Passive equalization method and device for battery pack and vehicle

Abstract

The invention discloses a passive equalization method and device of a battery pack and a vehicle. The passive equalization method comprises the following steps: determining a to-be-equalized battery cell in the battery pack and a target equalization electric quantity of the to-be-equalized battery cell; acquiring the temperature of the acquisition board; discharging the to-be-equalized battery cell by using the equalization circuit, and in the discharging process, adjusting the discharging current of the equalization circuit according to the temperature of the acquisition board; and ending discharging when the current equalization electric quantity of the to-be-equalized battery cell is equal to the target equalization electric quantity. Through the scheme of the invention, electric quantity equalization can be carried out on the battery cell monomers in the battery pack, the consistency among the battery cell monomers is improved, and the aging rate of the battery pack is slowed down. Besides, the temperature and the discharge current of the acquisition board can be balanced, the problem of over-temperature of the acquisition board caused by overheating of the equalization circuit is avoided while high passive equalization efficiency is ensured, and the safety of passive equalization work is improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of new energy vehicles, and in particular, to a passive equalization method, device and vehicle for a battery pack. Background Art

[0002] As a type of vehicle with the most development potential, pure electric vehicles have attracted the attention of the automotive fields of various countries in the world. It uses a power battery (i.e., a high-voltage battery) as the power source of the vehicle. The power battery contains several battery packs, and the differences between the individual battery cells in the battery pack will cause the overall capacity of the battery pack to decrease, affect the life of the battery pack, and further cause the cruising range of the vehicle to decrease.

[0003] Equalizing the individual battery cells in the battery pack can improve the consistency between the monomers and slow down the aging rate of the battery pack. Therefore, it is particularly important to equalize the monomers in the battery pack. Summary of the Invention

[0004] The embodiments of the present invention provide a passive equalization method, device and vehicle for a battery pack to improve the power equalization effect of the battery cells in the battery pack and extend the service life of the battery pack.

[0005] In a first aspect, the embodiments of the present invention provide a passive equalization method for a battery pack. The battery pack includes a plurality of battery cells and a plurality of equalization circuits, and at least some components of the equalization circuits are arranged on a collection board. The passive equalization method for the battery pack includes:

[0006] Determine the battery cells to be equalized in the battery pack and the target equalization power of the battery cells to be equalized;

[0007] Obtain the temperature of the collection board;

[0008] Discharge the battery cells to be equalized by using the equalization circuit, and during the discharging process, adjust the discharging current of the equalization circuit according to the temperature of the collection board;

[0009] End the discharging when the current equalization power of the battery cells to be equalized is equal to the target equalization power.

[0010] In a second aspect, the embodiments of the present invention further provide a passive equalization device for a battery pack, which is used to execute the passive equalization method for a battery pack provided in any embodiment of the present invention. The passive equalization device for a battery pack includes:

[0011] A battery cell to be equalized determination module, which is used to determine the battery cells to be equalized in the battery pack and the target equalization power of the battery cells to be equalized;

[0012] A collection board temperature acquisition module, which is used to obtain the temperature of the collection board;

[0013] The passive equalization execution module is used to discharge the cells to be equalized by using an equalization circuit, and during the discharging process, adjust the discharging current of the equalization circuit according to the temperature of the acquisition board.

[0014] The passive equalization end module is used to end the discharging when the current equalization power of the cells to be equalized is equal to the target equalization power.

[0015] In a third aspect, an embodiment of the present invention further provides a vehicle, including a battery pack and the passive equalization device of the battery pack provided in any embodiment of the present invention.

[0016] The passive equalization method of the battery pack provided by the embodiment of the present invention first determines the cells to be equalized in the battery pack and the target equalization power of the cells to be equalized, and obtains the temperature of the acquisition board; then discharges the cells to be equalized by using an equalization circuit, and during the discharging process, adjust the discharging current of the equalization circuit according to the temperature of the acquisition board; finally, end the discharging when the current equalization power of the cells to be equalized is equal to the target equalization power. By using the above method, the power of the cell monomers in the battery pack can be equalized, the consistency between the cell monomers can be improved, and the aging rate of the battery pack can be slowed down. In addition, the temperature of the acquisition board and the discharging current can be balanced, while ensuring a relatively high passive equalization efficiency, avoiding the problem of over-temperature of the acquisition board caused by overheating of the equalization circuit, and improving the working safety of passive equalization. Description of the Drawings

