Method for diagnosing the status of power battery high voltage pre-charging circuit

Abstract

The present invention relates to the technical field of power batteries, and in particular to a method for diagnosing the status of a high-voltage pre-charging circuit of a power battery. MCU =R PC / (R PC +R B )*U B , U ACU =R PC / (R PC +R B )*U B The negative pole, pre-charge relay and accessory relay are all adhered; if U MCU =R PC / (R PC +R B )*U B And U ACU is 0, the negative pole and pre-charge relay are bonded but the accessory relay is not bonded; if U MCU , U ACU If both are 0, the BMS will close the negative relay. MCU Gradually getting bigger and U ACU is 0, the pre-charge relay is stuck and the accessory relay is not stuck; if U MCU with U ACU Both gradually increase and are equal at the same time, then the pre-charge and accessory relays are both stuck; if U MCU , U ACU If both are 0, it means that the pre-charge relay is not sticky, and the BMS pulls in the pre-charge relay. ACU becomes larger, it indicates that the accessory relay is sticking; if U ACU If it is 0, the accessory relay is not stuck. This method performs a more comprehensive diagnosis of the pre-charging circuit including the status of the pre-charging relay and the accessory relay, and the pre-charging circuit status diagnosis is more comprehensive and has higher safety.

Description

Technical Field

[0001] The present invention relates to the technical field of power batteries, and in particular to a method for diagnosing the state of a high-voltage pre-charging circuit of a power battery. Background Art

[0002] The power battery is the energy unit of electric vehicles. In actual application, a series of high-voltage power-on operations are required to control the high-voltage relay to execute the action so that the electrical energy can be safely supplied to the on-board electrical load.

[0003] Figure 1 This is a common high-voltage circuit diagram of a power battery. If the power battery directly energizes the positive and negative relays and accessory relays to supply power to the relevant on-board electrical loads, the voltage of the power battery is more than 300 volts. According to the capacitive characteristics of the relevant electrical loads, the moment the relay is energized, the capacitance voltage of the electrical load is 0. In this way, the entire high-voltage circuit is equivalent to a short circuit, and the circuit current is extremely large, causing the high-voltage relay to stick and causing vehicle safety. Based on this, the power battery high-voltage circuit must have a pre-charging circuit, and the power battery must be pre-charged before the high voltage is powered on. Therefore, it is very necessary to diagnose the status of the pre-charging circuit during pre-charging.

[0004] The Chinese patent application with publication number CN109398152A proposes a pre-charge circuit diagnosis method. Its technical solution is to directly close the pre-charge relay after the BMS wakes up, and judge the power battery voltage and the MCU side terminal voltage within 1s. If the MCU side terminal voltage does not increase, it is determined that the pre-charge relay fails to close. If the voltage difference between the power battery voltage and the MCU side terminal voltage is less than 8V, it is determined that the negative pole relay is stuck. When the MCU side terminal voltage increases and the voltage difference between the power battery voltage and the MCU side terminal voltage is not less than 8V, the BM S then attracts the negative pole and pre-charging relay, and detects the MCU side terminal voltage and bus current after 100ms. If the MCU side terminal voltage is less than 30V and the bus current is 0, it is judged as a pre-charging short circuit. If the MCU side terminal voltage is less than 30V and the bus current is not 0, it is judged as a negative pole relay closing failure. If the MCU side terminal voltage is greater than 30V, the voltage difference between the power battery voltage and the MCU side terminal voltage is less than 8V, and the running time is within 1s, the pre-charging circuit is normal, the pre-charging process is OK, and the pre-charging is completed. If the running time exceeds 1s, it is judged as a pre-charging timeout.

[0005] Although this technical solution performs some relevant diagnosis on the pre-charging circuit, it does not diagnose the status of the pre-charging relay and accessory relay on the pre-charging circuit. Its diagnosis of the pre-charging circuit status is rather one-sided and still poses certain safety risks. Summary of the invention

[0006] The purpose of the present invention is to address the defects of the prior art and provide a method for diagnosing the status of a high-voltage pre-charging circuit of a power battery. The method performs a more comprehensive diagnosis of the pre-charging circuit, including the status of the pre-charging relay and the accessory relay. The pre-charging circuit status diagnosis is more comprehensive and safer.

