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 includes a sensing unit that detects a terminal voltage and a charge / discharge current of a battery having a characteristic in which a voltage inflection section changes depending on a current rate, a memory unit that stores a first Kalman filter using an equivalent circuit model and an SOC-OCV curve of the battery and a second Kalman filter using a constant current charge / discharge map of the battery, and a control unit that determines a first SOC estimate by inputting a voltage value of the terminal voltage, a current value of the charge / discharge current, and a previous SOC estimate into the first Kalman filter, and determines a second SOC estimate by inputting the current value and the previous SOC estimate into the second Kalman filter.

Description

[Technical Field]

[0001] The present invention relates to a technique for estimating the state of charge of a battery.

[0002] This application claims priority based on Korean Patent Application No. 10-2023-0082153, filed on June 26, 2023, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings thereof. [Background technology]

[0003] Recently, with the rapid increase in demand for portable electronic products such as laptops, video cameras, and mobile phones, and the full-scale development of electric vehicles, energy storage batteries, robots, satellites, and other products, active research is being conducted on high-performance batteries that can be repeatedly charged and discharged.

[0004] Currently commercially available batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium batteries. Of these, lithium batteries are attracting attention due to their advantages over nickel-based batteries, such as almost no memory effect, allowing for free charging and discharging, a very low self-discharge rate, and a high energy density.

[0005] One of the important parameters required to control the charging and discharging of a battery is the state of charge (SOC). SOC is a parameter that indicates the relative ratio of the current capacity to the maximum capacity, which is the total electrical energy when the battery is fully charged, and can be expressed as 0 to 1 (or 0% to 100%). For example, if the maximum capacity of a battery is 1000Ah (ampere-hours) and the current capacity stored in the battery is 750Ah, the SOC of the battery is 0.75 (or 75%).

[0006] The Extended Kalman Filter (EKF) is widely used to estimate the SOC of a battery.

[0007] A typical extended Kalman filter is an SOC estimation logic that uses an equivalent circuit model (ECM) and an SOC-OCV (Open Circuit Voltage) curve that are created in advance to match the electrochemical characteristics of the battery. When the battery voltage and current are input as input variables, the filter outputs an estimated SOC value, which is one of the state variables.

[0008] Meanwhile, the SOC-OCV (Open Circuit Voltage) curve of some types of batteries, such as lithium iron phosphate (LFP) batteries, has a voltage inflection section. However, the SOC-CCV (Closed Circuit Voltage) curve, which is obtained by repeatedly measuring the terminal voltage of the battery in a constant current charge mode and / or a constant current discharge mode, has a characteristic that the voltage inflection section is not as clear as the SOC-OCV curve, and the voltage inflection section becomes weaker or disappears completely as the current rate increases.

[0009] In order to faithfully reflect the characteristics of the battery's voltage inflection period in the EKF, the ECM must be precisely designed. However, as the ECM design precision increases, the number of elements included in the ECM increases excessively, and the interconnections between these elements inevitably become more complex, resulting in increased computational complexity and data storage space required for SOC estimation. Furthermore, even if the ECM design precision is improved, it is difficult to fully reflect the change characteristics of the voltage inflection period described above depending on the current rate.

[0010] To solve these problems caused by ECM limitations, a method can be considered to estimate the battery SOC using ampere counting instead of EKF during constant current charge / discharge mode. Ampere counting is a method of estimating the battery SOC by converting the integrated current flowing through the battery into the amount of change in SOC. However, as the duration of constant current charge / discharge mode increases, current measurement errors also accumulate over time, which has the disadvantage of gradually reducing the accuracy of SOC estimation using ampere counting. 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 pack that estimates the SOC of a battery having a characteristic in which a voltage inflection section changes depending on a current rate by using two extended Kalman filters in parallel that are complementary to each other, an electric vehicle including the battery pack, and a battery management method.

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

[0013] A battery management system according to one aspect of the present invention is for a battery having a characteristic in which a voltage inflection period changes depending on a current rate. The battery management system includes a sensing unit configured to detect the terminal voltage and charge / discharge current of the battery, a memory unit configured to store a first Kalman filter, which is SOC estimation logic using an equivalent circuit model of the battery and a SOC (State Of Charge)-OCV (Open Circuit Voltage) curve, and a second Kalman filter, which is SOC estimation logic using a constant current charge / discharge map of the battery, and a control unit configured to determine a voltage value of the detected terminal voltage and a current value of the detected charge / discharge current. The control unit is configured to input the voltage value, the current value, and a previous SOC estimate into the first Kalman filter to determine a first SOC estimate, and to input the current value and the previous SOC estimate into the second Kalman filter to determine a second SOC estimate. The control unit is configured to determine a current SOC of the battery based on at least one of the first SOC estimate and the second SOC estimate.

[0014] The control unit may be configured to determine whether the battery is in a first state in which the battery is not being charged or discharged at a constant current, or a second state in which the battery is being charged or discharged at a constant current, based on current time-series data representing a time-dependent change history of the current value or the charge / discharge current. In response to determining that the battery is in the first state, the control unit may be configured to determine a current SOC of the battery similar to the first SOC estimate. In response to determining that the battery is in the second state, the control unit may be configured to determine a current SOC of the battery similar to the second SOC estimate.

[0015] The control unit may be configured to determine whether the battery is in a first state in which the battery is not being charged or discharged at a constant current, or a second state in which the battery is being charged or discharged at a constant current, based on current time-series data representing a history of changes over time in the current value or the charge / discharge current. In response to determining that the battery is in the first state, the control unit may be configured to determine a first weight having a positive correlation with the duration of the first state and a second weight having a negative correlation with the duration of the first state. The control unit may be configured to determine the current SOC of the battery as a weighted average of the first SOC estimate and the second SOC estimate using the first weight and the second weight.

[0016] The first weight may be greater than the second weight, and the sum of the first weight and the second weight may be one.

[0017] The control unit may be configured to determine, based on current time-series data representing a history of changes over time in the current value or the charge / discharge current, whether the battery is in a first state in which it is not being charged or discharged at a constant current, or a second state in which it is being charged or discharged at a constant current. In response to determining that the battery is in the second state, the control unit may be configured to determine a third weight negatively correlated with the duration of the second state and a fourth weight positively correlated with the duration of the second state. The control unit may be configured to determine a weighted average of the first SOC estimate and the second SOC estimate using the third weight and the fourth weight as the current SOC of the battery.

[0018] The third weight may be less than the fourth weight, and the sum of the third weight and the fourth weight may be one.

[0019] The constant current charge / discharge map may include a plurality of charge curves representing the relationship between the SOC and voltage of the battery during constant current charging using a plurality of current rates, and a plurality of discharge curves representing the relationship between the SOC and voltage of the battery during constant current discharging using a plurality of the current rates.

