JP7718191B2 - Charge and discharge control device - Google Patents

Description

The present invention relates to a charge/discharge control device.

Patent Document 1 describes a technique that, if the temperature of the power storage device is above a predetermined temperature when the vehicle's ignition switch is switched from on to off and the time that has elapsed since the ignition switch was switched off is less than a predetermined time, the interior air conditioning system and cooling system are activated to cool the power storage device, and then charging of the power storage device using an AC power source begins. This technique prevents the power storage device from becoming too hot during charging, thereby preventing deterioration of the power storage device.

JP 2015-095985 A

As stated in Patent Document 1, maintaining a battery at a high temperature and high SOC (State of Charge) accelerates battery degradation. However, Patent Document 1 does not disclose how to suppress battery degradation when the battery is at a high temperature in a high SOC state.

The present invention therefore aims to provide a charge/discharge control device that can suppress battery degradation under high temperature and high SOC conditions.

In order to solve the above problems, the present invention comprises a temperature detection unit that detects the temperature of a battery, a cooling unit that cools the battery using power from the battery, and a control unit that limits the SOC of the battery to a predetermined SOC upper limit value, wherein the control unit sets the SOC upper limit value lower the higher the temperature of the battery, and when the SOC of the battery is equal to or higher than the SOC upper limit value, activates the cooling unit, and stops the cooling unit when the SOC of the battery reaches the SOC upper limit value based on the temperature of the battery at the time the cooling unit starts operating .

In this way, the present invention can suppress battery degradation at high temperatures and high SOC conditions.

FIG. 1 is a block diagram of a vehicle equipped with a charge/discharge control device according to an embodiment of the present invention. FIG. 2 is a flowchart showing the procedure of the battery cooling control process of the charge/discharge control device according to one embodiment of the present invention.

A charge/discharge control device according to one embodiment of the present invention includes a temperature detection unit that detects the temperature of a battery, a cooling unit that cools the battery using power from the battery, and a control unit that limits the battery's SOC to a predetermined SOC upper limit value. The control unit is configured to set a lower SOC upper limit value the higher the battery temperature, and to activate the cooling unit when the battery's SOC is equal to or higher than the SOC upper limit value.

As a result, a charge/discharge control device according to one embodiment of the present invention can suppress battery degradation under high temperature and high SOC conditions.

The following describes in detail a charge/discharge control device according to an embodiment of the present invention, with reference to the drawings.

In FIG. 1, a vehicle 1 equipped with a charge/discharge control device according to one embodiment of the present invention includes a motor 2, an inverter 3, a battery 4, a cooling unit 5, and a control unit 9.

Motor 2 is, for example, a synchronous motor equipped with a rotor embedded with multiple permanent magnets and a stator wound with a stator coil. When three-phase AC power is applied to the stator coil, a rotating magnetic field is formed in the stator, which rotates the rotor and generates driving force.

Motor 2 is also driven so that the rotational resistance generated during power generation is used to brake vehicle 1. This gives motor 2 the ability to generate power through regeneration. In this way, motor 2 also functions as a generator, generating electricity to charge battery 4.

The inverter 3 supplies three-phase AC power to the motor 2. The inverter 3 also converts the three-phase AC power generated by the motor 2 into DC power to charge the battery 4.

The battery 4 is, for example, a nickel storage battery or a lithium storage battery, and is configured by connecting multiple cells in series. The battery 4 supplies power to the motor 2 via the inverter 3. The battery 4 is provided with a battery state sensor 41 that serves as a temperature detection unit. The battery state sensor 41 detects the charge/discharge current, voltage, and battery temperature of the battery 4. The battery state sensor 41 is connected to the control unit 9. The control unit 9 is able to detect the temperature and state of charge (hereinafter referred to as "SOC") of the battery 4 based on the output of the battery state sensor 41.

