Battery equipment and battery management system

Abstract

The battery management system determines a charging current for charging the battery pack in each section based on a derating coefficient of a charging cycle including a plurality of sections, updates the derating coefficient based on a result of comparing the voltage of the battery pack in each section with a voltage upper limit value set for the corresponding section, and uses the updated derating coefficient for the next charging cycle.

Description

[Technical field]

[0001] Cross-reference to related applications This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0140418 dated October 20, 2021, and all contents disclosed in the documents of the Korean Patent Application are incorporated herein by reference.

[0002] The disclosed subject matter relates to a battery device and a battery management system. [Background technology]

[0003] Electric vehicles or hybrid vehicles are vehicles that obtain power by driving a motor using a battery as a power source, and research into them is being actively conducted as an alternative that can solve the pollution and energy problems of internal combustion vehicles. In addition, rechargeable batteries are used in various external devices other than vehicles.

[0004] As the capacity of batteries used in various external devices such as vehicles increases and decreases, technologies to fast charge batteries are being used. A typical fast charging algorithm charges the battery by gradually reducing the current from high to low in order to minimize deterioration of the battery cells.

[0005] As a battery cell degrades, its resistance increases and the voltage during charging may rise. The increase in voltage reduces the negative electrode potential of the battery cell, causing active material (e.g., lithium) precipitation, which may accelerate the degradation of the battery cell. In this case, the fast charging algorithm uses logic to charge the battery cell based on its state. For example, logic to reduce the charging current or charging capacity based on the degradation state (SOH), or logic to set a voltage upper limit for each stage and proceed to the next charging stage when the voltage increases due to resistance degradation, may be used. However, degradation cannot be completely prevented due to limitations caused by SOH estimation errors, and when the voltage upper limit is reached and the next stage is proceeded to, the charging time may continue to increase compared to the beginning of life (BOL). Summary of the Invention [Problem to be solved by the invention]

[0006] An embodiment may provide a battery device and a battery management system that can minimize degradation of battery cells. [Means for solving the problem]

[0007] According to an embodiment, a battery device including a battery pack and a battery management system may be provided, in which the battery management system determines a charging current for charging the battery pack in each section based on a derating factor of a charging cycle including a plurality of sections, updates the derating factor based on a result of comparing the voltage of the battery pack in each section with a voltage upper limit value set for the corresponding section, and uses the updated derating factor for a next charging cycle.

[0008] In one embodiment, a basic charging current is set for each of the plurality of sections, and the battery management system may determine the charging current by reflecting the derating factor in the basic charging current.

[0009] In one embodiment, the battery management system may set the derating factor to be the same for the plurality of sections, and determine the charging current for each section by multiplying the derating factor by the base charging current for the corresponding section.

[0010] In one embodiment, the battery management system may update the derating coefficient based on the number of sections in which the voltage of the battery pack exceeds the upper voltage limit value among the plurality of sections.

[0011] In one embodiment, if the number of intervals exceeding the upper voltage limit exceeds a critical value, the battery management system may decrease the derating factor.

[0012] In one embodiment, if the number of intervals exceeding the upper voltage limit does not exceed the critical value, the battery management system may maintain the derating factor.

[0013] In one embodiment, the battery management system may set the derating coefficients individually for the plurality of sections, and determine the charging current for each section by multiplying the derating coefficient for each section by the basic charging current for the corresponding section.

[0014] In one embodiment, the battery management system may reduce the derating factor for a section in which the voltage of the battery pack exceeds the upper voltage limit value among the plurality of sections.

[0015] In one embodiment, the battery management system may increase the derating factor for a corresponding section in which the voltage of the battery pack does not exceed the upper voltage limit value among the plurality of sections.

[0016] According to another embodiment, a battery management system for a battery pack may be provided. The battery management system may include a monitoring circuit for monitoring a voltage of the battery pack, a memory, and a processor. The base memory may store a voltage upper limit value and a derating factor in each section of a charging cycle including a plurality of sections. The processor may determine a charging current of the battery pack in each section of the charging cycle based on the derating factor, and may update the derating factor based on the number of sections in which the voltage of the battery pack exceeds the voltage upper limit value among the plurality of sections.

