A power battery equalization method and device

Abstract

The present application belongs to the technical field of battery system, and particularly relates to a power battery equalization method and device, which is used for solving the problem that when the capacity of batteries is inconsistent, the end voltage of the battery with low capacity in the battery pack is possibly higher than that of other batteries during or after charging, overcharging is easily caused, and the service life of the battery is affected. The present application adopts a two-stage equalization strategy, divides the equalization into two stages, adopts different strategies in different stages, discharges the battery with low single-charging capacity, and the equalization target is that all batteries reach the full state at the same time. The present application completes the equalization of the battery, keeps the voltage deviation of the lithium ion battery or the voltage deviation of the battery pack within the expected range, thereby ensuring that each single battery maintains the same state during normal use, so as to avoid overcharging and overdischarging. In the present application, the various inconsistencies caused by the battery itself and the use process after the battery is grouped are eliminated, and the influence of the battery inconsistency is reduced.

Description

Technical Field

[0001] This invention relates to the field of battery system technology, and in particular to a method and apparatus for balancing power batteries. Background Technology

[0002] To meet the power and voltage requirements of electric vehicles, battery packs require numerous individual cells connected in series and parallel. During manufacturing, due to process variations and material inconsistencies, cells of the same model from the same batch may have inconsistent parameters such as capacity and internal resistance. During vehicle installation, these inconsistencies are further exacerbated by factors such as temperature, ventilation, and self-discharge levels among the individual cells. This leads to a decrease in battery pack capacity and a reduction in battery lifespan.

[0003] In existing technologies, to reduce the impact of battery pack inconsistencies, improve battery pack performance, extend battery pack lifespan, and ensure battery safety and reliability, battery pack balancing management is typically required. Currently, a common balancing strategy uses the terminal voltage of individual battery cells as a reference constraint. Balancing is initiated when the voltage difference between the cells in the pack reaches a certain threshold, and ends when the voltage difference is no longer significant. However, when a lower-capacity cell in the pack is charging or has been charged, its terminal voltage may be higher than other cells. Using this method, which does not consider battery capacity, will further widen the gap in the current chargeable capacity of the cells after significant inconsistencies in battery capacity have occurred.

[0004] In summary, when there is a significant inconsistency in battery capacity in the existing technology, the battery with the lower capacity in the battery pack may have a higher terminal voltage than other batteries during or after charging, which can easily lead to overcharging and affect the battery's lifespan. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a power battery balancing method and apparatus. The aim is to resolve the issue that when there is a significant inconsistency in battery capacity, the lower-capacity batteries in a battery pack may have higher terminal voltages during or after charging, potentially leading to overcharging and affecting battery lifespan. This invention employs a two-stage balancing strategy, dividing the balancing process into two phases, each using different strategies. Batteries with lower individual rechargeable capacities are discharged, with the balancing goal being for all batteries to reach a fully charged state simultaneously.

[0006] A power battery balancing method, comprising,

[0007] The first stage of equalization discharges the cells with high SOC to make the SOC of all cells consistent.

[0008] The second stage of equalization discharges batteries with low individual rechargeable capacity, ensuring that the rechargeable capacity of all individual batteries remains consistent, achieving the equalization goal of all batteries reaching full charge simultaneously.

[0009] Furthermore, the battery equalization is divided into battery resting state and charging state. When the battery is resting, only the first stage of equalization is performed. When the battery is charging, the first stage of equalization and the second stage of equalization are performed in sequence.

[0010] Furthermore, in the battery resting or charging state, the first stage of equalization uses the maximum voltage difference and time between batteries as the starting conditions for the first stage of equalization. This stage performs discharge equalization on batteries with excessively large individual voltage differences to achieve consistent SOC.

[0011] During charging, the second stage of equalization uses the rechargeable capacity and the difference between the average rechargeable capacity as the equalization activation condition. It uses the individual cell voltage and the battery pack SOC to estimate the individual cell SOC and calculate the individual cell rechargeable capacity. Based on multiple iterations, the estimated value is dynamically adjusted to achieve consistent rechargeable capacity.

