Battery capacity determination method and apparatus, 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 the priority of a Chinese patent application filed with the China National Intellectual Property Administration on March 29, 2022, with an application number of 202210३18139.5 and an application title of "Battery Capacity Determination Method and Apparatus, Storage Medium, and Battery", and all of its contents are incorporated herein by reference.

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

Background Art

[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 plants. Lithium-ion batteries gradually deteriorate during continuous charge and discharge cycles, and their performance gradually decreases. Specifically, phenomena such as a decrease in capacity, an increase in internal resistance, and a decrease in power occur. The degree of battery deterioration is expressed as SOH (State of Health). SOH can be defined by multiple methods such as remaining capacity, internal resistance, and number of cycles. Among them, the most common and intuitive method is to define it by the battery remaining capacity, that is, the percentage of the capacity of the battery after deterioration to the initial capacity of the battery (also called SOHC, State of Health Capacity, the state of health of the battery capacity).

[0004] Currently, for the battery remaining capacity, mainly by fully charging and fully discharging the battery, the total Electricity in the charging or discharging stage is calculated, or charging and discharging are performed in a certain SOC (State of Charge) interval, and the total battery capacity is calculated based on the charge or discharge amount and the corresponding SOC interval.

[0005] However, all of the above methods for calculating battery remaining capacity have drawbacks. Specifically, fully charging and fully discharging a battery not only consumes more time and equipment resources, but can also cause a series of safety-related problems such as ignition due to overcharging and even explosion. Furthermore, since users usually charge the battery before it is completely discharged, the fully discharged state is rarely triggered, and when it is triggered, it affects the lifespan of the battery itself. Therefore, calculating battery remaining capacity based on fully charging and fully discharging is not practical in applications. In addition, when obtaining battery remaining capacity by charging or discharging within a specific State of Charge (SOC) interval, it is necessary to select a sufficiently long SOC interval, which similarly presents the problem of being difficult to trigger. Moreover, there is a high requirement for the accuracy of SOC estimation, and inaccurate SOC estimation can easily lead to large errors in the results. [Overview of the project] [Means for solving the problem]

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

[0007] A second object of the present invention is to provide a non-temporary 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 objective, in a first embodiment, the present invention provides a method for determining battery capacity, the method for determining the first inflection point voltage of a battery and the corresponding first inflection point Electricity , second inflection point voltage and its corresponding second inflection point Electricity A step of obtaining the first inflection point voltage being greater than the second inflection point voltage; controlling the battery to charge and recording the first charging curve of the battery in real time; determining a target inflection point based on the first charging curve; and controlling the battery until charging is complete. ElectricitySteps include detecting the first inflection point of the battery and obtaining 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, and if the determined target inflection point includes the first inflection point, Electricity The process includes the steps of, calculating the current capacity of the battery based on the first charge amount and the second charge amount, and the first inflection point Electricity If we define the first charge amount, the second charge amount, and the current capacity of the battery as Q_HVTP, Qch_HVTP, Qch_End, and Qnow, respectively, then Q_HVTP, Qch_HVTP, Qch_End, and Qnow satisfy the relation Qnow = Q_HVTP + Qch_End - Qch_HVTP.

[0010] Preferably, if the determined target inflection point further includes the second inflection point, the third charge amount when the battery is charged up to the second inflection point is obtained, and the second inflection point Electricity , based on the first charge amount and the third charge amount, the first inflection point Electricity The process further includes a step of correcting the second inflection point Electricity If we define the third charge amount as Q_LVTP and Qch_LVTP, respectively, then 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, the first charging curve is analyzed to determine the target inflection point, and when it is detected that the battery is fully charged, i.e., charging is complete, the first charge amount when the battery is charged up to the first inflection point and the second charge amount when the battery is fully charged are obtained, and if the determined target inflection point includes the first inflection point, the first inflection point of the battery ElectricityBased on the first and second charge levels, the current capacity of the battery can be calculated. That is, in the calculation method according to the embodiment of the present invention, the calculation can be accurately performed at any starting state before the target inflection point, there is no need to deep discharge the battery before charging, it avoids loss of the battery itself due to full charging or full discharging, extends the battery's service life, and improves charging safety. Furthermore, when calculating the current capacity of the battery, it is only necessary to detect the first charge level when the battery is charged to the first inflection point and the second charge level when the battery is fully charged, which is advantageous for quickly calculating the battery capacity, there is no need to select a SOC interval, and compared to selecting a specific SOC interval and charging or discharging to calculate the battery capacity, it is possible to avoid calculation errors in the battery state due to inaccurate SOC estimation, thereby improving the accuracy of battery capacity calculation. Furthermore, when calculating the current capacity of the battery, the second inflection point Electricity Based on the first charge level and the third charge level when the battery is charged to its second inflection point, the first inflection point of the degraded battery Electricity It can also correct for the first inflection point of the battery in its current degraded state. Electricity The exact value can be obtained, thereby determining the first inflection point due to battery degradation. Electricity This method avoids inaccurate calculations of the battery's current capacity caused by changes in the battery's capacity, which is advantageous for improving the accuracy of battery capacity calculations. In summary, the battery capacity determination method of the present invention can significantly improve the speed and accuracy of battery capacity calculations.

