Fault diagnosis method and system for echelon utilization battery

Abstract

The invention belongs to the technical field of power batteries, and particularly relates to an echelon utilization battery fault diagnosis method and system, and the method comprises the steps: obtaining a standard open-circuit voltage change rate value of an echelon utilization battery under a charging condition, and pre-storing the standard open-circuit voltage change rate value in a detection module; in the process of charging the echelon utilization battery, an acquisition module is used for acquiring open-circuit voltage information of the echelon utilization battery and sending the open-circuit voltage information to a detection module; the open-circuit voltage information comprises a first open-circuit voltage value of the echelon utilization battery and a corresponding time value; calculating an actual open-circuit voltage change rate value of the echelon utilization battery in real time according to the received open-circuit voltage information by utilizing a detection module; and the detection module judges whether internal short circuit occurs in the echelon utilization battery or not according to a 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 in particular relates to a method and system for diagnosing faults of second-life batteries. Background Art

[0002] The second-life utilization of power batteries refers to the use of batteries that have been used in power equipment such as electric vehicles and whose performance has been reduced but still have residual capacity, after testing, classification, reorganization and other steps, for reuse 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 batteries and reduce resource waste, but also reduce the demand for the production of new batteries, thereby alleviating pressure on the environment.

[0003] However, power batteries may face some technical challenges during the cascade utilization process, one of which is how to accurately detect battery failures. Since these batteries have been used for a period of time, their internal structure and performance may have changed, so traditional fault detection methods may no longer be applicable. In addition, batteries that are used in cascades 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 power battery recycling is of great significance. This method needs to be able to accurately and quickly detect faults in the battery system so that timely repairs or replacements can be made to ensure the safe and stable operation of the battery system. At the same time, this method also needs to be able to adapt to batteries of different types and states to meet the needs of practical applications.

[0005] Existing methods for diagnosing faults in second-hand batteries usually focus on detecting and warning about fault types such as overvoltage, undervoltage, and inconsistent pressure differences, and take corresponding measures. However, after a period of use, second-hand batteries begin to show defects such as lithium deposition or micro-short circuits inside the battery (when lithium deposition occurs in the battery, the voltage usually changes abnormally. In lithium-ion batteries, when lithium metal is deposited on the surface of the negative electrode, a lithium dendrite structure is formed. This structure pierces the diaphragm and causes an internal short circuit in the battery, causing the battery voltage to drop rapidly). These problems are usually difficult to detect in time through existing methods for diagnosing faults in second-hand batteries, which makes it difficult to detect the potential internal short circuit risks of second-hand batteries in time, thereby ensuring the technical problem of safe and stable operation of second-hand battery systems. Summary of the invention

[0006] The present invention provides a second-use battery fault diagnosis method and system to solve the technical problem that the existing second-use battery fault diagnosis methods usually have difficulty in timely detecting the potential internal short circuit risk of the second-use battery, thereby making it difficult to ensure the safe and stable operation of the second-use battery system.

[0007] The technical solution adopted by the present invention is: A method for diagnosing a battery failure in a second-life battery comprises the following steps: 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 based on 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, step 2 is repeated until the charging of the second-use battery is completed.

[0008] 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 based on the pre-stored standard open-circuit voltage change rate value and the calculated actual open-circuit voltage change rate value, thereby enabling the second-use battery fault diagnosis method provided by the present invention to 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.

[0009] Furthermore, 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; The standard open circuit voltage change rate value is calculated based on the obtained open circuit voltage-time data.

[0010] Furthermore, 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.

[0011] In another technical solution, 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.

[0012] Furthermore, each open circuit voltage change rate calculated value is calculated using the following formula: ;

[0013] 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.

[0014] Furthermore, in the step 2, during the charging of the second-life battery, the detection module performs multiple real-time calculations of 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.

[0015] Furthermore, the actual open circuit voltage change rate value corresponding to any real-time calculation is calculated using the following formula: ;

[0016] 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.

[0017] Furthermore, 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.

[0018] After charging the second-use battery for a second preset time, 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 as the time period, thereby ensuring that the power supply used to charge the second-use battery has entered a 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 an error 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.

[0019] Furthermore, the first preset time length is thirty seconds, and the second preset time length is three minutes.

[0020] Furthermore, the method in which the detection module determines whether an internal short circuit occurs in the second-life battery 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.

[0021] By introducing the two judgment criteria of the product of the first magnification rate and the standard open-circuit voltage change rate value, and the product of the second magnification rate and the standard open-circuit voltage change rate value, it can ensure that the detection module accurately determines that the 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 rate and the standard open-circuit voltage change rate value), and can also avoid the misjudgment that the internal short circuit has occurred in the cascade utilization battery 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 rate and the standard open-circuit voltage change rate value), which can effectively improve the accuracy of the detection module in judging whether the internal short circuit has occurred in the cascade utilization battery and reduce the occurrence of misjudgment.

[0022] Furthermore, the several times is four times.

[0023] According to the second-use battery fault diagnosis method provided by the present invention, the present invention also provides a second-use battery fault diagnosis system: comprising a detection module and a collection module arranged in the 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-hand battery has an internal short circuit based on the pre-stored standard open-circuit voltage change rate value and the calculated actual open-circuit voltage change rate value, and to issue an alarm signal when it is determined that the second-hand battery has an internal short circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the implementation mode will be briefly introduced below. Obviously, the drawings described below are only some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1 This is a flow chart of the method for diagnosing faults of second-life batteries in Example 1. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0027] Embodiment 1:

[0028] like Figure 1 As shown, embodiment 1 provides a method for diagnosing a fault of a second-life battery, comprising the following steps: 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-use battery, the acquisition module is used to collect the open circuit voltage information of the second-use battery, and the open circuit voltage information is sent to the detection module; the open circuit voltage information includes a first open circuit voltage value of the second-use battery and a corresponding time value; The detection module is used to calculate the actual open circuit voltage change rate value of the battery in cascade utilization in real time according to the received open circuit voltage information; The detection module determines whether an internal short circuit occurs in the second-use 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 occurs in the second-use battery, the detection module sends an alarm signal; if it is determined that an internal short circuit does not occur in the second-use battery, step 2 is repeated until the charging of the second-use battery is completed.

