A battery pack power balancing method and system

Abstract

The present invention discloses a battery pack charge balancing method and system, wherein the method includes: obtaining the battery status of individual cells in the battery pack; determining the battery operating condition of the individual cells based on the battery status; determining whether the battery pack requires balancing based on the battery operating condition; if it is determined that the battery pack requires balancing, determining the target cells in the battery pack to be balanced based on the battery status and the battery operating condition; and performing charge balancing on the target cells. The present invention provides a battery pack charge balancing method and system, which increases balancing flexibility, improves battery pack consistency, and increases the available capacity and available energy of the battery pack.

Description

Technical Field

[0001] Embodiments of the present invention relate to the technical field of power batteries, and in particular to a method and system for balancing the charge of a battery pack. Background Art

[0002] Currently, most electric vehicle battery packs are constructed from single cells connected in series. Due to variations in the manufacturing process and during the battery pack's charge and discharge cycles, individual cells exhibit varying levels of rated capacity, voltage, and internal resistance. This inconsistency in the battery pack is a significant factor in the overall performance degradation of the battery pack. Unbalanced battery packs reduce capacity and energy utilization, lower input and output power levels, and shorten the pack's service life. To improve battery pack consistency during use, the pack must be balanced based on the degree of imbalance between cells.

[0003] Prior art typically screens batteries before assembly into a battery pack. Initially, the consistency of individual cells is relatively good, but as the pack ages, inconsistencies persist. During battery pack operation, equalization is typically performed under fixed operating conditions. This inadequate equalization control can affect battery pack consistency and overall balancing effectiveness. Summary of the Invention

[0004] The present invention provides a battery pack power balancing method and system, which increases balancing flexibility, improves battery pack consistency, and increases the available capacity and available energy of the battery pack.

[0005] In a first aspect, an embodiment of the present invention provides a method for balancing a battery pack, including:

[0006] Get the battery status of the single battery in the battery pack;

[0007] determining a battery operating condition of the single battery according to the battery status;

[0008] determining whether the battery pack requires balancing based on the battery operating condition, and if it is determined that the battery pack requires balancing, determining a target battery in the battery pack that requires balancing based on the battery status and the battery operating condition;

[0009] Performing battery balancing on the target battery.

[0010] Optionally, the battery operating condition includes a charging end condition; and judging whether the battery pack needs balancing according to the battery operating condition includes:

[0011] Determining a first threshold voltage and a second threshold voltage according to the single battery; wherein the first threshold voltage is less than the second threshold voltage;

[0012] Obtaining the voltage of each of the single cells in the battery pack;

[0013] The battery pack is balanced based on the relationship between the voltage of the single cell, the first threshold voltage and the second threshold voltage; wherein, if the voltage of at least some of the single cells is less than the first threshold voltage, and the voltage of at least some of the single cells is greater than the second threshold voltage, it is determined that the battery pack requires balancing.

[0014] Optionally, determining a target battery to be balanced in the battery pack according to the battery state and the battery operating condition includes:

[0015] determining a third threshold voltage according to the single battery, wherein the third threshold voltage is less than the first threshold voltage;

[0016] determining a target battery according to the lowest voltage of the single battery, the first threshold voltage, the second threshold voltage, and the third threshold voltage; wherein, if the lowest voltage of the single battery is greater than or equal to the third threshold voltage, marking the single battery having a voltage greater than the second threshold voltage as the target battery;

[0017] If the lowest voltage of the single battery is lower than the third threshold voltage, the single battery having the voltage higher than the first threshold voltage is marked as the target battery.

[0018] Optionally, the first threshold voltage is the voltage value corresponding to the first preset charge state when the voltage of the single cell reaches the end of charging; the second threshold voltage is the voltage value corresponding to the second preset charge state when the voltage of the single cell reaches the end of charging; the third threshold voltage is the voltage value corresponding to the third preset charge state when the voltage of the single cell reaches the end of charging; wherein, the second preset charge state is greater than the first preset charge state; and the first preset charge state is greater than the third preset charge state.

[0019] Optionally, the battery operating condition includes a fully static operating condition; and determining a target battery to be balanced in the battery pack according to the battery state and the battery operating condition includes:

[0020] When the open circuit voltage of the single battery after sufficient rest is within a linear variation range of the relationship between the open circuit voltage and the state of charge, obtaining the battery capacity of the single battery and the average capacity of the single battery;

[0021] determining a reference capacity threshold according to the battery capacity and the average capacity;

[0022] The target battery is determined according to the battery capacity and the reference capacity threshold, wherein if the battery capacity is greater than the reference capacity threshold, the single cell is marked as the target battery.

[0023] Optionally, determining a target battery to be balanced in the battery pack according to the battery state and the battery operating condition further includes:

[0024] When the open circuit voltage is within a nonlinear variation range of the relationship between the open circuit voltage and the state of charge, obtaining the voltage of the single battery, the average voltage of the single battery, and the lowest voltage of the single battery;

[0025] Determining a first reference voltage according to an average voltage of the single battery and a lowest voltage of the single battery;

[0026] The target cell is determined according to the voltage of the single cell and the first reference voltage, wherein if the difference between the voltage of the single cell and the first reference voltage is greater than a preset equalization value, the single cell is marked as the target cell.

[0027] Optionally, the battery operating condition includes a charging condition; if it is determined that the battery pack requires balancing, determining a target battery in the battery pack to be balanced according to the battery state and the battery operating condition includes:

[0028] Obtaining the voltage of the single battery, the average voltage of the single battery, the lowest voltage of the single battery, and the maximum voltage of the single battery during the charging process;

[0029] If the voltage of the single battery is greater than the maximum voltage, it is determined that the battery pack needs balancing;

[0030] A second reference voltage is obtained according to the average voltage of the single cells, the lowest voltage of the single cells and a preset voltage floating amount. When the voltage of the single cell is greater than the second reference voltage, the single cell is marked as the target cell.

[0031] Optionally, the battery operating condition includes a charging end condition, a fully resting condition, and a charging condition, wherein the fully resting condition includes a condition where the open circuit voltage is within a linear variation range of the relationship between the open circuit voltage and the state of charge and a condition where the open circuit voltage is within a nonlinear variation range of the relationship between the open circuit voltage and the state of charge;

[0032] The priority of performing battery balancing on the target battery is: the priority of the end-of-charging condition is greater than the priority of the open-circuit voltage being within a linear variation interval of the relationship between the open-circuit voltage and the state of charge;

[0033] The priority of the open circuit voltage when it is in the linear variation interval of the relationship between the open circuit voltage and the state of charge is greater than the priority of the open circuit voltage when it is in the nonlinear variation interval of the relationship between the open circuit voltage and the state of charge;

[0034] The priority of the open circuit voltage when it is within the nonlinear change interval of the relationship between the open circuit voltage and the charge state is greater than the priority of the charging condition.

[0035] Optionally, the process of performing battery balancing on the target battery includes:

[0036] Obtaining the balancing temperature of the single battery, and if the balancing temperature is greater than a preset upper temperature limit, reducing the balancing current;

[0037] If the balancing temperature is lower than the preset temperature lower limit, the balancing current is restored.

