Methods and systems for charge equalization in vehicle battery packs and vehicles.

Abstract

Invention details;

Description

A method and system for balancing the power of a vehicle battery pack and a vehicle

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on August 28, 2023, with application number 202311088276.5 and application name “A method, system and vehicle for balancing the charge of a vehicle battery pack”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of vehicle power battery management and balancing, and in particular to a method, system, vehicle, and computer-readable storage medium for balancing the power of a vehicle battery pack. Background Art

[0003] A lithium iron phosphate battery (LIFP) is a lithium-ion battery that uses lithium iron phosphate (LiFePO4) as the positive electrode material and carbon as the negative electrode material. Its single-cell rated voltage is 3.2V, and its charge cutoff voltage is 3.6V to 3.65V. During charging, some lithium ions in the LFP escape, transfer through the electrolyte to the negative electrode, and embed themselves in the negative electrode's carbon material. Simultaneously, electrons are released from the positive electrode and travel through the external circuit to the negative electrode, maintaining the chemical reaction balance. During discharge, lithium ions escape from the negative electrode and travel through the electrolyte to the positive electrode. Simultaneously, electrons are released from the negative electrode and travel through the external circuit to the positive electrode, providing energy to the outside world.

[0004] Lithium iron phosphate (LIFP) materials are composed of LiFePO4, an olivine-like structure. LFP batteries offer advantages such as long cycle life, low heat generation, excellent thermal stability, and low cost. Due to its price advantage and the increasing maturity and application of cell-to-pack (CTP) technology, which has increased the energy density of LFP battery systems, LFP batteries are experiencing increasing demand in the power battery market and are widely used in plug-in hybrid and pure electric vehicles.

[0005] The disadvantages of lithium iron phosphate batteries are also obvious: (1) poor power performance at low temperatures; (2) because the platform voltage of lithium iron phosphate is very stable during the charge and discharge process and basically does not change, the error in calculating the SOC (State of Charge, used to reflect the remaining capacity of the battery) by the open circuit voltage and ampere-hour integration method (by integrating the current and time during the battery discharge process to calculate the battery capacity) is large. There are many reasons for battery inconsistency, such as different self-discharge rates of different single cells, inconsistent environmental conditions such as operating temperature, and differences caused by the manufacturing process when the battery leaves the factory. In addition, the continuous changes in temperature, polarization, and usage cycle lead to greater deviations in SOC estimation than other materials. Different battery cells in the battery pack are also prone to voltage differences, resulting in differences in the consistency of the cells in the battery pack. The use environment and working conditions of lithium iron phosphate batteries used in plug-in hybrid electric vehicles and pure electric vehicles are complex. During use, the single cells will inevitably have performance and voltage inconsistencies. The inconsistency of the battery pack cells will affect the performance of the entire battery pack and reduce the service life of the battery pack.

[0006] Therefore, a balancing system is needed to address the voltage differential problem within the battery pack. However, the voltage characteristics of lithium iron phosphate (LiFePO4) batteries limit balancing opportunities, making it difficult to accurately calculate balancing time. This leads to a high incidence of misbalancing, reducing the lifespan and performance of the LiFePO4 battery pack. In severe cases, it can even damage the battery pack or create safety hazards.

[0007] Therefore, the existing technology still needs to be improved and developed.

[0008] Summary of the Invention

[0009] The main purpose of this application is to provide a method, system, vehicle and computer-readable storage medium for balancing the power of a vehicle battery pack, aiming to solve the problem in the prior art that due to the voltage characteristics of the vehicle battery pack (lithium iron phosphate), there are few balancing opportunities, which makes it difficult to accurately calculate the balancing time, resulting in many misbalancing situations and long passive balancing time, which reduces the life and performance of the vehicle battery pack (lithium iron phosphate battery pack), and in severe cases even causes damage to the vehicle battery pack or creates safety hazards.

[0010] The first aspect of the present application provides a method for balancing the power of a vehicle battery pack, comprising the following steps: if the vehicle is in a powered-on state and the vehicle meets the balancing conditions for triggering balancing, collecting battery data of the vehicle battery pack; calculating the balancing time and the power required for balancing based on the battery data, and selecting a balancing method based on the usage scenario and usage habits; obtaining the number of low-voltage battery cells, and if the number of low-voltage battery cells is less than or equal to the preset number of battery cells, selecting a battery with a preset voltage to supplement the low-voltage battery cells until the target power is reached through balancing, and if the number of low-voltage battery cells is greater than the preset number of battery cells, using a resistance power consumption method to reduce the power of the high-power battery cells to the target power.

[0011] According to the above technical means, the embodiment of the present application can collect relevant battery data of the vehicle battery pack when it is detected that the vehicle meets one of multiple balancing conditions, so as to calculate the balancing time and the power required for balancing. Then, according to the different usage scenarios and usage habits of the user, the balancing method is intelligently selected, and the balancing time is calculated as accurately as possible to avoid incorrect balancing. Finally, based on the comparison between the number of low-voltage battery cells and the preset number of battery cells, supplementary balancing or discharge balancing is selected. Supplementary balancing is to select a battery with a preset voltage to supplement the low-voltage battery cells until the target power is reached, reducing the balancing load, improving the balancing efficiency, and reducing the resistance energy consumption to balance the system load. Discharge balancing is to use the resistance power consumption method to reduce the power of the high-power battery cells to the target power, consume the high-power battery cells, and the balancing current is small.

[0012] Optionally, in one embodiment of the present application, the balancing conditions include: the minimum SOC of the battery cell is greater than a first percentage, the difference between the maximum SOC and the minimum SOC of the battery cell is greater than a second percentage, the maximum voltage difference of the battery cell is greater than a preset voltage value, the remaining balancing time is greater than 0, the entire vehicle has no faults, the balancing circuit temperature is less than a first temperature and the battery cell temperature is less than a second temperature, and the battery power is greater than a third percentage SOC during power replenishment and balancing; when any one of the balancing conditions is met, it indicates that the vehicle meets the balancing conditions for triggering balancing.

[0013] According to the above technical means, the embodiment of the present application can set multiple balancing conditions, and increase the balancing opportunity through multi-point balancing triggering conditions. The balancing conditions involve the minimum SOC of the battery cell, the difference between the maximum SOC and the minimum SOC of the battery cell, the maximum voltage difference of the battery cell, the remaining balancing time, the fault-free state of the entire vehicle, the balancing circuit temperature and the battery cell temperature, and the battery power during power replenishment balancing. When any one of the balancing conditions is met, it means that the vehicle meets the balancing conditions for triggering balancing, which increases the conditions for triggering battery balancing, thereby increasing the balancing opportunities of the vehicle battery pack.

[0014] Optionally, in one embodiment of the present application, the battery data includes battery voltage, battery power and battery current.

[0015] According to the above technical means, the embodiment of the present application can collect the battery voltage, battery power and battery current of the vehicle battery pack when the vehicle is in the powered-on state and the vehicle meets the balancing conditions for triggering balancing, thereby facilitating the subsequent accurate calculation of the balancing time and the power required for balancing based on the battery voltage, battery power and battery current data.

[0016] Optionally, in one embodiment of the present application, the balancing time includes: passive resistance balancing time and battery recharge balancing time; passive resistance balancing time = ΔE / (I 2*R), where ΔE is the balancing charge, I is the balancing current, and R is the balancing resistance; battery recharge balancing time = ΔE / (P*η), ​​where ΔE is the balancing charge, P is the battery balancing power, and η is the loss factor.

[0017] According to the above technical means, the balancing time in the embodiment of the present application includes passive resistance balancing time and battery replenishment balancing time. Passive resistance balancing is performed by resistance power consumption, and battery replenishment balancing is performed by battery replenishment. The passive resistance balancing time is calculated based on the balancing power, balancing current and balancing resistance. The battery replenishment balancing time is calculated based on the balancing power, battery balancing power and loss factor, which is convenient for using the calculated corresponding balancing time when performing discharge balancing or replenishment balancing later.

