A battery pack fault detection circuit and a battery pack fault detection method

Abstract

The present application provides a battery pack fault detection circuit, a fault detection method, a power supply system and an electric vehicle, relating to the technical field of battery safety. The battery pack includes k battery modules connected in series, each battery module includes at least one battery cell, and k is an integer greater than 1. The detection circuit includes a sampling circuit and a controller. The sampling circuit samples the output voltage of each battery module and sends the sampling result to the controller; whenever the controller determines that the average output voltage of the k battery modules is within a preset voltage range by using the sampling result: determine whether the i-th battery module has a fault according to the change amount of the output voltage of the i-th battery module, or, obtain the difference between the output voltage of the i-th battery module and the average output voltage, and determine whether the i-th battery module has a fault according to the change amount of the difference, where i = 1, 2,..., k. This solution can perform fault detection both when the battery pack is charging or discharging, and has strong applicability.

Description

Technical Field

[0001] The present application relates to the technical field of battery safety, and particularly to a battery pack fault detection circuit, a fault detection method, a power supply system and an electric vehicle. Background Art

[0002] Currently, the energy density of battery packs applied in fields such as electronic devices, energy storage systems, and electric vehicles is continuously increasing. By detecting faults in the battery pack, the probability of safety accidents can be reduced.

[0003] Among them, detecting internal short circuits in the battery pack is an important part of fault detection. A battery pack generally includes multiple cells. An internal short circuit refers to a connection relationship where the positive and negative electrodes of a cell form a connection through a resistor that cannot be disconnected by a Battery Management System (BMS), which can cause overcurrent and even overheating in the battery pack, and may lead to fire or explosion in extreme cases.

[0004] When detecting internal short circuit faults in a battery pack using a method of the prior art, it is necessary to limit the battery pack to be in a charging state. Here, the detection method will be described by taking a battery pack including two cells as an example.

[0005] See Figure 1 , which is a schematic diagram of a charging voltage curve used in the prior art.

[0006] During charging, obtain the charging voltage curves and charging cut-off times of cells Cell1 and Cell2. Taking the curve that ends charging first as the standard, that is, this charging takes the curve of Cell1 as the standard. The charging current is I, the charging cut-off time of Cell1 is t1, and the charging cut-off time of Cell2 is t2. For this charging, after Cell1 finishes charging, the remaining charging power of Cell2 The remaining charging power of Cell1 for this charging is zero. Obtain the remaining charging powers corresponding to Cell1 and Cell2 during each subsequent charging. When the increment of the remaining charging power exceeds a preset threshold, it is determined that the corresponding cell has an internal short circuit fault. The detection principle is similar when the number of cells is greater than 2.

[0007] However, this method can only detect faults when the battery pack is in a charging state and cannot detect when the battery pack is in a power supply state, so its applicability is weak. Summary of the Invention

[0008] In order to solve the above problems existing in the prior art, the present application provides a battery pack fault detection circuit, a fault detection method, a power supply system and an electric vehicle, which can detect internal short circuit faults in different states such as charging or discharging of the battery pack, and has strong applicability.

[0009] In a first aspect, the present application provides a battery pack fault detection circuit. The detection circuit is connected to a battery pack, and the battery pack includes k battery modules connected in series, where k is an integer greater than 1, and each battery module includes at least one battery cell. The battery pack fault detection circuit includes a sampling circuit and a controller. Among them, the sampling circuit is used to sample the output voltage of each battery module and send the sampling result to the controller. The controller is configured to, whenever it is determined that the average output voltage of the i-th battery module is within a preset voltage range by using the sampling result: determine whether the i-th battery module has a fault according to the change amount of the output voltage of the i-th battery module, or, obtain the difference between the output voltage of the i-th battery module and the average output voltage, and determine whether the i-th battery module has a fault according to the change amount of the difference, where i = 1, 2,..., k.

[0010] When the average output voltage of the i-th battery module is within the preset voltage range, the controller of the detection circuit can use the sampling result to perform fault detection, without restricting the battery working state. Fault detection can be performed during the battery charging, discharging, and standby stages, with strong applicability, and can timely determine whether there is a fault in the battery module, improving safety.

[0011] By reasonably selecting the preset voltage range, the accuracy of fault detection can be improved. For example, in practical applications, the voltage range of the battery module when the state of charge of the battery cell is at a medium level can be selected as the preset voltage range. This is because in the discharge process of the battery module, over-discharge is generally avoided, that is, the open-circuit voltage and state of charge of each battery cell are controlled not to be too low. Therefore, the state of charge of the battery cell is at a medium level for a relatively large proportion of the usage cycle. Performing short-circuit fault detection when the state of charge of the battery cell is at a medium level can cover different working states such as battery pack charging and discharging, with high practicality.

[0012] In combination with the first aspect, in a possible implementation manner, within the preset voltage range, the open-circuit voltage of the battery module is positively correlated with the state of charge of the battery module. At this time, the preset voltage range is the voltage range of the battery module when the state of charge of the battery cell is at a medium level, and this range can cover different working states such as battery pack charging and discharging.

[0013] In combination with the first aspect, in a possible implementation manner, the controller determines the short-circuit resistance of the i-th battery module according to any one of the change amount of the output voltage or the change amount of the difference, the capacity of the i-th battery module, the sampling result of the output voltage of the i-th battery module, and the sampling time, and determines that the i-th battery module has a fault when the short-circuit resistance is less than a preset resistance value.

[0014] In combination with the first aspect, in a possible implementation manner, since the battery pack is more likely to fail when it is in the charging state, the preset resistance value when the battery pack is charging is greater than the preset resistance value when the battery pack is discharging, so as to more timely determine the internal short - circuit fault of the battery pack during charging.

[0015] In combination with the first aspect, in a possible implementation manner, the controller determines the short - circuit current of the i - th battery module according to any one of the change amount of the output voltage or the change amount of the difference, the capacity of the i - th battery module, and the sampling time of the output voltage of the i - th battery module, and determines that the i - th battery module has a fault when the short - circuit current is greater than the preset current value.

[0016] In combination with the first aspect, in a possible implementation manner, since the battery pack is more likely to fail when it is in the charging state, the preset current value when the battery pack is charging is less than the preset current value when the battery pack is discharging, so as to more timely determine the internal short - circuit fault of the battery pack during charging.

[0017] In combination with the first aspect, in a possible implementation manner, the controller determines that the i - th battery module has a fault when the change amount of the output voltage is greater than the first preset voltage value, or when the change amount of the difference is greater than the second preset threshold.

[0018] In combination with the first aspect, in a possible implementation manner, since the battery pack is more likely to fail when it is in the charging state, the first preset voltage value when the battery pack is charging is less than the first preset voltage value when the battery pack is discharging; the second preset voltage value when the battery pack is charging is less than the second preset voltage value when the battery pack is discharging, so as to more timely determine the internal short - circuit fault of the battery pack during charging.

[0019] In combination with the first aspect, in a possible implementation manner, each battery module is also connected in parallel with an equalization circuit. The equalization circuit is used to equalize the charge amounts of k battery modules. The controller is also used to determine the first error value generated by the equalization circuit on the output voltage of the i - th battery module, and use the first error value to compensate the change amount of the output voltage of the i - th battery module, or compensate the change amount of the difference of the i - th battery module.

[0020] In combination with the first aspect, in a possible implementation manner, the equalization circuit includes a controllable switch and a resistor connected in series. The controller is specifically used to determine the first error value according to the working time of the equalization circuit of the i - th battery module, the output voltage of the i - th battery module, the resistance value of the resistor, and the capacity of the i - th battery module.

[0021] In combination with the first aspect, in a possible implementation, the controller is further configured to determine a second error value caused by the impedance value inconsistency in the output voltage of the i-th battery module according to the difference between the impedance value of the i-th battery module and the average impedance value of the k battery modules, and the discharge current of the i-th battery module, and use the second error value to compensate for the change in the output voltage of the i-th battery module, or compensate for the change in the difference of the i-th battery module.

[0022] In combination with the first aspect, in a possible implementation, since the battery pack is more likely to fail when it is in the charging state, the sampling frequency of the sampling circuit during battery pack charging is greater than the sampling frequency of the sampling circuit during battery pack discharging, so as to more timely determine the internal short circuit fault of the battery pack during charging.

