Battery cell voltage balance control method and system

Abstract

The invention provides a cell voltage balance control method and system, and the method comprises the steps: collecting the voltage of each cell, and calculating a voltage maximum value, a voltage minimum value, and a voltage average value; judging whether a first voltage difference value between the voltage maximum value and the voltage average value is greater than a first voltage threshold value or not; if the voltage difference value is greater than the first voltage threshold value, further judging whether a second voltage difference value between the voltage of each battery cell and the voltage average value is greater than a balance starting voltage difference or not; if the voltage difference value is smaller than or equal to the first voltage threshold value, whether the voltage minimum value is larger than the balance starting voltage or not is judged, and whether the difference value between the voltage of each battery cell and the voltage minimum value is larger than the balance starting voltage difference or not is judged; according to the battery cell voltage equalization control method and system provided by the invention, the equalization effect can be improved, and the performance of the battery can be improved.

Description

Technical Field

[0001] The present application mainly relates to the field of battery technology, and in particular to a method and system for balancing control of battery cell voltage. Background Art

[0002] Battery cells are naturally inconsistent due to differences in manufacturing and use processes. The inconsistency of battery cells will further deteriorate over time under the influence of random factors such as temperature and vibration conditions. Although the trend cannot be reversed, intervention can be made to reduce the rate of deterioration. In this field, battery management systems are generally used to balance the cells to achieve the purpose of intervention. There are two forms of balancing: active balancing and passive balancing. Passive balancing mainly discharges the power of high-voltage lithium batteries in the form of heat. Therefore, the heat generated by passive balancing needs to be dissipated. Since lithium batteries are more sensitive to heat, it is necessary to avoid external temperature increases. The heat generated by passive balancing will cause local heating of the battery and increase the failure rate of components.

[0003] The passive balancing method currently used in the field does not take into account the active heat dissipation of the BMS circuit board when the balancing is turned on for a long time. As a result, the number of cells that are balanced at the same time will affect the temperature. When the temperature exceeds the threshold, the balancing ability will decrease and the failure rate of components will increase, resulting in the balancing effect being less than expected and the balancing effect being average. Summary of the invention

[0004] The technical problem to be solved by the present application is to provide a method and system for balancing control of battery cell voltage, which can improve the balancing effect and help improve the performance of the battery.

[0005] In order to solve the above technical problems, the present application provides a method for balancing the voltage of a battery cell, comprising the following steps: collecting the voltage of each battery cell, and calculating the maximum voltage, the minimum voltage and the average voltage; judging whether a first voltage difference between the maximum voltage and the average voltage is greater than a first voltage threshold; if the voltage difference is greater than the first voltage threshold, further judging whether a second voltage difference between the voltage of each battery cell and the average voltage is greater than a balancing start-up voltage difference; if the judgment result is yes, judging that the battery cell needs to be balanced, and recording the number of balanced cells; if the judgment result is no, judging that the battery cell does not need to be balanced; if the voltage difference is less than or equal to the first voltage threshold, judging whether the minimum voltage is greater than the balancing start-up voltage, and judging whether the difference between the voltage of each battery cell and the minimum voltage is greater than the balancing start-up voltage difference; if the judgment results are all yes, judging that the battery cell needs to be balanced, and recording the number of balanced cells; if any judgment result is no, judging that the battery cell does not need to be balanced.

[0006] Optionally, the control method further comprises sending a start balancing instruction to start a balancing mode if it is determined that the battery cell needs balancing, and sending a stop balancing instruction if it is determined that the battery cell does not need balancing.

[0007] Optionally, the control method further includes acquiring the cell temperature of each of the cell and the board temperature of the BMS board through a temperature acquisition module.

