Charging control method, controller and battery management system

Abstract

The invention discloses a charging control method, a controller and a battery management system, the charging control method is used for charging a battery, the battery comprises a plurality of single cells, and the method comprises the following steps: in a constant current charging mode, when a maximum single cell voltage value (Vcell) exceeds a preset voltage threshold value, controlling the battery to enter a constant voltage charging mode, in the constant-voltage charging mode: when a first condition is satisfied, a charging request current value (Ireq) is reduced to enter a first constant-voltage charging sub-mode; when a second condition is satisfied, a charging request current value (Ireq) is increased to enter a second constant voltage charging sub-mode, the charging request current value being used to indicate a desired charging current magnitude. The problem of how to improve the charging efficiency of the battery is solved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a charging control method, a controller, and a battery management system. Background Technology

[0002] In actual lithium battery charging, a constant current-constant voltage (CC-CV) charging strategy is commonly used. During the constant current charging phase, if the current does not decrease, as the battery terminal voltage gradually approaches the upper charging limit (e.g., 4.2V), continuing with constant current will lead to overvoltage in the cell, causing lithium dendrite formation, heat generation, and even thermal runaway. Therefore, it is necessary to switch to constant voltage charging, which automatically reduces the current to prevent voltage overshoot. During the constant current charging phase, the battery terminal voltage increases with the state of charge (SOC). When the terminal voltage first reaches the preset voltage threshold (e.g., 4.2V), the charging strategy switches from constant current to constant voltage. From this moment on, the charger control terminal voltage remains at 4.2V and does not increase further, while the internal polarization of the battery gradually weakens, causing the charging current to decrease naturally until the battery is fully charged.

[0003] However, this method has shortcomings in low-temperature conditions: under low-temperature conditions, the battery is more likely to reach the constant voltage and decreasing current point. This means that the battery enters the constant voltage mode faster during charging under low-temperature conditions, the charging current decreases, and the charging efficiency is reduced. Summary of the Invention

[0004] This application provides a charging control method, a controller, and a battery management system to address the problem of how to improve battery charging efficiency.

[0005] The technical solution adopted in this application is as follows.

[0006] In a first aspect, this application provides a charging control method for charging a battery, the battery comprising multiple individual battery cells, characterized in that the method includes: When the battery is charging, obtain the maximum single cell voltage value (Vcell) of multiple individual cells. When the maximum single cell voltage (Vcell) does not exceed the preset voltage threshold, the battery is controlled to enter constant current charging mode; In constant current charging mode, when the maximum single cell voltage (Vcell) exceeds a preset voltage threshold, the battery is controlled to enter constant voltage charging mode. In constant voltage charging mode: when the first condition is met, the charging request current value (Ireq) is reduced to enter the first constant voltage charging sub-mode; when the second condition is met, the charging request current value (Ireq) is increased to enter the second constant voltage charging sub-mode. The charging request current value is used to indicate the expected charging current magnitude; when the third condition is met, the battery is controlled to exit the charging state. The first condition includes the maximum single cell voltage value (Vcell) being between the first voltage threshold (Vfull) and the second voltage threshold (VHcell); the second condition includes the maximum single cell voltage value (Vcell) being lower than the third voltage threshold (VLcell); and the third condition includes the maximum single cell voltage value (Vcell) exceeding the first voltage threshold (Vfull), the first voltage threshold (Vfull) being greater than the second voltage threshold (VHcell), and the second voltage threshold (VHcell) being greater than the third voltage threshold (VLcell).

[0007] By obtaining the maximum single cell voltage value (Vcell) during battery charging, and entering constant voltage charging mode after reaching a preset voltage threshold, and then switching to the first constant voltage charging mode or the second constant voltage charging mode according to different voltage ranges, the charging request current value (Ireq) can not only be reduced, but also increased when the conditions are met. Compared to the traditional constant-voltage charging stage where the charging current can only decrease monotonically, this method achieves dynamic adjustment of the charging current by setting a first constant-voltage charging mode and a second constant-voltage charging mode: When the maximum single-cell voltage value (Vcell) is between the first voltage threshold (Vfull) and the second voltage threshold (VHcell), the charging request current value (Ireq) is reduced, which can effectively suppress the terminal voltage from continuing to rise rapidly, prevent cell overvoltage, and ensure the safety of the charging process; when the maximum single-cell voltage value (Vcell) is lower than the third voltage threshold (VLcell), the charging request current value (Ireq) is increased, which can avoid the decrease in charging efficiency caused by the continuous decrease in current, especially under low-temperature conditions where the cell internal resistance is large and the voltage is more likely to trigger constant-voltage current reduction in advance. By increasing the current, the insufficient energy input can be compensated, thereby improving the overall charging efficiency; furthermore, when the maximum single-cell voltage value (Vcell) exceeds the first voltage threshold (Vfull), the charging state is exited, which can prevent cell overcharging and reduce the risk of thermal runaway.

[0008] In conjunction with the first aspect, in one possible implementation, reducing the charging request current value (Ireq) includes: The first current value (I1) is calculated based on the battery capacity. The first current value is less than the minimum value of the charging request current value in the second constant voltage charging sub-mode. The second current value (I2) is calculated based on the current reduction coefficient and the charging request current value (Ireq) during the most recent second constant voltage charging sub-mode. The maximum value between the first current value (I1) and the second current value (I2) is taken as the charging request current value (Ireq). Among them, the current reduction coefficient is less than 1, and the charging request current value in the second constant voltage charging sub-mode is determined based on the temperature value and capacity value of the individual cell.