[0012] Preferably, the battery capacity determination method is such that if the determined target inflection point includes only the first inflection point, the first inflection point Electricity If the time from the previous correction to the current time is greater than a predetermined time, the predetermined first inflection point Electricity Based on the empirical formula for the change over time, the first inflection point Electricity This further includes a step to correct the error.

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

[0014] Preferably, the step of determining the target inflection point by comparing the peak voltage with the first inflection point voltage and the second inflection point voltage includes the step of setting the maximum point as the target inflection point and the target inflection point as the first inflection point if 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 if the peak voltage is less than the second inflection point voltage.

[0015] Preferably, the step of determining the target inflection point by comparing the peak voltage with the first inflection point voltage and the second inflection point voltage further includes the step of continuing to charge the battery and searching 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 and corresponding first capacity data during charging of the battery. The step of obtaining the voltage derivative curve of the first charging curve includes smoothing the first charging curve, taking the first derivative of the first voltage data with respect to the first capacity data, obtaining the 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 Electricity , second inflection point voltage and its corresponding second inflection point ElectricityThe step of obtaining includes the step of obtaining the second charging curve of the battery, the step of determining the first inflection point and the second inflection point based on the second charging curve, the first inflection point voltage corresponding to the first inflection point and the first inflection point Electricity , and the step of obtaining the second inflection point voltage and the second inflection point corresponding to the second inflection point Electricity .

[0018] Preferably, the step of obtaining the second charging curve of the battery includes the step of determining one or more reference batteries, the step of performing constant current charging after completely discharging the reference batteries, the step of recording the second capacity data and the corresponding second voltage data during the constant current charging, and the step of 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 step of obtaining the initial capacity of the battery and the step of calculating the state of health of the capacity (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 step of collecting and recording at least one parameter of the voltage, current, temperature, current charging time, and charging amount of the battery by a battery management system (BMS), and the step of obtaining the first charging curve according to a BMS charging algorithm.

[0021] Preferably, the second inflection point voltage and the second inflection point Electricity are the voltage and the inflection point corresponding to the low voltage plateau inflection point in the second charging curve Electricity .

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

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

[0024] Preferably, the third inflection point when the battery is charged to the second inflection point. Electricity The step of obtaining the third inflection point of the battery is performed by the Battery Management System (BMS) when the battery has been charged to the second inflection point. Electricity This includes the step of obtaining [something].

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

[0026] In a second embodiment, the present invention provides a non-temporary computer-readable storage medium in which a computer program is stored, and when the computer program is executed, the battery capacity determination method described above is performed.

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

[0028] In a third embodiment, the present invention provides a battery capacity determination device including at least one processor and a memory communicated to the at least one processor. A command that can be processed by the at least one processor is stored in the memory, and when the command is processed by the at least one processor, the battery capacity determination method described above is executed.

[0029] According to the battery capacity determination device of the present invention, the calculation speed and accuracy of the battery capacity can be significantly improved by having the processor execute the above-mentioned battery capacity determination method.

[0030] The present invention provides a battery, the capacity of which can be calculated by the battery capacity determination method described above.

[0031] According to the battery according to the embodiment of the present invention, the calculation speed and accuracy of the battery capacity can be significantly improved by calculating the current capacity of the battery using the above-described battery capacity determination method.

[0032] Additional aspects and advantages of the present invention are, in part, shown in the following description, and in part, become apparent in the following description or are understood through the practice of the present invention. [Brief explanation of the drawing]

[0033] To more clearly illustrate the technical means of the embodiments of the present invention, the drawings necessary for the embodiments will be briefly described below. Clearly, the drawings described below represent only a few 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] This is a schematic diagram comparing the first charging curve and the charging voltage differential curve of batteries with different degrees of degradation according to one embodiment of the present invention. [Figure 2] This is a flowchart of a battery capacity determination method according to one embodiment of the present invention. [Figure 3] This is a functional block diagram of a battery capacity determination device according to one embodiment of the present invention. [Modes for carrying out the invention]

[0035] To further clarify the purpose, technical means, and advantages of this application, exemplary embodiments of this application will be described in detail below with reference to the drawings. Clearly, the embodiments described are only a selection of embodiments of this application, not all embodiments. It should be understood that this application is not limited to the exemplary embodiments described herein. All other embodiments that a person skilled in the art can obtain based on the embodiments described herein, without any creative work, are all within the scope of protection of this application.

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

[0037] In contrast to the problems present in the prior art, the battery capacity determination method according to the embodiment of the present invention can significantly improve the calculation speed and accuracy of battery capacity. The general concept of the calculation method in the embodiment of the present invention is to detect the voltage-capacity curve of the battery to be detected in real time during charging, analyze the curve characteristics, find characteristic points of the curve, and accurately calculate the battery capacity even when the initial state of charge (SOC) of the battery is unknown and there is no need to perform a deep discharge on the battery before charging.

[0038] First, the characteristic features of the curves used in the embodiments of the present invention will be described.