[0018] Optionally, in one embodiment of the present application, the amount of electricity required for equalization is calculated based on the battery data, specifically including: obtaining the battery cell voltage difference, and determining whether the battery cell voltage difference is greater than a pressure difference threshold; if the battery cell voltage difference is greater than the pressure difference threshold, determining whether the vehicle's stationary time is greater than a preset time and determining whether the SOC interval is within a preset range SOC interval; if the vehicle's stationary time is greater than the preset time and the SOC interval is within the preset range SOC interval, selecting the OCV-SOC table lookup method to calculate the amount of electricity required for equalization; if the vehicle's stationary time is not greater than the preset time or the SOC interval is not within the preset range SOC interval, determining whether the vehicle is in a DC charging state; if the vehicle is in a DC charging state, calculating the amount of electricity required for equalization through the vehicle battery pack constant current charging dQ / dV-SOC curve; if the vehicle is not in a DC charging state, determining whether the vehicle is in an AC charging state; if the vehicle is in an AC charging state, screening the battery cells at the charging end, and calculating the amount of electricity required for equalization when the SOC is greater than the fourth percentage.

[0019] According to the above technical means, the embodiment of the present application can select a method for calculating the amount of electricity required for equalization based on the judgment of the battery cell voltage difference, the vehicle's static time, the SOC range, and the DC and AC charging states. It includes three methods for calculating the amount of electricity required for equalization, namely the OCV-SOC table lookup method, the vehicle battery pack constant current charging dQ / dV-SOC curve, and the charging terminal calculation. It can accurately calculate the amount of electricity to be equalized, which is convenient for the use of the calculated amount of electricity required for equalization in subsequent discharge equalization or replenishment equalization.

[0020] Optionally, in one embodiment of the present application, the balancing method is selected according to the usage scenario and usage habits, specifically including: judging whether the entire vehicle is powered on; if the entire vehicle is not powered on, using parking offline balancing; if the entire vehicle is powered on, judging whether the vehicle speed is 0; if the vehicle speed is 0, using static balancing; if the vehicle speed is not 0, using driving balancing.

[0021] According to the above technical means, the embodiment of the present application can intelligently select the balancing method according to the user's usage scenarios and usage habits. The balancing methods include parking offline balancing, static balancing and driving balancing. In this way, the most appropriate balancing method can be selected according to different situations, which is conducive to improving the safety of vehicle battery pack balancing.

[0022] Optionally, in one embodiment of the present application, the number of low-voltage battery cells is obtained. If the number of low-voltage battery cells is less than or equal to the preset number of battery cells, a battery with a preset voltage is selected to supplement the low-voltage battery cells until the target power is reached in balance. If the number of low-voltage battery cells is greater than the preset number of battery cells, a resistance power consumption method is used to reduce the power of the high-power battery cells to the target power. Specifically, it includes: obtaining the number of low-voltage battery cells, judging whether the number of low-voltage battery cells is less than or equal to A*the total number of battery cells, where A is a constant less than 0.5; if the number of low-voltage battery cells is less than or equal to A*the total number of battery cells, a battery with a preset voltage is selected to supplement the low-voltage battery cells through a high-low voltage DC converter until the target power is reached in balance; if the number of low-voltage battery cells is greater than A*the total number of battery cells, a resistance power consumption method is used to reduce the power of the high-power battery cells to the target power.

[0023] According to the above technical means, the embodiment of the present application can select replenishment balancing or discharge balancing based on the comparison between the number of low-voltage battery cells and the preset number of battery cells. If the number of low-voltage battery cells is less than or equal to the total number of A* battery cells, then replenishment balancing is selected, that is, a battery with a preset voltage is selected to replenish the low-voltage battery cells through a high-low voltage DC converter until the target power is reached, the balancing load is reduced, the balancing efficiency is improved, and the resistance energy consumption is reduced to balance the system load. If the number of low-voltage battery cells is greater than the total number of A* battery cells, then discharge balancing is selected, that is, the resistance power consumption method is used to reduce the power of the high-power battery cells to the target power, and the high-power battery cells are consumed, and the balancing current is small.

[0024] Optionally, in one embodiment of the present application, the battery balancing method of the vehicle battery pack also includes: when the low-voltage battery cell is replenished with power by a battery of a preset voltage, if the power of the battery is lower than the fifth percentage SOC, the battery exits balancing, and the vehicle battery pack replenishes the battery. If the balancing conditions are met, the battery is controlled to perform balanced replenishment. If the replenishment reaches the target power or the replenishment conditions are not met, the replenishment is stopped.

[0025] According to the above technical means, the embodiment of the present application can control the vehicle to perform reverse charging when the battery power is lower than a certain SOC, that is, the battery is charged by the vehicle battery pack. After the battery is charged, if the balancing conditions are met, the balancing charging will continue, or the charging will be stopped when the charging is unable to be performed or the charging reaches the target power. This can avoid the inability to perform the balancing operation of the vehicle battery pack when the battery power is too low.

[0026] Optionally, in one embodiment of the present application, the number of low-voltage battery cells is obtained. If the number of low-voltage battery cells is less than or equal to a preset number of battery cells, a battery with a preset voltage is selected to supplement the low-voltage battery cells until the target power is reached. If the number of low-voltage battery cells is greater than the preset number of battery cells, the power of the high-power battery cells is reduced to the target power by using a resistance power consumption method. The method then includes: determining whether the balancing time is greater than 0; if the balancing time is greater than 0, saving the balancing time in real time, and performing subtraction processing on the balancing time; determining whether there is a fault or restriction condition that affects balancing; if there is no fault or restriction condition that affects balancing, determining whether a power-off request is detected; if a power-off request is detected, storing the remaining balancing time and balancing parameters and then powering off.

[0027] According to the above technical means, the embodiment of the present application can determine whether the balancing time is greater than 0 after selecting the optimal balancing strategy for balancing based on the vehicle status, the selected balancing method and the calculated balancing time, compared with the last incomplete balancing. If the balancing time is greater than 0, the balancing time is saved in real time and the balancing time is subtracted. The subtraction processing is to judge the balancing condition after balancing for a certain time, and subtract the balanced time from the balanced time to obtain the remaining balanced time. Then, it is determined whether there is a fault or restriction condition that affects the balancing. If there is no fault or restriction condition that affects the balancing, it is finally determined whether a power-off request is detected. If a power-off request is detected, the remaining balancing time and the balancing parameters are stored and the power is turned off, so that the battery balancing operation of the vehicle battery pack is more comprehensive and safer.

[0028] Optionally, in one embodiment of the present application, the method for balancing the battery pack of a vehicle further includes: if the vehicle is not in a powered-on state, determining whether the battery management system (BMS) satisfies the timed wake-up condition or the offline balancing condition; if the BMS system satisfies the timed wake-up condition or the offline balancing condition, reading the historical remaining balancing time and balancing method; determining whether the historical remaining balancing time is greater than the offline balancing time threshold; if the historical remaining balancing time is greater than the offline balancing time threshold, setting the offline balancing time to the offline balancing time threshold and then performing offline balancing; setting the BMS wake-up time to: offline balancing time threshold + preset time.

[0029] According to the above technical means, the embodiment of the present application can further determine whether the BMS system meets the timed wake-up or offline balancing conditions when the vehicle is not powered on, that is, if the vehicle is parked for a long time without starting, the entire vehicle will wake up the BMS system at a certain time interval. If the BMS system meets the timed wake-up or offline balancing conditions, the historical remaining balancing time and balancing method are read, and then it is determined whether the historical remaining balancing time is greater than the offline balancing time threshold. If the historical remaining balancing time is greater than the offline balancing time threshold, the offline balancing time is set to the offline balancing time threshold and then offline balancing is performed, and the BMS wake-up time is set to: offline balancing time threshold + preset time. This can avoid the failure to perform the battery balancing operation of the vehicle when the vehicle is not powered on.

[0030] Optionally, in one embodiment of the present application, the determining whether the historical remaining balancing time is greater than the offline balancing time threshold further includes: if the historical remaining balancing time is not greater than the offline balancing time threshold, directly setting the BMS wake-up time to: the offline balancing time threshold + the preset time.

[0031] According to the above technical means, the embodiment of the present application can directly set the BMS wake-up time to: offline balancing time threshold + preset time when the historical remaining balancing time is not greater than the offline balancing time threshold, making the battery balancing operation of the vehicle battery pack more comprehensive and intelligent.