[0020] The second SOC estimated value may be output from the second Kalman filter when any one of the plurality of charge curves and the plurality of discharge curves is provided to the second Kalman filter.

[0021] The control unit may be configured to provide the second Kalman filter with one of the plurality of charge curves associated with a current rate corresponding to the current value in response to the battery being constant current charged, and the control unit may be configured to provide the second Kalman filter with one of the plurality of discharge curves associated with a current rate corresponding to the current value in response to the battery being constant current discharge.

[0022] A battery pack according to another aspect of the present invention includes the battery management system.

[0023] An electric vehicle according to yet another aspect of the present invention includes the battery pack.

[0024] According to another aspect of the present invention, a battery management method for a battery having a characteristic in which a voltage inflection period changes depending on a current rate includes the steps of detecting a terminal voltage and a charge / discharge current of the battery and determining a voltage value of the detected terminal voltage and a current value of the detected charge / discharge current, determining a first estimated SOC value by inputting the voltage value, the current value, and a previous estimated SOC value into a first Kalman filter, which is an SOC estimation logic that uses an equivalent circuit model of the battery and an SOC (State Of Charge)-OCV (Open Circuit Voltage) curve of the battery, determining a second estimated SOC value by inputting the current value and the previous estimated SOC value into a second Kalman filter, which is an SOC estimation logic that uses a constant current charge / discharge map of the battery, and determining a current SOC of the battery based on at least one of the first estimated SOC value and the second estimated SOC value.

[0025] The step of determining the current SOC of the battery may include the steps of: determining whether the battery is in a first state in which the battery is not being charged or discharged at a constant current, or a second state in which the battery is being charged or discharged at a constant current, based on current time series data representing a time-dependent change history of the current value or the charge / discharge current; determining the first SOC estimate value as the current SOC of the battery in response to determining that the battery is in the first state; and determining the second SOC estimate value as the current SOC of the battery in response to determining that the battery is in the second state.

[0026] The step of determining the current SOC of the battery may include the steps of: determining whether the battery is in a first state in which the battery is not being charged or discharged at a constant current, or a second state in which the battery is being charged or discharged at a constant current, based on current time-series data representing a time-dependent change history of the current value or the charge / discharge current; determining, in response to the determination that the battery is in the first state, a first weight having a positive correlation with the duration of the first state and a second weight having a negative correlation with the duration of the first state; and determining, as the current SOC of the battery, a weighted average of the first SOC estimate and the second SOC estimate using the first weight and the second weight.

[0027] The step of determining the current SOC of the battery can include the steps of: determining whether the battery is in a first state in which the battery is not being charged or discharged at a constant current, or a second state in which the battery is being charged or discharged at a constant current, based on current time-series data representing a time-dependent change history of the current value or the charge / discharge current; determining, in response to the determination that the battery is in the second state, a third weight having a negative correlation with the duration of the second state and a fourth weight having a positive correlation with the duration of the second state; and determining, as the current SOC of the battery, a weighted average of the first SOC estimate and the second SOC estimate using the third weight and the fourth weight.

[0028] The constant current charge / discharge map may include a plurality of charge curves representing the relationship between the SOC and voltage of the battery during constant current charging using a plurality of current rates, and a plurality of discharge curves representing the relationship between the SOC and voltage of the battery during constant current discharging using a plurality of the current rates.

[0029] The second SOC estimated value may be output from the second Kalman filter when any one of the plurality of charge curves and the plurality of discharge curves is provided to the second Kalman filter. [Effects of the Invention]

[0030] According to at least one embodiment of the present invention, when estimating the SOC of a battery having a characteristic in which the voltage inflection section changes depending on the current rate, by using two extended Kalman filters in parallel that are complementary to each other, SOC estimation errors that occur in response to changes in the battery's charge / discharge mode can be reduced compared to a method using a single extended Kalman filter, thereby improving the accuracy of SOC estimation.

[0031] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0032] 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 concepts of the present invention. Therefore, the present invention should not be interpreted as being limited to only the matters described in the drawings. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a diagram illustrating the configuration of an electric vehicle according to the present invention; [Figure 2] FIG. 2 illustrates an exemplary equivalent circuit model of the battery shown in FIG. 1. [Figure 3] FIG. 2 is a diagram illustrating an example of an SOC-OCV curve of the battery shown in FIG. 1. [Figure 4] FIG. 2 is a diagram referred to for explaining a constant current charge / discharge map according to the present invention. [Figure 5] 1 is a flowchart illustrating a battery management method for estimating SOC according to a first embodiment of the present invention. [Figure 6] 6 is a flowchart illustrating a battery management method for estimating SOC according to a second embodiment of the present invention. [Figure 7] 10 is a flowchart illustrating a battery management method for estimating SOC according to a third embodiment of the present invention. [Figure 8] FIG. 8 is a diagram to be referred to in order to explain the method according to FIG. 7. [Figure 9] 10 is a flowchart illustrating a battery management method for estimating SOC according to a fourth embodiment of the present invention. [Figure 10] FIG. 10 is a diagram to be referred to in order to explain the method according to FIG. 9. [Figure 11] 10 is a flowchart illustrating a battery management method for estimating SOC according to a fifth embodiment of the present invention. [Figure 12] 1 is a flowchart illustrating a method for determining whether a battery is being charged or discharged at a constant current. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and phrases used in the specification and claims should not be construed as being limited to their ordinary and dictionary meanings, but should be construed as having meanings and concepts corresponding to the technical ideas of the present invention, in accordance with the principle that the inventors themselves can appropriately define the concepts of terms in order to best describe the invention.

[0035] Therefore, it should be understood that the configurations shown in the embodiments described in this specification are merely the most desirable embodiments 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 for them at the time of this application.

[0036] Terms including ordinal numbers, such as first, second, etc., are used to distinguish one of the various components from the rest, and are not used to limit the components by such terms.

[0037] Throughout the specification, when a part "comprises" a certain element, this does not mean that it excludes other elements, but that it may further include other elements, unless otherwise specified. Furthermore, terms such as "control unit" used in the specification refer to a unit that processes at least one function or operation, and can be realized by hardware, software, or a combination of hardware and software.

[0038] Throughout this specification, when a part is said to be "connected" to another part, this includes not only the case where the part is "directly connected" to another part, but also the case where the part is "indirectly connected" via another element between them.

[0039] FIG. 1 is a diagram illustrating the configuration of an electric vehicle according to the present invention.

[0040] The electric vehicle 1 includes a vehicle controller 2, a battery pack 10, a relay 20, an inverter 30, and an electric motor 40. The charge / discharge terminals P+ and P- of the battery pack 10 can be electrically coupled to a charger 3 via a charging cable or the like. The charger 3 is included in the electric vehicle 1 or is provided at a charging station.

