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

Abstract

A battery management system according to the present disclosure includes a current sensor that measures a battery current as a current flowing through the battery, a voltage sensor that measures a battery voltage as a voltage across the battery, and a control circuit. When the control circuit receives an on signal during a first rest period of the battery, the control circuit determines a fixed rest time, a fixed open circuit voltage (OCV), and a fixed state of charge (SOC), and determines an integrated current value of the battery current during a cycle period of the battery. When the control circuit receives an off signal during the cycle period, the control circuit starts a second rest period of the battery. The control circuit determines an interested SOC corresponding to an interested OCV as the battery voltage during the second rest period. The control circuit determines a state of health (SOH) of the battery based on the fixed SOC, the integrated current value, and the interested SOC.

Description

Technical Field

[0001] The present disclosure relates to a technique for determining a state of health (SOH) of a battery during a battery rest period.

[0002] This application claims the benefit of Korean Patent Application No. 10-2019-0164891, filed with the Korean Intellectual Property Office on Dec. 11, 2019, the disclosure of which is incorporated herein by reference in its entirety. Background Art

[0003] Recently, the demand for portable electronic products such as laptop computers, cameras, and mobile phones has rapidly increased, and with the widespread development of electric vehicles, energy storage accumulators for energy storage, robots, and satellites, much research is being conducted on high-performance batteries that can be repeatedly recharged.

[0004] Currently, commercially available batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium batteries, etc., and among them, lithium batteries have little or no memory effect, and thus are receiving more attention than nickel-based batteries due to their advantages of being rechargeable whenever convenient, having a very low self-discharge rate, and a high energy density.

[0005] A battery repeatedly undergoes a cycle period in a cycling state and a rest period in a rest state. The cycling state refers to a state in which charging / discharging of the battery is being performed. The rest state refers to a state in which charging / discharging of the battery is interrupted (stopped) - that is, no battery current flows.

[0006] To determine the state of health (SOH) of a battery, the state of charge of the battery (hereinafter referred to as "SOC") is required. In a cycling state, battery current-based methods such as current integration (referred to as "ampere counting") or a Kalman filter are useful in determining the SOC of the battery.

[0007] Conversely, in a rest state in which no battery current flows, it is more desirable to determine the SOC of the battery based on an OCV-SOC curve based on data defining the relationship between the open circuit voltage (hereinafter referred to as "OCV") and the SOC of the battery rather than ampere counting or a Kalman filter.

[0008] Before enough time has elapsed since the battery transitions from a cycling state to a rest state, the SOC of the battery is constant, while the voltage across the battery is not maintained constantly due to hysteresis generated by the cycling history in the cycling state.

[0009] However, since the OCV-SOC curve has no hysteresis of the battery at all, conventional techniques use the OCV-SOC curve to determine the SOC of the battery after a predetermined time (e.g., 2 hours) required to stabilize the battery since the battery has transitioned from the cycling state to the resting state has elapsed. Therefore, the SOC of the battery cannot be determined based on the OCV-SOC curve, or its accuracy is low, before the predetermined time has elapsed since the transition from the cycling state to the resting state.

[0010] Additionally, the battery voltage and the battery current corresponding to the information necessary to determine the SOC of the battery are measured by a voltage sensor and a current sensor, respectively. However, due to offset errors (corresponding to the difference between the actual value and the measured value), each of the voltage sensor and the current sensor may have low SOC accuracy. In particular, the offset error of the current sensor accumulates over time. Summary of the Invention

[0011] Technical Problem

[0012] The present disclosure aims to accurately determine the state of health (SOH) of a battery in a resting state by determining the change in the state of charge (SOC) from the end time of the cycling period of the previous cycle at predetermined time intervals while the battery remains in the resting state based on the period of time the battery has remained in the resting state.

[0013] Additionally, the present disclosure further aims to determine, while the battery is in the resting state, the weights for eliminating the error components of the SOH determined at predetermined time intervals while the battery is in the resting state, based on the cycling history (such as cycling time, integrated current value) in the cycling period of the previous cycle, the resting time of each of the resting periods of the previous cycle and the current cycle, the offset error of the voltage sensor, and the offset error of the current sensor.

[0014] These and other objects and advantages of the present disclosure will be understood from the following description and will be apparent from the embodiments of the present disclosure. Additionally, it will be readily understood that the objects and advantages of the present disclosure can be achieved by the means set forth in the appended claims and their combinations.