[0009] The second current value is calculated based on the current reduction coefficient and the charging request current value in the most recent second constant-voltage charging mode. This allows for a gradual decrease in current during the constant-voltage charging phase, effectively suppressing voltage overshoot and improving charging safety. However, when the cell temperature is low or the SOC is too high, the second current value may rapidly approach zero. If this current value is used continuously at this time, the battery may be unable to maintain its charging state, prematurely interrupting the charging process. Therefore, the first current value is calculated based on the battery capacity and is guaranteed to be lower than the minimum current value in the second constant-voltage charging mode. This serves as a "backup current" to maintain the continuity of the charging process when the second current value approaches zero. By using the maximum value of I1 and I2, this application ensures smooth current reduction with the second current value under normal operating conditions and avoids charging interruption with the first current value under special operating conditions, thereby improving the stability and charging efficiency during the constant-voltage charging phase.

[0010] In conjunction with the first aspect, in one possible implementation, the second current value (I2) is calculated based on the current reduction coefficient and the charging request current value (Ireq) during the most recent second constant-voltage charging sub-mode, including: The current reduction factor is determined based on the extent to which the maximum single cell voltage (Vcell) exceeds the second voltage threshold (VHcell); The second current value (I2) is obtained by multiplying the current reduction factor by the charging request current value (Ireq) during the most recent second constant voltage charging sub-mode.

[0011] The current reduction coefficient is determined by the extent to which the maximum single-cell voltage (Vcell) exceeds the second voltage threshold (VHcell). This current is then combined with the charging request current value from the most recent second constant-voltage charging mode to calculate the second current value, enabling dynamic response of the current regulation process to changes in cell voltage. Specifically, when Vcell just exceeds VHcell, the exceedance is small, and the calculated current reduction coefficient is close to 1. The resulting second current value is close to the most recent charging request current value, achieving a smooth current decrease and avoiding premature and significant current reduction that could affect charging efficiency. As Vcell continues to rise and further exceeds VHcell, the exceedance increases, the current reduction coefficient gradually decreases, and the calculated second current value also gradually decreases, effectively suppressing the continued rapid rise of the terminal voltage and avoiding overvoltage risks. Through this adaptive adjustment based on the extent of cell voltage exceedance, this application can more sensitively reduce the current when the battery approaches its charging limit and maintain a higher charging current when the battery condition allows, thus balancing safety and charging efficiency and improving the dynamic control capability during the constant-voltage charging phase.

[0012] In conjunction with the first aspect, in one possible implementation, calculating the first current value (I1) based on the battery capacity includes: The first current value is calculated based on the following formula: I1 = a * C; The second current value (I2) is calculated based on the current reduction factor and the charging request current value (Ireq) during the most recent second constant voltage charging sub-mode, including: The second current value is calculated based on the following formula: I2=Ireq2-k*(Vcell-VHcell)*Ireq2; Wherein, I1 is the first current value, a is the correction coefficient, C is the battery capacity, I2 is the second current value, Vcell is the maximum single cell voltage value, VHcell is the second voltage threshold, Ireq2 is the charging request current value in the second constant voltage charging mode, and k is the preset coefficient.

[0013] By incorporating the battery capacity C and correction coefficient a into the calculation of the first current value (I1), the first current value can be proportionally set according to the battery capacity, ensuring a reasonable minimum charging current for batteries of different capacities. This allows the battery to remain in a charging state even when the second current value (I2) approaches zero, preventing premature interruption of charging and ensuring charging integrity. Furthermore, this claim calculates the second current value (I2) using the formula I2 = (100 - (Vcell - VHcell) * 2) * 0.01 * Ireq2. This is dynamically adjusted based on the extent to which the maximum single-cell voltage Vcell exceeds the second voltage threshold VHcell: when Vcell is only slightly higher than VHcell, the coefficient (100 - (Vcell - VHcell) * 2) approaches 100%, making I2 close to Ireq2, thus maintaining a high charging current and ensuring charging efficiency; as Vcell continues to rise and exceeds VHcell by a larger margin, the coefficient gradually decreases, and I2 decreases significantly, effectively suppressing the current and preventing further voltage overshoot. Through this dual constraint method, this application not only ensures that the minimum charging capacity can still be maintained when the current is extremely low, but also realizes dynamic current reduction adjustment with voltage changes, taking into account both charging safety and charging efficiency, and improving the overall control accuracy of the constant voltage stage.

[0014] In conjunction with the first aspect, in one possible implementation, increasing the charging request current value (Ireq) includes: Based on the temperature (T) and state of charge (SOC) of a single battery cell, the corresponding charging request current (Ireq) is determined.

