Methods for measuring battery self-discharge rate

Abstract

This application provides a method for measuring the self-discharge rate of a battery. The method includes: obtaining the dOCV / dQ of the battery under test at a target SOC; charging the battery under test to the target SOC to obtain the battery under test at the target SOC; obtaining the self-discharge current of the battery under test at the target SOC; and calculating the self-discharge rate of the battery under test at the target SOC based on the dOCV / dQ and the self-discharge current. This method calculates the self-discharge rate of the battery under test at the target SOC based on the dOCV / dQ and the self-discharge current. Compared to obtaining the voltage drop of the open-circuit voltage of the battery under test, obtaining the self-discharge current requires less time, which improves measurement efficiency. Furthermore, because the resting time required to obtain the self-discharge current is short, the self-discharge rate is less affected by environmental changes and the accuracy of the measuring instrument during the resting process, which improves the accuracy of the measurement results.

Description

Technical Field

[0001] This application relates primarily to the field of battery technology, and more specifically to a method for measuring the self-discharge rate of a battery. Background Technology

[0002] Lithium-ion batteries are widely used in digital electronics and power energy industries due to their advantages such as high energy density, long cycle life, and no memory effect. The spontaneous capacity loss that occurs when a lithium-ion battery is left in an open-circuit storage state is called self-discharge, or charge retention capacity. Self-discharge measurement methods mainly include capacity measurement, open-circuit voltage measurement, and current measurement. Among these, the open-circuit voltage measurement method (also known as the K-value measurement method) is more widely used. This method measures the battery's self-discharge rate by measuring the voltage drop over a unit of time. However, the open-circuit voltage measurement method requires the battery to be left to rest for a relatively long time, resulting in a long measurement cycle. Furthermore, many factors affect the accuracy of the open-circuit voltage measurement results, such as the battery's depolarization effect, the ambient temperature during rest, the resting time, and the accuracy of the measuring instrument. Therefore, the accuracy of the open-circuit voltage measurement results is relatively low.

[0003] Therefore, how to quickly and accurately measure the self-discharge rate of lithium batteries is an urgent problem to be solved. Summary of the Invention

[0004] The technical problem to be solved by this application is to provide a method for measuring the self-discharge rate of a battery, which can quickly and accurately measure the self-discharge rate of a lithium battery.

[0005] The technical solution adopted in this application to solve the above-mentioned technical problems is a method for measuring battery self-discharge rate, including: obtaining the dOCV / dQ corresponding to the target SOC of the battery under test; charging the battery under test to the target SOC to obtain the target SOC battery under test; obtaining the self-discharge current of the target SOC battery under test; and calculating the self-discharge rate of the battery under test corresponding to the target SOC based on the dOCV / dQ and the self-discharge current.

[0006] In one embodiment of this application, the method for obtaining the dOCV / dQ corresponding to the battery under test and the target SOC includes: obtaining the correspondence between the equivalent OCV, equivalent Q and equivalent SOC of the equivalent battery under test; calculating the equivalent dOCV / dQ according to the correspondence between the equivalent OCV and equivalent Q; and obtaining the dOCV / dQ corresponding to the battery under test and the target SOC according to the correspondence between the equivalent dOCV / dQ and the equivalent SOC.

[0007] In one embodiment of this application, a method for obtaining the correspondence between the equivalent OCV, equivalent Q, and equivalent SOC of an equivalent battery under test includes: charging the equivalent battery under test according to preset charging conditions to obtain a fully charged equivalent battery under test; and discharging the fully charged equivalent battery under test according to preset discharging conditions to obtain the correspondence between the equivalent OCV, equivalent Q, and equivalent SOC of the equivalent battery under test.

[0008] In one embodiment of this application, the preset charging conditions are: charging the equivalent battery under test to a first cutoff voltage with a constant charging current, and then charging the equivalent battery under test to a fully charged state with the first cutoff voltage as the charging voltage.

[0009] In one embodiment of this application, the preset discharge condition is: the equivalent battery under test in the fully charged state is discharged to the second cutoff voltage with a constant discharge current.

[0010] In one embodiment of this application, the self-discharge current of the target SOC battery under test is obtained under preset conditions after the target SOC battery is left to stand.

[0011] In one embodiment of this application, the settling time is 12h to 24h.

[0012] In one embodiment of this application, the temperature of the preset condition is 20°C to 30°C.