[0007] The method for diagnosing the state of a power battery high-voltage pre-charging circuit of the present invention has the following technical solutions:

[0008] After BMS wakes up, detect the voltage U at the MCU terminal MCU And the accessory terminal voltage U ACU and the real-time voltage U B Compare, if U MCU =R PC / (R PC +R B )*U B , U ACU =R PC / (R PC +R B )*U B This indicates that the negative electrode, pre-charge relay and accessory relay are all adhered; if U MCU =R PC / (R PC +R B )*U B And U ACU If U is 0, it means that the negative pole and pre-charge relay are adhered but the accessory relay is not adhered; MCU , U ACU If both are 0, proceed to the next step of diagnosis;

[0009] BMS attracts the negative relay, if U MCU Gradually getting bigger and U ACU If U is 0, it means that the pre-charge relay is stuck and the accessory relay is not stuck; MCU with U ACU Both gradually increase and are equal at the same time, indicating that the pre-charge and accessory relays are both stuck; if U MCU , U ACU If both are 0, it means that the pre-charge relay is not stuck, and the next step of diagnosis is carried out;

[0010] BMS pulls in the pre-charge relay, if U ACU becomes larger, it indicates that the accessory relay is sticking; if U ACU If it is 0, it means that the accessory relay is not stuck;

[0011] Among them, R PC is the pre-charge resistor value, R B It is the real-time internal resistance of the power battery.

[0012] Through the above judgment process, the method realizes the judgment of the adhesion state of the pre-charge relay and the accessory relay, and its diagnosis process is more comprehensive and the safety is higher.

[0013] Preferably, if after the BMS closes the pre-charge relay, U ACU is 0, it further includes:

[0014] The BMS closes the accessory relay, starts pre-charging the high-voltage circuit of the power battery, and starts timing the pre-charge time t;

[0015] If when t reaches the first set time threshold N, the MCU terminal voltage U MCU,NR <the theoretical value of the MCU terminal voltage at time N U MCU,NT , it indicates that the pre-charge circuit is abnormal.

[0016] Preferably, if the pre-charge circuit is abnormal, it further includes:

[0017] If the current of the pre-charge circuit is always 0 within the time interval when t is less than or equal to N, it indicates that there is an open-circuit fault in the pre-charge circuit;

[0018] If the current I of the pre-charge circuit is greater than or equal to U B / (R PC +R B ) within the time interval when t is less than or equal to N, it indicates that there is a short-circuit fault in the pre-charge circuit.

[0019] Through the above technical solutions, the diagnosis of pre-charge short-circuit and pre-charge open-circuit faults is realized, and its diagnosis process is more comprehensive and the safety is higher.

[0020] Preferably, it further includes:

[0021] If when t reaches the second set time threshold K, the MCU terminal voltage U MCU,NR <the theoretical value of the MCU terminal voltage at time K U MCU,KT , it indicates that there is a pre-charge timeout fault in the pre-charge circuit;

[0022] Or when the MCU terminal voltage U MCU =U MCU,KT , if the pre-charge time t>K, it indicates that there is a pre-charge timeout fault in the pre-charge circuit.

[0023] Through the above technical solutions, the pre-charge timeout node is accurately defined according to the load capacitance specification of the high-voltage circuit of the power battery, and the pre-charge timeout judgment can be made more accurately.

[0024] Preferably, if there is an open-circuit fault in the pre-charge circuit, the cause of the open-circuit fault in the pre-charge circuit is further analyzed, including:

[0025] Check whether the BMS has a high-voltage interlock fault. If so, it indicates that the cause of the circuit breaker fault in the pre-charging circuit is that the high-voltage wiring harness of the pre-charging circuit is not connected or disconnected. Otherwise, it indicates that the high-voltage wiring harness of the pre-charging circuit is in normal condition.

