Series battery cell equalization method, device and electronic device

Abstract

The present application relates to the technical field of energy storage batteries, and specifically relates to a series battery cell equalization method, device, and electronic device. This method reads the static cell voltage of the battery cells, then determines the target battery cells to be equalized according to the magnitude of the cell voltage, and determines the equalization time corresponding to the target battery cells according to the cell voltage. Then, charging / discharging equalization is performed on the target battery cells according to the equalization time to equalize the battery cells in the battery pack. This solution determines the SOC data corresponding to charging / discharging according to the voltage magnitude, calculates the equalization time of the target battery cells based on this, and then controls the on / off of each switch and cooperates with the equalization capacitor, so that only the energy transfer inside the battery pack is required during the cell equalization process, and it is not necessary to exchange energy with the external circuit, which improves the equalization efficiency while ensuring the equalization effect.

Description

Technical Field

[0001] This application relates to the technical field of energy storage batteries, and specifically to a series battery cell equalization method, device, and electronic device. Background Art

[0002] After multiple battery cells are connected in series, due to individual differences, the battery levels of each battery cell will be unbalanced. After multiple battery cells form a battery pack, the charge and discharge capacity of the entire battery pack is directly related to the battery cell with the lowest capacity among them. The differences between individual battery cells may also affect the service life of the battery pack. In the prior art, a passive equalization method is generally adopted. The battery pack achieves equalization by exchanging energy with an external circuit. For example, an external discharge resistor is connected, and the battery cell with a high battery level is discharged to a level close to that of the battery cell with a low battery level. This method has low efficiency, serious heat generation, and waste of electric energy. Another example is to connect an external power supply to charge the battery cell with a low battery level to a level close to that of the battery cell with a high battery level. This method requires additional power supply from an external power source, resulting in high costs. Moreover, during the equalization process, the voltage of the battery cell is a dynamic voltage. Even if the dynamic voltages of each battery cell are adjusted to the same voltage, after the equalization is completed, when the dynamic voltage drops to the static voltage, and the static voltage is usually not equal to the dynamic voltage. In order to equalize all the battery cells of the battery pack, multiple or repeated equalizations are required, resulting in low efficiency. In addition, due to the existence of the battery cell plateau region, because the pressure difference in the plateau region is very small, even if the voltages of the battery cells differ by only a few millivolts, the difference in the capacities of the battery cells may be very large. Therefore, the equalization can usually only be performed at the end of charging or discharging. Summary of the Invention

[0003] The embodiments of this application mainly solve the technical problem that the existing battery cell equalization methods have low efficiency and large losses.

[0004] To solve the above technical problem, a technical solution adopted in the embodiments of this application is: to provide a series battery cell equalization method, which is applied to a series battery cell equalization circuit. The circuit includes an equalization capacitor, a transformer, and a battery pack composed of at least two battery cells connected in series. Each battery cell is connected to a corresponding battery cell switch and is connected in parallel with the equalization capacitor through the corresponding battery cell switch. The primary side of the transformer is connected in parallel with the equalization capacitor through a first control switch, and the secondary side of the transformer is connected in parallel with both ends of the battery pack through a second control switch. The method includes: reading the static battery cell voltage of the battery cell; determining the target battery cell to be equalized according to the magnitude of the battery cell voltage; determining the equalization time corresponding to the target battery cell according to the battery cell voltage; and performing charge / discharge equalization on the target battery cell according to the equalization time to equalize the battery cells in the battery pack.

[0005] In some embodiments, the target battery cells that need to be balanced include high-voltage battery cells that need discharge balancing and low-voltage battery cells that need charge balancing; determining the target battery cells that need to be balanced according to the voltage magnitude of the battery cells includes: determining the high-voltage battery cells and the low-voltage battery cells according to the voltage magnitude of the battery cells.

[0006] In some embodiments, determining the high-voltage battery cells and the low-voltage battery cells according to the voltage magnitude of the battery cells includes: sorting the battery cells according to the voltage magnitude of the battery cells; determining the high-voltage battery cells and the low-voltage battery cells from the battery cells according to the sorting result, wherein the number of the high-voltage battery cells is equal to the number of the low-voltage battery cells.

[0007] In some embodiments, determining the high-voltage battery cells and the low-voltage battery cells from the battery cells according to the sorting result includes: obtaining the k battery cells with the largest voltage from the sorting result as the high-voltage battery cells, and obtaining the k battery cells with the smallest voltage from the sorting result as the low-voltage battery cells, wherein k is a positive integer less than n / 2, and n is the total number of battery cells in the battery pack.

[0008] In some embodiments, determining the balancing time corresponding to the target battery cells according to the voltage of the battery cells includes: determining a charging reference value and a discharging reference value according to the voltages of all the battery cells; obtaining the charging state of charge value corresponding to the voltage of the target battery cells as the charging SOC value, and obtaining the discharging state of charge value corresponding to the voltage of the target battery cells as the discharging SOC value; calculating the absolute value of the difference between the charging SOC value of the target battery cells and the charging reference value as the charging SOC difference value of the target battery cells, and calculating the absolute value of the difference between the discharging SOC value of the target battery cells and the discharging reference value as the discharging SOC difference value of the target battery cells; determining the final SOC difference value of the target battery cells according to the charging SOC difference value and the discharging SOC difference value; calculating the balancing time of the target battery cells according to the final SOC difference value.

[0009] In some embodiments, determining the charging reference value and the discharging reference value according to the voltages of all the battery cells includes: obtaining the median value of all the battery cell voltages as the median voltage; obtaining the charging state of charge value corresponding to the median voltage as the charging reference value, and obtaining the discharging state of charge value corresponding to the median voltage as the discharging reference value.

[0010] In some embodiments, determining the final SOC difference value of the target battery cells according to the charging SOC difference value and the discharging SOC difference value includes: obtaining the relatively smaller value of the charging SOC difference value and the discharging SOC difference value as the final SOC difference value of the target battery cells.

