection point power amount, respectively, but as the battery is used, the battery capacity decreases and the voltage values ​​corresponding to the first inflection point and the second inflection point 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.

[0046] In an embodiment of the present invention, for a battery whose lot and specifications have been determined, the voltage and inflection point power corresponding to the high-voltage plateau inflection point or the low-voltage plateau inflection point in its voltage-capacity characteristic curve can both be determined, and the values ​​of these characteristic quantities can be obtained from only the voltage-capacity characteristic curves of a small number of batteries. A specific method for obtaining these characteristic quantities will be described in detail later.

[0047] In step S2, the battery is controlled to be charged, and a first charging curve of the battery is recorded in real time.

[0048] In the embodiment of the present invention, when charging a battery with an unknown SOC state, a first capacity data and a 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, charging amount, etc. 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 is omitted here.

[0049] In step S3, a target inflection point is determined based on the first charging curve.

[0050] In an embodiment of the present invention, the first charging curve is analyzed to obtain an inflection point thereof, 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 a first inflection point), and a specific method for determining the target inflection point will be described in detail later.

[0051] In step S4, the amount of power of the battery is detected until charging is completed, and a first amount of charge when the battery is charged to the first inflection point and a second amount of charge when charging is completed are obtained. Note that charging completion refers to when the battery reaches a fully charged state.

[0052] In an embodiment of the present invention, when it is detected that the power of the battery reaches the full charge amount, the charge amount of the battery from the start of charging to the first inflection point is set as the first charge amount, and the charge amount of the battery 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 the description is omitted here. For example, the power amount of the battery at the start of charging is 10% of the battery capacity, and after charging for a certain period of time, the battery is charged to the first inflection point, at this time, the power amount of the battery reaches 60% of the battery capacity, in this case, the first charge amount is 60% when charging to the first inflection point minus 10% at the start of charging, that is, the first charge amount is 50% of the battery capacity. Similarly, if the battery is continuously charged, the battery reaches 100% of the battery capacity at the completion of charging. Since the second charge amount is the charge amount when the battery is fully charged, in this case, the second charge amount is 100% minus 10% at the start of charging, i.e., the second charge amount is 90% of the battery capacity. However, it should be noted that the battery capacity will decrease as the battery is used for an extended period of time due to factors such as battery deterioration. In other words, the first charge amount and the second charge amount will gradually decrease as the battery deteriorates.

[0053] In step S5, if the determined target inflection point includes the first inflection point, calculate a current capacity of the battery based on the first inflection point power amount, the first charge amount, and the second charge amount, and the current capacity of the battery is the total power amount of the battery in a current state.

[0054] As can be understood, for a battery with an unknown SOC state, at least a 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 current capacity of the battery is calculated based on the first inflection point power amount, the first charge amount, and the second charge amount, and the state of the battery is determined based on the current capacity of the battery, which is advantageous to realizing timely updating of the battery state.

[0055] Specifically, in the embodiment of the present invention, the first inflection point energy, 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 the first inflection point energy Q_HVTP, the first charge amount Qch_HVTP, the second charge amount Qch_End, and the current capacity Qnow of the battery satisfy the relational expression Qnow=Q_HVTP+Qch_End-Qch_HVTP. In other words, in the battery capacity determination method according to the embodiment of the present invention, if the first inflection point energy 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 expression.

[0056] 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, and 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., high voltage plateau inflection point) and a second charge amount when the battery is fully charged are obtained, and when the determined target inflection point includes the first inflection point, the current capacity of the battery can be calculated based on the obtained first inflection point power amount, first charge amount, and second charge amount of the battery. That is, the calculation method of the embodiment of the present invention can accurately calculate the current capacity of the battery in any starting state before the target inflection point, and does not require deep discharging the battery before charging, which avoids the loss of the battery itself due to full charging or full discharging, extends the service life of the battery, and improves 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 and the second charge amount when the battery is fully charged, which is advantageous for quickly calculating the battery capacity and does not require the selection of an SOC range, which is more effective than calculating the battery capacity by selecting a specific SOC range and charging or discharging the battery, thereby avoiding calculation errors in the battery state due to inaccurate SOC estimation, thereby improving the calculation accuracy of the battery capacity. In summary, the battery capacity determination method of the present invention can significantly improve the calculation speed and accuracy of the battery capacity.

[0057] Note that, in the embodiment of the present invention, step S1 of acquiring a first inflection point voltage and its corresponding first inflection point power amount, and a second inflection point voltage and its corresponding second inflection point power amount of a battery 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 acquiring the first inflection point voltage and the first inflection point power amount corresponding to the first inflection point, and the second inflection point voltage and the second inflection point power amount corresponding to the second inflection point.