[0015] Technical Solution

[0016] A battery management system according to an aspect of the present disclosure includes: a current sensor configured to measure a battery current indicative of a current flowing through a battery; a voltage sensor configured to measure a battery voltage indicative of a voltage across the battery; and a control circuit coupled to the voltage sensor and the current sensor. When the control circuit receives a key-on signal at a first time point during a first rest period of the battery, the control circuit is configured to determine a fixed open-circuit voltage (OCV) that is the battery voltage at the first time point, and a fixed state of charge (SOC) that is the SOC of the battery at the first time point, and start a cycling period of the battery. The control circuit is configured to determine an integrated current value of the battery current during the cycling period. When the control circuit receives a key-off signal at a second time point during the cycling period, the control circuit is configured to start a second rest period of the battery. The control circuit is configured to determine an SOC of interest, which is the SOC of the battery corresponding to an OCV of interest that is the battery voltage during the second rest period. The control circuit is configured to determine a state of health (SOH) of the battery based on the fixed SOC, the integrated current value, and the SOC of interest.

[0017] The control circuit may further be configured to: determine a fixed rest time that is a time period from a start time of the first rest period to the first time point, a cycling time that is a time period from a start time of the cycling period to the second time point, and an interest rest time that is a length of time elapsed from a start time of the second rest period.

[0018] The control circuit may be configured to determine a first error factor based on the cycling time, the integrated current value, and a current offset error. The current offset error indicates an offset error of the current sensor. The control circuit may be configured to determine a second error factor and a third error factor based on the fixed OCV, the fixed SOC, the OCV of interest, the SOC of interest, and a voltage offset error. The voltage offset error indicates an offset error of the voltage sensor. The control circuit may be configured to determine a fourth error factor based on the fixed rest time. The control circuit may be configured to determine a fifth error factor based on the interest rest time. The control circuit may be configured to determine a representative error factor based on the first to fifth error factors. The control circuit may be configured to determine a weight indicative of the reliability of the SOH based on the representative error factor.

[0019] The control circuit may be configured to: determine the first error factor as a value equal to a result of dividing a product of the cycling time and the current offset error by the integrated current value.

[0020] The control circuit can be configured to determine a SOC change indicative of a difference between a fixed SOC and an SOC of interest. The control circuit can be configured to determine a first corrected OCV by adding a voltage offset error to a fixed OCV or subtracting the voltage offset error from the fixed OCV. The control circuit can be configured to determine a first corrected SOC corresponding to the first corrected OCV from a predetermined OCV curve. The OCV curve can define the association between the OCV and the SOC when the hysteresis of the battery is 0. The control circuit can be configured to determine a second error factor as a value equal to the result of dividing the difference between the fixed SOC and the first corrected SOC by the SOC change.

[0021] The control circuit can be configured to: determine a second corrected OCV by adding the voltage offset error to an OCV of interest or subtracting the voltage offset error from the OCV of interest. The control circuit can be configured to determine a second corrected SOC corresponding to the second corrected OCV from the OCV curve. The control circuit can be configured to determine a third error factor as a value equal to the result of dividing the difference between the SOC of interest and the second corrected SOC by the SOC change.

[0022] The control circuit can be configured to determine a fourth error factor as a value equal to a first error value corresponding to a fixed rest time according to a first error curve. The first error curve is data defining the association between the rest time and the error value for a first reference SOC that is the SOC of the battery at the start time of a first rest period.

[0023] The control circuit can be configured to determine a fifth error factor as a value equal to a second error value corresponding to an interest rest time according to a second error curve. The second error curve is data defining the association between the rest time and the error value for a second reference SOC that is the SOC of the battery at the start time of a second rest period.

[0024] The control circuit can be configured to determine a weight using the following equation:

[0025] <Equation>

[0026]

[0027] where W SOH represents the weight, M represents a predetermined first conversion constant greater than 1, K represents a predetermined second conversion constant greater than 0, and F SOH represents a representative error factor.

[0028] The control circuit can be configured to determine an effective SOH as a weighted average of a predetermined number of SOHs based on a predetermined number of SOHs and a predetermined number of weights in a most recently determined order during a second rest period.

[0029] A battery pack according to another aspect of the present disclosure includes the battery management system.

[0030] An electric vehicle according to yet another aspect of the present disclosure includes the battery pack.

[0031] A battery management method according to still another aspect of the present disclosure can be executed by the battery management system.

[0032] Advantageous effects

[0033] According to at least one of the embodiments of the present disclosure, it is possible to accurately determine the state of health (SOH) of a battery in a resting state by determining the change in the state of charge (SOC) of the end time of the cycle period from the previous cycle at a predetermined time interval based on the period during which the battery remains in a resting state when the battery is in a resting state.

[0034] In addition, according to at least one of the embodiments of the present disclosure, it is possible to determine, when the battery is in a resting state, the weight for eliminating the error component of the SOH determined at a predetermined time interval based on each of the cycle history (such as cycle time, integrated current value) in the cycle period of the previous cycle, the resting time in the resting period of the previous cycle, the resting time in the resting period of the current cycle, the offset error of the voltage sensor, and the offset error of the current sensor.

[0035] The effects of the present disclosure are not limited to the effects mentioned above, and those skilled in the art will clearly understand these and other effects from the appended claims. Brief Description of the Drawings

[0036] The drawings illustrate preferred embodiments of the present disclosure and, together with the detailed description of the present disclosure described below, are used to provide a further understanding of the technical aspects of the present disclosure. Therefore, the present disclosure should not be construed as being limited to the drawings.

