Battery SOH estimation method and battery system providing the method

Abstract

The present invention relates to a method for estimating a battery SOH (State Of Health) and a battery system that provides the method. The battery system of the present invention includes a battery and a BMS (Battery Management System) that acquires degradation conditions related to the degradation of the battery at each predetermined monitoring period, determines a relational equation showing the relationship between the total energy of the battery and the SOH of the battery based on the degradation conditions at each monitoring period, and estimates the SOH of the battery according to the relational equation, where the total energy of the battery is the sum of the charging energy and discharging energy of the battery.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0178549, dated December 11, 2023, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a method for estimating the SOH (State Of Health) of a battery and a battery system that provides the method. [Background technology]

[0003] Batteries installed in high-power products such as electric or hybrid vehicles contain multiple cells connected in series or parallel to supply high voltage to the load. In eco-friendly vehicles, battery performance is directly linked to the performance of the vehicle, so the role of a Battery Management System (BMS) that efficiently manages the battery status is important.

[0004] The BMS estimates the battery (or battery cell) SOC (State of Charge), SOH (State of Health), and energy used for charging and discharging the battery based on the battery current flowing through the battery, the cell voltages of the battery cells, and the battery temperature, and diagnoses the battery condition based on the estimated results.

[0005] However, due to the nonlinearity of battery cells, it is impossible to directly measure the battery's SOH, etc. Therefore, the BMS includes multiple SOH estimation models, each of which estimates the battery's SOH, etc. based on battery data. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a battery SOH (State Of Health) estimation method for estimating the SOH of a battery according to the state of the battery that changes in real time, and a battery system that provides this method. [Means for solving the problem]

[0007] A battery system according to one aspect of the present invention includes a battery and a BMS that acquires degradation conditions related to the degradation of the battery for each predetermined monitoring period, determines a relationship between the total energy of the battery and the SOH of the battery based on the degradation conditions for each monitoring period, and estimates the SOH of the battery according to the relationship, wherein the total energy of the battery is the sum of the charging energy and discharging energy of the battery.

[0008] The degradation conditions may include the temperature of the battery, the charge rate of the battery, the discharge rate of the battery, the upper SOC limit of the battery, and the lower SOC limit of the battery.

[0009] The BMS can measure the temperature of the battery, the charge rate of the battery, and the discharge rate of the battery, and estimate an upper SOC limit of the battery and a lower SOC limit of the battery.

[0010] The BMS calculates the SOH change rate of the battery based on the relational expression for each monitoring period, and estimates the current SOH of the battery by subtracting the sum of the multiple SOH change rates calculated for each period from the initial SOH of the battery.

[0011] The BMS may estimate a first SOH of the battery based on the total energy amount of the battery when the monitoring period starts, estimate a second SOH of the battery based on the total energy amount of the battery when the monitoring period ends, and calculate the difference between the first SOH and the second SOH as the SOH change rate.

[0012] According to another aspect of the present invention, a battery SOH estimation method includes the steps of: acquiring degradation conditions related to degradation of the battery for each predetermined monitoring period; calculating the total energy of the battery by summing the charge energy of the battery and the discharge energy of the battery; and determining a relational equation showing the relationship between the total energy of the battery and the SOH of the battery based on the degradation conditions for each monitoring period; and estimating the SOH of the battery according to the relational equation.

[0013] The degradation conditions may include the temperature of the battery, the charge rate of the battery, the discharge rate of the battery, the upper SOC limit of the battery, and the lower SOC limit of the battery.

[0014] The step of obtaining the degradation condition may include measuring the temperature of the battery, the charge rate of the battery, and the discharge rate of the battery, and estimating an upper SOC limit value and a lower SOC limit value of the battery.

[0015] The step of estimating the SOH of the battery may include the steps of: calculating a SOH change rate of the battery based on the relational expression for each monitoring period; and subtracting an integrated value of the SOH change rates calculated for each period from the SOH of the battery.