[0039] Referring to Figure 1, generally, the voltage-capacity characteristic curve (i.e., charging curve) of a battery (e.g., a lithium-ion battery) has three intervals where the voltage change is slow, called voltage plateau regions. Between each pair of voltage plateau regions, there is an interval where the voltage change is fast. The point in these regions where the voltage change is fastest is called the voltage plateau inflection point, and it is distinguished by voltage level: the one with a high voltage is called the high-voltage plateau inflection point (HVTP), and the one with a low voltage is called the low-voltage plateau inflection point (LVTP). Voltage plateau inflection points are represented as the maximum points of the curve in the voltage differential curve, and in practical applications, high-voltage and low-voltage plateau inflection points can be distinguished based on the voltage value. Taking the lithium-ion power battery of an electric vehicle as an example, if the state of charge (SOC) at the start of charging is uncertain and charging starts from a low SOC interval (e.g., 5%), two plateau inflection points, HVTP and LVTP, can be detected during charging. If charging starts from an intermediate SOC interval (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 curves of several batteries, where different curves represent batteries with different degrees of degradation. It can be seen that the curve of a battery with less 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 Figure 1, as a battery degrades, the voltage-capacity characteristic curve of the battery shifts overall toward the lower capacity direction, and in the process of this shift, the inflection point corresponding to LVTP Electricity Q_LVTP (or called low-voltage plateau inflection point characteristic capacitance) does not change fundamentally, i.e., the inflection point Electricity Q_LVTP is a fixed value, and the inflection point corresponds to HVTP. Electricity Although Q_HVTP (or referred to as 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 shift of the characteristic curve, so the detected plateau inflection points can be distinguished by voltage.

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

[0042] Figure 2 is a flowchart of a battery capacity determination method according to one embodiment of the present invention. As shown in Figure 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 Electricity , second inflection point voltage and its corresponding second inflection point Electricity The first inflection point voltage is greater than the second inflection point voltage. As a person skilled in the art will understand, the first inflection point voltage and the first inflection point Electricity This refers to the voltage and inflection point corresponding to the high-voltage plateau inflection point. Electricity The second inflection point voltage and the second inflection point Electricity This refers to the voltage and inflection point corresponding to the low-voltage plateau inflection point. Electricity Therefore, the first inflection point voltage and the first inflection point Electricity These are all 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 Electricity These are all characteristic parameters at the time of battery shipment and correspond to the second inflection point at the time of battery shipment. The first and second inflection points are characteristic points of the battery and change as the battery deteriorates. At the time of shipment, the first and second inflection points correspond to the first inflection point voltage and the second inflection point voltage, respectively, or the first and second inflection points correspond to the first inflection point Electricity , second inflection point Electricity While this is true, 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 embodiments 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 low-voltage plateau inflection point in its voltage-capacity characteristic curve Electricity All of these can be determined, and the values ​​of these features can be obtained using only the voltage-capacitance characteristic curve of a small battery. The specific method for obtaining them will be described in detail later.

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

[0046] In an embodiment of the present invention, when charging a battery whose State of Charge (SOC) state is unknown, first capacity data and its corresponding first voltage data are recorded in real time during the 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 voltage, current, temperature, charging time, and charge amount of the lithium-ion power battery are collected and recorded by a BMS (Battery Management System), and a charging curve of the lithium-ion power battery can be obtained according to the BMS charging algorithm, but the explanation is omitted here.

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

[0048] In embodiments 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 whose state of charge (SOC) is unknown, at least a high-voltage plateau inflection point can be detected during charging, meaning that the target inflection point includes at least a high-voltage plateau inflection point (defined as the first inflection point), and the specific method for determining the target inflection point will be described in detail later.

[0049] In step S4, until charging is complete, the battery Electricity The system detects this and obtains the first charge level when the battery is charged to the first inflection point and the second charge level when the battery is fully charged. Note that "fully charged" refers to the battery reaching a fully charged state.

[0050] In this embodiment of the present invention, the battery Electricity When it is detected that the battery has reached full charge, the charge amount from the start of charging to the first inflection point is defined as the first charge amount, and the charge amount from the start of charging to the completion of charging is defined as the second charge amount, with the first charge amount being smaller than the second charge amount. The charge amount of the battery during charging can be obtained by the BMS described above, and the explanation is omitted here. For example, at the start of charging of the battery Electricity This is 10% of the battery capacity, and after charging for a certain period of time, the battery is charged to the first inflection point, and at this time the battery Electricity The battery capacity reaches 60%. In this case, the first charge level is 60% of the capacity reached at the first inflection point minus 10% of the initial charge level. That is, the first charge level is 50% of the battery capacity. Similarly, if the battery is continued to be charged, it will reach 100% of its capacity when charging is complete. The second charge level is the charge level at the end of charging. In this case, the second charge level is 100% minus 10% of the initial charge level. That is, the second charge level is 90% of the battery capacity. However, it should be noted that the battery capacity will decrease with increasing usage time due to factors such as battery degradation. In other words, the first and second charge levels will gradually decrease as the battery degrades.

[0051] In step S5, if the determined target inflection point includes the first inflection point, the first inflection point Electricity Based on the first charge amount and the second charge amount, the current capacity of the battery is calculated. The current capacity of the battery is the total capacity of the battery in its current state. Electricity That is the case.

