Controller of battery

Abstract

To balance suppression of deterioration of a battery caused by high-rate charge and discharge with improving of energy efficiency and drivability caused by the high-rate charge and discharge at a high level.SOLUTION: A controller of a battery mounted on a vehicle (1) with a motor (4) as a power source comprises: a current sensor (SN3) which measures charge / discharge current of a battery (B); and a controller (14) which determines an upper limit current value to allow charge / discharge of the battery based on the measured charge / discharge current. The controller is constituted to calculate energy loss per unit time in the vehicle based on an operation state of the vehicle, calculate a limited current value that is smaller than the upper limit current value, where a difference between the energy loss in a case where the charge / discharge of the battery is performed by the limited current value and the energy loss in a case where the charge / discharge of the battery is performed by the upper limit current value is a prescribed loss threshold value or less, and control the charge / discharge of the battery so that the charge / discharge current of the battery is the limited current value.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a control device for a battery mounted on a vehicle equipped with a motor as a power source. [Background technology]

[0002] 2. Description of the Related Art Conventionally, in vehicles equipped with a motor as a power source, such as electric vehicles and hybrid vehicles, secondary batteries such as lithium ion batteries are used to supply power to the motor.

[0003] In electric and hybrid vehicles, it is desirable to be able to charge and discharge large currents (high-rate charge and discharge) during motor acceleration and regenerative braking to achieve desired driving performance and good energy efficiency. However, repeated high-rate charge and discharge can cause imbalances in the ion concentration distribution in the electrolyte, temporarily increasing the battery's internal resistance. Furthermore, if the imbalance in the ion concentration distribution continues, it will remain undistributed, resulting in permanent deterioration of battery performance.

[0004] Therefore, in order to suppress permanent deterioration of the battery due to high-rate charging and discharging, a technology has been proposed that prevents uneven ion concentration distribution by setting a current limit for charging or discharging when high-rate charging or discharging is performed continuously (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Application Publication No. 2020-079595 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the technology described in Patent Document 1, if current limiting during discharge is implemented, sufficient power cannot be supplied from the battery to the motor due to high-rate discharge, which may result in the driver's desired acceleration not being achieved and fuel economy being reduced by also using the internal combustion engine. Furthermore, if current limiting during charging is implemented, the battery cannot be charged at a high rate using regenerative braking, and sufficient deceleration cannot be achieved using regenerative braking alone. Therefore, friction braking must be used to achieve the required deceleration, which may result in reduced energy efficiency and fluctuations in deceleration.

[0007] The present invention has been made to solve the problems of the conventional technology described above, and aims to provide a battery control device that can achieve, at a high level, both the suppression of battery deterioration caused by high-rate charging and discharging and the improvement of energy efficiency and drivability through high-rate charging and discharging. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a control device for a battery mounted on a vehicle equipped with a motor as a power source, comprising: a current sensor that measures the charge / discharge current of the battery; and a controller that determines an upper limit current value at which charging and discharging of the battery is permitted based on the measured charge / discharge current. The controller is configured to calculate the energy loss per unit time in the vehicle based on the driving state of the vehicle, calculate a limit current value that is smaller than the upper limit current value, and such that the difference between the energy loss when charging and discharging the battery at the limit current value and the energy loss when charging and discharging the battery at the upper limit current value is equal to or less than a predetermined loss threshold, and control the charging and discharging of the battery so that the charge / discharge current of the battery becomes the limit current value. In the present invention configured as described above, the controller calculates a limit current value at which the difference between the energy loss when charging and discharging the battery at a limit current value lower than the upper limit current value and the energy loss when charging and discharging the battery at the upper limit current value is equal to or less than a predetermined loss threshold. The controller then controls the battery charging and discharging so that the battery charging and discharging current is equal to the limit current value, thereby limiting the charging and discharging current to a value even lower than the upper limit current value within a range that allows for an acceptable increase in energy loss. This strengthens the limit on the charging and discharging current while minimizing the increase in energy loss, ensuring a margin before battery degradation due to high-rate charging and discharging occurs, and preparing for situations where high-rate charging and discharging is required. This achieves both suppression of battery degradation due to high-rate charging and discharging and improved energy efficiency and drivability by enabling high-rate charging and discharging when necessary.

[0009] In the present invention, the loss threshold during charging of the battery is preferably smaller than the loss threshold during discharging. In the present invention configured as described above, the loss threshold during charging is smaller than during discharging, so the limit current during charging can be made larger than during discharging. Therefore, when using regenerative braking, the battery can be charged with as large a current as possible, achieving the desired deceleration force and good energy efficiency.

