Method of calculating battery aging degree and device for calculating battery aging degree

Abstract

The present disclosure relates to a method for calculating a degree of battery deterioration and an apparatus for calculating a degree of battery deterioration, the method including the steps of: when a usage state of a battery changes from a first state to a second state, acquiring a duration for which the battery is in the first state; detecting whether the acquired duration is greater than or equal to a first reference time; when the duration is less than the first reference time, calculating an average temperature of the battery based on a first algorithm, and when the duration is greater than or equal to the reference time, calculating an average temperature of the battery based on a second algorithm; and calculating a degree of battery deterioration based on the calculated average temperature.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method and apparatus for calculating an aging degree of a battery. BACKGROUND

[0002] Recently, as electronic devices such as smart phones and the development of electric vehicles are spreading, research on secondary batteries as power sources has been actively conducted. The secondary battery is provided in the form of a battery pack including a battery module in which a plurality of battery cells are connected in series and / or in parallel, and a battery management system (BMS) that manages the operation of the battery module.

[0003] The aging degree of the battery pack is continuously monitored with respect to the aging degree (aging state) to ensure that it provides normal performance. The aging degree of the battery pack is estimated based on the internal resistance of the battery cell included in the battery pack, and the internal resistance of the battery cell is highly dependent on the temperature. Therefore, in order to accurately estimate the aging degree of the battery pack, it is necessary to accurately measure the temperature of the battery cell. SUMMARY

[0004] TECHNICAL PROBLEM

[0005] The present disclosure is made to solve such a problem, and provides a method and apparatus for calculating an aging degree in which an appropriate temperature of a battery cell for accurately estimating an aging degree of a battery pack can be calculated to estimate an accurate internal resistance of the battery cell, and an accurate aging degree of the battery can be calculated based on the accurate internal resistance.

[0006] TECHNICAL SOLUTION

[0007] To solve the above technical problem, according to one aspect of an embodiment of the present disclosure, there is provided a method of calculating an aging degree of a battery, the method including the steps of: obtaining a duration for which the battery is in a first state when a use state of the battery changes from the first state to a second state; determining whether the obtained duration is greater than or equal to a first reference time; calculating an average temperature of the battery based on a first algorithm when the duration is less than the first reference time, and calculating the average temperature of the battery based on a second algorithm when the duration is greater than or equal to the reference time; and calculating the aging degree of the battery based on the calculated average temperature.

[0008] According to another feature of an embodiment of the present disclosure, the first algorithm can calculate the average temperature of the battery by using a minimum temperature value of the battery calculated before the first state of the battery begins and a temperature measurement value of a temperature sensor installed on the battery.

[0009] According to another feature of the embodiments of the present disclosure, the second algorithm can calculate a minimum temperature value of the battery based on a temperature measurement value of a first temperature sensor installed on the battery and a temperature measurement value of a second temperature sensor installed on a cooling device of the battery, and calculate an average temperature of the battery using the temperature measurement value of the first temperature sensor and the calculated minimum temperature value.

[0010] According to another feature of the embodiments of the present disclosure, the second algorithm can calculate a minimum temperature value using a value indicating a relationship between a maximum temperature value and a minimum temperature value of the battery, the maximum temperature value and the minimum temperature value being calculated and stored before a first state of the battery begins.

[0011] According to another feature of the embodiments of the present disclosure, the first temperature sensor can include a sensor disposed in a maximum temperature region of the battery.

[0012] According to another feature of the embodiments of the present disclosure, the minimum temperature value of the battery can include a temperature value of a region of the battery adjacent to the cooling device.

[0013] According to another feature of the embodiments of the present disclosure, the first algorithm and the second algorithm are used for initial value setting when the state of the battery becomes a second state.

[0014] According to another feature of the embodiments of the present disclosure, when the state of the battery is the second state, a minimum temperature value of the battery is calculated based on a first location of a first temperature sensor installed on the battery, a second location of a second temperature sensor installed on a cooling device of the battery, and a heat transfer model between the battery and a third location of the battery where the battery and the cooling device contact each other.

[0015] According to another feature of the embodiments of the present disclosure, at least one of a space between the first location and the third location and a space between the third location and the second location is modeled by using an RC model.

[0016] According to another feature of the embodiments of the present disclosure, when the duration is a second reference time that is longer than the first reference time, an average temperature is calculated by a third algorithm instead of the second algorithm, and the third algorithm uses a temperature measurement value of a first temperature sensor installed on the battery as the average temperature.

[0017] According to another feature of the embodiments of the present disclosure, the first state can include a parked state of an electric vehicle, and the second state can include a driving state of the electric vehicle.

[0018] According to another feature of the embodiments of the present disclosure, the first state can include a state in which the battery is used as an output that is less than a reference output, and the second state can include a state in which the battery is used as an output that is greater than or equal to the reference output.

[0019] To solve the above-described technical problem, according to another aspect of an embodiment of the disclosure, there is provided an apparatus for calculating an aging degree of a battery, the apparatus including: a time comparison unit that determines whether a duration of a first state of the battery is greater than or equal to a first reference time when a use state of the battery is changed from the first state to a second state; an average temperature calculation unit that calculates an average temperature of the battery based on a first algorithm when the duration is less than the first reference time, and calculates the average temperature of the battery based on a second algorithm when the duration is greater than or equal to the reference time; and an aging degree calculation unit that calculates the aging degree of the battery based on the calculated average temperature.

[0020] According to another feature of an embodiment of the disclosure, the first algorithm can calculate the average temperature of the battery by using a minimum temperature value of the battery calculated before the first state of the battery begins and a temperature measurement value of a temperature sensor installed on the battery.

[0021] According to another feature of an embodiment of the disclosure, the second algorithm can calculate a minimum temperature value of the battery based on a temperature measurement value of a first temperature sensor installed on the battery and a temperature measurement value of a second temperature sensor installed on a cooling device of the battery, and calculate the average temperature of the battery using the temperature measurement value of the first temperature sensor and the calculated minimum temperature value.

