Battery state of health (SOH) estimating method and battery system providing same

Abstract

The present invention relates to a battery state of health (SOH) estimating method and a battery system providing same. The battery system of the present invention comprises a battery and a battery management system (BMS) which obtains a degradation condition related to degradation of the battery at each predetermined monitoring cycle, determines a relational expression representing the relationship between the total amount of energy of the battery and the SOH of the battery according to the degradation condition at each of the monitoring cycles, and estimates the SOH of the battery according to the relational expression, wherein the total amount of energy of the battery is the sum of the charging energy and the discharging energy of the battery.

Description

Battery SOH estimation method and battery system providing the method

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0178549, filed December 11, 2023, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a method for estimating the SOH (State Of Health) of a battery and a battery system providing the method.

[0004] Batteries used in high-power products like electric and hybrid vehicles must supply high voltages to the load, so they contain multiple cells connected in series or parallel. In eco-friendly vehicles, battery performance is directly linked to the vehicle's performance, making the Battery Management System (BMS) crucial for efficiently managing battery health.

[0005] The BMS estimates the SOC (State of Charge) of the battery (or battery cell), the SOH (State of Health) of the battery, the energy used for charging and discharging the battery, etc. based on the battery current flowing in the battery, the multiple cell voltages of multiple battery cells, the battery temperature, etc., and diagnoses the state of the battery based on the estimated results.

[0006] Meanwhile, due to the nonlinearity of battery cells, direct measurement of battery SOH and other parameters is impossible. Therefore, the BMS includes multiple SOH estimation models, each of which estimates battery SOH and other parameters based on battery data.

[0007] The present invention aims to provide a battery SOH estimation method for estimating the SOH (State Of Health) of a battery according to the state of the battery that changes in real time, and a battery system providing the method.

[0008] A battery system according to one feature of the present invention comprises a battery and a BMS that obtains, at each predetermined monitoring cycle, a degradation condition related to the degradation of the battery, and determines, at each monitoring cycle, a relational expression representing a relationship between the total energy of the battery and the SOH of the battery according to the degradation condition, and estimates the SOH of the battery according to the relational expression, wherein the total energy of the battery is the sum of the charging energy and the discharging energy of the battery.

[0009] The above degradation conditions may include the temperature of the battery, the charging speed of the battery, the discharging speed of the battery, the upper SOC of the battery, and the lower SOC of the battery.

[0010] The BMS can measure the temperature of the battery, the charging speed of the battery, and the discharging speed of the battery, and estimate the upper SOC of the battery and the lower SOC of the battery.

[0011] The BMS can calculate the SOH change rate of the battery based on the relationship for each monitoring cycle, and estimate the current SOH of the battery by subtracting the accumulated value of the multiple SOH change rates calculated for each cycle from the initial SOH of the battery.

[0012] The BMS may estimate a first SOH of the battery based on the total energy amount of the battery when the monitoring period starts, and may estimate a second SOH of the battery based on the total energy amount of the battery when the monitoring period ends, and may calculate a difference between the first SOH and the second SOH as the SOH change rate.

[0013] A battery SOH estimation method according to another feature of the present invention includes the steps of: obtaining, at each predetermined monitoring cycle, a degradation condition related to the degradation of the battery; calculating the total energy of the battery by adding the charging energy of the battery and the discharging energy of the battery; and determining, at each monitoring cycle, a relational expression representing the relationship between the total energy of the battery and the SOH of the battery according to the degradation condition, and estimating the SOH of the battery according to the relational expression.

[0014] The above degradation conditions may include the temperature of the battery, the charging speed of the battery, the discharging speed of the battery, the upper SOC of the battery, and the lower SOC of the battery.

[0015] The step of obtaining the above degradation condition may include the step of measuring the temperature of the battery, the charging speed of the battery, and the discharging speed of the battery, and the step of estimating the upper SOC of the battery and the lower SOC of the battery.

