Method and device for preventing overdischarge of power battery under under-voltage, and battery management controller

Abstract

The application provides a method and device for preventing overdischarge of a power battery under voltage drop, and a battery management controller. The method comprises: obtaining a working state of the battery; judging whether the battery is under voltage drop according to the working state of the battery; when the battery is under voltage drop, reducing the calculation frequency of the battery module controller and the communication frequency between the battery module controller and the battery management controller, so as to reduce the power supply loop current of the battery to the battery module controller. When the method identifies that the battery is under voltage drop, the calculation and communication frequency of the battery module controller is actively reduced to the maximum extent, the loop current between the battery and the battery module controller is no longer the current under normal working, so that the battery is protected to the maximum extent, overdischarge of the battery under voltage drop for a long time is avoided, thermal runaway caused by serious overdischarge is avoided, and completely irreversible loss is avoided. Furthermore, the method does not need to increase additional hardware, and does not increase additional cost.

Description

Technical Field

[0001] This invention relates to the field of vehicle battery control technology, and in particular to a method and device for preventing over-discharge under undervoltage conditions of a power battery, and a battery management controller. Background Technology

[0002] To address increasing environmental demands and maintain ecological sustainability, new energy vehicles have become widely adopted, particularly electric vehicles and hybrid electric vehicles. Both types of new energy vehicles rely on batteries as their core component, which require a Battery Management System (BMS) to manage and prevent overcharging, over-discharging, overcurrent, and overheating during use, which could trigger a chain reaction leading to thermal runaway.

[0003] Both ternary lithium batteries and lithium iron phosphate batteries have their safe operating voltage ranges. Ternary lithium batteries are generally between 2.8 and 4.2V, while lithium iron phosphate batteries are generally between 2.5 and 3.65V. Currently, when a power battery is undervoltage, the common strategy of the Battery Management System (BMS) is to detect the undervoltage and actively lower the voltage (by disconnecting the main positive and main negative relays) or coordinate with the vehicle controller to lower the voltage to prevent further battery drain.

[0004] Battery Management Systems (BMS) generally have two architectures: centralized and distributed. In a centralized architecture, the BMS consists of a single controller responsible for battery voltage and temperature sampling, equalization, high-voltage sampling, current sampling, relay control, and the core SOX algorithm. A centralized controller is typically large and lacks flexible placement. In a distributed architecture, the BMS is functionally divided into a Battery Management Controller (BMC) and a Cell Module Control Unit (CMC). The CMC primarily handles battery voltage and temperature sampling and equalization (directly related to the battery), while the BMC handles high-voltage and other functions. The BMC can be placed within the Battery Disconnect Unit (BDU). The placement of the controllers in a distributed architecture is flexible. The BMC and CMC communicate via CAN or a daisy-chain connection. In a distributed architecture, the BMC is typically powered by the vehicle's 12V power supply, while the CMC draws power directly from the battery.

[0005] When the power battery experiences undervoltage, the vehicle's high voltage is cut off, and the power battery ceases to output power. However, since the CMC directly draws power from the battery, a loop is formed between the battery and the CMC sampling chip. Under normal operating conditions, the loop current is 15-20mA. If the vehicle's 12V power supply is still present at this time, the BMC controller is in a wake-up state, and there is still interaction between the BMC and CMC. The CMC is also in a normal operating state. The undervoltage battery needs to continuously supply power to the CMC, causing the battery module voltage to drop lower and lower, resulting in increasingly severe undervoltage and irreversible damage to the battery. Severe undervoltage over-discharge can lead to thermal runaway. Summary of the Invention

[0006] In view of the above-mentioned deficiencies of the prior art, the present invention provides a method and device for preventing over-discharge under undervoltage conditions of a power battery, as well as a battery management controller, to solve the technical problem in a distributed architecture where the power battery continues to supply power after undervoltage, leading to increasingly severe undervoltage.

