Battery management system, battery pack, electric vehicle, and battery management method

Abstract

A battery management system, a battery pack, an electric vehicle, and a battery management method are provided. The battery management system according to the present invention includes a sensing unit for detecting a voltage, a current, and a pressure of a battery cell, a memory for storing first relationship data indicating a relationship between an OCV and an SOC, and second relationship data indicating a relationship between a pressure and an SOC, and a control unit for determining a voltage value indicating the detected voltage, a current value indicating the detected current, and a pressure value indicating the detected pressure, and determining an estimated SOC value of the battery cell for every set time. The control unit compares a previous estimated SOC value with a flat section, and executes at least one of (i) a first SOC estimation logic based on the voltage value, the current value, and the first relationship data, and (ii) a second SOC estimation logic based on the pressure value and the second relationship data, to determine a current estimated SOC value.

Description

[Technical field]

[0001] The present invention relates to a technique for estimating the SOC (State of Charge) of a battery cell.

[0002] This application claims priority to Korean Patent Application No. 10-2022-0120521 filed on September 23, 2022 and Korean Patent Application No. 10-2023-0062661 filed on May 15, 2023, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings. [Background technology]

[0003] In recent years, as the demand for portable electronic products such as laptops, video cameras, and mobile phones has grown rapidly and the development of electric vehicles, energy storage batteries, robots, and artificial satellites has progressed in earnest, research into high-performance batteries that can be repeatedly charged and discharged is being actively conducted.

[0004] Currently commercially available batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium batteries. Among them, lithium batteries are attracting attention due to their advantages of being able to be freely charged and discharged since they have almost no memory effect compared to nickel-based batteries, as well as their extremely low self-discharge rate and high energy density.

[0005] A battery pack for applications requiring large capacity and high voltage, such as an electric vehicle or an energy storage system, includes tens to hundreds of battery cells connected in series with each other. A battery management system is provided to obtain battery parameters (e.g., voltage, current, SOC, etc.) of each battery cell and perform various functions (e.g., balancing, cooling) to ensure the reliability and safety of each battery.

[0006] Currently, various types of rechargeable battery cells are widely used, and some types of battery cells, such as LFP cells and LiS cells, show a flat characteristic over a portion of the total SOC range (e.g., SOC 20-80%). A flat characteristic is a characteristic in which the change in OCV (Open Circuit Voltage) relative to the change in SOC is very small, and can be recorded in a data set showing the relationship between SOC and OCV (e.g., SOC-OCV curve).

[0007] When a battery cell has an SOC range that shows a flat characteristic, the SOC-OCV curve (which may be called an "OCV map") is useful for estimating the SOC outside the SOC range that shows the flat characteristic, but within the SOC range, even a small measurement error in the OCV can cause a large difference between the estimated SOC value and the actual SOC value, making it difficult to accurately determine the SOC of the battery cell during charging and discharging from the SOC-OCV curve. Therefore, when the SOC of the battery cell is within a flat section (SOC range that shows a flat characteristic), it is preferable to determine the SOC of the battery cell based on the current integration amount of the battery cell instead of the SOC-OCV curve.

[0008] However, when charging and discharging are alternately performed and the SOC of the battery cell is maintained within a plateau for a long period of time, the error between the actual value and the detected value of the battery cell current continuously accumulates in the current accumulation amount, and the estimation accuracy of the SOC gradually deteriorates.

[0009] One solution to this problem is to intentionally charge or discharge the battery cell so that the SOC of the battery cell deviates from the plateau, and then estimate the SOC according to the OCV of the battery cell using the SOC-OCV curve.

[0010] However, the above-mentioned method has a problem in that power is unnecessarily wasted due to intentional charging or discharging of the battery cell, and the time required for estimating the SOC increases accordingly. Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made to solve the above problems, and aims to provide a battery management system, a battery pack, an electric vehicle, and a battery management method that can prevent a decrease in the estimation accuracy of the SOC of a battery cell even if a situation occurs in which the SOC of the battery cell enters a plateau during charging or discharging of the battery cell.

[0012] Other objects and advantages of the present invention can be understood from the following description and will become more apparent from the embodiments of the present invention. Also, the objects and advantages of the present invention can be realized by the means and combinations thereof as set forth in the claims. [Means for solving the problem]

[0013] According to an aspect of the present invention, a battery management system is for a battery cell having a plateau section, which is an SOC range in which a rate of change of OCV is maintained below a reference value. The battery management system includes a sensing unit for detecting a voltage, a current, and a pressure of the battery cell, a memory for storing first relationship data indicating a relationship between an OCV and SOC of the battery cell and second relationship data indicating a relationship between a pressure and SOC of the battery cell, and a control unit configured to determine a voltage value indicating the detected voltage, a current value indicating the detected current, and a pressure value indicating the detected pressure, and to determine an estimated SOC value of the battery cell for every set time.

[0014] The control unit is configured to compare a previous SOC estimate with the flat section, and, depending on a result of the comparison, determine a current SOC estimate equal to a weighted average of any one or two of: (i) a first SOC estimate obtained through a first SOC estimation logic based on the voltage value, the current value, and the first relationship data; and (ii) a second SOC estimate obtained through a second SOC estimation logic based on the pressure value and the second relationship data.

[0015] The controller may be configured to determine the current SOC estimate to be equal to the first SOC estimate if the previous SOC estimate is outside the plateau interval.

[0016] The controller may be configured to determine the current SOC estimate to be equal to the second SOC estimate if the previous SOC estimate is within the plateau interval.

[0017] The controller may be configured to determine a first weight associated with the first SOC estimation logic and a second weight associated with the second SOC estimation logic in response to a difference between a lower limit or an upper limit of the plateau interval and the previous SOC estimate when the previous SOC estimate is outside the plateau interval. The controller may be configured to determine the current SOC estimate equal to a first weighted average of the first SOC estimate based on the first weight and the second SOC estimate based on the second weight.

[0018] The first weighting value may be negatively correlated to a difference between a lower limit or an upper limit of the plateau and the previous SOC estimate, and the second weighting value may be positively correlated to a difference between a lower limit or an upper limit of the plateau and the previous SOC estimate.

[0019] The controller may be configured to determine the current SOC estimate to be equal to a second weighted average of the first SOC estimate based on a third weight associated with the first SOC estimation logic and the second SOC estimate based on a fourth weight associated with the second SOC estimation logic when the previous SOC estimate is within the plateau interval, the third weight may be less than the first weight, and the fourth weight may be greater than the second weight.

[0020] The controller may be configured to determine, based on a time series of the SOC estimates, a dwell time of the SOC estimate within the plateau interval when the previous SOC estimate is within the plateau interval. The controller may be configured to correct a third weight associated with the first SOC estimation logic and a fourth weight associated with the second SOC estimation logic according to the dwell time. The controller may be configured to determine the current SOC estimate equal to a second weighted average of the first SOC estimate based on the corrected third weight and the second SOC estimate based on the corrected fourth weight. The third weight may be less than the first weight. The fourth weight may be greater than the second weight.

