A method and system for diagnosing faults in cascade - utilized batteries

Abstract

The present invention belongs to the technical field of power battery, and specifically relates to a method and system for fault diagnosis of second-life batteries. The above-mentioned fault diagnosis method includes: obtaining the standard open-circuit voltage change rate value of the second-life battery under the charging condition, and pre-storing the standard open-circuit voltage change rate value in the detection module; during the charging process of the second-life battery, using the acquisition module to collect the open-circuit voltage information of the second-life battery, and sending the open-circuit voltage information to the detection module; the open-circuit voltage information includes the first open-circuit voltage value of the second-life battery and the corresponding time value; using the detection module to calculate the actual open-circuit voltage change rate value of the second-life battery in real time according to the received open-circuit voltage information; the detection module determines whether the second-life battery has an internal short circuit according to the pre-stored standard open-circuit voltage change rate value and the calculated actual open-circuit voltage change rate value.

Description

Technical Field

[0001] The present invention belongs to the technical field of power batteries, and particularly relates to a method and system for diagnosing faults in second-life batteries. Background Art

[0002] The second-life utilization of power batteries refers to the process of reusing batteries that have been used in power equipment such as electric vehicles and have reduced performance but still have remaining capacity. After detection, classification, recombination, etc., these batteries are reused in other fields, such as energy storage systems, low-speed electric vehicles, etc. This utilization method can not only effectively extend the service life of the batteries, reduce resource waste, but also reduce the production demand for new batteries, thereby alleviating the environmental pressure.

[0003] However, power batteries may face some technical challenges during the second-life utilization process. One of them is how to accurately detect battery faults. Since these batteries have been used for a period of time, their internal structures and performances may have changed. Therefore, traditional fault detection methods may no longer be applicable. In addition, second-life batteries often need to form large-scale battery systems, which further increases the complexity of fault detection.

[0004] Therefore, the research on fault detection methods for the second-life utilization of power batteries is of great significance. Such a method needs to be able to accurately and quickly detect faults in the battery system in order to perform repairs or replacements in a timely manner, thereby ensuring the safe and stable operation of the battery system. At the same time, this method also needs to be able to adapt to different types and states of batteries to meet the requirements of practical applications.

[0005] Existing methods for diagnosing faults in second-life batteries usually focus on detecting and giving fault warnings for fault types such as overvoltage, undervoltage, and inconsistent voltage differences, and taking corresponding measures. However, due to the use of second-life batteries for a certain period, defects such as lithium plating or micro-short circuits inside the batteries begin to appear (when lithium plating occurs in the battery, the voltage usually changes abnormally. In a lithium-ion battery, when lithium metal precipitates on the surface of the negative electrode, a lithium dendrite structure will be formed. This structure will pierce the separator and cause an internal short circuit in the battery, resulting in a rapid drop in the battery voltage). These problems are usually difficult to detect in a timely manner through existing methods for diagnosing faults in second-life batteries, making it difficult for existing methods for diagnosing faults in second-life batteries to timely detect the potential internal short-circuit risk of second-life batteries, and thus difficult to ensure the safe and stable operation of the second-life battery system. Summary of the Invention

[0006] The present invention provides a method and system for diagnosing faults in cascade - utilized batteries, which solves the technical problem that existing methods for diagnosing faults in cascade - utilized batteries usually have difficulty in promptly detecting potential internal short - circuit risks in cascade - utilized batteries, thus making it difficult to ensure the safe and stable operation of cascade - utilized battery systems.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for diagnosing faults in cascade - utilized batteries, comprising the following steps:

[0009] Step 1: Obtain the standard open - circuit voltage change rate value of the cascade - utilized battery under the charging condition, and pre - store the standard open - circuit voltage change rate value in the detection module;

[0010] Step 2: During the charging process of the cascade - utilized battery, use the acquisition module to collect the open - circuit voltage information of the cascade - utilized battery, and send the open - circuit voltage information to the detection module; the open - circuit voltage information includes the first open - circuit voltage value of the cascade - utilized battery and the corresponding time value;

[0011] Use the detection module to calculate the actual open - circuit voltage change rate value of the cascade - utilized battery in real - time according to the received open - circuit voltage information;

[0012] The detection module determines whether the cascade - utilized battery has an internal short - circuit according to the pre - stored standard open - circuit voltage change rate value and the calculated actual open - circuit voltage change rate value. If it is determined that the cascade - utilized battery has an internal short - circuit, the detection module issues an alarm signal; if it is determined that the cascade - utilized battery has no internal short - circuit, repeat Step 2 until the charging of the cascade - utilized battery ends this time.