[0008] Optionally, the control method also includes sending an instruction that PWM is a first percentage if the balanced number is 0; sending an instruction that PWM is a second percentage if the balanced number is less than or equal to the first percentage of the total number of battery cells; sending an instruction that PWM is the second percentage if the balanced number is greater than the first percentage of the total number of battery cells and less than or equal to the second percentage of the total number of battery cells, and the battery cell temperature is less than or equal to a first temperature threshold; sending an instruction that PWM is a third percentage and sending an instruction to turn on the battery cell fan if the balanced number is greater than the first percentage of the total number of battery cells and less than or equal to the second percentage of the total number of battery cells, and the battery cell temperature is greater than the first temperature threshold, and sending an instruction that PWM is a third percentage and sending an instruction to turn on the battery cell fan, and if the onboard temperature is greater than the onboard temperature threshold at this time, sending an instruction to turn on the onboard fan; if the balanced number is greater than the second percentage of the total number of battery cells, directly sending an instruction to turn on the battery cell fan and sending an instruction to turn on the onboard fan.

[0009] Optionally, the control method also includes, when the balanced number is greater than the second proportion of the total number of battery cells, determining whether the battery cell temperature exceeds a second temperature threshold; if the determination result is yes, sending an instruction for PWM to be a fourth percentage, wherein the second temperature threshold is greater than the first temperature threshold.

[0010] Optionally, the battery core fan includes five working modes, wherein, when the battery core temperature is greater than a first temperature threshold, the output power of the battery core fan is 0% to 20%; when the battery core temperature is greater than a second temperature threshold, the output power of the battery core fan is 21% to 40%; when the battery core temperature is greater than a third temperature threshold, the output power of the battery core fan is 41% to 60%; when the battery core temperature is greater than a fourth temperature threshold, the output power of the battery core fan is 61% to 80%; when the battery core temperature is greater than a fifth temperature threshold, the output power of the battery core fan is 81% to 100%.

[0011] Optionally, the onboard fan includes five working modes, wherein, when the onboard temperature is greater than a first temperature threshold, the output power of the onboard fan is 0% to 20%; when the onboard temperature is greater than a second temperature threshold, the output power of the onboard fan is 21% to 40%; when the onboard temperature is greater than a third temperature threshold, the output power of the onboard fan is 41% to 60%; when the onboard temperature is greater than a fourth temperature threshold, the output power of the onboard fan is 61% to 80%; when the onboard temperature is greater than a fifth temperature threshold, the output power of the onboard fan is 81% to 100%.

[0012] Optionally, the control method further includes recording the number of times the temperature acquisition module fails and retaining the previous output power of the fan, and when the number of failures exceeds a preset number, reporting the temperature acquisition module failure information.

[0013] In order to solve the above technical problems, the present application provides a cell voltage balancing control system, comprising: a voltage acquisition module, configured to collect the voltage of each cell; a processing center, configured to calculate the maximum voltage, the minimum voltage and the average voltage of all the cells, and determine whether a first voltage difference between the maximum voltage and the average voltage is greater than a first voltage threshold; if the voltage difference is greater than the first voltage threshold, then further determine whether a second voltage difference between the voltage of each cell and the average voltage is greater than a balancing start-up voltage difference; if the determination result is yes, then determine that the cell needs to be balanced, and record the number of balanced cells; if the determination result is no, then determine that the cell does not need to be balanced; if the voltage difference is less than or equal to the first voltage threshold, then determine whether the minimum voltage is greater than the balancing start-up voltage, and determine whether the difference between the voltage of each cell and the minimum voltage is greater than the balancing start-up voltage difference; if the determination results are all yes, then determine that the cell needs to be balanced, and record the number of balanced cells; if any determination result is no, then determine that the cell does not need to be balanced.

[0014] Optionally, the balancing control system further comprises a power management module, which is adapted to receive a start balancing instruction and a stop balancing instruction sent by the processing center, and to start the balancing mode according to the start balancing instruction and to stop the balancing mode according to the stop balancing instruction.

[0015] Optionally, the balancing control system further includes a temperature acquisition module, and the temperature acquisition module is suitable for acquiring the cell temperature of each of the cell and the onboard temperature of the BMS board.

[0016] Optionally, the balancing control system also includes a fault indication module. When the temperature acquisition module fails, the fault indication module records the number of faults and retains the previous output power of the fan. When the number of faults recorded by the fault indication module exceeds a preset number, the temperature acquisition module fault information is sent to the processing center.

