Method for characterizing a plurality of battery cells, battery parameter estimation device and method

Abstract

A method for characterizing a plurality of battery cells, a battery parameter estimation device and method, including applying a preliminary discharge / charge cycle to the plurality of battery cells to obtain an initial capacity of each battery cell, applying a plurality of small current discharge / charge cycles to the plurality of battery cells to minimize initial voltage deviation of the plurality of battery cells, configuring a first battery cell to be tested at a plurality of first test points, configuring a second battery cell to be tested at a plurality of second test points, configuring a third battery cell to be tested at a plurality of third test points, wherein the first battery cell, the second battery cell, and the third battery cell are tested simultaneously to generate an OCV-SOC curve, and the plurality of first test points, the plurality of second test points, and the plurality of third test points are arranged in an alternating manner.

Description

TECHNICAL FIELD

[0001] The present invention relates to an apparatus and method for generating OCV-SOC curve, and in particular embodiments, to a method for efficiently generating OCV-SOC curve by testing multiple battery cells simultaneously. BACKGROUND

[0002] With further development of technology, various electronic devices such as mobile phones, tablets, smart watches, wireless earphones, VR devices, etc. have become popular. In portable devices, it is difficult to measure the remaining energy accumulated in the battery. At the same time, it is very important for the user of the portable device to know information about how much energy is left and how long the portable device can be used.

[0003] The state of charge (SOC) of a battery indicates the energy remaining in the battery. A battery management system (BMS) is used to measure various parameters of the battery and estimate the SOC of the battery based on the measured parameters. The open circuit voltage (OCV)-battery SOC estimation method is a well-known method to achieve reliable SOC estimation. The OCV of a battery cell is the potential difference between the positive and negative terminals of the battery cell when no current flows through and the battery cell has been resting for a predetermined time. The OCV-based battery SOC estimation method relies on the OCV-SOC curve to estimate the remaining energy in the battery cell.

[0004] The OCV-SOC curve is a very important part of estimating the SOC of the battery. Obtaining the SOC-OCV relationship curve applicable to various situations is the basis for accurately estimating the SOC of the battery.

[0005] A battery cell can be fully charged by a constant current and constant voltage charging control scheme. After the battery cell is fully charged, the SOC is 100% SOC. In order to obtain the OCV-SOC curve, the battery cell is placed in different ambient temperatures in turn and discharged in a constant current discharge mode. Each time the SOC of the battery cell decreases by a certain SOC, the discharging process is stopped. Once the battery cell has been resting for a predetermined time (e.g., one hour), the OCV value is collected. Repeat the process to collect multiple OCV values at different ambient temperatures and different SOC values. According to the measured OCV values and SOC values, the OCV-SOC curve is obtained.

[0006] The above OCV characterization process is very time-consuming. It is desirable to have a simple and effective method to generate an accurate OCV-SOC curve. The present disclosure addresses this need. SUMMARY

[0007] The preferred embodiments of the present disclosure generally address or overcome these and other problems by providing a method of efficiently generating OCV-SOC curves by testing multiple battery cells simultaneously.

[0008] According to one embodiment, a method for characterizing a plurality of battery cells includes configuring a first battery cell of the plurality of battery cells to be tested at a plurality of first test points and configuring a second battery cell of the plurality of battery cells to be tested at a plurality of second test points, wherein the first battery cell and the second battery cell are tested simultaneously, the plurality of first test points and the plurality of second test points are alternately arranged over a range from a fully charged state of the plurality of battery cells to a fully discharged state of the plurality of battery cells.

[0009] According to another embodiment, a method includes applying a preliminary discharge / charge cycle to a plurality of battery cells to obtain an initial capacity of each battery cell, applying a plurality of small current discharge / charge cycles to the plurality of battery cells to minimize an initial voltage deviation of the plurality of battery cells, configuring a first battery cell of the plurality of battery cells to be tested at a plurality of first test points, configuring a second battery cell of the plurality of battery cells to be tested at a plurality of second test points, and configuring a third battery cell of the plurality of battery cells to be tested at a plurality of third test points, wherein the first battery cell, the second battery cell, and the third battery cell are tested simultaneously to produce OCV-SOC curves, the plurality of first test points, the plurality of second test points, and the plurality of third test points are alternately arranged.

[0010] According to yet another embodiment, an apparatus includes a voltage sensor configured to measure an OCV value of each battery cell of a plurality of battery cells configured to be tested simultaneously in a chamber, a current sensor configured to measure a current value of each battery cell of the plurality of battery cells, and a control circuit configured to receive the OCV measurements and the current measurements of the plurality of battery cells, generate an OCV-SOC curve for each battery cell, and combine the OCV-SOC curves of the plurality of battery cells into a single OCV-SOC curve.

[0011] The foregoing has outlined rather broadly the features and technical advantages of the present disclosure so that it can be better understood in view of the following detailed description. Additional features and advantages of the present disclosure will be described in the detailed description which follows, and additional features and advantages of the present disclosure will be readily apparent to those skilled in the art from the following description, or can be learned by practice of the present disclosure. The novel features of the present disclosure will be particularly pointed out in the claims. BRIEF DESCRIPTION OF DRAWINGS

[0012] For a more complete understanding of the present application, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings in which:

[0013] Figure 1 A block diagram of an apparatus for testing a plurality of battery cells and generating OCV-SOC curves is shown in accordance with various embodiments of the present disclosure;

[0014] Figure 2 A first embodiment of a method for generating OCV-SOC curves is shown in accordance with various embodiments of the present disclosure;

[0015] Figure 3 A second embodiment of a method for generating OCV-SOC curves is shown in accordance with various embodiments of the present disclosure;

[0016] Figure 4 A flowchart of a method for generating OCV-SOC curves is shown in accordance with various embodiments of the present disclosure;

[0017] Figure 5 A flowchart of another method for generating OCV-SOC curves is shown in accordance with various embodiments of the present disclosure;

[0018] Figure 6 A block diagram of a processing system is shown in accordance with various embodiments of the present disclosure.