[0017] In one embodiment, the memory may store a magnitude of a base charging current for each section of the charging cycle, and the processor may set the derating factor to be the same for the sections and determine the charging current for each section by multiplying the derating factor by the base charging current for the corresponding section.

[0018] In one embodiment, if the number of intervals exceeding the upper voltage limit exceeds a critical value, the processor may decrease the derating factor.

[0019] In one embodiment, if the number of intervals exceeding the upper voltage limit does not exceed the critical value, the processor may maintain the derating factor.

[0020] According to another embodiment, a battery management system for a battery pack may be provided. The battery management system may include a monitoring circuit for monitoring a voltage of the battery pack, a memory, and a processor. The memory may store a derating coefficient for each section of a charging cycle including a plurality of sections and a voltage upper limit value for each section of the charging cycle. The processor may determine a charging current of the battery pack in each section based on the derating coefficient for each section, and update the derating coefficient for the corresponding section based on the voltage of the battery pack in each section and the voltage upper limit value.

[0021] In one embodiment, the memory may store a magnitude of a base charging current for each section of the charging cycle, and the processor may set the derating factor for each section individually and determine the charging current for each section by multiplying the base charging current for the corresponding section by the derating factor for the corresponding section.

[0022] In one embodiment, the processor may reduce the derating factor for a section in which the voltage of the battery pack exceeds the upper voltage limit among the plurality of sections.

[0023] In an embodiment, the processor may increase the derating factor for a corresponding section in which the voltage of the battery pack does not exceed the upper voltage limit value among the plurality of sections. Effect of the Invention

[0024] According to an embodiment, a charging current can be adjusted according to a degradation state of a battery cell, so that degradation of the battery cell can be minimized without excessively increasing a charging time. [Brief description of the drawings]

[0025] [Figure 1]FIG. 1 illustrates an example of a battery device according to one embodiment.

[0026] [Diagram 2] FIG. 4 is a diagram illustrating an example of a voltage upper limit value in a charging cycle in a battery management system according to an embodiment.

[0027] [Diagram 3] FIG. 2 illustrates an example of a base charging current in a charging cycle in a battery management system according to one embodiment.

[0028] [Figure 4] 4 is a flowchart illustrating an example of a charging control method in a battery management system according to an embodiment.

[0029] [Diagram 5] 11 is a flowchart illustrating an example of a charging control method in a battery management system according to another embodiment.

[0030] [Figure 6] FIG. 11 is a diagram showing an example of a change in charging current due to a charging control method in a battery management system according to another embodiment.

[0031] [Figure 7] 13 is a flowchart illustrating an example of a charging control method in a battery management system according to still another embodiment.

[0032] [Figure 8] FIG. 11 is a diagram illustrating an example of a voltage change due to a charge control method in a battery management system according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts that are not necessary for the explanation are omitted, and similar parts are designated by similar reference numerals throughout the specification.

[0034] When a component is said to be "connected" to another component, it should be understood that the component may be directly connected to the other component, but there may also be other components in between. Conversely, when a component is said to be "directly connected" to another component, it should be understood that there are no other components in between.

[0035] In the following description, expressions described as singular can be interpreted as singular or plural, unless expressly stated otherwise, such as "one" or "single".

[0036] In the flow charts described with reference to the figures, the order of operations may be changed, various operations may be combined or certain operations may be separated, and certain operations may not be performed.

[0037] FIG. 1 is a diagram showing an example of a battery device according to an embodiment, FIG. 2 is a diagram showing an example of a voltage upper limit value in a charging cycle in a battery management system according to an embodiment, and FIG. 3 is a diagram showing an example of a basic charging current in a charging cycle in a battery management system according to an embodiment.

[0038] 1, the battery device 100 has a structure that is electrically connected to an external device. When the external device is a load, the battery device 100 operates as a power source that supplies power to the load and is discharged. When the external device is a charger 10, the battery device 100 is charged by receiving external power through the charger. The external device operating as a load may be, for example, an electronic device, a vehicle, or an energy storage system (ESS), and the vehicle may be, for example, a vehicle such as an electric vehicle, a hybrid vehicle, or a smart mobility vehicle.

[0039] The battery device 100 includes a battery pack 110 and a battery management system 120 .