[0052] To understand this, for a battery whose SOC state is unknown, it is possible to detect at least a high-voltage plateau inflection point (i.e., the first inflection point) during charging, meaning that the first inflection point is more easily triggered. Therefore, in embodiments 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 Electricity Based on the first and second charge levels, the current capacity of the battery is calculated, and the state of the battery is determined based on the current capacity of the battery, which is advantageous for realizing timely updates of the battery state.

[0053] Specifically, in the embodiment of the present invention, the first inflection point Electricity If we define the first charge amount, the second charge amount, and the current capacity of the battery as Q_HVTP, Qch_HVTP, Qch_End, and Qnow, respectively, then the first inflection point Electricity Q_HVTP, the first charge amount Qch_HVTP, the second charge amount Qch_End, and the current capacity of the battery Qnow satisfy the relation Qnow = Q_HVTP + Qch_End - Qch_HVTP. In other words, in the battery capacity determination method according to an embodiment of the present invention, the first inflection point Electricity By determining Q_HVTP, the first charge amount Qch_HVTP, and the second charge amount Qch_End, the current capacity Qnow of the battery can be quickly calculated based on the aforementioned relational expression.

[0054] As described above, according to the battery capacity determination method of the embodiment of the present invention, when charging a battery whose SOC state is unknown, the first charging curve of the battery is analyzed to determine the target inflection point, and when it is detected that the battery is fully charged, i.e., charging is complete, the first charge amount when the battery is charged up to the first inflection point (i.e., the high-voltage plateau inflection point) and the second charge amount when the battery is fully charged are obtained, and if the determined target inflection point includes the first inflection point, the obtained first inflection point of the battery ElectricityBased on the first and second charge levels, the current capacity of the battery can be calculated. In other words, the calculation method according to the embodiment of the present invention can accurately calculate the capacity at any starting state before the target inflection point, there is no need to deep discharge the battery before charging, it avoids loss of the battery itself due to full charging or full discharging, extends the battery's lifespan, and improves charging safety. Furthermore, when calculating the current capacity of the battery, it is only necessary to detect the first charge level when the battery is charged to the first inflection point and the second charge level when the battery is fully charged, which is advantageous for quickly calculating the battery capacity, there is no need to select a SOC interval, and compared to selecting a specific SOC interval and charging or discharging to calculate the battery capacity, it is possible to avoid calculation errors in the battery state due to inaccurate SOC estimation, thereby improving the accuracy of the battery capacity calculation. In summary, the battery capacity determination method of the present invention can significantly improve the calculation speed and accuracy of the battery capacity.

[0055] In the embodiments of the present invention, the first inflection point voltage of the battery and its corresponding first inflection point Electricity , second inflection point voltage and its corresponding second inflection point Electricity Step S1 to obtain the first inflection point voltage and the first inflection point voltage corresponding to the first inflection point is specifically the step of obtaining the second charging curve of the battery, the step of determining the first inflection point and the second inflection point based on the second charging curve, and the step of obtaining the first inflection point voltage and the first inflection point Electricity , and the second inflection point voltage and the second inflection point corresponding to the second inflection point Electricity This includes the step of obtaining the following.

[0056] Specifically, during the battery testing phase, a selection of reference batteries from multiple batteries of the same lot and specifications is made, fully discharged, and then charged with a constant current. The second capacity data and its corresponding second voltage data are recorded during the charging of the reference batteries, and the second charging curve can be obtained by establishing a voltage-capacity characteristic curve based on the second capacity data and second voltage data during the charging of the reference batteries. Furthermore, by analyzing the curve characteristics of the second charging curve, the first inflection point voltage corresponding to the first inflection point (i.e., the high-voltage plateau inflection point) and its corresponding first inflection point can be determined. Electricity , as well as the second inflection point voltage corresponding to the second inflection point (i.e., the low-voltage plateau inflection point) and the corresponding second inflection point Electricity This can be determined, and the specific analysis process is the same as the process for analyzing the battery charging curve during the test phase in conventional technology, so the explanation is omitted here.

[0057] To make it easier to understand, for a battery with a determined lot, the inflection points corresponding to the high-voltage and low-voltage plateau inflection points Electricity Q_HVTP, Q_LVTP, and their corresponding voltages are all determined, and the values ​​of these features can be determined from only a small amount of battery characteristic curves. Therefore, the reference battery in the embodiment of the present invention may be the battery being detected itself, or it may be one or more batteries selected from batteries of the same lot as the battery being detected. Also, the second charging curve, the first inflection point voltage and its corresponding first inflection point Electricity , and the second inflection point voltage and the corresponding second inflection point Electricity This may be pre-stored in a non-volatile computer-readable storage medium such as NVM (non-volatile memory) included in the BMS or other software.

[0058] In the embodiments of the present invention, step S3 for determining the target inflection point based on the first charging curve specifically includes the steps of: obtaining the voltage differential curve of the first charging curve; obtaining the peak voltage corresponding to the maximum point of the voltage differential curve; and determining the target inflection point by comparing the peak voltage with the first inflection point voltage and the second inflection point voltage.

[0059] In some embodiments, the step of obtaining the voltage derivative curve of the first charging curve includes smoothing the first charging curve, taking the first derivative of the first voltage data with respect to the first capacitance data, obtaining the rate of change of the first voltage data with respect to the first capacitance data, and establishing the voltage derivative curve of the first charging curve shown in Figure 1 based on the rate of change and the first capacitance data.

