JP7740102B2 - Vehicle battery unit control device - Google Patents

Description

The disclosed technology relates to a control device for a battery unit installed in a vehicle.

Vehicles that run using motor output, such as hybrid vehicles and electric vehicles, are equipped with large-capacity battery units consisting of secondary batteries such as lithium-ion batteries as their driving source.

Depending on the vehicle's driving conditions, high output may be required from the motor, or the motor may be used as a generator to generate high output. In such cases, the battery unit undergoes instantaneous charging and discharging with extremely large currents. It is known that repeated instantaneous charging and discharging with such large currents accelerates the deterioration of the battery unit's performance (so-called high-rate degradation).

In response to this, Patent Document 1 discloses technology that estimates the degree of high-rate degradation and limits the charging and discharging power before it exceeds the allowable range.

JP 2017-50981 A

The technology in Patent Document 1 can slow the progression of high-rate degradation of the battery unit, but does not suppress high-rate degradation itself. Therefore, in vehicles where instantaneous charging and discharging with large currents is performed frequently, a decrease in battery unit performance is unavoidable. The technology in Patent Document 1 leaves room for improvement.

The disclosed technology therefore aims to realize a control device for a vehicle battery unit that can suppress high-rate degradation itself.

The disclosed technology relates to a control device for a battery unit installed in a vehicle as a driving power source.

The control device includes a high-rate charge/discharge prediction unit that predicts high-rate charging, which charges the battery unit at a power equal to or greater than a predetermined reference value set according to the performance of the battery unit, and high-rate discharging, which discharges the battery unit at a power equal to or greater than the reference value, while the vehicle is in operation, and a charge/discharge state change unit that changes the charge/discharge state of the battery unit based on the predictions of the high-rate charge/discharge prediction unit.

The charge/discharge state change unit then executes a counter-charge process to temporarily charge the battery by increasing the power when the high-rate discharge is predicted, and also executes a counter-discharge process to temporarily discharge the battery by increasing the power when the high-rate charge is predicted.

In other words, with this control device, high-rate charging and high-rate discharging are predicted, i.e., estimated in advance, by the high-rate charging/discharging prediction unit while the vehicle is in operation. Then, when high-rate discharging is predicted, the charge/discharge state change unit executes a counter-charge process, which is the opposite state, and when high-rate charging is predicted, the charge/discharge state change unit executes a counter-discharge process, which is the opposite state.

As will be explained in more detail below, the inventors have discovered that by temporarily creating this reverse state before high-rate charging and discharging, it is possible to suppress high-rate degradation itself. Therefore, this control device makes it possible to suppress high-rate degradation itself, thereby reducing performance degradation of the battery unit.

The control device may also be configured so that the vehicle includes a drive motor connected to the battery unit via an inverter, and when high-rate charging is predicted during powered operation of the vehicle, the charge/discharge state change unit executes the counter-discharge process by reducing the efficiency of the inverter.

This allows counter-discharge processing to be performed without affecting the vehicle's powered operation.

The control device may also be configured such that, if the vehicle is equipped with an auxiliary device that operates on power supplied from the battery unit, when high-rate charging is predicted during powered operation of the vehicle, the charge/discharge state change unit executes the counter-discharge process by supplying power to the auxiliary device.

This method also allows counter-discharge processing to be performed without affecting the vehicle's powered operation. The discharge state can be adjusted by selecting the auxiliary equipment, making it highly versatile. It also has the advantage of making it easier to ensure a sufficient amount of discharge. It is even more effective when combined with the previous method.

The control device may also be configured such that, if the vehicle is equipped with a generator driven by a generator engine, when high-rate discharge is predicted during regenerative operation of the vehicle, the charge/discharge state change unit executes the counter-charge process by charging the battery unit with power generated by the generator.

This allows counter-charging processing to be performed properly even when the amount of charge from regenerative driving is small and counter-charging cannot be performed properly on its own.

The disclosed technology is also suitable when the battery unit includes multiple battery modules that can be charged and discharged individually. In other words, in this case, when high-rate charging is predicted during powered operation of the vehicle, the charge/discharge state change unit executes the counter-discharge process by discharging some of the multiple battery modules.

In this case, by adjusting the charge and discharge of each individual battery module, the charge and discharge amount can be adjusted within the battery unit. This method also allows counter-discharge processing to be performed using only the amount of discharge due to powered operation.

The control device may also be configured so that the charge/discharge state change unit executes the counter-discharge process by discharging some of the plurality of battery modules and charging the remaining ones.

This method allows the amount of discharge to be increased by charging other battery modules, even when counter-discharge processing cannot be performed properly using only the amount of discharge from powered operation. Therefore, counter-discharge processing can be performed properly in a specific battery module.

The control device may also be configured such that, if the vehicle is equipped with an auxiliary device that operates on power supplied from the battery unit, the charge/discharge state change unit complements the counter-discharge process by supplying power to the auxiliary device.

Depending on the capacity of the battery module, even if the above method is adopted, it may not be possible to properly execute the counter-discharge process. Even in such cases, this method utilizes auxiliary equipment, allowing the counter-discharge process to be properly executed.