[0019] Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless context dictates otherwise. The drawings are drawn to illustrate the relevant aspects of the various embodiments and are not necessarily to scale. DETAILED DESCRIPTION

[0020] The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present disclosure provides many applicable inventive concepts that can be applied in a variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the application, and do not limit the scope of the application.

[0021] The present disclosure will be described with respect to preferred embodiments in a specific context, namely a method for efficiently generating OCV-SOC curves by testing a plurality of battery cells simultaneously. However, the present disclosure can also be applied to estimate various battery parameters, such as the internal resistance of a battery. Various embodiments will be described in detail below with reference to the attached drawing figures.

[0022] Figure 1 A block diagram of an apparatus for testing a plurality of battery cells and generating OCV-SOC curves is shown in accordance with various embodiments of the present disclosure. A plurality of battery cells are placed in a chamber 104. For simplicity, Figure 1Only first battery cell 101, second battery cell 102, and third battery cell 103 among the plurality of battery cells are shown.

[0023] It should be noted that, Figure 1 The three battery cells shown in FIG. 1 are merely examples. Any number of battery cells can be tested to generate OCV-SOC curves. The present disclosure is not limited to any particular number of battery cells.

[0024] As Figure 1 shown, voltage sensor 111 is configured to measure the open circuit voltage (OCV) of each battery cell. Voltage sensor 111 can be implemented using voltage measurement circuits commonly used in the art (e.g., source measurement units). Current sensor 112 is configured to measure the current flowing through each battery cell. Current sensor 112 can be implemented using current measurement circuits commonly used in the art (e.g., source measurement units). Temperature sensor 113 is configured to measure the temperature inside chamber 104. Temperature sensor 113 can be implemented using temperature measurement circuits commonly used in the art (e.g., digital multimeters).

[0025] It should be noted that, Figure 1 The single voltage sensor, single current sensor, and single signal temperature sensor shown are merely examples. Additional sensors can be used to meet measurement requirements depending on different applications and design requirements.

[0026] The output of voltage sensor 111, the output of current sensor 112, and the output of temperature sensor 113 are connected to control circuit 110. The outputs of these three sensors transmit the data measured from battery cells 101, 102, and 103 to control circuit 110.

[0027] Control circuit 110 is configured to generate OCV-SOC curves for each battery cell based on the measurement data sent from the three sensors. In addition, control circuit 110 merges the OCV-SOC curves of the plurality of battery cells into a single OCV-SOC curve. This single OCV-SOC curve is used for SOC estimation and other suitable battery management system (BMS) applications.

[0028] Control circuit 110 can be implemented as a processor, an application specific integrated circuit (ASIC), a logic circuit, a register, a digital signal processor (DSP), any combination thereof to perform the operations described above.

[0029] In operation, battery cells 101, 102, and 103 are tested simultaneously in chamber 104. Specifically, after various preliminary discharge / charge cycles are applied to these three battery cells, battery cells 101, 102, and 103 are set at 100% SOC.

[0030] In operation, the first battery cell 101 is tested at a plurality of first test points. In some embodiments, the plurality of first test points is obtained by dividing the SOC of the first battery cell in 7.5% units between 97.5% to 0% SOC of the first battery cell 101. The second battery cell 102 is tested at a plurality of second test points. In some embodiments, the plurality of second test points is obtained by dividing the SOC of the second battery cell in 7.5% units between 95% to 5% SOC of the second battery cell 102. The third battery cell 103 is tested at a plurality of third test points. In some embodiments, the plurality of third test points is obtained by dividing the SOC of the third battery cell in 7.5% units between 92.5% to 2.5% SOC of the third battery cell 103.

[0031] In some embodiments, the plurality of first test points of the first battery cell 101, the plurality of second test points of the second battery cell 102, and the plurality of third test points of the third battery cell 103 are arranged in an alternating manner ranging from a fully charged state (100% SOC) of the plurality of battery cells to a fully discharged state (0% SOC) of the plurality of battery cells.

[0032] In operation, a new SOC is set using the pulse current source. In particular, once the OCV value of a battery cell (e.g., the first battery cell 101) at a previous SOC is measured, the pulse current source is turned on to discharge the battery cell to the new SOC. The current sensor is used to monitor the current flowing through the battery cell. Based on the current flowing through the battery and the discharge time, the control circuit 110 is able to determine the new SOC value of the battery cell. At this new SOC, the OCV test result is obtained by applying the voltage rest method. Specifically, after the battery cell has been discharged to this new SOC, the OCV of the battery cell at this new SOC is measured after the battery cell is rested for a predetermined period of time.

[0033] In operation, the first battery cell 101 is tested at a plurality of first test points. Once the control circuit 110 obtains the OCV test results and the SOC test results at the plurality of first test points, the control circuit 110 is able to generate a first OCV-SOC curve for the first battery cell 101 from the OCV test results and the SOC test results measured at the plurality of first test points.

[0034] Likewise, the second battery cell 102 is tested at a plurality of second test points. Once the control circuit 110 obtains the OCV test results and the SOC test results at the plurality of second test points, the control circuit 110 is able to generate a second OCV-SOC curve for the second battery cell 102 from the OCV test results and the SOC test results measured at the plurality of second test points.

[0035] The third battery cell 103 is tested at a plurality of third test points. Once the control circuit 110 obtains the OCV test results and the SOC test results at the plurality of third test points, the control circuit 110 is able to generate a third OCV-SOC curve for the third battery cell 103 according to the OCV test results and the SOC test results measured at the plurality of third test points.