[0037] Figure 1 is a diagram exemplarily showing the configuration of an electric vehicle according to the present disclosure.

[0038] Figure 2 is a diagram exemplarily showing an open circuit voltage - state of charge (OCV - SOC) curve.

[0039] Figure 3 is a diagram exemplarily showing Figure 1 the change in the SOC of a battery over the cycle period and the resting period of the battery.

[0040] Figure 4 is a diagram exemplarily showing Figure 1 the change in the integrated current value caused by the offset error of the current sensor during the cycle period of the battery.

[0041] Figure 5 Exemplarily shows the change in battery voltage when the Figure 1 battery is switched to the rest state during charging.

[0042] Figure 6 Exemplarily shows the change in battery voltage when the Figure 1 battery is switched to the rest state during discharging.

[0043] Figure 7 Is a diagram exemplarily showing the correlation between the rest time and the error value.

[0044] Figures 8 to 11 Is a flowchart of each of the battery management methods using the Figure 1 battery management system. Detailed Description of the Invention

[0045] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms or words used in the specification and the appended claims should not be construed as being limited to the general and dictionary meanings, but should be interpreted based on the meanings and concepts corresponding to the technical aspects of the present disclosure on the basis of the principle that allows the inventor to appropriately define the terms for the best explanation.

[0046] Terms including ordinal numbers such as "first", "second", etc. are used to distinguish one element from another among various elements, and are not intended to limit the elements by the terms.

[0047] Unless otherwise clearly indicated by the context, it will be understood that when used in this specification, the term "comprises" specifies the presence of the stated elements, but does not exclude the presence or addition of one or more other elements. Additionally, as used herein, the term "control unit" refers to a processing unit of at least one function or operation, and can be implemented by hardware and software either alone or in combination.

[0048] Furthermore, throughout this specification, it will be further understood that when an element is referred to as being "connected to" another element, it can be directly connected to the other element or there can be intervening elements.

[0049] Figure 1 Is a diagram exemplarily showing the configuration of an electric vehicle according to the present disclosure.

[0050] Referring to Figure 1 , the electric vehicle 1 includes a vehicle controller 2, a battery pack 20, a switch 30, an inverter 40, and a motor 50.

[0051] The vehicle controller 2 is configured to generate an ON signal in response to a user turning an engine start button (not shown) provided in the electric vehicle 1 to the ON position. The vehicle controller 2 is configured to generate an OFF signal in response to the user turning the engine start button to the OFF position.

[0052] The switch 30 is provided on the power line 3 for charging and discharging the battery pack 20. That is, the switch 30 is connected in series to the battery B via the power line 3. When the switch 30 is in the ON state, power can be transferred from either the battery pack 20 or the inverter 40 to the other. The switch 30 can include any one of well-known switching devices such as a relay and a field effect transistor (FET) or a combination thereof.

[0053] The inverter 40 converts the DC power supplied from the battery B into AC power and supplies it to the motor 50. The motor 50 converts the AC power from the inverter 40 into kinetic energy for the electric vehicle 1.

[0054] The battery pack 20 includes the battery B and the battery management system 100.

[0055] The battery B includes at least one battery cell. The battery cell is not limited to a specific type and includes any type of rechargeable battery or cell, such as a lithium-ion cell.

[0056] The battery management system 100 includes a voltage sensor 110, a current sensor 120, a memory 140, and a control circuit 150. The battery management system 100 may further include at least one of a temperature sensor 130 or a communication circuit 160.

[0057] The voltage sensor 110 is arranged to be electrically connected to the positive and negative terminals of the battery B. The voltage sensor 110 is configured to measure the voltage across the battery B (hereinafter referred to as "battery voltage") at a predetermined time interval and output a signal indicating the measured battery voltage to the control circuit 150.

[0058] The current sensor 120 is provided on the power line 3 and is connected in series to the battery B via the power line 3. For example, the current sensor 120 may include a shunt resistor or a Hall effect device. The current sensor 120 is configured to measure the current flowing through the power line 3 (hereinafter referred to as "battery current") at a predetermined time interval and output a signal indicating the measured battery current to the control circuit 150. The battery current measured during the discharge of the battery B may be referred to as "discharge current", and the battery current measured during the charging of the battery B may be referred to as "charging current".

[0059] The temperature sensor 130 is located at a predetermined distance from the battery B. For example, a thermocouple can be used as the temperature sensor 130. The temperature sensor 130 is configured to measure the temperature of the battery B (hereinafter referred to as "battery temperature") at a predetermined time interval and output a signal indicating the measured battery temperature to the control circuit 150.

[0060] The memory 140 is configured to store programs and data necessary for performing the battery management method according to an embodiment as described below. The memory 140 may include at least one type of storage medium such as a flash type, a hard disk type, a solid state disk (SSD) type, a silicon disk drive (SDD) type, a multimedia card micro 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).