[0017] Optionally, the balancing control system further includes a battery cell fan control module and an onboard fan control module, wherein the battery cell fan control module controls turning on and off the battery cell fan, and the onboard fan control module controls turning on and off the onboard fan.

[0018] Compared with the prior art, the present application determines whether the battery cell needs to be balanced by the battery cell voltage and records the number of battery cells that need to be balanced, which can effectively obtain relevant information about battery cell balancing and better balance the temperature of the battery cell during balancing. Furthermore, the present application also controls the heat dissipation of the battery cell by the battery cell temperature and the onboard temperature of the BMS board, and further controls the intensity of heat dissipation by controlling the duty cycle of the fan. The heat dissipation intensity can be flexibly adjusted according to the actual situation of balancing, which can improve the balancing effect of the battery cell, thereby further improving the performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are included to provide a further understanding of the present application. They are included and constitute a part of the present application. The accompanying drawings illustrate embodiments of the present application and together with the present specification serve to explain the principles of the present application. In the accompanying drawings:

[0020] Figure 1 It is a flow chart of a method for balancing the voltage of a battery cell in one embodiment of the present application;

[0021] Figure 2 It is a module schematic diagram of a cell voltage balancing control system in one embodiment of the present application;

[0022] Figure 3 to Figure 6 It is a logic flow diagram of a method for balancing the voltage of a battery cell in one embodiment of the present application. DETAILED DESCRIPTION

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0024] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0025] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0026] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0027] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0028] In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

[0029] This application refers to Figure 1 A method 10 for controlling the voltage balance of a battery cell (hereinafter referred to as "control method 10") is shown. A flowchart is used in the present application to illustrate the operations performed by the system according to an embodiment of the present application. It should be understood that the previous or following operations are not necessarily performed precisely in order. Instead, various steps may be processed in reverse order or simultaneously. At the same time, other operations may be added to these processes, or one or more operations may be removed from these processes. Specifically, control method 10 includes the following steps:

[0030] S1: Collect the voltage of each battery cell and calculate the maximum voltage, minimum voltage and average voltage;

[0031] S2: Determine whether a first voltage difference between a maximum voltage and an average voltage is greater than a first voltage threshold;

[0032] S3: If the voltage difference is greater than the first voltage threshold, further determine whether a second voltage difference between the voltage of each battery cell and the voltage average is greater than the equalization start voltage difference. If the determination result is yes, determine that the battery cell needs to be equalized, and record the number of equalizations. If the determination result is no, determine that the battery cell does not need to be equalized.

[0033] S4: If the voltage difference is less than or equal to the first voltage threshold, determine whether the minimum voltage is greater than the equalization start voltage, and determine whether the difference between the voltage of each battery cell and the minimum voltage is greater than the equalization start voltage difference. If the judgment results are all yes, it is determined that the battery cells need to be balanced, and the number of balanced cells is recorded. If any judgment result is no, it is determined that the battery cells do not need to be balanced.

[0034] In order to better implement the above control method, the present application also proposes a cell voltage balancing control system, which is applicable to the cell voltage balancing control method proposed in any embodiment of the present application, such as the above control method 10. Figure 2 , Figure 2 FIG. 1 is a block diagram of a cell voltage balancing control system 20 (hereinafter referred to as “control system 20”) suitable for the control method 10. Figure 2 to Figure 6 How to implement the control method 10 through the control system 20 will be described in detail.

[0035] Reference Figure 2 and Figure 3 The control system 20 mainly includes a voltage acquisition module and a processing center, wherein the voltage acquisition module is configured to collect the voltage of each battery cell, and the processing center is configured to calculate the maximum voltage, the minimum voltage and the average voltage of all battery cells, and determine whether a first voltage difference between the maximum voltage and the average voltage is greater than a first voltage threshold; if the voltage difference is greater than the first voltage threshold, then further determine whether a second voltage difference between the voltage of each battery cell and the average voltage is greater than a balancing start voltage difference; if the determination result is yes, then determine that the battery cell needs to be balanced, and record the number of batteries that need to be balanced, and determine whether the number of balanced batteries is less than the total number of battery cells; if the number of balanced batteries is less than the total number of battery cells, then continuously perform new battery cell balancing status judgments until all battery cells are determined to need to be balanced before terminating.