[0021] The corrected third weight value may be less than or equal to the third weight value. The corrected fourth weight value may be greater than or equal to the fourth weight value. A difference between the corrected third weight value and the third weight value and a difference between the corrected fourth weight value and the fourth weight value may each have a positive correlation with the residence time.

[0022] The control unit may be configured to determine a first weight value associated with the first SOC estimation logic and a second weight value associated with the second SOC estimation logic in response to a difference between a lower limit or an upper limit of the plateau interval and the previous SOC estimate when the previous SOC estimate is outside the plateau interval. The control unit may be configured to determine a residence time of the SOC estimate outside the plateau interval based on a time series of the SOC estimate. The control unit may be configured to correct the first weight value and the second weight value in response to the residence time. The control unit may be configured to determine the current SOC estimate equal to a first weighted average of the first SOC estimate based on the corrected first weight value and the second SOC estimate based on the corrected second weight value. The third weight value may be less than the first weight value. The fourth weight value may be greater than the second weight value.

[0023] A battery pack according to another aspect of the present invention includes the battery management system.

[0024] An electric vehicle according to yet another aspect of the present invention includes the battery pack.

[0025] According to yet another aspect of the present invention, a battery management method is provided to be executable by the battery management system at every set time, the battery management method includes: determining a voltage value indicating a voltage of the battery cell, a current value indicating a current of the battery cell, and a pressure value indicating a pressure of the battery cell, comparing a previous SOC estimate of the battery cell with the flat section, and, depending on a result of the comparison, determining a current SOC estimate of the battery cell equal to a weighted average of either or both of (i) a first SOC estimate obtained through a first SOC estimation logic based on the voltage value, the current value, and the first relationship data, and (ii) a second SOC estimate obtained through a second SOC estimation logic based on the pressure value and the second relationship data.

[0026] The determining a current SOC estimate of the battery cell may determine the current SOC estimate to be equal to the first SOC estimate if the previous SOC estimate is outside the plateau interval. The determining a current SOC estimate of the battery cell may determine the current SOC estimate to be equal to the second SOC estimate if the previous SOC estimate is within the plateau interval.

[0027] Determining a current SOC estimate of the battery cell may include, when the previous SOC estimate is outside the plateau interval, determining a first weighting value associated with the first SOC estimation logic and a second weighting value associated with the second SOC estimation logic according to a difference between a lower limit or an upper limit of the plateau interval and the previous SOC estimate, and determining the current SOC estimate equal to a first weighted average of the first SOC estimate based on the first weighting value and the second SOC estimate based on the second weighting value.

[0028] Determining a current SOC estimate of the battery cell may include, if the previous SOC estimate is within the plateau interval, obtaining a third weighting value associated with the first SOC estimation logic and a fourth weighting value associated with the second SOC estimation logic, and determining the current SOC estimate equal to a second weighted average of the first SOC estimate based on the third weighting value and the second SOC estimate based on the fourth weighting value. The third weighting value may be less than the first weighting value. The fourth weighting value may be greater than the second weighting value. Effect of the Invention

[0029] According to an aspect of the present invention, even if a situation occurs in which the SOC of a battery cell enters a plateau section during charging or discharging of the battery cell, it is possible to prevent the accuracy of estimating the SOC of the battery cell from decreasing.

[0030] Furthermore, according to one embodiment of the present invention, instead of solely utilizing the SOC-OCV curve (corresponding to the "first relationship data" in the claims) to estimate the SOC of the battery, the accuracy of SOC estimation over the entire SOC range including the flat section can be improved by further utilizing the SOC-P curve (corresponding to the "second relationship data" in the claims) which shows the relationship between the SOC and pressure of the battery.

[0031] Furthermore, according to one aspect of the present invention, a first SOC estimated value based on the first relationship data and a second SOC estimated value based on the second relationship data are combined so that their influences differ depending on the difference between the estimated SOC value of the battery and the lower limit or upper limit of the flat section, thereby calculating an estimated SOC value for each set time, thereby improving the accuracy of SOC estimation within the entire SOC range.

[0032] Furthermore, according to one aspect of the present invention, the accuracy of SOC estimation within the entire SOC range can be improved by calculating an SOC estimate for each set time by combining a first SOC estimate based on the first relationship data and a second SOC estimate based on the second relationship data so that the respective SOC estimate values ​​have different influences depending on the duration that the battery's SOC estimate remains within or outside the flat section.

[0033] The effects of the present invention are not limited to the effects described above, and other effects of the present invention not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0034] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to further understand the technical ideas of the present invention. Therefore, the present invention should not be interpreted as being limited only to the matters described in the drawings. [Brief description of the drawings]

[0035] [Figure 1] 1 is a diagram showing an example of the configuration of an electric vehicle according to the present invention; [Diagram 2] 1 is a graph showing an example of an SOC-OCV curve of a battery cell. [Diagram 3] 1 is a graph showing an example of an SOC-P curve of a battery cell. [Figure 4] 1 is a graph showing an example of a State of Health (SOH)-P curve of a battery cell. [Diagram 5] 2 is a flow diagram showing an example of a battery management method executed by the battery management system shown in FIG. 1. [Figure 6] FIG. 6 is a flow chart showing an example of a sub-routine of step S530 in FIG. 5. [Figure 7] 7 is a flow chart showing an example of another sub-routine of step S530 of FIG. 5. [Figure 8] 8 is an example of a weighting map that may be used in the subroutine of FIG. 7. [Figure 9] 7 is a flow chart showing an example of still another sub-routine of step S530 of FIG. 5. [Figure 10] 10 is an example of a weighting map that may be used in the subroutine of FIG. 9. [Figure 11] 7 is a flow chart showing an example of still another sub-routine of step S530 of FIG. 5. [Figure 12] 12 is an example of a weighting map that may be used in the subroutine of FIG. 11. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, the terms and words used in the present specification and claims should not be interpreted as being limited to their ordinary and dictionary meanings, but should be interpreted as having meanings and concepts corresponding to the technical ideas of the present invention, in accordance with the principle that the inventor himself can appropriately define the concepts of terms in order to best describe the invention.

[0037] Therefore, it should be understood that the embodiment described in this specification and the configurations shown in the drawings are merely the most preferred embodiment of the present invention and do not represent the entire technical idea of ​​the present invention, and that there may be various equivalents and modifications that can be substituted therefor at the time of this application.

[0038] Terms including ordinal numbers such as first, second, etc. are used to distinguish one of various components from other components, and are not intended to limit the components.

[0039] Throughout the specification, when a part "includes" a certain component, this does not mean to exclude other components, but means that other components may be further included, unless otherwise specified. Furthermore, terms such as "controller" described in the specification refer to a unit that processes at least one function or operation, and may be embodied in hardware, software, or a combination of hardware and software.