[0015] By incorporating the cell temperature (T) and state of charge (SOC) as criteria during the increase of the charging request current (Ireq), the increase in charging current is no longer a fixed value or a simple ratio, but rather dynamically adjusted based on the real-time state of the cell. When the cell temperature is within a suitable range and the SOC is at a low to medium level, the battery's internal resistance is relatively low, allowing for a larger charging current input. In this case, increasing Ireq can accelerate the energy injection rate, thereby significantly improving charging efficiency. When the cell temperature is too high or the SOC is close to saturation, cell polarization intensifies and internal resistance increases. If a large current is still maintained, it can easily cause overheating or voltage overshoot. Therefore, the determined Ireq is limited to a smaller range in this case, thereby ensuring the safety of the charging process. Through this temperature- and SOC-based adaptive control mechanism, this application can achieve dynamic current increase in the second constant-voltage charging mode, while limiting the current within a safety boundary, thus achieving a balance between efficiency and safety in the charging process.

[0016] In conjunction with the first aspect, in one possible implementation, the corresponding charging request current value (Ireq) is determined based on the temperature value (T) and state of charge (SOC) of a single battery cell, including: Based on the maximum single cell temperature (Tmax) and state of charge (SOC), the corresponding third current value (I3) is determined. Based on the minimum single cell temperature (Tmin) and charge (SOC), the corresponding fourth current value (I4) is determined. The charging request current value (Ireq) is determined based on the minimum value between the third current value (I3) and the fourth current value (I4).

[0017] By determining the third current value (I3) based on Tmax and SOC, it is ensured that the current level at the highest temperature cell remains within a safe range. By determining the fourth current value (I4) based on Tmin and SOC, the current boost effect at the lowest temperature cell can be utilized, avoiding an overly conservative limitation on the overall charging rate. Furthermore, using the minimum of I3 and I4 as the final charging request current Ireq ensures that all cells in the entire battery pack are in a safe charging state, preventing thermal runaway due to individual cell differences, while maintaining the highest possible charging current when conditions permit.

[0018] In conjunction with the first aspect, in one possible implementation, the charging request current value (Ireq) is determined based on the minimum of the third current value (I3) and the fourth current value (I4), including: Multiply the third current value (I3) by the minimum of the fourth current value (I4) and the battery health value (SOH) to obtain the charging request current value (Ireq).

[0019] By multiplying the minimum of I3 and I4 by the State of Health (SOH), the charging current of degraded cells can be automatically reduced, thereby ensuring the reliability of the entire battery pack during charging. This method achieves charging efficiency while dynamically adapting to differences in battery state, preventing damaged cells from being affected by overcurrent or overvoltage, thus extending battery life and improving the overall safety and stability of the system.

[0020] In conjunction with the first aspect, in one possible implementation, the first condition includes the maximum single-cell voltage value (Vcell) being between a first voltage threshold (Vfull) and a second voltage threshold (VHcell), and being maintained for a first duration; The second condition includes the maximum single cell voltage value (Vcell) being lower than the third voltage threshold (VLcell) and maintaining this for a second duration; The third condition includes the maximum single cell voltage value (Vcell) exceeding the first voltage threshold (Vfull) and remaining there for a third duration.

[0021] By incorporating duration considerations for the first, second, and third conditions, the switching of charging modes is made not only dependent on the instantaneous maximum single-cell voltage (Vcell), but also comprehensively considers the voltage stability over a certain period. This setting effectively suppresses unnecessary mode switching caused by measurement noise or transient fluctuations in the cell, and avoids frequent fluctuations in the charging request current (Ireq), thereby improving the stability and reliability of the charging process. During the constant voltage charging phase, the duration of the first condition ensures that the battery maintains a stable current-reducing mode between Vfull and VHcell, preventing premature reduction of the charging current due to short-term voltage exceeding the threshold; the duration of the second condition ensures that the charging current is moderately increased only when Vcell is lower than VLcell, thus avoiding repeated fluctuations; and the duration of the third condition ensures that the charging state is exited only when Vcell exceeds the charging cutoff voltage, preventing accidental termination of charging due to transient overvoltage.

[0022] Secondly, this application also provides a controller, including a memory and a processor, wherein the memory is used to store computer programs or instructions; when the computer programs or instructions are executed by the processor, the method in the first aspect or any optional implementation of the first aspect is implemented.

[0023] Thirdly, this application also provides a battery management system, including: The sampling module is used to obtain the maximum single cell voltage value (Vcell). The controller is connected to the sampling output terminal of the sampling module and is used to implement the method in the first aspect or any of the optional implementations of the first aspect.

[0024] The beneficial effects of the second and third aspects described above can be referenced to the first aspect or any possible implementation thereof, and will not be elaborated upon here. Based on the implementations provided in the above aspects, this application can also be further combined to provide more implementations.

[0025] Other advantages, objectives and features of this application will be partly apparent from the description below, and partly understood by those skilled in the art through study and practice of this application. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the Rint equivalent circuit shown in an exemplary embodiment of this application; Figure 2 This is a flowchart illustrating a charging control method in an exemplary embodiment of this application; Figure 3 This is a schematic diagram illustrating the variation of the maximum single-cell voltage (Vcell) with charge (SOC) in an exemplary embodiment of this application; Figure 4 This is a flowchart of the process for calculating the charging request current value when the charging request current value is reduced; Figure 5 This is a flowchart for calculating the charging request current value when the charging request current value is increased; Figure 6 This is the schematic diagram of the controller; Figure 7 This is a schematic diagram of a battery management system. Detailed Implementation

[0028] It should be noted that, in this application, the terms "exemplary" or "for example" are used to indicate that something is being described as an example, illustration, or illustration. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design solutions. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0029] The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items. In this application, "at least one" means one or more, and "more than one" means two or more. The terms "first," "second," and other ordinal terms used in this application may be used to describe various constituent elements, but these constituent elements are not limited by these terms. The purpose of using these terms is solely to distinguish one constituent element from others and should not be construed as indicating or implying relative importance. For example, without departing from the scope of this application, a first constituent element may be named a second constituent element, and similarly, a second constituent element may be named a first constituent element.