[0040] The battery pack 110 includes a plurality of battery cells (not shown). In one embodiment, the battery cells may be rechargeable secondary batteries. In one embodiment, a predetermined number of battery cells may be connected in series to configure a battery module in the battery pack 110 to supply a desired power. In one embodiment, a predetermined number of battery modules may be connected in series or in parallel to supply a desired power in the battery pack 110.

[0041] A battery management system (BMS) 120 monitors the battery pack 110 and controls a charging current of the battery pack 110 based on a monitoring result of the battery pack 110 when charging the battery pack 110. In one embodiment, the battery management system 120 may include a monitoring circuit 121, a processor 122, and a charging current control circuit 123.

[0042] The monitoring circuit 121 may include a voltage measurement circuit that monitors the voltage of the battery pack 110. In one embodiment, the monitoring circuit 121 may further include a temperature sensor that measures the temperature of the battery pack 110. In one embodiment, the monitoring circuit 121 may further include a current sensor that measures the current of the battery pack 110, i.e., the charging current or the discharging current.

[0043] The processor 122 may determine the magnitude of the charging current of the battery pack 110 based on the voltage of the battery pack 110 monitored by the monitoring circuit 121. The processor 122 may calculate a state of charge (SOC) of the battery pack 110 based on the information monitored by the monitoring circuit 121. The charging current control circuit 123 may control the charging current of the battery pack 110 based on the magnitude of the charging current determined by the processor 122. That is, the charging current control circuit 123 may control the charging current so that the charging current supplied to the battery pack 110 from the charger 10 connected to the battery device 100 has the magnitude determined by the processor 122.

[0044] 2 and 3, the charging cycle of the battery pack 110 is divided into a plurality of sections according to the SOC. As shown in FIG. 2, a voltage upper limit value 210 is set in each section of the charging cycle. The voltage upper limit value 210 may be set to be proportional to the SOC. In one embodiment, the voltage upper limit value 210 may be set to a value that can minimize deterioration of the battery cell, and may be determined in advance, for example, through an experiment. In one embodiment, the voltage upper limit values ​​210 may be set to be the same within the same section. For example, the voltage upper limit value 210 in a first section may be set lower than the voltage upper limit value 210 in a second section corresponding to a higher SOC than the first section. Although FIG. 2 shows that the voltage upper limit value 210 is set in a section of 8% to 80% of the SOC, the voltage upper limit value 210 may also be set in sections not shown.

[0045] As shown in FIG 3, a basic charging current 310 is set for each section of a charging cycle. In one embodiment, the basic charging current 310 may be a charging current at BOL. The magnitude of the basic charging current 310 may be set to be inversely proportional to the SOC. In one embodiment, the magnitudes of the basic charging current 310 within the same section may be set to be the same. For example, the basic charging current 310 in a first section may be set to be higher than the basic charging current 310 in a second section corresponding to a higher SOC than the first section.

[0046] In one embodiment, the battery management system 120 may further include a memory 124 for storing data used by the processor 122. In one embodiment, the memory 124 may store a voltage upper limit value and a basic charging current magnitude for each section of a charging cycle. In one embodiment, the memory 124 may store a control value (e.g., a derating factor) for controlling the charging current.

[0047] FIG. 4 is a flowchart illustrating an example of a charging control method in a battery management system according to an embodiment.

[0048] Referring to FIG. 4, a charger is connected to a battery device and a charging cycle for charging a battery pack (e.g., 110 in FIG. 1) is started. A battery management system (e.g., a processor (e.g., 122 in FIG. 1)) determines a charging current to be used for charging the battery pack 110 based on a derating factor (current derating factor) (S410). The processor 122 may determine a charging current to be used for charging the battery pack 110 by reflecting the derating factor in a basic charging current (S410). In one embodiment, the processor 122 may determine a value obtained by multiplying the basic charging current by the derating factor (S410) as the charging current. In one embodiment, the derating factor is set to a basic value (e.g., 1) at an initial state (beginning of life, BOL) of the battery pack 110 and may be updated as the charging cycle is repeated. In one embodiment, the derating factor may be set separately for each section of the charging cycle. In one embodiment, the derating factor may be set to the same value for multiple sections of the charging cycle.