[0041] The vehicle controller 2 (e.g., ECU: Electronic Control Unit) is configured to transmit a key-on signal to the battery management system 100 in response to a start button (not shown) provided on the electric vehicle 1 being switched to an 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 a start button being switched to an OFF position by a user. The charger 3 communicates with the vehicle controller 2 and can supply constant current or constant voltage charging power via the charging and discharging terminals P+ and P- of the battery pack 10.

[0042] The battery pack 10 includes a battery module 11 and a battery management system 100 .

[0043] The battery module 11 includes at least one battery B. The battery B can be repeatedly charged and discharged. The type of battery B is not particularly limited as long as it has the characteristic that the voltage inflection section changes depending on the current rate, such as an LFP battery.

[0044] When the battery module 11 includes multiple batteries, the multiple batteries may be interconnected in series, parallel, or series-parallel combinations.

[0045] The relay 20 is electrically connected in series to the battery module 11 via a power path connecting the battery module 11 and the inverter 30. In FIG. 1 , the relay 20 is shown connected between the positive terminal of the battery module 11 and the charge / discharge terminal P+. The relay 20 is controlled to be turned on / off in response to a switching signal from the battery management system 100. The relay 20 may be a mechanical contactor that is turned on / off by the magnetic force of a coil, or may be a semiconductor switch such as a metal oxide semiconductor field effect transistor (MOSFET).

[0046] An inverter 30 is provided to convert direct current from the battery module 11 to alternating current in response to commands from the battery management system 100 or the vehicle controller 2 .

[0047] The electric motor 40 is driven by AC power from the inverter 30. As the electric motor 40, for example, a three-phase AC motor 40 can be used.

[0048] The battery management system 100 includes a voltage detection unit 111, a current detection unit 113, a temperature detection unit 115, and a control unit 130. The battery management system 100 may further include a communication circuit 150.

[0049] The voltage detection unit 111 is connected to the positive and negative terminals of the battery B included in the battery module 11, and is configured to detect the terminal voltage, which is the voltage across both ends of the battery B, and output a voltage signal SV representing the detected terminal voltage to the control unit 130.

[0050] The current detection unit 113 is connected in series to the battery module 11 via a current path between the battery module 11 and the inverter 30. The current detection unit 113 is configured to detect a charge / discharge current, which is a current flowing through the battery module 11, and output a current signal SI representing the detected charge / discharge current to the control unit 130. The current detection unit 113 can be realized by, for example, one or a combination of two or more known current detection elements such as a shunt resistor and a Hall effect element.

[0051] The temperature detection unit 115 is configured to detect the temperature of the battery B and output a temperature signal ST representing the detected temperature to the control unit 130. The temperature detection unit 115 can be realized by one or a combination of two or more known temperature detection elements such as a thermocouple, a thermistor, a bimetal, etc.

[0052] The voltage detection unit 111, the current detection unit 113, and the temperature detection unit 115 are sometimes called "sensing units."

[0053] The communication circuit 150 is configured to support wired or wireless communication between the control unit 130 and the vehicle controller 2. The wired communication may be, for example, CAN (controller area network) communication, and the wireless communication may be, for example, Zigbee (registered trademark) or Bluetooth (registered trademark) communication. Of course, the type of communication protocol is not particularly limited as long as it supports wired or wireless communication between the control unit 130 and the vehicle controller 2. The communication circuit 150 may include an output device (e.g., a display, a speaker) that provides information received from the control unit 130 and / or the vehicle controller 2 in a format that can be recognized by a user.

[0054] The control unit 130 is operably coupled to the relay 20, the voltage detection unit 111, the current detection unit 113, the temperature detection unit 115, and the communication circuit 150. Two components being operably coupled means that the two components are directly or indirectly connected so as to be able to send and receive signals in one direction or two directions.

[0055] The control unit 130 can collect the voltage signal SV from the voltage detection unit 111, the current signal SI from the current detection unit 113, and / or the temperature signal ST from the temperature detection unit 115. The control unit 130 can use an ADC (Analog to Digital Converter) provided inside the control unit 130 to convert the analog signals collected from the detection units 111, 113, and 115 into digital values ​​and record them.

[0056] The control unit 130 may also be referred to as a "control circuit" or a "battery controller" and may be implemented in hardware using at least one of ASICs (application specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays), microprocessors, or other electrical units for performing functions.

[0057] The memory unit 140 may include at least one type of storage medium, such as a flash memory type, a hard disk type, a solid state disk type (SSD type), a silicon disk drive type (SDD type), a micro multimedia card type, a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), or a programmable read-only memory (PROM). The memory unit 140 may store data and programs required for calculations performed by the control unit 130. The memory unit 140 may store data indicating the results of calculations performed by the control unit 130. Although the memory unit 140 is shown in FIG. 1 as being physically independent from the control unit 130, it may also be incorporated within the control unit 130.

[0058] The memory unit 140 can store an equivalent circuit model (see FIG. 2), an SOC-OCV curve (see FIG. 3), a constant current charge / discharge map (see FIG. 4), a first extended Kalman filter, and a second extended Kalman filter. The SOC-OCV curve, the constant current charge / discharge map, the first extended Kalman filter, and the second extended Kalman filter will be described in more detail below.

[0059] The control unit 130 can turn on the relay 20 in response to a key-on signal. The control unit 130 can turn off the relay 20 in response to a key-off signal. The key-off signal indicates switching from the cycle mode to the sleep mode. Alternatively, the on / off control of the relay 20 can be performed by the vehicle controller 2 instead of the control unit 130.

[0060] While the relay 20 is turned on, the battery B of the battery module 11 is in cycle mode. The cycle mode refers to an operating state in which charging and discharging are possible. The cycle mode can be divided into a constant current charging mode, a constant current discharging mode, and a non-constant current charging and discharging mode.

[0061] The constant current charging mode refers to a state in which a constant rate of charging current flows to battery B. The constant current discharging mode refers to a state in which a constant rate of discharging current flows to battery B. The non-constant current charging / discharging mode refers to a state in which a non-constant charging or discharging current flows to battery B.

[0062] While the relay 20 is turned off, the battery B of the battery module 11 is in a sleep mode, which refers to an operating state in which charging and discharging are disabled because the charging and discharging current is cut off.

[0063] In this specification, the term "battery B is in the first operating state" means that battery B is in a rest mode or a non-constant current charge / discharge mode, and the term "battery B is in the second operating state" means that battery B is in a constant current charge mode or a constant current discharge mode.

[0064] While the battery module 11 is in the cycle mode, the control unit 130 determines the voltage value, the current value, and the temperature value based on the voltage signal SV, the current signal SI, and the temperature signal ST, respectively, and then determines (estimates) the SOC of the battery B based on the voltage value, the current value, and / or the temperature value. The SOC represents the ratio of the remaining capacity of the battery B to the fully charged capacity (maximum capacity).