[0022] Advantageous Effects

[0023] With the above-described structure, a proper temperature of a battery cell for accurately estimating an aging degree of a battery pack can be calculated to estimate an accurate internal resistance of the battery cell, and based on the accurate internal resistance, an accurate aging degree of the battery can be calculated. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A structure of a battery pack according to an embodiment of the disclosure is schematically illustrated.

[0025] Figure 2 is a block diagram showing a functional structure of a battery management system according to an embodiment of the disclosure.

[0026] Figure 3 A method of calculating an aging degree according to an embodiment of the disclosure is schematically illustrated.

[0027] Figure 4 Heat transfer inside a battery module is conceptually illustrated.

[0028] Figure 5 is a schematic diagram for describing heat transfer modeling.

[0029] Figure 6is a graph illustrating a temperature change calculated by a heat transfer model.

[0030] Figure 7 An RC heat transfer model according to an embodiment of the disclosure is illustrated.

[0031] Figure 8 Parameters used in a method of calculating an aging degree according to an embodiment of the disclosure are illustrated.

[0032] Figure 9 An aging degree calculated according to an embodiment of the disclosure is illustrated.

[0033] Figures 10a to 10c An RC heat transfer model according to an embodiment of the disclosure is illustrated.

[0034] Figure 11 is a flowchart illustrating a method of calculating an aging degree according to an embodiment of the disclosure.

[0035] Figure 12 is a flowchart illustrating a method of calculating an aging degree according to another embodiment of the disclosure.

[0036] Figure 13 A hardware configuration of a battery management system according to an embodiment of the disclosure is shown. DETAILED DESCRIPTION

[0037] Hereinafter, various embodiments of the disclosure will be described in detail with reference to the accompanying drawings. In this document, the same reference numerals are used for the same components in the drawings, and the same components will not be repeatedly described.

[0038] For each of the various embodiments of the disclosure disclosed in this document, the specific structural or functional descriptions are merely exemplified for the purpose of describing the embodiments of the disclosure, and each of the various embodiments of the disclosure can be implemented in various forms, and should not be interpreted as being limited to the embodiments described in this document.

[0039] As used in various embodiments, the terms "1st", "2nd", "first", "second", and the like can modify various components regardless of importance and do not limit the components. For example, a first component can be named a second component, and likewise, a second component can be named a first component, without departing from the scope of the disclosure.

[0040] The terms used in this document are only used to describe specific exemplary embodiments of the disclosure, and can not be intended to limit the scope of other exemplary embodiments of the disclosure. It should be understood that the singular form includes the plural reference, unless the context clearly dictates otherwise.

[0041] Figure 1The structure of a battery pack 1 according to an embodiment of the disclosure is exemplified.

[0042] Referring to Figure 1 , the battery pack 1 can include a battery module 10 including one or more battery cells 11 and being chargeable / dischargable, a switching unit 30 connected in series to a positive (+) terminal side or a negative (-) terminal side of the battery module 10 to control a charge / discharge current of the battery module 10, and a battery management system (BMS) 20 for controlling and managing to prevent overcharging and overdischarging by monitoring a voltage, a current, a temperature, etc. of the battery cells 11 and / or the battery module 10. The battery pack 1 can further include a battery protection unit (BPU) 40.

[0043] The battery module 10 can include one or more battery cells 11 that are chargeable and dischargeable. In the battery module 10, a plurality of battery cells 11 can be connected in series and / or in parallel to each other according to a required specification of the battery pack 1. That is, the number of battery cells 11 and the connection form therebetween can be determined according to a required output (voltage, current, etc.) of the battery pack 1. An output voltage of the battery module 10 can be supplied to the outside as a pack voltage through a PACK (+) terminal and a PACK (-) terminal as output terminals. The battery cells 11 can be a lithium ion (Li-ion) battery, a lithium ion polymer battery, a nickel-cadmium (Ni-Cd) battery, a nickel-hydrogen (Ni-MH) battery, etc., and can not be limited thereto when the battery cells 11 are chargeable batteries.

[0044] The BMS 20 can control and manage the overall operation of the battery pack 1. The BMS 20 can control the operation of the switching unit 30 to control the charge / discharge operation of the battery module 10. In addition, the BMS 20 can monitor a voltage, a current, a temperature, etc. of the battery module 10 and / or each battery cell included in the battery module 10. A sensor or various measurement modules (not shown) for the monitoring performed by the BMS 20 can be additionally installed at a random position of the battery module 10, a charge / discharge path, or the battery pack 1, etc. The BMS 20 can calculate a parameter (e.g., SOC or SOH, etc.) indicating a state of the battery module 10 based on a measured value such as a monitored voltage, current, temperature, etc. That is, the BMS 20 can function as the voltage measurement unit 21, the current measurement unit 22, and the control unit 25 described below. That is, the BMS 20 can function as the voltage measurement unit 21, the current measurement unit 22, the temperature measurement unit 23, the storage unit 24, and the control unit 25.

[0045] The BMS 20 can include various components such as a memory storing a computer program that is a command for controlling and managing the overall operation of the battery pack 1, a microcomputer that executes the program and controls the overall operation of the BMS 20 as a controller, input / output devices such as sensors, measuring devices, and the like, and other peripheral circuits, and the like. Additionally, the BMS 20 can include a circuit configuration for monitoring the voltage, current, temperature, and the like of the battery cells as described above.

[0046] The switching unit 30 can be a component for controlling the current for charging or discharging of the battery module 10. As the switching unit 30, a semiconductor switching element such as a relay, a MOSTET, or the like can be used. The on / off operation of the switching unit 30 can be controlled by the BMS 20.

[0047] The battery pack 1 can be communicatively connected to an external upper controller 2. That is, the BMS 20 can transmit various data about the battery pack 1 to the upper controller 2. The BMS 20 can receive a control signal about the operation of the battery pack 1 from the upper controller 2. The BMS 20 can receive a signal indicating the state of a load from the upper controller 2, the load being a device on which the battery pack 1 is mounted. The upper controller 2 can be a control system provided in the load. The load can be any device on which the battery pack 1 is mounted to operate by using the power supplied by the battery pack 1, such as an electric vehicle, an electric bicycle, or the like. When the battery pack 1 is mounted on an electric vehicle, the upper controller 2 can be a vehicle controller for controlling the travel of the vehicle.