[0010] In the present invention, preferably, the higher the vehicle speed, the higher the loss threshold value during battery discharge. In the present invention configured as described above, the higher the vehicle speed, the higher the loss threshold during battery discharge, so the higher the vehicle speed, the lower the limit current value during discharge. Therefore, the higher the vehicle speed and the greater the regenerative energy during deceleration, the more strict the limit on discharge current during discharge when regenerative braking is not being used, ensuring a margin before battery degradation occurs and preparing for a situation where high-rate charging is required during subsequent deceleration regeneration.

[0011] In the present invention, preferably, the higher the vehicle speed, the smaller the loss threshold value during charging of the battery. In the present invention configured as described above, the higher the vehicle speed, the smaller the loss threshold during battery charging, so the higher the vehicle speed, the larger the limit current during charging can be. Therefore, when the vehicle speed is high and the regenerative energy during deceleration is large, the limit on the charging current during charging using regenerative braking can be reduced, making the charging current as large as possible and improving energy efficiency.

[0012] In the present invention, preferably, the greater the amount of deceleration of the vehicle in the most recent predetermined time period, the greater the loss threshold value during battery discharge. In the present invention configured as described above, since the greater the deceleration rate of the nearest vehicle, the greater the loss threshold during battery discharge, the greater the deceleration rate of the nearest vehicle, the smaller the limit current value during discharge. Therefore, when the nearest vehicle decelerates significantly and deceleration is required, the limit on discharge current is strengthened during discharge when regenerative braking is not being used, ensuring a margin before battery degradation occurs and preparing for a situation where high-rate charging is required during subsequent deceleration regeneration.

[0013] In the present invention, preferably, the greater the amount of deceleration of the vehicle in the most recent predetermined time period, the smaller the loss threshold value during battery charging. In the present invention configured as described above, the greater the deceleration of the nearest vehicle, the smaller the loss threshold during battery charging, so the greater the deceleration of the nearest vehicle, the greater the limit current value during charging. Therefore, when the nearest vehicle is decelerating rapidly and deceleration is necessary, the limit on the charging current during charging using regenerative braking can be reduced, and the charging current can be made as large as possible, thereby improving energy efficiency.

[0014] In the present invention, the controller is preferably configured to set the upper limit current value as an initial value for the limit current value, and to search for the minimum limit current value by reducing the limit current value until the difference between the energy loss when charging and discharging the battery at the limit current value and the energy loss when charging and discharging the battery at the upper limit current value reaches a loss threshold. In the present invention configured as described above, it is possible to appropriately determine the smallest possible limiting current value within the range in which an increase in energy loss is tolerable. [Effects of the Invention]

[0015] According to the battery control device of the present invention, it is possible to suppress battery degradation caused by high-rate charging and discharging while improving energy efficiency and drivability through high-rate charging and discharging at a high level. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a plan view showing a schematic configuration of a vehicle to which a battery control device according to an embodiment of the present invention is applied; [Figure 2] 1 is a block diagram showing a functional configuration of a battery control device according to an embodiment of the present invention; [Figure 3] 1 is a diagram showing a simplified structure of a lithium-ion battery according to an embodiment of the present invention; [Figure 4] FIG. 1 is a diagram illustrating an example of deterioration of a lithium ion battery. [Figure 5] 4 is a flowchart illustrating a battery control process according to an embodiment of the present invention. [Figure 6] 4 is a flowchart illustrating a limited current value calculation process according to an embodiment of the present invention. [Figure 7] 10 is a diagram illustrating an example of the relationship between the current value and the loss power when the effect of the current limit on the loss power is small. FIG. [Figure 8] 10 is a diagram illustrating an example of the relationship between the current value and the loss power when the current limit has a large effect on the loss power. FIG. [Figure 9]FIG. 10 is a diagram illustrating an example of the relationship between vehicle speed and loss threshold value. [Figure 10] FIG. 10 is a diagram illustrating an example of the relationship between past deceleration amounts and loss thresholds. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, a battery control device according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0018] <System configuration> First, the configuration of the battery control device according to this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a plan view showing a schematic configuration of a vehicle to which the battery control device according to this embodiment is applied, and Figure 2 is a block diagram showing the functional configuration of the battery control device according to this embodiment.

