Balancing control method for lithium iron battery pack

Abstract

The present invention discloses a balancing control method for an iron-lithium battery pack, comprising: judging the current working condition; marking the balancing mark bit according to the working condition, if it is slow charging, marking it according to the difference between the voltage of the single cell and the lowest voltage of each single cell; if it is fast charging, no marking; if it is a 1-hour rest wake-up working condition, marking it according to the lowest state of charge of each single cell and the difference between the state of charge of the single cell and the state of charge of the single cell; if it is a 60-hour rest wake-up working condition and the current is not greater than 2A, marking it according to the lowest state of charge of each single cell and the difference between the state of charge of the single cell and the state of charge of the single cell; if it is a discharge working condition and the current is not greater than 5A, marking it according to the difference between the voltage of the single cell and the lowest voltage of each single cell: turning on balancing when the start condition is met, and exiting balancing when the exit condition is met. The balancing control method for an iron-lithium battery pack of the present invention adopts different balancing strategies under different working conditions, improves balancing reliability, extends the service life of the battery cell, reduces costs, and improves user satisfaction.

Description

Technical Field

[0001] The present invention relates to the technical field of power battery balancing control, and in particular to a balancing control method for an iron-lithium battery pack. Background Art

[0002] Power battery balancing control strategies have always been a crucial aspect of power battery design. Failure in balancing can severely impact the consistency of cells and modules, reducing cell performance and service life. In severe cases, this can lead to battery failure and interruption of the vehicle's driving power. Therefore, an effective power battery balancing control strategy can prevent these issues, extend cell service life, and save costs. Therefore, power battery balancing control strategies are a crucial technical consideration.

[0003] The balancing methods currently used in the market include active balancing and passive balancing. Active balancing involves discharging high-voltage modules and charging low-voltage modules. This method has a complex balancing circuit, a difficult strategy to implement, and a high cost. Passive balancing involves discharging high-voltage modules. This method has a simple circuit, low cost, but an imperfect strategy.

[0004] Therefore, there is an urgent need for a balancing control method for a lithium iron battery pack. Summary of the Invention

[0005] The purpose of the present invention is to provide a balancing control method for an iron-lithium battery pack to solve the problems in the above-mentioned prior art, extend the service life of the battery cell, save costs, improve user satisfaction, solve the problem of imperfect passive balancing strategy, and reduce costs.

[0006] The present invention provides a method for controlling the balancing of an iron-lithium battery pack, which includes:

[0007] Determine the current battery operating condition;

[0008] According to the current battery working condition, mark the balance flag bit, including:

[0009] If the charging condition is slow charging, the current single cell is marked with a balance flag according to the voltage difference between the current single cell voltage in the battery pack and the lowest voltage among all single cells;

[0010] If the charging condition is fast charging, the balancing flag is not marked;

[0011] If the system is in a static state and wakes up after 1 hour, the current battery is marked with a balancing flag based on the lowest state of charge of each battery in the battery pack and the charge difference between the current battery state and the lowest state of charge.

[0012] If the system is in a static state and wakes up after 60 hours, and the absolute value of the battery pack current is less than or equal to 2A, the current battery will be marked with a balancing flag based on the minimum state of charge of each battery in the battery pack and the charge difference between the current battery state and the minimum state of charge;

[0013] If it is a discharge condition and the absolute value of the battery pack current is less than or equal to 5A, the current single cell voltage in the battery pack is marked with the balancing flag bit according to the voltage difference between the current single cell voltage and the lowest voltage among all single cells:

[0014] Under the corresponding current battery operating condition, when the preset balancing start condition is met, the balancing control is turned on, and when the preset balancing exit condition is met, the balancing control is exited.