[0013] By pre - determining the standard open - circuit voltage change rate value of the cascade - utilized battery under the charging condition, then using the detection module to calculate the actual open - circuit voltage change rate value of the cascade - utilized battery in real - time; and based on the characteristic that when lithium deposition or micro - short - circuit and other defects occur inside the cascade - utilized battery, the voltage usually shows abnormal changes, the detection module determines whether the cascade - utilized battery has an internal short - circuit according to the pre - stored standard open - circuit voltage change rate value and the calculated actual open - circuit voltage change rate value. Furthermore, the method for diagnosing faults in cascade - utilized batteries provided by the present invention can promptly detect potential internal short - circuit risks in cascade - utilized batteries, and thus ensure the safe and stable operation of cascade - utilized battery systems.

[0014] Further, the method for obtaining the standard open - circuit voltage change rate value of the cascade - utilized battery under the charging condition includes:

[0015] Perform grading charge detection on the second-life battery to obtain the open-circuit voltage-time data of the second-life battery during the grading charge process;

[0016] Based on the obtained open-circuit voltage-time data, calculate the standard open-circuit voltage change rate value.

[0017] Furthermore, the method for calculating the standard open-circuit voltage change rate value includes:

[0018] Perform curve fitting on the obtained open-circuit voltage-time data based on the least squares method to obtain an open-circuit voltage-time curve and the corresponding curve function;

[0019] Take the derivative of the obtained curve function to obtain the absolute value of the maximum slope of the open-circuit voltage-time curve;

[0020] Use the absolute value of the maximum slope as the standard open-circuit voltage change rate value.

[0021] In another technical solution, the method for calculating the standard open-circuit voltage change rate value includes:

[0022] Based on the obtained open-circuit voltage-time data, obtain the second open-circuit voltage values corresponding to each detection time node of the second-life battery during the grading charge process;

[0023] Based on the second open-circuit voltage values corresponding to each detection time node, calculate the calculated values of the open-circuit voltage change rate of the second-life battery between two adjacent detection time nodes; use the maximum value among the absolute values of the obtained calculated values of the open-circuit voltage change rate as the standard open-circuit voltage change rate value.

[0024] Furthermore, the calculated values of the open-circuit voltage change rate are calculated using the following formula:

[0025] ;

[0026] where V n+1 is the second open-circuit voltage value corresponding to the (n + 1)-th detection time node arranged in chronological order; V n is the second open-circuit voltage value corresponding to the n-th detection time node arranged in chronological order; T n+1 is the time value of the (n + 1)-th detection time node arranged in chronological order; T n is the time value of the n-th detection time node arranged in chronological order; k n is the calculated value of the open-circuit voltage change rate of the second-life battery between the n-th detection time node and the (n + 1)-th detection time node arranged in chronological order.

[0027] Further, in step 2, during the charging process of the second-life battery, the detection module calculates the actual open-circuit voltage change rate value of the second-life battery in real time multiple times with a first preset time period as the time cycle;

[0028] In any real-time calculation, the detection module calculates the actual open-circuit voltage change rate value corresponding to this real-time calculation through the open-circuit voltage information received within the time cycle corresponding to this real-time calculation.

[0029] Further, the actual open-circuit voltage change rate value corresponding to any real-time calculation is calculated using the following formula:

[0030] ;

[0031] where V m1 is the first open-circuit voltage value received by the detection module at the end of the time cycle corresponding to the mth real-time calculation; V m2 is the first open-circuit voltage value received by the detection module at the start of the time cycle corresponding to the mth real-time calculation; T m1 is the time value received by the detection module at the end of the time cycle corresponding to the mth real-time calculation; T m2 is the time value received by the detection module at the end of the time cycle corresponding to the mth real-time calculation; k m is the actual open-circuit voltage change rate value corresponding to the mth real-time calculation.