[0060] In some embodiments, the step of determining the target inflection point by comparing the peak voltage with the first inflection point voltage and the second inflection point voltage specifically includes the step of setting the maximum point as the target inflection point and the target inflection point as the first inflection point if the peak voltage is greater than the first inflection point voltage, or the step of setting the maximum point as the target inflection point and the target inflection point as the second inflection point if the peak voltage is less than the second inflection point voltage. As will 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 search for the next peak voltage to compare with the first voltage or the second voltage continues.

[0061] Specifically, referring to Figure 1, for a battery of any degree of degradation, the first inflection point (HVTP) and the second inflection point (LVTP) can be determined by combining the voltage values ​​of the first and second inflection point voltages according to the corresponding voltage derivative curve. More specifically, a maximum point is selected within the interval of the voltage derivative curve, and it is determined whether or not this point is a local maximum of the voltage derivative curve. If it is not a local maximum, the battery is continuously charged, and the first voltage data and 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 derivative curve is obtained based on this local maximum, and the peak voltage is compared with the first inflection point voltage in the second charging curve. If the peak voltage is greater than the first inflection point voltage, then the peak voltage is the target inflection point, and the target inflection point Electricity This is the first inflection point Electricity This indicates that the peak voltage is smaller than the second inflection point voltage in the second charging curve, and if the peak voltage is smaller than the second inflection point voltage, then the peak voltage is the target inflection point, and the target inflection point Electricity The second inflection point Electricity This indicates that the battery is in a specific state. If the peak voltage is below the first inflection point voltage and above the second inflection point threshold, charging continues to search for the target inflection point. Therefore, in the embodiments of the present invention, by increasing the voltage limit condition, it is possible to determine whether the detected target inflection point is the first or second inflection point, and it is also possible to filter out misjudgments due to abnormal data in the intermediate section in special cases, thereby improving the accuracy of battery state calculations.

[0062] As mentioned above, as the battery degrades, the voltage-capacity characteristic curve of the battery shifts overall towards lower capacity, and in the process of this shift, the first inflection point corresponding to the first inflection point (HVTP) Electricity Q_HVTP changes within a certain degradation range and corresponds to the second inflection point (LVTP). Electricity Q_LVTP basically does not change. The first inflection point Electricity Because Q_HVTP changes due to battery degradation, the first inflection point ElectricityThe accuracy of the current battery capacity Qnow calculated based on 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 is the first inflection point Electricity This further includes a step to correct Q_HVTP.

[0063] Specifically, as shown in Figure 2, in some embodiments, the method for determining the battery capacity is as follows: If the determined target inflection point further includes the second inflection point, the third charge amount when the battery is charged up to the second inflection point is obtained, and the second inflection point Electricity , based on the first charge amount and the third charge amount, the first inflection point Electricity The process further includes step S6, which corrects the result.

[0064] The third charge amount is smaller than the first charge amount, and the third charge amount when the battery is charged up to the second inflection point can be obtained by the BMS described above, which will not be explained here.

[0065] In an embodiment of the present invention, if the third charge amount is defined as Qch_LVTP, then the first inflection point Electricity Q_HVTP, the second inflection point Electricity Q_LVTP, the first charge amount Qch_HVTP, and the third charge amount Qch_LVTP satisfy the relationship Q_HVTP = Q_LVTP + Qch_HVTP - Qch_LVTP. In other words, the second inflection point Electricity After determining Q_LVTP and obtaining the third charge amount Qch_LVTP and the first charge amount Qch_HVTP, the first inflection point Electricity Q_HVTP can be corrected.

[0066] To make it easier to understand, for batteries whose lot and specifications have been determined, the second inflection point Electricity Q_LVTP is a fixed value that does not change with degradation, and the third charge amount Qch_LVTP and the first charge amount Qch_HVTP at any degradation state of the battery are determined values ​​acquired in real time during the charging of the battery, therefore the second inflection point ElectricityBased on Q_LVTP, the first charge amount Qch_HVTP, and the third charge amount Qch_LVTP, the first inflection point of the degraded battery Electricity By correcting Q_HVTP, the first inflection point of the battery in its current degraded state is determined. Electricity The exact value of Q_HVTP can be obtained, thereby determining the first inflection point due to battery degradation. Electricity This avoids inaccurate calculations of the current battery capacity Qnow caused by changes in Q_HVTP, which is advantageous for improving the accuracy of the battery capacity calculation.

[0067] Furthermore, it can be understood that different users have different habits regarding the charging and discharging of batteries. Some users are accustomed to discharging the battery to a low SOC range before charging it, while others only occasionally discharge the battery to a low SOC range before charging it. Thus, during charging, the second inflection point of the battery is frequently or occasionally triggered, and the first inflection point in the above embodiment Electricity Based on the Q_HVTP correction method, the first inflection point of the battery Electricity Q_HVTP is the second inflection point Electricity Q_LVTP, the first charge amount Qch_HVTP, and the third charge amount Qch_LVTP can be corrected in a timely manner. However, some users are accustomed to charging the battery before discharging it to a low SOC interval. In this case, the second inflection point may not be triggered for a long time during charging, and furthermore, the first inflection point Electricity Q_HVTP is the second inflection point Electricity It is not possible to correct in a timely manner based on Q_LVTP, the first charge amount Qch_HVTP, and the third charge amount Qch_LVTP.

