control device

Abstract

The present invention provides a control device that can more effectively perform current suppression control of an energy storage device. [Solution] A control device for controlling the current of an energy storage device is configured to perform current suppression control to reduce the current of the energy storage device during the period when the current of the energy storage device exceeds a threshold, while measuring at least one of the elapsed time since the current of the energy storage device became greater than the threshold and the change in the current of the energy storage device, and to record the measured data. Furthermore, after the current of the energy storage device becomes less than the threshold due to the current suppression control, the control device is configured to determine the amount by which the threshold has decreased using the recorded data, and to lower the threshold according to the determined amount of decrease (S33).

Description

Technical Field

[0001] The present disclosure relates to a control device.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2012-223044 (Patent Document 1) discloses a technique for performing current suppression control (Li precipitation suppression control) of an in-vehicle battery when the charging current of the in-vehicle battery exceeds a threshold value (Itag). In this technique, the control device determines a regeneration limit rate (the time change rate of the charging current) based on the vehicle speed, as well as the temperature and SOC (State Of Charge) of the in-vehicle battery, and decreases the charging current according to the determined regeneration limit rate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above technique, the threshold value (Itag) is changed according to the regeneration limit rate. However, by such a method, the threshold value is not necessarily set to an appropriate value.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a control device capable of more appropriately performing current suppression control of a power storage device.

Means for Solving the Problems

[0006] According to one embodiment of the present disclosure, a control device for controlling the current of an energy storage device is provided. The control device is configured to perform current suppression control to reduce the current of the energy storage device during a period when the current of the energy storage device exceeds a threshold, while measuring at least one of the elapsed time since the current of the energy storage device became greater than the threshold and the change in the current of the energy storage device, and to record the measured data. After the current of the energy storage device has become less than the threshold due to the current suppression control, the control device is configured to determine the amount by which the threshold has decreased using the recorded data, and to lower the threshold according to the determined amount of decrease. [Effects of the Invention]

[0007] This disclosure makes it possible to provide a control device that can more appropriately perform current suppression control of an energy storage device. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the configuration of a vehicle according to an embodiment of the present disclosure. [Figure 2] This flowchart shows the charge and discharge control according to this embodiment. [Figure 3] This figure illustrates the process for determining the first threshold shown in Figure 2. [Figure 4] This is a time chart showing a first example of the operation of the vehicle according to this embodiment. [Figure 5] This is a time chart showing a second example of the operation of the vehicle according to this embodiment. [Figure 6] This figure illustrates the process for determining the second threshold shown in Figure 2. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0010] Figure 1 shows the configuration of a vehicle 1000 according to this embodiment. The vehicle 1000 includes a battery pack 100 containing one or more batteries. The battery pack 100 is fixed, for example, under the floor of the vehicle 1000. However, the mounting configuration of the battery pack 100 is arbitrary. For example, the battery pack 100 may be placed on the floor of the vehicle 1000.

[0011] Vehicle 1000 is further equipped with an ECU (Electronic Control Unit) 500 that performs charge and discharge control of the battery pack 100, and various sensors (position sensor, outside temperature sensor, vehicle speed sensor, odometer, etc., not shown) that detect the status of vehicle 1000 in real time. The detection results of the various sensors are output to the ECU 500.

[0012] The ECU 500 includes a processor 510 and a storage device 520. The storage device 520 is configured to store stored information. In the ECU 500, various controls are performed by the processor 510 executing a program stored in the storage device 520. In addition to the program, the storage device 520 also stores various information used by the program. The ECU 500 also has a timer function. The ECU 500 measures the elapsed time from a predetermined event (trigger) using the timer function. The timer function may be implemented by a timer circuit (hardware) or by software. The ECU 500 is an example of a "control device" according to this disclosure.

[0013] The vehicle 1000 further comprises a drive unit 20 for driving the vehicle 1000, an inlet 410, a charger 420, and an HMI (Human Machine Interface) 600.

[0014] The HMI600 includes an input device and a display device. The HMI600 may also include a touch panel display. The input device outputs signals to the ECU500 in response to user input. The input device of the HMI600 includes driving controls (e.g., an accelerator pedal, a brake pedal, and a steering wheel) for the user to request acceleration, deceleration, and steering from the vehicle 1000 (ECU500). The display device may include an instrument panel and / or a center display.