[0032] Further, after charging the second-life battery for a second preset time period, the detection module calculates the actual open-circuit voltage change rate value of the second-life battery in real time multiple times with a first preset time period as the time cycle.

[0033] By having the detection module calculate the actual open-circuit voltage change rate value of the second-life battery in real time multiple times with a first preset time period as the time cycle after charging the second-life battery for a second preset time period, it can be ensured that the power source for charging the second-life battery has entered the stable output stage (i.e., has passed through the voltage ramp-up stage of the power source), effectively avoiding the situation where the calculated actual open-circuit voltage change rate value has an error due to unstable output of the power source, and ensuring the accuracy of the detection module in determining whether the second-life battery has an internal short circuit.

[0034] Further, the first preset time period is thirty seconds, and the second preset time period is three minutes.

[0035] Further, the method by which the detection module determines whether the second-life battery has an internal short circuit includes:

[0036] If the actual open - circuit voltage change rate value corresponding to any real - time calculation is greater than the product of the first multiple and the standard open - circuit voltage change rate value; or the actual open - circuit voltage change rate values corresponding to at least two of any consecutive several real - time calculations are greater than the product of the second multiple and the standard open - circuit voltage change rate value, it is determined that an internal short - circuit has occurred in the second - life battery; otherwise, it is determined that no internal short - circuit has occurred in the second - life battery;

[0037] Wherein, both the first multiple and the second multiple are greater than 1, and the first multiple is greater than the second multiple.

[0038] By introducing the two judgment criteria of the product of the first multiple and the standard open - circuit voltage change rate value, and the product of the second multiple and the standard open - circuit voltage change rate value, it can not only ensure that when the actual open - circuit voltage of the second - life battery fluctuates greatly (in the present invention, that is, when the actual open - circuit voltage change rate value corresponding to any real - time calculation is greater than the product of the first multiple and the standard open - circuit voltage change rate value), it can accurately determine that an internal short - circuit has occurred in the second - life battery, but also avoid misjudging that an internal short - circuit has occurred in the second - life battery when the actual open - circuit voltage of the second - life battery accidentally fluctuates slightly (in the present invention, that is, when only one of any consecutive several real - time calculations has an actual open - circuit voltage change rate value greater than the product of the second multiple and the standard open - circuit voltage change rate value), which can effectively improve the accuracy of the detection module in judging whether an internal short - circuit has occurred in the second - life battery and reduce the occurrence of misjudgment.

[0039] Further, the "several times" is four times.

[0040] According to the second - life battery fault diagnosis method provided by the present invention, the present invention also provides a second - life battery fault diagnosis system: including a detection module and a collection module arranged in the second - life battery;

[0041] The collection module is used to collect the open - circuit voltage information of the second - life battery and send the open - circuit voltage information to the detection module; the open - circuit voltage information includes the first open - circuit voltage value of the second - life battery and the corresponding time value;

[0042] The standard open - circuit voltage change rate value of the second - life battery is pre - stored in the detection module;

[0043] The detection module is used to calculate the actual open - circuit voltage change rate value of the second - life battery in real - time according to the received open - circuit voltage information;

[0044] The detection module is further configured to determine whether an internal short circuit occurs in the second-life battery according to the pre-stored standard open-circuit voltage change rate value and the calculated actual open-circuit voltage change rate value, and send an alarm signal when it is determined that an internal short circuit has occurred in the second-life battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings without creative efforts based on these drawings.

[0046] Figure 1 It is a flowchart of the second-life battery fault diagnosis method in Embodiment 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.

[0048] Embodiment 1:

[0049] As Figure 1 shown, Embodiment 1 provides a second-life battery fault diagnosis method, including the following steps:

[0050] Step 1: Obtain the standard open-circuit voltage change rate value of the second-life battery under the charging condition, and pre-store the standard open-circuit voltage change rate value in the detection module;

[0051] Step 2: During the charging process of the second-life battery, use the acquisition module to collect the open-circuit voltage information of the second-life battery, and send the open-circuit voltage information to the detection module; the open-circuit voltage information includes the first open-circuit voltage value of the second-life battery and the corresponding time value;

[0052] Use the detection module to calculate the actual open-circuit voltage change rate value of the second-life battery in real time according to the received open-circuit voltage information;

[0053] The detection module determines whether an internal short circuit occurs in the second-life battery according to the pre-stored standard open-circuit voltage change rate value and the calculated actual open-circuit voltage change rate value. If it is determined that an internal short circuit has occurred in the second-life battery, the detection module sends an alarm signal; if it is determined that an internal short circuit has not occurred in the second-life battery, repeat Step 2 until the current charging of the second-life battery ends.