[0032] Optionally, in one embodiment of the present application, the vehicle battery pack includes: a lithium iron phosphate battery pack.

[0033] According to the above technical means, the embodiment of the present application can be mainly aimed at the power balancing method of lithium iron phosphate battery packs, because lithium iron phosphate battery packs are the most representative battery packs for vehicles, that is, the multi-point triggered high-efficiency intelligent balancing of the present application is mainly aimed at lithium iron phosphate battery packs, but is not limited to lithium iron phosphate battery packs.

[0034] A second aspect of the present application provides a power balancing system for a vehicle battery pack, the power balancing system for the vehicle battery pack comprising: a data acquisition module for collecting battery data of the vehicle battery pack when the vehicle is in a powered-on state and the vehicle meets the balancing conditions for triggering balancing; a balancing calculation module for calculating the balancing time and the power required for balancing based on the battery data, and selecting a balancing method based on the usage scenario and usage habits; a balancing control module for obtaining the number of low-voltage battery cells, and if the number of low-voltage battery cells is less than or equal to the preset number of battery cells, selecting a battery with a preset voltage to supplement the low-voltage battery cells until the target power is reached; if the number of low-voltage battery cells is greater than the preset number of battery cells, using a resistance power consumption method to reduce the power of the high-power battery cells to the target power.

[0035] Optionally, in one embodiment of the present application, the balancing conditions include: the minimum SOC of the battery cell is greater than a first percentage, the difference between the maximum SOC and the minimum SOC of the battery cell is greater than a second percentage, the maximum voltage difference of the battery cell is greater than a preset voltage value, the remaining balancing time is greater than 0, the entire vehicle has no faults, the balancing circuit temperature is less than a first temperature and the battery cell temperature is less than a second temperature, and the battery power is greater than a third percentage SOC during power replenishment and balancing; when any one of the balancing conditions is met, it indicates that the vehicle meets the balancing conditions for triggering balancing.

[0036] Optionally, in one embodiment of the present application, the battery data includes battery voltage, battery power and battery current.

[0037] Optionally, in one embodiment of the present application, the balancing time includes: passive resistance balancing time and battery recharge balancing time; passive resistance balancing time = ΔE / (I 2*R), where ΔE is the balancing charge, I is the balancing current, and R is the balancing resistance; battery recharge balancing time = ΔE / (P*η), ​​where ΔE is the balancing charge, P is the battery balancing power, and η is the loss factor.

[0038] Optionally, in one embodiment of the present application, the equalization calculation module includes: a cell pressure difference acquisition and comparison unit, used to obtain the cell pressure difference and determine whether the cell pressure difference is greater than a pressure difference threshold; a stationary time and SOC interval judgment unit, used to determine whether the vehicle stationary time is greater than a preset time and whether the SOC interval is within a preset range SOC interval if the cell pressure difference is greater than the pressure difference threshold; a first equalization required power calculation unit, used to select the OCV-SOC lookup table method to calculate the equalization required power if the vehicle stationary time is greater than the preset time and the SOC interval is within the preset range SOC interval; a DC charging state judgment unit, used to determine whether ... DC charging state judgment unit, used to determine whether the vehicle stationary time is greater than the preset time and the SOC interval is within the preset range SOC interval; a DC charging state judgment unit, used to determine whether the vehicle stationary time is greater than the preset time and the SOC interval is within the preset range SOC interval; a DC charging state judgment unit, used to determine whether the vehicle stationary time is greater than the preset time and the SOC interval is within the preset range SOC interval; a DC charging state judgment unit, used to determine whether the vehicle stationary time is greater than the preset time and the SOC interval is within the preset range SOC interval; a DC charging state judgment unit, used to determine whether If the vehicle is stationary for no longer than the preset time or the SOC interval is not within the preset range, it is determined whether the vehicle is in a DC charging state; a second equalization required power calculation unit is used to calculate the equalization required power through the vehicle battery pack constant current charging dQ / dV-SOC curve if the vehicle is in a DC charging state; an AC charging state judgment unit is used to determine whether the vehicle is in an AC charging state if the vehicle is not in a DC charging state; a third equalization required power calculation unit is used to screen the battery cells at the charging terminal if the vehicle is in an AC charging state, and calculate the equalization required power when the SOC is greater than a fourth percentage.

[0039] Optionally, in one embodiment of the present application, the balancing calculation module also includes: a first vehicle power-on judgment unit, used to judge whether the vehicle is powered on; a first balancing mode selection unit, used to adopt parking offline balancing if the vehicle is not powered on; a vehicle speed judgment unit, used to judge whether the vehicle speed is 0 if the vehicle is powered on; a second balancing mode selection unit, used to adopt static balancing if the vehicle speed is 0; and a third balancing mode selection unit, used to adopt driving balancing if the vehicle speed is not 0.

[0040] Optionally, in one embodiment of the present application, the balancing control module includes: a low-voltage battery cell number acquisition comparison unit, used to obtain the number of low-voltage battery cells and determine whether the number of low-voltage battery cells is less than or equal to the total number of A* battery cells, where A is a constant less than 0.5; a power balancing unit, used to select a battery with a preset voltage to supplement the low-voltage battery cells through a high-low voltage DC converter if the number of low-voltage battery cells is less than or equal to the total number of A* battery cells, until the target power is balanced; a discharge balancing unit, used to use a resistance power consumption method to reduce the power of the high-power battery cells to the target power if the number of low-voltage battery cells is greater than the total number of A* battery cells.

[0041] Optionally, in one embodiment of the present application, the system of the embodiment of the present application further includes: a reverse charging unit, which is used to, when charging the low-voltage battery cell with a preset voltage battery, if the battery charge is lower than the fifth percentage SOC, the battery exits balancing, and the vehicle battery pack charges the battery, and controls the battery to perform balanced charging if the balancing conditions are met, and stops charging if the charging reaches the target charge or the charging conditions are not met. A balancing time judgment unit, which is used to judge whether the balancing time is greater than 0; a balancing time processing unit, which is used to save the balancing time in real time and perform subtraction processing on the balancing time if the balancing time is greater than 0; a fault or restriction condition judgment unit, which is used to judge whether there is a fault or restriction condition that affects balancing; a power-off request judgment unit, which is used to judge whether a power-off request is detected if there is no fault or restriction condition that affects balancing; and a power-off storage unit, which is used to store the remaining balancing time and balancing parameters before powering off if a power-off request is detected. The BMS system judgment unit is used to determine whether the BMS system meets the scheduled wake-up or offline balancing conditions if the vehicle is not in the power-on state. The balancing time and balancing mode reading unit is used to read the historical remaining balancing time and balancing mode if the BMS system meets the scheduled wake-up or offline balancing conditions. The historical remaining balancing time judgment unit is used to determine whether the historical remaining balancing time is greater than the offline balancing time threshold. The offline balancing unit is used to set the offline balancing time to the offline balancing time threshold and then perform offline balancing if the historical remaining balancing time is greater than the offline balancing time threshold. The first wake-up time setting unit is used to set the BMS wake-up time to: offline balancing time threshold + preset time. The second wake-up time setting unit is used to directly set the BMS wake-up time to: offline balancing time threshold + preset time if the historical remaining balancing time is not greater than the offline balancing time threshold.

[0042] Optionally, in one embodiment of the present application, the vehicle battery pack includes: a lithium iron phosphate battery pack.

[0043] A third aspect of the present application provides a vehicle, comprising: a memory, a processor, and a vehicle battery pack charge balancing program stored in the memory and executable on the processor. When the vehicle battery pack charge balancing program is executed by the processor, the steps of the vehicle battery pack charge balancing method as described in the above embodiment are implemented.

[0044] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, which stores a charge balancing program for a vehicle battery pack. When the charge balancing program for the vehicle battery pack is executed by a processor, the steps of the charge balancing method for the vehicle battery pack as described in the above embodiment are implemented.

[0045] Beneficial effects of this application:

[0046] (1) This application adds balancing conditions and increases the balancing opportunities through multi-point balancing triggering conditions. When any one of the balancing conditions is met, it means that the vehicle meets the balancing conditions for triggering balancing, and the conditions for triggering battery balancing are added, thereby increasing the balancing opportunities of the vehicle battery pack.