[0026] Check whether the BMS receives the CAN message from the MCU. If so, it indicates that the MCU wake-up work has been completed. Otherwise, it indicates that the cause of the circuit breaker failure in the pre-charging circuit is that the MCU wake-up work has not been completed.

[0027] If the high-voltage harness of the pre-charging circuit is in normal condition and the MCU wake-up work has been completed, it indicates that the cause of the short circuit fault in the pre-charging circuit is the open circuit of the pre-charging resistor.

[0028] Preferably, if the pre-filling circuit has a short circuit fault, further analyzing the cause of the pre-filling circuit short circuit fault includes:

[0029] Check the matching of the positive and negative poles of the high-voltage wiring harness and the positive and negative poles of the power battery. If they match, it indicates that the high-voltage wiring harness is normal. Otherwise, it indicates that the cause of the short circuit fault in the pre-charging circuit is the short circuit of the high-voltage wiring harness.

[0030] Disconnect the accessory relay. If the pre-charge short-circuit fault of the pre-charge circuit is eliminated, it indicates that the cause of the short-circuit fault in the pre-charge circuit is the accessory short-circuit;

[0031] If the high-voltage wiring harness is normal and the accessories are not short-circuited, it indicates that the cause of the short-circuit fault in the pre-charge circuit is the MCU short circuit.

[0032] Through the above technical solution, the pre-charge short circuit and pre-charge open circuit faults were further analyzed, and the causes of the pre-charge short circuit and pre-charge open circuit could be specifically identified, which helps to quickly eliminate the faults.

[0033] The beneficial effects of the present invention are as follows: the method realizes the judgment of the adhesion state of the negative electrode, the pre-charging relay, and the accessory relay, detects abnormal conditions of the pre-charging process such as pre-charging open circuit, pre-charging short circuit, and pre-charging timeout, and further diagnoses and analyzes the pre-charging open circuit and pre-charging short circuit faults. A more comprehensive diagnosis and analysis of the pre-charging circuit is carried out, which improves the diagnostic efficiency and ensures the high-voltage safety of the power battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a common schematic diagram of a power battery high voltage circuit;

[0035] Figure 2 This is a flow chart for diagnosing the adhesion status of the negative relay of the pre-charging circuit, the pre-charging relay and the accessory relay of the present invention;

[0036] Figure 3 This is a flow chart of the fault diagnosis of pre-charging circuit open circuit, pre-charging short circuit and pre-charging timeout of the pre-charging circuit of the present invention;

[0037] Figure 4 It is a schematic diagram of the process of troubleshooting the cause of the pre-charging circuit breaker failure of the present invention;

[0038] Figure 5 This is a schematic diagram of the process for troubleshooting the cause of a pre-charging short circuit failure in the pre-charging circuit of the present invention. DETAILED DESCRIPTION

[0039] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0040] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0041] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0042] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0043] As used in the specification and appended claims of this application, the term "if" can be interpreted as "when" or "uponce" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "uponce it is determined" or "in response to determining" or "uponce [described condition or event] is detected" or "in response to detecting [described condition or event]", depending on the context.

[0044] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0045] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways. "Multiple" means "two or more".

[0046] Embodiment 1

[0047] Figure 2 Shows a preferred embodiment of the present application ( Figure 2 The figure shows a schematic flow chart of the diagnosis of the adhesion state of the negative relay, pre-charging relay and accessory relay of the pre-charging circuit in a method for diagnosing the state of the high-voltage pre-charging circuit of a power battery provided in the first embodiment of the present application. For the convenience of explanation, only the part related to the present embodiment is shown, which is described in detail as follows:

[0048] After BMS wakes up, detect the voltage U at the MCU terminal MCU And the accessory terminal voltage U ACU and the real-time voltage U B Compare, if U MCU =R PC / (R PC +R B )*U B , U ACU =R PC / (R PC +R B )*U B This indicates that the negative electrode, pre-charge relay and accessory relay are all adhered. MCU =R PC / (R PC +R B )*U B , U ACU If it is 0, it means that the negative electrode is adhered to the pre-charge relay, but the accessory relay is not adhered. When the relay is adhered, the BMS will report the relay adhesion fault and notify the replacement. PC is the pre-charge resistor value, R B is the real-time internal resistance of the power battery, U MCU , U ACU When both are 0, proceed to the next step of diagnosis.