[0013] In one embodiment of this application, the self-discharge current is acquired when the target SOC battery under test is in a stable self-discharge state.

[0014] In one embodiment of this application, the formula for calculating the self-discharge rate of the battery under test corresponding to the target SOC based on the dOCV / dQ and the self-discharge current is: K = (dOCV / dQ) × I, where K represents the self-discharge rate of the battery under test corresponding to the target SOC, and I represents the self-discharge current.

[0015] The measurement method of this application calculates the battery self-discharge rate based on dOCV / dQ and self-discharge current corresponding to the target SOC. It eliminates the need to obtain the voltage drop across the open-circuit voltage of the battery under test; instead, it obtains the self-discharge current. Compared to obtaining the voltage drop across the open-circuit voltage, obtaining the self-discharge current requires a shorter time, thus improving measurement efficiency. Furthermore, because the resting time required to obtain the self-discharge current is shorter, the self-discharge rate of this application is less affected by environmental changes and the accuracy of the measuring instrument during the resting process, thereby improving the accuracy of the measurement results. Attached Figure Description

[0016] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings, wherein:

[0017] Figure 1 This is an exemplary flowchart of a method for measuring battery self-discharge rate according to an embodiment of this application;

[0018] Figure 2 This is an OCV-SOC curve of a battery during self-discharge according to an embodiment of this application;

[0019] Figure 3 This is the dOCV / dQ-SOC curve during the self-discharge process of a battery according to an embodiment of this application. Detailed Implementation

[0020] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein, and therefore this application is not limited to the specific embodiments disclosed below.

[0022] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0023] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application. In addition, although the terminology used in this application is selected from commonly known and used terms, some terms mentioned in this application's specification may have been chosen by the applicant according to his or her judgment, and their detailed meanings are explained in the relevant sections of this description. Moreover, this application should be understood not only through the actual terms used, but also through the meaning implied by each term.

[0024] Flowcharts are used in this application to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, various steps can be processed in reverse order or simultaneously. Furthermore, other operations may be added to these processes, or one or more steps may be removed from these processes.

[0025] The measurement method of this application will be described below through specific embodiments.

[0026] Figure 1 This is an exemplary flowchart of a method for measuring battery self-discharge rate according to one embodiment. (See reference) Figure 1 As shown, the measurement method of this embodiment includes the following steps:

[0027] Step S110: Obtain the dOCV / dQ corresponding to the target SOC of the battery under test;

[0028] Step S120: Charge the battery under test to the target SOC to obtain the target SOC battery under test;

[0029] Step S130: Obtain the self-discharge current of the target SOC battery under test;

[0030] Step S140: Calculate the self-discharge rate of the battery under test corresponding to the target SOC based on dock / dQ and self-discharge current.

[0031] Where SOC represents the state of charge of the battery, OCV represents the open circuit voltage of the battery, Q represents the discharge capacity of the battery, and dOCV / dQ represents the derivative of the open circuit voltage with respect to the discharge capacity.

[0032] The following details steps S110 to S140.

[0033] In step S110, the method for obtaining the dOCV / dQ corresponding to the target SOC of the battery under test includes:

[0034] Step S111: Obtain the correspondence between the equivalent OCV, equivalent Q, and equivalent SOC of the equivalent battery under test;

[0035] Step S112: Calculate the equivalent dOCV / dQ based on the correspondence between the equivalent OCV and the equivalent Q;

[0036] Step S113: Obtain the dOCV / dQ corresponding to the target SOC of the battery under test based on the correspondence between the equivalent dOCV / dQ and the equivalent SOC.

[0037] In steps S111 to S113, the equivalent battery under test (BUT) has the same specifications as the battery under test (SUT), and its electrical performance is the same or approximately the same. Therefore, the electrical parameters of the BUT (e.g., equivalent dOCV / dQ, equivalent SOC, and the correspondence between them) can be used to represent the electrical parameters of the BUT (dOCV / dQ corresponding to the target SOC). Thus, when there are many BUTs, compared to obtaining the electrical parameters of each BUT individually, using the equivalent BUT's electrical parameters to represent the BUT's electrical parameters can shorten the time required to obtain them. It should be noted that the method for obtaining the dOCV / dQ corresponding to the target SOC of the BUT in this application is not limited to steps S111 to S113. In some embodiments, the dOCV / dQ corresponding to the target SOC of the BUT can also be obtained based on the BUT's electrical parameters, for example, by performing steps S111 to S113 based on the BUT. The batteries to be tested in this application include ternary lithium batteries and lithium iron phosphate batteries.