[0058] Specifically, in the battery test stage, a reference battery is selected from a plurality of batteries of the same lot and specifications, and is fully discharged and then charged at a constant current, and second capacity data and corresponding second voltage data during the charging of the reference battery are recorded, 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 and its corresponding first inflection point power corresponding to the first inflection point (i.e., high voltage plateau inflection point), and a second inflection point voltage and its corresponding second inflection point power corresponding to the second inflection point (i.e., low voltage plateau inflection point) can be determined, and the specific analysis process is the same as the process of analyzing the charging curve of a battery in the test stage in the prior art, and therefore a description thereof will be omitted here.

[0059] As can be understood, the inflection point energy amounts Q_HVTP, Q_LVTP and their corresponding voltages corresponding to the high voltage and low voltage plateau inflection points are all determined for a battery of a determined lot, and the values ​​of these characteristic amounts can be determined only by a small amount of battery characteristic curves, so the reference battery in the embodiment of the present invention may be the battery to be detected itself, or one or more batteries selected from batteries of the same lot as the battery to be detected. In addition, the second charging curve, the first inflection point voltage and its corresponding first inflection point energy amount, and the second inflection point voltage and its corresponding second inflection point energy amount may be pre-stored in a non-transitory computer-readable storage medium such as an NVM (non-volatile memory) or other software included in a BMS.

[0060] In addition, in an embodiment of the present invention, the 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 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.

[0061] 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 a voltage derivative curve of the first charging curve shown in FIG. 1 based on the rate of change and the first capacity data.

[0062] 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 method continues to search for a next peak voltage to be compared with the first voltage or the second voltage.

[0063] Specifically, referring to FIG. 1, for a battery at any deterioration 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, select a maximum point within the section of the voltage differential curve, determine whether the point is a local maximum point of the voltage differential curve, if it is not a local maximum point, continue charging the battery, and find the local maximum point of the curve by recording the first voltage data and the first capacity data during charging in real time, if it is a local maximum point, obtain a peak voltage corresponding to the local maximum point of the voltage differential curve based on the local maximum point, compare the peak voltage with the first inflection point voltage of the second charging curve, if the peak voltage is greater than the first inflection point voltage, indicate that the peak voltage is the target inflection point and the target inflection point power amount is the first inflection point power amount, compare the peak voltage with the second inflection point voltage of the second charging curve, if the peak voltage is less than the second inflection point voltage, indicate that the peak voltage is the target inflection point and the target inflection point power amount is the second inflection point power amount. If the peak voltage is less than the first inflection point voltage and greater than the second inflection point threshold, continue charging to find the target inflection point. Therefore, in an embodiment of the present invention, by increasing the limiting condition of the voltage value, 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 due to abnormal data in the intermediate section in special cases, thereby improving the calculation accuracy of the battery state.

[0064] As described above, as the battery deteriorates, the voltage-capacity characteristic curve of the battery generally shifts toward a lower capacity, and in the process of the shift, the first inflection point energy Q_HVTP corresponding to the first inflection point (HVTP) changes within a certain deterioration range, and the second inflection point energy Q_LVTP corresponding to the second inflection point (LVTP) basically does not change. Since the first inflection point energy Q_HVTP changes due to the deterioration of the battery, the accuracy of the current capacity Qnow of the battery calculated based on the first inflection point energy Q_HVTP is affected. In order to improve the calculation accuracy of the battery capacity, the battery capacity determination method according to the embodiment of the present invention further includes a step of correcting the first inflection point energy Q_HVTP.

[0065] Specifically, as shown in FIG. 2, in some embodiments, the method for determining battery capacity includes: If the determined target inflection point further includes the second inflection point, the method further includes a step S6 of obtaining a third charge amount when the battery is charged to the second inflection point, and correcting the first inflection point power amount based on the second inflection point power amount, the first charge amount, and the third charge amount.

[0066] 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 a description thereof will be omitted here.

[0067] In the embodiment of the present invention, when the third charge amount is defined as Qch_LVTP, the first inflection point energy Q_HVTP, the second inflection point energy Q_LVTP, the first charge amount Qch_HVTP and the third charge amount Qch_LVTP satisfy a relational expression Q_HVTP=Q_LVTP+Qch_HVTP-Qch_LVTP. In other words, after determining the second inflection point energy Q_LVTP and obtaining the third charge amount Qch_LVTP and the first charge amount Qch_HVTP, the first inflection point energy Q_HVTP can be corrected.

