Battery cell passive equalization method, electronic device, and vehicle

Abstract

The application provides a battery cell passive balancing method, an electronic device and a vehicle, and the battery cell passive balancing method comprises the following steps: S1, judging whether a battery pack composed of a plurality of battery cells is in an electrochemical balance state; S2, when the battery pack is in the electrochemical balance state, judging whether battery cell balancing is needed; S3, when the battery cell balancing is needed, screening and removing weak battery cells from the battery pack, and calculating the battery capacity percentage that each remaining battery cell needs to be balanced based on the remaining battery cells; and S4, starting the battery cell balancing by opening or closing a balancing switch until the battery capacity percentage that each remaining battery cell needs to be balanced is 0, and stopping the battery cell balancing. The battery cell passive balancing method provided by the application can identify weak battery cells existing in the battery pack, so that frequent battery cell balancing of the weak battery cells can be avoided, and unnecessary energy waste can be prevented.

Description

Technical Field

[0001] This invention relates to the field of vehicle batteries, and more particularly to a passive battery cell balancing method, electronic device, and vehicle. Specifically, it relates to a passive battery cell balancing method, electronic device, and vehicle that can avoid frequent balancing of battery cells and thus avoid unnecessary energy waste. Background Technology

[0002] With the continuous development of vehicle technology, people's acceptance and demand for electric and hybrid vehicles are gradually increasing. The battery pack is the power source of a vehicle, therefore, the performance and requirements of the battery pack in a vehicle are gradually becoming an important part of vehicle development.

[0003] Battery pack consistency refers to the convergence of important characteristic parameters of the battery cells that make up the battery pack, such as the consistency of battery cell voltage. Ideally, the voltage difference between battery cells should all be within a small range. At this time, the consistency of battery cells can be considered good. When the consistency of battery cells in the battery pack is poor, it may be because the voltage of one or two battery cells is sometimes too low.

[0004] Normally, when battery cell inconsistency is poor, the battery management system can perform cell balancing to bring the voltage of cells with higher voltages to the same level or close to that of other cells. However, in some cases, the voltage of some cells may be too high or too low, causing cell balancing to be triggered frequently, resulting in excessive energy waste.

[0005] The aforementioned battery cells with excessively high or low voltage are defined as weak battery cells. Under current technology, these weak battery cells are difficult to detect in advance and can only be discovered after use. Therefore, there is a need for a passive battery cell equalization method that can identify these weak battery cells and prevent frequent battery cell equalization during the battery cell equalization process, thereby avoiding excessive energy consumption. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] The primary objective of this invention is to provide a passive battery cell balancing method that can identify weak battery cells, thereby addressing the problem of energy waste caused by frequent balancing of weak battery cells.

[0008] A second objective of this invention is to provide an electronic device that executes a computer program for a passive battery cell balancing method that identifies weak battery cells, thereby solving the problem of energy waste caused by frequent balancing of weak battery cells.

[0009] A third objective of the present invention is to provide a vehicle including the above-described electronic equipment to solve the problem of energy waste caused by frequent equalization of weak battery cells.

[0010] (II) Technical Solution

[0011] To address the aforementioned technical problems, this invention provides a passive battery cell balancing method, comprising: step S1: determining whether a battery pack composed of multiple battery cells is in electrochemical equilibrium; step S2: when the battery pack is in electrochemical equilibrium, determining whether battery cell balancing is required; step S3: when battery cell balancing is required, selecting and removing weak battery cells from the battery pack, and calculating the percentage of battery capacity that needs to be balanced for each remaining battery cell based on the remaining battery cells; and step S4: initiating battery cell balancing by turning the balancing switch on or off until the percentage of battery capacity that needs to be balanced for each remaining battery cell is 0, and then stopping battery cell balancing.

[0012] Optionally, in step S1, the battery pack is determined to be in electrochemical equilibrium when there is no current flowing into the battery pack for a predetermined time, or when the sleep time of the electronic control unit recorded by the local timer is greater than or equal to the predetermined time.

[0013] Optionally, in step S2, when the battery pack is in electrochemical equilibrium and simultaneously satisfies the following relationship, it is determined that cell balancing needs to be activated:

[0014] SOC min <SOC real <SOC max ;as well as

[0015] (V max –V min )>K1×V active ,

[0016] Among them, SOC min State of Charge (SOC) indicates the minimum dischargeable battery percentage of the battery pack. real State of Charge (SOC) indicates the actual percentage of battery charge in the battery pack. max V represents the maximum rechargeable battery capacity percentage of the battery pack. max This indicates the maximum voltage of the battery cells in the battery pack, V. min V represents the minimum voltage of the battery cells in the battery pack. active K1 represents the threshold voltage for enabling battery cell balancing, and K1 represents the first coefficient, which changes inversely according to the battery's health status.