If the battery unit includes multiple battery modules that can be charged and discharged individually, and if high-rate charging is predicted during regenerative driving of the vehicle, the control device may be configured so that the charge/discharge state change unit executes the counter-discharge process on a specified battery module and charges the remaining battery modules with power obtained by regeneration and power obtained by discharging the specified battery module.

With such a battery unit, counter-discharge processing can be performed even during regenerative operation. That is, as shown here, counter-discharge processing can be performed in a specified battery module, and the remaining battery modules can be charged with power obtained by regeneration and power obtained by discharging in the specified battery module. In this way, counter-discharge processing can be performed.

If the battery unit includes multiple battery modules that can be charged and discharged individually, and if high-rate discharge is predicted during powered operation of the vehicle, the control device may be configured to cause the charge/discharge state change unit to execute the counter-charge process on a specified battery module and cause the remaining battery modules to discharge the power consumed during powered operation as well as the power charged to the specified battery module.

This allows counter-charging processing to be performed only within the battery unit during powered operation. Therefore, counter-charging processing can be performed without affecting powered operation or other devices.

The control device may also be configured such that, if the vehicle is equipped with a generator driven by a generator engine, the charge/discharge state change unit complements the counter-charging process by charging the electric power generated by the generator.

This allows counter-charging to be performed properly even when the previous method fails. It also reduces the amount of discharge in the remaining battery modules. Therefore, this is effective when the capacity of the remaining battery modules is low.

If the battery unit includes multiple battery modules that can be charged and discharged individually, and if high-rate discharge is predicted during regenerative operation of the vehicle, the control device may be configured so that the charge/discharge state change unit executes the counter-charge process by charging a predetermined portion of the battery modules with power obtained through regeneration.

In this case, by adjusting the charging and discharging of each individual battery module, the amount of charging and discharging can be adjusted within the battery unit. This method also allows counter-charging processing to be performed using only charging through regenerative operation.

The control device may also be configured so that the charge/discharge state change unit performs the counter charging process by charging the predetermined portion of the battery modules with power obtained by regeneration and power obtained by discharging the remaining battery modules.

This method allows the charge amount to be increased by discharging the remaining battery modules, even when counter-charging processing cannot be performed properly using only the charge amount from regenerative operation. Therefore, counter-charging processing can be performed properly in a specified battery module.

The control device may also be configured such that, if the vehicle is equipped with a generator driven by a generator engine, the charge/discharge state change unit complements the counter-charging process by charging the electric power generated by the generator.

Depending on the capacity of the battery module, even if the above method is adopted, it may not be possible to properly execute the counter-charging process. Even in such cases, this method uses a generator, allowing the counter-charging process to be properly executed.

A control device for a vehicle battery unit that applies the disclosed technology makes it possible to suppress high-rate degradation itself, thereby reducing performance degradation of the battery unit.

1 is a schematic diagram of a vehicle according to a first embodiment. FIG. 2 is a block diagram showing the relationship between the control device and its main associated devices. FIG. 10 is a diagram for explaining a mechanism for suppressing high-rate degradation. FIG. 10 is a diagram for explaining a mechanism for suppressing high-rate degradation. 1 is a graph showing the results of a verification test. FIG. 1 is a diagram for explaining high-rate charging and discharging. 4 is a flowchart showing an example of control in the vehicle of the first embodiment. 4 is a flowchart showing an example of control in the vehicle of the first embodiment. 4 is a flowchart showing an example of control in the vehicle of the first embodiment. FIG. 10 is a schematic diagram of a vehicle according to a second embodiment. 10 is a flowchart showing an example of control in a vehicle according to a second embodiment. 10 is a flowchart showing an example of control in a vehicle according to a second embodiment.

Embodiments of the disclosed technology are described in detail below with reference to the accompanying drawings. However, the following description is merely exemplary in nature and does not limit the present invention, its applications, or its uses.

First Embodiment
1 shows a schematic diagram of a vehicle 1 according to a first embodiment. The disclosed technology can be applied to any vehicle that is equipped with a driving power source and runs on the power from that power source, such as an electric vehicle or a hybrid vehicle. The first embodiment shows an example of application to an electric vehicle.

The exemplary vehicle 1 is equipped with electrical equipment that makes up a high-voltage electrical system, including a battery unit 2, a battery controller 2a, a drive-side inverter 3, a drive motor 4, a power-generating inverter 5, a generator 6, a power-generating engine 7, and auxiliary equipment 8. These electrical devices are connected via electrical wiring 9 that is compatible with high voltages and large currents.

In addition to the accelerator, brake, steering, and other devices necessary for driving, the vehicle 1 is also equipped with various common electrical components such as an air conditioner and car navigation system. Since these are well known, illustrations and explanations of them will be omitted unless specifically necessary.

The battery unit 2 is a high-voltage, high-capacity secondary battery that is installed in the vehicle 1 as a driving power source. The battery unit 2 is composed of a large number of connected battery cells (lithium ion batteries). The battery controller 2a is a dedicated control device specialized for controlling the charge/discharge state of the battery unit 2, and is attached to the battery unit 2.

The drive motor 4 is connected to the battery unit 2 via the drive-side inverter 3. The drive-side inverter 3 converts the DC power supplied from the battery unit 2 into three-phase AC current and outputs it to the drive motor 4. This causes the drive wheels 1a connected to the output shaft of the drive motor 4 to rotate, causing the vehicle 1 to travel (so-called power running).

