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

Abstract

This application discloses a method, system, and vehicle for equalizing the charge of a vehicle battery pack. The method includes: when the vehicle is powered on and meets the equalization conditions for triggering equalization, collecting battery data of the vehicle battery pack; calculating the equalization time and the charge required for equalization based on the battery data, and selecting an equalization method according to the usage scenario and usage habits; obtaining the number of low-voltage cells; if the number of low-voltage cells is less than or equal to a preset number of cells, selecting a battery with a preset voltage to replenish the low-voltage cells until the target charge is reached; if the number of low-voltage cells is greater than the preset number of cells, using a resistor power dissipation method to reduce the charge of high-charge cells to the target charge. This application adds equalization conditions for triggering battery equalization, intelligently selects the equalization method, accurately calculates the equalization time, avoids erroneous equalization, and selects either replenishment equalization or discharge equalization according to the situation, thereby improving the performance and service life of the vehicle battery pack.

Description

Technical Field

[0001] This application relates to the field of vehicle power battery management and balancing technology, and in particular to a method, system, vehicle, and computer-readable storage medium for balancing the charge of a vehicle battery pack. Background Technology

[0002] A lithium iron phosphate (LFP) battery is a lithium-ion battery that uses lithium iron phosphate (LiFePO4) as the positive electrode material and carbon as the negative electrode material. The rated voltage of a single cell is 3.2V, and the charging cut-off voltage is 3.6V~3.65V. During charging, some lithium ions are released from the lithium iron phosphate and transferred to the negative electrode via the electrolyte, where they are embedded in the carbon material. Simultaneously, electrons are released from the positive electrode and travel from the external circuit to the negative electrode, maintaining the chemical reaction balance. During discharging, lithium ions are released from the negative electrode, travel through the electrolyte to the positive electrode, and simultaneously, electrons are released from the negative electrode and travel from the external circuit to the positive electrode, providing energy to the external environment.

[0003] Lithium iron phosphate (LFP) materials are composed of olivine-structured LiFePO4. LFP batteries offer advantages such as long cycle life, low heat generation, good thermal stability, and low cost. Due to its price advantage, and with the maturity and application of cell-to-pack (CTP) technology, which has improved the energy density of LFP battery systems, the demand for LFP batteries in the power battery market is continuously increasing, and they are widely used in plug-in hybrid and pure electric vehicles.

[0004] The disadvantages of lithium iron phosphate batteries are also obvious: (1) poor power performance at low temperatures; (2) because the plateau voltage of lithium iron phosphate batteries is very stable during the charging and discharging process and does not change much, the error in calculating SOC (State of Charge, which reflects the remaining capacity of the battery) by using 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 relatively large. There are many reasons for battery inconsistency, such as different self-discharge rates of different individual cells, inconsistent environmental conditions such as operating temperature, and differences caused by manufacturing processes when the battery leaves the factory. In addition, the continuous changes in temperature, polarization, and usage cycle lead to a larger deviation in SOC estimation compared to other materials. Different cells in the battery pack are also prone to voltage differences, resulting in inconsistencies in cell consistency within the battery pack. The operating environment and working conditions of lithium iron phosphate batteries used in plug-in hybrid electric vehicles and pure electric vehicles are complex. During use, individual cells will inevitably experience performance and voltage inconsistencies. Inconsistencies in individual cells in the battery pack will affect the overall performance of the battery pack and reduce the battery pack's service life.

[0005] Therefore, a balancing system is needed to address the voltage difference issue among individual cells within the battery pack. However, due to the voltage characteristics of lithium iron phosphate batteries, balancing opportunities are limited, making it difficult to accurately calculate the balancing time. This leads to more instances of incorrect balancing, reducing the lifespan and performance of the lithium iron phosphate battery pack, and in severe cases, even causing battery pack damage or safety hazards.

[0006] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0007] The main objective of this application is to provide a method, system, vehicle, and computer-readable storage medium for equalizing the charge of a vehicle battery pack. The aim is to solve the problems in the prior art where, due to the voltage characteristics of the vehicle battery pack (lithium iron phosphate), there are few equalization opportunities, making it difficult to accurately calculate the equalization time, resulting in more false equalizations, longer passive equalization times, reduced lifespan and performance of the vehicle battery pack (lithium iron phosphate battery pack), and in severe cases, even damage to the vehicle battery pack or safety hazards.

[0008] The first aspect of this application provides a method for equalizing the power of a vehicle battery pack, comprising the following steps: when the vehicle is powered on and meets the equalization conditions for triggering equalization, battery data of the vehicle battery pack is collected; the equalization time and the amount of power required for equalization are calculated based on the battery data, and an equalization method is selected according to the usage scenario and usage habits; the number of low-voltage cells is obtained, and if the number of low-voltage cells is less than or equal to a preset number of cells, a battery with a preset voltage is selected to replenish the low-voltage cells until the equalization reaches the target power; if the number of low-voltage cells is greater than the preset number of cells, a resistor power consumption method is used to reduce the power of high-power cells to the target power.

[0009] Based on the above technical means, the embodiments of this application can collect relevant battery data of the vehicle battery pack when the vehicle is detected to meet one of multiple equalization conditions, thereby calculating the equalization time and the amount of electricity required for equalization. Then, according to different user scenarios and usage habits, the equalization method is intelligently selected to calculate the equalization time as accurately as possible and avoid false equalization. Finally, based on the comparison between the number of low-voltage cells and the preset number of cells, either supplementary equalization or discharge equalization is selected. Supplementary equalization selects a battery with a preset voltage to supplement the low-voltage cells until the equalization reaches the target amount of electricity, reducing the equalization load, improving equalization efficiency, and reducing the load of the resistance energy consumption equalization system. Discharge equalization uses a resistance energy consumption method to reduce the amount of electricity in high-capacity cells to the target amount of electricity, consuming electricity from the high-capacity cells, resulting in a small equalization current.

[0010] Optionally, in one embodiment of this application, the equalization conditions include: the lowest SOC of a single cell is greater than a first percentage, the difference between the highest and lowest SOC of a single cell is greater than a second percentage, the maximum voltage difference of a single cell is greater than a preset voltage value, the remaining equalization time is greater than 0, the vehicle has no faults, the temperature of the equalization circuit is less than a first temperature and the cell temperature is less than a second temperature, and the battery charge is greater than a third percentage of SOC during charging equalization; when any one of the equalization conditions is met, it indicates that the vehicle meets the equalization conditions for triggering equalization.

[0011] Based on the above technical means, the embodiments of this application can set multiple equalization conditions. By using multiple equalization trigger conditions, the equalization opportunities are increased. The equalization conditions involve the minimum SOC of a single cell, the difference between the maximum and minimum SOC of a single cell, the maximum voltage difference of a single cell, the remaining equalization time, the absence of faults in the entire vehicle, the temperature of the equalization circuit and the temperature of the cells, and the battery charge during charging equalization. When any one of the equalization conditions is met, it means that the vehicle meets the equalization conditions for triggering equalization, thus increasing the conditions for triggering battery equalization and increasing the equalization opportunities of the vehicle battery pack.

[0012] Optionally, in one embodiment of this application, the battery data includes battery voltage, battery charge, and battery current.

[0013] Based on the above technical means, the embodiments of this application can collect the battery voltage, battery charge, and battery current of the vehicle battery pack after the vehicle is powered on and meets the equalization conditions for triggering equalization, thereby facilitating the subsequent accurate calculation of equalization time and the amount of electricity required for equalization based on the data of battery voltage, battery charge, and battery current.

[0014] Optionally, in one embodiment of this application, the equalization time includes: passive resistance equalization time and battery charging equalization time; passive resistance equalization time = ΔE / (I 2 *R), where ΔE is the equalization charge, I is the equalization current, and R is the equalization resistance; Battery charging equalization time = ΔE / (P*η), ​​where ΔE is the equalization charge, P is the battery equalization power, and η is the loss factor.

[0015] According to the above technical means, the balancing time in this application embodiment includes passive resistance balancing time and battery charging balancing time. Passive resistance balancing is achieved by balancing through resistance power consumption, and battery charging balancing is achieved by balancing through battery charging. The passive resistance balancing time is calculated based on the balancing charge, balancing current, and balancing resistance. The battery charging balancing time is calculated based on the balancing charge, battery balancing power, and loss factor, so that the calculated corresponding balancing time can be used later when performing discharge balancing or charging balancing.