[0017] Optionally, step S3 includes: step S31: calculating the target voltage; step S32: comparing the voltage of each battery cell with the target voltage, and based on the comparison result, dividing each battery cell into a first battery cell with a voltage greater than the target voltage and a second battery cell with a voltage less than the target voltage, and recording the number of the first battery cells as a first quantity; step S33: filtering and removing weak battery cells according to the first quantity; step S34: calculating the percentage of battery capacity that needs to be balanced for each remaining battery cell based on the remaining battery cells.

[0018] Optionally, in step S31, the target voltage is calculated according to the following formula:

[0019] V target =K2×(V max +V min )+K3×V active ,

[0020] Among them, V target Indicates the target voltage, V max This indicates the maximum voltage of the battery cells in the battery pack, V. min V represents the minimum voltage of the battery cells in the battery pack. active K1 represents the threshold voltage for enabling battery cell balancing, K2 represents the second coefficient, which depends on the voltage platform of the battery cell, and K3 represents the third coefficient, which changes inversely according to the battery health status.

[0021] Optionally, in step S33, when the ratio of the first quantity to the total number of battery cells in the battery pack is greater than the fourth coefficient, the second battery cell is regarded as a weak battery cell, wherein the fourth coefficient depends on the consistency of the battery cells; when the ratio of the first quantity to the total number of battery cells in the battery pack is less than the fourth coefficient, there are no weak battery cells in the battery pack.

[0022] Optionally, in step S34, the battery percentage is calculated according to the following formula:

[0023] ΔSOC i =F(V cell_i )–F(V target ),

[0024] Wherein, ΔSOC i V represents the percentage of battery capacity that the i-th battery cell needs to balance. cell_i V represents the voltage of the i-th battery cell. target Indicates the target voltage.

[0025] Optionally, step S4 includes: Step S41: Calculate the real-time battery capacity percentage that needs to be balanced for each remaining battery cell according to the following formula:

[0026] ΔSOCi =ΔSOC i ×Cell Capacity ×SOH–[(VT i / R i )×ΔT],

[0027] Wherein, ΔSOC i ' represents the real-time battery charge percentage that the i-th battery cell needs to balance, ΔSOC i This represents the percentage of battery capacity that the i-th battery cell needs to balance. Capacity The battery cell capacity is indicated by SOH, and the battery cell health status is indicated by VT. i R represents the terminal voltage of the i-th battery cell. i ΔT represents the internal resistance of the i-th battery cell, and ΔT represents the duration of the equalization switch being closed; Step S42: When the real-time battery charge percentage to be equalized is not equal to 0, continue to execute step S41; When the real-time battery charge percentage to be equalized is equal to 0, stop battery cell equalization.

[0028] On the other hand, the present invention also provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement a battery cell passive balancing method according to an embodiment of the present invention.

[0029] In another aspect, the present invention also provides a vehicle that includes electronic equipment according to embodiments of the present invention.

[0030] (III) Beneficial Effects

[0031] This invention provides a passive battery cell balancing method, comprising: step S1: determining whether a battery pack composed of multiple battery cells is in electrochemical equilibrium; step S2: when the battery pack is in electrochemical equilibrium, determining whether battery cell balancing is required; step S3: when battery cell balancing is required, screening and removing weak battery cells from the battery pack, and calculating the percentage of battery capacity that needs to be balanced for each remaining battery cell based on the remaining battery cells; and step S4: initiating battery cell balancing by turning a balancing switch on or off until the percentage of battery capacity that needs to be balanced for each remaining battery cell is 0, and then stopping the battery cell balancing. The passive battery cell balancing method provided by this invention can identify weak battery cells in a battery pack, thereby avoiding frequent battery cell balancing of weak battery cells and preventing unnecessary energy waste. Attached Figure Description

[0032] The above and other objects, features and other advantages of this disclosure will become clearer from the following detailed description, taken in conjunction with the accompanying drawings, wherein:

[0033] Figure 1This is a circuit diagram illustrating a battery pack according to an embodiment of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the description of this invention, it should be noted that the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] On one hand, embodiments of the present invention provide a passive balancing method for battery cells. Figure 1 This is a circuit diagram of a battery pack according to an embodiment of the present invention. The passive balancing method of the battery cells according to the present invention is applicable to battery packs in power vehicles, which consists of multiple battery cells connected in series with a fixed resistor. The voltage of each battery cell can be measured by a data acquisition chip, and the balancing switch set on each battery cell can be turned on by the vehicle management system.