[0007] To achieve the above and other related objectives, this invention provides a method for preventing over-discharge under undervoltage conditions of a power battery, applied to a distributed battery management system. The battery management system includes a battery management controller and at least one battery module controller. The battery management controller is powered by an auxiliary power supply, and the battery module controller is powered by a battery. The battery management controller and the battery module controller are communicatively connected. The method for preventing over-discharge includes the following steps: acquiring the operating state of the battery; determining whether the battery is undervoltage based on the operating state of the battery; when the battery is undervoltage, reducing the calculation frequency of the battery module controller and its communication frequency with the battery management controller to reduce the current in the power supply circuit from the battery to the battery module controller.

[0008] In one embodiment of the present invention, when the battery is undervoltage, the calculation frequency of the battery module controller and its communication frequency with the battery management controller are reduced to decrease the power supply circuit current from the battery to the battery module controller. This includes: when the battery is undervoltage, obtaining the on / off state of a high-voltage relay to determine whether the high-voltage relay is off; when the high-voltage relay is off, reducing the calculation frequency of the battery module controller and its communication frequency with the battery management controller to decrease the power supply circuit current from the battery to the battery module controller; otherwise, first disconnecting the high-voltage relay, and then reducing the calculation frequency of the battery module controller and its communication frequency with the battery management controller.

[0009] In one embodiment of the present invention, when the high-voltage relay is disconnected, the calculation frequency of the battery module controller and its communication frequency with the battery management controller are reduced to decrease the power supply circuit current from the battery to the battery module controller. This includes: when the high-voltage relay is disconnected, obtaining the operating status of the battery management controller to determine whether the battery management controller is working normally; if yes, then reducing the calculation frequency of the battery module controller and its communication frequency with the battery management controller to decrease the power supply circuit current from the battery to the battery module controller; if no, then not changing the communication frequency between the battery management controller and the battery module controller.

[0010] In one embodiment of the present invention, reducing the computing frequency of the battery module controller and its communication frequency with the battery management controller to reduce the power supply circuit current from the battery to the battery module controller includes: calculating the maximum allowable frequency of the battery module controller; reducing the computing frequency of the battery module controller and its communication frequency with the battery management controller to the maximum allowable frequency or below the maximum allowable frequency to reduce the power supply circuit current from the battery to the battery module controller.

[0011] In one embodiment of the present invention, calculating the maximum allowable frequency of the battery module controller includes: obtaining the contributeable capacity of the battery and the power depletion time of the auxiliary power supply; obtaining the maximum allowable average current of the battery module controller based on the contributeable capacity and the power depletion time; and obtaining the maximum allowable frequency based on the maximum allowable average current, the normal calculation and communication frequency of the battery module controller, and the loop current value of the battery module controller at the normal calculation and communication frequency.

[0012] In one embodiment of the present invention, obtaining the contributeable capacity of the battery and the power depletion time of the auxiliary power supply includes: obtaining the minimum value of the single cell voltage of the battery when it is in an undervoltage state and the minimum temperature of the battery module; obtaining the contributeable capacity based on the minimum value of the single cell voltage of the battery and the minimum temperature; and obtaining the power depletion time based on the ambient temperature of the vehicle.

[0013] In one embodiment of the present invention, the maximum allowable average current of the battery module controller is obtained based on the contributeable capacity and the energy depletion time, including: calculating a first ratio of the contributeable capacity to the energy depletion time; and calculating the product of the first ratio and a preset coefficient to obtain the maximum allowable average current.

[0014] In one embodiment of the present invention, the maximum allowable frequency is obtained based on the maximum allowable average current, the normal calculation and communication frequency of the battery module controller, and the loop current value of the battery module controller at the normal calculation and communication frequency. This includes: calculating a second ratio between the normal calculation and communication frequency of the battery module controller and the loop current value of the battery module controller at the normal calculation and communication frequency; and calculating the product of the second ratio and the maximum allowable average current to obtain the maximum allowable frequency.

[0015] To achieve the above and other related objectives, the present invention also provides an over-discharge protection device for a power battery under undervoltage conditions, applied to a distributed battery management system. The battery management system includes a battery management controller and at least one battery module controller. The battery management controller is powered by an auxiliary power supply, and the battery module controller is powered by a battery. The battery management controller and the battery module controller are communicatively connected. The over-discharge protection device includes: a data acquisition unit for acquiring the operating state of the battery; a judgment unit for judging whether the battery is undervoltage; and a control unit for reducing the calculation frequency of the battery module controller and its communication frequency with the battery management controller when the battery is undervoltage, thereby reducing the power supply circuit current from the battery to the battery module controller.