[0047] (2) This application accurately calculates the balancing time and the amount of power required for balancing based on the battery voltage, battery power, and battery current, making it easier to use the calculated corresponding balancing time and amount of power required for balancing when performing discharge balancing or replenishment balancing, and intelligently selects the balancing method based on the user's usage scenarios and habits, which is beneficial to improving the safety of vehicle battery pack balancing.

[0048] (3) This application selects supplementary power balancing or discharge balancing based on the comparison between the number of low-voltage battery cells and the preset number of battery cells, and selects a battery with a preset voltage to supplement the low-voltage battery cells through a high-low voltage DC converter until the target power is reached, thereby reducing the balancing load, improving the balancing efficiency, and reducing the resistance energy consumption to balance the system load, or selects discharge point balancing, that is, using a resistance power consumption method to reduce the power of the high-power battery cells to the target power, and consume the power of the high-power battery cells, with a small balancing current.

[0049] (4) When the battery charge is lower than a certain SOC, the present application controls the vehicle to perform reverse charging, that is, to charge the battery through the vehicle battery pack. After the battery charging is completed, if the balancing conditions are met, the balancing charging will continue, or if the charging is not possible or the charging reaches the target charge, the charging will be stopped. This can avoid the inability to perform the balancing operation of the vehicle battery pack when the battery charge is too low.

[0050] (5) When the present application detects that the vehicle meets one of the multiple balancing conditions, it collects the relevant battery data of the vehicle battery pack to calculate the balancing time and the amount of electricity required for balancing. Then, according to the different usage scenarios and usage habits of the users, it intelligently selects the balancing method, calculates the balancing time as accurately as possible, and avoids the occurrence of false balancing. Finally, according to the comparison between the number of low-voltage cells and the preset number of cells, it selects the replenishment balancing or discharge balancing. The replenishment balancing is to select a battery with a preset voltage to replenish the low-voltage cells until the target amount of electricity is reached, thereby reducing the balancing load, improving the balancing efficiency, and reducing the resistance energy consumption to balance the system load. The discharge balancing is to use the resistance consumption method to reduce the amount of high-capacity cells to the target amount of electricity, consume the high-capacity cells, and the balancing current is small, thereby improving the safety and service life of the vehicle battery pack.

[0051] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0053] FIG1 is a flow chart of a preferred embodiment of a method for balancing the charge of a vehicle battery pack according to the present application;

[0054] FIG2 is a schematic diagram of an OCV-SOC curve of a lithium iron phosphate battery cell in a preferred embodiment of the method for balancing the charge of a vehicle battery pack of the present application;

[0055] FIG3 is a schematic diagram of a dQ / dV-SOC curve of a lithium iron phosphate battery in constant current charging in a preferred embodiment of the method for balancing the battery pack of a vehicle of the present application;

[0056] FIG4 is a flow chart of an intelligent balancing strategy in a preferred embodiment of the method for balancing the power of a vehicle battery pack of the present application;

[0057] FIG5 is a schematic diagram of a balancing circuit in a preferred embodiment of the method for balancing the charge of a vehicle battery pack of the present application;

[0058] FIG6 is a flowchart showing specific implementation steps of the entire execution process of a preferred embodiment of the method for balancing the power of a vehicle battery pack of the present application;

[0059] FIG7 is a schematic structural diagram of a preferred embodiment of a power balancing system for a vehicle battery pack of the present application;

[0060] FIG8 is a schematic structural diagram of a preferred embodiment of the vehicle of the present application.

[0061] Among them, 10 is the vehicle battery pack power balancing system; 100 is the data acquisition module, 200 is the balancing calculation module, 300 is the balancing control module; 501 is the memory, 502 is the processor and 503 is the communication interface. DETAILED DESCRIPTION

[0062] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0063] In the prior art, there is a passive balancing system for lithium iron phosphate battery packs. It uses the precise difference in remaining charge (SOC) as the basis for balancing, and performs passive balancing when the lithium iron phosphate battery pack is at the high-voltage end. It separates the screening of the balancing judgment basis from the execution of the balancing action, so that the separated balancing judgment and execution timing are not necessarily performed at the same time. It provides a complete passive balancing solution, which can balance for a long time after entering the balancing stage. However, it can only confirm the selection of cells to be balanced and determine the balancing capacity in certain SOC ranges. Moreover, long-term use of the battery pack in the lithium iron phosphate battery platform area cannot accurately calculate the balancing time, and the opportunity to trigger balancing is rare. In addition, when performing balancing, high-capacity cells consume power, the balancing current is small, and energy is wasted. When only individual cell voltages are low, the balancing system load is large, and the balancing time required is long. In the prior art, there is also a method of determining balancing by different scenarios. Its balancing includes driving balancing method, charging balancing method, short-term storage balancing method, and long-term storage balancing method. The balancing time is determined by different scenarios, making the balancing time more accurate. However, its essence is still to calculate the balancing time through the OCV-SOC (battery open circuit voltage-state of charge) curve lookup table. In each balancing scenario, if the battery pack SOC range is in the lithium iron phosphate battery platform voltage segment, the balancing time cannot be accurately calculated; and when performing balancing, high-capacity cells consume power and the balancing current is small. When only the voltage of individual cells is low, the balancing system load is large, the balancing time required is long, and energy is wasted.

[0064] Traditional passive balancing of lithium iron phosphate requires first determining the standing time. The time before and after restart must be greater than 2 hours or the current must be less than 0.03C (C represents the current rate. For example, for a 28Ah cell, 1C discharge is 28A, and 0.03C discharge is 0.03*28A). The standing time must be greater than 2 hours before the cell open circuit voltage can be read, and the balancing time can be calculated in the non-platform voltage area. Due to the voltage characteristics of lithium iron phosphate battery packs and lithium iron phosphate, there are few opportunities for balancing, which makes it difficult to calculate the balancing time accurately, resulting in more misbalancing; the disadvantage is that the passive balancing time is long. Failure to balance in time or misbalancing will lead to increased cell voltage difference and increased inconsistency, reducing the life and performance of the lithium iron phosphate battery pack. In severe cases, it may even damage the battery pack or create safety hazards. This application aims to provide a multi-point triggering, efficient, and intelligent balancing strategy for lithium iron phosphate battery packs to solve the balancing problem of lithium iron phosphate battery packs and improve the performance and service life of lithium iron phosphate battery packs.

[0065] The following describes a method, system, and vehicle for balancing a battery pack of a vehicle according to an embodiment of the present application with reference to the accompanying drawings. In response to the problem mentioned in the above background technology that due to the voltage characteristics of the vehicle battery pack (lithium iron phosphate), there are few balancing opportunities, which makes it difficult to accurately calculate the balancing time, resulting in a large number of false balancing situations and a long passive balancing time, which reduces the life and performance of the vehicle battery pack (lithium iron phosphate battery pack). In severe cases, it may even cause damage to the vehicle battery pack or create safety hazards. The present application provides a method for balancing the power of a vehicle battery pack. In this method, when it is detected that the vehicle meets one of multiple balancing conditions, the relevant battery data of the vehicle battery pack is collected to calculate the balancing time and the power required for balancing. Then, according to the different usage scenarios and usage habits of the user, the balancing method is intelligently selected to calculate the balancing time as accurately as possible to avoid false balancing. Finally, based on the comparison between the number of low-voltage cells and the preset number of cells, supplementary balancing or discharge balancing is selected. Supplementary balancing is to select a battery with a preset voltage to supplement the low-voltage cells until the target power is reached, reducing the balancing load, improving the balancing efficiency, and reducing the resistance energy consumption balancing system load. Discharge balancing is to use a resistance consumption method to reduce the power of the high-power cells to the target power, consume the high-power cells, and the balancing current is small; thereby improving the performance and service life of the vehicle battery pack. This solves the technical problem in the related art that due to the voltage characteristics of the vehicle battery pack (lithium iron phosphate), there are few balancing opportunities, which makes it difficult to calculate the balancing time accurately, resulting in many misbalancing situations, long passive balancing time, reduced vehicle battery pack (lithium iron phosphate battery pack) life and performance, and in severe cases even causing damage to the vehicle battery pack or safety hazards.