The drive motor 4 is also used as a generator during deceleration. That is, the drive-side inverter 3 converts the AC current generated by the drive motor 4 into DC current and outputs it to the battery unit 2. In this way, the battery unit 2 is charged (so-called regenerative operation).

The generator engine 7 is a small engine dedicated to generating electricity. Therefore, the generator 6 is operated by driving the generator engine 7. The generator 6 is connected to the battery unit 2 via the generator-side inverter 5. The generator-side inverter 5 converts the three-phase AC current supplied from the generator 6 into DC current and outputs it to the battery unit 2.

In other words, this vehicle 1 is a type of electric vehicle known as a range extender. By driving the generator engine 7, the battery unit 2 can be charged as needed, thereby extending the driving range.

Auxiliary equipment 8 is a general term for electrical equipment that operates using power supplied from the battery unit 2. However, the auxiliary equipment 8 in this case is a specific piece of equipment (specific auxiliary equipment) that does not affect the running or operating state of the vehicle 1 even when the auxiliary equipment 8 is operating. Specific examples of auxiliary equipment 8 include an electric compressor and an electric water pump.

(BCU)
The vehicle 1 is equipped with a BCU 10 (battery control unit, an example of a control device) to control the battery unit 2 according to the vehicle's operating state. The BCU 10 is a control device positioned above the battery controller 2a, and controls the charge/discharge state of the battery unit 2 in cooperation with the battery controller 2a.

As shown in Figure 1, the BCU 10 is composed of hardware such as a processor 10a, memory 10b, and interface 10c, and software such as control programs and control data implemented in memory 10b. As shown in Figure 2, the BCU 10 also has a high-rate charge/discharge prediction unit 10d and a charge/discharge state change unit 10e as functional components obtained by this hardware and software. These are the main components of the disclosed technology, and will be described separately below.

As shown simply in Figure 2, the BCU 10 is connected to various related devices via a low-voltage electrical system 12 used for control. The BCU 10 is connected to various on-board sensors 11 installed on the vehicle 1, such as an accelerator position sensor and a vehicle speed sensor. From these on-board sensors 11, information necessary to understand the operating state of the vehicle 1, such as accelerator position, driving speed, and the rotation speed of the drive motor 4, is obtained.

The BCU 10 is also connected to the battery controller 2a. The BCU 10 sends and receives control signals and data signals bidirectionally to and from the battery controller 2a. This allows the BCU 10 to monitor the remaining capacity and charge/discharge state of the battery unit 2. The BCU 10 is also connected to the auxiliary equipment 8, drive-side inverter 3, generator-side inverter 5, and generator engine 7, and sends control signals to these as needed to control their operation.

(High rate charge/discharge)
In the case of the vehicle 1 of this embodiment, for example, when starting to travel, the vehicle 1 needs to be driven solely by the output of the drive motor 4. Therefore, the drive motor 4 needs to output high torque, and a large current flows instantaneously through the battery unit 2 (more specifically, each battery cell constituting the battery unit 2) to energize (discharge) the drive-side inverter 3.

Even in hybrid vehicles, a large current flows when the motor assists the engine. Discharge caused by a large current flowing through the battery unit 2 is called "high-rate discharge."

Situations in which a large current flows through the battery unit 2 frequently occur not only when the vehicle starts to move, but also while the vehicle 1 is in operation. For example, if the vehicle suddenly accelerates during powered operation, a large output is required from the drive motor 4 in a short period of time. Therefore, the battery unit 2 undergoes high-rate discharge.

On the other hand, if the vehicle suddenly decelerates during regenerative driving, a large amount of power is supplied from the drive motor 4 in a short period of time. In this case, a large current flows through the battery unit 2 to charge the large amount of power. Charging performed by passing a large current through the battery unit 2 in this way is called "high-rate charging."

When driving on roads with large gradient changes, this situation occurs repeatedly in a short period of time. In other words, high-rate charging and discharging occurs frequently. When high-rate charging and discharging occurs frequently, high-rate degradation is accelerated, and the performance of the battery unit 2 deteriorates.

For example, when high-rate discharge is performed, the internal resistance of the battery temporarily increases. It takes some time for the increased internal resistance to return to normal. Therefore, if high-rate discharge is performed again while the internal resistance is already elevated, the increase in internal resistance accelerates, causing an irreversible increase in internal resistance. This causes deterioration of the battery unit 2 (high-rate degradation). If this condition occurs repeatedly, high-rate degradation will be accelerated, and the performance of the battery unit 2 will deteriorate.

(Suppression of high-rate degradation)
The inventors have discovered that high-rate degradation can be suppressed by temporarily performing the reverse charge-discharge (counter-discharge and counter-charge) at higher power before high-rate charge-discharge. The disclosed technology is based on this finding. Here, the mechanism is specifically described.

Figure 3 shows a schematic diagram of a battery cell 50 that constitutes the battery unit 2. This battery cell 50 is a lithium-ion battery. Inside the battery cell 50, a positive electrode current collector 50a that constitutes the positive electrode and a negative electrode current collector 50b that constitutes the negative electrode are arranged with a separator 50c between them. An electrolyte solution containing lithium ions is present between the positive electrode current collector 50a and the negative electrode current collector 50b.