[0019] As shown in FIG. 1, the vehicle 1 of this embodiment is a hybrid vehicle equipped with an internal combustion engine 2 and a motor 4, which serve as power sources for the vehicle 1. The internal combustion engine 2 and the motor 4 are mounted, for example, in the front of the vehicle body of the vehicle 1. The internal combustion engine 2 is, for example, a gasoline engine or a diesel engine. Torque output from the internal combustion engine 2 and the motor 4 is transmitted to a transmission 6 via a clutch (not shown). The transmission 6 outputs the input torque to a pair of drive shafts 8 at a predetermined reduction ratio. This drives a pair of drive wheels 10 (left and right front wheels in the example of FIG. 1) attached to the outer ends of each drive shaft 8 in the vehicle width direction. In addition, the motor 4 functions as a generator that outputs regenerative power when the vehicle 1 decelerates.

[0020] Battery B, which supplies power to motor 4, is a lithium-ion battery and is mounted, for example, at the rear of the vehicle body 1. Battery B has, for example, an output voltage of 48 V, a maximum discharge current value of 80 A, and a capacity of 1 kWh. Furthermore, an inverter 12 is disposed near motor 4. Inverter 12 converts DC power supplied from battery B into AC power and supplies it to motor 4, and converts regenerative power generated by motor 4 into DC power and supplies it to battery B, thereby charging battery B. In addition, inverter 12 is electrically connected to controller 14, allowing control signals to be input and output to and from controller 14.

[0021] The vehicle 1 also has a temperature sensor SN1 that detects the temperature of battery B, a voltage sensor SN2 that detects the voltage of battery B, a current sensor SN3 that detects the charge / discharge current value of battery B, a vehicle speed sensor SN4 that detects the vehicle speed, and an acceleration sensor SN5 that detects the acceleration of the vehicle 1. Each of these sensors is electrically connected directly or indirectly to the controller 14, and outputs a detection signal corresponding to each detection value to the controller 14.

[0022] A controller 14 performs various controls in the vehicle 1. As shown in Fig. 2, the controller 14 has a processor 16 and a memory 18 (ROM, RAM, etc.) for storing various programs (including basic control programs such as an OS and application programs that are started on the OS and realize specific functions) that are interpreted and executed by the processor 16, and various data.

[0023] The controller 14 functions as a controller of the powertrain system of the vehicle 1. That is, the controller 14 controls the internal combustion engine 2 and the inverter 12 in response to the driver's operation of the accelerator pedal, and causes the battery B to supply electric power to the motor 4 via the inverter 12, or causes the motor 4 to supply regenerative electric power to the battery B, thereby realizing a desired output torque or regenerative torque in response to the accelerator operation. Furthermore, the controller 14 is configured to control the charging and discharging of the battery B based on signals input from the various sensors SN1 to SN5 described above.

[0024] Next, the structure of battery B of this embodiment will be described with reference to Figures 3 to 5. Figure 3 is a simplified diagram showing the structure of a lithium ion battery, Figure 4 is a diagram showing an example of lithium ion battery degradation, and Figure 5 is a diagram illustrating a map for determining the limit integrated current amount of a lithium ion battery.

[0025] Battery B of this embodiment is a lithium-ion battery, and as shown in FIG. 3, includes a positive electrode, a negative electrode, and a separator that insulates the positive electrode from the negative electrode, and uses a nonaqueous electrolyte solution as a supporting electrolyte, in which a main electrolyte and a secondary electrolyte are dissolved in a nonaqueous solvent.

[0026] The positive electrode is formed by mixing a positive electrode active material and additives (binder and conductive additive) and applying the mixture to a current collector. A preferred current collector is, for example, aluminum foil.

[0027] Preferable positive electrode active materials include composite metal oxides containing one or more elements selected from the group consisting of cobalt, manganese, and nickel and lithium, lithium phosphate compounds, and lithium silicate compounds. Lithium phosphate compounds are particularly preferred. These positive electrode active materials may be used alone or in combination of two or more.

[0028] The negative electrode is formed by mixing a negative electrode active material and additives (binder and conductive additive) and applying the mixture to a current collector. A preferred current collector is, for example, copper foil.

[0029] As the negative electrode active material, it is preferable to use a graphite-based carbon material, i.e., artificial graphite or natural graphite. From the viewpoint of improving the ability to absorb and release Li ions, graphite-based carbon materials with a low degree of graphitization are preferred. Artificial graphite with a low degree of graphitization and hard carbon are preferred as negative electrode active materials. Highly crystalline natural graphite deteriorates quickly when used alone, so it is preferable to use it in combination with surface-treated natural graphite or artificial graphite.

[0030] The separator is not particularly limited, but may be a single-layer or multi-layer microporous film, woven fabric, nonwoven fabric, or the like, made of polyolefin such as polypropylene or polyethylene.

[0031] The non-aqueous electrolyte solution is a solution in which a lithium salt (supporting electrolyte) is dissolved in a non-aqueous solvent, and additives are added as needed.