[0040] Furthermore, throughout this specification, when a part is referred to as being "connected" to another part, this includes not only a "direct connection" but also an "indirect connection" through other elements.

[0041] In this specification, SOC (State of Charge) refers to the ratio of remaining capacity to the fully charged capacity of a storage unit (eg, battery cell, cell group) expressed as a percentage from 0 to 100%.

[0042] Fig. 1 is a diagram showing an example of the configuration of an electric vehicle according to the present invention, Fig. 2 is a graph showing an example of an SOC-OCV curve of a battery cell, Fig. 3 is a graph showing an example of an SOC-P curve of a battery cell, and Fig. 4 is a graph referred to in explaining the relationship between the SOH and the SOC-P curve of a battery cell. Hereinafter, when describing contents common to battery cells, the reference character "C" will be used.

[0043] 1, an electric vehicle 1 includes a vehicle controller 2, a battery pack 10, and an electric load 30. Charging and discharging terminals P+, P- of the battery pack 10 may be electrically coupled to a charger 40 via a charging cable or the like. The charger 40 may be included in the electric vehicle 1 or may be provided in a charging station outside the electric vehicle 1.

[0044] The vehicle controller 2 (e.g., an electronic control unit (ECU)) is configured to transmit a key-on signal to the battery management system 100 in response to an engine start button (not shown) provided on the electric vehicle 1 being switched to an on (ON) position by a user. The vehicle controller 2 is configured to transmit a key-off signal to the battery management system 100 in response to the engine start button being switched to an off (OFF) position by a user. The charger 40 can communicate with the vehicle controller 2 to supply charging power (e.g., constant current, constant voltage, constant power) through the charging and discharging terminals P+, P- of the battery pack 10.

[0045] The battery pack 10 includes a cell group 11 , a relay 20 and a battery management system 100 .

[0046] The cell group 11 includes at least one battery cell C. FIG. 1 shows a plurality of battery cells C1 to C m (m is a natural number of 2 or more) is included in the cell group 11. m When explaining content common to both, we will use the symbol C.

[0047] In the cell group 11, a plurality of battery cells C1 to C m Each of the battery cells C1 and C2 has a positive electrode lead and a negative electrode lead, and the positive electrode lead of one (e.g., C1) of two adjacent battery cells (e.g., C1 and C2) is joined to the negative electrode lead of the other (e.g., C2) by welding or the like. m The series connection to the positive electrode lead of the battery cell C is disposed within the cell group 11. Hereinafter, the positive electrode lead and the negative electrode lead of the battery cell C may be referred to as the "positive electrode" and the "negative electrode", respectively.

[0048] Multiple battery cells C1~C mmay be manufactured to have the same electrochemical specifications and charge / discharge characteristics. The type of battery cell C is not particularly limited as long as it can be repeatedly charged and discharged and has flat characteristics, such as an LFP battery.

[0049] The series circuit of the cell group 11 and the current detection circuit 114 is electrically connected to the electric load 30 and / or the charger 40 through the relay 20 .

[0050] The relay 20 is provided on a power line PL that serves as a current path for charging and discharging the battery pack 10. While the relay 20 is turned on, power can be transmitted from one of the battery pack 10 and the electrical load 30 to the other. The relay 20 may be realized by combining any one or more of known switching devices such as a mechanical contactor, a field effect transistor (FET), etc. The control unit 130 may control the relay 20 from one of a turned-on state and a turned-off state to the other.

[0051] The electric load 30 includes an inverter 31 and an electric motor 32. The inverter 31 is provided to convert a direct current from the cell group 11 included in the battery pack 10 into an alternating current in response to a command from the battery management system 100 or the vehicle controller 2. The electric motor 32 is driven using the AC power from the inverter 31. As the electric motor 32, for example, a three-phase AC motor may be used.

[0052] The state in which the relay 20 is turned on and the cell group 11 is being charged or discharged may be referred to as a load state (cycle state). The voltage of the battery cell C detected in the load state may be referred to as a load voltage or a closed circuit voltage (CCV).

[0053] When the relay 20 is switched from an on state to an off state, the cell group 11 is in a no-load state (rest state, calendar state). The voltage applied across the battery cell C in the no-load state may be called a no-load voltage. The no-load voltage is a term that collectively refers to a relaxation voltage and an open circuit voltage (OCV). Specifically, when the battery cell C is switched from a loaded state to a no-load state, the polarization generated in the battery cell C begins to be naturally eliminated, and the no-load voltage of the battery cell C converges to the OCV. The OCV indicates a no-load voltage in which the battery cell C is maintained in a no-load state for a predetermined time (e.g., 2 hours) or more and the voltage change rate of the battery cell C is less than a certain value. That is, the OCV is a no-load voltage in a state in which the polarization of the battery cell C is negligibly small. The relaxation voltage indicates a no-load voltage before the polarization is sufficiently small.

[0054] The battery management system 100 includes a plurality of battery cells C1 to C m A monitor is provided for monitoring the status of each of the

[0055] The battery management system 100 includes a sensing unit 110, a memory 120, and a control unit 130. The battery management system 100 may further include a communication unit 140.

[0056] The sensing unit 110 includes a voltage detection circuit 112, a current detection circuit 114, and a plurality of pressure sensors PS. The sensing unit 110 may further include a plurality of temperature sensors TS.

[0057] The voltage detection circuit 112 detects a plurality of battery cells C1 to C mThe voltage detection circuit 112 detects a voltage across the battery cell C (hereinafter, may be simply referred to as a "battery cell voltage" or a "cell voltage") using a potential difference between a pair of sensing lines respectively connected to the positive and negative electrodes of the battery cell C. The voltage detection circuit 112 may transmit a voltage signal indicating the detected cell voltage of the battery cell C to the control unit 130 through analog-to-digital conversion.

[0058] The current detection circuit 114 is connected in series to the cell group 11 through a current path between the cell group 11 and the electrical load 30. The current detection circuit 114 may be implemented by one or a combination of two or more of known current detection elements such as a shunt resistor, a Hall effect element, etc. m are connected in series, so multiple battery cells C1 to C m A charging / discharging current of the same magnitude and in the same direction flows through the

[0059] 1 shows that a shunt resistor is used as the current detection circuit 114. In this case, the voltage detection circuit 112 can output a current signal indicating the direction and magnitude of the charge / discharge current to the control unit 130 based on the voltage applied across the shunt resistor. Of course, the current detection circuit 114 may be configured to directly generate a current signal indicating the charge / discharge current flowing through the cell group 11 and output it to the control unit 130.