[0037] The passive battery cell balancing method according to an embodiment of the present invention may include: step S1: determining whether a battery pack composed of multiple battery cells is in an electrochemical equilibrium state; step S2: when the battery pack is in an electrochemical equilibrium state, determining whether battery cell balancing is required; step S3: when battery cell balancing is required, screening and removing weak battery cells from the battery pack, and calculating the percentage of battery capacity that needs to be balanced for each remaining battery cell based on the remaining battery cells; and step S4: starting the battery cell balancing by turning the balancing switch on or off until the percentage of battery capacity that needs to be balanced for each remaining battery cell is 0, and stopping the battery cell balancing.

[0038] Specifically, firstly, the passive battery cell balancing method according to an embodiment of the present invention needs to determine whether the current battery pack is in an electrochemical equilibrium state. Therefore, in step S1, the electrochemical equilibrium state of the battery pack can be determined by whether there is current flow in the battery pack. That is, when the interval between the last current flow and the current flow is greater than or equal to a predetermined time, it can be determined that the battery pack is in an electrochemical equilibrium state. Alternatively, it can also be determined that the battery pack is in an electrochemical equilibrium state based on the sleep time of the electronic control unit recorded by the vehicle's local timer or when the time in low power consumption mode is greater than or equal to a predetermined time. Optionally, the predetermined time can be 3600 seconds.

[0039] Further, after determining that the battery pack is in electrochemical equilibrium, it is determined whether cell balancing is necessary. In step S2, under electrochemical equilibrium conditions, cell balancing requires the following two conditions to be met simultaneously: the minimum dischargeable battery capacity of the battery pack must be less than the actual battery capacity of the battery pack, and the actual battery capacity of the battery pack must be less than the maximum rechargeable battery capacity of the battery pack; the ratio of the difference between the maximum and minimum voltages of the battery cells in the battery pack to the threshold voltage for initiating cell balancing must be greater than a first coefficient. These two conditions can be expressed by the following formula:

[0040] SOC min <SOC real <SOC max ;as well as

[0041] (V max –V min )>K1×V active ,

[0042] Among them, SOC min State of Charge (SOC) indicates the minimum dischargeable battery percentage of the battery pack. real State of Charge (SOC) indicates the actual percentage of battery charge in the battery pack. max V represents the maximum rechargeable battery capacity percentage of the battery pack. max This indicates the maximum voltage of the battery cells in the battery pack, V. min V represents the minimum voltage of the battery cells in the battery pack. active K1 represents the threshold voltage for enabling battery cell equalization. K1 represents the first coefficient, which increases when the battery health status decreases. That is, the first coefficient can change in the opposite direction according to the battery health status, and optionally, the first coefficient can be 1.

[0043] Furthermore, once it is determined that battery cell balancing is required, the amount of battery capacity to be balanced for each battery cell needs to be calculated in order to perform battery cell balancing for each battery cell that needs to be balanced. At this time, in order to avoid performing battery cell balancing on weak battery cells, it is also necessary to screen out these weak battery cells and exclude these screened weak battery cells during battery cell balancing.

[0044] Specifically, step S3 may further include: step S31: calculate the target voltage; step S32: compare the voltage of each battery cell with the target voltage, and based on the comparison result, divide each battery cell into a first battery cell with a voltage greater than the target voltage and a second battery cell with a voltage less than the target voltage, and record the number of the first battery cells as the first quantity; step S33: filter and remove weak battery cells according to the first quantity; step S34: calculate the percentage of battery capacity that needs to be balanced for each remaining battery cell based on the remaining battery cells.

[0045] In step S31, the target voltage can be the consistent voltage value achieved after equalization of each battery cell, and can be calculated according to the following formula:

[0046] V target =K2×(V max +V min )+K3×V active ,

[0047] Among them, V target Indicates the target voltage, V max This indicates the maximum voltage of the battery cells in the battery pack, V. min V represents the minimum voltage of the battery cells in the battery pack. active K1 represents the threshold voltage for enabling battery cell balancing, K2 represents the second coefficient, which depends on the voltage plateau of the battery cell, and K3 represents the third coefficient, which changes inversely according to the battery's health status. Optionally, the second coefficient can be 0.5 and the third coefficient can be 0.1.