[0029] By predetermining the standard open-circuit voltage change rate value of the second-use battery under charging conditions, and then using a 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 an internal short circuit occurs in the second-use battery according to the pre-stored standard open-circuit voltage change rate value and the calculated actual open-circuit voltage change rate value, thereby enabling the second-use battery fault diagnosis method provided by the present invention to 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.

[0030] In one embodiment, a method for obtaining a standard open circuit voltage change rate value of a second-life battery under charging conditions includes: Performing capacity-divided charging detection on the second-life battery to obtain the open circuit voltage-time data of the second-life battery during the capacity-divided charging process; Based on the obtained open circuit voltage-time data, the standard open circuit voltage change rate value is calculated.

[0031] There are many methods for calculating the standard open circuit voltage change rate value based on the obtained open circuit voltage-time data, including but not limited to the following methods: Method 1: Methods for calculating the standard open circuit voltage change rate value include: Performing curve fitting on the obtained open circuit voltage-time data based on the least square method to obtain an open circuit voltage-time curve and a corresponding curve function; The obtained curve function is differentiated to obtain the maximum slope absolute value of the open circuit voltage-time curve; The maximum slope absolute value is taken as the standard open circuit voltage change rate value.

[0032] Method 2: Methods for calculating the standard open circuit voltage change rate value include: According to the obtained open circuit voltage-time data, the 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 open circuit voltage change rate calculation value of the cascade utilization battery between each two adjacent detection time nodes is calculated; the maximum value among the absolute values ​​of the obtained open circuit voltage change rate calculation values ​​is used as the standard open circuit voltage change rate value.

[0033] Specifically, in the above method 2, each open circuit voltage change rate calculation value is calculated using the following formula: ;

[0034] 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-utilized 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.

[0035] In one of the embodiments, in the above step 2, during the charging of the second-life battery, the detection module performs multiple real-time calculations of 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.

[0036] Specifically, the actual open circuit voltage change rate value corresponding to any real-time calculation is calculated using the following formula: ;

[0037] 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 T is the time value received by the detection module at the end of the time period corresponding to the mth real-time calculation; 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 mth real-time calculation.

[0038] Preferably, in the present embodiment 1, after the second-use battery is charged for the second preset time, 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 as the time period.

[0039] 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 value 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 an error 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.

[0040] Among them, the above-mentioned first preset time length and second preset time length can also be used in the process of performing capacity-divided charging detection on the battery used in cascade; for example: in the above-mentioned method 2, the first detection time node is the second preset time length of the capacity-divided charging; the first preset time length is separated from the two adjacent detection time nodes.

[0041] Preferably, in this embodiment 1, the first preset time length is thirty seconds, and the second preset time length is three minutes.

[0042] Specifically, in this embodiment 1, the method in which the detection module determines whether an internal short circuit occurs in the second-life battery 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.

[0043] By introducing the two judgment criteria of 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 be ensured 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 it 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 number of 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.

[0044] Specifically, in this embodiment 1, the several times mentioned above is four times.

[0045] Embodiment 2:

[0046] According to the second-use battery fault diagnosis method provided in Example 1, Example 2 provides a second-use battery fault diagnosis system: comprising a detection module and a collection module arranged in the second-use battery; The acquisition module is used to acquire the open circuit voltage information of the cascade 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 cascade utilization battery and the corresponding time value; The detection module pre-stores the standard open circuit voltage change rate value of the second-life battery; The detection module is used to calculate the actual open circuit voltage change rate value of the cascade utilization battery in real time according to the received open circuit voltage information; The detection module is also used to determine whether an internal short circuit occurs in the second-hand battery based on a pre-stored standard open-circuit voltage change rate value and a calculated actual open-circuit voltage change rate value, and to send an alarm signal when it is determined that an internal short circuit occurs in the second-hand battery.

[0047] The second-life battery fault diagnosis method and system provided by the present invention have at least the following technical effects or advantages: 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.

[0048] 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.

[0049] 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.

[0050] 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 failures in cascade utilization, It is 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 based on 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, step 2 is repeated until the charging of the second-use battery is completed.

2. The method for diagnosing a second-life battery fault according to claim 1, Features: 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; The standard open circuit voltage change rate value is calculated based on the obtained open circuit voltage-time data.

3. The method for diagnosing a second-life battery fault according to claim 2, Features: 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.

4. The method for diagnosing a second-life battery fault according to claim 2, Features: 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.

5. The method for diagnosing a second-life battery fault according to claim 4, Features: 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.

6. The method for diagnosing a second-life battery fault according to claim 1, Features: In the step 2, during the charging of the second-life battery, the detection module performs multiple real-time calculations of 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.

7. The method for diagnosing a second-life battery fault according to claim 6, Features: 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 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 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.

8. The method for diagnosing a second-life battery fault according to claim 6, Features: 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.

9. The method for diagnosing a second-life battery fault according to claim 6, Features: 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.

10. A second-life battery fault diagnosis system, Features: 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-hand 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-hand battery has an internal short circuit; The charging pile fault detection system is used to execute the steps in the second-life battery fault diagnosis method as described in any one of claims 1-9.

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