[0060] The pressure sensors PS are connected to the battery cells C1 to C m The pressure sensor PS may be, for example, a piezoelectric element. The cell group 11 may be provided with a plurality of support plates (not shown), and the plurality of support plates may support the plurality of battery cells C1 to C2. mA space is formed in which each of the battery cells C can be independently placed. The pressure sensor PS may be located between the exterior material of the battery cell C and the support plate of the cell group 11. The battery cell C may expand or contract due to the expansion of an electrode plate housed therein, gas, or the like. As an example, as the expansion amount of the battery cell C increases, the exterior material of the battery cell C becomes closer to the support plate, and therefore the pressure acting on the pressure sensor PS increases. The pressure sensor PS may be configured to output a pressure signal indicating the pressure applied thereto to the control unit 130 in response to a change in volume due to the expansion (swelling) of the battery cell C.

[0061] The plurality of temperature sensors TS are connected to the plurality of battery cells C1 to C m The temperature sensor TS may be directly attached to the exterior material of the battery cell C or may be provided at a certain distance therefrom. The temperature sensor TS may be configured to output a temperature signal indicating the temperature of the battery cell C to the control unit 130. As the temperature sensor TS, for example, a thermocouple may be used.

[0062] Programs and various data required for executing a battery management method according to an embodiment described below may be stored in advance in the memory 120. The memory may include at least one type of computer-readable recording medium, such as a flash memory, a hard disk, a solid state disk (SSD), a solid disk drive (SDD), a multimedia micro card, a random access memory (RAM), a static RAM (SRAM), a read only memory (ROM), an electrically erasable programmable ROM (EEPROM), or a programmable ROM (PROM).

[0063] The control unit 130 is operably coupled to the relay 20, the sensing unit 110, the memory 120 and / or the communication unit 140. Two components being operably coupled means that the two components are directly or indirectly connected to each other so as to be able to transmit and receive signals in one or both directions.

[0064] The control unit 130 may be implemented in hardware using at least one of digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), microprocessors, and other electrical units for performing functions.

[0065] The control unit 130 may determine a voltage value, a current value, a temperature value, and a pressure value based on the voltage signal, the current signal, the temperature signal, and the pressure signal received from the sensing unit 110 at set time intervals (e.g., 0.01 seconds), and record these values ​​in the memory 120. Since the current signal includes information on the direction of the current, the control unit 130 may determine whether the battery pack 10 is charging, discharging, or at rest based on the current signal. At rest (or at rest state) is a state in which both charging and discharging of the battery pack 10 are suspended.

[0066] The control unit 130 may determine the current accumulation amount based on the current signal using ampere counting (current accumulation method). The current accumulation amount at any point in time indicates the total amount of current accumulated over the period from the point in time when the current accumulation amount was last initialized to the point in time.

[0067] The communication unit 140 may be communicatively coupled to the vehicle controller 2 of the electric vehicle 1. The communication unit 140 may transmit messages from the vehicle controller 2 to the control unit 130 and may transmit messages from the control unit 130 to the vehicle controller 2. The messages from the control unit 130 may include information for notifying the state of the battery cell C (e.g., voltage, SOC, over-discharge, low voltage, over-charge, over-voltage). For communication between the communication unit 140 and the vehicle controller 2, a wired network such as a local area network (LAN), a controller area network (CAN), or a daisy chain and / or a short-range wireless network such as Bluetooth (registered trademark), ZigBee (registered trademark), and WiFi (registered trademark) may be utilized. The battery management system 100 may further include an output device (e.g., a display, a speaker) that provides information received by the communication unit 140 from the control unit 130 and / or the vehicle controller 2 in a form that can be recognized by a user. The vehicle controller 2 may control the electric loads 30 based on information collected through communication with the battery management system 100.

[0068] 2, the memory 120 stores first relationship data including a SOC-OCV curve 200. The SOC-OCV curve 200 includes a flat section (Z A ~Z B ) has been recorded.

[0069] When a plurality of temperature intervals are predefined, the memory 120 may prerecord first relationship data created individually for each temperature interval. The control unit 130 may obtain from the memory 120 the first relationship data related to a single temperature interval to which the temperature value of the battery cell C belongs among the plurality of temperature intervals, and use the first relationship data to estimate the SOC. Similarly, when a plurality of SOH intervals are predefined, the memory 120 may prerecord first relationship data created individually for each SOH interval. The control unit 130 may obtain from the memory 120 the first relationship data related to a single SOH interval to which the SOH of the battery cell C belongs among the plurality of SOH intervals, and use the first relationship data to estimate the SOC. For example, when there are 10 temperature intervals and 20 SOH intervals, a total of 200 pieces of first relationship data may be prestored in the memory 120.

[0070] Battery cell C is in the flat section (Z A ~Z B ) the OCV remains almost constant throughout the plateau (Z A ~Z B ), the rate of change of OCV with respect to SOC (e.g., the differential value) is maintained at or below a predetermined reference value. A ~Z B ) remaining range (0~Z A %, Z B 100%), the rate of change of OCV relative to SOC is greater than a predetermined reference value. This makes it possible to determine the SOC corresponding to the identified OCV from the SOC-OCV curve 200 with high accuracy, once the OCV is identified.

[0071] It is known that most rechargeable batteries, including battery cell C, have the characteristic of deteriorating relatively quickly when continuously used (charged and discharged) at an SOC of around 0% or 100% beyond the appropriate range. The safe voltage range (V1~V2) is determined in advance in consideration of the relationship between the SOC of battery cell C and the rate of deterioration. The SOC (Z1) corresponding to the lower limit (V1) of the safe voltage range (V1~V2) is the lower limit (Z AThe SOC (Z2) corresponding to the upper limit (V2) of the safe voltage range (V1 to V2) is smaller than the OCV corresponding to the upper limit (Z B ) The range from Z1 to Z2 corresponding to the safe voltage range (V1 to V2) can be called a safe zone.

[0072] The control unit 130 periodically calculates the SOC estimate value of the battery cell C at every set time, and determines whether the previous SOC estimate value is in a flat section (Z A ~Z B ) lower limit (Z A ) is smaller than the set value or is in the flat section (Z A ~Z B ) upper limit (Z B ) by a set value or more (for example, outside a safe zone), the pressure sensor PS can be deactivated. That is, when the SOC estimate is calculated, if there is no need or very little need for the SOC-P curve 300 described below, the pressure sensor PS is deactivated, thereby saving the power required to drive the pressure sensor PS and reducing the amount of calculation load required to process the pressure signal.

[0073] On the other hand, in a battery cell C manufactured to include a specific material (e.g., lithium metal) in the electrode, an insertion or desorption reaction of working ions (e.g., lithium ions) occurs in the electrode lattice during charging and discharging, causing a change in volume. Therefore, the present inventors have recognized that the change in pressure of the battery cell C detected by the pressure sensor PS over time is sufficiently related to the change in SOC of the battery cell C over time.

