Relay Diagnosis Device and Method for In-vehicle Lithium Battery System

Abstract

The present invention relates to the technical field of relay diagnosis, and discloses a relay diagnosis device for an in-vehicle lithium battery system, including a relay K1, a detection circuit, a voltage dividing circuit S1, a voltage dividing circuit S2, and an MCU. The first end of the relay K1 is connected to the positive extreme of the battery pack, the second end of the relay K1 is connected to KL30, the detection circuit is connected in parallel across the two ends of the relay K1, the detection circuit is connected to the MCU, one end of the voltage dividing circuit S1 is connected to the detection circuit, the other end of the voltage dividing circuit S1 is connected to the MCU, one end of the voltage dividing circuit S2 is connected to KL30, the other end of the voltage dividing circuit S2 is connected to the MCU, the relay K1 is connected to the MCU, the MCU is communicatively connected to the VCU, and the negative extreme of the battery pack is connected to KL31. The relay diagnosis device of the present invention can greatly increase the effectiveness of relay state diagnosis by adding a detection circuit across the relay contacts, and the overall cost is relatively low.

Description

Technical Field

[0001] The present invention relates to the technical field of relay diagnosis, and particularly to a relay diagnosis device and method for an in-vehicle lithium battery system. Background Art

[0002] In the fields of in-vehicle energy storage, start-stop batteries, etc., with the development of technology and the demand for electric energy, due to the excellent characteristics of lithium-ion batteries such as high energy density, small volume, high cycle life, and low self-discharge rate, the scale of the corresponding in-vehicle lithium battery system has gradually increased. In order to ensure the safety and stability of the lithium battery system, a battery management system (BMS) is usually equipped in the battery pack. The battery management system monitors the working state of the battery and controls the relays in the charge and discharge circuits of the battery pack to ensure that the battery pack is always in a safe working state. Since the relay may experience adhesive failure due to unexpected short circuits, high voltages, large currents, etc., there are potential safety hazards for circuit protection. When the circuit experiences overheating, overcurrent, overvoltage, short circuit, etc., the relay cannot be normally cut off, resulting in system failures and even personal hazards. Therefore, it is necessary to diagnose the state of the relay.

[0003] In the prior art for diagnosing in-vehicle relays, the commonly used method is to judge by detecting the pressure difference inside and outside the relay or detecting the resistance value of the coil and the normally closed contact. There are disadvantages such as low detection accuracy, complex circuit, high cost, and easy misjudgment. Moreover, the relay diagnosis in the parking state is not considered, and the failure state of the relay during the next driving process cannot be judged, resulting in system risks. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a relay diagnosis device and method for an in-vehicle lithium battery system. By adding a detection circuit at both ends of the relay contact, the effectiveness of relay state diagnosis can be greatly increased, and the diagnosis can be carried out in the parking state, which can provide guarantee for the next vehicle operation and has a relatively low overall cost.

[0005] To achieve the above object, the present invention provides a relay diagnostic device for an in-vehicle lithium battery system, including a relay K1, a detection circuit, a voltage dividing circuit S1, a voltage dividing circuit S2, and an MCU (Micro Controller Unit). The relay K1 is arranged on the positive main circuit of the lithium battery system. The first end of the relay K1 is connected to the positive terminal of the battery pack, the second end of the relay K1 is connected to KL30, the detection circuit is connected in parallel at both ends of the relay K1, the detection circuit is connected to the MCU, one end of the voltage dividing circuit S1 is connected to the detection circuit, the other end of the voltage dividing circuit S1 is connected to the MCU, one end of the voltage dividing circuit S2 is connected to KL30, the other end of the voltage dividing circuit S2 is connected to the MCU, the relay K1 is connected to the MCU, the MCU is communicatively connected to a VCU (Vehicle Control Unit), and the negative terminal of the battery pack is connected to KL31.

[0006] A further setting of the present invention is that: the detection circuit includes a MOS transistor Q1 and a diode D1. The source electrode of the MOS transistor Q1 is connected to the first end of the relay K1. The drain electrode of the MOS transistor Q1 is connected in series with the anode of the diode D1. The cathode of the diode D1 is connected to KL30. The gate electrode of the MOS transistor Q1 is connected to the drive signal pin of the MCU. One end of the voltage dividing circuit S1 is connected to the drain electrode of the MOS transistor Q1 for collecting the voltage of the MOS transistor Q1.