[0032] Battery B is provided with a heater for heating battery B and a heat exchanger for cooling battery B. The heater raises the temperature of battery B when the temperature is low, for example, at room temperature, to a temperature of, for example, about 45°C. This temperature increase makes it possible to increase the limit integrated current amount, as will be described later. The heater may be, for example, an electric heater, but is not limited to this. For example, when the temperature of the coolant for the internal combustion engine 2 is high, equal to or higher than a predetermined temperature, the coolant can be used to raise the temperature.

[0033] The heat exchanger is activated when the temperature of battery B reaches a predetermined temperature (for example, 50°C) and prevents the temperature of battery B from rising above an allowable upper limit temperature (for example, 60°C). Any suitable heat exchanger can be used, such as an air-cooled or water-cooled type.

[0034] Figure 4 is a graph showing the relationship between the magnitude of the charge / discharge current and degradation of a lithium-ion battery. The horizontal axis shows the magnitude of the charge / discharge current (effective current) when the lithium-ion battery is in use, and the vertical axis shows the rate of resistance degradation (increase in internal resistance) after 10 years. Normal degradation, shown by the dashed line in Figure 4, is also called aging degradation, and is not significantly affected by the effective current. In other words, even when the effective current is relatively large, the resistance degradation caused by normal degradation does not worsen significantly.

[0035] On the other hand, permanent degradation, shown by the solid line in Figure 4, occurs when charging and discharging at a large current above a certain level (high-rate charging and discharging) are continued, resulting in a biased ion concentration distribution in the electrolyte, and is also called high-rate degradation. Even if the internal resistance of a lithium-ion battery temporarily increases when high-rate charging and discharging are performed for a short period of time, the internal resistance decreases and can be restored to its original state by suspending charging and discharging. However, once high-rate degradation occurs, the internal resistance of a lithium-ion battery will not return to its original state even if charging and discharging are suspended. Therefore, it is necessary to avoid long-term high-rate charging and discharging that can cause high-rate degradation.

[0036] High-rate degradation can be prevented by limiting the charge / discharge current to a predetermined small current or less (for example, 40 A or less). However, implementing such current limitation may result in insufficient power being supplied from battery B to motor 4 or in insufficient deceleration force being obtained by regenerative braking. Therefore, it is necessary to control the charge / discharge of battery B so as to simultaneously suppress the degradation of battery B caused by high-rate charge / discharge and improve energy efficiency and drivability through high-rate charge / discharge.

[0037] <Battery control> Next, the battery control process according to this embodiment will be described with reference to Figures 5 and 6. Figure 5 is a flowchart showing the battery control process according to this embodiment, and Figure 6 is a flowchart showing the limited current value calculation process according to this embodiment. The battery control process shown in Figure 5 is repeatedly executed by the controller 14 at a predetermined interval when the power supply of the vehicle 1 is ON.

[0038] When the battery control process is started, the controller 14 acquires signals from the sensors SN1 to SN5 (step S1). The acquisition of signals from the sensors SN1 to SN5 is constantly performed in the background even in the processes after step S1.

[0039] Next, the controller 14 calculates a required current value Ireq (step S2). The required current value Ireq is a charge / discharge current value required for charging / discharging the battery B in accordance with the driving operation of the driver and the operating state of the vehicle 1. The required current value Ireq includes, for example, a charge / discharge current required for the motor 4 to generate a required output torque or a required regenerative torque set based on the driving operation of the driver.

[0040] Next, the controller 14 calculates the effective current value Irms of the battery B based on the signal acquired from the current sensor SN3 in step S1 (step S3).

[0041] Next, the controller 14 calculates the integrated current amount based on the effective current value Irms calculated in step S3 (step S4). The integrated current amount [Ah] is a value expressed by the product of the effective current value Irms during charging and discharging of the lithium-ion battery and the charging and discharging time. The controller 14 calculates the integrated current amount up to the present time by, for example, adding the product of the effective current value Irms calculated in step S3 and the time from the last time the integrated current amount was calculated to the present (e.g., the calculation period of the battery control process) to the last calculated integrated current amount. If the effective current value Irms calculated in step S3 is 0, that is, if charging and discharging of battery B is paused, the controller 14 subtracts a value corresponding to the pause time from the last calculated integrated current amount. If the pause time is equal to or longer than a predetermined time, the integrated current amount may be reset to 0.

