Battery management system, battery pack and electric device

Abstract

The application discloses a battery management system, a battery pack and a power utilization device. The battery management system comprises a first switch, a second switch, a third switch, a voltage sampling module, a first current sampling module, a second current sampling module and a processor. The first switch is electrically connected between a first sampling point and a second sampling point; the second switch is electrically connected between a positive electrode of a first battery and a negative electrode of a second battery, and a positive electrode of the second battery is electrically connected with the first sampling point; the third switch is electrically connected between the negative electrode of the second battery and a reference point; the voltage sampling module collects a voltage of the first sampling point, a voltage of the second sampling point, a voltage of the first battery and a voltage of the second battery; the first current sampling module collects a main loop current; the second current sampling module collects a branch current of the first battery; and the processor is used for determining whether each switch is faulty according to the collected voltage and current. According to the embodiment of the application, the accuracy of switch diagnosis can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery management, in particular to a battery management system, a battery pack and a power utilization device. BACKGROUND

[0002] With the development of new energy vehicles, in order to solve the charging anxiety, new energy vehicles are developing towards fast charging 800V system, and the output voltage of some charging piles currently applied is only 400V, which cannot meet the charging requirements of 800V high voltage system.

[0003] In view of this problem, a 400V / 800V switching high voltage topology is proposed in the related art, and a switch (such as a relay) is needed to control the series or parallel connection of two batteries in the high voltage topology. If the switch fails, battery short circuit or failure to achieve charging / discharging purpose is likely to occur, so it is crucial to diagnose the switch failure. SUMMARY

[0004] The present application provides a battery management system, a battery pack and a power utilization device, which can improve the accuracy of switch failure diagnosis and avoid missed diagnosis.

[0005] In a first aspect, the present application provides a battery management system, comprising a first switch, a second switch, a third switch, a voltage sampling module, a first current sampling module, a second current sampling module and a processor; the first switch is electrically connected between a first sampling point and a second sampling point; the second switch is electrically connected between the positive electrode of a first battery and the negative electrode of a second battery, and the positive electrode of the second battery is electrically connected with the first sampling point; the third switch is electrically connected between the negative electrode of the second battery and a reference point; the voltage sampling module is electrically connected with the first sampling point, the second sampling point, the first battery and the second battery, and is used to collect a first sampling voltage of the first sampling point, a second sampling voltage of the second sampling point, a first battery voltage of the first battery and a second battery voltage of the second battery; the first current sampling module is electrically connected with the reference point, and is used to collect a main loop current; the second current sampling module is electrically connected with a branch in which the first battery is located, and is used to collect a branch current; the processor is connected with the voltage sampling module, the first current sampling module and the second current sampling module, and is used to determine whether the first switch, the second switch and the third switch exist faults according to the first sampling voltage, the second sampling voltage, the first battery voltage, the second battery voltage, the main loop current and the branch current.

[0006] According to the battery management system provided in the embodiments of the present application, the battery management system comprises a first switch, a second switch, a third switch, a voltage sampling module, a first current sampling module, a second current sampling module and a processor. The first switch is electrically connected between a first sampling point and a second sampling point. The second switch is electrically connected between a positive electrode of a first battery and a negative electrode of a second battery, and the positive electrode of the second battery is electrically connected with the first sampling point. The third switch is electrically connected between the negative electrode of the second battery and a reference point. The voltage sampling module is electrically connected with the first sampling point, the second sampling point, the first battery and the second battery, and is configured to collect a first sampling voltage of the first sampling point, a second sampling voltage of the second sampling point, a first battery voltage of the first battery and a second battery voltage of the second battery. The first current sampling module is electrically connected with the reference point, and is configured to collect a main loop current. The second current sampling module is electrically connected with a branch in which the first battery is located, and is configured to collect a branch current. The processor is connected with the voltage sampling module, the first current sampling module and the second current sampling module, and is configured to determine whether the first switch, the second switch and the third switch have faults according to the first sampling voltage, the second sampling voltage, the first battery voltage, the second battery voltage, the main loop current and the branch current. According to the embodiments of the present application, the voltage sampling module, the battery voltage and the current value are combined to comprehensively diagnose whether the switch has a fault, which can avoid the risk of misdiagnosis and missed diagnosis caused by invalid single sampling data, improve the diagnosis accuracy, and avoid missed diagnosis.

[0007] In a possible implementation of the first aspect, the battery management system further comprises an active fuse electrically connected between the first sampling point and a third sampling point.

[0008] The voltage sampling module is further electrically connected with the third sampling point, and is configured to collect a third sampling voltage of the third sampling point.

[0009] The processor is further configured to determine that the voltage sampling module has a sampling fault in a case where a deviation between the first sampling voltage and the third sampling voltage is greater than a first preset deviation.

[0010] The battery management system provided in the embodiments of the present application can timely and accurately diagnose the sampling fault of the voltage sampling module by adding the active fuse and the third sampling point and the sampling fault diagnosis function of the processor. If the voltage sampling module has a sampling fault, the processor may obtain incorrect voltage data, which affects the judgment of the battery state, the switch state and the like, and even may cause an incorrect control decision, thereby threatening the safety and performance of the battery pack. The fault diagnosis method based on the deviation between the first sampling voltage and the third sampling voltage can effectively improve the reliability and safety of the battery management system.

[0011] In a possible implementation of the first aspect, the processor is further configured to: in a case where the voltage sampling module fails to collect the first sampling voltage and succeeds in collecting the third sampling voltage, replace the first sampling voltage with the third sampling voltage to perform the diagnosis of the switching failure.

[0012] The application adopts a replacement diagnosis mechanism. In a case where the voltage sampling module fails to collect the first sampling voltage, the third sampling voltage is used to replace the first sampling voltage to perform the diagnosis of the switching failure, and the switching failure diagnosis can still be ensured. In actual operation, the voltage sampling module may fail to collect the first sampling voltage due to various reasons (such as sensor failure, poor line contact, etc.). Without the replacement diagnosis mechanism, the system cannot perform the switching failure diagnosis, thereby affecting the safe operation of the battery pack. With the mechanism, the system can continue to perform the failure diagnosis when the first sampling voltage is collected abnormally, discover the switching failure in a timely manner, and avoid potential safety hazards.

[0013] In a possible implementation of the first aspect, the processor is further configured to:

[0014] In a case where the voltage sampling module fails to collect the second sampling voltage and succeeds in collecting the first battery voltage, the first battery voltage is used to replace the second sampling voltage to perform the diagnosis of the switching failure.

[0015] The application adopts a replacement diagnosis mechanism. In a case where the voltage sampling module fails to collect the second sampling voltage, the first battery voltage is used to replace the second sampling voltage to perform the diagnosis of the switching failure, and the switching failure diagnosis can still be ensured. In actual operation, the voltage sampling module may fail to collect the second sampling voltage due to various reasons. Without the replacement diagnosis mechanism, the system cannot perform the switching failure diagnosis, thereby affecting the safe operation of the battery pack. With the mechanism, the system can continue to perform the failure diagnosis when the second sampling voltage is collected abnormally, discover the switching failure in a timely manner, and avoid potential safety hazards.

[0016] In a possible implementation of the first aspect, the processor is configured to:

[0017] In a case where the first switch, the second switch, and the third switch are all disconnected, if the first sampling voltage is greater than the first threshold value, it is determined that at least one of the first switch, the second switch, and the third switch has a sticking failure.

[0018] The processor of the application can determine whether the switches have a sticking failure by judging whether the first sampling voltage is greater than the first threshold value in a case where the first switch, the second switch, and the third switch are all disconnected, thereby providing an effective switching sticking failure diagnosis mechanism and ensuring the safety and reliability of the battery management system.

[0019] In a possible implementation of the first aspect, the processor is configured to:

[0020] In the case where the first switch, the second switch and the third switch are all open, if at least one of the following three relationships is satisfied, it is determined that the first switch or the third switch has a sticking fault:

[0021] |U1-U2|≤a1*U2;

[0022] |U1-VM1|≤a1*VM1;

[0023] |U1-VM2|≤a1*VM2;

[0024] U1 represents the first sampling voltage, U2 represents the second sampling voltage, VM1 represents the first battery voltage, VM2 represents the second battery voltage, and a1 is a preset value less than 0.5.

[0025] The embodiments of the present application can accurately determine whether the first switch or the third switch has a sticking fault by limiting the proportional relationship of |U1-U2|, |U1-VM1|, |U1-VM2| and the corresponding voltage, because the fault can be determined in the case where the above at least one relationship is satisfied, and the robustness of diagnosis is improved.

[0026] In a possible implementation of the first aspect, the processor is further configured to:

[0027] In the case where |U1-VM1|<|U1-VM2|, it is determined that the first switch has a sticking fault.

[0028] The embodiments of the present application can directly determine whether the first switch has a sticking fault by comparing the magnitudes of |U1-VM1| and |U1-VM2|, and the efficiency of fault diagnosis is improved.

[0029] In a possible implementation of the first aspect, the processor is further configured to:

[0030] In the case where |U1-VM1|>|U1-VM2|, it is determined that the third switch has a sticking fault.

[0031] The embodiments of the present application can directly determine whether the third switch has a sticking fault by comparing the magnitudes of |U1-VM1| and |U1-VM2|, and the efficiency of fault diagnosis is improved.

[0032] In a possible implementation of the first aspect, the processor is configured to:

[0033] In the case where the first switch, the second switch and the third switch are all open, if at least one of the following two relationships is satisfied, it is determined that the second switch has a sticking fault:

[0034] |U1-2*U2|≤a2*2*U2;

[0035] |U1-(VM1+VM2)|≤a2*(VM1+VM2);

[0036] U1 represents the first sampling voltage, U2 represents the second sampling voltage, VM1 represents the first battery voltage, VM2 represents the second battery voltage, and a2 is a preset value less than 0.5.

[0037] The embodiments of the application can directly determine whether the second switch has a sticking fault through the determination of the above relationship, thereby improving the efficiency of fault diagnosis.

[0038] In a possible implementation of the first aspect, the battery management system further includes a main loop switch, and the processor is configured to:

[0039] In a case where the first switch is closed and the second switch, the third switch and the main loop switch are open, if U1≤b1*U2, it is determined that the first switch has an open circuit fault.

[0040] U1 represents the first sampling voltage, U2 represents the second sampling voltage, and b1 is a preset value less than 0.5.