[0030] Before introducing the embodiments of this application, the technical terms and background technology involved in this application will be introduced first.

[0031] Rint equivalent circuit: Reference Figure 1 The Rint equivalent circuit is a mathematical modeling method that simplifies the electrochemical characteristics of batteries. It represents the complex internal processes of a battery using equivalent circuit elements, thus facilitating the analysis of the battery's voltage, current, and internal resistance behavior under different operating conditions. In its most basic form, a battery can be represented by an open-circuit power source (whose voltage is the open-circuit voltage, OCV) and an equivalent resistance (representing the battery's internal resistance, R), i.e.: Terminal voltage = Open-circuit voltage + Charging current * Internal resistance. Here, the state of charge (SOC) and open-circuit voltage (OCV) are positively correlated, the state of charge (SOC) and internal resistance (R) are positively correlated, and temperature and internal resistance (R) are negatively correlated. As the state of charge (SOC) increases, the influence of internal resistance (R) on the terminal voltage gradually exceeds that of the state of charge (SOC).

[0032] In related technologies, a constant current-constant voltage (CC-CV) charging strategy is commonly used in the actual charging process of lithium batteries. In the constant current stage (CC stage), the charger output current remains constant, typically within the range of 0.5C to 1C of the battery's rated capacity. The main purpose of this stage is to quickly charge the battery to near the upper charging limit voltage (e.g., 4.2V), with the State of Charge (SOC) gradually increasing. Since the battery terminal voltage consists of open-circuit voltage and internal resistance voltage drop, the terminal voltage rises with increasing SOC. When the terminal voltage first approaches the set charging cutoff voltage, the constant voltage stage begins. The constant current stage allows for rapid replenishment of charge within a safe voltage range, while the constant current facilitates control of temperature rise and battery life. In the constant voltage stage (CV stage), the charger output voltage remains constant, fluctuating around the upper charging limit voltage (e.g., 4.2V), while the charging current gradually decreases with increasing battery SOC. The main purpose of this stage is to prevent battery overvoltage, protect battery safety, and gradually complete charging to full capacity. As the SOC approaches 100%, the internal polarization of the battery weakens, and the current naturally decreases until the battery is fully charged. At this point, the charger can either cut off or maintain trickle charging.

[0033] This method has shortcomings in low-temperature conditions: low temperatures will increase the internal resistance of the battery cell, resulting in a higher terminal voltage at low temperatures than at normal temperatures for the same charging current and open-circuit voltage. Therefore, the battery cell is more likely to reach the constant voltage and current reduction point at low temperatures. This means that the battery enters the constant voltage mode faster during charging at low temperatures, the charging current decreases, and the charging efficiency is reduced.

[0034] To address the aforementioned issues, this application provides a charging control method. By subdividing the constant-voltage charging phase into a first constant-voltage charging sub-mode and a second constant-voltage charging sub-mode, and dynamically adjusting the charging request current based on the maximum single-cell voltage, temperature, charge level, and battery health status, this method achieves flexible adjustment of the charging current. Compared to the traditional CC-CV strategy where the charging current monotonically decreases during the constant-voltage phase, this application can timely increase the charging request current based on the single-cell status under low-temperature conditions. This improves charging efficiency under low-temperature conditions while ensuring safety, addressing the problems of slow charging and low efficiency in low-temperature environments inherent in traditional methods.

[0035] The following describes one or more exemplary operating environments to facilitate a clearer understanding of the functions and intentions of the various implementation methods in this application. An energy storage system can serve as the implementation environment for the charging control method provided in this application. This implementation environment includes a battery, a battery management system (BMS), and a controller. A local BMS is connected to the battery and is used to collect voltage, temperature, and charge information from multiple individual cells, transmitting the data to the controller in real time. The controller is connected to the BMS and is used to receive the collected data and execute the charging control method of this application, serving as the main execution entity in the method embodiments of this application. Through the execution of the controller, the charging request current can be dynamically adjusted based on the maximum individual cell voltage, cell temperature, charge level, and battery health value, enabling switching between constant current charging, a first constant voltage charging sub-mode, and a second constant voltage charging sub-mode, and stopping charging when necessary. Through this operating environment, this application can obtain the cell status in real time and dynamically adjust the charging current, not only improving charging efficiency under low temperature or special operating conditions but also ensuring the safety and stability of the charging process.

