A battery pack balancing method

Abstract

The present invention discloses a battery pack equalization method, belonging to the technical field of batteries. This method is applied to a battery management system; the battery pack includes at least one battery cell group, and the battery cell group includes multiple battery cells; the battery management system includes a main control board and slave boards corresponding to each battery cell group one by one; this method includes: an active equalization mode, which includes multiple equalization cycles; the equalization cycle includes: an equalization start stage: the main control board obtains an equalization start time threshold and sends an equalization start instruction to each slave board, so that each slave board equalizes the connected battery cell group until the equalization time reaches the equalization start time threshold; an equalization stop stage: the main control board obtains an equalization stop time threshold and sends an equalization stop instruction to each slave board, so that each slave board stops equalizing the connected battery cell group until the equalization stop time reaches the equalization stop time threshold. The embodiments of the present invention are beneficial to improving the consistency of the voltages of each battery cell monomer during the equalization process and enhancing the equalization effect.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a method for balancing a battery pack. Background Art

[0002] A battery pack usually consists of multiple battery cells used together in a system. The inconsistency of the battery cell monomers will cause more battery cells to be unable to charge enough electricity or discharge enough capacity, resulting in a sharp drop in the overall capacity of the battery pack, and further leading to a serious decline in the effective life of the battery pack. Long-term operation will also greatly reduce the reliability and safety of the battery pack. Therefore, it is crucial to perform balancing maintenance on the battery pack.

[0003] Active balancing of a battery management system refers to transferring the energy of the battery cells with a higher state of charge in the battery pack to the battery cells with a lower state of charge through an intermediate energy storage element, a switching element, and a control logic, etc., so as to achieve the purpose of balancing. However, currently, in the active balancing strategies of related technologies, continuously charging and discharging the battery cells that need to be balanced may cause the individual voltage of the battery cells to be falsely high or falsely low, resulting in over-balancing or under-balancing phenomena, affecting the consistency of the individual voltages of the battery cells during the balancing process and the balancing effect. Summary of the Invention

[0004] The present invention provides a method for balancing a battery pack to improve the consistency of the individual voltages of the battery cells during the balancing process and the balancing effect.

[0005] An embodiment of the present invention provides a method for balancing a battery pack, which is applied to a battery management system; the battery pack includes at least one battery cell group, and each of the battery cell groups includes multiple battery cells; the battery management system includes a main control board and a slave board corresponding to each of the battery cell groups one by one;

[0006] The method for balancing the battery pack includes: an active balancing mode, which includes multiple balancing cycles;

[0007] Each of the balancing cycles includes:

[0008] A balancing start stage: the main control board obtains a balancing start time threshold and sends a start balancing instruction to each of the slave boards, so that each of the slave boards performs balancing on the connected battery cell group until the balancing time reaches the balancing start time threshold;

[0009] A balancing stop stage: the main control board obtains a balancing stop time threshold and sends a stop balancing instruction to each of the slave boards, so that each of the slave boards stops balancing the connected battery cell group until the balancing stop time reaches the balancing stop time threshold;

[0010] Among them, in the equalization period, the main control board executes an equalization control process every first preset time interval; the equalization start stage includes at least one round of the equalization control process, and the equalization stop stage includes at least one round of the equalization control process;

[0011] In each round of the equalization control process in the equalization start stage, the main control board adjusts the equalization count to record the equalization time; in each round of the equalization control process in the equalization stop stage, the main control board adjusts the equalization interval count to record the equalization stop time.

[0012] Optionally, in the equalization start stage, every time one round of the equalization control process is executed, the main control board decrements the equalization count by one;

[0013] In the equalization stop stage, every time one round of the equalization control process is executed, the main control board decrements the equalization interval count by one;

[0014] Among them, the equalization start stage covers each round of the equalization control process where the equalization interval count is 0 and the equalization count is not 0; the equalization stop stage covers each round of the equalization control process where the equalization interval count is not 0.

[0015] Optionally, the equalization control process includes:

[0016] Judge whether the equalization interval count is 0;

[0017] In the case where the equalization interval count is 0, execute the following steps:

[0018] If the equalization count is 0, set the initial value of the equalization count and send the start equalization instruction to each slave board; among them, the product of the initial value of the equalization count and the first preset time is equal to the equalization start time threshold;

[0019] If the equalization count is not 0, decrement the equalization count by one and send the start equalization instruction to each slave board; among them, if the equalization count is equal to 1 after decrementing, set the initial value of the equalization interval count; the product of the initial value of the equalization interval count and the first preset time is equal to the equalization stop time threshold;

[0020] In the case where the equalization interval count is not 0, decrement the equalization interval count by one and send the stop equalization instruction to each slave board.

[0021] Optionally, before judging whether the equalization interval count is 0, it further includes:

[0022] When the active balancing start condition is not met and / or there is a balancing fault, send a stop balancing instruction to each of the slave boards, and clear the balancing interval count and the balancing count;

[0023] When the active balancing start condition is met and there is no such balancing fault, perform the step of determining whether the balancing interval count is 0.

[0024] Optionally, the slave board includes: a balancing control module and a power supply; the balancing control module is connected to the power supply and is respectively connected to each of the battery cells in the battery cell group corresponding to the slave board;

[0025] The active balancing start condition includes:

[0026] There is at least one battery cell to be balanced in the battery pack; among them, the battery cells to be balanced include battery cells to be charged and / or battery cells to be discharged; the single - cell voltage of the battery cell to be charged is lower than the average voltage of all the battery cells, and the difference exceeds the charging balance start threshold, and the single - cell voltage of the battery cell to be charged is within the charging balance allowable voltage range; the single - cell voltage of the battery cell to be discharged is higher than the average voltage of all the battery cells, and the difference exceeds the discharging balance start threshold, and the single - cell voltage of the battery cell to be discharged is within the discharging balance allowable voltage range;

[0027] And for each of the battery cell groups, the sum of the total discharging balance power of each of the battery cells to be discharged in the battery cell group and the available power of the power supply is greater than or equal to the total charging balance power of each of the battery cells to be charged in the battery cell group;

[0028] The balancing fault includes at least one of: battery cell voltage detection component fault, current detection component fault in the battery management system, temperature detection component fault in the battery management system, balancing over - current fault, balancing over - temperature fault, balancing control module fault, battery cell single - cell voltage out - of - limit, battery cell temperature out - of - limit, master board - slave board communication fault, and power supply fault.

[0029] Optionally, the slave board includes: a balancing control module and a power supply; the balancing control module is connected to the power supply and is respectively connected to each of the battery cells in the battery cell group corresponding to the slave board;

[0030] Before setting the initial value of the balancing count, it further includes:

[0031] For any one of the slave boards:

[0032] Determine the battery cells to be charged, the battery cells to be discharged, and the battery cell with the highest balancing priority in the battery cell group connected to the slave board; among them, the battery cell with the highest balancing priority is the battery cell in the battery cell group with the largest difference between the single - cell voltage and the average voltage of all the battery cells in the battery pack;

[0033] Determine the compensation power that the power supply needs to provide according to the number of the to-be-discharged battery cells in the battery cell group, the discharge equalization release power of a single to-be-discharged battery cell, the number of the to-be-charged battery cells, and the charging equalization power consumption of a single to-be-charged battery cell;

[0034] Generate the enable equalization instruction corresponding to the slave board according to the highest-equalization-priority battery cell and the compensation power.