[0036] The plurality of first test points, the plurality of second test points and the plurality of third test points are arranged alternately in the range from 100% SOC to 0% SOC. The battery cells 101, 102 and 103 are tested simultaneously to produce OCV and SOC test results from 100% SOC to 0% SOC. Once the three OCV-SOC curves are available, the control circuit 110 is able to combine the above OCV-SOC curves into a single OCV-SOC curve. The single OCV-SOC curve is used for SOC estimation and other suitable BMS applications. The detailed process of generating the OCV-SOC curve will be described below in connection with Figure 2 and Figure 3 The detailed process of generating the OCV-SOC curve will be described below in connection with

[0037] In operation, the battery cell is tested at 40 test points in the range from 100% SOC to 0% SOC according to the conventional method of characterizing the battery cell. In addition, the charge characteristics have to be characterized at seven different temperatures of -20 degrees, -10 degrees, 0 degrees, 10 degrees, 25 degrees, 40 degrees and 50 degrees. The discharge characteristics have to be characterized at five different temperatures of 0 degrees, 10 degrees, 25 degrees, 40 degrees and 50 degrees. Therefore, the battery cell is tested at 12 different temperatures. At each temperature, there are 40 test points. The battery cell has to be tested for approximately 480 times (480 charge or discharge processes) in total. In each charge / discharge process, the battery cell has to be rested for about one hour. Therefore, the total characterization time is about 20 days. In comparison, according to the above method, the test points at each temperature are about one third of the conventional method. Therefore, the total characterization time is about 8.5 days.

[0038] has Figure 1One advantageous feature of the illustrated apparatus is that the control circuit 110 can efficiently generate the OCV-SOC curve by testing three battery cells simultaneously. The conventional method of generating the OCV-SOC curve is based on testing a single battery cell. The single battery cell is tested at a predetermined number of test points using the voltage rest method. However, the voltage rest method is time consuming (e.g., it takes about 20 days to complete the test of generating the OCV-SOC curve). In the present disclosure, the predetermined number of test points is distributed among the three battery cells. The three battery cells are tested simultaneously. The number of test points applied to each of the three battery cells is about one-third of the test points used in the conventional method. By reducing the test points and testing three battery cells simultaneously, the test efficiency can be significantly improved (e.g., the test time is reduced from about 20 days to about 8.5 days).

[0039] Figure 2 A first embodiment of a method for generating an OCV-SOC curve according to various embodiments of the present disclosure is shown. Figure 1 The first battery cell 101 shown is at Figure 2 referred to as Cell 1. Figure 1 The second battery cell 102 shown is at Figure 2 referred to as Cell 2. Figure 1 The third battery cell 103 shown is at Figure 2 referred to as Cell 3. The curves in the dashed rectangle 202 represent the discharging process of each battery cell from 100% SOC to 0% SOC. In the dashed rectangle 202, the horizontal axis represents the time interval. The vertical axis represents the open circuit voltage of the three battery cells.

[0040] In operation, the first test point for Cell 1 is 100% SOC for Cell 1. Once the OCV value for Cell 1 at the first test point is measured, Cell 1 is discharged from 100% SOC to the next SOC (e.g., 97.5% SOC) using a predetermined discharge rate using a pulsed current. At each test point for Cell 1, the corresponding OCV value for Cell 1 is measured using the voltage rest method. The SOC value is calculated from the current flowing through Cell 1 and the discharge time. Once the OCV and SOC values are obtained, the control circuit is configured to process the next SOC using the same process described above. The multiple first test points for Cell 1 are shown in the first column of Table 1 below.

[0041] Similarly, the first test point for cell 2 is 100% of the SOC of cell 2. Once the OCV value of cell 2 at the first test point is measured, cell 2 is discharged from 100% of the SOC to the next SOC (e.g., 95% of the SOC) using a predetermined discharge rate using a pulsed current. At each test point of cell 2, the corresponding OCV value of cell 2 is measured using the voltage rest method. The SOC value is calculated from the current flowing through cell 2 and the discharge time. Once the OCV and SOC values are obtained, the control circuit is configured to process the next SOC using the same process described above. The multiple second test points for cell 2 are shown in the second column of Table 1.

[0042] The first test point for cell 3 is 100% of the SOC of cell 3. Once the OCV value of cell 3 at the first test point is measured, cell 3 is discharged from 100% of the SOC to the next SOC (e.g., 92.5% of the SOC) using a predetermined discharge rate using a pulsed current. At each test point of cell 3, the corresponding OCV value of cell 3 is measured using the voltage rest method. The SOC value is calculated from the current flowing through cell 3 and the discharge time. Once the OCV and SOC values are obtained, the control circuit is configured to process the next SOC using the same process described above. The multiple third test points for cell 3 are shown in the third column of Table 1.

[0043] Table 1 shows the test points for each battery cell. In Table 1, the numbers (e.g., 100) represent the SOC values. For example, test point 100 indicates that the OCV and SOC values are obtained at 100% of the SOC.

[0044] Unit 1 Unit 2 Unit 3 100 100 100 97.5 95 92.5 90 87.5 85 82.5 80 77.5 75 72.5 70 67.5 65 62.5 60 57.5 55 52.5 50 47.5 45 42.5 40 37.5 35 32.5 30 27.5 25 22.5 20 17.5 15 12.5 10 7.5 5 2.5 0 0 0

[0045] Table 1

[0046] As shown in Table 1, cell 1 is tested at multiple first test points, including 100, 97.5, 90, 82.5, 75, 67.5, 60, 52.5, 45, 37.5, 30, 22.5, 15, 7.5, and 0. The multiple first test points for cell 1 are obtained by dividing between 97.5% and 0% of the SOC of cell 1 in units of 7.5%.