[0015] In the above-mentioned balancing control method for the iron-lithium battery pack, preferably, when the current battery operating condition is a charging condition and is slow charging, the step of marking a balancing flag bit for the current single cell according to the voltage difference between the voltage of the current single cell in the battery pack and the lowest voltage among the single cells specifically includes:

[0016] When T min ≤25℃ and the maximum temperature difference of each single battery in the battery pack is ≤5℃, or T min >25℃,V max >3.62V, |I|≤5A, if V n -V min ≥50mV, the single cell corresponding to the serial number n is marked with the balance mark bit, where T min Indicates the lowest temperature of each single cell in the battery pack, V max Indicates the maximum voltage of each single cell in the battery pack, |I| indicates the absolute value of the current of the battery pack, V n Indicates the voltage of the nth single cell in the battery pack,

[0017] The corresponding balancing start condition is this time mark, and it will be started at the next power-on;

[0018] The corresponding equilibrium exit condition is if V n -V min ≤40mV, the balancing mark of the single cell corresponding to serial number n will be cleared.

[0019] In the above-mentioned balancing control method for the iron-lithium battery pack, preferably, when the current battery operating condition is a static operating condition and the battery is awakened for 1 hour, the step of marking the balancing flag bit of the current single cell according to the lowest state of charge of each single cell in the battery pack and the charge difference between the state of charge of the current single cell and the lowest state of charge specifically includes:

[0020] If SOCmin ≥95% and SOC n -SOC min ≥1.5%, then mark the single cell corresponding to the serial number n with the balance mark bit, where SOC min Indicates the lowest state of charge of each single cell in the battery pack, SOC n Indicates the state of charge of the nth single cell in the battery pack; the corresponding balancing start condition is this flag, this time start; the corresponding balancing exit condition is if SOC n -SOC min =0, then the balancing mark of the single cell corresponding to sequence number n will be cleared;

[0021] If SOC min ∈[50%, 70%], and SOC n -SOC min ≥6%, then mark the single cell corresponding to serial number n with the balancing flag bit; the corresponding balancing start condition is this time mark, this time start; the corresponding balancing exit condition is if SOC n -SOC min If the balance rate is less than or equal to 4.5%, the balance mark of the single cell corresponding to the serial number n will be cleared.

[0022] In the above-mentioned balancing control method for the iron-lithium battery pack, preferably, when the current battery operating condition is a static condition and the battery is awakened after 60 hours, and the absolute value of the current of the battery pack is less than or equal to 2A, the method of marking the balancing flag bit of the current single battery according to the minimum state of charge of each single battery in the battery pack and the charge difference between the state of charge of the current single battery and the minimum state of charge specifically includes:

[0023] If SOC min ≥95% and SOC n -SOC min ≥1.5%, then mark the single cell corresponding to serial number n with the balancing flag bit; the corresponding balancing start condition is this time mark, this time start; the corresponding balancing exit condition is if SOC n -SOC min =0, then the balancing mark of the single cell corresponding to sequence number n will be cleared;

[0024] If SOC min ∈[50%, 70%], and SOC n -SOC min ≥6%, then mark the single cell corresponding to the serial number n with the balancing flag; the corresponding balancing start condition is this time mark, this time start; the corresponding balancing exit condition is if SOC n -SOC min If the balance rate is less than or equal to 4.5%, the balance mark of the single cell corresponding to the serial number n will be cleared.

[0025] In the above-mentioned balancing control method for the iron-lithium battery pack, preferably, when the current battery operating condition is a discharge condition and the absolute value of the current of the battery pack is less than or equal to 5A, the step of marking the balancing flag bit of the current single cell according to the voltage difference between the voltage of the current single cell in the battery pack and the lowest voltage among the single cells specifically includes:

[0026] When T min ≤25℃ and the maximum temperature difference of each single battery in the battery pack is ≤5℃, or T min >25℃, corresponding voltage V max ∈[3.225,3.25], |I|≤5A for 1min, if V n -V min ≥15mV, the single cell corresponding to the serial number n is marked with the balancing flag bit; the corresponding balancing start condition is this time mark, this time start; the corresponding balancing exit condition is if V n -V min ≤10mV, the balancing mark of the single cell corresponding to sequence number n will be cleared.

[0027] As described above, the balancing control method for the iron-lithium battery pack, wherein preferably, the balancing control method for the iron-lithium battery pack further comprises:

[0028] Under static working condition and T min When the temperature is ≤0℃, no equilibrium judgment is performed.