[0038] In a second aspect, an embodiment of the present invention further provides a battery balancing control system for a battery pack, comprising:

[0039] An acquisition module, used to acquire the battery status of a single battery in a battery pack;

[0040] an operating condition determination module, configured to determine a battery operating condition of the single battery according to the battery state;

[0041] a judgment module, configured to judge whether the battery pack requires balancing according to the battery operating condition, and if it is determined that the battery pack requires balancing, determine a target battery in the battery pack that requires balancing according to the battery status and the battery operating condition;

[0042] The balancing module is used to balance the power of the target battery.

[0043] The technical solution provided by the embodiment of the present invention determines the current battery operating condition of the battery pack through the battery status of the single battery cell, and performs balancing judgment on the battery pack according to different battery operating conditions. If the balancing requirements are met, the target battery to be balanced in the battery pack is determined according to the battery status and battery operating condition, thereby performing power balancing on the target battery. Specifically, the target battery is judged and selected based on the battery operating condition, thereby avoiding the conditional restrictions brought about by balancing judgment under a single operating condition, improving the flexibility of power balancing, improving the consistency of the battery pack, and improving the available capacity and available energy of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic flow chart of a method for balancing battery pack power provided by an embodiment of the present invention;

[0045] Figure 2A schematic diagram of a flow chart for determining cell balancing of a battery pack under a charging completion condition is provided for an embodiment of the present invention;

[0046] Figure 3 A schematic diagram of a process for determining a target battery to be balanced in a battery pack according to the battery status and battery operating condition is provided for an embodiment of the present invention;

[0047] Figure 4 A schematic diagram of a process for determining and selecting a target battery for battery balancing of a battery pack under fully static working conditions is provided for an embodiment of the present invention;

[0048] Figure 5 A schematic diagram of a flow chart for determining and selecting a target battery for cell balancing of a battery pack under fully static working conditions is provided for an embodiment of the present invention;

[0049] Figure 6 A schematic diagram of a flow chart for determining cell balancing of a battery pack under charging conditions is provided for an embodiment of the present invention;

[0050] Figure 7 A schematic structural diagram of a battery balancing control system for a battery pack is provided in accordance with an embodiment of the present invention;

[0051] Figure 8 A schematic structural diagram of a battery management system is provided for an embodiment of the present invention;

[0052] Figure 9 A flow chart of another balancing control method is provided for an embodiment of the present invention;

[0053] Figure 10 A schematic diagram of a flow chart of a balance judgment is provided for an embodiment of the present invention;

[0054] Figure 11 A schematic diagram of a process for processing balance judgment is provided for an embodiment of the present invention;

[0055] Figure 12 A schematic diagram of the circuit structure of a balancing module is provided for an embodiment of the present invention;

[0056] Figure 13 A schematic diagram of a balancing branch structure is provided for an embodiment of the present invention. DETAILED DESCRIPTION

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0058] Figure 1 This is a flow chart of a battery pack charge balancing method provided by an embodiment of the present invention. This embodiment is applicable to battery balancing situations. The method can be executed by a battery balancing control system, which can be implemented in hardware and / or software. The method specifically includes the following steps:

[0059] S110, obtaining the battery status of the single battery in the battery pack;

[0060] The battery status refers to the operating status of a single cell, which is characterized by parameters such as the current, voltage, and temperature of the cell. The operating status of a single cell can be acquired using corresponding sensors, sensor chips, and other acquisition devices.

[0061] S120, determining a battery operating condition of a single battery according to a battery status;

[0062] Specifically, the battery pack undergoes charging and resting processes during use, so the operating conditions of the battery pack include at least one of the following: a charging end condition, a fully resting condition, and a charging condition. For example, the charging end condition refers to the state at which the battery is fully charged after the charging current reduction is completed. A fully resting condition refers to a state where the battery current is less than a preset current for a preset period of time. Alternatively, the battery management system reads the system time after powering off at low voltage and then powering on again. If the power-on time and the last power-off time exceed the preset time, the battery is also considered to be fully rested.

[0063] The charging condition includes the charging condition and the post-charging condition. The charging condition refers to the condition in which a single cell battery can continuously maintain a charging current exceeding the preset current for a certain period of time. For example, a single cell battery continuously maintains a charging current exceeding 2A for 5 seconds. The post-charging condition refers to the condition in which the current in the preset range from the charging condition or the post-charging condition continues for more than the preset time, that is, it jumps to the post-charging condition. For example, if the current within the preset range from -2A to 10A continues for more than 1 minute, it jumps to the post-charging condition. If there is a discharge current exceeding 10A, it jumps to the non-charging state. Among them, the preset time and corresponding voltage settings can be selected and set according to the battery type.

[0064] S130, performing a balancing judgment on the battery pack according to the battery operating condition. If it is determined whether the battery pack needs balancing, then determining a target battery in the battery pack that needs balancing according to the battery status and the battery operating condition;

[0065] Specifically, based on the specific determined battery operating conditions, the degree of imbalance of the battery pack under the corresponding operating conditions is judged. If balancing is required, the battery that needs to be balanced is determined based on the current, voltage and other parameters of the battery according to the current corresponding operating conditions and marked, that is, the target battery is obtained. For example, taking the end-of-charge operating condition as an example to judge the balance, the first threshold voltage and the second threshold voltage are determined according to the battery performance. For example, taking the battery as an iron phosphate battery as an example, the first threshold voltage VL1 is selected as 3.5V and the second threshold voltage VH is selected as 3.55V. If the voltage of all single cells is less than the first threshold voltage VL1, it means that the voltage of all single cells is low, and the battery does not need to be balanced at this time. If the voltage of all single cells is greater than the second threshold voltage VH, it means that the voltage of all single cells has reached the voltage target, and the battery does not need to be balanced at this time. If the voltage of some single cells is greater than the second threshold voltage VH and the voltage of some single cells is less than the first threshold voltage VL1, that is, the voltage of the battery is uneven, then the battery is unbalanced, and it means that the single cells need to be balanced.

[0066] At the end of charge, if the average voltage of the individual cells is less than the first threshold voltage VL1, it indicates that there are more cells with low voltage. Therefore, cells with voltages above the second threshold voltage VH need to be discharged and balanced for a longer time at the same current. If the average voltage is greater than or equal to the first threshold voltage VL1, it indicates that there are fewer cells with low voltage. Therefore, cells with voltages above the second threshold voltage VH need to be discharged and balanced for a shorter time at the same current. To improve the determination of the degree of balancing, the comparison thresholds can be adaptively increased. For example, the third threshold voltage VL2 can be selected as 3.45V and the fourth threshold voltage VL3 can be selected as 3.39V to obtain the lowest voltage among the individual cells. The lowest voltage refers to the lowest voltage value among all the individual cells. If the lowest voltage is greater than or equal to the third threshold voltage VL2, the cell with a voltage above the second threshold voltage VH can be selected as the target cell. If the average voltage of the single cells is less than the first threshold voltage VL1 at this time, where the average voltage refers to the average value of the voltages of all single cells, it means that there are more single cells with low voltages. Therefore, the single cells with voltages higher than the second threshold voltage VH are used as target cells for discharge balancing of the first charge. If the average voltage is greater than or equal to the first threshold voltage VL1, it means that there are fewer single cells with low voltages. Therefore, it is necessary to perform discharge balancing of the second charge on the target cells with voltages higher than the second threshold voltage VH to ensure that there is no over-balancing, where the first charge is lower than the second charge. If the lowest voltage is less than the third threshold voltage VL2, the battery with a voltage higher than the first threshold voltage VL1 is discharged as the target battery. To further subdivide the discharge balancing capacity, the fourth threshold voltage VL3 can be used to accordingly divide the discharge balancing capacity to ensure balancing performance. For example, if the lowest voltage is less than the third threshold voltage VL2 but not less than the fourth threshold voltage VL3, the battery with a voltage higher than the first threshold voltage VL1 is discharged as the target battery, and discharge balancing of the third capacity is performed. If the lowest voltage is less than the fourth threshold voltage VL3, the battery with a voltage higher than the first threshold voltage VL1 is discharged as the target battery, and discharge balancing of the fourth capacity is performed. The third capacity is less than the fourth capacity.