[0017] Figure 1 It is a schematic flowchart of a passive equalization method of a battery pack provided in Embodiment 1 of the present invention;

[0018] Figure 2 It is a schematic flowchart of a passive equalization method of a battery pack provided in Embodiment 2 of the present invention;

[0019] Figure 3 It is a schematic flowchart of a passive equalization method of a battery pack provided in Embodiment 3 of the present invention;

[0020] Figure 4 It is a schematic flowchart of a passive equalization method of a battery pack provided in Embodiment 4 of the present invention;

[0021] Figure 5 It is a schematic structural diagram of a passive equalization device of a battery pack provided in Embodiment 5 of the present invention. Detailed Embodiments

[0022] The present invention will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. In addition, it should be noted that for the convenience of description, only parts related to the present invention are shown in the drawings, rather than all the structures.

[0023] Before discussing the exemplary embodiments in more detail, it should be noted that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts depict operations (or steps) as sequential processes, many of the operations can be performed in parallel, concurrently, or simultaneously. In addition, the order of the operations can be rearranged. The process can be terminated when its operations are completed, but it can also have additional steps not included in the figures. The process can correspond to a method, function, procedure, subroutine, subprogram, etc. In addition, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0024] The term "comprising" and its variations used in the present invention are open-ended, that is, "including but not limited to". The term "based on" is "at least partially based on". The term "one embodiment" means "at least one embodiment".

[0025] It should be noted that the concepts such as "first" and "second" mentioned in the present invention are only used to distinguish the corresponding contents, and are not used to limit the order or the interdependent relationship.

[0026] It should be noted that the modifications of "one" and "plural" mentioned in the present invention are illustrative rather than restrictive. Those skilled in the art should understand that unless otherwise clearly specified in the context, it should be understood as "one or more".

[0027] Embodiment 1

[0028] Figure 1 The flowchart shows a passive equalization method for a battery pack provided in Embodiment 1 of the present invention. This method is applicable to new energy vehicles to passively equalize the battery levels of the individual battery cells in the battery pack of new energy vehicles. This passive equalization method can be executed by the passive equalization device of the battery pack provided in the embodiments of the present invention, where the passive equalization device can be implemented by software and / or hardware and can be integrated on the vehicle controller, such as integrated on the BMS control board or the BMS acquisition board, but not limited thereto.

[0029] As Figure 1 shown, a passive equalization method for a battery pack provided in Embodiment 1 of the present invention includes the following steps:

[0030] S110. Determine the battery cells to be equalized in the battery pack and the target equalization battery levels of the battery cells to be equalized.

[0031] The battery pack includes a plurality of cells and a plurality of balancing circuits, and at least some components of the balancing circuits are arranged on the acquisition board. The cells and the balancing circuits can be electrically connected one by one, and the balancing circuits are used to discharge the cells. Discharging the cells to be balanced can be called passive balancing, and passive balancing can reduce the power of the cells to be balanced with higher power, thereby ensuring the consistency of power of each cell.

[0032] The number of cells in the battery pack is not limited and can be set according to actual needs. In the embodiment of the present invention, it is possible to first determine which cells in the battery pack are to be balanced and record the numbers of the cells to be balanced, and at the same time determine the target balancing power that the cells to be balanced need to balance.

[0033] The cells to be balanced are the cells with higher power in the battery pack, and the target balancing power refers to the power that needs to be balanced by the balancing cells, that is, the power that needs to be discharged through passive balancing. Depending on the actual situation, the number of cells to be balanced may be one or more.

[0034] Among them, the specific determination method of the battery cells to be balanced and the target balanced power of the battery cells to be balanced is not limited, and those skilled in the art can set it according to actual needs. Exemplarily, in some embodiments, the single cell remaining power of each battery cell can be obtained when the battery pack is in a fully charged static state (i.e., fully charged and static state), and the average remaining power of all the battery cells in the battery pack can be determined. The battery cell whose single cell remaining power is higher than the average remaining power is the battery cell to be balanced, and the difference between the single cell remaining power and the average remaining power is the target balanced power.