[0068] To accommodate different user habits regarding battery charging and discharging, in some other embodiments, the battery capacity determination method is the first inflection point Electricity 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, then the predetermined first inflection point ElectricityBased on the empirical formula for the change over time, the first inflection point Electricity This further includes a step to correct the error.

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

[0070] Specifically, in the embodiment of the present invention, the first inflection point Electricity The time from the previous correction of Q_HVTP to the current time is defined as ΔT, and the first inflection point Electricity The empirical formula for the time-dependent change of Q_HVTP is defined as f(ΔT), and the corrected first inflection point Electricity If we define Q_HVTP_ΔT, then the first inflection point Electricity Q_HVTP, the empirical formula f(ΔT), and the corrected first inflection point Electricity Q_HVTP_ΔT satisfies the relationship Q_HVTP_ΔT = Q_HVTP - f(ΔT).

[0071] As is well known to those skilled in the art, for batteries of different lots and different specifications, the first inflection point Electricity Although the empirical formula f(ΔT) for the time-dependent change of Q_HVTP differs, for batteries whose lot and specifications have been determined, the first inflection point Electricity 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 batteries in which the second inflection point is not triggered for a long time during charging, the previously corrected first inflection point Electricity Q_HVTP and the first inflection point obtained by testing Electricity Based on the empirical formula f(ΔT) for the time-dependent change of Q_HVTP, the first inflection point Electricity Q_HVTP can be corrected, and in this way, the first inflection point due to battery degradation Electricity Changes in Q_HVTP and the first inflection point Electricity Q_HVTP corresponds to the second inflection point that triggered the second inflection point Electricity This method avoids inaccurate calculations of the battery's current capacity Qnow, which can be caused by failing to correct Q_LVTP in a timely manner, thereby improving the accuracy of the battery state calculations.

[0073] The first inflection point Electricity Based on the two methods described above for correcting Q_HVTP, the battery capacity determination method according to an embodiment of the present invention can accommodate different user usage habits for charging and discharging the battery. To understand that, based on either correction method, the corrected first inflection point Electricity Q_HVTP and the first inflection point Electricity The correction time for Q_HVTP may be stored in a readable storage medium such as the NVM included in the aforementioned BMS or other software, in order to facilitate the calculation of the battery state for the next time.

[0074] Furthermore, in embodiments of the present invention, the battery capacity determination method further includes the steps of obtaining the initial capacity of the battery and calculating the SOHC of the battery based on the current capacity of the battery and the initial capacity of the battery. Specifically, if the initial capacity of the battery is defined as Qnew, then the SOHC of the battery, the current capacity of the battery Qnow, and the initial capacity of the battery Qnew satisfy the relation SOHC = Qnow / Qnew * 100%.

[0075] Preferably, in order to eliminate calculation errors in 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 in the previous n times can be obtained, the weighted current capacity Qnow of the battery can be calculated based on the current capacity of the battery calculated in the previous n times, and the SOHC of the battery can be calculated based on the weighted current capacity Qnow of the battery. Specifically, the weighted current capacity Qnow of the battery can be calculated based on the following formula.

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

[0077] Here, 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, where n1 to n n n is a weight parameter corresponding to the current capacity of the battery n times, where n1 + n2 + ... n n = 1, n1~n n The specific value can be set according to the battery's history data and current operating status, and is not limited to this.

[0078] After calculating the current capacity Qnow of the battery after weighting, the SOHC of the battery is calculated based on the aforementioned SOHC calculation formula, resulting in a more accurate calculation result.

[0079] The following describes the battery capacity determination method in an embodiment of the present invention, using the power battery of an electric vehicle as an example. The battery capacity determination method mainly includes the following steps 1 to 4 when executed.

[0080] In Step 1, after the batteries have been shipped, a portion of the batteries to be detected with the same specifications are selected as reference batteries. After completely discharging the reference batteries, they are charged to a fully charged state with a constant current. The voltage-capacity curve of the reference batteries during charging (i.e., the second charging curve mentioned above) is recorded, and the charging voltage curve characteristics are analyzed to determine the first inflection point voltage and the first inflection point corresponding to the high-voltage plateau inflection point of the batteries (i.e., the first inflection point). Electricity Q_HVTP, and the second inflection point voltage and second inflection point corresponding to the low-voltage plateau inflection point of the battery (i.e., the second inflection point) Electricity Q_LVTP is obtained, the first inflection point Q_HVTP is stored in the NVM of the BMS, and the second inflection point Electricity Q_LVTP is written as a fixed value to the corresponding software in the BMS, allowing it to be quickly recalled to perform subsequent calculations.

[0081] In step 2, charging is started for a battery to be detected whose SOC state is unknown in actual vehicle applications. The voltage-capacity curve of the battery after charging has started (i.e., the first charging curve mentioned above) is recorded in real time, and the 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 the charging of the battery, the charge amount at each node of the battery is obtained in real time, including the first charge amount Qch_HVTP when the battery is charged to the first inflection point, the second charge amount Qch_End when the battery is fully charged, and the third charge amount Qch_LVTP when the battery is charged to the second inflection point.