[0029] As described above, the balancing control method for the iron-lithium battery pack, wherein preferably, the balancing control method for the iron-lithium battery pack further comprises:

[0030] When the vehicle is powered on again after waking up for 1 hour, the lithium-ion battery controller checks each battery pack for voltage differential faults at preset intervals. If a voltage differential fault occurs, the serial number of the single battery corresponding to the minimum voltage at the moment of the fault is determined as the faulty single battery:

[0031] If the serial number of the single cell corresponding to the minimum voltage at the time of the pressure difference fault is consistent with the serial number of the single cell corresponding to the minimum voltage at the time of the balancing flag judgment, the lithium-ion battery controller clears the balancing flag of all single cells and turns off balancing;

[0032] If the serial number of the single cell corresponding to the minimum voltage at the time of the pressure difference fault is one of the single cells in the module to be balanced after the balancing flag is determined, the lithium-ion battery controller clears the balancing flag of the faulty single cell, and the remaining modules to be balanced continue to execute the balancing start process;

[0033] If the serial number of the single cell corresponding to the minimum voltage at the time of the pressure difference fault is neither consistent with the serial number of the single cell corresponding to the minimum voltage at the time of the balancing flag judgment, nor is it one of the single cells of the module to be balanced after the balancing flag judgment, all the modules to be balanced will continue to execute the balancing start process.

[0034] In the above-mentioned balancing control method for the iron-lithium battery pack, preferably, the preset balancing exit condition corresponding to each current battery operating condition includes: if the total balancing time exceeds the preset time, then balancing is exited.

[0035] The present invention provides a balancing control method for an iron-lithium battery pack. The method adopts different balancing control strategies under different operating conditions, proposes balancing judgment, start-up and exit conditions covering all vehicle operating conditions, and promptly and effectively judges and balances the consistency of battery cells and modules, thereby improving the reliability of balancing and extending the service life of the battery cells. The method does not require redundant components or complex circuits to implement functions, which can greatly reduce costs and improve user satisfaction. The method can solve the problem that passive balancing is affected by different operating conditions and cannot determine whether balancing is performed, as well as the balancing error caused by the influence of SOC and SOH. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described below with reference to the accompanying drawings, in which:

[0037] Figure 1 This is a flow chart of an embodiment of the balancing control method for the iron-lithium battery pack provided by the present invention. DETAILED DESCRIPTION

[0038] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The description of the exemplary embodiments is merely illustrative and is in no way intended to limit the present disclosure, its application, or use. The present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to make the present disclosure thorough and complete and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that unless otherwise specifically stated, the relative arrangement of parts and steps, the composition of materials, numerical expressions, and numerical values set forth in these embodiments should be interpreted as being merely exemplary and not as limiting.

[0039] The terms "first," "second," and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are simply used to distinguish different parts. Terms such as "include" or "comprising" mean that the elements preceding the term include the elements listed after the term, and do not exclude the possibility of also including other elements. Terms such as "upper," "lower," and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0040] In the present disclosure, when a specific component is described as being located between a first component and a second component, there may or may not be an intervening component between the specific component and the first component or the second component. When a specific component is described as being connected to another component, the specific component may be directly connected to the other component without an intervening component, or may not be directly connected to the other component but have an intervening component.

[0041] All terms (including technical or scientific terms) used in this disclosure have the same meaning as those understood by one of ordinary skill in the art to which this disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in, for example, general dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an idealized or highly formal sense, unless explicitly defined herein.

[0042] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0043] The basis of balancing control strategy is to select appropriate balancing variables. Current balancing control strategies mostly use battery state of charge (SOC) or remaining available capacity or voltage as balancing variables.

[0044] In balancing control strategies that use SOC as a balancing variable, the battery's SOC is used as the condition for balancing to start. After balancing, the capacities of the individual cells in the battery pack are essentially the same, and all individual cells can reach the charge and discharge cutoff voltage when the battery module is subsequently charged or discharged. However, using SOC as a balancing indicator also has its limitations and disadvantages. First, if the SOC estimation accuracy is high, small SOC differences during charging and discharging, static state, or the initial power-up period may be difficult to identify. As the differences grow larger in the later stages, the pressure on balancing management will be greater, and even the balancing effect may not be fully achieved. Furthermore, the current during balancing will also affect the SOC estimation.