[0007] As a further setting of the present invention, it further includes a voltage dividing circuit S3. One end of the voltage dividing circuit S3 is connected to the positive terminal of the battery pack, and the other end is connected to the MCU. The voltage dividing circuit S3 is used for collecting the voltage at the positive terminal of the battery pack.

[0008] As a further setting of the present invention, the MOS transistor Q1 is a P-channel MOSFET.

[0009] As a further setting of the present invention, the diode D1 is a rectifier diode.

[0010] As a further setting of the present invention, the relay K1 is a magnetic latching relay.

[0011] In addition, to achieve the above object, the present invention also proposes a relay diagnosis method for an in-vehicle lithium battery system of the above relay diagnostic device for an in-vehicle lithium battery system. The method includes:

[0012] In the parking state, the VCU sends a parking signal to the BMS;

[0013] After the BMS receives the parking signal, it controls the relay K1 to turn off through the MCU, and at the same time controls the MOS transistor Q1 to conduct through the MCU;

[0014] The voltage divider circuit S1 collects the voltage V of the MOS transistor Q1 S1 , and outputs it to the MCU;

[0015] The voltage divider circuit S2 collects the voltage V of KL30 S2 , and outputs it to the MCU;

[0016] The MCU diagnoses whether the state of the relay is normal according to the obtained voltage V S1 and the voltage V S2 .

[0017] As a further setting of the present invention, the step of the MCU diagnosing whether the working state of the relay is normal according to the obtained voltage V S1 and the voltage V S2 specifically includes:

[0018] If the MCU detects that |V S2 -V S1 |>X and V S1 is within the normal voltage range, it means that there is power supply outside the battery, and the relay K1 is disconnected, and the VCU is reported that the state of the relay K1 is normal;

[0019] If the MCU detects that 0.3V < |V S2 -V S1 | < X, V S1 is within the normal voltage range, and V S1 -V S2 ≈V D1 , it means that there is no power supply outside the battery, and the relay K1 is disconnected, and the VCU is reported that the state of the relay K1 is normal;

[0020] If the MCU detects that |V S2 -V S1 | < 0.3V, it means that the relay K1 has not executed the disconnection instruction, and it is judged as a sticking fault of the relay K1, and the VCU is reported with the sticking fault of the relay K1;

[0021] Among them, X is corrected according to the difference between the actual charger voltage and the open-circuit voltage of the fully charged battery, and V D1 is the voltage drop across the diode D1.

[0022] As a further setting of the present invention, after the step of the MCU diagnosing whether the working state of the relay is normal according to the obtained voltage V S1 and the voltage V S2 , the method further includes:

[0023] The voltage divider circuit S3 collects the voltage V at the positive terminal of the battery pack S3 and outputs it to the MCU;

[0024] Based on the obtained voltage V, the MCU S1 and the voltage V S2 as well as the voltage V S3 judges whether the working state of the detection circuit is abnormal.

[0025] As a further setting of the present invention, the step in which the MCU judges whether the working state of the detection circuit is abnormal based on the obtained voltage V S1 and the voltage V S2 as well as the voltage V S3 specifically includes:

[0026] If the MCU detects that |V S1 | < 0.3V, |V S2 | < 0.3V, and V S3 = V B+ , it indicates that there is no external power supply for the battery, the relay K1 normally executes the turn-off instruction, but the detection circuit is abnormal, and the VCU relay detection circuit abnormality is reported;

[0027] If it is detected that |V S1 | < 0.3V, and it is detected that |V S3 - V S2 | > X, it indicates that there is an external power supply for the battery, the relay K1 normally executes the turn-off instruction, but the detection circuit is abnormal, and the VCU relay detection circuit abnormality is reported;

[0028] Among them, V B+ is the voltage value at the positive terminal of the battery pack.