[0067] S140: Perform power balancing on the target battery.

[0068] Specifically, under corresponding operating conditions, corresponding balancing times are performed on the target batteries, thereby achieving battery charge balancing based on the battery operating conditions. For example, under the end-of-charge operating condition, if the lowest voltage is greater than or equal to the third threshold voltage VL2 and the average voltage is less than the first threshold voltage VL1, it indicates that there are many cells with low voltages. Therefore, it is necessary to select a first charge balancing method for cells with voltages greater than the second threshold voltage VH, for example, balancing at 0.7% of the actual battery capacity. If the average voltage is greater than or equal to the first threshold voltage VL1, it indicates that there are few cells with low voltages. Therefore, it is necessary to perform a second charge balancing method for target batteries with voltages greater than the second threshold voltage VH, for example, balancing at 0.5% of the actual battery capacity, to ensure that over-balancing is not performed. If the lowest voltage is less than the third threshold voltage VL2 but not less than the fourth threshold voltage VL3, a third discharge equalization is performed on the batteries having a voltage higher than the first threshold voltage VL1, for example, 1% of the actual battery capacity. If the lowest voltage is less than the fourth threshold voltage VL3, a fourth discharge equalization is performed on the batteries having a voltage higher than the first threshold voltage VL1, for example, 2% of the actual battery capacity. This allows appropriate charge equalization to be selected based on different operating conditions and batteries having different voltage equalization degrees.

[0069] The technical solution provided by the embodiment of the present invention determines the current battery operating condition of the battery pack through the battery status of the single battery cell, and performs balancing judgment on the battery pack according to different battery operating conditions. If the balancing requirements are met, the target battery to be balanced in the battery pack is determined according to the battery status and battery operating condition, thereby performing power balancing on the target battery. Specifically, the target battery is judged and selected based on the battery operating condition, thereby avoiding the conditional restrictions brought about by balancing judgment under a single operating condition, improving the flexibility of power balancing, improving the consistency of the battery pack, and improving the available capacity and available energy of the battery pack.

[0070] Figure 2 The present invention provides a flow chart of a battery balancing judgment process for a battery pack under a charging end condition. Figure 2 , the method steps include:

[0071] S210, determining a first threshold voltage and a second threshold voltage according to a single battery; wherein the first threshold voltage is less than the second threshold voltage;

[0072] Specifically, at the end of charging, a balancing judgment is made based on the voltage of the single cell, and two threshold voltages are set, namely the first threshold voltage VL1 and the second threshold voltage VH. For example, if the battery is an iron phosphate battery, the first threshold voltage VL1 is 3.5V and the second threshold voltage VH is 3.55V. Different first threshold voltages VL1 and second threshold voltages VH need to be selected for different types of batteries. For example, the first threshold voltage VL1 is selected based on the voltage value corresponding to the single cell voltage reaching approximately 98.5% SOC at the end of charging, and the second threshold voltage VH is selected based on the voltage value corresponding to the single cell voltage reaching approximately 99% SOC at the end of charging. Among them, the size of the SOC can be adjusted according to the voltage difference range required for battery balancing. For example, if the SOC difference between the first threshold voltage VL1 and the second threshold voltage VH is large, the voltage interval formed by the first threshold voltage VL1 and the second threshold voltage VH becomes larger, that is, the range required for battery balancing becomes relatively smaller, which is equivalent to lowering the balancing requirement. If the SOC difference between the first threshold voltage VL1 and the second threshold voltage VH is small, the voltage interval formed by the first threshold voltage VL1 and the second threshold voltage VH becomes smaller, that is, the range required for battery balancing becomes relatively larger, which is equivalent to increasing the balancing requirement.

[0073] S220, obtaining the voltage of each single cell in the battery pack;

[0074] S230. Perform a balancing judgment on the battery pack based on the relationship between the voltage of the single cells, the first threshold voltage, and the second threshold voltage; wherein, if the voltage of at least some of the single cells is less than the first threshold voltage, and the voltage of at least some of the single cells is greater than the second threshold voltage, it is determined that the battery pack needs balancing.

[0075] Specifically, if the voltages of all cells are less than the first threshold voltage VL1, it indicates that the voltages do not meet the requirements, and the cells do not need to be balanced. If all voltages are greater than the second threshold voltage VH, it indicates that the voltages and the SOC of the cells basically meet the charging requirements, and the cells do not need to be balanced. If some cells have voltages greater than the second threshold voltage VH and some cells have voltages less than the first threshold voltage VL1, that is, if the voltages of the cells vary, it indicates that there are consistency differences between the cells, and the battery pack is determined to require balancing.

[0076] Based on the above embodiments, Figure 3 The present invention provides a flow chart of determining the target battery to be balanced in the battery pack according to the battery status and battery operating condition. Figure 3 , the method steps include:

[0077] S310, determining a third threshold voltage according to the single battery, wherein the third threshold voltage is less than the first threshold voltage;

[0078] Specifically, for different types of batteries, a different third threshold voltage VL2 needs to be selected. The third threshold voltage VL2 is lower than the first threshold voltage VL1. For example, taking the battery as an iron phosphate battery, the third threshold voltage VL2 is 3.45V. For example, the third threshold voltage VL2 is selected based on the voltage corresponding to the cell voltage reaching approximately 97% SOC at the end of charging. The SOC can be adjusted according to the required balancing voltage difference range of the battery. The SOC corresponding to the third threshold voltage VL2 is set to be lower than the SOC of the first threshold voltage VL1. Multiple groups of threshold voltages can be set for threshold division, thereby improving the battery balancing judgment and screening criteria through threshold division, making the target battery screening more optimized and further improving the balancing effect. For example, for different types of batteries, a fourth threshold voltage VL3 is selected. The fourth threshold voltage VL3 is lower than the third threshold voltage VL2. For example, taking the battery as an iron phosphate battery, the fourth threshold voltage VL3 is 3.39V. For example, the fourth threshold voltage VL3 is selected based on the voltage corresponding to the cell voltage reaching approximately 96% SOC at the end of charging.

[0079] S320, determining a target battery according to the lowest voltage, the first threshold voltage, the second threshold voltage, and the third threshold voltage of the single battery; wherein, if the lowest voltage of the single battery is greater than or equal to the third threshold voltage, the single battery with a marking voltage greater than the second threshold voltage is the target battery;

[0080] If the lowest voltage of the single battery is lower than the third threshold voltage, the single battery with a marking voltage higher than the first threshold voltage is the target battery.