[0036] Furthermore, if the judgment result of whether the second voltage difference between the voltage of each battery cell and the voltage average value is greater than the equalization start-up voltage difference is no, it is judged that the battery cell does not need to be balanced. If the battery cell is already in the equalization mode at this time, the power management module is instructed to turn off the equalization state of the battery cell. If the battery cell is not in the equalization mode at this time, the battery cell is marked as not needing to be balanced.

[0037] On the other hand, if the first voltage difference is less than or equal to the first voltage threshold, it is determined whether the minimum voltage is greater than the equalization start-up voltage, and whether the difference between the voltage of each battery cell and the minimum voltage is greater than the equalization start-up voltage difference. If the judgment results are all yes, it is determined that the battery cell needs to be balanced, and the number of balanced cells is recorded, and it is determined whether the number of balanced cells is less than the total number of battery cells. If the number of balanced cells is less than the total number of battery cells, new battery cell balance status judgments are continuously performed until all battery cells are determined whether they need to be balanced and then the process ends. If any of the judgment results of determining whether the minimum voltage is greater than the equalization start-up voltage and determining whether the difference between the voltage of each battery cell and the minimum voltage is greater than the equalization start-up voltage difference is no, it is determined that the battery cell does not need to be balanced. If the battery cell is already in the balance mode at this time, the power management module is instructed to turn off the balance state of the battery cell. If the battery cell is not in the balance mode at this time, the battery cell is marked as not needing to be balanced.

[0038] Furthermore, the control system 20 also includes a power management module, which is suitable for receiving an on-balance instruction and a off-balance instruction sent by the processing center. When the processing center determines that the battery needs to be balanced, it will send an on-balance instruction to the power management module to turn on the balancing mode. When the processing center determines that the battery does not need to be balanced, it will send an off-balance instruction to the power management module to turn off the balancing mode. Exemplarily, the power management module may include a power management chip AFE.

[0039] On the other hand, the control system 20 also includes a temperature acquisition module, a battery fan control module and an onboard fan control module. In the present embodiment, the temperature acquisition module can adopt NTC contact measurement, infrared temperature measurement and other measurement methods, the temperature acquisition module includes an onboard temperature acquisition module and a battery temperature acquisition module, the onboard temperature acquisition module is used to obtain the onboard temperature of the BMS board, and the battery temperature acquisition module is used to obtain the battery temperature of each battery cell. In the present embodiment, a battery fan is set in the battery cell area to dissipate heat for the battery cell, and an onboard fan is set in the onboard (BMS board) area to dissipate heat for the BMS board, and the battery fan control module controls the opening and closing of the battery fan, and the onboard fan control module controls the opening and closing of the onboard fan.

[0040] Further references Figure 4After the battery cell is powered on, the processing center is initialized. At this time, the onboard temperature acquisition module acquires the onboard temperature, the battery cell temperature acquisition module acquires the battery cell temperature, and the voltage acquisition module acquires the battery cell voltage. It should be noted that in other embodiments of the present application, the onboard temperature acquisition module, the battery cell temperature acquisition module and the voltage acquisition module can acquire the corresponding temperature or voltage at the same time, or they can be acquired in different orders, and the present application does not limit this. After acquiring the onboard temperature, battery cell temperature and battery cell voltage, the processing center determines whether the battery cell needs to be balanced. When the processing center determines that the battery needs to be balanced, it will send a command to turn on the balancing mode to the power management module. When the processing center determines that the battery does not need to be balanced, it will send a command to turn off the balancing mode to the power management module.

[0041] In this embodiment, the processing center can also determine whether the battery fan and the onboard fan need to be turned on according to the balance and temperature status. If the balance does not need to be turned on at this time, the battery fan and the onboard fan do not need to be turned on. If the battery fan and the onboard fan are in the on state at this time, the battery fan can be turned off through the battery fan control module and the onboard fan can be turned off through the onboard fan control module. In this embodiment, a collection cycle can also be set to achieve periodic monitoring. When a collection cycle has passed, the onboard temperature, battery temperature and battery voltage can be re-collected, which can more accurately determine whether the battery needs to be balanced.