[0041] The embodiments of the application can diagnose the open circuit fault of the first switch in a timely manner, thereby ensuring the normal charging of the first battery alone.

[0042] In a possible implementation of the first aspect, the battery management system further includes a main loop switch, and the processor is configured to:

[0043] In a case where the third switch is closed and the first switch, the second switch and the main loop switch are open, if U1≤b1*U2, it is determined that the third switch has an open circuit fault.

[0044] U1 represents the first sampling voltage, U2 represents the second sampling voltage, and b1 is a preset value less than 0.5.

[0045] The embodiments of the application can diagnose the open circuit fault of the third switch in a timely manner, thereby ensuring the normal charging of the second battery alone.

[0046] In a possible implementation of the first aspect, the battery management system further includes a main loop switch, and the processor is configured to:

[0047] In a case where the first switch and the third switch are closed and the second switch and the main loop switch are open, if U1≤b1*U2, it is determined that the first switch and the third switch have an open circuit fault.

[0048] U1 represents the first sampling voltage, U2 represents the second sampling voltage, and b1 is a preset value less than 0.5.

[0049] The embodiment of the application can diagnose the open-circuit fault of the first switch and the third switch in time, thereby ensuring that the first battery and the second battery can normally perform parallel charging.

[0050] In a possible implementation of the first aspect, the battery management system further includes a main loop switch, and the processor is configured to:

[0051] In a case where the first switch, the main loop switch are closed and the second switch is open, if at least one of the following two relationships is satisfied, it is determined that the first switch has an open-circuit fault:

[0052] U1≤b1*U2;

[0053] |Shunt2|≤I1 and |Shunt1|≥I2;

[0054] U1 represents the first sampling voltage, U2 represents the second sampling voltage, Shunt1 represents the main loop current, Shunt2 represents the branch current, b1 is a preset value less than 0.5, I1 and I2 are preset values, and I1<I2.

[0055] The embodiment of the application can more accurately diagnose whether the first switch has an open-circuit fault by comprehensively judging the sampling data of the voltage and the current, and the redundant fault diagnosis mechanism improves the reliability of the system, and can ensure that the first switch is detected and processed in time when the first switch has an open-circuit fault.

[0056] In a possible implementation of the first aspect, the battery management system further includes a main loop switch, and the processor is configured to:

[0057] In a case where the third switch, the main loop switch are closed and the second switch is open, if at least one of the following two relationships is satisfied, it is determined that the third switch has an open-circuit fault:

[0058] U1≤b2*U2;

[0059] |Shunt1-Shunt2|≤b2*Shunt1 and |Shunt1|≥I2;

[0060] U1 represents the first sampling voltage, Shunt1 represents the main loop current, Shunt2 represents the branch current, b2 is a preset value less than 0.5, and I2 is a preset value.

[0061] The embodiment of the application can more accurately diagnose whether the third switch has an open-circuit fault by comprehensively judging the sampling data of the voltage and the current, and the redundant fault diagnosis mechanism improves the reliability of the system, and can ensure that the third switch is detected and processed in time when the third switch has an open-circuit fault.

[0062] In a possible implementation of the first aspect, the processor is configured to:

[0063] If U1≤b3*U2, it is determined that the second switch has an open-circuit fault when the first switch and the third switch are open and the second switch is closed.

[0064] U1 represents the first sampling voltage, U2 represents the second sampling voltage, and b3 is a preset value less than 0.5.

[0065] The embodiments of the application can diagnose the open-circuit fault of the second switch in a timely manner, thereby ensuring that the first battery and the second battery can normally perform series charging / discharging.

[0066] In a possible implementation of the first aspect, the processor is further configured to:

[0067] When the output voltage of the charging device electrically connected to the battery management system is greater than the threshold voltage, the second switch is controlled to be closed, and the first switch and the third switch are in an open state.

[0068] The embodiments of the application can fully utilize the high output voltage (such as 800V high voltage) of the charging device by using the series charging mode of the first battery and the second battery when the output voltage of the charging device is greater than the threshold voltage, thereby reducing the charging time and improving the charging efficiency.

[0069] In a possible implementation of the first aspect, the processor is further configured to:

[0070] When the output voltage of the charging device electrically connected to the battery management system is less than the threshold voltage, if |VM1-VM2|≤V1, the first switch and the third switch are controlled to be closed, and the second switch is in an open state.

[0071] VM1 represents the first battery voltage, VM2 represents the second battery voltage, and V1 is a preset value.

[0072] The embodiments of the application are the charging strategy of the battery management system when the output voltage of the charging device is less than the threshold voltage. For example, when the output voltage of the charging device is 400V, the battery parallel charging mode can be used. Before entering the parallel charging mode, it can be determined whether the difference between the first battery voltage VM1 and the second battery voltage VM2 is small enough, thereby ensuring that the voltage difference between the two batteries is not too large during parallel charging, thereby avoiding current imbalance and potential battery damage, and ensuring the safety and reliability of the charging process.

[0073] In a possible implementation of the first aspect, the processor is further configured to:

[0074] In the case that the output voltage of the charging device electrically connected to the battery management system is less than the threshold voltage, if VM1-VM2>V1, the third switch is controlled to be closed first, and the first switch and the second switch are in an open state, until the voltage of the second battery is charged to the case that the voltage difference with the first battery is less than V2, the charging current Ia is requested, and after the charging current is reduced to below Ia, the first switch is controlled to be closed;

[0075] VM1 represents the first battery voltage, VM2 represents the second battery voltage, V1 and V2 are preset values, and V2

[0076] The embodiment of the application is a charging strategy of the battery management system in the case that the output voltage of the charging device is less than the threshold voltage and the voltage difference between the first battery and the second battery is large (VM1-VM2>V1). By the way of charging the battery with a lower voltage (such as the second battery) first and then gradually charging in parallel, the risk of excessive current or battery damage caused by unbalanced battery voltage is avoided, the battery pack can be safely and efficiently charged under the condition of unbalanced voltage, and finally voltage balancing is achieved. In addition, the current safety threshold Ia is set during the charging process to avoid the impact of large current on the battery, ensure the safety and reliability of the charging process, and prolong the service life of the battery.

[0077] In a possible implementation of the first aspect, the processor is further configured to:

[0078] In the case that the output voltage of the charging device electrically connected to the battery management system is less than the threshold voltage, if VM2-VM1>V1, the first switch is controlled to be closed first, and the third switch and the second switch are in an open state, until the voltage of the first battery is charged to the case that the voltage difference with the second battery is less than V2, the charging current Ia is requested, and after the charging current is reduced to below Ia, the third switch is controlled to be closed;

[0079] VM1 represents the first battery voltage, VM2 represents the second battery voltage, V1 and V2 are preset values, and V2

[0080] The embodiment of the application is a charging strategy of the battery management system in the case that the output voltage of the charging device is less than the threshold voltage and the voltage difference between the first battery and the second battery is large (VM1-VM2>V1). By the way of charging the battery with a lower voltage (such as the first battery) first and then gradually charging in parallel, the risk of excessive current or battery damage caused by unbalanced battery voltage is avoided, the battery pack can be safely and efficiently charged under the condition of unbalanced voltage, and finally voltage balancing is achieved. In addition, the current safety threshold Ia is set during the charging process to avoid the impact of large current on the battery, ensure the safety and reliability of the charging process, and prolong the service life of the battery.

[0081] In a possible implementation of the first aspect, the battery management system further includes:

[0082] The first fuse is connected in series with the first switch between the first sampling point and the second sampling point.

[0083] And / or, the second fuse is connected in series with the third switch between the negative electrode of the second battery and the reference point.

[0084] The first fuse newly added in the embodiment of the application is connected in series with the first switch between the first sampling point and the second sampling point. When the current flowing through the first fuse exceeds the rated value thereof, the fuse inside the first fuse will be melted due to overheating, thereby cutting off the circuit and preventing the device from being damaged due to excessive current. The second fuse newly added is connected in series with the third switch between the negative electrode of the second battery and the reference point. When the current flowing through the second fuse exceeds the rated value thereof, the fuse inside the second fuse will be melted due to overheating, thereby cutting off the circuit and preventing the device from being damaged due to excessive current.

[0085] Based on the same inventive concept, in a second aspect, the embodiment of the application provides a battery pack, including a first battery, a second battery and the battery management system of any one of the embodiments of the first aspect.

[0086] The battery pack provided by the embodiment of the application includes the battery management system in any one of the above embodiments, and therefore has the beneficial effects of the battery management system provided by any one of the above embodiments.

[0087] Based on the same inventive concept, in a third aspect, the embodiment of the application provides a power consumption device, including the battery pack of any one of the embodiments of the first aspect.

[0088] The power consumption device provided by the embodiment of the application includes the battery pack, and the battery pack includes the battery management system in any one of the above embodiments, and therefore has the beneficial effects of the battery management system provided by any one of the above embodiments.

[0089] The above description is only a summary of the technical solutions of the application. In order to enable the technical means of the application to be more clearly understood, and to be implemented according to the content of the description, and in order to enable the above and other purposes, characteristics and advantages of the application to be more apparent, the specific embodiments of the application are described below. BRIEF DESCRIPTION OF DRAWINGS

[0090] The features, advantages and technical effects of the exemplary embodiments of the application will be described below with reference to the accompanying drawings.

[0091] Figure 1 A structural schematic diagram of a battery management system according to an embodiment of the application;

[0092] Figure 2A structural schematic diagram of a battery management system according to another embodiment of the present application;

[0093] Figure 3 A structural schematic diagram of a battery management system according to another embodiment of the present application;

[0094] Figure 4 A structural schematic diagram of a battery management system according to another embodiment of the present application;

[0095] Figure 5 A structural schematic diagram of a battery management system according to another embodiment of the present application;

[0096] Figure 6 A structural schematic diagram of a battery management system according to another embodiment of the present application;

[0097] Figure 7 A structural schematic diagram of a battery management system according to another embodiment of the present application;

[0098] Figure 8 A structural schematic diagram of a battery management system according to another embodiment of the present application; DETAILED DESCRIPTION

[0099] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative work fall within the scope of protection of the present application.

[0100] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used in the specification of the present application are only for the purpose of describing specific embodiments of the present application, and are not intended to limit the present application; the terms “include” and “have” and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion. The terms “first”, “second” and the like in the specification and claims of the present application and the above description of drawings are used to distinguish different objects, and are not intended to describe a particular order or primary and secondary relationships.