[0016] To achieve the above and other related objectives, the present invention also provides a battery management controller for performing the over-discharge prevention method described above.

[0017] The beneficial effects of this invention are as follows: This invention proposes a method and device for preventing over-discharge under undervoltage conditions of a power battery, as well as a battery management controller. When the battery is detected to be undervoltage, the method actively reduces the calculation and communication frequency of the battery module controller to the greatest extent possible, so that the current in the circuit between the battery and the battery module controller is no longer that of normal operation, thereby protecting the battery to the greatest extent. Under the condition of undervoltage, the battery will not be over-discharged for a long time, thus avoiding thermal runaway that may be caused by severe over-discharge and avoiding completely irreversible losses. Moreover, this method does not require additional hardware and will not increase additional costs. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a diagram of a centralized BMS architecture provided in an embodiment of the present invention;

[0020] Figure 2 This is a distributed BMS architecture diagram provided in an embodiment of the present invention;

[0021] Figure 3 This is a high-voltage architecture diagram of a power battery provided in an embodiment of the present invention;

[0022] Figure 4 A flowchart of a first method for preventing over-discharge according to an embodiment of the present invention;

[0023] Figure 5 A flowchart of a second over-discharge prevention method provided in an embodiment of the present invention;

[0024] Figure 6 A flowchart of a third over-discharge prevention method provided in an embodiment of the present invention;

[0025] Figure 7 A flowchart for calculating the maximum permissible frequency is provided as an embodiment of the present invention;

[0026] Figure 8 A detailed flowchart of step S210 provided in an embodiment of the present invention;

[0027] Figure 9 A flowchart for calculating the maximum permissible average current is provided in one embodiment of the present invention;

[0028] Figure 10 A detailed flowchart of step S230 provided in an embodiment of the present invention;

[0029] Figure 11 This is a structural diagram of an over-discharge protection device provided in an embodiment of the present invention.

[0030] Explanation of reference numerals in the attached drawings: 101, data acquisition unit; 102, judgment unit; 103, control unit. Detailed Implementation

[0031] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art and the description of the present invention by those skilled in the art, any prior art methods, equipment, and materials similar to or equivalent to those described in the embodiments of the present invention can be used to implement the present invention.

[0032] It should be understood that the terminology used in the embodiments of this invention is for describing specific implementations and not for limiting the scope of protection of this invention. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0033] The structures, proportions, and sizes illustrated in the accompanying drawings are solely for illustrative purposes and to aid those skilled in the art in understanding and reading the invention. They are not intended to limit the implementation of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and objectives of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the drawings only show components relevant to the invention and are not drawn according to the actual number, shape, and size of components in practice. In actual implementation, the type, quantity, and proportion of each component can be arbitrarily changed, and the component layout may be more complex.

[0034] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In some embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0035] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functions, and operations that may be implemented in the methods and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0036] Figure 1 and Figure 2 Corresponding to the centralized and distributed BMS architectures mentioned in the background section, this invention is mainly used for... Figure 2The distributed BMS architecture shown is described above. This invention applies to a distributed battery management system, which includes a battery management controller (BMC) and at least one battery module controller (CMC). The BMC is powered by an auxiliary power source, and the CMC is powered by the battery. The BMC and CMC are communicatively connected. The high-voltage architecture diagram of the power battery in this distributed management system is shown below. Figure 3 As shown.

[0037] Please see Figure 4 , Figure 4 An embodiment of the present invention provides a method for preventing over-discharge of a power battery under undervoltage conditions, comprising steps S100 to S200, which are described in detail below.

[0038] Step S100: Obtain the battery's operating status. Obtaining the battery's operating status is mainly used to determine whether the battery is undervoltage. Only when the battery is undervoltage is further control required to prevent the battery from continuing to over-discharge for an extended period of time.