[0081] Specifically, the lowest voltage among the cells is obtained. If the lowest voltage is greater than or equal to the third threshold voltage VL2, cells with voltages higher than the second threshold voltage VH can be selected as target cells for discharge balancing. If the average voltage of the cells is less than the first threshold voltage VL1, this indicates that there are more cells with low voltages. Therefore, cells with voltages higher than the second threshold voltage VH are selected as target cells for discharge balancing at the same current for a longer period of time. If the average voltage is greater than or equal to the first threshold voltage VL1, this indicates that there are fewer cells with low voltages. Therefore, target cells with voltages higher than the second threshold voltage VH need to be discharged for a shorter period of time at the same current. If the lowest voltage is less than the third threshold voltage VL2, cells with voltages higher than the first threshold voltage VL1 are selected as target cells for discharge. To further subdivide the discharge balancing capacity, the fourth threshold voltage VL3 can be used to divide the discharge balancing capacity accordingly to ensure balancing performance. For example, if the lowest voltage is less than the third threshold voltage VL2 but not less than the fourth threshold voltage VL3, the battery with a voltage higher than the first threshold voltage VL1 is discharged as the target battery to perform discharge balancing of the third capacity. If the lowest voltage is less than the fourth threshold voltage VL3, the battery with a voltage higher than the first threshold voltage VL1 is discharged as the target battery to perform discharge balancing of the fourth capacity. The third capacity is less than the fourth capacity.

[0082] Optionally, the first threshold voltage is the voltage value corresponding to the first preset charge state reached by the voltage of the single cell at the end of charging; the second threshold voltage is the voltage value corresponding to the second preset charge state reached by the voltage of the single cell at the end of charging; and the third threshold voltage is the voltage value corresponding to the third preset charge state reached by the voltage of the single cell at the end of charging; wherein the second preset charge state is greater than the first preset charge state; and the first preset charge state is greater than the third preset charge state;

[0083] Specifically, for different types of batteries, different first threshold voltages VL1, second threshold voltages VH, and third threshold voltages VL2 need to be selected. To increase the accuracy of balancing judgment, a fourth threshold voltage VL3 can be further selected, and voltage values ​​corresponding to different states of charge can be selected. By setting multiple sets of threshold voltages, the balancing judgment screening criteria of the battery can be improved. For example, taking the battery as an iron phosphate battery, the first threshold voltage VL1 is 3.5V, the second threshold voltage VH is 3.55V, the third threshold voltage VL2 is 3.45V, and the fourth threshold voltage VL3 is 3.39V. The first threshold voltage VL1 is selected based on the voltage value corresponding to the cell voltage reaching approximately 98.5% SOC at the end of charging, the second threshold voltage VH is selected based on the voltage value corresponding to the cell voltage reaching approximately 99% SOC at the end of charging, the third threshold voltage VL2 is selected based on the voltage value corresponding to the cell voltage reaching approximately 97% SOC at the end of charging, and the fourth threshold voltage VL3 is selected based on the voltage value corresponding to the cell voltage reaching approximately 96% SOC at the end of charging. The SOC can be adjusted based on the voltage differential range required for battery balancing. For example, if the SOC difference between the first threshold voltage VL1 and the second threshold voltage VH is large, the voltage interval formed by the first threshold voltage VL1 and the second threshold voltage VH becomes larger, meaning the range required for battery balancing becomes relatively smaller, effectively lowering the balancing requirement. If the SOC difference between the first threshold voltage VL1 and the second threshold voltage VH is small, the voltage interval formed by the first threshold voltage VL1 and the second threshold voltage VH becomes smaller, meaning the range required for battery balancing becomes relatively larger, effectively raising the balancing requirement. The SOC corresponding to the third threshold voltage VL2 and the fourth threshold voltage VL3 is set to be smaller than the SOC of the first threshold voltage VL1. This threshold division improves the battery balancing judgment and screening criteria, enabling better target battery selection and further enhancing the balancing effect.

[0084] Figure 4 The present invention provides a flowchart of a battery balancing process for selecting a target battery for a battery pack under fully static working conditions. Figure 4 , the method steps include:

[0085] S410, when the open circuit voltage of the single battery after sufficient rest is within the linear variation range of the relationship between the open circuit voltage and the state of charge, obtaining the battery capacity of the single battery and the average capacity of the single battery;

[0086] Specifically, after the battery has been fully rested, its voltage is the open circuit voltage (OCV). This refers to the battery energy storage system's BMS not being powered off, and the current being less than a specified current for a preset time, for example, less than 0.1C for one hour. Alternatively, if the BMS is powered off due to low voltage, and the system time is read after powering on again, the battery can also be considered fully rested if the power-on time and the last power-off time exceed the preset time.

[0087] The OCV-SOC relationship curve can determine the corresponding open circuit voltage values ​​at different SOC values. Depending on the battery type, the OCV-SOC relationship curve includes corresponding linear variation ranges. For example, for an iron phosphate battery, the open circuit voltage range in the OCV-SOC linear range is 2.5V-3.27V, while other voltages are considered to be in the nonlinear range.

[0088] S420, determining a reference capacity threshold according to the battery capacity and the average capacity;

[0089] Specifically, the baseline capacity threshold is the threshold for judging whether a single cell needs to be balanced. Within the linear variation range of OCV-SOC, the OCV of the single cell is used to estimate the SOC value of the single cell, and the current battery capacity of each single cell is converted according to the SOC value. The battery is balanced according to the difference in the capacity of each battery. The average capacity of each battery is calculated, and the sum of the average capacity and the battery capacity multiplied by the weight (for example, a weight of 50%) is used as the baseline capacity threshold. Taking the average capacity and battery capacity into consideration avoids selecting a single parameter and improves data accuracy. Among them, the weight is the proportion of the average capacity to the battery capacity. The proportion can be adjusted according to the actual situation and has greater flexibility.

[0090] S430 : Determine a target battery according to the battery capacity and a reference capacity threshold, wherein if the battery capacity is greater than the reference capacity threshold, mark the single cell as a target battery.

[0091] Specifically, batteries with capacities above a baseline capacity threshold are discharged and balanced. For example, to prevent over-balancing, the baseline capacity threshold can be added to a preset multiple of the current actual capacity of the individual battery as a floating amount for determination. For example, a battery with a capacity above the baseline capacity threshold + 1.5% * current actual capacity is determined as the target battery. The preset multiple can be adjusted based on actual application. In subsequent balancing, the battery's required discharge capacity is the individual battery's current capacity minus the baseline capacity threshold.

[0092] Figure 5The present invention provides another embodiment of a flow chart of a battery balancing process for selecting a target battery in a fully static working condition. Figure 5 , the method steps include:

[0093] S510, when the open circuit voltage is within a nonlinear variation range of the relationship between the open circuit voltage and the state of charge, obtaining the voltage of the single cell, the average voltage of the single cell, and the lowest voltage of the single cell;

[0094] Specifically, when the open circuit voltage is within the nonlinear variation range of OCV-SOC, the SOC value of each single cell cannot be obtained based on the OCV. Therefore, the voltage difference method is used to determine the battery that needs to be balanced and the balancing time. The acquisition equipment is used to obtain the voltage of each single cell and the lowest voltage among the voltages, and the average voltage of the single cell is obtained based on the voltage of each single cell.