[0101] In the description of the present application, it should be pointed out that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting", "attachment" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be direct connection, or indirect connection through intermediate medium, or internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0102] Before describing the technical solutions provided by the embodiments of the present application, in order to facilitate the understanding of the embodiments of the present application, the present application first specifically describes the problems existing in the related art:

[0103] With the rapid development of the new energy automobile industry, the 800V high-voltage architecture parts industry has become mature, such as motor, inverter, on-board charger (OBC), DC-DC converter (DCDC), air conditioner compressor and other high-voltage parts, which have the ability to support 800V system work.

[0104] Increasing the voltage platform can improve work efficiency, reduce vehicle energy consumption and increase the cruising range, and at the same time, the high-voltage platform can also increase the charging speed.

[0105] At present, most new energy vehicles have adopted 800V voltage platform. However, due to the relatively slow updating speed of charging piles in some areas, some charging piles are still 400V charging piles, and there is a situation that the charging pile voltage does not match the vehicle voltage platform, which brings challenges to the charging of new energy vehicles.

[0106] In order to solve the problem of charging 800V battery pack by 400V charging pile, the related technology adopts DCDC booster or multiplex inverter as the scheme of boost module. However, this scheme has the following defects:

[0107] Limited charging power: DCDC booster and inverter have a certain power upper limit, and the charging power is limited by them, which cannot meet the demand of large rate charging. Large rate charging is crucial to shorten the charging time and improve user experience, but the related technology cannot meet this demand, which limits the further improvement of new energy vehicles in charging efficiency.

[0108] Cost increase: due to the need to bypass the DCDC booster and inverter, a boost relay is needed to control the bypass. This not only increases the hardware cost, but also makes the system structure more complex, increases the probability of failure and maintenance cost.

[0109] Therefore, in the related art, a 400V / 800V switching high-voltage topology is proposed, in which a switch (such as a relay) is needed to control the series or parallel connection of two batteries. For example, two 400V battery packs are connected in parallel when charging to adapt to 400V charging piles; and connected in series when discharging to make the output voltage reach 800V to meet the power demand of vehicle driving.

[0110] Since a switch (such as a relay) needs to be added to control the connection mode of the battery pack, it is important to detect the fault condition of the switch in time to ensure the safe operation of the battery pack. For example, when the switch has a sticking fault, it may cause a short circuit of the battery, leading to overheating, fire or even explosion; and when the switch has an open circuit fault, it may cause the battery to be unable to charge and discharge normally, affecting the normal use of the vehicle.

[0111] Based on this, the embodiments of the present application provide a battery management system, a battery pack and a power consumption device, which can comprehensively diagnose whether the switch has a fault by combining the sampling point voltage, the battery voltage and the current value, can avoid the risk of single sampling failure, improve the diagnostic accuracy, and avoid missed diagnosis.

[0112] The battery management system provided by the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0113] Figure 1 is a structural schematic diagram of a battery management system provided by the embodiments of the present application, as shown in Figure 1 The battery management system 100 can include a first switch 10, a second switch 20, a third switch 30, a voltage sampling module 40, a first current sampling module 50, a second current sampling module 60 and a processor 70.

[0114] The first switch 10 is electrically connected between the first sampling point S1 and the second sampling point S2.

[0115] The second sampling point S2 is electrically connected to the positive electrode of the first battery 200.

[0116] Specifically, the first switch 10 is arranged between the first sampling point S1 and the second sampling point S2, so that the state change of the first switch 10 will directly affect the electrical connection between the first sampling point S1 and the second sampling point S2.

[0117] The second switch 20 is electrically connected between the positive terminal of the first battery 200 and the negative terminal of the second battery 300. The positive terminal of the second battery 300 is electrically connected to the first sampling point S1.

[0118] Specifically, the second switch 20 is positioned between the two batteries (the first battery 200 and the second battery 300), so the second switch 20 can control the connection between the first battery 200 and the second battery 300.

[0119] The third switch 30 is electrically connected between the negative terminal of the second battery 300 and the reference point G.

[0120] Among them, reference point G can be the reference location for high-pressure sampling.

[0121] Specifically, the third switch 30 is located between the negative terminal of the second battery 300 and the reference point G, so the state of the third switch 30 will affect the electrical connection between the second battery 300 and the reference point G.

[0122] For example, the first switch 10, the second switch 20, and the third switch 30 can be relays or other types of switches.

[0123] By controlling the states of the first switch 10, the second switch 20, and the third switch 30, the battery management system 100 can switch between the following four operating modes:

[0124] 1) Series 800V charging / discharging mode.

[0125] With the first switch 10 and the third switch 30 open and the second switch 20 closed, the first battery 200 and the second battery 300 are connected in series. For example, it can be used to power the 800V high-voltage components of the vehicle; or an 800V charging device can be used to charge the first battery 200 and the second battery 300.

[0126] 2) Parallel 400V charging mode.

[0127] When the first switch 10 and the third switch 30 are closed and the second switch 20 is open, the first battery 200 and the second battery 300 are connected in parallel.

[0128] For example, such as Figure 2 As shown, the first sampling point S1 is electrically connected to the positive terminal P+, and the reference point G is electrically connected to the negative terminal p-. The positive terminal P+ and the negative terminal p- are respectively electrically connected to the positive and negative terminals of the 400V charging device, so that the first battery 200 and the second battery 300 can be charged using the 400V charging device.

[0129] 3) The first battery 200V is charged separately in 400V charging mode.

[0130] In the case that the first switch 10 is closed, and the second switch 20 and the third switch 30 are opened, the first battery 200 can be charged alone by using the 400V charging device.

[0131] 4) Second battery 300 alone 400V charging mode.

[0132] In the case that the third switch 30 is closed, and the first switch 10 and the second switch 20 are opened, the second battery 300 can be charged alone by using the 400V charging device.

[0133] The voltage sampling module 40 is electrically connected with the first sampling point S1, the second sampling point S2, the first battery 200 and the second battery 300, and is used to collect the first sampling voltage of the first sampling point S1, the second sampling voltage of the second sampling point S2, the first battery voltage of the first battery 200 and the second battery voltage of the second battery 300.

[0134] Specifically, the voltage sampling module 40 can be used for voltage sampling, such as collecting the first sampling voltage of the first sampling point S1, the second sampling voltage of the second sampling point S2, the first battery voltage of the first battery 200 and the second battery voltage of the second battery 300.

[0135] In the case that the first battery 200 includes a plurality of series-connected battery cells, the first battery voltage of the first battery 200 can be the sum of the voltages of the plurality of battery cells in the first battery. In the case that the second battery 300 includes a plurality of series-connected battery cells, the second battery voltage of the second battery 300 can be the sum of the voltages of the plurality of battery cells in the second battery.

[0136] The first current sampling module 50 is electrically connected with the reference point G, and is used to collect the main loop current.

[0137] The main loop current represents the current on the communication path of the positive terminal P+ and the negative terminal P-.

[0138] In the case that the first switch 10 and the third switch 30 are opened, and the second switch 20 is closed, the first battery 200 and the second battery 300 are connected in the communication path of the positive terminal P+ and the negative terminal P-, and the first battery 200 and the second battery 300 are connected in series.

[0139] In the case that the first switch 10 and the third switch 30 are closed, and the second switch 20 is opened, the first battery 200 and the second battery 300 are connected in the communication path of the positive terminal P+ and the negative terminal P-, and the first battery 200 and the second battery 300 are connected in parallel.

[0140] In the case that the first switch 10 is closed, and the second switch 20 and the third switch 30 are disconnected, the first battery 200 is connected in the communication path of the positive terminal P+ and the negative terminal P-, and the second battery 300 is not connected in the communication path of the positive terminal P+ and the negative terminal P-.

[0141] In the case that the third switch 30 is closed, and the first switch 10 and the second switch 20 are disconnected, the second battery 300 is connected in the communication path of the positive terminal P+ and the negative terminal P-, and the first battery 200 is not connected in the communication path of the positive terminal P+ and the negative terminal P-.

[0142] When the switch fails, it may cause the main circuit current to be abnormal, and the first current sampling module 50 can capture the change of the main circuit current in time.

[0143] The second current sampling module 60 is electrically connected with the branch in which the first battery 200 is located, and is used to collect the branch current.

[0144] The branch current mainly reflects the current condition of the branch in which the first battery 200 is located.

[0145] Specifically, the current condition of the branch in which the first battery 200 is located cooperates with the main circuit current, so that the current distribution of the battery management system and the influence of the switch on the current can be comprehensively understood.

[0146] The processor 70 is connected with the voltage sampling module 40, the first current sampling module 50 and the second current sampling module 60, and is used to determine whether the first switch 10, the second switch 20 and the third switch 30 exist faults according to the first sampling voltage, the second sampling voltage, the first battery voltage, the second battery voltage, the main circuit current and the branch current.

[0147] The processor 70 is a core control unit of the entire battery management system 100, and the processor 70 includes but is not limited to a microcontroller unit (MCU).

[0148] The processor 70 can comprehensively diagnose whether the first switch 10, the second switch 20 and the third switch 30 exist faults according to the first sampling voltage, the second sampling voltage, the first battery voltage, the second battery voltage, the main circuit current and the branch current. For example, the processor 70 can compare the voltage values of different sampling points and the battery, and combine the change of the current to determine whether the switch exists faults such as sticking and open circuit, so as to avoid the risk of misdiagnosis and missed diagnosis caused by invalid single sampling data, improve the diagnosis accuracy, and avoid missed diagnosis.