[0029] The beneficial effects of the present invention are:

[0030] 1. By adding a detection circuit at both ends of the relay contact to unidirectionally detect the relay state after the relay is turned off, the effectiveness of relay diagnosis can be greatly increased. The circuit structure is not only simple, the detection accuracy is relatively high, but also the cost is low;

[0031] 2. The relay diagnosis occurs in the parking state, which can provide guarantee for the next vehicle operation, and the specific diagnosis time and response strategy can be analyzed and processed according to the actual working conditions;

[0032] 3. During the diagnosis, the circuit is not affected by the external power supply, which can effectively ensure the stability and safety of the BMS system during the diagnosis. Description of the Drawings

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0034] Figure 1 is a schematic structural diagram of the first embodiment of a relay diagnostic device for an in-vehicle lithium battery system according to the present invention;

[0035] Figure 2 is a schematic structural diagram of the second embodiment of a relay diagnostic device for an in-vehicle lithium battery system according to the present invention;

[0036] Figure 3 is a schematic flowchart of the first embodiment of a relay diagnostic method for an in-vehicle lithium battery system according to the present invention;

[0037] Figure 4 is a schematic flowchart of the second embodiment of a relay diagnostic method for an in-vehicle lithium battery system according to the present invention;

[0038] Figure 5 is a schematic circuit timing diagram of a relay diagnostic device for an in-vehicle lithium battery system according to the present invention. Specific Embodiments

[0039] The following will clearly and completely describe the technical solutions of the present invention in combination with specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0040] See Figure 1 , an embodiment of the present invention provides a relay diagnostic device for an in-vehicle lithium battery system, including a relay K1, a detection circuit, a voltage dividing circuit S1, a voltage dividing circuit S2, and an MCU (Micro Controller Unit). The relay K1 is arranged on the positive main circuit of the lithium battery system. The first end of the relay K1 is connected to the positive terminal of the battery pack, the second end of the relay K1 is connected to KL30. The detection circuit is connected in parallel at both ends of the relay K1 and is connected to the MCU. One end of the voltage dividing circuit S1 is connected to the detection circuit, the other end of the voltage dividing circuit S1 is connected to the MCU. One end of the voltage dividing circuit S2 is connected to KL30, the other end of the voltage dividing circuit S2 is connected to the MCU. The voltage dividing circuit S2 is used to collect the voltage V of KL30 S2, the relay K1 is connected to the MCU, and the MCU is communicatively connected to the VCU (Vehicle Control Unit). The VCU is usually connected to the MCU through communication methods such as CAN and LIN. The negative terminal of the battery pack is connected to KL31. It should be noted that KL30 and KL31 are respectively the power supply wiring of the vehicle. KL30 is the power supply for the ECU, connected to the vehicle-mounted battery to provide the operating voltage of the ECU. KL31 is the grounding source of the ECU, and the K31 signal is connected to the common grounding terminal of the vehicle. The relay diagnostic device of this embodiment can greatly increase the effectiveness of relay diagnosis, enhance the stability and safety of the vehicle-mounted lithium battery system, with a simple circuit structure, high detection accuracy and low cost by adding a detection circuit at both ends of the contacts of the relay K1 to unidirectionally detect the state after the relay is turned off.

[0041] See Figure 2 , based on the above first embodiment, a second embodiment of the relay diagnostic device for the vehicle-mounted lithium battery system of the present invention is proposed. In this embodiment, the detection circuit includes an MOS transistor Q1 and a diode D1. The MOS transistor Q1 and the diode D1 are connected in series to form a bypass, which is connected in parallel across the main circuit relay K1. The source S of the MOS transistor Q1 is connected to the first end of the relay K1. The drain D of the MOS transistor Q1 is connected in series with the anode of the diode D1. The cathode of the diode D1 is connected to KL30. The gate G of the MOS transistor Q1 is connected to the drive signal pin of the MCU. One end of the voltage division circuit S1 is connected to the drain D of the MOS transistor Q1 for collecting the voltage V of the MOS transistor Q1 S1 . The MOS transistor Q1 is a P-channel MOSFET transistor, and the diode D1 is a rectifier diode with its cathode connected to KL30 for freewheeling and reverse protection. The relay K1 is a magnetic latching relay. It also includes a voltage division circuit S3. One end of the voltage division circuit S3 is connected to the positive terminal of the battery pack, and the other end is connected to the MCU. The voltage division circuit S3 is used to collect the voltage V of the positive terminal of the battery pack S3 . The relay state diagnostic detection circuit of this embodiment uses the MCU to control its switch Q1 and adds a diode S1 to act as a voltage drop and unidirectional conduction. The MCU collects the diagnostic signals V S1 、V S2 and V S3 . According to the diagnostic signals V S1 、V S2 and V S3 , the state after the relay is turned off and driven can be judged in the case of parking, which can provide guarantee for the next vehicle operation. The circuit is not affected by external power supply during diagnosis, which can effectively guarantee the stability and safety of the diagnostic device BMS system. At the same time, the MCU can also determine according to the detected diagnostic signals V S1 、V S2 and V S3Judge the working state of the detection circuit to ensure that the detection circuit is always in a normal working state, effectively diagnose the relay in the parking state, and when the detection circuit is abnormal, it can report to the VCU in time for processing, providing guarantee for the vehicle operation safety.