[0039] Step S200: Determine if the battery is undervoltage based on its operating state. When the battery is undervoltage, reduce the calculation frequency of the battery module controller and its communication frequency with the battery management controller to reduce the current in the power supply circuit from the battery to the battery module controller. Understandably, when the battery is not undervoltage, there is no need to reduce the calculation frequency of the battery module controller and its communication frequency with the battery management controller. Here, the calculation frequency refers to the frequency at which the battery module controller collects relevant data and performs calculations, and the communication frequency refers to the communication frequency between the CMC and BMC, or the interaction frequency. Each time the CMC performs a calculation or communicates with the BMC, it increases energy consumption. In this step, by reducing the calculation frequency of the CMC and simultaneously reducing the communication frequency between the BMC and CMC, the energy consumption of the CMC is reduced, effectively preventing the battery from becoming completely undervoltage.

[0040] The CMC's computation frequency and communication frequency can take different values ​​or the same value. In some embodiments described below, these two frequencies are taken as the same value and are collectively referred to as the computation and communication frequencies. That is, the CMC performs calculations first, and then communicates with the BMC for data transmission. Please refer to [link to relevant documentation]. Figure 5In a specific embodiment of the present invention, when the battery is undervoltage, the calculation frequency of the battery module controller and its communication frequency with the battery management controller are reduced to decrease the current in the power supply circuit from the battery to the battery module controller. This includes: when the battery is undervoltage, obtaining the on / off state of the high-voltage relay to determine whether the high-voltage relay is open; if the high-voltage relay is open, reducing the calculation frequency of the battery module controller and its communication frequency with the battery management controller to decrease the current in the power supply circuit from the battery to the battery module controller; otherwise, first opening the high-voltage relay, and then reducing the calculation frequency of the battery module controller and its communication frequency with the battery management controller. After the battery is undervoltage, a common BMS strategy is to open the high-voltage relays (including the main positive relay and the main negative relay) to prevent the high-voltage battery from continuing to output energy. Therefore, in this embodiment, when the battery is undervoltage, the on / off state of the high-voltage relay is further obtained to ensure that the high-voltage relay is opened, thus providing more reliable battery protection. If the high-voltage relay is not yet open, it needs to be opened first, and then the calculation and communication frequency of the CMC is reduced.

[0041] Please see Figure 6 In a specific embodiment of the present invention, when the high-voltage relay is disconnected, the calculation frequency of the battery module controller and its communication frequency with the battery management controller are reduced to decrease the current in the power supply circuit from the battery to the battery module controller. This includes: when the high-voltage relay is disconnected, obtaining the operating status of the battery management controller to determine whether the battery management controller is working normally; if so, reducing the calculation frequency of the battery module controller and its communication frequency with the battery management controller to decrease the current in the power supply circuit from the battery to the battery module controller; if not, not changing the communication frequency between the battery management controller and the battery module controller. After the high-voltage relay is disconnected, the main power consumption of the battery module controller is due to calculations performed by the battery module controller and its interaction with the battery management controller. Therefore, in this embodiment, it is necessary to first determine whether the battery management controller is working normally.

[0042] In one specific embodiment of the present invention, reducing the calculation frequency of the battery module controller and its communication frequency with the battery management controller to reduce the power supply circuit current from the battery to the battery module controller includes: calculating the maximum allowable frequency of the battery module controller; and reducing the calculation frequency of the battery module controller and its communication frequency with the battery management controller to or below the maximum allowable frequency to reduce the power supply circuit current from the battery to the battery module controller. The lower the calculation and communication frequency of the battery module controller, the lower its power consumption. The reason for setting a maximum allowable frequency is to ensure that the battery module controller does not deplete a battery already in an undervoltage state to a completely irreversible state.

[0043] Please see Figure 7In a specific embodiment of the present invention, the maximum allowable frequency of the battery module controller is calculated, including steps S210 to S230.