[0035] Optionally, the enable equalization instruction includes an equalization command and a power supply control command; the equalization command includes an equalization flag bit corresponding to the highest-equalization-priority battery cell;

[0036] The process of the slave board equalizing the connected battery cell group includes:

[0037] The power supply responds to the power supply control command to turn on and provide the compensation power;

[0038] If the equalization flag bit indicates that the highest-equalization-priority battery cell is a to-be-charged battery cell, the equalization control module responds to the equalization command to perform charging equalization on the highest-equalization-priority battery cell; wherein, the charging electric energy of the to-be-charged battery cell is provided by the power supply and / or provided by the to-be-discharged battery cells in the battery cell group during other equalization cycles when discharging equalization is performed;

[0039] If the equalization flag bit indicates that the highest-equalization-priority battery cell is a to-be-discharged battery cell, the equalization control module responds to the equalization command to perform discharge equalization on the highest-equalization-priority battery cell.

[0040] Optionally, the determining the compensation power that the power supply needs to provide includes:

[0041] Determine the charge-discharge power multiple and the to-be-supplemented power of a single to-be-charged battery cell according to the charging equalization power consumption of a single to-be-charged battery cell and the discharge equalization release power of a single to-be-discharged battery cell;

[0042] Determine the number of rechargeable battery cells and the number of remaining to-be-discharged battery cells according to the number of to-be-discharged battery cells in the battery cell group and the charge-discharge power multiple;

[0043] If the number of the to-be-charged battery cells is less than or equal to the number of rechargeable battery cells, calculate the compensation power according to the number of the to-be-charged battery cells and the to-be-supplemented power of a single to-be-charged battery cell;

[0044] If the number of the cells to be charged is greater than the number of rechargeable cells, calculate a first power gap according to the number of rechargeable cells and the power to be supplemented of a single cell to be charged; calculate a second power gap according to the number of the remaining cells to be charged except for the number of rechargeable cells and the power consumption for charge equalization of a single cell to be charged; calculate the remaining releasable power according to the number of the remaining cells to be discharged and the power release for discharge equalization of a single cell to be discharged; and calculate the compensation power according to the first power gap, the second power gap and the remaining releasable power.

[0045] Optionally, determining a charge-discharge power multiple and the power to be supplemented of a single cell to be charged according to the power consumption for charge equalization of a single cell to be charged and the power release for discharge equalization of a single cell to be discharged includes:

[0046] Dividing the power consumption for charge equalization of a single cell to be charged by the power release for discharge equalization of a single cell to be discharged, taking the obtained quotient as the charge-discharge power multiple, and taking the obtained remainder as the power to be supplemented of a single cell to be charged;

[0047] Determining the number of rechargeable cells and the number of the remaining cells to be discharged according to the number of the cells to be discharged in the cell group and the charge-discharge power multiple includes:

[0048] Dividing the number of the cells to be discharged in the cell group by the charge-discharge power multiple, taking the obtained quotient as the number of rechargeable cells, and taking the obtained remainder as the number of the remaining cells to be discharged.

[0049] Optionally, the daughter board includes: an equalization control module and a power supply, the equalization control module includes a plurality of equalization control units, each equalization control unit is connected to a part of the cells in the cell group, and one cell is only correspondingly connected to one equalization control unit; each of the equalization control units is connected to the power supply; at the same moment, one equalization control unit only controls one connected cell to perform equalization;

[0050] After subtracting one from the equalization count, it further includes:

[0051] When the supply voltage of the power supply is greater than the safe supply voltage threshold, gradually reduce the number of the equalization control units that are performing discharge equalization on the connected cells until the supply voltage of the power supply is less than the safe supply voltage threshold.

[0052] Optionally, in the equalization startup stage, it further includes:

[0053] If an equalization failure occurs, the main control board sends the stop equalization instruction to each of the slave boards; wherein, each slave board includes: an equalization control module and a power supply; the equalization control module is connected to the power supply and is respectively connected to each of the battery cells in the battery cell group corresponding to the slave board; the equalization failure includes at least one of the following: a failure of the battery cell voltage detection component, a failure of the current detection component in the battery management system, a failure of the temperature detection component in the battery management system, an equalization overcurrent failure, an equalization overtemperature failure, a failure of the equalization control module, an overlimit of the single battery cell voltage, an overlimit of the battery cell temperature, a communication failure between the main control board and the slave board, and a power supply failure;

[0054] and / or,

[0055] For any slave board: If the slave board detects an equalization anomaly, the slave board turns off the equalization of the connected battery cell group in the current equalization cycle and does not respond to the start equalization instruction sent by the main control board; wherein, the equalization anomaly includes: an equalization overcurrent or equalization overtemperature occurs in the battery cell group connected to the slave board, or a failure of the equalization control module in the slave board.

[0056] Optionally, in the active equalization mode, for any equalization cycle:

[0057] If the temperature of the battery cell with the highest temperature in the battery pack reaches the first preset temperature threshold, the equalization start time threshold in the equalization cycle is the first start time threshold, and the equalization stop time threshold is the first stop time threshold;

[0058] If the temperature of the battery cell with the highest temperature in the battery pack is lower than the second preset temperature threshold, the equalization start time threshold in the equalization cycle is the second start time threshold, and the equalization stop time threshold is the second stop time threshold;

[0059] Wherein, the first preset temperature threshold is greater than the second preset temperature threshold, the first start time threshold is less than the second start time threshold, and the first stop time threshold is greater than the second stop time threshold.

[0060] Optionally, the battery management system further includes a host computer connected to each of the slave boards;

[0061] The battery pack equalization method further includes:

[0062] Forced equalization mode: The host computer directly controls whether each of the slave boards equalizes the connected battery cell group.

[0063] In the battery pack equalization method provided by the embodiments of the present invention, by setting an equalization stop stage in each equalization cycle of the active equalization mode to interrupt the equalization of the battery pack, it is equivalent to providing a static stage for the battery pack, providing the characteristic recovery time for each battery cell in each battery cell group, which is beneficial to avoiding the phenomenon of virtual high or virtual low single - cell voltage caused by long - term continuous charge and discharge of the battery cells, avoiding over - equalization and under - equalization caused by the detection error of the single - cell voltage of the battery cells, and improving the accuracy of the single - cell voltage of each battery cell. Moreover, by setting to execute an equalization control process every first preset time interval, the timing of the equalization time and the equalization stop time is converted into the counting of equalization count and equalization interval count, which is convenient for the implementation and execution of the active equalization - related programs in the main control board. Therefore, the embodiments of the present invention can improve the consistency of the single - cell voltage of each battery cell during the equalization process and enhance the equalization effect.

[0064] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0066] Figure 1 is a schematic structural diagram of a battery management system provided by the embodiments of the present invention;

[0067] Figure 2 is a schematic diagram of the processing flow within an equalization cycle provided by the embodiments of the present invention;

[0068] Figure 3 is a schematic diagram of the calculation flow of a compensation power provided by the embodiments of the present invention;

[0069] Figure 4 is a schematic diagram of the process of an active equalization mode provided by the embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0070] In order to enable those skilled in the art to better understand the solutions of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0071] It should be noted that the terms "first", "second", etc. in the description, claims and above-mentioned drawings of the present invention are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion.

[0072] An embodiment of the present invention provides a battery pack balancing method, which is applied to a battery management system in an energy storage system and can effectively improve the balancing effect. To facilitate the explanation of this balancing method, the relevant structures in the energy storage system will be briefly described below in conjunction with Figure 1 , and briefly explain the relevant structures in the energy storage system.