[0042] Based on the above relay diagnosis device for an in-vehicle lithium battery system, the present invention also provides a relay diagnosis method for an in-vehicle lithium battery system. Refer to Figure 3 , Figure 3 which is a schematic flowchart of the first embodiment of the relay diagnosis method for the in-vehicle lithium battery system of the present invention. In this embodiment, the relay diagnosis method for the in-vehicle lithium battery system includes the following steps:

[0043] S1. In the parking state, the VCU sends a parking signal to the BMS;

[0044] S2. After receiving the parking signal, the BMS controls the relay K1 to turn off through the MCU, and at the same time controls the MOS transistor Q1 to conduct through the MCU;

[0045] S3. The voltage divider circuit S1 collects the voltage V S1 of the MOS transistor Q1 and outputs it to the MCU;

[0046] S4. The voltage divider circuit S2 collects the voltage V S2 of KL30 and outputs it to the MCU;

[0047] S5. The MCU diagnoses whether the state of the relay is normal according to the obtained voltage V S1 and voltage V S2 .

[0048] In specific implementation, step S5 in this embodiment includes:

[0049] S51. If the MCU detects that |V S2 -V S1 |>X and V S1 is within the normal voltage range, it indicates that there is power supply outside the battery and the relay K1 is disconnected, and reports to the VCU that the state of the relay K1 is normal;

[0050] S52. If the MCU detects that 0.3V < |V S2 -V S1 | < X, V S1 is within the normal voltage range, and V S1 -V S2 ≈V D1 , it indicates that there is no power supply outside the battery and the relay K1 is disconnected, and reports to the VCU that the state of the relay K1 is normal;

[0051] S53. If the MCU detects that |V S2 -VS1 If it is less than 0.3V, it indicates that the relay K1 has not executed the disconnection instruction, and it is determined that the relay K1 is stuck, and the VCU is reported with the stuck fault of the relay K1;

[0052] Among them, X is corrected according to the difference between the actual charger voltage and the open-circuit voltage of the fully charged battery, V D1 is the voltage drop across the diode D1.

[0053] It should be understood that in the relay diagnosis method of the on-vehicle lithium battery system in this embodiment, the voltage V of the MOS transistor Q1 is collected through the voltage dividing circuit S1 S1 and the voltage V of KL30 is collected through the voltage dividing circuit S2 S2 , and transmitted to the MCU, so that the MCU can judge the state of the relay K1 according to the detected diagnostic signals V S1 and V S2 . When the relay K1 fails, the VCU can be reported in time to provide guarantee for the next operation of the vehicle.

[0054] See Figure 4 , Figure 4 This is a schematic flow chart of the second embodiment of the relay diagnosis method for the on-vehicle lithium battery system of the present invention. Based on the first embodiment of the relay diagnosis method for the on-vehicle lithium battery system described above, after the step S5 of this embodiment, the relay diagnosis method for the on-vehicle lithium battery system further includes:

[0055] S6, the voltage dividing circuit S3 collects the voltage V at the positive terminal of the battery pack S3 , and outputs it to the MCU;

[0056] S7, the MCU judges whether the working state of the detection circuit is abnormal according to the obtained voltage V S1 and the voltage V S2 and the voltage V S3 .

[0057] In specific implementation, the step S7 of this embodiment specifically includes:

[0058] S71, if the MCU detects |V S1 | < 0.3V, |V S2 | < 0.3V, and V S3 = V B+ , it indicates that there is no power supply outside the battery, the relay K1 normally executes the turn-off instruction, but the detection circuit is abnormal, and the VCU is reported with the abnormal relay detection circuit;

[0059] S72, if it is detected that |V S1 | < 0.3V, and it is detected that |V S3 - V S2If |V| > X, it indicates that there is external power supply for the battery, the relay K1 normally executes the turn-off instruction, but the detection circuit is abnormal, and the VCU is reported with an abnormal relay detection circuit;

[0060] Among them, V B+ is the voltage value at the positive extreme of the battery pack.