[0015] The drive unit 20 includes a PCU (Power Control Unit) 21, an MG (Motor Generator) 22, and an engine 23. The vehicle 1000 is configured to run using the power output from the battery pack 100. The user can manually drive the vehicle 1000 through the driving control unit. The vehicle 1000 is, for example, a PHEV (Plug-in Hybrid Electric Vehicle). However, the vehicle 1000 may be another electric vehicle (xEV), such as a BEV (Battery Electric Vehicle) or an HEV (Hybrid Electric Vehicle).

[0016] The battery pack 100 comprises a plurality of cells 10 (energy storage cells), each of which functions as a secondary battery. The plurality of cells 10 are stacked and constrained in a predetermined direction to form a battery stack. The battery stack is an energy storage module in which a plurality of electrically connected cells 10 are modularized. For example, all the cells 10 included in the battery stack are constrained by a pair of end plates (restraining plates). In this embodiment, liquid lithium-ion batteries are used as cells 10. However, the cells 10 are not limited to lithium-ion batteries, but may 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, but may also be an all-solid-state secondary battery.

[0017] The battery pack 100 includes one current sensor Sa, a plurality of voltage sensors Sb provided for each cell 10, and a plurality of temperature sensors Sc provided for each cell 10. The detection results of each sensor are output to the ECU 500. The ECU 500 may function as a BMS (Battery Management System) together with these sensors. In this embodiment, all the cells 10 included in the battery pack 100 are connected in series, and the same magnitude of current flows through all the cells 10. Therefore, one current sensor Sa is shared by all the cells 10. However, it is not limited to this, and the battery pack 100 may include a plurality of cells connected in parallel. A current sensor may be provided for each cell.

[0018] The vehicle 1000 shown in FIG. 1 is configured to travel in one driving mode selected from a plurality of types of driving modes. For example, the vehicle 1000 is configured to be able to travel in a first driving mode in which driving is performed only by the MG22 (motor), a second driving mode in which driving is performed by the MG22 and the engine 23, and a third driving mode in which driving is performed only by the engine 23. The ECU 500 may switch the first to third driving modes according to the situation of the vehicle 1000.

[0019] Also, the vehicle 1000 is configured to perform external charging of the battery pack 100 (charging of the in-vehicle battery with electric power supplied from outside the vehicle) during parking. The inlet 410 is configured to be connectable to a charging cable of a power supply facility outside the vehicle. The charger 420 is an in-vehicle charger that performs AC / DC conversion. The ECU 5️00 controls the charger 420 during external charging. The charger 420 converts AC power into DC power according to a command from the ECU 500 and outputs the DC power to the battery pack 100. Thereby, each battery included in the battery pack 100 is charged.

[0020] The PCU 21 includes, for example, an inverter. The MG 22 functions as a driving motor and rotates the driving wheels 24 of the vehicle 1000. The MG 22 drives the vehicle 1000 using the electric power output from the battery in the battery pack 100. Specifically, the PCU 21 drives the MG 22 using the electric power supplied from the battery pack 100. As a result, the MG 22 enters the power running state. The MG 22 in the power running state converts electric power into torque. The torque is transmitted to the driving wheels 24. Also, the MG 22 enters the regenerative state when the vehicle 1000 decelerates, and charges each battery included in the battery pack 100 with the generated regenerative electric power.

[0021] The engine 23 functions as an internal combustion engine and drives the vehicle 1000 using the combustion energy of fuel. Specifically, the engine 23 generates power by the combustion energy of fuel supplied from a fuel tank (not shown). The generated power is transmitted to the driving wheels 24. The exhaust pipe 23a is connected to the engine 23 and discharges the exhaust of the engine 23 to the outside of the vehicle.

[0022] The vehicle 1000 further includes an SMR (System Main Relay) 100b. The SMR 100b is, for example, an electromagnetic mechanical relay. The SMR 100b is located between the battery pack 100 and each of the drive device 20 and the charger 420. While the vehicle 1000 is traveling in the first or second driving mode, the SMR 100b is maintained in the connected state.