[0048] Further, in step S32, after calculating the target voltage, the voltage of each battery cell is compared with the target voltage, and based on the comparison result, the battery cell with a voltage greater than the target voltage is defined as the first battery cell, the battery cell with a voltage less than the target voltage is defined as the second battery cell, and the number of the first battery cells is recorded and defined as the first quantity.

[0049] Further, in step S33, the first quantity is compared with the total number of battery cells in the battery pack, and weak battery cells are identified. Specifically, when the ratio of the first quantity to the total number of battery cells in the battery pack is greater than a fourth coefficient, the second battery cell can be defined as a weak battery cell, where the fourth coefficient depends on the consistency of the battery cells. And when the ratio of the first quantity to the total number of battery cells in the battery pack is less than the fourth coefficient, it can be determined that there are no weak battery cells in the battery pack requiring battery cell balancing. Optionally, the fourth coefficient can be 0.9.

[0050] Furthermore, after screening and eliminating weak battery cells, it is necessary to perform cell balancing on the remaining battery cells in the battery pack. At this time, the percentage of battery capacity that needs to be balanced can be calculated according to the following formula:

[0051] ΔSOC i =F(V cell_i )–F(V target ),

[0052] Wherein, ΔSOC i V represents the percentage of battery capacity that the i-th battery cell needs to balance. cell_i V represents the voltage of the i-th battery cell. targetThis represents the target voltage. That is, for a battery cell, the percentage of battery charge that needs to be balanced can be the difference between the open-circuit voltage of that battery cell and the calculated target voltage, expressed as a function.

[0053] After step S3 above, the percentage of battery charge that needs to be balanced in each of the remaining battery cells after excluding the weak battery cells in the battery pack is obtained. At this time, the passive battery cell balancing method according to the embodiment of the present invention can balance the voltage of each battery cell by connecting the balancing switch in series in each battery cell until the percentage of battery charge that needs to be balanced is 0. Further, step S4 may further include: step S41: calculating the real-time percentage of battery charge that needs to be balanced in each remaining battery cell; and step S42: determining whether it is necessary to continuously turn on battery cell balancing.

[0054] Specifically, in step S41, the real-time battery capacity percentage that needs to be balanced for each remaining battery cell can be calculated according to the following formula:

[0055] ΔSOC i =ΔSOC i ×Cell Capacity ×SOH–[(VT i / R i )×ΔT],

[0056] Wherein, ΔSOC i ' represents the real-time battery charge percentage that the i-th battery cell needs to balance, ΔSOC i This represents the percentage of battery capacity that the i-th battery cell needs to balance. Capacity The battery cell capacity is indicated by SOH, and the battery cell health status is indicated by VT. i R represents the terminal voltage of the i-th battery cell. i ΔT represents the internal resistance of the i-th battery cell, and ΔT represents the duration of the equalization switch being closed.

[0057] Furthermore, in step S42, if the real-time battery percentage that needs to be balanced is not equal to 0, step S41 continues; if the real-time battery percentage that needs to be balanced is equal to 0, battery cell balancing stops.

[0058] The passive battery cell balancing method provided by the embodiments of the present invention can identify weak battery cells in the battery pack during the balancing process and exclude them, thereby avoiding unnecessary energy waste caused by frequent balancing of weak battery cells.

[0059] On the other hand, the present invention also provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. The electronic device can execute the computer program via the processor to implement the passive battery cell balancing method provided by the present invention.

[0060] In another aspect, the present invention also provides a vehicle comprising an electronic device capable of implementing the battery cell passive balancing method described above.

