Power battery charging circuit and relay diagnosis method

Abstract

The invention provides a power battery charging circuit and a relay diagnosis method. According to the power battery charging circuit, additional elements and a voltage sensor are added, and more reference information is provided for a corresponding diagnosis method. The relay diagnosis method is realized on the basis of the power battery charging circuit, and specifically, judgment is carried out on the basis of a first voltage, a second voltage and a third voltage, and whether at least one of the fast charging positive relay and the fast charging negative relay has a clamping stagnation normally-closed fault and / or a clamping stagnation normally-open fault or not is diagnosed. According to the configuration, due to the fact that more detection information is added, more diagnosis logics can be designed in a targeted mode, corresponding diagnosis logics are designed for the fast-charging negative relay, and therefore the problems that in the prior art, the time for diagnosing the fast-charging relay is short, and the diagnosis range is not comprehensive enough are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicle battery management, and particularly relates to a power battery charging circuit and a relay diagnosis method. Background Art

[0002] The electric vehicle battery management system realizes the connection and disconnection between the power battery and the charging pile by controlling the closing and opening of the main relay and the fast charging relay. Due to various reasons during the use of the relay, faults such as stuck normally closed or stuck normally open may occur. A stuck normally closed state will cause inability to charge, and a stuck normally open state may cause the charging port at the vehicle end to be charged, posing a harm to personal safety. Therefore, it is necessary to diagnose the stuck fault of the fast charging relay in a timely and accurate manner.

[0003] As Figure 1 shown, the current power battery charging circuit includes: a positive input terminal 1, a fast charging positive relay 2, a main positive relay 3, a power battery main body module 6, a main negative relay 7, a fast charging negative relay 8, and a negative input terminal 9 connected in sequence. The power battery main body module includes: a power battery 61, a fuse 62, and a current sensor 63. A pre-charge relay 4 and a pre-charge resistor 5 are also connected in parallel to the bypass of the main positive relay 3. The connection positions of the first voltage sensor 11, the second voltage sensor 12, and the fourth voltage sensor 13 are as Figure 1 shown. Among them, the first voltage sensor 11 outputs a first voltage U1, the second voltage sensor 12 outputs a second voltage U2, and the fourth voltage sensor 13 outputs a fourth voltage U4.

[0004] The current fast charging relay diagnosis strategy is introduced as follows:

[0005] 1) When there is no charging request in the high-voltage state, at this time the main positive and main negative are closed. If the U1 voltage is close to the battery pack voltage, and the difference between the U1 and U2 voltages is less than the threshold, it is considered that the fast charging positive relay is stuck normally closed.

[0006] 2) When there is a charging request in the high-voltage state:

[0007] · Before the system requests the fast charging positive to close, diagnose the fast charging positive for being stuck normally closed according to the description in 1) above.

[0008] · When the system requests the fast charging positive to close, if the U1 voltage is close to the battery pack voltage, and the U2 voltage is much smaller than the U1 voltage, it is considered that the fast charging positive relay is stuck normally open; at this time, the stuck normally closed fault of the fast charging negative relay cannot be diagnosed because in this working condition, no matter whether there is a stuck fault in the fast charging negative relay, the voltages at each sampling point do not change significantly.

[0009] 3) When exiting the charging process:

[0010] · The system requests to disconnect the fast - charging negative relay, and at this time, it is impossible to accurately diagnose the stuck - closed fault of the fast - charging negative relay.

[0011] · The system requests to disconnect the fast - charging positive relay. If the voltage U1 is close to the battery pack voltage at this time, and the difference between U2 and U1 is less than the threshold value, it is considered that the fast - charging positive relay is stuck - closed.

[0012] From the above description, it can be seen that the current fast - charging relay diagnosis scheme has the following disadvantages:

[0013] 1) Few diagnosis opportunities: When there is no charging request, only the stuck - closed fault of the fast - charging positive relay can be diagnosed, and other stuck faults cannot be diagnosed.

[0014] 2) The stuck fault of the fast - charging negative relay cannot be diagnosed.