[0082] In step 4, after charging is complete, the first inflection point is determined based on the target inflection point and the amount of charge corresponding to the target inflection point. Electricity 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, the second inflection point Electricity The first inflection point based on Q_LVTP, the first charge amount Qch_HVTP, and the third charge amount Qch_LVTP Electricity 1. Correct Q_HVTP and store its update time in NVM for use in subsequent calculations. 2. If the second inflection point (LVTP) has not been detected, and the first inflection point Electricity If the time since the last update of Q_HVTP exceeds a predetermined time, the first inflection point is determined according to the empirical formula f(ΔT). Electricity Q_HVTP is corrected, and its update time is stored in NVM and used in subsequent calculations. For more detailed information on the two correction methods described above, please refer to the related information mentioned earlier, and the explanation will be omitted here.

[0083] In step 4, after the battery has been fully charged, the current capacity Qnow of the battery is calculated. After the current capacity Qnow 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 Qnow of the battery and the SOHC of the battery, please refer to the related information mentioned above, and the explanation will be omitted here.

[0084] To make it easier to understand, generally, batteries for electric vehicles need to be replaced when their capacity decay exceeds 20%. Therefore, for batteries for electric vehicles, it is possible to detect a high-voltage plateau inflection point (first inflection point) located in at least a high SOC (State of Charge) section. Thus, the battery capacity determination method according to the embodiment of the present invention is particularly suitable for power batteries of electric vehicles.

[0085] In short, when calculating the state of a battery using the battery capacity determination method according to the embodiment of the present invention, there is no need to perform a deep discharge on the battery before charging, thus avoiding losses to the battery itself due to full charge or full discharge, which is advantageous for extending the battery's lifespan and improving 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 its first inflection point (i.e., the high-voltage plateau inflection point) and the second charge amount when the battery is fully charged, thus determining the state of the battery's first inflection point Electricity (i.e., high-voltage plateau inflection point characteristic capacity) The battery capacity can be quickly calculated in accordance with this, and there is no need to select an SOC interval. Compared to selecting a specific SOC interval and charging or discharging to calculate the battery capacity, it is possible to avoid calculation errors in the battery state due to inaccurate SOC estimation, thereby improving the accuracy of battery capacity calculation. Furthermore, if the determined target inflection point includes the first and second inflection points (i.e., low-voltage plateau inflection point), the second inflection point Electricity (i.e., low-voltage plateau inflection point characteristic capacity), first charge amount, and third charge amount when the battery is charged to the second inflection point, based on these, the first inflection point Electricity It is also possible to correct this, and the determined target inflection point includes only the first inflection point, and the first inflection point Electricity If the time since the previous correction is greater than a predetermined time, the predetermined first inflection point Electricity Based on the empirical formula for the change over time, the first inflection point Electricity This can be corrected. In this way, the first inflection point Electricity By correcting this in a timely manner, the first inflection point due to battery degradation can be corrected. Electricity This avoids inaccurate calculations of the battery's current capacity caused by changes in the first inflection point, which is advantageous for improving the accuracy of battery state calculations, and also for the first inflection point. Electricity Since there are two correction methods, the battery capacity determination method according to the embodiment of the present invention can accommodate different user habits regarding battery charging and discharging.

[0086] In the non-temporary computer-readable storage medium according to the second embodiment of the present invention, a computer program is stored, and when the computer program is executed, the battery capacity determination method according to any of the above embodiments is executed.

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

[0088] Figure 3 is a functional block diagram of a battery capacity determination device 1 according to a third embodiment of the present invention. As shown in Figure 3, the battery capacity determination device 1 according to the present invention includes at least one processor 10 and a memory 20 that is communicated to the at least one processor 10. A command that can be processed by the at least one processor 10 is stored in the memory 20, and when the command is 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 present invention, the processor 10 can significantly improve the calculation speed and accuracy of the battery capacity by executing any of the battery capacity determination methods according to the above embodiment.

[0090] Furthermore, the present invention provides a battery, and the capacity of the battery can be calculated by the battery capacity determination method according to any of the above embodiments. According to the battery according to the embodiment of the present invention, the calculation speed and accuracy of the battery capacity can be greatly improved by calculating the current capacity of the battery using the battery capacity determination method.

[0091] In this description of the present invention, any reference to terms such as "examples," "specific examples," or "examples" means that the specific features, structures, materials, or properties described in combination with such examples are included in at least one example of the present invention. In this specification, exemplary expressions of the above terms do not necessarily refer to the same examples. Furthermore, the specific features, structures, materials, or properties described can be appropriately combined in any one or more examples.

[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 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 obtaining the first inflection point voltage of a battery and its corresponding first inflection point charge, the second inflection point voltage and its corresponding second inflection point charge, wherein the first inflection point voltage is greater than the second inflection point voltage (S1), Step (S2) involves controlling the battery to charge and recording the first charging curve of the battery in real time. The steps include determining a target inflection point based on the first charging curve (S3), Step (S4) involves detecting the amount of electricity in the battery until charging is complete, and obtaining a first charge amount when the battery is charged to a first inflection point and a second charge amount when charging is complete. If the determined target inflection point includes the first inflection point, the current capacity of the battery is calculated based on the first inflection point charge, the first charge, and the second charge (S5), If we define the first inflection point charge, the first charge, the second charge, and the current capacity of the battery as Q_HVTP, Qch_HVTP, Qch_End, and Qnow, respectively, then Q_HVTP, Qch_HVTP, Qch_End, and Qnow are related by the following equation: Qnow=Q_HVTP+Qch_End−Qch_HVTP A method for determining battery capacity, characterized by satisfying the following conditions.