[0074] Referring to FIG. 3, the memory 120 stores second relationship data including an SOC-P(Pressure) curve 300 indicating a relationship between the SOC and pressure of the battery cell C. When a plurality of temperature intervals are predefined, the memory 120 may prerecord second relationship data created individually for each temperature interval. The control unit 130 may obtain, from the memory 120, second relationship data related to a single temperature interval to which the temperature value of the battery cell C belongs among the plurality of temperature intervals, and use the second relationship data to estimate the SOC. Similarly, when a plurality of SOH intervals are predefined, the memory 120 may prerecord second relationship data created individually for each SOH interval. The control unit 130 may obtain, from the memory 120, second relationship data related to a single SOH interval to which the SOH of the battery cell C belongs among the plurality of SOH intervals, and use the second relationship data to estimate the SOC. For example, when there are 10 temperature intervals and 20 SOH intervals, a total of 200 pieces of second relationship data may be prestored in the memory 120.

[0075] According to the SOC-P curve 300, it can be seen that as the SOC of the battery cell C increases from 0% to 100%, the pressure of the battery cell C also gradually increases. That is, unlike the SOC-OCV curve 200 having a flat section described above with reference to FIG. 2, the pressure of the battery cell C has an approximately linear relationship with the SOC. Therefore, when the SOC of the battery cell C approaches the flat section (Z A ~Z B ), the SOC of battery cell C can be estimated with high accuracy by using SOC-P curve 300 alone or a combination of SOC-OCV curve 200 and SOC-P curve 300 instead of SOC-OCV curve 200.

[0076] 4, the memory 120 stores third relationship data including an SOH-P curve 400 indicating a relationship between the SOH and pressure of the battery cell C. When a plurality of temperature intervals are predefined, the memory 120 may pre-record third relationship data created individually for each temperature interval. The control unit 130 may obtain, from the memory 120, the third relationship data associated with a single temperature interval to which the temperature value of the battery cell C belongs among the plurality of temperature intervals, and use the third relationship data to estimate the SOH.

[0077] Each SOH-P curve 400 shown in Fig. 4 may be prepared in advance for different SOCs. It can be seen from Fig. 3 that even if the SOC of the battery cell C is the same as a specific value, the pressure of the battery cell C gradually increases almost linearly as the battery cell C deteriorates (i.e., the SOH becomes smaller). Also, as described above, it can be seen from Fig. 3 that even if the SOH of the battery cell C is the same as a specific value, the pressure of the battery cell C gradually increases almost linearly as the SOC of the battery cell C increases.

[0078] The SOH can be estimated by any one or a combination of two or more of various known methods. As an example, the control unit 130 may calculate the current maximum capacity of the battery cell C by dividing the integrated current amount during the period from when the SOC of the battery cell C is a first value to when it reaches a second value by the change in SOC (i.e., the difference between the first value and the second value). Thereafter, the control unit 130 may determine the SOH estimate value by converting the value obtained by dividing the maximum capacity of the battery cell C by the design capacity (maximum capacity of a new battery) of the battery cell C into a percentage.

[0079] When the battery cell C is in a load state, the control unit 130 may determine (estimate) the OCV of the battery cell C based on the voltage and current (to which temperature may be added) of the battery cell C detected by the sensing unit 110. As an example, an estimated OCV value of the battery cell C may be calculated by subtracting a voltage value corresponding to the product of the current value of the battery cell C and the internal resistance of the battery cell C from the voltage value of the battery cell C according to Ohm's law. The control unit 130 may determine the internal resistance of the battery cell C based on a ratio of a voltage change amount and a current change amount of the battery cell C per set time according to Ohm's law. Alternatively, the internal resistance of the battery cell C may be determined from a resistance map in which a relationship between the SOC, temperature, and internal resistance of the battery cell C is defined.

[0080] Fig. 5 is a flow diagram illustrating an example of a battery management method executed by the battery management system illustrated in Fig. 1. The method of Fig. 5 may be periodically and repeatedly executed by the battery management system 100 at set times when the battery cell C is being charged or discharged or when the rest time during which the battery cell C is maintained in a rest state is less than a predetermined stabilization time. For reference, if the rest time is not long enough, the no-load voltage of the battery cell C detected by the voltage detection circuit 112 may have a non-negligible difference from the OCV corresponding to the actual SOC of the battery cell C even during rest.

[0081] 1 to 5, in step S510, the control unit 130 determines a voltage value, a current value, and a pressure value of the battery cell C based on the voltage signal, the current signal, and the pressure signal collected from the sensing unit 110. At this time, the control unit 130 may further collect a temperature signal from the sensing unit 110 and further determine a temperature value.

[0082] In step S520, the control unit 130 sets the previous SOC estimate value within a flat section (Z A ~Z B ) for comparison.

[0083] In step S530, the control unit 130 executes at least one of (i) a first SOC estimation logic based on the voltage value, the current value, and the first relationship data, and (ii) a second SOC estimation logic based on the pressure value and the second relationship data, depending on the comparison result of step S520, to determine a current SOC estimation value.

[0084] The first SOC estimation logic may be created to determine an estimated OCV value of the battery cell C based on a voltage value and a current value (including a temperature), and then output an SOC value related to the estimated OCV value among the SOC values ​​recorded in the first relationship data as a first estimated SOC value. The first SOC estimation logic may be created to determine an estimated OCV value of the battery cell C based on a voltage value and a current value (including a temperature), and then output an SOC value related to the estimated OCV value among the SOC values ​​recorded in the first relationship data as a first estimated SOC value. A ~Z B ), the first SOC estimation logic may be configured to determine an OCV estimate by subtracting a voltage value due to the internal resistance from a voltage value indicating the CCV of the battery cell C. The first SOC estimation logic may be configured to determine an OCV estimate by subtracting a voltage value due to the internal resistance from a voltage value indicating the CCV of the battery cell C while the SOC estimate of the battery cell C is outside the plateau interval (Z A ~Z B ), the estimated SOC of battery cell C is within the plateau (Z A ~Z B The SOC change amount corresponding to the current integration amount calculated while the SOC estimate is in the plateau section (Z A ~Z B ) to determine a first SOC estimate.

[0085] The second SOC estimation logic may be configured to output, as a second SOC estimate, a SOC value associated with the pressure value determined in step S510 among the pressure values ​​recorded in the second relationship data.

[0086] Thus, the current SOC estimate determined in step S530 is equal to any one of the first SOC estimate, the second SOC estimate, and a weighted average of the two.

[0087] The "current SOC estimate" determined in step S530 is the same as the flat section (Z A ~Z B ) is compared with the “previous SOC estimated value”. In addition, the control unit 130 sequentially records the SOC estimated value in the memory 120 every time step S530 is executed, so that a change history (time series) of the SOC estimated value is generated in the memory 120.

[0088] FIG. 6 is a flow chart showing an example of a sub-routine of step S530 in FIG.

[0089] 1 to 6, in step S610, the control unit 130 determines whether the previous SOC estimation value is in a flat section (Z A ~Z B ), i.e., outside the plateau (Z A ~Z B ) lower limit (Z A ) or is less than the plateau (Z A ~Z B ) upper limit (Z B If the value of step S610 is "yes", proceed to step S620. If the value of step S610 is "no", it means that the previous SOC estimate is in the plateau zone (Z A ~Z B If the value of step S610 is "No", proceed to step S630.