[0015] In summary, in the prior art, there are problems of few opportunities to diagnose the fast - charging relay and an incomplete diagnosis scope. Summary of the Invention

[0016] The purpose of the present invention is to provide a power battery charging circuit and a relay diagnosis method, so as to solve the problems of few opportunities to diagnose the fast - charging relay and an incomplete diagnosis scope in the prior art.

[0017] To solve the above - mentioned technical problems, the present invention provides a power battery charging circuit, which is applied to an electric vehicle. The power battery charging circuit includes: a positive input terminal, a fast - charging positive relay, a main positive relay, a power battery main body module, a main negative relay, a fast - charging negative relay, and a negative input terminal connected in sequence. The power battery main body module includes: a power battery; the power battery charging circuit further includes: a first voltage sensor disposed between a first connection point and a second connection point, a second voltage sensor disposed between a third connection point and the second connection point, a third voltage sensor disposed between the third connection point and a fourth connection point, and a shunt resistor disposed between the third connection point and the fourth connection point.

[0018] Wherein, the first connection point is the connection point of the fast - charging positive relay and the main positive relay, the second connection point is the connection point of the main negative relay and the fast - charging negative relay, the third connection point is the connection point of the positive input terminal and the fast - charging positive relay, and the fourth connection point is the connection point of the fast - charging negative relay and the negative input terminal.

[0019] To solve the above - mentioned technical problems, the present invention also provides a relay diagnosis method, which is implemented based on the above - mentioned power battery charging circuit. The first voltage sensor is used to output a first voltage, the second voltage sensor is used to output a second voltage, and the third voltage sensor is used to output a third voltage.

[0020] The relay diagnosis method makes a judgment based on the first voltage, the second voltage, and the third voltage, and diagnoses whether at least one of the fast charge positive relay and the fast charge negative relay has a fault of being stuck in the normally closed state and / or stuck in the normally open state.

[0021] Optionally, the relay diagnosis method includes executing a first diagnosis strategy in a high-voltage state and when the fast charge gun is not detected, and executing a second diagnosis strategy under the fast charge charging closed condition.

[0022] Optionally, the first diagnosis strategy includes: if the absolute value of the difference between the second voltage and the third voltage ≤ a first threshold and the duration exceeds a first time period, it is determined that the fast charge positive relay and the fast charge negative relay are both stuck in the normally closed state; otherwise, it is determined that the fast charge positive relay and the fast charge negative relay are not both stuck in the normally closed state.

[0023] Optionally, the first diagnosis strategy includes: if the fast charge positive relay and the fast charge negative relay are not both stuck in the normally closed state, continue the diagnosis; if the absolute value of the difference between the first voltage and the second voltage ≤ a second threshold and the duration exceeds a second time period, it is determined that the fast charge positive relay is stuck in the normally closed state; otherwise, it is determined that the fast charge positive relay is not stuck in the normally closed state.

[0024] Optionally, the first diagnosis strategy further includes: if the fast charge positive relay and the fast charge negative relay are not both stuck in the normally closed state, continue the diagnosis; output a control signal that can drive the fast charge positive relay to close under non-fault conditions; if the absolute value of the difference between the first voltage and the second voltage ≥ a third threshold and the duration exceeds a third time period, it is determined that the fast charge positive relay is stuck in the normally open state; otherwise, it is determined that the fast charge positive relay is not stuck in the normally open state.

[0025] Optionally, the first diagnosis strategy further includes: if it is determined that the fast charge positive relay is not stuck in the normally open state, continue the diagnosis; if the absolute value of the difference between the second voltage and the third voltage ≤ a fourth threshold and the duration exceeds a fourth time period, it is determined that the fast charge negative relay is stuck in the normally closed state; otherwise, it is determined that the fast charge negative relay is not stuck in the normally closed state; stop outputting the control signal that can drive the fast charge positive relay to close under non-fault conditions; if the absolute value of the difference between the first voltage and the second voltage ≤ a fifth threshold and the duration exceeds a fifth time period, it is determined that the fast charge positive relay is stuck in the normally closed state; otherwise, it is determined that the fast charge positive relay is not stuck in the normally closed state.

