management device

Abstract

The present application provides a management device capable of estimating the internal temperature of a battery with high precision. The management device that manages a battery acquires an internal-external temperature difference saturation value of the battery at a constant current according to the current of the battery. Also, the management device acquires an internal-external temperature difference of the battery according to the acquired internal-external temperature difference saturation value of the battery at the constant current. Also, the management device acquires the internal temperature of the battery according to the external temperature of the battery and the acquired internal-external temperature difference of the battery.

Description

Technical Field

[0001] This invention relates to a battery management device. Background Technology

[0002] Japanese Patent Application Publication No. 2018-170144 (Patent Document 1) discloses a technology that uses a temperature equivalent circuit model with thermal resistance and thermal capacity as parameters and a Kalman filter to estimate the internal temperature of a battery based on the internal temperature of the battery pack, the external surface temperature of the battery, the current of the battery, and the internal resistance of the battery.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2018-170144 Summary of the Invention

[0004] In the aforementioned techniques, the internal temperature of a battery is estimated by analyzing various heat transfers related to the battery using a temperature equivalent circuit model and a Kalman filter. However, it is difficult to analyze all heat transfers related to the battery. For example, Patent Document 1 mentions the battery's self-heating, the heat transfer between the air surrounding the battery and the battery's outer surface, and the heat transfer between the cooling water or heater and the battery's outer surface, but makes no mention of the heat transfer between the battery's external terminals (fastening parts) and the battery's outer surface. Therefore, it is believed that the internal temperature of the battery estimated using the aforementioned techniques is more likely to be higher than the actual internal temperature of the battery.

[0005] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a management device that can accurately estimate the internal temperature of a battery.

[0006] According to one aspect of the present invention, a management device as shown below is provided. This management device manages a battery, and is configured to: obtain a saturation value of the internal and external temperature difference of the battery at a constant current based on the battery's current; obtain the internal and external temperature difference of the battery based on the obtained saturation value of the internal and external temperature difference; and obtain the internal temperature of the battery based on the external temperature of the battery and the internal and external temperature difference of the battery.

[0007] Invention Effects

[0008] According to the present invention, a management device capable of accurately estimating the internal temperature of a battery can be provided. Attached Figure Description

[0009] Figure 1 This is a diagram showing a schematic structure of a vehicle according to an embodiment of the present invention.

[0010] Figure 2 This is a diagram used to illustrate the fast charging method involved in this embodiment.

[0011] Figure 3This is a diagram showing the structure of the management device involved in this embodiment.

[0012] Figure 4 It is used for explanation Figure 3 The diagram shows the mapping table.

[0013] Figure 5 It means in execution Figure 2 The processing flow shown is a graph of the measured data.

[0014] Figure 6 It means Figure 3 A diagram showing a modified example of the management device.

[0015] Figure 7 This is a flowchart illustrating a method for setting the initial value of the internal and external temperature difference of a battery while it is parked in a modified example. Detailed Implementation

[0016] The embodiments of the present invention will be described in detail with reference to the accompanying drawings. Identical or corresponding parts in the drawings are labeled with the same symbols, and their descriptions are not repeated. In each drawing, for the directions of the three orthogonal axes (X-axis, Y-axis, and Z-axis), "+" is used to indicate the direction pointed to by the arrow, and "-" is used to indicate the opposite direction.

[0017] Figure 1 This is a diagram illustrating the structure of the vehicle involved in this embodiment. Figure 1 In this context, the -X side corresponds to the vehicle's direction of travel, and the -Z side corresponds to the vertical direction (the direction of gravity). (Reference) Figure 1 The vehicle 1000 includes a battery pack 100. The battery pack 100 is, for example, fixed under the floor of the vehicle 1000. The mounting method of the battery pack 100 is arbitrary. For example, the casing of the battery pack 100 may form part of the vehicle body (e.g., floor panel).

[0018] The vehicle 1000 also includes: an Electronic Control Unit (ECU) 500 that manages the battery pack 100; and various sensors (including an external temperature sensor 45) to detect the vehicle 1000's status (position, speed, etc.) and environment in real time. The external temperature sensor 45 detects the ambient temperature of the vehicle 1000 (the external temperature around the vehicle 1000). The detection results from the various sensors are output to the ECU 500. The ECU 500 includes a processor and a storage device. The storage device is configured to store the information. In addition to the program, the storage device also stores various information used in the program. In the ECU 500, the processor executes the program stored in the storage device, thereby performing various controls. The ECU 500 is an example of the "management device" involved in this invention.

[0019] The vehicle 1000 also includes: a drive unit 20 for driving the vehicle 1000; and a socket 410 and a charging relay 420 for charging the battery pack 100.

[0020] The drive unit 20 includes a power control unit (PCU) 21, a motor generator (MG) 22, and an engine 23. The vehicle 1000 is configured to operate using electricity output from the battery pack 100. The vehicle 1000 is, for example, a plug-in hybrid electric vehicle (PHEV). Alternatively, the vehicle 1000 could also be, for example, a battery electric vehicle (BEV) or other electric vehicle (xEV).