[0011] In some embodiments, calculating the equalization time of the target battery cell according to the final value of the SOC difference includes: obtaining the battery cell capacity and the equalization current; calculating the equalization time of the target battery cell according to the following formula: Equalization time T = Final value of SOC difference * Battery cell capacity Cap / Equalization current I.

[0012] In some embodiments, performing charge / discharge equalization on the target battery cell according to the equalization time to equalize the battery cells in the battery pack includes: according to the equalization time, in combination with the equalization capacitor, by controlling the on / off of the battery cell switch, the first control switch, and the second control switch, based on a preset equalization logic, performing discharge equalization on the high-voltage battery cell, or performing charge equalization on the low-voltage battery cell, where the preset equalization logic includes: controlling the battery cell switch corresponding to the high-voltage battery cell to conduct, and controlling the first control switch and the second control switch to disconnect, to perform discharge equalization on the high-voltage battery cell according to the equalization time, and updating the equalization time in real time until the equalization time is zero or the equalization capacitor is fully charged; controlling the battery cell switch corresponding to the low-voltage battery cell to conduct, and controlling the first control switch and the second control switch to disconnect, to perform charge equalization on the low-voltage battery cell according to the equalization time, and updating the equalization time in real time until the equalization time is zero or the equalization capacitor is emptied.

[0013] In some embodiments, the preset equalization logic further includes: controlling the first control switch and the second control switch to conduct, and controlling all the battery cell switches to disconnect, so that the equalization capacitor charges the battery pack until the equalization capacitor is emptied; controlling the first control switch and the second control switch to conduct, and controlling all the battery cell switches to disconnect, so that the battery pack charges the equalization capacitor until the equalization capacitor is fully charged.

[0014] In some embodiments, the preset equalization logic further includes: when the battery cell equalization is not triggered, controlling the first control switch, the second control, and all the battery cell switches to remain in the disconnected state to maintain the initialization state; when an interrupt command is triggered, controlling the first control switch, the second control, and all the battery cell switches to disconnect to interrupt the battery cell equalization; after the equalization of all the target battery cells is completed, controlling the first control switch, the second control, and all the battery cell switches to disconnect to terminate the battery cell equalization.

[0015] In some embodiments, performing charge / discharge equalization on the target battery cell according to the equalization time to equalize the battery cells in the battery pack further includes: after the current target battery cell completes equalization, obtaining the next target battery cell that needs to be equalized, and performing equalization on the next target battery cell until there is no next target battery cell that needs to be equalized or an interrupt command is triggered.

[0016] To solve the above technical problems, another technical solution adopted in the embodiments of the present application is: to provide a series battery cell balancing device, including: a battery cell voltage acquisition module for reading the static battery cell voltage of the battery cell; a target battery cell determination module for determining a target battery cell to be balanced according to the magnitude of the battery cell voltage; an equalization time determination module for determining the equalization time corresponding to the target battery cell according to the battery cell voltage; and a battery cell equalization control module for performing charge / discharge equalization on the target battery cell according to the equalization time, so as to equalize the battery cells in the battery pack.

[0017] To solve the above technical problems, another technical solution adopted in the embodiments of the present application is: to provide an electronic device, including: at least one processor and a memory; the memory is coupled to the processor, and the memory is used to store instructions or programs. When the instructions or programs are executed by the at least one processor, the at least one processor is caused to execute the series battery cell equalization method as described above.

[0018] To solve the above technical problems, another technical solution adopted in the embodiments of the present application is: to provide a computer storage medium, the computer storage medium stores instructions or programs. When the instructions or programs are executed by at least one processor, the at least one processor is caused to execute the series battery cell equalization method as described above.

[0019] Different from the related art, the embodiments of the present application provide a series battery cell equalization method, device and electronic device. The method reads the static battery cell voltage of the battery cell, then determines the target battery cell to be balanced according to the magnitude of the battery cell voltage, determines the equalization time corresponding to the target battery cell according to the battery cell voltage, and then performs charge / discharge equalization on the target battery cell according to the equalization time, so as to equalize the battery cells in the battery pack. This solution determines the SOC data corresponding to charge / discharge according to the magnitude of the static voltage, calculates the equalization time of the target battery cell, and then controls the on / off of each switch and cooperates with the equalization capacitor, so that only the energy transfer inside the battery pack is required during the battery cell equalization process, and there is no need to exchange energy with the external circuit. While improving the equalization efficiency, the equalization effect is ensured, and the problem of repeated equalization is avoided. In addition, after obtaining the static voltage data to obtain the SOC value of the battery cell, the process of performing charge / discharge equalization on the battery cell can be full-time equalization. Whether the battery pack is in the charging condition, discharging condition or stationary condition, equalization can be performed; for the charging condition or discharging condition, it can be the front end, middle end or end of charge / discharge. Description of the Drawings

[0020] One or more embodiments are exemplarily illustrated by corresponding drawings. These exemplary illustrations do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, unless otherwise stated. The figures in the drawings do not constitute a scale limitation.