[0042] Further references Figure 5 , the present application can also perform heat dissipation to different degrees according to the number of balanced cells, and the following is now explained:

[0043] If the number of balanced cells is 0, the processing center sends a command to the battery management module that the PWM is a first percentage. Exemplarily, the first percentage is 0%, that is, when the number of balanced cells is 0, both the battery cell fan and the onboard fan are in a closed state;

[0044] If the number of balanced cells is less than or equal to the first percentage of the total number of cells, a PWM instruction of the second percentage is sent. For example, the first percentage is 1 / 4 and the second percentage is 100%. That is, when the number of balanced cells is less than 1 / 4 of the total number of cells, the heat generated inside the cells is not much and does not affect the balancing effect. Therefore, the cells or BMS board do not need to be cooled at this time. Therefore, the cell fan and the onboard fan are both in the off state at this time.

[0045] If the balanced number is greater than the first proportion of the total number of battery cells and less than or equal to the second proportion of the total number of battery cells, and the battery cell temperature is less than or equal to the first temperature threshold T1, then send a PWM instruction of the second percentage. For example, the second proportion is 1 / 2, and the second percentage is 100%. That is, when the balanced number is greater than 1 / 4 of the total number of battery cells but less than or equal to 1 / 2 of the total number of battery cells, the battery cell temperature does not exceed the first temperature threshold T1. At this time, it is determined that the battery cell does not need to be cooled, and the output PWM is 100%. At this time, the battery cell fan and the onboard fan are both in the off state.

[0046] If the number of balanced cells is greater than the first percentage of the total number of cells and less than or equal to the second percentage of the total number of cells, and the cell temperature is greater than the first temperature threshold, a PWM instruction of the third percentage is sent, and the third percentage is 80% by way of example. That is, when the number of balanced cells is greater than 1 / 4 of the total number of cells but less than or equal to 1 / 2 of the total number of cells, but the cell temperature exceeds the first temperature threshold T1, heat dissipation is required at this time, otherwise it will affect the balancing effect of the cells, so an instruction to turn on the cell fan is sent, and further determine whether the onboard temperature is greater than the onboard temperature threshold Tb. If the determination result is yes, an instruction to turn on the onboard fan is sent, otherwise the onboard fan is not turned on;

[0047] If the number of cells to be balanced is greater than the second percentage of the total number of cells, then directly send an instruction to turn on the cell fan and an instruction to turn on the onboard fan, and determine whether the cell temperature exceeds the second temperature threshold T2. If the result of the determination is yes, then send an instruction that PWM is the fourth percentage. If the result of the determination is no, then send an instruction that PWM is the third percentage, wherein the second temperature threshold is greater than the first temperature threshold. Exemplarily, the fourth percentage is 50%, which means that when the number of cells to be balanced is greater than 1 / 2 of the total number of cells, the cell fan and the onboard fan can be turned on directly. When the cell temperature is greater than the second temperature threshold, it means that the heat dissipated inside the cell is too high, which will affect the balancing effect. Then, the PWM is controlled to 50%, and the heat dissipation intensity of the cell fan and the onboard fan is increased to dissipate heat in time. If the cell temperature is less than the second temperature threshold, high-intensity heat dissipation is not required, so the duty cycle of the cell fan and the onboard fan is 80% at this time.

[0048] Furthermore, through the heat dissipation effect of the battery fan and the onboard fan, when the battery temperature acquisition module detects that the temperature of the battery is less than the first temperature threshold T1, the duty cycle is output at 100% to turn off the battery fan and the onboard fan. By adjusting the duty cycle of the battery fan and the onboard fan to control the intensity of heat dissipation, the flexibility of the heat dissipation of the whole machine can be further improved, and the energy saving effect can be further achieved.