[0021] PCU21 includes, for example, an inverter. MG22 functions as a drive motor, rotating the drive wheels 24 of vehicle 1000. PCU21 uses power supplied from battery pack 100 to drive MG22. Thus, MG22 is in a powered operation state. In the powered operation state, MG22 converts electricity into torque. The torque is transmitted to drive wheels 24. Furthermore, MG22 enters a regenerative state, for example, when vehicle 1000 decelerates, charging the batteries included in battery pack 100 through regenerative power generation.

[0022] Engine 23 functions as an internal combustion engine, rotating the drive wheels 24 of vehicle 1000. Engine 23 generates power by burning fuel supplied from a fuel tank (not shown). The power generated by engine 23 is transmitted to the drive wheels 24. Exhaust pipe 23a is connected to engine 23, discharging the exhaust from engine 23 to the outside of the vehicle.

[0023] The battery pack 100 includes multiple battery cells 10 (rechargeable battery cells), each functioning as a secondary battery. The multiple battery cells 10 are stacked and constrained, for example, in the X direction, thereby forming a battery stack. The battery stack is a modular energy storage module that connects multiple battery cells 10 electrically. In this embodiment, liquid lithium-ion batteries are used as battery cells 10. However, the battery cells 10 are not limited to lithium-ion batteries; for example, they can be other secondary batteries such as nickel-metal hydride batteries or sodium-ion batteries. The type of secondary battery is not limited to liquid secondary batteries; it can also be an all-solid-state secondary battery. The battery stack may include only battery cells of the same type or may include battery cells of different types.

[0024] like Figure 1As shown in the lower part, the battery cell 10 includes a housing 11, a storage section 12 housed within the housing 11, a positive terminal 13, and a negative terminal 14. The housing 11 is, for example, a rectangular metal housing, fixed to the bottom wall 100a of the battery pack 100. The positive terminal 13 and the negative terminal 14 are also made of metal. The positive terminal 13 and the negative terminal 14 each have a first terminal portion 13a and 14a located outside the housing 11 and a second terminal portion 13b and 14b housed within the housing 11. The first terminal portions 13a and 14a are portions protruding from the surface of the housing 11 (the +Z side surface F10), respectively, and function as external terminals. In this embodiment, the first terminal portion and the second terminal portion of the positive terminal 13 and the negative terminal 14 are integrally formed and seamlessly connected. However, this is not a limitation; the first terminal portion and the second terminal portion may also be formed separately and then joined together.

[0025] The energy storage unit 12 includes a laminate formed of multiple positive electrode plates and multiple negative electrode plates. This laminate is formed by alternately stacking positive and negative electrode plates. A positive electrode plate includes, for example, a positive current collector and a positive active material layer. A negative electrode plate includes, for example, a negative current collector and a negative active material layer. Each electrode plate can be formed by coating an active material onto the surface of a metal foil that serves as the current collector. A separator can be disposed between the positive and negative electrode plates. The housing 11 also contains electrolyte, together with the energy storage unit 12. Electrolyte can be injected into the housing 11 through an injection port (not shown), and the injection port can be blocked after injection. A gas vent valve can be provided on the housing 11.

[0026] In addition, the aforementioned laminated body functions as an electrode body. The electrode body included in the energy storage unit 12 is not limited to a laminated body formed by unidirectionally stacking multiple electrode sheets, but may also be a wound body (for example, a wound body formed by winding an alternating stacked positive and negative electrode sheets).

[0027] Collector tabs 13c and 14c are provided on the energy storage unit 12. Collector tabs 13c and 14c are collections of multiple tabs (e.g., tab bundles). The electrode plates and tabs can be formed and joined separately, or they can be formed seamlessly as a single unit. Collector tab 13c is electrically connected to each of the multiple positive electrode plates included in the energy storage unit 12, and is also electrically connected to the second terminal portion 13b of the positive terminal 13. Collector tab 14c is electrically connected to each of the multiple negative electrode plates included in the energy storage unit 12, and is also electrically connected to the second terminal portion 14b of the negative terminal 14. With the above structure, the potentials of the positive and negative electrode plates included in the energy storage unit 12 are output to the first terminal portions 13a and 14a (external terminals) via collector tabs 13c and 14c and the second terminal portions 13b and 14b, respectively.

[0028] A temperature sensor 41 for detecting the external temperature of the battery cell 10 is provided on the outer surface F10 of the housing 11. The temperature sensor 41 can be a thermistor. Furthermore, a voltage sensor 42 for detecting the voltage between the positive terminal 13 (first terminal 13a) and the negative terminal 14 (first terminal 14a) is provided on the battery cell 10. The temperature sensor 41 and the voltage sensor 42 are provided for each battery cell 10.

[0029] The battery pack 100 also includes a current sensor 43 for detecting the current flowing through the battery cells 10 (energy storage unit 12). In this embodiment, all the battery cells 10 included in the battery pack 100 are connected in series, and the same current flows through all the battery cells 10. Therefore, one current sensor 43 can be used in all the battery cells 10. However, it is not limited to this; the battery pack 100 may also include multiple battery cells connected in parallel. The current sensor 43 can be provided for each battery cell 10. The detection results from the temperature sensor 41, voltage sensor 42, and current sensor 43 are output to the ECU 500.