[0021] Figure 1 It is a schematic structural diagram of a series battery cell equalization circuit provided by an embodiment of the present application;

[0022] Figure 2 It is a schematic flowchart of a series battery cell equalization method provided by an embodiment of the present application;

[0023] Figure 3 It is a schematic flowchart of a method for determining the equalization time of a target battery cell provided by an embodiment of the present application;

[0024] Figure 4 It is an example diagram of a battery cell OCV-SOC curve provided by an embodiment of the present application;

[0025] Figure 5 It is an example chart of the charging SOC value and discharging SOC value of a target battery cell provided by an embodiment of the present application;

[0026] Figure 6 It is an example chart of the charging SOC difference and discharging SOC difference of a target battery cell provided by an embodiment of the present application;

[0027] Figure 7 It is an example flowchart of a battery cell equalization process provided by an embodiment of the present application;

[0028] Figure 8 It is a schematic structural diagram of a series battery cell equalization device provided by an embodiment of the present application;

[0029] Figure 9 It is a schematic structural diagram of an electronic device provided by an embodiment of the present application. Detailed implementation manners

[0030] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0031] It should be noted that if there is no conflict, the various features in the embodiments of the present application can be combined with each other, and all are within the protection scope of the present application. In addition, although the functional modules are divided in the device schematic diagram and the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different module division from that in the device schematic diagram or a different order from that in the flowchart. Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not used to limit the present application. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0032] An embodiment of the present application provides a series balancing circuit. Please refer to Figure 1 , the series balancing circuit includes a balancing capacitor, a transformer, and a battery pack composed of at least two battery cells connected in series. As Figure 1 shown, C1 represents the balancing capacitor, T1 represents the transformer, and BT1, BT2, BT3... BTn represent the n battery cells in the battery pack. Each battery cell is connected with a corresponding cell switch and is connected in parallel with the balancing capacitor C1 through the corresponding cell switch. Figure 1 In Figure 1 shown, DPDT1, DPDT2, DPDT3... DPDTn respectively represent the cell switches corresponding to the n battery cells. The primary side of the transformer is connected in parallel with the balancing capacitor C1 through the first control switch, and the secondary side of the transformer is connected in parallel with both ends of the battery pack through the second control switch. As Figure 1 shown, DPDT_C represents the first control switch, and DPDT_DC represents the second control switch. Based on this circuit, when any one of the cell switches is turned on (the first control switch and the second control switch are turned off), the corresponding battery cell can form a charging or discharging loop with the balancing capacitor C1 based on the cell switch, realizing the energy transfer between the corresponding battery cell and the balancing capacitor C1; when the first control switch and the second control switch are turned on (the cell switches are turned off), the battery pack forms a charging or discharging loop with the balancing capacitor C1 through the transformer, realizing the energy transfer between the battery pack and the balancing capacitor C1. It can be understood that the switching devices in the above circuit can be any devices with a switching function, and the present solution does not limit their types. For example, it can be a double-pole double-throw switch as Figure 1 shown, or it can also be a MOSFET serving as a switching tube, etc.

[0033] In addition to being connected to the balancing circuit, the above battery pack can also be connected to an external circuit, which may include an external power source, an external load, an external charging switch, and an external discharging switch. By opening and closing the external charging switch and the external discharging switch, the real-time operating state of the battery pack can be controlled and the operating condition of the battery pack can be determined. When the external charging switch is closed, the external power source can charge the battery pack, and the battery pack is in the charging condition. When the external discharging switch is closed, the battery pack can supply power to the external load, and the battery pack is in the discharging condition. When both the external discharging switch and the external charging switch are open, it means that the battery pack is in the static condition.

[0034] Based on the above series balancing circuit, an embodiment of the present application provides a series cell balancing method. Please refer to Figure 2 , and the series cell balancing method includes:

[0035] S11. Read the static cell voltage of the cell.

[0036] The static cell voltage refers to the voltage across the cell measured without an external load (i.e., without charging or discharging). The method for obtaining the static cell voltage varies depending on the operating condition of the battery pack. The operating condition of the battery pack refers to the real-time operating state of the battery pack connected to the external circuit, including charging, discharging, and static. When the battery pack is in the static state, the voltage of each cell can be directly sampled to obtain the static cell voltage of each cell. When the battery pack is in the charging or discharging state, the terminal voltage of each cell needs to be sampled and further calculated to obtain its open-circuit voltage (i.e., the static voltage). The methods for obtaining the open-circuit voltage from the terminal voltage include the voltage-time curve method, the mathematical model method (such as the equivalent circuit model), the look-up table method, etc.

[0037] For the above method of obtaining the static cell voltage, it is preferred to directly sample and obtain it when the battery pack is in the static state. The static time of the battery module / cell can be obtained by real-time sampling. It is preferred to sample the static cell voltage after the static time is greater than 30 minutes. This is because when the battery pack / cell has just finished charging (especially at the end of charging), its voltage may be relatively high, but after a period of static, the voltage will gradually decrease and tend to be stable. Similarly, when the battery pack / cell has just finished discharging (especially at the end of discharging), its voltage may be relatively low, and after a period of static, the voltage will gradually increase and tend to be stable.

[0038] It can be understood that in some embodiments, the battery cells can also be numbered. After obtaining the cell voltages of each battery cell, the voltage values are associated with the corresponding cell numbers for easy distinction. When determining charge equalization or discharge equalization in subsequent steps, the cell numbers can be recorded to assist in planning the equalization sequence. For example, a battery pack includes 4 battery cells. Suppose the cell voltage of cell 1 is 3.7V and discharge equalization is required; the cell voltage of cell 2 is 3.4V and charge equalization is required; the cell voltage of cell 3 is 3.3V and charge equalization is required; the cell voltage of cell 4 is 3.8V and discharge equalization is required. Then in the subsequent equalization steps, discharge equalization can be performed on cell 1 and cell 4 in sequence according to the cell numbers, or charge equalization can be performed on cell 2 and cell 3 in sequence according to the cell numbers.

[0039] S12. Determine the target battery cells to be equalized according to the magnitude of the cell voltage.

[0040] In the embodiments of the present application, the target battery cells to be equalized include high-voltage battery cells that require discharge equalization and low-voltage battery cells that require charge equalization. Determining the high-voltage battery cells and low-voltage battery cells according to the magnitude of the cell voltage facilitates planning different equalization methods for battery cells at different voltage levels in the subsequent process, that is, charge equalization or discharge equalization, without the need to process all battery cells, thereby improving the cell equalization efficiency and reducing the total time required for equalization.

