Management methods and management systems for secondary batteries

Abstract

The present invention provides a method and management system for managing a secondary battery, the secondary battery comprising N battery cells connected in series, where N is a positive integer of 2 or more. The management method includes a step of acquiring the voltage and battery capacity parameters at both ends of the secondary battery in real time during at least one of the charging and discharging processes. It also includes a step of determining feature points in the voltage change process, specifically, when the voltage reaches a predetermined range, the ratio of the change in the voltage divided by the change in the battery capacity parameter is calculated in real time, and if the ratio exceeds a feature threshold, it is determined that a feature point occurred in the voltage change process. Furthermore, it includes a step of determining the consistency of the secondary battery based on the number of feature points. According to the management method and management system of the present invention, the number of sampling lines can be reduced and the use of AFE chips is not dependent, resulting in excellent practicality and reduced product costs.

Description

Technical Field

[0001] The present invention mainly relates to the field of secondary batteries, and particularly to a management method and a management system for secondary batteries.

Background Art

[0002] A secondary battery usually consists of a plurality of cells connected in series, in parallel, or in a mixed connection. Since a secondary battery uses a highly active material, it has a high energy density and requires monitoring to prevent overcharging and over-discharging during the charge and discharge process. However, since the self-discharge rates of the plurality of cells are different from each other, a discrepancy occurs in the SOC (State of Charge) of each cell. Therefore, it is necessary to determine the balance state of the entire secondary battery, and if it is unbalanced, control means must be taken to make the SOC of all cells substantially coincide. In the current method, an analog front end (AFE) chip is used to perform battery sampling, consistency determination, and balance control. However, AFE is mainly monopolized by overseas semiconductor manufacturers, and it is expensive. Moreover, each cell needs to be connected to the AFE by a wire harness. Therefore, the wiring structure becomes complicated, the risk of short circuit increases, additional costs are required for safety design, and as a result, the overall cost further increases.

Summary of the Invention

[0003] The problem to be solved by the present invention is to provide a management method and a control system for a secondary battery that can easily detect consistency, effectively prevent overcharging and over-discharging, and have a low cost.

[0004] In order to solve the above problems, according to the present invention, a management method for a secondary battery is provided. The secondary battery includes N battery cells connected in series, where N is a positive integer of 2 or more. The management method is as follows: A step of acquiring the voltage across both ends of the secondary battery and the battery capacity parameters in real time during at least one of the charging and discharging processes, A step of determining characteristic points of the voltage during the change process, comprising: when the voltage reaches a predetermined range, calculating in real time the ratio of the change in the voltage to the change in the battery capacity parameter, and determining that a characteristic point has appeared in the voltage change process if the ratio is greater than a characteristic threshold; A step of determining the consistency of the secondary battery based on the number of feature points, Includes.

[0005] In one embodiment of the present invention, the step of acquiring the voltage and battery capacity parameters at both ends of the secondary battery in real time during the charging process includes the step of acquiring the charging voltage and charging battery capacity parameters at both ends of the secondary battery in real time. The step of determining the characteristic points of the voltage during the change process includes, when the charging voltage exceeds the initial total charging value, calculating in real time a first ratio of the change in the charging voltage to the change in the charging battery capacity parameter, and determining that a charging characteristic point has appeared in the charging process if the first ratio is greater than a first threshold. The step of determining the consistency of the secondary battery based on the number of feature points includes, if the charging voltage is equal to or greater than the total charging termination voltage, obtaining the number of charging feature points, and if the number of charging feature points is equal to N, determining that the consistency of the secondary battery is good.

[0006] In one embodiment of the present invention, the total charging termination voltage is equal to N times the maximum charging voltage of the battery cell.

[0007] In one embodiment of the present invention, a first upper limit is set for the first ratio, and if the first ratio exceeds the first upper limit, it is determined that two or more overlapping charging feature points have appeared in the charging process, and the actual number of overlapping charging feature points is added to the number of charging feature points.

[0008] In one embodiment of the present invention, the step of determining the consistency of the secondary battery based on the number of feature points further includes the step of determining that the consistency of the secondary battery is poor if the number of charging feature points is less than N, setting the charging mode to balance charging mode if it is determined that the consistency of the secondary battery is poor, and in the balance charging mode, stopping the charging process after charging a first predetermined amount if the number of charging feature points is equal to N.

[0009] In one embodiment of the present invention, constant voltage charging is employed in the balance charging mode, the range of the constant voltage is between the total charging termination voltage and the total clamp voltage, and the total clamp voltage is equal to N times the shuttle agent clamp voltage of the battery cell.

[0010] In one embodiment of the present invention, constant current charging is employed in the balance charging mode, and the constant current is less than or equal to the allowable current of the shuttle agent of the battery cell.

[0011] In one embodiment of the present invention, the first predetermined amount of energy is equal to the increase in battery capacity required to charge the battery cell from the maximum charging voltage of the battery cell to the shuttle agent clamping voltage.

[0012] In one embodiment of the present invention, in the balance charging mode, the time interval between adjacent charging feature points is recorded, and the capacity difference of different battery cells is obtained based on the time interval.

[0013] In one embodiment of the present invention, the step of acquiring the voltage and battery capacity parameters at both ends of the secondary battery in real time during the discharge process includes the step of acquiring the discharge voltage and discharge battery capacity parameters at both ends of the secondary battery in real time. The step of determining the characteristic points of the voltage during the change process includes, if the discharge voltage is lower than the initial total discharge value, calculating a second ratio of the change in the discharge voltage to the change in the discharge battery capacity parameter in real time, and if the second ratio is greater than a second threshold, determining that a discharge characteristic point has appeared in the discharge process. The step of determining the consistency of the secondary battery based on the number of feature points includes, when the discharge of the secondary battery is completed, obtaining the number of discharge feature points, and determining that the consistency of the secondary battery is good if the number of discharge feature points is equal to N.

[0014] In one embodiment of the present invention, when the discharge voltage is less than or equal to the total discharge termination voltage, the discharge of the secondary battery is terminated.