[0026] Optionally, the second diagnosis strategy includes: if the absolute value of the difference between the first voltage and the second voltage ≤ a sixth threshold and the duration exceeds a sixth time period, it is determined that the fast charge positive relay is stuck in the normally closed state; otherwise, it is determined that the fast charge positive relay is not stuck in the normally closed state.

[0027] Optionally, the second diagnostic strategy further includes: outputting a control signal capable of driving the fast charge positive relay to close under non-fault conditions; if the absolute value of the difference between the first voltage and the second voltage ≥ a seventh threshold and the duration exceeds a seventh duration, it is determined that the fast charge positive relay is stuck open, otherwise, it is determined that the fast charge positive relay is not stuck open.

[0028] Optionally, the second diagnostic strategy further includes: if it is determined that the fast charge positive relay is not stuck open, continue the diagnosis; if the absolute value of the difference between the second voltage and the third voltage ≤ an eighth threshold and the duration exceeds an eighth duration, it is determined that the fast charge negative relay is stuck closed, otherwise, it is determined that the fast charge negative relay is not stuck closed; outputting a control signal capable of driving the fast charge negative relay to close under non-fault conditions; if the absolute value of the difference between the second voltage and the third voltage ≥ a ninth threshold and the duration exceeds a ninth duration, it is determined that the fast charge negative relay is stuck open, otherwise, it is determined that the fast charge negative relay is not stuck open.

[0029] Compared with the prior art, in a power battery charging circuit and a relay diagnostic method provided by the present invention, additional components and voltage sensors are added to the power battery charging circuit, providing more reference information for the corresponding diagnostic method. The relay diagnostic method is implemented based on the power battery charging circuit. Specifically, it is determined based on the first voltage, the second voltage, and the third voltage whether at least one of the fast charge positive relay and the fast charge negative relay has a fault of being stuck closed and / or stuck open. With such a configuration, due to the addition of more detection information, more diagnostic logics can be designed specifically, and a corresponding diagnostic logic is designed for the fast charge negative relay, thus solving the problems in the prior art that there are few opportunities to diagnose the fast charge relay and the diagnostic scope is not comprehensive enough. Description of the Drawings

[0030] Those of ordinary skill in the art will understand that the provided drawings are used to better understand the present invention and do not constitute any limitation to the scope of the present invention. Among them:

[0031] Figure 1 is a circuit schematic diagram of a power battery charging circuit in the prior art;

[0032] Figure 2 is a circuit schematic diagram of a power battery charging circuit according to an embodiment of the present invention;

[0033] Figure 3 is a flowchart of a first diagnostic logic according to an embodiment of the present invention;

[0034] Figure 4It is a flowchart of the second diagnostic logic according to an embodiment of the present invention.

[0035] Wherein:

[0036] 1 - Positive input terminal; 2 - Fast charge positive relay; 3 - Main positive relay; 4 - Pre - charge relay; 5 - Pre - charge resistor; 6 - Power battery main body module; 7 - Main negative relay; 8 - Fast charge negative relay; 9 - Negative input terminal; 10 - Jumper resistor;

[0037] 61 - Power battery; 62 - Fuse; 63 - Current sensor; 11 - First voltage sensor; 12 - Second voltage sensor; 13 - Fourth voltage sensor; 14 - Third voltage sensor. Detailed implementation manners

[0038] To make the objectives, advantages and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the accompanying drawings are in very simplified forms and are not drawn to scale, only for facilitating and clearly assisting in explaining the objectives of the embodiments of the present invention. In addition, the structures shown in the accompanying drawings are often part of the actual structures. In particular, the emphases to be shown in the respective drawings are different, and sometimes different scales are used.