[0061] It should be understood that for the relay diagnosis method of the on-vehicle lithium battery system in this embodiment, by adding a voltage-dividing circuit S3 to collect the voltage V at the positive extreme of the battery pack S3 and output it to the MCU, so that the MCU can, based on the detected V S1 and V S2 as well as V S3 judge the working state of the detection circuit. When the detection circuit is abnormal, the state of the relay K1 cannot be accurately diagnosed. At this time, the MCU timely reports the abnormal situation of the detection circuit to the VCU for processing, thereby avoiding the failure of diagnosing the state of the relay K1.

[0062] Refer to Figure 5 , Figure 5 , which is the circuit timing schematic diagram of the relay diagnosis device of the on-vehicle lithium battery system of the present invention. Based on Figure 5 the working principle of the present invention is described as follows:

[0063] When the on-vehicle lithium battery is in a parked state, the VCU sends a parking signal to the BMS for a duration of t1. After a time t4, the BMS receives the parking signal and turns off the relay K1 through the MCU. The turn-off signal lasts for a duration of t2. After a time t4 after the relay K1 is turned off, the MCU drives the MOS transistor Q1 to conduct, and the conduction lasts for a duration of t3 + t5;

[0064] 1. After a time t3 after the MOS transistor Q1 conducts, if the MCU detects that |V S2 - V S1 | > X (X is corrected according to the difference between the actual charger voltage and the fully charged battery OCV voltage), and V S1 is within the normal voltage range, it indicates that there is external power supply for the battery and the relay K1 is off, and the VCU is reported with the normal state of the relay K1;

[0065] 2. After a time t3 after the MOS transistor Q1 conducts, if the MCU detects that 0.3V < |V S2 - V S1 | < X, V S1 is within the normal voltage range, and V S1 - V S2 ≈ V D1 (V D1If the voltage drop across diode D1 is (), it indicates that there is no external power supply for the battery, and relay K1 is disconnected. Report that the status of relay K1 in the VCU is normal;

[0066] 3. After time t3 when MOS transistor Q1 is turned on, if the MCU detects |V S2 -V S1 | < 0.3V, it indicates that relay K1 has not executed the disconnection instruction. Judge it as a sticking fault of relay K1 and report the sticking fault of relay K1 in the VCU;

[0067] 4. After time t3 when MOS transistor Q1 is turned on, if the MCU detects |V S1 | < 0.3V, |V S2 | < 0.3V, and V S3 = V B+ , it indicates that there is no external power supply for the battery, relay K1 normally executes the turn-off instruction, but the relay detection circuit is abnormal. Report the abnormality of the relay detection circuit in the VCU;

[0068] 5. After time t3 when MOS transistor Q1 is turned on, if the MCU detects |V S1 | < 0.3V, and detects |V S3 -V S2 | > X, it indicates that there is an external power supply for the battery, relay K1 normally executes the turn-off instruction, but the relay detection circuit is abnormal. Report the abnormality of the relay detection circuit in the VCU.

[0069] The relay diagnosis device and method of the on-vehicle lithium battery system of the present invention can improve the stability and intelligence of the system and provide guarantee for the safety of vehicle operation.