[0066] In this application, if the vehicle is in a powered-on state and the vehicle meets the balancing conditions for triggering balancing, the battery data of the vehicle battery pack is collected; the balancing time and the power required for balancing are calculated based on the battery data, and the balancing method is selected according to the usage scenario and usage habits; the number of low-voltage battery cells is obtained, and if the number of low-voltage battery cells is less than or equal to the preset number of battery cells, a battery with a preset voltage is selected to replenish the low-voltage battery cells until the target power is reached through balancing; if the number of low-voltage battery cells is greater than the preset number of battery cells, the resistance power consumption method is used to reduce the power of the high-power battery cells to the target power, thereby improving the performance and service life of the vehicle battery pack.

[0067] Specifically, FIG1 is a flow chart of a method for balancing the charge of a vehicle battery pack provided in an embodiment of the present application.

[0068] As shown in FIG1 , the battery balancing method for a vehicle battery pack includes the following steps:

[0069] In step S1 , if the vehicle is in a powered-on state and the vehicle meets the balancing conditions for triggering balancing, battery data of the vehicle battery pack is collected.

[0070] It can be understood that the vehicle battery pack described in the embodiment of the present application includes a lithium iron phosphate battery pack. The multi-point triggered high-efficiency intelligent balancing of the present application is mainly aimed at the lithium iron phosphate battery pack. Figure 2 shows an OCV-SOC curve of a lithium iron phosphate battery cell. As shown in Figure 2, it can be seen that in the 30-95% SOC range, the OCV change is not obvious, and there is not enough slope to provide SOC correction and balancing time calculation. Therefore, the present application increases the SOC range of lithium iron phosphate that can be used to calculate the balancing time as much as possible.

[0071] Therefore, the balancing conditions in the embodiment of the present application include (i.e., balancing start-up conditions): the minimum SOC of the battery cell is greater than the first percentage (for example, the first percentage is preferably 10%), the difference between the maximum SOC and the minimum SOC of the battery cell is greater than the second percentage (for example, the second percentage is preferably 2%), the maximum voltage difference of the battery cell is greater than the preset voltage value (for example, the preset voltage value is preferably 10mV), the remaining balancing time is greater than 0, the vehicle has no faults, the balancing circuit temperature is less than the first temperature (for example, the first temperature is preferably 80°C) and the battery temperature is less than the second temperature (for example, the second temperature is preferably 55°C), and the battery power is greater than the third percentage SOC (for example, the third percentage is preferably 30%) during replenishment balancing; when any one of the balancing conditions is met, it means that the vehicle meets the balancing conditions for triggering balancing.

[0072] The reason why the embodiment of the present application sets multiple balancing conditions is to increase the chance of balancing through multi-point balancing trigger conditions. The balancing conditions involve the minimum SOC of the battery cell, the difference between the maximum SOC and the minimum SOC of the battery cell, the maximum voltage difference of the battery cell, the remaining balancing time, the whole vehicle is fault-free, the balancing circuit temperature and the battery cell temperature, and the battery charge during the power replenishment balancing. When any one of these balancing conditions is met, it means that the vehicle meets the balancing conditions for triggering balancing, which increases the conditions for triggering battery balancing, thereby increasing the balancing chance of the vehicle battery pack. The present application increases the balancing chance through multiple trigger conditions. In addition to the traditional static balancing object screening and balancing time calculation in the 10%-30% SOC range, static balancing object screening and balancing time calculation in the low SOC range (for example, 3-10%), constant current charging balancing object screening and balancing time calculation of 50% SOC and below, AC full charge balancing, and large pressure difference balancing screening are added.

[0073] The battery data in the embodiment of the present application includes battery voltage, battery power and battery current. The embodiment of the present application can collect data such as battery voltage, battery power and battery current of the vehicle battery pack when the vehicle is in a powered-on state and the vehicle meets the balancing conditions for triggering balancing, thereby facilitating the subsequent accurate calculation of the balancing time and the power required for balancing based on the battery voltage, battery power and battery current data.

[0074] In step S2, the balancing time and the amount of electricity required for balancing are calculated based on the battery data, and a balancing method is selected based on the usage scenario and usage habits.

[0075] It is understandable that the balancing time described in the embodiment of the present application includes: passive resistance balancing time and battery charging balancing time; passive resistance balancing time = ΔE / (I 2*R), where ΔE is the balancing charge, I is the balancing current, and R is the balancing resistance; battery charging balancing time = ΔE / (P*η), ​​where ΔE is the balancing charge, P is the battery balancing power, and η is the loss factor. In the embodiment of the present application, passive resistance balancing is performed by balancing through resistance power consumption, and battery charging balancing is performed by charging a battery (a 12V battery is preferably used in this application). The passive resistance balancing time is calculated based on the balancing charge, balancing current, and balancing resistance, and the battery charging balancing time is calculated based on the balancing charge, battery balancing power, and loss factor. This facilitates the use of the calculated corresponding balancing time in subsequent discharge balancing or charging balancing, and the balancing time is calculated as accurately as possible to avoid incorrect balancing.

[0076] Figure 3 shows the dQ / dV-SOC curve of the constant current charging of the lithium iron phosphate battery. As shown in Figure 3, during constant current charging, dQ / dV and SOC can accurately correspond when the SOC is below 50%. If it is in the DC charging state, the DC charging is a constant current step charging method. When the SOC is below 50%, the dQ / dV-SOC curve of the constant current charging of the lithium iron phosphate battery can accurately calculate the amount of electricity to be balanced.

[0077] Further, as shown in FIG4 , the cell pressure difference is obtained to determine whether the cell pressure difference is greater than the pressure difference threshold; if the cell pressure difference is greater than the pressure difference threshold, determine whether the vehicle is stationary for longer than a preset time (for example, the preset time is preferably 2 hours) and whether the SOC interval is within a preset range SOC interval (for example, the preset range SOC interval is preferably 10%-30%); if the vehicle is stationary for longer than the preset time (2 hours) and the SOC interval is within the preset range SOC interval (10%-30%), select the OCV-SOC lookup table method to calculate the amount of electricity required for balancing; if the vehicle is stationary for longer than the preset time (2 hours) and the SOC interval is within the preset range SOC interval (10%-30%), select the OCV-SOC lookup table method to calculate the amount of electricity required for balancing; if the vehicle is stationary for longer than the preset time (2 hours) and the SOC interval is within the preset range SOC interval (10%-30%), select the OCV-SOC lookup table method to calculate the amount of electricity required for balancing If the setting time is not greater than the preset time (2h) or the SOC interval is not within the preset range SOC interval (10%-30%), it is determined whether the vehicle is in a DC charging state; if the vehicle is in a DC charging state, the amount of electricity required for equalization is calculated through the constant current charging dQ / dV-SOC curve of the lithium iron phosphate battery (as shown in Figure 3); if the vehicle is not in a DC charging state, it is determined whether the vehicle is in an AC charging state; if the vehicle is in an AC charging state, the battery cells are screened at the charging end, and the amount of electricity required for equalization is calculated when the SOC is greater than a fourth percentage (for example, the fourth percentage is preferably 97%).

[0078] The embodiment of the present application can select a method for calculating the amount of electricity required for equalization based on the cell voltage difference, the vehicle's static time, the SOC range, and the DC and AC charging states. The method includes three methods for calculating the amount of electricity required for equalization, namely, the OCV-SOC table lookup method, the vehicle battery pack constant current charging dQ / dV-SOC curve, and the charging terminal calculation. The method can accurately calculate the amount of electricity required for equalization, making it easier to use the calculated amount of electricity required for equalization in subsequent discharge equalization or replenishment equalization.

[0079] Furthermore, as shown in Figure 4, the balancing scenario is mainly divided into three steps: determining whether the vehicle is powered on; if the vehicle is not powered on, using parked offline balancing; if the vehicle is powered on, determining whether the vehicle speed is zero; if the vehicle speed is zero, using static balancing; if the vehicle speed is not zero, using driving balancing. The embodiment of the present application can intelligently select the balancing method based on the user's usage scenario and usage habits. The balancing methods include parked offline balancing, static balancing, and driving balancing. This allows the most appropriate balancing method to be selected according to different situations, which is conducive to improving the safety of vehicle battery pack balancing.