Particles of positive electrode active material 50e are attached to the surface of positive electrode current collector 50a by binder 50d. Particles of negative electrode active material 50f are attached to the surface of negative electrode current collector 50b by binder 50g. During discharge, electrons flow from negative electrode current collector 50b to positive electrode current collector 50a outside the battery cell 50. As a result, lithium ions contained in the electrolyte move to the positive electrode side and are inserted into positive electrode active material 50e, as shown in Figure 3(a).

On the other hand, during charging, electrons flow from the positive electrode current collector 50a to the negative electrode current collector 50b outside the battery cell 50, causing lithium ions to move to the negative electrode side. Therefore, as shown in Figure 3(b), the lithium ions inserted into the positive electrode active material 50e leave the positive electrode active material 50e and return to the electrolyte.

Figure 4 shows an enlarged schematic diagram of the interface region between the positive electrode active material 50e and the electrolyte. (A) in the upper part of Figure 4 shows the distribution of lithium ions when normal high-rate discharge is performed. (B) in the lower part of Figure 4 shows the distribution of lithium ions when high-rate discharge is performed using the disclosed technology.

As mentioned above, during discharge, lithium ions in the electrolyte migrate to the positive electrode side and are inserted into the positive electrode active material 50e. As shown in (i) on the left side of (A), lithium ions are uniformly distributed in the electrolyte. Therefore, when high-rate discharge is performed, a large number of lithium ions migrate through the electrolyte and, as shown in (ii) on the right side of (A), are incorporated into the positive electrode active material 50e via the interfacial region. Because a relatively large resistance occurs during this process, a large current cannot be drawn instantaneously. As a result, the internal resistance of the battery increases.

In contrast, the disclosed technology performs the opposite charge (counter charge) before high-rate discharge. As a result, as shown in (i') on the left side of (B), the lithium ions inserted into the positive electrode active material 50e are moved to the interface region of the positive electrode active material 50e, and as shown in (i) in the center of (B), the lithium ions are concentrated in that interface region.

If high-rate discharge is performed in this state, the resistance during absorption will be reduced, making it possible to absorb a large amount of lithium ions into the positive electrode active material 50e, as shown in (ii) on the left side of (B), and it is thought that a large current can be extracted instantaneously.

High-rate charging is similar to high-rate discharging, except that the charging and discharging states are reversed. In other words, before high-rate charging, a temporary discharge with increased power (counter-discharge) can be performed.

(Verification test)
To verify the mechanism described above, the inventors conducted a test using a typical battery cell, in which a 1-second counter-charge at different charge rates was performed immediately before a 10-second high-rate discharge.

The internal resistance of the battery when the voltage momentarily dropped due to high-rate discharge was compared with the internal resistance of the battery when the voltage recovered after high-rate discharge. The test results are shown in Figure 5. The dashed line in Figure 5 represents the instantaneous internal resistance immediately after high-rate discharge. The solid line in Figure 5 represents the internal resistance when the voltage recovered after high-rate discharge (10 minutes later in the test).

It was confirmed that at 0C, i.e., during normal high-rate discharge without counter-charging, internal resistance increases. On the other hand, it was confirmed that counter-charging reduces the increase in internal resistance, and the higher the charge rate, the less the increase in internal resistance.

In other words, when high-rate discharge is performed, the internal resistance temporarily increases. It takes some time for the increased internal resistance to return to its original state, as the electrolyte and electrodes must return to their original state. Therefore, if high-rate discharge is performed again when the internal resistance is already elevated, the increase in internal resistance will be accelerated, resulting in an irreversible increase in internal resistance. In other words, high-rate degradation will progress.

On the other hand, counter charging can reduce the increase in internal resistance that accompanies high-rate discharge and shorten the time it takes for the increased internal resistance to return to normal. It is particularly effective to perform counter charging by increasing the power, i.e., at a high rate. This reduces the cumulative increase in internal resistance, making it possible to suppress high-rate degradation itself.

The same is true for counter discharge. Therefore, counter charge/discharge is effective for high-rate charge/discharge, and high-rate counter charge/discharge is particularly preferable. By performing counter charge/discharge, it is possible to suppress high-rate degradation.

(High-rate charge/discharge prediction unit, charge/discharge state change unit)
In order to suppress high-rate deterioration of the battery unit 2, the BCU 10 of this vehicle 1 is provided with the high-rate charge/discharge prediction unit 10d and the charge/discharge state change unit 10e, as described above.

The high-rate charge/discharge prediction unit 10d predicts high-rate charging and high-rate discharging while the vehicle 1 is in operation. In other words, when charging or discharging is performed on the battery unit 2 while the vehicle 1 is in operation, the high-rate charge/discharge prediction unit 10d makes an inference as to whether the charging or discharging is a high-rate charging or high-rate discharging based on the operating state of the vehicle 1, etc., before the charging or discharging is performed.

Here, high-rate charging and high-rate discharging are determined based on predetermined reference values set according to the performance of the battery unit 2 (specifically, its battery cells), such as battery capacity. Figure 6 shows the relationship between the current value and the rate of increase in internal resistance observed for a specified battery cell. In the case of this battery cell, there is a tendency for the rate of increase in internal resistance to increase sharply when the current value exceeds i0.