[0049] BMS pulls in the negative relay, if U MCUGradually getting bigger, U ACU If it is 0, it means that the pre-charge relay is stuck and the accessory relay is not stuck. MCU with U ACU If both become larger and equal at the same time, it means that the pre-charge and accessory relays are both stuck. MCU , U ACU If both are 0, it means that the pre-charge relay is not stuck and proceed to the next step of diagnosis.

[0050] BMS pulls in the pre-charge relay, if U ACU If the U ACU If it is 0, it means that the accessory relay is not stuck and proceed to the next step of diagnosis.

[0051] Embodiment 2

[0052] Figure 3 Shows a preferred embodiment of the present application ( Figure 3 The figure shows a flow chart of the diagnosis of pre-charging circuit open circuit, pre-charging short circuit and pre-charging timeout fault in a method for diagnosing the state of a high-voltage pre-charging circuit of a power battery provided in the first embodiment of the present application. For the convenience of explanation, only the part related to the present embodiment is shown, which is described in detail as follows:

[0053] The BMS pulls in the accessory relay and starts timing t. According to the Kirchhoff circuit principle, the capacitor is charged. At the beginning, the voltage across the capacitor is 0 and the current in the circuit is U / R. At time t, the voltage across the capacitor is U t =U*(1-e -t / RC ), the current I at time t t =(UU t ) / R, U is the external limit voltage, R is the resistance of the charging circuit, and C is the capacitance value. When charging, the voltage across the capacitor increases continuously and the current decreases continuously.

[0054] When t = Nms (N is less than 50), record the MCU terminal voltage U at this time MCU,NR According to Kirchhoff circuit principle, the external limit voltage is the real-time voltage U of the power battery. B The resistance of the charging circuit is the sum of the pre-charging resistance and the real-time internal resistance of the power battery. The capacitance is the sum of the capacitances of MCU, DCDC, AC, and OBC. The theoretical voltage value of the MCU terminal at time N is U MCU,NT For U B *(1-e -(N / ((R PC +R B )*(C MCU +C DCDC +C AC+C OBC ))) ). If U MCU,NR MCU,NT If the current of the pre-charging circuit is always 0 during the N time interval, it indicates that there is a circuit breaker fault in the pre-charging circuit. If the current I of the pre-charging circuit is greater than or equal to U B / (R PC +R B ) indicates that there is a short circuit fault in the pre-charge circuit.

[0055] Normally, the capacitor is fully charged when the terminal voltage of the capacitor reaches 95% of the external voltage. Specifically, for the power battery pre-charging circuit, the condition for the pre-charging process to be completed is that the terminal voltage on the MCU side is 95% of the real-time voltage of the power battery. According to the Kirchhoff circuit principle, U MCU,KT =U B *(1-e -(K / ((R PC +R B )*(C MCU +C DCDC +C AC +C OBC ))) ), U MCU,KT =95%*U B The above two formulas can be used to calculate the time for pre-charging to be completed: K = 3*(R PC +R B )*(C MCU +C DCDC +C AC +C OBC ). When the pre-charge time t = K, detect the MCU terminal voltage U MCU,NR , U MCU,NR MCU,KT , or when the MCU terminal voltage U MCU =U MCU,KT When the pre-charging time t is recorded, if t>K, it indicates that the pre-charging circuit has a pre-charging timeout fault.

[0056] During the pre-charging process, the terminal voltage on the MCU side shows an increasing trend, which is in line with the Kirchhoff circuit principle. If there are no abnormal conditions such as pre-charging open circuit, pre-charging short circuit and pre-charging timeout, it can be diagnosed that the high-voltage pre-charging circuit of the power battery is normal, and the high-voltage circuit of the power battery can normally perform the next high-voltage power-on operation.