[0038] The following example illustrates steps S111 to S113.

[0039] In step S111, several equivalent test batteries are taken and charged according to preset charging conditions to obtain a fully charged equivalent test battery. This application does not limit the number of equivalent test batteries; there can be one equivalent test battery or any natural number greater than 1. When there are multiple equivalent test batteries, the average value of their electrical parameters can be used to represent the electrical parameters of the test battery.

[0040] In one embodiment, the preset charging conditions are: charging the equivalent battery under test to a cutoff voltage OCV1 with a constant charging current I1, and then charging the equivalent battery under test to a fully charged state using the cutoff voltage OCV1 as the charging voltage. In some embodiments, during the charging process of the equivalent battery under test at the cutoff voltage OCV1, the charging current is detected, and charging of the equivalent battery under test is stopped when the charging current drops to the cutoff current I2. Here, the cutoff current I2 represents the charging current of the equivalent battery under test when it is fully charged; in other words, whether the equivalent battery under test is in a fully charged state can be determined by detecting the current during the charging process. It should be understood that "fully charged state" does not refer to a strictly fully charged state, but includes an approximate fully charged state, such as when the battery is at 98% SOC, it can also be considered to be in a fully charged state. In some embodiments, the charging current I1 can be any value from 0.3C to 0.5C, and the specific value of OCV1 is related to the type of the equivalent battery under test. For example, when the equivalent battery under test is a ternary lithium battery, OCV1 can be 4.2V; when the equivalent battery under test is a lithium iron phosphate battery, OCV1 can be 3.65V.

[0041] The equivalent battery under test in a fully charged state is discharged according to the preset discharge conditions to obtain the correspondence between the equivalent OCV, equivalent Q and equivalent SOC of the equivalent battery under test.

[0042] During the discharge process of the equivalent battery under test, the SOC, Q, and OCV of the equivalent battery under test all change as discharge progresses, and there is a corresponding relationship among the three. To distinguish them from the SOC, Q, and OCV of the battery under test, the SOC, Q, and OCV of the equivalent battery under test are referred to as equivalent OCV, equivalent Q, and equivalent SOC, respectively. During the discharge process, the equivalent OCV, equivalent Q, and equivalent SOC of the equivalent battery under test, as well as the corresponding relationship among them, are recorded. For ease of description, the corresponding relationship between equivalent OCV and equivalent SOC is denoted as (equivalent OCV, equivalent SOC).

[0043] In some embodiments, the preset discharge condition is: discharging the fully charged equivalent battery under test to the cutoff voltage OCV2 with a constant discharge current I3. This application does not limit the discharge current I3 and the cutoff voltage OCV2; the specific discharge current I3 and cutoff voltage OCV2 can be set according to the battery specifications and measurement requirements. In some embodiments, the discharge current I3 can be 0.02C, and the specific value of the cutoff voltage OCV2 is related to the type of the equivalent battery under test. For example, when the equivalent battery under test is a ternary lithium battery, OCV2 can be 2.75V; when the equivalent battery under test is a lithium iron phosphate battery, OCV2 can be 2.5V.

[0044] As mentioned above, there is a correspondence between the equivalent OCV, equivalent Q, and equivalent SOC. Figure 2 This is an example of an OCV-SOC curve during battery self-discharge, where the horizontal axis represents the equivalent SOC of the battery under test, and the vertical axis represents the equivalent OCV of the battery under test. The curve can be plotted based on the correspondence between the equivalent OCV and the equivalent SOC. Figure 2 The OCV-SOC curve is shown. A similar OCV-Q curve exists between the equivalent OCV and the equivalent Q, which will not be elaborated here.

[0045] In step S112, the equivalent dOCV / dQ is calculated based on the correspondence between the equivalent OCV and the equivalent Q obtained in step S111. In some embodiments, the equivalent dOCV / dQ can be calculated by differentiating the equivalent OCV with respect to the equivalent Q.