In other words, for this battery cell, it can be determined that high-rate degradation occurs in the region where the current value is i0 or greater, and that high-rate degradation does not occur in the region where the current value is less than i0. In this way, whether or not high-rate charging/discharging is occurring can be determined by a predetermined reference value specific to that battery cell.

Therefore, by conducting experiments or the like in advance on the battery cells that make up the battery unit 2, a reference value that serves as the judgment standard for the battery unit 2 is identified, and this reference value is set in the BCU 10. The high-rate charge/discharge prediction unit 10d determines whether or not high-rate charge/discharge is occurring based on this reference value.

High-rate charging and high-rate discharging are predicted based on the driver's operation and the driving state of the vehicle 1. For example, when the driver steps on the accelerator, that information is sent from the accelerator position sensor to the BCU 10, so it is possible to predict whether high-rate discharging will be performed.

Predictions can also be made based on car navigation information. In other words, the GPS function allows the route vehicle 1 will take to be predicted in advance, and the road conditions on which vehicle 1 will travel can be known in advance. The execution of high-rate charging or high-rate discharging can be predicted based on road conditions and vehicle 1's traveling speed, etc.

The charge/discharge state change unit 10e changes the charge/discharge state of the battery unit 2 based on the predictions of the high-rate charge/discharge prediction unit 10d. That is, when high-rate discharge is predicted, the charge/discharge state change unit 10e executes a process (counter-charge process) to perform a counter-charge immediately before that, and when high-rate charge is predicted, it executes a process (counter-discharge process) to perform a counter-discharge immediately before that.

As mentioned above, a high rate of counter charging/discharging is preferable. Therefore, a target high rate of charging/discharging value (target charging/discharging value) is set in advance in the BCU 10. The charging/discharging state change unit 10e executes counter charging/discharging processing with the aim of achieving that target charging/discharging value.

<Example of control performed by the BCU>
There are various possible patterns of control for executing the counter-discharging process and the counter-charging process depending on the specifications of the vehicle 1. Here, the basic control as well as main control examples corresponding to the vehicle 1 of the first embodiment are shown.

Figure 7 shows the basic control flow performed by the BCU 10. When the ignition is turned on, the vehicle is in driving mode, and the vehicle 1 begins to travel, the BCU 10 checks the state of the vehicle 1, such as vehicle speed and road conditions, based on signals input from various on-board sensors 11 (step S1). As a result, while the vehicle 1 is in operation, the BCU 10 (high-rate charge/discharge prediction unit 10d) constantly predicts high-rate charging and high-rate discharging.

When the high-rate charge/discharge prediction unit 10d predicts high-rate charging (Yes in step S2), the BCU 10 (charge/discharge state change unit 10e) works with the battery controller 2a to execute counter-discharge processing (step S3). When the high-rate charge/discharge prediction unit 10d predicts high-rate discharging (Yes in step S4), the charge/discharge state change unit 10e works with the battery controller 2a to execute counter-charge processing (step S5).

If neither high-rate charging nor high-rate discharging is predicted (No in step S4), that is, if it is predicted that the battery unit 2 will not charge or discharge, or if it will charge or discharge, it will do so at a rate below a predetermined reference value (non-high-rate charging or discharging), the BCU 10 executes normal control and maintains the normal charging and discharging state (step S6).

(Counter discharge treatment 1)
8 shows an example of control of the counter discharge process performed by the BCU 10 (charge/discharge state change unit 10e). When the vehicle 1 is in powered operation (Yes in step S10), the battery unit 2 is discharging due to powering. In normal operation, this discharging is a non-high-rate discharge, and in order to perform counter discharge, it is necessary to additionally discharge the battery unit 2 at an even greater power. Even if the discharging due to powering is a high-rate discharge, it is preferable to discharge at a greater power.

The BCU 10 therefore selects a means to reduce the efficiency of the drive-side inverter 3 (step S11). This allows a large amount of power to be discharged from the battery unit 2 without affecting power running. If this allows the target charge/discharge value to be achieved and counter-discharge processing can be executed appropriately (Yes in step S12), the BCU 10 executes counter-discharge processing by reducing the efficiency of the drive-side inverter 3 (step S13). This allows counter-discharge processing to be executed effectively.

On the other hand, if the target charge/discharge value cannot be achieved using that means alone and the counter-discharge process cannot be performed properly (No in step S12), the BCU 10 further selects a means for supplying power to the auxiliary equipment 8 (step S14).

As mentioned above, the auxiliary equipment 8 is an electric compressor, an electric water pump, or the like, and any one of these may be used, or multiple may be used. It can be freely discharged as needed. In the case of this vehicle 1, the generator 6 can also be used as the auxiliary equipment 8.

In other words, the generator 6 and generator engine 7 are stopped except when generating electricity. Therefore, by using the generator 6 as a motor and motoring the generator engine 7, a large amount of power can be discharged from the battery unit 2. The BCU 10 uses these means to execute the counter discharge process (step S13). This allows the counter discharge process to be executed more effectively.

Of the steps described above, steps S11 and S12 may be omitted, and the BCU 10 may directly select a means for supplying power to the auxiliary equipment 8 and execute the counter-discharge process (steps S14 and S13). Alternatively, steps S11 and S14 may be reversed to change the priority order between the means for reducing inverter efficiency and the means for supplying power to the auxiliary equipment 8.