[0047] Cell 2 is tested at multiple second test points, including 100, 95, 87.5, 80, 72.5, 65, 57.5, 50, 42.5, 35, 27.5, 20, 12.5, 5, and 0. The multiple second test points for cell 2 are obtained by dividing between 95% and 5% of the SOC of cell 2 in units of 7.5%.

[0048] Unit 3 was tested at multiple third test points, including 100, 92.5, 85, 77.5, 70, 62.5, 55, 47.5, 40, 32.5, 25, 17.5, 10, 2.5, and 0. These third test points for Unit 3 were obtained by dividing the SOC of Unit 3 into 7.5% increments between 92.5% and 2.5%. As shown in Table 1, the multiple first test points of Unit 1, the multiple second test points of Unit 2, and the multiple third test points of Unit 3 are alternated. It is important to note that once the test results of the three battery units are combined into a single OCV-SOC curve, the test points are within the range of 100% SOC to 0% SOC, and the interval between two adjacent test points is 2.5% SOC.

[0049] The OCV and SOC test results of the three battery cells are displayed in the dashed rectangle 204. The horizontal axis in the dashed rectangle 204 represents the SOC value. The vertical axis in the dashed rectangle 204 represents the OCV test results of the three battery cells. In the dashed rectangle 204, the circle represents the OCV test result of cell 1. The triangle represents the OCV test result of cell 2. The square represents the OCV test result of cell 3.

[0050] like Figure 2 As shown, the OCV test results of the three battery cells are distributed alternately. In some embodiments, the circles in the dashed rectangle 204 form the first OCV-SOC curve. The triangles in the dashed rectangle 204 form the second OCV-SOC curve. The squares in the dashed rectangle 204 form the third OCV-SOC curve. By using appropriate data estimation techniques (e.g., interpolation), the three OCV-SOC curves can be merged into a single OCV-SOC curve for SOC estimation applications.

[0051] One advantage of having a single OCV-SOC curve is that it helps improve the accuracy of SOC estimation. More specifically, by combining data from three battery cells, the OCV data bias of each battery cell can be eliminated.

[0052] Figure 3 A second embodiment of a method for generating OCV-SOC curves according to various embodiments of the present disclosure is shown. Figure 3 The second embodiment shown is similar to Figure 2 The first embodiment shown differs from the following five in several ways.

[0053] First, as shown in dashed rectangle 302, preliminary discharge / charge cycles are applied to the three battery cells before testing. Figure 3As shown, in the preliminary discharge / charge cycle, each battery cell is discharged from 100% SOC to 0% SOC, and then each battery cell is charged from 0% SOC to 100% SOC. The initial capacity of each battery cell is calculated based on the test results of the preliminary discharge / charge cycle.

[0054] Second, a plurality of small current discharge / charge cycles are applied to the three battery cells before testing the three battery cells. As a result of applying the plurality of small current discharge / charge cycles to the three battery cells, the initial voltage deviation of the three battery cells is controlled within a predetermined voltage deviation range. In some embodiments, the predetermined voltage deviation range is about -2mV to about 2mV.

[0055] Third, each battery cell (e.g., cell 1) is characterized using a plurality of test points (e.g., test points of cell 1 shown in the first column of Table 2 below) to obtain a plurality of SOC test results based on the initial capacity obtained in the preliminary discharge / charge cycle. After completing the characterization process of each battery cell, an updated capacity of each battery cell is calculated based on the plurality of SOC test results. Based on the updated capacity, the SOC value of each battery cell is recalculated to improve the measurement accuracy.

[0056] In some embodiments, the initial capacity of a battery cell can be a certain battery capacity (e.g., 2000mAh) based on the test results obtained in the preliminary discharge / charge cycle. The capacity measured in the preliminary discharge / charge cycle is different from the capacity in the multiple discharge / charge processes. In order to obtain better SOC accuracy, the rated capacity of each cell will be updated after the characterization is completed. Specifically, during the discharge process of this battery cell, the control circuit records the capacity drop value at each SOC point. After the battery cell is fully discharged, the control circuit can calculate the updated capacity by adding all the capacity drop values together. For example, the sum of the capacity drop values can be a different battery capacity (e.g., 2050mAh). Then, the newly measured result (e.g., 2050mAh) can be used as the updated capacity to recalculate the SOC test results.

[0057] Fourth, in subsequent SOC characterization steps, multiple calibration test points are used to reset SOC integration errors. For example, as shown in Table 2 below, a first calibration test point (e.g., 80 in the first column of Table 2) is placed among the plurality of first test points of cell 1. A second calibration test point (e.g., 80 in the second column of Table 2) is placed among the plurality of second test points of cell 2. A third calibration test point (e.g., 80 in the third column of Table 2) is placed among the plurality of third test points of cell 3. In operation, the three battery cells are discharged to the same OCV associated with 80% SOC according to the previously known OCV-SOC relationship. During the discharge of cell 1, the control circuit is configured to obtain a first SOC of cell 1 according to the discharge current flowing through cell 1 and the discharge time. Likewise, during the discharge of cell 2, the control circuit is configured to obtain a second SOC of cell 2 according to the discharge current flowing through cell 2 and the discharge time. During the discharge of cell 3, the control circuit is configured to obtain a third SOC of cell 3 according to the discharge current flowing through cell 3 and the discharge time. Next, the control circuit is configured to determine whether the first SOC of cell 1, the second SOC of cell 2, and the third SOC of cell 3 are evenly distributed around a predetermined calibration SOC (e.g., 80% SOC). If the first SOC, the second SOC, and the third SOC are evenly distributed around the predetermined calibration SOC, the average of the first SOC, the second SOC, and the third SOC is used to replace the first SOC, the second SOC, and the third SOC in order to reset SOC integration errors in subsequent SOC characterization steps. If the first SOC, the second SOC, and the third SOC are not evenly distributed, the deviated SOC is deleted and the adjacent SOC test results are recalculated.