[0039] As used in the present invention, the singular forms "a", "an" and "the" include plural referents, the term "or" is generally used in the sense of including "and / or", the term "several" is generally used in the sense of including "at least one", the term "at least two" is generally used in the sense of including "two or more". In addition, the terms "first", "second", "third" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", "third" may explicitly or implicitly include one or at least two of such features. "One end" and "the other end", as well as "proximal end" and "distal end" generally refer to two corresponding parts, which include not only the endpoints. The terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral body; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and may be the communication inside two components or the interaction relationship between two components. In addition, as used in the present invention, one component being disposed on another component generally only indicates that there is a connection, coupling, cooperation or transmission relationship between the two components, and the two components may be directly or indirectly connected, coupled, cooperated or transmitted through an intermediate component, and should not be construed as indicating or implying the spatial position relationship between the two components, that is, one component may be inside, outside, above, below or on one side of the other component, etc., in any orientation, unless otherwise explicitly specified in the content. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] The core idea of the present invention is to provide a power battery charging circuit and a relay diagnosis method to solve the problems of few opportunities for diagnosing a fast charge relay and an insufficiently comprehensive diagnosis scope in the prior art.

[0041] The following is a description with reference to the accompanying drawings.

[0042] Please refer to Figure 2 In this embodiment, a power battery charging circuit is provided, which is applied to an electric vehicle. The power battery charging circuit includes: a positive input terminal 1, a fast charge positive relay 2, a main positive relay 3, a power battery main body module 6, a main negative relay 7, a fast charge negative relay 8, and a negative input terminal 9 connected in sequence. The power battery main body module 6 includes: a power battery 61 and some other auxiliary components or modules, such as a fuse 62, a current sensor 63, etc. A pre-charge relay 4 and a pre-charge resistor 5 are also connected in parallel with the main positive relay 3. The pre-charge relay 4 and the pre-charge resistor 5 have little connection with this case.

[0043] The power battery charging circuit further includes: a first voltage sensor 11 disposed between the first connection point and the second connection point, a second voltage sensor 12 disposed between the third connection point and the second connection point, a fourth voltage sensor 13 disposed between the second connection point and the fourth connection point, a third voltage sensor 14 disposed between the third connection point and the fourth connection point, and a jumper resistor 10 disposed between the third connection point and the fourth connection point. The resistance value of the jumper resistor is usually very large, so that when the positive input terminal 1 is closed to an external power supply and the negative input terminal 9 is not closed, the voltage of the negative input terminal 9 can be pulled up. In one embodiment, the resistance value of the jumper resistor is 100 KΩ. The fourth voltage sensor 13 has little relation to the present application and is used for other control algorithms and control strategies.

[0044] Wherein, the first connection point is the connection point of the fast charge positive relay 2 and the main positive relay 3, the second connection point is the connection point of the main negative relay 7 and the fast charge negative relay 8, the third connection point is the connection point of the positive input terminal 1 and the fast charge positive relay 2, and the fourth connection point is the connection point of the fast charge negative relay 8 and the negative input terminal 9.

[0045] It should be understood that the above power battery charging circuit provides necessary information for the diagnosis of relay faults. Those skilled in the art can set different diagnostic schemes based on the output signals of the first voltage sensor to the third voltage sensor to diagnose stuck normally closed / stuck normally open. For example, it is entirely possible to exhaustively list the fault states under laboratory conditions and use the neural network fitting method to correspond the signals and phenomena, which can also solve the corresponding technical problems. Therefore, the above power battery charging circuit itself can already solve the technical problems proposed by the present invention.

[0046] This embodiment also provides a relay diagnosis method, which is implemented based on the above power battery charging circuit. For the convenience of description, it is agreed that: the first voltage sensor is used to output a first voltage U1, the second voltage sensor is used to output a second voltage U2, the fourth voltage sensor is used to output a fourth voltage U4, and the third voltage sensor is used to output a third voltage U3.

[0047] The relay diagnosis method makes a judgment based on the first voltage, the second voltage and the third voltage, and diagnoses whether at least one of the fast charge positive relay and the fast charge negative relay has a fault of stuck normally closed and / or stuck normally open.