[0054] By pre-determining the standard open-circuit voltage change rate value of the second-life battery under the charging condition, and then using the detection module to calculate the actual open-circuit voltage change rate value of the second-life battery in real time; and based on the characteristic that when lithium plating or micro-short circuit and other defects occur inside the second-life battery, the voltage usually shows abnormal changes, the detection module determines whether the second-life battery has an internal short circuit according to the pre-stored standard open-circuit voltage change rate value and the calculated actual open-circuit voltage change rate value, so that the second-life battery fault diagnosis method provided by the present invention can timely detect the potential internal short circuit risk of the second-life battery, and then ensure the safe and stable operation of the second-life battery system.

[0055] In one embodiment, the method for obtaining the standard open-circuit voltage change rate value of the second-life battery under the charging condition includes:

[0056] Perform grading charge detection on the second-life battery to obtain the open-circuit voltage-time data of the second-life battery during the grading charge process;

[0057] According to the obtained open-circuit voltage-time data, calculate the standard open-circuit voltage change rate value.

[0058] Among them, there are various methods for calculating the standard open-circuit voltage change rate value according to the obtained open-circuit voltage-time data, including but not limited to the following methods:

[0059] Method 1:

[0060] The method for calculating the standard open-circuit voltage change rate value includes:

[0061] Based on the least squares method, perform curve fitting on the obtained open-circuit voltage-time data to obtain the open-circuit voltage-time curve and the corresponding curve function;

[0062] Derive the obtained curve function to obtain the absolute value of the maximum slope of the open-circuit voltage-time curve;

[0063] Take the absolute value of the maximum slope as the standard open-circuit voltage change rate value.

[0064] Method 2:

[0065] The method for calculating the standard open-circuit voltage change rate value includes:

[0066] According to the obtained open-circuit voltage-time data, obtain the corresponding second open-circuit voltage values at each detection time node of the second-life battery during the grading charge process;

[0067] According to the second open-circuit voltage values corresponding to each detection time node, the calculated values of the open-circuit voltage change rate of the cascade utilization battery between two adjacent detection time nodes are obtained; the maximum value among the absolute values of the obtained calculated values of the open-circuit voltage change rate is used as the standard open-circuit voltage change rate value.

[0068] Specifically, in the above method two, the calculated values of the open-circuit voltage change rate are calculated by the following formula:

[0069] ;

[0070] where, V n+1 is the second open-circuit voltage value corresponding to the (n + 1)-th detection time node sorted in chronological order; V n is the second open-circuit voltage value corresponding to the n-th detection time node sorted in chronological order; T n+1 is the time value of the (n + 1)-th detection time node sorted in chronological order; T n is the time value of the n-th detection time node sorted in chronological order; k n is the calculated value of the open-circuit voltage change rate of the cascade utilization battery between the n-th detection time node and the (n + 1)-th detection time node in chronological order, the (n + 1)-th detection time node.

[0071] In one embodiment, in the above step 2, during the charging process of the cascade utilization battery, the detection module calculates the actual open-circuit voltage change rate value of the cascade utilization battery in real time multiple times with the first preset duration as the time period;

[0072] In any real-time calculation, the detection module calculates the actual open-circuit voltage change rate value corresponding to the real-time calculation through the open-circuit voltage information received within the time period corresponding to the real-time calculation.

[0073] Specifically, the actual open-circuit voltage change rate value corresponding to any real-time calculation is calculated by the following formula:

[0074] ;

[0075] where, V m1 is the first open-circuit voltage value received by the detection module at the end of the time period corresponding to the m-th real-time calculation; V m2 is the first open-circuit voltage value received by the detection module at the beginning of the time period corresponding to the m-th real-time calculation; T m1 is the time value received by the detection module at the end of the time period corresponding to the m-th real-time calculation; T m2 is the time value received by the detection module at the end of the time period corresponding to the m-th real-time calculation; k mis the actual open-circuit voltage change rate value corresponding to the m-th real-time calculation.