[0065] In this specification, the SOC is expressed in the range of 0 to 1, with an SOC of 0 representing a fully discharged state and an SOC of 1 representing a fully charged state.

[0066] In this specification, when U is a variable, it is assumed that "U[k-1]" represents the value of U in the previous period, and "U[k]" represents the value of U in the current period. The symbol k used together with the symbol [ ] is a time index that increases by 1 each time a predetermined set time (Δt, for example, 0.001 seconds) has elapsed from the initial time point t0.

[0067] At the initial time t0, k may be set to 0. For example, k=10 indicates that a time period of Δt×10 has elapsed since the initial time t0, and that the SOC estimate has been calculated 10 times during this time period. The initial time t0 is the time when a predetermined event occurs, and may be the time when an event occurs in which the control unit 130 switches from a sleep state to a wake-up state, for example. The control unit 130 may switch from the sleep state to a wake-up state in response to key-on of the electric vehicle 1, and may switch from the wake-up state to the sleep state in response to key-off of the electric vehicle 1.

[0068] Next, we will explain the equivalent circuit model and SOC-OCV curve used by the first extended Kalman filter. The following formulas 1 to 8 are equations related to the first extended Kalman filter, and when explaining each of formulas 1 to 8, duplicate explanations of variables that have already been explained may be omitted.

[0069] The first extended Kalman filter uses state equations (see Equations 4-1 and 4-2 below) that include the SOC and polarization voltage as state variables, and Equation 1 below represents the relationship between the SOC and the charge / discharge current in terms of ampere counts.

[0070] <Formula 1>

number

[0071] In Equation 1, I[k-1] is the previously detected charge / discharge current, Q iis the maximum capacity of battery B, SOC[k-1] is the previous SOC, and SOC[k] is the current SOC. I[0] can be 0A. Q i represents the maximum charge that can be stored in battery B. In other words, the maximum capacity Q i is equal to the integrated value of the charging and discharging current from the fully charged state or the fully discharged state of battery B to the other state.

[0072] Next, FIG. 2 is a diagram showing an exemplary equivalent circuit model 200 of battery B shown in FIG. 1, and FIG. 3 is a diagram showing an example SOC-OCV curve of battery B shown in FIG.

[0073] Referring to FIG. 2, an equivalent circuit model 200 includes a voltage source 210, a resistor R DC and RC pair R P、 C P The symbol I represents the charging current.

[0074] The output voltage V of the voltage source 210 OCV represents the OCV of battery B after it has been in rest mode for a long time and has reached equilibrium.

[0075] 3 shows two SOC-OCV curves 310 and 320. SOC-OCV curve 310 represents the change in OCV of Battery B during a charge cycle, and SOC-OCV curve 320 represents the change in OCV of Battery B during a discharge cycle. At the same SOC, the OCV of SOC-OCV curve 310 is slightly higher than the OCV of SOC-OCV curve 320, and this difference is due to the hysteresis of Battery B due to the charge and discharge cycles.

[0076] In both of the two SOC-OCV curves 310 and 320, the SOC and OCV of Battery B have a nonlinear positive correlation. OCV and f SOC When the are inverse functions of each other, OCV=f OCV (SOC), SOC=f SOC (OCV).

[0077] The SOC-OCV curves 310, 320 shown in FIG. 3 are associated with a particular temperature or a particular temperature range, and other SOC-OCV curves associated with other temperatures or temperature ranges may also be stored in the memory unit 140.

[0078] Meanwhile, both SOC-OCV curves 310 and 320 have voltage inflection sections, which are SOC ranges where the rate of change of OCV relative to SOC (which may be an absolute value) is equal to or greater than a reference value. That is, in FIG. 3 , reference numeral 311 denotes the voltage inflection section of SOC-OCV curve 310, and reference numeral 321 denotes the voltage inflection section of SOC-OCV curve 320.

[0079] Resistance R DC Battery B's IR drop V DC Related to IR Drop V DC is the instantaneous change in the terminal voltage of battery B due to the charge / discharge current. The memory unit 140 stores the SOC, temperature, and resistance R DC The control unit 130 obtains the resistance R corresponding to the previous (or current) SOC and temperature from the first lookup table. DC can be determined.

[0080] The RC pair consists of resistor R P and capacitor C P and the polarization voltage (sometimes called "overpotential") of battery B, V P The time constant of the RC pair is related to the resistance R P and capacitor C P The memory unit 140 stores the SOC, the temperature, and the RC pair R P、 C P The control unit 130 may store a second lookup table that defines a correspondence relationship between the SOC and the temperature of the previous (or current) battery. P and capacitor C P The resistance RP and capacitor C P To determine the resistance R P Resistance value of and capacitor C P This may mean determining the capacitance of

[0081] V ecm is a variable representing the voltage across both ends of the equivalent circuit model 200, and can represent the predicted value of the terminal voltage of battery B. As shown in the following Equation 2-1, V ecm is the output voltage V OCV , IR Drop V DC and polarization voltage V P It can be expressed as the sum of

[0082] <Formula 2-1>

number

[0083] In Formula 2-1, R DC [k] is the resistance R DC resistance value, I[k] is the charge / discharge current measured this time, V OCV [k] is the estimated value of OCV, V P [k] is the estimated value of the polarization voltage this time. Equation 2-1 can be expressed as Equation 2-2 below.

[0084] <Formula 2-2>

number

[0085] In Equation 2-2, C[k] is a system matrix with two components c[k] and 1. c[k] is a function f OCV SOC[k] to V OCV [k]. That is, the product of c[k] and SOC[k] is V OCV Equals [k].

[0086] In the equivalent circuit model 200, the polarization voltage V Pcan be calculated (estimated) using the following Equation 3-1 or Equation 3-2.

[0087] <Formula 3-1>

number

[0088] <Formula 3-2>

number

[0089] In Formula 3-1 and Formula 3-2, V P [k] is the polarization voltage, V P [k-1] is the previous polarization voltage, τ is the RC pair R P、 C P time constant, R P [k] is the resistance R P τ represents the resistance value of R P [k-1] and R P [k] and C P [k-1] and C P It can be a product of any one of [k]. P [0] can be set to 0V.

[0090] Next, the first extended Kalman filter will be described in detail. The state equation of the first extended Kalman filter can be expressed as the following Equation 4-1 or Equation 4-2. Equation 4-1 is related to Equation 1 and Equation 3-1, and Equation 4-2 is related to Equation 1 and Equation 3-2.

[0091] <Formula 4-1>

number

[0092] <Formula 4-2>

number

[0093] In Formula 4-1 and Formula 4-2, SOC ^ [k-1] is the previously estimated SOC, V P^ [k-1] is the previously estimated polarization voltage, Q i is the maximum capacity of battery B, τ is the RC pair R P、 C P represents the time constant x ^ - [k] is the current state matrix, and the SOC included in it ^ - [k] and V P^ - [k] are state variables that represent the currently predicted SOC and polarization voltage, respectively.