[0030] The vehicle 1000 also includes a cooler 31 and a heater 32. The cooler 31 includes a flow path 31a for the flow of a heat medium. The heat medium is pressurized by a pump (not shown) controlled by the ECU 500 and flows within the flow path 31a. The heat medium flowing within the flow path 31a exchanges heat with all the battery cells 10 included in the battery pack 100. The heater 32 heats the heat medium according to the requirements from the ECU 500. The heat medium flowing in the flow path 31a cools the battery pack 100 as the temperature of the battery pack 100 rises. Wherein, when the temperature of the battery pack 100 is low due to weather or location (e.g., cold region), the heat medium heated by the heater 32 raises the temperature of the battery pack 100. The cooler 31 and the heater 32 respectively adjust the temperature of all the battery cells 10 included in the battery pack 100. In this embodiment, water is used as the heat medium. However, the heat medium is not limited to water and may also be other liquids (antifreeze, etc.) or gases (carbon dioxide, etc.).

[0031] The vehicle 1000 is configured to, while parked, receive DC power from an external power supply and simultaneously charge all battery cells 10 (batteries) included in the battery pack 100 using the supplied DC power. This charging method will be referred to as "fast charging". The rated output of the power supply equipment used for fast charging is, for example, 50 kW or more (current 125 A or more).

[0032] Figure 2 This is a diagram illustrating the controls related to fast charging performed by ECU500. (Reference) Figure 2The Electric Vehicle Supply Equipment (EVSE) 900 is configured to supply DC power to the battery pack 100 from outside the vehicle 1000. Specifically, the EVSE 900 includes a control device 910, a power circuit 920, and a charging cable 930. The power circuit 920 is configured to adjust the output power and is controlled by the control device 910. The power circuit 920 outputs DC power requested from the control device 910 to the charging cable 930. In this embodiment, the EVSE 900 is installed indoors. However, it is not limited to this; the vehicle 1000 may also use an outdoor power supply device to perform fast charging of the battery pack 100.

[0033] When the vehicle 1000 is in a parked state, the ECU 500 is in a stopped state (including a sleep state). Then, if the front end 930a (connector) of the charging cable 930 is connected to the socket 410 of the vehicle 1000, the ECU 500 is activated. The activated ECU 500 then connects the charging relay 420 to the connected state (closed state) and sends a charging request signal to the control device 910. Thus, the EVSE 900 begins to supply power for fast charging.

[0034] The ECU 500 and control device 910 can communicate via wired or wireless means through charging cable 930. The charging request signal includes a charging allowable current. The charging allowable current represents the upper limit of the charging current. The charging request signal requests power from the EVSE 900; however, power supply exceeding the charging allowable current is not permitted by the EVSE 900. The control device 910 controls the power circuit 920 based on the received charging request signal. This controls the DC power output from the EVSE 900 so that the current input to the socket 410 does not exceed the charging allowable current. The charging allowable current included in the charging request signal corresponds to the initial value of the charging allowable current, set to a small value (e.g., close to 0A) that sufficiently suppresses the degradation of the battery cell 10. Alternatively, the initial value of the charging allowable current can be 0A. In this case, even if the ECU 500 sends a charging request signal, fast charging will not begin immediately; instead, fast charging will begin by sending a charging allowable current exceeding 0A to the EVSE 900 in S16 (described later).

[0035] After sending the aforementioned charging request signal, ECU500 begins... Figure 2 The process flow shown is F1. "S" in the flowchart represents a step.

[0036] In processing flow F1, ECU 500 obtains the external temperature of battery cell 10 in S11 based on the output from temperature sensor 41. The external temperature of each battery cell 10 included in the battery pack 100 is obtained. In subsequent S12, ECU 500 obtains the squared value of the current of battery cell 10 based on the output from current sensor 43. At this time, ECU 500 can correct for errors in current sensor 43 (e.g., errors in the output value when no current is flowing) and use the corrected detection value to calculate the squared value of the current. Hereinafter, the current of battery cell 10 is sometimes labeled "IB".

[0037] In subsequent step S13, ECU500 uses the external temperature of battery cell 10 obtained in S11 and the square of the current of battery cell 10 obtained in S12 to obtain the internal temperature of battery cell 10. The internal temperature of each battery cell 10 included in the battery pack 100 is obtained. Details regarding S13 will be described later (see reference). Figure 3 In the subsequent S14, the ECU 500 acquires the State of Charge (SOC) of the battery cell 10. The SOC is acquired for each battery cell 10 included in the battery pack 100. SOC represents the charge rate. The charge rate is, for example, the ratio of the current stored capacity to the stored capacity in a fully charged state, expressed as 0 to 100%. Known methods such as the current integration method or the OCV (open-circuit voltage) estimation method can be used to determine the SOC.

[0038] In the subsequent S15, ECU500 uses the internal temperature of battery cell 10 obtained in S13 and the SOC of battery cell 10 obtained in S14 to determine the charging allowable current. Details regarding S15 will be described later (see reference). Figure 3 Next, in S16, ECU 500 sends the acquired charging allowable current to control device 910. In S15, if different charging allowable currents are acquired for the multiple battery cells 10 included in battery pack 100, ECU 500 sends the smallest charging allowable current among the charging allowable currents acquired for each battery cell 10 to control device 910 in S16. Control device 910 controls power circuit 920 based on the latest received charging allowable current. Control device 910 can control power circuit 920 to bring the current input from EVSE 900 to vehicle 1000 (socket 410) close to the charging allowable current.