[0068] As can be seen, for a battery whose lot and specifications have been determined, the second inflection point energy 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 at any deterioration state of the battery are determined values ​​obtained in real time while the battery is being charged. Therefore, by correcting the first inflection point energy Q_HVTP of the battery after deterioration based on the second inflection point energy Q_LVTP, the first charge amount Qch_HVTP and the third charge amount Qch_LVTP, an accurate value of the first inflection point energy Q_HVTP of the battery in a current deterioration state can be obtained, thereby avoiding inaccurate calculation of the current capacity Qnow of the battery caused by changes in the first inflection point energy Q_HVTP due to battery deterioration, which is advantageous to improving the calculation accuracy of the battery capacity.

[0069] It can also be understood that different users have different usage habits for charging and discharging the battery. Some users are accustomed to charging the battery after discharging the battery to a low SOC range, while other users sometimes charge the battery after discharging the battery to a low SOC range. In this way, the second inflection point is frequently or occasionally triggered during charging of the battery, and based on the correction method of the first inflection point energy Q_HVTP in the above embodiment, the first inflection point energy Q_HVTP of the battery can be corrected in a timely manner based on the second inflection point energy 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 the battery to a low SOC range. In this way, during charging of the battery, the second inflection point may not be triggered for a long time, and further, the first inflection point energy Q_HVTP cannot be timely corrected based on the second inflection point energy Q_LVTP, the first charge amount Qch_HVTP, and the third charge amount Qch_LVTP.

[0070] In order to accommodate different user usage habits for charging and discharging a battery, in some other embodiments, the battery capacity determination method further includes a step of correcting the first inflection point power amount based on a predetermined empirical formula for the time-dependent change of the first inflection point power amount when a time from a previous correction of the first inflection point power amount to a current time is greater than a predetermined time and the determined target inflection point includes only the first inflection point.

[0071] 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, and for a battery with a fast deterioration rate, the predetermined time can be 4 months, 5 months or 6 months, and the predetermined time can be set based on the specific deterioration rate of the battery, and is not limited thereto.

[0072] Specifically, in an embodiment of the present invention, the time from the previous correction of the first inflection point power amount Q_HVTP to the current time is defined as ΔT, the empirical equation for the change over time of the first inflection point power amount Q_HVTP is defined as f(ΔT), and the corrected first inflection point power amount Q_HVTP_ΔT is defined. The first inflection point power amount Q_HVTP, the empirical equation f(ΔT), and the corrected first inflection point power amount Q_HVTP_ΔT satisfy the relational equation Q_HVTP_ΔT=Q_HVTP-f(ΔT).

[0073] As is well known to those skilled in the art, the empirical formula f(ΔT) of the change in the first inflection point electric energy Q_HVTP over time differs for batteries of different lots and different specifications, but for a battery with a determined lot and specifications, the empirical formula f(ΔT) of the change in the first inflection point electric energy Q_HVTP over time can be obtained through multiple tests, and therefore, a description thereof will be omitted here.

[0074] As described above, for a battery in which the second inflection point is not triggered for a long time during charging, the first inflection point energy Q_HVTP can be corrected based on the previously corrected first inflection point energy Q_HVTP and the empirical equation f(ΔT) of the change over time of the first inflection point energy Q_HVTP obtained by testing. In this way, it is possible to avoid inaccurate calculation of the current capacity Qnow of the battery caused by a change in the first inflection point energy Q_HVTP due to deterioration of the battery and a failure to timely correct the first inflection point energy Q_HVTP based on the second inflection point energy Q_LVTP corresponding to the triggered second inflection point, and improve the calculation accuracy of the battery state.

[0075] Based on the above two methods of correcting the first inflection point energy Q_HVTP, 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. As can be understood, based on any correction method, the corrected first inflection point energy Q_HVTP and the correction time of the first inflection point energy Q_HVTP may both be stored in a readable storage medium such as an NVM or other software included in the BMS described above, in order to facilitate the calculation of the state of the battery next time.

[0076] 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 the SOHC of the battery according to 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%.

[0077] 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 current capacity of the battery calculated n times in the past can be obtained, and the current capacity Qnow of the battery after weighting can be calculated according to the current capacity Qnow of the battery after weighting, and the SOHC of the battery can be calculated according to the current capacity Qnow of the battery after weighting. Specifically, the current capacity Qnow of the battery after weighting can be calculated according to the following formula:

[0078] Qnow=n 1 Qnow 1 +n 2 Qnow 2 +...+n n Qnow n

[0079] where Qnow is the current capacity of the battery after weighting, and Qnow 1 ~Qnow nis the current capacity of the battery calculated n times, 1 ~n n is a weight parameter corresponding to the current capacity of the battery at n times, 1 +n 2 +...n n = 1, and n 1 ~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.