[0016] The step of estimating the SOH of the battery may include a step of calculating a rate of change in the SOH of the battery based on the relationship for each monitoring period, and a step of subtracting a value obtained by accumulating a plurality of SOH rate changes calculated for each period from the SOH of the battery.

[0017] The step of calculating the SOH change rate of the battery may include the step of estimating the first SOH of the battery based on the total energy amount of the battery when the monitoring period starts, the step of estimating the second SOH of the battery based on the total energy amount of the battery when the monitoring period ends, and the step of calculating the difference between the first SOH and the second SOH as the SOH change rate.

[0018] A battery SOH estimation method capable of estimating a highly reliable battery SOH by estimating the SOH (State Of Health) of a battery according to the state of the battery that changes in real time, and a battery system providing the method are provided.

[0019] FIG. 1 is a diagram illustrating a battery system according to one embodiment.

[0020] FIG. 2 is a flowchart illustrating a method for estimating battery SOH according to a relational expression representing the relationship between the total energy of a battery and the battery SOH according to one embodiment.

[0021] FIG. 3 is a graph according to a relational expression showing the relationship between the total energy of a battery and the SOH of the battery according to one embodiment.

[0022] FIG. 4 is a graph according to a relational expression showing the relationship between the total energy of a battery and the SOH of the battery according to one embodiment.

[0023] FIG. 5 is a graph according to a relational expression showing the relationship between the total energy of a battery and the SOH of the battery according to one embodiment.

[0024] Figure 6 is a graph showing SOH changing in real time according to one embodiment.

[0025] The embodiments described in this specification and the configurations illustrated in the drawings are preferred examples of the disclosed invention, and there may be various modified examples that can replace the embodiments and drawings of this specification at the time of filing of this application.

[0026] In describing the embodiments disclosed in this specification, detailed descriptions of related known technologies will be omitted if it is determined that such detailed descriptions may obscure the gist of the embodiments disclosed in this specification. In addition, the attached drawings are provided solely to facilitate understanding of the embodiments disclosed in this specification, and the technical concepts disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, and substitutes included within the spirit and technical scope of the present invention.

[0027] Terms that include ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely to distinguish one component from another.

[0028] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0029] In this application, terms such as “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but should be understood not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0030] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings.

[0031] FIG. 1 is a diagram illustrating a battery system according to one embodiment.

[0032] Referring to FIG. 1, the 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).

[0033] Two terminals (TE1, 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) may be located at a predetermined location within the battery system (100), for example, in an area adjacent to the battery (110), or may be located by being physically coupled to the battery (110).

[0034] The battery (110) includes a plurality of battery cells, and the plurality of battery cells may be connected in series / parallel. In FIG. 1, the battery (110) is illustrated as including a plurality of battery cells (Cell1-Celln) connected in series. However, the configurations and connection relationships between the configurations illustrated in FIG. 1 are merely examples and the invention is not limited thereto.

[0035] The relay (120) controls the 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 perform charging or discharging. When the relay (120) is turned off, the battery system (100) and the external device are electrically separated. The external device may be a load or a charger.

[0036] The current sensor (130) is connected in series to the current path between the battery (110) and the external device. The current sensor (130) can measure the current flowing in the battery (110) and transmit a detection signal (CS) indicating the measurement result to the BMS. The current flowing in the battery (110) may be a charging current for charging the battery (110) or a discharging current supplied from the battery (110) to the external device.

[0037] A temperature sensor (140) can detect the temperature of a location and transmit a signal (TS) indicating the detected temperature to the BMS. The temperature sensor (140) is not limited to that shown in FIG. 1, and at least two temperature sensors may be provided to detect the temperature of cells of multiple batteries.

[0038] BMS (150) includes a monitoring unit (151), MCU (Main Control Unit) (152), and memory (153).

[0039] The monitoring unit (151) is electrically connected to the positive and negative poles of each of the plurality of battery cells (Cell1-Celln) and measures the voltage of each of the plurality of battery cells (Cell1-Celln).