[0049] As charging occurs, the battery management system measures (S420) the voltage of the battery pack 110. In one embodiment, a monitoring circuit (e.g., 121 in FIG. 1 ) of the battery management system monitors the voltage of the battery pack 110, and the processor 122 can measure the voltage of the battery pack 110 based on the monitoring result of the monitoring circuit 121.

[0050] The processor 122 compares the voltage of the battery pack 110 measured in each section of the charging cycle with the upper voltage limit value in the corresponding section (S430). The processor 122 determines a derating coefficient based on the comparison result between the voltage of the battery pack 110 in each section and the upper voltage limit value in the corresponding section (S440). The determined derating coefficient can be used to determine the charging current in the next charging cycle (S410). In one embodiment, the derating coefficient for the entire charging cycle can be updated based on the comparison result between the voltage of the battery pack 110 in each section and the upper voltage limit value in the corresponding section. In one embodiment, the derating coefficient for at least a portion of the sections of the charging cycle can be updated based on the comparison result between the voltage of the battery pack 110 in each section and the upper voltage limit value in the corresponding section. In one embodiment, the derating coefficient can be maintained without being updated based on the comparison result between the voltage of the battery pack 110 in each section and the upper voltage limit value in the corresponding section.

[0051] According to the embodiment described above, since the voltage of the battery pack 110 increases during charging as the battery cells degrade, the derating coefficient can be determined according to the degradation state of the battery cells. As a result, the charging current can be adjusted according to the degradation state of the battery cells, so that the charging time is not excessively increased and degradation of the battery cells can be minimized.

[0052] FIG. 5 is a flowchart showing an example of a charge control method in a battery management system according to another embodiment, and FIG. 6 is a diagram showing an example of a change in charge current due to the charge control method in a battery management system according to another embodiment.

[0053] Referring to FIG. 5, a charger is connected to a battery device to start a charging cycle for charging a battery pack (e.g., 110 in FIG. 1). A battery management system (e.g., a processor (e.g., 122 in FIG. 1)) determines a charging current for each section of the charging cycle based on a derating factor (current derating factor) (S510). The processor 122 can determine the charging current for each section of the charging cycle by reflecting the derating factor in a basic charging current (S510). The derating factor is set to be the same for multiple sections of the charging cycle. In one embodiment, the battery management system can determine the charging current for the corresponding section as a value obtained by multiplying the basic charging current for each section by the corresponding derating factor. In one embodiment, the derating factor is set to a basic value (e.g., 1) in the BOL of the battery pack 110 and can be updated as the charging cycle is repeated.

[0054] As charging occurs, the battery management system measures (S520) the voltage of the battery pack 110. In one embodiment, a monitoring circuit (e.g., 121 in FIG. 1 ) of the battery management system monitors the voltage of the battery pack 110, and a processor (e.g., 122 in FIG. 1 ) can measure the voltage of the battery pack 110 based on the monitoring result of the monitoring circuit 121.

[0055] The processor 122 compares the voltage of the battery pack 110 measured in each section of the charging cycle with the upper voltage limit value for the corresponding section (S530). The processor 122 calculates a penalty value indicating the number of sections in which the voltage of the battery pack 110 exceeds the upper voltage limit value among the multiple sections of the charging cycle (S540). In one embodiment, the processor 122 may increment a counter by 1 when the voltage of the battery pack 110 in a certain section exceeds the upper voltage limit value for the corresponding section, and determine the counter value as the penalty value after the multiple sections of the charging cycle are completed.

[0056] The processor 122 compares the penalty value to a critical value (S550). If the penalty value exceeds the critical value, the processor 122 updates the derating factor (S560). In one embodiment, the processor 122 may update the derating factor by decreasing the derating factor. In one embodiment, the processor 122 may store the updated derating factor in memory (e.g., 124 in FIG. 1). If the penalty value does not exceed the critical value, the processor 122 maintains the derating factor without updating it (S570).

[0057] As a result, in the next cycle, the charging current can be determined based on the derating factor stored in the memory 124. If the voltage of the battery pack 110 frequently exceeds the upper voltage limit (i.e., if the penalty value is greater than the critical value), the charging current can be reduced in the next charging cycle by decreasing the derating factor. For example, as shown in Fig. 6, the charging current 620 in the next charging cycle can be reduced from the charging current 610 in the current charging cycle by decreasing the derating factor. In this case, the charging current can be reduced in the entire period because the reduced derating factor is used in the entire period.