[0036] Several embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the following embodiments can be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0037] refer to Figure 2 In a first aspect, this application provides a charging control method, comprising: S101: When the battery is in a charging state, obtain the maximum single cell voltage value (Vcell) of multiple individual cells. S103: When the maximum single cell voltage (Vcell) does not exceed the preset voltage threshold, control the battery to enter constant current charging mode; S105: In constant current charging mode, when the maximum single cell voltage (Vcell) exceeds the preset voltage threshold, the battery is controlled to enter constant voltage charging mode. In constant voltage charging mode: when the first condition is met, the charging request current value (Ireq) is reduced to enter the first constant voltage charging sub-mode; when the second condition is met, the charging request current value (Ireq) is increased to enter the second constant voltage charging sub-mode. The charging request current value is used to indicate the expected charging current magnitude; when the third condition is met, the battery is controlled to exit the charging state.

[0038] The first condition includes the maximum single cell voltage value (Vcell) being between the first voltage threshold (Vfull) and the second voltage threshold (VHcell); the second condition includes the maximum single cell voltage value (Vcell) being lower than the third voltage threshold (VLcell); and the third condition includes the maximum single cell voltage value (Vcell) exceeding the first voltage threshold (Vfull), the first voltage threshold (Vfull) being greater than the second voltage threshold (VHcell), and the second voltage threshold (VHcell) being greater than the third voltage threshold (VLcell).

[0039] By subdividing the constant-voltage charging stage into a first constant-voltage charging sub-mode and a second constant-voltage charging sub-mode, and dynamically adjusting the charging request current based on the maximum single-cell voltage, temperature, capacity, and battery health status, flexible adjustment of the charging current is achieved. Compared to the traditional CC-CV strategy where the charging current monotonically decreases during the constant-voltage stage, this application can timely increase the charging request current based on the single-cell status under low-temperature conditions, thereby improving charging efficiency under low-temperature conditions while ensuring safety, and addressing the problems of slow charging and low efficiency in low-temperature environments caused by traditional methods.

[0040] The following combination Figure 1-5 The steps S101 to S105 and other optional steps are described in detail.

[0041] Regarding S101 : When the battery is in a charging state, obtain the maximum single cell voltage value (Vcell) of multiple individual cells.

[0042] This step is designed to monitor the state of the cells closest to their maximum charging limit in the entire battery pack in real time, thereby improving the safety of the charging process.

[0043] Specifically, a battery consists of multiple individual cells, each with a slightly different voltage value due to variations in capacity, temperature, or aging. During charging, the voltage of each cell changes as the State of Charge (SOC) increases, but the magnitude of this change differs for each cell due to the aforementioned differences. By using a sampling module or BMS to read the voltage value of each individual cell in real time, the voltage distribution of the entire battery can be obtained. The highest voltage value among all individual cells is selected as the maximum individual cell voltage (Vcell). This value represents the cell most likely to reach the constant voltage drop point or the upper limit of charging, and is a key parameter for limiting charging current and preventing overvoltage.

[0044] Regarding step S103: When the maximum single cell voltage value (Vcell) does not exceed the preset voltage threshold, control the battery to enter constant current charging mode.

[0045] The purpose of step S103 is to ensure that the battery pack is charged with constant current within a safe voltage range in order to achieve fast and efficient charging.

[0046] Regarding step S105: In constant current charging mode, when the maximum single cell voltage value (Vcell) exceeds the preset voltage threshold, the battery is controlled to enter constant voltage charging mode. In constant voltage charging mode: when the first condition is met, the charging request current value (Ireq) is reduced to enter the first constant voltage charging sub-mode; when the second condition is met, the charging request current value (Ireq) is increased to enter the second constant voltage charging sub-mode. The charging request current value is used to indicate the expected charging current magnitude; when the third condition is met, the battery is controlled to exit the charging state.

[0047] The first condition includes the maximum single cell voltage value (Vcell) being between the first voltage threshold (Vfull) and the second voltage threshold (VHcell); the second condition includes the maximum single cell voltage value (Vcell) being lower than the third voltage threshold (VLcell); and the third condition includes the maximum single cell voltage value (Vcell) exceeding the first voltage threshold (Vfull), the first voltage threshold (Vfull) being greater than the second voltage threshold (VHcell), and the second voltage threshold (VHcell) being greater than the third voltage threshold (VLcell).

[0048] It should be noted that the requested charging current (Ireq) is different from the charging current. The charging current is the current measured in the circuit when the battery is charging, while the requested charging current (Ireq) is the calculated value that the charging current needs to reach. In practice, the charging current will chase the requested charging current (Ireq) until the charging current equals the requested charging current (Ireq).

[0049] refer to Figure 1 According to the Rint equivalent circuit model described above, during the charging process, the charge (SOC) gradually increases, and the open-circuit voltage (OCV) and internal resistance (R) increase with the increase of charge (SOC). When the charging current decreases, the following three situations will occur: one is that the effect of the decrease in charging current is insufficient to offset the effect of the increase in internal resistance (R) with the increase of charge (SOC), and the terminal voltage still increases; another situation is that the effect of the decrease in charging current exactly offsets the effect of the increase in internal resistance (R) with the increase of charge (SOC), and the terminal voltage remains unchanged; the third situation is that the effect of the decrease in charging current exceeds the effect of the increase in internal resistance (R) with the increase of charge (SOC), and the terminal voltage decreases. This application uses the principle of the third situation to decrease the terminal voltage and uses the principle of the first situation to increase the terminal voltage.