(Counter charge process 1)
9 shows an example of control of the counter charge process performed by the BCU 10 (charge/discharge state change unit 10e) in this vehicle 1. When the vehicle 1 is in regenerative operation (Yes in step S18), the battery unit 2 is being charged by regeneration. If this charging is a high-rate charge and the target charge/discharge value has been reached, the counter charge process does not need to be executed. However, normally, the target charge/discharge value is often not reached.

In contrast, as described above, this vehicle 1 is equipped with a generator 6 that can generate electricity as needed. The BCU 10 can select a means for supplying power to the battery unit 2 using the generator 6. The BCU 10 executes counter-charging processing with the power generated by the generator 6 added to the regenerative power (step S19). This allows the counter-charging processing to be executed more effectively.

Second Embodiment
10 shows a schematic diagram of a vehicle (second vehicle 1B) according to the second embodiment. The second vehicle 1B is an electric vehicle, similar to the vehicle 1 (hereinafter referred to as the first vehicle 1A) according to the first embodiment.

The basic configuration of the second vehicle 1B, including high-voltage equipment such as the battery unit 2, battery controller 2a, drive inverter 3, drive motor 4, generator inverter 5, generator 6, generator engine 7, and auxiliary equipment 8, as well as general equipment equipped on the vehicle 1, is the same as that of the first vehicle 1A. The basic configuration of the BCU 10 is also the same between the second vehicle 1B and the first vehicle 1A. Therefore, the same reference numerals are used for components with the same content, and their description will be omitted.

The second vehicle 1B differs from the first vehicle 1A in the configuration of its battery unit 2. That is, the battery unit 2 of the second vehicle 1B (hereinafter referred to as the second battery unit 2B) includes multiple battery modules 20 that can be charged and discharged individually. The second battery unit 2B is composed of multiple battery modules 20 connected in parallel. Note that while the illustrated example shows three battery modules 20 (first battery module 21, second battery module 22, and third battery module 23), the number of battery modules 20 may be two or four or more.

Each battery module 20, like the battery unit 2 of the first vehicle 1A, is constructed by connecting a large number of battery cells 50 (lithium ion batteries). The battery controller 2a of the second battery unit 2B controls the charge/discharge state of the second battery unit 2B (the entire battery module 20) by controlling the charge/discharge state of each battery module 20. Therefore, charging and discharging of multiple battery modules 20 can be performed either together or partially.

<Example of control performed by the BCU>
The basic control performed by the BCU 10 of the second vehicle 1B is the same as that of the first vehicle 1A. That is, the counter-discharging process and the counter-charging process are also performed in the second vehicle 1B in accordance with the control shown in FIG.

(Counter discharge treatment 2)
11 shows an example of counter-discharge processing control performed by the BCU 10 (charge/discharge state change unit 10e) of the second vehicle 1B. When the second vehicle 1B is not in powering operation, i.e., in regenerative operation (No in step S20), the second battery unit 2B is charged with regenerative power. Normally, this power is distributed equally to each battery module 20.

The BCU 10 performs a counter-discharge process on a selected battery module 20 among the multiple battery modules 20, and determines whether it is possible to charge the remaining battery modules 20 with the power obtained by regeneration and the power obtained by discharging the selected battery module 20 (step S21).

For example, if a counter-discharge process is performed in the first battery module 21, the regenerative power distributed to the first battery module 21 must be distributed to the second battery module 22 and the third battery module 23. Furthermore, the power generated by the counter-discharge in the first battery module 21 must also be distributed to these battery modules 20.

The BCU 10 determines whether such processing is possible based on the battery capacity of each battery module 20. Note that counter-discharge processing is not limited to one battery module 20. It may also be performed on multiple battery modules 20. This method allows counter-discharge processing to be performed effectively without affecting regenerative operation.

As a result, if the BCU 10 determines that the counter discharge process can be performed (Yes in step S21), it performs the counter discharge process (step S22).The BCU 10 then changes (switches) the battery module 20 that is the target of the counter discharge process, and repeats the counter discharge process (step S23).

For example, once the counter-discharge process for the first battery module 21 is complete, the counter-discharge process is then performed for the second battery module 22, and once that is complete, the counter-discharge process is performed for the third battery module 23. This allows counter-discharge processes to be performed for multiple battery modules 20, making it possible to fully handle high-rate charging even at high capacities.

On the other hand, when the second vehicle 1B is in powered operation (Yes in step S20), power is being discharged from the second battery unit 2B. Normally, this power is distributed evenly to each battery module 20.

The BCU 10 determines whether the counter-discharge process can be performed by discharging some of the battery modules 20 (step S24). In other words, the power distributed among the battery modules 20 is concentrated in some of the battery modules 20, thereby increasing the amount of power discharged by those some of the battery modules 20.

For example, discharging in the first battery module 21 and the second battery module 22 is suspended, and the power required for power running is discharged only from the third battery module 23. By doing so, a counter-discharge process is performed in the third battery module 23. The counter-discharge process can be performed effectively without affecting power running.

As a result, if the BCU 10 determines that the counter discharge process can be performed (Yes in step S24), it performs the counter discharge process (step S22).The BCU 10 then changes the battery module 20 to be subjected to the counter discharge process and repeats the counter discharge process (step S23).