[0094] The following equation 5 is a time update equation for the first extended Kalman filter.

[0095] <Formula 5>

number

[0096] In Equation 5, P[k-1] is the previously estimated error covariance matrix, W is the process noise covariance matrix, and P - [k] represents the error covariance matrix predicted this time. A1 in Equation 5 is the Jacobian of the function f1 in Equation 4-1 and Equation 4-2. Jacobian (A1) can be expressed as Equation 5-1 below.

[0097] <Formula 5-1>

number

[0098] A1 Tis the transpose matrix of A1. When k=0, P[0]=[1 0 ; 0 1 ]. When the time update process using Equation 4-1 or Equation 4-2 and Equation 5 is completed, the control unit 130 performs the measurement update process.

[0099] Equation 6 below is the first measurement update equation for the first extended Kalman filter.

[0100] <Formula 6>

number

[0101] In Equation 6, K[k] is the current Kalman gain, H1 is the Jacobian of the function h1 according to the following Equation 6-1, H1 T is the transpose of H1, and L is the measurement noise covariance matrix.

[0102] Regarding Equation 6, the state matrix (x ^ - By relating [k]) to Equation 2-1, the terminal voltage prediction equation (output equation) shown in Equation 6-1 below can be derived.

[0103] <Formula 6-1>

number

[0104] The Jacobian (H1) of Equation 6 can be expressed as Equation 6-2 below.

[0105] <Formula 6-2>

number

[0106] Equation 7 below is the second measurement update equation for the first extended Kalman filter.

[0107] <Formula 7>

number

[0108] In Equation 7, P[k] is P from Equation 5. - [k] is the result corrected by Equation 7.

[0109] Equation 8 below is the third measurement update equation for the first extended Kalman filter.

[0110] <Formula 8>

number

[0111] In Equation 8, z[k] is the terminal voltage detected this time, z ^ [k] is the terminal voltage estimated this time, SOC ^ [k] is the SOC estimated this time (representing the "first SOC estimate" in the claims), V P^ [k] is the polarization voltage estimated this time. x according to Equation 8 ^ [k] is the x in Equation 4 in the next round. ^ It can be used as [k-1].

[0112] When the first extended Kalman filter is executed by the control unit 130, a first SOC estimate representing the current SOC of battery B is output from the first extended Kalman filter through the above process. The control unit 130 can execute the second extended Kalman filter in parallel while executing the first extended Kalman filter. That is, the first extended Kalman filter and the second extended Kalman filter can be executed simultaneously.

[0113] Next, the constant current charge / discharge map will be explained first, and then the second extended Kalman filter will be explained in detail.

[0114] 4 is a diagram referred to in explaining a constant current charge / discharge map 400 according to the present invention. The constant current charge / discharge map 400 includes a plurality of charge curves 411-416 and a plurality of discharge curves 421-426.

[0115] Each of the multiple charging curves 411-416 shows the terminal voltage versus SOC of Battery B during a constant current charging cycle using a different current rate (sometimes called a "C-rate"). CCV can be a term that refers to the terminal voltage of Battery B measured during charging or discharging. During a charging cycle, the higher the current rate, the higher the CCV at the same SOC.

[0116] Each of the multiple discharge curves 421-426 shows the voltage CCV versus SOC of battery B during a constant current discharge cycle using a different current rate. During the discharge cycle, the higher the current rate, the lower the CCV at the same SOC.

[0117] There are six each of the plurality of charge curves 411-416 and the plurality of discharge curves 421-426, and the current rates are 0.05 C, 0.15 C, 0.25 C, 0.50 C, 1.00 C, and 1.50 C, in descending order of magnitude. Each curve included in the constant current charge / discharge map 400 can be stored in the memory unit 140 in the form of a function.

[0118] For ease of understanding, Figure 4 shows the two SOC-OCV curves 310 and 320 of Figure 3, along with multiple charge curves 411-416 and multiple discharge curves 421-426. As can be seen from Figure 4, as the current rate used in the charge cycle increases, the voltage inflection section present in SOC-OCV curve 310 gradually disappears. Similarly, as the current rate used in the discharge cycle increases, the voltage inflection section present in SOC-OCV curve 320 gradually disappears.

[0119] As described above, it is not easy to design equivalent circuit model 200 to perfectly represent the so-called fading characteristics, in which the voltage inflection section disappears as the current rate increases. Furthermore, if equivalent circuit model 200 that cannot represent the fading characteristics at a certain level or higher during constant current charging or constant current discharging is used to estimate the SOC of battery B, there is a possibility that an excessive discrepancy will occur between the actual SOC value and the estimated SOC value.

[0120] Therefore, during constant current charging or constant current discharging, the SOC of battery B can be estimated based solely on the output value of the second extended Kalman filter using constant current charging / discharging map 400 instead of the output value of the first extended Kalman filter, or the SOC of battery B can be estimated by combining (e.g., weighted averaging) the output value of the first extended Kalman filter and the output value from the second extended Kalman filter, thereby largely resolving the above-mentioned problem.

[0121] Unlike the first extended Kalman filter, whose state variables are the SOC and polarization voltage, the second extended Kalman filter uses only the SOC excluding the polarization voltage as its state variable, and can be expressed as the following Equation 9.

[0122] <Formula 9>

number

[0123] In Equation 9, x ^ [k-1] is the previous estimated SOC value, i[k] is the current value of the charge / discharge current detected this time, Q i is the maximum capacity of battery B, x ^ - [k] is the current SOC prediction value. x ^ - [k] is the SOC that represents the predicted SOC. ^ - [k] is equal to f2(x ^ [k-1]) is x ^ It can be the same as [k-1].

[0124] The following equation 10 is a time update equation for the second extended Kalman filter.

[0125] <Formula 10>

number

[0126] In Equation 10, P[k-1] is the previously estimated error covariance, w is the process noise covariance, and P - [k] represents the error covariance predicted this time. A2 is the Jacobian of the function f2 in Equation 9. Jacobian (A2) can be expressed as in Equation 10-1 below.

[0127] <Formula 10-1>

number

[0128] A2 T is the transpose matrix of A2. When k=0, P[0]=0. After the time update process using Equations 9 and 10 is completed, the control unit 130 performs the measurement update process.

[0129] The following equation (11) is the first measurement update equation for the second extended Kalman filter.

[0130] <Formula 11>

number

[0131] In Equation 11, K[k] is the current Kalman gain, H2 is the Jacobian of function h2 in Equation 11-1 below, H2 T is the transpose of H2, and l is the measurement noise covariance.

[0132] Regarding Equation 11, unlike the first extended Kalman filter, the second extended Kalman filter uses the constant current charge / discharge map 400, and therefore can derive a terminal voltage prediction equation (output equation) such as the following Equation 12-1.