[0015] In one embodiment of the present invention, if the discharge voltage becomes less than the total discharge threshold and the number of discharge feature points increases by one before the discharge voltage reaches the total discharge termination voltage, the discharge of the secondary battery is terminated after continuing to discharge a second predetermined amount of energy, and the total discharge threshold is less than the initial total discharge value and greater than the total discharge termination voltage.

[0016] In one embodiment of the present invention, a second upper limit is set for the second ratio, and if the second ratio exceeds the second upper limit, it is determined that at least two overlapping discharge feature points have appeared in the discharge process, and the actual number of overlapping discharge feature points is added to the number of discharge feature points.

[0017] In one embodiment of the present invention, the step of determining the consistency of the secondary battery based on the number of feature points further includes the step of determining that the consistency of the secondary battery is poor if the number of discharge feature points is less than N, and if it is determined that the consistency of the secondary battery is poor, setting the charging mode of the next charging process to a balance charging mode.

[0018] In one embodiment of the present invention, the battery cell includes one type of lithium battery, sodium battery, and potassium battery or any combination thereof.

[0019] In one embodiment of the present invention, the battery capacity parameter includes any one or a combination of the current battery capacity, the state of charge, and the battery usage time.

[0020] The present invention further provides a management system for a secondary battery to solve the above problems. The secondary battery includes N battery cells connected in series, where N is a positive integer greater than or equal to 2. The management system includes a controller and at least one sampling circuit. The at least one sampling circuit is connected to both ends of the secondary battery and is used to collect the voltage of the secondary battery and transmit the voltage to the controller. The controller is configured to execute the above management method.

[0021] The secondary battery management method of the present invention can determine the consistency of the secondary battery during the charging process and / or the discharging process, and control the charging process and discharging process of the battery based on the result, effectively preventing overcharging and over-discharging. In addition, the secondary battery management system of the present invention reduces the number of sampling lines, has excellent practicality, and does not depend on the use of an AFE chip. Thereby, the number of AFE channels can be reduced, and in some cases, it is not necessary to use an AFE chip, which can greatly reduce the product cost.

Brief Description of the Drawings

[0022] The accompanying drawings are provided to further understand the present invention and constitute a part of the present invention. The accompanying drawings show the embodiments of the present invention and serve to explain the principles of the present invention together with this specification.

[0023] [Figure 1A] It is a block diagram of a control system for a secondary battery according to an embodiment of the present invention. [Figure 1B]It is a block diagram of a control system for a secondary battery according to another embodiment of the present invention. [Figure 2] It is an exemplary flowchart of a method for managing a secondary battery according to an embodiment of the present invention. [Figure 3] It is a schematic diagram of a charging curve of a battery cell in a secondary battery according to an embodiment of the present invention. [Figure 4] It is a schematic diagram of a discharging curve of a battery cell in a secondary battery according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0024] To more clearly explain the technical solutions of the embodiments of the present invention, the drawings that need to be used in the following description of the embodiments will be briefly explained. Obviously, the drawings in the following description are only some examples or embodiments of the present invention, and those skilled in the art can also apply the present invention to other similar scenarios based on these drawings without creative efforts. Unless otherwise clear from the language environment or stated otherwise, the same reference numerals in the figures represent the same structure or operation.

[0025] As shown in the present invention and the claims, terms such as "1", "one", "a kind", and / or "its" can include singular or plural unless the context explicitly indicates exceptional situations. Generally, the terms "include" and "contain" only indicate that they include clearly identified steps and elements, and these steps and elements do not constitute an exclusive list, and the method or device may also include other steps or elements.

[0026] Unless otherwise specified, the relative arrangements, digital expressions, and numerical values ​​of the components and steps described in these embodiments do not limit the scope of the present invention. The dimensions of the parts shown in the drawings are not necessarily drawn according to actual proportional relationships, but for illustrative purposes. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of this specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as illustrative only, not limiting. Therefore, other examples of these embodiments may have different values. In the following drawings, the same reference numerals and letters indicate the same item; therefore, if an item is defined in one drawing, further explanation in the following drawings is not necessary.

[0027] Furthermore, the use of terms such as "first," "second," etc., to limit parts is merely for the purpose of making it easier to distinguish corresponding parts, and unless otherwise explained, these terms have no special meaning and cannot be understood as limiting the scope of protection of the present invention. In addition, the terms used in the present invention have been selected from commonly known terms, but some terms mentioned in the specification may have been selected at the applicant's discretion, and their detailed meanings are explained in the relevant parts of this specification. Moreover, it is necessary to understand the present invention not only by the actual terms used, but also by the meanings contained in each term.

[0028] In this invention, the operations performed by the system according to the embodiment of the present invention will be described using a flowchart. Note that the following operations do not necessarily have to be performed in exact order. Conversely, various steps may be processed in reverse order or simultaneously. Simultaneously, other operations may be added to these processes, or certain steps or several steps may be removed from these processes.

[0029] The secondary battery management method and management system of the present invention are applicable to all types of secondary batteries, such as lithium batteries, sodium batteries, and potassium batteries, and are particularly suitable for secondary batteries that are at risk of overcharging or over-discharging. Lithium batteries include lithium-ion batteries and lithium metal batteries. Taking lithium-ion batteries as an example, the clamp voltage of the battery cell can be set by adding a shuttle agent. Battery cells of lithium-ion batteries include, but are not limited to, lithium iron phosphate batteries and ternary lithium-ion batteries. Lithium metal batteries include, but are not limited to, lithium sulfur batteries and lithium air batteries. Sodium batteries include sodium-ion batteries and sodium metal batteries, and potassium batteries include potassium-ion batteries and potassium metal batteries.

[0030] Figure 1A is a block diagram of a secondary battery management system according to one embodiment of the present invention. The secondary battery of the present invention includes N battery cells connected in series, where N is a positive integer of 2 or more. These N battery cells constitute two battery packs 111 and 112. A battery cell is also called a cell. The specific battery cell may have different charge and discharge characteristics depending on the model and manufacturer. The number of battery cells 120 in different battery packs may be the same or different.