[0040] The monitoring unit (151) transmits information about the cell voltage of each of the measured plurality of battery cells (Cell1-Celln) to the MCU (152). Specifically, the monitoring unit (151) can measure the cell voltage 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 voltage to the MCU (152).

[0041] The MCU (152) can estimate the SOC (state of charge) of each of the plurality of battery cells using the cell voltage of each of the plurality of battery cells (Cell1-Celln) received from the monitoring unit (151) during the rest period.

[0042] The MCU (152) can obtain the current level flowing in the battery (110) during the battery (110) charging / discharging period according to the detection signal (CS) received from the current sensor (130), and can obtain the temperature level of the battery (110) according to the detection signal (TS) received from the temperature sensor (140).

[0043] The memory (153) stores programs and data for controlling and managing the configurations included in the BMS (150), and can store information obtained by the current sensor (130), temperature sensor (140), monitoring unit (151), and information calculated by the MCU (152).

[0044] Hereinafter, a method for estimating battery SOH in an MCU (152) using information stored in a memory (153) will be described with reference to FIGS. 2 to 6.

[0045] FIG. 2 is a flowchart illustrating a method for estimating battery SOH according to a relational expression representing the relationship between the total energy of a battery and the battery SOH according to one embodiment.

[0046] FIGS. 3 to 5 are graphs according to a relational expression showing the relationship between the total energy of a battery and the battery SOH according to one embodiment.

[0047] Figure 6 is a graph showing SOH changing in real time according to one embodiment.

[0048] Referring to FIG. 2, the BMS can obtain degradation conditions at each predetermined monitoring cycle to estimate the SOH of the battery (110) that changes in real time according to the use of the battery (110) (S1000).

[0049] As the battery (110) is used, the SOH of the battery (110) decreases, which is called degradation, and the battery (110) degradation conditions refer to factors involved in the degradation.

[0050] Specifically, the degradation conditions may include the temperature of the battery (110), the charging speed of the battery (110), the discharging speed of the battery (110), the upper SOC of the battery (110), and the lower SOC of the battery (110).

[0051] The BMS (150) can obtain the temperature level of the battery (110) according to the detection signal (TS) received from the temperature sensor (140).

[0052] In addition, the BMS (150) can obtain the current level flowing in the battery (110) during the battery (110) charging / discharging period according to the detection signal (CS) received from the current sensor (130), and can measure the charging speed (C-rate) of the battery (110) and the discharging speed (C-rate) of the battery (110) based on the current flowing in the battery (110).

[0053] Specifically, the BMS (150) can measure the charging speed 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 speed 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 the capacity decrease according 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 according to the number of cells of the battery (110) and the chemical composition of the battery, etc.

[0054] The BMS (150) can estimate the SOC of the battery (110) by using one of the following methods: a current integration method that integrates the charge and discharge current, an electrochemical modeling technique that represents the chemical reaction inside the cell at the molecular level, a mathematical technique that expresses the dynamic behavior of the operating time and the state of charge (SOC) of the battery (110) as 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).

[0055] Additionally, the BMS (150) can determine the SOC upper limit of the battery (110) and the SOC lower limit of the battery (110). The SOC range of the battery (110) according to the SOC upper limit of the battery (110) and the SOC lower limit of the battery (110) means the SOC range in which the battery (110) is mainly charged and discharged.

[0056] The BMS (150) can determine the SOC as the lower SOC value of the battery (110) when charging the battery (110) starts, and can determine the SOC as the upper SOC value of the battery (110) when charging the battery (110) ends. When the battery (110) is charged multiple times, the BMS (150) can determine the average of the lower SOC values ​​as the lower SOC value, and determine the average of the upper SOC values ​​as the upper SOC value.

[0057] The BMS (150) can determine a relationship between the total energy of the battery (110) and the SOH of the battery (110) according to the degradation conditions at each monitoring cycle (S1100).