[0042] Next, based on the integrated current calculated in step S4, controller 14 determines whether to limit the charge / discharge current to prevent high-rate degradation of battery B (step S5). Specifically, controller 14 determines to limit the charge / discharge current when the integrated current calculated in step S4 is equal to or greater than the limit integrated current. Here, the limit integrated current is the upper limit of the integrated current at which high-rate charging / discharging can be performed without causing high-rate degradation. In other words, when the integrated current reaches the limit integrated current, it is necessary to limit the charge / discharge current to prevent high-rate degradation. The limit integrated current is, for example, preset and stored in memory 18. Furthermore, since the limit integrated current changes depending on the temperature and effective current value Irms of battery B, controller 14 may be configured to calculate the limit integrated current as needed, reflecting these parameters.

[0043] In step S5, if it is determined that the charge / discharge current will not be limited to prevent high-rate degradation of battery B (step S5: NO), that is, if the integrated current amount calculated in step S4 has not reached the limit integrated current amount and there is still room for high-rate degradation to occur, the controller 14 determines the required current value Ireq calculated in step S2 as the current value to be used for charging and discharging battery B (step S6).

[0044] On the other hand, if it is determined in step S5 that the charge / discharge current should be limited to prevent high-rate degradation of battery B (step S5: YES), i.e., if the integrated current calculated in step S4 has reached the limit integrated current and it is necessary to limit the charge / discharge current to prevent high-rate degradation, controller 14 calculates a high-rate degradation prevention upper limit current value Ihr (step S7). The high-rate degradation prevention upper limit current value Ihr is an upper limit of the charge / discharge current to prevent high-rate degradation. That is, high-rate degradation can be prevented by limiting the effective current value Irms of the charge / discharge current to or below the high-rate degradation prevention upper limit current value Ihr. The high-rate degradation prevention upper limit current value Ihr may be preset and stored in memory 18, for example, or may be obtained from a map stored in memory 18 in advance, based on the temperature and SOC of battery B, the state of vehicle 1, and the like.

[0045] Next, the controller 14 calculates the limit current value Iope (step S8). The limit current value Iope is a current value for further limiting the charge / discharge current than the high-rate degradation prevention upper limit current value Ihr, within an allowable range for an increase in energy loss (loss power) of the vehicle 1 due to the limit on the charge / discharge current, and is calculated to be a value smaller than the high-rate degradation prevention upper limit current value Ihr.

[0046] The process of calculating the limited current value Iope will now be described in detail with reference to Fig. 6. When the process of calculating the limited current value Iope is started, the controller 14 calculates the loss power Lhr when the charge / discharge current of the battery B is limited to the high-rate degradation prevention upper limit current value Ihr, based on the driving state of the vehicle 1 (step S21).

[0047] Loss power [W] is the energy loss in vehicle 1 per unit time, and is calculated as the total value of the losses according to the operating state of each device installed in vehicle 1, such as internal combustion engine 2, motor 4, and battery B. The larger the charge / discharge current of battery B, the higher the energy efficiency tends to be, so the smaller the charge / discharge current of battery B, the greater the loss power tends to be.

[0048] Controller 14 calculates losses according to the state of each part of vehicle 1, including signals acquired from sensors SN1 to SN5, using, for example, maps and models set in advance and stored in memory 18, and then adds up the losses to calculate loss power. At this time, loss power Lhr can be calculated by setting the upper limit of the charge / discharge current of battery B to the high-rate degradation prevention upper limit current value Ihr and performing the calculation.

[0049] Next, the controller 14 sets the high-rate degradation prevention upper limit current value Ihr as the initial value of the limit current value Iope (step S22).

[0050] Next, the controller 14 sets the high-rate degradation prevention upper limit current value Ihr as the initial value of the search value Itmp used to find the limit current value Iope (step S23).

[0051] Next, the controller 14 calculates the loss power Ltmp when the upper limit value of the charge / discharge current of the battery B is Itmp (step S24).

[0052] Next, the controller 14 calculates the difference Ldiff between the loss power Ltmp calculated in step S24 and the loss power Lhr calculated in step S21 (step S25). This Ldiff represents the increase in loss power when the current value is further limited from the high-rate degradation prevention upper limit current value Ihr to Itmp.

[0053] Next, the controller 14 determines whether Ldiff calculated in step S25 is greater than a predetermined loss threshold Lth (step S26). The loss threshold Lth represents the maximum allowable increase in loss power when the charge / discharge current is further limited beyond the high-rate degradation prevention upper limit current value Ihr. In other words, the larger the loss threshold Lth, the smaller the limit current value can be. This loss threshold Lth is, for example, preset and stored in the memory 18.

[0054] If the determination result in step S26 is that Ldiff is not greater than the loss threshold Lth (ie, Ldiff is equal to or less than the loss threshold Lth) (step S26: NO), the controller 14 records the current search value Itmp as the limit current value Iope (step S27).