[0149] According to the battery management system 100 provided in the embodiment of the present application, the battery management system 100 comprises a first switch 10, a second switch 20, a third switch 30, a voltage sampling module 40, a first current sampling module 50, a second current sampling module 60 and a processor 70. The first switch 10 is electrically connected between a first sampling point S1 and a second sampling point S2. The second switch 20 is electrically connected between a positive electrode of a first battery 200 and a negative electrode of a second battery 300, and the positive electrode of the second battery 300 is electrically connected with the first sampling point S1. The third switch 30 is electrically connected between the negative electrode of the second battery 300 and a reference point G. The voltage sampling module 40 is electrically connected with the first sampling point S1, the second sampling point S2, the first battery 200 and the second battery 300, and is configured to collect a first sampling voltage of the first sampling point S1, a second sampling voltage of the second sampling point S2, a first battery voltage of the first battery 200 and a second battery voltage of the second battery 300. The first current sampling module 50 is electrically connected with the reference point G, and is configured to collect a main loop current. The second current sampling module 60 is electrically connected with a branch in which the first battery 200 is located, and is configured to collect a branch current. The processor 70 is connected with the voltage sampling module 40, the first current sampling module 50 and the second current sampling module 60, and is configured to determine whether the first switch 10, the second switch 20 and the third switch 30 have faults according to the first sampling voltage, the second sampling voltage, the first battery voltage, the second battery voltage, the main loop current and the branch current. According to the embodiment of the present application, the voltage of the sampling point, the battery voltage and the current value are combined to comprehensively diagnose whether the switch has a fault, which can avoid the risk of misdiagnosis or missed diagnosis caused by invalidation of single sampling data, improve the diagnostic accuracy and avoid missed diagnosis.

[0150] It should be noted that the inventors have found that in the related art, the diagnosis of relay sticking is basically based on the voltage across the relay. A sampling point needs to be arranged at both ends of each relay, a large number of sampling points need to be arranged, and in the case that the voltage at the sampling point cannot be collected or is not accurately collected, misdiagnosis or missed diagnosis is easily caused. However, the embodiment of the present application does not need to arrange a sampling point at both ends of each switch, the number of sampling points is reduced, and the voltage of the sampling point, the battery voltage and the current value are combined to comprehensively diagnose whether the switch has a fault, which can avoid misdiagnosis or missed diagnosis caused by the fact that the voltage across the switch cannot be collected or the voltage across the switch is not accurately collected, avoid the risk of invalidation of single sampling data, and improve the diagnostic accuracy.

[0151] Figure 3 FIG. 8 is another structural schematic diagram of the battery management system 100 provided in the embodiment of the present application.

[0152] In some embodiments, as shown in FIG. 8, the battery management system 100 can further comprise an active fuse 81, which is electrically connected between the first sampling point S1 and a third sampling point S3. Figure 3 In some embodiments, as shown in FIG. 8, the battery management system 100 can further comprise an active fuse 81, which is electrically connected between the first sampling point S1 and a third sampling point S3.

[0153] The voltage sampling module 40 is also electrically connected with the third sampling point S3, for collecting a third sampling voltage of the third sampling point S3.

[0154] The processor 70 is further configured to determine that the voltage sampling module 40 has a sampling fault, when a deviation between the first sampling voltage and the third sampling voltage is greater than a first preset deviation.

[0155] The active fuse 81 is an electrical element with an active protection function. For example, when the current sampling module detects an abnormal current, the processor 70 can trigger the active fuse to act, and timely cut off the circuit to protect the battery pack and other electrical elements from damage. The active fuse 81 is an active fuse of the main circuit. Once an emergency occurs (such as a collision, thermal runaway, and other extreme working conditions), the processor 70 can drive the active fuse 81 to actively disconnect the high-voltage circuit, so as to avoid the spread of harm.

[0156] Normal voltage relationship: when the battery management system 100 is normally operating, since the first sampling point S1 and the third sampling point S3 are connected through the active fuse 81, and the resistance of the active fuse 81 is relatively small in the case of no fault, the influence on the voltage can be ignored. Therefore, the first sampling voltage of the first sampling point S1 and the third sampling voltage of the third sampling point S3 should be similar in theory, that is, the deviation between the two should be within a small range.

[0157] Sampling fault judgment condition: the processor 70 can pre-set a first preset deviation value. When the deviation between the first sampling voltage and the third sampling voltage is greater than the first preset deviation, it means that there may be a problem when the voltage sampling module 40 collects the voltage of the first sampling point S1 and the third sampling point S3, that is, there is a sampling fault. At this time, the battery management system 100 can report a fault, and does not respond to the high-voltage instruction of the whole vehicle (because it cannot be distinguished which of the first sampling point S1 and the third sampling point S3 has a sampling problem).

[0158] The size of the first preset deviation value and other preset values in the following can be set according to the actual situation, which is not limited in the present application.

[0159] The battery management system 100 provided by the embodiments of the present application can timely and accurately diagnose the sampling fault of the voltage sampling module 40 by adding the active fuse 81 and the third sampling point S3 and the sampling fault diagnosis function of the processor 70. If the voltage sampling module 40 has a sampling fault, the processor 70 may obtain incorrect voltage data, which affects the judgment of the battery state, the switch state and the like, and even may cause an incorrect control decision, such as misjudging the overcharging and overdischarging of the battery, thereby threatening the safety and performance of the battery pack. By using the fault diagnosis method based on the deviation of the first sampling voltage and the third sampling voltage, the reliability and safety of the battery management system 100 can be effectively improved.

[0160] In one example, the voltage sampling module can include a plurality of analog-to-digital converters ADC, and different sampling points can use different analog-to-digital converters ADC. Independent ADC channels are configured for different sampling points, which can avoid the simultaneous failure of multiple voltage signals caused by a single ADC fault, and improve the fault tolerance and stability of the system. For the battery voltage of the first battery and the second battery, an analog front-end AFE sampling can be used. The AFE is an integrated chip for battery signal acquisition. By using the integrated advantage of the analog front-end AFE sampling, high-precision and high-reliability battery voltage monitoring can be achieved. The two different sampling schemes can avoid single failure risk.

[0161] The specific process of using the alternative diagnosis mechanism of the battery management system 100 provided by the embodiments of the present application to improve the robustness of the entire strategy is introduced below.

[0162] In some embodiments, the processor 70 can also be configured to, in the case that the voltage sampling module 40 cannot collect the first sampling voltage and can collect the third sampling voltage, use the third sampling voltage to replace the first sampling voltage to diagnose the switch fault.

[0163] The active fuse 81 is equivalent to a very small resistance. In normal operation, the voltages at the first sampling point S1 and the third sampling point S3 can be considered to be equal.

[0164] During the operation of the battery management system 100, the processor 70 continuously monitors the collection of the voltage sampling module 40 on the voltage of each sampling point. When the voltage sampling module 40 cannot collect the first sampling voltage but can collect the third sampling voltage, the processor 70 will start the voltage replacement diagnosis mechanism, that is, use the third sampling voltage to replace the first sampling voltage to diagnose the switch fault.

[0165] It should be noted that after the third sampling voltage is used to replace the first sampling voltage, the processor 70 needs to adjust the logic of the switch fault diagnosis. The algorithm for fault judgment based on the first sampling voltage and other voltage and current data needs to be modified to be based on the third sampling voltage and other related data for judgment.

[0166] It should also be noted that this replacement diagnosis mechanism is part of the data redundancy and fault-tolerant design of the battery management system 100. By adding the third sampling point S3 and collecting its voltage, the system can use the third sampling voltage to ensure the continuity and accuracy of the switch fault diagnosis when the voltage collection at the first sampling point S1 is abnormal. Just as in a data backup system, when the main data source has a problem, the standby data source can take over in time to ensure the normal operation of the system. In the battery management system 100, the third sampling voltage is equivalent to the standby data source, which can play a role when the first sampling voltage is unavailable. The redundant switch diagnosis scheme (replacement diagnosis mechanism) provided by the embodiments of the application can ensure the accuracy of the switch diagnosis and avoid false negatives.

[0167] The embodiments of the application use a replacement diagnosis mechanism. When the voltage sampling module 40 has a sampling fault of the first sampling voltage, the third sampling voltage is used to replace the first sampling voltage for switch fault diagnosis, and the accuracy of the switch fault diagnosis can still be ensured. In actual operation, the voltage sampling module 40 may fail to collect the first sampling voltage due to various reasons (such as sensor failure, poor line contact, etc.). If there is no replacement diagnosis mechanism, the system will not be able to perform switch fault diagnosis, thereby affecting the safe operation of the battery pack. With this mechanism, the system can continue to perform fault diagnosis when the first sampling voltage collection is abnormal, discover switch faults in time, and avoid potential safety hazards.

[0168] In some embodiments, the processor 70 can also be configured to:

[0169] In the case where the voltage sampling module 40 cannot collect the second sampling voltage and can collect the first battery voltage, the first battery voltage is used to replace the second sampling voltage for switch fault diagnosis.

[0170] When the second sampling voltage collection is abnormal, the first battery voltage can be used to ensure the continuity and accuracy of the switch fault diagnosis. After the first battery voltage is used to replace the second sampling voltage, the processor 70 needs to adjust the logic of the switch fault diagnosis accordingly. The algorithm for fault judgment based on the second sampling voltage and other voltage and current data needs to be modified to be based on the first battery voltage and other related data for judgment.

[0171] The application embodiment adopts a substitute diagnosis mechanism. When the second sampling voltage sampling failure occurs in the voltage sampling module 40, the first battery voltage is used to substitute the second sampling voltage for the diagnosis of the switch failure, and the accuracy of the switch failure diagnosis can still be ensured. In actual operation, the voltage sampling module 40 may fail to collect the second sampling voltage due to various reasons (such as sensor failure, poor line contact, electromagnetic interference, etc.). If there is no substitute diagnosis mechanism, the system will not be able to perform switch failure diagnosis, thereby affecting the safe operation of the battery pack. With the mechanism, the system can continue to perform failure diagnosis when the second sampling voltage collection is abnormal, discover the switch failure in time, and avoid potential safety hazards.

[0172] The specific process of judging the switch sticking failure of the battery management system 100 provided by the application embodiment is introduced below.

[0173] The diagnosis opportunity of the switch sticking is before the closing instruction is issued to the switch or after the opening instruction is issued to the switch.

[0174] In some embodiments, the processor 70 can be configured to:

[0175] In the case where the first switch 10, the second switch 20 and the third switch 30 are all open, if the first sampling voltage is greater than the first threshold value, it is determined that at least one of the first switch 10, the second switch 20 and the third switch 30 has a sticking failure.

[0176] Specifically, in a normal case, when the first switch 10, the second switch 20 and the third switch 30 are all open, the first sampling voltage of the first sampling point S1 should theoretically be in a relatively low voltage state (such as zero voltage or a small voltage). When at least one of the first switch 10, the second switch 20 or the third switch 30 has a sticking failure, the first sampling point S1 and the reference point G are connected, and at least one of the first battery and the second battery is included in the connection path between the first sampling point S1 and the reference point G, so that the voltage of the first sampling point S1 rises. Therefore, when the first sampling voltage of the first sampling point S1 is greater than the preset first threshold value, it indicates that at least one of the first switch 10, the second switch 20 and the third switch 30 has a sticking failure.