[0041] Specifically, all battery cells can be sorted according to the magnitude of the cell voltage. According to the sorting result, the high-voltage battery cells and low-voltage battery cells are determined from these battery cells. This solution can more easily locate the battery cells with the highest and lowest voltages, that is, the battery cells with the most unbalanced power in the battery pack, through sorting, so as to quickly determine the high-voltage battery cells and low-voltage battery cells that need to be equalized. In the embodiments of the present application, the number of high-voltage battery cells is equal to the number of low-voltage battery cells. For example, still taking the battery pack including cells 1-4 in the above example as an illustration, cells 1-4 are sorted according to the voltage magnitude. Assuming in ascending order, the sorting result is: cell 3 (3.3V), cell 2 (3.4V), cell 1 (3.7V), cell 4 (3.8V). On this basis, it can be planned that cell 3 and cell 2 are low-voltage battery cells and require charge equalization; cell 1 and cell 4 are high-voltage battery cells and require discharge equalization, thereby quickly and automatically determining the high-voltage battery cells and low-voltage battery cells, as well as the corresponding equalization methods.

[0042] In some embodiments, the specific logic for determining the high-voltage battery cells and low-voltage battery cells according to the sorting result can be as follows: Obtain the k battery cells with the highest voltage from the sorting result as the high-voltage battery cells, and obtain the k battery cells with the lowest voltage from the sorting result as the low-voltage battery cells, where k is a positive integer less than n / 2, and n is the total number of battery cells included in the battery pack. By setting the value of k in this solution, the number of battery cells that need to be balanced can be flexibly determined according to the actual usage environment and the characteristics of the battery pack. For example, assume that in the current scenario, a high requirement for the consistency of the battery cell power is required, such as a very strict requirement for the power difference between the battery cells in the battery pack, or a relatively low requirement for the balancing time. Then, a relatively large k value, such as close to n / 2, can be set to facilitate the subsequent balancing of the power of most battery cells to the required power range. If, in the current scenario, the requirement for the consistency of the battery cell power is relatively low, or the requirement for the balancing time is relatively high, such as the need to complete the power balancing of the battery cells in a relatively short time, then a relatively small k value can be set. Combining the sorting result, only a small number of battery cells with the most unbalanced power are balanced, and it is not necessary to process all the battery cells, achieving the effect of fast balancing and improving the balancing efficiency.

[0043] S13. Determine the balancing time corresponding to the target battery cell according to the voltage of the battery cell.

[0044] After determining the target battery cells that need to be balanced, by calculating the balancing time corresponding to the target battery cells and performing corresponding balancing processing according to the balancing time, the safety risk caused by excessive voltage difference between the battery cells in the battery pack can be reduced. Please refer to Figure 3 , and this step specifically includes:

[0045] S131. Determine a charging reference value and a discharging reference value based on all the cell voltages. In the embodiments of the present application, the charging reference value and the discharging reference value are used as reference values for balancing control, which can reflect the overall state of the battery pack and facilitate the subsequent calculation of the balancing time of the target cell. In the embodiments of the present application, the median value of all the cell voltages can be obtained as the median voltage; then, the charging state of charge value corresponding to the median voltage is obtained as the charging reference value, and the discharging state of charge value corresponding to the median voltage is obtained as the discharging reference value. Among them, the state of charge value (SOC) represents the ratio of the remaining power of the cell to the total capacity, usually expressed as a percentage. On this basis, the charging state of charge value corresponding to the median voltage refers to the SOC corresponding to the median voltage during the charging process; the discharging state of charge value corresponding to the median voltage refers to the SOC corresponding to the median voltage during the discharging process. The median voltage, as the center point of the cell voltage distribution, can better represent the average level of the cell voltages in the entire battery pack. Even if there are abnormal voltages in individual cells, it will not have too much impact on the overall reference value and can reflect the overall state of the battery pack. In addition, combined with the sorting result in the foregoing steps, the median value of all the cell voltages can be directly determined as the median voltage according to the sorting result, which simplifies the calculation process, reduces the calculation complexity and system resource consumption. Therefore, using the charging state of charge value (charging reference value) and the discharging state of charge value (discharging reference value) corresponding to the median voltage as the reference for balancing control can improve the balancing efficiency of the cells.

[0046] In some other embodiments, the average value of all the cell voltages can also be obtained as the average voltage; then, the charging state of charge value corresponding to the average voltage is obtained as the charging reference value, and the discharging state of charge value corresponding to the average voltage is obtained as the discharging reference value. It can be understood that whether it is the median voltage or the average voltage, they are both used to reflect the overall voltage state of the battery pack. In different usage scenarios, the appropriate calculation method can be selected according to the actual environment.

[0047] S132. Obtain the charging state of charge value corresponding to the cell voltage of the target cell as the charging SOC value, and obtain the discharging state of charge value corresponding to the cell voltage of the target cell as the discharging SOC value. Generally, during the charging or discharging process of a cell, the OCV value (Open Circuit Voltage) of the cell has a corresponding SOC value. Please refer to Figure 4 , Figure 4It is an example diagram of the OCV-SOC curve corresponding to a certain battery cell under the charging condition at 25°C and the discharging condition at 25°C. The test method of this OCV-SOC curve can be Hybrid Pulse Power Characterization (HPPC) test. In the figure, the abscissa represents the SOC value, and the values 20, 40, 60, 80, and 100 shown represent the percentage values of the SOC value. For example, 20 in the figure represents that the SOC value is 20%; the ordinate in the figure represents the OCV value. For example, 3.3 in the figure represents that the OCV value is 3.3V. In this solution, the battery cell voltage of the battery cell is used as the OCV value for calculation, that is, 3.3 in the figure also represents that the battery cell voltage is 3.3V. According to this OCV-SOC curve, the corresponding charging SOC value and discharging SOC value of the target battery cell can be determined according to the battery cell voltage of the target battery cell. It can be understood that the above method of obtaining the charging SOC value and discharging SOC value of the target battery cell using the OCV-SOC curve is only an example of an implementation manner provided in the embodiments of the present application. In some other embodiments, the charging SOC value and discharging SOC value of the target battery cell can also be obtained according to the charging OCV-SOC table and discharging OCV-SOC table corresponding to the battery cell, or other reasonable methods. That is, this solution protects the technical concept of determining the charging SOC value and discharging SOC value of the target battery cell according to the battery cell voltage, but does not limit its specific obtaining method.