[0058] The total energy of the battery (110) means the sum of the energy charged to the battery (110) (hereinafter, battery charge energy) and the energy discharged from the battery (110) (hereinafter, battery discharge energy).

[0059] According to one embodiment, a relationship representing the relationship between the total energy of the battery (110) and the SOH of the battery (110) can be defined as in mathematical expression 1.

[0060] [Mathematical Formula 1]

[0061]

[0062] α can be defined as in mathematical expression 2.

[0063] [Equation 2]

[0064]

[0065] α0, α1, α2, α3, and α4 are parameters determined according to the chemical properties of the battery (110), which can be determined using a table stored in the memory (153). T is the temperature of the battery (110), C is the charging speed of the battery (110), D is the discharging speed of the battery (110), and SOC U means the upper SOC of the battery (110), and SOC l refers to the lower SOC of the battery (110).

[0066] The BMS (150) can determine a relational expression representing the relationship between the total energy of the battery (110) and the SOH of the battery (110) according to a predetermined mathematical expression and a stored table.

[0067] Referring to FIGS. 3 to 5, one can see graphs according to a relational expression representing the relationship between the total energy of the battery (110) and the SOH of the battery (110) in batteries (110) having different chemical properties and degradation conditions, respectively.

[0068] FIG. 4 is a graph (f1) according to the first relational expression representing the relationship between the total energy of the battery (110) and the SOH of the battery (110) when α is 2, FIG. 5 is a graph (f2) according to the second relational expression representing the relationship between the total energy of the battery (110) and the SOH of the battery (110) when α is 3, and FIG. 6 is a graph (f3) according to the third relational expression representing the relationship between the total energy of the battery (110) and the SOH of the battery (110) when α is 2.

[0069] The BMS (150) can determine different relationships depending on the degradation conditions that change for each monitoring period. Referring to FIG. 6, the BMS (150) can estimate the SOH of the battery (110) using the graph (f1) according to the first relationship when α is 2 in the first period (T1) among multiple monitoring periods, can estimate the SOH of the battery (110) using the graph (f2) according to the second relationship when α is 3 in the second period (T2), and can estimate the SOH of the battery (110) using the graph (f3) according to the third relationship when α is 10 in the third period (T3).

[0070] The BMS (150) can calculate the rate of change in the SOH of the battery (110) during the monitoring period (S1200). Specifically, the BMS (150) can calculate the difference between the SOH of the battery (110) based on the total energy amount of the battery at the start of the monitoring period and the SOH of the battery (110) based on the total energy amount of the battery at the end of the monitoring period as the rate of change in the SOH of the battery (110).

[0071] The BMS (150) can calculate the total energy of the battery (110) as the sum of the battery charging energy and the battery discharging energy since the battery (110) first started operating. Specifically, the BMS (150) can calculate the charging energy of the battery (110) by multiplying the product of the voltage and current used during charging by the charging time, and can 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 obtaining the charging energy and the discharging energy of the battery (110) is not limited thereto and can be implemented according to various known technologies.

[0072] Referring to FIG. 6, the BMS (150) can set the SOH of the battery (110) to 100% (P1) when the total energy of the battery (110) is 0 [kWh]. The BMS (150) can calculate the total energy of the battery (110) at the end of the first cycle (T1). When 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 can calculate the difference of 23% 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) as the SOH change rate (ΔSOC1).

[0073] BMS (150) can set the SOH of the battery (110) to 77% (P2) when the total energy of the battery (110) is 40 [kWh]. 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) as 48% (P3), and can calculate the difference 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), which is 29%, as the SOH change rate (ΔSOC2), and in the same way, can calculate the difference 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), which is 29%, as the SOH change rate (ΔSOC3).

[0074] The BMS (150) can accumulate multiple SOH change rates calculated for each cycle (S1300). Specifically, the BMS (150) can accumulate multiple SOH change rates calculated at the end of each cycle.