[0023] Figure 2 is a flowchart showing the charge / discharge control by the ECU 500. The processing flow F1 shown in Figure 2 is repeatedly executed by the ECU 500 during the driving period of the vehicle 1000. The driving period means a period during which the control system (including the ECU 500) of the vehicle 1000 is operating and the vehicle 1000 is not in the parked state. In addition to the period during which the vehicle 1000 is traveling, the period during which the vehicle 1000 is temporarily stopped is also included in the driving period. When the vehicle 1000 enters the parked state, the driving period ends. "S" in the flowchart means a step.

[0024] In processing flow F1, the ECU 500 determines in S10 whether the battery pack 100 is charging or not. The ECU 500 may determine whether the battery pack 100 is charging or not based on the charge control status (for example, whether or not a charge command has been issued to the PCU 21). Alternatively, the ECU 500 may determine whether the battery pack 100 is charging or not based on the direction of the current in the battery pack 100 detected by the current sensor Sa. The charging current may be indicated by a negative value, and the discharging current may be indicated by a positive value. However, when comparing the magnitude of the current, the absolute value is used regardless of the sign (+ / -). That is, the closer the value is to 0, the smaller the current. When setting upper and lower limits for the charging current, the upper limit is located on the side where the absolute value of the charging current is larger, and the lower limit is located on the side where the absolute value of the charging current is smaller.

[0025] For example, when the battery pack 100 is being charged by the regenerative power generated by MG22, S10 determines YES and the process proceeds to S11. In S11, the ECU 500 determines whether the charging current of the battery pack 100 detected by the current sensor Sa is greater than the first threshold (hereinafter referred to as "Itag1").

[0026] As will be explained in detail later, Itag1 is set to a value lower than the limit value of the charging current related to Li deposition (hereinafter referred to as "Ilim1"). Ilim1 corresponds to the upper limit of the recommended range of charging current that suppresses degradation of cell 10 (see Figures 4 and 5 described later). If the charging current of the battery pack 100 exceeds Ilim1, lithium (Li) is more likely to precipitate inside cell 10. Li deposition accelerates the degradation of cell 10. The value obtained by subtracting Itag1 (absolute value) from Ilim1 (absolute value) corresponds to the margin. The larger the margin, the stricter the input limit becomes, and the smaller the maximum current that can be input to the battery pack 100 becomes. Ilim1 may be variable or fixed depending on the state of the battery pack 100. The ECU 500 may set Ilim1 using a map that has been stored in the memory device 520 in advance.

[0027] If the charging current is greater than Itag1 (YES in S11), the ECU 500 performs battery input suppression control in S12 to reduce the current to the battery pack 100. The ECU 500 suppresses the input current to the battery pack 100 so that the charging current to the battery pack 100 is less than Itag1. The ECU 500 may also control the PCU 21 to reduce the current to the battery pack 100. If the vehicle 1000 is running in the third driving mode, the ECU 500 may switch to the first or second driving mode. If the charging current to the battery pack 100 reaches Ilim1, the ECU 500 may shut off the SMR 100b to prevent power input to the battery pack 100. In this case, if the vehicle 1000 is running in the first or second driving mode, the ECU 500 may switch to the third driving mode and continue driving the vehicle 1000 with the engine 23. Battery input suppression control inhibits the degradation of cell 10.

[0028] Furthermore, in S12, the ECU 500 performs the above-mentioned battery input suppression control while measuring the elapsed time since the charging current exceeded Itag1 and the change in the charging current. In the subsequent S13, the ECU 500 records the measured data (elapsed time since the charging current exceeded Itag1 and the change in the charging current) in the storage device 520. The ECU 500 measures the elapsed time using its timer function and the charging current using the current sensor Sa, and records the measured charging current in the storage device 520, linked to the measurement time. Once the process in S13 is executed, the process returns to the first step (S11). Hereinafter, the data recorded in S13 will be referred to as the "first current excess data".

[0029] The above battery input suppression control (S12) reduces the charging current of the battery pack 100. However, it takes time from the time the ECU 500 starts the battery input suppression control until the charging current falls below Itag1. During the period when the charging current exceeds Itag1 (hereinafter referred to as the "first current excess period"), the processes of S12 and S13 are repeatedly executed. As a result, the first current excess data is accumulated in the storage device 520. In addition, the above battery input suppression control is continuously executed during the first current excess period.