2. If the determined target inflection point further includes a second inflection point, the method further includes the step (S6) of obtaining the third charge amount when the battery is charged up to the second inflection point, and correcting the first inflection point charge amount based on the second inflection point charge amount, the first charge amount, and the third charge amount. If we define the second inflection point charge and the third charge as Q_LVTP and Qch_LVTP, respectively, Q_HVTP, Qch_HVTP, Q_LVTP, and Qch_LVTP are related by the following equations: Q_HVTP=Q_LVTP+Qch_HVTP−Qch_LVTP The battery capacity determination method according to claim 1, characterized in that it satisfies the requirements.

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

4. The step of determining the target inflection point based on the first charging curve is: The steps include obtaining a curve obtained by differentiating the voltage of the first charging curve with respect to capacitance, The steps include obtaining the peak voltage corresponding to the maximum point of the curve obtained by differentiating the aforementioned voltage with respect to capacitance, The battery capacity determination method according to claim 1, comprising the step of determining the target inflection point by comparing the peak voltage with the first inflection point voltage and the second inflection point voltage.

5. The step of determining the target inflection point by comparing the peak voltage with the first inflection point voltage and the second inflection point voltage is: The battery capacity determination method according to claim 4, characterized in that, if the peak voltage is greater than the first inflection point voltage, the maximum point is set as the target inflection point and the target inflection point is set as the first inflection point, or if the peak voltage is less than the second inflection point voltage, the maximum point is set as the target inflection point and the target inflection point is set as the second inflection point.

6. The step of determining the target inflection point by comparing the peak voltage with the first inflection point voltage and the second inflection point voltage is: The battery capacity determination method according to claim 5, further comprising the step of continuing to charge the battery and searching for a target inflection point when 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.

7. The first charging curve is a voltage-capacitance characteristic curve established based on first voltage data and corresponding first capacity data during the charging of the battery, and the step of obtaining a curve obtained by differentiating the voltage of the first charging curve with respect to capacitance is: The battery capacity determination method according to claim 4, characterized in that it includes the steps of performing a smoothing filter process on the first charging curve, taking the first derivative of the first voltage data with respect to the first capacity data, obtaining the 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 steps of obtaining the first inflection point voltage and its corresponding first inflection point charge, the second inflection point voltage and its corresponding second inflection point charge of the battery are: The steps include determining one or more reference batteries, The steps include obtaining the second charging curve of the reference battery, A step of determining the first and second inflection points based on the second charging curve, The battery capacity determination method according to claim 1, comprising the step of obtaining the first inflection point voltage and the first inflection point electric quantity corresponding to the first inflection point, and the second inflection point voltage and the second inflection point electric quantity corresponding to the second inflection point.

9. The step of obtaining the second charging curve of the aforementioned reference battery is: The steps include: performing constant current charging after completely discharging the aforementioned reference battery, The steps include recording the second capacitance data and the corresponding second voltage data during the constant current charging, The battery capacity determination method according to claim 8, comprising the step of 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. The steps include obtaining the initial capacity of the aforementioned battery, The battery capacity determination method according to claim 1, further comprising the step of calculating the state of healthy capacity (SOHC) of the battery based on the current capacity of the battery and the initial capacity of the battery.

11. The step of recording the first charging curve of the battery in real time is: The steps include: collecting and recording at least one parameter of the battery, such as voltage, current, temperature, current charging time, and charge amount, using a battery management system (BMS); A method for determining battery capacity according to claim 1, comprising the step of obtaining the first charging curve according to a BMS charging algorithm.

12. The battery capacity determination method according to claim 8, characterized in that the first inflection point voltage and the first inflection point charge are the voltage and inflection point charge corresponding to the high-voltage plateau inflection point in the second charging curve.

13. The battery capacity determination method according to claim 8, characterized in that the second inflection point voltage and the second inflection point charge are the voltage and inflection point charge corresponding to the low-voltage plateau inflection point in the second charging curve.

14. The step of obtaining the third electric quantity when the battery has been charged to its second inflection point is: The battery capacity determination method according to claim 2, characterized in that it includes the step of obtaining a third amount of electricity when the battery is charged to the second inflection point using a battery management system (BMS).

15. A non-temporary computer-readable storage medium in which a computer program is stored, characterized in that when the computer program is executed by a processor, the battery capacity determination method described in any one of claims 1 to 14 is executed.

16. A computer program characterized by being executed by a computer to perform the battery capacity determination method described in any one of claims 1 to 14.

17. At least one processor (10), A battery capacity determination device (1) comprising a memory (20) that is communicated to the at least one processor (10), wherein the memory (20) stores a command that can be processed by the at least one processor (10), and when the command is processed by the at least one processor (10), the battery capacity determination method according to any one of claims 1 to 14 is executed.

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