A charger 42 and a charging connector 43 are connected to the battery 4. The charging connector 43 connects the charger 42 to an external power source of a power supply facility 110 installed outside the vehicle 1. The charger 42 is connected to the charging connector 43 and includes a converter that converts AC power supplied from the external power source via the charging connector 43 into DC power, and a boost circuit that boosts the DC power.

Power from the battery 4 is supplied to the cooling unit 5, lead battery 7, and auxiliary devices 8 via a DC-DC converter 44. The DC-DC converter 44 converts the voltage of the power output from the battery 4 and supplies it to the cooling unit 5, lead battery 7, and auxiliary devices 8. The lead battery 7 has an output voltage of approximately 12V, and supplies power to drive various auxiliary devices 8, such as the vehicle 1's electrical system.

The cooling unit 5 uses the power of the battery 4 to cool the battery 4. The cooling unit 5 is composed of, for example, a compressor, a blower fan, etc. The cooling unit 5 is driven or stopped under the control of the control unit 9.

The communication unit 6 communicates with the smartphone 100 and the like via a communication medium such as wireless communication or short-range wireless communication to send and receive information. The control unit 9 can send and receive information with the smartphone 100 and the like via the communication unit 6.

The control unit 9 is composed of a computer unit equipped with a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), flash memory for storing backup data, input ports, and output ports.

The ROM of this computer unit stores various constants, maps, etc., as well as a program that causes the computer unit to function as the control unit 9.

In other words, the CPU uses RAM as a working area and executes programs stored in ROM, causing the computer unit to function as the control unit 9 in this embodiment.

In addition to the battery status sensor 41 mentioned above, various sensors and switches, including an outside air temperature sensor 91, are connected to the input port of the control unit 9. The outside air temperature sensor 91 detects the temperature of the outside air around the vehicle 1.

Various control targets, including the inverter 3, cooling unit 5, and charger 42, are connected to the output port of the control unit 9.

In this embodiment, the control unit 9 limits the SOC of the battery 4 to a predetermined SOC upper limit value.

The control unit 9 sets a lower SOC upper limit value the higher the temperature of the battery 4, and when the SOC of the battery 4 is equal to or higher than the SOC upper limit value, it activates the cooling unit 5 to cool the battery 4.

When the SOC of the battery 4 reaches the SOC upper limit, the control unit 9 will not operate the cooling unit 5 until a predetermined time has elapsed.

The control unit 9 stops the cooling unit 5 when the SOC of the battery 4 reaches the upper SOC limit based on the temperature of the battery 4 at the time the cooling unit 5 starts operating.

When the battery 4 is being charged by an external power source, the control unit 9 starts charging the battery 4 if the SOC of the battery 4 falls below the SOC upper limit a predetermined period of time after the cooling unit 5 is stopped.

The control unit 9 extends the specified period the higher the outside air temperature is than the temperature of the battery 4 when the cooling unit 5 is stopped.

When a user requests charging, the control unit 9 charges the battery 4 to full charge or to the SOC specified by the user, regardless of the current battery 4 temperature, and prohibits the cooling unit 5 from operating at an SOC upper limit value according to the battery 4 temperature.

The user may, for example, use an app running on the smartphone 100 to request charging from the control unit 9 or specify the SOC to be charged. The user may also be able to know the SOC and temperature of the battery 4 using an app running on the smartphone 100.

In addition, instead of an app running on the smartphone 100, a dedicated device may be used to request charging and specify the SOC to be charged to the control unit 9. Also, a switch or the like provided on the vehicle 1 may be used to request charging and specify the SOC to be charged.

In response to a user instruction, the control unit 9 cancels the prohibition on driving the cooling unit 5 based on the SOC upper limit value corresponding to the battery 4 temperature.

The battery cooling control process performed by the charge/discharge control device of this embodiment configured as described above will be described with reference to Figure 2. The battery cooling control process described below begins when the control unit 9 starts operating, and is executed at preset time intervals.

In step S1, the control unit 9 acquires the temperature of the battery 4. After performing the processing of step S1, the control unit 9 performs the processing of step S2.