[0030] If the charging current is less than or equal to Itag1 (NO in S11), the process proceeds to S15. In S15, the ECU 500 determines whether or not the end of the first current excess period has been detected. For example, if the charging current is less than or equal to Itag1 due to the battery input suppression control (S12) executed in the previous processing routine, and NO is determined in S11 of the current processing routine, the ECU 500 detects the end of the first current excess period. On the other hand, if the battery input suppression control (S12) was not executed in the previous processing routine, that is, if the charging current remains below Itag1, the end of the first current excess period is not detected.

[0031] If the end of the first current excess period is detected (YES in S15), the ECU 500 increments 1 in S16 to a parameter indicating the number of times the charging current has exceeded Itag1 (hereinafter referred to as the "first excess count"). The first excess count is pre-stored in the memory device 520.

[0032] Next, in S17, the ECU 500 uses the first current overload data (S13) to calculate the charging current overload frequency, the maximum charging current overload value, and the charging current overload amount, and stores the calculated data in the memory device 520, linked to the corresponding first current overload period. The first current overload period corresponds to the period during which the charging current of the battery pack 100 was greater than the threshold (Itag1). The first current overload data includes the first current overload period (start time and end time) and the progression of the charging current during the first current overload period. The ECU 500 may also calculate the charging current overload frequency by dividing the number of first overloads by the time from the initial (e.g., at the time of shipment) to the present. The ECU 500 may also extract the peak (maximum value) of the charging current during the first current overload period from the progression of the charging current during the first current overload period. Alternatively, the ECU500 may obtain the maximum excess value of the charging current by subtracting Itag1 (absolute value) from the maximum value (absolute value) of the extracted charging current. The maximum excess value of the charging current corresponds to the peak of the charging current expressed with Itag1 as the reference level (0). The ECU500 may also calculate the excess amount of charging current (integral value of the excess) by accumulating the portion of the charging current exceeding Itag1 during the first current excess period. When the process in S17 is executed, the process proceeds to S19.

[0033] If the end of the first current excess period is not detected (NO in S15), the ECU 500 measures in S18 the time during which the charging current of the battery pack 100 does not exceed Itag1 (hereinafter referred to as "Tc"). Tc indicates the elapsed time since the end of the most recent first current excess period was detected. The ECU 500 may also increment a counter indicating Tc in S18. Once the process in S18 is executed, the process proceeds to S19.

[0034] In S19, the ECU500 determines Itag1 using the data acquired in S17 or S18. As a result, in the next processing routine, the decision in S11 is made based on the latest determined Itag1. Figure 3 is a diagram illustrating the process in S19 (the process of determining Itag1).

[0035] In step S19 of Figure 2, the processing flow F2 shown in Figure 3 is executed. In processing flow F2, the ECU 500 determines in S31 whether the Tc obtained in S18 of Figure 2 is equal to or greater than a predetermined reference value (hereinafter referred to as "Th1"). If Tc is less than Th1 (NO in S31), the ECU 500 determines in S32 whether the first excess count has increased in the current processing routine. If the first excess count has been incremented in the current processing routine (S16 in Figure 2), it is determined to be YES in S32, and the process proceeds to S33. On the other hand, if the first excess count has not been incremented in the current processing routine, it is determined to be NO in S32. In this case, processing flow F2 ends, and the process returns to the first step (S11) of processing flow F1. As long as the charging current of the battery pack 100 does not exceed Itag1, the process in S18 of Figure 2 is repeatedly executed, and Tc increases. However, when the process in S35 shown in Figure 3 (described later) is executed, Tc is set to "0" (initialized).

[0036] In S33, ECU500 lowers Itag1. This tightens the input restriction. Specifically, as Itag1 becomes lower (closer to 0), it becomes easier for S11 in Figure 2 to determine YES, and the battery input suppression control (S12) is more likely to be executed.

[0037] In S33, the ECU500 uses the charging current overload frequency, maximum overload value, and overload amount obtained in S17 of Figure 2 to determine the amount of decrease in Itag1 (the degree to which Itag1 is reduced), and lowers Itag1 according to the determined amount of decrease. The larger the decrease in Itag1, the stricter the input limit becomes.