[0035] The structure of the balancing circuit is not limited and can be implemented by any existing technology. Exemplarily, the balancing circuit may include a discharge balancing resistor and a discharge balancing switch, and the discharge balancing switch may be a relay or a field effect transistor. Taking a field effect transistor as an example, one end of the discharge balancing resistor can be electrically connected to the positive electrode of the battery cell, the other end of the discharge balancing resistor can be connected to the drain of the field effect transistor, the source of the field effect transistor is electrically connected to the negative electrode of the battery cell, and the gate of the field effect transistor is connected to the passive balancing device of the battery pack. During the discharge process, the passive balancing device of the battery pack controls the field effect transistor to conduct, so that the balancing circuit is closed, thereby causing the discharge balancing resistor to heat up to release the electrical energy on the battery cell to be balanced.

[0036] When the number of cells to be balanced is large, the discharge operations of the multiple cells to be balanced may be performed simultaneously or in different time periods, which is not limited in the embodiment of the present invention.

[0037] S120: Obtain the temperature of the acquisition board.

[0038] Any component for implementing the acquisition of cell data may also be provided on the acquisition board, which is not elaborated or limited in the embodiments of the present invention. Among them, the inventor found through research that when discharging using the balancing circuit, since the discharge balancing resistor generates heat, the temperature of the acquisition board will increase. If the temperature of the acquisition board is too high, the acquisition board may be burned out, affecting the normal operation of the cells.

[0039] Based on this, the embodiments of the present invention propose that the temperature sensor on the acquisition board can be used to detect the temperature of the acquisition board in real time and send the temperature of the acquisition board to the passive balancing device of the battery pack. Subsequently, the passive balancing device of the battery pack can perform passive balancing work in combination with the temperature of the acquisition board, avoiding the problem of abnormal increase in the temperature of the acquisition board caused by excessive heat generation of the discharge balancing resistor.

[0040] S130. Discharge the cells to be balanced using the balancing circuit. During the discharge process, adjust the discharge current of the balancing circuit according to the temperature of the acquisition board.

[0041] Further, after the cells to be balanced are determined, the balancing circuit corresponding to the cells to be balanced can be used for discharging. Among them, during the discharge process, the discharge current (i.e., the balancing current) of the balancing circuit can be adjusted in real time according to the obtained temperature of the acquisition board. While ensuring that the heat generation of the discharge balancing resistor is within the temperature limit threshold of the acquisition board, the discharge current is made as large as possible to improve the passive balancing efficiency. Avoid the problem of overheating of the acquisition board caused by overheating of the discharge balancing resistor, and improve the safety of the passive balancing work.

[0042] Exemplarily, in some embodiments, the corresponding relationship between the temperature of the acquisition board and the discharge current can be determined in advance and stored. In actual application, the discharge current corresponding to the current temperature of the acquisition board is determined according to this corresponding relationship. Or, in some other embodiments, the upper threshold value of the temperature of the acquisition board and the lower threshold value of the temperature of the acquisition board can be set in advance. When the current temperature of the acquisition board exceeds the upper threshold value of the temperature of the acquisition board, the discharge current is reduced; when the current temperature of the acquisition board is lower than the lower threshold value of the temperature of the acquisition board, the discharge current is increased.

[0043] In addition, the embodiments of the present invention do not limit the specific manner of adjusting the discharge current, and any solution capable of adjusting the discharge current is within the scope of the technical solutions protected by the embodiments of the present invention.

[0044] S140. End the discharge when the current balanced power of the cells to be balanced is equal to the target balanced power.

[0045] Further, during the process of performing passive equalization, the current equalization power of each cell to be equalized can be calculated and recorded in real time. The current equalization power is the power that has been equalized for the cell to be equalized, that is, the power that has been discharged during the process of performing passive equalization. Once the current equalization power of the cell to be equalized reaches the target equalization power, the equalization channel of the cell can be closed to end the passive equalization work.

[0046] A passive equalization method for a battery pack provided in Embodiment 1 of the present invention first determines the cells to be equalized in the battery pack and the target equalization power of the cells to be equalized, and obtains the temperature of the acquisition board; then uses an equalization circuit to discharge the cells to be equalized, and during the discharging process, adjusts the discharging current of the equalization circuit according to the temperature of the acquisition board; finally, ends the discharging when the current equalization power of the cells to be equalized is equal to the target equalization power. Using the above method, the power of the individual cells in the battery pack can be equalized, the consistency between the individual cells can be improved, and the aging rate of the battery pack can be slowed down. In addition, the temperature of the acquisition board and the discharging current can be balanced, while ensuring the passive equalization efficiency, avoiding the problem of overheating of the acquisition board caused by overheating of the equalization circuit, and improving the safety of the passive equalization work.