[0061] The control circuit 150 is operatively coupled to the vehicle controller 2, the switch 30, the voltage sensor 110, the temperature sensor 130, the current sensor 120, the memory 140, and the communication circuit 160. "Operatively coupled" means a connection that enables one-way or two-way signal transmission and reception. The control circuit 150 may be implemented in hardware using at least one of an application specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field programmable gate array (FPGA), a microprocessor, or an electrical unit for performing other functions.

[0062] The communication circuit 160 may be coupled to the vehicle controller 2 to enable communication therebetween. The communication circuit 160 may transmit a message from the vehicle controller 2 to the control circuit 150 and transmit a message from the control circuit 150 to the vehicle controller 2. Communication between the communication circuit 160 and the vehicle controller 2 may use, for example, a wired network such as a local area network (LAN), a controller area network (CAN), and a daisy chain, and / or a short-range wireless network such as Bluetooth, Zigbee, and WiFi.

[0063] The control circuit 150 may determine the SOC of the battery B based on the battery voltage, the battery current, and / or the battery temperature. Determination of the SOC during cycling of the battery B may use well-known methods such as ampere counting and Kalman filters. Determination of the SOC of the resting battery B will be described in detail below.

[0064] Figure 2 is a diagram exemplarily showing an OCV-SOC curve, Figure 3 is exemplarily shown over the cycling period and the resting period of the battery Figure 1Graph of the change in the SOC of the battery, Figure 4 exemplarily shows the change in the integrated current value caused by the offset error of the current sensor during the cycling period of the battery in Figure 1 Graph of the change in the integrated current value caused by the offset error of the current sensor during the cycling period of the battery, Figure 5 exemplarily shows the change in the battery voltage when the battery in Figure 1 is switched to the rest state during charging, Figure 6 exemplarily shows the change in the battery voltage when the battery in Figure 1 is switched to the rest state during discharging, and Figure 7 exemplarily shows the graph of the correlation between the rest time and the error value.

[0065] Referring to Figure 2 , the OCV-SOC curve 200 is a data set that defines the correlation between OCV and SOC without any hysteresis of battery B. For example, the OCV-SOC curve 200 can be data pre-acquired from the results of the following discharge test: the discharge test is performed by maintaining a constant current discharge for the first test time and a rest for the second test time (e.g., 5 days) from full charge to full discharge of another battery (or multiple batteries) having the same specifications as battery B in an environment where a predetermined reference temperature (e.g., 25 °C) is maintained. The method for determining the OCV-SOC curve is not limited to a specific type. The memory 140 can pre-store multiple OCV-SOC curves corresponding to multiple temperature ranges in a one-to-one relationship.

[0066] Figure 3 shows the time-series change in the SOC of battery B at time point t A0 when it changes from charging to the rest state, at time point t A1 when it changes from the rest state to the discharge state, at time point t B0 when it changes from discharging to the rest state and remains in the rest state until time point t B1 .

[0067] The time period from time point t A0 to time point t A1 is referred to as the "first rest period", the time period from time point t A1 to time point t B0 is referred to as the "cycling period (discharge period in Figure 3 ), and the time period from time point t B0 to time point t B1 is referred to as the "second rest period". The duration of the first rest period t A0 ~t A1 , the first rest time Δt R1 is (t A1 -t A0), cycle period t A1 ~t B0 The duration of, cycle time Δt CD is (t B0 -t A1 ), and the second rest period t B0 ~t B1 The duration of, second rest time Δt R2 is (t B1 -t B0 ). Based on the time point t B1 , the first rest period t A0 ~t A1 has ended, and thus the first rest time Δt R1 is a fixed value. In contrast, based on the time point t B1 , the second rest period t B0 ~t B1 is in progress, and thus the second rest time Δt R2 increases. Therefore, the first rest time Δt R1 is called "fixed rest time" and the second rest time Δt R2 is called "rest time of interest".

[0068] When the control circuit 150 receives a shutdown signal during the charging / discharging of the battery B, the control circuit 150 can determine a reference SOC that is the SOC of the battery B when the shutdown signal is received, and start the rest period of the battery B. The start of the rest period refers to the transition from the cycle to the rest state. For example, in Figure 2 , 3 , 5, and 6, the SOC A0 indicates the reference SOC at the start time t A0 ~t A1 of the first rest period t A0 , and the SOC B0 indicates the reference SOC at the start time t B0 ~t B1 of the second rest period t B0 . The control circuit 150 can determine the reference OCV V A0 corresponding to the reference SOC SOC A0 and the reference OCV V B0 corresponding to the reference SOC SOC B0 from the OCV-SOC curve 200.