[0057] Embodiment 3

[0058] Figure 4 Shows a preferred embodiment of the present application (​​ Figure 4 The flowchart of troubleshooting the cause of a pre-charging circuit breaker fault in a power battery high-voltage pre-charging circuit state diagnosis method provided in the first embodiment of the present application is shown. For ease of explanation, only the part related to this embodiment is shown, which is described in detail as follows:

[0059] There are three main possible reasons for the pre-charging circuit to have a pre-charging circuit breaker fault, namely reason ① the high-voltage wiring harness of the pre-charging circuit is virtual or disconnected, reason ② the MCU, DCDC, AC, and OBC are not awakened, and reason ③ the pre-charging resistor is open. For reason ①, the high-voltage wiring harness status of the pre-charging circuit is checked and analyzed as follows: if the high-voltage wiring harness is virtual or disconnected, the high-voltage interlock is abnormal, so check whether the BMS has a high-voltage interlock fault. If there is a high-voltage interlock fault, it indicates that the high-voltage wiring harness of the pre-charging circuit is virtual or disconnected, otherwise the high-voltage wiring harness of the pre-charging circuit is normal. For reason ②, the MCU, DCDC, AC, and OBC wake-up status is checked and analyzed as follows: if the MCU is awakened, there will be a CAN communication message, so check whether the BMS has received the CAN message of the MCU, etc. If there is a CAN message, it indicates that the MCU, etc. has been awakened, otherwise the MCU, etc. has not been awakened. If the first two reasons have been ruled out, the cause of the pre-charging circuit breaker is the open circuit of the pre-charging resistor.

[0060] Embodiment 4

[0061] Figure 5 Shows a preferred embodiment of the present application ( Figure 5 The flowchart of troubleshooting the cause of a pre-charging circuit breaker fault in a power battery high-voltage pre-charging circuit state diagnosis method provided in the first embodiment of the present application is shown. For ease of explanation, only the part related to this embodiment is shown, which is described in detail as follows:

[0062] There are three main possible reasons for the pre-charge short circuit failure in the pre-charge circuit, namely reason ① short circuit of the high-voltage wiring harness of the pre-charge circuit, reason ② short circuit of accessories (DCDC, AC, OBC), and reason ③ short circuit of MCU. For reason ①, the short circuit of the high-voltage wiring harness is caused by the reverse connection of the positive and negative terminals, so the troubleshooting method is to match the positive and negative terminals of the high-voltage wiring harness with the positive and negative terminals of the power battery. If the two are consistent, it indicates that the high-voltage wiring harness is normal, otherwise the high-voltage wiring harness is short-circuited. For reason ②, the troubleshooting method is: disconnect the accessory relay. If the pre-charge short circuit failure of the pre-charge circuit is eliminated, it indicates that the pre-charge short circuit failure is caused by the accessory short circuit. If the first two reasons have been eliminated, the cause of the pre-charge short circuit in the pre-charge circuit is the MCU short circuit.

[0063] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of protection of the present disclosure. The attached method claims present the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy described.

[0064] In the above detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are clearly stated in each claim. On the contrary, as reflected in the appended claims, the invention is in a state of having less than all the features of the disclosed individual embodiments. Therefore, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0065] The disclosed embodiments are described above to enable any person skilled in the art to implement or use the present invention. Various modifications of these embodiments are obvious to those skilled in the art, and the general principles defined herein may also be applied to other embodiments without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0066] The above description includes examples of one or more embodiments. Of course, it is impossible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it should be recognized by those skilled in the art that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the word is covered in a manner similar to the term "including", just as "including," is explained as a transitional word in the claims. In addition, any term "or" used in the specification of the claims is intended to mean "non-exclusive or".