[0058] In some embodiments, among the three SOC test results, one is the SOC median. A deviated SOC is defined as a SOC that is far away from the SOC median. For example, if the difference between a SOC (e.g., the first SOC test result) and the SOC median (e.g., the second SOC test result) is at least 1.5 times the difference between the other SOC (e.g., the third SOC test result) and the SOC median, the SOC (e.g., the first SOC test result) is a deviated SOC.

[0059] In operation, if the first SOC of cell 1 is a deviated SOC, the first SOC will be replaced by the average of the second SOC and the third SOC. Furthermore, at least half of the SOC values are obtained before recalculating the first SOC in order to reset SOC integration errors. In Table 2 below, for cell 1, there are four SOC values between 100% SOC and 80% SOC. If the first SOC of cell 1 at 80% SOC is a deviated SOC, at least the SOC values at 90% and 82.5% SOC should be recalculated to improve the measurement accuracy.

[0060] Fifth, the control circuit is configured to filter out OCV test results that deviate from adjacent OCV test results to improve measurement accuracy. Based on the characteristics of the battery cell, the OCV-SOC relationship is linear within a small range. However, due to various factors such as equipment errors, the OCV test results may deviate from the linear curve within a small range. For example, in the dashed rectangle 304, circles that deviate from adjacent test results are filtered out to improve measurement accuracy.

[0061] The table shows the test points for each battery cell. In Table 2, the numbers (e.g., 100) represent the SOC value. For example, test point 100 indicates that the OCV and SOC values ​​were obtained at 100% SOC.

[0062] Unit 1 Unit 2 Unit 3 100 100 100 97.5 95 92.5 90 87.5 85 82.5 80 80 80 72.5 77.5 75 65 70 67.5 60 62.5 60 57.5 60 52.5 50 55 45 42.5 47.5 40 40 40 37.5 35 32.5 30 27.5 25 22.5 20 20 20 12.5 17.5 15 5 10 7.5 0 2.5 0 0

[0063] Table 2

[0064] As shown in Table 2, Unit 1 is tested at multiple first test points, including 100, 97.5, 90, 82.5, 80, 75, 67.5, 60, 52.5, 45, 40, 37.5, 30, 22.5, 20, 15, 7.5, and 0. Compared with the first test points shown in Table 1, test points 80, 40, and 20 are added. Test points 80, 60, 40, and 20 in the first test points serve as SOC calibration test points.

[0065] Unit 2 is tested at multiple second test points, including 100, 95, 87.5, 80, 72.5, 65, 60, 57.5, 50, 42.5, 40, 35, 27.5, 20, 12.5, 5, and 0. Test points 60 and 40 are added compared to the second test points shown in Table 1. Test points 80, 60, 40, and 20 in the second test points serve as SOC calibration test points.

[0066] Unit 3 is tested at multiple third test points, including 100, 92.5, 85, 80, 77.5, 70, 62.5, 60, 55, 47.5, 40, 32.5, 25, 20, 17.5, 10, 2.5, and 0. Test points 80, 60, and 20 are added compared to the third test points shown in Table 1. Test points 80, 60, 40, and 20 in the third test points serve as SOC calibration test points.

[0067] OCV and SOC test results for the three battery cells are shown in dashed rectangle 304. The horizontal axis in dashed rectangle 304 represents SOC values. The vertical axis in dashed rectangle 304 represents OCV test results for the three battery cells. In dashed rectangle 304, circles represent OCV test results for cell 1. Triangles represent OCV test results for cell 2. Squares represent OCV test results for cell 3.

[0068] In some embodiments, the circles in dashed rectangle 304 constitute a first OCV-SOC curve. The triangles in dashed rectangle 304 constitute a second OCV-SOC curve. The squares in dashed rectangle 304 constitute a third OCV-SOC curve. The three OCV-SOC curves can be combined into a single OCV-SOC curve for SOC estimation applications by using a suitable data estimation technique (e.g., interpolation).

[0069] Figure 4 A flowchart showing one method of generating OCV-SOC curves in accordance with various embodiments of the present disclosure is shown. Figure 4 This flowchart shown is merely an example which should not unduly limit the scope of claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. For example, some of the steps shown can be added, deleted, replaced, rearranged, combined, and repeated. Figure 4

[0070] Referring back to Figure 1 , the voltage sensor is configured to measure OCV values for a plurality of battery cells (e.g., the three battery cells shown in Figure 1 ). The three battery cells are tested simultaneously in one chamber. The current sensor is configured to measure current values for each of the three battery cells. The control circuit is configured to receive the OCV measurements and the current measurements for the three battery cells, generate OCV-SOC curves for each of the three battery cells, and combine the OCV-SOC curves for the three battery cells into a single OCV-SOC curve.

[0071] At step 402, a first battery cell of the plurality of battery cells is configured to be tested at a plurality of first test points.

[0072] At step 404, a second battery cell of the plurality of battery cells is configured to be tested at a plurality of second test points. The first battery cell and the second battery cell are tested simultaneously, and the plurality of first test points and the plurality of second test points are arranged alternately in a range from a fully charged state of the plurality of battery cells to a fully discharged state of the plurality of battery cells.

[0073] ​The method further includes configuring a third battery cell of the plurality of battery cells to be tested at a plurality of third test points, wherein the first battery cell, the second battery cell, and the third battery cell are tested simultaneously, and the plurality of first test points, the plurality of second test points, and the plurality of third test points are arranged in another alternating manner.

[0074] Returning to Figure 2 In Table 1, the plurality of first test points are obtained by dividing the SOC of the first battery cell in units of 7.5% between 97.5% and 0% of the SOC of the first battery cell. The plurality of second test points are obtained by dividing the SOC of the second battery cell in units of 7.5% between 95% and 5% of the SOC of the second battery cell. The plurality of third test points are obtained by dividing the SOC of the third battery cell in units of 7.5% between 92.5% and 2.5% of the SOC of the third battery cell.