[0177] The processor 70 of the application embodiment can determine whether the switch has a sticking failure by judging whether the first sampling voltage is greater than the first threshold value in the case where the first switch 10, the second switch 20 and the third switch 30 are all open, thereby providing an effective switch sticking failure diagnosis mechanism and ensuring the safety and reliability of the battery management system 100.

[0178] In some embodiments, the processor 70 can be configured to:

[0179] When the first switch 10, the second switch 20 and the third switch 30 are all open, if at least one of the following three relationships is satisfied, it is determined that the first switch 10 or the third switch 30 has a sticking fault.

[0180] |U1-U2|≤a1*U2;

[0181] |U1-VM1|≤a1*VM1;

[0182] |U1-VM2|≤a1*VM2;

[0183] U1 represents the first sampling voltage, U2 represents the second sampling voltage, VM1 represents the first battery voltage, VM2 represents the second battery voltage, and a1 is a preset value less than 0.5.

[0184] Specifically, if the first switch 10 is stuck, the first sampling point S1 will be connected to the first battery 200 through the stuck first switch 10, resulting in a smaller difference between U1 and VM1 or between U1 and U2. If the third switch 30 is stuck, the first sampling point S1 will be connected to the second battery 300 through the stuck third switch 30, resulting in a smaller difference between U1 and VM2. Therefore, when the first switch 10, the second switch 20 and the third switch 30 are all open, if at least one of the above three relationships is satisfied, the processor 70 can determine that the first switch 10 or the third switch 30 has a sticking fault.

[0185] a1 is a preset value, for example, a1 is 5%. Of course, the size of a1 can be designed according to actual conditions, which is not limited in the present application.

[0186] The embodiment of the present application limits the difference ratio, for example, by limiting the proportional relationship between |U1-U2|, |U1-VM1|, |U1-VM2| and the corresponding voltage, whether the first switch 10 or the third switch 30 has a sticking fault can be accurately determined. Since the fault can be determined when the above at least one relationship is satisfied, the robustness of the diagnosis is improved.

[0187] In some embodiments, the processor 70 can also be configured to:

[0188] In the case of |U1-VM1|<|U1-VM2|, it is determined that the first switch 10 has a sticking fault.

[0189] Specifically, in the case that the first switch 10, the second switch 20 and the third switch 30 are all disconnected, if the first switch 10 has a sticking fault, the first sampling point S1 will form an electrical path with the first battery 200 through the sticking first switch 10. At this time, the value of U1 will be close to VM1, so that the value of |U1-VM1| is relatively small. Therefore, when |U1-VM1|<|U1-VM2|, it can be inferred that the first switch 10 has a sticking fault.

[0190] The embodiment of the application can directly determine whether the first switch 10 has a sticking fault by comparing the values of |U1-VM1| and |U1-VM2|, thereby improving the efficiency of fault diagnosis.

[0191] In some embodiments, the processor 70 can also be configured to:

[0192] In the case that |U1-VM1|>|U1-VM2|, it is determined that the third switch 30 has a sticking fault.

[0193] Specifically, in the case that the first switch 10, the second switch 20 and the third switch 30 are all disconnected, if the third switch 30 has a sticking fault, the first sampling point S1 will form an electrical path with the second battery 300 through the sticking third switch 30, so that the value of |U1-VM2| is relatively small. Therefore, in the case that |U1-VM1|>|U1-VM2|, it can be determined that the third switch 30 has a sticking fault.

[0194] The embodiment of the application can directly determine whether the third switch 30 has a sticking fault by comparing the values of |U1-VM1| and |U1-VM2|, thereby improving the efficiency of fault diagnosis.

[0195] It should be noted that if |U1-VM1|=|U1-VM2|, the first switch 10 / third switch 30 sticking cannot be distinguished, and it can be determined that the first switch 10 or the third switch 30 is sticking.

[0196] In some embodiments, the processor 70 can be configured to:

[0197] In the case that the first switch 10, the second switch 20 and the third switch 30 are all disconnected, if at least one of the following two relationships is satisfied, it is determined that the second switch 20 has a sticking fault.

[0198] |U1-2*U2|≤a2*2*U2;

[0199] |U1-(VM1+VM2)|≤a2*(VM1+VM2);

[0200] U1 represents a first sampling voltage, U2 represents a second sampling voltage, VM1 represents a first battery voltage, VM2 represents a second battery voltage, and a2 is a preset value less than 0.5.

[0201] Specifically, when the first switch 10, the second switch 20, and the third switch 30 are all in the open state, if the second switch 20 has a sticking fault, the first sampling point S1, the second battery 300, the second sampling point S2, and the first battery 200 will form an electrical path based on the sticking second switch 20, that is, the first battery 200 and the second battery 300 will be connected in series. Therefore, if at least one of the above two relationships is satisfied, it can be determined that the second switch 20 has a sticking fault.

[0202] a2 is a preset value, for example, a2 is 5%. Of course, the size of a2 can be designed according to actual conditions, which is not limited in the present application.

[0203] The above relationship can be used to directly determine whether the second switch 20 has a sticking fault, thereby improving the efficiency of fault diagnosis.

[0204] The above is an introduction to the switch sticking diagnosis scheme.

[0205] The following describes a specific process of determining a switch open-circuit fault of the battery management system 100 provided in an embodiment of the present application.

[0206] The diagnosis timing of the switch open circuit is before the disconnection instruction is issued to the switch or after the closing instruction is issued to the switch.

[0207] Figure 4 is another structural schematic diagram of the battery management system 100 provided in an embodiment of the present application.

[0208] In some embodiments, as shown in Figure 4 The battery management system 100 can further include a main loop switch 82, and the processor 70 can be configured to:

[0209] In a case where the first switch 10 is closed and the second switch 20, the third switch 30, and the main loop switch 82 are open, if U1≤b1*U2, it is determined that the first switch 10 has an open-circuit fault.

[0210] U1 represents a first sampling voltage, U2 represents a second sampling voltage, and b1 is a preset value less than 0.5 (such as 0.4).

[0211] Specifically, in the case that the first switch 10 is normally closed and other switches are open, it is equivalent to the first battery 200 being charged in the 400V single mode, and theoretically, the first sampling point S1 should be electrically connected to the first battery 200 through the first switch 10. If the first switch 10 has an open circuit fault, although the control signal indicates that it is closed, in fact, there is no electrical connection between the first sampling point S1 and the first battery 200, and thus if U1≤b1*U2, it can be determined that the first switch 10 has an open circuit fault.

[0212] The embodiment of the application can diagnose the open circuit fault of the first switch 10 in time, thereby ensuring the normal charging of the first battery 200 in the 400V single mode.

[0213] It should be noted that the positive terminal P+ is connected to the main circuit switch 82 in the drawings for illustration, which does not limit the application. For example, in other examples, the positive terminal P+ and the negative terminal P- are respectively connected to the main circuit switch 82, or the negative terminal P- is connected to the main circuit switch 82.

[0214] In some embodiments, still referring to Figure 4 , the battery management system 100 can further include a main circuit switch 82, and the processor 70 can be configured to:

[0215] In the case that the third switch 30 is closed and the first switch 10, the second switch 20 and the main circuit switch 82 are open, if U1≤b1*U2, it is determined that the third switch 30 has an open circuit fault.

[0216] U1 represents the first sampling voltage, U2 represents the second sampling voltage, and b1 is a preset value less than 0.5.

[0217] Specifically, in the case that the third switch 30 is normally closed and other switches are open, it is equivalent to the second battery 300 being charged in the 400V single mode, and theoretically, the first sampling point S1 should be electrically connected to the second battery 300 through the third switch 30. If the third switch 30 has an open circuit fault, although the control signal indicates that it is closed, in fact, there is no electrical connection between the first sampling point S1 and the second battery 300, and thus if U1≤b1*U2, it can be determined that the third switch 30 has an open circuit fault.

[0218] The embodiment of the application can diagnose the open circuit fault of the third switch 30 in time, thereby ensuring the normal charging of the second battery 300 in the 400V single mode.

[0219] In some embodiments, still referring to Figure 4 , the battery management system 100 can further include a main circuit switch 82, and the processor 70 can be configured to:

[0220] In a case where the first switch 10 and the third switch 30 are closed and the second switch 20 and the main loop switch 82 are disconnected, if U1≤b1*U2, it is determined that the first switch 10 and the third switch 30 have an open circuit fault.

[0221] U1 represents the first sampling voltage, U2 represents the second sampling voltage, and b1 is a preset value less than 0.5.

[0222] Specifically, in a case where the first switch 10 and the third switch 30 are normally closed and other switches are disconnected, which is equivalent to a parallel 400V charging mode, theoretically, the first sampling point S1 should form an electrical connection with the first battery 200 through the first switch 10, and the first sampling point S1 should form an electrical connection with the second battery 300 through the third switch 30. If the first switch 10 and the third switch 30 both have an open circuit fault, although the control signal indicates that they are closed, in fact, there is no electrical connection between the first sampling point S1 and the first battery 200, and there is also no electrical connection between the first sampling point S1 and the second battery 300, so if U1≤b1*U2, it can be determined that the first switch 10 and the third switch 30 have an open circuit fault.

[0223] The embodiment of the present application can diagnose the open circuit fault of the first switch 10 and the third switch 30 in time, thereby ensuring that the first battery 200 and the second battery 300 can normally perform parallel 400V charging.

[0224] It should be noted that the open circuit diagnosis of the first switch 10 / third switch 30 described above is before high voltage (the main loop switch 82 is disconnected). In a case where the second switch 20 is disconnected and the main loop switch 82 is disconnected, if the first switch 10 and the third switch 30 are closed, at this time, if only one of the switches has an open circuit, the open circuit fault cannot be diagnosed, because even if one of the first switch 10 and the third switch 30 is stuck, the first sampling point S1 can still sample the voltage of the first battery 200 or the second battery 300, which cannot satisfy the determination condition, at this time, the open circuit diagnosis of the first switch 10 or the third switch 30 can be distinguished after high voltage.