[0016] The step of calculating the SOH change rate of the battery may include the steps of estimating a first SOH of the battery based on the total energy amount of the battery when the monitoring period starts, estimating a second SOH of the battery based on the total energy amount of the battery when the monitoring period ends, and calculating a difference between the first SOH and the second SOH as the SOH change rate. [Effects of the Invention]

[0017] A battery SOH (State Of Health) estimation method capable of estimating a battery SOH with high reliability by estimating the SOH of a battery according to the battery state that changes in real time, and a battery system that provides the method. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram illustrating a battery system according to an embodiment. [Figure 2] 1 is a flowchart illustrating a method for estimating a battery SOH according to a relational expression that indicates a relationship between a total energy amount of a battery and the battery SOH according to an embodiment. [Figure 3] 1 is a graph showing a relationship between the total energy of a battery and the battery SOH according to an embodiment; [Figure 4] 1 is a graph showing a relationship between the total energy of a battery and the battery SOH according to an embodiment; [Figure 5] 1 is a graph showing a relationship between the total energy of a battery and the battery SOH according to an embodiment; [Figure 6] 1 is a graph illustrating SOH changing in real time according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] The embodiments described in this specification and the configurations shown in the drawings are preferred examples of the disclosed invention, and there may be various modifications that can replace the embodiments and drawings in this specification at the time of filing this application.

[0020] In describing the embodiments disclosed herein, if it is determined that a detailed description of related publicly known technology may obscure the gist of the embodiments disclosed herein, the detailed description will be omitted. In addition, the attached drawings are merely provided to facilitate understanding of the embodiments disclosed herein, and the technical ideas disclosed herein should not be limited by the attached drawings, and should be understood to include all modifications, equivalents, and alternatives included within the spirit and technical scope of the present invention.

[0021] Terms including ordinal numbers such as "first," "second," etc. may be used to describe various components, but the components are not limited by the terms. The terms are used only to distinguish one component from another.

[0022] When a component is said to be "coupled" or "connected" to another component, it should be understood that it may be directly coupled or connected to the other component, but that there may be other components in between. Conversely, when a component is said to be "directly coupled" or "directly connected" to another component, it should be understood that there are no other components in between.

[0023] In this application, the terms "comprise" or "have" and the like are intended to specify the presence of any feature, number, step, operation, component, part, or combination thereof stated in the specification, and should be understood as not precluding the possible presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0024] Hereinafter, the embodiments disclosed in this specification will be described in detail with reference to the accompanying drawings.

[0025] FIG. 1 is a diagram illustrating a battery system according to an embodiment.

[0026] Referring to FIG. 1, a battery system 100 includes a battery 110, a relay 120, a current sensor 130, a temperature sensor 140, and a battery management system (BMS) 150.

[0027] Two terminals TE1 and TE2 of the battery system 100 are connected to the positive and negative poles of the battery 110, a relay 120 is connected between the positive pole of the battery 110 and the terminal TE1, and a current sensor 130 is connected between the negative pole of the battery 110 and the terminal TE2. The temperature sensor 140 can be located at a predetermined position within the battery system 100, for example, in an area adjacent to the battery 110 or physically coupled to the battery 110.

[0028] The battery 110 includes a plurality of battery cells, which may be connected in series or parallel. Although the battery 110 is shown in FIG. 1 as including a plurality of battery cells Cell1-Celln connected in series, the configuration and the connections between the configurations shown in FIG. 1 are merely examples, and the present invention is not limited thereto.

[0029] The relay 120 controls an electrical connection between the battery system 100 and an external device. When the relay 120 is turned on, the battery system 100 and the external device are electrically connected to each other to perform charging or discharging, and when the relay 120 is turned off, the battery system 100 and the external device are electrically isolated from each other. The external device may be a load or a charger.

[0030] The current sensor 130 is connected in series to a current path between the battery 110 and the external device. The current sensor 130 measures the current flowing through the battery 110 and transmits a detection signal CS indicating the measurement result to the BMS. The current flowing through the battery 110 may be a charging current that charges the battery 110 or a discharging current supplied from the battery 110 to the external device.

[0031] The temperature sensor 140 can sense the temperature of the portion where it is located and transmit a signal TS indicating the sensed temperature to the BMS. The temperature sensor 140 is not limited to the one shown in FIG. 1, and at least two temperature sensors can be provided to sense the temperatures of multiple battery cells.

[0032] The BMS 150 includes a monitoring unit 151 , an MCU (Main Control Unit) 152 , and a memory 153 .

[0033] The monitoring unit 151 is electrically connected to the positive and negative electrodes of each of the plurality of battery cells Cell1 to Celln, and measures the voltage of each of the plurality of battery cells Cell1 to Celln.