[0076] Preferably, in Embodiment 1 of the present invention, after charging the second preset duration for the second-life battery, the detection module performs multiple real-time calculations on the actual open-circuit voltage change rate value of the second-life battery with the first preset duration as the time period.

[0077] By performing multiple real-time calculations on the actual open-circuit voltage change rate value of the second-life battery with the first preset duration as the time period after charging the second preset duration for the second-life battery, it can be ensured that the power source for charging the second-life battery has entered the stable output stage (i.e., has passed the voltage ramp-up stage of the power source), effectively avoiding the situation where the calculated actual open-circuit voltage change rate value has an error due to the unstable output of the power source, and ensuring the accuracy of the detection module in determining whether the second-life battery has an internal short circuit.

[0078] Among them, the above first preset duration and second preset duration can also be applied in the process of performing grading charge detection on the second-life battery; for example: in Method 2 above, the first detection time node is at the second preset duration of grading charge; the interval between two adjacent detection time nodes is the first preset duration.

[0079] Preferably, in Embodiment 1 of the present invention, the first preset duration is thirty seconds, and the second preset duration is three minutes.

[0080] Specifically, in Embodiment 1 of the present invention, the method for the detection module to determine whether the second-life battery has an internal short circuit includes:

[0081] If the actual open-circuit voltage change rate value corresponding to any real-time calculation is greater than the product of the first magnification factor and the standard open-circuit voltage change rate value; or the actual open-circuit voltage change rate values corresponding to at least two real-time calculations among any consecutive several real-time calculations are greater than the product of the second magnification factor and the standard open-circuit voltage change rate value, it is determined that the second-life battery has an internal short circuit; otherwise, it is determined that the second-life battery does not have an internal short circuit;

[0082] Among them, both the first magnification factor and the second magnification factor are greater than one, and the first magnification factor is greater than the second magnification factor.

[0083] By introducing two judgment criteria, namely the product of the first magnification and the standard open-circuit voltage change rate value, and the product of the second magnification and the standard open-circuit voltage change rate value, it can not only ensure that the detection module accurately determines that the secondary utilization battery has an internal short circuit when the actual open-circuit voltage of the secondary utilization battery fluctuates greatly (in the present invention, that is, when the actual open-circuit voltage change rate value corresponding to any real-time calculation is greater than the product of the first magnification and the standard open-circuit voltage change rate value), but also avoid misjudging that the secondary utilization battery has an internal short circuit when the actual open-circuit voltage of the secondary utilization battery accidentally fluctuates slightly (in the present invention, that is, when only one of the real-time calculations in any consecutive several real-time calculations has an actual open-circuit voltage change rate value greater than the product of the second magnification and the standard open-circuit voltage change rate value). It can effectively improve the accuracy of the detection module in judging whether the secondary utilization battery has an internal short circuit and reduce the occurrence of misjudgment situations.

[0084] Specifically, in Embodiment 1, the above-mentioned several times is four times.

[0085] Embodiment 2:

[0086] According to the secondary utilization battery fault diagnosis method provided in Embodiment 1, Embodiment 2 provides a secondary utilization battery fault diagnosis system: including a detection module and a collection module arranged in the secondary utilization battery;

[0087] The collection module is used to collect the open-circuit voltage information of the secondary utilization battery and send the open-circuit voltage information to the detection module; the open-circuit voltage information includes the first open-circuit voltage value of the secondary utilization battery and the corresponding time value;

[0088] The standard open-circuit voltage change rate value of the secondary utilization battery is pre-stored in the detection module;

[0089] The detection module is used to calculate the actual open-circuit voltage change rate value of the secondary utilization battery in real time according to the received open-circuit voltage information;

[0090] The detection module is also used to judge whether the secondary utilization battery has an internal short circuit according to the pre-stored standard open-circuit voltage change rate value and the calculated actual open-circuit voltage change rate value, and send an alarm signal when it is determined that the secondary utilization battery has an internal short circuit.