[0048] The BPU 40 can include a component for stabilizing the operation of the battery pack 1. The BPU 40 can include a cooling device for adjusting the temperature in the battery pack 1. As the cooling device, any method such as water cooling using cooling water, air cooling using a cooling fan, or the like can be used. The BPU 40 can further include a fuse for blocking a current path when an overcurrent is generated due to occurrence of a short circuit or the like.

[0049] The BMS 20 according to the present disclosure can calculate an appropriate average temperature of the battery pack 1 according to the temperature of a specific battery cell 11 to calculate an accurate degree of aging of the battery pack 1. The BMS 20 can calculate the average temperature by using the highest temperature and the lowest temperature of the battery pack 1. The average temperature can be calculated by an algorithm determined according to the state of the battery pack 1. Hereinafter, a detailed method of calculating the degree of aging of the battery in the battery pack 1 according to the present disclosure will be described. Here, when the degree of aging of the battery is calculated, this can mean calculating the degree of aging of the battery cell 11. Alternatively, when the degree of aging of the battery is calculated, this can mean calculating the degree of aging of the battery module 10 or the battery pack 1.

[0050] Figure 2is a block diagram illustrating a functional configuration of a BMS 20 according to an embodiment of the present disclosure.

[0051] Referring to Figure 2 The BMS 20 can include a voltage measurement unit 21, a current measurement unit 22, a temperature measurement unit 23, a storage unit 24, and a control unit 25.

[0052] The voltage measurement unit 21 can be configured to measure a voltage of the battery module 10 and / or the battery cell 11. Also, the voltage measurement unit 21 can measure an open circuit voltage (OCV) of the battery cell 11. The voltage measurement unit 21 can provide the measured voltage of the battery cell 11, the measured OCV of the battery cell 11, etc. to the control unit 25. The voltage of the battery cell 11 can be a discharge voltage or a charge voltage, which is a voltage when a current flows through the battery cell 11. The OCV of the battery cell 11 can be a voltage corresponding to a case where no current flows through the battery cell 11. The voltage measurement unit 21 can store the measured voltage of the battery cell 11, the measured OCV of the battery cell 11, etc. in the storage unit 24. The voltage measurement unit can be configured to measure a voltage of each of a plurality of battery cells 11.

[0053] The current measurement unit 22 can be configured to measure a current output from the battery cell 11. The current measurement unit 22 can further include a current sensor disposed on a main current path outputting from the battery module 10 to a load. The current measurement unit 22 can provide the measured current of the battery cell 11 to the control unit 25. Also, the current measurement unit 22 can store the measured current of the battery cell 11 in the storage unit 24. Although the current measurement unit 22 is further described as measuring a current of the battery cell 11, the current measurement unit 22 can also be implemented to measure a current of the battery module 10. The current measurement unit 22 can be configured to measure a current of each of a plurality of battery cells 11.

[0054] The temperature measurement unit 23 can be configured to measure a temperature of the battery module 10 and / or the battery cell 11. The temperature measurement unit 23 can measure a temperature at a position where a temperature is expected to be at least the highest among a plurality of positions in the battery module 10. Alternatively, the temperature measurement unit 23 can measure a temperature of each of a plurality of positions in the battery module 10. The temperature measurement unit 23 can further include a temperature sensor disposed in a position where a temperature is to be measured.

[0055] The temperature measurement unit 23 can be configured to measure the temperature of a predetermined position of the cooling device operating as the BPU 40. The temperature measurement unit 23 can measure the temperature of a position in which the temperature is expected to be the lowest among the cooling device. For example, the position in which the temperature is expected to be the lowest can be a position in which cooling water is introduced. Alternatively, the position in which the temperature is expected to be the lowest can be a position in which a cooling fan is installed and thus cooling wind is introduced.

[0056] The storage unit 24 can store various computer programs required for the operation of the control unit 25. The storage unit 24 can store formulas, algorithms, etc. required for the operation of the resistance calculation unit 250, the time comparison unit 251, the average temperature calculation unit 252, and the aging degree calculation unit 253, which will be described later. That is, the storage unit 24 can store various computer programs required to calculate the aging degree of the battery.

[0057] The storage unit 24 can store various data generated by the operation of the control unit 25. For example, data about the voltage measured by the voltage measurement unit 21, data about the current measured by the current measurement unit 22, data about the temperature measured by the temperature measurement unit 23, various data calculated by the operation of the control unit 25, etc. can be stored in the storage unit 24.

[0058] The storage unit 24 can further store a reference resistance table. The reference resistance table can be a table in which the temperature of the battery and the BOL resistance of the battery are mapped to each other. That is, by the table, when the temperature is designated, the BOL resistance of the battery at the temperature can be obtained.

[0059] The control unit 25 can control the operation of the voltage measurement unit 21, the current measurement unit 22, the temperature measurement unit 23, and the storage unit 24. The control unit 25 can calculate the measurement results of the voltage measurement unit 21, the current measurement unit 22, and the temperature measurement unit 23, and calculate the aging degree of the battery based on the data obtained from the storage unit 24. That is, the control unit 25 can perform a function as a device for calculating the aging degree of the battery. The control unit 25 can include the resistance calculation unit 250, the time comparison unit 251, the average temperature calculation unit 252, and the aging degree calculation unit 253.

[0060] The resistance calculation unit 250 can be configured to calculate the current internal resistance of the battery. That is, the resistance calculation unit 250 can calculate a parameter indicating the current aging state of the battery. To calculate the internal resistance, the resistance calculation unit 250 can receive, as input, the voltage of the battery cell 11 measured by the voltage measurement unit 21, the OCV of the battery cell 11, and the current measured by the current measurement unit 22. The resistance calculation unit 250 can use the voltage of the battery cell 11 at a certain point in time, the OCV of the battery cell 11, and the current of the battery cell 11. Alternatively, the resistance calculation unit 250 can use the average of the voltage of the battery cell 11 measured over a predetermined period of time, the average of the OCV of the battery cell 11 measured over a predetermined period of time, and the average of the current of the battery cell 11 measured over a predetermined period of time. In this case, the resistance calculation unit 250 can be configured to calculate the average based on the received values, and receive the average already calculated.