[0069] When the control circuit 150 receives a turn-on signal while the battery B is in a rest state, the control circuit 150 can determine a fixed OCV and a fixed SOC respectively indicating the battery voltage and the SOC when receiving the turn-on signal, and start a cycle period of the battery B. The start of the cycle period refers to the transition from the rest state to the cycle state. For example, in Figure 2 V A1 and SOC A1 respectively indicate the fixed OCV and the fixed SOC starting from the end of the first rest period t A0 to t A1 . A1

[0070] The control circuit 150 can determine an OCV of interest as the battery voltage at a predetermined time interval (e.g., 1 min) while the battery B is in a rest state. For example, in Figure 2 and 6 V B1 indicates the OCV of interest at the time point t B1 . The control circuit 150 can determine the SOC of interest SOC B1 corresponding to the OCV of interest V B1 from the OCV-SOC curve 200.

[0071] The control circuit 150 can determine an integrated current value of the battery current at a predetermined time interval during charging / discharging of the battery B. Referring to Figure 4 , the curve 401 indicates the change in the actual battery current during the cycle period t A1 to t B0 . In Figure 2 , since the battery B discharges during the cycle period t A1 to t B0 , Figure 4 shows the actual battery current as a negative value. The curve 402 indicates the result of reflecting the current offset error ΔI OE of the current sensor 120 on the curve 401. For example, when the actual battery current is -10 A and ΔI OE is 0.06 A, the battery current measured by the current sensor 120 is between (-10 - 0.06) A and (-10 + 0.06) A.

[0072] The curve 411 indicates the change in the integrated current value based on the curve 401. The curve 412 indicates the change in the integrated current value based on the curve 402. As shown, when a difference as large as the current offset error ΔI A1 is maintained between the curve 401 and the curve 402 during the cycle period t B0 , at the time point t OE , a difference of ΔQ in magnitude occurs between the curve 411 and the curve 412 at the time point t B0 .​OE = ΔI OE ×Δt CD of the difference.

[0073] Reference Figure 2 and 5 fixing OCV V A1 can be at time point t A1 for the actual battery voltage V A2 the voltage offset error ΔV of the voltage sensor 110 generated in the negative direction OE value. Therefore, at the fixed SOC SOC A1 and SOC A2 a difference of magnitude ΔSOC occurs between OE1 of the difference.

[0074] Reference Figure 2 and 6 the OCV V of interest B1 can be at time point t B1 for the actual battery voltage V B2 the voltage offset error ΔV generated in the positive direction OE value. Therefore, between the SOC of interest SOC B1 and SOC B2 a difference of magnitude ΔSOC can occur between OE2 of the difference.

[0075] In Figure 7 the curve 701 indicates the association between the rest time and the error value for the reference SOC SOC pre-stored in the memory 140 A0 The curve 701 can be data pre-acquired from the results of the following rest test: The rest test is performed by monitoring the rest time and the battery voltage after transitioning to the rest state following a constant current discharge from 100% SOC to the reference SOC SOC A0 in an environment where a predetermined reference temperature (e.g., 25°C) is maintained, with another battery (or multiple batteries) having the same specifications as the battery B.

[0076] Reference Figure 2 , 5 and 7, as Δt R1 is longer, V A1 gets closer to V A0 , and thus as the difference between SOC A0 and SOC A1 the absolute value of ΔSOC as the difference between RT1 is smaller. The control circuit 150 can determine from the curve 701 the value corresponding to Δt R1Error value E R1 The error value E R1 can be represented by the following Equation 1.

[0077] <Equation 1>

[0078]

[0079] In Equation 1, V test_int1 is the battery voltage measured for the first time after the start of the rest state through the rest test, and V test_R1 is the battery voltage measured through the rest test when the rest state is maintained over Δt R1 .

[0080] Curve 702 indicates the association between the rest time and the error value for the reference SOC SOC B0 stored in the memory 140. Curve 702 can be data pre-acquired from the results of the following rest test: the rest test is performed by monitoring the rest time and the battery voltage after transitioning to the rest state following a constant current discharge of another battery (or multiple batteries) having the same specifications as the battery B from 100% SOC until the reference SOC SOC B0 in an environment where a predetermined reference temperature (e.g., 25 °C) is maintained.

[0081] Reference Figure 2 、 5 and 6, as Δt R2 becomes longer, V B1 gets closer to V B0 , and thus the absolute value of ΔSOC B0 as the difference between SOC B1 and SOC RT2 becomes smaller. The control circuit 150 can determine the error value E R2 corresponding to Δt R2 . The error value E R2 can be represented by the following Equation 2.

[0082] <Equation 2>

[0083]

[0084] In Equation 2, V test_int2 is the battery voltage measured for the first time after the start of the rest state through the rest test, and V test_R2 is the battery voltage measured through the rest test when the rest state is maintained over Δt R2 .

[0085] Alternatively, the memory cell 140 may store Equation 1 to replace Curve 701 and store Equation 2 to replace Curve 702. In this case, the control circuit 150 may determine the error value E A1 by substituting V test_R1 for V R1 in Equation 1, and determine the error value E B1 by substituting V test_R2 for V R2 .