[0048] S133. Calculate the absolute value of the difference between the charging SOC value of the target battery cell and the charging reference value as the charging SOC difference value of the target battery cell, and calculate the absolute value of the difference between the discharging SOC value of the target battery cell and the discharging reference value as the discharging SOC difference value of the target battery cell. It can be understood that in the embodiments of the present application, for the charging SOC difference value and discharging SOC difference value of the target battery cell, only the numerical value is considered, and the positive and negative are not considered. The difference value is calculated by taking the absolute value, directly quantifying the deviation degree between the charging / discharging SOC value corresponding to the target battery cell and the charging / discharging reference value.

[0049] S134. Determine the final value of the SOC difference of the target battery cell according to the charging SOC difference value and the discharging SOC difference value. In the embodiments of the present application, after obtaining the charging SOC difference value and discharging SOC difference value of the target battery cell, select the one with a relatively smaller numerical value as the final value of the SOC difference of the target battery cell. As a conservative evaluation of the target battery cell, it helps to reserve some safety margins during balancing, indirectly reducing the time required for balancing and improving the balancing efficiency.

[0050] In the embodiments of the present application, specific examples are given for illustration. For example, a battery pack contains 26 battery cells, that is, n = 26, which are numbered with letters from A to Z respectively. All the battery cells are sorted according to the cell voltage. Assuming k = 4, the group with the highest voltage is obtained from the sorting result, High = [3.8, 3.7, 3.7, 3.6]. Assuming they are battery cell A (3.8V), battery cell B (3.7V), battery cell D (3.7V), and battery cell Q (3.6V) respectively, these 4 battery cells are high-voltage battery cells; the group with the lowest voltage is obtained from the sorting result, Low = [3.0, 3.1, 3.2, 3.2]. Assuming they are battery cell L (3.0V), battery cell M (3.1V), battery cell P (3.2V), and battery cell S (3.2V) respectively, these 4 battery cells are low-voltage battery cells. Thus, the cell numbers of the 8 battery cells to be balanced and the corresponding cell voltages can be quickly determined. For the obtained cell voltages, according to the above steps S131 and S132, the corresponding charging SOC values and discharging SOC values are obtained respectively. Please refer to Figure 5 , for example, the corresponding charging SOC value and discharging SOC value are obtained through the charging OCV-SOC table and the discharging OCV-SOC table as Figure 5 shown. In the figure, high represents high-voltage battery cells, low represents low-voltage battery cells, and medium represents the median voltage. The charging SOC value corresponding to the median voltage is the charging reference value, and the discharging SOC value corresponding to the median voltage represents the discharging reference value. For the obtained charging SOC value and discharging SOC value, according to the above steps S133 and S134, in combination with the charging reference value and the discharging reference value, the final value of the SOC difference of the target battery cell is determined. Please combine Figure 6 , subtract the charging SOC value of the target battery cell from the charging reference value and take the absolute value as the charging SOC difference of the target battery cell, and subtract the discharging SOC value of the target battery cell from the discharging reference value and take the absolute value as the discharging SOC difference of the target battery cell; then select the smaller value of the two as the final value of the SOC difference of the target battery cell. It can be understood that only the numerical magnitude is considered in the above calculation process, without considering the positive or negative, that is, take the absolute value after subtracting from the reference value.

[0051] S135. Calculate the equalization time of the target battery cell according to the final value of the SOC difference. In the embodiment of the present application, by obtaining the battery cell capacity and the equalization current, the equalization time corresponding to the target battery cell is calculated according to the calculation formula "equalization time T = final value of SOC difference * battery cell capacity Cap / equalization current I". For example, assume that the final value of the SOC difference of a certain target battery cell is 5%, the battery cell capacity is 100 Ah, and the equalization current is 5 A. Then the equalization time Time of this target battery cell = 0.05 * 100 / 5 = 1, and the calculation result is 1 h. This solution calculates the equalization time by using the final value of the SOC difference, the battery cell capacity, and the equalization current, which can achieve precise control of the equalization process, help adjust the target battery cell to reach the expected state during the equalization process, and thus improve the overall performance and battery cell consistency of the battery pack.

[0052] S14. Perform charge / discharge equalization on the target battery cell according to the equalization time to equalize the battery cells in the battery pack. In the embodiment of the present application, according to the equalization time, in combination with the equalization capacitor, by controlling the on / off of the battery cell switch, the first control switch, and the second control switch, based on the preset equalization logic, perform discharge equalization on the high-voltage battery cell, or perform charge equalization on the low-voltage battery cell. Based on the above series battery cell equalization circuit, by changing the on / off state of each switch, the energy transfer between the target battery cell and the equalization capacitor, or between the battery pack and the equalization capacitor is realized. Utilizing the energy storage function of the equalization capacitor, perform discharge equalization on the high-voltage battery cell and charge equalization on the low-voltage battery cell to improve the consistency of the battery cells in the battery pack.

[0053] In some embodiments, the above method further includes: after the current target battery cell completes equalization, obtain the next target battery cell that needs to be equalized, and perform equalization on the next target battery cell until there is no next target battery cell that needs to be equalized, or an interrupt command is triggered. This solution can equalize all target battery cells in the battery pack by means of cyclic equalization to achieve the equalization of the entire battery pack, improving the overall performance and consistency of the battery pack. In addition, this solution is applicable to battery packs composed of multiple series-connected battery cells, and is not limited by the type and number of battery cells, having strong adaptability and scalability.