[0031] The management system of the present invention further includes a controller and at least one sampling circuit. The at least one sampling circuit is connected to both ends of the secondary battery and is used to collect the voltage and battery capacity parameters of the secondary battery. As shown in Figure 1A, the management system 101 of this embodiment includes one controller 130 and one sampling circuit 140. The sampling circuit 140 is connected to one end of the battery pack 111 and the other end of the battery pack 112, respectively, that is, to both ends of the secondary battery 110 (i.e., the total positive electrode and the total negative electrode), and only two sampling lines are required. The sampling circuit 140 is also electrically connected to the controller 130 and transmits the collected voltage of the secondary battery 110 to the controller 130.

[0032] Figure 1B is a block diagram of a secondary battery management system according to another embodiment of the present invention. The management system 102 of this embodiment includes two sampling circuits 141 and 142. The sampling circuits correspond one-to-one with the battery pack. Sampling circuit 141 is connected to both ends of battery pack 111 and can transmit the voltage across both ends of battery pack 111 to the controller 130. Sampling circuit 142 is connected to both ends of battery pack 112 and can transmit the voltage across both ends of battery pack 112 to the controller 130, which is equivalent to transmitting the voltage across both ends of secondary battery 110 to the controller 130. In some embodiments, the controller 130 is an MCU.

[0033] The battery capacity parameters obtained in this invention refer to any parameter that characterizes the battery capacity. For example, this could be the current battery capacity or the State of Charge (SOC). SOC represents the ratio of the battery's remaining capacity to its total capacity in a fully charged state, and the value obtained by multiplying SOC by the total capacity is the current battery capacity, i.e., the battery's remaining capacity. Therefore, the two can be treated as equivalent. In one embodiment, since the battery capacity shows a certain tendency to change as the battery usage time elapses, the battery usage time can also be used as a type of battery capacity parameter for evaluating the battery capacity. Here, in the charging process, the battery usage time refers to the charging time, and in the discharging process, it refers to the discharge time.

[0034] According to the management system 101 of the present invention, the sampling circuit 140 can acquire the voltage of the secondary battery 110, and the controller 130 can acquire the voltage across both ends of the secondary battery and the battery capacity parameter during at least one of the charging and discharging processes of the secondary battery 110, and perform the management method of the present invention to determine the consistency of the secondary battery. This further prevents the risk of overcharging or over-discharging of the secondary battery 110. Compared to conventional solutions using AFE chips, this management system has the advantages of a simpler structure and fewer sampling lines. As a result, the number of AFE channels can be reduced, and the number of expensive AFE chips used can be reduced. Furthermore, it is possible to configure the system without using AFE chips, which can significantly reduce product costs.

[0035] In the management system 102, sampling circuits 141 and 142 are connected to the controller 130, respectively, to determine the consistency of multiple battery cells in battery packs 111 and 112. The controller 130 can also acquire all signals from sampling circuits 141 and 142 and determine the consistency of multiple battery cells in the two battery packs 111 and 112 of the entire secondary battery 110.

[0036] While the management system of the present invention can implement the management method disclosed herein, the management method of the present invention can also be implemented by other management systems. In this specification, the management method of the present invention will be explained using the management system 101 shown in Figure 1A, but this does not limit the specific entity that implements this management method.

[0037] Figure 2 is an illustrative flowchart of a secondary battery management method according to one embodiment of the present invention. As shown in Figure 2, the management method of this embodiment includes the following steps. Step S210: During at least one of the charging and discharging processes, acquire the voltage across the secondary battery and the battery capacity parameters in real time. Step S220: Determine feature points in the voltage change process. This includes calculating the ratio of the change in voltage to the change in battery capacity parameter in real time when the voltage reaches a predetermined range, and determining that a feature point has appeared in the voltage change process if the value of the ratio exceeds a feature threshold. Step S230: Determine the consistency of the secondary battery based on the number of feature points.

[0038] According to step S210, this method is suitable for application to the charging process only, the discharging process only, or both the charging and discharging processes simultaneously. Below, the two processes, the charging process and the discharging process, will be described separately.

[0039] Figure 3 is a schematic diagram showing the charging curve of a battery cell in a secondary battery according to one embodiment of the present invention. As shown in Figure 3, the horizontal axis is State of Charge (SOC) in units of %, and the vertical axis is voltage in units of V (volts). In Figure 3, SOC increases from left to right along the horizontal axis from the origin, and voltage increases from bottom to top along the vertical axis. The relationship between the current battery capacity and voltage is similar to the relationship between SOC and voltage, and the trends of the corresponding charging curves are also consistent. Therefore, in some embodiments, the horizontal axis may represent the current battery capacity. Furthermore, since the trend of voltage change with respect to battery usage time is similar to the trend of change with respect to SOC, in some embodiments, the horizontal axis may represent the battery usage time, i.e., the charging time.

[0040] Furthermore, feature points may be determined by comprehensively considering voltage, current battery capacity, SOC, and battery usage time. For example, the acquired feature points can be verified based on the relationship between voltage and any two or three of the current battery capacity, SOC, and battery usage time. Those skilled in the art can make various modifications according to actual circumstances, and all of these are covered within the scope of the present invention.

[0041] As shown in Figure 3, the voltage of the battery cell is low at the initial stage, in the range of 2.8 to 2.9V, and charging is required. The slope of this charging curve is characterized by a large slope at both ends and a small slope in the middle. In the initial stage, the slope of the charging curve is large, and the voltage reaches a high voltage value at a relatively fast rate, reaching the inflection point P1 in Figure 3. After that, the slope of the charging curve becomes smaller, and the rate of voltage increase slows down, but when the inflection point P2 is reached, the slope becomes large again, and the rate of voltage increase also increases again. In Figure 3, the inflection point P1 corresponds to a relatively small SOC, and the voltage is in the range of 3.2 to 3.3V. On the other hand, the inflection point P2 corresponds to a relatively large SOC, and the voltage is in the range of 3.4 to 3.5V. Figure 3 shows the charging characteristics of a battery cell, and in the case of a secondary battery 110 configured by connecting N battery cells 120 in series as shown in Figure 1A, the overall charging curve shows a similar trend. However, because the State of Charge (SOC) of each battery cell does not necessarily coincide, the overall charging curve of the secondary battery 110 is not simply a superposition of the charging curves of the N battery cells, but rather undergoes certain fluctuations, resulting in the formation of multiple inflection points on the overall charging curve.