[0023] In combination with the first aspect, in a possible implementation, the controller is integrated with the controller of the Battery Management System (BMS).

[0024] In a second aspect, the present application further provides a method for detecting battery pack faults. The battery pack includes k battery modules connected in series, and each battery module includes one or more battery cells, where k is an integer greater than 1. The method for detecting battery pack faults includes:

[0025] Sampling the output voltage of each battery module to obtain a sampling result;

[0026] Whenever it is determined that the average output voltage of the k battery modules is within a preset voltage range by using the sampling result:

[0027] Determine whether the i-th battery module has a fault according to the change in the output voltage of the i-th battery module,

[0028] Or, obtain the difference between the output voltage of the i-th battery module and the average output voltage, and determine whether the i-th battery module has a fault according to the change in the difference, where i = 1, 2,..., k.

[0029] In combination with the second aspect, in a possible implementation, within the preset voltage range, the open circuit voltage of the battery module is positively correlated with the state of charge level of the battery module.

[0030] In combination with the second aspect, in a possible implementation, determining whether the i-th battery module has a fault according to the change in the output voltage of the i-th battery module specifically includes:

[0031] Determine the short - circuit resistance of the i - th battery module according to the change amount of the output voltage, the capacity of the i - th battery module, and the sampling result and sampling time of the output voltage of the i - th battery module, and determine that the i - th battery module has a fault when the short - circuit resistance is less than a preset resistance value;

[0032] Determine whether the i - th battery module has a fault according to the change amount of the difference, specifically including:

[0033] Determine the short - circuit resistance of the i - th battery module according to the change amount of the difference, the capacity of the i - th battery module, and the sampling result and sampling time of the output voltage of the i - th battery module, and determine that the i - th battery module has a fault when the short - circuit resistance is less than a preset resistance value.

[0034] Combined with the second aspect, in a possible implementation, the preset resistance value during battery pack charging is greater than the preset resistance value during battery pack discharging.

[0035] Combined with the second aspect, in a possible implementation, determine whether the i - th battery module has a fault according to the change amount of the output voltage of the i - th battery module, specifically including:

[0036] Determine the short - circuit current of the i - th battery module according to the change amount of the output voltage, the capacity of the i - th battery module, and the sampling time of the output voltage of the i - th battery module, and determine that the i - th battery module has a fault when the short - circuit current is greater than a preset current value;

[0037] Determine whether the i - th battery module has a fault according to the change amount of the said difference, specifically including:

[0038] Determine the short - circuit current of the i - th battery module according to the change amount of the difference, the capacity of the i - th battery module, and the sampling time of the output voltage of the i - th battery module, and determine that the i - th battery module has a fault when the short - circuit current is greater than a preset current value.

[0039] Combined with the second aspect, in a possible implementation, the preset current value during battery pack charging is less than the preset current value during battery pack discharging.

[0040] Combined with the second aspect, in a possible implementation, determine whether the i - th battery module has a fault according to the change amount of the output voltage of the i - th battery module, specifically including:

[0041] When the change amount of the output voltage is greater than a first preset voltage value, determine that the i - th battery module has a fault;

[0042] Determine whether the i - th battery module has a fault according to the change amount of the difference, specifically including:

[0043] When the change amount of the difference is greater than the second preset voltage value, it is determined that the i-th battery module has a fault.

[0044] Combined with the second aspect, in a possible implementation, the first preset voltage value during battery pack charging is less than the first preset voltage value during battery pack discharging; the second preset voltage value during battery pack charging is less than the second preset voltage value during battery pack discharging.

[0045] Combined with the second aspect, in a possible implementation, each battery module is also connected in parallel with an equalization circuit for equalizing the charge amounts of k battery modules. The method further includes:

[0046] Determine the first error value generated by the output voltage of the i-th battery module by the equalization circuit of the i-th battery module, and use the first error value to compensate the change amount of the output voltage of the i-th battery module, or compensate the change amount of the difference of the i-th battery module.

[0047] Combined with the second aspect, in a possible implementation, the equalization circuit includes a controllable switch and a resistor connected in series. Determining the first error value generated by the output voltage of the i-th battery module by the equalization circuit of the i-th battery module specifically includes:

[0048] Determine the first error value according to the working time of the equalization circuit of the i-th battery module, the output voltage of the i-th battery module, the resistance value of the resistor, and the capacity of the i-th battery module.

[0049] Combined with the second aspect, in a possible implementation, the method further includes determining the second error value generated by the output voltage of the i-th battery module due to impedance value inconsistency according to the difference between the impedance value of the i-th battery module and the average impedance value of k battery modules, and the discharge current of the i-th battery module, and using the second error value to compensate the change amount of the output voltage of the i-th battery module, or compensate the change amount of the difference of the i-th battery module.

[0050] Combined with the second aspect, in a possible implementation, the sampling frequency of the output voltage of each battery module during battery pack charging is greater than the sampling frequency of the output voltage of each battery module during battery pack discharging.

[0051] In a third aspect, the present application further provides a power supply system, which includes the battery pack fault detection circuit provided in the above implementation, and further includes a battery pack and a battery management system. The battery pack includes k battery modules connected in series, each battery module includes one or more battery cells, and k is an integer greater than 1. The battery management system is used to monitor and manage the battery pack.

[0052] In combination with the third aspect, in a possible implementation, the battery pack fault detection circuit is integrated with the battery management system.

[0053] In a fourth aspect, the present application further provides an electric vehicle, which includes the power supply system provided by the above implementation and also includes a motor. The power supply system is used to supply power to the motor; the motor is used to convert electrical energy into mechanical energy to drive the electric vehicle.

[0054] In a fifth aspect, the present application further provides an electronic device, which includes the power supply system provided by the above implementation and also includes a load circuit. The power supply system is used to supply power to the load circuit. Description of the Drawings

[0055] Figure 1 Schematic diagram of the charging voltage curve used in the prior art;

[0056] Figure 2 Structural diagram of an exemplary electric vehicle system provided by an embodiment of the present application;

[0057] Figure 3 Schematic diagram of a battery pack fault detection circuit provided by an embodiment of the present application;

[0058] Figure 4 Schematic diagram of the relationship between the open circuit voltage and the state of charge of the battery cell provided by an embodiment of the present application;

[0059] Figure 5 Schematic voltage relationship curve provided by an embodiment of the present application;

[0060] Figure 6 Schematic diagram of another battery pack fault detection circuit provided by an embodiment of the present application;

[0061] Figure 7 Another schematic voltage relationship curve provided by an embodiment of the present application;

[0062] Figure 8 Flowchart of a battery pack fault detection method provided by an embodiment of the present application;

[0063] Figure 9 Flowchart of another battery pack fault detection method provided by an embodiment of the present application;

[0064] Figure 10 Schematic diagram of a power supply system provided by an embodiment of the present application;

[0065] Figure 11 Schematic diagram of another power supply system provided by an embodiment of the present application;

[0066] Figure 12Schematic diagram of an electric vehicle provided by an embodiment of the present application;

[0067] Figure 13 Schematic diagram of an electronic device provided by an embodiment of the present application. Detailed implementation manners

[0068] In order to enable those skilled in the art to more clearly understand the technical solutions provided by the embodiments of the present application, the application scenarios of the technical solutions provided by the present application will be introduced first below.

[0069] With the continuous increase in the energy density of battery packs applied in fields such as electronic devices, energy storage systems, and electric vehicles, fault detection of battery packs can effectively reduce the probability of safety accidents.

[0070] The battery pack fault detection circuit provided by the present application can be applied to battery packs of types such as lithium-ion batteries to detect whether there is an internal short circuit fault in the battery modules connected in series in the battery pack. The battery pack includes multiple battery modules, and the present application does not make specific limitations on the number of battery modules.

[0071] Each battery module may include one battery cell, that is, at this time, the battery pack includes multiple battery cells connected in series. This battery module can be applied in electronic devices, and the embodiments of the present application do not make specific limitations on the electronic devices. For example, it can be a mobile phone, a tablet computer, a notebook computer, a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, and a smart home appliance device (such as a floor cleaning robot), etc.