[0073] Figure 1 is a schematic structural diagram of a battery management system provided by an embodiment of the present invention. Refer to Figure 1 , the energy storage system may include a battery pack and a battery management system. The battery pack includes at least one battery cell group 30, and each battery cell group includes a plurality of battery cells; the battery management system includes a main control board SBMU and at least one slave board VCMU, and each slave board VCMU is arranged in one-to-one correspondence with each battery cell group 30. Among them, the slave board VCMU is connected between the main control board SBMU and the battery cell group 30, and is used to balance the battery cells in the battery cell group 30 according to the control of the main control board SBMU. Exemplarily, the slave board VCMU may include: a balancing control module 210 and a power supply 220; the balancing control module 210 is connected to the power supply 220 and is respectively connected to each battery cell in the battery cell group 30 corresponding to the slave board VCMU. The balancing control module 210 can perform charge balancing and discharge balancing on any connected battery cell according to the control of the main control board SBMU; among them, the electric energy for the balancing control module 210 to perform charge balancing on the battery cell can come from the electric energy provided by any battery cell during the discharge balancing process and / or from the power supply 220. An exemplary description will be given below of a specific structure that the balancing control module 210 may have, but it is not a limitation to the present invention.

[0074] Exemplarily, at least one battery cell string may be included in a battery cell group 30. Each battery cell string is composed of a plurality of battery cells connected in series. The battery cell strings can be connected in series and / or in parallel as needed to form the battery cell group 30. The battery cell groups can be connected in series and / or in parallel as needed to form a battery pack. The equalization control module 210 may include equalization control units corresponding one by one to the battery cell strings in the battery cell group. The equalization control unit may include a switch assembly and an energy storage assembly; the switch assembly is connected to each battery cell in the battery cell string, and the energy storage assembly can be connected between the power supply 220 and the switch assembly. When it is necessary to perform discharge equalization on a certain battery cell, the state of the switch assembly can be controlled to connect the battery cell to the energy storage assembly and discharge to the energy storage assembly. When it is necessary to perform charge equalization on a certain battery cell, the state of the switch assembly can be controlled to connect the battery cell to the energy storage assembly and charge the battery cell from the energy storage assembly. When it is necessary to stop the equalization of the battery cell string, the state of the switch assembly can be controlled to disconnect all the battery cells in the battery cell string from the energy storage assembly, and / or, the energy storage assembly can be controlled to stop working.

[0075] A battery cell string includes, for example, n battery cells, where n is a positive integer. The switch assembly includes, for example, n + 1 equalization switches and two trunk switches; the n + 1 equalization switches are respectively connected to the positive electrode, the negative electrode of the battery cell string, and the connection nodes between every two adjacent battery cells. Each equalization switch is connected to the two trunk switches, and the two trunk switches are respectively connected to the positive electrode and the negative electrode of the energy storage assembly. When the equalization switch at both ends of the battery cell is turned on, the battery cell can be connected to the energy storage assembly through the equalization switch and the trunk switch. At the connection node between two adjacent battery cells, the two battery cells share one equalization switch, and then this equalization switch connects the positive electrode of one battery cell and the negative electrode of the other battery cell. By setting the trunk switches, the connection relationship between the equalization switches and the energy storage assembly can be adjusted, so that when any battery cell is connected to the energy storage assembly, it can be connected to the positive electrode of the energy storage assembly through the equalization switch connected to the positive electrode of the battery cell and the trunk switch, and connected to the negative electrode of the energy storage assembly through the equalization switch connected to the negative electrode of the battery cell and the trunk switch, so as to realize the adjustment of the connection polarity.

[0076] For example, both of the main circuit switches exhibit the switch characteristics of single-pole double-throw. Sort the equalization switches according to the positive electrode to the negative electrode (or the negative electrode to the positive electrode) of the battery cell string. The odd-level equalization switches are connected to the first selection terminals of the two main circuit switches, and the even-level equalization switches are connected to the second selection terminals of the two main circuit switches; the fixed connection terminals of the two main circuit switches are correspondingly connected to the positive electrode and the negative electrode of the energy storage assembly. When the first selection terminal and the fixed connection terminal of any one of the main circuit switches are connected, the second selection terminal and the fixed connection terminal of the other main circuit switch are connected. Specifically, during the active equalization process, at the same moment, two equalization switches connected to both ends of a battery cell can be controlled to conduct, the first selection terminal of a main circuit switch is connected to its fixed connection terminal, and the second selection terminal of the other main circuit switch is connected to its fixed connection terminal. In this way, at the same moment, only one battery cell in a battery cell string can perform equalization, and the positive electrode of this battery cell is connected to the positive electrode of the energy storage assembly, and the negative electrode of this battery cell is connected to the negative electrode of the energy storage assembly.

[0077] The battery pack equalization method will be specifically described below.

[0078] The battery pack equalization method includes: an active equalization mode; the active equalization mode includes a plurality of equalization cycles. Figure 2 It is a schematic diagram of the processing flow within an equalization cycle provided by an embodiment of the present invention. Refer to Figure 2 , the equalization cycle includes:

[0079] S110. Equalization start stage: The main control board obtains the equalization start time threshold and sends an equalization start instruction to each slave board, so that each slave board equalizes the connected battery cell group until the equalization time reaches the equalization start time threshold.

[0080] Among them, the equalization start time threshold can be directly set by the main control board; alternatively, the battery management system may further include a host computer connected to the main control board, the equalization start time threshold can be set by the host computer, and the main control board can obtain the equalization start time threshold from the host computer. The equalization start time thresholds in different equalization cycles can be the same or different, and can be specifically set according to actual requirements.

[0081] Exemplarily, in the equalization start stage, the main control board can start timing from the start moment of the equalization start stage until the equalization time reaches the equalization start time threshold and enters the next stage and clears the timing. Or, starting from the start moment of the equalization start stage, the main control board can start counting down based on the equalization start time threshold until the count reaches 0, indicating the end of the equalization start stage.

[0082] Exemplarily, the slave board may include at least one analog front-end chip (AFE). An equalization control unit may be integrated in each analog front-end chip. Additionally, a battery cell detection component may be configured in the analog front-end chip to detect the individual information of each connected battery cell, such as individual current, individual voltage, and individual temperature. The individual information of each battery cell collected by the slave board may be summarized to the master board. The master board may determine the battery cells that need to be equalized in the battery pack (hereinafter referred to as the battery cells to be equalized) based on the individual information of each battery cell, and generate an equalization start instruction for each slave board accordingly. The equalization start instruction may include control commands respectively for the power supply and the equalization control module in the slave board, so that the relevant modules in the slave board respond to the corresponding control commands to perform equalization control on the battery cell group connected to the slave board. The battery cells to be equalized in the battery cell group specifically include the battery cells to be charged and the battery cells to be discharged. According to the equalization start instruction, the slave board may perform charging equalization on the battery cells to be charged and discharge the battery cells to be discharged, so that the power of each battery cell in the battery cell group tends to be consistent, improving the consistency of each battery cell to achieve equalization.

[0083] S120. Equalization stop stage: The master board obtains an equalization stop time threshold and sends a stop equalization instruction to each slave board, causing each slave board to stop equalizing the connected battery cell group until the equalization stop time reaches the equalization stop time threshold.

[0084] Among them, the equalization stop time threshold can be directly set by the master board; or, the battery management system may further include a host computer connected to the master board, and the equalization stop time threshold can be set by the host computer, and the master board can obtain the equalization stop time threshold from the host computer. The equalization stop time threshold can be any non-zero value, and the equalization stop time thresholds in different equalization cycles can be the same or different, and can be specifically set according to actual needs. And, the total duration of each equalization cycle can be the same or different, and can be specifically set according to actual needs, which is not limited here.

[0085] Exemplarily, when the equalization current is small or the equalization temperature is low, the safety of the equalization process is relatively high, and the time proportion of the equalization start stage in the entire equalization cycle can be set relatively large, such as increasing the equalization start time threshold and / or decreasing the equalization stop time threshold; conversely, when the equalization current is large or the equalization temperature is high, the time proportion of the equalization start stage in the entire equalization cycle can be set relatively small, such as decreasing the equalization start time threshold and / or increasing the equalization stop time threshold. Among them, the equalization current is, for example, the current of a single battery cell during the charging equalization or discharging equalization process, and the equalization temperature is, for example, the temperature of a single battery cell during the charging equalization or discharging equalization process.