[0039] In the subsequent S17, ECU 500 determines whether the prescribed charging end condition is met. The charging end condition is met when the SOC of at least one battery cell 10 reaches a predetermined value (e.g., the SOC value representing a full charge). Alternatively, the charging end condition may also be met when the user instructs ECU 500 to stop charging. The charging end condition can be appropriately changed. For example, the charging end condition may be met after a predetermined time has elapsed after fast charging has begun.

[0040] If the charging termination condition is determined to be false ("No" in S17), the process returns to S11. Therefore, during fast charging (i.e., when vehicle 1000 charges the battery using DC power supplied from EVSE900), processes S11 to S17 are repeated. Thus, in S13, the internal temperature of battery cell 10 is estimated, and in S16, the charging allowable current based on the latest internal temperature of battery cell 10 is sent to EVSE900. Then, EVSE900 supplies power to vehicle 1000 based on the latest charging allowable current. On the other hand, if the charging termination condition is determined to be true ("Yes" in S17), ECU500 sends a charging termination notification (a notification to end fast charging) to control device 910 in S18, and then the process ends. Figure 2 The processing flow F1 is shown. For example, if the SOC of at least one battery cell 10 reaches the specified value through fast charging, the charging termination condition is determined to be met. Upon receiving the charging termination notification, the control device 910 controls the power circuit 920 to stop supplying power from the EVSE 900 to the vehicle 1000.

[0041] Figure 3 This is a diagram showing the structure of ECU500. (Reference) Figure 3 The ECU 500 includes a battery internal temperature estimator 510 (hereinafter referred to as "estimator 510") and a charging allowable current calculator 520 (hereinafter referred to as "calculator 520"). The estimator 510 includes a mapping table 511, a first-order hysteresis equation 512 (hereinafter referred to as "equation 512"), and a subtractor 513. The mapping table 511 and equation 512 are stored in the storage device of the ECU 500.

[0042] Current flows through the internal resistance of battery cell 10 (reference) Figure 1 The battery cell 10 generates heat. It is known that the heat generated inside the battery cell 10 is proportional to the square of the current in the battery cell 10. However, the square of the current in the battery cell 10 (hereinafter referred to as "IB")... 2The correlation between the saturation value of the temperature difference between the inside and outside of the battery cell 10 at constant current (hereinafter denoted as "fs") and the saturation value of the temperature difference between the inside and outside of the battery cell 10 is a discovery made by the inventors and is not publicly known. Mapping table 511 is prepared based on the above-mentioned relationship confirmed in advance through experiments or simulations. Mapping table 511 represents IB 2 The relationship with fs. The following uses... Figure 4 The mapping table 511 will be explained. Furthermore, the temperature difference between the inside and outside of the battery cell 10 is equivalent to the absolute value of the difference between the internal temperature and the external temperature of the battery cell 10.

[0043] Figure 4 This is a diagram used to illustrate mapping table 511. Figure 4 Lines L11 to L13 in the diagram represent the current values ​​of battery cell 10 (and thus, IB). 2 The data was acquired under constant conditions. Line L11 represents the change in external temperature of battery cell 10. Line L12 represents the change in internal temperature of battery cell 10. Line L13 represents the change in the temperature difference between the inside and outside of battery cell 10. In line L13, the saturation value of the temperature difference between the inside and outside of battery cell 10 is equivalent to the current value relative to IB. 2 fs. By changing IB 2 Similarly, the determination is made relative to another IB. 2 The fs can target multiple IBs. 2 Each fs is obtained. A predetermined number of IBs are obtained beforehand through experiments. 2 The data is combined with fs and then created into a mapping table. A lower limit protection value is then set for the experimental data as needed. For example, mapping table 511 is created in this way. The created mapping table 511 is stored in the storage device of ECU 500.

[0044] Figure 4 Line L14 in the diagram represents an example of mapping table 511. As shown by line L14, mapping table 511 specifies IB. 2 The larger the value, the larger the value of fs. Specifically, in IB... 2 Become the specified value ( Figure 4 "IB" 2 In the region below "_ST", the fs specified in mapping table 511 is defined as close to the specified lower limit protection value ( Figure 4 (in "fs_MIN"). Figure 4 In the experimental data shown by line L14a (dashed line) in IB, 2 In small areas, IB 2 The larger the value, the larger the value of fs. However, in mapping table 511, the minimum value of fs is defined by the aforementioned lower limit protection value (fs_MIN). The fs shown in mapping table 511 is always above the lower limit protection value.

[0045] After vehicle 1000 is parked, if it remains parked for an extended period, the temperature difference between the inside and outside of battery cell 10 gradually decreases during this time. However, it is rare for the temperature difference between the inside and outside of battery cell 10 to completely disappear before fast charging begins. Therefore, in this embodiment, a lower limit protection value (fs_MIN) is provided. This ensures that the initial value of the temperature difference between the inside and outside of battery cell 10 is close to the actual value, making it easier to estimate the internal temperature of battery cell 10 with high accuracy. In this embodiment, the lower limit protection value is set to a fixed value.