[0044] Step S210: Obtain the battery's contributeable capacity and the auxiliary power supply's energy depletion time. The contributeable capacity corresponds to the maximum energy that the battery module controller can consume, i.e., the contributeable capacity within the voltage difference range from an undervoltage state (or from a state where the high-voltage relay is disconnected) to a completely irreversible state. Exceeding this value will cause the battery to transition from an undervoltage state to a completely irreversible state, resulting in battery performance degradation, accelerated aging, and reduced safety. Therefore, it is necessary to ensure that the battery does not enter a completely irreversible state. The auxiliary power supply's energy depletion time corresponds to the theoretical operating time of the battery management controller. As mentioned above, the main reason for battery power consumption is the calculation performed by the battery module controller and the interaction with the battery management controller. The battery management controller is powered by the auxiliary power supply. Therefore, when the auxiliary power supply's energy is depleted, the battery management controller stops working, thus ceasing interaction with the battery module controller. The battery module controller also stops performing calculations, preventing further energy consumption by the battery module controller.

[0045] Step S220: Obtain the maximum allowable average current of the battery module controller based on the available capacity and energy depletion time. Step S230: Obtain the maximum allowable frequency based on the maximum allowable average current, the normal calculation and communication frequency of the battery module controller, and the loop current value of the battery module controller at the normal calculation and communication frequency. The maximum allowable average current of the battery module controller is positively correlated with the calculation and communication frequency. If the calculated maximum allowable average current is large, the calculation and communication frequency of the battery module controller can be reduced less; conversely, if the calculated maximum allowable average current is large, the calculation and communication frequency of the battery module controller should be reduced more.

[0046] Please see Figure 8 In a specific embodiment of the present invention, step S210 includes steps S211 and S213.

[0047] Step S211: Obtain the minimum single-cell voltage and the minimum temperature of the battery module when the battery is in an undervoltage state. The reason for obtaining the minimum single-cell voltage is to ensure that each battery cell does not experience undervoltage or over-discharge, so the minimum value is used for subsequent calculations.

[0048] Step S212: Based on the minimum single-cell voltage and minimum temperature of the battery, obtain the contributing capacity. The contributing capacity can be obtained, for example, by looking up a table, as shown in Table 1 below.

[0049] Table 1: Capacity that can be released from minimum single-cell voltage to irreversible state (unit: mAh)

[0050] Minimum voltage of a single unit V 2.0 2.2 2.4 2.6 Minimum module temperature ≥ 0℃ Q1 Q2 Q3 Q4 Minimum module temperature < 0℃ Q5 Q6 Q7 Q8

[0051] In Table 1, Q1 to Q8 are all known quantities. For example, if the minimum single-cell voltage of the battery is 2.4V and the minimum module temperature is 5℃, then the corresponding contributeable capacity obtained from the table is Q3. For the minimum single-cell voltage not listed in the table, such as 2.3V, the corresponding contributeable capacity can be calculated using interpolation.

[0052] Step S212: Calculate the battery depletion time based on the ambient temperature of the vehicle. The battery depletion time can also be obtained using a lookup table; please refer to Table 2 below.

[0053] Table 2: Usable time of vehicle battery management controller under 12V constant power (unit: hours)

[0054] Ambient temperature Below 0℃ 0～25℃ 25℃ and above time t1 t2 t3

[0055] In Table 2, t1 to t3 are all known quantities, corresponding to the usable time of the battery management controller when the auxiliary power supply is fully charged. For example, when the ambient temperature is 16℃, the time for the battery to deplete is t2.

[0056] Please see Figure 9 In a specific embodiment of the present invention, step S220 includes: S221, calculating a first ratio of the contributeable capacity to the energy depletion time; S222, calculating the product of the first ratio and a preset coefficient to obtain the maximum allowable average current. The unit of the first ratio is mA (milliampere), which can be used as the maximum allowable average current. However, considering that this calculation result corresponds to the case where the energy is just used up, for safety reasons, some margin should be reserved. Therefore, in this embodiment, a preset coefficient is introduced in step S222. The value of the preset coefficient is between 0 and 1, and can be adjusted as needed, for example, it can be 0.1, 0.2, 0.3, ..., 0.9, etc. Let the contributeable capacity be Q, the energy depletion time be t, and the preset coefficient be a, then the maximum allowable average current I = a*Q / t.