[0048] Specifically, the relay diagnosis method includes executing a first diagnosis strategy when in a high-voltage state and the fast-charging gun is not detected, and executing a second diagnosis strategy under the fast-charging closed condition. The high-voltage state means the state where the voltages outside the main positive relay and the main negative relay are pulled up by a high-voltage source. The fast-charging closed condition means the process of normally closing the fast-charging positive relay and the fast-charging negative relay during fast charging.

[0049] Please refer to Figure 3 , the first diagnosis strategy includes: S11, if the absolute value of the difference between the second voltage and the third voltage |U2 - U3| ≤ the first threshold and the duration exceeds the first time period, it is determined that the fast-charging positive relay and the fast-charging negative relay are both stuck in the normally closed state; otherwise, it is determined that the fast-charging positive relay and the fast-charging negative relay are not both stuck in the normally closed state.

[0050] The first diagnosis strategy further includes: if the fast-charging positive relay and the fast-charging negative relay are not both stuck in the normally closed state, continue the diagnosis; S12, if the absolute value of the difference between the first voltage and the second voltage |U1 - U2| ≤ the second threshold and the duration exceeds the second time period, it is determined that the fast-charging positive relay is stuck in the normally closed state; otherwise, it is determined that the fast-charging positive relay is not stuck in the normally closed state.

[0051] The first diagnosis strategy further includes: if the fast-charging positive relay and the fast-charging negative relay are not both stuck in the normally closed state, continue the diagnosis; S13, output a control signal that can drive the fast-charging positive relay to close under non-fault conditions; S14, if the absolute value of the difference between the first voltage and the second voltage |U1 - U2| ≥ the third threshold and the duration exceeds the third time period, it is determined that the fast-charging positive relay is stuck in the normally open state; otherwise, it is determined that the fast-charging positive relay is not stuck in the normally open state.

[0052] The first diagnosis strategy further includes: if it is determined that the fast-charging positive relay is not stuck in the normally open state, continue the diagnosis; S15, if the absolute value of the difference between the second voltage and the third voltage |U2 - U3| ≤ the fourth threshold and the duration exceeds the fourth time period, it is determined that the fast-charging negative relay is stuck in the normally closed state; otherwise, it is determined that the fast-charging negative relay is not stuck in the normally closed state; S16, stop outputting the control signal that can drive the fast-charging positive relay to close under non-fault conditions; S17, if the absolute value of the difference between the first voltage and the second voltage |U1 - U2| ≤ the fifth threshold and the duration exceeds the fifth time period, it is determined that the fast-charging positive relay is stuck in the normally closed state; otherwise, it is determined that the fast-charging positive relay is not stuck in the normally closed state.

[0053] When it is determined that the fast charging positive relay and the fast charging negative relay are both stuck in the normally closed state, or the fast charging positive relay is stuck in the normally open state, step S18 is directly executed and the detection ends. Because at this time, the preconditions for subsequent diagnosis are no longer met and subsequent diagnosis cannot be performed.

[0054] It can be understood that Figure 3 What is shown is a preferred embodiment. In other embodiments, some steps can also be selectively deleted. For example, step S12 is deleted. Such an embodiment can also play a diagnostic role in specific scenarios.

[0055] Any two of the first duration, the second duration, the third duration, the fourth duration, and the fifth duration can be the same or different. Any two of the first threshold, the second threshold, the third threshold, the fourth threshold, and the fifth threshold can be the same or different.

[0056] Please refer to Figure 4 , the second diagnostic strategy includes: S21, if the absolute value of the difference between the first voltage and the second voltage |U1 - U2| ≤ the sixth threshold and the duration exceeds the sixth duration, it is determined that the fast charging positive relay is stuck in the normally closed state; otherwise, it is determined that the fast charging positive relay is not stuck in the normally closed state.

[0057] The second diagnostic strategy further includes: S22, outputting a control signal that can drive the fast charging positive relay to close under non - fault conditions; S23, if the absolute value of the difference between the first voltage and the second voltage |U1 - U2| ≥ the seventh threshold and the duration exceeds the seventh duration, it is determined that the fast charging positive relay is stuck in the normally open state; otherwise, it is determined that the fast charging positive relay is not stuck in the normally open state.