[0046] Refer again Figure 3 Equation 512 is a first-order hysteresis equation related to the thermal changes (heating or heat dissipation) of the battery cell 10. In this embodiment, Equation 512 is expressed as follows.

[0047] dT(t+dt)=dT(t)+(fs-dT(t))×β×dt

[0048] In the above formula, dT(t+dt) represents the current value of the temperature difference between the inside and outside of battery cell 10. Figure 2 The internal temperature of battery cell 10 obtained in S13 is shown. As described above, the temperature difference between the inside and outside of battery cell 10 is expressed as a function of time t. dT(0) is the initial value of the temperature difference between the inside and outside of battery cell 10. dT(t) represents the previous value of the temperature difference between the inside and outside of battery cell 10. dt represents the operation cycle of ECU500 ( Figure 2 The cycle of S11 to S17 shown is repeated. In this embodiment, in the first processing routine of processing flow F1, ECU 500 sets fs (hereinafter referred to as "fs_IN") obtained according to mapping table 511 to dT (0). When fast charging starts, the current of battery cell 10 is 0A or close to 0A, so fs_IN is the same as the lower limit protection value mentioned above ( Figure 4 The temperature difference between the inside and outside of battery cell 10 tends to decrease during fast charging (see below). Figure 5 Therefore, fs_IN corresponds to the maximum temperature difference between the inside and outside of battery cell 10. As mentioned above, fs is based on IB. 2 And changes (reference) Figure 4 ), and determined according to mapping table 511. β is the first-order hysteresis coefficient related to the thermal changes of battery cell 10. In this embodiment, the pre-calculated β (fixed value) is stored in the storage device of ECU 500.

[0049] exist Figure 2 In S13, the processor of ECU500 uses mapping table 511 to obtain IB based on the output from current sensor 43. 2 ( Figure 2The corresponding fs is obtained from S12. Furthermore, the processor of ECU500 substitutes the obtained fs into Equation 512 to calculate dT(t+dt). The calculated dT(t+dt) is equivalent to the internal and external temperature difference of battery cell 10.

[0050] During fast charging, the heating of the metal parts of the battery cell 10 is the primary factor affecting its temperature rise. Specifically, during fast charging, a large current flows through the battery cell 10. In the battery cell 10 with this large current, the heating of the metal parts contributes more to the temperature rise than the self-heating within the battery cell 10. This is believed to be because the heat capacity of the metal parts (positive terminal 13, negative terminal 14, etc.) is greater than that of the electrode body (energy storage section 12). The heating of the metal parts has minimal influence other than the current. Therefore, the internal and external temperature difference of the battery cell 10 can be uniquely determined based on the current of the battery cell 10. Therefore, as described above, the ECU 500 determines fs based on the current of the battery cell 10 and then determines the internal and external temperature difference of the battery cell 10 based on the obtained fs.

[0051] Figure 3 The subtractor 513 shown is configured to subtract the temperature difference between the inside and outside of the battery cell 10 from the external temperature of the battery cell 10. In this embodiment, the processor of the ECU 500 functions as the subtractor 513. A portion of the electronic circuitry constituting the processor can function as the subtractor 513. The ECU 500 subtracts the external temperature of the battery cell 10 (obtained from the output of the temperature sensor 41) from the external temperature of the battery cell 10. Figure 2 The S11 value and the calculated dT(t+dt) are input to the subtractor 513. The subtractor 513 then outputs the value obtained by subtracting dT(t+dt) from the external temperature of the battery cell 10. The value output from the subtractor 513 corresponds to the internal temperature of the battery cell 10. The estimator 510 estimates the internal temperature of the battery cell 10 as described above.

[0052] Figure 3 The calculator 520 shown uses the internal temperature of the battery cell 10 and the state of charge (SOC) of the battery cell 10 estimated by the estimator 510. Figure 2 The charging allowable current is calculated using S14. In this embodiment, in the ECU 500, the processor performs calculations based on a mapping table stored in a storage device, thereby functioning as a calculator 520. The calculator 520 can use... Figure 3The allowable charging current is obtained from the mapping tables represented by lines L21 and L22. Each mapping table shows the relationship between the internal temperature of the battery cell 10 and the allowable charging current. Line L21 represents the mapping table related to the battery cell 10 at low SOC. Line L22 represents the mapping table related to the battery cell 10 at high SOC. In the battery cell 10 at low and high SOC, if the current (charging current) of the battery cell 10 exceeds the allowable charging current shown by lines L21 and L22, respectively, lithium (Li) is easily deposited inside the battery cell 10. Li deposition promotes the degradation of the battery cell 10.

[0053] For example, as shown in lines L21 and L22, the internal temperature of battery cell 10 is lower than the first temperature ( Figure 3 In the region marked "Te1", the calculator 520 increases the allowable charging current as the internal temperature of the battery cell 10 increases. In the region where the internal temperature of the battery cell 10 is above Te1 and below Te2, the calculator 520 sets the allowable charging current to a constant value (fixed value). Te2 is a second temperature higher than the first temperature. Then, in the region where the internal temperature of the battery cell 10 exceeds Te2, the calculator 520 decreases the allowable charging current as the internal temperature of the battery cell 10 increases. Furthermore, the calculator 520 decreases the allowable charging current when the SOC of the battery cell 10 exceeds a predetermined value. The calculator 520 can decrease the allowable charging current as the SOC of the battery cell 10 increases.