[0049] On the other hand, refer to Figure 6The fan (including the battery core fan and the onboard fan) provided in this embodiment has three different working modes, namely, fan mode 1, fan mode 2 and fan mode 3. Figure 6 It can be seen that when the fan is in fan mode 1, the fan is turned on as long as the battery is powered on. When the fan is in fan mode 2, whether the fan is turned on depends on the state of balance. If the balance is turned on, the fan is turned on. After the balance is turned off, the fan is turned off for a preset time. The preset time can be set according to the actual operation situation to ensure the heat dissipation of the battery. For example, the preset time can be 3 minutes.

[0050] Furthermore, the fan may also adopt fan mode 3. When the fan is in fan mode 3, the opening and closing of the fan is controlled by temperature, that is, the battery cell fan is controlled by the battery cell temperature, and the onboard fan is controlled by the onboard temperature.

[0051] In this embodiment, the control system 20 also includes a fault indication module. When the fan is in fan mode 3, before the fan is turned on, the fault indication module will also record the number of times the temperature acquisition module fails and retain the previous output power of the fan. When the number of failures exceeds a preset number, the temperature acquisition module fault information is reported to the processing center. For example, the preset number can be set according to the actual operating conditions, for example, it can be set to 3.

[0052] Furthermore, taking the battery fan as an example, if the battery temperature collection module does not have a fault, then:

[0053] When the battery core temperature is greater than the first temperature threshold T1, the output power of the battery core fan is 20%. In other embodiments of the present application, the output power of the battery core fan can be 0% to 20%, such as 5%, 10%, or 15%, and the present application does not limit this;

[0054] When the battery core temperature is greater than the second temperature threshold T2, the output power of the battery core fan is 40%. In other embodiments of the present application, the output power of the battery core fan can be 21% to 40%, such as 25%, 30%, or 35%, and the present application does not limit this;

[0055] When the battery cell temperature is greater than the third temperature threshold T3, the output power of the battery cell fan is 60%. At this time, it is determined whether the balancing current is a small current. If so, it is determined whether the balancing current needs to be increased according to the actual state of the battery cell. If necessary, a large current balancing is turned on to achieve a better balancing effect. In other embodiments of the present application, the output power of the battery cell fan can be 41% to 60%, such as 45%, 50%, and 55%, and the present application does not limit this;

[0056] When the battery core temperature is greater than the fourth temperature threshold value T4, the output power of the battery core fan is 80%. In other embodiments of the present application, the output power of the battery core fan can be 61% to 80%, such as 65%, 70%, 75%, and the present application does not limit this;

[0057] When the battery core temperature is greater than the fifth temperature threshold T5, the output power of the battery core fan is 100%. This means that if the current battery core temperature is greater than the fifth temperature threshold T5, the battery core fan works at the maximum power to achieve the strongest heat dissipation purpose. At this time, it is determined whether the battery core balancing time is greater than the preset time t1. If the balancing time is greater than t1, the balancing current is reduced so that the battery core temperature no longer rises to achieve balanced control of temperature and balancing effect. In other embodiments of the present application, the output power of the battery core fan can be 81% to 100%, for example 85%, 90%, 95%, and the present application does not limit this.

[0058] Exemplarily, the fifth temperature threshold T5 is greater than the fourth temperature threshold T4; the fourth temperature threshold T4 is greater than the third temperature threshold T3; the third temperature threshold T3 is greater than the second temperature threshold T2; and the second temperature threshold T2 is greater than the first temperature threshold T1.

[0059] Furthermore, the onboard fan can be controlled according to the temperature of the BMS board. The control method thereof can refer to the control method of the battery cell fan mentioned above, and will not be elaborated here.

[0060] Return to reference Figure 2 The control system 20 also includes a power module, a communication module and a balance display module. The power module can supply power to the processing center, the fan control module and other modules, the communication module can realize the communication between different modules and the processing center, and the balance display module can display the current balance status of the battery.

[0061] This application determines whether the battery cell needs to be balanced by the battery cell voltage and records the number of battery cells that need to be balanced, which can effectively obtain relevant information about battery cell balancing and better balance the temperature of the battery cell during balancing. Furthermore, this application also controls the heat dissipation of the battery cell by the battery cell temperature and the onboard temperature of the BMS board, and further controls the heat dissipation intensity by controlling the duty cycle of the fan. It can flexibly adjust the heat dissipation intensity according to the actual situation of balancing, which can improve the balancing effect of the battery cell, thereby further improving the performance of the battery.