Claims

1. A relay diagnostic device for an in-vehicle lithium battery system, characterized in that: It includes relay K1, a detection circuit, voltage division circuit S1, voltage division circuit S2, and an MCU. The relay K1 is arranged on the main positive circuit of the lithium battery system. The first end of the relay K1 is connected to the positive terminal of the battery pack, the second end of the relay K1 is connected to KL30. The detection circuit is connected in parallel across the two ends of the relay K1 and is connected to the MCU. One end of the voltage division circuit S1 is connected to the detection circuit, and the other end of the voltage division circuit S1 is connected to the MCU. One end of the voltage division circuit S2 is connected to KL30, where KL30 is the power supply for the ECU, and the other end of the voltage division circuit S2 is connected to the MCU. The relay K1 is connected to the MCU, and the MCU is communicatively connected to the VCU. The negative terminal of the battery pack is connected to KL31, and KL31 is the grounding source for the ECU; The detection circuit includes MOS transistor Q1 and diode D1. The source of the MOS transistor Q1 is connected to the first end of the relay K1. The drain of the MOS transistor Q1 is connected in series with the anode of the diode D1. The cathode of the diode D1 is connected to KL30. The gate of the MOS transistor Q1 is connected to the drive signal pin of the MCU. One end of the voltage division circuit S1 is connected to the drain of the MOS transistor Q1 for collecting the voltage of the MOS transistor Q1; The diagnostic method of the relay diagnostic device for the on-vehicle lithium battery system includes: In the parking state, the VCU sends a parking signal to the BMS; After receiving the parking signal, the BMS controls the relay K1 to turn off through the MCU, and at the same time controls the MOS transistor Q1 to turn on through the MCU; The voltage divider circuit S1 collects the voltage V of the MOS transistor Q1 S1 and outputs it to the MCU; The voltage V of KL30 is collected by the voltage division circuit S2 S2 and output to the MCU; The MCU diagnoses whether the state of the relay is normal according to the obtained voltage V S1 and the voltage V S2 ​ The MCU diagnoses whether the working state of the relay is normal according to the obtained voltage V S1 and voltage V S2 The steps are as follows: If the MCU detects that |V S2 -V S1 | > X and V S1 is within the normal voltage range, it indicates that there is external power supply for the battery and the relay K1 is disconnected, and report that the status of the VCU relay K1 is normal; If the MCU detects that 0.3V < |V S2 -V S1 | < X, V S1 is within the normal voltage range, and V S1 -V S2 ≈ V D1 , it indicates that there is no external power supply for the battery, and the relay K1 is disconnected. Report that the status of the VCU relay K1 is normal; If the MCU detects that |V S2 -V S1 | < 0.3V, it indicates that the relay K1 has not executed the disconnection instruction, and it is judged as the adhesion fault of the relay K1, and the adhesion fault of the relay K1 is reported to the VCU; wherein, X is corrected according to the difference between the actual charger voltage and the open-circuit voltage of the fully charged battery, and V D1 is the voltage drop across diode D1.

2. The relay diagnostic device for an in-vehicle lithium battery system according to claim 1, characterized in that: It further includes a voltage division circuit S3. One end of the voltage division circuit S3 is connected to the positive terminal of the battery pack, and the other end is connected to the MCU. The voltage division circuit S3 is used for collecting the voltage at the positive terminal of the battery pack.

3. The relay diagnostic device for an in-vehicle lithium battery system according to claim 1, characterized in that: The MOS transistor Q1 is a P-channel MOSFET.

4. The relay diagnostic device for an in-vehicle lithium battery system according to claim 1, characterized in that: The diode D1 is a rectifier diode.

5. The relay diagnostic device for an in-vehicle lithium battery system according to claim 1, characterized in that: The relay K1 is a magnetic latching relay.

6. A diagnostic method for the relay diagnostic device for an in-vehicle lithium battery system according to any one of claims 1 to 5, characterized in that, The MCU, based on the obtained voltage V S1 and voltage V S2 After the step of diagnosing whether the working state of the relay is normal, the method further includes: The voltage divider circuit S3 collects the voltage V at the positive terminal of the battery pack S3 and outputs it to the MCU; The MCU determines whether the operating state of the detection circuit is abnormal based on the obtained voltage V S1 and the voltage V S2 as well as the voltage V S3 ​ 7. The diagnostic method for the relay diagnostic device for an in-vehicle lithium battery system according to claim 6, characterized in that, The MCU determines whether the working state of the detection circuit is abnormal according to the obtained voltage V S1 and voltage V S2 and voltage V S3 The steps are as follows: If the MCU detects that |V S1 | < 0.3V, |V S2 | < 0.3V, and V S3 = V B+ , it indicates that there is no external power supply for the battery. The relay K1 normally executes the turn-off instruction, but the detection circuit is abnormal, and an abnormal detection circuit of the VCU relay is reported; If |V S1 | < 0.3V is detected, and |V S3 -V S2 | > X is detected, it indicates that there is external power supply for the battery, the relay K1 normally executes the turn-off instruction, but the detection circuit is abnormal, and the VCU relay detection circuit abnormality is reported; Among them, V B+ is the voltage value at the positive extreme of the battery pack.

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