[0080] In step S3, the number of low-voltage battery cells is obtained. If the number of low-voltage battery cells is less than or equal to the preset number of battery cells, a battery with a preset voltage is selected to replenish the low-voltage battery cells until the target power is reached. If the number of low-voltage battery cells is greater than the preset number of battery cells, the power consumption of the high-power battery cells is reduced to the target power by using a resistance power consumption method.

[0081] It can be understood that, as shown in Figure 4, the preset number of battery cells in this application = A*total number of battery cells (different battery cells with different capacities are different), the number of low-voltage battery cells is obtained, and it is determined whether the number of low-voltage battery cells is less than or equal to A*total number of battery cells, where A is a constant less than 0.5; if the number of low-voltage battery cells is less than or equal to A*total number of battery cells, a battery with a preset voltage (12V) is selected to supplement the low-voltage battery cells through a high-low voltage DC converter (DC-DC) until the target power is balanced; if the number of low-voltage battery cells is greater than A*total number of battery cells, a resistance power consumption method is used to reduce the power of the high-power battery cells to the target power.

[0082] The embodiment of the present application can select replenishment balancing or discharge balancing based on the comparison between the number of low-voltage battery cells and the preset number of battery cells. If the number of low-voltage battery cells is less than or equal to the total number of A* battery cells, then replenishment balancing is selected, that is, a battery with a preset voltage is selected to replenish the low-voltage battery cells through a high-low voltage DC converter until the target power is reached, thereby reducing the balancing load, improving the balancing efficiency, and reducing the resistance energy consumption to balance the system load. If the number of low-voltage battery cells is greater than the total number of A* battery cells, then discharge balancing is selected, that is, the resistance power consumption method is used to reduce the power of the high-power battery cells to the target power, and the high-power battery cells are consumed with a small balancing current.

[0083] Specifically, as shown in FIG4 , the intelligent balancing strategy process of this application is as follows:

[0084] start;

[0085] Step S10, obtaining the cell voltage difference, and determining whether the cell voltage difference is greater than a voltage difference threshold; if the cell voltage difference is greater than the voltage difference threshold, executing step S11;

[0086] Step S11, determining whether the vehicle has been stationary for more than 2 hours and whether the SOC interval is in a non-plateau segment (i.e., whether the SOC interval is between 10% and 30%); if the vehicle has been stationary for more than 2 hours and the SOC interval is in a non-plateau segment, executing step S12;

[0087] If the vehicle has been stationary for no more than 2 hours or the SOC interval is not in a non-plateau section, executing step S13;

[0088] Step S12: If the vehicle has been stationary for more than 2 hours and the SOC interval is in a non-plateau section, use the OCV-SOC lookup table method to calculate the power required for equalization;

[0089] Step S13, determining whether the vehicle is in a DC charging state; if the vehicle is in a DC charging state, executing step S14;

[0090] If the vehicle is not in the DC charging state, execute step S15;

[0091] Step S14: If the vehicle is in a DC charging state, the amount of electricity required for equalization is calculated using the dQ / dV-SOC curve of the lithium iron phosphate battery constant current charge;

[0092] Step S15: If the vehicle is not in the DC charging state, determine whether the vehicle is in the AC charging state; if the vehicle is in the AC charging state, execute step S16;

[0093] Step S16: If the vehicle is in AC charging state, the battery cells are screened at the charging terminal, and the power required for balancing is calculated when the SOC is greater than 97%;

[0094] Step S17, determine whether the vehicle is powered on; if the vehicle is not powered on, execute step S18;

[0095] If the vehicle is powered on, execute step S19;

[0096] Step S18: If the vehicle is not powered on, parking and offline balancing are performed;

[0097] Step S19, determine whether the vehicle speed is 0; if the vehicle speed is 0, execute step S20;

[0098] If the vehicle speed is not 0, execute step S21;

[0099] Step S20: If the vehicle speed is 0, static balancing is adopted;

[0100] Step S21: If the vehicle speed is not 0, then use driving balance;

[0101] Step S22, obtaining the number of low-voltage battery cells, and determining whether the number of low-voltage battery cells is less than or equal to the total number of A* battery cells; if the number of low-voltage battery cells is greater than the total number of A* battery cells, executing step S23;

[0102] If the number of low-voltage battery cells is less than or equal to A*total number of battery cells, execute step S24;

[0103] Step S23: If the number of low-voltage cells is greater than the total number of A* cells, a resistance power consumption method (discharge balancing) is adopted to reduce the power of the high-capacity cells to the target power;

[0104] Step S24: If the number of low-voltage cells is less than or equal to the total number of A* cells, a battery with a preset voltage (12V) is selected to supplement the low-voltage cells with electricity (supplementary balance) through a high-low voltage DC converter (DC-DC) until the target amount of electricity is reached.

[0105] Step S25, determining whether the balancing reaches the target power or does not meet the balancing condition; if the balancing reaches the target power or does not meet the balancing condition, then the process ends;

[0106] If the balancing does not reach the target power or the balancing condition is met, the process returns to step S23 or step S24;

[0107] Finish.

[0108] Furthermore, when the low-voltage cell is replenished with power by a battery of a preset voltage (12V), if the battery charge is lower than the fifth percentage (for example, the fifth percentage is preferably 30%) SOC, the battery exits balancing, and the vehicle battery pack replenishes the battery (i.e., reverse replenishment). If the balancing conditions are met, the battery is controlled to perform balanced replenishment. If the replenishment reaches the target charge or the replenishment conditions are not met, the replenishment is stopped. In the embodiment of the present application, when the battery charge is lower than a certain SOC, the vehicle can be controlled to perform reverse replenishment, that is, the battery is replenished by the vehicle battery pack. After the battery replenishment is completed, if the balancing conditions are met, the balanced replenishment is continued, or if replenishment is not possible or the replenishment reaches the target charge, the replenishment is stopped. This can avoid the inability to perform balancing operations on the vehicle battery pack when the battery charge is too low.

[0109] This application uses a 12V battery to replenish power for low-voltage cells, reducing the balancing load and improving the balancing efficiency. When the voltage of some cells is lower than the average voltage and reaches the balancing voltage difference standard, the 12V low-voltage power supply (battery) can be used to reversely replenish power to the cells through the DC-DC module of the on-board OBC. The replenishment current is large and the balancing efficiency is high. When the power of the 12V low-voltage power supply (battery) is low, balancing is stopped and the battery pack replenishes power to the 12V low-voltage power supply (battery). This can improve the balancing efficiency and reduce the resistance energy consumption and the load of the balancing system.

[0110] Furthermore, Figure 5 is a schematic diagram of the balancing circuit of the present application. In the embodiment of the present application, the balancing system can balance the energy consumption of cells with excessive energy through resistors, or it can supplement the energy consumption of cells with lower voltage through a 12V battery via a DC-DC converter. The battery cell voltage is collected in real time, and the balancing condition is determined based on the collected data and the vehicle status. The appropriate balancing strategy is selected based on the vehicle and battery status. For example, if the voltage of cell C1 in Figure 5 is determined to be too high, the balanced discharge condition is met and discharge is required. The control circuit opens the corresponding discharge circuit and discharges through the balancing resistor (R1 in Figure 5). After discharge reaches the target value (or the balancing limit condition is reached), discharge balancing automatically stops. If the voltage of cell C1 in Figure 5 is determined to be too low, the balanced charging condition is met and supplemental charging is required. The control circuit opens the corresponding supplemental charging circuit and supplements the energy through the 12V battery. When the 12V battery charge falls below 30% SOC, the vehicle battery pack (large battery pack) supplements the 12V battery via a DC-DC converter. After the 12V battery is supplemented, balancing and supplemental charging continue. When the charging reaches the target value or the charging conditions are not met, the charging stops automatically. By combining charging balancing and resistance discharge balancing, the balancing efficiency is improved and the load on the balancing system is reduced.