[0034] The monitoring unit 151 transmits information about the measured cell voltages of each of the plurality of battery cells Cell1-Celln to the MCU 152. Specifically, the monitoring unit 151 may measure the cell voltages of each of the plurality of battery cells Cell1-Celln at predetermined intervals during a rest period in which no charging or discharging occurs, and transmit the measured cell voltages to the MCU 152.

[0035] The MCU 152 can estimate the SOC (State of Charge) of each of the battery cells Cell1-Celln by using the cell voltages of each of the battery cells Cell1-Celln received from the monitoring unit 151 during the pause period.

[0036] The MCU 152 can obtain the current level flowing through the battery 110 during the charging / discharging period of the battery 110 from the sensing signal CS received from the current sensor 130, and can obtain the temperature level of the battery 110 from the sensing signal TS received from the temperature sensor 140.

[0037] The memory 153 stores programs and data for controlling and managing the configuration included in the BMS 150, and can store information acquired by the current sensor 130, the temperature sensor 140, and the monitoring unit 151, information calculated by the MCU 152, etc.

[0038] Hereinafter, a method for estimating the battery SOH in the MCU 152 using information stored in the memory 153 will be described with reference to FIGS.

[0039] FIG. 2 is a flowchart illustrating a method for estimating a battery SOH according to a relational expression that indicates the relationship between the total energy amount of a battery and the battery SOH, according to one embodiment.

[0040] 3 to 5 are graphs based on a relational expression showing the relationship between the total energy amount of a battery and the battery SOH according to an embodiment.

[0041] FIG. 6 is a graph showing SOH changing in real time according to one embodiment.

[0042] Referring to FIG. 2, the BMS can acquire degradation conditions at predetermined monitoring intervals to estimate the SOH of the battery 110, which changes in real time as the battery 110 is used (S1000).

[0043] As the battery 110 is used, the SOH of the battery 110 decreases, which is called degradation, and the degradation conditions of the battery 110 refer to factors that contribute to degradation.

[0044] Specifically, the degradation conditions may include the temperature of the battery 110, the charging rate of the battery 110, the discharging rate of the battery 110, the upper limit of the SOC of the battery 110, and the lower limit of the SOC of the battery 110.

[0045] The BMS 150 can obtain the temperature level of the battery 110 through the sensing signal TS received from the temperature sensor 140 .

[0046] In addition, the BMS 150 can obtain the current level flowing through the battery 110 during the charging and discharging period of the battery 110 through the sensing signal CS received from the current sensor 130, and can measure the charging rate (C-rate) and discharging rate (C-rate) of the battery 110 based on the current flowing through the battery 110.

[0047] Specifically, the BMS 150 can measure the charging rate of the battery 110 by dividing the current flowing when charging the battery 110 by the current capacity of the battery 110, and can measure the discharging rate of the battery 110 by dividing the current flowing when discharging the battery 110 by the current capacity of the battery 110. The current capacity of the battery 110 can be determined as a value obtained by subtracting a capacity reduction due to the current degradation of the battery 110 from the initial capacity of the battery 110. The initial capacity of the battery 110 is the capacity before the battery 110 is used and can be determined by the number of cells of the battery 110, the chemical composition of the battery, etc.

[0048] The BMS 150 can estimate the SOC of the battery 110 using one of the following methods: a current integration method that integrates charge and discharge currents; an electrochemical modeling technique that shows the chemical reactions inside the cell at the molecular level; a mathematical modeling technique that expresses the dynamic behavior of the operating time and State of Charge (SOC) of the battery 110 using a purely mathematical empirical formula; and a voltage modeling technique that uses the relationship between the open circuit voltage (OCV) and the State of Charge (SOC).

[0049] In addition, the BMS 150 may determine an upper SOC limit value and a lower SOC limit value of the battery 110. The SOC range of the battery 110 defined by the upper SOC limit value and the lower SOC limit value of the battery 110 refers to the SOC range in which the battery 110 is mainly charged and discharged.

[0050] The BMS 150 can determine the SOC as the battery 110 SOC lower limit when charging of the battery 110 starts, and can determine the SOC as the battery 110 SOC upper limit when charging of the battery 110 ends. When the battery 110 is charged multiple times, the BMS 150 can determine the average of the multiple SOC lower limit values ​​as the SOC lower limit value, and can determine the average of the multiple SOC upper limit values ​​as the SOC upper limit value.