[0012] Furthermore, the first-stage equalization includes determining the maximum cell voltage MaxCellVolt and the minimum cell voltage MinCellVolt, and calculating the voltage difference: DeltaCellVolt = MaxCellVolt – MinCellVolt;

[0013] When the voltage difference DeltaCellVolt is greater than the set first target voltage difference TargetDeltaV1 and this phenomenon continues for more than the set time Wait seconds, the first stage of equalization is entered.

[0014] The difference between the voltage of each battery cell and the minimum voltage is detected. When the difference is greater than the set second target voltage difference TargetDeltaV2, the equalization command for that battery cell is turned on; otherwise, it is turned off.

[0015] BalCmd = ((CellVoltages - MinCellVolt) > TargetDeltaV2), where BalCmd is a Boolean value;

[0016] When the BalCmd of all individual cells is zero, the equalization completion flag flgBalCompl is set to 1, completing the first stage of equalization.

[0017] The second stage of balancing includes, if it is in a static state, the first stage of balancing is turned off and it returns to the initial state of judging whether to turn on balancing;

[0018] If it is in the charging state, it will enter the second stage of equalization. In the second stage, the battery voltage difference is already less than TargetDeltaV2.

[0019] During the charging process, the current is relatively stable. With the addition of information on temperature and battery cell terminal voltage, the SOC of a single cell can be estimated by looking up a table based on the dynamic current terminal voltage. Based on the offline calibrated charging current curve, the SOC of the single cell can be obtained, and the current chargeable capacity of the single cell can be calculated accordingly. For batteries with smaller chargeable capacity, discharge equalization can be performed.

[0020] Furthermore, the battery SOC can be calculated using the current integration method, open-circuit voltage method, Kalman filtering method, or neural network method.

[0021] A power battery balancing device, comprising,

[0022] The first-stage equalization unit discharges batteries with excessively high SOC to make the SOC of all individual batteries uniform.

[0023] The second-stage equalization unit discharges individual batteries with low rechargeable capacity to make the rechargeable capacity of all individual batteries consistent, achieving the equalization goal of all batteries reaching full charge simultaneously.

[0024] Furthermore, the battery balancing is divided into a static battery state and a charging state. When the battery is static, only the first stage balancing unit is executed. When the battery is charging, the first stage balancing unit and the second stage balancing unit are executed sequentially.

[0025] Furthermore, the first-stage equalization unit, when the battery is in a resting or charging state, uses the maximum voltage difference and time between the batteries as the conditions for starting the first-stage equalization. This stage performs discharge equalization on batteries with excessively large individual voltage differences to achieve consistent SOC.

[0026] The second-stage equalization unit, in the charging state, uses the chargeable capacity and the difference between the average chargeable capacity as the equalization activation condition. It uses the individual cell voltage and the battery pack SOC to estimate the individual cell SOC and calculate the individual cell chargeable capacity. Based on multiple iterations, it dynamically adjusts the estimated value to achieve consistent chargeable capacity.

[0027] Furthermore, the first-stage equalization unit includes determining the maximum cell voltage MaxCellVolt and the minimum cell voltage MinCellVolt, and calculating the voltage difference: DeltaCellVolt = MaxCellVolt – MinCellVolt;

[0028] When the voltage difference DeltaCellVolt is greater than the set first target voltage difference TargetDeltaV1 and this phenomenon continues for more than the set time Wait seconds, the first stage of equalization is entered.

[0029] The difference between the voltage of each battery cell and the minimum voltage is detected. When the difference is greater than the set second target voltage difference TargetDeltaV2, the equalization command for that battery cell is turned on; otherwise, it is turned off.

[0030] BalCmd = ((CellVoltages - MinCellVolt) > TargetDeltaV2), where BalCmd is a Boolean value;

[0031] When the BalCmd of all individual cells is zero, the equalization completion flag flgBalCompl is set to 1, completing the first stage of equalization.

[0032] The second-stage equalization unit includes, if it is in a static state, the first-stage equalization is turned off and it returns to the initial state of determining whether to turn on equalization;

[0033] If it is in the charging state, it will enter the second stage of equalization. In the second stage, the battery voltage difference is already less than TargetDeltaV2.