[0016] Optionally, in one embodiment of this application, calculating the required power for balancing based on the battery data specifically includes: 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, determining whether the vehicle's idle time is greater than a preset time and whether the SOC range is within a preset range; if the vehicle's idle time is greater than the preset time and the SOC range is within the preset range, selecting the OCV-SOC lookup table method to calculate the required power for balancing; if the vehicle's idle time is not greater than the preset time or the SOC range is not within the preset range, determining whether the vehicle is in a DC charging state; if the vehicle is in a DC charging state, calculating the required power for balancing using the constant current charging dQ / dV-SOC curve of the vehicle battery pack; 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 cells at the charging end, and calculating the required power for balancing when the SOC is greater than the fourth percentage.

[0017] Based on the above technical means, the embodiments of this application can select the method for calculating the amount of electricity required for balancing based on the cell voltage difference, the vehicle's resting time, the SOC range, and the judgment of DC and AC charging status. There are three methods for calculating the amount of electricity required for balancing: OCV-SOC lookup table method, constant current charging dQ / dV-SOC curve of the vehicle battery pack, and calculation at the end of charging. It can accurately calculate the amount of electricity to be balanced, which is convenient for subsequent discharge balancing or charging balancing to use the calculated amount of electricity required for balancing.

[0018] Optionally, in one embodiment of this application, the step of selecting the balancing method according to the usage scenario and usage habits specifically includes: determining whether the vehicle is powered on; if the vehicle is not powered on, then offline balancing is used; if the vehicle is powered on, determining whether the vehicle speed is 0; if the vehicle speed is 0, then static balancing is used; if the vehicle speed is not 0, then driving balancing is used.

[0019] Based on the above technical means, the embodiments of this application can intelligently select the balancing method according to the user's usage scenario and usage habits. The balancing methods include offline balancing when parked, static balancing, and driving balancing. This allows the most suitable balancing method to be selected according to different situations, which is beneficial to improving the safety of vehicle battery pack balancing.

[0020] Optionally, in one embodiment of this application, the step of obtaining the number of low-voltage cells includes: if the number of low-voltage cells is less than or equal to a preset number of cells, then selecting a battery with a preset voltage to replenish the low-voltage cells until the target charge level is reached; if the number of low-voltage cells is greater than the preset number of cells, then using a resistor-based power consumption method to reduce the charge level of the high-charge cells to the target charge level. Specifically, this includes: obtaining the number of low-voltage cells; determining whether the number of low-voltage cells is less than or equal to A * the total number of cells, where A is a constant less than 0.5; if the number of low-voltage cells is less than or equal to A * the total number of cells, then selecting a battery with a preset voltage and using a high-low voltage DC-DC converter to replenish the low-voltage cells until the target charge level is reached; if the number of low-voltage cells is greater than A * the total number of cells, then using a resistor-based power consumption method to reduce the charge level of the high-charge cells to the target charge level.

[0021] Based on the above technical means, the embodiments of this application can select either supplementary equalization or discharge equalization based on the comparison between the number of low-voltage cells and the preset number of cells. If the number of low-voltage cells is less than or equal to A * the total number of cells, then supplementary equalization is selected, that is, a battery with a preset voltage is selected to supplement the low-voltage cells through a high-low voltage DC converter until the equalization reaches the target capacity, thereby reducing the equalization load, improving the equalization efficiency, and reducing the load of the resistance energy consumption equalization system. If the number of low-voltage cells is greater than A * the total number of cells, then discharge equalization is selected, that is, a resistance power consumption method is used to reduce the capacity of high-capacity cells to the target capacity, thereby consuming power from the high-capacity cells, resulting in a small equalization current.

[0022] Optionally, in one embodiment of this application, the power balancing method of the vehicle battery pack further includes: when the low-voltage cells are replenished with power by a battery with a preset voltage, if the power of the battery is lower than the fifth percentage of SOC, the battery exits the balancing process, and the vehicle battery pack replenishes the power of the battery. If the balancing conditions are met, the battery is controlled to perform balancing replenishment. If the replenishment reaches the target power or does not meet the replenishment conditions, the replenishment is stopped.

[0023] Based on the above technical means, the embodiments of this application can control the vehicle to perform reverse charging when the battery charge is lower than a certain SOC, that is, to charge the battery through the vehicle battery pack. After the battery is charged, if the balancing conditions are met, the equalization charging will continue, or the charging will stop when the battery cannot be charged or the target charge is reached. This can avoid the inability to achieve the equalization operation of the vehicle battery pack when the battery charge is too low.

[0024] Optionally, in one embodiment of this application, the step of obtaining the number of low-voltage cells includes: if the number of low-voltage cells is less than or equal to a preset number of cells, then selecting a battery with a preset voltage to replenish the low-voltage cells until the target charge level is reached; if the number of low-voltage cells is greater than the preset number of cells, then using a resistor power-dissipating method to reduce the charge level of the high-charge cells to the target charge level; and further including: 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 subtracting the balancing time; determining whether there are any faults or limiting conditions affecting the balancing; if there are no faults or limiting conditions affecting the balancing, determining whether a power-down request is detected; if a power-down request is detected, storing the remaining balancing time and balancing parameters before powering down.

[0025] Based on the above technical means, the embodiments of this application can, after selecting the optimal balancing strategy based on the vehicle status, the selected balancing method, and the calculated balancing time, compare it with the previous incomplete balancing and perform balancing, determine whether the balancing time is greater than 0. If the balancing time is greater than 0, the balancing time is saved in real time, and a subtraction process is performed on the balancing time. The subtraction process is that after balancing for a certain period of time, the balancing condition is judged by subtracting the already balanced time from the balancing time to obtain the remaining balancing time. Then, it is judged whether there are any faults or restrictions affecting the balancing. If there are no faults or restrictions affecting the balancing, it is judged whether a power-down request is detected. If a power-down request is detected, the remaining balancing time and balancing parameters are stored before powering down, making the battery pack power balancing operation more comprehensive and safer.

[0026] Optionally, in one embodiment of this application, the battery pack power balancing method further includes: if the vehicle is not powered on, determining whether the BMS system meets the timed wake-up or offline balancing conditions; if the BMS system meets the timed wake-up or offline balancing conditions, 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.

[0027] Based on the above technical means, this application embodiment 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, when the vehicle is parked for a long time without starting, the vehicle will wake up the BMS system at certain time intervals. 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 offline balancing is performed. The BMS wake-up time is set to: offline balancing time threshold + preset time. This can avoid the failure to perform battery pack balancing operation when the vehicle is not powered on.

[0028] Optionally, in one embodiment of this application, the step of 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, then the BMS wake-up time is directly set to: offline balancing time threshold + preset time.

[0029] Based on the above technical means, the embodiments of this 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, so as to make the power balancing operation of the vehicle battery pack more comprehensive and intelligent.

[0030] Optionally, in one embodiment of this application, the vehicle battery pack includes a lithium iron phosphate battery pack.

[0031] Based on the above technical means, the embodiments of this application can mainly be aimed at the power balancing method of lithium iron phosphate battery packs, because lithium iron phosphate battery packs are the most representative battery packs in vehicles. That is, the multi-point triggered high-efficiency intelligent balancing method of this application is mainly aimed at lithium iron phosphate battery packs, but is not limited to lithium iron phosphate battery packs.

[0032] A second aspect of this application provides a power balancing system for a vehicle battery pack. The system includes: a data acquisition module for acquiring battery data of the vehicle battery pack when the vehicle is powered on and meets the balancing conditions for triggering balancing; a balancing calculation module for calculating the balancing time and required power based on the battery data, and selecting a balancing method based on the usage scenario and usage habits; and a balancing control module for obtaining the number of low-voltage cells. If the number of low-voltage cells is less than or equal to a preset number of cells, a battery with a preset voltage is selected to replenish the low-voltage cells until the target power level is reached. If the number of low-voltage cells is greater than the preset number of cells, a resistor-based power consumption method is used to reduce the power of high-voltage cells to the target power level.

[0033] Optionally, in one embodiment of this application, the equalization conditions include: the lowest SOC of a single cell is greater than a first percentage, the difference between the highest and lowest SOC of a single cell is greater than a second percentage, the maximum voltage difference of a single cell is greater than a preset voltage value, the remaining equalization time is greater than 0, the vehicle has no faults, the temperature of the equalization circuit is less than a first temperature and the cell temperature is less than a second temperature, and the battery charge is greater than a third percentage of SOC during charging equalization; when any one of the equalization conditions is met, it indicates that the vehicle meets the equalization conditions for triggering equalization.