[0045] In a balancing control strategy that uses the remaining available capacity as a balancing variable, the current remaining available capacity is used as a balancing indicator. When the aging levels of individual cells within a battery pack vary significantly, even if the SOC of each cell is consistent at a given moment, the differences in the rate of change of the remaining charge between different cells will lead to inconsistencies with each step or cycle. If the remaining available capacity is used as a balancing variable, subsequent inconsistencies will essentially be eliminated. The disadvantage of using the remaining available capacity as a balancing indicator is that it requires real-time estimation of the power battery's capacity. Current capacity estimation methods mostly rely on offline estimation, and the accuracy of the estimation cannot be guaranteed.

[0046] In balancing control strategies that use voltage as a balancing variable, the power battery voltage is a physical quantity that can be collected during data acquisition. Since voltage can be observed, and open-circuit voltage has a certain relationship with SOC, when the open-circuit voltage of each power battery is roughly the same, it also indicates that the battery pack's SOC consistency is relatively good. Therefore, using open-circuit voltage as a balancing variable when the battery pack is idle can, to a certain extent, improve the battery pack's inconsistency. Using voltage as a balancing variable is also simple in concept and relatively easy to implement, with low hardware processor overhead. However, it is also limited by operating conditions and cannot cover all operating conditions.

[0047] like Figure 1 As shown, the balancing control method for the iron-lithium battery pack provided in this embodiment includes the following steps during actual execution:

[0048] Step S1, determining the current battery operating condition;

[0049] Step S2: Mark the balancing flag according to the current battery operating condition.

[0050] Step S3: Under the corresponding current battery operating condition, when a preset balancing start condition is met, balancing control is started; when a preset balancing exit condition is met, balancing control is exited.

[0051] In one embodiment of the balancing control method of the iron-lithium battery pack of the present invention, step S2 may specifically include:

[0052] Step S21: If the charging condition is slow charging, then a balance flag is marked on the current single cell according to the voltage difference between the voltage of the current single cell in the battery pack and the lowest voltage among the single cells.

[0053] Specifically, when T min ≤25℃ and the maximum temperature difference of each single battery in the battery pack is ≤5℃, or T min >25℃,V max >3.62V, |I|≤5A, if V n -V min ≥50mV, the single cell corresponding to the serial number n is marked with the balance mark bit, where T min Indicates the lowest temperature of each single cell in the battery pack, V max Indicates the maximum voltage of each single cell in the battery pack, |I| indicates the absolute value of the current of the battery pack, V n Indicates the voltage of the nth single cell in the battery pack,

[0054] The corresponding balancing start condition is this time mark, and it will be started at the next power-on;

[0055] The corresponding equilibrium exit condition is if V n -V min ≤40mV, the balancing mark of the single cell corresponding to serial number n will be cleared.

[0056] Step S22: If the operating condition is charging and fast charging, the balancing flag is not marked.

[0057] Step S23: If the battery is in a static state and is awakened after 1 hour, a balance flag is set for the current battery according to the lowest state of charge of each battery in the battery pack and the charge difference between the current battery state and the lowest state of charge.

[0058] Specifically, if SOC min ≥95% and SOC n -SOC min ≥1.5%, then mark the single cell corresponding to the serial number n with the balance mark bit, where SOC min Indicates the lowest state of charge of each single cell in the battery pack, SOC n Indicates the state of charge of the nth single cell in the battery pack; the corresponding balancing start condition is this flag, this time start; the corresponding balancing exit condition is if SOC n -SOC min =0, then the balancing mark of the single cell corresponding to sequence number n will be cleared;

[0059] If SOC min ∈[50%, 70%], and SOC n -SOC min ≥6%, then mark the single cell corresponding to serial number n with the balancing flag bit; the corresponding balancing start condition is this time mark, this time start; the corresponding balancing exit condition is if SOC n -SOC min If the balance rate is less than or equal to 4.5%, the balance mark of the single cell corresponding to the serial number n will be cleared.