[0034] During the charging process, the current is relatively stable. With the addition of information on temperature and battery cell terminal voltage, the SOC of a single cell can be estimated by looking up a table based on the dynamic current terminal voltage. Based on the offline calibrated charging current curve, the SOC of the single cell can be obtained, and the current chargeable capacity of the single cell can be calculated accordingly. For batteries with smaller chargeable capacity, discharge equalization can be performed.

[0035] Furthermore, the battery SOC can be calculated using the current integration method, open-circuit voltage method, Kalman filtering method, or neural network method.

[0036] This invention achieves battery balancing, keeping the voltage deviation of individual lithium-ion battery cells or battery packs within the expected range, thereby ensuring that each individual battery cell remains in the same state during normal use and avoiding overcharging and over-discharging.

[0037] This invention eliminates various inconsistencies that arise after battery pack assembly and during use, thereby mitigating the impact of battery inconsistencies.

[0038] In this invention, when there are large differences in the values ​​of a single lithium-ion battery, the BMS (BATTERY MANAGEMENT SYSTEM) controls the equalization voltage of the batteries, which can maximize the service life of the lithium battery pack.

[0039] This invention employs a time-division and graded balancing strategy, dividing battery balancing into two stages, thereby making the balancing more thorough and the balancing objectives more reasonable.

[0040] This invention employs different balancing strategies during the battery charging and resting stages to meet the battery balancing requirements under different operating conditions and achieve better balancing results.

[0041] This invention uses voltage as the criterion for balancing during the resting phase. Balancing is performed when the voltage difference between individual cells is large, which can mitigate the impact of battery inconsistency to some extent. Adopting stricter voltage difference limits can also reduce power consumption caused by passive balancing.

[0042] During the charging phase, after the first stage of equalization is completed, the present invention does not need to overly consider the power consumption caused by passive equalization, and can perform deeper equalization to achieve a better equalization effect.

[0043] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 The diagram illustrates inconsistencies in SOC (State of Charge, i.e., the remaining battery capacity) and capacity.

[0046] Figure 2 The diagrams show the first-stage equilibrium and the second-stage equilibrium. Detailed Implementation

[0047] 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.

[0048] In the field of battery technology, existing technologies typically require battery pack balancing to reduce the impact of inconsistencies, improve battery pack performance, extend battery life, and ensure battery safety and reliability. Currently, a common balancing strategy uses the terminal voltage of individual cells as a reference constraint. Balancing is initiated when the voltage difference between cells in the pack reaches a certain threshold, and ends when the voltage difference is no longer significant. However, when a lower-capacity cell in the pack is charging or has been charged, its terminal voltage may be higher than other cells. Using this method, which disregards battery capacity, will further widen the gap in the current chargeable capacity of the cells after significant inconsistencies in capacity have occurred.

[0049] In existing technologies, when there is a significant inconsistency in battery capacity, the lower-capacity battery in the battery pack may have a higher terminal voltage than other batteries during or after charging, which can easily lead to overcharging and affect the battery's lifespan.

[0050] Therefore, the present invention proposes a power battery balancing method and a power battery balancing device.

[0051] This invention employs a two-stage equalization strategy, dividing the equalization process into two phases, each using a different strategy. Batteries with low individual rechargeable capacity are discharged, with the equalization goal being for all batteries to reach a fully charged state simultaneously. For the passive equalization circuit, a hierarchical, time-sharing equalization control strategy is used.

[0052] Voltage difference is the first-level judgment condition. For batteries with excessively large individual voltage differences, discharge equalization is performed to achieve consistent State of Charge (SOC). When the individual voltage difference is less than a certain threshold, equalization is initiated based on the rechargeable capacity and the difference between the rechargeable capacities. The individual battery SOC is estimated using the individual battery voltage and the battery pack SOC, and the rechargeable capacity of each individual battery is calculated. This estimated value is dynamically adjusted through multiple iterations to achieve consistent rechargeable capacity. For passive equalization, batteries requiring equalization are divided into two levels, and the equalization time is adjusted according to different thresholds.

[0053] In a first aspect, the present invention provides a power battery balancing method, comprising:

[0054] The first stage of equalization discharges the cells with high SOC to make the SOC of all cells consistent.

[0055] The second stage of equalization discharges batteries with low individual rechargeable capacity, ensuring that the rechargeable capacity of all individual batteries remains consistent, achieving the equalization goal of all batteries reaching full charge simultaneously.