[0072] Each battery module may also include multiple battery cells. At this time, the battery pack can be applied in occasions with large power requirements, such as in electric vehicles. Usually, multiple battery cells are first connected in parallel to form a battery module, and then multiple battery modules are connected in series to increase the output voltage and output energy of the battery pack.

[0073] The following will be described by taking the scenario of an electric vehicle as an example.

[0074] Refer to Figure 2 , this figure is a schematic structural diagram of an exemplary electric vehicle system provided by an embodiment of the present application.

[0075] The illustrated system includes a power supply system 10, a vehicle control unit (VCU) 20, an on-board charger (OBC) 30, a fast charging interface 40, and a high-voltage distribution box 50.

[0076] Among them, the power supply system 10 is used to provide the electric energy required for the electric vehicle.

[0077] The power supply system 10 includes a battery pack 100 and a battery management system 101.

[0078] The battery management system 101 is a functional unit for monitoring and managing the charging and discharging of the battery pack, and is used to ensure that the power supply system is within a safe and controllable state range.

[0079] The illustrated system includes a high-voltage line circuit and a Controller Area Network (CAN) circuit. Among them, the high-voltage line circuit is a power circuit with the power supply system 10 as the core. And the Controller Area Network circuit is a communication circuit with the vehicle controller 20 as the core.

[0080] When the electric vehicle is in a driving state, the power supply system 10 provides energy to the motor of the electric vehicle.

[0081] When the electric vehicle is in a charging state, an external charging pile supplements energy to the power supply system 10 through an on-vehicle charger 30 or a fast charging interface 40.

[0082] An application scenario of the technical solution of the present application is the power supply system 10 of an electric vehicle. By detecting whether there is a short-circuit risk in the battery modules in the battery pack 100, the safety of the power supply system 10 is evaluated, so as to realize the detection of the safety state of the battery pack.

[0083] In order to enable those skilled in the art to more clearly understand the solution of the present application, the technical solution in the embodiments of the present application will be described below in conjunction with the accompanying drawings in the embodiments of the present application.

[0084] The terms "first", "second", etc. used in the description of the present application are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features.

[0085] In the present application, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or integrated; it can be a direct connection, or an indirect connection through an intermediate medium.

[0086] Embodiment 1:

[0087] The embodiment of the present application provides a battery pack fault detection circuit, which will be specifically described below in conjunction with the accompanying drawings.

[0088] See Figure 3 , this figure is a schematic diagram of a battery pack fault detection circuit provided by the embodiment of the present application.

[0089] The battery pack fault detection circuit 200 is connected to the battery pack 100, and the battery pack 100 includes a plurality of battery modules 110 connected in series. Each battery module 110 includes one or more battery cells.

[0090] When the battery module 101 includes a plurality of battery cells, the plurality of battery cells can be connected in parallel inside the battery module 101, or first connected in series and then in parallel inside the battery module 101, or first connected in parallel and then in series inside the battery module 101. The embodiments of the present application do not limit the specific number and specific connection manner of the plurality of battery cells in the battery module 101.

[0091] The battery pack fault detection circuit 200 includes a sampling circuit 201 and a controller 202.

[0092] Among them, the sampling circuit 201 samples the output voltage of each battery module 110 and sends the sampling result of the voltage to the controller 202. Generally speaking, the sampling result sent by the sampling circuit 201 to the controller 202 is an analog signal, and the controller 202 is integrated with an Analog to Digital Converter (ADC) for converting the acquired analog signal into a digital signal for subsequent processing.

[0093] Each time of sampling, the sampling circuit 201 samples all the battery modules. When the controller 202 determines that the average output voltage of all the current battery modules is within a preset range by using the acquired sampling result of this time, it indicates that the sampling result at this time is valid and is retained for subsequent steps. Otherwise, the sampling result is invalid and deleted. The data used by the following controller 202 are all validly retained data.

[0094] In a possible implementation manner, the controller 202 determines whether the i-th battery module has a fault according to the change amount of the output voltage of the i-th battery module.

[0095] In practical applications, the sampling circuit 201 samples at the same time interval. Therefore, the magnitude of the change amount of the output voltage can be used to represent the magnitude of the change rate of the output voltage, that is, the larger the change amount, the larger the standardized rate.

[0096] In another possible implementation manner, the controller 202 obtains the difference between the output voltage of each battery module and the average output voltage.

[0097] Taking the i-th battery module among the k battery modules of the battery pack as an example, where k is an integer greater than 1 and i = 1, 2,..., k, the difference obtained by the controller for this sampling is △V1.

[0098] After multiple samplings, the controller 202 can obtain multiple differences corresponding to the i-th battery module, namely, △V1, △V2, △V3, …. The controller 202 determines whether there is an internal short circuit fault in the i-th battery module according to the change amount of the obtained differences.

[0099] The following describes the principle by which the controller 202 determines whether there is an internal short circuit fault in the battery module.

[0100] See Figure 4 , which is a schematic diagram of the relationship between the open circuit voltage and the state of charge of the battery cell provided by the embodiment of the present application.

[0101] The state of charge (SOC), which is the ratio of the current available capacity to the current rated capacity, 0% indicates full discharge, and 100% indicates full charge.

[0102] Under normal working conditions, the open circuit voltage of the battery cell is positively correlated with the state of charge of the battery cell, and this relationship remains basically unchanged during the aging cycle of the battery cell. When the state of charge of the battery cell is at a medium level, the open circuit voltage of the battery cell has a linear relationship with the state of charge. In some typical examples, when the state of charge is between 60% and 90%, the linear relationship presented by the open circuit voltage and the state of charge can be characterized as a linear function. At this time, the voltage range corresponding to this state of charge is the preset voltage range, which can be determined in advance by calibration.

[0103] When the open circuit voltage and the state of charge present a linear relationship, the ratio of the change amount of the open circuit voltage to the change amount of the state of charge is constant.

[0104] And the output voltage of the battery cell is equal to the open circuit voltage of the battery cell minus the voltage drop across the internal resistance of the battery cell. Therefore, the output voltage of the battery cell also presents a linear relationship with the state of charge of the battery cell.

[0105] Furthermore, the ratio of the change amount of the output voltage of the battery cell to the change amount of the state of charge of the battery cell is constant.

[0106] Considering that in practical applications, the sampling circuit generally samples at a constant sampling period. Therefore, the greater the change amount of the state of charge of the battery cell, the greater the change rate of the state of charge, which can characterize that the discharge current of the battery cell is greater at this time, and characterize that the short circuit resistance of the battery cell is smaller, and the probability of the battery pack having an internal short circuit fault is higher. Therefore, the change amount of the output voltage of the battery cell can be used as a fault criterion. When one or more battery cells form a battery module, the change amount of the output voltage of the battery module can be used as a fault criterion.

[0107] In some other embodiments, as the battery cells age, the inconsistency among the battery cells increases. Therefore, when directly using the change amount of the output voltage of the battery module as a criterion, the deviation caused by the inconsistency may be misjudged as the deviation caused by the internal short circuit fault. Therefore, the controller can also obtain the average output voltage V of the battery module avg , and use the change amount of the difference between the battery module and V avg as a criterion to reduce the influence of the cell inconsistency.

[0108] In practical applications, for battery packs used in fields such as electronic devices, energy storage systems, and electric vehicles, measures will be taken to avoid over-discharging during the discharging process, so that the output voltage and charge level of the battery pack will not be too low, that is, the open-circuit voltage and charge level of each battery cell will not be too low. Therefore, the charge level of the battery cell is at a medium level for a relatively long time during the usage cycle. Detecting the short circuit fault when the charge level of the battery cell is at a medium level can cover different working states such as charging and discharging of the battery pack, and has high practicability.

[0109] The controller 202 in this embodiment may be an Application Specific Integrated Circuit (ASIC), a Programmable Logic Device (PLD), a Digital Signal Processor (DSP), or a combination thereof. The above PLD may be a Complex Programmable Logic Device (CPLD), a Field-programmable Gate Array (FPGA), a Generic Array Logic (GAL), or any combination thereof. The embodiments of the present application do not make specific limitations in this regard.