[0060] Step S24: If the battery is in a stationary state and has been awakened after 60 hours, and the absolute value of the current of the battery pack is less than or equal to 2A, then the current battery is marked with a balance flag bit based on the minimum state of charge of each battery in the battery pack and the charge difference between the current battery state and the minimum state of charge.

[0061] Specifically, if SOC min ≥95% and SOC n -SOC min ≥1.5%, then mark the single cell corresponding to serial number n with the balancing flag bit; the corresponding balancing start condition is this time mark, this time start; the corresponding balancing exit condition is if SOC n -SOCmin =0, then the balancing mark of the single cell corresponding to sequence number n will be cleared;

[0062] If SOC min ∈[50%, 70%], and SOC n -SOC min ≥6%, then mark the single cell corresponding to the serial number n with the balancing flag; the corresponding balancing start condition is this time mark, this time start; the corresponding balancing exit condition is if SOC n -SOC min If the balance rate is less than or equal to 4.5%, the balance mark of the single cell corresponding to the serial number n will be cleared.

[0063] Step S25: If it is a discharge condition and the absolute value of the current of the battery pack is less than or equal to 5A, then a balance flag is marked on the current single cell according to the voltage difference between the voltage of the current single cell in the battery pack and the lowest voltage among the single cells.

[0064] Specifically, when T min ≤25℃ and the maximum temperature difference of each single battery in the battery pack is ≤5℃, or T min >25℃, corresponding voltage V max ∈[3.225,3.25], |I|≤5A for 1min, if V n -V min ≥15mV, the single cell corresponding to the serial number n is marked with the balancing flag bit; the corresponding balancing start condition is this time mark, this time start; the corresponding balancing exit condition is if V n -V min ≤10mV, the balancing mark of the single cell corresponding to sequence number n will be cleared.

[0065] The start-up conditions, start-up time and exit conditions corresponding to different working conditions are shown in Table 1.

[0066] Furthermore, as shown in Table 1, the preset balancing exit conditions corresponding to each current battery operating condition include: if the total balancing duration exceeds a preset duration (e.g., 153 hours), balancing is exited, thus providing timeout protection. It should be noted that the present invention does not impose a specific limitation on the preset duration.

[0067] Table 1

[0068]

[0069]

[0070]

[0071] Furthermore, in some embodiments of the present invention, the balancing control method of the lithium iron battery pack further includes:

[0072] Step S4: Under static working condition and T min When the temperature is ≤0℃, no equilibrium judgment is performed.

[0073] Furthermore, in some embodiments of the present invention, the balancing control method of the lithium iron battery pack further includes:

[0074] Step S5: When the vehicle is powered on again after waking up 1 hour later, the lithium-ion battery controller determines whether there is a voltage difference fault in each single cell of the battery pack at a preset time. If there is a voltage difference fault, the serial number of the single cell corresponding to the minimum voltage at the time of the fault is determined as the faulty single cell.

[0075] Among them, after the vehicle wakes up and powers on again after 1 hour, the vehicle controller (VCU) and lithium-ion battery controller (LBC) are activated. The LBC always judges whether there is a pressure difference fault (such as static pressure difference and dynamic pressure difference). By judging the pressure difference fault, the location of the faulty battery can be determined and marked to avoid using the faulty single cell as the balancing mark during the next balancing.

[0076] Specifically, if the serial number of the single cell corresponding to the minimum voltage at the time of the pressure difference fault is consistent with the serial number of the single cell corresponding to the minimum voltage at the time of the balancing flag judgment, the lithium-ion battery controller clears the balancing flag of all single cells and turns off balancing;

[0077] If the serial number of the single cell corresponding to the minimum voltage at the time of the pressure difference fault is one of the single cells in the module to be balanced after the balancing flag is determined, the lithium-ion battery controller clears the balancing flag of the faulty single cell, and the remaining modules to be balanced continue to execute the balancing start process;

[0078] If the serial number of the single cell corresponding to the minimum voltage at the time of the pressure difference fault is neither consistent with the serial number of the single cell corresponding to the minimum voltage at the time of the balancing flag judgment, nor is it one of the single cells of the module to be balanced after the balancing flag judgment, all the modules to be balanced will continue to execute the balancing start process.