[0086] Exemplarily, in the equalization stop phase, the main control board can also start positive or countdown timing from the start moment of the equalization stop phase. The specific timing method can refer to the description of the equalization start phase and will not be elaborated here. The stop equalization instructions corresponding to any slave board can include control commands respectively for the power supply and the equalization control module in the slave board, so that the relevant modules in the slave board respond to the corresponding control commands to stop working. For example, the power supply shuts down, and the equalization control module cuts off the connection between each battery cell and the energy storage component that it is connected to.

[0087] In the equalization stop phase, the equalization of the battery pack stops, which is equivalent to providing a static phase for the battery pack, facilitating the characteristic recovery of each battery cell and avoiding the occurrence of voltage drift of the battery cell monomers, such as the cases of being falsely high or falsely low, so that the subsequent battery cell voltage detection and the subsequent equalization process can be carried out more accurately.

[0088] Among them, in each equalization cycle, the main control board executes one round of equalization control process every other first preset time. In each round of equalization control process, the main control board mainly determines whether to issue an equalization start instruction or an equalization stop instruction to each slave board after a series of judgments; after the judgment is over, it exits this round of equalization control process and waits for the first preset time before entering the next round of equalization control process. Among them, the equalization start phase includes at least one round of equalization control process, and the equalization stop phase includes at least one round of equalization control process.

[0089] During the equalization control process, the main control board uses equalization counting to count the elapsed time of the equalization start phase and uses equalization time counting to count the elapsed time of the equalization stop phase. That is to say, in each round of equalization control process in the equalization start phase, the main control board adjusts the equalization counting to record the equalization time; in each round of equalization control process in the equalization stop phase, the main control board adjusts the equalization interval counting to record the equalization stop time. Exemplarily, both the equalization counting and the equalization time counting are integers, and the corresponding counting in each round of equalization control process can be incremented or decremented by one to achieve positive timing or countdown timing. Since there is a first preset time interval between every two rounds of equalization control processes, the actual elapsed time can be obtained by multiplying the change amount of the counting by the first preset time. Here, it is equivalent to converting the timing into counting. Exemplarily, two registers can be set in the main control board respectively for the above two types of counting.

[0090] In the battery pack equalization method provided by the embodiments of the present invention, by setting an equalization stop stage in each equalization cycle of the active equalization mode to interrupt the equalization of the battery pack, it is equivalent to providing a static stage for the battery pack, providing the characteristic recovery time for each battery cell in each battery cell group, which is beneficial to avoiding the phenomenon of virtual high or virtual low of the single cell voltage caused by long-term continuous charge and discharge of the battery cells, avoiding over-equalization and under-equalization caused by the detection error of the single cell voltage of the battery cells, and improving the accuracy of the single cell voltage of each battery cell. Moreover, by setting to execute an equalization control process every first preset time interval, the timing of the equalization time and the equalization stop time is converted into the counting of equalization count and equalization interval count, which is convenient for the implementation and execution of the active equalization related programs in the main control board. Therefore, the embodiments of the present invention can improve the consistency of the single cell voltage of each battery cell during the equalization process and improve the equalization effect.

[0091] On the basis of the above embodiments, optionally, a countdown method can be adopted for both the equalization start stage and the equalization stop stage. The initial value of the equalization count can be determined according to the start time threshold, and the initial value of the equalization interval count can be determined according to the equalization stop time threshold. In the equalization start stage, in each execution of an equalization control process, the main control board subtracts one from the equalization count until it is reduced to 0. In the equalization stop stage, in each execution of an equalization control process, the main control board subtracts one from the equalization interval count until it is reduced to 0. When the equalization interval count is 0 and the equalization count is not 0, the main control board issues an equalization start instruction to each slave board; when the equalization interval count is not 0, the main control board issues an equalization stop instruction to each slave board. Then, the equalization start stage covers each equalization control process in which the equalization interval count is 0 and the equalization count is not 0; the equalization stop stage covers each equalization control process in which the equalization interval count is not 0.

[0092] Specifically, a series of processing procedures of the main control board in the equalization control process may include:

[0093] Judge whether the equalization interval count is 0.

[0094] Among them, when the equalization interval count is not 0, it indicates that the current is in the equalization stop stage, and vice versa, when the equalization interval count is 0, it indicates that the current is not in the equalization stop stage.

[0095] In the case where the equalization interval count is 0, the following steps are executed:

[0096] If the equalization count is 0, set the initial value of the equalization count and issue an equalization start instruction to each slave board; among them, the product of the initial value of the equalization count and the first preset time is equal to the equalization start time threshold.

[0097] When both the equalization interval count and the equalization count are 0, it can be considered that after the end of the previous equalization cycle, the first round of equalization control process in this equalization cycle can be used as the equalization preparation stage. During this equalization control process, the main control board can set the initial value of the equalization count based on the equalization start time threshold. Since the main control board sends the corresponding equalization start commands to each slave board during this equalization control process, it can be considered that the equalization start stage is entered when this equalization control process ends.

[0098] If the equalization count is not 0, subtract 1 from the equalization count and send the equalization start commands to each slave board; among them, if the equalization count equals 1 after subtraction, set the initial value of the equalization interval count; the product of the initial value of the equalization interval count and the first preset time is equal to the equalization stop time threshold.

[0099] Among them, when the equalization interval count is 0 and the equalization count is not 0, it indicates that the current is in the equalization start stage. When the equalization count equals 1 after subtraction, it indicates that after the first preset time after this equalization control process, the duration of the equalization start stage will reach the equalization start time threshold, and the next round of equalization control process needs to enter the equalization stop stage. Therefore, when the equalization count equals 1 after subtraction, the main control board can set the initial value of the equalization interval count based on the equalization stop time threshold.

[0100] When the equalization interval count is not 0, subtract 1 from the equalization interval count and send the equalization stop commands to each slave board.

[0101] In this embodiment, by setting the main control board to execute a round of equalization control process every first preset time, converting the timing of each stage of the equalization cycle into the reciprocal counting of the equalization interval count and the equalization count, the program is easy to implement. Among them, the first preset time can be set according to requirements, for example, it is 500 ms.

[0102] Based on the above embodiments, optionally, during any equalization control process, before judging whether the equalization interval count is 0, it further includes:

[0103] When the active equalization start condition is not met, and / or, there is an equalization fault, send the equalization stop commands to each slave board and clear the equalization interval count and the equalization count.

[0104] When the active equalization start condition is met and there is no equalization fault, execute the step of judging whether the equalization interval count is 0.

[0105] Among them, the judgment of the balance fault can be used as an external factor and a hard condition for whether the balance can be carried out. The active balance start condition can be used as an internal factor for judging whether the balance is necessary. When there is no balance fault and the active balance start condition is met, the active balance is turned on, which can ensure the safety and reliability of the balance and avoid unnecessary resource waste. Moreover, in the embodiment of the present invention, an equalization period is set to include multiple rounds of equalization control processes, which is equivalent to judging whether the active equalization start condition is met and whether the equalization fault exists multiple times, which is beneficial to improving the safety of the equalization.

[0106] Among them, the active balance start conditions include the following:

[0107] 1) There is at least one cell to be balanced in the battery pack.

[0108] That is to say, there is a balance demand in the battery pack. Among them, the cells to be balanced include cells to be charged and / or cells to be discharged. By comparing the highest single-cell voltage and the lowest single-cell voltage of the cells connected by a single AFE with the average voltage of all the cells in the battery pack, it can be judged whether there is a balance demand in the cell string. If the highest single-cell voltage is higher than the average voltage, and the difference between the highest single-cell voltage and the average voltage is greater than the discharge balance start threshold, the balance control unit in the AFE needs to turn on the discharge balance. If the lowest single-cell voltage is lower than the average voltage, and the difference between the average voltage and the lowest single-cell voltage is greater than the charge balance start threshold, the charge balance needs to be turned on. Among them, the discharge balance start threshold and the charge balance start threshold can be the same or different. For example, if they are the same, both can be set to 20 mV.