[0086] Figures 8 to 11 is a flowchart of each of the battery management methods of the battery management system using Figure 1 . The control circuit 150 may execute the method of Figure 8 in response to receiving an ON signal from the vehicle controller when the battery B is in a rest state. For convenience of description, it is described based on the time period from the time point t Figure 3 shown in A0 to the time point t B0 .

[0087] Refer to Figure 1 , 2 to 6 and 8. In step S810, the control circuit 150 determines a fixed rest time Δt R1 , a fixed OCVV A1 and a fixed SOC SOC A1 .

[0088] In step S820, the control circuit 150 changes the battery B from the rest state to the cycling state. That is, the cycling period t A1 ~t B0 starts.

[0089] In step S830, the control circuit 150 determines the integrated current value of the battery current. The integrated current value is the value obtained by summing the battery currents measured by the current sensor 120 at a predetermined time interval (for example, 0.1 sec) from the start time of the cycling period t A1 ~t B0 , and its unit is ampere-hour (Ah).

[0090] In step S840, the control circuit 150 determines whether a turn-off signal is received from the vehicle controller 2. Step S830 may be repeated at a predetermined time interval (for example, 0.1 sec) until a turn-off signal is received.

[0091] When a turn-off signal is received while the method of Figure 8 is being executed,[[]] Figure 8 the method of Figure 9 may end and the method of B0Describe the time period.

[0092] Reference Figure 1 、 2 Refer to FIGS. 6 and 9. In step S910, the control circuit 150 determines the cycle time Δt CD and the reference SOC SOC B0 .

[0093] In step S920, the control circuit 150 changes the battery B from the cycling state to the rest state. That is, the second rest period t B0 ~t B1 starts.

[0094] In step S930, the control circuit 150 determines the rest time of interest Δt R2 、the open circuit voltage of interest V B1 and the state of charge of interest SOC B1 .

[0095] In step S940, the control circuit 150 determines the SOH of the battery B. The SOH is information of the battery B associated with the ratio of the current maximum capacity to a predetermined reference capacity indicated in the range of 0 to 1 or 0 to 100%. The reference capacity refers to the maximum amount of charge that can be stored in the original battery B (i.e., at the start of life). The control circuit 150 can determine the SOH using Equation 3 below.

[0096] <Equation 3>

[0097]

[0098] In Equation 3, SOH R2 represents the SOH when the rest time of interest Δt B0 ~t B1 has elapsed since the start of the second rest period, Q R2 represents the reference capacity, ΔQ int represents the last determined integrated current value before the end of CD , and ΔSOC Figure 8 represents the change in SOC indicating the change between the fixed SOC SOC CD and the state of charge of interest SOC A1 and SOC of interest B1 . The SOH determined in step S940 can be referred to as the "temporary SOH".

[0099] In step S950, the control circuit 150 determines the representative error factor. The representative error factor indicates the inaccuracy of the SOH determined in step S940. The representative error factor corresponds to the difference between the actual SOH and the SOH determined in step S940. The following will refer toFigure 10 Describe in detail the determination of the representative error factor.

[0100] In step S960, the control circuit 150 determines a weight based on the representative error factor. The weight indicates the reliability of the SOH determined in step S940. As the representative error factor is larger, the reliability of the SOH determined in step S940 is lower. Therefore, the representative error factor and the weight have a relationship where when one of the two items decreases, the other increases. For example, the control circuit 150 can determine the weight using the following Equation 4.

[0101] <Equation 4>

[0102]

[0103] In Equation 4, W SOH represents the weight, M represents a predetermined first conversion constant greater than 1 (e.g., the Euler number e), K represents a predetermined second conversion constant greater than 0 (e.g., 0.8), and F SOH represents the representative error factor.

[0104] The values determined by steps S930 to S960 can be sequentially stored in a predetermined number of buffers in the memory cell 140 according to the first-in, first-out method. The buffer is an information storage area.

[0105] In step S970, the control circuit 150 increments the count index by 1. The count index indicates the number of repetitions of steps S930 to S960 during the second rest period t B0 ~t B1 period.

[0106] In step S980, the control circuit 150 determines whether an on signal is received from the vehicle controller. When the on signal is received when the Figure 9 method is executed, Figure 9 the method can end and Figure 8 the method can start. When Figure 9 the method ends, the count index can be reset to 0.

[0107] Steps S930 to S970 can be repeated at a predetermined time interval (e.g., 1 min) until an on signal is received.

[0108] Figure 10 is a flowchart exemplarily showing the sub-steps of step S950.

[0109] Refer to Figure 10 , in step S1010, the control circuit 150 is based on the cycle time Δt CD , the integrated current value ΔQ CD and the current offset error ΔIOE Determine the first error factor. The first error factor can be equal to the result of dividing the product of the cycle time Δt CD and the current offset error ΔI OE by the integrated current value ΔQ CD . The first error factor corresponds to the error component in the SOH determined in step S940 that occurs due to the current offset error ΔI A1 accumulated over the cycle period t B0 ~t OE .