[0034] Optionally, in one embodiment of this application, the battery data includes battery voltage, battery charge, and battery current.

[0035] Optionally, in one embodiment of this application, the equalization time includes: passive resistance equalization time and battery charging equalization time; passive resistance equalization time = ΔE / (I 2 *R), where ΔE is the equalization charge, I is the equalization current, and R is the equalization resistance; Battery charging equalization time = ΔE / (P*η), ​​where ΔE is the equalization charge, P is the battery equalization power, and η is the loss factor.

[0036] Optionally, in one embodiment of this application, the equalization calculation module includes: a cell voltage difference acquisition and comparison unit, used to acquire the cell voltage difference and determine whether the cell voltage difference is greater than a voltage difference threshold; a resting time and SOC range judgment unit, used to determine whether the vehicle resting time is greater than a preset time and whether the SOC range is within a preset range if the cell voltage difference is greater than the voltage difference threshold; a first equalization required power calculation unit, used to calculate the equalization required power using the OCV-SOC lookup table method if the vehicle resting time is greater than the preset time and the SOC range is within the preset range; and a DC charging status judgment unit, used for... If the vehicle's stationary time is not greater than the preset time or the SOC range is not within the preset SOC range, then it is determined whether the vehicle is in DC charging mode; the second equalization power calculation unit is used to calculate the equalization power required by means of the constant current charging dQ / dV-SOC curve of the vehicle battery pack if the vehicle is in DC charging mode; the AC charging status judgment unit is used to determine whether the vehicle is in AC charging mode if the vehicle is not in DC charging mode; the third equalization power calculation unit is used to screen the cells at the end of the charging process if the vehicle is in AC charging mode, and calculate the equalization power required when the SOC is greater than the fourth percentage.

[0037] Optionally, in one embodiment of this application, the equalization calculation module further includes: a first vehicle power-on judgment unit, used to determine whether the vehicle is powered on; a first equalization mode selection unit, used to use offline equalization when the vehicle is not powered on; a vehicle speed judgment unit, used to determine whether the vehicle speed is 0 when the vehicle is powered on; a second equalization mode selection unit, used to use static equalization when the vehicle speed is 0; and a third equalization mode selection unit, used to use driving equalization when the vehicle speed is not 0.

[0038] Optionally, in one embodiment of this application, the equalization control module includes: a low-voltage cell count acquisition and comparison unit, used to acquire the number of low-voltage cells and determine whether the number of low-voltage cells is less than or equal to A * the total number of cells, where A is a constant less than 0.5; a charge equalization unit, used to select a battery with a preset voltage and charge the low-voltage cells through a high-low voltage DC-DC converter if the number of low-voltage cells is less than or equal to A * the total number of cells, until the equalization reaches the target charge level; and a discharge equalization unit, used to reduce the charge level of the high-charge cells to the target charge level by using a resistor power consumption method if the number of low-voltage cells is greater than A * the total number of cells.

[0039] Optionally, in one embodiment of this application, the system further includes: a reverse charging unit, used to, when charging the low-voltage cells with a battery of preset voltage, if the battery charge is below the fifth percentage of SOC, the battery exits the equalization process, and the vehicle battery pack charges the battery; if the equalization conditions are met, the battery is controlled to perform equalization charging again; if the charging reaches the target charge or the charging conditions are not met, the charging stops; an equalization time judgment unit, used to determine whether the equalization time is greater than 0; an equalization time processing unit, used to, if the equalization time is greater than 0, save the equalization time in real time and subtract the equalization time; a fault or limitation condition judgment unit, used to determine whether there are faults or limitations affecting the equalization; a power-down request judgment unit, used to, if there are no faults or limitations affecting the equalization, determine whether a power-down request is detected; and a power-down storage unit, used to, if a power-down request is detected, store the remaining equalization time and equalization parameters before powering down. The BMS system judgment unit is used to determine whether the BMS system meets the conditions for timed wake-up or offline balancing if the vehicle is not powered on. The balancing time and balancing method reading unit is used to read the historical remaining balancing time and balancing method if the BMS system meets the conditions for timed wake-up or offline balancing. 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 before performing 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.

[0040] Optionally, in one embodiment of this application, the vehicle battery pack includes a lithium iron phosphate battery pack.

[0041] A third aspect of this application provides a vehicle, the vehicle including: a memory, a processor, and a vehicle battery pack power balancing program stored in the memory and executable on the processor, wherein when the vehicle battery pack power balancing program is executed by the processor, it implements the steps of the vehicle battery pack power balancing method as described in the above embodiments.

[0042] A fourth aspect of this application provides a computer-readable storage medium storing a power balancing program for a vehicle battery pack. When executed by a processor, the power balancing program for the vehicle battery pack implements the steps of the power balancing method for the vehicle battery pack as described in the above embodiments.

[0043] The beneficial effects of this application are:

[0044] (1) This application adds equalization conditions and increases the chance of equalization by using multiple equalization trigger conditions. When any one of the equalization conditions is met, it means that the vehicle meets the equalization trigger condition, which increases the conditions for triggering battery equalization and thus increases the chance of equalization of the vehicle battery pack.

[0045] (2) This application uses data such as battery voltage, battery capacity and battery current to accurately calculate the balancing time and the amount of power required for balancing, so that the calculated balancing time and the amount of power required for balancing can be used when performing discharge balancing or charge balancing, and the balancing method can be intelligently selected according to the user's usage scenario and usage habits, which is conducive to improving the safety of vehicle battery pack balancing.

[0046] (3) This application selects either power replenishment or power discharge balance based on the comparison between the number of low-voltage cells and the preset number of cells. The battery with the preset voltage is selected to replenish the low-voltage cells through a high-low voltage DC converter until the balance reaches the target capacity, thereby reducing the balance load, improving the balance efficiency, and reducing the load of the resistance energy consumption balance system. Alternatively, power discharge balance can be selected, that is, the resistance power consumption method is used to reduce the capacity of the high-capacity cells to the target capacity and consume the power of the high-capacity cells, resulting in a small balance current.

[0047] (4) When the battery charge is lower than a certain SOC, this application controls the vehicle to perform reverse charging, that is, to charge the battery through the vehicle battery pack. After the battery is charged, if the balancing conditions are met, the equalization charging will continue, or the charging will stop when the battery cannot be charged or the target charge is reached. This can avoid the inability to achieve equalization operation of the vehicle battery pack when the battery charge is too low.

[0048] (5) When the vehicle is detected to meet one of the multiple equalization conditions, this application collects relevant battery data of the vehicle battery pack to calculate the equalization time and the amount of electricity required for equalization. Then, according to the user's different usage scenarios and habits, the equalization method is intelligently selected to calculate the equalization time as accurately as possible and avoid false equalization. Finally, based on the comparison between the number of low-voltage cells and the preset number of cells, the application selects either supplementary equalization or discharge equalization. Supplementary equalization selects the battery with the preset voltage to supplement the low-voltage cells until the equalization reaches the target amount of electricity, thereby reducing the equalization load, improving equalization efficiency, and reducing the load of the resistance energy consumption equalization system. Discharge equalization uses the resistance energy consumption method to reduce the amount of electricity in the high-capacity cells to the target amount of electricity, thereby consuming electricity in the high-capacity cells. The equalization current is small, which improves the safety and service life of the vehicle battery pack.

[0049] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0051] Figure 1 This is a flowchart of a preferred embodiment of the battery pack power balancing method of this application;

[0052] Figure 2 This is a schematic diagram of the OCV-SOC curve of a lithium iron phosphate cell in a preferred embodiment of the power balancing method for the vehicle battery pack of this application;

[0053] Figure 3 This is a schematic diagram of the dQ / dV-SOC curve of a lithium iron phosphate battery during constant current charging in a preferred embodiment of the battery pack power balancing method of this application.

[0054] Figure 4 This is a flowchart of the intelligent balancing strategy in a preferred embodiment of the battery pack power balancing method of this application;

[0055] Figure 5 This is a schematic diagram of the equalization circuit in a preferred embodiment of the power equalization method for the vehicle battery pack of this application.

[0056] Figure 6 This is a flowchart illustrating the specific implementation steps of the entire execution process in a preferred embodiment of the battery pack power balancing method of this application.