[0090] In step S620, the control unit 130 executes only the first SOC estimation logic among the first SOC estimation logic and the second SOC estimation logic, thereby obtaining a first SOC estimation value.

[0091] In step S630, the control unit 130 executes only the second SOC estimation logic among the first SOC estimation logic and the second SOC estimation logic, thereby obtaining a second SOC estimation value.

[0092] In step S640, the controller 130 determines a current SOC estimate to be equal to the first SOC estimate obtained in step S620 or the second SOC estimate obtained in step S630.

[0093] FIG. 7 is a flow chart showing an example of another sub-routine of step S530 in FIG. 5, and FIG. 8 is an example of a weighting value map that can be used in the sub-routine in FIG.

[0094] 1 to 5, 7 and 8, in step S710, the control unit 130 determines whether the previous SOC estimation value is in a flat section (Z A ~Z B If the value of step S710 is "yes", the process proceeds to step S720. If the value of step S710 is "no", the process proceeds to step S730.

[0095] In step S720, the control unit 130 determines whether the flat section (Z A ~Z B ) lower limit (Z A ) or upper limit (Z B ) and the previous SOC estimation value, a first weight value associated with the first SOC estimation logic and a second weight value associated with the second SOC estimation logic are determined. The first weight value is set to the flat section (Z A ~Z B ) lower limit (Z A ) or upper limit (Z B ) may be negatively correlated with the difference between the previous SOC estimate and the plateau interval (Z A ~Z B ) lower limit (Z A ) or upper limit (Z B ) may have a positive correlation with the difference between the previous SOC estimate and the first weighting value. The sum of the first weighting value and the second weighting value may be a predetermined value (e.g., 1), and when one of the first weighting value and the second weighting value is determined, the other may also be determined.

[0096] FIG. 8 illustrates a weight map 800 in which the relationship between the first weight and the difference is recorded. The weight map 800 may be stored in advance in the memory 120. In FIG. 8, the difference being close to 0 means that the previous SOC estimation value is in the flat section (Z A ~Z B ), and the difference is close to the lower limit (Z A ) or upper limit (Z B ), the previous SOC estimate is close to the plateau (Z A ~Z B ) means that the previous SOC estimate is far from the lower limit (Z A ), the lower limit (Z A ) can be set to the maximum value of the horizontal axis of FIG. 8, and the previous SOC estimate can be set to the upper limit (Z B ), the upper limit (Z B ) can be set to the maximum value of the horizontal axis in FIG.

[0097] In step S724, the control unit 130 executes both the first SOC estimation logic and the second SOC estimation logic, thereby obtaining a first SOC estimate value and a second SOC estimate value.

[0098] In step S728, the control unit 130 determines a first weighted average of the first SOC estimated value according to the first SOC estimation logic and the second SOC estimated value according to the second SOC estimation logic based on the first weight and the second weight. For example, if the first weight is 0.8, the second weight is 0.2, the first SOC estimated value is 25%, and the second SOC estimated value is 26%, the first weighted average is (first SOC estimated value x first weight) + (second SOC estimated value x second weight) = (25% x 0.8) + (26% x 0.2) = 20% + 5.2% = 25.2%.

[0099] The previous SOC estimate was in the plateau (Z A ~Z B In step S730, which is performed when the SOC is within the flat section (ZA ~Z B ) lower limit (Z A ) or upper limit (Z B The first and second weightings may be predetermined values, unlike the first and second weightings which are variable depending on the difference between the current SOC estimate and the previous SOC estimate. The third weighting may be equal to or smaller than the minimum value that can be set for the first weighting. The fourth weighting may be equal to or larger than the maximum value that can be set for the second weighting. The sum of the third and fourth weightings may be a predetermined value (e.g., 1).

[0100] In step S734, the control unit 130 executes both the first SOC estimation logic and the second SOC estimation logic.

[0101] In step S738, the control unit 130 determines a second weighted average of the first SOC estimated value according to the first SOC estimation logic and the second SOC estimated value according to the second SOC estimation logic based on the third weight and the fourth weight. For example, when the third weight is 0.3, the fourth weight is 0.7, the first SOC estimated value is 60%, and the second SOC estimated value is 61%, the second weighted average is (first SOC estimated value x third weight) + (second SOC estimated value x fourth weight) = (60% x 0.3) + (61% x 0.7) = 18% + 42.7% = 60.7%.

[0102] In step S740, the controller 130 determines a current SOC estimate equal to the first weighted average obtained in step S728 or the second weighted average obtained in step S738.

[0103] FIG. 9 is a flow diagram showing an example of yet another sub-routine of step S530 in FIG. 5, and FIG. 10 is an example of a weighting value map that can be used in the sub-routine in FIG.

[0104] 1 to 5, 9 and 10, in step S910, the control unit 130 determines whether the previous SOC estimate is in a flat section (Z A ~Z BIf the value of step S910 is "yes", the process proceeds to step S920. If the value of step S910 is "no", the process proceeds to step S930.

[0105] In step S920, the control unit 130 determines whether the flat section (Z A ~Z B ) lower limit (Z A ) or upper limit (Z B ) and the previous SOC estimation value, a first weight value associated with the first SOC estimation logic and a second weight value associated with the second SOC estimation logic are determined. The operation of step S920 is the same as step S720, and therefore, a duplicated description will be omitted.

[0106] In step S922, the control unit 130 determines a flat section (Z A ~Z B ) to determine the residence time of the SOC estimate outside the plateau interval (Z A ~Z B How long has the plateau (Z A ~Z B ) whether it remains outside.

[0107] In step S923, the control unit 130 corrects the first weight value and the second weight value according to the dwell time determined in step S924.

[0108] 10 illustrates a first correction coefficient map 1000 in which the relationship between the correction coefficient used to correct the first weight value and the dwell time is recorded. The first correction coefficient map 1000 may be stored in the memory 120 in advance.

[0109] Referring to FIG. 10, the residence time is a predetermined reference time (t R1 ), the correction coefficient for the first weighting value may have a positive correlation with the residence time. R1), the correction coefficient for the first weighting value may have a negative correlation with the residence time. The minimum value of the correction coefficient for the first weighting value may be 1. The critical value (L) may be greater than 1 and may be a preset value for the purpose of preventing the corrected first weighting value from becoming excessively large.

[0110] Flat section (Z A ~Z B ), the longer the retention time outside the reference time (t R1 ) is appropriately selected, the SOC of battery cell C will remain in the plateau (Z A ~Z B This can prevent a decrease in the accuracy of SOC estimation caused by excessively long residence outside the storage tank.

[0111] In this regard, Fig. 10 shows the reference time (t R1 ) the correction coefficient for the first weighting value changes linearly, but this should be understood as merely an example.