[0110] In some embodiments, the controller 300 may be independently provided; in some other embodiments, the controller may be integrated with the controller of the Battery Management System (BMS), that is, integrated with the controller of the battery management system 102 in Figure 1 .

[0111] The embodiments of the present application do not specifically limit the type of the battery pack. For example, the battery pack may use a lithium-ion battery.

[0112] In summary, by using the battery pack fault detection circuit provided in the embodiments of the present application, when the average output voltage of the i-th battery module is within the preset voltage range, the sampling results can be used for fault detection without restricting the battery working state. Therefore, fault detection can be performed during the battery charging, discharging, and standby stages, with strong applicability, and it can promptly determine whether there is a fault in the battery module, improving safety.

[0113] The working principle of the battery pack fault detection circuit is described below in conjunction with specific implementation manners.

[0114] Embodiment 2:

[0115] The principle of using the change amount of the difference between the output voltage and the average output voltage for fault detection is described below first.

[0116] Refer to Figure 5 , which is a schematic voltage relationship curve diagram provided in the embodiments of the present application.

[0117] Taking the number of battery modules being greater than 2 as an example, in the figure, the waveform V1 represents the output voltage waveform corresponding to battery module 1, V2 represents the output voltage waveform corresponding to battery module 2, and Vavg represents the average output voltage waveform of all battery modules.

[0118] The time interval between any two adjacent sampling moments in the figure is Δt.

[0119] The waveform V2 is selected for description below.

[0120] When at the first preset moment t1, the difference between the output voltage of battery module 2 and the average output voltage is:

[0121] ΔV1 = V2(t1) - Vavg(t1) (1)

[0122] When at the second preset moment t2, the difference between the output voltage of battery module 2 and the average output voltage is:

[0123] ΔV2 = V2(t2) - Vavg(t2) (2)

[0124] Then the change amount of the difference at the t1 preset moment and the difference at the t2 preset moment is:

[0125] ΔdV2 = ΔV1 - ΔV2 (3)

[0126] …

[0127] And so on, when at the (j + 1)-th preset moment t j+1 , the difference between the output voltage of battery module 2 and the average output voltage is:

[0128] ΔVj+1 = V2(t j+1 ) - Vavg(t j+1 ) (4)

[0129] Then t j The difference between the preset times and t j+1 The change in the difference between the preset times is:

[0130] ΔdV j+1 = ΔV j - ΔV j+1 (5)

[0131] Continue to refer to Figure 4 The relationship diagram shown, and then determine the discharge capacity ΔSOC of the i-th battery module according to the obtained change in the difference:

[0132]

[0133] Among them, the coefficient α is pre-calibrated according to the battery characteristics.

[0134] In the first possible implementation manner, the controller determines the short-circuit current I j+1 of the i-th battery module according to the change in the difference ΔdV cup , the capacity C of the i-th battery module j and the sampling time of the output voltage of the i-th battery module (taking t j+1 and t ISC as an example to determine the sampling time interval Δt), specifically referring to the following formula:

[0135]

[0136] When the short-circuit current I ISC is greater than the preset current value I0, the controller determines that the i-th battery module has a fault, and the preset current value I0 can be preset and stored in the memory.

[0137] In practical applications, since the battery pack is more likely to fail when it is in the charging state, the preset current value during battery pack charging is less than the preset current value during battery pack discharging, so as to more timely determine the internal short-circuit fault of the battery pack during charging.

[0138] In the second possible implementation manner, the controller is used to determine the short-circuit resistance R j+1 of the i-th battery module according to the change in the difference ΔdV cup , the capacity C of the i-th battery module j , the sampling result V(t) of the output voltage of the i-th battery module and the sampling time (taking t j+1 and tISC , that is, based on formula (7), specifically refer to the following formula:

[0139]

[0140] When the short-circuit resistance R of the controller ISC is less than the preset resistance value R0, it is determined that the i-th battery module has a fault. The preset current value R0 can be preset and stored in the memory.

[0141] In practical applications, since the battery pack is more likely to fail when it is in the charging state, the preset resistance value during battery pack charging is greater than the preset resistance value during battery pack discharging, so as to more timely determine the internal short-circuit fault of the battery pack during charging.

[0142] In the third possible implementation manner, when the change amount of the difference is greater than the second preset threshold, the controller determines that the i-th battery module has a fault, where the second preset threshold can be preset and stored in the memory.

[0143] In practical applications, the battery pack is more likely to fail when it is in the charging state. Therefore, the second preset voltage value during battery pack charging is less than the second preset voltage value during battery pack discharging, so as to more timely determine the internal short-circuit fault of the battery pack during charging.

[0144] The controller performs the same processing on other battery modules as the above process, and then determines whether there is an internal short-circuit fault in each battery module in the battery pack.

[0145] Among them, the memory can be a non-volatile memory (Non-Volatile Memory, NVM), such as a read-only memory (Read-only Memory, ROM), specifically an electrically erasable programmable read-only memory (Electrically Erasable Programmable Read-only Memory, EEROM) or an erasable programmable read-only memory (Erasable Programmable Read-only Memory, EPROM).

[0146] In some embodiments, since the battery pack is more likely to fail when it is in the charging state, the sampling frequency of the sampling circuit 201 during battery pack charging is greater than the sampling frequency of the sampling circuit during battery pack discharging.

[0147] In some power supply systems, an equalization circuit is further included. The equalization circuit can receive the control signal of the battery management system and dissipate energy from each battery module to equalize the charge amounts of each battery module. Due to the effect of the equalization circuit, the voltages of each battery module will change, thereby affecting the change amount of the determined difference. In order to reduce the influence of the equalization circuit on the judgment of the internal short circuit fault, the embodiment of the present application also provides a battery pack fault detection circuit, which will be specifically described below with reference to the drawings.

[0148] See Figure 6 , which is a schematic diagram of another battery pack fault detection circuit provided by the embodiment of the present application.

[0149] The difference between this detection circuit and the Figure 4 shown detection circuit is that it further includes an equalization circuit module 300. The equalization circuit module 300 includes a plurality of equalization circuits, and an equalization circuit is connected in parallel at both ends of each battery module 101.

[0150] The working states of the respective equalization circuits are controlled by the controller of the battery management system. The embodiment of the present application does not limit the specific implementation manner of the equalization circuit. In the figure, an example is given where the equalization circuit includes a series-connected controllable switch and a resistor.

[0151] Among them, the controllable switch can be an Insulated Gate Bipolar Transistor (IGBT), a Metal Oxide Semiconductor Field Effect Transistor (MOSFET, hereinafter referred to as MOS transistor), a Silicon Carbide Metal Oxide Semiconductor (SiC MOSFET), a relay, etc. The embodiment of the present application does not make specific limitations on this.

[0152] The controller of the battery management system can send a Pulse Width Modulation (PWM) signal to the controllable switch to control the working state of the controllable switch. When the controllable switch is controlled to close, the resistor in the equalization circuit dissipates energy from the battery module 101. The resistance values of the resistors are all known parameters.

[0153] The controller is further configured to determine a first error value generated by the equalization circuit of the i-th battery module on the output voltage of the i-th battery module, and use the first error value to compensate the change amount of the difference corresponding to the i-th battery module, which will be specifically described below.

[0154] For the i-th battery module, let Ri denote the resistance value of the resistor in the equalization circuit of the i-th battery module. In practical applications, generally, the resistance values of the resistors in each equalization circuit are the same.

[0155] Let Ti denote the working time of the equalization circuit between the j-th preset moment (i.e., t1 moment) and the (j + 1)-th preset moment (i.e., t2 moment). In some embodiments, the controller of the battery management system sends a pulse width modulation signal to the controllable switch of the equalization circuit, and Ti can be determined by using the duration and duty cycle of this pulse width modulation signal.