[0061] The resistance calculation unit 250 can further calculate the current internal resistance taking into account the temperature value measured by the temperature measurement unit 23.

[0062] The time comparison unit 251 can compare the duration of time for which the usage state of the battery remains in the first state (hereinafter simply referred to as "duration") with the first reference time. To this end, the duration of time for each state of the battery can be counted by a timer (not shown). When the usage state of the battery changes from the first state to the second state, the time comparison unit 251 can obtain the duration of time for which the battery was in the first state, and compare the obtained duration of time with the first reference time. The time comparison unit 251 can determine whether the duration of time is greater than or equal to the first reference time based on the comparison. Here, the first state can be a parked state of the electric vehicle, and the second state can be a driving state of the electric vehicle. Alternatively, the first state can be a state in which the battery is used as an output smaller than a reference output, and the second state can be a state in which the battery is used as an output greater than or equal to the reference output.

[0063] Meanwhile, the control unit 25 can receive data on the state of the load from the upper controller 2. Alternatively, the state of the battery pack 1 can be determined by monitoring the output of the battery pack 1. The time comparison unit 251 can obtain the duration of time for which the state of the battery is identified based on the use of the above-described method.

[0064] The average temperature calculation unit 252 can determine the algorithm for calculating the average temperature based on the comparison result of the time comparison unit 251. Although it has been described that the time comparison unit 251 determines whether the duration of time is greater than the first reference time, the average temperature calculation unit 252 can also perform this operation.

[0065] When the duration is less than the first reference time, the average temperature calculation unit 252 can calculate the average temperature of the battery based on a first algorithm. The first algorithm is a scheme of calculating an average temperature value of the battery by using a minimum temperature of the battery calculated before the first state of the battery begins and a temperature measurement value of a temperature sensor installed on the battery. Here, the temperature sensor installed on the battery can be a sensor disposed in a highest temperature region of the battery. Alternatively, the temperature sensor installed on the battery can be a sensor disposed in a region estimated to be a highest temperature region of the battery.

[0066] When the duration is greater than or equal to the reference time, the average temperature calculation unit 252 can calculate the average temperature of the battery based on a second algorithm. The second algorithm can calculate a minimum temperature value of the battery based on a temperature measurement value of the temperature sensor installed on the battery and a temperature measurement value of a second temperature sensor installed on the cooling device of the battery (here, the minimum temperature value of the battery can be a temperature value of a region of the battery adjacent to the cooling device). In this case, a value (a proportional coefficient) indicating a relationship between a maximum temperature value of the battery calculated and stored before the first state begins and the minimum temperature value can be used to calculate the minimum temperature value. Thereafter, the average temperature of the battery can be calculated using the temperature measurement value of the first temperature sensor and the calculated minimum temperature value.

[0067] The average temperature calculation unit 252 can calculate the average temperature of the battery using the first algorithm or the second algorithm and set an initial average temperature used when the state of the battery changes from the first state to the second state. That is, the first algorithm and the second algorithm can be used for initial value setting when the state of the battery changes to the second state.

[0068] The aging degree calculation unit 253 can calculate the aging degree of the battery based on the average temperature calculated by the average temperature calculation unit 252. The aging degree calculation unit 253 can calculate the aging degree based on the initial internal resistance and the current internal resistance. For example, the aging degree calculation unit 235 can calculate the aging degree based on a variation amount of the current internal resistance with respect to the initial internal resistance. More specifically, the aging degree can be calculated by [Equation 1].

[0069] [Equation 1]

[0070]

[0071] The SOHR, Resistance_current, and Resistance_BOL can represent the aging degree, the current internal resistance, and the initial internal resistance, respectively.

[0072] Figure 3 A method of calculating an aging degree according to an embodiment of the disclosure is schematically illustrated.

[0073] The resistance calculation unit 250 can receive, as inputs, the voltage of the battery cell 11 measured by the voltage measurement unit 21, the OCV of the battery cell 11, and the current measured by the current measurement unit 22. The voltage input to the resistance calculation unit 250 can be an average cell voltage that is an average voltage of the battery cell 11. The OCV input to the resistance calculation unit 250 can be an average value of the OCV of the battery cell 11. The resistance calculation unit 250 can calculate the current internal resistance R cal based on the input voltage, the OCV, and the current. The resistance calculation unit 250 can further calculate the current internal resistance based on the temperature of the battery cell 11. As a method of calculating the internal resistance, various well-known methods can be used. For example, the internal resistance can be calculated by estimating the resistance value of an equivalent circuit model (ECM) through a recursive least square method. However, such a method of calculating the internal resistance can be merely an example and can not be limited thereto.

[0074] The maximum temperature value T cell_max and the minimum temperature value T cell_min of the battery cell 11, and the temperature value T coolant in the cooling device can be input to the average temperature calculation unit 252. The average temperature calculation unit 252 can calculate the average temperature T cell_avg based on the comparison result of the time comparison unit 251, using the above input values, through a first algorithm or a second algorithm. When the state is changed from the first state to the second state, the calculated average temperature can be set as an initial average temperature value in the second state.

[0075] The R cal calculated by the resistance calculation unit 250 can be input to the aging degree calculation unit 253. The T cell_avg calculated by the average temperature calculation unit 252 can be input to the aging degree calculation unit 253. The aging degree calculation unit 253 can calculate the aging degree by using the T Tcell_avg as the average temperature value, searching for and obtaining the initial internal resistance R ref of the battery at a corresponding temperature from the reference resistance table 240. Finally, the aging degree calculation unit 253 can calculate the aging degree based on the current internal resistance R cal and the reference internal resistance R ref .

[0076] In the present disclosure, it is described that the control unit 25 corresponds to an apparatus for calculating the aging degree of the battery, but the present disclosure is not limited thereto. For example, components including at least some of the voltage measurement unit 21, the current measurement unit 22, the temperature measurement unit 23, and the storage unit 24 can be understood to correspond to the apparatus for calculating the aging degree of the battery.

[0077] In the method of calculating the degree of aging, generally, the reference internal resistance is calculated using the measurement value of the specific temperature sensor in the battery without any change. As a result, since the calculated degree of aging is not accurate, it can be impossible to determine the accurate life span of the battery. Also, generally, in the sense that the degree of aging of the battery is calculated regardless of the state of the battery, it can be impossible to calculate the accurate degree of aging.