[0057] Figure 7 This is a schematic diagram of a preferred embodiment of the power balancing system for the vehicle battery pack of this application;

[0058] Figure 8 This is a structural schematic diagram of a preferred embodiment of the vehicle described in this application.

[0059] Among them, 10-the power balancing system of the vehicle battery pack; 100-data acquisition module, 200-balancing calculation module, 300-balancing control module; 501-memory, 502-processor and 503-communication interface. Detailed Implementation

[0060] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0061] Existing technologies include passive balancing systems for lithium iron phosphate (LFP) battery packs. These systems use precise differences in remaining charge (SOC) as the basis for balancing and perform passive balancing when the LFP battery pack is at its high-voltage side. They separate the selection of balancing criteria from the execution of the balancing action, ensuring that the balancing judgment and execution timing are not necessarily simultaneous. This provides a complete passive balancing scheme, allowing for prolonged balancing once initiated. However, it only identifies and selects cells requiring balancing within certain SOC ranges to determine the balancing capacity. Furthermore, prolonged use of the battery pack in the LFP battery plateau region makes accurate calculation of balancing time difficult, resulting in infrequent balancing triggers. Additionally, during balancing, high-charge cells consume power, resulting in a small balancing current and wasted energy. When only a few cells have low voltage, the balancing system experiences a high load, leading to prolonged balancing times. Existing technologies also employ balancing methods that determine balancing based on different scenarios. These methods include driving balancing, charging balancing, short-term storage balancing, and long-term storage balancing. By determining the balancing time based on these scenarios, the balancing time becomes more accurate. However, its essence is still to calculate the balancing time by looking up the OCV-SOC (open circuit voltage-state of charge) curve. In various balancing scenarios, if the battery pack's SOC range is in the lithium iron phosphate battery platform voltage range, the balancing time still cannot be accurately calculated. Furthermore, when performing balancing, the high-capacity cells consume power, resulting in a small balancing current. When only a few cells have low voltage, the balancing system load is large, the balancing time is long, and energy is wasted.

[0062] Traditional passive balancing of lithium iron phosphate (LFP) batteries requires determining the resting time. This resting time must be greater than 2 hours before or after restarting, or the current must be less than 0.03C (C represents the current ratio; for example, a 28Ah cell at 1C discharge is 28A, and at 0.03C it's 0.03*28A). Only after a resting time greater than 2 hours can the cell's open-circuit voltage be read, and the balancing time can only be calculated in the non-plateau voltage range. Given the limited balancing opportunities and voltage characteristics of LFP battery packs, accurate balancing time calculation is difficult, leading to numerous false balancing errors. The long passive balancing time further exacerbates the problem. Insufficient or false balancing increases cell voltage differences, intensifies inconsistencies, reduces the lifespan and performance of the LFP battery pack, and in severe cases, can even damage the battery pack or create safety hazards. This application aims to provide a multi-point triggered, efficient, and intelligent balancing strategy for LFP battery packs, solving the balancing problem and improving the performance and lifespan of LFP battery packs.

[0063] The following description, with reference to the accompanying drawings, describes a method, system, and vehicle for balancing the power of a vehicle battery pack according to embodiments of this application. To address the issues mentioned in the background technology, such as the limited equalization opportunities due to the voltage characteristics of vehicle battery packs (lithium iron phosphate), leading to inaccurate equalization time calculations, frequent false equalizations, and prolonged passive equalization times, which reduce the lifespan and performance of vehicle battery packs (lithium iron phosphate battery packs), and in severe cases even cause damage or safety hazards, this application provides a method for equalizing the charge of a vehicle battery pack. In this method, when the vehicle meets one of several equalization conditions, relevant battery data of the vehicle battery pack is collected to calculate the equalization time and the required charge. Then, based on different user scenarios and habits, the equalization method is intelligently selected to calculate the equalization time as accurately as possible, avoiding false equalizations. Finally, based on a comparison between the number of low-voltage cells and a preset number of cells, either supplementary equalization or discharge equalization is selected. Supplementary equalization uses a battery with a preset voltage to supplement the low-voltage cells until the target charge is reached, reducing the equalization load, improving equalization efficiency, and reducing the load on the resistive energy consumption equalization system. Discharge equalization uses resistive power consumption to reduce the charge of high-charge cells to the target charge, consuming power from the high-charge cells with a small equalization current, thus improving the performance and lifespan of the vehicle battery pack. This solves the technical problem in related technologies where the voltage characteristics of vehicle battery packs (lithium iron phosphate) result in fewer opportunities for equalization, making it difficult to accurately calculate the equalization time, leading to more false equalizations, longer passive equalization times, reduced lifespan and performance of vehicle battery packs (lithium iron phosphate battery packs), and in severe cases, even damage to the vehicle battery pack or safety hazards.

[0064] In this application, if the vehicle is powered on and meets the equalization conditions for triggering equalization, battery data of the vehicle battery pack is collected; the equalization time and the amount of electricity required for equalization are calculated based on the battery data, and the equalization method is selected according to the usage scenario and usage habits; the number of low-voltage cells is obtained, and if the number of low-voltage cells is less than or equal to the preset number of cells, a battery with a preset voltage is selected to replenish the low-voltage cells until the equalization reaches the target amount of electricity; if the number of low-voltage cells is greater than the preset number of cells, a resistor power consumption method is used to reduce the charge of high-charge cells to the target charge, thereby improving the performance and service life of the vehicle battery pack.

[0065] Specifically, Figure 1 This is a flowchart illustrating a method for balancing the charge of a vehicle battery pack, as provided in an embodiment of this application.

[0066] like Figure 1 As shown, the battery pack power equalization method for this vehicle includes the following steps:

[0067] In step S1, if the vehicle is powered on and meets the equalization conditions for triggering equalization, the battery data of the vehicle battery pack is collected.

[0068] It is understood that the vehicle battery pack described in this application embodiment includes a lithium iron phosphate battery pack, and the multi-point triggered high-efficiency intelligent balancing in this application mainly targets lithium iron phosphate battery packs. Figure 2 This shows the OCV-SOC curve of a lithium iron phosphate battery cell, such as... Figure 2 As shown, in the 30-95% SOC range, the OCV change is not significant, and there is not enough slope to provide SOC correction and equalization time calculation. Therefore, this application increases the SOC range of lithium iron phosphate that can be used to calculate the equalization time as much as possible.

[0069] Therefore, the equalization conditions in this application embodiment include (i.e., equalization activation conditions): the lowest SOC of a single cell is greater than a first percentage (e.g., the first percentage is preferably 10%), the difference between the highest and lowest SOC of a single cell is greater than a second percentage (e.g., the second percentage is preferably 2%), the maximum voltage difference of a single cell is greater than a preset voltage value (e.g., the preset voltage value is preferably 10mV), the remaining equalization time is greater than 0, the vehicle has no faults, the temperature of the equalization circuit is less than a first temperature (e.g., the first temperature is preferably 80℃) and the cell temperature is less than a second temperature (e.g., the second temperature is preferably 55℃), and the battery charge is greater than a third percentage SOC during charging equalization (e.g., the third percentage is preferably 30%). When any one of the equalization conditions is met, it means that the vehicle meets the equalization conditions for triggering equalization.

[0070] The reason for setting multiple balancing conditions in this application is to increase the balancing opportunities through multi-point balancing triggering conditions. These balancing conditions involve the minimum SOC of a single cell, the difference between the maximum and minimum SOC of a single cell, the maximum voltage difference of a single cell, the remaining balancing time, the absence of vehicle faults, the temperature of the balancing circuit and the cell temperature, and the battery charge during charging balancing. Meeting any one of these balancing conditions indicates that the vehicle meets the balancing triggering conditions, thus increasing the conditions for triggering battery balancing and consequently increasing the balancing opportunities for the vehicle's battery pack. This application increases balancing opportunities through multiple triggering conditions. In addition to the traditional 10%-30% SOC range static balancing target selection and balancing time calculation, it adds static balancing target selection and balancing time calculation in the low SOC range (e.g., 3-10%), constant current charging balancing target selection and balancing time calculation at 50% SOC and below, AC full charge balancing, and large voltage difference balancing screening.

[0071] The battery data in this embodiment includes battery voltage, battery charge, and battery current. This embodiment can collect data such as battery voltage, battery charge, and battery current of the vehicle battery pack after the vehicle is powered on and meets the equalization conditions for triggering equalization. This facilitates the subsequent accurate calculation of equalization time and the amount of electricity required for equalization based on the data of battery voltage, battery charge, and battery current.