[0055] Next, the controller 14 updates the current search value Itmp by subtracting a predetermined value ΔI from the current search value Itmp (step S28). Thereafter, the controller 14 searches for the limit current value Iope by repeating the processes of steps S24 to S28 until it is determined in step S26 that Ldiff is greater than the loss threshold Lth.

[0056] If the result of the determination in step S26 is that Ldiff is greater than the loss threshold Lth (step S26: YES), the controller 14 ends the calculation process of the limit current value Iope and returns to the battery control process of Fig. 5. That is, the current value last recorded in step S27 is used as the minimum limit current value Iope.

[0057] Here, with reference to Figures 7 and 8, we will explain how the limited current value Iope differs between situations where the impact of limiting the charge / discharge current on loss power is large and small. Figure 7 is a diagram illustrating an example of the relationship between the current value and loss power when the impact of the current limit on loss power is small, and Figure 8 is a diagram illustrating an example of the relationship between the current value and loss power when the impact of the current limit on loss power is large. In Figures 7 and 8, the horizontal axis represents the current value, and the vertical axis represents loss power.

[0058] When the effect of current limiting on loss power is small, the rate of increase in loss power is gradual when the current value is further limited from the high-rate degradation prevention upper limit current value Ihr, as shown in Fig. 7. Therefore, the limit current value Iope (Itmp just before the increase in loss power Ldiff = Ltmp - Lhr exceeds the loss threshold Lth) can be made much smaller than the high-rate degradation prevention upper limit current value Ihr.

[0059] On the other hand, when the effect of current limiting on loss power is large, as shown in Fig. 8, the rate of increase in loss power when the current value is further limited from the high-rate degradation prevention upper limit current value Ihr is steeper than in Fig. 7. Therefore, the limit current value Iope (Itmp just before the increase in loss power Ldiff = Ltmp - Lhr exceeds the loss threshold Lth) is closer to the high-rate degradation prevention upper limit current value Ihr than in the case of Fig. 7.

[0060] 5, the controller 14 determines the smaller of the requested current value Ireq calculated in step S2 and the limited current value Iope calculated in step S8 as the current value to be used for charging and discharging the battery B (step S9). After the processing of step S6 or S9, the controller 14 ends the battery control processing.

[0061] In this way, controller 14 controls battery B to limit the charge / discharge current to a value even smaller than the high-rate degradation prevention upper limit current value Ihr, within a range that allows for an increase in loss power. This strengthens the limit on the charge / discharge current while minimizing the increase in loss power, thereby suppressing increases in the integrated current amount and promoting decreases, and ensuring a margin in the integrated current amount relative to the limit integrated current amount in preparation for situations where high-rate charging / discharging is required. Therefore, it is possible to both suppress deterioration of battery B due to high-rate charging / discharging and improve energy efficiency and drivability through high-rate charging / discharging.

[0062] <Modification> Next, a modified example of the embodiment of the present invention will be described.

[0063] In the above-described embodiment, the loss threshold Lth is described as being set in advance and stored in the memory 18, for example. However, the loss threshold Lth may be varied depending on the state of the vehicle 1. Here, with reference to Fig. 9 and Fig. 10, an example in which the loss threshold Lth varies depending on the state of the vehicle 1 will be described. Fig. 9 is a diagram illustrating an example of the relationship between the vehicle speed and the loss threshold Lth, and Fig. 10 is a diagram illustrating an example of the relationship between the past deceleration amount and the loss threshold Lth.

[0064] For example, as shown in Figures 9 and 10, the loss threshold Lth may be different during non-regeneration (discharging) as indicated by the dashed line and during regeneration (charging) as indicated by the solid line. Specifically, the loss threshold Lth may be set to be smaller during regeneration than during non-regeneration.

[0065] During regeneration, it is desirable to charge battery B with as large a current as possible to obtain the desired deceleration force and achieve good energy efficiency. Therefore, to maximize the charging current during regeneration, the loss threshold Lth is set smaller than when not regenerating (i.e., the limit current value Iope approaches the high-rate degradation prevention upper limit current value Ihr).

[0066] Furthermore, since the higher the vehicle speed, the greater the regenerative energy generated when the vehicle 1 decelerates, it is desirable from the viewpoint of energy efficiency to charge the battery B with as large a current value as possible. Therefore, in order to make the charging current during regeneration as large as possible as the vehicle speed increases, the loss threshold value Lth during regeneration may be set to decrease as the vehicle speed increases, as shown in Fig. 9.