[0109] On this basis, it can also be specified that when the single-cell voltage of the cell is within the charge balance allowable voltage range, charging balance is allowed for the cell; when the single-cell voltage of the cell is within the discharge balance allowable voltage range, discharge balance is allowed for the cell to ensure the safety of the balance. Among them, the lower limit of the charge balance allowable voltage range is less than or equal to the lower limit of the discharge balance allowable voltage range, and the upper limit of the charge balance allowable voltage range is less than or equal to the upper limit of the discharge balance allowable voltage range. For example, the charge balance allowable voltage range is [2.5V, 3.4V], and the discharge balance allowable voltage range is [3.0V, 3.7V].

[0110] To sum up, the characteristics of each cell to be balanced are as follows: the single-cell voltage of each cell to be charged is lower than the average voltage of all the cells in the battery pack, and the difference exceeds the charge balance start threshold; the single-cell voltage of each cell to be discharged is higher than the average voltage of all the cells, and the difference exceeds the discharge balance start threshold. The single-cell voltage of the cell to be charged is within the charge balance allowable voltage range; the single-cell voltage of the cell to be discharged is within the discharge balance allowable voltage range.

[0111] Exemplarily, in the active balancing mode, real-time balancing is performed, and the slave board can monitor the individual information of each battery cell in real time.

[0112] 2) For each battery cell group, the sum of the total discharge balancing power of each battery cell to be discharged and the available power of the power supply in the battery cell group is greater than or equal to the total charge balancing power of each battery cell to be charged in the battery cell group.

[0113] Exemplarily, this condition can be expressed by the following formula:

[0114] 0 < M * Pch - N * Pdc < P0, where M is the number of battery cells to be charged in the battery cell group, Pch is the power consumption of a single battery cell for charge balancing, N is the number of battery cells to be discharged in the battery cell group, Pdc is the power released by a single battery cell for discharge balancing, and P0 is the available power of the power supply. The power supply can be, for example, an AC-DC power supply, and P0 is, for example, 80W. On this basis, it is also necessary to satisfy M + N < the total number of battery cells in the battery cell group to ensure that the values of M and N are accurately available. Exemplarily, for each battery cell string in the battery cell group, an equalization control unit can only turn on the charge balancing or discharge balancing of 1 battery cell at the same time.

[0115] Based on the above embodiments, optionally, when the balancing is turned on, the individual voltage of the battery cell can be normally collected, and voltage compensation can be performed on the battery cell to be balanced and its adjacent battery cells during the balancing process. For the battery cell to be balanced, its individual voltage value V1 can be stored before the balancing is turned on, and the voltage difference (positive or negative) of this battery cell before and after the balancing is turned on can be calculated after the balancing is turned on; in the subsequent balancing-on stage, if the type of the battery cell to be balanced changes, this voltage difference can be directly used to compensate the individual voltage value of this battery cell.

[0116] Based on the above embodiments, optionally, the battery management system includes a host computer. Through the host computer, the balancing state of the active balancing mode can be set, such as turning on and turning off the balancing. The host computer can control the turning on and turning off of the active balancing mode by sending corresponding commands to the main controller.

[0117] Among them, in different system states, such as when the energy storage system is in the charging, discharging, and idle states, the host computer can control whether to allow the active balancing mode to be turned on. Exemplarily, it can be default set to turn on the active balancing mode in all stages.

[0118] Based on the above embodiments, optionally, the balancing faults include at least one of the following fault types: faults of the cell voltage detection component, faults of the current detection component in the battery management system, faults of the temperature detection component in the battery management system, balancing overcurrent faults (e.g., the balancing current exceeds 5 A), balancing overtemperature faults (e.g., the balancing temperature exceeds 60 °C), faults of the balancing control module (e.g., any switch in the switch component fails), overlimit of the cell single voltage, overlimit of the cell temperature (e.g., the cell single temperature exceeds 55 °C), communication faults between the main control board and the slave board (e.g., V-CAN communication faults), and power supply faults (e.g., EE faults). Among them, the above-mentioned detection components are, for example, arranged in the slave board and / or the main control board, and are used to detect the single voltage, current, and temperature of the cells. The above-mentioned balancing faults are all faults related to prohibiting balancing in the battery management system, and any one of them requires stopping the balancing.

[0119] In the above embodiments, it is mentioned that when the main control board controls to start balancing and enters the balancing start stage, it is necessary to time the balancing time, and stop the balancing when the balancing start time threshold is reached. Exemplarily, the balancing starts and lasts for 55S, and the balancing stops and lasts for 5S. However, the above-mentioned balancing stop condition is not the only balancing stop condition in the embodiments of the present invention. In other embodiments, other balancing stop conditions can also be set, which are exemplarily described below.

[0120] In one embodiment, optionally, for the main control board, in the balancing start stage, it further includes: if a balancing fault occurs, the main control board sends a stop balancing instruction to each slave board. Among them, the types of balancing faults can be seen in the above description. When any type of balancing fault occurs, the main control board needs to send a stop balancing instruction to each slave board.

[0121] In another embodiment, optionally, for any slave board: if the slave board detects a balancing abnormality, the slave board closes the balancing of the connected cell group in the current balancing cycle and does not respond to the start balancing instruction sent by the main control board. Among them, the balancing abnormality includes: overcurrent or overtemperature occurs in the cell group connected to the slave board, or the balancing control module in the slave board fails. Among them, when the type of balancing abnormality is the failure of the switch component in the balancing control module, the slave board can report the switch abnormality to the main control board, and at this time, the main control board can control the slave board to power off to clear the fault.

[0122] Based on the above embodiments, optionally, when the active balancing start condition is met, the main control board can set the allow balancing flag, for example, set it to 0; when the main control board detects any type of balancing fault or receives a balancing fault reported by the slave board, the main control board can set the balancing fault flag, for example, set it to 1. Then, at the beginning of each round of balancing control process, the main control board can determine whether active balancing can be performed by reading the allow balancing flag and the balancing fault flag. For example, when both the allow balancing flag and the balancing fault flag are 0, then enter the step of judging whether the balancing interval count is 0, otherwise directly exit this round of balancing control process.

[0123] Based on the above embodiments, optionally, during any balancing control process, before setting the initial value of the balancing count, it further includes:

[0124] For any slave board:

[0125] 1) Determine the battery cell to be charged, the battery cell to be discharged, and the battery cell with the highest balancing priority in the battery cell group connected to the slave board; among them, the battery cell with the highest balancing priority is the battery cell with the largest difference between the single cell voltage and the average voltage of each battery cell in the battery pack.

[0126] Among them, the slave board can detect the single cell voltages of the connected battery cells, and the judgment process of each type of battery cell in this step can be performed in the slave board or the main control board. The main control board can extract the number of battery cells to be discharged, the number of battery cells to be charged, and the required balancing type and the position in the battery cell group of the battery cell with the highest balancing priority from the information reported by the slave board, and then the battery cell with the highest balancing priority can be preferentially balanced in the subsequent start balancing instruction.

[0127] 2) Determine the compensation power that the power supply needs to provide according to the number of battery cells to be discharged in the battery cell group and the discharge balancing release power of a single battery cell to be discharged, as well as the number of battery cells to be charged and the charging balancing power consumption of a single battery cell to be charged.

[0128] 3) Generate the corresponding start balancing instruction for the slave board according to the battery cell with the highest balancing priority and the compensation power.