[0062] The basic concepts have been described above. Obviously, for those skilled in the art, the above application disclosure is only an example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0063] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0064] Some aspects of the present application may be performed entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. The above hardware or software may be referred to as "data blocks", "modules", "engines", "units", "components" or "systems". The processor may be one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DAPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, or combinations thereof. In addition, various aspects of the present application may be expressed as computer products located in one or more computer-readable media, which include computer-readable program codes. For example, computer-readable media may include, but are not limited to, magnetic storage devices (e.g., hard disks, floppy disks, tapes ...), optical disks (e.g., compact disks CDs, digital versatile disks DVDs ...), smart cards, and flash memory devices (e.g., cards, sticks, key drives ...).

[0065] A computer-readable medium may include a propagated data signal containing computer program code, such as in baseband or as part of a carrier wave. The propagated signal may have a variety of manifestations, including electromagnetic, optical, etc., or a suitable combination. A computer-readable medium may be any computer-readable medium other than a computer-readable storage medium, which may be connected to an instruction execution system, device or apparatus to communicate, propagate or transmit a program for use. The program code on the computer-readable medium may be propagated via any suitable medium, including radio, cable, fiber optic cable, radio frequency signal, or similar medium, or any combination of the above mediums.

[0066] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more application embodiments, in the above description of the embodiments of this application, multiple features are sometimes merged into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0067] In some embodiments, numbers describing the number of components and attributes are used. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0068] Although the present application has been described with reference to the current specific embodiments, ordinary technicians in this technical field should recognize that the above embodiments are only used to illustrate the present application, and various equivalent changes or substitutions may be made without departing from the spirit of the present application. Therefore, as long as the changes and modifications to the above embodiments are within the essential spirit of the present application, they will fall within the scope of the claims of the present application.

Claims

1. A method for balancing the voltage of a battery cell, characterized in that: The steps include: Collect the voltage of each battery cell and calculate the maximum voltage, minimum voltage and average voltage; Determine whether a first voltage difference between the maximum voltage and the average voltage is greater than a first voltage threshold; If the voltage difference is greater than the first voltage threshold, further determine whether a second voltage difference between the voltage of each of the battery cells and the voltage average is greater than a balancing start voltage difference; if the determination result is yes, determine that the battery cells need to be balanced, and record the number of balanced cells; if the determination result is no, determine that the battery cells do not need to be balanced; If the voltage difference is less than or equal to the first voltage threshold, determine whether the minimum voltage is greater than the equalization start-up voltage, and determine whether the difference between the voltage of each battery cell and the minimum voltage is greater than the equalization start-up voltage difference. If the judgment results are all yes, determine that the battery cells need to be balanced, and record the number of balanced cells. If any judgment result is no, determine that the battery cells do not need to be balanced.

2. The control method according to claim 1, characterized in that: The method further includes sending a start-up balancing instruction to start a balancing mode if it is determined that the battery cell needs balancing, and sending a stop-balancing instruction if it is determined that the battery cell does not need balancing.

3. The control method according to claim 1, characterized in that: It also includes obtaining the cell temperature of each of the cell and the onboard temperature of the BMS board through a temperature acquisition module.

4. The control method according to claim 3, characterized in that: Also included is sending an instruction that PWM is a first percentage if the balanced number is 0; If the balanced number is less than or equal to the first percentage of the total number of battery cells, sending a command that PWM is a second percentage; If the balanced number is greater than the first proportion of the total number of battery cells and less than or equal to the second proportion of the total number of battery cells, and the battery cell temperature is less than or equal to the first temperature threshold, then send an instruction that the PWM is the second percentage; If the balanced number is greater than the first proportion of the total number of battery cells and less than or equal to the second proportion of the total number of battery cells, and the battery cell temperature is greater than the first temperature threshold, then send a command that the PWM is a third percentage and send a command to turn on the battery cell fan, and if the onboard temperature is greater than the onboard temperature threshold at this time, then send a command to turn on the onboard fan; If the balanced number is greater than the second proportion of the total number of battery cells, a command to turn on the battery cell fan and a command to turn on the onboard fan are directly sent.