[0095] S520, determining a first reference voltage according to an average voltage of the single cells and a lowest voltage of the single cells;

[0096] Specifically, the first reference voltage is a threshold value for judging whether the single battery cells need to be balanced. The average voltage and the lowest voltage are summed and averaged to obtain the first reference voltage.

[0097] S530 , determining a target cell according to the voltage of the single cell and a first reference voltage, wherein if the difference between the voltage of the single cell and the first reference voltage is greater than a preset equalization value, marking the single cell as a target cell.

[0098] Specifically, if the difference between a single cell's voltage and a first reference voltage is greater than or equal to a preset difference, the cell is determined to be a target cell requiring balancing. By setting different preset differences, the battery's balancing capacity or balancing time is correspondingly set. By categorizing the cells according to the preset differences, corresponding balancing times can be implemented to improve balancing accuracy. For example, if the cell's voltage minus the first reference voltage is ≥30mV, the cell is determined to require 20 hours of balancing at the same current. If the cell's voltage minus the first reference voltage is ≥15mV, the cell is determined to require 10 hours of balancing at the same current.

[0099] Figure 6 The present invention provides a flow chart of battery balancing judgment of a battery pack under charging conditions, see Figure 6 , the method steps include:

[0100] S610, obtaining the voltage of the single cell, the average voltage of the single cell, the minimum voltage of the single cell, and the maximum voltage of the single cell during the charging process;

[0101] The maximum voltage Vr of a single cell during charging refers to the voltage at which a significant inflection point appears during the voltage rise of the single cell during charging. For example, for a lithium iron phosphate battery, the maximum voltage Vr is 3.4V.

[0102] S620: If the voltage of the single cell is greater than the maximum voltage, it is determined that the battery pack needs balancing. A second reference voltage is obtained based on the average voltage of the single cell, the minimum voltage of the single cell, and a preset voltage floating amount. When the voltage of the single cell is greater than the second reference voltage, it is determined that the single cell needs balancing.

[0103] Specifically, after equalization at the end of charging, battery voltage consistency can be gradually improved. Furthermore, because the equalization time is a fixed and conservative value, some batteries may not be able to achieve sufficient equalization time, preventing further improvement in battery voltage consistency. To further enhance equalization, when battery voltages vary significantly during charging, a voltage difference-based equalization method is used. When the voltage of a single cell exceeds the maximum voltage (Vr), the target cell for equalization is re-identified. The second reference voltage serves as the threshold for selecting target cells. The second reference voltage is the sum of the average and minimum voltages, and then added with a preset voltage fluctuation. This preset voltage fluctuation can be configured based on battery performance. For example, for a lithium iron phosphate battery with a maximum voltage (Vr) of 3.4V, if the voltage of a single cell exceeds 3.4V during charging, the second reference voltage is (average voltage and minimum voltage) / 2 + 20mV. Cells with voltages greater than the second reference voltage are identified as target cells, and the equalization time is set to 3 minutes. Because voltages vary rapidly during charging, the target cell is re-identified based on the voltage differences of the single cells every 3 minutes.

[0104] Based on the above embodiment, optionally, the battery operating condition includes a charging end condition, a fully static condition, and a charging condition, wherein the fully static condition includes a condition where the open circuit voltage is within a linear variation range of the relationship between the open circuit voltage and the state of charge and a condition where the open circuit voltage is within a nonlinear variation range of the relationship between the open circuit voltage and the state of charge;

[0105] The priority of battery balancing for the target battery is that the priority of the charging end condition is higher than the priority of the open circuit voltage being within the linear variation range of the relationship between the open circuit voltage and the state of charge;

[0106] The priority when the open circuit voltage is in the linear change range of the relationship between the open circuit voltage and the charge state is greater than the priority when the open circuit voltage is in the nonlinear change range of the relationship between the open circuit voltage and the charge state;

[0107] The priority when the open circuit voltage is within the nonlinear change range of the relationship between the open circuit voltage and the charge state is greater than the priority of the charging condition.

[0108] Specifically, battery packs undergo both charging and resting processes during use. Therefore, the operating conditions of the battery pack include at least one of the end-of-charge condition, the fully rested condition, and the charging condition. Therefore, by setting balancing priorities, when executing high-priority balancing under various operating conditions, low-priority balancing processes must wait until the high-priority balancing process is complete before they can be triggered. This improves the flexibility of battery balancing and enhances balancing effectiveness. For example, during the control process, the initial balancing mode is 0. Balancing mode 1 represents balancing when the open-circuit voltage is within the nonlinear variation range of the open-circuit voltage and state of charge. Balancing mode 2 represents balancing when the open-circuit voltage is within the nonlinear variation range of the open-circuit voltage and state of charge. Balancing mode 3 represents balancing in the end-of-charge condition. Balancing modes for charging conditions are stored in memory. A higher balancing mode value indicates a higher priority. A lower-priority balancing mode can only be triggered after the waiting time for balancing for a higher-priority balancing mode reaches 0.

[0109] Optionally, the process of performing battery balancing on the target battery includes:

[0110] Get the balancing temperature of the single battery. If the balancing temperature is greater than the preset upper temperature limit, reduce the balancing current; if the balancing temperature is less than the preset lower temperature limit, restore the balancing current.

[0111] Specifically, a preset upper and lower temperature limit are set. During the balancing process, the temperature of the individual cells (i.e., the balancing temperature) is collected. When the highest balancing temperature is greater than or equal to the preset upper temperature limit, for example, 80°C, the balancing current is reduced to lower the balancing temperature. For example, the balancing start command and the balancing stop command are executed alternately, so that the effective balancing current is reduced by half, thereby lowering the balancing temperature. When the highest balancing temperature falls below the preset lower temperature limit, the balancing current is restored, the balancing start command is maintained, and the balancing process continues.

[0112] Figure 7 A schematic diagram of a battery balancing control system for a battery pack is provided in accordance with an embodiment of the present invention. Figure 7 ,include:

[0113] An acquisition module 110 is configured to acquire the battery status of a single battery in a battery pack;

[0114] The operating condition determination module 120 is used to determine the battery operating condition of the single battery according to the battery status;

[0115] A determination module 130 is configured to determine whether the battery pack requires balancing based on the battery operating conditions. If the battery pack requires balancing, the target battery in the battery pack that requires balancing is determined based on the battery status and the battery operating conditions.

[0116] The balancing module 140 is used to balance the power of the target battery.

[0117] Specifically, the acquisition module 110 acquires the battery status of the single cells in the battery pack, the operating condition determination module 120 determines the current battery operating condition of the battery pack through the battery status of the single cells, and the judgment module performs a balancing judgment on the battery pack for different battery operating conditions. If the balancing requirements are met, the target battery to be balanced in the battery pack is determined according to the battery status and battery operating condition, and the balancing module 130 performs power balancing on the target battery. Among them, the judgment module 140 makes a judgment and selects the target battery based on the battery operating condition, avoiding the condition restrictions brought about by the balancing judgment under a single operating condition, improving the flexibility of power balancing, improving the consistency of the battery pack, and improving the available capacity and available energy of the battery pack.