[0129] Among them, the start balancing instruction can include a balancing command and a power supply control command; the balancing command includes the balancing flag bit corresponding to the battery cell with the highest balancing priority. Each battery cell can have a balancing flag bit, which is used to indicate that the battery cell does not need balancing, needs charging balancing, or needs discharging balancing. Exemplarily, after the balancing stops, the main control board can clear the balancing flag bits of each battery cell and re-check the table for balancing judgment.

[0130] Correspondingly, the process of the slave board balancing the connected battery cell group includes:

[0131] For the power supply: The power supply responds to the power control command to turn on and provide compensation power.

[0132] For the balancing control module:

[0133] If the balancing flag indicates that the cell with the highest balancing priority is the cell to be charged, the balancing control module responds to the balancing command to perform charging balancing on the cell with the highest balancing priority; wherein, the charging electric energy of the cell to be charged is provided by the power supply, and / or provided by the cells to be discharged in the cell group during other balancing cycles when discharging and balancing.

[0134] If the balancing flag indicates that the cell with the highest balancing priority is the cell to be discharged, the balancing control module responds to the balancing command to perform discharging balancing on the cell with the highest balancing priority.

[0135] In this embodiment, a balancing flag is set for the cells. After receiving the enable balancing instruction sent by the main control board, the slave board performs corresponding type of balancing on the cells marked as needing balancing. When the slave board receives the stop balancing instruction sent by the main control board, or does not receive the enable balancing instruction sent by the main board within the second preset time, the balancing of all the connected cells is turned off. The second preset time is greater than the first preset time, and the second preset time is, for example, 5s.

[0136] Figure 3 It is a schematic diagram of the calculation process of the compensation power provided by an embodiment of the present invention. Refer to Figure 3 , in one implementation, optionally, the steps of determining the compensation power that the power supply needs to provide include:

[0137] S301. Determine the charge-discharge power multiple K1 and the power r1 to be supplemented for a single cell to be charged according to the charging balancing power consumption Pch of a single cell to be charged and the discharging balancing release power Pdc of a single cell to be discharged.

[0138] Among them, the quotient obtained by dividing the charging balancing power consumption of a single cell to be charged by the discharging balancing release power of a single cell to be discharged can be used as the charge-discharge power multiple, and the remainder obtained can be used as the power r1 to be supplemented for a single cell to be charged, that is, Pch / Pdc = K1 remainder r1. The above formula shows that the total power provided when K1 cells to be discharged perform discharging and balancing is all provided to one cell to be charged, and there is still a power gap of r1 to meet the charging balancing requirement of the cell to be charged.

[0139] S302. Determine the number K2 of rechargeable cells and the number r2 of remaining cells to be discharged according to the number N of cells to be discharged in the cell group and the charge-discharge power multiple K1.

[0140] Among them, the number of rechargeable cells can be obtained by dividing the number of cells to be discharged in the cell group by the charge-discharge power multiple, and the quotient obtained is used as the number of rechargeable cells, and the remainder obtained is used as the number of remaining cells to be discharged, that is, N / K1 = K2 remainder r2. The above formula indicates that among all the cells to be discharged in a cell group, the charging balance requirements of K2 cells to be charged can be supported, and there are still less than K1 cells left, specifically r2 cells to be discharged.

[0141] S303. Determine whether the number M of cells to be charged in the cell group ≤ K2? If yes, execute S304; if not, execute S305.

[0142] S304. Calculate the compensation power according to M and r1.

[0143] Among them, when the number of cells to be charged is less than or equal to the number of rechargeable cells, the actual number of cells to be charged by the daughter board is equal to M. The compensation power = M * r1, that is, the power supply only needs to supplement the remaining power gap of each cell to be charged other than being powered by the cells to be discharged.

[0144] S305. Calculate the first power gap according to K2 and r1, calculate the second power gap according to M, K2 and Pch, and calculate the remaining available power according to r2 and Pdc.

[0145] Among them, the first power gap Pc1 = K2 * r1, which represents the sum of the power to be supplemented of K2 cells to be charged; the second power gap Pc2 = (M - K2) * Pch, which represents the power required for the remaining cells to be charged that need to be fully powered by the power supply; the remaining available power Pc3 = r2 * Pdc, which represents the power that the remaining r2 cells to be discharged can provide.

[0146] S306. Calculate the compensation power according to the first power gap, the second power gap and the remaining available power.

[0147] Among them, the compensation power = Pc1 + Pc2 - Pc3.

[0148] This embodiment provides the compensation power that the power supply needs to provide under different conditions based on S301 - S306 to meet the balance requirements of the corresponding cell group of the daughter board.

[0149] On the basis of the above embodiments, optionally, when M > K2, it is also possible to determine again whether the sum of the total discharge balance power of each cell to be discharged in the cell group and the available power of the power supply is ≥ the total charge balance power of each cell to be charged in the cell group to ensure that the active balance can proceed normally. The specific judgment steps can be:

[0150] Calculate the remaining compensable power Pc4 of the power supply: Pc4 = P0 - K2 * r1;

[0151] Calculate the remaining releasable power Pc3: Pc3 = r2 * Pdc;

[0152] Calculate the actual number of rechargeable cells MM: MM = K2 + (Pc3 + Pc4) / Pch;

[0153] If MM ≥ M, it indicates that the sum of the discharge equalization total power of each to-be-discharged cell in the cell group and the available power of the power supply ≥ the charge equalization total power of each to-be-charged cell in the cell group.

[0154] Based on the above embodiments, optionally, the slave board includes: an equalization control module and a power supply. The equalization control module includes a plurality of equalization control units. Each equalization control unit is connected to a part of the cells in the cell group, and one cell is only correspondingly connected to one equalization control unit; each equalization control unit is connected to the power supply; at the same moment, one equalization control unit only controls one connected cell for equalization. During any equalization control process, after subtracting one from the equalization count, it further includes:

[0155] When the supply voltage (or output voltage) of the power supply is greater than the safe supply voltage threshold, gradually reduce the number of equalization control units that are discharging and equalizing the connected cells until the supply voltage of the power supply is less than the safe supply voltage threshold.

[0156] Among them, if the supply voltage of the power supply is greater than the safe supply voltage threshold, the equalization current is relatively large, which will increase the heat of the equalization circuit. To ensure the stability of the equalization system, controlling the supply voltage within the safe supply voltage threshold can be used as a precondition for the active equalization mode. Exemplarily, the safe supply voltage threshold can be 28V.

[0157] Specifically, in this step, the equalization control unit can reduce one equalization control unit that is discharging and equalizing the connected cells by disconnecting the energy storage component from the cell that is undergoing discharge equalization. Each time one equalization control unit that is discharging and equalizing the connected cells is reduced, it can be judged whether the current supply voltage of the power supply has dropped below the safe supply voltage threshold.

[0158] Based on the above embodiments, optionally, in the active equalization mode, for any equalization cycle:

[0159] If the temperature of the cell with the highest temperature in the battery pack reaches the first preset temperature threshold, the equalization start time threshold in the equalization cycle is the first start time threshold, and the equalization stop time threshold is the first stop time threshold.

[0160] If the temperature of the cell with the highest temperature in the battery pack is lower than the second preset temperature threshold, the equalization start time threshold in the equalization cycle is the second start time threshold, and the equalization stop time threshold is the second stop time threshold.

[0161] Among them, the first preset temperature threshold is greater than the second preset temperature threshold, the first turn-on time threshold is less than the second turn-on time threshold, and the first stop time threshold is greater than the second stop time threshold.