[0075] Referring to FIG. 6, the BMS (150) can calculate the sum of the SOH change rate (ΔSOC1) of the first cycle and the SOH change rate (ΔSOC2) of the second cycle as the final SOH change rate after the second cycle ends, and can update the sum of the SOH change rate (ΔSOC1) of the first cycle, the SOH change rate (ΔSOC2) of the second cycle, and the SOH change rate (ΔSOC3) of the third cycle as the final SOH change rate after the third cycle ends.

[0076] BMS (150) can estimate the current SOH by subtracting the accumulated SOH change rate from the initial battery SOH (S1400).

[0077] For example, if the present is the end of the third cycle, the sum of the SOH change rate (ΔSOC1) of the first cycle, the SOH change rate (ΔSOC2) of the second cycle, and the SOH change rate (ΔSOC3) of the third cycle, which is 81%, can be subtracted from the initial battery (110) SOH of 100% to estimate the current battery (110) SOH as 19%.

[0078] Additionally, the BMS (150) may communicate with the vehicle control unit to notify the user when the battery (110) SOH falls below a predetermined value.

[0079] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by 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. Battery; and At each predetermined monitoring cycle, the degradation conditions related to the degradation of the battery are acquired, Including a BMS (Battery Management System) that determines a relationship between the total energy of the battery and the SOH (State Of Health) of the battery according to the degradation condition at each of the monitoring periods and estimates the SOH of the battery according to the relationship; A battery system in which the total energy of the battery is the sum of the charging energy and the discharging energy of the battery.

2. In paragraph 1, The above degenerative conditions are, A battery system including a temperature of the battery, a charge rate of the battery, a discharge rate of the battery, an upper SOC of the battery, and a lower SOC of the battery.

3. In paragraph 2, The above BMS, A battery system that measures the temperature of the battery, the charging speed of the battery, and the discharging speed of the battery, and estimates the upper SOC of the battery and the lower SOC of the battery.

4. In paragraph 1, The above BMS, A battery system for calculating the SOH change rate of the battery based on the above relationship for each of the above monitoring periods, and estimating the current SOH of the battery by subtracting the accumulated value of multiple SOH change rates calculated for each period from the initial SOH of the battery.

5. In paragraph 4, The above BMS, A battery system that estimates a first SOH of the battery based on the total energy amount of the battery when the monitoring period starts, estimates a second SOH of the battery based on the total energy amount of the battery when the monitoring period ends, and calculates a difference between the first SOH and the second SOH as the SOH change rate.

6. A step of obtaining a degradation condition related to the degradation of the battery at each predetermined monitoring cycle; A step of calculating the total energy of the battery by adding the charging energy of the battery and the discharging energy of the battery; and A battery SOH estimation method comprising the step of determining a relationship representing a relationship between the total energy of the battery and the SOH (State Of Health) of the battery according to the degradation condition at each of the monitoring periods, and estimating the SOH of the battery according to the relationship.

7. In paragraph 6, The above degenerative conditions are, A battery SOH estimation method including a temperature of the battery, a charge rate of the battery, a discharge rate of the battery, an upper SOC of the battery, and a lower SOC of the battery.

8. In paragraph 7, The step of obtaining the above degenerate condition is: A step of measuring the temperature of the battery, the charging speed of the battery and the discharging speed of the battery; and A battery SOH estimation method comprising the steps of estimating an upper SOC of the battery and a lower SOC of the battery.

9. In paragraph 6, The step of estimating the SOH of the above battery is: A step of calculating the SOH change rate of the battery based on the above relationship at each of the above monitoring periods; and A battery SOH estimation method comprising a step of subtracting a value obtained by accumulating multiple SOH change rates calculated for each period from the SOH of the battery.

10. In paragraph 9, Step for calculating the SOH change rate of the above battery A step of estimating a first SOH of the battery based on the total energy amount of the battery when the monitoring period starts; A step of estimating a second SOH of the battery based on the total energy amount of the battery when the monitoring period ends; and A battery SOH estimation method comprising a step of calculating a difference between the first SOH and the second SOH as the SOH change rate.

Images