[0118] Figure 8 A schematic diagram of a battery management system is provided for the embodiment of the present invention. Figure 8 The system comprises a battery cluster 810 consisting of series-connected single cells, a primary master control module (MBMU), a secondary master control module (SBMU), a voltage slave control module (VCMU), a temperature slave board (TCMU), a high-voltage management unit (HMU), and a human interface (HMI). It should be noted that the number of battery clusters 810 can be expanded and configured according to energy storage requirements to achieve high-voltage battery system management.

[0119] The battery management system (BMS) and the VCMU (Volume Control Unit) integrated with the balancing module participate in balancing control. The corresponding functions of the operating condition determination module and the judgment module are integrated into the SBMU. The balancing strategy is mainly determined by the SBMU, and the balancing operation is started and stopped. The SBMU sends the corresponding start or stop balancing command to the VCMU. The VCMU controls the opening and closing of the balancing hardware according to the SBMU's control command and executes the balancing process of the single cells. Balancing commands are implemented through CAN communication and are sent in a periodic manner. The SBMU periodically sends balancing commands to the VCMU. After receiving the balancing command, the VCMU starts or shuts down the balancing hardware and transmits the balancing execution status via the CAN bus. The VCMU and TCMU collect parameters such as the voltage, temperature, and current of the single cells. The implementation of functions such as the acquisition module and the balancing module can be integrated into the VCMU.

[0120] The battery management system has a variety of external interfaces that can meet the application requirements of various occasions. These interfaces include: voltage acquisition input interface, temperature acquisition input interface, fan control output interface, fan signal feedback input interface, heating control output interface, CAN2.0 interface, Ethernet interface, RS485 interface, dry contact output interface, switch input / output interface, current high-speed acquisition input interface, and high-voltage signal acquisition input interface.

[0121] Figure 9 A flow chart of another balancing control method is provided for an embodiment of the present invention, see Figure 9 S710: The control entry is called every preset time, illustratively every 200ms, and execution begins. S720: Retrieve relevant fault information for balancing control, such as cell voltage detection failure, temperature detection failure, current detection failure, V-CAN communication failure, and storage failure. S730: Determine whether the fully rested battery condition is met. If so, S740: Mark the battery as being fully rested for balancing. If not, skip S740.

[0122] S750: Determine whether the post-charging operating condition is met. If so, S760: Mark the post-charging operating condition as the balance determination. If not, skip S760.

[0123] S770: Determine whether the charging end condition is met. If so, S780: Mark the balance determination according to the charging end condition. If not, skip S780.

[0124] S790: Determine whether the batteries in each marked operating condition meet the balancing conditions. The balancing conditions for the fully resting condition are: the battery management system has no faults that prohibit balancing, such as cell voltage detection faults, temperature detection faults, current detection faults, V-CAN communication faults, EE faults, etc.; the battery temperature is ≥45°C; and the balancing temperature is ≥100°C. The difference between the accumulated total voltage of each cell received by the SBMU and the total voltage detected is less than 10V. The lowest cell voltage is greater than the lower threshold for balancing in the fully resting condition (e.g., 3.1V). There is no high-priority balancing mode. If the SBMU determines that the above conditions are met, a fully resting condition balancing is triggered. S800: Call the judgment function to select the target cell, and S810: balancing is executed. The SBMU determines the cell to be balanced and the corresponding balancing time based on the cell voltage, lowest voltage, average voltage, OCV-SOC table, etc. The balancing time is stored in memory for easy recall.

[0125] After charging is complete, the conditions for determining the balancing condition are as follows: the battery management system has no faults prohibiting balancing, such as cell voltage detection failures, temperature detection failures, current detection failures, V-CAN communication failures, or storage failures; the battery temperature is ≥45°C, and the balancing temperature is ≥100°C. The lowest cell voltage is greater than the threshold for balancing (e.g., 3.1V); the current is less than 0.35C, and the maximum cell voltage remains greater than Vr (e.g., 3.4V) for at least one minute. The battery checks every three minutes to see if these conditions are met. If so, a balancing condition determination is triggered after charging is complete. S800 calls a determination function to select the target cell. It determines if the cell voltage is greater than (average voltage + minimum voltage) / 2 + a preset float (configurable, such as 20mV) and requires balancing. At S810, balancing is performed. The balancing time is fixed at 3 minutes and is not stored.

[0126] The conditions for determining equalization during the end-of-charge condition are: the battery management system has no faults that prohibit equalization, such as single-cell voltage detection faults, temperature detection faults, current detection faults, V-CAN communication faults, communication faults, etc., the battery temperature is ≥45°C, and the equalization temperature is ≥100°C. The lowest voltage of the single cell is greater than the voltage threshold allowed for equalization (e.g., 3.1V). The SBMU determines whether the above conditions are met. If so, it triggers an end-of-charge condition determination and equalization, i.e., S800 calls the judgment function to select the target cell. The SBMU determines the cell that needs equalization based on the cell's maximum voltage, minimum voltage, average voltage, VH, VL1, VL2, VL3, etc., and then S810 executes the equalization. The equalization is performed according to the corresponding equalization time, which is stored in the memory, and the equalization mode is set to 3.

[0127] If S790 does not meet the conditions, S820 determines whether the conditions for starting balancing are met, such as single cell voltage detection failure, temperature detection failure, current detection failure, V-CAN communication failure, storage failure, battery temperature ≥45°C and balancing temperature ≥100°C, etc., and the lowest single cell voltage is greater than the voltage threshold allowed to start balancing (such as 3.1V), then it means that the start conditions are met, and S830 calls the start function to start the operation.

[0128] If the conditions in S820 are not met, S840 determines whether the conditions for stopping balancing are met. These conditions include the battery management system having a fault that prohibits balancing, such as a cell voltage detection fault, a temperature detection fault, a current detection fault, a V-CAN communication fault, a storage fault, a battery temperature ≥ 45°C, or a balancing temperature ≥ 100°C. The lowest voltage is less than or equal to the stop balancing voltage threshold (e.g., 3.08V). If any of these conditions are met, the SBMU will stop balancing for all cells.

[0129] If the SBMU starts balancing, it needs to count the balancing time. When the balancing time of a single cell is completed, the balancing flag of the cell needs to be cleared. When the balancing time of all cells is completed, balancing stops. If any of the above situations occurs, S850 calls the stop balancing function.

[0130] In addition, to prevent the battery from being stored for too long and causing the previously determined balancing time to become unreliable, the S850 will mark the need to clear balancing when it determines that the time interval between the last BMS power-off and the current power-on exceeds 240 hours, and there are no faults related to the battery management system prohibiting balancing. When the difference between the accumulated total voltage received by the SBMU and the detected total voltage is less than 10V, it will be marked that balancing needs to be cleared. The S870 will call the clear balancing function to clear the stored balancing time.