[0156] Let Ui(t) denote the output voltage of the i-th battery module, and let Ii denote the equalization current of this equalization circuit. Then, the following relationship exists:

[0157]

[0158] The discharge amount Qi of the equalization circuit of the i-th battery module satisfies:

[0159] Qi = Ii × Ti (10)

[0160] The capacity of the i-th battery module is C cap , then the error value V e1 generated by the i-th battery module due to the equalization circuit satisfies:

[0161]

[0162] Among them, the coefficient α characterizes the change rate of the open-circuit voltage of the battery module with respect to the SOC of the battery module, which is pre-calibrated according to the battery characteristics. The controller uses the error value V e1 obtained by Equation (11) to compensate for the change amount of the difference obtained by Equation (5), and obtains the compensated change amount ΔdV j+1 ’, specifically as follows:

[0163] ΔdV j+1 ’ = ΔdV j+1 + V e1 (12)

[0164] In summary, the controller of this detection circuit can also compensate for the influence of the equalization circuit on the judgment of the internal short circuit fault, further improving the accuracy of detecting the internal short circuit fault.

[0165] Furthermore, the controller can also correct the change amount of the difference obtained by Equation (5) according to the inconsistency existing between the impedances of each battery module. The following is a specific description.

[0166] The controller, according to the impedance value zi i of the i-th battery module and the average impedance value zavg The difference Δzi, and the discharge current I(t) of the i-th battery module, to determine the second error value V generated by the impedance value inconsistency on the output voltage of the i-th battery module e2 , specifically see the following formula:

[0167] V e2 = I(t1)Δzi - I(t2)Δzi (13)

[0168] Wherein, the impedance values of all battery modules are pre-determined parameters, that is, the impedance value Δzi of the i-th battery module can be pre-determined and stored in the memory.

[0169] The controller then uses the second error value V e2 to correct the change amount of the difference obtained by formula (5) to obtain the compensated change amount of the difference ΔdV j+1 ”, specifically see the following formula:

[0170] ΔdV j+1 ” = ΔdV j+1 ’ + V e2 (14)

[0171] The controller then determines whether the battery module has a fault by using the compensated change amount of the difference.

[0172] Embodiment Three:

[0173] The following describes another implementation manner of the battery pack fault detection circuit.

[0174] Refer to Figure 7 , this figure is another schematic voltage relationship curve graph provided by the embodiment of the present application.

[0175] The controller can also determine whether the i-th battery module has a fault according to the change amount of the output voltage of the i-th battery module, which is specifically described below.

[0176] The following continues to describe with waveform V2. Any two adjacent sampling moments in the figure are separated by Δt.

[0177] When at the first preset moment t1, the output voltage of battery module 2 is V2(t1).

[0178] When at the second preset moment t2, the output voltage of battery module 2 is V2(t2).

[0179] Then the change amount ΔV1’ of the output voltage determined by the difference at the t1 preset moment and the t2 preset moment is as follows:

[0180] ΔV1’ = V2(t1) - V2(t2) (15)

[0181] Correspondingly, then t j The difference between the preset times and t j+1 The change in the output voltage determined at the preset time is as follows:

[0182] ΔV j ’ = V2(t j ) - V2(t j+1 ) (16)

[0183] Continue to refer to Figure 4 the relationship schematic diagram shown, and then determine the discharge amount ΔSOC of the i-th battery module according to the obtained change in the output voltage:

[0184]

[0185] Among them, the coefficient β is pre-calibrated according to the battery characteristics.

[0186] In the first possible implementation manner, the controller determines the short-circuit current I j of the i-th battery module according to the change in the output voltage ΔV cup ’, the capacity C j of the i-th battery module, and the sampling time of the output voltage of the i-th battery module (taking t j+1 and t ISC as an example, used to determine the sampling time interval Δt), specifically referring to the following formula:

[0187]

[0188] When the short-circuit current I ISC is greater than the preset current value I0, the controller determines that the i-th battery module has a fault, and the preset current value I0 can be preset and stored in the memory.

[0189] In practical applications, the battery pack is more likely to fail when it is in the charging state. Therefore, the preset current value during battery pack charging is less than the preset current value during battery pack discharging, so as to more timely determine the internal short-circuit fault of the battery pack during charging.

[0190] In the second possible implementation manner, the controller determines the short-circuit resistance R j of the i-th battery module according to the change in the output voltage ΔV cup ’, the capacity C j of the i-th battery module, the sampling result V(t) of the output voltage of the i-th battery module, and the sampling time (taking t j+1 and t ISC as an example, used to determine the sampling time interval Δt), that is, on the basis of formula (18), specifically referring to the following formula:

[0191]

[0192] When the short - circuit resistance R of the controller ISC is less than the preset resistance value R0, it is determined that the i - th battery module has a fault. The preset current value R0 can be preset and stored in the memory.

[0193] In practical applications, the battery pack is more likely to fail when it is in the charging state. Therefore, the preset resistance value during battery pack charging is greater than the preset resistance value during battery pack discharging, so as to more timely determine the internal short - circuit fault of the battery pack during charging.

[0194] In the third possible implementation manner, when the change amount of the output voltage of the controller is greater than the first preset voltage value, it is determined that the i - th battery module has a fault, where the first preset threshold can be preset and stored in the memory.

[0195] In practical applications, the battery pack is more likely to fail when it is in the charging state. Therefore, the first preset voltage value during battery pack charging is less than the preset voltage value during battery pack discharging, so as to more timely determine the internal short - circuit fault of the battery pack during charging.

[0196] Continue to refer to Figure 6 , and the principle of reducing the influence of the equalization circuit on the judgment of internal short - circuit faults is described below.

[0197] Ti represents the working time of the equalization circuit between the j - th preset moment (i.e., t1 moment) and the j + 1 - th preset moment (i.e., t2 moment). Let Ui(t) represent the output voltage of the i - th battery module, and Ii represent the equalization current of the equalization circuit, then the following relationship exists:

[0198]

[0199] The discharge amount Qi of the equalization circuit of the i - th battery module satisfies:

[0200] Qi = Ii×Ti (10)

[0201] The capacity of the i - th battery module is C cap , then the error value V e1 ' generated by the i - th battery module due to the equalization circuit satisfies:

[0202]

[0203] Among them, the coefficient β characterizes the change rate of the open - circuit voltage of the battery module with the SOC of the battery module, which is pre - calibrated according to the battery characteristics. The controller uses the error value V obtained by formula (20) e1Compensate for the change in the output voltage obtained from Equation (16) to obtain the compensated change ΔV j ”, as specifically shown in the following equation:

[0204] ΔV j ” = ΔV j ’ + V e1 ’ (21)

[0205] In summary, the controller of this detection circuit can also compensate for the influence of the equalization circuit on the judgment of internal short - circuit faults, further improving the accuracy of detecting internal short - circuit faults.

[0206] Furthermore, the controller can also correct the change in the output voltage obtained from Equation (16) according to the inconsistency existing between the impedances of each battery module. The following is a specific description.

[0207] The controller determines the second error value V i generated by the impedance value inconsistency on the output voltage of the i - th battery module based on the difference Δzi between the impedance value zi avg of the i - th battery module and the average impedance value z e2 of k battery modules, and the discharge current I(t) of the i - th battery module, as specifically shown in the following equation:

[0208] V e2 = I(t1)Δzi - I(t2)Δzi (13)

[0209] Among them, the impedance values of all battery modules are pre - determined parameters, that is, the impedance value Δzi of the i - th battery module can be pre - determined and stored in the memory.

[0210] The controller then uses the second error value V e2 to correct the change in the output voltage obtained from Equation (16) to obtain the compensated change in the difference ΔV j ”’, as specifically shown in the following equation:

[0211] ΔV j1 ”’ = ΔV j ” + V e2 (22)

[0212] The controller then determines whether a battery module fails by using the compensated change in the difference.

[0213] Embodiment 4:

[0214] Based on the battery pack fault detection circuit provided in the above embodiments, the embodiments of the present application also provide a corresponding fault detection method for the battery pack. The following is a specific description with reference to the accompanying drawings.

[0215] SeeFigure 8 , which is a flowchart of a method for detecting faults in a battery pack provided by an embodiment of the present application.

[0216] This method is applied to detect faults in a battery pack. The battery pack includes k battery modules connected in series, and each battery module includes one or more battery cells. k is an integer greater than 1. The method includes the following steps:

[0217] S801: Sample the output voltage of each battery module to obtain a sampling result.