[0162] Exemplarily, the above-mentioned equalization turn-on time threshold and equalization stop time threshold can be adjusted by the main control board or the host computer. The temperature of the cell with the highest temperature in the battery pack can be called the highest equalization temperature. When the highest equalization temperature ≥ the first preset temperature threshold, the safety of the equalization process is poor, and equalization current reduction control is required. The main control board reduces the equivalent equalization current to reduce the equalization temperature. The first preset temperature threshold is, for example, 55°C. When the highest equalization temperature < the second preset temperature threshold, the equalization process is relatively safe, and the default conventional equalization method can be restored. Taking the equalization period of 1 minute as an example, in the conventional equalization method, the second turn-on time threshold can be set to 55 s, and the second stop time threshold can be set to 5 s; in the equalization current reduction control, the first turn-on time threshold can be set to 30 s, and the first stop time threshold can be set to 30 s, and the effective equalization current can be reduced by nearly half.

[0163] Based on the above embodiments, optionally, the battery management system further includes a host computer; on the basis that the number of slave boards does not exceed the recognition ability of the slave board connection port of the host computer, the host computer can directly connect to each slave board through the slave board connection port. Correspondingly, the battery pack equalization method further includes: forced equalization mode: the host computer directly controls whether each slave board equalizes the connected cell group. For example, if the battery management system only includes one single slave board, it can be directly connected to the host computer, and whether it equalizes can be forcibly controlled by the host computer. By adding the forced equalization mode in this embodiment, the flexibility of the battery pack equalization method can be improved. Exemplarily, when the host computer forcibly turns on equalization, a single command can only be turned on for 10 minutes.

[0164] Figure 4 It is a schematic flow chart of an active equalization mode provided by an embodiment of the present invention. Refer to Figure 4 , in one embodiment, the active equalization mode specifically includes the following steps:

[0165] S401. Wake up the main control board.

[0166] This step is equivalent to powering on the main control board, and after powering on, the main control board can control each slave board to power on.

[0167] S402. Confirm the main control board system information.

[0168] In this step, the main control board system information may include information such as the software and hardware versions in the main control board. This step is equivalent to the initialization process of the main control board.

[0169] S403. Call the active equalization task once every first preset time.

[0170] Among them, calling an active balancing task once means executing a round of balancing control process, which is equivalent to entering the function entry related to the active balancing task every first preset time. Figure 4 The part enclosed by the dashed line in the figure represents a round of balancing control process.

[0171] S404. Determine whether both the balancing fault flag and the allowable balancing flag are 0; if so, execute S405; if not, execute S419.

[0172] S405. Determine whether the balancing interval count is 0; if so, execute S406; if not, execute S417.

[0173] S406. Determine whether the balancing count is 0; if so, execute S407; if not, execute S412.

[0174] S407. Obtain the system state and the cell information of each cell.

[0175] Among them, the system state includes the state of the energy storage system being in charging, discharging or standby; the cell information includes the voltage and temperature of the cell, etc.

[0176] S408. Determine the cell with the highest balancing priority, the number M of cells to be charged, and the number N of cells to be discharged.

[0177] S409. Determine whether M < 0? If so, exit this round of balancing control process; if not, execute S410.

[0178] This step is equivalent to providing a step of exception judgment. Normally, M should be ≥ 0. If M < 0 appears, it indicates that the program may have an exception and can be directly exited.

[0179] S410. Determine the compensation power that the power supply needs to provide according to M and N.

[0180] The specific process of this step can be referred to Figure 3 . It can be understood that S408 - S410 are the related processes for a single slave board. The main control board needs to execute S408 - S410 for each slave board. After determining the compensation power of the power supply in each slave board, the main control board can generate an enable balancing instruction for each slave board.

[0181] S411. Set the initial value of the balancing count and send an enable balancing instruction to each slave board.

[0182] S412. Decrease the balancing count by one.

[0183] S413. When the power supply voltage of the power supply is greater than the safe power supply voltage threshold, gradually reduce the number of equalization control units that are discharging and equalizing the connected battery cells until the power supply voltage of the power supply is less than the safe power supply voltage threshold.

[0184] S414. Send an enable equalization instruction to each slave board.

[0185] S415. Determine whether the equalization count is 1; if so, execute S416; if not, exit this round of equalization control process.

[0186] S416. Set the initial value of the equalization interval count.

[0187] S417. Decrement the equalization interval count by one.

[0188] S418. Send a stop equalization instruction to each slave board.

[0189] In this step, the equalization count can also be cleared simultaneously.

[0190] S419. Send a stop equalization instruction to each slave board, and clear the equalization interval count and the equalization count.

[0191] This embodiment provides a complete equalization strategy in the active equalization mode based on S401 - S419. Compared with passive equalization, active equalization is a non-dissipative equalization. Through the energy transfer between the battery cells to be charged and the battery cells to be discharged, energy loss can be effectively reduced, and the available capacity and available energy of the battery pack can be improved. This active equalization mode can effectively improve the consistency of each battery cell, which is beneficial to extending the service life of the battery pack.

[0192] It should be understood that various forms of the processes shown above can be used, reordering, adding or deleting steps. For example, the steps described in the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. This is not limited herein.

[0193] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A battery pack balancing method, characterized in that, Applied to a battery management system; the battery pack includes at least one battery cell group, and each of the battery cell groups includes a plurality of battery cells; the battery management system includes a main control board and slave boards corresponding to each of the battery cell groups one by one; The battery pack equalization method includes: an active equalization mode, which includes a plurality of equalization cycles; The equalization cycle includes: Equalization start stage: The main control board obtains an equalization start time threshold and sends an equalization start command to each of the slave boards, so that each of the slave boards equalizes the connected battery cell group until the equalization time reaches the equalization start time threshold; Equalization stop stage: The main control board obtains an equalization stop time threshold and sends an equalization stop command to each of the slave boards, so that each of the slave boards stops equalizing the connected battery cell group until the equalization stop time reaches the equalization stop time threshold; Wherein, in the equalization cycle, the main control board executes an equalization control process every first preset time; the equalization start stage includes at least one round of the equalization control process, and the equalization stop stage includes at least one round of the equalization control process; In each round of the equalization control process in the equalization start stage, the main control board adjusts the equalization count to record the equalization time; in each round of the equalization control process in the equalization stop stage, the main control board adjusts the equalization interval count to record the equalization stop time; In the equalization start stage, every time one round of the equalization control process is executed, the main control board subtracts one from the equalization count; In the equalization stop stage, every time one round of the equalization control process is executed, the main control board subtracts one from the equalization interval count; Wherein, the equalization start stage covers each round of the equalization control process in which the equalization interval count is 0 and the equalization count is not 0; the equalization stop stage covers each round of the equalization control process in which the equalization interval count is not 0; The equalization control process includes: Judging whether the equalization interval count is 0; In the case where the equalization interval count is 0, the following steps are executed: If the equalization count is 0, set the initial value of the equalization count and send the equalization start command to each of the slave boards; wherein, the product of the initial value of the equalization count and the first preset time is equal to the equalization start time threshold; If the equalization count is not 0, subtract one from the equalization count and send the equalization start command to each of the slave boards; wherein, if the equalization count minus one is equal to 1, set the initial value of the equalization interval count; the product of the initial value of the equalization interval count and the first preset time is equal to the equalization stop time threshold; In the case where the equalization interval count is not 0, subtract one from the equalization interval count and send the equalization stop command to each of the slave boards; The slave board includes: an equalization control module and a power supply; the equalization control module is connected to the power supply and is respectively connected to each of the battery cells in the battery cell group corresponding to the slave board; Before setting the initial value of the equalization count, it further includes: For any one of the slave boards: Determine the battery cell to be charged, the battery cell to be discharged, and the battery cell with the highest equalization priority in the battery cell group connected to the slave board; wherein, the battery cell with the highest equalization priority is the battery cell in the battery cell group with the largest difference between the single cell voltage and the average voltage of each battery cell in the battery pack; Determine the compensation power that the power supply needs to provide according to the number of battery cells to be discharged in the battery cell group, the discharge equalization release power of a single battery cell to be discharged, the number of battery cells to be charged, and the charging equalization power consumption of a single battery cell to be charged; Generate the enabling equalization instruction corresponding to the slave board according to the battery cell with the highest equalization priority and the compensation power; The determination of the compensation power that the power supply needs to provide includes: Determine the charge-discharge power multiple and the power to be supplemented for a single battery cell to be charged according to the charging equalization power consumption of a single battery cell to be charged and the discharge equalization release power of a single battery cell to be discharged; Determine the number of rechargeable battery cells and the number of remaining battery cells to be discharged according to the number of battery cells to be discharged in the battery cell group and the charge-discharge power multiple; If the number of battery cells to be charged is less than or equal to the number of rechargeable battery cells, calculate the compensation power according to the number of battery cells to be charged and the power to be supplemented for a single battery cell to be charged; If the number of battery cells to be charged is greater than the number of rechargeable battery cells, calculate the first power gap according to the number of rechargeable battery cells and the power to be supplemented for a single battery cell to be charged; calculate the second power gap according to the number of remaining battery cells to be charged except for the number of rechargeable battery cells and the charging equalization power consumption of a single battery cell to be charged; calculate the remaining available power according to the number of remaining battery cells to be discharged and the discharge equalization release power of a single battery cell to be discharged; and calculate the compensation power according to the first power gap, the second power gap, and the remaining available power.