[0112] The difference between the corrected first weight value and the first weight value and the difference between the corrected second weight value and the second weight value may each have a positive correlation with the dwell time. The corrected first weight value may be equal to the product of the first weight value and the correction coefficient determined from the first correction coefficient map 1000. When the corrected first weight value is determined, the control unit 130 may calculate the corrected second weight value so that the sum of the corrected first weight value and the corrected second weight value is equal to a predetermined value (e.g., 1).

[0113] In step S924, the control unit 130 executes both the first SOC estimation logic and the second SOC estimation logic.

[0114] In step S928, the control unit 130 determines a first weighted average of the first SOC estimated value according to the first SOC estimation logic and the second SOC estimated value according to the second SOC estimation logic based on the corrected first weighted value and the corrected second weighted value. For example, if the corrected first weighted value is 0.81, the corrected second weighted value is 0.19, the first SOC estimated value is 25%, and the second SOC estimated value is 26%, the first weighted average is "(first SOC estimated value x corrected first weighted value) + (second SOC estimated value x corrected second weighted value) = (25% x 0.81) + (26% x 0.19) = 20.25% + 4.94% = 25.19%".

[0115] In other words, even if the first SOC estimated value and the second SOC estimated value are 25% and 26%, respectively, which are the same as the example described above with reference to FIG. 7, the corrected first weighting value corrected according to the length of the residence time is increased compared to the original first weighting value, and the corrected second weighting value is decreased compared to the original second weighting value, so that the first weighted average also shifts to 25.19%, which is closer to the first SOC estimated value than 25.2% illustrated with reference to FIG. 7.

[0116] In step S930, the control unit 130 obtains a third weight value associated with the first SOC estimation logic and a fourth weight value associated with the second SOC estimation logic from the memory 120. The third weight value and the fourth weight value have been described above with reference to FIG. 7, and therefore, repeated description will be omitted.

[0117] In step S934, the control unit 130 executes both the first SOC estimation logic and the second SOC estimation logic.

[0118] In step S938, the control unit 130 determines a second weighted average of the first SOC estimated value according to the first SOC estimation logic and the second SOC estimated value according to the second SOC estimation logic based on the third weight value and the fourth weight value.

[0119] In step S940, the controller 130 determines a current SOC estimate equal to the first weighted average obtained in step S928 or the second weighted average obtained in step S938.

[0120] FIG. 11 is a flow chart showing an example of yet another sub-routine of step S530 in FIG. 5, and FIG. 12 is an example of a weighting value map that can be used in the sub-routine in FIG.

[0121] 1 to 5, 11 and 12, in step S1110, the control unit 130 determines whether the previous SOC estimation value is in a flat section (Z A ~Z B If the value of step S1110 is "yes", the process proceeds to step S1120. If the value of step S1110 is "no", the process proceeds to step S1130.

[0122] In step S1120, the control unit 130 determines whether the flat section (Z A ~Z B ) lower limit (Z A ) or upper limit (Z B ) and the previous SOC estimation value, a first weight value associated with the first SOC estimation logic and a second weight value associated with the second SOC estimation logic are determined. The operation of step S1120 is the same as step S720, and therefore, a duplicated description will be omitted.

[0123] In step S1124, the control unit 130 executes both the first SOC estimation logic and the second SOC estimation logic, thereby obtaining a first SOC estimated value and a second SOC estimated value.

[0124] In step S1128, the control unit 130 determines a first weighted average of the first SOC estimated value according to the first SOC estimation logic and the second SOC estimated value according to the second SOC estimation logic based on the first weight value and the second weight value.

[0125] In step S1130, the control unit 130 obtains from the memory 120 a third weight value associated with the first SOC estimation logic and a fourth weight value associated with the second SOC estimation logic.

[0126] In step S1132, the control unit 130 determines a flat section (Z A ~Z B ) is determined. That is, the time that the SOC estimate remains within the plateau (Z A ~Z B How long has the flat section (Z A ~Z B ) is determined.

[0127] In step S1133, the control unit 130 corrects the third weight and the fourth weight according to the dwell time determined in step S1132.

[0128] FIG. 12 illustrates a second correction coefficient map 1200 in which the relationship between the correction coefficient used to correct the fourth weight value and the dwell time is recorded. The second correction coefficient map 1200 may be stored in advance in the memory 120. Referring to FIG. 12, when the dwell time is a predetermined reference time (t R2 ) until the reference time (t R2 After reaching the threshold (U), the correction coefficient may be maintained at a critical value (U). The critical value (U) may be greater than 1 and may be a value preset for preventing the corrected fourth weighted value from becoming excessively large.

[0129] In this regard, Fig. 12 shows the reference time (t R2 ) Although the correction factor for the fourth weighting value is shown to vary linearly over the following time ranges, it should be understood that this is merely an example.

[0130] The difference between the corrected third weighting value and the third weighting value and the difference between the corrected fourth weighting value and the fourth weighting value may each have a positive correlation with the dwell time. The corrected fourth weighting value may be equal to the product of the correction coefficient determined from the second correction coefficient map 1200 and the fourth weighting value. When the corrected fourth weighting value is determined, the control unit 130 may calculate the corrected third weighting value so that the sum of the corrected fourth weighting value and the corrected third weighting value is equal to a predetermined value (e.g., 1).

[0131] In step S1134, the control unit 130 executes both the first SOC estimation logic and the second SOC estimation logic, thereby obtaining a first SOC estimated value and a second SOC estimated value.

[0132] When the corrected third weight value and the corrected fourth weight value are determined, in step S1138, the control unit 130 determines a second weighted average of the first SOC estimated value according to the first SOC estimation logic and the second SOC estimated value according to the second SOC estimation logic based on the corrected third weight value and the corrected fourth weight value. For example, when the corrected third weight value is 0.25, the corrected fourth weight value is 0.75, the first SOC estimated value is 60%, and the second SOC estimated value is 61%, the second weighted average is "(first SOC estimated value x corrected third weight value) + (second SOC estimated value x corrected fourth weight value) = (60% x 0.25) + (61% x 0.75) = 15% + 45.75% = 60.75%".

[0133] In other words, even if the first and second SOC estimated values ​​are 60% and 61%, respectively, which are the same as the example in FIG. 7, the corrected third weighting value corrected according to the length of residence time is smaller than the original third weighting value, and the corrected fourth weighting value is larger than the original fourth weighting value, so that the second weighted average shifts to 60.75%, which is closer to the second SOC estimated value than 60.7% in FIG. 7.

[0134] In operation S1140, the controller 130 determines a current SOC estimate value equal to the first weighted average obtained in operation S1128 or the second weighted average obtained in operation S1138.

[0135] Meanwhile, the correction operation for the first weight value and the second weight value described above with reference to FIGS. 9 and 10 and the correction operation for the third weight value and the fourth weight value described above with reference to FIGS. 11 and 12 are not implemented alternatively, and the battery management system 100 may be configured to perform correction of any one of the first weight value to the fourth weight value in step S530.