[0091] Through the secondary utilization battery fault diagnosis method and system provided by the present invention, it has at least the following technical effects or advantages:

[0092] 1. By predetermining the standard open-circuit voltage change rate value of the second-use battery under charging conditions, and then using the detection module to calculate the actual open-circuit voltage change rate value of the second-use battery in real time; and based on the characteristic that when defects such as lithium deposition or micro-short circuits occur inside the second-use battery, the voltage usually changes abnormally, the detection module determines whether the second-use battery has an internal short circuit according to the pre-stored standard open-circuit voltage change rate value and the calculated actual open-circuit voltage change rate value, so that the second-use battery fault diagnosis method provided by the present invention can timely discover the potential internal short circuit risk of the second-use battery, thereby ensuring the safe and stable operation of the second-use battery system.

[0093] 2. After charging the second-use battery for the second preset time, the detection module performs multiple real-time calculations on the actual open-circuit voltage change rate of the second-use battery with the first preset time as the time period, thereby ensuring that the power supply for charging the second-use battery has entered the stable output stage (that is, has passed the voltage climbing stage of the power supply), and can effectively avoid the situation where the calculated actual open-circuit voltage change rate value produces errors due to unstable power supply output, thereby ensuring the accuracy of the detection module in determining whether an internal short circuit occurs in the second-use battery.

[0094] 3. By introducing the product of the first magnification and the standard open-circuit voltage change rate value, and the product of the second magnification and the standard open-circuit voltage change rate value as two judgment criteria, it can ensure that the detection module accurately determines that an internal short circuit has occurred in the cascade utilization battery when the actual open-circuit voltage of the cascade utilization battery fluctuates greatly (in the present invention, that is, when the actual open-circuit voltage change rate value corresponding to any real-time calculation is greater than the product of the first magnification and the standard open-circuit voltage change rate value), and can also avoid the situation where the cascade utilization battery is misjudged to have an internal short circuit when the actual open-circuit voltage of the cascade utilization battery accidentally fluctuates slightly (in the present invention, that is, when only one actual open-circuit voltage change rate value corresponding to any consecutive real-time calculations is greater than the product of the second magnification and the standard open-circuit voltage change rate value). This can effectively improve the accuracy of the detection module in judging whether an internal short circuit has occurred in the cascade utilization battery and reduce the occurrence of misjudgment.

[0095] The above are only specific application examples of the present invention and do not constitute any limitation to the protection scope of the present invention. Any technical solutions formed by equivalent transformation or equivalent replacement shall fall within the protection scope of the present invention.

Claims

1. A method for diagnosing battery faults during cascade utilization, characterized in that: The following steps are involved: Step 1: obtaining a standard open circuit voltage change rate value of a second-life battery under charging conditions, and pre-storing the standard open circuit voltage change rate value in a detection module; Step 2: In the process of charging the second-life battery, using the acquisition module to collect the open circuit voltage information of the second-life battery, and sending the open circuit voltage information to the detection module; the open circuit voltage information includes a first open circuit voltage value of the second-life battery and a corresponding time value; Utilizing the detection module to calculate in real time the actual open circuit voltage change rate value of the second-life battery according to the received open circuit voltage information; The detection module determines whether the second-use battery has an internal short circuit according to the pre-stored standard open-circuit voltage change rate value and the calculated actual open-circuit voltage change rate value. If it is determined that the second-use battery has an internal short circuit, the detection module sends an alarm signal; if it is determined that the second-use battery has no internal short circuit, the step 2 is repeated until the charging of the second-use battery is completed. The method for obtaining the standard open circuit voltage change rate value of the second-life battery under charging conditions includes: Performing capacity-divided charging detection on the second-life battery to obtain open circuit voltage-time data of the second-life battery during the capacity-divided charging process; Calculating the standard open circuit voltage change rate value according to the obtained open circuit voltage-time data; In the step 2, during the charging process of the second-life battery, the detection module performs multiple real-time calculations on the actual open-circuit voltage change rate value of the second-life battery with a first preset time period as a time period; In any real-time calculation, the detection module calculates the actual open-circuit voltage change rate value corresponding to the real-time calculation through the open-circuit voltage information received within the time period corresponding to the real-time calculation.