[0054] Among them, the preset equalization logic includes:

[0055] a. Control the battery cell switch corresponding to the high-voltage battery cell to conduct, and control the first control switch and the second control switch to disconnect, so as to perform discharge equalization on the high-voltage battery cell according to the equalization time, and update the equalization time in real time until the equalization time is zero, or the equalization capacitor is fully charged. The above equalization logic a corresponds to the stage of controlling the high-voltage battery cell to discharge to the equalization capacitor. When the equalization capacitor can be charged, perform discharge equalization on the high-voltage battery cell.

[0056] b. Control the cell switch corresponding to the low-voltage cell to conduct, and control the first control switch and the second control switch to disconnect, so as to perform charge equalization on the low-voltage cell according to the equalization time, and update the equalization time in real time until the equalization time is zero or the equalization capacitor is discharged. The above equalization logic b corresponds to the stage of controlling the equalization capacitor to charge the low-voltage cell. When the equalization capacitor can discharge, charge equalization is performed on the low-voltage cell.

[0057] Combined with the above equalization logic, it is possible to perform discharge equalization on the high-voltage cells respectively and charge equalization on the low-voltage cells, so that the cells in the battery pack are balanced.

[0058] In some embodiments, the preset equalization logic further includes:

[0059] c. Control the first control switch and the second control switch to conduct, and control all the cell switches to disconnect, so that the equalization capacitor charges the battery pack until the equalization capacitor is discharged. After the equalization capacitor is fully charged, it cannot continue to provide discharge equalization for the high-voltage cells. The above equalization logic c corresponds to the stage of controlling the equalization capacitor to discharge to the battery pack. After the discharge is completed, the equalization capacitor can continue to provide discharge equalization for the high-voltage cells.

[0060] d. Control the first control switch and the second control switch to conduct, and control all the cell switches to disconnect, so that the battery pack charges the equalization capacitor until the equalization capacitor is fully charged. After the equalization capacitor is discharged, it cannot continue to provide charge equalization for the low-voltage cells. The above equalization logic d corresponds to the stage of controlling the battery pack to charge the equalization capacitor. After the charging is completed, the equalization capacitor can continue to provide charge equalization for the low-voltage cells.

[0061] Combined with the above equalization logic, it can ensure that the equalization process of the target cell will not be stuck due to the power of the equalization capacitor, ensuring the safety of the cell equalization process.

[0062] In some embodiments, the preset equalization logic further includes:

[0063] e. When the cell equalization is not triggered, control the first control switch, the second control, and all the cell switches to maintain the disconnected state to maintain the initialization state. When there is no need to equalize the cells, controlling all the switches in the series cell equalization circuit to disconnect can reduce energy loss and improve the safety of the circuit. It can be understood that before equalizing the target cell, that is, in the initial state, controlling all the switches in the circuit to maintain the disconnected state ensures that the circuit will not accidentally start the equalization process without equalization requirements, thus maintaining a relatively safe and stable initialization state.

[0064] f. When the interrupt command is triggered, the first control switch, the second control switch and all the cell switches are controlled to be disconnected, and the cell balancing is interrupted. When the user needs to stop the balancing process, he can actively exit from the balancing process by triggering the interrupt command, which optimizes the user experience. In addition, at any stage of the balancing process, there will not be two or more cell switches turned on at the same time. When the balancing process needs to be interrupted, all switches in the circuit can be directly disconnected at any time without causing damage to the circuit.

[0065] g. After completing the balancing of all the target cells, the first control switch, the second control switch and all the cell switches are controlled to be disconnected to terminate the cell balancing. After all the target cells are balanced, the consistency of the cells in the battery pack is relatively high, the balancing process is terminated and all switches in the circuit are controlled to be disconnected to ensure the integrity and controllability of the balancing process and avoid unnecessary energy loss and possible system misoperation.

[0066] Based on the above preset balancing logic, the present application embodiment provides an example of a cell balancing process and describes it based on the example. Figure 7 , according to the above-mentioned series cell balancing method, the target cell and its balancing time are determined, and the balancing process is triggered to start. In this example, it is set to process the high-voltage cell first and then the low-voltage cell. The discharge balancing is carried out in sequence according to the number of the high-voltage cell, and the corresponding balancing time is updated in real time in the balancing process of each high-voltage cell. In this stage, it is detected whether the balancing capacitor is full. If it is not full, the discharge balancing of all high-voltage cells can be completed in sequence; if the balancing capacitor is fully charged in the middle, the balancing capacitor is triggered to discharge to the battery pack. After the discharge is completed, the target cell and its balancing time are determined again according to the above method, and the balancing process is re-entered. When all high-voltage cells have completed the discharge balancing, the charging balancing stage of the low-voltage cell is entered. The charging balancing is carried out in sequence according to the number of the low-voltage cell, and the corresponding balancing time is updated in real time in the balancing process of each low-voltage cell. In this stage, it is detected whether the balancing capacitor is empty. If it is not empty, the charging balancing of all low-voltage cells can be completed in sequence; if the balancing capacitor is empty in the middle, the battery pack is triggered to charge the balancing capacitor. After the charging is completed, the target cell and its balancing time are determined again according to the above method, and the balancing process is re-entered. Since the logic in this example is to process high-voltage cells first and then low-voltage cells, when all low-voltage cells are balanced, it means that all target cells have been balanced, that is, the cell balancing process of the current battery pack is completed and the balancing process ends. In addition, at any time during the entire balancing process, if an interrupt instruction is triggered, all switches in the circuit will be immediately disconnected to interrupt the cell balancing process.