[0042] Figure 3 is illustrative only and does not limit the actual charging curve and voltage values ​​of battery cell 120. Steps S210 to S230 of Example 1 will be described below with reference to Figures 1A and 3.

[0043] In Example 1, in step S210, the voltage across the secondary battery and battery capacity parameters are acquired in real time during the charging process.

[0044] In some embodiments, step S210 includes the following steps: Step S211: The charging voltage and battery capacity parameters at both ends of the secondary battery are acquired in real time. Here, the battery capacity parameters are the real-time battery capacity parameters at both ends of the secondary battery during the charging process.

[0045] Step S220 includes the following steps: Step S221: If the charging voltage exceeds the initial total charging value, a first ratio of the change in charging voltage to the change in the rechargeable battery capacity parameter is calculated. If the first ratio exceeds a first threshold, it is determined that a charging characteristic point has appeared during the charging process.

[0046] Step S230 includes the following steps: Step S231: If the charging voltage is equal to or greater than the total charging termination voltage, the number of charging feature points is obtained, and if the number of charging features is equal to N, it is determined that the secondary battery has good compatibility.

[0047] Referring to Figure 1A, during the charging process in step S211, the charging voltage U1 across the secondary battery 110 can be acquired in real time via the sampling circuit 140 and transmitted to the controller 130 in real time. The charging current is either known or can be acquired by the controller 130, and the controller 130 calculates the current battery capacity Q1 based on this charging current. For example, the battery capacity Q1 can be obtained by integrating the charging current with respect to time. This allows for the formation of a charging curve with Q1 on the horizontal axis and U1 on the vertical axis. Similarly, the current SOC can be acquired, and a curve similar to the change trend shown in Figure 3 can be obtained.

[0048] In some embodiments, the sampling circuit 140 can directly calculate the current battery capacity Q1 based on the charging current and transmit the charging voltage U1 and battery capacity Q1 to the controller 130.

[0049] When a charging curve is obtained, the charging characteristic points correspond to inflection points on the charging curve. In other embodiments, it is not necessary to obtain a charging curve, and the charging characteristic points can be calculated directly by step S221. The following description will explain the case where a charging curve is obtained as an example, but the management method of the present invention is not necessarily limited to cases where a charging curve must be obtained.

[0050] In step S221, first, the initial total charge value Uc0 is set, and only when U1 exceeds Uc0 does the real-time calculation of the first ratio R1 begin, thereby recording the number of charging inflection points on the charging curve. Referring to Figure 3, in the initial stage of charging, the initial voltage of the secondary battery is low, and the charging speed is fast at this time. Subsequently, it transitions to a slow charging stage, and the risk of overcharging is relatively low, so there is no need to detect the risk of overcharging at this stage. Also, because the voltage rises rapidly, making a judgment at this stage may yield an incorrect result. Therefore, by setting the initial total charge value Uc0, it is possible to prevent the occurrence of misjudgments.

[0051] In some embodiments, the initial total charge value Uc0 is set based on the characteristics of the battery cell and is N times the voltage value at the point when the slope of the battery cell's charging curve changes from a fast state to a gentle state. For example, as shown in Figure 3, if the voltage value at the inflection point P1 of the battery cell is 3.3V, the initial total charge value Uc0 is set to 3.3 × N[V]. In actual applications, the initial total charge value can be set as a range, for example, with a variation of 20% before and after 3.3 × N[V].

[0052] In some embodiments, the first ratio R1 can be calculated using the following formula (1). R1 = dU1 / dQ1 (1) If R1 > Th1 is satisfied, it is considered that a charging inflection point has appeared on the charging curve. Here, Th1 represents the first threshold.

[0053] The first threshold Th1 is set based on the performance of the battery cell used, and this invention does not limit its specific value. For example, the first threshold Th1 can be determined experimentally. The first threshold Th1 is set based on the performance of the battery cell used, and this invention does not limit its specific value. For example, the first threshold Th1 can be determined experimentally.

[0054] In step S231, the total charge termination voltage Ucc is further set. In some embodiments, the total charge termination voltage Ucc is equal to N times the maximum charge voltage Ucmax of the battery cell. The maximum charge voltage Ucmax of the battery cell refers to the maximum voltage value at which the battery cell can be charged within a safe range. For example, when Ucmax = 3.6V is set, Ucc = 3.6×N [V]. In other embodiments, the total charge termination voltage Ucc does not necessarily have to be equal to N×Ucmax, and it may be set within a certain range near N×Ucmax. That is, the total charge termination voltage Ucc may be greater than or less than N times the maximum charge voltage Ucmax of the battery cell.

[0055] For the battery cell, it can include the preset maximum charge voltage Ucmax, dangerous high voltage Ux, minimum discharge voltage Udmin, and shuttle agent clamp voltage Uclamp. The magnitude relationship among these is Udmin < Ucmax < Uclamp < Ux. As an example, Udmin = 2.5 [V], Ucmax = 3.6 [V], Uclamp = 3.65 [V], and Ux = 3.8 [V] can be set. Note that the shuttle agent clamp voltage Uclamp may vary depending on the type of shuttle agent, and Uclamp can be set by adjusting the components of the shuttle agent.

[0056] In step S231, when U1≧Ucc and the number of charge characteristic points is equal to N, it is determined that the consistency of the secondary battery 110 is good, and charging can be stopped at this point.

[0057] In some embodiments, in step S231, when U1≧Ucc and the number of charge inflection points is less than N, it is determined that the consistency of the secondary battery 110 is poor and the balance property is low. Therefore, the balance charging mode is activated.