In step S2, the control unit 9 sets the SOC upper limit value based on the temperature of the battery 4. After performing the process of step S2, the control unit 9 performs the process of step S3.

In step S3, the control unit 9 acquires the SOC of the battery 4. After performing the process of step S3, the control unit 9 performs the process of step S4.

In step S4, the control unit 9 determines whether the SOC of the battery 4 is equal to or greater than the SOC upper limit.

If it is determined that the SOC of battery 4 is equal to or greater than the SOC upper limit, the control unit 9 executes the process of step S5. If it is determined that the SOC of battery 4 is not equal to or greater than the SOC upper limit, the control unit 9 terminates the battery cooling control process.

In step S5, the control unit 9 drives the cooling unit 5. After executing the processing of step S5, the control unit 9 ends the battery cooling control processing.

In this way, in this embodiment, the control unit 9 sets a lower SOC upper limit value as the temperature of the battery 4 increases, and when the SOC of the battery 4 is equal to or higher than the SOC upper limit value, it activates the cooling unit 5 to cool the battery 4.

As a result, by setting the SOC upper limit lower the higher the temperature of battery 4, it is possible to prevent high SOC at high temperatures and accelerated deterioration of battery 4.

Furthermore, if the temperature of battery 4 rises due to an increase in ambient temperature or other factors after charging to the SOC upper limit, the actual SOC may exceed the SOC upper limit. This could accelerate deterioration of battery 4. Therefore, by cooling battery 4, it is possible to adjust the temperature of battery 4 to a temperature at which the actual SOC becomes appropriate, thereby preventing accelerated deterioration of battery 4.

Furthermore, when the SOC of the battery 4 reaches the SOC upper limit, the control unit 9 will not operate the cooling unit 5 until a predetermined time has elapsed.

This prevents the cooling unit 5 from being driven until a predetermined time has passed during which it is assumed that there will be little impact on the battery 4, thereby reducing consumption of the battery 4's SOC.

In addition, the control unit 9 stops the cooling unit 5 when the SOC of the battery 4 reaches the upper SOC limit based on the temperature of the battery 4 at the time the cooling unit 5 starts operating.

As a result, if the cooling unit 5 is controlled so that the actual SOC is equal to the SOC upper limit based on the temperature of the battery 4 during cooling, the SOC upper limit will rise as the battery 4 is cooled, and the cooling unit 5 will immediately be stopped. At this time, the temperature of the battery 4 rises again as the cooling unit 5 is stopped, causing the SOC upper limit to fall, and the cooling unit 5 will be started again. In this way, if the SOC upper limit is set based on the temperature of the battery 4 during cooling, the cooling unit 5 will frequently be turned on and off. At this time, the cooling unit 5 performs cooling using a compressor, a blower fan, etc., and these devices are driven by the motor 2. Furthermore, since the motor 2 generally consumes the most power during startup, frequent on-off switching of the motor 2 may result in excessive power consumption without sufficient cooling effect, which could result in a drop in the actual SOC.

Therefore, in this embodiment, the cooling unit 5 is continuously operated up to the upper SOC limit based on the temperature of the battery 4 at the time the cooling unit 5 starts operating, allowing the battery 4 to be cooled efficiently.

Furthermore, when the battery 4 is being charged by an external power source, the control unit 9 starts charging the battery 4 if the SOC of the battery 4 falls below the SOC upper limit after a predetermined period of time has elapsed since the cooling unit 5 was stopped.

When the cooling unit 5 is stopped, the SOC of the battery 4 is the upper SOC limit based on the temperature of the battery 4 before cooling. Therefore, if a specified period is not set, charging may begin immediately after the cooling unit 5 is stopped. In this case, if the temperature of the battery 4 rises again due to charging, etc., the actual SOC will exceed the upper SOC limit, charging will be stopped, and the cooling unit 5 will be activated again. In other words, charging and discharging may be repeated frequently.

Therefore, by keeping charging stopped for a predetermined period after the cooling unit 5 stops, deterioration of the battery 4 due to frequent repeated charging and discharging can be suppressed.