[0225] It should be further noted that the main loop switch 82 being disconnected means before high voltage, and the main loop switch 82 being closed means after high voltage.

[0226] In some embodiments, still referring to Figure 4 , the battery management system 100 can further include a main loop switch 82, and the processor 70 can be configured to:

[0227] In a case where the first switch 10 and the main loop switch 82 are closed and the second switch 20 is disconnected, if at least one of the following two relationships is satisfied, it is determined that the first switch 10 has an open circuit fault.

[0228] U1≤b1*U2;

[0229] |Shunt2|≤I1 and |Shunt1|≥I2;

[0230] U1 represents the first sampling voltage, U2 represents the second sampling voltage, Shunt1 represents the main loop current, Shunt2 represents the branch current, b1 is a preset value less than 0.5, I1 and I2 are preset values, and I1 < I2.

[0231] The preset values b1, I1 and I2 are used to set the judgment threshold to distinguish between normal and fault conditions. By adjusting the size of these preset values, the sensitivity and accuracy of fault diagnosis can be adjusted, which can be set according to actual needs, and the embodiments of the application are not limited.

[0232] For example, I1 is a small current such as 5A, and I2 is a large current such as 100A.

[0233] Specifically, when the first switch 10 and the main loop switch 82 are closed, and the second switch 20 is open, theoretically, the first sampling point and the first battery 200 can form an electrical connection through the first switch 10 and the main loop. In this case, the voltage U1 of the first sampling point S1 should be close to the positive voltage of the first battery 200, that is, close to the voltage U2 of the second sampling point S2. If the first switch 10 has an open circuit fault, although the control signal indicates that it is closed, in fact, the first battery 200 and the first sampling point S1 do not form an effective electrical connection, so in the case of U1≤b1*U2, it can be determined that the first switch 10 has an open circuit fault.

[0234] In addition, in the normal case, when the first switch 10 is closed, the branch current Shunt2 should reflect the current condition of the branch where the first battery 200 is located, and the main loop current Shunt1 reflects the current condition of the entire main loop. Therefore, whether the first switch 10 has an open circuit fault can be determined by comparing the size relationship between the branch current Shunt2 and the preset value I1, and the size relationship between the main loop current Shunt1 and the preset value I2. When |Shunt2|≤I1 and |Shunt1|≥I2, it can be considered that the branch current of the first battery 200 is abnormally small and the main loop current is relatively large, so it is inferred that the first switch 10 may have an open circuit fault.

[0235] The embodiments of the application can more accurately diagnose whether the first switch 10 has an open circuit fault by combining the sampling data of voltage and current, and the redundant fault diagnosis mechanism improves the reliability of the system, which can ensure timely detection and processing when the first switch 10 has an open circuit fault.

[0236] In some embodiments, please continue to refer to Figure 4The battery management system 100 can further include a main loop switch 82, and the processor 70 can be configured to:

[0237] In a case where the third switch 30 and the main loop switch 82 are closed and the second switch 20 is open, if at least one of the following two relationships is satisfied, it is determined that the third switch 30 has an open circuit fault.

[0238] U1≤b2*U2;

[0239] |Shunt1-Shunt2|≤b2*Shunt1 and |Shunt1|≥I2;

[0240] U1 represents the first sampling voltage, Shunt1 represents the main loop current, Shunt2 represents the branch current, b2 is a preset value less than 0.5 (for example, 5%), and I2 is a preset value.

[0241] Specifically, when the third switch 30 and the main loop switch 82 are closed and the second switch 20 is open, theoretically, the first sampling point S1 and the second battery 300 can form an electrical connection through the third switch 30. In this case, the voltage U1 of the first sampling point S1 should be close to the positive voltage of the second battery 300. If the third switch 30 has an open circuit fault, although the control signal indicates that it is closed, in fact, there is no effective electrical connection between the second battery 300 and the first sampling point S1, so it can be determined that the third switch 30 has an open circuit fault in the case of U1≤b1*U2.

[0242] In addition, whether the third switch 30 has an open circuit fault can also be determined by comparing the difference between the main loop current Shunt1 and the branch current Shunt2 of the first battery 200, and the size relationship between the main loop current Shunt1 and the preset value I2.

[0243] The embodiments of the present application can more accurately diagnose whether the third switch 30 has an open circuit fault by combining the sampling data of voltage and current, and the redundant fault diagnosis mechanism improves the reliability of the system, which can ensure timely detection and processing when the third switch 30 has an open circuit fault.

[0244] It should be noted that by adding current as a supplementary judgment condition, the judgment of the first switch 10 and the third switch 30 does not need to distinguish the states of each other.

[0245] In some embodiments, the processor 70 can be configured to:

[0246] In a case where the first switch 10 and the third switch 30 are open and the second switch 20 is closed, if U1≤b3*U2, it is determined that the second switch 20 has an open circuit fault.

[0247] U1 represents a first sampling voltage, U2 represents a second sampling voltage, and b3 is a preset value less than 0.5.

[0248] b3 is a preset value less than 0.5, such as 0.4.

[0249] Specifically, in the case where the first switch 10 and the third switch 30 are open and the second switch 20 is closed, theoretically, the first sampling point S1, the second battery 300, and the first battery 200 can form an electrical connection through the second switch 20, and therefore, if U1≤b3*U2, it can be determined that the second switch 20 has an open circuit fault.

[0250] The embodiments of the present application can diagnose the open circuit fault of the second switch 20 in time, thereby ensuring that the first battery 200 and the second battery 300 can normally perform 800V series charging / discharging.

[0251] It should be noted that the embodiments of the present application provide a redundant relay diagnosis scheme, which arranges three high-voltage samplings (the first sampling point S1, the second sampling point S2, and the third sampling point S3) to diagnose the sticking / open circuit of the three switches, and simultaneously checks and verifies the coupling current sampling value between the multiple sampling points and the voltage accumulation of the two battery cells, thereby improving the accuracy of the sticking and open circuit diagnosis of the switches, and ensuring that the sticking of the switches will not be missed, so as to prevent the mis-closed switches from causing the battery pack to short circuit and causing serious consequences.

[0252] The above is the specific process of diagnosing the sticking fault (the sticking fault can be simply understood as a fault type in which the switch should be open but is not open) and the open circuit fault (the open circuit fault can be simply understood as a fault type in which the switch should be closed but is not closed) of the battery management system 100 provided by the embodiments of the present application. The sticking of the switch has a safety risk, and therefore the sticking diagnosis is combined with the high-voltage sampling and the voltage accumulation of the battery cells to improve the accuracy of the strategy. The open circuit diagnosis has a lower safety risk, and therefore the high-voltage sampling is used for judgment, and only in the case where the high-voltage sampling is invalid, the voltage accumulation of the battery cells is used instead, thereby improving the robustness of the strategy.

[0253] The charging strategy of the battery management system 100 provided by the embodiments of the present application will be introduced below.

[0254] In some embodiments, the processor 70 can also be configured to:

[0255] In the case where the output voltage of the charging device 400 electrically connected to the battery management system 100 is greater than the threshold voltage, the second switch 20 is closed, and the first switch 10 and the third switch 30 are in an open state.

[0256] The charging device 400 can be configured to charge the battery.

[0257] Specifically, in the case that the output voltage of the charging device 400 is greater than the threshold voltage, it is illustrated that the charging device 400 is an 800V charging device, at this time, the second switch 20 can be closed by control, and the first switch 10 and the third switch 30 are in an open state, so that the first battery 200 and the second battery 300 are connected in series, thereby realizing the series 800V charging mode.

[0258] The embodiment of the present application adopts the series charging mode of the first battery 200 and the second battery 300 in the case that the output voltage of the charging device 400 is greater than the threshold voltage, so that the battery pack (the first battery 200 and the second battery 300) can fully utilize the high output voltage (such as 800V high voltage) of the charging device 400, reduce the charging time, and improve the charging efficiency.

[0259] It should be noted that the two batteries are connected in parallel for charging only when the 400V charging pile is detected, and the series 800V charging is used in other working conditions. Due to the difference in battery consistency and internal resistance, there is a voltage difference between the two batteries in the actual use process. If the 400V charging device is detected in the case of a large voltage difference, the switch (such as a relay) is directly closed, which is easy to cause the sticking fault of the relay. Therefore, it is necessary to control when the relay switches to the 400V charging.

[0260] In some embodiments, the processor 70 can also be used for:

[0261] In the case that the output voltage of the charging device 400 electrically connected to the battery management system 100 is less than the threshold voltage, if |VM1-VM2|≤V1, the first switch 10 and the third switch 30 are controlled to be closed, and the second switch 20 is in an open state.

[0262] VM1 represents the first battery voltage, VM2 represents the second battery voltage, and V1 is a preset value.

[0263] Before deciding to enter the parallel charging mode, it is judged whether the difference between the first battery voltage VM1 and the second battery voltage VM2 is small enough to ensure that the voltage difference between the two batteries is not too large when charging in parallel, thereby avoiding current imbalance and potential battery damage.

[0264] Specifically, the processor 70 can monitor the output voltage of the charging device 400, and if it is less than the preset threshold voltage, it is determined that the charging device 400 cannot support the series charging mode. When the processor 70 detects that the output voltage of the charging device 400 is lower than the preset threshold voltage, it will further judge the difference between the first battery voltage VM1 and the second battery voltage VM2. If the difference satisfies |VM1-VM2|≤V1 (V1 is a preset value, such as 5V), the processor 70 will control the first switch 10 and the third switch 30 to be closed, and control the second switch 20 to be opened, thereby entering the parallel charging mode.

[0265] The charging strategy of the battery management system 100 when the output voltage of the charging device 400 is less than the threshold voltage is that, for example, when the output voltage of the charging device 400 is 400 V, the battery parallel charging mode can be adopted. Before entering the parallel charging mode, it can also be judged whether the difference between the first battery voltage VM1 and the second battery voltage VM2 is small enough, so as to ensure that the voltage difference between the two batteries is not too large when parallel charging, thereby avoiding current imbalance and potential battery damage, and ensuring the safety and reliability of the charging process.