[0078] However, in calculating the average temperature of the battery as described above, the device for calculating the degree of aging of the battery according to the present disclosure uses a different algorithm for calculating the average temperature of the battery according to the duration of the first state when the state of the battery changes from the first state to the second state. In addition, the device for calculating the degree of aging of the battery according to the present disclosure can calculate the average temperature of the battery by calculating the minimum temperature of the battery using the RC heat transfer model, thereby accurately measuring the appropriate average temperature of the battery for calculating the degree of aging.

[0079] Hereinafter, the method of calculating the minimum temperature of the battery will be described in detail.

[0080] Figure 4 The heat transfer inside the battery module 10 is conceptually illustrated.

[0081] Referring to Figure 4 The first temperature sensor 230 can be provided at a first position of the upper end of the battery module 10. The first position can be a position in which the temperature is expected to be the highest in the battery module 10. The first temperature sensor 230 can be disposed in a highest temperature region of the battery module 10. On one side of the battery module 10, a cooling device 400 for cooling the battery module 10 can be provided. The cooling device 400 can be a water-cooled type cooling device, and can prevent the battery module 10 from overheating as cooling water flows through a flow path. The second temperature sensor 231 can be provided at a second position where the cooling water is introduced in the cooling device 400. The second position can be a position in which the temperature is expected to be the lowest in the battery pack 1. The second temperature sensor 231 can be disposed in a lowest temperature region of the battery pack 1.

[0082] Assuming such an inner side of the battery pack 1, heat transfer can occur from the first position of the battery module 10 to a third position corresponding to a region in which the battery module 10 and the cooling device 400 are adjacent to each other, and then, heat transfer can occur from the third position to the second position of the cooling device 400. The third position can be a position in which the temperature is expected to be the lowest in the battery module 10. Here, the first position can be denoted as a first node n1, the second position as a second node n2, and the third position as a third node n3.

[0083] The heat transfer from the first node n1 to the second node n2 and the heat transfer from the second node n2 to the third node n3 can be understood as a heat transfer between two solids in contact with each other. The heat transfer between solids can be described as follows.

[0084] Figure 5 is a schematic diagram for describing heat transfer modeling. Referring to Figure 5 , it can be assumed that the temperature of the solid B is constant (T ∞ ) and heat transfer can occur on the contact surface A with the solid A. The rate of change of the internal energy of the solid A and the surface heat transfer rate between them can be expressed as follows.

[0085] [Equation 2]

[0086]

[0087] or

[0088] [Equation 3]

[0089]

[0090] Here, k can represent thermal conductivity (W / m·k), L can represent the distance (m) between the two solids (centers), and ρ, V, c can represent the density (kg / m 3 ), the volume (m 3 ), and the specific heat (J / kg·K) of the solid A, respectively.

[0091] The temperature difference provided in [Equation 3] can be defined as [Equation 4] provided below.

[0092] [Equation 4]

[0093] θ = T - T ∞

[0094] In the case of (dθ / dt) = (dT / dt) and constant T ∞ , [Equation 4] can be expressed as [Equation 5].

[0095] [Equation 5]

[0096]

[0097] By separating the variables in [Equation 5] and integrating with respect to the initial condition T(0) = T_i at time t = 0, [Equation 6] can be obtained.

[0098] [Equation 6]

[0099]

[0100] Here, by θ i = T i -T ∞ and integrating, [Equation 7] or [Equation 8] can be obtained.

[0101] [Equation 7]

[0102]

[0103] [Equation 8]

[0104]

[0105] By using [Equation 7], the time required for the solid to reach a certain temperature T can be obtained. In contrast, by using [Equation 8], the temperature reached by the solid at a certain time t can be calculated. As can be seen from [Equation 8], as the time t approaches infinity, the temperature difference θ between the solid A and the solid B that maintains a constant temperature can exponentially decrease and thus become 0. That is, as the time t approaches infinity, the temperature of the solid A can approach the temperature T ∞ of the solid B. Figure 6 The corresponding behavior is shown in FIGS. 1 and 2.

[0106] Figure 6 is a graph for describing a temperature change calculated by a heat transfer model. Figure 6 shows a transient temperature response of the solid A with respect to a thermal time constant.

[0107] From [Equation 8], (1 / (kA / L))(pVc) can be interpreted as a thermal time constant and can be expressed as follows.

[0108] [Equation 9]

[0109]

[0110] R th may represent a thermal resistance, and C th may represent a lumped heat capacity of the solid A. R th or an increase in C th may represent that the solid reacts slowly to a change in a thermal environment. This phenomenon can be very similar to a decrease in voltage that occurs when a capacitor is discharged through a resistor in an electrical RC circuit.

[0111] By applying a solid heat transfer model based on the above heat transfer principle to a battery module (or a battery pack), the temperature of a battery cell can be calculated.

[0112] Referring back to Figure 4 , a description will be continued.

[0113] A region expected to have the lowest temperature in the battery module 10 can be a lower end portion of the lower end of the outermost battery cell 11 in the battery module 10 (a region indicated by a broken line) (third node n3). As indicated by arrows, a heat transfer path from the first node n1 to the third node n3 and from the third node n3 to the second node n2 can be simplified. Then, heat transfer between the first node n1 and the third node n3 can be explained as heat transfer between two solids. That is, the two solids can be a virtual solid representing a temperature value of the battery module 10 and the lower end portion of the outermost battery cell 11. Heat transfer between the third node n3 and the second node n2 can be explained as heat transfer between two different solids. That is, the two solids can be the lower end portion of the outermost battery cell 11 and a virtual solid representing a cooling water temperature. The first node n1, the second node n2, and the third node n3 can be represented in the form of an electrical RC circuit.

[0114] Figure 7 An RC heat transfer model according to an embodiment of the disclosure is exemplified.

[0115] The above-described C th The concentrated heat capacity C th In the two capacitors, R1 and R2 can be equal. On the other hand, R1 and R2 can be different from each other because the thermal resistance is determined by the characteristics of the two virtual solids,

[0116] To calculate the temperature in real time by the BMS 20, it is necessary to use a differential form with respect to time in [Equation 8], resulting in [Equation 10].