[0067] It should be noted that the above-mentioned charge / discharge balance is based on Figure 1It is implemented by the equalization circuit represented by the solid line part in the figure; and the equalization can be performed under any working condition, that is, the real-time operating state of the battery pack connected to the external circuit can be any one of charging, discharging, and standing still; and for charging or discharging, whether it is the front end, middle end, or end of the charge / discharge, it can be performed.

[0068] The series battery cell equalization method provided by the embodiment of the present application is applied to a series battery cell equalization circuit. This method reads the static battery cell voltage of the battery cells, then determines the target battery cells that need to be equalized according to the magnitude of the battery cell voltage, and determines the equalization time corresponding to the target battery cells according to the battery cell voltage. Then, charge / discharge equalization is performed on the target battery cells according to the equalization time to equalize the battery cells in the battery pack. This solution determines the SOC data corresponding to the charge / discharge according to the magnitude of the static voltage, calculates the equalization time of the target battery cells based on this, and then controls the on / off of each switch and cooperates with the equalization capacitor, so that only the energy transfer inside the battery pack can occur during the battery cell equalization process, and there is no need to exchange energy with the external circuit. While improving the equalization efficiency, the equalization effect is ensured. In addition, the problem of repeated equalization can be avoided. And the process of performing charge / discharge equalization on the battery cells can be full-time equalization, and equalization can be performed regardless of whether the battery pack is in a charging working condition, a discharging working condition, or a standing still working condition; for the charging working condition or the discharging working condition, it can be the front end, middle end, or end of the charge / discharge.

[0069] Please refer to Figure 8 , the embodiment of the present application provides a series battery cell equalization device, as Figure 8 shown. The series battery cell equalization device 200 includes a battery cell voltage acquisition module 201, a target battery cell determination module 202, an equalization time determination module 203, and a battery cell equalization control module 204. Specifically, the battery cell voltage acquisition module 201 can read the static battery cell voltage of the battery cells; the target battery cell determination module 202 can determine the target battery cells that need to be equalized according to the magnitude of the battery cell voltage; the equalization time determination module 203 can determine the equalization time corresponding to the target battery cells according to the battery cell voltage; the battery cell equalization control module 204 can perform charge / discharge equalization on the target battery cells according to the equalization time to equalize the battery cells in the battery pack.

[0070] It should be noted that the above-mentioned series battery cell equalization device can execute the series battery cell equalization method provided by the embodiment of the present application, and has the corresponding functional modules and beneficial effects for executing the method. For the technical details not described in detail in the embodiment of the series battery cell equalization device, reference can be made to the series battery cell equalization method provided by the embodiment of the present application.

[0071] The embodiment of the present application provides an electronic device, as Figure 9 shown. The electronic device 300 includes: one or more processors 301 and a memory 302,Figure 9 Take a processor 301 as an example.

[0072] The processor 301 and the memory 302 can be connected through a bus or other means. Figure 9 Take the connection through the bus as an example.

[0073] The memory 302, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs, non-volatile computer-executable programs, and modules, such as the program instructions / modules corresponding to the series cell balancing method in the embodiments of the present invention. The processor 301 executes various functional applications and data processing of the solid-state drive by running the non-volatile software programs, instructions, and modules stored in the memory 302, that is, implements the series cell balancing method in the above method embodiments.

[0074] The memory 302 can include a program storage area and a data storage area. Among them, the program storage area can store an operating system and application programs required for at least one function. In addition, the memory 302 can include high-speed random access memory and can also include non-volatile memory, such as at least one magnetic disk storage device, a flash memory device, or other non-volatile solid-state storage devices. In some embodiments, the memory 302 may optionally include a memory remotely set relative to the processor 301.

[0075] The one or more modules are stored in the memory 302 and, when executed by the one or more processors 301, execute the series cell balancing method in any of the above method embodiments. For example, execute the Figure 2 , Figure 3 method steps described above.

[0076] The above product can execute the series cell balancing method provided by the embodiments of the present invention and has functional modules corresponding to the execution method. For technical details not described in detail in this embodiment, reference can be made to the series cell balancing method provided by the embodiments of the present invention.

[0077] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0078] Through the description of the above embodiments, those of ordinary skill in the art can clearly understand that each embodiment can be implemented by means of software plus a general hardware platform, and of course, it can also be implemented by hardware. Those of ordinary skill in the art can understand that all or part of the processes in the above-described method for implementing the embodiments can be completed by instructing relevant hardware through a computer program. The program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the above-described method embodiments. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM), etc.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; under the idea of the present application, the technical features in the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order, and there are many other changes in different aspects of the present application as described above. For the sake of brevity, they are not provided in detail; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for balancing series cells, applied to a balancing circuit for series cells, characterized in that: The circuit includes a balancing capacitor, a transformer, and a battery pack consisting of at least two battery cells connected in series, each battery cell is connected to a corresponding battery cell switch, and is connected in parallel with the balancing capacitor through the corresponding battery cell switch, the primary side of the transformer is connected in parallel with the balancing capacitor through a first control switch, and the secondary side of the transformer is connected in parallel with two ends of the battery pack through a second control switch, and the method includes: Reading the static cell voltage of the cell; Determining a target battery cell that needs to be balanced according to the voltage of the battery cell; Determine the balancing time corresponding to the target battery cell according to the battery cell voltage; Performing charge / discharge balancing on the target battery cell according to the balancing time to balance the battery cells in the battery pack; Wherein, determining the balancing time corresponding to the target battery cell according to the battery cell voltage further includes: Determine a charging reference value and a discharging reference value according to the voltages of all the battery cells; Obtaining a charging state of charge value corresponding to the cell voltage of the target cell as a charging SOC value, and obtaining a discharging state of charge value corresponding to the cell voltage of the target cell as a discharging SOC value; Calculating the absolute value of the difference between the charging SOC value of the target battery cell and the charging reference value as the charging SOC difference of the target battery cell, and calculating the absolute value of the difference between the discharging SOC value of the target battery cell and the discharging reference value as the discharging SOC difference of the target battery cell; Determining a final SOC difference value of the target battery cell according to the charging SOC difference value and the discharging SOC difference value; The balancing time of the target battery cell is calculated according to the final value of the SOC difference.