[0080] After calculating the weighted current capacity Qnow of the battery, the SOHC of the battery is calculated according to the above-mentioned SOHC calculation formula, so that the calculation result is more accurate.

[0081] Hereinafter, the battery capacity determination method according to the embodiment of the present invention will be described taking 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.

[0082] In step 1, after a battery is shipped, a part of batteries to be detected having the same specifications is selected as a reference battery, the reference battery is fully discharged and then charged to a fully charged state at a constant current, and a voltage-capacity curve during charging of the reference battery (i.e., the above-mentioned second charging curve) is recorded, and a charging voltage curve characteristic is analyzed to obtain a first inflection point voltage and a first inflection point energy Q_HVTP corresponding to a high voltage plateau inflection point (i.e., the first inflection point) of the battery, and a second inflection point voltage and a second inflection point energy Q_LVTP corresponding to a low voltage plateau inflection point (i.e., the second inflection point) of the battery, and the first inflection point Q_HVTP is stored in the NVM of the BMS, and the second inflection point energy Q_LVTP is written into the corresponding software of the BMS as a fixed value, so that it can be quickly called up to realize subsequent calculations.

[0083] In step 2, charging is started for a battery to be detected, the SOC state of which is unknown in an actual vehicle application, a voltage-capacity curve after charging of the battery is started (i.e., the above-mentioned first charging curve) is recorded in real time, and a target inflection point of the battery is determined based on the first charging curve, the first inflection point voltage, and the second inflection point voltage obtained in step 1. During charging of the battery, a charge amount when charging to each node of the battery is 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 charged to the completion of charging, and a third charge amount Qch_LVTP when the battery is charged to the second inflection point.

[0084] In step 4, after charging is completed, the first inflection point energy Q_HVTP is corrected and updated based on the determined target inflection point and the charge amount corresponding to the target inflection point, and a specific correction method includes the following: 1. When the first inflection point (HVTP) and the second inflection point (LVTP) are detected simultaneously, the first inflection point energy Q_HVTP is corrected based on the second inflection point energy Q_LVTP, the first charge amount Qch_HVTP, and the third charge amount Qch_LVTP, and the update time is stored in the NVM for use in subsequent calculations. 2. When the second inflection point (LVTP) is not detected and the time until the last update of the first inflection point energy Q_HVTP exceeds a predetermined time, the first inflection point energy Q_HVTP is corrected according to an empirical formula f(ΔT), and the update time is stored in the NVM for use in subsequent calculations. For more detailed information about the two above correction methods, please refer to the above related content, and the description will be omitted here.

[0085] In step 4, after the battery is fully charged, calculate the current capacity Qnow of the battery, and after the current capacity Qnow of the battery is calculated, further calculate the SOHC of the battery according to the current capacity of the battery. For detailed calculation methods of the current capacity Qnow and the SOHC of the battery, please refer to the above-mentioned related content, and the description will be omitted here.

[0086] As can be seen, since batteries for electric vehicles generally need to be replaced when the capacity fade exceeds 20%, at least a high voltage plateau inflection point (first inflection point) located in the high SOC range can be detected for batteries for electric vehicles, and thus the battery capacity determination method according to the embodiment of the present invention is particularly suitable for power batteries for electric vehicles.

[0087] In short, when calculating the state of a battery using the battery capacity determination method according to the embodiment of the present invention, it is not necessary to perform deep discharging of the battery before charging, and it is advantageous to avoid loss of the battery itself due to full charging or full discharging, and to extend the service life of the battery and improve the safety of charging. In addition, when calculating the current capacity of the battery, it is possible to quickly calculate the capacity of the battery according to the first inflection point power amount (i.e., high voltage plateau inflection point characteristic capacity) of the battery by only detecting the first charge amount when the battery is charged to the first inflection point (i.e., high voltage plateau inflection point) of the battery and the second charge amount when the battery is fully charged, and 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, it is possible to avoid calculation errors of the battery state due to inaccurate SOC estimation, thereby improving the calculation accuracy of the battery capacity. In addition, if the determined target inflection point includes the first inflection point and the second inflection point (i.e., the low-voltage plateau inflection point), the first inflection point power amount can be corrected based on the second inflection point power amount (i.e., the 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. If the determined target inflection point includes only the first inflection point and the time since the previous correction of the first inflection point power amount is greater than a predetermined time, the first inflection point power amount can be corrected based on an empirical formula of a predetermined change in the first inflection point power amount over time. In this way, by correcting the first inflection point power amount in a timely manner, it is possible to avoid an inaccurate calculation of the current capacity of the battery caused by a change in the first inflection point power amount due to deterioration of the battery, which is advantageous to improving the calculation accuracy of the battery state. In addition, since there are two correction methods for the first inflection point power amount, 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.