[0110] In step S1020, the control circuit 150 determines a second error factor and a third error factor based on the fixed OCV, fixed SOC, OCV of interest, SOC of interest, and voltage offset error.

[0111] The determination of the second error factor will be described. The control circuit 150 determines a first corrected OCV by adding the voltage offset error ΔV OE to the fixed OCV V A1 or subtracting the voltage offset error ΔV A1 from the fixed OCV V OE . In this case, the first corrected OCV is equal to (V A1 +ΔV OE ) or (V A1 -ΔV OE ). Subsequently, the control circuit 150 determines a first corrected SOC corresponding to the first corrected OCV from the OCV-SOC curve 200. Subsequently, the control circuit 150 can determine the second error factor to be equal to the result of dividing the difference between the fixed SOC SOC A1 and the first corrected SOC by the SOC change ΔSOC CD . The second error factor corresponds to the error component in the SOH determined in step S940 that occurs due to the voltage offset error ΔV A1 at the start time t B0 ~t A1 of the cycle period t OE .

[0112] The determination of the third error factor will be described. The control circuit 150 determines a second corrected OCV by adding the voltage offset error ΔV OE to the OCV of interest V B1 or subtracting the voltage offset error ΔV B1 from the OCV of interest V OE . In this case, the second corrected OCV is equal to (V B1 +ΔV OE ) or (V B1 -ΔV OE)。Subsequently, the control circuit 150 determines a second calibrated SOC corresponding to the second calibrated OCV from the OCV-SOC curve 200. Subsequently, the control circuit 150 may determine a third error factor to be equal to the value obtained by dividing the difference between the SOC of interest SOC B1 and the second calibrated SOC by the SOC change ΔSOC CD . The third error factor corresponds to the error component in the SOH determined in step S940 that occurs at the time point t B0 ~t B1 during the second rest period t B1 due to the voltage offset error ΔV OE .

[0113] In step S1030, the control circuit 150 may determine a fourth error factor based on the fixed rest time Δt R1 . Referring to Figure 7 , the fourth error factor may be equal to the error value E according to Equation 1 R1 . The fourth error factor corresponds to the error component in the SOH determined in step S940 that occurs due to the insufficiently long fixed rest time Δt R1 .

[0114] In step S1040, the control circuit 150 may determine a fifth error factor based on the rest time of interest Δt R2 . Referring to Figure 7 , the fifth error factor may be equal to the error value E according to Equation 2 R2 . The fifth error factor corresponds to the error component in the SOH determined in step S940 that occurs due to the insufficiently long rest time of interest Δt R2 .

[0115] Although Figure 10 steps S1010 to S1040 are shown as being executed in a sequential order, this is provided by way of example and the steps may be executed in a different order.

[0116] The control circuit 150 may determine a representative error factor using Equation 5 below.

[0117] <Equation 5>

[0118]

[0119] In Equation 5, F SOH represents the representative error factor, F i represents the i-th error factor, and w i represents the i-th predetermined weight greater than 0. For example, each of w1, w2, w3, w4, and w5 may be 1.

[0120] Figure 11 The method can start each time step S970 is executed.

[0121] In step S1110, the control circuit 150 determines whether the count index is equal to or greater than a predetermined value N (e.g., 10). That is, the control circuit 150 determines whether at least N SOHs and at least N weights are sequentially stored in the buffer within the memory cell 140. A value of “Yes” in step S1110 indicates that steps S930 to S970 are executed at least N times during the second rest period t B0 ~t B1 period.

[0122] In step S1120, the control circuit 150 obtains N SOHs from the memory cell 140 in the most recently determined order. That is, the control circuit 150 obtains a data set indicating the values of N SOHs starting from the SOH last stored in the memory cell 140.

[0123] In step S1130, the control circuit 150 obtains N weights from the memory cell 140 in the most recently determined order. That is, the control circuit 150 obtains a data set indicating the values of N weights starting from the weight last stored in the memory cell 140.

[0124] In step S1140, the control circuit 150 determines the effective SOH based on the N SOHs and the N weights. The effective SOH can be a weighted average of the N SOHs by the N weights. For example, assume that SOH R2 [1] to SOH R2 [N] are obtained as the N SOHs, and W SOH [1] to W SOH [N] are obtained as the N weights. Then, the control circuit 150 can determine the effective SOH using the following Equation 6.

[0125] <Equation 6>

[0126]

[0127] In Equation 6, SOH eff represents the effective SOH.

[0128] When the effective SOH is equal to or less than a threshold (e.g., 75%), the control circuit 150 can perform a predetermined protection operation. The protection operation can be, for example, the output of an alarm message, the turning off of switch 30, etc. The alarm message can be transmitted to the vehicle controller 2 through the communication circuit 160.