[0058] The second diagnostic strategy further includes: if it is determined that the fast charging positive relay is not stuck in the normally open state, continue the diagnosis; S24, if the absolute value of the difference between the second voltage and the third voltage |U2 - U3| ≤ the eighth threshold and the duration exceeds the eighth duration, it is determined that the fast charging negative relay is stuck in the normally closed state; otherwise, it is determined that the fast charging negative relay is not stuck in the normally closed state; S25, outputting a control signal that can drive the fast charging negative relay to close under non - fault conditions; S26, if the absolute value of the difference between the second voltage and the third voltage |U2 - U3| ≥ the ninth threshold and the duration exceeds the ninth duration, it is determined that the fast charging negative relay is stuck in the normally open state; otherwise, it is determined that the fast charging negative relay is not stuck in the normally open state.

[0059] When it is determined that the fast charging positive relay is stuck in the normally open state, step S27 is directly executed and the detection ends. Because at this time, the preconditions for subsequent diagnosis are no longer met and subsequent diagnosis cannot be performed.

[0060] It can be understood thatFigure 4 What is shown is a preferred embodiment. In other embodiments, some steps may be selectively deleted, for example, step S21 may be deleted. Such an embodiment may also play a diagnostic role in a specific scenario.

[0061] Any two of the sixth duration, the seventh duration, the eighth duration, and the ninth duration may be the same or different. Any two of the sixth threshold, the seventh threshold, the eighth threshold, and the ninth threshold may be the same or different.

[0062] Compared with the existing fast charging relay stuck fault diagnosis technology, the beneficial effects of this embodiment are as follows:

[0063] 1) In the non-charging high-voltage state, more diagnostic windows are created by actively closing and disconnecting the fast-charging positive relay, which increases the diagnostic opportunities and enables more timely detection of faults.

[0064] 2) By optimizing the high-voltage architecture, the stuck fault diagnosis of the fast-charging negative relay is realized.

[0065] In summary, the present embodiment provides a power battery charging circuit and a relay diagnostic method. The power battery charging circuit adds additional components and voltage sensors to provide more reference information for the corresponding diagnostic method. The relay diagnostic method is implemented based on the power battery charging circuit. Specifically, based on the first voltage, the second voltage and the third voltage, it is judged whether at least one of the fast charging positive relay and the fast charging negative relay has a stuck normally closed and / or stuck normally open fault. With such a configuration, since more detection information is added, more diagnostic logics can be designed in a targeted manner, and corresponding diagnostic logic can be designed for the fast charging negative relay, thereby solving the problems in the prior art of few opportunities to diagnose the fast charging relay and the insufficiently comprehensive diagnostic range.

[0066] The above description is only a description of the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A power battery charging circuit, characterized in that: Applied to electric vehicles, the power battery charging circuit includes: a positive input terminal, a fast-charging positive relay, a main positive relay, a power battery main module, a main negative relay, a fast-charging negative relay and a negative input terminal connected in sequence, and the power battery main module includes: a power battery; the power battery charging circuit also includes: a first voltage sensor arranged between a first connection point and a second connection point, a second voltage sensor arranged between a third connection point and the second connection point, a third voltage sensor arranged between the third connection point and the fourth connection point, and a jumper resistor arranged between the third connection point and the fourth connection point; Among them, the first connection point is the connection point between the fast charging positive relay and the main positive relay, the second connection point is the connection point between the main negative relay and the fast charging negative relay, the third connection point is the connection point between the positive input terminal and the fast charging positive relay, and the fourth connection point is the connection point between the fast charging negative relay and the negative input terminal.

2. A relay diagnosis method, characterized in that: Based on the implementation of the power battery charging circuit according to claim 1, the first voltage sensor is used to output a first voltage, the second voltage sensor is used to output a second voltage, and the third voltage sensor is used to output a third voltage; The relay diagnosis method makes a judgment based on the first voltage, the second voltage and the third voltage to diagnose whether at least one of the fast charging positive relay and the fast charging negative relay has a stuck normally closed and / or stuck normally open fault.