[0266] In some embodiments, the processor 70 can also be used for:

[0267] In the case where the output voltage of the charging device 400 to which the battery management system 100 is electrically connected is less than the threshold voltage, if VM1-VM2>V1, the third switch 30 is first controlled to be closed, and the first switch 10 and the second switch 20 are in an open state, until the voltage of the second battery 300 is charged to a voltage difference with the first battery 200 less than V2, the charging current Ia is requested, and after the charging current is reduced to below Ia, the first switch 10 is controlled to be closed.

[0268] VM1 represents the first battery voltage, VM2 represents the second battery voltage, V1 and V2 are preset values, and V2V1, and Ia is a current safety threshold.

[0269] After the new energy vehicle plug-in gun, the battery management system 100 can interact with the charging device to obtain the charging device related information and judge the output voltage of the charging device.

[0270] Specifically, when the processor 70 detects that the output voltage of the charging device 400 is lower than the preset threshold voltage, it will further judge the difference between the first battery voltage VM1 and the second battery voltage VM2. If the difference satisfies |VM1-VM2|>V1 (V1 is a preset value, such as 5V), it indicates that the voltages of the two batteries are unbalanced, and the following charging strategy needs to be adopted to avoid closing the switch directly when the branch voltage difference is too large, thereby avoiding causing the switch to stick:

[0271] 1) Charging the battery with lower voltage separately (by judging the voltage difference between VM1 and VM2, it can be determined which branch needs to be charged preferentially, such as the second battery 300).

[0272] Switch control: the processor 70 controls the third switch 30 to be closed, while ensuring that the first switch 10 and the second switch 20 are open, so that the second battery 300 is connected to the charging device 400 alone and starts charging.

[0273] Charging target: through separate charging, gradually increase the voltage of the second battery 300 until its voltage difference with the first battery 200 is less than V2 (V2 is a preset voltage difference threshold, V2 needs to have a certain hysteresis interval with V1 to avoid the relay repeatedly opening and closing due to zero point jumping, for example, 3V).

[0274] 2) Request charging current Ia and monitor.

[0275] Request charging current: when the voltage of the second battery 300 approaches the voltage of the first battery 200 (the voltage difference is less than V2), the processor 70 requests the charging device 400 to provide the charging current Ia (Ia is a current safety threshold, and there is no risk of relay closing under load at this current, for example, 5A).

[0276] Current monitoring: during charging, the processor 70 monitors the charging current in real time to ensure that it does not exceed Ia. This is to prevent battery overheating or damage caused by excessive current.

[0277] 3) Close the first switch 10 to achieve parallel charging.

[0278] When the charging current decreases below Ia, the processor 70 controls the first switch 10 to be closed while keeping the second switch 20 open (to ensure that a series path is not formed). At this time, the first battery 200 and the second battery 300 form a parallel relationship for parallel charging, and finally the first battery 200 and the second battery 300 are charged in parallel until full charge.

[0279] The embodiments of the application are the charging strategy of the battery management system 100 when the output voltage of the charging device 400 is less than the threshold voltage, and the voltage difference between the first battery 200 and the second battery 300 is large (VM1-VM2>V1). By first charging the battery with a lower voltage (such as the second battery 300) and then gradually charging in parallel, the risk of excessive current or battery damage caused by uneven battery voltage is avoided, ensuring safe and efficient charging of the battery pack under uneven voltage conditions and ultimately achieving voltage balancing. And set a current safety threshold Ia during charging to avoid the impact of high current on the battery, ensuring the safety and reliability of the charging process and prolonging the service life of the battery.

[0280] In some embodiments, the processor 70 can also be used for:

[0281] In the case that the output voltage of the charging device 400 electrically connected to the battery management system 100 is less than the threshold voltage, if VM2-VM1>V1, the first switch 10 is first controlled to be closed, and the third switch 30 and the second switch 20 are in an open state, until the voltage of the first battery 200 is charged to the case that the voltage difference with the second battery 300 is less than V2, the charging current Ia is requested, and after the charging current is reduced to below Ia, the third switch 30 is controlled to be closed.

[0282] VM1 represents the first battery voltage, VM2 represents the second battery voltage, V1 and V2 are preset values, and V2

[0283] Specifically, when the processor 70 detects that the output voltage of the charging device 400 is lower than the preset threshold voltage, it further judges the difference between the first battery voltage VM1 and the second battery voltage VM2. If the difference satisfies |VM1-VM2|>V1 (V1 is a preset value), it indicates that the voltages of the two batteries are unbalanced, and a special charging strategy needs to be adopted: separately charging the battery with lower voltage (such as the first battery 200); closing the third switch 30 to realize parallel charging.

[0284] The embodiment of the present application is a charging strategy of the battery management system 100 when the output voltage of the charging device 400 is less than the threshold voltage, and the voltage difference between the first battery 200 and the second battery 300 is large (VM1-VM2>V1). By first separately charging the battery with lower voltage (such as the first battery 200) and then gradually charging in parallel, the risk of excessive current or battery damage caused by unbalanced battery voltage is avoided, which can ensure safe and efficient charging of the battery pack under unbalanced voltage conditions and ultimately achieve voltage balancing. Moreover, the current safety threshold Ia is set during the charging process to avoid the impact of large current on the battery, ensuring the safety and reliability of the charging process and prolonging the service life of the battery.

[0285] Figure 5 is another structural schematic diagram of the battery management system 100 provided by the embodiment of the present application.

[0286] In some embodiments, as shown in Figure 5 The battery management system 100 can further include a first fuse 83.

[0287] The first fuse 83 is connected in series between the first sampling point S1 and the second sampling point S2.

[0288] The first fuse 83 newly added in the embodiment of the present application is connected in series between the first sampling point S1 and the second sampling point S2. When the current flowing through the first fuse 83 exceeds its rated value, the fuse inside the first fuse 83 will melt due to overheating, thereby cutting off the circuit and preventing equipment damage caused by excessive current.

[0289] In some embodiments, referring to Figure 4 , the battery management system 100 can further include a second fuse 84.

[0290] The second fuse 84 is connected in series between the negative electrode of the second battery 300 and the reference point G with the third switch 30.

[0291] The second fuse 84 newly added in the embodiments of the present application is connected in series between the negative electrode of the second battery 300 and the reference point G with the third switch 30. When the current flowing through the second fuse 84 exceeds its rated value, the fuse inside the second fuse 84 will melt due to overheating, thereby cutting off the circuit and preventing damage to the equipment caused by excessive current. For example, if the first battery 200 branch is short-circuited, it can be protected by the passive fuse (first fuse 83); if the second battery 300 branch is short-circuited, it is protected by the passive fuse (second fuse 84), avoiding serious consequences caused by battery short-circuit.

[0292] In one example, the first switch 10, the second switch 20 and the third switch 30 are all relays, and 2 400V battery packs are connected in series and parallel by 3 relays. The main circuit uses the active fuse 81 for short-circuit protection, and the two branches use passive fuses (such as the first fuse 83 and the second fuse 84) for short-circuit protection, to meet the functional safety protection design.

[0293] Figure 6 A charging flowchart of a battery management system according to one scenario embodiment of the present application.

[0294] In one scenario example, as shown in Figure 6 , the charging process of the battery management system 100 can include steps S110-S168.

[0295] S110, plug in the gun.

[0296] After the new energy vehicle is plugged in, the battery management system 100 can interact with the charging device 400 to obtain relevant information of the charging device 400 and determine the output voltage of the charging device 400.

[0297] Steps S121-S123 are the charging process when the charging device 400 is an 800V charging device.

[0298] S121, according to the output voltage of the charging device 400, it is determined that the charging device 400 is an 800V charging device.

[0299] S122, in the case that the charging device 400 is an 800V charging device, the second switch 20 is closed.

[0300] S123, the first battery 200 and the second battery 300 are charged in series.

[0301] Steps S130-S168 are charging procedures when the charging device 400 is a 400V charging device.

[0302] Steps S141-S143 are charging procedures when the voltage difference between the first battery 200 and the second battery 300 is small.

[0303] S130, according to the output voltage of the charging device 400, it is determined that the charging device 400 is a 400V charging device.

[0304] S141, in the case that the charging device 400 is a 400V charging device, it is determined whether |VM1-VM2|≤V1 is satisfied.

[0305] S142, in the case that |VM1-VM2|≤V1 (V1 is a preset value, such as 5V) is satisfied, it indicates that the voltage difference between the first battery 200 and the second battery 300 is small, and at this time, the first switch 10 and the third switch 30 can be closed.

[0306] S143, the first battery 200 and the second battery 300 are charged in parallel.

[0307] Steps S151-S158 are charging procedures when the voltage difference between the first battery 200 and the second battery 300 is large and the voltage of the second battery 300 is low.

[0308] S151, in the case that |VM1-VM2|≤V1 is not satisfied, it is further determined whether VM1-VM2>V1 is satisfied.

[0309] S152, in the case that VM1-VM2>V1 is satisfied, it indicates that the voltage difference between the first battery 200 and the second battery 300 is large and the voltage of the second battery 300 is low, and at this time, the third switch 30 can be closed.

[0310] S153, the second battery 300 is charged alone.

[0311] S154, it is determined whether VM1-VM2≤V2 (V2 is a preset voltage difference threshold, V2 needs to have a certain hysteresis interval with V1 to avoid the relay repeatedly opening and closing due to zero-point jumping, such as 3V) is satisfied.

[0312] S155, if VM1-VM2≤V2 is satisfied, it indicates that the voltage difference between the first battery 200 and the second battery 300 has become small, and at this time, the charging current Ia (Ia is a current safety threshold, and there is no risk of relay closing under load at this current, such as 5A) can be requested from the charging device 400.

[0313] S156, determining whether the loop current is less than or equal to Ia.

[0314] S157, in the case of loop current less than or equal to Ia, closing the first switch 10.

[0315] S158, the first battery 200 and the second battery 300 are charged in parallel.

[0316] Steps S161-S168 are the charging process in the case of large voltage difference between the first battery 200 and the second battery 300 and low voltage of the first battery 200.

[0317] S161, in the case of not satisfying |VM1-VM2|≤V1, determining whether VM2-VM1>V1.

[0318] S162, in the case of satisfying VM2-VM1>V1, closing the first switch 10.

[0319] S163, the first battery 200 is charged alone.

[0320] S164, determining whether VM2-VM1≤V2.

[0321] S165, if VM2-VM1≤V2, the charging current Ia can be requested from the charging device 400.

[0322] S166, determining whether the loop current is less than or equal to Ia.