[0072] In step S2, the balancing time and the amount of 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.

[0073] It is understood that the equalization time described in the embodiments of this application includes: passive resistance equalization time and battery charging equalization time; passive resistance equalization time = ΔE / (I 2 *R), where ΔE is the equalization charge, I is the equalization current, and R is the equalization resistance; Battery replenishment equalization time = ΔE / (P*η), ​​where ΔE is the equalization charge, P is the battery equalization power, and η is the loss factor. In this embodiment, passive resistance equalization is achieved through resistor power consumption, and battery replenishment equalization is achieved through battery replenishment (preferably a 12V battery). The passive resistance equalization time is calculated based on the equalization charge, equalization current, and equalization resistance, while the battery replenishment equalization time is calculated based on the equalization charge, battery equalization power, and loss factor. This allows for the use of the calculated equalization time during subsequent discharge equalization or replenishment equalization, ensuring the most accurate calculation of the equalization time and avoiding erroneous equalization.

[0074] Figure 3 The constant current charging dQ / dV-SOC curve of a lithium iron phosphate battery is shown below. Figure 3 As shown, during constant current charging, dQ / dV can accurately correspond to SOC when the SOC is below 50%. If it is in DC charging mode, DC charging is a constant current stepped charging method. When the SOC is below 50%, the amount of charge that needs to be balanced can be accurately calculated through the dQ / dV-SOC curve of the lithium iron phosphate battery constant current charging.

[0075] Furthermore, such as Figure 4As shown, the cell voltage difference is obtained, and it is determined whether the cell voltage difference is greater than the voltage difference threshold. If the cell voltage difference is greater than the voltage difference threshold, it is determined whether the vehicle's resting time is greater than a preset time (e.g., the preset time is preferably 2 hours) and whether the SOC range is within a preset range (e.g., the preset range SOC range is preferably 10%-30%). If the vehicle's resting time is greater than the preset time (2 hours) and the SOC range is within the preset range (10%-30%), the required charge for balancing is calculated using the OCV-SOC lookup table method. If the vehicle's resting time is not greater than the preset time (2 hours) or the SOC range is not within the preset range (10%-30%), it is determined whether the vehicle is in DC charging mode. If the vehicle is in DC charging mode, the dQ / dV-SOC curve of the lithium iron phosphate battery is used for constant current charging (e.g., ...). Figure 3 ) Calculate the amount of electricity required for equalization; if the vehicle is not in DC charging state, determine whether the vehicle is in AC charging state; if the vehicle is in AC charging state, screen the battery cells at the charging end, and calculate the amount of electricity required for equalization when the SOC is greater than the fourth percentage (for example, the fourth percentage is preferably 97%).

[0076] This application embodiment can select the method for calculating the amount of electricity required for balancing based on the cell voltage difference, vehicle resting time, SOC range, and DC and AC charging status. It includes three methods for calculating the amount of electricity required for balancing: OCV-SOC lookup table method, constant current charging dQ / dV-SOC curve of vehicle battery pack, and calculation at the end of charging. It can accurately calculate the amount of electricity to be balanced, which is convenient for subsequent discharge balancing or charging balancing to use the calculated amount of electricity required for balancing.

[0077] Furthermore, such as Figure 4 As shown, the balancing process is mainly divided into three stages: determining whether the vehicle is powered on; if the vehicle is not powered on, offline balancing is used; if the vehicle is powered on, determining whether the vehicle speed is 0; if the vehicle speed is 0, static balancing is used; if the vehicle speed is not 0, driving balancing is used. This application embodiment can intelligently select the balancing method according to the user's usage scenario and habits. The balancing methods include offline balancing, static balancing, and driving balancing. This allows for the selection of the most suitable balancing method based on different situations, which is beneficial for improving the safety of vehicle battery pack balancing.

[0078] In step S3, the number of low-voltage cells is obtained. If the number of low-voltage cells is less than or equal to the preset number of cells, a battery with a preset voltage is selected to replenish the low-voltage cells until the target charge level is reached. If the number of low-voltage cells is greater than the preset number of cells, a resistor power consumption method is used to reduce the charge level of the high-charge cells to the target charge level.

[0079] It is understandable that, such as Figure 4 As shown, in this application, the preset number of battery cells = A * total number of battery cells (different for different capacity cells), obtains the number of low-voltage battery cells, and determines 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, then a battery with a preset voltage (12V) is selected to replenish the low-voltage battery cells through a high-low voltage DC-DC converter until the target capacity is reached; if the number of low-voltage battery cells is greater than A * total number of battery cells, then a resistor power consumption method is used to reduce the capacity of the high-capacity battery cells to the target capacity.

[0080] In this embodiment, the choice between supplementary equalization and discharge equalization can be made based on a comparison between the number of low-voltage cells and the preset number of cells. If the number of low-voltage cells is less than or equal to A * the total number of cells, supplementary equalization is chosen. This involves using a battery with a preset voltage to supplement the low-voltage cells via a high-low voltage DC-DC converter until the target charge level is reached, thereby reducing the equalization load, improving equalization efficiency, and reducing the load on the resistance-based equalization system. If the number of low-voltage cells is greater than A * the total number of cells, discharge equalization is chosen. This involves using resistance-based power consumption to reduce the charge level of high-charge cells to the target charge level, thus consuming power from the high-charge cells and resulting in a smaller equalization current.

[0081] Specifically, such as Figure 4 As shown, the intelligent balancing strategy process of this application is as follows:

[0082] start;

[0083] Step S10: Obtain the cell voltage difference and determine whether the cell voltage difference is greater than the voltage difference threshold; if the cell voltage difference is greater than the voltage difference threshold, proceed to step S11.

[0084] Step S11: Determine whether the vehicle has been stationary for more than 2 hours and whether the SOC range is in a non-platform range (i.e., whether the SOC range is between 10% and 30%). If the vehicle has been stationary for more than 2 hours and the SOC range is in a non-platform range, proceed to step S12.

[0085] If the vehicle is stationary for no more than 2 hours or the SOC range is not in a non-platform segment, proceed to step S13.

[0086] Step S12: If the vehicle has been stationary for more than 2 hours and the SOC range is in a non-platform segment, select the OCV-SOC lookup table method to calculate the power required for balancing.

[0087] Step S13: Determine whether the vehicle is in DC charging mode; if the vehicle is in DC charging mode, proceed to step S14.

[0088] If the vehicle is not in DC charging mode, proceed to step S15;

[0089] Step S14: If the vehicle is in DC charging mode, calculate the required amount of electricity for equalization using the constant current charging dQ / dV-SOC curve of the lithium iron phosphate battery.

[0090] Step S15: If the vehicle is not in DC charging mode, determine whether the vehicle is in AC charging mode; if the vehicle is in AC charging mode, proceed to step S16.

[0091] Step S16: If the vehicle is in AC charging mode, the battery cells are screened at the charging end. When the SOC is greater than 97%, the amount of electricity required for balancing is calculated.

[0092] Step S17: Determine whether the vehicle is powered on; if the vehicle is not powered on, proceed to step S18.

[0093] If the vehicle is powered on, proceed to step S19;

[0094] Step S18: If the vehicle is not powered on, then offline balancing is performed while the vehicle is parked.

[0095] Step S19: Determine if the vehicle speed is 0; if the vehicle speed is 0, proceed to step S20.

[0096] If the vehicle speed is not 0, proceed to step S21;

[0097] Step S20: If the vehicle speed is 0, then static equilibrium is adopted;

[0098] Step S21: If the vehicle speed is not 0, then driving balance is applied;

[0099] Step S22: Obtain the number of low-voltage cells and determine whether the number of low-voltage cells is less than or equal to A * total number of cells; if the number of low-voltage cells is greater than A * total number of cells, proceed to step S23.

[0100] If the number of low-voltage cells is less than or equal to A * total number of cells, proceed to step S24;

[0101] Step S23: If the number of low-voltage cells is greater than A * total number of cells, then a resistance power consumption method (discharge equalization) is used to reduce the power of high-capacity cells to the target power.

[0102] Step S24: If the number of low-voltage cells is less than or equal to A* the total number of cells, then select a battery with a preset voltage (12V) and use a high-low voltage DC-DC converter to charge the low-voltage cells (charge equalization) until the target charge level is reached.