[0067] Furthermore, when the vehicle is not regenerating, it is desirable to provide a margin in the integrated current amount in preparation for subsequent deceleration. Therefore, the loss threshold Lth when the vehicle is not regenerating may be set to be larger as the vehicle speed increases, as shown in Figure 9, so that the current limit when the vehicle is not regenerating can be strengthened (i.e., the charging current can be reduced) as the vehicle speed increases.

[0068] Furthermore, the rate of change of the loss threshold Lth according to the vehicle speed (the slope in the graph shown in FIG. 9) may be greater in the medium vehicle speed range (the "medium" range in FIG. 9) than in the low vehicle speed range (the "low" range in FIG. 9), and may be even greater in the high vehicle speed range (the "high" range in FIG. 9) than in the medium vehicle speed range.

[0069] Furthermore, since the greater the deceleration of the vehicle 1 over the most recent predetermined period of time (e.g., 10 minutes) (e.g., the number of decelerations or the amount of speed change due to deceleration), the greater the regenerative energy generated during deceleration, it is desirable from the viewpoint of energy efficiency to charge the battery B with as large a current value as possible. Therefore, in order to make the charging current during regeneration as large as possible as the most recent deceleration amount is, the loss threshold value Lth during regeneration may be set to be smaller as the most recent deceleration amount is larger, as shown in Fig. 10.

[0070] Furthermore, when not regenerating, it is desirable to provide a margin in the integrated current amount in preparation for subsequent deceleration. Therefore, as shown in Fig. 10, the loss threshold Lth when not regenerating may be set to be larger as the most recent deceleration rate increases, so that the current limit when not regenerating can be strengthened (i.e., the charging current can be reduced) as the most recent deceleration rate increases.

[0071] Furthermore, the rate of change of the loss threshold Lth according to the most recent deceleration (the slope in the graph shown in FIG. 10) may be larger when the most recent deceleration is medium (the "medium" range in FIG. 10) than when the most recent deceleration is small (the "small" range in FIG. 10), and may be even larger when the deceleration is even larger than when the most recent deceleration is medium (the "large" range in FIG. 10).

[0072] Furthermore, in the above-described embodiment, the limit current value Iope is determined by gradually decreasing the search value Itmp, but Iope may also be determined selectively by multipoint evaluation.

[0073] Furthermore, in order to prevent high-rate degradation, not only can the charge / discharge current be limited to provide a margin for the integrated current amount, but also the rate balance between the charge current and the discharge current can be provided with a margin. For example, when the vehicle speed of vehicle 1 is high, the rate balance can be shifted toward the discharge side (i.e., the limit current value during discharge can be made larger than the limit current value during charge) compared to when the vehicle speed is low, thereby increasing the integrated current amount due to discharge in advance in preparation for subsequent high-rate charging by deceleration regeneration.

[0074] Furthermore, in the above-described embodiment, the vehicle 1 is a hybrid vehicle, but the present invention can also be applied to an electric vehicle that does not have an internal combustion engine 2 mounted thereon.

[0075] <Action and effect> Next, the effects of the battery control device according to the above-described embodiment and modified example will be described.

[0076] First, controller 14 calculates a limit current value Iope such that the difference between the energy loss when battery B is charged and discharged at a limit current value smaller than the high-rate degradation prevention upper limit current value Ihr and the energy loss when battery B is charged and discharged at the high-rate degradation prevention upper limit current value Ihr is equal to or less than a predetermined loss threshold Lth. Controller 14 then controls the charging and discharging of battery B so that the charge and discharge current of battery B is equal to the limit current value Iope, thereby limiting the charge and discharge current to a value even smaller than the high-rate degradation prevention upper limit current value Ihr within an acceptable range for increased energy loss. This strengthens the limit on the charge and discharge current while minimizing the increase in energy loss, ensuring a margin before battery B begins to deteriorate due to high-rate charging and discharging, and preparing for situations where high-rate charging and discharging are required. This allows for both suppression of battery B deterioration due to high-rate charging and discharging and improved energy efficiency and drivability by enabling high-rate charging and discharging when necessary.

[0077] Furthermore, the loss threshold Lth of battery B during charging is smaller than the loss threshold Lth during discharging. Therefore, since the loss threshold Lth during charging is smaller than that during discharging, the limit current value Iope during charging can be made larger than that during discharging. Therefore, when using regenerative braking, battery B can be charged with the largest possible current value, thereby achieving the desired deceleration force and good energy efficiency.