[0075] The method further includes applying a preliminary discharge / charge cycle to the plurality of battery cells before characterizing the plurality of battery cells, and calculating an initial capacity of each battery cell based on test results of the preliminary discharge / charge cycle.

[0076] The method further includes characterizing the first battery cell using the plurality of first test points based on the initial capacity obtained in the preliminary discharge / charge cycle to obtain a plurality of SOC test results, calculating an updated capacity of the first battery cell from the plurality of SOC test results after characterizing the first battery cell, and recalculating the plurality of SOC test results based on the updated capacity of the first battery cell.

[0077] The method further includes applying a plurality of small current discharge / charge cycles to the plurality of battery cells before characterizing the plurality of battery cells, wherein an initial voltage deviation of the plurality of battery cells is controlled within a predetermined voltage deviation range as a result of applying the plurality of small current discharge / charge cycles to the plurality of battery cells.

[0078] The method further includes configuring a third battery cell of the plurality of battery cells to be tested at a plurality of third test points, placing a first calibration test point in the plurality of first test points, placing a second calibration test point in the plurality of second test points, and placing a third calibration test point in the plurality of third test points, wherein the first calibration test point, the second calibration test point, and the third calibration test point have the same open circuit voltage (OCV).

[0079] The method further includes obtaining a first SOC of the first battery cell by discharging the first battery cell to the same open circuit voltage, obtaining a second SOC of the second battery cell by discharging the second battery cell to the same open circuit voltage, obtaining a third SOC of the third battery cell by discharging the third battery cell to the same open circuit voltage, and determining whether the first SOC, the second SOC, and the third SOC are evenly distributed. If the first SOC, the second SOC, and the third SOC are evenly distributed, using an average of the first SOC, the second SOC, and the third SOC to replace the first SOC, the second SOC, and the third SOC to reset SOC integration error in a subsequent SOC characterization step. If the first SOC, the second SOC, and the third SOC are not evenly distributed, deleting the deviated SOC and recalculating adjacent SOC test results.

[0080] The method further includes configuring a third battery cell of the plurality of battery cells to be tested at a plurality of third test points, obtaining a plurality of first OCV test results and a plurality of first SOC test results by testing the first battery cell at the plurality of first test points, obtaining a plurality of second OCV test results and a plurality of second SOC test results by testing the second battery cell at the plurality of second test points, obtaining a plurality of third OCV test results and a plurality of third SOC test results by testing the third battery cell at the plurality of third test points, obtaining a first OCV-SOC curve characterizing an OCV and SOC relationship of the first battery cell based on the plurality of first OCV test results and the plurality of first SOC test results, obtaining a second OCV-SOC curve characterizing an OCV and SOC relationship of the second battery cell based on the plurality of second OCV test results and the plurality of second SOC test results, obtaining a third OCV-SOC curve characterizing an OCV and SOC relationship of the third battery cell based on the plurality of third OCV test results and the plurality of third SOC test results, filtering OCV test results deviating from adjacent OCV test results, and merging the first OCV-SOC curve, the second OCV-SOC curve, and the third OCV-SOC curve into a single OCV-SOC curve based on linear interpolation.

[0081] Figure 5 A flowchart illustrating another method of generating an OCV-SOC curve in accordance with various embodiments of the present disclosure is shown. Figure 5 The flowchart shown is merely one example. It should not be used to limit the scope of the claims. Those having ordinary skill in the art will recognize many changes, alternatives, and modifications for the flowchart shown. Figure 5 The various steps shown in

[0082] Referring back to Figure 1 , the voltage sensor is configured to measure a plurality of battery cells (e.g., Figure 1OCV values of the three battery cells. The three battery cells are tested simultaneously in one chamber. The current sensor is configured to measure a current value of each of the three battery cells. The control circuit is configured to receive the OCV measurements and the current measurements of the three battery cells, generate an OCV-SOC curve for each battery cell, and merge the OCV-SOC curves of the three battery cells into a single OCV-SOC curve.

[0083] At step 502, a preliminary discharge / charge cycle is applied to the plurality of battery cells to obtain an initial capacity of each battery cell.

[0084] At step 504, a plurality of small current discharge / charge cycles are applied to the plurality of battery cells to minimize initial voltage deviation of the plurality of battery cells.

[0085] At step 506, a first battery cell of the plurality of battery cells is configured to be tested at a plurality of first test points.

[0086] At step 508, a second battery cell of the plurality of battery cells is configured to be tested at a plurality of second test points.

[0087] At step 510, a third battery cell of the plurality of battery cells is configured to be tested at a plurality of third test points.

[0088] The first battery cell, the second battery cell, and the third battery cell are tested simultaneously to generate an OCV-SOC curve. The plurality of first test points, the plurality of second test points, and the plurality of third test points are arranged alternately.

[0089] The method further includes characterizing each battery cell based on the initial capacity obtained in the preliminary discharge / charge cycle to obtain a respective SOC test result, calculating an updated capacity of each battery cell based on the respective SOC test result, and recalculating the SOC test result of each battery cell based on the updated capacity.

[0090] The method further includes discharging each battery cell from 100% SOC to 0% SOC and charging each battery cell from 0% SOC to 100% SOC during the preliminary discharge / charge cycle.

[0091] The method further includes obtaining a plurality of OCV test results for one of the plurality of battery cells by applying a voltage rest method, wherein at each test point, the battery cell is discharged to a corresponding SOC value, the battery cell is rested for a predetermined time, and the OCV of the battery cell at the corresponding SOC value is measured.