[0046] There is a correspondence between the equivalent dOCV / dQ and the equivalent OCV; that is, each equivalent OCV has a corresponding equivalent dOCV / dQ. For ease of explanation, this correspondence is denoted as (equivalent dOCV / dQ, equivalent OCV). Combining (equivalent dOCV / dQ, equivalent OCV) with the (equivalent OCV, equivalent SOC) mentioned earlier, we can obtain the correspondence between the equivalent dOCV / dQ and the equivalent SOC, denoted as (equivalent SOC, equivalent dOCV / dQ). Figure 3 This is a dOCV / dQ-SOC curve during the self-discharge process of a battery in one embodiment, where the horizontal axis represents the equivalent SOC and the vertical axis represents the equivalent dOCV / dQ. It can be plotted based on (equivalent SOC, equivalent dOCV / dQ). Figure 3 The dOCV / dQ-SOC curves are shown.

[0047] In step S113, the dOCV / dQ corresponding to the target SOC of the battery under test is obtained according to (equivalent SOC, equivalent dOCV / dQ) in step S112. As mentioned above, the electrical parameters of the battery under test can be represented by the electrical parameters of the equivalent battery under test. Therefore, the dOCV / dQ corresponding to the target SOC in the battery under test can be obtained according to the correspondence between equivalent SOC and equivalent dOCV / dQ (i.e., (equivalent SOC, equivalent dOCV / dQ)). For ease of description, the target SOC and the corresponding dOCV / dQ in the battery under test are represented as (target SOC, dOCV / dQ).

[0048] Methods for obtaining (target SOC, dOCV / dQ) from (equivalent SOC, equivalent dOCV / dQ) include table lookup and querying the dOCV / dQ-SOC curve. For example, refer to... Figure 3 As shown, Figure 3 The curve in the figure illustrates the correspondence between equivalent SOC and equivalent dOCV / dQ, meaning that each equivalent SOC has a corresponding equivalent dOCV / dQ. Assuming the target SOC is 5%, by querying... Figure 3 The equivalent dOCV / dQ can be obtained as 20 when the equivalent SOC is 5%. Therefore, the dOCV / dQ of the battery under test corresponding to 5% SOC is 20.

[0049] In step S120, the battery under test is charged to the target SOC to obtain a battery under test with a target SOC. Step S120 will continue to be explained using the above example. Assuming the target SOC is 5%, the battery under test is charged to 5% SOC to obtain a battery under test with a 5% SOC.

[0050] In one embodiment, the process of charging the battery under test to 5% SOC is as follows: First, the battery under test is charged using a constant current charging method with a charging current of I4 and a cutoff voltage of OCV3; then, the battery under test is charged using a constant voltage charging method with a charging voltage of OCV3 and a cutoff current of I5. The equivalent OCV corresponding to 5% SOC can be obtained based on (equivalent OCV, equivalent SOC), and this equivalent OCV is used as the cutoff voltage OCV3. The battery under test with 5% SOC is obtained through the above charging process. It should be noted that the method for obtaining the target SOC battery under test is not limited to the above process.

[0051] In step S130, the target SOC battery obtained in step S120 is subjected to self-discharge to obtain the self-discharge current of the target SOC battery.

[0052] In one embodiment, a method for obtaining the self-discharge current of a target SOC battery under test includes: subjecting the target SOC battery under test to a static state; and obtaining the self-discharge current of the target SOC battery under test under preset conditions. The static state treatment period can be any duration from 12 hours to 24 hours; the preset conditions include the humidity and / or temperature of the static state treatment period, and the temperature can be any temperature from 20°C to 30°C. After the battery is charged, the internal activity of the battery is relatively high, and the static state treatment helps to balance the lithium ions inside the target SOC battery under test.

[0053] In some embodiments, the target SOC battery under test can be placed in a temperature-controlled chamber, and the self-discharge current of the target SOC battery under test can be obtained using a self-discharge tester. In other embodiments, the self-discharge current is obtained when the target SOC battery under test is in a stable self-discharge state, and the self-discharge current in the stable self-discharge state can more accurately reflect the self-discharge characteristics of the target SOC battery under test.

[0054] In conventional techniques, when using the open-circuit voltage measurement method to obtain the self-discharge rate of a battery, the battery under test needs to be left to stand for a relatively long time to obtain the voltage drop of the open-circuit voltage during the standing period. This application eliminates the need to obtain the voltage drop of the open-circuit voltage; instead, it obtains the self-discharge current of the battery under test. Compared to obtaining the voltage drop of the open-circuit voltage, obtaining the self-discharge current requires a shorter time, thus improving the efficiency of measuring the battery's self-discharge rate.