[0047] Based on the above embodiments, the present invention proposes a variant embodiment of the above embodiments. It should be noted here that for the sake of brevity of description, only the differences from the above embodiments are described in the variant embodiments.

[0048] In some embodiments, before (discharging the cells to be equalized using the equalization circuit) in the above (S130), it further includes: confirming that the vehicle is in a low-voltage power-on state.

[0049] In this embodiment, passive equalization work is performed during the low-voltage power-on process of the vehicle, which ensures that the discharging is completed in a relatively stable state of the battery pack, improves the passive equalization effect and safety, and more accurately adjusts the remaining power of the cells to be equalized.

[0050] Embodiment 2

[0051] Figure 2 It is a schematic flowchart of a passive equalization method for a battery pack provided in Embodiment 2 of the present invention. Embodiment 2 is optimized based on the above embodiments. In this embodiment, (adjusting the discharging current of the equalization circuit according to the temperature of the acquisition board) in (S130) is further specified as: during the discharging process, adjusting the number of cells to be equalized that are discharging simultaneously according to the temperature of the acquisition board, and / or adjusting the duty cycle of the equalization circuit according to the temperature of the acquisition board. For the content not detailed in this embodiment, please refer to Embodiment 1.

[0052] As Figure 2 shown, a passive equalization method for a battery pack provided in Embodiment 2 of the present invention includes the following steps:

[0053] S210. Determine the cells to be balanced in the battery pack and the target balancing power of the cells to be balanced.

[0054] S220. Obtain the temperature of the acquisition board.

[0055] S231. Discharge the cells to be balanced using the balancing circuit.

[0056] S232. During the discharging process, adjust the number of cells to be balanced that are discharging simultaneously according to the temperature of the acquisition board, and / or adjust the duty cycle of the balancing circuit according to the temperature of the acquisition board.

[0057] In this embodiment, the solutions for adjusting the discharging current of the balancing circuit include at least one of the following. The first solution is to adjust the number of cells to be balanced that are simultaneously performing passive balancing, that is, to adjust the number of cells to be balanced that are discharging simultaneously, and change the discharging current of the overall balancing circuit within the entire battery pack by changing the number of balancing circuits that are working simultaneously, thereby adjusting the heat generation of the discharging balancing resistor. The second solution is to adjust the duty cycle of the balancing circuit in the discharging state, that is, to adjust the duty cycle of the control voltage signal received by the balancing circuit, so as to adjust the discharging current of each balancing circuit in the working state, thereby adjusting the heat generation of the discharging balancing resistor.

[0058] The control logics of the above two solutions for adjusting the discharging current are relatively simple and easy to implement, which is beneficial to simplifying the control logic.

[0059] S240. End the discharging when the current balancing power of the cells to be balanced is equal to the target balancing power.

[0060] The passive balancing method of the battery pack provided in the second embodiment of the present invention can control the discharging current in a relatively simple manner by adjusting the number of cells to be balanced that are discharging simultaneously according to the temperature of the acquisition board, and / or adjusting the duty cycle of the balancing circuit according to the temperature of the acquisition board.

[0061] Based on the above embodiment, a variant embodiment of the above embodiment is proposed.

[0062] In one embodiment, the above (adjusting the number of cells to be balanced that are discharging simultaneously according to the temperature of the acquisition board) can be specifically implemented as follows: when the temperature of the acquisition board is greater than or equal to the first temperature threshold, control the first number of cells to be balanced to discharge simultaneously; when the temperature of the acquisition board is less than the first temperature threshold, control the second number of cells to be balanced to discharge simultaneously; where the first number is less than the second number.

[0063] In some embodiments, a first temperature threshold may be preset. The first temperature threshold is a relatively high temperature threshold, which may correspond to the upper limit threshold of the temperature of the acquisition board in the above embodiments. When it is detected that the current temperature of the acquisition board is greater than or equal to the first temperature threshold, it indicates that the discharge equalization resistor generates too much heat. At this time, a smaller number (the first number) of cells to be equalized can be adjusted to perform passive equalization simultaneously, that is, the number of discharging cells is reduced, so as to reduce the heat generated by discharge equalization and lower the temperature of the acquisition board. When it is detected that the current temperature of the acquisition board is less than the first temperature threshold, it indicates that the discharge equalization resistor generates less heat. At this time, a larger number (the second number) of cells to be equalized can be adjusted to perform passive equalization simultaneously, so as to increase the discharge rate and improve the efficiency of passive equalization.