[0050] In the first constant-voltage charging mode, reducing the charging request current (Ireq) causes the charging current to decrease in line with the charging request current (Ireq), thereby gradually reducing the maximum single-cell voltage (Vcell) (the maximum single-cell voltage (Vcell) is positively correlated with the battery's terminal voltage). Simultaneously, as the state of charge (SOC) gradually increases, the decreasing trend of the maximum single-cell voltage (Vcell) gradually flattens until it becomes an increasing trend, resulting in a smoother change in the maximum single-cell voltage (Vcell). Similarly, in the second constant-voltage charging mode, increasing the charging request current (Ireq) can gradually increase the maximum single-cell voltage (Vcell).

[0051] For example, the first condition includes the maximum single cell voltage value (Vcell) being between a first voltage threshold (Vfull) and a second voltage threshold (VHcell) and remaining there for a first duration; the second condition includes the maximum single cell voltage value (Vcell) being lower than a third voltage threshold (VLcell) and remaining there for a second duration; and the third condition includes the maximum single cell voltage value (Vcell) exceeding the first voltage threshold (Vfull) and remaining there for a third duration.

[0052] By incorporating duration considerations for the first, second, and third conditions, the switching of charging modes is made not only dependent on the instantaneous maximum single-cell voltage value (Vcell), but also comprehensively considers the voltage stability over a certain period of time. This setting can effectively suppress unnecessary mode switching caused by measurement noise or transient fluctuations in the cell, and avoid frequent fluctuations in the charging request current (Ireq), thereby improving the stability and reliability of the charging process.

[0053] As the charging process progresses, the state of charge (SOC) gradually increases, and the battery polarization and reactivity become increasingly higher. This causes the open-circuit voltage (OCV) and internal resistance (R) to increase at an increasingly faster rate. As a result, in the first constant voltage charging mode, the maximum single cell voltage (Vcell) rises to exceed the first voltage threshold (Vfull) in a time shorter than the first duration. After maintaining this voltage for a third duration, the power control system (MCU) determines that the battery is fully charged, so the MCU controls the battery to exit the charging state.

[0054] The following example illustrates the battery charging process of this application, showing the change in the maximum single-cell voltage (Vcell) with the state of charge (SOC) as shown in the diagram. Figure 3 As shown.

[0055] When the battery begins charging, it first enters a constant current charging phase, where the requested charging current (Ireq) remains at a relatively high value. As the state of charge (SOC) increases, the maximum single-cell voltage (Vcell) gradually increases. When the maximum single-cell voltage (Vcell) exceeds a preset voltage threshold, the battery enters a constant voltage charging mode. The maximum single-cell voltage (Vcell) continues to increase with the state of charge (SOC). When the first condition is met (the maximum single-cell voltage (Vcell) rises to between the second voltage threshold (VHcell) and the first voltage threshold (Vfull), and remains there for a first duration), the charging request current value (Ireq) is reduced, and the battery enters a first constant voltage charging sub-mode. The maximum single-cell voltage value (Vcell) gradually decreases until the second condition is met (the maximum single-cell voltage value (Vcell) gradually decreases). When the voltage drops below the third voltage threshold (VLcell) and remains below it for a second duration, the charging request current value (Ireq) is increased, and the battery enters the second constant voltage charging sub-mode. The maximum single cell voltage value (Vcell) gradually increases until the first condition is met, and the charging request current value (Ireq) is decreased, and the battery enters the first constant voltage charging sub-mode. The battery cycles repeatedly between the first and second constant voltage charging sub-modes, enabling the battery to charge more power with higher charging efficiency. After the battery enters the second constant voltage charging sub-mode for the last time, the maximum single cell voltage (Vcell) increases to exceed the first voltage threshold (Vfull) in a time shorter than the first duration and remains above it for a third duration (i.e., the third condition is met). At this point, the power control system (MCU) determines that the battery is fully charged, so the MCU controls the battery to exit the charging state.

[0056] refer to Figure 4 In some implementations, the method further includes: S201: Calculate a first current value (I1) based on the battery capacity. The first current value (I1) is less than the minimum value of the charging request current value (Ireq) in the second constant voltage charging sub-mode. For example, calculating a first current value (I1) based on the battery capacity includes: The first current value is calculated based on the following formula: I1 = a * C; Where 'a' is a correction factor and 'C' is the battery capacity. 'a' is set according to the battery type; in this embodiment, 'a' = 0.1.

[0057] S203: Calculate the second current value (I2) based on the current reduction coefficient and the charging request current value (Ireq) during the most recent second constant voltage charging sub-mode, wherein the current reduction coefficient is less than 1, and the charging request current value during the second constant voltage charging sub-mode is determined based on the temperature value and capacity value of the individual cell. For example, the current reduction factor is determined based on the extent to which the maximum single-cell voltage value (Vcell) exceeds the second voltage threshold (VHcell); the current reduction factor is multiplied by the charging request current value (Ireq) during the most recent second constant voltage charging mode to obtain the second current value (I2), that is, the second current value (I2) is calculated based on the following formula: I2=Ireq2-k*(Vcell-VHcell)*Ireq2; Where I1 is the first current value, C is the battery capacity, I2 is the second current value, Vcell is the maximum single cell voltage value, VHcell is the second voltage threshold, Ireq2 is the charging request current value in the second constant voltage charging mode, and k is a preset coefficient.