[0054] By repeatedly performing during fast charging Figure 2 In the processes shown in S11 to S16, the estimator 510 and the calculator 520 respectively acquire the internal temperature and charging allowable current of each battery cell 10. Through the process in S13, the transient internal temperature of the battery cell 10 when the current (IB) of the battery cell 10 changes is acquired. Through the process in S15, the charging allowable current of each battery cell 10 included in the battery pack 100 is acquired sequentially. Then, the ECU 500 sends the smallest charging allowable current among the charging allowable currents acquired for each battery cell 10 to the control device 910. Figure 2 (S16).

[0055] As explained above, the ECU 500 (management device) managing the battery pack 100 obtains the saturation value (fs) of the internal and external temperature difference of the battery cell 10 at a constant current based on the current of the battery cell 10 (battery) included in the battery pack 100. Furthermore, the ECU 500 obtains the internal and external temperature difference (dT(t+dt)) of the battery cell 10 based on the obtained saturation value. Additionally, the ECU 500 obtains the internal temperature of the battery cell 10 based on the external temperature of the battery cell 10 and the internal and external temperature difference. With this structure, the internal temperature of the battery cell 10 can be estimated without using the resistance of the metal heating element of the battery cell 10, which is particularly difficult to determine. Therefore, the ECU 500 can estimate the internal temperature of the battery cell 10 with high accuracy.

[0056] ECU 500 is configured to repeatedly execute [the following commands] when vehicle 1000 uses DC power supplied from EVSE 900 to charge the individual batteries included in battery pack 100. Figure 2 The processes shown in S11 to S16 can suppress battery degradation and improve charging speed. Specifically, in low-temperature regions (e.g., Figure 3 In areas smaller than Te1 (as shown), if the internal temperature of the battery cell 10 is mistakenly detected as a high-temperature side, Li precipitation is likely to occur. Furthermore, in high-temperature regions (e.g., Figure 3 In the vicinity of Te2 (as shown), if the internal temperature of battery cell 10 is mistakenly detected as high-temperature, the charging speed slows down due to excessive current limitation. The ECU 500 can accurately estimate the internal temperature of battery cell 10, thus suppressing degradation of battery cell 10 and charging it at high speed. In this embodiment, Figure 2 The processes S11, S12, S15, and S16 shown correspond to an example of the "first process", "second process", "sixth process", and "seventh process" involved in this invention, respectively (see reference). Figure 3 ).and, Figure 2 The process S13 shown is equivalent to an example of the "third process", "fourth process" and "fifth process" involved in this invention (see reference). Figure 3 and Figure 4 ).

[0057] Figure 5 Indicated based on Figure 2 The data measured during fast charging in the processing flow F1 shown. Figure 5 In the diagram, line L31 represents the shift in the current (charging current) of battery cell 10 obtained in S12. Line L32 represents the shift in current obtained from equation 512 in S13. Figure 3 The shift in the internal and external temperature difference of the battery cell 10 output by the subtractor 513 in S13. Line L33 indicates the shift in the internal and external temperature difference of the battery cell 10 output by the subtractor 513 in S13. Figure 3 The graph shows the temperature shift of the internal components of the output battery cell 10. Line L34 represents the state of charge (SOC) of the battery cell 10 obtained in S14. The horizontal axis of the graph represents the time elapsed since the start of fast charging. Figure 5 In the example shown, at the start of fast charging, the internal temperature of battery cell 10 is -10°C, and the state of charge (SOC) of battery cell 10 is 10%. Based on actual measured data, it can be confirmed that both battery degradation suppression and charging speed improvement are achieved.

[0058] In the above embodiment, the initial value of the temperature difference between the inside and outside of the battery cell 10 is ( Figure 3 In dT(0)), the lower limit protection value is adopted ( Figure 4 The initial value of fs_MIN is a fixed value. However, it is not limited to this; the initial value of the temperature difference between the inside and outside of the battery cell 10 can also be variable. Figure 6 It means Figure 3 The diagram shows a modified example of the ECU500.

[0059] refer to Figure 6 The ECU500A involved in the modified example basically has the same characteristics as... Figure 3 The ECU500 shown has the same structure, but is equipped with a battery internal temperature estimator 510A (hereinafter referred to as "estimator 510A") instead. Figure 3 The estimator 510 is shown. In addition to mapping table 511, equation 512, and subtractor 513, estimator 510A also includes mapping table 514. Mapping table 514 specifies the relationship between the ambient temperature of vehicle 1000 and fs_IN. Mapping table 514 is pre-created through experimentation or simulation and stored in the storage device of ECU 500A. ECU 500A uses mapping table 514 to obtain the ambient temperature of vehicle 1000 detected by external temperature sensor 45 (…). Figure 6 The fs_IN corresponding to "T_IN" in the equation. In this variant, the fs_IN obtained through mapping table 514 is set to dT(0) in equation 512. Furthermore, in IB 2 for Figure 4 IB in 2 During the period below _ST, fs_IN obtained through mapping table 514 is set to fs in equation 512. In IB 2 More than IB 2 In the case of _ST, according to mapping table 511 ( Figure 4 The line L14 in the middle is set to fs.