[0067] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for diagnosing the state of a power battery high-voltage pre-charging circuit, characterized in that: include After BMS wakes up, detect the voltage U at the MCU terminal MCU And the accessory terminal voltage U ACU and the real-time voltage U B Compare, if U MCU =R PC / (R PC +R B )*U B , U ACU =R PC / (R PC +R B )*U B This indicates that the negative electrode, pre-charge relay and accessory relay are all adhered; if U MCU =R PC / (R PC +R B )*U B AndU ACU If U is 0, it means that the negative pole and pre-charge relay are adhered but the accessory relay is not adhered; MCU , U ACU If both are 0, proceed to the next step of diagnosis; BMS attracts the negative relay, if U MCU Gradually getting bigger and U ACU If U is 0, it means that the pre-charge relay is stuck and the accessory relay is not stuck; MCU with U ACU Both gradually increase and are equal at the same time, indicating that the pre-charge and accessory relays are both stuck; if U MCU , U ACU If both are 0, it means that the pre-charge relay is not stuck, and the next step of diagnosis is carried out; BMS pulls in the pre-charge relay, if U ACU becomes larger, it indicates that the accessory relay is sticking; if U ACU If it is 0, it means that the accessory relay is not stuck; Among them, R PC is the pre-charge resistor value, R B Real-time internal resistance of the power battery; If the BMS pulls in the pre-charge relay, U ACU is 0, it also includes: The BMS pulls in the accessory relay, starts precharging the power battery high-voltage circuit, and starts counting the precharging time t; When t reaches the first set time threshold N, the voltage U at the MCU side MCU,NR <The theoretical value of the voltage at the MCU side at time N, U MCU,NT , it indicates that the pre-charge circuit is abnormal; If the pre-charging circuit is abnormal, the method further includes: If the current of the pre-charging circuit is always 0 during the time interval when t is less than or equal to N, it indicates that there is a circuit breaker fault in the pre-charging circuit; If t is less than or equal to N, the current I of the pre-charge circuit is greater than or equal to U B / (R PC +R B ), it indicates that there is a short circuit fault in the pre-charging circuit; Also includes: When t reaches the second set time threshold K, the voltage U at the MCU side MCU,NR <The theoretical value of the voltage at the MCU side at time K is U MCU,KT , indicating that there is a pre-charge timeout fault in the pre-charge circuit; Or when the MCU terminal voltage U MCU =U MCU,KT If the pre-charging time t>K, it means that the pre-charging circuit has a pre-charging timeout fault.

2. The method for diagnosing the state of a power battery high-voltage pre-charging circuit according to claim 1, characterized in that: If the pre-charging circuit has a circuit breaker fault, further analyzing the cause of the pre-charging circuit breaker fault includes: Check whether the BMS has a high-voltage interlock fault. If so, it indicates that the cause of the circuit breaker fault in the pre-charging circuit is that the high-voltage wiring harness of the pre-charging circuit is not connected or disconnected. Otherwise, it indicates that the high-voltage wiring harness of the pre-charging circuit is in normal condition. Check whether the BMS receives the CAN message from the MCU. If so, it indicates that the MCU wake-up work has been completed. Otherwise, it indicates that the cause of the circuit breaker failure in the pre-charging circuit is that the MCU wake-up work has not been completed. If the high-voltage harness of the pre-charging circuit is in normal condition and the MCU wake-up work has been completed, it indicates that the cause of the circuit breaker failure in the pre-charging circuit is the open circuit of the pre-charging resistor.

3. The method for diagnosing the state of a power battery high-voltage pre-charging circuit according to claim 1, characterized in that: If the pre-charging circuit has a short circuit fault, further analyzing the cause of the pre-charging circuit short circuit fault includes: Check the matching of the positive and negative poles of the high-voltage wiring harness and the positive and negative poles of the power battery. If they match, it indicates that the high-voltage wiring harness is normal. Otherwise, it indicates that the cause of the short circuit fault in the pre-charging circuit is the short circuit of the high-voltage wiring harness. Disconnect the accessory relay. If the pre-charge short-circuit fault of the pre-charge circuit is eliminated, it indicates that the cause of the short-circuit fault in the pre-charge circuit is the accessory short-circuit; If the high-voltage wiring harness is normal and the accessories are not short-circuited, it indicates that the cause of the short-circuit fault in the pre-charge circuit is the MCU short circuit.

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