[0058] In this embodiment, the formula for calculating the second current value (I2) can be: I2=(100-(Vcell-VHcell)*2)*0.01*Ireq2; That is, k=2, where the downflow coefficient is (100-(Vcell-VHcell)*2)*0.01.

[0059] The system dynamically adjusts the voltage based on the extent to which the maximum single-cell voltage Vcell exceeds the second voltage threshold VHcell: when Vcell is only slightly higher than VHcell, the preceding coefficient (100-(Vcell-VHcell)*2) approaches 100%, making I2 close to Ireq2, thereby maintaining a high charging current and ensuring charging efficiency; as Vcell continues to rise and exceeds VHcell by a larger margin, the preceding coefficient gradually decreases, and I2 decreases significantly, effectively suppressing the current and thus avoiding further voltage overshoot.

[0060] S205: Use the maximum value of the first current value (I1) and the second current value (I2) as the charging request current value (Ireq).

[0061] For example, increasing the charging request current value (Ireq) includes: determining the corresponding charging request current value (Ireq) based on the individual cell temperature value (T) and the state of charge (SOC).

[0062] When it is necessary to increase the charging request current value (Ireq) to enter the second constant voltage charging sub-mode, the charging request current value (Ireq) is determined based on a lookup table or function mapping. The individual cell temperature value (T) and the state of charge (SOC) are introduced as input parameters. The appropriate charging request current value (Ireq) is found and determined through a pre-set mapping table (T, SOC, Ireq mapping table). This can also determine the minimum value of the charging request current value (Ireq) in the second constant voltage charging mode, thus providing a basis for the first current value (I1) to be less than the minimum value of the charging request current value (Ireq) in the second constant voltage charging sub-mode.

[0063] refer to Figure 5 In some implementations, determining the corresponding charging request current value (Ireq) based on the individual cell temperature (T) and state of charge (SOC) specifically includes: S301: Determine the corresponding third current value (I3) based on the maximum single cell temperature value (Tmax) and the charge value (SOC). S303: Determine the corresponding fourth current value (I4) based on the minimum single cell temperature value (Tmin) and charge value (SOC). S305: Determine the charging request current value (Ireq) based on the minimum of the third current value (I3) and the fourth current value (I4).

[0064] In actual battery packs, temperature differences often exist between different individual cells. If the charging current is determined solely based on the average temperature or the temperature of a few cells, there is a risk that some cells may maintain a high charging current even when their temperature is too high, leading to localized overheating. By determining a third current value (I3) based on Tmax and SOC, it is ensured that the current level at the hottest cell remains within a safe range. By determining a fourth current value (I4) based on Tmin and SOC, the current boost at the coldest cell can be utilized, avoiding an overly conservative limitation on the overall charging rate. Based on this, using the minimum value between I3 and I4 as the final charging request current Ireq ensures that all cells in the entire battery pack are in a safe charging state, preventing thermal runaway due to individual cell differences, while maintaining the highest possible charging current when conditions permit.

[0065] For example, the charging request current value (Ireq) is obtained by multiplying the third current value (I3) by the minimum of the fourth current value (I4) and the battery health value (SOH).

[0066] In actual battery packs, even if the combined determination of Tmax and Tmin ensures temperature safety, some cells may experience capacity decay or increased internal resistance due to long-term cycling or aging. If charging continues using the charging current based on undegraded cells, it may still lead to localized overheating or accelerated degradation. By multiplying the minimum of I3 and I4 by the battery health value (SOH), the charging current for degraded cells can be automatically reduced, thereby ensuring the reliability of the entire battery pack during charging. This method achieves charging efficiency while dynamically adapting to differences in battery state, preventing unhealthy cells from being affected by overcurrent or overvoltage, thus extending battery life and improving the overall safety and stability of the system.

[0067] Secondly, based on the same technical concept, and referring to... Figure 6 This application also provides a controller 400, including a memory 401 and a processor 402. The memory 401 is used to store computer programs or instructions. When the computer program or instructions are executed by the processor, the method in the first aspect or any optional implementation of the first aspect is implemented.

[0068] The memory 401 includes at least one type of computer-readable storage medium, including flash memory, hard disk, multimedia card, random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), magnetic disk, optical disk, etc. In some embodiments, the computer-readable storage medium may be an internal storage unit of an electronic device, such as the hard disk or memory of the electronic device. In other embodiments, the computer-readable storage medium may also be an external storage device of the electronic device, such as a plug-in hard disk, secure digital card (SD card), flash memory card, etc., equipped on the electronic device. Of course, the computer-readable storage medium may include both internal storage units and external storage devices of the electronic device. In this embodiment, the computer-readable storage medium is typically used to store the operating system and various application software installed on the electronic device, such as the program code of the data processing method in the embodiment. In addition, the computer-readable storage medium may also be used to temporarily store various types of data that have been output or will be output.

[0069] In some embodiments, processor 402 may be a central processing unit (CPU), a microcontroller, a microprocessor, or other chip. This processor 402 is typically used to control the overall operation of the processing device, such as performing control and processing related to data interaction or communication with other entities. In this embodiment, the processor is used to run program code stored in memory or process data.