[0060] The modified ECU 500A is configured to determine the initial value of the internal and external temperature difference of the battery cell 10 based on the ambient temperature of the vehicle 1000. Therefore, even when the ambient temperature of the vehicle 1000 changes drastically, the internal temperature of the battery cell 10 can be easily estimated with high accuracy. For example, on a cold day, when the vehicle 1000 moves from outdoors into a warm garage (indoors), a temperature difference between the internal and external of the battery cell 10 is likely to occur due to the change in ambient temperature. Therefore, when fast charging begins indoors, the possibility of a residual temperature difference between the internal and external of the battery cell 10 increases. By using the mapping table 514, the internal and external temperature difference of the battery cell 10 at the start of charging can be obtained with high accuracy.

[0061] In the above embodiments, Figure 2 In the initial processing routine of the processing flow F1 shown, ECU500 sets fs (fs_IN) obtained from mapping table 511 as the initial value of the temperature difference between the inside and outside of the battery. Figure 3 dT(0) in the context of dT(0). However, it is not limited to this. Figure 3 The ECU500 shown can also be used while the vehicle 1000 is parked, via... Figure 7 The processing flow F2 shown updates the initial value of the temperature difference between the inside and outside of the battery sequentially. Then, when the above fast charging is started, ECU500 can use the latest initial value (dT(0)) set by processing flow F2 instead of fs_IN in the first processing routine of processing flow F1.

[0062] Figure 7 This is a flowchart illustrating a method for setting the initial value of the temperature difference between the inside and outside of the battery while the vehicle is parked. When the vehicle 1000 is parked, the ECU 500 enters a stopped state (including a sleep state). Then, while the vehicle 1000 is parked, it starts at a predetermined cycle. Figure 7 The processing flow F2 is shown. If processing flow F2 is started, ECU 500 is activated in S21. The activated ECU 500 executes the processing from S22 onwards.

[0063] In S22, ECU 500 acquires a temperature Tv related to the ambient temperature of battery pack 100. Specifically, ECU 500 can acquire the external temperature of battery cell 10 detected by temperature sensor 41 as temperature Tv. Alternatively, ECU 500 can acquire the ambient temperature of vehicle 1000 detected by external temperature sensor 45 as temperature Tv. ECU 500 functions as a Battery Management System (BMS) that monitors battery pack 100.

[0064] In the subsequent S23, the ECU500 associates the temperature Tv detected in S22 with the acquisition time and saves it. Thus, the data representing the progression of temperature Tv is stored in the storage device of the ECU500.

[0065] In subsequent step S24, ECU 500 acquires the absolute value of the difference between the previous value and the current value of temperature Tv. The previous value of temperature Tv is equivalent to the temperature Tv acquired in the previous processing routine S23. The current value of temperature Tv is equivalent to the temperature Tv acquired in the current processing routine S23. ECU 500 can read the previous and current values ​​of temperature Tv from the storage device and then calculate the difference between them. In the initial processing routine, ECU 500 can consider the temperature Tv detected before the start of the initial processing routine as the previous value of temperature Tv. Hereinafter, the absolute value of the difference between the previous and current values ​​of temperature Tv calculated in S24 is referred to as the "change in temperature Tv". The change in temperature Tv is equivalent to the change in ambient temperature per unit time of the battery pack 100 in the parked vehicle 100.

[0066] In the subsequent S25, ECU500 determines whether the change in temperature Tv is within a specified reference value. If the change in temperature Tv is within the reference value ("Yes" in S25), ECU500 sets the first value (hereinafter referred to as "Vx") to dT(0) in S26. If the change in temperature Tv is greater than the reference value ("No" in S25), ECU500 sets the second value (hereinafter referred to as "Vy") to dT(0) in S27. Vx and Vy are different from each other. Vx can be a value smaller than Vy. dT(0) represents the initial value of the temperature difference between the inside and outside of the battery cell 10. The reference value can be a fixed value or a variable value. A determination of "Yes" in S25 indicates that the ambient temperature of the battery pack 100 has not changed, or even if the ambient temperature changes, the change is slow.

[0067] If dT(0) is set through either process S26 or S27, then after ECU500 is in a stopped state (e.g., sleep state) in S28, process flow F2 ends. Then, if a predetermined time (unit time) elapses from the end of process flow F2, process flow F2 starts again. In this way, ECU500 periodically starts and executes process flow F2. Thus, dT(0) is updated sequentially during shutdown. Through processes S25 to S27, Vx or Vi is set to dT(0) based on the change in temperature Tv.

[0068] exist Figure 7In the above-described modified example, when the ambient temperature change per unit time of the battery in a parked vehicle is less than a reference value, the ECU 500 (management device) sets a first value as the initial value for the internal and external temperature difference (S26). When the ambient temperature change per unit time of the battery in a parked vehicle is greater than the reference value, a second value different from the first value is set as the initial value (S27). Furthermore, the ECU 500 (management device) obtains the internal and external temperature difference of the battery based on the set initial value and the internal and external temperature difference saturation value (for example, referring to...). Figure 2 The processing flow F1 shown is as follows: Figure 3 As shown in Equation 512). Such an ECU 500 (management device) can accurately obtain the temperature difference between the inside and outside of the battery.