However, there are cases where the amount of power consumed during power running is small, and even if that power running power is aggregated into one battery module 20, the target charge/discharge value is not reached. In such cases, the BCU 10 determines that it is not appropriate to perform the counter-discharge process (No in step S24) and determines whether it is possible to perform the counter-discharge process by discharging some of the multiple battery modules 20 and charging the remaining ones (step S25).

For example, assuming a counter-discharge process in the third battery module 23 as described above, in addition to the traction power, the third battery module 23 also discharges. In this case, the first battery module 21 and the second battery module 22 need to be charged with the power generated by the discharge of the third battery module 23.

As a result, if the BCU 10 determines that the counter discharge process can be performed appropriately (Yes in step S25), it performs the counter discharge process (step S22). This prevents power from being wasted and allows the counter discharge process to be performed more effectively. The BCU 10 then changes the battery module 20 to be subjected to the counter discharge process and repeats the counter discharge process (step S23).

On the other hand, if the BCU 10 determines that the counter discharge process cannot be performed appropriately even using this method (No in step S25), it selects a method of supplementing the counter discharge process by supplying power to the auxiliary device 8 (step S26). By supplying power to the auxiliary device 8, more power can be discharged freely, allowing the counter discharge process to be performed appropriately.

The BCU 10 executes counter-discharge processing on the specified target battery module 20 by discharging the power supplied to the auxiliary equipment 8 in addition to the power discharged to the other battery modules 20 and the traction power (step S22). This allows the counter-discharge processing to be executed more effectively. The BCU 10 then changes the battery module 20 targeted for the counter-discharge processing and repeats the counter-discharge processing (step S23).

(Counter charge process 2)
12 shows an example of counter-charging control performed by the BCU 10 (charge/discharge state change unit 10e) of the second vehicle 1B. When the second vehicle 1B is in powered operation (Yes in step S30), power is discharged from the second battery unit 2B. Normally, this power is distributed equally to each battery module 20.

The BCU 10 determines whether counter charging processing can be performed on some of the multiple battery modules 20 (step S31). Specifically, it performs counter charging processing on certain battery modules 20 and determines whether it is possible to discharge the remaining battery modules 20 by adding the power consumed during power running to the power charged to the certain battery modules 20.

For example, assuming that counter charging processing is performed in the first battery module 21, the traction power that was being discharged from the first battery module 21 must be distributed to the second battery module 22 and the third battery module 23. Furthermore, the power that needs to be charged to the first battery module 21 must also be distributed to these battery modules 20 for discharge. Therefore, the second battery module 22 and the third battery module 23 will need to discharge this power in addition to the traction power that was initially distributed.

As a result, if the BCU 10 determines that the counter charge process can be executed appropriately (Yes in step S31), it executes the counter charge process (step S32). The counter charge process can be executed effectively without affecting power running. The BCU 10 then changes the battery module 20 targeted for the counter charge process and repeats the counter charge process (step S33).

On the other hand, if the BCU 10 determines that the target charge/discharge value will not be reached by this means and that the counter-charging process cannot be executed appropriately (No in step S31), it selects a means to complement the counter-charging process by supplying power from the generator 6 (step S34). Supplying power from the generator 6 makes it possible to charge with the required power, and the counter-charging process can be executed appropriately.

The BCU 10 performs counter-charging by adding power from the generator 6 to the power obtained by discharging other battery modules 20 (step S32). This allows the counter-charging process to be performed more effectively. The BCU 10 then changes the battery module 20 to be subjected to the counter-charging process and repeats the counter-charging process (step S33).

In step S30, if the second vehicle 1B is not in powered operation, i.e., is in regenerative operation (No), the second battery unit 2B is being charged with regenerative power. Normally, this power is distributed evenly to each battery module 20.

The BCU 10 determines whether counter charging can be performed appropriately by concentrating the regenerated power in a predetermined portion of the battery modules 20 and charging them (step S35).

For example, assuming that counter-charging processing is performed in the first battery module 21, the regenerative power that was previously distributed to the second battery module 22 and the third battery module 23 is concentrated in the first battery module 21. This increases the amount of power that can be charged by the first battery module 21.

As a result, if the BCU 10 determines that the counter charge process can be executed appropriately (Yes in step S35), it executes the counter charge process (step S32). This allows the counter charge process to be executed effectively. The BCU 10 then changes the battery module 20 targeted for the counter charge process and repeats the counter charge process (step S33).

However, there are cases where the amount of power obtained through regeneration is small, and even if that regenerative power is concentrated in a single battery module 20, the target charge/discharge value is not reached. In such cases, the BCU 10 determines that it is not appropriate to perform counter charging processing (No in step S35).

In this case, the BCU 10 determines whether the counter-charging process can be performed appropriately by charging a predetermined portion of the battery modules 20 with the regenerated power and the power obtained by discharging the remaining battery modules 20 (step S36).

When counter-charging processing is performed in the first battery module 21, the second battery module 22 and/or the third battery module 23 are discharged, and the resulting power is added to the regenerated power and charged to the first battery module 21. This further increases the amount of power charged to the first battery module 21.

As a result, if the BCU 10 determines that the counter charge process can be executed appropriately (Yes in step S36), it executes the counter charge process (step S32). Because the charge amount increases, the counter charge process can be executed more effectively. The BCU 10 then changes the battery module 20 targeted for the counter charge process and repeats the counter charge process (step S33).