[0218] During each sampling, all battery modules are sampled. When it is determined, using the obtained sampling result of this time, that the average output voltage of all current battery modules is within a preset range, it indicates that the sampling result at this time is valid and is retained for subsequent steps. Otherwise, the sampling result is invalid and is deleted.

[0219] S802: Whenever it is determined, using the sampling result, that the average output voltage of the k battery modules is within a preset voltage range, determine whether the i-th battery module has a fault according to the change amount of the output voltage of the i-th battery module, where i = 1, 2,..., k.

[0220] Within the preset voltage range, the open-circuit voltage of the battery module is linearly related to the state of charge of the battery module, and the preset voltage range can be calibrated in advance.

[0221] In a first possible implementation manner, according to the change amount of the output voltage ΔV j ’, the capacity C of the i-th battery module cup and the sampling time of the output voltage of the i-th battery module (taking t j and t j+1 as an example, used to determine the sampling time interval Δt), determine the short-circuit current I of the i-th battery module ISC , and specifically, reference can be made to Equation (18).

[0222] In practical applications, the battery pack is more likely to fail when it is in a charging state. Therefore, the preset current value during battery pack charging is less than the preset current value during battery pack discharging, so as to more timely determine the internal short-circuit fault of the battery pack during charging.

[0223] In a second possible implementation manner, according to the change amount of the output voltage ΔV j ’, the capacity C of the i-th battery module cup , the sampling result V(t) of the output voltage of the i-th battery module and the sampling time (taking t j and t j+1 as an example, used to determine the sampling time interval Δt), determine the short-circuit resistance R of the i-th battery module ISC, specifically, reference can be made to Equation (19).

[0224] In practical applications, the battery pack is more likely to malfunction when it is in the charging state. Therefore, the preset resistance value during charging of the battery pack is greater than the preset resistance value during discharging of the battery pack, so as to more timely determine the internal short - circuit fault of the battery pack during charging.

[0225] In the third possible implementation manner, when the change amount of the output voltage is greater than the first preset voltage value, it is determined that the i - th battery module has a fault, where the first preset threshold can be preset and stored in the memory.

[0226] In practical applications, the battery pack is more likely to malfunction when it is in the charging state. Therefore, the first preset voltage value during charging of the battery pack is less than the preset voltage value during discharging of the battery pack, so as to more timely determine the internal short - circuit fault of the battery pack during charging.

[0227] When there is an equalization circuit for voltage equalization of the battery modules, in order to compensate for the influence of the equalization circuit on the judgment of the internal short - circuit fault and further improve the accuracy of detecting the internal short - circuit fault, the method further includes the following steps:

[0228] Determine the first error value generated by the equalization circuit on the output voltage of the i - th battery module, and use the first error value to compensate the change amount of the output voltage of the i - th battery module.

[0229] In some embodiments, the equalization circuit includes a controllable switch and a resistor connected in series. At this time, the first error value is determined according to the working time of the equalization circuit of the i - th battery module, the output voltage of the i - th battery module, the resistance value of the resistor, and the capacity of the i - th battery module. Specifically, reference can be made to Equation (20) and Equation (21).

[0230] In addition, the change amount of the obtained output voltage can be corrected according to the inconsistency between the impedances of each battery module. The specific steps are as follows:

[0231] According to the difference between the impedance value of the i - th battery module and the average impedance value of the k battery modules, and the discharge current of the i - th battery module, determine the second error value generated by the impedance value inconsistency on the output voltage of the i - th battery module;

[0232] Use the second error value to compensate the change amount of the output voltage of the i - th battery module.

[0233] Then, use the change amount of the compensated difference to determine whether the battery module has a fault.

[0234] The following describes another method for detecting faults of a battery pack.

[0235] See Figure 9, This figure is a flowchart of another method for detecting faults in a battery pack provided by an embodiment of the present application.

[0236] S901: Sample the output voltage of each battery module to obtain a sampling result.

[0237] During each sampling, all battery modules are sampled. When it is determined that the average output voltage of all current battery modules is within a preset range using the obtained sampling result of this time, it indicates that the sampling result is valid at this time and is retained for subsequent steps. Otherwise, the sampling result is invalid and deleted.

[0238] S902: Whenever it is determined that the average output voltage of k battery modules is within a preset voltage range using the sampling result, obtain the difference between the output voltage of the i-th battery module and the average output voltage, and determine whether the i-th battery module has a fault based on the change amount of the difference, where i = 1, 2,..., k.

[0239] In a first possible implementation manner, based on the change amount of the difference ΔdV j+1 , the capacity C of the i-th battery module cup , and the sampling time of the output voltage of the i-th battery module (taking t j and t j+1 as an example, used to determine the sampling time interval Δt), determine the short-circuit current I of the i-th battery module ISC , and specifically, reference can be made to Equation (7).

[0240] When the short-circuit current I ISC is greater than the preset current value I0, it is determined that the i-th battery module has a fault. The preset current value I0 can be preset in advance and stored in the memory.

[0241] In practical applications, since the battery pack is more likely to have a fault when it is in the charging state, the preset current value during battery pack charging is less than the preset current value during battery pack discharging, so as to more timely determine the internal short-circuit fault of the battery pack during charging.

[0242] In a second possible implementation manner, based on the change amount of the difference ΔdV j+1 , the capacity C of the i-th battery module cup , the sampling result V(t) of the output voltage of the i-th battery module and the sampling time (taking t j and t j+1 as an example, used to determine the sampling time interval Δt), determine the short-circuit resistance R of the i-th battery module ISC , and specifically, reference can be made to Equation (8).

[0243] In practical applications, since the battery pack is more likely to malfunction when it is in the charging state, the preset resistance value during charging of the battery pack is greater than the preset resistance value during discharging of the battery pack, so as to more timely determine the internal short-circuit fault of the battery pack during charging.

[0244] In the third possible implementation manner, when the change amount of the difference is greater than the second preset threshold, it is determined that the i-th battery module has a fault, where the second preset threshold can be preset and stored in the memory.

[0245] In practical applications, the battery pack is more likely to malfunction when it is in the charging state. Therefore, the second preset voltage value during charging of the battery pack is less than the second preset voltage value during discharging of the battery pack, so as to more timely determine the internal short-circuit fault of the battery pack during charging.

[0246] When there is an equalization circuit for voltage equalization of the battery modules, in order to compensate for the influence of the equalization circuit on the judgment of the internal short-circuit fault and further improve the accuracy of detecting the internal short-circuit fault, the method further includes the following steps:

[0247] Determine the first error value generated by the equalization circuit on the output voltage of the i-th battery module, and use the first error value to compensate the change amount of the difference of the i-th battery module.

[0248] In some embodiments, the equalization circuit includes a controllable switch and a resistor connected in series. At this time, the first error value is determined according to the working time of the equalization circuit of the i-th battery module, the output voltage of the i-th battery module, the resistance value of the resistor, and the capacity of the i-th battery module. Specifically, reference can be made to Equation (20) and Equation (21).

[0249] The method can also correct the change amount of the obtained output voltage according to the inconsistency between the impedances of the battery modules. The specific steps are as follows:

[0250] According to the difference between the impedance value of the i-th battery module and the average impedance value of the k battery modules, and the discharge current of the i-th battery module, determine the second error value generated by the impedance inconsistency on the output voltage of the i-th battery module;

[0251] Use the second error value to compensate the change amount of the difference of the i-th battery module. Specifically, reference can be made to Equation (13) and Equation (14).

[0252] Then use the compensated change amount of the difference to determine whether the battery module has a fault.

[0253] In summary, by using the detection method provided in the embodiments of the present application, when the average output voltage of the i-th battery module is within the preset voltage range, the sampling results can be used for fault detection. The working state of the battery is not limited, and fault detection can be performed during the charging, discharging, and standby stages of the battery. The applicability is relatively strong, and whether there is a fault in the battery module can be determined in a timely manner, improving the safety.

[0254] By reasonably selecting the preset voltage range, the accuracy of fault detection can be improved. For example, in practical applications, the voltage range of the battery module when the state of charge of the battery cell is at a medium level can be selected as the preset voltage range. This is because over-discharge is generally avoided during the discharge process of the battery module, that is, the open-circuit voltage and the state of charge of each battery cell are controlled not to be too low. Therefore, the state of charge of the battery cell is at a medium level for a relatively large proportion of the usage cycle. Conducting short-circuit fault detection when the state of charge of the battery cell is at a medium level can cover different working states such as charging and discharging of the battery pack, and the practicality is relatively high.