2. The method for diagnosing a second-life battery fault according to claim 1, characterized in that: The method for calculating the standard open circuit voltage change rate value includes: Performing curve fitting on the obtained open circuit voltage-time data based on the least squares method to obtain an open circuit voltage-time curve and a corresponding curve function; Derivative the obtained curve function to obtain the maximum slope absolute value of the open circuit voltage-time curve; The maximum slope absolute value is used as the standard open circuit voltage change rate value.

3. The method for diagnosing a second-life battery fault according to claim 1, characterized in that: The method for calculating the standard open circuit voltage change rate value includes: According to the obtained open circuit voltage-time data, a second open circuit voltage value corresponding to each detection time node of the cascade utilization battery in the divided capacity charging process is obtained; According to the second open circuit voltage value corresponding to each detection time node, the calculated value of the open circuit voltage change rate of the cascade utilization battery between each two adjacent detection time nodes is calculated; the maximum value among the absolute values ​​of the obtained calculated values ​​of the open circuit voltage change rate is used as the standard open circuit voltage change rate value.

4. The method for diagnosing a second-life battery fault according to claim 3, characterized in that: The open circuit voltage change rate calculation values ​​are calculated using the following formula: ， Among them, V n+1 is the second open circuit voltage value corresponding to the n+1th detection time node sorted in chronological order; V n is the second open circuit voltage value corresponding to the nth detection time node sorted in chronological order; T n+1 is the time value of the n+1th detection time node sorted in chronological order; T n is the time value of the nth detection time node sorted in chronological order; k n The open circuit voltage change rate calculation value of the cascade utilization battery between the nth detection time node and the n+1th detection time node sorted in chronological order is the n+1th detection time node.

5. The method for diagnosing a second-life battery fault according to claim 1, characterized in that: The actual open circuit voltage change rate value corresponding to any real-time calculation is calculated using the following formula: ， Among them, V m1 V is the first open circuit voltage value received by the detection module at the end of the time period corresponding to the mth real-time calculation; m2 is the first open circuit voltage value received by the detection module at the beginning of the time period corresponding to the mth real-time calculation; T m1 is the time value received by the detection module at the end of the time period corresponding to the mth real-time calculation; T m2 k is the time value received by the detection module at the end of the time period corresponding to the mth real-time calculation; m The actual open circuit voltage change rate value corresponding to the m-th real-time calculation.

6. The method for diagnosing a second-life battery fault according to claim 1, characterized in that: After the second-use battery is charged for a second preset time period, the detection module performs multiple real-time calculations on the actual open-circuit voltage change rate value of the second-use battery with the first preset time period as the time period.

7. The method for diagnosing a second-life battery fault according to claim 1, characterized in that: The method for the detection module to determine whether the second-life battery has an internal short circuit includes: If the actual open circuit voltage change rate value corresponding to any real-time calculation is greater than the product of the first multiple and the standard open circuit voltage change rate value; or the actual open circuit voltage change rate values ​​corresponding to at least two of any consecutive real-time calculations are greater than the product of the second multiple and the standard open circuit voltage change rate value, it is determined that the cascade utilization battery has an internal short circuit; otherwise, it is determined that the cascade utilization battery has no internal short circuit; The first magnification and the second magnification are both greater than one, and the first magnification is greater than the second magnification.

8. A second-life battery fault diagnosis system, characterized in that: It includes a detection module and a collection module arranged in a second-use battery; The acquisition module is used to acquire the open circuit voltage information of the second-life battery and send the open circuit voltage information to the detection module; the open circuit voltage information includes the first open circuit voltage value of the second-life battery and the corresponding time value; The detection module pre-stores a value of a standard open circuit voltage change rate of the second-life battery; The detection module is used to calculate the actual open circuit voltage change rate value of the second-life battery in real time according to the received open circuit voltage information; The detection module is also used to determine whether the second-life battery has an internal short circuit according to the pre-stored standard open-circuit voltage change rate value and the calculated actual open-circuit voltage change rate value, and to send an alarm signal when it is determined that the second-life battery has an internal short circuit; The second-life battery fault diagnosis system is used to execute the steps in the second-life battery fault diagnosis method as described in any one of claims 1-7.

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