[0064] Wherein, the specific values of the above first temperature threshold, the first number, and the second number are not limited, and those skilled in the art can set them according to the actual situation.

[0065] Exemplarily, in specific implementation, when the temperature of the acquisition board is greater than or equal to the first temperature threshold, the cells to be equalized with odd or even numbers can be controlled to perform passive equalization work simultaneously; when the temperature of the acquisition board is less than the first temperature threshold, all the cells to be equalized can be controlled to perform passive equalization work simultaneously.

[0066] In some other embodiments, the above (adjusting the duty cycle of the equalization circuit according to the temperature of the acquisition board) can be specifically implemented as: when the temperature of the acquisition board is greater than or equal to the first temperature threshold, adjusting the duty cycle of the equalization circuit to the first duty cycle; when the temperature of the acquisition board is less than the first temperature threshold, adjusting the duty cycle of the equalization circuit to the second duty cycle; wherein, the first duty cycle is less than the second duty cycle.

[0067] In some other embodiments, when it is detected that the current temperature of the acquisition board is greater than or equal to the first temperature threshold, the equalization circuit in the working state can be controlled to work with a smaller duty cycle (the first duty cycle), so as to reduce the discharge current of the equalization circuit, reduce the heat generated by discharge equalization, and lower the temperature of the acquisition board. When it is detected that the current temperature of the acquisition board is less than the first temperature threshold, the equalization circuit in the working state can be controlled to work with a larger duty cycle (the second duty cycle), so as to increase the discharge current of the equalization circuit, increase the discharge rate, and improve the efficiency of passive equalization work.

[0068] Wherein, the specific values of the first duty cycle and the second duty cycle are not limited, and those skilled in the art can set them according to the actual situation.

[0069] Embodiment III

[0070] Figure 3A flowchart of a passive equalization method for a battery pack provided in Embodiment 3 of the present invention. Embodiment 3 is optimized based on the above embodiments. In this embodiment, (S110) is further specified as follows: S311. Obtain the remaining power of each battery cell in the fully charged and stationary state; S312. Determine the battery cells to be equalized and the target equalization power according to the remaining power of each battery cell. For the content not detailed in this embodiment, please refer to Embodiments 1 and 2.

[0071] As Figure 3 shown, a passive equalization method for a battery pack provided in Embodiment 3 of the present invention includes the following steps:

[0072] S311. Obtain the remaining power of each battery cell in the fully charged and stationary state.

[0073] When the vehicle is charging, when the battery cell with the highest power in the battery pack reaches the upper cut-off voltage and the vehicle is still in a stationary state, calculate the remaining power of each battery cell.

[0074] The calculation method of the remaining power of the battery cell is not limited. For example, the ampere-hour integration method or the open-circuit voltage method can be selected, but it is not limited to this.

[0075] Exemplarily, in some embodiments, (S311) can be specifically refined as follows: when the battery cell is in the fully charged and stationary state, collect the open-circuit voltage of the battery cell; determine the remaining power of the battery cell according to the open-circuit voltage of the battery cell.

[0076] Specifically, when the battery pack is fully charged and in a stationary state, collect the open-circuit voltage of each battery cell, so as to determine the remaining power of each battery cell according to the open-circuit voltage. The corresponding relationship between the open-circuit voltage and the remaining power can be obtained by the staff in advance and stored in the passive equalization device of the battery pack. In actual application, after collecting the open-circuit voltage of each battery cell, the remaining capacity of each battery cell can be quickly and accurately obtained according to the open-circuit voltage of each battery cell.

[0077] S312. Determine the battery cells to be equalized and the target equalization power according to the remaining power of each battery cell.

[0078] Furthermore, it is possible to determine which battery cells are the battery cells to be equalized according to the remaining power of the battery cells, and calculate the target equalization power of each battery cell to be equalized.

[0079] The method for determining the battery cells to be equalized according to the remaining power of the battery cells can be referred to as described in Embodiment 1, or another method for determining the battery cells to be equalized is proposed in this embodiment.