[0255] Embodiment 5:

[0256] Based on the battery pack fault detection circuit provided in the above embodiments, the embodiments of the present application further provide a power supply system, which will be specifically described below with reference to the drawings.

[0257] See Figure 10 , which is a schematic diagram of a power supply system provided in the embodiments of the present application.

[0258] The illustrated power supply system includes a battery pack 100, a battery pack fault detection circuit 200, and a battery management system 101.

[0259] Among them, the battery pack fault detection circuit 200 is integrated with the controller of the battery management system 101.

[0260] The battery pack fault detection circuit includes a sampling circuit 201 and a controller 202. For the description of the working principle and specific implementation manner of this detection circuit, reference can be made to the above embodiments, and the embodiments of the present application will not elaborate here.

[0261] The controller 202 can be independently set or integrated with the controller of the battery management system 101. The embodiments of the present application do not make specific limitations on this.

[0262] The battery management system 101 is used to monitor and manage the battery pack, and specifically includes functions such as state estimation, battery balancing, safety monitoring, thermal management, charge and discharge management, and information recording.

[0263] Among them, state estimation refers to a functional unit that estimates the current capacity, state of charge (SOC), available power, and available energy of the battery module.

[0264] Battery equalization refers to controlling the equalization circuit 300 to equalize the charge amounts of each battery module.

[0265] Safety monitoring refers to monitoring whether the battery module has overvoltage, overcurrent, undervoltage, overtemperature, and faults (such as short circuit, open circuit, etc.).

[0266] Thermal management refers to controlling the temperature of the battery module within a preset temperature range to improve the charge and discharge efficiency of the battery module and extend the life of the battery module.

[0267] Charge and discharge management refers to ensuring that the state of charge is maintained within a reasonable range to prevent damage to the battery module caused by overcharging or over-discharging.

[0268] Information recording refers to recording the collected data and fault conditions.

[0269] The detection circuit provided in the embodiment of the present application is used for the safety monitoring of the battery management system. This detection circuit uses the output voltage of the battery module to detect the internal short circuit fault of the battery module, and feeds the detection result back to the controller of the battery management system as an important indicator for measuring the current safety state of the battery pack 100.

[0270] See Figure 11 , this figure is a schematic diagram of another power supply system provided by the embodiment of the present application.

[0271] Figure 11 Figure 10 The difference is that the battery pack fault detection circuit 200 and the battery management system 101 are not integrated together. At this time, the controller 202 and the controller of the battery management system are also independently set. The controller 202 detects the battery module with an internal short circuit fault and informs the controller of the battery management system of the detection result.

[0272] This power supply system includes the battery pack fault detection circuit provided by the embodiment of the present application. When the average output voltage of the i-th battery module is within the preset voltage range, the controller of this detection circuit can use the sampling result for fault detection, regardless of the battery working state. Fault detection can be carried out during the battery charging, discharging, and standby stages, with strong applicability. It can timely determine whether there is a fault in the battery module to early warn of the risk of thermal runaway of the battery pack, improving safety.

[0273] In addition, the fault detection circuit also takes into account the battery impedance difference, compensates the voltage consumed by balancing, eliminates the error caused by the voltage difference introduced by the inconsistency of battery impedance and balancing, and improves the accuracy of fault detection.

[0274] Embodiment Six:

[0275] Based on the battery pack fault detection circuit provided in the above embodiments, the embodiment of the present application also provides an electric vehicle, which will be specifically described below with reference to the accompanying drawings.

[0276] See Figure 12 , which is a schematic diagram of an electric vehicle provided by the embodiment of the present application.

[0277] The illustrated electric vehicle 80 includes the power supply system 801 and the motor 802 provided in the above embodiments.

[0278] The power supply system 801 is used to supply power to the motor 802.

[0279] The motor 802 is used to convert the obtained electric energy into mechanical energy to drive the electric vehicle 80.

[0280] Among them, the power supply system 801 includes a battery pack, a battery pack fault detection circuit, and a battery management system. For the description of the power supply system, reference can be made to Embodiment Five above.

[0281] The battery pack fault detection circuit includes a sampling circuit and a controller. For the working principle and specific implementation of the detection circuit, reference can be made to Embodiments One to Four above, and the embodiments of the present application will not repeat them here.

[0282] The power supply system of the electric vehicle includes the battery pack fault detection circuit provided by the embodiment of the present application. When the average output voltage of the i-th battery module is within the preset voltage range, the controller of the detection circuit can use the sampling results for fault detection, regardless of the battery working state. Fault detection can be performed during the battery charging, discharging, and standby stages, with strong applicability. It can timely determine whether there is a fault in the battery module to early warn of the risk of thermal runaway of the battery pack, improving the safety of the electric vehicle.

[0283] In addition, the fault detection circuit also takes into account the battery impedance difference, compensates the voltage consumed by balancing, eliminates the error caused by the voltage difference introduced by the inconsistency of battery impedance and balancing, and improves the accuracy of fault detection.

[0284] Embodiment Seven:

[0285] Based on the battery pack fault detection circuit provided in the above embodiments, the embodiment of the present application also provides an electronic device, which will be specifically described below with reference to the accompanying drawings.

[0286] See Figure 13 , which is a schematic diagram of an electronic device provided by an embodiment of the present application.

[0287] The illustrated electronic device 90 includes the power supply system 801 and the load circuit 901 provided in the above embodiments.

[0288] The power supply system 801 is used to supply power to the load circuit 901.

[0289] The specific implementation manner of the load circuit 901 is related to the electronic device, and the embodiments of the present application do not make specific limitations.

[0290] The embodiments of the present application do not make specific limitations on the type of the electronic device 90. For example, it can be a mobile phone, a tablet computer, a laptop computer, a virtual reality terminal device, an augmented reality terminal device, and a smart home appliance device (such as a floor cleaning robot), etc.

[0291] Taking the electronic device as a mobile phone as an example, the battery pack of the electronic device includes battery modules connected in series. Usually, each battery module includes a single battery cell. By connecting the battery modules in series, the output voltage of the battery pack is increased. In some embodiments, the mobile phone can adopt a folding architecture, that is, the mobile phone includes a first side and a second side, and at least one battery module is included on each side. All the battery modules are connected in series to form a battery pack.

[0292] The power supply system of the electronic device includes the battery pack fault detection circuit provided by the embodiments of the present application. When the average output voltage of the i-th battery module is within the preset voltage range, the controller of the detection circuit can use the sampling result for fault detection, without limiting the battery working state. Fault detection can be performed during the battery charging, discharging, and storage stages, with strong applicability. It can timely determine whether there is a fault in the battery module, so as to early warn of the risk of thermal runaway of the battery pack and improve the safety of the electronic device.

[0293] In addition, the fault detection circuit also considers the battery impedance difference and compensates the voltage consumed by balancing, eliminating the error caused by the voltage difference brought by the battery impedance and the inconsistency of balancing, and improving the accuracy of fault detection.

[0294] It should be understood that in this application, "at least one (item)" means one or more, and "a plurality" means two or more. "And / or" is used to describe the association relationship of associated objects and indicates that there can be three relationships. For example, "A and / or B" can mean: only A exists, only B exists, and both A and B exist at the same time. Among them, A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one (one) of the following" or its similar expression refers to any combination of these items, including any combination of single item (one) or plural items (ones). For example, at least one (one) of a, b, or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0295] Each embodiment in this specification is described in a progressive manner. For the same or similar parts between the embodiments, reference can be made to each other. The key point of each embodiment is to illustrate the differences from other embodiments. In addition, some or all of the units and modules can also be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without creative work.

[0296] The above are only specific implementation manners of this application. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of this application, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of this application.