[0038] In the example shown at the bottom of Figure 3, line L1 represents the progression of the charging current, line L2 represents Itag1, the period from time t1 to time t2 represents the first current excess period, and the value Ip represents the peak (maximum value) of the charging current. The value dIp, obtained by subtracting Itag1 (absolute value) from the value Ip (absolute value), represents the maximum excess value of the charging current. Furthermore, the value Iint, obtained by accumulating the charging current that exceeded Itag1 during the period from time t1 to time t2, represents the excess amount of the charging current. The maximum excess value and excess amount of the charging current used in S33 may be the latest value (current value) calculated in the current processing routine, or they may be representative values ​​(e.g., mean or median) of historical data including the current value and values ​​calculated before it. In this embodiment, the latest value (current value) is used.

[0039] The ECU500 may set the decrease in Itag1 when the frequency of exceeding the charging current exceeds the first reference value to be greater than the decrease in Itag1 when the frequency of exceeding the charging current is at or below the first reference value. The ECU500 may set the decrease in Itag1 to be greater as the frequency of exceeding the charging current increases. The ECU500 may set the decrease in Itag1 when the maximum value of exceeding the charging current exceeds the second reference value to be greater than the decrease in Itag1 when the maximum value of exceeding the charging current is at or below the second reference value. The ECU500 may set the decrease in Itag1 to be greater as the maximum value of exceeding the charging current increases. The ECU500 may set the decrease in Itag1 when the amount of exceeding the charging current exceeds the third reference value to be greater than the decrease in Itag1 when the amount of exceeding the charging current is at or below the third reference value. The ECU500 may set the decrease in Itag1 to be greater as the amount of exceeding the charging current increases.

[0040] As described above, determining the amount of decrease in Itag1 makes it easier to converge Itag1 to an appropriate value early on. The memory device 520 may pre-store information (hereinafter referred to as "charging limit information") that shows the relationship between the frequency of charging current overload, the maximum value of charging current overload, the amount of charging current overload, and the amount of decrease in Itag1. The ECU 500 may use this charging limit information (for example, a map) to obtain the amount of decrease in Itag1.

[0041] Figure 4 is a time chart showing the first operation example of vehicle 1000. In the time chart, "t" represents timing. In Figure 4, lines L11, L12, and L13 show the changes in charging current, Ilim1, and Itag1, respectively. Lines L20, L21, and L22 show the changes in the first overrun, margin coefficient, and margin, respectively.

[0042] In the example shown in Figure 4, the ECU500 calculates the margin as the product of the initial margin value and a coefficient (hereinafter referred to as the "margin coefficient"). The larger the margin coefficient, the larger the margin. The decrease in Itag1 is represented by the increase in the margin coefficient. The ECU500 increases the margin coefficient at S33 in Figure 3. The aforementioned charge limit information may also output the margin coefficient.

[0043] In the example shown in Figure 4, charging of the battery pack 100 begins at t11. This results in a YES judgment at S10 in Figure 2. The margin value at the start of charging is Mg1. Mg1 is, for example, the same as the margin value at the end of the previous charging cycle. Subsequently, at t12, when the charging current (line L11) becomes greater than Itag1 (line L13), a YES judgment is made at S11 in Figure 2. Then, at t13, when the first current excess period ends, the ECU 500 increments the first excess count (line L20) (S16 in Figure 2), and the ECU 500 increases the margin coefficient (line L21). The ECU 500 determines the amount of increase in the margin coefficient based on the charging current excess frequency, the maximum excess value, and the excess amount. The ECU 500 then increases the margin coefficient by the determined amount. For example, if the margin coefficient is 1 (i.e., the margin is at its initial value), ECU500 sets the margin coefficient to a value greater than 1 at S33 in Figure 3. Subsequently, ECU500 updates the margin (line L22) based on the margin coefficient. For example, ECU500 calculates the margin by multiplying the updated margin coefficient by the initial value of the margin. This changes the margin value from Mg1 to Mg2, where Mg2 is greater than Mg1. ECU500 also updates Itag1 based on the updated margin. For example, ECU500 calculates Itag1 (absolute value) by subtracting the calculated margin from Ilim1 (absolute value). As a result of the above update process at t13, Itag1 decreases.