In addition, the control unit 9 extends the specified period the higher the outside air temperature is than the temperature of the battery 4 when the cooling unit 5 is stopped.

The higher the outside air temperature is, the greater the probability that the temperature of the battery 4 will rise significantly after the cooling unit 5 is stopped. Therefore, if charging is resumed immediately, the SOC upper limit may drop due to the rise in battery 4 temperature, and the cooling unit 5 may be immediately activated, requiring cooling and discharging. In this case, charging and discharging may be repeated frequently.

In this case, the higher the outside air temperature is than the temperature of the battery 4, the longer the time until charging resumes, thereby preventing the battery 4 from deteriorating due to frequent charging and discharging.

In addition, when a charging request is received from the user, the control unit 9 charges the battery 4 to full charge or to the SOC specified by the user, regardless of the current battery 4 temperature, and prohibits the cooling unit 5 from operating at an SOC upper limit value according to the battery 4 temperature.

This allows the vehicle to be charged to a specified SOC upon user request, ensuring the vehicle reaches the specified SOC state without inconvenience to the user or the need to wait before boarding.

In addition, the control unit 9, upon instruction from the user, cancels the prohibition on driving the cooling unit 5 based on the SOC upper limit value corresponding to the temperature of the battery 4.

This allows the user to cancel the prohibition on operating the cooling unit 5 based on the SOC upper limit value corresponding to the current battery 4 temperature, improving usability for the user.

In this embodiment, an example has been described in which the control unit 9 performs various determinations and calculations based on information from various sensors. However, this is not limiting. The vehicle 1 may also be equipped with a communication unit capable of communicating with an external device such as an external server, and the external device may perform various determinations and calculations based on the detection information from the various sensors transmitted from the communication unit. The communication unit may then receive the determination and calculation results, and the received determination and calculation results may be used to perform various controls.

While embodiments of the present invention have been disclosed, it will be apparent to those skilled in the art that modifications may be made without departing from the scope of the present invention. All such modifications and equivalents are intended to be encompassed by the following claims.

REFERENCE SIGNS LIST 1 vehicle 4 battery 5 cooling unit 6 communication unit 9 control unit 41 battery state sensor (temperature detection unit)
91 Outside air temperature sensor

Claims (6)

a temperature detection unit that detects the temperature of the battery;
a cooling unit that cools the battery using power from the battery;
a control unit that limits the SOC of the battery to a predetermined SOC upper limit value,
The control unit sets the SOC upper limit value lower as the temperature of the battery increases, and when the SOC of the battery is equal to or higher than the SOC upper limit value, activates the cooling unit , and when the SOC of the battery reaches the SOC upper limit value based on the temperature of the battery at the time when the cooling unit starts to operate, stops the cooling unit . The charge/discharge control device according to claim 1, wherein the control unit does not activate the cooling unit until a predetermined time has elapsed after the battery's SOC reaches the SOC upper limit. The battery is configured to be chargeable from an external power source outside the vehicle,
3. The charge/discharge control device according to claim 1, wherein the control unit starts charging the battery when the SOC of the battery is below the SOC upper limit value after a predetermined period of time has elapsed since the cooling unit was stopped while the battery is being charged by the external power source. An outside air temperature sensor is provided to detect the outside air temperature of the vehicle.
The charge/discharge control device according to claim 3 , wherein the control unit extends the predetermined period as the outside air temperature increases to a temperature higher than the temperature of the battery when the cooling unit is stopped. 5. The charge/discharge control device according to claim 3, wherein the control unit, when receiving a charging request from a user, charges the battery to full charge or to an SOC specified by the user regardless of the current temperature of the battery, and prohibits operation of the cooling unit at the SOC upper limit value corresponding to the temperature of the battery . The charge/discharge control device according to claim 5 , wherein the control unit cancels the prohibition of driving the cooling unit based on the SOC upper limit value according to the temperature of the battery, in response to an instruction from a user.