[0323] S167, in the case of loop current less than or equal to Ia, closing the third switch 30.

[0324] S168, the first battery 200 and the second battery 300 are charged in parallel.

[0325] The embodiments of the application can intelligently select the most suitable charging mode according to the output voltage of the charging device 400 and the voltage difference between the first battery 200 and the second battery 300, including 800V series charging, 400V parallel charging, and charging the battery with low voltage first and then gradually charging in parallel at 400V, which ensures the efficiency of the charging process, ensures the safety and reliability of the charging process, and prolongs the service life of the battery.

[0326] It should be noted that the embodiments of the application mainly aim at fault diagnosis of three switches for 400V / 800V switching. The main positive, main negative, pre-charge, charge positive, and charge negative relays in the conventional high-voltage topology can use the conventional diagnosis scheme, and the sampling of high voltage and current can use the conventional sampling scheme, which can be realized by the processor 70 of the embodiments of the application.

[0327] Based on the same inventive concept, the application further provides a battery pack. As shown in Figure 7 The battery pack 1000 includes the first battery 200, the second battery 300 and the battery management system 100 in any of the above embodiments. It can be understood that the battery pack 1000 has the beneficial effects of the battery management system 100 provided by the embodiments of the application, and the specific description of the battery management system 100 can be referred to the above embodiments, which will not be repeated here.

[0328] Based on the same inventive concept, the application further provides a battery pack. As shown in Figure 8 The battery pack 1000 includes the first battery 200, the second battery 300 and the battery management system 100 in any of the above embodiments. It can be understood that the battery pack 1000 has the beneficial effects of the battery management system 100 provided by the embodiments of the application, and the specific description of the battery management system 100 can be referred to the above embodiments, which will not be repeated here.

[0329] It should be noted that the embodiments and features in the embodiments of the application can be combined with each other without conflict.

[0330] Although the application has been described with reference to the preferred embodiments, various modifications can be made to the application without departing from the scope of the application, and the components thereof can be replaced with equivalents, especially, the technical features mentioned in each embodiment can be combined in any way without structural conflict. The application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery management system, characterized in that, It includes a first switch, a second switch, a third switch, a voltage sampling module, a first current sampling module, a second current sampling module, and a processor; The first switch is electrically connected between the first sampling point and the second sampling point; The second switch is electrically connected between the positive terminal of the first battery and the negative terminal of the second battery, and the positive terminal of the second battery is electrically connected to the first sampling point. The third switch is electrically connected between the negative terminal of the second battery and the reference point; The voltage sampling module is electrically connected to the first sampling point, the second sampling point, the first battery, and the second battery, and is used to collect the first sampling voltage of the first sampling point, the second sampling voltage of the second sampling point, the first battery voltage of the first battery, and the second battery voltage of the second battery. The first current sampling module is electrically connected to the reference point and is used to collect the main circuit current; The second current sampling module is electrically connected to the branch where the first battery is located and is used to collect the branch current; The processor, connected to the voltage sampling module, the first current sampling module, and the second current sampling module, is used to compare the first sampled voltage, the second sampled voltage, the first battery voltage, and the second battery voltage, and, in conjunction with the changes in the main circuit current and the branch current, determine whether there is a sticking or open circuit fault in the first switch, the second switch, and the third switch.

2. The battery management system according to claim 1, characterized in that, The battery management system also includes an active fuse, which is electrically connected between the first sampling point and the third sampling point; The voltage sampling module is also electrically connected to the third sampling point, and is used to collect the third sampling voltage of the third sampling point; The processor is further configured to: determine that the voltage sampling module has a sampling fault when the deviation between the first sampling voltage and the third sampling voltage is greater than a first preset deviation.

3. The battery management system according to claim 2, characterized in that, The processor is further configured to: when the voltage sampling module cannot acquire the first sampling voltage but can acquire the third sampling voltage, use the third sampling voltage to replace the first sampling voltage for diagnosing switch faults.

4. The battery management system according to any one of claims 1-3, characterized in that, The processor is also used for: If the voltage sampling module cannot acquire the second sampling voltage but can acquire the first battery voltage, the first battery voltage is used to replace the second sampling voltage for diagnosing the switch fault.

5. The battery management system according to claim 1, characterized in that, The processor is used for: If the first sampling voltage is greater than the first threshold when the first switch, the second switch, and the third switch are all open, it is determined that at least one of the first switch, the second switch, and the third switch has an adhesion fault.

6. The battery management system according to claim 1, characterized in that, The processor is used for: If the first switch, the second switch, and the third switch are all open, and at least one of the following three relationships is satisfied, then it is determined that the first switch or the third switch has an adhesion fault. |U1-U2|≤a1*U2; |U1-VM1|≤a1*VM1; |U1-VM2|≤a1*VM2; U1 represents the first sampling voltage, U2 represents the second sampling voltage, VM1 represents the first battery voltage, VM2 represents the second battery voltage, and a1 is a preset value less than 0.

5.

7. The battery management system according to claim 6, characterized in that, The processor is also used for: If |U1-VM1| < |U1-VM2|, then the first switch is determined to have an adhesion fault.

8. The battery management system according to claim 6, characterized in that, The processor is also used for: If |U1-VM1|>|U1-VM2|, then the third switch is determined to have an adhesion fault.

9. The battery management system according to claim 1, characterized in that, The processor is used for: If the first switch, the second switch, and the third switch are all open, and at least one of the following two relationships is satisfied, then the second switch is determined to have an adhesion fault. |U1-2*U2|≤a2*2*U2; |U1-(VM1+VM2)|≤a2*(VM1+VM2); U1 represents the first sampling voltage, U2 represents the second sampling voltage, VM1 represents the first battery voltage, VM2 represents the second battery voltage, and a2 is a preset value less than 0.

5.

10. The battery management system according to claim 1, characterized in that, The battery management system also includes a main circuit switch, and the processor is used for: If U1≤b1*U2, and the first switch is closed while the second switch, the third switch, and the main circuit switch are open, then the first switch is determined to have an open circuit fault. U1 represents the first sampling voltage, U2 represents the second sampling voltage, and b1 is a preset value less than 0.

5.

11. The battery management system according to claim 1, characterized in that, The battery management system also includes a main circuit switch, and the processor is used for: If the third switch is closed and the first switch, the second switch, and the main circuit switch are open, and U1 ≤ b1 * U2, then the third switch is determined to have an open circuit fault. U1 represents the first sampling voltage, U2 represents the second sampling voltage, and b1 is a preset value less than 0.

5.

12. The battery management system according to claim 1, characterized in that, The battery management system also includes a main circuit switch, and the processor is used for: If U1≤b1*U2, and the first switch and the third switch are closed while the second switch and the main circuit switch are open, then it is determined that the first switch and the third switch have an open circuit fault. U1 represents the first sampling voltage, U2 represents the second sampling voltage, and b1 is a preset value less than 0.

5.

13. The battery management system according to claim 1, characterized in that, The battery management system also includes a main circuit switch, and the processor is used for: If the first switch and the main circuit switch are closed and the second switch is open, then the first switch is determined to have an open circuit fault if at least one of the following two relationships is satisfied. U1≤b1*U2; |Shunt2|≤I1 and |Shunt1|≥I2; U1 represents the first sampling voltage, U2 represents the second sampling voltage, Shunt1 represents the main circuit current, Shunt2 represents the branch current, b1 is a preset value less than 0.5, I1 and I2 are preset values, and I1 < I2.

14. The battery management system according to claim 1, characterized in that, The battery management system also includes a main circuit switch, and the processor is used for: If the third switch and the main circuit switch are closed and the second switch is open, then the third switch is determined to have an open circuit fault if at least one of the following two relationships is satisfied. U1≤b2*U2; |Shunt1-Shunt2|≤b2*Shunt1 and |Shunt1|≥I2; U1 represents the first sampling voltage, Shunt1 represents the main circuit current, Shunt2 represents the branch current, b2 is a preset value less than 0.5, and I2 is a preset value.

15. The battery management system according to claim 1, characterized in that, The processor is used for: If U1≤b3*U2, and the first switch and the third switch are open while the second switch is closed, then the second switch is determined to have an open circuit fault. U1 represents the first sampling voltage, U2 represents the second sampling voltage, and b3 is a preset value less than 0.

5.

16. The battery management system according to claim 1, characterized in that, The processor is also used for: When the output voltage of the charging device electrically connected to the battery management system is greater than the threshold voltage, the second switch is controlled to close, while the first switch and the third switch are in the open state.

17. The battery management system according to claim 1, characterized in that, The processor is also used for: If the output voltage of the charging device electrically connected to the battery management system is less than the threshold voltage, and |VM1-VM2|≤V1, the first switch and the third switch are closed, and the second switch is in the open state. VM1 represents the voltage of the first battery, VM2 represents the voltage of the second battery, and V1 is a preset value.

18. The battery management system according to claim 1, characterized in that, The processor is also used for: When the output voltage of the charging device electrically connected to the battery management system is less than the threshold voltage, if VM1-VM2>V1, the third switch is first controlled to close, and the first and second switches are in the open state. The charging current Ia is requested until the voltage difference between the second battery and the first battery is less than V2. The first switch is controlled to close after the charging current drops below Ia. VM1 represents the voltage of the first battery, VM2 represents the voltage of the second battery, V1 and V2 are preset values, and V2 < V1, and Ia is the current safety threshold.

19. The battery management system according to claim 1, characterized in that, The processor is also used for: When the output voltage of the charging device electrically connected to the battery management system is less than the threshold voltage, if VM2-VM1>V1, the first switch is first controlled to close, and the third switch and the second switch are in the open state. The charging current Ia is requested until the voltage of the first battery is charged to a level where the voltage difference with the second battery is less than V2. The third switch is then controlled to close. VM1 represents the voltage of the first battery, VM2 represents the voltage of the second battery, V1 and V2 are preset values, and V2 < V1, and Ia is the current safety threshold.

20. The battery management system according to claim 1, characterized in that, The battery management system also includes: The first fuse is connected in series with the first switch between the first sampling point and the second sampling point; And / or, a second fuse, connected in series with the third switch between the negative terminal of the second battery and the reference point.

21. A battery pack, characterized in that, It includes a first battery, a second battery, and a battery management system as described in any one of claims 1 to 20.

22. An electrical appliance, characterized in that, Includes the battery pack as described in claim 21.

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