2. The method according to claim 1, characterized in that: The target cells that need to be balanced include high-voltage cells that need to be discharged and balanced and low-voltage cells that need to be charged and balanced; determining the target cells that need to be balanced according to the voltage of the cell voltages includes: The high voltage battery cell and the low voltage battery cell are determined according to the voltage magnitude of the battery cell voltage.

3. The method according to claim 2, characterized in that Determining a high voltage cell and a low voltage cell according to the voltage of the cell voltage includes: Sorting the battery cells according to the voltage magnitudes of the battery cells; The high-voltage battery cells and the low-voltage battery cells are determined from the battery cells according to the sorting result, wherein the number of the high-voltage battery cells is equal to the number of the low-voltage battery cells.

4. The method according to claim 3, characterized in that Determining the high voltage battery cell and the low voltage battery cell from the battery cells according to the sorting result includes: The k battery cells with the largest voltages obtained from the sorting results are high-voltage battery cells, and the k battery cells with the smallest voltages obtained from the sorting results are low-voltage battery cells, wherein k is a positive integer less than n / 2, and n is the total number of battery cells in the battery pack.

5. The method according to claim 1, characterized in that Determining a charging reference value and a discharging reference value according to all the cell voltages includes: Obtaining a median value of all the cell voltages as a median voltage; A charging state of charge value corresponding to the median voltage is obtained as a charging reference value, and a discharging state of charge value corresponding to the median voltage is obtained as a discharging reference value.

6. The method according to claim 1, characterized in that Determining a final SOC difference value of the target battery cell according to the charging SOC difference value and the discharging SOC difference value includes: The smaller value between the charging SOC difference and the discharging SOC difference is obtained as the final SOC difference value of the target battery cell.

7. The method according to claim 1, characterized in that Calculating the balancing time of the target battery cell according to the final value of the SOC difference includes: Obtain cell capacity and balancing current; Calculate the target cell’s balancing time according to the following formula: Balancing time T = SOC difference final value * cell capacity Cap / balancing current I.

8. The method according to claim 2, characterized in that: The method further comprises: performing charge / discharge balancing on the target battery cell according to the balancing time so as to balance the battery cells in the battery pack, comprising: According to the balancing time, in combination with the balancing capacitor, by controlling the on / off of the cell switch, the first control switch and the second control switch, based on a preset balancing logic, the high voltage cell is discharged and balanced, or the low voltage cell is charged and balanced, wherein the preset balancing logic includes: Control the cell switch corresponding to the high-voltage cell to be turned on, and control the first control switch and the second control switch to be turned off, so as to discharge and balance the high-voltage cell according to the balancing time, and update the balancing time in real time until the balancing time is zero, or the balancing capacitor is fully charged; The cell switch corresponding to the low-voltage cell is controlled to be turned on, and the first control switch and the second control switch are controlled to be turned off, so as to charge and balance the low-voltage cell according to the balancing time, and update the balancing time in real time until the balancing time is zero or the balancing capacitor is discharged.

9. The method according to claim 8, characterized in that The preset balancing logic also includes: Controlling the first control switch and the second control switch to be turned on, and controlling all the cell switches to be turned off, so that the equalizing capacitor charges the battery pack until the equalizing capacitor is discharged; The first control switch and the second control switch are controlled to be turned on, and all the cell switches are controlled to be turned off, so that the battery pack charges the equalizing capacitor until the equalizing capacitor is fully charged.

10. The method according to claim 8, characterized in that The preset balancing logic also includes: When cell balancing is not triggered, controlling the first control switch, the second control switch and all cell switches to remain in an off state to maintain an initialization state; When the interrupt command is triggered, the first control switch, the second control switch and all the cell switches are controlled to be disconnected, so as to interrupt the cell balancing; After completing the balancing of all the target cells, the first control switch, the second control switch and all the cell switches are controlled to be turned off, thereby terminating the cell balancing.

11. The method according to claim 8, characterized in that The target battery cell is charged / discharged for equalization according to the equalization time so as to make the battery cells in the battery pack equalized, and further comprising: After the current target cell is balanced, the next target cell that needs to be balanced is obtained, and the next target cell is balanced until there is no next target cell that needs to be balanced, or an interrupt command is triggered.

12. A series cell balancing device, characterized in that: include: A cell voltage acquisition module, used for reading the static cell voltage of the cell; A target cell determination module, used to determine a target cell that needs to be balanced according to the voltage of the cell voltage; A balancing time determination module, used to determine the balancing time corresponding to the target battery cell according to the battery cell voltage; A cell balancing control module, used for performing charge / discharge balancing on the target cell according to the balancing time, so as to balance the cells in the battery pack; Wherein, the equalization time determination module is further used for: Determine a charging reference value and a discharging reference value according to the voltages of all the battery cells; Obtaining a charging state of charge value corresponding to the cell voltage of the target cell as a charging SOC value, and obtaining a discharging state of charge value corresponding to the cell voltage of the target cell as a discharging SOC value; Calculating the absolute value of the difference between the charging SOC value of the target battery cell and the charging reference value as the charging SOC difference of the target battery cell, and calculating the absolute value of the difference between the discharging SOC value of the target battery cell and the discharging reference value as the discharging SOC difference of the target battery cell; Determining a final SOC difference value of the target battery cell according to the charging SOC difference value and the discharging SOC difference value; The balancing time of the target battery cell is calculated according to the final value of the SOC difference.

13. An electronic device, characterized in that: include: at least one processor and memory; The memory is coupled to the processor, and the memory is used to store instructions or programs. When the instructions or programs are executed by the at least one processor, the at least one processor executes the series battery cell balancing method as described in any one of claims 1 to 11.

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