[0058] As can be understood, before the balance charging mode is activated, the secondary battery 110 can be controlled by the controller 130 and charged using a normal charging method. This includes a constant current charging method, the magnitude of which is set according to the charge / discharge capacity of the battery cells. Typically, this charging current is much larger than the current in balance charging mode.

[0059] In some embodiments, the balance charging mode includes a method employing constant voltage charging. The range of this constant voltage is between the total charging termination voltage Ucc and the total clamp voltage Uclamp1, where the total clamp voltage Uclamp1 is equal to N times the shuttle agent clamp voltage Uclamp of the battery cell. That is, Uclamp1 = Uclamp × N. According to the above example, the range of the constant voltage is (3.6 × N [V] to 3.65 × N [V]). Under balance charging mode, electrons in high-SOC battery cells are consumed by the shuttle agent, so there is no significant change in the energy content of high-SOC battery cells.

[0060] In some embodiments, the balance charging mode also includes a method employing constant current charging. In this case, the constant current value is less than or equal to the allowable current of the battery cell's shuttle agent. The allowable current of the shuttle agent is determined by the shuttle agent used, and specifically, this constant current value is significantly smaller than the charging current in a normal charging mode.

[0061] In balance charging mode, battery cells with a low SOC continue to charge, while the energy content of battery cells with a high SOC does not increase. As a result, the SOC of each battery cell in the secondary battery 110 becomes more uniform overall, improving the consistency and balance of the secondary battery 110. This prevents overcharging of the battery.

[0062] In balance charging mode, the number of charging characteristic points is continuously recorded, and when that number reaches N, it indicates that the voltage of N battery cells has already reached a certain value. At this point, the secondary battery 110 is further charged with a first predetermined energy amount Q11, and then the charging process is stopped. This effectively prevents overcharging. Note that the appearance of an inflection point does not mean that the battery cells are already fully charged. The purpose of further charging Q11 is to bring the battery cells to a fully charged state.

[0063] In some embodiments, the first predetermined energy quantity Q11 is equal to the increase in battery capacity required to charge the battery cell voltage from the maximum charging voltage Ucmax to the shuttle agent clamping voltage Uclamp. Since the maximum charging voltage Ucmax and the shuttle agent clamping voltage Uclamp can be known in advance, the first predetermined energy quantity Q11 is a constant.

[0064] In some cases, when the consistency is particularly high, for example, when two battery cells show an inflection point at the same time, an overlap of inflection points occurs on the charging curve of the charging voltage U1, and the number of recorded charging inflection points may be less than the actual number of inflection points. In such cases, even if the number of charging inflection points recorded in step S221 is less than N, it does not necessarily mean that the battery consistency is poor. To distinguish this phenomenon, the management method of the present invention sets a first upper limit value R1_up for the first ratio R1, and if the first ratio R1 exceeds the first upper limit value R1_up, it is determined that at least two overlapping charging feature points have occurred during the charging process. The actual number of overlapping charging feature points is then added to the number of charging feature points. For example, if it is detected that the first ratio R1 has exceeded the first upper limit value R1_up, it is determined that there are more than two overlapping charging feature points. Furthermore, within the first interval where the first ratio R1 exceeds the first upper limit R1_up, it can be determined that there are two overlapping points, and within the second interval, it can be determined that there are three overlapping points, and the value in the second interval is greater than that of the first interval. In this way, the number of overlapping points can be determined and added to the number of charging feature points.

[0065] In this invention, the specific numerical value of the first upper limit R1_up is not particularly limited. By experimentally determining the optimal values ​​of the first upper limit R1_up, the first interval, the second interval, etc., the detection sensitivity of overlapping feature points can be improved.

[0066] Steps S211, S221, and S231 described above effectively prevent overcharging during the charging process.

[0067] In some embodiments, the balance charging mode records the time interval between adjacent charging inflection points and calculates the capacity difference of each battery cell based on that time interval. According to these embodiments, when the secondary battery enters the balance charging mode, the time of occurrence of newly detected charging inflection points can be continuously recorded. By integrating the charging current with respect to time within the time difference interval, the resulting value becomes the capacity difference. Therefore, the time interval between adjacent charging inflection points can reflect the capacity difference between different battery cells, i.e., the difference in consistency. By obtaining this capacity difference, the user can determine the consistency status of the battery. The capacity difference information is obtained by the controller 130 and can be transmitted to a higher-level controller or the user. For example, if the capacity difference of a particular battery cell is large, that battery cell can be identified and removed or replaced in a subsequent process. Furthermore, the obtained capacity difference can also be used to verify the consistency of the battery determined based on the number of feature points.

[0068] Figure 4 is a schematic diagram of the discharge curve of a battery cell in a secondary battery according to one embodiment of the present invention. Similar to Figure 3, in Figure 4, the horizontal axis represents SOC (unit: %) and the vertical axis represents voltage (unit: V). Discharge is the reverse process of charging. As shown in Figure 4, from the origin, SOC gradually decreases from left to right on the horizontal axis, and voltage gradually increases from bottom to top on the vertical axis. If the horizontal axis represents the current battery capacity, the battery capacity decreases from left to right, and if the horizontal axis represents the battery discharge time, the discharge time increases from left to right. As shown in Figure 4, in the initial stage, the battery cell voltage is high, in the range of 3.4 to 3.5V, and in some cases, a discharge operation may be necessary. The absolute value of the slope of the discharge curve is also characterized by being large at both ends and small in the middle. In the initial stage, the absolute value of the slope is large, and the voltage decreases at a relatively fast rate, reaching the voltage value at the inflection point P3 in Figure 4. After that, the absolute value of the slope decreases, and the rate of voltage decrease slows down, but when the inflection point P4 is reached, the absolute value of the slope becomes large again, and the voltage decreases rapidly. In Figure 4, the SOC corresponding to the inflection point P3 is relatively large, and the voltage is slightly higher than approximately 3.3V. The SOC corresponding to the inflection point P4 is small, and the voltage is in the range of 3.1 to 3.2V. Figure 4 shows the discharge characteristics of the battery cell, and the discharge curve of the entire secondary battery 110 shown in Figure 1A shows a similar trend. However, because there are discrepancies in the State of Charge (SOC) of each battery cell, the overall discharge curve of the secondary battery 110 is not simply a superposition of the discharge curves of the N battery cells, but rather several fluctuations occur, resulting in the formation of multiple inflection points on the total discharge curve.