[0061] In summary, this invention provides a passive battery cell balancing method, an electronic device, and a vehicle. The passive battery cell balancing method includes: step S1: determining whether a battery pack composed of multiple battery cells is in electrochemical equilibrium; step S2: when the battery pack is in electrochemical equilibrium, determining whether battery cell balancing is required; step S3: when battery cell balancing is required, filtering and removing weak battery cells from the battery pack, and calculating the percentage of battery capacity that needs to be balanced for each remaining battery cell based on the remaining battery cells; and step S4: initiating battery cell balancing by turning a balancing switch on or off until the percentage of battery capacity that needs to be balanced for each remaining battery cell is 0, and then stopping the battery cell balancing. The passive battery cell balancing method provided by this invention can identify weak battery cells in a battery pack, thereby avoiding frequent battery cell balancing of weak battery cells and preventing unnecessary energy waste.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A passive equalization method for battery cells, characterized in that, include: Step S1: Determine whether the battery pack composed of multiple battery cells is in electrochemical equilibrium. Step S2: When the battery pack is in electrochemical equilibrium, determine whether cell balancing is required; Step S3: When the battery cell balancing is required, weak battery cells are screened and removed from the battery pack, and the percentage of battery capacity that needs to be balanced for each remaining battery cell is calculated based on the remaining battery cells. as well as Step S4: Initiate battery cell balancing by turning the balancing switch on or off until the battery percentage of each remaining battery cell that needs to be balanced is 0, and then stop the battery cell balancing. Step S3 includes: Step S31: Determine the target voltage; Step S32: Compare the voltage of each battery cell with the target voltage, and based on the comparison result, divide each battery cell into a first battery cell with a voltage greater than the target voltage and a second battery cell with a voltage less than the target voltage, and record the number of the first battery cells as a first quantity; Step S33: Filter and remove the weak battery cells according to the first quantity, wherein when the ratio of the first quantity to the total number of battery cells in the battery pack is greater than the fourth coefficient, the second battery cell is regarded as a weak battery cell, and when the ratio of the first quantity to the total number of battery cells in the battery pack is less than the fourth coefficient, the weak battery cell does not exist in the battery pack. Step S34: Calculate the percentage of battery capacity that each remaining battery cell needs to be balanced based on the remaining battery cells.

2. The passive balancing method for battery cells according to claim 1, characterized in that, In step S1, When there is no current flowing into the battery pack for a predetermined time, or, When the sleep time of the electronic control unit recorded by the local timer is greater than or equal to the predetermined time, it is determined that the battery pack is in electrochemical equilibrium.

3. The passive balancing method for battery cells according to claim 2, characterized in that, In step S2, When the battery pack is in electrochemical equilibrium and simultaneously satisfies the following relationship, it is determined that cell balancing needs to be activated: SOC min < SOC real < SOC max ,as well as (V max – V min ) > K1 × V active , Among them, SOC min State of Charge (SOC) represents the minimum dischargeable battery capacity percentage of the battery pack. real The State of Charge (SOC) indicates the actual battery charge percentage of the battery pack. max V represents the maximum rechargeable battery capacity percentage of the battery pack. max V represents the maximum voltage of the battery cells in the battery pack. min V represents the minimum voltage of the battery cells in the battery pack. active K1 represents the threshold voltage for enabling battery cell balancing, and K1 represents the first coefficient, which changes inversely according to the battery health status.

4. The passive balancing method for battery cells according to claim 3, characterized in that, In step S31, the target voltage is calculated according to the following formula: V target = K2× (V max + V min ) + K3 × V active , Among them, V target Indicates the target voltage, V max V represents the maximum voltage of the battery cells in the battery pack. min V represents the minimum voltage of the battery cells in the battery pack. active K1 represents the threshold voltage for enabling battery cell balancing, K2 represents the second coefficient which depends on the voltage platform of the battery cell, and K3 represents the third coefficient which changes inversely according to the battery health status.

5. The passive balancing method for battery cells according to claim 4, characterized in that, In step S33, the fourth coefficient depends on the consistency of the battery cells.

6. The passive balancing method for battery cells according to claim 5, characterized in that, In step S34, the battery charge percentage is calculated according to the following formula: SOC i = F(V cell_i ) – F(V target ), in, SOC i V represents the percentage of battery capacity that the i-th battery cell needs to balance. cell_i V represents the voltage of the i-th battery cell. target Indicates the target voltage.

7. The passive balancing method for battery cells according to claim 6, characterized in that, Step S4 includes: Step S41: Calculate the real-time battery capacity percentage that needs to be balanced for each remaining battery cell according to the following formula: SOC i ’ = SOC i × Cell Capacity × SOH – [(VT i / R i ) × T], in, SOC i 'Indicates the real-time battery charge percentage that the i-th battery cell needs to balance. SOC i This represents the percentage of battery capacity that the i-th battery cell needs to balance. Capacity The battery cell capacity is indicated by SOH, and the battery cell health status is indicated by VT. i R represents the terminal voltage of the i-th battery cell. i This represents the internal resistance of the i-th battery cell. T represents the duration of the equalization switch closure; Step S42: When the real-time battery percentage that needs to be balanced is not equal to 0, continue to execute step S41; when the real-time battery percentage that needs to be balanced is equal to 0, stop the battery cell balancing.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the battery cell passive balancing method according to any one of claims 1 to 7.

9. A vehicle, characterized in that, Including the electronic device according to claim 8.

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