[0103] Step S25: Determine whether the balancing has reached the target power level or does not meet the balancing conditions; if the balancing has reached the target power level or does not meet the balancing conditions, then the process ends.

[0104] If the balancing does not reach the target power or meets the balancing conditions, return to step S23 or step S24.

[0105] Finish.

[0106] Furthermore, when the low-voltage cells are recharged by a battery with a preset voltage (12V), if the battery charge is lower than the fifth percentage (e.g., the fifth percentage is preferably 30%) of the State of Charge (SOC), the battery exits the balancing process, and the vehicle battery pack recharges the battery (i.e., reverse recharge). If the balancing conditions are met, the battery is controlled to continue balancing and recharging. If the recharge reaches the target charge or the recharge conditions are not met, the recharge stops. This embodiment of the application can control the vehicle to perform reverse recharge when the battery charge is lower than a certain SOC, that is, to recharge the battery through the vehicle battery pack. After the battery recharge is completed, if the balancing conditions are met, balancing and recharging continues; otherwise, recharge stops when the recharge cannot be performed or the target charge is reached. This avoids the inability to perform balancing operations on the vehicle battery pack when the battery charge is too low.

[0107] This application uses a 12V battery to replenish low-voltage cells, reducing the balancing load and improving 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 replenish the cells in reverse through the DC-DC module of the vehicle's OBC. The replenishment current is large, resulting in high balancing efficiency. When the 12V low-voltage power supply (battery) has low power, balancing stops, and the battery pack replenishes the 12V low-voltage power supply (battery) again. This can improve balancing efficiency and reduce the load of the resistance-based energy balancing system.

[0108] Furthermore, Figure 5 This is a schematic diagram of the balancing circuit of this application. In the embodiments of this application, the balancing system can balance the energy consumption of cells with excessive energy through resistors, or it can replenish the energy of cells with low individual voltages through a 12V battery via DC-DC converter. The individual cell voltages are collected in real time, and the balancing conditions are determined based on the collected data and the overall vehicle status. An appropriate balancing strategy is then selected based on the vehicle and battery status. For example, if it is determined that... Figure 5 When the voltage of cell C1 in a single cell is too high, the equalization discharge condition is met, and discharge is required. The control circuit opens the corresponding discharge circuit, which discharges through the equalization resistor ( Figure 5 Discharge is performed using R1. Once the target value is reached (or the equalization limit is met), the discharge equalization process automatically stops. When the judgment... Figure 5When the voltage of a single cell C1 is too low, and the equalization charging condition is met, charging is required. The control circuit opens the corresponding charging circuit to charge the 12V battery. When the 12V battery charge is below 30% SOC, the vehicle battery pack (large battery pack) charges the 12V battery again via DC-DC. After the 12V battery is fully charged, equalization charging continues. Charging automatically stops when the target value is reached or the charging condition is no longer met. By combining equalization charging and resistive discharge equalization, equalization efficiency is improved and the load on the equalization system is reduced.

[0109] The following describes the entire implementation process in further detail according to the steps of implementing the battery pack power balancing method of this application, such as... Figure 6 As shown:

[0110] start;

[0111] Step S100: Determine whether the vehicle is powered on; if the vehicle is powered on, proceed to step S101.

[0112] If the vehicle is not powered on, proceed to step S112;

[0113] Step S101: If the vehicle is powered on, determine whether the vehicle meets the equilibrium condition; if the vehicle meets the equilibrium condition, proceed to step S103.

[0114] If the vehicle does not meet the equilibrium condition, proceed to step S102;

[0115] Step S102: If the vehicle does not meet the equilibrium conditions, then exit the equilibrium process.

[0116] Step S103: If the vehicle meets the equilibrium conditions, read the historical remaining equilibrium time and equilibrium method.

[0117] Step S104: Based on the current state of the vehicle, select the balancing method, calculate the balancing time, compare it with historical balancing information, and select the optimal balancing strategy.

[0118] Step S105: Determine if the equilibrium time is greater than 0; if the equilibrium time is equal to 0, proceed to step S106.

[0119] If the balancing time is greater than 0, proceed to step S107;

[0120] Step S106: If the equilibrium time is equal to 0, then exit the equilibrium process.

[0121] Step S107: If the balancing time is greater than 0, save the balancing time in real time, subtract the balancing time, and after balancing for a certain period of time (which may vary depending on the balancing system and battery pack), perform a balancing condition judgment and subtract the balancing time from the balancing duration to obtain the remaining balancing duration.

[0122] Step S108: Determine if there are any faults or limiting conditions that affect the equilibrium; if there are any faults or limiting conditions that affect the equilibrium, proceed to step S109.

[0123] If there are no faults or constraints affecting the balance, proceed to step S110;

[0124] Step S109: If there are faults or limitations that affect the equilibrium, then exit the equilibrium process.

[0125] Step S110: If there are no faults or limitations affecting the equalization, determine whether a power-down request is detected (the vehicle controller will send a power-down request signal); if no power-down request is detected, proceed to step S105 (that is, continue to determine whether the equalization time is greater than 0).

[0126] If a power-down request is detected, proceed to step S111;

[0127] Step S111: If a power-down request is detected, the remaining equalization time and equalization parameters are stored before powering down.

[0128] Step S112: If the vehicle is not powered on, determine whether the BMS system meets the timed wake-up or offline balancing conditions; if the BMS system does not meet the timed wake-up or offline balancing conditions, proceed to step S113.

[0129] If the BMS system meets the timed wake-up requirement or the offline load balancer requirement, proceed to step S114.

[0130] Step S113: If the BMS system does not meet the timed wake-up requirement (the vehicle will wake up the BMS system at certain intervals when it is parked for a long time without starting) or does not meet the offline balancing conditions, then offline balancing will not be performed.

[0131] Step S114: If the BMS system meets the timed wake-up or offline balancing conditions, read the historical remaining balancing time and balancing method.

[0132] 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, proceed to step S116.

[0133] If the remaining balancing time is not greater than the offline balancing time threshold t, proceed to step S117.

[0134] Step S116: If the remaining balancing time is greater than the offline balancing time threshold, then set the offline balancing time to the offline balancing time threshold (t) and perform offline balancing.

[0135] Step S117: Set the BMS wake-up time to: offline balancing time threshold + 2h (the battery resting time is greater than 2h to obtain the accurate open circuit voltage OCV), and re-determine whether offline balancing is required;

[0136] Finish.

[0137] In summary, the embodiments of this application can collect relevant battery data of the vehicle battery pack when the vehicle is detected to meet one of multiple equalization conditions, thereby calculating the equalization time and the amount of electricity required for equalization. Then, based on different user scenarios and habits, it intelligently selects the equalization method, calculates the equalization time as accurately as possible, and avoids false equalization. Finally, it selects either supplementary equalization or discharge equalization based on the comparison between the number of low-voltage cells and the preset number of cells. Supplementary equalization uses a battery with a preset voltage to supplement the low-voltage cells until the target amount of electricity is reached, reducing the equalization load, improving equalization efficiency, and reducing the load on the resistance-based energy-consuming equalization system. Discharge equalization uses a resistance-based power-consuming method to reduce the amount of electricity in high-capacity cells to the target amount of electricity, consuming electricity from the high-capacity cells. The equalization current is small, which improves the safety and service life of the vehicle battery pack.

[0138] Next, with reference to the accompanying drawings, a power balancing system for a vehicle battery pack according to an embodiment of this application is described.

[0139] Figure 7 This is a block diagram of the power balancing system of a vehicle battery pack according to an embodiment of this application.

[0140] like Figure 7 As shown, the battery pack power balancing system 10 of the vehicle includes: a data acquisition module 100, a balancing calculation module 200, and a balancing control module 300.

[0141] Specifically, the data acquisition module 100 is used to collect battery data of the vehicle battery pack when the vehicle is powered on and the vehicle meets the equalization conditions for triggering equalization.

[0142] The equalization calculation module 200 is used to calculate the equalization time and the amount of electricity required for equalization based on the battery data, and to select the equalization method according to the usage scenario and usage habits.

[0143] The equalization control module 300 is used to obtain the number of low-voltage cells. If the number of low-voltage cells is less than or equal to the preset number of cells, a battery with a preset voltage is selected to replenish the low-voltage cells until the equalization reaches the target charge. If the number of low-voltage cells is greater than the preset number of cells, a resistor power consumption method is used to reduce the charge of the high-charge cells to the target charge.