[0070] The memory 401 and the processor 402 typically communicate via a system bus, which includes a data bus, an address bus, and a control bus. The processor uses the address bus to tell the memory which memory location to access; the address bus is used for data transfer; the processor can read programs / data from the memory and write calculation results to the memory. The control bus ensures orderly data transfer and includes read / write control signals, clock signals, etc.

[0071] Thirdly, refer to Figure 7 Based on the same technical concept, this application also provides a battery management system 500, including: The sampling module 501 is used to obtain the maximum single cell voltage value (Vcell). The controller 400 is connected to the sampling output terminal of the sampling module 501 and is used to implement the method in the first aspect or any optional implementation of the first aspect.

[0072] The beneficial effects of the second and third aspects described above can be referenced to the first aspect or any possible implementation thereof, and will not be elaborated upon here. Based on the implementations provided in the above aspects, this application can also be further combined to provide more implementations.

[0073] It should be noted that the order in which the embodiments are described in this application is not intended to limit the priority of the embodiments. The reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0074] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application and in its specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0075] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many forms under the guidance of this application without departing from the spirit and scope of protection of the claims. All equivalent transformations made under the inventive concept of this application using the content of this application's specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A charge control method for charging a battery including a plurality of single cells, characterized by, The method comprises: acquiring a maximum single cell voltage value of the plurality of single cells when the battery is in a charging state; controlling the battery to enter a constant current charging mode when the maximum single cell voltage value does not exceed a preset voltage threshold value; in the constant current charging mode, when the maximum single cell voltage value exceeds the preset voltage threshold value, controlling the battery to enter a constant voltage charging mode, and in the constant voltage charging mode: when a first condition is met, reducing the charging request current value to enter a first constant voltage sub-mode; when a second condition is met, increasing the charging request current value to enter a second constant voltage sub-mode, the charging request current value being used to indicate an expected charging current size; when a third condition is met, controlling the battery to exit the charging state; wherein the first condition comprises that the maximum single cell voltage value is between a first voltage threshold value and a second voltage threshold value, the second condition comprises that the maximum single cell voltage value is lower than a third voltage threshold value, and the third condition comprises that the maximum single cell voltage value exceeds the first voltage threshold value, the first voltage threshold value being greater than the second voltage threshold value, and the second voltage threshold value being greater than the third voltage threshold value.

2. The method of claim 1, wherein, The reducing of the charging request current value comprises: calculating a first current value based on a battery capacity, the first current value being smaller than a minimum value of the charging request current value in the second constant voltage sub-mode; calculating a second current value based on a current reduction coefficient and a charging request current value in the second constant voltage sub-mode last time; taking a maximum value between the first current value and the second current value as the charging request current value; wherein the current reduction coefficient is less than 1, and the charging request current value in the second constant voltage sub-mode is determined based on a single cell temperature value and a power value.

3. The method of claim 2, wherein, The calculating of the second current value based on the current reduction coefficient and the charging request current value in the second constant voltage sub-mode last time comprises: determining the current reduction coefficient based on a magnitude by which the maximum single cell voltage value exceeds the second voltage threshold value; multiplying the current reduction coefficient and the charging request current value in the second constant voltage sub-mode last time to obtain the second current value.

4. The method of claim 2, wherein, The calculating of the first current value based on the battery capacity comprises: calculating the first current value based on a calculation formula as follows: I1=a*C; The calculating of the second current value based on the current reduction coefficient and the charging request current value in the second constant voltage sub-mode last time comprises: calculating the second current value based on a calculation formula as follows: I2=Ireq2-k*(Vcell-VHcell)*Ireq2; wherein I1 is the first current value, a is a correction coefficient, C is the battery capacity, I2 is the second current value, Vcell is the maximum single cell voltage value, VHcell is the second voltage threshold value, Ireq2 is the charging request current value in the second constant voltage sub-mode, and k is a preset coefficient.

5. The method according to any one of claims 1 to 4, characterized in that, The increasing of the charging request current value comprises: determining a corresponding charging request current value based on a single cell temperature value and a power value.

6. The method of claim 5, wherein, The determining of the charging request current value based on the single cell temperature value and the electric quantity value comprises: determining a third current value based on the maximum single cell temperature value and the electric quantity value; determining a fourth current value based on the minimum single cell temperature value and the electric quantity value; determining the charging request current value based on the minimum value between the third current value and the fourth current value.

7. The method of claim 6, wherein, The determining of the charging request current value based on the minimum value between the third current value and the fourth current value comprises: multiplying the minimum value between the third current value and the fourth current value and the battery health value to obtain the charging request current value.

8. The method of any one of claims 1-7, wherein: the first condition comprises that the maximum single cell voltage value is between a first voltage threshold and a second voltage threshold and is maintained for a first time length; the second condition comprises that the maximum single cell voltage value is lower than a third voltage threshold and is maintained for a second time length; the third condition comprises that the maximum single cell voltage value exceeds the first voltage threshold and is maintained for a third time length.

9. A controller characterized by comprising: The device comprises a memory and a processor, the memory is used to store computer instructions, and the processor is used to execute the computer instructions to execute the method of any one of claims 1-8.

10. A battery management system, characterized by, The device comprises: a sampling module, which is used to obtain the maximum single cell voltage value; a controller, which is connected to the sampling output end of the sampling module and is used to implement the method of any one of claims 1-8.

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