[0044] In the example shown in Figure 4, at t14, the charging current (line L11) again becomes greater than Itag1 (line L13). Then, at t15, the first current overload period ends. As a result, as described above, the number of overloads (line L20) is incremented, the margin coefficient (line L21) becomes larger, and the value of the margin (line L22) changes from Mg2 to Mg3. Mg3 is greater than Mg2. As a result, Itag1 decreases further. The maximum value and amount of charging current overload during the period from t14 to t15 (first current overload period) are greater than the maximum value and amount of charging current overload during the period from t12 to t13 (first current overload period), respectively. For this reason, the ECU500 makes the margin increase from Mg2 to Mg3 greater than the margin increase from Mg1 to Mg2. A larger margin increase means a larger decrease in Itag1.

[0045] As described above, in this embodiment, the charge limit information outputs a decrease in Itag1 based on input data including the frequency of charge current overload, the maximum overload value, and the overload amount. However, it is not limited to this, and one or two of the frequency of charge current overload, the maximum overload value, and the overload amount may be omitted from the input data. For example, the charge limit information may output a decrease in Itag1 based only on the maximum overload value of the charge current. Alternatively, the charge limit information may output a decrease in Itag1 based only on the overload amount of the charge current. The ECU500 may increase the decrease in Itag1 the longer the first current overload period. The ECU500 may determine the decrease in Itag1 using a trained model. The trained model may be generated by machine learning using AI (artificial intelligence). The trained model may be trained to output a decrease in Itag1 when at least one of the frequency of charge current overload, the maximum overload value, and the overload amount of the charge current is input. Alternatively, the trained model may be trained to output the decrease in Itag1 when the charging current pattern (charging progression) during the first current excess period is input.

[0046] In the processing flow F2 shown in Figure 3, if Tc becomes Th1 or greater (YES in S31), the ECU 500 increases Itag1 in S34. This relaxes the input restriction. Specifically, as Itag1 increases, it becomes less likely to be judged as YES in S11 in Figure 2, and the battery input suppression control (S12) becomes less likely to be executed. The ECU 500 may also calculate Itag1 (absolute value) in S34 by reducing the margin and subtracting the updated margin from Ilim1 (absolute value). However, if the margin reaches a predetermined lower limit, the ECU 500 does not reduce the margin below the lower limit in S34, but adjusts the margin to match the lower limit. The lower limit is a value greater than 0. As the margin decreases, Itag1 approaches Ilim1. However, based on the lower limit of the margin, the ECU 500 sets Itag1 to a value lower than Ilim1 (the limit value of the current related to lithium deposition in lithium-ion batteries). The amount of margin reduction may be a fixed value (for example, 0.1 times the initial margin value) or it may be variable. The ECU500 may reduce the amount of margin reduction in S34 as the margin decreases.

[0047] When the process in S34 is executed, the ECU500 resets (initializes) Tc in S35. This sets Tc to 0.

[0048] Figure 5 is a time chart showing a second operating example of vehicle 1000. In Figure 5, lines L31, L32, and L33 show the changes in charging current, Ilim1, and Itag1, respectively. Lines L40, L41, and L42 show the changes in Tc, margin coefficient, and margin, respectively.

[0049] In the example shown in Figure 5, charging of the battery pack 100 begins at t21. This results in a YES judgment at S10 in Figure 2. The margin value at the start of charging is Mg4. Mg4 is, for example, the same as the margin value at the end of the previous charge. In the example shown in Figure 5, Tc is set to 0 at the start of charging. However, this is not the only option; the value of Tc at the start of charging may be the same as the value of Tc at the end of the previous charge. During the period from t21 to t22, the charging current of the battery pack 100 (line L31) remains below Itag1 (line L33). Therefore, as time progresses, Tc (line L40) increases due to the processing at S18 in Figure 2. Subsequently, at t22, when Tc reaches Th1 (YES at S31 in Figure 3), the ECU 500 reduces the margin coefficient (line L41). For example, if the margin coefficient is 1 (i.e., the margin is at its initial value), ECU500 sets the margin coefficient to a value less than 1 (e.g., 0.9) in S34 of Figure 3. Then, ECU500 updates the margin (line L42) based on the margin coefficient. For example, ECU500 calculates the margin by multiplying the updated margin coefficient by the initial value of the margin. This changes the margin value from Mg4 to Mg5. Mg5 is smaller than Mg4. ECU500 updates Itag1 based on the updated margin. For example, ECU500 calculates Itag1 (absolute value) by subtracting the updated margin from Ilim1 (absolute value). As a result of the above update process at t22, Itag1 becomes higher. Also, Tc is reset (initialized) (S35 in Figure 3).