[0069] Figure 4 is illustrative only and does not limit the actual discharge curve and voltage value of battery cell 120. Steps S210 to S230 of Example 2 will be described below with reference to Figures 1A and 4.

[0070] In Example 2, step S210 acquires the voltage across the secondary battery and the battery capacity parameters in real time during the discharge process.

[0071] In some embodiments, step S210 includes the following steps: Step S212: Obtain the discharge voltage and discharge capacity parameters at both ends of the secondary battery in real time. The discharge capacity parameters are the real-time battery capacity parameters at both ends of the secondary battery during the discharge process.

[0072] Step S220 includes the following steps: Step S222: If the discharge voltage is less than the initial total discharge value, the second ratio of the change in discharge voltage to the change in the discharge battery capacity parameter is calculated in real time. If the second ratio exceeds the second threshold, it is determined that one discharge characteristic point has appeared in the discharge process.

[0073] Step S230 includes the following steps: Step S232: When the discharge of the secondary battery is complete, the number of discharge feature points is obtained, and if this number is equal to N, it is determined that the secondary battery has good compatibility.

[0074] Referring to Figures 1A and 4, during the discharge process in step S212, the discharge voltage U2 across the secondary battery 110 can be acquired in real time using the sampling circuit 140 shown in Figure 1A, and this discharge voltage U2 can be transmitted to the controller 130 in real time. The discharge current is known, and the controller 130 calculates the current discharge battery capacity Q2 based on the discharge current. For example, the discharge battery capacity Q2 can be obtained by integrating the discharge current with respect to time. This allows for the formation of a discharge curve with Q2 on the horizontal axis and U2 on the vertical axis. Similarly, the current SOC can be acquired, and a curve similar to the change trend shown in Figure 4 can be obtained.

[0075] In some embodiments, the sampling circuit 140 can directly calculate the current discharge battery capacity Q2 based on the discharge current, and the discharge voltage U2 and the discharge battery capacity Q2 can be transmitted together to the controller 130.

[0076] When a discharge curve is obtained, the discharge feature points correspond to the inflection points on the discharge curve. In other embodiments, it is not necessary to obtain a discharge curve, and the discharge feature points can be calculated directly in step S222. The following description will use the case where a discharge curve is obtained as an example, but the control method of the present invention is not necessarily limited to cases where a discharge curve must be obtained.

[0077] In step S222, first, the initial total discharge value Ud0 is set, and when U2 becomes less than Ud0, the number of discharge inflection points on the discharge curve is recorded. Referring to Figure 4, since the risk of over-discharge is small in the initial discharge stage, there is no need to detect the risk of over-discharge in the discharge stage before the inflection point P3. The set initial total discharge value Ud0 is the product of a value smaller than the voltage value at the inflection point P3 and N. For example, Ud0 can be set to Ud0 = 3.3 × N [V]. Referring to Figure 4, it can be seen that when the voltage of the battery cell reaches 3.3V, it enters a stable discharge stage.

[0078] In some examples, the second ratio R2 is calculated using the following formula (2). R2 = dU2 / dQ2 (2) If R2 > Th2 is satisfied, it is considered that a discharge inflection point has appeared on the discharge curve at that point. Here, Th2 represents the second threshold. In this invention, the specific numerical value of the second threshold Th2 is not particularly limited. The second threshold Th2 can be determined experimentally.

[0079] In step S232, the timing for stopping the discharge can be determined based on the magnitude of the discharge voltage, and this can be considered as the end of the discharge of the secondary battery.

[0080] In some embodiments, the total discharge termination voltage Udc is equal to N times the minimum discharge voltage Udmin of the battery cell. When the discharge voltage of a battery cell reaches the minimum discharge voltage Udmin, it indicates that the battery cell has already completed discharge. Therefore, when the total discharge voltage U2 of the secondary battery containing N battery cells falls below the total discharge termination voltage Udc, it means that the secondary battery has completed discharge and there is no need to continue discharging any further, so the discharge is stopped. At this point, if the number of detected discharge feature points is equal to N, it is determined that the consistency of the secondary battery is good.

[0081] In some embodiments, to prevent over-discharge, the discharge voltage U2 of the secondary battery is determined at a stage where the discharge voltage of the secondary battery has not yet reached Udc during the discharge process. When the discharge voltage U2 is smaller than the total discharge threshold value Ud1, the discharge characteristic points are further determined. When the number of discharge characteristic points increases by one, after continuously discharging the second predetermined amount of electric charge Q21, the discharge process is stopped. Here, the relationship of Udc < Ud1 < Ud0 holds. According to this embodiment, the fact that the discharge voltage U2 is smaller than the total discharge threshold value Ud1 indicates that most of the battery cells have entered the final stage of the discharge process. At this stage, the inflection point on the discharge curve is detected. When one inflection point occurs, it means that one battery cell is about to reach the minimum discharge voltage. Therefore, by stopping the discharge after further discharging the second predetermined amount of electric charge Q21, over-discharge of that battery cell can be prevented. At this point, although the discharge voltage U2 has not yet dropped to Udc, the discharge is not continued to prevent over-discharge of the battery cell. Furthermore, when the number of detected discharge characteristic points is equal to N, it is determined that the consistency of the secondary battery is good.

[0082] In some embodiments, the total discharge threshold value Ud1 is the product of the voltage value near the inflection point P4 and N. Here, the voltage value near the inflection point P4 refers to a narrow range including both sides of the voltage value, that is, the vicinity range centered on the voltage value. For example, it can be set as Ud1 = 3.2 × N [V]. Referring to FIG. 4, when the voltage reaches 3.2V, it is approaching the inflection point P4, indicating that the discharge process of one battery cell has entered the final stage at this time.