[0129] The embodiments of the present disclosure described above are not implemented only by devices and methods, and can be implemented by a program that executes functions corresponding to the configurations of the embodiments of the present disclosure or a recording medium having the program recorded thereon, and from the disclosure of the embodiments described above, those skilled in the art can easily implement such an implementation manner.

[0130] Although the present disclosure has been described above with respect to a limited number of embodiments and drawings, the present disclosure is not limited thereto, and it is obvious to those skilled in the art that various modifications and changes can be made within the technical scope of the present disclosure and the equivalent scope of the appended claims.

[0131] Additionally, since those skilled in the art can make many substitutions, modifications, and changes to the present disclosure described above without departing from the technical scope of the present disclosure, the present disclosure is not limited by the embodiments and drawings described above, and some or all of the embodiments can be selectively combined to allow various modifications.

Claims

1. A battery management system, comprising: a current sensor configured to measure a battery current indicative of a current flowing through the battery; a voltage sensor configured to measure a battery voltage indicative of a voltage across the battery; and a control circuit coupled to the voltage sensor and the current sensor, wherein the control circuit is configured to: when a turn-on signal is received at a first time point during a first rest period of the battery, determine a fixed open circuit voltage (OCV) that is the battery voltage at the first time point during the first rest period of the battery, and a fixed state of charge (SOC) that is the SOC of the battery at the first time point, and start a cycling period of the battery, determine an integrated current value of the battery current during the cycling period, when a turn-off signal is received at a second time point during the cycling period, start a second rest period of the battery, determine a fixed rest time that is a time period from a start time of the first rest period to the first time point, a cycling time that is a time period from a start time of the cycling period to the second time point, and an interested rest time that is a length of time elapsed from a start time of the second rest period, determine an interested SOC that is the SOC of the battery corresponding to an interested OCV that is the battery voltage during the second rest period, and determine a state of health (SOH) of the battery based on the fixed SOC, the integrated current value, and the interested SOC, wherein the control circuit is further configured to: determine a first error factor based on the cycling time, the integrated current value, and a current offset error, where the current offset error indicates an offset error of the current sensor, determine a second error factor and a third error factor based on the fixed OCV, the fixed SOC, the interested OCV, the interested SOC, and a voltage offset error, where the voltage offset error indicates an offset error of the voltage sensor, determine a fourth error factor based on the fixed rest time, determine a fifth error factor based on the interested rest time, determine a representative error factor based on the first error factor to the fifth error factor, and determine a weight indicating the reliability of the SOH based on the representative error factor.

2. The battery management system according to claim 1, wherein The control circuit is configured to: determine the first error factor as a value equal to a result of dividing a product of the cycling time and the current offset error by the integrated current value.

3. The battery management system according to claim 1, wherein, The control circuit is configured to: determine a SOC change indicating a difference between the fixed SOC and the interested SOC, determine a first corrected OCV by adding the voltage offset error to the fixed OCV or subtracting the voltage offset error from the fixed OCV, determine a first corrected SOC corresponding to the first corrected OCV from a predetermined OCV curve, where the OCV curve defines an association between OCV and SOC when the hysteresis of the battery is 0, and The second error factor is determined to be equal to a value obtained by dividing the difference between the fixed SOC and the first corrected SOC by the SOC change.

4. The battery management system according to claim 3, wherein, The control circuit is configured to: determine a second corrected OCV by adding the voltage offset error to or subtracting the voltage offset error from the OCV of interest, determine a second corrected SOC corresponding to the second corrected OCV from the OCV curve, and determine the third error factor to be equal to a value obtained by dividing the difference between the SOC of interest and the second corrected SOC by the SOC change.

5. The battery management system according to claim 1, wherein The control circuit is configured to determine the fourth error factor to be equal to a first error value corresponding to the fixed rest time according to a first error curve, and the first error curve is data defining the association between the rest time and the error value for a first reference SOC, the first reference SOC being the SOC of the battery at the start time of the first rest period.

6. The battery management system according to claim 5, wherein, The control circuit is configured to determine the fifth error factor to be equal to a second error value corresponding to the rest time of interest according to a second error curve, and the second error curve is data defining the association between the rest time and the error value for a second reference SOC, the second reference SOC being the SOC of the battery at the start time of the second rest period.

7. The battery management system according to claim 1, wherein, The control circuit is configured to determine a weight using the following equation: <Equation> Among them, W SOH represents a weight, M represents a predetermined first conversion constant greater than 1, K represents a predetermined second conversion constant greater than 0, and F SOH represents a representative error factor.

8. The battery management system according to claim 1, wherein, The control circuit is configured to determine an effective SOH, which is a weighted average of the predetermined number of SOHs, based on the predetermined number of SOHs in the most recently determined order and the predetermined number of weights during the second rest period.

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

10. An electric vehicle including the battery pack according to claim 9.

11. A battery management method executable by the battery management system according to any one of claims 1 to 8.

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