3. The relay diagnosis method according to claim 2, characterized in that: The relay diagnosis method includes executing a first diagnosis strategy when the relay is in a high voltage state and the fast charging gun is not detected, and executing a second diagnosis strategy under a fast charging closed condition.

4. The relay diagnosis method according to claim 3, characterized in that: The first diagnostic strategy includes: If the absolute value of the difference between the second voltage and the third voltage is ≤ the first threshold and the duration exceeds the first time length, it is determined that the fast charging positive relay and the fast charging negative relay are both stuck and normally closed; otherwise, it is determined that the fast charging positive relay and the fast charging negative relay are not both stuck and normally closed.

5. The relay diagnosis method according to claim 4, characterized in that: The first diagnostic strategy includes: If the fast-charge positive relay and the fast-charge negative relay are not double-stuck and normally closed, continue the diagnosis; If the absolute value of the difference between the first voltage and the second voltage is ≤ a second threshold value and lasts for more than a second time period, it is determined that the fast-charging positive relay is stuck and normally closed; otherwise, it is determined that the fast-charging positive relay is not stuck and normally closed.

6. The relay diagnosis method according to claim 5, characterized in that: The first diagnostic strategy also includes: If the fast-charge positive relay and the fast-charge negative relay are not double-stuck and normally closed, continue the diagnosis; Outputting a control signal capable of driving the fast charging positive relay to close in a non-fault condition; If the absolute value of the difference between the first voltage and the second voltage is ≥ the third threshold and lasts for more than a third time period, it is determined that the fast charging positive relay is stuck and normally open; otherwise, it is determined that the fast charging positive relay is not stuck and normally open.

7. The relay diagnosis method according to claim 6, characterized in that: The first diagnostic strategy also includes: If it is determined that the fast-charging positive relay is not stuck and normally open, continue diagnosis; If the absolute value of the difference between the second voltage and the third voltage is less than or equal to a fourth threshold value and the duration exceeds a fourth time period, it is determined that the fast-charge negative relay is stuck and normally closed; otherwise, it is determined that the fast-charge negative relay is not stuck and normally closed; Stop outputting the control signal capable of driving the fast charging positive relay to close in a non-fault condition; If the absolute value of the difference between the first voltage and the second voltage is ≤ the fifth threshold value and the duration exceeds the fifth time length, it is determined that the fast charging positive relay is stuck and normally closed; otherwise, it is determined that the fast charging positive relay is not stuck and normally closed.

8. The relay diagnosis method according to claim 3, characterized in that: The second diagnostic strategy includes: If the absolute value of the difference between the first voltage and the second voltage is ≤ the sixth threshold value and the duration exceeds the sixth time length, it is determined that the fast charging positive relay is stuck and normally closed; otherwise, it is determined that the fast charging positive relay is not stuck and normally closed.

9. The relay diagnosis method according to claim 8, characterized in that: The second diagnostic strategy also includes: Outputting a control signal capable of driving the fast charging positive relay to close in a non-fault condition; If the absolute value of the difference between the first voltage and the second voltage is ≥ the seventh threshold value and lasts for more than the seventh time period, it is determined that the fast charging positive relay is stuck and normally open; otherwise, it is determined that the fast charging positive relay is not stuck and normally open.

10. The relay diagnosis method according to claim 9, characterized in that: The second diagnostic strategy also includes: If it is determined that the fast-charging positive relay is not stuck and normally open, continue the diagnosis; If the absolute value of the difference between the second voltage and the third voltage is less than or equal to the eighth threshold value and the duration exceeds the eighth time period, it is determined that the fast-charge negative relay is stuck and normally closed; otherwise, it is determined that the fast-charge negative relay is not stuck and normally closed; Outputting a control signal capable of driving the fast charging negative relay to close in a non-fault condition; If the absolute value of the difference between the second voltage and the third voltage is ≥ the ninth threshold value and lasts for more than the ninth time period, it is determined that the fast charging negative relay is stuck and normally open; otherwise, it is determined that the fast charging negative relay is not stuck and normally open.

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