[0117] [Equation 10]

[0118]

[0119] The heat transfer path has been simplified so that τ th A difference between a theoretical value and an actual value can occur. Therefore, it can be required to use a heat dissipation / cooling condition test result of a battery, or the like, to perform additional correction. To minimize these correction factors, it is necessary to model without missing a heat transfer critical path of a dominant temperature change while simplifying the heat transfer critical path.

[0120] The finally corrected formula can be as shown in [Equation 11].

[0121] [Equation 11]

[0122]

[0123] By applying the battery module 10 to a case such as Figure 7The 2RC model can be expressed as [Equation 12] shown in the simplified 2RC model. Meanwhile, in the heat transfer model of the virtual model, it is assumed that the solid temperature is constant, but actually, the temperature at the first location and the temperature at the second location can change over time. However, by reducing Δt, it can be considered that the two temperatures are constant within a small time difference.

[0124] [Equation 12]

[0125] ΔTn = 1 / τ eff，1 (T n1 -T n-1 )exp(-Δt / τ eff，1 )+1 / τ eff，2 (T n2 -T n-1 )exp(-Δt / τ eff，2 )

[0126] T n1 and T n2 may represent the temperatures at the first location and the second location, respectively.

[0127] The temperature of the outermost cell of the battery cell 11 to be obtained can be as follows.

[0128] [Equation 13]

[0129] T n = T n-1 + ΔT n

[0130] As a result, it can be seen that this equation is a function of two temperature values T n1 , T n2 , and T n-1 (outermost cell temperature calculated in the previous step) measured using the first temperature sensor and the second temperature sensor.

[0131] [Equation 14]

[0132] T n = f(T n1 , T n2 , T n-1 )

[0133] The lowest temperature in the battery module 10 can be calculated based on such an RC model. In addition, the average temperature can be calculated based on the calculated lowest temperature. For example, the average temperature calculation unit 252 can calculate the average temperature as follows.

[0134] [Equation 15]

[0135] Tcell_avg = (Tcell_min + Tcell_max) / 2

[0136] T cell_max It can be the temperature value measured by the first temperature sensor located in the first position. Additionally, in the formula for the RC model derived above, T... cell_max It can correspond to T n1 T cell_min It could be the temperature at the third position. Additionally, in the RC model formula derived above, T... cell_min It can correspond to T n .

[0137] Figure 8 The parameters used in the method for calculating the degree of aging according to embodiments of the present disclosure are illustrated.

[0138] ① represents the temperature value of the first temperature sensor, which is the highest temperature; ② represents the temperature value of the second temperature sensor, which is the temperature of the cooling device; ③ represents the lowest temperature value of the battery module 10 estimated by the RC model; ④ represents the lowest temperature value of the battery module 10 (the true value of the lowest temperature value); and ⑤ represents the average temperature value.

[0139] Typically, the degree of battery aging has been calculated using the temperature value of a first temperature sensor, represented by ①. However, in embodiments of this disclosure, ③ can be estimated using an RC model, and ③ can be used to calculate the average temperature value, represented by ⑤, after which the degree of battery aging can be calculated based on the calculated average temperature value.

[0140] Figure 9 An example is shown of the degree of aging calculated according to an embodiment of the present disclosure.

[0141] The degree of battery aging calculated according to embodiments of the present disclosure can be represented by a triangle. The degree of battery aging calculated according to conventional techniques can be represented by a rectangle. When compared with the degree of battery aging calculated according to conventional techniques, the degree of battery aging calculated according to embodiments of the present disclosure has a low error rate.

[0142] Figures 10a to 10c Various variations of the RC model according to this disclosure are illustrated.

[0143] like Figure 7 and Figures 10a to 10c As shown, when the battery is in the second state, the minimum temperature value of the battery can be calculated based on the heat transfer model between the first position of the first temperature sensor mounted on the battery, the second position of the second temperature sensor mounted on the battery's cooling device, and the third position in the battery where the battery and the cooling device are in contact with each other. In this case, at least one of the spaces between the first and third positions and the spaces between the third and second positions is modeled using an RC model.

[0144] Although not shown, it can be understood that a proper number of temperature sensors can be added at proper locations to apply the model shown. For example, a plurality of temperature sensors disposed in a plurality of locations in the battery module 10 can be further used, and additionally / alternatively, a plurality of temperature sensors disposed in a plurality of locations of the cooling device 400 can be used. Figures 10a to 10c

[0145] Figure 11 is a flowchart illustrating a method of calculating an aging degree according to an embodiment of the disclosure.

[0146] Referring to Figure 11 When the electric vehicle is used in operation S100, power for driving can be supplied from the battery to the vehicle. During the vehicle is driven, the temperature of a first location of the battery can be measured in operation S101. The first location can be a location in which the temperature is expected to be the highest in the battery. The temperature of a second location of the battery can be measured in operation S102. The second location can be a location in which the temperature is expected to be the lowest in the battery. For example, the second location can be a part of the cooling device. The temperature of a third location of the battery can be calculated based on the temperature of the first location, the temperature of the second location, and RC modeling. The third location can be a location in which the temperature is expected to be the lowest among the battery cells 11 in the battery module 10. The third location can be a region of the battery module 10 adjacent to the cooling device 400.

[0147] In operation S103, the temperature of the third location of the battery is calculated based on the RC modeling. When the temperature of the third location is calculated, an average temperature can be calculated using the temperature of the first location and the temperature of the third location in operation S104, and a reference internal resistance can be obtained based on the calculated average temperature in operation S105.

[0148] Meanwhile, the operation of calculating the current internal resistance can be performed at the same time as or before or after the average temperature is calculated. To this end, the voltage and the current of the battery can be measured in operation S106. Then, by using the measured voltage value and the current value, the current internal resistance of the battery can be estimated in operation S107.

[0149] In operation S108, the aging degree of the battery can be calculated based on the reference internal resistance obtained in operation S105 and the current internal resistance estimated in operation S107.