[0092] The method further includes obtaining a plurality of calibration SOC test results by discharging the plurality of battery cells to the same OCV, and determining whether the plurality of calibration SOC test results are evenly distributed. If the plurality of calibration SOC test results are evenly distributed, using an average of the plurality of calibration SOC test results to replace the plurality of calibration SOC test results to reset the SOC integration error. If the plurality of calibration SOC test results are not evenly distributed, deleting the deviated SOC test results, and recalculating the SOC test results adjacent to the deviated SOC test results.

[0093] The method further includes obtaining a plurality of OCV test results and a plurality of SOC test results for each battery cell in the plurality of battery cells, obtaining an OCV-SOC curve for each battery cell based on the plurality of OCV test results and the plurality of SOC test results, and filtering out OCV test results deviated from adjacent OCV test results.

[0094] The method further includes generating a plurality of OCV-SOC curves for the plurality of battery cells, and merging the plurality of OCV-SOC curves to obtain the OCV-SOC curve after filtering out OCV test results deviated from adjacent OCV test results.

[0095] Figure 6 A block diagram of a processing system in accordance with various embodiments of the present disclosure is shown. Processing system 600 depicts a general purpose platform and general components and functions of an external computer or processing device that can be used to implement a partial embodiment SOC estimation device and / or interface with an embodiment SOC estimation device. For example, processing system 600 can be used to implement Figure 1 a portion of control circuit 110 shown. In some embodiments, processing system 600 can be used to determine and evaluate measurement parameters, and determine an OCV-SOC curve for use in SOC estimation applications from the measurement parameters.

[0096] Processing system 600 can include, for example, a central processing unit (CPU) 602 and memory 604 connected to bus 608, and can be configured to perform the processes described above. If desired, processing system 600 can also include a display adapter 610 to provide connectivity and input-output (I / O) adapter 614 to provide input-output interfaces for one or more input / output devices 616, such as a mouse, keyboard, flash drive, etc.

[0097] The processing system 600 also includes a network interface 618 that can be implemented by a network adapter configured to couple to a wired link, such as a network cable, USB interface, etc., and / or to be used in conjunction with a wireless / cellular connection for communicating with the network 620. The network interface 618 also includes suitable receivers and transmitters for wireless communication. It should be noted that the processing system 600 can include other components. For example, if implemented externally, the processing system 600 can include hardware components such as a power supply, cables, motherboard, removable storage media, housing, etc. While not shown, these other components are considered part of the processing system 600. In some embodiments, the processing system 600 can be implemented on a single monolithic semiconductor integrated circuit and / or on the same monolithic semiconductor integrated circuit as other disclosed system components.

[0098] In one embodiment, Figure 6 The processing system 600 shown in FIG. 6 can be implemented as a SOC estimation system for a battery. The memory 604 is configured to store a program for generating an OCV-SOV curve. The CPU 602 is configured to execute the program stored in the memory to implement the SOC estimation method for a battery described in the above embodiments.

[0099] While embodiments of the present disclosure and the advantages thereof have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the present disclosure as defined by the appended claims.

[0100] Further, the scope of the application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein can be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

1. A method for characterizing a plurality of battery cells, comprising: configuring a first battery cell of the plurality of battery cells to be tested at a plurality of first test points to obtain a first OCV-SOC curve characterizing the OCV and SOC relationship of the first battery cell; and configuring a second battery cell of the plurality of battery cells to be tested at a plurality of second test points to obtain a second OCV-SOC curve characterizing the OCV and SOC relationship of the second battery cell, wherein the first battery cell and the second battery cell are tested simultaneously, and the plurality of first test points and the plurality of second test points are arranged in an alternating manner within a range from a fully charged state of the plurality of battery cells to a fully discharged state of the plurality of battery cells; merging the first OCV-SOC curve and the second OCV-SOC curve into a single OCV-SOC curve.

2. The method of claim 1, further comprising: configuring a third battery cell of the plurality of battery cells to be tested at a plurality of third test points, wherein the first battery cell, the second battery cell and the third battery cell are tested simultaneously, and the plurality of first test points, the plurality of second test points and the plurality of third test points are arranged in another alternating manner.

3. The method of claim 2, wherein: the plurality of first test points are obtained by dividing the state of charge (SOC) of the first battery cell in 7.5% units between 97.5% and 0% of the SOC of the first battery cell; the plurality of second test points are obtained by dividing the SOC of the second battery cell in 7.5% units between 95% and 5% of the SOC of the second battery cell; and the plurality of third test points are obtained by dividing the SOC of the third battery cell in 7.5% units between 92.5% and 2.5% of the SOC of the third battery cell.

4. The method of claim 1, further comprising: applying a preliminary discharge / charge cycle to the plurality of battery cells before characterizing the plurality of battery cells; and calculating an initial capacity of each battery cell according to the test results of the preliminary discharge / charge cycle.

5. The method of claim 4, further comprising: characterizing the first battery cell by using the plurality of first test points to obtain a plurality of SOC test results based on the initial capacity obtained in the preliminary discharge / charge cycle; calculating an updated capacity of the first battery cell according to the plurality of SOC test results after characterizing the first battery cell; and re-calculating the plurality of SOC test results based on the updated capacity of the first battery cell.

6. The method of claim 1, further comprising: applying a plurality of small current discharge / charge cycles to the plurality of battery cells before characterizing the plurality of battery cells, wherein an initial voltage deviation of the plurality of battery cells is controlled within a predetermined voltage deviation range as a result of applying the plurality of small current discharge / charge cycles to the plurality of battery cells. ​ 7. The method of claim 1, further comprising: configuring a third battery cell of the plurality of battery cells to be tested at a plurality of third test points; setting a first calibration test point among the plurality of first test points; setting a second calibration test point among the plurality of second test points; and setting a third calibration test point among the plurality of third test points, wherein the first calibration test point, the second calibration test point, and the third calibration test point all have a same open circuit voltage (OCV).