[0111] The following further describes the entire implementation process according to the steps of executing the battery balancing method for the vehicle battery pack of the present application, as shown in Figure 6:

[0112] start;

[0113] Step S100, determining whether the vehicle is in a powered-on state; if the vehicle is in a powered-on state, executing step S101;

[0114] If the vehicle is not in the power-on state, execute step S112;

[0115] Step S101: If the vehicle is powered on, determine whether the vehicle meets the equilibrium condition; if the vehicle meets the equilibrium condition, execute step S103;

[0116] If the vehicle does not meet the equilibrium condition, execute step S102;

[0117] Step S102: If the vehicle does not meet the equilibrium condition, exit the equilibrium;

[0118] Step S103: If the vehicle meets the balancing condition, read the historical remaining balancing time and balancing method;

[0119] Step S104: Select an balancing method based on the current state of the vehicle, calculate the balancing time, compare it with historical balancing information, and select the optimal balancing strategy;

[0120] Step S105, determine whether the balancing time is greater than 0; if the balancing time is equal to 0, execute step S106;

[0121] If the balancing time is greater than 0, execute step S107;

[0122] Step S106: If the balancing time is equal to 0, exit balancing;

[0123] Step S107: If the balancing time is greater than 0, the balancing time is saved in real time and subtracted. After a certain balancing time (which may vary for different balancing systems and battery packs), the balancing condition is determined by subtracting the balancing time from the balancing time to obtain the remaining balancing time.

[0124] Step S108, determining whether there is a fault or restriction that affects balancing; if there is a fault or restriction that affects balancing, executing step S109;

[0125] If there is no fault or restriction affecting balancing, execute step S110;

[0126] Step S109: If there is a fault or restriction that affects balancing, then exit balancing;

[0127] Step S110: If there is no fault or restriction affecting balancing, determine whether a power-off request is detected (the vehicle controller will send a power-off request signal); if no power-off request is detected, execute step S105 (i.e., continue to determine whether the balancing time is greater than 0);

[0128] If a power-off request is detected, step S111 is executed;

[0129] Step S111: If a power-off request is detected, the remaining equalization time and the equalization parameters are stored and then the power is turned off;

[0130] Step S112: If the vehicle is not powered on, determine whether the BMS system meets the timed wake-up condition or the offline balancing condition; if the BMS system does not meet the timed wake-up condition or the offline balancing condition, execute step S113;

[0131] If the BMS system meets the timed wake-up requirement or the offline balancing requirement, execute step S114;

[0132] Step S113: If the BMS system does not meet the timed wake-up requirement (if the vehicle is parked for a long time without starting, the vehicle will wake up the BMS system at a certain time interval) or does not meet the offline balancing condition, offline balancing will not be performed;

[0133] Step S114: If the BMS system meets the timed wake-up condition or the offline balancing condition, read the historical remaining balancing time and balancing mode;

[0134] Step S115, determine whether the remaining balancing time is greater than the offline balancing time threshold t; if the remaining balancing time is greater than the offline balancing time threshold t, execute step S116;

[0135] If the remaining balancing time is not greater than the offline balancing time threshold t, execute step S117;

[0136] Step S116: If the remaining balancing time is greater than the offline balancing time threshold, the offline balancing time is set to the offline balancing time threshold (t) and then offline balancing is performed;

[0137] Step S117: Set the BMS wake-up time to: offline balancing time threshold + 2 hours (the battery must be at rest for more than 2 hours to obtain an accurate open circuit voltage (OCV)), and re-determine whether to perform offline balancing.

[0138] Finish.

[0139] In summary, the embodiment of the present application can collect relevant battery data of the vehicle battery pack when it is detected that the vehicle meets one of multiple balancing conditions, so as to calculate the balancing time and the power required for balancing. Then, according to the user's different usage scenarios and usage habits, the balancing method is intelligently selected, and the balancing time is calculated as accurately as possible to avoid incorrect balancing. Finally, based on the comparison between the number of low-voltage battery cells and the preset number of battery cells, supplementary balancing or discharge balancing is selected. Supplementary balancing is to select a battery with a preset voltage to supplement the low-voltage battery cells until the target power is reached, reducing the balancing load, improving the balancing efficiency, and reducing the resistance energy consumption to balance the system load. Discharge balancing is to use the resistance consumption method to reduce the power of the high-power battery cells to the target power, consume the high-power battery cells, and the balancing current is small, which improves the safety and service life of the vehicle battery pack.

[0140] Next, a charge balancing system for a vehicle battery pack according to an embodiment of the present application will be described with reference to the accompanying drawings.

[0141] FIG7 is a block diagram of a battery balancing system for a vehicle battery pack according to an embodiment of the present application.

[0142] As shown in FIG7 , the battery balancing system 10 for a vehicle battery pack includes a data acquisition module 100 , a balancing calculation module 200 and a balancing control module 300 .

[0143] Specifically, the data acquisition module 100 is used to collect battery data of the vehicle battery pack if the vehicle is in a powered-on state and the vehicle meets the balancing conditions for triggering balancing.

[0144] The balancing calculation module 200 is used to calculate the balancing time and the amount of electricity required for balancing according to the battery data, and select a balancing method according to the usage scenario and usage habits.

[0145] The balancing control module 300 is used to obtain the number of low-voltage battery cells. If the number of low-voltage battery cells is less than or equal to the preset number of battery cells, a battery with a preset voltage is selected to replenish the low-voltage battery cells until the target power is reached. If the number of low-voltage battery cells is greater than the preset number of battery cells, the power consumption of the high-power battery cells is reduced to the target power by using a resistance power consumption method.

[0146] Optionally, in one embodiment of the present application, the balancing conditions include: the minimum SOC of the battery cell is greater than a first percentage, the difference between the maximum SOC and the minimum SOC of the battery cell is greater than a second percentage, the maximum voltage difference of the battery cell is greater than a preset voltage value, the remaining balancing time is greater than 0, the entire vehicle has no faults, the balancing circuit temperature is less than a first temperature and the battery cell temperature is less than a second temperature, and the battery power is greater than a third percentage SOC during power replenishment and balancing; when any one of the balancing conditions is met, it indicates that the vehicle meets the balancing conditions for triggering balancing.

[0147] Optionally, in one embodiment of the present application, the battery data includes battery voltage, battery power and battery current.

[0148] Optionally, in one embodiment of the present application, the balancing time includes: passive resistance balancing time and battery recharge balancing time; passive resistance balancing time = ΔE / (I 2*R), where ΔE is the balancing charge, I is the balancing current, and R is the balancing resistance; battery recharge balancing time = ΔE / (P*η), ​​where ΔE is the balancing charge, P is the battery balancing power, and η is the loss factor.

[0149] Optionally, in one embodiment of the present application, the balancing calculation module 200 includes: a cell voltage difference acquisition and comparison unit, a standstill time and SOC interval judgment unit, a first balancing required power calculation unit, a DC charging state judgment unit, a second balancing required power calculation unit, an AC charging state judgment unit and a third balancing required power calculation unit.

[0150] The cell voltage difference obtaining and comparing unit is used to obtain the cell voltage difference and determine whether the cell voltage difference is greater than a voltage difference threshold.

[0151] The stationary time and SOC interval judgment unit is used to judge whether the stationary time of the entire vehicle is greater than a preset time and whether the SOC interval is within a preset range SOC interval if the battery cell voltage difference is greater than the pressure difference threshold.

[0152] The first equalization required power calculation unit is used to select the OCV-SOC table lookup method to calculate the equalization required power if the vehicle is stationary for longer than the preset time and the SOC interval is within the preset range SOC interval.

[0153] The DC charging state judgment unit is used to judge whether the vehicle is in the DC charging state if the vehicle is stationary for a period of time not greater than the preset time or the SOC interval is not within the preset range SOC interval.

[0154] The second equalization required power calculation unit is used to calculate the equalization required power through the vehicle battery pack constant current charging dQ / dV-SOC curve if the vehicle is in a DC charging state.

[0155] The AC charging state judgment unit is used to judge whether the vehicle is in the AC charging state if the vehicle is not in the DC charging state.

[0156] The third equalization required power calculation unit is used to screen the battery cells at the charging terminal if the vehicle is in an AC charging state, and calculate the equalization required power when the SOC is greater than a fourth percentage.