[0050] When the process in S33 or S35 in Figure 3 is executed, in the processing flow F1 shown in Figure 2, S19 is completed and the process returns to S11. In processing flow F1, if the battery pack 100 is discharging, it is determined to be NO in S10 and the process proceeds to S21. In S21 to S29, the same processes as in S11 to S19 described above are basically executed, except that the charging current changes to the discharging current. However, in S21, the second threshold (Itag2) is used instead of the first threshold (Itag1). Itag2 is, for example, the limit value regarding over-discharge of the battery pack 100 (the upper limit of the recommended range of discharge current). In S21, the ECU 500 determines whether the discharge current of the battery pack 100 is greater than Itag2. In S22, battery output suppression control is executed instead of battery input suppression control. In S22, ECU500 reduces the current of battery pack 100 so that the discharge current of battery pack 100 is less than Itag2. ECU500 may also control PCU21 to reduce the current of battery pack 100. In S22 and S23, second current excess data regarding the discharge current is measured and recorded. In S26, the second excess count, which indicates the number of times the discharge current has exceeded Itag2, is incremented. In S28, Td (the time during which the discharge current of battery pack 100 does not exceed Itag2) is used instead of Tc. In S28, ECU500 measures Td. Td indicates the elapsed time since the end of the most recent second current excess period was detected. The second current excess period is the period during which the discharge current exceeds Itag2. By providing separate parameters (Itag1, Itag2, Tc, Td, etc.) in the memory device 520 for charging and discharging, control tailored to the characteristics of charging and discharging can be achieved. In S29, the ECU 500 determines Itag2 using the data acquired in S27 or S28. Figure 6 is a diagram illustrating the process in S29 (the process of determining Itag2). In S29 in Figure 2, the processing flow F3 shown in Figure 6 is executed.

[0051] In steps S41 to S45, the same processing as in steps S31 to S35 shown in Figure 3 is basically performed, except that the charging current, Itag1, and Tc are changed to the discharge current, Itag2, and Td, respectively. That is, in step S43, the ECU 500 lowers Itag2. This makes the output limiting stricter. The ECU 500 determines the amount of Itag2 reduction using the frequency of discharge current overload, the maximum overload value, and the overload amount (see bottom of Figure 6). The larger the reduction in Itag2, the stricter the output limiting becomes. Note that, as with the method for determining the reduction in Itag1 mentioned above, the method for determining the reduction in Itag2 can be changed as appropriate.

[0052] As described above, the control device (ECU 500) according to this embodiment controls the current of the energy storage device (battery pack 100). During the period when the current of the battery pack 100 exceeds a threshold (Itag1 or Itag2), the ECU 500 performs current suppression control (battery input suppression control or battery output suppression control) to reduce the current of the battery pack 100, while measuring the elapsed time since the current of the battery pack 100 became greater than the threshold and the change in the current of the battery pack 100, and recording the measured data (S12, S13 or S22, S23 in Figure 2). Then, after the current of the battery pack 100 becomes less than the threshold due to the current suppression control, the ECU 500 uses the recorded data to determine the amount of reduction in the threshold and lowers the threshold according to the determined amount of reduction (S33 in Figure 3 or S43 in Figure 6).

[0053] The ECU 500 performs current suppression control during the first or second current overload period (the period during which the current of the battery pack 100 exceeds the threshold). After the current of the battery pack 100 falls below the threshold due to the current suppression control, the ECU 500 lowers the threshold. This makes it easier for the current suppression control to be performed, and prevents overcharging or over-discharging of the battery pack 100. The ECU 500 also uses the data measured during the first or second current overload period to determine the amount by which the threshold should be lowered. This data reflects the characteristics of the current suppression control by the power conversion circuit (e.g., PCU 21) (including the effects of aging of control components) and the characteristics of current fluctuations caused by the user's driving operations. By using the above data to determine the amount by which the threshold should be lowered, the ECU 500 can more easily converge the threshold to an appropriate value at an early stage.