[0057] Please see Figure 10In a specific embodiment of the present invention, step S230 includes: S231, calculating a second ratio between the normal calculation and communication frequency of the battery module controller and the loop current value of the battery module controller at the normal calculation and communication frequency; S232, calculating the product of the second ratio and the maximum allowable average current to obtain the maximum allowable frequency. The loop current value of the battery module controller at the normal calculation and communication frequency has a certain fluctuation range, for example, it can be 15~20mA. During calculation, the maximum value of the loop current should be used. Let the normal calculation and communication frequency of the battery module controller be k, and the maximum value of the loop current be I. MAX The maximum permissible frequency is k t Therefore, combining the above maximum permissible average current, we can obtain:

[0058]

[0059] Once the maximum allowable frequency is calculated, reduce the calculation frequency of the battery module controller and its communication frequency with the battery management controller to less than or equal to k. t That's all.

[0060] It should be noted that the steps of the various methods described above are only for clarity. In practice, they can be combined into one step or some steps can be split into multiple steps. As long as they contain the same logical relationship, they are all within the scope of protection of this patent. Adding insignificant modifications or introducing insignificant designs to the algorithm or process, but without changing the core design of the algorithm and process, are also within the scope of protection of this patent.

[0061] Please see Figure 11 , Figure 11 An embodiment of the present invention provides a device for preventing over-discharge under low voltage conditions of a power battery, which is also applied to a distributed battery management system. The battery management system includes a battery management controller and at least one battery module controller. The battery management controller is powered by an auxiliary power supply, and the battery module controller is powered by the battery. The battery management controller and the battery module controller are communicatively connected. The device for preventing over-discharge includes a data acquisition unit 101, a judgment unit 102, and a control unit 103. The data acquisition unit 101 is used to acquire the operating state of the battery; the judgment unit 102 is used to determine whether the battery is under-voltage; and the control unit 103 is used to reduce the calculation frequency of the battery module controller and its communication frequency with the battery management controller when the battery is under-voltage, so as to reduce the current in the power supply circuit from the battery to the battery module controller.

[0062] It should be noted that the over-discharge protection device in this embodiment is a device corresponding to the over-discharge protection method described above, and the functional modules in the over-discharge protection device may correspond to the corresponding steps in the over-discharge protection method. The over-discharge protection device in this embodiment can be implemented in conjunction with the over-discharge protection method; that is, without conflict, the relevant technical details mentioned in the over-discharge protection method of the above embodiment can also be applied to the over-discharge protection device in this embodiment.

[0063] In one specific embodiment of the present invention, a separate control module can be set up to execute the above-mentioned over-discharge protection method. However, in order to reduce costs, this embodiment provides a battery management controller to execute the above-mentioned over-discharge protection method. This makes very little improvement to the original system. It is only necessary to write the relevant program for executing the above-mentioned over-discharge protection method into the battery management controller.

[0064] In summary, the above-mentioned over-discharge prevention method actively reduces the calculation and communication frequency of the battery module controller to the greatest extent when it detects that the battery is under-voltage, so that the current in the circuit between the battery and the battery module controller is no longer the current under normal operation, thereby protecting the battery to the greatest extent and preventing it from being over-discharged for a long time when it is already under-voltage. This avoids thermal runaway that may be caused by severe over-discharge and avoids completely irreversible losses. At the same time, this method does not require additional hardware and will not increase additional costs.

[0065] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preventing over-discharge under under-voltage conditions of a power battery, characterized in that, The method is applied to a distributed battery management system, which includes a battery management controller and at least one battery module controller. The battery management controller is powered by an auxiliary power source, and the battery module controller is powered by a battery. The battery management controller and the battery module controller are communicatively connected. The over-discharge prevention method includes the following steps: Obtain the operating status of the battery; Based on the battery's operating status, determine whether the battery is undervoltage: When the battery is undervoltage, the calculation frequency of the battery module controller and its communication frequency with the battery management controller are reduced to decrease the power supply circuit current from the battery to the battery module controller. Reducing the computation frequency of the battery module controller and its communication frequency with the battery management controller to decrease the power supply circuit current from the battery to the battery module controller includes: Calculate the maximum allowable frequency of the battery module controller; Reduce the computing frequency of the battery module controller and its communication frequency with the battery management controller to the maximum allowable frequency or below the maximum allowable frequency, so as to reduce the power supply circuit current from the battery to the battery module controller; Calculating the maximum allowable frequency of the battery module controller includes: Obtain the contributeable capacity of the battery and the power depletion time of the auxiliary power source; Based on the available capacity and the energy depletion time, the maximum allowable average current of the battery module controller is obtained; The maximum allowable frequency is obtained based on the maximum allowable average current, the normal calculation and communication frequency of the battery module controller, and the loop current value of the battery module controller at the normal calculation and communication frequency.