[0078] Furthermore, the higher the speed of the vehicle 1, the larger the loss threshold Lth when the battery B is discharged. Therefore, the higher the vehicle speed, the larger the loss threshold Lth during discharge of battery B, and therefore the higher the vehicle speed, the smaller the limit current value Iope during discharge. Therefore, the higher the vehicle speed and the greater the regenerative energy during deceleration, the stronger the limit on the discharge current during discharge when regenerative braking is not used, ensuring a margin before battery B deteriorates and preparing for a situation where high-rate charging is required during subsequent deceleration regeneration.

[0079] Furthermore, the higher the speed of the vehicle 1, the smaller the loss threshold Lth when the battery B is being charged. Therefore, the higher the vehicle speed, the smaller the loss threshold Lth during charging of battery B, and therefore the higher the vehicle speed, the larger the limit current value Iope during charging. Therefore, when the vehicle speed is high and the regenerative energy during deceleration is large, the limit on the charging current during charging using regenerative braking can be reduced, making the charging current as large as possible and improving energy efficiency.

[0080] Furthermore, the greater the deceleration amount of the vehicle 1 in the most recent predetermined time period, the greater the loss threshold Lth during discharging of the battery B. Therefore, the greater the deceleration of the nearest vehicle 1, the greater the loss threshold Lth during discharge of battery B, and therefore the greater the deceleration of the nearest vehicle 1, the smaller the limit current value Iope during discharge can be. Therefore, the greater the deceleration of the nearest vehicle 1 and the greater the need for deceleration, the stronger the limit on the discharge current during discharge when regenerative braking is not being used, ensuring a margin before deterioration of battery B occurs and making it possible to prepare for a situation in which high-rate charging is required during subsequent deceleration regeneration.

[0081] Furthermore, the greater the deceleration of the vehicle 1 in the most recent predetermined time period, the smaller the loss threshold Lth during charging of the battery B. Therefore, the greater the deceleration of the nearest vehicle 1, the smaller the loss threshold Lth during charging of battery B, and therefore the greater the deceleration of the nearest vehicle 1, the greater the limit current value Iope during charging can be. Therefore, when the deceleration of the nearest vehicle 1 is greater and deceleration is necessary, the limit on the charging current during charging using regenerative braking can be reduced, and the charging current can be made as large as possible, thereby improving energy efficiency.

[0082] In addition, the controller 14 is configured to set the high-rate degradation prevention upper limit current value Ihr as the initial value of the limit current value, and to search for the minimum limit current value Iope by reducing the limit current value until the difference between the energy loss when charging and discharging battery B at the limit current value and the energy loss when charging and discharging battery B at the high-rate degradation prevention upper limit current value Ihr reaches the loss threshold value Lth. Therefore, it is possible to appropriately determine the limit current value Iope that is as small as possible within the range in which an increase in energy loss is tolerable. [Explanation of symbols]

[0083] 1 vehicle 2. Internal combustion engine 4 motors 6. Transmission 8 Drive shaft 10 drive wheels B Battery 12 inverters 14 Controller 16 processors 18 Memory SN1 Temperature Sensor SN2 Voltage Sensor SN3 Current Sensor SN4 Vehicle Speed ​​Sensor SN5 Accelerometer

Claims

1. A control device for a battery mounted on a vehicle equipped with a motor as a power source, a current sensor for measuring a charge / discharge current of the battery; a controller that determines an upper limit current value that is allowed for charging and discharging the battery based on the measured charging and discharging current; The controller Calculating an energy loss per unit time in the vehicle based on an operating state of the vehicle; calculating a limit current value that is smaller than the upper limit current value, such that a difference between the energy loss when charging and discharging the battery at the limit current value and the energy loss when charging and discharging the battery at the upper limit current value is equal to or less than a predetermined loss threshold; The charging and discharging of the battery is controlled so that the charging and discharging current of the battery becomes the limited current value. Battery control device.

2. the loss threshold when charging the battery is less than the loss threshold when discharging; The battery control device according to claim 1 .

3. The higher the vehicle speed, the higher the loss threshold during discharge of the battery. The battery control device according to claim 1 .

4. The higher the vehicle speed, the smaller the loss threshold when charging the battery. The battery control device according to claim 1 .

5. The greater the deceleration amount of the vehicle in the most recent predetermined time, the greater the loss threshold value when discharging the battery. The battery control device according to claim 1 .

6. The greater the deceleration amount of the vehicle in the most recent predetermined time period, the smaller the loss threshold value when charging the battery. The battery control device according to claim 1 .

7. The controller the upper limit current value is set as an initial value of the limited current value, and the limited current value is reduced until a difference between the energy loss when the battery is charged and discharged at the limited current value and the energy loss when the battery is charged and discharged at the upper limit current value reaches the loss threshold, thereby searching for a minimum limited current value. The battery control device according to any one of claims 1 to 6.

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