[0144] Optionally, in one embodiment of this application, the equalization conditions include: the lowest SOC of a single cell is greater than a first percentage, the difference between the highest and lowest SOC of a single cell is greater than a second percentage, the maximum voltage difference of a single cell is greater than a preset voltage value, the remaining equalization time is greater than 0, the vehicle has no faults, the temperature of the equalization circuit is less than a first temperature and the cell temperature is less than a second temperature, and the battery charge is greater than a third percentage of SOC during charging equalization; when any one of the equalization conditions is met, it indicates that the vehicle meets the equalization conditions for triggering equalization.

[0145] Optionally, in one embodiment of this application, the battery data includes battery voltage, battery charge, and battery current.

[0146] Optionally, in one embodiment of this application, the equalization time includes: passive resistance equalization time and battery charging equalization time; passive resistance equalization time = ΔE / (I 2 *R), where ΔE is the equalization charge, I is the equalization current, and R is the equalization resistance; Battery charging equalization time = ΔE / (P*η), ​​where ΔE is the equalization charge, P is the battery equalization power, and η is the loss factor.

[0147] Optionally, in one embodiment of this application, the equalization calculation module 200 includes: a cell voltage difference acquisition and comparison unit, a resting time and SOC range judgment unit, a first equalization required power calculation unit, a DC charging status judgment unit, a second equalization required power calculation unit, an AC charging status judgment unit, and a third equalization required power calculation unit.

[0148] The cell voltage difference acquisition and comparison unit is used to acquire the cell voltage difference and determine whether the cell voltage difference is greater than the voltage difference threshold.

[0149] The resting time and SOC range determination unit is used to determine whether the resting time of the whole vehicle is greater than a preset time and whether the SOC range is within a preset range if the cell voltage difference is greater than the voltage difference threshold.

[0150] The first equalization power calculation unit is used to calculate the equalization power required by selecting the OCV-SOC lookup table method if the vehicle's stationary time is greater than the preset time and the SOC range is within the preset range SOC range.

[0151] The DC charging status determination unit is used to determine whether the vehicle is in DC charging status if the vehicle's stationary time is not greater than the preset time or the SOC range is not within the preset range of SOC range.

[0152] The second equalization power calculation unit is used to calculate the equalization power required by means of the constant current charging dQ / dV-SOC curve of the vehicle battery pack if the vehicle is in DC charging state.

[0153] The AC charging status determination unit is used to determine whether the vehicle is in AC charging status if the vehicle is not in DC charging status.

[0154] The third equalization power calculation unit is used to screen the battery cells at the end of the charging process if the vehicle is in AC charging mode, and calculate the power required for equalization when the battery percentage is greater than the fourth percentage SOC.

[0155] Optionally, in one embodiment of this application, the equalization calculation module 200 further includes: a first vehicle power-on judgment unit, a first equalization mode selection unit, a vehicle speed judgment unit, a second equalization mode selection unit, and a third equalization mode selection unit.

[0156] The first vehicle power-on determination unit is used to determine whether the vehicle is powered on.

[0157] The first equalization mode selection unit is used to employ offline equalization when the vehicle is not powered on.

[0158] The vehicle speed determination unit is used to determine whether the vehicle speed is 0 when the vehicle is powered on.

[0159] The second equalization mode selection unit is used to employ static equalization if the vehicle speed is 0.

[0160] The third balance mode selection unit is used to employ driving balance if the vehicle speed is not 0.

[0161] Optionally, in one embodiment of this application, the equalization control module 300 includes: a low-voltage cell count acquisition and comparison unit, a power replenishment equalization unit, and a discharge equalization unit.

[0162] The low-voltage cell count acquisition and comparison unit is used to acquire the number of low-voltage cells and determine whether the number of low-voltage cells is less than or equal to A * total number of cells, where A is a constant less than 0.5.

[0163] The power replenishment and balancing unit is used to select a battery with a preset voltage and replenish the low-voltage cells through a high-low voltage DC-DC converter if the number of low-voltage cells is less than or equal to A * the total number of cells, until the target power level is reached.

[0164] The discharge equalization unit is used to reduce the charge of the high-charge cells to the target charge level by using a resistor-based power consumption method if the number of low-voltage cells is greater than A * the total number of cells.

[0165] Optionally, in one embodiment of this application, the vehicle battery pack power balancing system 10 of this application embodiment further includes: a reverse power replenishment unit, a balancing time judgment unit, a balancing time processing unit, a fault or limitation condition judgment unit, a power-down request judgment unit, a power-down storage unit, a BMS system judgment unit, a balancing time and balancing mode 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.

[0166] The reverse charging unit is used to charge the low-voltage cells through a battery with a preset voltage. If the battery charge is below the fifth percentage of SOC, the battery will exit the equalization process, and the vehicle battery pack will charge the battery. If the equalization conditions are met, the battery will be controlled to perform equalization charging again. If the charging reaches the target charge or the charging conditions are not met, the charging will stop.

[0167] The equalization time judgment unit is used to determine whether the equalization time is greater than 0.

[0168] The equalization time processing unit is used to save the equalization time in real time and perform subtraction on the equalization time if the equalization time is greater than 0.

[0169] The fault or limitation condition judgment unit is used to determine whether there are faults or limitations that affect the balance.

[0170] The power-down request determination unit is used to determine whether a power-down request has been detected if there are no faults or limitations affecting the balance.

[0171] The power-down storage unit is used to store the remaining equalization time and equalization parameters before powering down if a power-down request is detected.

[0172] The BMS system judgment unit is used to determine whether the BMS system meets the timed wake-up or offline balancing conditions if the vehicle is not powered on.

[0173] 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.

[0174] The historical remaining balance time judgment unit is used to determine whether the historical remaining balance time is greater than the offline balance time threshold.

[0175] The offline balancing unit is used to set the offline balancing time to the offline balancing time threshold before performing offline balancing if the remaining historical balancing time is greater than the offline balancing time threshold.

[0176] The first wake-up time setting unit is used to set the BMS wake-up time to: offline balancing time threshold + preset time.

[0177] 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.

[0178] Optionally, in one embodiment of this application, the vehicle battery pack includes a lithium iron phosphate battery pack.

[0179] It should be noted that the foregoing explanation of the embodiment of the power balancing method for vehicle battery packs also applies to the power balancing system of the vehicle battery pack in this embodiment, and will not be repeated here.

[0180] The vehicle battery pack power balancing system proposed in this application can collect relevant battery data of the vehicle battery pack when it detects that the vehicle meets one of multiple balancing conditions, thereby calculating the balancing time and the required power for balancing. Then, based on different user scenarios and habits, it intelligently selects the balancing method, calculates the balancing time as accurately as possible, and avoids erroneous balancing. Finally, it selects either supplementary balancing or discharge balancing based on the comparison between the number of low-voltage cells and the preset number of cells. Supplementary balancing uses a battery with a preset voltage to supplement the low-voltage cells until the target power is reached, reducing the balancing load, improving balancing efficiency, and reducing the load on the resistance-based power balancing system. Discharge balancing uses resistance-based power consumption to reduce the power of high-capacity cells to the target power, consuming power from the high-capacity cells with a small balancing current, thus improving the safety and lifespan of the vehicle battery pack.

[0181] This solves the technical problem in related technologies where the voltage characteristics of vehicle battery packs (lithium iron phosphate) result in fewer opportunities for equalization, making it difficult to accurately calculate the equalization time, leading to more false equalizations, longer passive equalization times, reduced lifespan and performance of vehicle battery packs (lithium iron phosphate battery packs), and in severe cases, even damage to the vehicle battery pack or safety hazards.

[0182] Figure 8 A schematic diagram of the structure of a vehicle provided in an embodiment of this application. The vehicle may include:

[0183] The memory 501, the processor 502, and the computer program stored on the memory 501 and capable of running on the processor 502.

[0184] When the processor 502 executes the program, it implements the power balancing method for the vehicle battery pack provided in the above embodiments.

[0185] Furthermore, the vehicle also includes:

[0186] Communication interface 503 is used for communication between memory 501 and processor 502.

[0187] The memory 501 is used to store computer programs that can run on the processor 502.

[0188] Memory 501 may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage device.