[0054] The ECU 500 raises the threshold value (S34 in Figure 3 or S44 in Figure 6) if the current of the battery pack 100 does not exceed the threshold value for a predetermined period of time (Th1 or Th2) during charging or discharging of the battery pack 100. If the threshold value is too low, the current of the battery pack 100 will continue to not exceed the threshold value. In such cases, the ECU 500 raises the threshold value.

[0055] The ECU 500 uses the data measured during the completed first or second current overload period to improve the current suppression control during the next first or second current overload period. Specifically, the margin converges to an appropriate value through repeated execution of the learning-based update process (S33, S34 in Figure 3 or S43, S44 in Figure 6). The larger the margin, the lower the threshold. For example, if the user's driving operations (especially accelerator / brake operations) are severe, the current fluctuations of the battery pack 100 tend to be more severe. The more severe the current fluctuations of the battery pack 100, the larger the required margin tends to be. If the initial value of the margin is too small, the battery pack 100 is more likely to overcharge or overdischarge. In such cases, the ECU 500 can increase the margin by executing the learning-based update process (S33 in Figure 3 or S43 in Figure 6). This suppresses overcharging or overdischarging of the battery pack 100. On the other hand, if the user's driving operation is gentle, the current fluctuations of the battery pack 100 also tend to be gentle. If the initial value of the margin is too large, the energy efficiency of the battery pack 100 will be poor. In such cases, the ECU 500 can reduce the margin by performing an update process based on the above learning (S34 in Figure 3 or S44 in Figure 6). This improves energy efficiency.

[0056] In the above embodiment, the threshold (Itag1 or Itag2) is updated based on the learning described above in both the charge control and the discharge control. However, the embodiment is not limited to this, and the threshold may be updated based on the learning described above in only one of the charge control or the discharge control.

[0057] The processing flows shown in Figures 2, 3, and 6 can be modified as needed. For example, the order of processing may be changed or unnecessary steps may be omitted depending on the purpose. Also, the content of any of the processes may be changed. For example, in the processing flow F1 shown in Figure 2, steps S21 to S29 may be omitted.

[0058] The vehicle configuration shown in Figure 1 can be modified as appropriate. The use of the control device is arbitrary. The control device may be applied to a stationary energy storage device instead of an on-board battery.

[0059] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0060] 10 cells, 100 battery packs, 500 ECUs, 520 memory devices, 1000 vehicles, Sa current sensors.

Claims

1. A control device for controlling the current of an energy storage device, The control device is During the period when the current of the energy storage device exceeds a threshold, current suppression control is performed to reduce the current of the energy storage device, while measuring at least one of the elapsed time since the current of the energy storage device became greater than the threshold and the change in the current of the energy storage device, and the measured data is recorded. A control device configured to determine the amount by which the threshold is reduced using the recorded data after the current of the energy storage device has become smaller than the threshold due to the current suppression control, and to lower the threshold according to the determined amount of reduction.

2. The control device is During the period when the current of the energy storage device exceeds the threshold, current suppression control is performed to reduce the current of the energy storage device, while the change in the current of the energy storage device is measured and the measured data is recorded. The control device according to claim 1, wherein, after the current of the energy storage device has become smaller than the threshold due to the current suppression control, the amount of the threshold decrease is increased as the maximum value of the current of the energy storage device during the period when the current of the energy storage device was larger than the threshold increases.

3. The control device is During the period when the current of the energy storage device exceeds the threshold, current suppression control is performed to reduce the current of the energy storage device, while the elapsed time since the current of the energy storage device became greater than the threshold is further measured, and the measured data is recorded. The control device according to claim 2, wherein the amount of the threshold decrease is increased as the cumulative value of the current of the energy storage device during the period when the current of the energy storage device was greater than the threshold is increased after the current suppression control has reduced the current of the energy storage device to less than the threshold.

4. The control device according to claim 1, wherein the control device is configured to raise the threshold value when the current of the energy storage device does not exceed the threshold value for a predetermined period of time while the energy storage device is charging or discharging.

5. The energy storage device includes a lithium-ion battery, The control device according to any one of claims 2 to 4, wherein the control device is configured to set the threshold value to a value lower than the limit value of the current related to lithium deposition in the lithium-ion battery.

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