[0088] 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.

[0089] According to the non-transitory computer-readable storage medium according to the embodiment of the present invention, by executing the stored computer program, the speed and accuracy of calculating the battery capacity can be significantly improved.

[0090] 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 device 1 executes a battery capacity determination method according to any of the above embodiments.

[0091] 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.

[0092] In addition, the present invention provides a battery, the capacity of which can be calculated by any of the above-mentioned battery capacity determination methods according to the embodiments. According to the battery of the embodiments of the present invention, the current capacity of the battery can be calculated by the above-mentioned battery capacity determination method, thereby greatly improving the speed and accuracy of calculating the battery capacity.

[0093] In the description of the present invention, a description that refers to the term "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 above terms do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples as appropriate.

[0094] 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 objectives of the present invention, and that the scope of the present invention is limited by the claims and their equivalents.

Claims

1. A step of acquiring a first inflection point voltage and a corresponding first inflection point power amount of a battery, and a second inflection point voltage and a corresponding second inflection point power amount of the battery, the first inflection point voltage being greater than the second inflection point voltage (S1); (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 power 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 (S4); If the determined target inflection point includes the first inflection point, calculating a current capacity of the battery based on the first inflection point power amount, the first charge amount, and the second charge amount; The first inflection point power amount, 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 are expressed by the following relational expressions: Qnow=Q_HVTP+Qch_End−Qch_HVTP A battery capacity determination method, comprising:

2. When 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 power amount is corrected based on the second inflection point power amount, the first charge amount, and the third charge amount (S6). The second inflection point power amount and the third charge amount 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 a battery capacity according to claim 1, wherein the above formula is satisfied.

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

4. The step of determining a target inflection point based on the first charging curve includes: Obtaining a voltage differential curve of the first charging curve; obtaining a peak voltage corresponding to a 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.

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 method of 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 less than or equal to a first inflection point voltage and greater than or equal to 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 voltage differential curve of the first charging curve includes:

7. The method for determining a battery capacity according to 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 voltage differential curve of the first charging curve 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 power amount of the battery, and a second inflection point voltage and a corresponding second inflection point power amount of the battery, obtaining a second charging curve of the battery; determining a first inflection point and a second inflection point based on the second charging curve; and acquiring the first inflection point voltage and the first inflection point power amount corresponding to the first inflection point, and the second inflection point voltage and the second inflection point power amount corresponding to the second inflection point. The battery capacity determination method according to any one of claims 1 to 7, further comprising:

9. obtaining a second charging curve of the battery, determining one or more reference cells; 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; The method of any one of claims 1 to 9, further comprising the step of: 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. 12. The method of claim 1, wherein the first amount of power is smaller than the second amount of power.

13. The battery capacity determination method according to any one of claims 1 to 12, characterized in that the first inflection point voltage and the first inflection point power are a voltage and an inflection point power corresponding to a high voltage plateau inflection point in the second charging curve.

14. The second inflection point voltage and the second inflection point power are a voltage and an inflection point power corresponding to a low voltage plateau inflection point in the second charging curve. The battery capacity determination method according to any one of claims 1 to 13.

15. The method for determining a battery capacity according to any one of claims 1 to 14, further comprising the steps of obtaining a current capacity of the battery calculated a previous n times, and calculating a weighted current capacity of the battery based on the current capacity of the battery calculated a previous n times.

16. 16. The method of claim 15, further comprising: calculating a state of health (SOHC) of the battery based on the current capacity of the battery after the weighting and the initial capacity of the battery.

17. The step of acquiring a third amount of power when the battery is charged to a second inflection point includes: The battery capacity determination method according to any one of claims 1 to 16, further comprising a step of acquiring a third amount of power when the battery is charged to the second inflection point by a battery management system (BMS).

18. The method for determining the capacity of a battery according to any one of claims 1 to 17, characterized in that it is used to calculate the capacity of a battery.

19. A non-transitory computer-readable storage medium having a computer program stored thereon, the non-transitory computer-readable storage medium being characterized in that, when the computer program is executed by a processor, the non-transitory computer-readable storage medium executes the battery capacity determination method according to any one of claims 1 to 18.

20. At least one processor (10); A battery capacity determination device (1), comprising: a memory (20) communicatively connected to the at least one processor (10); wherein the memory (20) stores commands processable by the at least one processor (10); 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 described in any one of claims 1 to 18.

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