[0079] The balancing control method for the iron-lithium battery pack provided in the embodiment of the present invention adopts different balancing control strategies under different working conditions, proposes balancing judgment, start-up and exit conditions covering all working conditions of the vehicle, and promptly and effectively judges and balances the consistency of battery cells and modules, thereby improving the reliability of balancing and extending the service life of the battery cells; it does not require redundant components or complex circuits to implement functions, which can greatly reduce costs and improve user satisfaction; it can solve the problem that passive balancing is affected by different working conditions and cannot judge whether to balance, as well as the balancing error caused by the influence of SOC and SOH.

[0080] Thus far, various embodiments of the present disclosure have been described in detail. To avoid obscuring the concept of the present disclosure, some details known in the art have not been described. Based on the above description, those skilled in the art can fully understand how to implement the technical solutions disclosed herein.

[0081] Although some specific embodiments of the present disclosure have been described in detail through examples, those skilled in the art will understand that the above examples are for illustration only and are not intended to limit the scope of the present disclosure. Those skilled in the art will understand that the above embodiments may be modified or some technical features may be replaced with equivalents without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A balancing control method for a lithium iron battery pack, characterized in that: include: Determine the current battery operating condition; According to the current battery working condition, mark the balance flag bit, including: If the charging condition is slow charging, the current single cell is marked with a balance flag according to the voltage difference between the current single cell voltage in the battery pack and the lowest voltage among all single cells; If the charging condition is fast charging, the balancing flag is not marked; If the system is in a static state and wakes up after 1 hour, the current battery is marked with a balancing flag based on the lowest state of charge of each battery in the battery pack and the charge difference between the current battery state and the lowest state of charge. If the system is in a static state and wakes up after 60 hours, and the absolute value of the battery pack current is less than or equal to 2A, the current battery will be marked with a balancing flag based on the minimum state of charge of each battery in the battery pack and the charge difference between the current battery state and the minimum state of charge; If it is a discharge condition and the absolute value of the battery pack current is less than or equal to 5A, the current single cell voltage in the battery pack is marked with the balancing flag bit according to the voltage difference between the current single cell voltage and the lowest voltage among all single cells: Under the corresponding current battery operating condition, when the preset balancing start condition is met, the balancing control is turned on, and when the preset balancing exit condition is met, the balancing control is exited.

2. The balancing control method for the iron-lithium battery pack according to claim 1, characterized in that: When the current battery operating condition is a charging condition and is slow charging, marking the current single cell battery with a balancing flag bit according to the voltage difference between the current single cell battery voltage in the battery pack and the lowest voltage among the single cells specifically includes: When T min ≤25℃ and the maximum temperature difference of each single battery in the battery pack is ≤5℃, or T min >25℃,V max >3.62V, |I|≤5A, if V n -V min ≥50mV, the single cell corresponding to the serial number n is marked with the balance mark bit, where T min Indicates the lowest temperature of each single cell in the battery pack, V max Indicates the maximum voltage of each single cell in the battery pack, |I| indicates the absolute value of the current of the battery pack, V n Indicates the voltage of the nth single cell in the battery pack, The corresponding balancing start condition is this time mark, and it will be started at the next power-on; The corresponding equilibrium exit condition is if V n -V min ≤40mV, the balancing mark of the single cell corresponding to serial number n will be cleared.

3. The balancing control method for the iron-lithium battery pack according to claim 1, characterized in that: When the current battery operating condition is a static condition and the battery is awakened after 1 hour, the step of marking the current single cell battery with a balancing flag bit according to the lowest state of charge of each single cell in the battery pack and the charge difference between the current single cell battery's state of charge and the lowest state of charge specifically includes: If SOC min ≥95% and SOC n -SOC min ≥1.5%, then mark the single cell corresponding to the serial number n with the balance mark bit, where SOC min Indicates the lowest state of charge of each single cell in the battery pack, SOC n Indicates the state of charge of the nth single cell in the battery pack; the corresponding balancing start condition is this flag, this time start; the corresponding balancing exit condition is if SOC n -SOC min =0, then the balancing mark of the single cell corresponding to sequence number n will be cleared; If SOC min ∈[50%, 70%], and SOC n -SOC min ≥6%, then mark the single cell corresponding to serial number n with the balancing flag bit; the corresponding balancing start condition is this time mark, this time start; the corresponding balancing exit condition is if SOC n -SOC min If the balance rate is less than or equal to 4.5%, the balance mark of the single cell corresponding to the serial number n will be cleared.