[0080] Exemplarily, (S312) can be specifically refined as follows: Determine the cell with the lowest remaining power in the battery pack as the first cell, and the remaining cells as the second cells. Then determine the remaining power of the first cell as the first remaining power and the remaining power of the second cells as the second remaining power. Calculate the difference between the second remaining power of each second cell and the first remaining power of the first cell respectively. Determine the second cells whose difference between the second remaining power and the first remaining power is greater than or equal to the equalization start power difference as the cells to be equalized, and the difference between the second remaining power and the first remaining power is the target equalization power.

[0081] Specifically, after determining the remaining power of each cell, the cell with the lowest remaining power can be marked as the first cell, and the remaining cells as the second cells. The remaining power of the first cell is marked as the first remaining power, and the remaining power of the second cells is the second remaining power. Subsequently, calculate the difference between the remaining power (second remaining power) of each second cell and the first remaining power. This difference can be simply referred to as the "power difference". Compare the power difference of each second cell with the equalization start power difference to determine whether the power difference of each second cell is greater than or equal to the equalization start power difference. The equalization start power difference can be preset by the staff and is a value representing poor consistency of the power of two cells.

[0082] When it is determined that the power difference of the second cell is greater than or equal to the equalization start power difference, mark this second cell as the cell to be equalized, and the corresponding power difference is the target equalization power of this second cell. When it is determined that the power difference of the second cell is less than the equalization start power difference, no marking is required, and there is no need to perform passive equalization on such second cells.

[0083] S320. Obtain the temperature of the acquisition board.

[0084] S330. Use the equalization circuit to discharge the cells to be equalized. During the discharging process, adjust the discharging current of the equalization circuit according to the temperature of the acquisition board.

[0085] S340. End the discharging when the current equalization power of the cells to be equalized is equal to the target equalization power.

[0086] For the specific implementation manners of the above S320 - S340, reference can be made to the above embodiments, and details are not described here again.

[0087] Embodiment 4

[0088] Figure 4 This is a flowchart of a passive equalization method for a battery pack provided by Embodiment 4 of the present invention. Embodiment 4 proposes a specific implementation manner of the passive equalization method for the battery pack, which can be referred to Figure 4 for an overall introduction to the passive equalization method for the battery pack provided by the embodiments of the present invention, as Figure 4As shown in the figure, the passive equalization method of the battery pack includes the following steps:

[0089] S410. Determine that the battery pack is in a fully charged and stationary state.

[0090] S411. When the battery cell is in a fully charged and stationary state, collect the open-circuit voltage of the battery cell.

[0091] S412. Determine the remaining power of the battery cell according to the open-circuit voltage of the battery cell.

[0092] S413. Determine the first battery cell, the second battery cell, the first remaining power of the first battery cell, and the second remaining power of the second battery cell.

[0093] Among the battery cells in the battery pack, the battery cell with the lowest remaining power is the first battery cell, and the rest are the second battery cells. The remaining power of the first battery cell is the first remaining power, and the remaining power of the second battery cell is the second remaining power.

[0094] S414. Calculate the difference between the second remaining power of each second battery cell and the first remaining power of the first battery cell respectively.

[0095] S415. Determine whether the difference between the second remaining power of the second battery cell and the first remaining power of the first battery cell is greater than or equal to the equalization start power difference.

[0096] If yes, execute S416; if no, execute S442.

[0097] S416. Mark it as the battery cell to be equalized, and calculate the target equalization power.

[0098] The target equalization power is the difference between the second remaining power of the second battery cell and the first remaining power of the first battery cell.

[0099] S420. Determine that the vehicle is in a low-voltage power-on state, and obtain the temperature of the acquisition board.

[0100] S430. Use the equalization circuit to discharge the battery cell to be equalized. During the discharge process, adjust the discharge current of the equalization circuit according to the temperature of the acquisition board.

[0101] S440. Calculate and record the current equalization power of each battery cell to be equalized in real time.

[0102] S441. Determine whether the current equalization power of each battery cell to be equalized is greater than or equal to the corresponding target equalization power.

[0103] If yes, execute S442; if no, execute S430.

[0104] S442. Close the equalization channel of the battery cell and end the passive equalization work.