[0056] In practice, different equalization methods are used to discharge batteries with low individual rechargeable capacity so that all batteries reach full charge at the same time. This avoids overcharging of individual batteries and improves battery life.

[0057] In this embodiment, the battery equalization is divided into battery resting state and charging state. When the battery is resting, only the first stage of equalization is performed. When the battery is charging, the first stage of equalization and the second stage of equalization are performed in sequence.

[0058] In practice, different balancing strategies are adopted depending on whether the battery is in a static or charging state.

[0059] In this embodiment, when the battery is in a resting or charging state, the first stage of equalization uses the maximum voltage difference and time between the batteries as the starting conditions for the first stage of equalization. This stage performs discharge equalization on batteries with excessively large individual voltage differences in order to achieve consistent SOC.

[0060] During charging, the second stage of equalization uses the rechargeable capacity and the difference between the average rechargeable capacity as the equalization activation condition. It uses the individual cell voltage and the battery pack SOC to estimate the individual cell SOC and calculate the individual cell rechargeable capacity. Based on multiple iterations, the estimated value is dynamically adjusted to achieve consistent rechargeable capacity.

[0061] In practice, the first stage of equalization is performed when the battery is idle. This involves discharging and equalizing batteries with large voltage differences to achieve consistent SOC, thus avoiding local over-discharge of the battery pack and extending battery life.

[0062] The charging process involves a first-stage equalization and a second-stage equalization. By balancing the discharge, all batteries reach full charge simultaneously, thus preventing individual batteries from overcharging and extending battery life.

[0063] In this embodiment, the first stage of equalization includes determining the maximum cell voltage MaxCellVolt and the minimum cell voltage MinCellVolt, and calculating the voltage difference: DeltaCellVolt = MaxCellVolt – MinCellVolt;

[0064] When the voltage difference DeltaCellVolt is greater than the set first target voltage difference TargetDeltaV1 and this phenomenon continues for more than the set time Wait seconds, the first stage of equalization is entered.

[0065] The difference between the voltage of each battery cell and the minimum voltage is detected. When the difference is greater than the set second target voltage difference TargetDeltaV2, the equalization command for that battery cell is turned on; otherwise, it is turned off.

[0066] BalCmd = ((CellVoltages - MinCellVolt) > TargetDeltaV2), where BalCmd is a Boolean value;

[0067] When the BalCmd of all individual cells is zero, the equalization completion flag flgBalCompl is set to 1, completing the first stage of equalization.

[0068] The second stage of balancing includes, if it is in a static state, the first stage of balancing is turned off and it returns to the initial state of judging whether to turn on balancing;

[0069] If it is in the charging state, it will enter the second stage of equalization. In the second stage, the battery voltage difference is already less than TargetDeltaV2.

[0070] During the charging process, the current is relatively stable. With the addition of information on temperature and battery cell terminal voltage, the SOC of a single cell can be estimated by looking up a table based on the dynamic current terminal voltage. Based on the offline calibrated charging current curve, the SOC of the single cell can be obtained, and the current chargeable capacity of the single cell can be calculated accordingly. For batteries with smaller chargeable capacity, discharge equalization can be performed.

[0071] In practice, the current is relatively stable during the charging process. With the information of temperature and battery cell terminal voltage, the SOC of a single cell can be estimated by looking up a table based on the dynamic current terminal voltage. The SOC of a single cell can be obtained based on the offline calibrated charging current curve, i.e., the open-circuit voltage method is used to estimate the battery SOC.

[0072] In this embodiment, the battery SOC can be calculated using the current integration method, open-circuit voltage method, Kalman filtering method, or neural network method.

[0073] In practice, battery SOC estimation can also be achieved using alternative methods such as current integration, Kalman filtering, or neural networks.

[0074] The current integration method estimates the state of charge (SOC) by accumulating the amount of electricity charged and discharged during battery charging and discharging.

[0075] The Kalman filter method calculates the current "optimal value" based on the current instrument's "measured value", the previous moment's "predicted value", and the "error".

[0076] The neural network method uses the BP (backpropagation) neural network method to estimate SOC.