[0055] Furthermore, since the settling time required to obtain the self-discharge current is relatively short, the self-discharge rate of this application is less affected by environmental changes and the accuracy of the measuring instrument during the settling process, thus improving the accuracy of the measurement results.

[0056] In step S140, the self-discharge rate of the battery under test corresponding to the target SOC is calculated based on dOCV / dQ and the self-discharge current. Continuing with the previous example, step S140 is explained as follows: In the aforementioned example, the target SOC is 5% SOC, and in step S110, it is known that the dOCV / dQ corresponding to 5% SOC is 20; assuming the self-discharge current of the battery under test at 5% SOC is I6; the self-discharge rate of the battery under test corresponding to 5% SOC is calculated based on dOCV / dQ = 20 and 5% SOC.

[0057] In one embodiment, the formula for calculating the self-discharge rate of the battery under test corresponding to the target SOC based on dOCV / dQ and the self-discharge current is: K = (dOCV / dQ) × I, where K represents the self-discharge rate of the battery under test corresponding to the target SOC, and I represents the self-discharge current. Referring to the above example, substituting dOCV / dQ = 20 and the self-discharge current I6 into the above formula, we obtain: at 5% SOC, the self-discharge rate of the battery under test is K = 20 × I6. It should be noted that the target SOC value can be set according to requirements. The target SOC is not limited to the 5% SOC mentioned above. For example, the target SOC can be any value among 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% SOC.

[0058] In conventional techniques, when using the open-circuit voltage measurement method to obtain the self-discharge rate of a battery, the battery under test needs to be left to stand for a relatively long time to obtain the voltage drop of the open-circuit voltage during the standing time. The measurement method for calculating the battery self-discharge rate based on dOCV / dQ and self-discharge current corresponding to the target SOC in the above embodiments of this application does not require the battery to stand for a long time, thus shortening the time required to measure the battery self-discharge rate.

[0059] To better understand the measurement method of this application, a specific embodiment is given here. This embodiment includes the following steps:

[0060] Step 1: Take a lithium iron phosphate battery as the equivalent test battery, and charge the equivalent test battery with a constant current of 0.3C and a cutoff voltage of 3.65V; then charge the equivalent test battery with a constant voltage of 3.65V and a cutoff current of 0.02C.

[0061] Step 2: Discharge the equivalent battery under test with a discharge current of 0.02C and a cutoff voltage of 2.5V; record the OCV and Q of the equivalent battery under test during the discharge process, as well as the correspondence between the SOC and OCV of the equivalent battery under test. A plot can be drawn based on the correspondence between the SOC and OCV of the equivalent battery under test, as shown below. Figure 2 The OCV-SOC curve is shown.

[0062] Table 1 is a table for calculating the self-discharge rate. The OCV during the discharge process of the equivalent battery under test is recorded in Table 1.

[0063] Step 3: Differentiate OCV with respect to Q to obtain dOCV / dQ for different OCV values; according to Figure 1 The correspondence between SOC and OCV represented by the curve in the middle is used to obtain dOCV / dQ for different SOCs. The correspondence between SOC and dOCV / dQ can be plotted as follows: Figure 3 The curve shown.

[0064] Step 4: Take 30 batteries to be tested, divide them into 10 groups, and number each group sequentially as 1#, 2#, 3#, 4#, 5#, 6#, 7#, 8#, 9#, and 10#. The target SOCs of the batteries in each group are 10% SOC, 20% SOC, 30% SOC, 40% SOC, 50% SOC, 60% SOC, 70% SOC, 80% SOC, 90% SOC, and 100% SOC, respectively. Adjust the SOC of the batteries in groups 1# to 10# to their respective target SOCs. The adjustment process is as follows: first, constant current charging is performed at a charging current of 0.3C, and the cutoff voltage starts from... Figure 2 The data was obtained from the middle; then constant voltage charging was performed, with a cutoff current of 0.02C; the test batteries in groups 1 to 10 were left to stand at room temperature for 24 hours.

[0065] according to Figure 3 Alternatively, the data obtained in steps 1 to 3 can correspond to the dOCV / dQ of the target SOC mentioned above. For example, this can be achieved through... Figure 3 Query the equivalent battery under test for the corresponding dOCV / dQ of each target SOC, and record the queried dOCV / dQ in Table 1. There is a correspondence between the target SOC and dOCV / dQ in the same row.