[0105] Embodiment 5

[0106] Figure 5 FIG. 1 is a schematic structural diagram of a passive equalization device for a battery pack provided in Embodiment 5 of the present invention. The passive equalization device for the battery pack is applicable to new energy vehicles to passively equalize the power of the battery cells in the battery pack of the new energy vehicle. The passive equalization device for the battery pack can be implemented by software and / or hardware and can be integrated on a vehicle controller, such as integrated on a BMS control board or a BMS acquisition board, but is not limited thereto. The battery pack includes a plurality of battery cells and a plurality of equalization circuits, and at least some components of the equalization circuits are arranged on the acquisition board. As Figure 5 shown, the passive equalization device for the battery pack includes:

[0107] An unbalanced battery cell determination module 100 for determining the unbalanced battery cells in the battery pack and the target equalization power of the unbalanced battery cells.

[0108] An acquisition board temperature acquisition module 200 for acquiring the temperature of the acquisition board.

[0109] A passive equalization execution module 300 for discharging the unbalanced battery cells by using the equalization circuit, and adjusting the discharge current of the equalization circuit according to the temperature of the acquisition board during the discharging process.

[0110] A passive equalization end module 400 for ending the discharge when the current equalization power of the unbalanced battery cells is equal to the target equalization power.

[0111] The passive equalization device for the battery pack provided in the embodiment of the present invention can equalize the power of the battery cells in the battery pack, improve the consistency between the battery cells, and slow down the aging rate of the battery pack. In addition, it can also balance the temperature of the acquisition board and the discharge current, avoid the over-temperature problem of the acquisition board caused by overheating of the equalization circuit while ensuring the passive equalization efficiency, and improve the working safety of the passive equalization.

[0112] Optionally, in a possible embodiment, the passive equalization execution module may further be configured to: adjust the number of unbalanced battery cells discharging simultaneously according to the temperature of the acquisition board during the discharging process, and / or adjust the duty cycle of the equalization circuit according to the temperature of the acquisition board.

[0113] Optionally, in a possible embodiment, the passive equalization execution module may specifically be configured to: control a first number of unbalanced battery cells to discharge simultaneously when the temperature of the acquisition board is greater than or equal to a first temperature threshold; control a second number of unbalanced battery cells to discharge simultaneously when the temperature of the acquisition board is less than the first temperature threshold; wherein, the first number is less than the second number.

[0114] Optionally, in a possible embodiment, the passive equalization execution module is specifically configured to: when the temperature of the acquisition board is greater than or equal to the first temperature threshold, adjust the duty cycle of the equalization circuit to the first duty cycle; when the temperature of the acquisition board is less than the first temperature threshold, adjust the duty cycle of the equalization circuit to the second duty cycle; wherein, the first duty cycle is less than the second duty cycle.

[0115] Optionally, in a possible embodiment, the cell to be equalized determination module includes a remaining power acquisition unit and a cell to be equalized determination unit. The remaining power acquisition unit is used to acquire the remaining power of each cell in the fully charged and stationary state. The cell to be equalized determination unit is used to determine the cell to be equalized and the target equalization power according to the remaining power of each cell.

[0116] Optionally, in a possible embodiment, the cell to be equalized determination unit is specifically configured to determine the cell with the lowest remaining power in the battery pack as the first cell, the remaining cells as the second cells, and determine the remaining power of the first cell as the first remaining power and the remaining power of the second cells as the second remaining power; calculate the difference between the second remaining power of each second cell and the first remaining power of the first cell respectively; determine the second cell whose difference between the second remaining power and the first remaining power is greater than or equal to the equalization start power difference as the cell to be equalized, and the difference between the second remaining power and the first remaining power is the target equalization power.

[0117] Optionally, in a possible embodiment, the remaining power acquisition unit is specifically configured to collect the open-circuit voltage of the cell when the cell is in the fully charged and stationary state; determine the remaining power of the cell according to the open-circuit voltage of the cell.

[0118] Optionally, in a possible embodiment, the passive equalization execution module is further configured to confirm that the vehicle is in the low-voltage power-on state before discharging the cell to be equalized by using the equalization circuit.

[0119] The passive equalization device of the above battery pack can execute the passive equalization method of the battery pack provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method.

[0120] Embodiment Six

[0121] Embodiment Six of the present invention provides a vehicle, including a battery pack and the passive equalization device of the battery pack provided in any embodiment of the present invention. The vehicle can be a new energy vehicle, for example, a pure electric vehicle. The vehicle provided in Embodiment Six of the present invention has all the technical features and corresponding beneficial effects of the passive equalization device of the battery pack provided in any embodiment of the present invention, and will not be described in detail here.