[0051] The BMS 150 can determine a relational expression that indicates the relationship between the total energy amount of the battery 110 and the SOH of the battery 110 according to the degradation conditions for each monitoring period (S1100).

[0052] The total energy amount of the battery 110 means the sum of the energy charged to the battery 110 (hereinafter referred to as battery charge energy) and the energy discharged from the battery 110 (hereinafter referred to as battery discharge energy).

[0053] According to one embodiment, a relationship between the total energy of the battery 110 and the SOH of the battery 110 may be defined as Equation 1.

[0054] [Formula 1]

number

[0055] α can be defined as in Equation 2.

[0056] [Formula 2]

number

[0057] α0, α1, α2, α3, and α4 are parameters determined by the chemical properties of the battery 110, which can be determined using a table stored in memory 153. T is the temperature of the battery 110, C is the charge rate of the battery 110, D is the discharge rate of the battery 110, and SOC U means the upper limit of SOC of battery 110, and SOC l means the lower limit of the SOC of the battery 110.

[0058] The BMS 150 can determine a relationship between the total energy of the battery 110 and the SOH of the battery 110 using a predetermined formula and a stored table.

[0059] 3 to 5, graphs showing the relationship between the total energy of the battery 110 and the SOH of the battery 110 for batteries 110 having different chemistries and degradation conditions can be seen.

[0060] Figure 3 is a graph (f1) based on the first relational expression showing the relationship between the total energy amount of battery 110 and battery 110SOH when α is 2, Figure 4 is a graph (f2) based on the second relational expression showing the relationship between the total energy amount of battery 110 and battery 110SOH when α is 3, and Figure 5 is a graph (f3) based on the third relational expression showing the relationship between the total energy amount of battery 110 and battery 110SOH when α is 10.

[0061] The BMS 150 may determine different relational expressions depending on the degradation conditions that change for each monitoring period. Referring to Figure 6, the BMS 150 may estimate the battery 110 SOH using a graph (f1) based on a first relational expression when α is 2 in a first period (T1) among a plurality of monitoring periods, may estimate the battery 110 SOH using a graph (f2) based on a second relational expression when α is 3 in a second period (T2), and may estimate the battery 110 SOH using a graph (f3) based on a third relational expression when α is 10 in a third period (T3).

[0062] The BMS 150 may calculate a battery 110 SOH change rate during a monitoring period (S1200). Specifically, the BMS 150 may calculate the battery 110 SOH change rate as the difference between the battery 110 SOH based on the total energy amount of the battery at the start of the monitoring period and the battery 110 SOH based on the total energy amount of the battery at the end of the monitoring period.

[0063] The BMS 150 may calculate the sum of the battery charge energy and the battery discharge energy since the battery 110 was first operated as the total energy of the battery 110. Specifically, the BMS 150 may calculate the charge energy of the battery 110 by multiplying the product of the voltage and current used during charging by the charging time, and may calculate the discharge energy of the battery 110 by multiplying the product of the voltage and current used during discharging by the discharging time. However, the method of calculating the charge energy and the discharge energy of the battery 110 is not limited thereto and may be implemented using various known techniques.

[0064] 6, when the total energy of the battery 110 is 0 kWh, the BMS 150 can set the SOH of the battery 110 to 100% (P1). The BMS 150 can calculate the total energy of the battery 110 at the end of the first cycle (T1). If the total energy of the battery 110 is 40 kWh at the end of the first cycle (T1), the BMS 150 can estimate the SOH of the battery 110 to be 77% (P2) and calculate the SOH change rate (ΔSOC1) as 23%, which is the difference between the SOH of the battery 110 at the start of the first cycle (T1) and the SOH of the battery 110 at the end of the first cycle (T1).

[0065] When the total energy of the battery 110 is 40 kWh, the BMS 150 can set the SOH of the battery 110 to 77% (P2). When the total energy of the battery 110 is 78 kWh at the end of the second cycle (T2), the BMS 150 can estimate the SOH of the battery 110 to 48% (P3), and can calculate the difference of 29% between the SOH of the battery 110 at the start of the second cycle (T2) and the SOH of the battery 110 at the end of the second cycle (T2) as the SOH change rate (ΔSOC2). In a similar manner, the BMS 150 can calculate the difference of 29% between the SOH of the battery 110 at the start of the third cycle (T3) and the SOH of the battery 110 at the end of the third cycle (T3) as the SOH change rate (ΔSOC3).