[0133] <Formula 12-1>

number

[0134] In Formula 12-1, the function f CCV_I[k] is a function that defines one of the charge curves or discharge curves associated with the current rate corresponding to I[k] among the curves included in the constant current charge / discharge map 400. In response to the fact that I[k] is the charge current, the control unit 130 selects one of the charge curves corresponding to I[k] from among the plurality of charge curves 411 to 416. The selection of one of the charge curves is performed by selecting the function f CCV_I[k] Then, the control unit 130 acquires the state variable (SOC ^ - [k]), the function f CCV_I[k] The output value (z ^ Similarly to [k]), the predicted value of the terminal voltage of Battery B at this time can be set.

[0135] Moreover, the Jacobian (H) of Equation 12-1 can be expressed as Equation 12-2 below.

[0136] <Formula 12-2>

number

[0137] Equation 13 below is the second measurement update equation for the second extended Kalman filter.

[0138] <Formula 13>

number

[0139] In Equation 13, P[k] is P from Equation 10. - [k] is the result corrected by Equation 13.

[0140] Equation 14 below is the third measurement update equation for the second extended Kalman filter.

[0141] <Formula 14>

number

[0142] In Equation 14, z[k] is the terminal voltage detected this time, z ^ [k] is the terminal voltage estimated this time, SOC ^ [k] is the SOC estimated this time (representing the "second SOC estimate" in the claims). x according to Equation 14 ^ [k] is the x in Equation 9 in the next round. ^ It can be used as [k-1].

[0143] The SOC estimation of battery B using the first extended Kalman filter and the second extended Kalman filter has been described above.

[0144] The control unit 130 calculates the maximum capacity (Q i ) can be determined using Equation 15 below:

[0145] <Formula 15>

number

[0146] In Equation 15, ΔSOC is the SOC change during the capacity update period, and ΔQ is the current integration value due to the ampere count during the capacity update period. In Equation 15, a is a time index corresponding to the start point of the capacity update period, and b is a time index corresponding to the end point of the capacity update period. The capacity update period may be the most recent period in which ΔSOC becomes equal to or greater than a critical change (e.g., 0.5).

[0147] As Battery B deteriorates, its maximum capacity gradually decreases. Therefore, once Battery B's deterioration level exceeds a certain level, it is highly likely that it will suddenly become unusable. Therefore, it is necessary to estimate the SOC more precisely.

[0148] 5 is a flowchart illustrating a battery management method for estimating SOC according to a first embodiment of the present invention. The method of FIG. 5 can be repeatedly performed at set time intervals starting from the time when a predetermined event occurs.

[0149] Referring to Figures 1 to 5, in step S510, the control unit 130 detects the terminal voltage (V[k]) and charge / discharge current (I[k]) of battery B, and determines the voltage value (V[k]) of the terminal voltage and the current value (I[k]) of the charge / discharge current.

[0150] In step S520, the control unit 130 determines a first SOC estimate by inputting the voltage value (V[k]), the current value (I[k]), and the previous SOC estimate to the first extended Kalman filter. The first extended Kalman filter is an SOC estimation logic that uses the equivalent circuit model 200 of battery B and the SOC-OCV curves 310 and 320. The first SOC estimate can be considered a candidate value representing the current SOC of battery B. The terminal voltage value (V[k]) can be used as z[k] in Equation 8. If the current value (I[k]) indicates the charging direction, the control unit 130 can provide the SOC-OCV curve 310 of the two SOC-OCV curves 310 and 320 to the first extended Kalman filter. On the other hand, when the current value (I[k]) indicates the discharging direction, the control unit 130 may provide the SOC-OCV curve 320 of the two SOC-OCV curves 310 and 320 to the first extended Kalman filter.

[0151] In step S530, the control unit 130 determines a second SOC estimate by inputting the current value and the previous SOC estimate into the second extended Kalman filter. The second extended Kalman filter is an SOC estimation logic that uses the constant current charge / discharge map 400 of battery B. The second SOC estimate can be considered as another candidate value representing the current SOC of battery B. If the current value (I[k]) indicates the charge direction, the control unit 130 can provide the second extended Kalman filter with any one of the multiple charge curves 411-416 associated with a current rate corresponding to the current value (I[k]). On the other hand, if the current value (I[k]) indicates the discharge direction, the control unit 130 can provide the second extended Kalman filter with any one of the multiple discharge curves 421-426 associated with a current rate corresponding to the current value (I[k]).

[0152] When the time index k is 1, the average values ​​of the two SOCs corresponding to the OCVs at the initial time point (t0) in the two curves 310 and 320 can be input to the first and second extended Kalman filters as the previous SOC estimation values ​​in steps S520 and S530.

[0153] In step S540, the control unit 130 determines the current SOC of the battery B based on at least one of the first SOC estimated value and the second SOC estimated value.

[0154] 6 is a flowchart illustrating a battery management method for estimating SOC according to a second embodiment of the present invention. The method of FIG. 6 may be an example of a subroutine set of step S540 of the battery management method according to FIG.

[0155] Referring to FIG. 6, in step S610, the control unit 130 determines whether battery B is being charged or discharged at a constant current based on current time-series data representing a time-dependent change history of the current value (I[k]) or the charge / discharge current. As an example, when the time index k=100, the current time-series data includes I[1] to I

[0100] as data points. If the value of step S610 is "No," this means that battery B is in a first state where it is not being charged or discharged at a constant current. If the value of step S610 is "No," the process proceeds to step S620. If the value of step S610 is "Yes," this means that battery B is in a second state where it is being charged or discharged at a constant current. If the value of step S610 is "Yes," the process proceeds to step S630.

[0156] In step S620, control unit 130 determines the current SOC of battery B in the same manner as the first SOC estimate.

[0157] In step S630, control unit 130 determines the current SOC of battery B in the same manner as the second SOC estimate.

[0158] Fig. 7 is a flowchart illustrating a battery management method for estimating SOC according to a third embodiment of the present invention, and Fig. 8 is a diagram referred to for explaining the method according to Fig. 7. The method of Fig. 7 may be another example of the subroutine set of step S540 of the battery management method according to Fig. 5. That is, the third embodiment is a modified example of the second embodiment.

[0159] 7, in step S710, control unit 130 determines whether battery B is being charged or discharged at a constant current based on current time-series data that represents the history of changes over time in the current value (I[k]) or the charge / discharge current. If the result of step S710 is "No," the process proceeds to step S720. If the result of step S710 is "Yes," the process proceeds to step S730.

[0160] In step S720, the control unit 130 determines a first weight and a second weight that are positively and negatively correlated with the duration of the first state, respectively. The first weight may be greater than the second weight. The sum of the first weight and the second weight may be a predetermined constant (e.g., 1). In this case, once either the first weight or the second weight is determined, the other may also be determined.