[0122] Note that the above is only a preferred embodiment of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments here, and various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A passive balancing method for a battery pack, characterized in that: The battery pack includes a plurality of battery cells and a plurality of balancing circuits, and at least some components of the balancing circuits are arranged on a collection board; Passive balancing methods for battery packs include: Determining the cells to be balanced in the battery pack and the target balanced power of the cells to be balanced; Get the temperature of the acquisition board; Discharging the battery cells to be balanced by using a balancing circuit, and during the discharging process, adjusting the discharge current of the balancing circuit according to the temperature of the acquisition board; The discharging is terminated when the current balancing power of the battery cell to be balanced is equal to the target balancing power.

2. The passive equalization method of a battery pack according to claim 1, characterized in that: During the discharge process, the discharge current of the balancing circuit is adjusted according to the temperature of the acquisition board, including: During the discharge process, the number of the cells to be balanced that are discharged simultaneously is adjusted according to the temperature of the acquisition board, and / or the duty cycle of the balancing circuit is adjusted according to the temperature of the acquisition board.

3. The passive equalization method of a battery pack according to claim 2, characterized in that: Adjusting the number of the cells to be balanced that are discharged simultaneously according to the temperature of the acquisition board includes: When the temperature of the acquisition board is greater than or equal to a first temperature threshold, a first number of the cells to be balanced are controlled to discharge simultaneously; when the temperature of the acquisition board is less than the first temperature threshold, a second number of the cells to be balanced are controlled to discharge simultaneously; Wherein, the first number is smaller than the second number.

4. The passive equalization method of a battery pack according to claim 2, characterized in that: Adjusting the duty cycle of the balancing circuit according to the temperature of the acquisition board includes: When the temperature of the acquisition board is greater than or equal to the first temperature threshold, the duty cycle of the balancing circuit is adjusted to the first duty cycle; when the temperature of the acquisition board is less than the first temperature threshold, the duty cycle of the balancing circuit is adjusted to the second duty cycle; The first duty cycle is smaller than the second duty cycle.

5. The passive equalization method of a battery pack according to claim 1, characterized in that: Determining the cells to be balanced in the battery pack and the target balanced power of the cells to be balanced, including: Obtaining the remaining power of each battery cell when it is fully charged and in a static state; The battery cells to be balanced and the target balanced power are determined according to the remaining power of each of the battery cells.

6. The passive equalization method of a battery pack according to claim 5, characterized in that: Determining the battery cells to be balanced and the target balanced power according to the remaining power of each of the battery cells includes: Determine that the battery cell with the lowest remaining power in the battery pack is a first battery cell, and the remaining battery cells are second battery cells, and determine that the remaining power of the first battery cell is a first remaining power, and the remaining power of the second battery cell is a second remaining power; respectively calculating the difference between the second remaining power of each of the second battery cells and the first remaining power of the first battery cell; The second battery cell whose difference between the second remaining power and the first remaining power is greater than or equal to the balancing start power difference is determined as the battery cell to be balanced, and the difference between the second remaining power and the first remaining power is the target balancing power.

7. The passive equalization method of a battery pack according to claim 5, characterized in that: Obtaining the remaining power of each battery cell in a fully charged static state, including: When the battery cell is in a fully charged static state, collecting the open circuit voltage of the battery cell; The remaining power of the battery cell is determined according to the open circuit voltage of the battery cell.

8. The passive equalization method of a battery pack according to claim 1, characterized in that: Before discharging the battery cells to be balanced by using the balancing circuit, the method further includes: Confirm that the vehicle is in low voltage power-on state.

9. A passive balancing device for a battery pack, characterized in that: Used to perform the passive balancing method of the battery pack according to any one of claims 1 to 8, the passive balancing device of the battery pack comprising: A module for determining cells to be balanced, used for determining cells to be balanced in the battery pack and target balanced power of the cells to be balanced; The acquisition board temperature acquisition module is used to obtain the acquisition board temperature; A passive balancing execution module, used for discharging the battery cells to be balanced by using a balancing circuit, and during the discharging process, adjusting the discharge current of the balancing circuit according to the temperature of the acquisition board; The passive balancing end module ends the discharge when the current balancing power of the battery cell to be balanced is equal to the target balancing power.

10. A vehicle, characterized in that: The invention comprises a battery pack and a passive balancing device for the battery pack as claimed in claim 9.

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