[0189] If the memory 501, processor 502, and communication interface 503 are implemented independently, then the communication interface 503, memory 501, and processor 502 can be interconnected via a bus to complete communication between them. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EIS) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of representation, Figure 8 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0190] Optionally, in a specific implementation, if the memory 501, processor 502, and communication interface 503 are integrated on a single chip, then the memory 501, processor 502, and communication interface 503 can communicate with each other through an internal interface.

[0191] 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 this application.

[0192] This embodiment also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method for balancing the power of a vehicle battery pack.

[0193] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0194] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0195] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or N executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0196] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing 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 (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable storage medium" can be any means that can contain, store, communicate, propagate, or transmit programs 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: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable storage medium could be paper or other suitable media on which the program can be printed, since the program can be obtained electronically by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0197] It should be understood that the various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0198] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0199] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0200] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

[0201] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method of balancing the charge of a vehicle battery pack, the method comprising: The battery pack power balancing method includes: If the vehicle is powered on and meets the equalization conditions for triggering equalization, the battery data of the vehicle battery pack is collected. The balancing time and the amount of 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 cells is obtained. If the number of low-voltage cells is less than or equal to the preset number of cells, a battery with a preset voltage is selected to replenish the low-voltage cells until the target capacity is reached. If the number of low-voltage cells is greater than the preset number of cells, a resistor power consumption method is used to reduce the capacity of the high-capacity cells to the target capacity. The step of calculating the required power for balancing based on the battery data specifically includes: Obtain the cell voltage difference and determine whether the cell voltage difference is greater than the voltage difference threshold. If the cell voltage difference is greater than the voltage difference threshold, determine whether the vehicle's static time is greater than a preset time and whether the SOC range is within a preset range of SOC range. If the vehicle's stationary time exceeds the preset time and the SOC range is within the preset SOC range, the OCV-SOC lookup table method is selected to calculate the power required for balancing. If the vehicle's static time is not greater than the preset time or the SOC range is not within the preset SOC range, then it is determined whether the vehicle is in DC charging mode. If the vehicle is in DC charging mode, the amount of electricity required for equalization is calculated by the constant current charging dQ / dV-SOC curve of the vehicle battery pack. If the vehicle is not in DC charging mode, then determine whether the vehicle is in AC charging mode. If the vehicle is in AC charging mode, the battery cells are screened at the charging end, and the amount of electricity required for balancing is calculated when the state of charge (SOC) is greater than the fourth percentage.

2. The method of claim 1, wherein, The equalization conditions include: the lowest SOC of a single cell is greater than a first percentage, the difference between the highest and lowest SOC of a single cell is greater than a second percentage, the maximum voltage difference of a single cell is greater than a preset voltage value, the remaining equalization time is greater than 0, the vehicle has no faults, the temperature of the equalization circuit is less than a first temperature and the cell temperature is less than a second temperature, and the battery charge is greater than a third percentage of SOC during charging equalization; if any one of the equalization conditions is met, it means that the vehicle meets the equalization conditions for triggering equalization.

3. The method of claim 1, wherein, The battery data includes battery voltage, battery charge, and battery current.

4. The method for equalizing the charge of a vehicle battery pack according to claim 1, characterized in that, The equalization time includes: passive resistor equalization time and battery charging equalization time; Passive resistance equalization time = ΔE / (I 2 *R), where ΔE is the equalization electric quantity, I is the equalization current, and R is the equalization resistance. Battery charging and equalization time = ΔE / (P * η), where ΔE is the equalization capacity, P is the battery equalization power, and η is the loss factor.

5. The method for equalizing the charge of a vehicle battery pack according to claim 1, characterized in that, The selection of a balancing method based on usage scenarios and habits specifically includes: Determine if the vehicle is powered on; If the vehicle is not powered on, offline balancing will be used. If the vehicle is powered on, determine if the vehicle speed is 0. If the vehicle speed is 0, then static equilibrium is used; If the vehicle speed is not 0, then driving balance is used.

6. The method for equalizing the charge of a vehicle battery pack according to claim 1, characterized in that, The process of obtaining the number of low-voltage cells involves several steps. If the number of low-voltage cells is less than or equal to a preset number of cells, a battery with a preset voltage is selected to replenish the low-voltage cells until the target charge level is reached. If the number of low-voltage cells is greater than the preset number of cells, a resistor-based power dissipation method is used to reduce the charge level of the high-charge cells to the target charge level. Specifically, this includes: 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, where A is a constant less than 0.5; If the number of low-voltage cells is less than or equal to A*the total number of cells, then a battery with a preset voltage is selected to replenish the low-voltage cells through a high-low voltage DC-DC converter until the target capacity is reached. If the number of low-voltage cells is greater than A * the total number of cells, then a resistance power consumption method is used to reduce the power of the high-capacity cells to the target power.

7. The method for equalizing the charge of a vehicle battery pack according to claim 1 or 6, characterized in that, The battery pack power balancing method also includes: When the low-voltage cells are recharged by the battery with a preset voltage, if the battery charge is below the fifth percentage of SOC, the battery will exit the balancing process, and the vehicle battery pack will recharge the battery. If the balancing conditions are met, the battery will be controlled to perform balancing and recharging again. If the recharge reaches the target charge or the recharge conditions are not met, the recharge will stop.

8. The method for equalizing the charge of a vehicle battery pack according to claim 1, characterized in that, The process of obtaining the number of low-voltage cells includes: if the number of low-voltage cells is less than or equal to a preset number of cells, then selecting a battery with a preset voltage to replenish the low-voltage cells until the target charge level is reached; if the number of low-voltage cells is greater than the preset number of cells, then using a resistor-based power dissipation method to reduce the charge level of the high-charge cells to the target charge level. The process also includes: Determine if the equilibrium time is greater than 0; If the equilibrium time is greater than 0, save the equilibrium time in real time and subtract it from the equilibrium time. Determine if there are any faults or limiting conditions that affect the equilibrium; If there are no faults or limitations affecting the balance, determine whether a power-down request has been detected; If a power-down request is detected, the remaining balancing time and balancing parameters will be stored before powering down.

9. The method for equalizing the charge of a vehicle battery pack according to claim 1, characterized in that, The battery pack power balancing method also includes: If the vehicle is not powered on, determine whether the BMS system meets the timed wake-up requirement or the offline balancing condition. If the BMS system meets the timed wake-up or offline balancing conditions, read the historical remaining balancing time and balancing method. Determine whether the historical remaining equilibrium time is greater than the offline equilibrium time threshold; If the remaining historical balancing time is greater than the offline balancing time threshold, then the offline balancing time is set to the offline balancing time threshold before offline balancing is performed. Set the BMS wake-up time to: offline balancing time threshold + preset time.

10. The method for equalizing the charge of a vehicle battery pack according to claim 9, characterized in that, The step of determining whether the remaining historical balancing time is greater than the offline balancing time threshold also includes: If the remaining historical balancing time is not greater than the offline balancing time threshold, then the BMS wake-up time is directly set to: offline balancing time threshold + preset time.

11. The method for equalizing the charge of a vehicle battery pack according to claim 1, characterized in that, The vehicle battery pack includes a lithium iron phosphate battery pack.

12. A power balancing system for a vehicle battery pack, characterized in that, The power balancing system of the vehicle battery pack is used to implement the power balancing method of the vehicle battery pack according to any one of claims 1-11, and the power balancing system of the vehicle battery pack includes: The data acquisition module is used to collect battery data of the vehicle battery pack when the vehicle is powered on and the vehicle meets the equalization conditions for triggering equalization. The equalization calculation module is used to calculate the equalization time and the amount of power required for equalization based on the battery data, and to select the equalization method according to the usage scenario and usage habits; The equalization control module is used to obtain the number of low-voltage cells. If the number of low-voltage cells is less than or equal to the preset number of cells, a battery with a preset voltage is selected to replenish the low-voltage cells until the equalization reaches the target charge. If the number of low-voltage cells is greater than the preset number of cells, a resistor power consumption method is used to reduce the charge of the high-charge cells to the target charge.

13. A vehicle, characterized in that, The vehicle includes: a memory, a processor, and a battery equalization program for the vehicle battery pack stored in the memory and executable on the processor, wherein when the battery equalization program for the vehicle battery pack is executed by the processor, it implements the steps of the battery equalization method for the vehicle battery pack as described in any one of claims 1-11.

14. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a power balancing program for a vehicle battery pack, which, when executed by a processor, implements the steps of the power balancing method for a vehicle battery pack as described in any one of claims 1-11.

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