On the other hand, if the BCU 10 determines that the counter-charging process is not appropriate using that method (No in step S36), it selects a method to complement the counter-charging process by supplying power using the generator 6 (step S37). Supplying power using the generator 6 allows charging with the required power, and appropriate counter-charging can be performed.

The BCU 10 performs counter-charging by adding the power generated by the generator 6 to the power obtained through regenerative power and additional charging from other battery modules 20 (step S32). This allows the counter-charging process to be performed more effectively. The BCU 10 then changes the battery module 20 targeted for counter-charging and repeats the counter-charging process (step S33).

In this way, with a BCU 10 incorporating the disclosed technology, high-rate degradation itself can be suppressed by executing counter charge/discharge processing, so performance degradation of the battery unit 2 can be effectively suppressed even when the BCU 10 is installed in a vehicle 1 where high-rate charge/discharge occurs frequently.

Note that the disclosed technology is not limited to the above-described embodiments, but also encompasses various other configurations.

For example, the vehicle models and configurations of the above-mentioned embodiments are not too similar. As mentioned at the beginning, any vehicle, such as a hybrid vehicle, that is equipped with a battery unit as a driving power source and runs on that power may be used. The control described in each embodiment is also an example. Various means can be selected depending on the vehicle model and configuration.

1 Vehicle 2 Battery unit 2a Battery controller 3 Drive side inverter 4 Drive motor 5 Power generation side inverter 6 Generator 7 Power generation engine 8 Auxiliary equipment 9 Electrical wiring 10 BCU (control unit)
10d High-rate charge/discharge prediction unit 10e Charge/discharge state change unit

Claims (13)

A control device for a battery unit mounted on a vehicle as a driving power source,
a high-rate charge/discharge prediction unit that predicts high-rate charging, which charges the battery unit with power equal to or greater than a predetermined reference value set in accordance with the performance of the battery unit, and high-rate discharging, which discharges the battery unit with power equal to or greater than the reference value, while the vehicle is in operation;
a charge/discharge state changing unit that changes the charge/discharge state of the battery unit based on the prediction by the high-rate charge/discharge prediction unit;
Equipped with
A control device in which the charge/discharge state change unit executes a counter charge process to increase power and temporarily charge when the high-rate discharge is predicted, and executes a counter discharge process to increase power and temporarily discharge when the high-rate charge is predicted. 2. The control device according to claim 1,
the vehicle includes a drive motor connected to the battery unit via an inverter;
When the high-rate charging is predicted during power running of the vehicle, the charge/discharge state changing unit executes the counter-discharge process by reducing efficiency of the inverter. 3. The control device according to claim 1,
the vehicle includes an auxiliary device that operates using power supplied from the battery unit;
When the high-rate charging is predicted during powering of the vehicle, the charge/discharge state changing unit executes the counter-discharge process by supplying power to the auxiliary equipment. 2. The control device according to claim 1,
the vehicle includes a generator driven by a generator engine;
When the high-rate discharge is predicted during regenerative operation of the vehicle, the charge/discharge state change unit executes the counter charge process by charging the battery unit with electric power generated by the generator. 2. The control device according to claim 1,
the battery unit includes a plurality of battery modules that can be charged and discharged individually;
When the high-rate charging is predicted during powering operation of the vehicle, the charge/discharge state changing unit executes the counter-discharge process by discharging some of the plurality of battery modules. 6. The control device according to claim 5,
The charge/discharge state changing unit executes the counter-discharge process by discharging some of the plurality of battery modules and charging the remaining battery modules. 7. The control device according to claim 6,
the vehicle includes an auxiliary device that operates using power supplied from the battery unit;
The charge/discharge state changing unit complements the counter-discharge process by supplying power to the auxiliary device. 2. The control device according to claim 1,
the battery unit includes a plurality of battery modules that can be charged and discharged individually;
When the high-rate charging is predicted during regenerative operation of the vehicle, the charge/discharge state change unit executes the counter-discharge process in a specified battery module, and charges the remaining battery modules with power obtained by discharging in the specified battery module together with power obtained by regeneration. 2. The control device according to claim 1,
the battery unit includes a plurality of battery modules that can be charged and discharged individually;
When the high-rate discharge is predicted during powered operation of the vehicle, the charge/discharge state change unit executes the counter charge process in a predetermined battery module, and causes the remaining battery modules to discharge the power consumed during powered operation and the power charged to the predetermined battery module. 10. The control device according to claim 9,
the vehicle includes a generator driven by a generator engine;
The charge/discharge state changing unit complements the counter charging process by charging the electric power generated by the generator. 2. The control device according to claim 1,
the battery unit includes a plurality of battery modules that can be charged and discharged individually;
When the high-rate discharge is predicted during regenerative operation of the vehicle, the charge/discharge state change unit executes the counter charge process by charging a predetermined portion of the battery modules with the power obtained through regeneration. The control device according to claim 11,
The charge/discharge state changing unit executes the counter charging process by charging the predetermined portion of the battery modules with power obtained by regeneration and power obtained by discharging the remaining battery modules. 13. The control device according to claim 12,
the vehicle includes a generator driven by a generator engine;
The charge/discharge state changing unit complements the counter charging process by charging the electric power generated by the generator.