[0066] Step 5: Place the batteries to be tested in groups 1# to 10# in a constant temperature room, with the temperature controlled at 25±1℃; use a self-discharge tester to detect the self-discharge current of each battery to be tested, and record the self-discharge current value when the current is stable; calculate the average self-discharge current of each group of batteries to be tested, and record the calculation results in Table 1.

[0067] Step 6: Calculate the self-discharge rate K of each group of batteries according to the formula K=(dOCV / dQ)×I. The calculation results are shown in Table 1. There is a corresponding relationship between the self-discharge rate and the target SOC in the same row. For example, the target SOC of the battery under test in group 4# is 70%, and the corresponding self-discharge rate K is 0.02100.

[0068] Table 1. Self-discharge rate calculation table

[0069] serial number OCV(mV) Target SOC dOCV / dQ(mV / mAh) Self-discharge current (mA) K(mV / h) 1# 3561.05 100％ 1.0320135 64 66.04886 2# 3319.8 90％ 0.0002221 59 0.01310 3# 3316.64 80％ 0.0002667 52 0.01387 4# 3311.81 70％ 0.0005123 41 0.02100 5# 3282.01 60％ 0.0008941 35 0.03129 6# 3275.54 50％ 0.0001992 28 0.00558 7# 3272.01 40％ 0.0003444 25 0.00861 8# 3257.43 30％ 0.0016531 21 0.03472 9# 3223.91 20％ 0.0029789 16 0.04766 10# 3181.08 10％ 0.0010534 12 0.01264

[0070] The basic concepts have been described above. Obviously, for those skilled in the art, the above disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore remain within the spirit and scope of the exemplary embodiments of this application.

[0071] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0072] In some embodiments, numbers are used to describe the quantity of components and attributes. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise stated, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the description and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the settings of such numerical values ​​are as accurate as possible within the feasible range.

Claims

1. A method for measuring the self-discharge rate of a battery, characterized in that, include: Obtain the dOCV / dQ corresponding to the battery under test and the target SOC; The battery under test is charged to the target SOC to obtain the battery under test with the target SOC. Obtain the self-discharge current I of the target SOC battery under test; as well as The self-discharge rate K of the battery under test corresponding to the target SOC is calculated based on the dOCV / dQ and the self-discharge current I. The formula for calculating the self-discharge rate K of the battery under test corresponding to the target SOC based on the dOCV / dQ and the self-discharge current I is as follows: 。 2. The measurement method as described in claim 1, characterized in that, Methods for obtaining the dOCV / dQ of the battery under test and the target SOC include: Obtain the correspondence between the equivalent OCV, equivalent Q, and equivalent SOC of the equivalent battery under test; Calculate the equivalent dOCV / dQ based on the correspondence between the equivalent OCV and the equivalent Q; The dOCV / dQ corresponding to the target SOC of the battery under test is obtained based on the correspondence between the equivalent dOCV / dQ and the equivalent SOC.

3. The measurement method as described in claim 2, characterized in that, Methods for obtaining the correspondence between the equivalent OCV, equivalent Q, and equivalent SOC of the equivalent battery under test include: The equivalent battery under test is charged according to preset charging conditions to obtain a fully charged equivalent battery under test. The equivalent battery under test in its fully charged state is discharged according to preset discharge conditions to obtain the correspondence between the equivalent OCV, equivalent Q and equivalent SOC of the equivalent battery under test.

4. The measurement method as described in claim 3, characterized in that, The preset charging conditions are: charging the equivalent battery under test to a first cutoff voltage with a constant charging current, and then charging the equivalent battery under test to a full charge state with the first cutoff voltage as the charging voltage.

5. The measurement method as described in claim 3, characterized in that, The preset discharge condition is: the equivalent battery under test in the fully charged state is discharged to the second cutoff voltage with a constant discharge current.

6. The measurement method as described in claim 1, characterized in that, After the target SOC battery under test is left to stand, the self-discharge current of the target SOC battery under test is obtained under preset conditions.

7. The measurement method as described in claim 6, characterized in that, The settling time is 12h to 24h.

8. The measurement method as described in claim 6, characterized in that, The preset temperature is 20℃~30℃.

9. The measurement method as described in claim 6, characterized in that, The self-discharge current is obtained when the target SOC battery under test is in a stable self-discharge state.

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