2. The battery pack balancing method according to claim 1, wherein Before determining whether the equalization interval count is 0, it further includes: Under the condition that the active equalization start condition is not met, and / or there is an equalization fault, send a stop equalization instruction to each slave board, and clear the equalization interval count and the equalization count; Under the condition that the active equalization start condition is met and there is no equalization fault, execute the step of determining whether the equalization interval count is 0.

3. The battery pack balancing method according to claim 2, wherein The slave board includes: an equalization control module and a power supply; the equalization control module is connected to the power supply and is respectively connected to each battery cell in the battery cell group corresponding to the slave board; The active equalization start conditions include: There is at least one battery cell to be equalized in the battery pack; wherein, the battery cells to be equalized include battery cells to be charged and / or battery cells to be discharged; the single cell voltage of the battery cell to be charged is lower than the average voltage of all battery cells, and the difference exceeds the charging equalization start threshold, and the single cell voltage of the battery cell to be charged is within the charging equalization allowable voltage range; the single cell voltage of the battery cell to be discharged is higher than the average voltage of all battery cells, and the difference exceeds the discharge equalization start threshold, and the single cell voltage of the battery cell to be discharged is within the discharge equalization allowable voltage range; Moreover, for each of the battery cell groups, the sum of the total discharge equalization power of the battery cells to be discharged in the battery cell group and the available power of the power supply is greater than or equal to the total charge equalization power of the battery cells to be charged in the battery cell group; The equalization faults include at least one of the following: faults of the battery cell voltage detection component, faults of the current detection component in the battery management system, faults of the temperature detection component in the battery management system, overcurrent equalization faults, overtemperature equalization faults, faults of the equalization control module, overlimit of the voltage of a single battery cell, overlimit of the temperature of a battery cell, communication faults between the main control board and the slave board, and power supply faults.

4. The battery pack balancing method according to claim 1, wherein The enabling equalization instruction includes an equalization command and a power supply control command; The equalization command includes the equalization flag bit corresponding to the battery cell with the highest equalization priority; The process of the slave board equalizing the connected battery cell group includes: The power supply responds to the power supply control command to turn on and provide the compensation power; If the equalization flag bit indicates that the battery cell with the highest equalization priority is a battery cell to be charged, the equalization control module responds to the equalization command to perform charge equalization on the battery cell with the highest equalization priority; wherein, the charging electric energy of the battery cell to be charged is provided by the power supply, and / or provided by the battery cells to be discharged in the battery cell group during other equalization cycles when discharging equalization is performed; If the equalization flag bit indicates that the battery cell with the highest equalization priority is a battery cell to be discharged, the equalization control module responds to the equalization command to perform discharge equalization on the battery cell with the highest equalization priority.

5. The battery pack balancing method according to claim 1, wherein Determining the charge-discharge power multiple and the power to be supplemented for a single battery cell to be charged according to the charge equalization power consumption of the single battery cell to be charged and the discharge equalization release power of the single battery cell to be discharged includes: Dividing the charge equalization power consumption of a single battery cell to be charged by the discharge equalization release power of a single battery cell to be discharged, using the obtained quotient as the charge-discharge power multiple, and using the obtained remainder as the power to be supplemented for the single battery cell to be charged; Determining the number of rechargeable battery cells and the number of remaining battery cells to be discharged according to the number of battery cells to be discharged in the battery cell group and the charge-discharge power multiple includes: Dividing the number of battery cells to be discharged in the battery cell group by the charge-discharge power multiple, using the obtained quotient as the number of rechargeable battery cells, and using the obtained remainder as the number of remaining battery cells to be discharged.

6. The battery pack equalization method according to claim 1, characterized in that, The slave board includes an equalization control module and a power supply. The equalization control module includes a plurality of equalization control units. Each equalization control unit is connected to a part of the battery cells in the battery cell group, and one battery cell is only connected to one equalization control unit; each of the equalization control units is connected to the power supply; at the same time, one equalization control unit only controls one connected battery cell to perform equalization; After subtracting one from the equalization count, it further includes: When the supply voltage of the power supply is greater than the safe supply voltage threshold, gradually reducing the number of equalization control units that are performing discharge equalization on the connected battery cells until the supply voltage of the power supply is less than the safe supply voltage threshold.

7. The battery pack balancing method according to any one of claims 1-6, characterized in that, During the equalization enabling stage, it further includes: If an equalization failure occurs, the master board sends the stop equalization instruction to each slave board; wherein, the slave board includes: an equalization control module and a power supply; the equalization control module is connected to the power supply and is respectively connected to each of the battery cells in the battery cell group corresponding to the slave board; the equalization failure includes at least one of the following: a failure of the battery cell voltage detection component, a failure of the current detection component in the battery management system, a failure of the temperature detection component in the battery management system, an equalization overcurrent failure, an equalization overtemperature failure, a failure of the equalization control module, an overlimit of the single battery cell voltage, an overlimit of the battery cell temperature, a communication failure between the master board and the slave board, and a power supply failure; and / or, For any slave board: if the slave board detects an equalization anomaly, the slave board turns off the equalization of the connected battery cell group in the current equalization cycle and does not respond to the start equalization instruction sent by the master board; wherein, the equalization anomaly includes: an equalization overcurrent or an equalization overtemperature occurs in the battery cell group connected to the slave board, or, a failure of the equalization control module in the slave board.

8. The battery pack equalization method according to any one of claims 1-6, characterized in that, In the active equalization mode, for any one of the equalization cycles: If the temperature of the battery cell with the highest temperature in the battery pack reaches the first preset temperature threshold, the equalization start time threshold in the equalization cycle is the first start time threshold, and the equalization stop time threshold is the first stop time threshold; If the temperature of the battery cell with the highest temperature in the battery pack is lower than the second preset temperature threshold, the equalization start time threshold in the equalization cycle is the second start time threshold, and the equalization stop time threshold is the second stop time threshold; Wherein, the first preset temperature threshold is greater than the second preset temperature threshold, the first start time threshold is less than the second start time threshold, and the first stop time threshold is greater than the second stop time threshold.

9. The battery pack equalization method according to any one of claims 1-6, characterized in that The battery management system further includes a host computer, which is connected to each slave board; The battery pack equalization method further includes: Forced equalization mode: The host computer directly controls whether each slave board equalizes the connected battery cell group.

Images