[0150] As such, the method of calculating the aging degree of the battery according to the disclosure can calculate the average temperature of the battery by calculating the lowest temperature of the battery using the RC heat transfer model, thereby accurately measuring the proper average temperature of the battery for calculating the aging degree. As a result, an accurate battery reference internal resistance can be obtained, thereby calculating an accurate aging degree of the battery.

[0151] ​In the above-described scenario (i.e., when the battery is in either the first or second state, that is, when there is no state change), the average temperature of the battery cell can be calculated based on an RC model using heat transfer analysis. However, when a state change occurs as the battery transitions from the first to the second state, the initial temperature setting used to calculate the average temperature needs to be different. Therefore, in embodiments of this disclosure, at least two different algorithms can be used to calculate the initial average temperature.

[0152] Figure 12 This is a flowchart illustrating a method for calculating the degree of aging according to another embodiment of the present disclosure.

[0153] In description Figure 12 Previously, control unit 25 could execute the termination process (described later) when a load such as a vehicle entered a first state. The termination process can be executed when the vehicle enters a parking state. Alternatively, the termination process can be executed when the battery output is less than a reference output.

[0154] The termination process can store data about the initial minimum temperature value to be used when the vehicle transitions from the first state to the second state. During the termination process, the following scaling factor can be calculated and stored in storage unit 24.

[0155] [Formula 16]

[0156] k=(T n -T n2 ) / (T n1 -T n2 )

[0157] T n This can represent the temperature at the third location (i.e., the lowest temperature value). T n It can correspond to Figure 3 T in cell_min T n1 This can represent the temperature at the first location (i.e., the highest temperature value). T n1 It can correspond to Figure 3 T in cell_max T n2 This can represent the temperature at the second location. T n2 It can correspond to Figure 3 T in coolant .

[0158] The control unit 25 can store the calculated proportional coefficient and the minimum temperature value Tn in the storage unit 24.

[0159] The proportional coefficient and the minimum temperature value can be stored as described above, and the control unit 25 can continue to monitor the state of the vehicle in operation S200. When monitoring the state of the vehicle, this can mean monitoring the state of the battery. Alternatively, when monitoring the state of the vehicle, this can mean receiving a signal about the state of the vehicle from the superior controller 2. The control unit 25 can count the duration for which the first state is maintained in operation S201. The control unit 25 can monitor whether the state changes from the first state to another state, and when it is determined that the state changes from the first state to another state (NO in operation S201), the control unit 25 can determine whether the vehicle changes to the second state in operation S202. When the control unit 25 determines that the vehicle changes to the second state (YES in operation S202), the control unit 25 obtains the duration for which the battery is maintained in the first state in operation S203.

[0160] The control unit 25 can determine whether the obtained duration is greater than or equal to a first reference time in operation S204. The reference time can be, for example, 30 minutes. However, this is merely an example, and the reference time can be a random appropriate time such as 1 minute, 5 minutes, 10 minutes, 30 minutes, 1 hour, etc.

[0161] When the duration is less than the first reference time, the control unit 25 can calculate the average temperature by using a first algorithm. The first algorithm can calculate the average temperature value of the battery by using the minimum temperature of the battery calculated before the first state of the battery begins and the temperature measurement value of the temperature sensor installed on the battery. That is, in the first algorithm, the minimum temperature value of the battery calculated and stored before the first state begins is used.

[0162] When the duration is greater than or equal to the first reference time, the control unit 25 can calculate the average temperature by using a second algorithm in operation S207. The second algorithm can calculate the minimum temperature value of the battery based on the temperature measurement value of the first temperature sensor and the temperature measurement value of the second temperature sensor installed on the cooling device of the battery. In this case, the minimum temperature value can be calculated using the proportional coefficient calculated and stored before the battery begins the first state. For example, based on a calculation such as T n = T n2 + k(T n1 - T n2 ), the minimum temperature value can be calculated. Thereafter, in the second algorithm, the average temperature of the battery can be calculated using the temperature measurement value of the first temperature sensor and the calculated minimum temperature value.

[0163] As an additional embodiment, as Figure 12As illustrated in operation S206, when it is determined that the duration is greater than or equal to the first reference time, it can be further determined whether the duration is greater than or equal to a second reference time. The second reference time can be longer than the first reference time. When it is determined in operation S206 that the duration is greater than or equal to the second reference time, a third algorithm instead of the second algorithm can be used in operation S208 to calculate the average temperature. The third algorithm can use the temperature measurement value of the first temperature sensor mounted on the battery as the average temperature. For example, when the vehicle is kept in the parked state for a long time, the highest temperature value of the battery, the lowest temperature value of the battery, and the temperature value of the cooling device can be actually equal to each other. Accordingly, when the time of keeping the first state is longer than the second reference time, the highest temperature value can be used as the average temperature.

[0164] When the average temperature is calculated by any one of the first to third algorithms, the reference internal resistance can be calculated in operation S209 based on the calculated average temperature in the same manner as described above. Then, by using the calculated reference internal resistance and the current internal resistance, the degree of aging of the battery can be calculated in operation S210.

[0165] Accordingly, when the average temperature of the battery is calculated as described above, according to the method and apparatus for calculating the degree of aging of the battery according to the present disclosure, when the state of the battery changes from the first state to the second state, according to the duration of the first state, different algorithms for calculating the average temperature of the battery can be used, thereby accurately calculating the average temperature of the battery. Accordingly, the degree of aging of the battery can be accurately calculated.

[0166] Figure 13 A hardware configuration of the BMS 20 according to an embodiment of the present disclosure is illustrated.

[0167] Referring to Figure 13 , the BMS 20 can include a controller (micro control unit (MCU)) 200, a memory 201, a communication interface 202, and an input / output interface (I / F) 203.

[0168] The MCU 200 can process various operations and calculations in the BMS 20 and control each component.

[0169] In the memory 201, an operating system program and a program for executing the functions of the MCU 200 can be recorded. The memory 201 can include a volatile memory and a non-volatile memory. For example, at least one of various storage media such as a semiconductor memory like a random access memory (RAM), a read only memory (ROM), a flash memory, etc., and a magnetic disk, an optical disk, etc. can be used as the memory 201. The memory 201 can be a memory embedded in the MCU 200 or an additional memory installed separately from the MCU 200.