[0083] In some embodiments, the second predetermined amount of electric charge Q21 is equal to the discharge amount of the battery capacity required when discharging the voltage of the battery cell from the voltage at the time of inflection point generation to the minimum discharge voltage Udmin.

[0084] In some embodiments, the second predetermined amount of electric charge Q21 can be set in advance as a constant.

[0085] In some embodiments, experiments have allowed for the identification of more appropriate Ud0 and Ud1 values, thereby enabling a more sensitive reflection of the relationship between the inflection point and the discharge state of the battery cell. In actual applications, however, the values ​​of Ud0 and Ud1 can vary within a certain range and are not limited to a specific point.

[0086] In some cases, when the consistency is particularly high, an overlapping phenomenon of inflection points occurs on the discharge curve, and the number of recorded discharge inflection points may be less than the actual number of inflection points. To address such cases, in some embodiments, the control method of the present invention further includes the following steps: A second upper limit value R2_up is set for the second ratio R2, and if the second ratio R2 exceeds the second upper limit value R2_up, it is determined that at least two overlapping discharge feature points occurred during the discharge process, and the actual number of these overlapping discharge feature points is added to the number of discharge feature points. For example, if it is detected that the second ratio R2 exceeds the second upper limit value R2_up, it is determined that there are more than two overlapping discharge feature points. Furthermore, it can be determined that there are two overlapping points in the third interval where the second ratio R2 exceeds the second upper limit value R2_up, and three overlapping points in the fourth interval, and the value of the fourth interval is greater than that of the third interval. In this way, the number of overlapping points can be determined, and their actual number can be added to the number of discharge feature points.

[0087] In this invention, the specific numerical value of the second upper limit R2_up is not particularly limited. By experimentally determining the optimal values ​​for the second upper limit R2_up, the third interval, the fourth interval, etc., the detection sensitivity of overlapping feature points can be improved.

[0088] During the discharge process, the number of discharge inflection points is recorded, and if this number is equal to N, it is determined that the consistency of the secondary battery 110 is good. On the other hand, if the number of discharge inflection points is less than N and there are no overlapping inflection points, it is determined that the consistency of the secondary battery 110 is poor. In these embodiments, the control method of the present invention further includes the following steps: If the consistency of the battery cells in the battery is poor, the charging mode for the next charging process is set to balance charging mode. In this way, battery mismatch can be detected during the discharge process, and the user can be prompted to use balance charging mode directly during the next charging. Also, in some situations, if the secondary battery has a certain charge limit and that limit is lower than the total charge termination voltage, the balance charging mode may not be activated. Therefore, if poor consistency is detected during the discharge process, the balance charging mode can be automatically set for the next charging process, thereby preventing overcharging and improving battery mismatch.

[0089] The control method of the present invention further includes Example 3. In step S210 of Example 3, the voltage across the secondary battery and battery capacity parameters are acquired in real time during both the charging and discharging processes. For the charging process, steps S211, S221, and S231 of Example 1 can be referenced, and for the discharging process, steps S212, S222, and S232 of Example 2 can be referenced. Since the above descriptions can all be applied to the description of Example 3, a detailed explanation is omitted here.

[0090] Furthermore, the specific settings of various parameters used in this management method, such as the initial total charge value Uc0, the first threshold Th1, the second threshold Th2, the total charge termination voltage Ucc, the maximum charge voltage Ucmax, the critical high voltage Ux, the minimum discharge voltage Udmin, the shuttle agent clamp voltage Uclamp, the initial total discharge value Ud0, the total discharge termination voltage Udc, the total discharge threshold Ud1, the first predetermined energy amount Q11, and the second predetermined energy amount Q21, may depend on other reference values, such as battery temperature, charge / discharge current, and battery degradation status. Therefore, by pre-setting parameter values ​​corresponding to different reference values ​​and adjusting each parameter in the management method of the present invention in real time, for example, using a table reference method, the control accuracy can be improved.

[0091] By employing the battery management method and management system of the present invention, the consistency of batteries can be determined by detecting characteristic points, and the charging and discharging processes can be controlled based on this determination. This effectively prevents overcharging and over-discharging, reduces the number of sampling lines, and offers superior practicality. Furthermore, the use of expensive AFE chips can be reduced or eliminated, significantly lowering product costs.

[0092] Although the basic concepts have been explained above, for those skilled in the art, the disclosure of the invention above is merely illustrative and does not limit the present invention. Although not explicitly described herein, those skilled in the art can make various modifications, improvements, and alterations to the present invention. Such modifications, improvements, and alterations are proposed in the present invention and therefore remain within the spirit and scope of the exemplary embodiments of the present invention.

[0093] At the same time, the present invention uses specific words to describe embodiments of the invention. “One embodiment,” “one embodiment,” and / or “several embodiments” mean features, structures, or characteristics relating to at least one embodiment of the present invention. Therefore, it should be emphasized that “one embodiment,” “one embodiment,” or “alternative embodiment” mentioned more than once in different locations herein do not necessarily refer to the same embodiment. In addition, some features, structures, or characteristics of one or more embodiments of the present invention can be appropriately combined.

[0094] Similarly, it should be noted that, in order to simplify the expressions disclosed in the present invention and to aid in the understanding of one or more embodiments of the invention, multiple features may be included in a single embodiment, drawing, or description thereof in the above description of embodiments of the present invention. However, such a method of disclosure does not mean that there are more features necessary for the subject matter of the present invention than the features described in the claims. In fact, the features of the embodiments are fewer than all the features of a single embodiment disclosed above.