[0131] Figure 10 A flow chart of a balance judgment process is provided for an embodiment of the present invention. Figure 10 The judgment process includes the charging end condition, the battery fully resting condition and the post-charging condition. The specific method steps include:

[0132] S900, determine the entry of the balancing function, S901, stop balancing, S910, determine whether it is the charging end condition, if it is the charging end condition, S920, clear the balancing mark, balancing mode and balancing time, S930, determine whether the maximum voltage of the single cell is less than the first threshold voltage VL1, such as 3.5V, if the maximum voltage is less than the first threshold voltage VL1, it means that the voltage of all single cells is less than the first threshold voltage VL1, which means that the voltage does not meet the requirement, and at this time, the single cells do not need to be balanced. If the maximum voltage is greater than the first threshold voltage VL1, then S940, determine whether the minimum voltage of the single cell is less than the first threshold voltage VL1, such as 3.5V; if the minimum voltage is less than the first threshold voltage VL1, then S950, determine whether the minimum voltage of the single cell is less than the third threshold voltage VL2, such as 3.45V; if the minimum voltage is greater than the third threshold voltage VL2, then S960, determine whether the average voltage is less than the first threshold voltage VL1; if the average voltage is less than the first threshold voltage VL1 at this time, then S970, indicate that there are more single cells with low voltage, and a longer balancing time is selected for the single cells with voltage higher than the second threshold voltage VH, for example, the balancing time is set to the balancing time corresponding to 0.7% of the actual battery capacity.

[0133] If the average voltage is greater than the first threshold voltage VL1 at this time, then S980 indicates that there are fewer single cells with low voltages. Therefore, it is necessary to perform discharge balancing for a shorter time on the target cells with voltages higher than the second threshold voltage VH. For example, the balancing time is set to the balancing time corresponding to 0.5% of the actual battery capacity. S990 updates the balancing mark and balancing time of each battery, and sets the balancing mode to balancing mode 3. S1001 saves the balancing time and balancing mode.

[0134] If the minimum voltage is less than the third threshold voltage VL2, then S1002 determines whether the minimum voltage of the single battery is less than a fourth threshold voltage VL3, such as 3.39V. If the minimum voltage is greater than the third threshold voltage VL2, S1003 sets the balancing time for the battery whose voltage is greater than the first threshold voltage VL1 to the balancing time corresponding to 1% of the actual battery capacity. If the minimum voltage is less than the third threshold voltage VL2, S1004 sets the balancing time for the battery whose voltage is greater than the first threshold voltage VL1 to the balancing time corresponding to 2% of the actual battery capacity.

[0135] If the battery is not in the fully rested state, S1005 determines whether the battery is in a fully rested state and whether the current balancing mode priority is lower than balancing mode 3. If the battery is in a fully rested state, S1006 clears the balancing flag. S1007 calculates the reference capacity threshold and the first reference voltage. S1008 determines whether the open-circuit voltage is within the linear range. If so, S1009 calculates the difference between the battery capacity of each cell and the reference capacity threshold. Cells with capacities exceeding the reference capacity threshold are then discharged and balanced. For example, to prevent over-balancing, the reference capacity threshold can be added to a preset multiple of the cell's current actual capacity as a floating amount. For example, a cell with a capacity exceeding the reference capacity threshold + 1.5% * the current actual capacity is considered the target cell. The preset multiple can be adjusted based on actual application. In subsequent balancing, the battery's required discharge capacity is the cell's current capacity minus the reference capacity threshold. S1010 updates the balancing flag and balancing time for each cell, and sets the balancing mode to balancing mode 2. S1011. Save the equalization time and equalization mode.

[0136] If the open-circuit voltage is within the nonlinear range, then S1012 determines whether the current balancing mode has a lower priority than balancing mode 2. If so, S1013 determines if the difference between the voltage of each cell and the first reference voltage exceeds the configured value, and if the cell voltage minus the first reference voltage is ≥30mV, then the cell is balanced for 20 hours. If the cell voltage minus the first reference voltage is ≥15mV, then the cell is balanced for 10 hours. S1014 updates the balancing flag and balancing time for each cell, setting the balancing mode to balancing mode 1. S1011 saves the balancing time and balancing mode.

[0137] If the battery is not fully rested, S1015 determines whether it is post-charging. If so, S1016 clears the balancing flag. S1017 calculates the second reference voltage. S1018 marks any cells whose voltages differ from the second reference voltage by more than the configured value as requiring balancing. S1019 sets the balancing time to 3 minutes.

[0138] Figure 11 A schematic diagram of a process for processing a balance judgment is provided for an embodiment of the present invention. Figure 11 S1100, process the balancing entry, S1101, determine whether balancing is on, if it is on, S1102, determine whether the time for voltage differential balancing after charging is completed is greater than zero, if so, S1103, determine whether the time for voltage differential balancing after charging is completed is less than 200ms, S1104, determine whether the time for voltage differential balancing after charging is zero, if not, return to S1102. If so, S1105, clear the balancing flag of each battery and stop voltage differential balancing. S1106, determine whether to update the balancing flag to enable or update the balancing time, if so, S1107, update the balancing flag according to the balancing time, S1108, determine whether the remaining balancing time is not zero, if so, S1109 start balancing, S1110 determine whether the highest balancing temperature of the battery is greater than or equal to 80°C, if greater than or equal to 80°C, S1111, reduce the equivalent balancing current. If it is less than 80°C, S1112 determines whether the maximum battery balancing temperature is less than 70°C. If so, S1113 determines whether the equivalent balancing current returns to normal. S1114 determines whether the current balancing state is off or has reached the 30s balancing time. If so, S1115 disables balancing instructions for all batteries. Otherwise, S1116 sends a start or stop battery balancing instruction based on the balancing flag.

[0139] Figure 12 A schematic diagram of a circuit structure of a balancing module is provided in an embodiment of the present invention. Figure 13 A schematic diagram of a balanced branch structure is provided for an embodiment of the present invention. Figure 12 and Figure 13 , including: a control unit 220 and a plurality of balancing branches 210, each balancing branch 210 is connected to a single battery.

[0140] Among them, the control unit can include an ADBMS6815 battery management chip. Resistors R1, R2, R4, and R5 are voltage divider resistors for NTC temperature measurement. The resistance value under the current temperature conditions is calculated by collecting the voltage divider on resistor R1. By looking up the RT table of the NTC sensor used in the project, the temperature value corresponding to the resistance value can be found.

[0141] The effective balancing current requirement should be ≥60mA@3.2V. Divide 3.2V by 0.06A, and the corresponding balancing resistor cannot exceed 53Ω. Since voltage acquisition automatically turns off the balancing function during voltage measurement, the maximum effective utilization rate of balancing is generally 90%. 53Ω*90%, the balancing resistor needs to be controlled below 47.7Ω. Considering certain reserve and resistor accuracy factors, the actual design scheme is 39Ω. Based on the maximum balancing voltage Uc=4.2V, the balancing resistor power P is calculated as P=4.2*4.2 / 39=0.45W, and the resistor power is selected as 1.5W. Checking the resistor derating curve, at an ambient temperature of 85℃, the resistor derating rate is 80%. The corresponding available power is: 1.5W*0.8=1.2W. Therefore, at 85℃, the maximum operating power of the balancing resistor is the rated power of the resistor: 0.45W / 1.2W=37.5%. The power selection reserve is sufficient to meet the design requirements. The balancing process of the balancing branch:

[0142] The balancing circuit is activated and deactivated by turning on and off electronic switch Q1. For example, electronic switch Q1 can be an NMOS switch. At the start of balancing, the control unit outputs a control signal to control terminal 1 of electronic switch Q1, turning on first terminal 2 and second terminal 3 of electronic switch Q1. The voltage of the positive battery cell BAT01_01 flows through resistors R2, R3, R4, and electronic switch Q1 to the negative battery cell, achieving balanced discharge. At the end of balancing, the control unit outputs a control signal to turn off electronic switch Q1. This process is repeated for other similar battery groups, achieving balanced discharge control for each individual battery cell.