[0069] In the above embodiment, β (first-order hysteresis coefficient) in Equation 512 is a fixed value. However, it is not limited to this; β can also be variable. Specifically, depending on the battery, there are batteries with a large difference between the first-order hysteresis during heating and the first-order hysteresis during cooling. Therefore, ECU 500 can determine whether the internal temperature change of the battery cell 10 is rising or falling, and change the value of β in Equation 512 during heating and cooling. Specifically, ECU 500 in Figure 2 When the internal temperature of battery cell 10 is obtained in step S13, the obtained internal temperature of battery cell 10 (current value) can be compared with the internal temperature of battery cell 10 obtained in the previous processing routine (previous value). If the current value is higher than the previous value, it is determined that the temperature has increased; if the current value is lower than the previous value, it is determined that the temperature has decreased. Then, ECU 500 can determine β of formula 512 to be used in the next processing routine based on the determination result. In detail, when it is determined that the internal temperature of battery cell 10 has increased, ECU 500 sets a first coefficient for β in formula 512; when it is determined that the internal temperature of battery cell 10 has decreased, it sets a second coefficient for β in formula 512. The first coefficient and the second coefficient represent different values. These coefficients are obtained through prior experiments or simulations and stored in the storage device of ECU 500. According to the above structure, the internal temperature of a battery can be easily estimated with high accuracy for a wide variety of batteries.

[0070] Figure 2 The processing flow F1 shown can be modified as appropriate. For example, the order of processing can be changed according to the purpose, or unnecessary steps can be omitted. For example, the processing of S11 can be performed after S12 (e.g., between S12 and S13).

[0071] The structure of a vehicle is not limited to Figure 1The structure shown is not limited to a four-wheeled car; it can also be a bus or a truck. The management device can also be used in vehicles other than automobiles (ships, airplanes, etc.), unmanned mobile bodies (unmanned transport vehicles, robots, etc.), or buildings (residential buildings, factories, etc.).

[0072] It should be considered that the embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the invention is set forth in the claims rather than by the description of the above embodiments, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0073] Symbol Explanation

[0074] 10-Battery cell, 41-Temperature sensor, 43-Current sensor, 45-External temperature sensor, 100-Battery pack, 500-ECU, 510-Battery internal temperature estimator, 511, 514-Mapping table, 512-Formula, 513-Subtractor, 520-Charging allowable current calculator, 1000-Vehicle.

Claims

1. A management device for managing a battery, characterized in that, The management device is configured such that, The saturation value of the internal and external temperature difference of the battery at a constant current is obtained based on the current of the battery. The internal and external temperature difference of the battery is obtained based on the acquired internal and external temperature difference saturation value; and The internal temperature of the battery is obtained based on the external temperature of the battery and the temperature difference between the inside and outside of the battery.

2. The management device according to claim 1, characterized in that, The management device includes a storage device for storing mapping tables and similar formats. The mapping table represents the relationship between the square of the battery current and the saturation value of the internal and external temperature difference. The equation is a first-order hysteresis equation related to the thermal changes of the battery. The management device is configured to obtain the internal temperature of the battery by performing the following process. The first process involves obtaining the external temperature of the battery based on the output from a temperature sensor. The second process involves obtaining the square of the current in the battery based on the output from the current sensor. The third process involves using the mapping table to obtain the saturation value of the internal and external temperature difference corresponding to the square of the current of the battery obtained. The fourth process involves using the acquired saturation value of the internal and external temperature difference and the formula to obtain the internal and external temperature difference of the battery; and The fifth step is to subtract the obtained temperature difference between the inside and outside of the battery from the obtained external temperature of the battery.

3. The management device according to claim 2, characterized in that, The battery is mounted in the vehicle. The vehicle is configured to receive DC power from an external power supply while parked, and simultaneously use the supplied DC power to charge the battery. The management device is also configured to perform the following processes: The sixth process uses the internal temperature of the battery obtained through the first to fifth processes to determine the upper limit of the charging current; and The seventh step involves sending the obtained upper limit value of the charging current to the power supply device. The management device is configured to repeatedly execute the first to seventh processes when the vehicle charges the battery using DC power supplied from the power supply equipment.

4. The management device according to claim 3, characterized in that, The formula defines the current value of the internal and external temperature difference of the battery based on the previous value of the internal and external temperature difference. The management device is configured to determine an initial value for the temperature difference between the inside and outside of the battery based on the ambient temperature of the vehicle.

5. The management device according to any one of claims 2 to 4, characterized in that, The formula includes a first-order hysteresis coefficient related to the thermal changes of the battery. The management device is configured such that, When the internal temperature of the battery rises, the first coefficient is set as the first-order hysteresis coefficient; and When the internal temperature of the battery decreases, a second coefficient, which is different from the first coefficient, is set as the first-order hysteresis coefficient.

6. The management device according to claim 1, characterized in that, The battery is mounted in a vehicle. The management device is configured to: when the ambient temperature change of the battery in the parked vehicle per unit time is less than a reference value, set a first value as the initial value of the internal and external temperature difference; when the ambient temperature change of the battery in the parked vehicle per unit time is greater than the reference value, set a second value different from the first value as the initial value; and obtain the internal and external temperature difference of the battery based on the set initial value and the internal and external temperature difference saturation value.

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