[0066] The BMS 150 can integrate a plurality of SOH change rates calculated for each period (S1300). Specifically, the BMS 150 can integrate a plurality of SOH change rates calculated each time a period ends.

[0067] Referring to FIG. 6, after the second period ends, BMS150 can calculate the sum of the SOH change rate of the first period (ΔSOC1) and the SOH change rate of the second period (ΔSOC2) as the final SOH change rate, and after the third period ends, BMS150 can update the sum of the SOH change rate of the first period (ΔSOC1), the SOH change rate of the second period (ΔSOC2), and the SOH change rate of the third period (ΔSOC3) as the final SOH change rate.

[0068] The BMS 150 can estimate the current SOH by subtracting the accumulated SOH change rate from the initial battery SOH (S1400).

[0069] For example, if the third cycle has now ended, the sum of the SOH change rate in the first cycle (ΔSOC1), the SOH change rate in the second cycle (ΔSOC2), and the SOH change rate in the third cycle (ΔSOC3), which is 81%, can be subtracted from the initial battery 110SOH of 100% to estimate the current battery 110SOH as 19%.

[0070] The BMS 150 can also communicate with the vehicle control unit to notify the user if the battery 110 SOH drops below a predetermined value.

[0071] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to these, and various modifications and improvements made by a person having ordinary skill in the art to which the present invention pertains also fall within the scope of the present invention.

Claims

1. Batteries; and obtaining a degradation condition associated with degradation of the battery; a BMS (Battery Management System) that determines a relational expression indicating a relationship between a total energy amount of the battery and a State of Health (SOH) of the battery according to the degradation condition, and estimates the SOH of the battery according to the relational expression; A battery system wherein the total energy of the battery is the sum of the charging energy and discharging energy of the battery.

2. The degeneration conditions are: The battery system according to claim 1 , further comprising: a temperature of the battery; a charge rate of the battery; a discharge rate of the battery; an upper limit SOC value of the battery; and a lower limit SOC value of the battery.

3. The BMS includes: The battery system according to claim 2 , wherein the temperature of the battery, the charge rate of the battery, and the discharge rate of the battery are measured, and the upper limit value of the SOC of the battery and the lower limit value of the SOC of the battery are estimated.

4. The BMS includes:

2. The battery system of claim 1, wherein the SOH change rate of the battery is calculated based on the relational expression for each predetermined monitoring period, and the current SOH of the battery is estimated by subtracting an integrated value of the SOH change rates calculated for each period from the initial SOH of the battery.

5. The BMS includes:

5. The battery system of claim 4, wherein a first SOH of the battery is estimated based on a total amount of energy of the battery when the monitoring period starts, a second SOH of the battery is estimated based on a total amount of energy of the battery when the monitoring period ends, and a difference between the first SOH and the second SOH is calculated as the SOH change rate.

6. obtaining a degradation condition associated with degradation of the battery; calculating a total energy amount of the battery by summing the charging energy of the battery and the discharging energy of the battery; and determining a relational expression representing a relationship between the total energy amount of the battery and the SOH (State Of Health) of the battery according to the degradation condition; and estimating the SOH of the battery according to the relational expression.

7. The degeneration conditions are: The battery SOC estimation method according to claim 6, further comprising: a temperature of the battery; a charge rate of the battery; a discharge rate of the battery; an upper limit SOC value of the battery; and a lower limit SOC value of the battery.

8. The step of obtaining the degeneration condition includes: measuring the temperature of the battery, the charge rate of the battery, and the discharge rate of the battery; and The method of claim 7 , further comprising estimating an upper SOC limit value of the battery and a lower SOC limit value of the battery.

9. The step of estimating the SOH of the battery includes: calculating a rate of change in SOH of the battery based on the relationship for each predetermined monitoring period; and The method of claim 6, further comprising: subtracting a value obtained by integrating a plurality of SOH change rates calculated for each period from the SOH of the battery.

10. The step of calculating the SOH change rate of the battery comprises: estimating a first SOH of the battery based on a total energy amount of the battery at the start of the monitoring period; estimating a second SOH of the battery according to the total energy of the battery when the monitoring period ends; and The method of claim 9 , further comprising calculating a difference between the first SOH and the second SOH as the SOH change rate.

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