[0157] Optionally, in one embodiment of the present application, the balancing calculation module 200 further includes: a first vehicle power-on judgment unit, a first balancing mode selection unit, a vehicle speed judgment unit, a second balancing mode selection unit and a third balancing mode selection unit.

[0158] Among them, the first vehicle power-on judgment unit is used to judge whether the vehicle is powered on.

[0159] The first balancing mode selection unit is used to adopt parking offline balancing if the vehicle is not powered on.

[0160] The vehicle speed judgment unit is used to judge whether the vehicle speed is 0 if the vehicle is powered on.

[0161] The second balancing mode selection unit is used to adopt static balancing if the vehicle speed is 0.

[0162] The third balancing mode selection unit is used to adopt driving balancing if the vehicle speed is not 0.

[0163] Optionally, in one embodiment of the present application, the balancing control module 300 includes: a low-voltage battery cell number acquisition and comparison unit, a power replenishment and balancing unit, and a discharge and balancing unit.

[0164] Among them, the low-voltage battery cell number acquisition comparison unit is used to obtain the number of low-voltage battery cells and determine whether the number of low-voltage battery cells is less than or equal to A*the total number of battery cells, wherein A is a constant less than 0.5.

[0165] The power replenishment and balancing unit is used to select a battery with a preset voltage to replenish the low-voltage battery cells through a high-low voltage DC converter if the number of low-voltage battery cells is less than or equal to the total number of A*battery cells, until the target power is reached.

[0166] The discharge equalization unit is used to reduce the power of the high-capacity battery cells to the target power by using a resistance power consumption method if the number of the low-voltage battery cells is greater than the total number of A* battery cells.

[0167] Optionally, in one embodiment of the present application, the power balancing system 10 of the vehicle battery pack of the embodiment of the present application also includes: a reverse power replenishment unit, a balancing time judgment unit, a balancing time processing unit, a fault or restriction condition judgment unit, a power-off request judgment unit, a storage power-off unit, a BMS system judgment unit, a balancing time and balancing method reading unit, a historical remaining balancing time judgment unit, an offline balancing unit, a first wake-up time setting unit and a second wake-up time setting unit.

[0168] Among them, the reverse charging unit is used to charge the low-voltage battery cell through a battery with a preset voltage. If the battery power is lower than the fifth percentage SOC, the battery will exit balancing and the vehicle battery pack will charge the battery. If the balancing conditions are met, the battery will be controlled to perform balancing charging. If the charging reaches the target power or the charging conditions are not met, the charging will be stopped.

[0169] The balancing time judgment unit is used to judge whether the balancing time is greater than 0.

[0170] The balancing time processing unit is used to save the balancing time in real time and perform subtraction processing on the balancing time if the balancing time is greater than 0.

[0171] The fault or restriction condition judgment unit is used to judge whether there is a fault or restriction condition that affects balancing.

[0172] The power-off request judging unit is configured to judge whether a power-off request is detected if there is no fault or restriction condition affecting balancing.

[0173] The storage power-off unit is configured to store the remaining equalization time and the equalization parameters and then power off if a power-off request is detected.

[0174] The BMS system judgment unit is used to judge whether the BMS system meets the timed wake-up condition or whether it meets the offline balancing condition if the vehicle is not in the power-on state.

[0175] The balancing time and balancing mode reading unit is used to read the historical remaining balancing time and balancing mode if the BMS system meets the timed wake-up or offline balancing conditions.

[0176] The historical remaining balancing time judgment unit is used to judge whether the historical remaining balancing time is greater than the offline balancing time threshold.

[0177] The offline balancing unit is configured to set the offline balancing time to the offline balancing time threshold and then perform offline balancing if the historical remaining balancing time is greater than the offline balancing time threshold.

[0178] The first wake-up time setting unit is configured to set the BMS wake-up time to: offline balancing time threshold + preset time.

[0179] The second wake-up time setting unit is configured to directly set the BMS wake-up time to: the offline balancing time threshold + the preset time if the historical remaining balancing time is not greater than the offline balancing time threshold.

[0180] Optionally, in one embodiment of the present application, the vehicle battery pack includes: a lithium iron phosphate battery pack.

[0181] It should be noted that the aforementioned explanation of the embodiment of the method for balancing the battery pack of a vehicle is also applicable to the battery balancing system for the battery pack of a vehicle in this embodiment, and will not be repeated here.

[0182] According to the power balancing system of the vehicle battery pack proposed in the embodiment of the present application, when it is detected that the vehicle meets one of multiple balancing conditions, the relevant battery data of the vehicle battery pack can be collected to calculate the balancing time and the power required for balancing. Then, according to the different usage scenarios and usage habits of the users, the balancing method is intelligently selected, and the balancing time is calculated as accurately as possible to avoid incorrect balancing. Finally, based on the comparison between the number of low-voltage battery cells and the preset number of battery cells, replenishment balancing or discharge balancing is selected. Replenishment balancing is to select a battery with a preset voltage to replenish the low-voltage battery cells until the target power is reached, reducing the balancing load, improving the balancing efficiency, and reducing the resistance energy consumption balancing system load. Discharge balancing is to use a resistance consumption method to reduce the power of the high-power battery cells to the target power, consume the high-power battery cells, and the balancing current is small, thereby improving the safety and service life of the vehicle battery pack.

[0183] This solves the technical problem in the related art that due to the voltage characteristics of the vehicle battery pack (lithium iron phosphate), there are few balancing opportunities, which makes it difficult to calculate the balancing time accurately, resulting in many misbalancing situations, long passive balancing time, reduced vehicle battery pack (lithium iron phosphate battery pack) life and performance, and in severe cases even causing damage to the vehicle battery pack or safety hazards.

[0184] FIG8 is a schematic diagram of the structure of a vehicle provided in an embodiment of the present application. The vehicle may include:

[0185] Memory 501 , processor 502 , and computer programs stored in the memory 501 and executable on the processor 502 .

[0186] When the processor 502 executes the program, the method for balancing the battery pack of a vehicle provided in the above embodiment is implemented.

[0187] Furthermore, the vehicle further comprises:

[0188] The communication interface 503 is used for communication between the memory 501 and the processor 502 .

[0189] The memory 501 is used to store computer programs that can be run on the processor 502 .

[0190] The memory 501 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0191] If the memory 501, processor 502, and communication interface 503 are implemented independently, the communication interface 503, memory 501, and processor 502 can be interconnected via a bus and communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EIS) bus. Buses can be divided into address buses, data buses, control buses, etc. For ease of illustration, FIG8 shows only one thick line, but this does not mean that there is only one bus or only one type of bus.

[0192] Optionally, in a specific implementation, if the memory 501, the processor 502 and the communication interface 503 are integrated on a chip, the memory 501, the processor 502 and the communication interface 503 can communicate with each other through an internal interface.

[0193] The processor 502 may be a central processing unit (CPU), an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0194] This embodiment also provides a computer-readable storage medium having a computer program stored thereon. When the program is executed by a processor, the above-mentioned method for balancing the battery pack of a vehicle is implemented.

[0195] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0196] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this application, "N" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0197] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing a custom logical function or process step, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may be performed in a different order than shown or discussed, including performing functions in a substantially simultaneous manner or in a reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present application pertain.

[0198] The logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing the logical functions, and can be embodied in any computer-readable storage medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (e.g., a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable storage medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable storage media include the following: an electrical connection having one or N wires (electronic devices), a portable computer disk cartridge (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disc read-only memory (CDROM). In addition, the computer-readable storage medium may even be paper or other suitable medium on which the program is printed, since the program can be obtained electronically by optically scanning the paper or other medium and then editing, interpreting or processing it in other suitable ways as necessary, and then storing it in a computer memory.

[0199] It should be understood that various parts of the present application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiment, the N steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used to implement: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0200] Those skilled in the art will understand that all or part of the steps in the method of the above embodiment can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiment.

[0201] In addition, the functional units in the various embodiments of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into a module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0202] The storage medium mentioned above may be a read-only memory, a magnetic disk, or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application. Persons skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

[0203] It should be understood that the application of this application is not limited to the above examples. For ordinary technicians in this field, they can make improvements or changes based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to this application.

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