[0077] Secondly, the present invention provides a power battery balancing device, comprising:

[0078] The first-stage equalization unit discharges batteries with excessively high SOC to make the SOC of all individual batteries uniform.

[0079] The second-stage equalization unit discharges individual batteries with low rechargeable capacity to make the rechargeable capacity of all individual batteries consistent, achieving the equalization goal of all batteries reaching full charge simultaneously.

[0080] In practical implementation, this invention employs different balancing strategies during the battery charging and resting stages to meet the battery balancing requirements under different operating conditions and achieve better balancing results. By discharging batteries with low individual rechargeable capacity, the balancing goal is for all batteries to reach a fully charged state simultaneously.

[0081] In this embodiment, the battery balancing is divided into a static battery state and a charging state. When the battery is static, only the first stage balancing unit is executed. When the battery is charging, the first stage balancing unit and the second stage balancing unit are executed in sequence.

[0082] In this embodiment, the first-stage equalization unit uses the maximum voltage difference and time between batteries as the start condition for the first-stage equalization when the battery is in a resting or charging state. This stage performs discharge equalization on batteries with excessively large individual voltage differences to achieve consistent SOC.

[0083] The second-stage equalization unit, in the charging state, uses the chargeable capacity and the difference between the average chargeable capacity as the equalization activation condition. It uses the individual cell voltage and the battery pack SOC to estimate the individual cell SOC and calculate the individual cell chargeable capacity. Based on multiple iterations, it dynamically adjusts the estimated value to achieve consistent chargeable capacity.

[0084] In this embodiment, the first-stage equalization unit includes determining the maximum cell voltage MaxCellVolt and the minimum cell voltage MinCellVolt, and calculating the voltage difference: DeltaCellVolt = MaxCellVolt – MinCellVolt;

[0085] When the voltage difference DeltaCellVolt is greater than the set first target voltage difference TargetDeltaV1 and this phenomenon continues for more than the set time Wait seconds, the first stage of equalization is entered.

[0086] The difference between the voltage of each battery cell and the minimum voltage is detected. When the difference is greater than the set second target voltage difference TargetDeltaV2, the equalization command for that battery cell is turned on; otherwise, it is turned off.

[0087] BalCmd = ((CellVoltages - MinCellVolt) > TargetDeltaV2), where BalCmd is a Boolean value;

[0088] When the BalCmd of all individual cells is zero, the equalization completion flag flgBalCompl is set to 1, completing the first stage of equalization.

[0089] The second-stage equalization unit includes, if it is in a static state, the first-stage equalization is turned off and it returns to the initial state of determining whether to turn on equalization;

[0090] If it is in the charging state, it will enter the second stage of equalization. In the second stage, the battery voltage difference is already less than TargetDeltaV2.

[0091] During the charging process, the current is relatively stable. With the addition of information on temperature and battery cell terminal voltage, the SOC of a single cell can be estimated by looking up a table based on the dynamic current terminal voltage. Based on the offline calibrated charging current curve, the SOC of the single cell can be obtained, and the current chargeable capacity of the single cell can be calculated accordingly. For batteries with smaller chargeable capacity, discharge equalization can be performed.

[0092] In this embodiment, the battery SOC can be calculated using the current integration method, open-circuit voltage method, Kalman filtering method, or neural network method.

[0093] To enable those skilled in the art to better understand the present invention, the principles of the present invention are explained below in conjunction with the accompanying drawings:

[0094] This invention employs a two-stage equilibrium strategy, dividing the equilibrium process into two stages, with different strategies used in each stage. The working mode is as follows: Figure 1 As shown, Figure 1 The left side shows an inconsistent SOC state, which is balanced by differentially discharging different batteries. The right side shows an inconsistent capacity state, which is balanced by differentially discharging different batteries to maintain a consistent rechargeable capacity. Batteries with lower rechargeable capacity are discharged, with the goal of all batteries reaching full charge simultaneously. A hierarchical, time-sharing balancing control strategy is employed for the passive balancing circuit.