[0143] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A battery pack charge balancing method, characterized in that: include: Get the battery status of the single battery in the battery pack; determining a battery operating condition of the single battery according to the battery status; determining whether the battery pack requires balancing based on the battery operating condition, and if it is determined that the battery pack requires balancing, determining a target battery in the battery pack that requires balancing based on the battery status and the battery operating condition; performing battery balancing on the target battery; The battery operating condition includes a charging end condition; and determining a target battery to be balanced in the battery pack according to the battery state and the battery operating condition includes: determining a first threshold voltage, a second threshold voltage, and a third threshold voltage according to the single battery, wherein the first threshold voltage is lower than the second threshold voltage, and the third threshold voltage is lower than the first threshold voltage; determining a target battery according to the lowest voltage of the single battery, the first threshold voltage, the second threshold voltage, and the third threshold voltage; wherein, if the lowest voltage of the single battery is greater than or equal to the third threshold voltage, marking the single battery having a voltage greater than the second threshold voltage as the target battery; If the lowest voltage of the single battery is lower than the third threshold voltage, the single battery having the voltage higher than the first threshold voltage is marked as the target battery.

2. The battery pack power balancing method according to claim 1, characterized in that: The battery operating condition includes a charging end condition; Determining whether the battery pack needs balancing according to the battery operating condition includes: Obtaining the voltage of each of the single cells in the battery pack; The battery pack is balanced based on the relationship between the voltage of the single cell, the first threshold voltage and the second threshold voltage; wherein, if the voltage of at least some of the single cells is less than the first threshold voltage, and the voltage of at least some of the single cells is greater than the second threshold voltage, it is determined that the battery pack requires balancing.

3. The battery pack charge balancing method according to claim 1, wherein: The first threshold voltage is the voltage value corresponding to the first preset charge state when the voltage of the single battery reaches the end of charging; the second threshold voltage is the voltage value corresponding to the second preset charge state when the voltage of the single battery reaches the end of charging; The third threshold voltage is the voltage value corresponding to the third preset charge state when the voltage of the single battery reaches the end of charging; wherein, the second preset charge state is greater than the first preset charge state; and the first preset charge state is greater than the third preset charge state.

4. The battery pack power balancing method according to any one of claims 1 to 3, characterized in that: The battery operating condition includes a fully static operating condition; and determining a target battery to be balanced in the battery pack according to the battery state and the battery operating condition includes: When the open circuit voltage of the single battery after sufficient rest is within a linear variation range of the relationship between the open circuit voltage and the state of charge, obtaining the battery capacity of the single battery and the average capacity of the single battery; taking the sum of the average capacity and the battery capacity multiplied by the weight as a reference capacity threshold; The target battery is determined according to the battery capacity and the reference capacity threshold, wherein if the battery capacity is greater than the reference capacity threshold, the single cell is marked as the target battery.

5. The battery pack power balancing method according to claim 4, characterized in that: Determining a target battery to be balanced in the battery pack according to the battery state and the battery operating condition further includes: When the open circuit voltage is within a nonlinear variation range of the relationship between the open circuit voltage and the state of charge, obtaining the voltage of the single battery, the average voltage of the single battery, and the lowest voltage of the single battery; Determining a first reference voltage according to an average voltage of the single battery and a lowest voltage of the single battery; The target cell is determined according to the voltage of the single cell and the first reference voltage, wherein if the difference between the voltage of the single cell and the first reference voltage is greater than a preset equalization value, the single cell is marked as the target cell.

6. The battery pack power balancing method according to any one of claims 1 to 3, characterized in that: The battery operating condition includes a charging condition; if it is determined that the battery pack requires balancing, determining a target battery in the battery pack to be balanced based on the battery state and the battery operating condition, including: Obtaining the voltage of the single battery, the average voltage of the single battery, the lowest voltage of the single battery, and the maximum voltage of the single battery during the charging process; If the voltage of the single battery is greater than the maximum voltage, it is determined that the battery pack needs balancing; A second reference voltage is obtained according to the average voltage of the single cells, the lowest voltage of the single cells and a preset voltage floating amount. When the voltage of the single cell is greater than the second reference voltage, the single cell is marked as the target cell.

7. The battery pack power balancing method according to any one of claims 1 to 3, characterized in that: The battery operating conditions include a charging end condition, a fully resting condition, and a charging condition, wherein the fully resting condition includes a condition where the open circuit voltage is within a linear variation range of the relationship between the open circuit voltage and the state of charge, and a condition where the open circuit voltage is within a nonlinear variation range of the relationship between the open circuit voltage and the state of charge; The priority of performing battery balancing on the target battery is: the priority of the end-of-charging condition is greater than the priority of the open-circuit voltage being within a linear variation interval of the relationship between the open-circuit voltage and the state of charge; The priority of the open circuit voltage when it is in the linear variation interval of the relationship between the open circuit voltage and the state of charge is greater than the priority of the open circuit voltage when it is in the nonlinear variation interval of the relationship between the open circuit voltage and the state of charge; The priority of the open circuit voltage when it is within the nonlinear change interval of the relationship between the open circuit voltage and the charge state is greater than the priority of the charging condition.

8. The battery pack power balancing method according to any one of claims 1 to 3, characterized in that: The process of performing battery balancing on the target battery includes: Obtaining the balancing temperature of the single battery, and if the balancing temperature is greater than a preset upper temperature limit, reducing the balancing current; If the balancing temperature is lower than the preset temperature lower limit, the balancing current is restored.

9. A battery balancing control system for a battery pack, characterized in that: include: An acquisition module, used to acquire the battery status of a single battery in a battery pack; an operating condition determination module, configured to determine a battery operating condition of the single battery according to the battery state; a judgment module, configured to judge whether the battery pack requires balancing according to the battery operating condition, and if it is determined that the battery pack requires balancing, determine a target battery in the battery pack that requires balancing according to the battery status and the battery operating condition; a balancing module, configured to balance the charge of the target battery; Wherein, the battery operating condition includes a charging end condition; The judgment module is used to determine a first threshold voltage, a second threshold voltage, and a third threshold voltage according to the single battery, wherein the first threshold voltage is lower than the second threshold voltage, and the third threshold voltage is lower than the first threshold voltage; determining a target battery according to the lowest voltage of the single battery, the first threshold voltage, the second threshold voltage, and the third threshold voltage; wherein, if the lowest voltage of the single battery is greater than or equal to the third threshold voltage, marking the single battery having a voltage greater than the second threshold voltage as the target battery; If the lowest voltage of the single battery is lower than the third threshold voltage, the single battery having the voltage higher than the first threshold voltage is marked as the target battery.

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