[0058] According to the embodiment described above, since the voltage of the battery pack 110 increases during charging as the battery cells degrade, the derating coefficient can be determined according to the degradation state of the battery cells. As a result, the charging current can be adjusted according to the degradation state of the battery cells, so that the charging time is not excessively increased and degradation of the battery cells can be minimized.

[0059] FIG. 7 is a flowchart showing an example of a charge control method in a battery management system according to another embodiment, and FIG. 8 is a diagram showing an example of a voltage change caused by the charge control method in a battery management system according to another embodiment.

[0060] Referring to FIG. 7, a charger is connected to a battery device to start a charging cycle for charging a battery pack (e.g., 110 in FIG. 1). A battery management system (e.g., a processor (e.g., 122 in FIG. 1)) determines a charging current for each section of the charging cycle based on a derating factor (current derating factor) (S710). The processor 122 may determine a charging current for each section by reflecting a derating factor for the section corresponding to a basic charging current for each section of the charging cycle (S710). A derating factor is set individually for a plurality of sections of the charging cycle. In one embodiment, the battery management system may determine a value obtained by multiplying a basic charging current for each section by a derating factor for the corresponding section as the charging current for the corresponding section. In one embodiment, the derating factor may be set as a basic value (e.g., 1) in the BOL of the battery pack 110 and updated as the charging cycle is repeated.

[0061] As charging occurs, the battery management system measures (S720) the voltage of the battery pack 110. In one embodiment, a monitoring circuit (e.g., 121 in FIG. 1 ) of the battery management system monitors the voltage of the battery pack 110, and a processor (e.g., 122 in FIG. 1 ) can measure the voltage of the battery pack 110 based on the monitoring result of the monitoring circuit 121.

[0062] The processor 122 compares the voltage of the battery pack 110 measured in each section of the charging cycle with the upper voltage limit value in the corresponding section (S730). In one embodiment, the processor 122 may update the derating coefficient of the corresponding section based on the comparison result in each section (S740, S750). If the voltage of the battery pack 110 measured in a certain section exceeds the upper voltage limit value in the corresponding section, the processor 122 may update the derating coefficient by decreasing the derating coefficient of the corresponding section (S740). If the voltage of the battery pack 110 measured in a certain section does not exceed the upper voltage limit value in the corresponding section, the processor 122 may update the derating coefficient by increasing the derating coefficient of the corresponding section (S750). The processor 122 may update the derating coefficients of multiple sections of the charging cycle through this process (S760). In one embodiment, the processor 122 may store the updated derating coefficient in a memory (e.g., 124 in FIG. 1). In one embodiment, if the voltage of the battery pack 110 measured in a certain section does not exceed the upper voltage limit value for the corresponding section, the processor 122 may maintain the derating coefficient for the corresponding section (S750).

[0063] As a result, in the next cycle, the charging current can be determined based on the derating coefficient stored in the memory 124. In a section where the voltage of the battery pack 110 exceeds the upper voltage limit, the charging current can be decreased in the next charging cycle by decreasing the derating coefficient, and in a section where the voltage of the battery pack 110 does not exceed the upper voltage limit, the charging current can be increased in the next charging cycle by increasing the derating coefficient. As a result, as shown in FIG 8, the derating coefficient 810 is set for each section, and the voltage 820 of the battery pack 110 during charging can follow the upper voltage limit 830.

[0064] According to the embodiment described above, since the voltage of the battery pack 110 increases during charging as the battery cells degrade, the derating factor can be determined according to the degradation state of the battery cells. As a result, the charging current can be adjusted according to the degradation state of the battery cells, so that the degradation of the battery cells can be minimized without excessively increasing the charging time. In addition, an optimal derating factor (i.e., charging current) that allows the voltage of the battery pack 110 to follow the upper voltage limit can be determined.