[0170] The communication I / F 202 can be a component capable of communicating with the outside, wired and / or wirelessly.

[0171] The input / output I / F 203 can perform input / output of various input signals and output signals.

[0172] When the MCU 200 executes the program stored in the memory 201, the MCU 200 can perform the functions of each component included in the control unit 25 of the BMS 20. In addition, the MCU 200 can function as the voltage measurement unit 21, the current measurement unit 22, and the temperature measurement unit 23 based on the program stored in the memory 201 and various measurement signals received through the input / output I / F 203.

[0173] The memory 201 can function as the storage unit 24. The MCU 200 can function as a communication device that communicates with the upper controller 2 by operating together with the communication I / F 202.

[0174] The above-described terms such as "include," "comprise," or "have" can mean that the corresponding component can be inherent (unless otherwise mentioned), and thus should be interpreted to further include other components rather than exclude other components. Unless otherwise defined, all terms including technical or scientific terms can be interpreted as having the same meaning as commonly understood by one of ordinary skill in the art. Terms commonly used as they are defined in a dictionary should be interpreted to have the same meaning as the context of the relevant art, and should not be interpreted to have an ideal or excessively formal meaning, unless they are clearly defined in the present disclosure.

[0175] The above description is merely an example of the technical idea of the present disclosure, and those of ordinary skill in the art to which the present disclosure pertains can make various modifications and changes without departing from the essential characteristics of the present disclosure. Accordingly, the embodiments disclosed in the present disclosure are intended to describe and not to limit the technical spirit of the present disclosure, and the scope of the technical spirit of the present disclosure is not limited by the embodiments. The scope of protection of the present disclosure should be interpreted by the appended claims, and all technical spirits falling within the same scope should be understood to be included in the scope of the present disclosure.

[0176] Cross Reference to Related Applications

[0177] This application claims priority to and the benefit of Korean Patent Application No. 10-2020-0130580, filed on October 8, 2020, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference.

Claims

1. A method for calculating the degree of aging of a battery, the method comprising the following steps: When the battery's usage state changes from a first state to a second state, the duration for which the battery is in the first state is obtained; Determine whether the obtained duration is greater than or equal to the first reference time; When the duration is less than the first reference time, the average temperature of the battery is calculated based on the first algorithm, and when the duration is greater than or equal to the first reference time, the average temperature of the battery is calculated based on the second algorithm. as well as Based on the calculated average temperature, the degree of aging of the battery is calculated. The second algorithm calculates the minimum temperature of the battery based on the temperature measurement values ​​of a first temperature sensor mounted on the battery and a second temperature sensor mounted on the battery's cooling device. It then uses the temperature measurement values ​​from the first temperature sensor and the calculated minimum temperature value to calculate the average temperature of the battery. Specifically, when the battery is in the second state, the minimum temperature value of the battery is calculated based on the heat transfer model of the first position of the first temperature sensor installed on the battery, the second position of the second temperature sensor installed on the cooling device of the battery, and the third position where the battery and the cooling device are in contact with each other.

2. The method according to claim 1, wherein, The first algorithm calculates the average temperature of the battery by using the lowest temperature value of the battery calculated before the battery begins its first state and the temperature measurement value of the temperature sensor installed on the battery.

3. The method according to claim 1, wherein, The second algorithm uses a value indicating the relationship between the highest and lowest temperature values ​​of the battery to calculate the lowest temperature value, which is calculated and stored before the battery enters its first state.

4. The method according to claim 1, wherein, The first temperature sensor includes a sensor arranged in the highest temperature region of the battery.

5. The method according to claim 1, wherein, The minimum temperature value of the battery includes the temperature value of the area of ​​the battery adjacent to the cooling device.

6. The method according to claim 1, wherein, When the state of the battery changes to the second state, the first algorithm and the second algorithm are used for initial value setting.

7. The method according to claim 1, wherein, The heat transfer model models at least one of the spaces between the first and third positions and between the third and second positions using an RC model.

8. The method according to claim 1, wherein, When the duration is a second reference time that is longer than the first reference time, the average temperature is calculated by a third algorithm instead of the second algorithm, and the third algorithm uses the temperature measurement value of the first temperature sensor installed on the battery as the average temperature.

9. The method according to claim 1, wherein, The first state includes the electric vehicle being parked, and the second state includes the electric vehicle being in motion.

10. The method according to claim 1, wherein, The first state includes a state in which the battery is used as an output less than the reference output, and the second state includes a state in which the battery is used as an output greater than or equal to the reference output.

11. An apparatus for calculating the degree of aging of a battery, the apparatus comprising: A time comparison unit determines whether the duration of the first state is greater than or equal to a first reference time when the battery's usage state changes from a first state to a second state. An average temperature calculation unit calculates the average temperature of the battery based on a first algorithm when the duration is less than the first reference time, and calculates the average temperature of the battery based on a second algorithm when the duration is greater than or equal to the first reference time. as well as An aging degree calculation unit calculates the aging degree of the battery based on the calculated average temperature. The second algorithm calculates the minimum temperature of the battery based on the temperature measurement values ​​of a first temperature sensor mounted on the battery and a second temperature sensor mounted on the battery's cooling device. It then uses the temperature measurement values ​​of the first temperature sensor and the calculated minimum temperature value to calculate the average temperature of the battery. Specifically, when the battery is in the second state, the minimum temperature value of the battery is calculated based on the heat transfer model of the first position of the first temperature sensor installed on the battery, the second position of the second temperature sensor installed on the cooling device of the battery, and the third position where the battery and the cooling device are in contact with each other.

12. The device according to claim 11, wherein, The first algorithm calculates the average temperature of the battery by using the lowest temperature value of the battery calculated before the battery begins its first state and the temperature measurement value of the temperature sensor installed on the battery.

13. The device according to claim 11, wherein, The second algorithm uses a value indicating the relationship between the highest and lowest temperature values ​​of the battery to calculate the lowest temperature value, which is calculated and stored before the battery enters its first state.

14. The device according to claim 11, wherein, When the state of the battery changes to the second state, the first algorithm and the second algorithm are used for initial value setting.

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