Claims

1. A battery pack fault detection circuit for connecting to a battery pack, the battery pack comprising k battery modules connected in series, each battery module including at least one battery cell, where k is an integer greater than 1, characterized in that, The battery pack fault detection circuit includes a sampling circuit and a controller, where: The sampling circuit samples the output voltage of each battery module and sends the sampling result to the controller; The controller is configured to obtain the difference between the output voltage of the i-th battery module and the average output voltage whenever it is determined that the average output voltage of the k battery modules is within a preset voltage range using the sampling result, where i = 1, 2,..., k, and the preset voltage range is the voltage range of the battery module when the state of charge of the battery cell is at a medium level; Based on the change amount of the difference, the capacity of the i-th battery module, the sampling result of the output voltage of the i-th battery module and the sampling time, and a coefficient calibrated in advance representing the change rate of the open-circuit voltage of the battery module with respect to the state of charge SOC of the battery module, determine the short-circuit resistance of the i-th battery module, and determine that the i-th battery module has a fault when the short-circuit resistance is less than a preset resistance value. The short-circuit resistance is inversely proportional to the capacity of the i-th battery module, inversely proportional to the change amount of the difference, proportional to the coefficient calibrated in advance representing the change rate of the open-circuit voltage of the battery module with respect to the state of charge SOC of the battery module, and proportional to the sampling result of the output voltage of the i-th battery module and the sampling time; Alternatively, based on the change amount of the difference, the capacity of the i-th battery module, the sampling time of the output voltage of the i-th battery module, and a coefficient calibrated in advance representing the change rate of the open-circuit voltage of the battery module with respect to the state of charge SOC of the battery module, determine the short-circuit current of the i-th battery module, and determine that the i-th battery module has a fault when the short-circuit current is greater than a preset current value. The short-circuit current is proportional to the capacity of the i-th battery module, proportional to the change amount of the difference, inversely proportional to the sampling time of the output voltage of the i-th battery module, and inversely proportional to the coefficient calibrated in advance representing the change rate of the open-circuit voltage of the battery module with respect to the state of charge SOC of the battery module; Wherein, within the preset voltage range, the open-circuit voltage of the battery module is positively correlated with the state of charge of the battery module and shows a linear relationship.

2. The battery pack fault detection circuit according to claim 1, wherein, The preset resistance value during battery pack charging is greater than the preset resistance value during battery pack discharging.

3. The battery pack fault detection circuit according to claim 1, wherein, The preset current value during battery pack charging is less than the preset current value during battery pack discharging.

4. The battery pack fault detection circuit according to claim 1, wherein Each battery module is also connected in parallel with an equalization circuit for equalizing the charge amounts of the k battery modules. The controller is further configured to determine a first error value generated by the equalization circuit on the output voltage of the i-th battery module and use the first error value to compensate for the change amount of the difference of the i-th battery module.

5. The battery pack fault detection circuit according to claim 4, wherein, The equalization circuit includes a controllable switch and a resistor connected in series, and the controller is specifically configured to determine the first error value according to the working time of the equalization circuit of the i-th battery module, the output voltage of the i-th battery module, the resistance value of the resistor, and the capacity of the i-th battery module.

6. The battery pack fault detection circuit according to any one of claims 1-5, characterized in that, The controller is further configured to determine a second error value generated by the output voltage of the i-th battery module due to the impedance value inconsistency according to the difference between the impedance value of the i-th battery module and the average impedance value of the k battery modules, and the discharge current of the i-th battery module, and compensate for the change amount of the difference of the i-th battery module by using the second error value.

7. The battery pack fault detection circuit according to any one of claims 1-5, characterized in that, When the battery pack is charging, the sampling frequency of the sampling circuit is greater than that when the battery pack is discharging.

8. The battery pack fault detection circuit according to any one of claims 1-5, characterized in that The controller is integrated with the controller of the battery management system BMS.

9. A battery pack fault detection method for detecting faults in a battery pack, the battery pack comprising k battery modules connected in series, each battery module comprising one or more battery cells, where k is an integer greater than 1; characterized in that, The battery pack fault detection method includes: Sampling the output voltage of each battery module to obtain a sampling result; Whenever it is determined by using the sampling result that the average output voltage of the k battery modules is within a preset voltage range: obtaining the difference between the output voltage of the i-th battery module and the average output voltage, where i = 1, 2,..., k, and the preset voltage range is the voltage range of the battery module when the state of charge of the battery cell is at a medium level; Determining the short-circuit resistance of the i-th battery module according to the change amount of the difference, the capacity of the i-th battery module, the sampling result of the output voltage of the i-th battery module and the sampling time, and a coefficient calibrated in advance representing the change rate of the open-circuit voltage of the battery module with the state of charge SOC of the battery module, and determining that the i-th battery module has a fault when the short-circuit resistance is less than a preset resistance value. The short-circuit resistance is inversely proportional to the capacity of the i-th battery module, inversely proportional to the change amount of the difference, proportional to the coefficient calibrated in advance representing the change rate of the open-circuit voltage of the battery module with the state of charge SOC of the battery module, and proportional to the sampling result of the output voltage of the i-th battery module and the sampling time; Alternatively, determining the short-circuit current of the i-th battery module according to the change amount of the difference, the capacity of the i-th battery module, the sampling time of the output voltage of the i-th battery module, and a coefficient calibrated in advance representing the change rate of the open-circuit voltage of the battery module with the state of charge SOC of the battery module, and determining that the i-th battery module has a fault when the short-circuit current is greater than a preset current value. The short-circuit current is proportional to the capacity of the i-th battery module, proportional to the change amount of the difference, inversely proportional to the sampling time of the output voltage of the i-th battery module, and inversely proportional to the coefficient calibrated in advance representing the change rate of the open-circuit voltage of the battery module with the state of charge SOC of the battery module; Wherein, within the preset voltage range, the open-circuit voltage of the battery module is positively correlated with the state of charge of the battery module and shows a linear relationship.

10. The battery pack fault detection method according to claim 9, characterized in that, The preset resistance value during charging of the battery pack is greater than the preset resistance value during discharging of the battery pack.

11. The battery pack fault detection method according to claim 9, wherein, The preset current value during charging of the battery pack is less than the preset current value during discharging of the battery pack.

12. The battery pack fault detection method according to claim 9, wherein, Each of the battery modules is also connected in parallel with an equalization circuit for equalizing the charge amounts of the k battery modules. The method further includes: Determining a first error value generated by the equalization circuit of the i-th battery module on the output voltage of the i-th battery module, and compensating for the change amount of the difference of the i-th battery module by using the first error value.

13. The battery pack fault detection method according to claim 12, characterized in that, The equalization circuit includes a controllable switch and a resistor connected in series. Determining the first error value generated by the equalization circuit of the i-th battery module on the output voltage of the i-th battery module specifically includes: Determining the first error value according to the working time of the equalization circuit of the i-th battery module, the output voltage of the i-th battery module, the resistance value of the resistor, and the capacity of the i-th battery module.

14. The battery pack fault detection method according to any one of claims 9-13, characterized in that, The method further includes: Determining a second error value generated by the impedance inconsistency on the output voltage of the i-th battery module according to the difference between the impedance value of the i-th battery module and the average impedance value of the k battery modules, and the discharge current of the i-th battery module, and compensating for the change amount of the difference of the i-th battery module by using the second error value.

15. The battery pack fault detection method according to any one of claims 9-13, characterized in that, The sampling frequency of the output voltage of each battery module during charging of the battery pack is greater than the sampling frequency of the output voltage of each battery module during discharging of the battery pack.

16. A power supply system, characterized in that, Including the battery pack fault detection circuit according to any one of claims 1-8, and further including a battery pack and a battery management system; The battery pack includes k battery modules connected in series, each battery module includes one or more battery cells, and k is an integer greater than 1; The battery management system is used for monitoring and managing the battery pack.

17. The power supply system according to claim 16, wherein, The battery pack fault detection circuit is integrated with the battery management system.

18. An electric vehicle, characterized in that, The electric vehicle includes the power supply system according to claim 16 or 17, and further includes a motor; The power supply system is used for supplying power to the motor; The motor is used for converting electrical energy into mechanical energy to drive the electric vehicle.

19. An electronic device, characterized in that, The electronic device includes the power supply system according to claim 16 or 17, and further includes a load circuit; The power supply system is used for supplying power to the load circuit.

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