[0065] In one embodiment, a processor (e.g., 122 in FIG. 1) may perform operations on a program for performing the charging method described above. The program for performing the charging method may be loaded into a memory. Such memory may be the same memory as the memory (e.g., 124 in FIG. 1) that stores the table, or a separate memory. When the program is loaded into the memory, it may include instructions that cause the processor 122 to perform the charging method. That is, the processor may perform operations for the charging method by executing the instructions of the program.

[0066] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. Battery packs, and A battery management system that determines a charging current for charging the battery pack in each section based on a derating coefficient of a charging cycle including a plurality of sections, updates the derating coefficient based on a result of comparing the voltage of the battery pack in each section with a voltage upper limit value set for the corresponding section, and uses the updated derating coefficient for a next charging cycle. A battery device including:

2. A basic charging current is set for each of the plurality of sections, The battery device according to claim 1 , wherein the battery management system determines the charging current by reflecting the derating coefficient in the basic charging current.

3. The battery management system The derating coefficient is set to be the same in the plurality of sections; 3. The battery device according to claim 2, wherein the derating coefficient is applied to the basic charging current of each section to determine the charging current of the corresponding section.

4. The battery device according to claim 3 , wherein the battery management system updates the derating coefficient based on the number of sections in which the voltage of the battery pack exceeds the upper voltage limit value among the plurality of sections.

5. The battery device according to claim 4 , wherein the battery management system reduces the derating factor when the number of sections exceeding the upper voltage limit exceeds a critical value.

6. The battery device according to claim 5 , wherein the battery management system maintains the derating factor when the number of sections exceeding the upper voltage limit does not exceed the critical value.

7. The battery management system The derating coefficient is set individually for each of the plurality of sections; 3. The battery device according to claim 2, wherein the charging current for each section is determined by multiplying the derating coefficient for each section by the basic charging current for that section.

8. The battery device according to claim 7 , wherein the battery management system reduces the derating coefficient of a corresponding section in which the voltage of the battery pack exceeds the upper voltage limit value among the plurality of sections.

9. The battery device according to claim 7 , wherein the battery management system increases the derating coefficient of a corresponding section in which the voltage of the battery pack does not exceed the upper voltage limit value among the plurality of sections.

10. A battery management system for a battery pack, comprising: a monitoring circuit for monitoring a voltage of the battery pack; a memory for storing a voltage upper limit value and a derating factor for each section of a charging cycle including a plurality of sections; a processor for determining a charging current for the battery pack during each interval of the charging cycle based on the derating factor, and updating the derating factor based on the number of intervals in which the voltage of the battery pack exceeds the upper voltage limit among the plurality of intervals; A battery management system including:

11. the memory stores a basic charging current magnitude for each interval of the charging cycle; The processor The derating coefficient is set to be the same in the plurality of sections; The battery management system according to claim 10 , wherein the derating coefficient is multiplied by the basic charging current of each section to determine the charging current of the corresponding section.

12. The battery management system of claim 11 , wherein the processor decreases the derating factor when a number of intervals exceeding the upper voltage limit exceeds a critical value.

13. The battery management system of claim 12 , wherein the processor maintains the derating factor if the number of intervals exceeding the upper voltage limit does not exceed the critical value.

14. A battery management system for a battery pack, comprising: a monitoring circuit for monitoring a voltage of the battery pack; a memory for storing a derating coefficient for each section of a charging cycle including a plurality of sections and a voltage upper limit value for each section of the charging cycle; a processor for determining a charging current of the battery pack in each section based on the derating coefficient in the corresponding section, and updating the derating coefficient in the corresponding section based on the voltage of the battery pack in each section and the voltage upper limit value; A battery management system including:

15. the memory stores a basic charging current magnitude for each interval of the charging cycle; The processor The derating coefficient is set individually for each of the plurality of sections; The battery management system according to claim 14 , wherein the charging current for each section is determined by multiplying the basic charging current for the corresponding section by the derating coefficient for the corresponding section.

16. The battery management system of claim 15 , wherein the processor reduces the derating coefficient of a corresponding section in which the voltage of the battery pack exceeds the upper voltage limit value among the plurality of sections.

17. The battery management system of claim 15 , wherein the processor increases the derating coefficient of a corresponding section in which the voltage of the battery pack does not exceed the upper voltage limit value among the plurality of sections.

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