[0136] The above-described embodiments of the present invention may be embodied not only by an apparatus and a method, but also through a program that realizes functions corresponding to the configuration of the embodiments of the present invention or a recording medium on which the program is recorded, and such implementation would be easily embodied by a person skilled in the art from the description of the above-described embodiments.

[0137] As described above, the present invention has been described using limited embodiments and drawings. However, the present invention is not limited thereto, and it goes without saying that various modifications and variations can be made by a person having ordinary knowledge in the technical field to which the present invention belongs within the technical spirit of the present invention and the equivalent scope of the claims.

[0138] Furthermore, the present invention described above is susceptible to various substitutions, modifications and alterations by those having ordinary knowledge in the technical field to which the present invention pertains, within the scope not departing from the technical spirit of the present invention, and is not limited to the above-described embodiments and the accompanying drawings, but may be configured by selectively combining all or part of each embodiment for various modifications.

Claims

1. A battery management system for a battery cell having a plateau section, which is an SOC range in which a rate of change of OCV is maintained below a reference value, comprising: a sensing unit for detecting a voltage, a current, and a pressure of the battery cell; a memory for storing first relationship data indicating a relationship between an OCV and an SOC of the battery cell, and second relationship data indicating a relationship between a pressure and an SOC of the battery cell; a control unit configured to determine a voltage value indicative of the detected voltage, a current value indicative of the detected current, and a pressure value indicative of the detected pressure, and to determine an estimated SOC value of the battery cell for each set time; The control unit is Comparing the previous SOC estimate with the plateau section; the battery management system is configured to determine, depending on a result of the comparison, a current SOC estimate equal to a weighted average of either or both of: (i) a first SOC estimate obtained through a first SOC estimation logic based on the voltage value, the current value, and the first relationship data; and (ii) a second SOC estimate obtained through a second SOC estimation logic based on the pressure value and the second relationship data.

2. The control unit is The battery management system of claim 1 , configured to determine the current SOC estimate equal to the first SOC estimate if the previous SOC estimate is outside the plateau interval.

3. The control unit is The battery management system of claim 1 , configured to determine the current SOC estimate equal to the second SOC estimate if the previous SOC estimate is within the plateau interval.

4. The control unit is If the previous SOC estimate is outside the flat interval, determining a first weighting value associated with the first SOC estimation logic and a second weighting value associated with the second SOC estimation logic according to a difference between a lower limit or an upper limit of the flat section and the previous SOC estimation value; 2. The battery management system of claim 1, configured to determine the current SOC estimate equal to a first weighted average of the first SOC estimate based on the first weighting value and the second SOC estimate based on the second weighting value.

5. the first weighting value has a negative correlation with a difference between a lower limit or an upper limit of the flat section and the previous SOC estimated value; The battery management system according to claim 4 , wherein the second weight value is positively correlated with a difference between a lower limit or an upper limit of the flat section and the previous SOC estimate.

6. The control unit is If the previous SOC estimate is within the flat section, determining the current SOC estimate equal to a second weighted average of the first SOC estimate based on a third weight associated with the first SOC estimation logic and the second SOC estimate based on a fourth weight associated with the second SOC estimation logic; the third weight is less than the first weight; The battery management system of claim 4 , wherein the fourth weighted value is greater than the second weighted value.

7. The control unit is If the previous SOC estimate is within the flat section, determining a residence time of the estimated SOC value within the flat section based on a time series of the estimated SOC value; correcting a third weight value associated with the first SOC estimation logic and a fourth weight value associated with the second SOC estimation logic according to the dwell time; determining the current SOC estimate equal to a second weighted average of the first SOC estimate based on a corrected third weighting value and the second SOC estimate based on a corrected fourth weighting value; the third weight is less than the first weight; The battery management system of claim 4 , wherein the fourth weighted value is greater than the second weighted value.

8. the corrected third weight value is less than or equal to the third weight value; the corrected fourth weight value is equal to or greater than the fourth weight value; 8. The battery management system of claim 7, wherein a difference between the corrected third weighted value and the third weighted value and a difference between the corrected fourth weighted value and the fourth weighted value each have a positive correlation with the residence time.

9. The control unit is If the previous SOC estimate is outside the flat interval, determining a first weighting value associated with the first SOC estimation logic and a second weighting value associated with the second SOC estimation logic according to a difference between a lower limit or an upper limit of the flat section and the previous SOC estimation value; determining a residence time of the estimated SOC value outside the flat section based on a time series of the estimated SOC value; correcting the first weight value and the second weight value according to the residence time; determining the current SOC estimate equal to a first weighted average of the first SOC estimate based on a corrected first weighting value and the second SOC estimate based on a corrected second weighting value; the third weight is less than the first weight; The battery management system of claim 1 , wherein the fourth weighted value is greater than the second weighted value.

10. A battery pack comprising a battery management system according to any one of claims 1 to 9.

11. An electric vehicle comprising the battery pack of claim 10.

12. A battery management method executed at set time intervals by the battery management system according to any one of claims 1 to 9, comprising: determining a voltage value indicative of a voltage of the battery cell, a current value indicative of a current of the battery cell, and a pressure value indicative of a pressure of the battery cell; comparing a previous SOC estimate of the battery cell with the plateau; and determining, depending on a result of the comparison, a current SOC estimate of the battery cell equal to a weighted average of either or both of: (i) a first SOC estimate obtained through a first SOC estimation logic based on the voltage value, the current value, and the first relationship data; and (ii) a second SOC estimate obtained through a second SOC estimation logic based on the pressure value and the second relationship data.

13. The step of determining a current SOC estimate of the battery cell includes: If the previous SOC estimate is outside the flat interval, determining the current SOC estimate to be equal to the first SOC estimate; The battery management method of claim 12 , further comprising determining the current SOC estimate to be equal to the second SOC estimate if the previous SOC estimate is within the plateau interval.

14. The step of determining a current SOC estimate of the battery cell includes: determining a first weighting value associated with the first SOC estimation logic and a second weighting value associated with the second SOC estimation logic according to a difference between a lower limit or an upper limit of the flat interval and the previous SOC estimation value when the previous SOC estimation value is outside the flat interval; and determining the current SOC estimate equal to a first weighted average of the first SOC estimate based on the first weight and the second SOC estimate based on the second weight.

15. The step of determining a current SOC estimate of the battery cell includes: obtaining a third weight value associated with the first SOC estimation logic and a fourth weight value associated with the second SOC estimation logic when the previous SOC estimation value is within the flat interval; determining the current SOC estimate equal to a second weighted average of the first SOC estimate based on the third weight and the second SOC estimate based on the fourth weight; the third weight is less than the first weight; The battery management method of claim 12 , wherein the fourth weighted value is greater than the second weighted value.

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