4. The balancing control method for a lithium iron battery pack according to claim 1, characterized in that: When the current battery operating condition is a static condition and the battery is awakened after 60 hours, and the absolute value of the current of the battery pack is less than or equal to 2A, the balancing flag bit of the current single battery is marked according to the minimum state of charge of each single battery in the battery pack and the charge difference between the current state of charge of the single battery and the minimum state of charge, specifically including: If SOC min ≥95% and SOC n -SOC min ≥1.5%, then mark the single cell corresponding to serial number n with the balancing flag bit; the corresponding balancing start condition is this time mark, this time start; the corresponding balancing exit condition is if SOC n -SOC min =0, then the balancing mark of the single cell corresponding to sequence number n will be cleared; If SOC min ∈[50%, 70%], and SOC n -SOC min ≥6%, then mark the single cell corresponding to serial number n with the balancing flag bit; the corresponding balancing start condition is this time mark, this time start; the corresponding balancing exit condition is if SOC n -SOC min If the balance rate is less than or equal to 4.5%, the balance mark of the single cell corresponding to the serial number n will be cleared.

5. The balancing control method for the iron-lithium battery pack according to claim 1, characterized in that: When the current battery operating condition is a discharge condition and the absolute value of the current of the battery pack is less than or equal to 5A, marking the balancing flag bit of the current single cell according to the voltage difference between the voltage of the current single cell in the battery pack and the lowest voltage among the single cells specifically includes: When T min ≤25℃ and the maximum temperature difference of each single battery in the battery pack is ≤5℃, or T min >25℃, corresponding voltage V max ∈[3.225,3.25], |I|≤5A for 1min, if V n -V min ≥15mV, the single cell corresponding to the serial number n is marked with the balancing flag bit; the corresponding balancing start condition is this time mark, this time start; the corresponding balancing exit condition is if V n -V min ≤10mV, the balancing mark of the single cell corresponding to sequence number n will be cleared.

6. The balancing control method for a lithium iron battery pack according to claim 1, characterized in that: The balancing control method of the iron-lithium battery pack further includes: Under static conditions and T min When the temperature is ≤0℃, no equilibrium judgment is performed.

7. The balancing control method for a lithium iron battery pack according to claim 1, characterized in that: The balancing control method of the iron-lithium battery pack further includes: When the vehicle is powered on again after waking up for 1 hour, the lithium-ion battery controller checks each battery pack for voltage differential faults at preset intervals. If a voltage differential fault occurs, the serial number of the single battery corresponding to the minimum voltage at the moment of the fault is determined as the faulty single battery: If the serial number of the single cell corresponding to the minimum voltage at the time of the pressure difference fault is consistent with the serial number of the single cell corresponding to the minimum voltage at the time of the balancing flag judgment, the lithium-ion battery controller clears the balancing flag of all single cells and turns off balancing; If the serial number of the single cell corresponding to the minimum voltage at the time of the pressure difference fault is one of the single cells in the module to be balanced after the balancing flag is determined, the lithium-ion battery controller clears the balancing flag of the faulty single cell, and the remaining modules to be balanced continue to execute the balancing start process; If the serial number of the single cell corresponding to the minimum voltage at the time of the pressure difference fault is neither consistent with the serial number of the single cell corresponding to the minimum voltage at the time of the balancing flag judgment, nor is it one of the single cells of the module to be balanced after the balancing flag judgment, all the modules to be balanced will continue to execute the balancing start process.

8. The balancing control method for a lithium iron battery pack according to claim 1, characterized in that: The preset balancing exit conditions corresponding to each current battery operating condition include: if the total balancing time exceeds the preset time, balancing is exited.

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