[0095] Voltage difference is the first-level judgment condition. For batteries with excessively large individual voltage differences, discharge equalization is performed to achieve consistent State of Charge (SOC). When the individual voltage difference is less than a certain threshold, equalization is initiated based on the rechargeable capacity and the difference between the rechargeable capacities. The individual battery SOC is estimated using the individual battery voltage and the battery pack SOC, and the rechargeable capacity of each individual battery is calculated. This estimate is dynamically adjusted through multiple iterations to achieve consistent rechargeable capacity. For passive equalization, batteries requiring equalization are divided into two levels, and the equalization time is adjusted according to different thresholds.

[0096] like Figure 2 As shown, it includes a first-stage equilibrium unit and a second-stage equilibrium unit;

[0097] The first-stage equalization unit is used to make the SOC of all individual batteries consistent.

[0098] The second-stage equalization unit is used to keep the rechargeable capacity of all individual batteries consistent.

[0099] Battery balancing is divided into two stages, with different balancing units used in each stage.

[0100] The equalization function will only be activated when the battery is idle or charging. When idle, it will only perform the first stage of equalization based on the voltage difference; when charging, it will perform time-sharing and phased equalization.

[0101] Initially, equalization is off. The BMS continuously monitors the individual cell voltages and determines the maximum cell voltage (MaxCellVolt) and the minimum cell voltage (MinCellVolt). It then calculates the voltage difference.

[0102] DeltaCellVolt=MaxCellVolt–MinCellVolt

[0103] When a voltage difference DeltaCellVolt > TargetDeltaV1 (the set target voltage difference 1) occurs and this phenomenon lasts for more than Wait (settable) seconds, the first stage of equalization begins.

[0104] The system detects the difference between the voltage of each battery cell and its minimum voltage. When the difference exceeds TargetDeltaV2 (the set target voltage difference of 2), the equalization command for that battery cell is activated; otherwise, it is deactivated.

[0105] BalCmd = ((CellVoltages - MinCellVolt) > TargetDeltaV2), where BalCmd is a Boolean value;

[0106] When the BalCmd of all individual cells is zero, the equalization completion flag flgBalCompl is set to 1, completing the first stage of equalization. The system then enters the equalization off state.

[0107] If the system is in a static state, turning off equalization will return it to the initial state of determining whether equalization should be turned on.

[0108] If it is in the charging state, it will enter the second stage of equalization. In the second stage, the battery voltage difference is already less than TargetDeltaV2.

[0109] During the charging process, the current is relatively stable. With the addition of information on temperature and battery cell terminal voltage, the SOC of a single cell can be estimated by looking up a table based on the dynamic current terminal voltage. Based on the offline calibrated charging current curve, the SOC of the single cell can be obtained, and the current chargeable capacity of the single cell can be calculated accordingly. For batteries with smaller chargeable capacity, discharge equalization can be performed.

[0110] 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 method for balancing power batteries, characterized in that, include, The first stage of equalization discharges the cells with high SOC to make the SOC of all cells consistent. The second stage of equalization discharges batteries with low individual rechargeable capacity, so that the rechargeable capacity of all individual batteries is kept consistent, and the equalization goal is for all batteries to reach a fully charged state at the same time. The first stage of equalization includes determining the maximum cell voltage MaxCellVolt and the minimum cell voltage MinCellVolt, and calculating the voltage difference: DeltaCellVolt = MaxCellVolt – MinCellVolt; When the voltage difference DeltaCellVolt is greater than the set first target voltage difference TargetDeltaV1 and this phenomenon continues for more than the set time Wait seconds, the first stage of equalization is entered. The difference between the voltage of each individual cell and the minimum voltage is detected. When the difference is greater than the set second target voltage difference TargetDeltaV2, the individual cell equalization command is activated; otherwise, it is deactivated. BalCmd=((CellVoltages-MinCellVolt)>TargetDeltaV2), where BalCmd is a Boolean value; When the BalCmd of all individual cells is zero, the equalization completion flag flgBalCompl is set to 1, completing the first stage of equalization. The second stage of balancing includes, if it is in a static state, the first stage of balancing is turned off and it returns to the initial state of judging whether to turn on balancing; If it is in the charging state, it will enter the second stage of equalization. In the second stage, the battery voltage difference is already less than TargetDeltaV2. During the charging process, the current is relatively stable. With the addition of information on temperature and battery cell terminal voltage, the SOC of a single cell can be estimated by looking up a table based on the dynamic current terminal voltage. Based on the offline calibrated charging current curve, the SOC of the single cell can be obtained, and the current chargeable capacity of the single cell can be calculated accordingly. For batteries with smaller chargeable capacity, discharge equalization can be performed.