[0095] In some embodiments, numbers are used to describe the number of components and attributes, but it should be understood that in some examples, the numbers used for description are modified with the modifiers “approximately,” “approximately,” or “about.” Unless otherwise specified, “approximately,” “approximately,” or “substantially” indicates that the numbers allow for a variation of ±20%. Accordingly, in some embodiments, all numerical parameters used in the specification and claims are approximations, and these approximations can be changed according to the characteristics required for the individual embodiment. In some embodiments, numerical parameters should employ a general bit-retention method, taking into account a predetermined number of significant digits. In some embodiments of the present invention, numerical fields and parameters for confirming their range are approximations, but in specific embodiments, the setting of such numerical values ​​should be as accurate as possible.

Claims

1. A method for managing secondary batteries, The aforementioned secondary battery includes N battery cells connected in series, where N is a positive integer of 2 or more. The aforementioned management method is, A step of acquiring the voltage across both ends of the secondary battery and the battery capacity parameters in real time during at least one of the charging and discharging processes, A step of determining characteristic points of the voltage during the change process, comprising: when the voltage reaches a predetermined range, calculating in real time the ratio of the change in the voltage to the change in the battery capacity parameter, and determining that a characteristic point has appeared in the voltage change process if the ratio is greater than a characteristic threshold; A step of determining the consistency of the secondary battery based on the number of feature points, A management method characterized by including the following.

2. The step of acquiring the voltage across the terminals of the secondary battery and the battery capacity parameters in real time during the charging process includes the step of acquiring the charging voltage across the terminals of the secondary battery and the charging battery capacity parameters in real time. The step of determining the characteristic points of the voltage during the change process includes, when the charging voltage exceeds the initial total charging value, calculating in real time a first ratio of the change in the charging voltage to the change in the charging battery capacity parameter, and determining that a charging characteristic point has appeared in the charging process if the first ratio is greater than a first threshold. The management method according to claim 1, characterized in that the step of determining the consistency of the secondary battery based on the number of feature points includes the step of obtaining the number of charging feature points if the charging voltage is equal to or greater than the total charging termination voltage, and determining that the consistency of the secondary battery is good if the number of charging feature points is equal to N.

3. The management method according to claim 2, characterized in that the total charging termination voltage is equal to N times the maximum charging voltage of the battery cell.

4. The management method according to claim 2, further comprising the step of setting a first upper limit for the first ratio, determining that two or more overlapping charging feature points have appeared in the charging process if the first ratio exceeds the first upper limit, and adding the actual number of overlapping charging feature points to the number of charging feature points.

5. The management method according to claim 2, characterized in that the step of determining the consistency of the secondary battery based on the number of feature points is further characterized by including the step of determining that the consistency of the secondary battery is poor if the number of charging feature points is less than N, setting the charging mode to balance charging mode if it is determined that the consistency of the secondary battery is poor, and in the balance charging mode, stopping the charging process after charging a first predetermined amount if the number of charging feature points is equal to N.

6. The management method according to claim 5, characterized in that, in the balance charging mode, constant voltage charging is employed, the range of the constant voltage is between the total charging termination voltage and the total clamp voltage, and the total clamp voltage is equal to N times the shuttle agent clamp voltage of the battery cell.

7. The management method according to claim 5, characterized in that constant current charging is employed in the balance charging mode, and the constant current is less than or equal to the allowable current of the shuttle agent of the battery cell.

8. The management method according to claim 5, characterized in that the first predetermined amount of energy is equal to the increase in battery capacity required to charge the voltage of the battery cell from the maximum charging voltage of the battery cell to the shuttle agent clamping voltage.

9. The management method according to claim 5, characterized in that, in the balance charging mode, the time interval between adjacent charging feature points is recorded, and the capacity difference of different battery cells is obtained based on the time interval.

10. The step of acquiring the voltage and battery capacity parameters at both ends of the secondary battery in real time during the discharge process includes the step of acquiring the discharge voltage and discharge battery capacity parameters at both ends of the secondary battery in real time. The step of determining the characteristic points of the voltage during the change process includes, if the discharge voltage is lower than the initial total discharge value, calculating a second ratio of the change in the discharge voltage to the change in the discharge battery capacity parameter in real time, and if the second ratio is greater than a second threshold, determining that a discharge characteristic point has appeared in the discharge process. The management method according to claim 1, characterized in that the step of determining the consistency of the secondary battery based on the number of feature points includes the step of obtaining the number of discharge feature points of the discharge feature points when the discharge of the secondary battery is completed, and determining that the consistency of the secondary battery is good if the number of discharge feature points is equal to N.

11. The management method according to claim 10, characterized in that the discharge of the secondary battery ends when the discharge voltage is less than or equal to the total discharge termination voltage.

12. The management method according to claim 10, further comprising the following: if, before the discharge voltage reaches the total discharge termination voltage, the discharge voltage becomes less than the total discharge threshold and the number of discharge feature points increases by one, the discharge of the secondary battery is terminated after continuing to discharge a second predetermined amount of energy, and the total discharge threshold is less than the initial total discharge value and greater than the total discharge termination voltage.

13. The management method according to claim 10, further comprising setting a second upper limit for the second ratio, determining that at least two overlapping discharge feature points appeared in the discharge process if the second ratio exceeds the second upper limit, and adding the actual number of overlapping discharge feature points to the number of discharge feature points.

14. The management method according to claim 10, characterized in that the step of determining the consistency of the secondary battery based on the number of feature points further includes the step of determining that the consistency of the secondary battery is poor if the number of discharge feature points is less than N, and if it is determined that the consistency of the secondary battery is poor, setting the charging mode of the next charging process to a balance charging mode.

15. The control method according to claim 1, characterized in that the battery cell includes one of a lithium battery, a sodium battery, and a potassium battery, or any combination thereof.

16. The management method according to claim 1, characterized in that the battery capacity parameters include one or more combinations of the current battery capacity, charge state, and battery usage time.

17. A management system for secondary batteries, The aforementioned secondary battery includes N battery cells connected in series, where N is a positive integer of 2 or more. The management system comprises a controller and at least one sampling circuit, the at least one sampling circuit being connected to both ends of the secondary battery and used to collect the voltage of the secondary battery and transmit the voltage to the controller, and the controller being configured to perform the management method described in any one of claims 1 to 16.

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