8. The method of claim 7, further comprising: obtaining a first SOC of the first battery cell by discharging the first battery cell to the same OCV; obtaining a second SOC of the second battery cell by discharging the second battery cell to the same OCV; obtaining a third SOC of the third battery cell by discharging the third battery cell to the same OCV; and determining whether the first SOC, the second SOC, and the third SOC are evenly distributed, wherein: if the first SOC, the second SOC, and the third SOC are evenly distributed, using an average of the first SOC, the second SOC, and the third SOC to replace the first SOC, the second SOC, and the third SOC to reset SOC integration errors in a subsequent SOC characterization step; and if the first SOC, the second SOC, and the third SOC are not evenly distributed, deleting the deviated SOC and recalculating adjacent SOC test results.

9. The method of claim 1, further comprising: configuring a third battery cell of the plurality of battery cells to be tested at a plurality of third test points; obtaining a plurality of first OCV test results and a plurality of first SOC test results by testing the first battery cell at the plurality of first test points; obtaining a plurality of second OCV test results and a plurality of second SOC test results by testing the second battery cell at the plurality of second test points; obtaining a plurality of third OCV test results and a plurality of third SOC test results by testing the third battery cell at the plurality of third test points; obtaining a first OCV-SOC curve characterizing OCV and SOC relationship of the first battery cell based on the plurality of first OCV test results and the plurality of first SOC test results; obtaining a second OCV-SOC curve characterizing OCV and SOC relationship of the second battery cell based on the plurality of second OCV test results and the plurality of second SOC test results; obtaining a third OCV-SOC curve characterizing OCV and SOC relationship of the third battery cell based on the plurality of third OCV test results and the plurality of third SOC test results; filtering out OCV test results deviated from adjacent OCV test results; and merging the first OCV-SOC curve, the second OCV-SOC curve, and the third OCV-SOC curve into a single OCV-SOC curve based on linear interpolation.

10. A method of battery parameter estimation, comprising: performing a preliminary discharge / charge cycle on a plurality of battery cells to obtain an initial capacity of each battery cell; performing a plurality of small current discharge / charge cycles on the plurality of battery cells to minimize initial voltage deviation of the plurality of battery cells; configuring a first battery cell of the plurality of battery cells to be tested at a plurality of first test points to obtain a first OCV-SOC curve characterizing OCV and SOC relationship of the first battery cell; configuring a second battery cell of the plurality of battery cells to be tested at a plurality of second test points to obtain a second OCV-SOC curve characterizing OCV and SOC relationship of the second battery cell; and configuring a third battery cell of the plurality of battery cells to be tested at a plurality of third test points to obtain a third OCV-SOC curve characterizing OCV and SOC relationship of the third battery cell, wherein the first battery cell, the second battery cell and the third battery cell are tested simultaneously to produce OCV-SOC curves, and the plurality of first test points, the plurality of second test points and the plurality of third test points are arranged alternately; combining the first OCV-SOC curve, the second OCV-SOC curve and the third OCV-SOC curve into a single OCV-SOC curve.

11. The method of claim 10, further comprising: performing a characterization of each battery cell according to the initial capacity obtained in the preliminary discharge / charge cycle to obtain a corresponding SOC test result; calculating an updated capacity of each battery cell according to the corresponding SOC test result; and recomputing the SOC test result of each battery cell according to the updated capacity.

12. The method of claim 10, further comprising: for one of the plurality of battery cells, obtaining a plurality of OCV test results using a voltage rest method, wherein at each test point, the battery cell is discharged to a corresponding SOC value, and after the battery cell is rested for a predetermined time, the OCV of the battery cell at the corresponding SOC value is measured.

13. The method of claim 10, further comprising: obtaining a plurality of calibration SOC test results by discharging the plurality of battery cells to the same OCV; and determining whether the plurality of calibration SOC test results are evenly distributed, if the plurality of calibration SOC test results are evenly distributed, replacing the plurality of calibration SOC test results with an average of the plurality of calibration SOC test results to reset SOC integration error; if the plurality of calibration SOC test results are not evenly distributed, deleting deviated SOC test results and recalculating SOC test results adjacent to the deviated SOC test results.

14. The method of claim 10, further comprising: obtaining a plurality of OCV test results and a plurality of SOC test results for each of the plurality of battery cells; obtaining an OCV-SOC curve for each battery cell based on the plurality of OCV test results and the plurality of SOC test results; and Filtering out OCV test results that are deviated from adjacent OCV test results.

15. A battery parameter estimation apparatus comprising: a voltage sensor configured to measure OCV values of each of a plurality of battery cells, the plurality of battery cells configured to be tested simultaneously in one chamber; a current sensor configured to measure current values of each of the plurality of battery cells; and a control circuit configured to receive the OCV and current measurements of the plurality of battery cells, generate OCV-SOC curves for each of the battery cells and merge the OCV-SOC curves of the plurality of battery cells into a single OCV-SOC curve.

16. The apparatus of claim 15, wherein the control circuit is configured to cause: a preliminary discharge / charge cycle to be performed on the plurality of battery cells to obtain an initial capacity of each of the battery cells; a plurality of small current discharge / charge cycles to be applied to the plurality of battery cells to minimize initial voltage deviation of the plurality of battery cells; a first battery cell of the plurality of battery cells to be tested at a plurality of first OCV-SOC test points; a second battery cell of the plurality of battery cells to be tested at a plurality of second OCV-SOC test points; and a third battery cell of the plurality of battery cells to be tested at a plurality of third OCV-SOC test points, wherein the plurality of first OCV-SOC test points, the plurality of second OCV-SOC test points, and the plurality of third OCV-SOC test points are arranged alternately.

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