5. The control method according to claim 4, characterized in that: It also includes, when the balanced number is greater than the second proportion of the total number of battery cells, determining whether the battery cell temperature exceeds a second temperature threshold; if the determination result is yes, sending an instruction for PWM to be a fourth percentage, wherein the second temperature threshold is greater than the first temperature threshold.

6. The control method according to claim 5, characterized in that: The battery fan has five working modes, among which: When the battery core temperature is greater than a first temperature threshold, the output power of the battery core fan is 0% to 20%; When the battery core temperature is greater than a second temperature threshold, the output power of the battery core fan is 21% to 40%; When the battery core temperature is greater than a third temperature threshold, the output power of the battery core fan is 41% to 60%; When the battery core temperature is greater than a fourth temperature threshold, the output power of the battery core fan is 61% to 80%; When the battery core temperature is greater than a fifth temperature threshold, the output power of the battery core fan is 81% to 100%.

7. The control method according to claim 6, characterized in that: The onboard fan includes five working modes, wherein: When the onboard temperature is greater than a first temperature threshold, the output power of the onboard fan is 0% to 20%; When the onboard temperature is greater than a second temperature threshold, the output power of the onboard fan is 21% to 40%; When the onboard temperature is greater than a third temperature threshold, the output power of the onboard fan is 41% to 60%; When the onboard temperature is greater than a fourth temperature threshold, the output power of the onboard fan is 61% to 80%; When the onboard temperature is greater than a fifth temperature threshold, the output power of the onboard fan is 81% to 100%.

8. The control method according to claim 7, characterized in that: Also includes: The number of times the temperature acquisition module fails is recorded and the previous output power of the fan is retained. When the number of failures exceeds a preset number, the temperature acquisition module failure information is reported.

9. A cell voltage balancing control system, characterized in that: include: A voltage acquisition module is configured to acquire the voltage of each battery cell; A processing center is configured to calculate a maximum voltage, a minimum voltage, and an average voltage of all the battery cells, and determine whether a first voltage difference between the maximum voltage and the average voltage is greater than a first voltage threshold; If the voltage difference is greater than the first voltage threshold, further determine whether a second voltage difference between the voltage of each of the battery cells and the voltage average is greater than a balancing start voltage difference; if the determination result is yes, determine that the battery cells need to be balanced, and record the number of balanced cells; if the determination result is no, determine that the battery cells do not need to be balanced; If the voltage difference is less than or equal to the first voltage threshold, determine whether the minimum voltage is greater than the equalization start-up voltage, and determine whether the difference between the voltage of each battery cell and the minimum voltage is greater than the equalization start-up voltage difference. If the judgment results are all yes, determine that the battery cells need to be balanced, and record the number of balanced cells. If any judgment result is no, determine that the battery cells do not need to be balanced.

10. The balancing control system according to claim 9, characterized in that: It also includes a power management module, which is suitable for receiving an on-balance instruction and a off-balance instruction sent by the processing center, and turning on the balancing mode according to the on-balance instruction and turning off the balancing mode according to the off-balance instruction.

11. The balancing control system according to claim 9, characterized in that: It also includes a temperature acquisition module, which is suitable for acquiring the cell temperature of each of the battery cells and the onboard temperature of the BMS board.

12. The balancing control system according to claim 11, characterized in that: It also includes a fault indication module. When the temperature acquisition module fails, the fault indication module records the number of faults and retains the previous output power of the fan. When the number of faults recorded by the fault indication module exceeds a preset number, the temperature acquisition module fault information is sent to the processing center.

13. The balancing control system according to claim 9, characterized in that: It also includes a battery cell fan control module and an onboard fan control module. The battery cell fan control module controls the opening and closing of the battery cell fan, and the onboard fan control module controls the opening and closing of the onboard fan.

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