[0161] FIG. 8 is a graph illustrating the change in the first weight with respect to the duration of the first state. Referring to FIG. 8, the minimum value of the first weight is 0.6, and the first weight is 0.6 within the time range (0 to t S1 ), the first weight increases as the duration of the first state increases, and the first weight increases as the duration of the first state increases. S1 ), the first weight remains constant at 1.

[0162] In step S722, the control unit 130 determines the current SOC of battery B as a weighted average of the first SOC estimate and the second SOC estimate using the first weight and the second weight. As an example, if the first weight is 0.8, the second weight is 1 minus the first weight, the first SOC estimate is 0.60, and the second SOC estimate is 0.62, then the weighted average is (0.8×0.60)+(0.2×0.62)=0.604. That is, the current SOC of battery B may be determined to be 60.4%.

[0163] In step S730, control unit 130 determines the current SOC of battery B in the same manner as the second SOC estimate.

[0164] Fig. 9 is a flowchart illustrating a battery management method for estimating SOC according to a fourth embodiment of the present invention, and Fig. 10 is a diagram referred to for explaining the method according to Fig. 9. The method of Fig. 9 may be another example of a subroutine set of step S540 of the battery management method according to Fig. 5. That is, the fourth embodiment is a further modification of the second embodiment.

[0165] 9, in step S910, control unit 130 determines whether battery B is being charged or discharged at a constant current based on current time-series data that indicates a history of changes over time in the current value or the charge / discharge current. If the result of step S910 is "No," the process proceeds to step S920. If the result of step S910 is "Yes," the process proceeds to step S930.

[0166] In step S920, control unit 130 determines the current SOC of battery B in the same manner as the first SOC estimate.

[0167] In step S930, the control unit 130 determines a third weight and a fourth weight that are negatively and positively correlated with the duration of the second state, respectively. The third weight may be smaller than the fourth weight. The sum of the third weight and the fourth weight may be a predetermined constant (e.g., 1). In this case, once either the third weight or the fourth weight is determined, the other may also be determined.

[0168] FIG. 10 is a graph illustrating the change in the third weight with respect to the duration of the second state. Referring to FIG. 10, the maximum value of the third weight is 0.4, and the change in the third weight with respect to the duration of the second state is 0.4. S2 ), the third weight decreases as the duration of the second state increases, and the duration of the second state decreases as the second reference time (t S2 ), the third weight remains constant at 0.

[0169] In step S932, the control unit 130 determines the current SOC of battery B as a weighted average of the first SOC estimate and the second SOC estimate using the third and fourth weights. As an example, if the third weight = 0.1, the fourth weight = 1 - the third weight = 0.9, the first SOC estimate = 0.60, and the second SOC estimate = 0.62, the weighted average = (0.1 x 0.60) + (0.9 x 0.62) = 0.618. That is, the current SOC of battery B may be determined to be 61.8%.

[0170] Fig. 11 is a flowchart illustrating a battery management method for estimating SOC according to a fifth embodiment of the present invention. The method of Fig. 11 may be another example of the subroutine set of step S540 of the battery management method according to Fig. 5. That is, the fifth embodiment is a further modification of the second embodiment.

[0171] 11, in step S1110, control unit 130 determines whether battery B is being charged or discharged at a constant current based on current time-series data that indicates a history of changes over time in the current value or the charge / discharge current. If the result of step S1110 is "No," the process proceeds to step S1120. If the result of step S1110 is "Yes," the process proceeds to step S1130.

[0172] In step S1120, the control unit 130 determines a first weight and a second weight that are positively and negatively correlated, respectively, with the duration of the first state.

[0173] In step S1122, control unit 130 determines the current SOC of battery B as a weighted average of the first SOC estimate and the second SOC estimate using the first weight and the second weight.

[0174] Steps S1120 and S1122 are equivalent to steps S720 and S722 in FIG.

[0175] In step S1130, control unit 130 determines a third weight and a fourth weight that are negatively and positively correlated with the duration of the second state, respectively.

[0176] In step S1132, control unit 130 determines the current SOC of battery B as a weighted average of the first SOC estimate and the second SOC estimate using the third weight and the fourth weight.

[0177] Steps S1130 and S1132 are equivalent to steps S930 and S932 in FIG.

[0178] 12 is a flowchart illustrating a method for determining whether a battery is being charged or discharged at a constant current. The method in FIG. 12 may be a subroutine set of at least one of step S610 in FIG. 6, step S710 in FIG. 7, step S910 in FIG. 9, and step S1110 in FIG. 11.

[0179] In step S1210, the control unit 130 filters the current time-series data using a high-pass filter (HPF). The high-pass filter is a filter that removes signal components below a predetermined cutoff frequency and passes only signal components above the cutoff frequency. If battery B is in the second state or in a resting state, the output value of the high-pass filter is 0; otherwise, the output value of the high-pass filter may be other than 0. The smaller the fluctuations in the current flowing through battery B, the closer the output value of the high-pass filter is to 0.

[0180] In step S1220, control unit 130 determines whether the output value of the high-pass filter is within a reference range (for example, −0.001 to 0.001). If the value of step S1220 is “Yes,” control can proceed to step S1230. The reference range can be appropriately determined in advance, taking into consideration the filtering accuracy of the high-pass filter and the detection accuracy of current detection unit 113. If the value of step S1220 is “No,” control proceeds to one of step S620 in FIG. 6, step S720 in FIG. 7, step S920 in FIG. 9, and step S1120 in FIG. 11.

[0181] In step S1230, control unit 130 determines whether the current value is 0 [A]. If the value of step S1230 is "YES", the process proceeds to one of step S620 in Fig. 6, step S720 in Fig. 7, step S920 in Fig. 9, and step S1120 in Fig. 11. If the value of step S1230 is "NO", the process proceeds to one of step S630 in Fig. 6, step S730 in Fig. 7, step S930 in Fig. 9, and step S1130 in Fig. 11.

[0182] Meanwhile, step S610 in Fig. 6, step S710 in Fig. 7, step S910 in Fig. 9, and step S1110 in Fig. 11 have been described as subroutines of step S540, but this should be understood as one example. For example, at least one of step S610 in Fig. 6, step S710 in Fig. 7, step S910 in Fig. 9, and step S1110 in Fig. 11 can be performed using the current value determined in step S510 before performing step S520 or step S530 in Fig. 5.

[0183] The above-described embodiments of the present invention can be realized not only by an apparatus and a method, but also by 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. Such realization can be easily carried out by an expert in the technical field to which the present invention pertains based on the description of the above-described embodiments.

[0184] Although the present invention has been described above using limited embodiments and drawings, it goes without saying that the present invention is not limited thereto, and that various modifications and variations can be made by a person having ordinary knowledge in the technical field to which the present invention pertains within the technical spirit of the present invention and the equivalent scope of the claims set forth below.