2. The power battery balancing method according to claim 1, characterized in that, The battery equalization is divided into two states: battery resting or charging. When the battery is resting, only the first stage of equalization is performed. When the battery is charging, the first stage of equalization and the second stage of equalization are performed sequentially.

3. The power battery balancing method according to claim 1, characterized in that, When the battery is in a resting or charging state, the first stage of equalization uses the maximum voltage difference and time between the batteries as the conditions for starting the first stage of equalization. This stage is used to discharge equalize batteries with excessively large individual voltage differences in order to achieve consistent SOC. During charging, the second stage of equalization uses the rechargeable capacity and the difference between the average rechargeable capacity as the equalization activation condition. It uses the individual cell voltage and the battery pack SOC to estimate the individual cell SOC and calculate the individual cell rechargeable capacity. Based on multiple iterations, the estimated value is dynamically adjusted to achieve consistent rechargeable capacity.

4. The power battery balancing method according to claim 1, characterized in that, Battery SOC can be calculated using the current integration method, open-circuit voltage method, Kalman filtering method, or neural network method.

5. A power battery balancing device, characterized in that, include, The first-stage equalization unit discharges batteries with excessively high SOC to make the SOC of all individual batteries uniform. The second-stage equalization unit discharges individual batteries with low rechargeable capacity to make the rechargeable capacity of all individual batteries consistent, achieving the equalization goal of all batteries reaching full charge at the same time. The first-stage equalization unit includes determining the maximum cell voltage MaxCellVolt and the minimum cell voltage MinCellVolt, and calculating the voltage difference: DeltaCellVolt = MaxCellVolt – MinCellVolt; When the voltage difference DeltaCellVolt is greater than the set first target voltage difference TargetDeltaV1 and this phenomenon continues for more than the set time Wait seconds, the first stage of equalization is entered. The difference between the voltage of each individual cell and the minimum voltage is detected. When the difference is greater than the set second target voltage difference TargetDeltaV2, the individual cell equalization command is activated; otherwise, it is deactivated. BalCmd=((CellVoltages-MinCellVolt)>TargetDeltaV2), where BalCmd is a Boolean value; When the BalCmd of all individual cells is zero, the equalization completion flag flgBalCompl is set to 1, completing the first stage of equalization. The second-stage equalization unit includes, if it is in a static state, the first-stage equalization is turned off and it returns to the initial state of determining whether to turn on equalization; If it is in the charging state, it will enter the second stage of equalization. In the second stage, the battery voltage difference is already less than TargetDeltaV2. During the charging process, the current is relatively stable. With the addition of information on temperature and battery cell terminal voltage, the SOC of a single cell can be estimated by looking up a table based on the dynamic current terminal voltage. Based on the offline calibrated charging current curve, the SOC of the single cell can be obtained, and the current chargeable capacity of the single cell can be calculated accordingly. For batteries with smaller chargeable capacity, discharge equalization can be performed.

6. A power battery balancing device according to claim 5, characterized in that, The battery balancing process is divided into two states: battery rest or charging. When the battery is resting, only the first stage balancing unit is executed. When the battery is charging, the first stage balancing unit and the second stage balancing unit are executed sequentially.

7. A power battery balancing device according to claim 5, characterized in that, The first-stage equalization unit uses the maximum voltage difference and time between batteries as the starting conditions for equalization when the battery is in a resting or charging state. This stage is used to discharge and equalize batteries with large individual voltage differences in order to achieve consistent SOC. The second-stage equalization unit, in the charging state, uses the chargeable capacity and the difference between the average chargeable capacity as the equalization activation condition. It uses the individual cell voltage and the battery pack SOC to estimate the individual cell SOC and calculate the individual cell chargeable capacity. Based on multiple iterations, it dynamically adjusts the estimated value to achieve consistent chargeable capacity.

8. A power battery balancing device according to claim 5, characterized in that, Battery SOC can be calculated using the current integration method, open-circuit voltage method, Kalman filtering method, or neural network method.

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