2. The method for preventing over-discharge under undervoltage conditions of a power battery according to claim 1, characterized in that, When the battery is undervoltage, the calculation frequency of the battery module controller and its communication frequency with the battery management controller are reduced to decrease the power supply circuit current from the battery to the battery module controller, including: When the battery is undervoltage, the on / off state of the high-voltage relay is obtained to determine whether the high-voltage relay is off: When the high-voltage relay is disconnected, the calculation frequency of the battery module controller and its communication frequency with the battery management controller are reduced, so as to reduce the power supply circuit current from the battery to the battery module controller. Otherwise, first disconnect the high-voltage relay, and then reduce the calculation frequency of the battery module controller and its communication frequency with the battery management controller.

3. The method for preventing over-discharge under undervoltage conditions of a power battery according to claim 2, characterized in that, When the high-voltage relay is disconnected, the calculation frequency of the battery module controller and its communication frequency with the battery management controller are reduced to decrease the power supply circuit current from the battery to the battery module controller, including: When the high-voltage relay is disconnected, the operating status of the battery management controller is obtained to determine whether the battery management controller is working properly: If so, reduce the calculation frequency of the battery module controller and its communication frequency with the battery management controller to reduce the power supply circuit current from the battery to the battery module controller. If not, the calculation frequency of the battery module controller and its communication frequency with the battery management controller will not be changed.

4. The method for preventing over-discharge under undervoltage conditions of a power battery according to claim 1, characterized in that, Obtaining the contributeable capacity of the battery and the power depletion time of the auxiliary power supply includes: Obtain the minimum single-cell voltage and the minimum temperature of the battery module when the battery is in an undervoltage state; The contributeable capacity is obtained based on the minimum single-cell voltage of the battery and the minimum temperature. The time it takes for the electrical energy to be depleted is determined based on the ambient temperature of the vehicle.

5. The method for preventing over-discharge under undervoltage conditions of a power battery according to claim 1, characterized in that, Based on the available capacity and the energy depletion time, the maximum allowable average current of the battery module controller is obtained, including: Calculate a first ratio of the available capacity to the energy depletion time; The maximum allowable average current is obtained by multiplying the first ratio and the preset coefficient.

6. The method for preventing over-discharge under undervoltage conditions of a power battery according to claim 1, characterized in that, The maximum allowable frequency is obtained based on the maximum permissible average current, the normal calculation and communication frequency of the battery module controller, and the loop current value of the battery module controller at the normal calculation and communication frequency, including: Calculate a second ratio between the normal calculation and communication frequency of the battery module controller and the loop current value of the battery module controller at the normal calculation and communication frequency; The maximum permissible frequency is obtained by multiplying the second ratio by the maximum permissible average current.

7. An over-discharge protection device for implementing the over-discharge protection method for a power battery under undervoltage conditions according to any one of claims 1 to 6, characterized in that, The method is applied to a distributed battery management system, which includes a battery management controller and at least one battery module controller. The battery management controller is powered by an auxiliary power source, and the battery module controller is powered by a battery. The battery management controller and the battery module controller are communicatively connected. The over-discharge protection device includes: The data acquisition unit is used to acquire the operating status of the battery; The determination unit is used to determine whether the battery is undervoltage; The control unit is used to reduce the calculation frequency of the battery module controller and its communication frequency with the battery management controller when the battery is undervoltage, so as to reduce the power supply circuit current from the battery to the battery module controller.

8. A battery management controller, characterized in that, Used to perform the over-discharge prevention method as described in any one of claims 1 to 6.

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