[0185] Furthermore, the present invention described above is not limited to the above-described embodiments and accompanying drawings, and various substitutions, modifications, and alterations can be made by a person having ordinary knowledge in the technical field to which the present invention pertains, without departing from the technical spirit of the present invention. Instead, the present invention can be configured by selectively combining all or part of each embodiment to allow for various modifications.

Claims

1. 1. A battery management system for a battery, comprising: a sensing unit configured to detect a terminal voltage and a charge / discharge current of the battery; a memory unit configured to store a first Kalman filter, which is an SOC estimation logic using an equivalent circuit model of the battery and an SOC (State Of Charge)-OCV (Open Circuit Voltage) curve, and a second Kalman filter, which is an SOC estimation logic using a constant current charge / discharge map of the battery; a control unit configured to determine a voltage value of the detected terminal voltage and a current value of the detected charging / discharging current; The control unit determining a first SOC estimation value by inputting the voltage value, the current value, and a previous SOC estimation value into the first Kalman filter; determining a second SOC estimate by inputting the current value and the previous SOC estimate into the second Kalman filter; a battery management system configured to determine a current SOC of the battery based on at least one of the first SOC estimate and the second SOC estimate.

2. The control unit determining whether the battery is in a first state in which the battery is not being charged or discharged at a constant current, or a second state in which the battery is being charged or discharged at a constant current, based on current time-series data that represents a time-dependent change history of the current value or the charge / discharge current; In response to determining that the battery is in the first state, determining a current SOC of the battery as well as the first SOC estimate; The battery management system of claim 1 , configured to determine a current SOC of the battery as well as the second SOC estimate in response to determining that the battery is in the second state.

3. The control unit determining whether the battery is in a first state in which the battery is not being charged or discharged at a constant current, or a second state in which the battery is being charged or discharged at a constant current, based on current time-series data that represents a time-dependent change history of the current value or the charge / discharge current; In response to determining that the first state is present, determining a first weight that is positively correlated with the duration of the first state and a second weight that is negatively correlated with the duration of the first state; The battery management system according to claim 1 , configured to determine the current SOC of the battery as a weighted average of the first SOC estimate and the second SOC estimate using the first weight and the second weight.

4. the first weight is greater than the second weight; The battery management system of claim 3 , wherein the sum of the first weight and the second weight is one.

5. The control unit determining whether the battery is in a first state in which the battery is not being charged or discharged at a constant current, or a second state in which the battery is being charged or discharged at a constant current, based on current time-series data that represents a time-dependent change history of the current value or the charge / discharge current; In response to determining that the second state is present, determining a third weight negatively correlated with the duration of the second state and a fourth weight positively correlated with the duration of the second state; 2. The battery management system according to claim 1, configured to determine a weighted average of the first SOC estimate value and the second SOC estimate value using the third weight and the fourth weight as the current SOC of the battery.

6. the third weight is less than the fourth weight; The battery management system of claim 5 , wherein the sum of the third weight and the fourth weight is one.

7. The constant current charge / discharge map is a plurality of charging curves showing the relationship between the SOC and the voltage of the battery during constant current charging using a plurality of current rates; a plurality of discharge curves representing the relationship between the SOC and the voltage of the battery during constant current discharge using a plurality of the current rates; Including, The second SOC estimate is The battery management system according to claim 1 , wherein the second Kalman filter outputs one of the plurality of charge curves and the plurality of discharge curves when the second Kalman filter is provided with the one of the plurality of charge curves and the plurality of discharge curves.

8. The control unit In response to the battery being charged with a constant current, providing the second Kalman filter with any one of the plurality of charging curves associated with a current rate corresponding to the current value; 8. The battery management system of claim 7, configured to provide the second Kalman filter with any one of the plurality of discharge curves associated with a current rate corresponding to the current value in response to the battery being constantly discharged.

9. A battery pack comprising the battery management system according to any one of claims 1 to 8.

10. An electric vehicle comprising the battery pack of claim 9.

11. 1. A battery management method for a battery, comprising: detecting a terminal voltage and a charge / discharge current of the battery, and determining a voltage value of the detected terminal voltage and a current value of the detected charge / discharge current; determining a first estimated SOC value by inputting the voltage value, the current value, and a previous estimated SOC value into a first Kalman filter, which is an SOC estimation logic that uses an equivalent circuit model of the battery and an SOC (State Of Charge)-OCV (Open Circuit Voltage) curve; determining a second estimated SOC value by inputting the current value and the previous estimated SOC value into a second Kalman filter, which is an SOC estimation logic that uses a constant current charge / discharge map of the battery; determining a current SOC of the battery based on at least one of the first SOC estimate and the second SOC estimate; a battery management method,

12. The step of determining the current SOC of the battery includes: determining whether the battery is in a first state in which the battery is not being charged or discharged at a constant current, or a second state in which the battery is being charged or discharged at a constant current, based on current time-series data representing a time-varying history of the current value or the charge / discharge current; In response to determining that the battery is in the first state, determining the first estimated SOC value as a current SOC of the battery; In response to determining that the battery is in the second state, determining the second estimated SOC value as a current SOC of the battery; The battery management method of claim 11 , comprising:

13. The step of determining the current SOC of the battery includes: determining whether the battery is in a first state in which the battery is not being charged or discharged at a constant current, or a second state in which the battery is being charged or discharged at a constant current, based on current time-series data representing a time-varying history of the current value or the charge / discharge current; determining, in response to determining the first state, a first weight that is positively correlated with the duration of the first state and a second weight that is negatively correlated with the duration of the first state; determining a weighted average of the first SOC estimate value and the second SOC estimate value using the first weight and the second weight as a current SOC of the battery; The battery management method of claim 11 , comprising:

14. The step of determining the current SOC of the battery includes: determining whether the battery is in a first state in which the battery is not being charged or discharged at a constant current, or a second state in which the battery is being charged or discharged at a constant current, based on current time-series data representing a time-varying history of the current value or the charge / discharge current; determining, in response to determining that the second state is present, a third weight negatively correlated with the duration of the second state and a fourth weight positively correlated with the duration of the second state; determining a weighted average of the first SOC estimate value and the second SOC estimate value using the third weight and the fourth weight as a current SOC of the battery; The battery management method of claim 11 , comprising:

15. The constant current charge / discharge map is a plurality of charging curves showing the relationship between the SOC and the voltage of the battery during constant current charging using a plurality of current rates; a plurality of discharge curves representing the relationship between the SOC and the voltage of the battery during constant current discharge using a plurality of the current rates; Including, The second SOC estimate is The battery management method according to claim 11, wherein the curve is output from the second Kalman filter when any one of the plurality of charge curves and the plurality of discharge curves is provided to the second Kalman filter.

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