WO2013098904A1

WO2013098904A1 - Power storage system

Info

Publication number: WO2013098904A1
Application number: PCT/JP2011/007367
Authority: WO
Inventors: 沖　良二
Original assignee: トヨタ自動車株式会社
Priority date: 2011-12-28
Filing date: 2011-12-28
Publication date: 2013-07-04

Abstract

[Problem] To suppress the occurrence of memory effect in a power storage device that outputs drive power for auxiliary machinery. [Solution] A power storage system has a first power storage device and a second power storage device. The first power storage device outputs travel energy for a vehicle, and the second power storage device outputs drive power for auxiliary machinery mounted in the vehicle. A DC/DC converter converts voltage output from the second power storage device to the first power storage device, and also converts voltage output from the first power storage device to the second power storage device. A controller, by way of the DC/DC converter, performs charging and discharging processing in which the second power storage device is charged by discharging the first power storage device, after the first power storage device has been charged by discharging the second power storage device.

Description

Power storage system

The present invention relates to a power storage system including a power storage device that outputs driving power of an auxiliary machine and a power storage device that outputs energy used for traveling of a vehicle.

The system described in Patent Document 1 includes a battery that drives a 14V load and a battery that drives a 42V load, in addition to the high voltage battery (200V system) that outputs the running energy of the vehicle. Here, a nickel metal hydride battery or a lithium ion battery is used as the high-voltage battery or the 42V battery, and a lead storage battery is used as the 14V battery.

JP 2008-110700 A JP 2003-348774 A Japanese Patent Laid-Open No. 10-290532 JP 2000-035467 A

It is known that a memory effect occurs in a secondary battery. A low-voltage battery such as a 14V battery described in Patent Document 1 is difficult to discharge in order to ensure system operation. This may cause a memory effect in the low voltage battery. Even if the memory effect occurs, it is difficult to eliminate the memory effect.

The power storage system according to the first invention of the present application includes a first power storage device and a second power storage device. The first power storage device outputs the traveling energy of the vehicle, and the second power storage device outputs the driving power of the auxiliary equipment mounted on the vehicle. The DC / DC converter converts an output voltage from the second power storage device to the first power storage device, and converts an output voltage from the first power storage device to the second power storage device. The controller performs a charging / discharging process of charging the second power storage device by discharging the first power storage device after charging the first power storage device by discharging the second power storage device via the DC / DC converter.

According to the first invention of the present application, the memory effect can be suppressed from occurring in the second power storage device by positively discharging the second power storage device. In addition, power loss can be prevented by temporarily storing the output power of the second power storage device in the first power storage device and returning the power stored in the first power storage device to the second power storage device. . Although only the second power storage device is discharged, the occurrence of the memory effect can be suppressed, but the discharge power may be wasted only by discharging the second power storage device. According to the first invention of the present application, it is possible to prevent waste of power by returning the power when the second power storage device is discharged to the second power storage device.

When it is determined that the memory effect is occurring in the second power storage device, the charge / discharge process can be performed. Thereby, the memory effect can be eliminated. On the other hand, it is also possible to perform the charge / discharge process without determining that the memory effect has occurred.

When the amount of power that can charge the first power storage device is higher than the threshold value, the charge / discharge process can be performed. The amount of power that can charge the first power storage device is the amount of power when charging the first power storage device from the current charging state to the fully charged state. If the amount of charge power of the first power storage device is higher than the threshold, the amount of power when discharging the second power storage device can be secured, and the memory effect can be easily eliminated by discharging the second power storage device. it can.

When charging the first power storage device using power from an external power supply, a charge / discharge process can be performed. When charging the first power storage device using power from the external power source, the second power storage device may not output drive power to the auxiliary machine. In this state, the second power storage device can be positively discharged, and the above-described charge / discharge treatment can be performed.

Here, after the charge / discharge treatment is performed, the power from the external power source can be supplied to the first power storage device. When the charge / discharge process is performed, a slight power loss may occur depending on the conversion efficiency of the DC / DC converter. When a power loss occurs, the power from the external power supply can be used to compensate for the loss power. When charging the first power storage device using electric power from an external power source, a charger can be used. The charger can incorporate the above-described DC / DC converter.

In the charging / discharging process, the second power storage device can be charged until the amount of power when charging the second power storage device reaches the amount of power when discharging the second power storage device. Thereby, the SOC (State （of Charge) of the second power storage device can be returned to the state before the second power storage device is discharged.

When performing the charge / discharge process, the charge / discharge characteristics of the second power storage device can be acquired. If the charge / discharge process is performed a plurality of times, a plurality of charge / discharge characteristics can be acquired. By comparing these charge / discharge characteristics, it is possible to confirm whether or not the memory effect is eliminated in the second power storage device.

The nominal voltage of the second power storage device is lower than the nominal voltage of the first power storage device. Here, the DC / DC converter can perform a boosting process when supplying power from the second power storage device to the first power storage device. Further, the DC / DC converter can perform a step-down process when supplying power from the first power storage device to the second power storage device. As the second power storage device, a nickel metal hydride battery or a lithium ion battery can be used.

The second invention of the present application is a control method for controlling charging / discharging between the first power storage device that outputs the running energy of the vehicle and the second power storage device that outputs the driving power of the auxiliary device mounted on the vehicle. First, the output voltage from the second power storage device to the first power storage device is converted, and the first power storage device is charged by discharging the second power storage device. Next, after charging the first power storage device, the output voltage from the first power storage device to the second power storage device is converted, and the second power storage device is charged by discharging the first power storage device. Also in the second invention of the present application, the same effect as that of the first invention of the present application can be obtained.

It is a figure which shows the one part system of a vehicle. It is a flowchart which shows the process which suppresses a memory effect.

Hereinafter, examples of the present invention will be described.

A vehicle that is Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a part of a system mounted on a vehicle. Vehicles include hybrid cars and electric cars. The hybrid vehicle includes an engine or a fuel cell as a power source for running the vehicle in addition to the assembled battery described later. The electric vehicle includes only an assembled battery described later as a power source for running the vehicle.

The assembled battery (corresponding to the first power storage device) 10 has a plurality of unit cells 11 connected in series. As the cell 11, a secondary battery such as a nickel metal hydride battery or a lithium ion battery can be used. An electric double layer capacitor (capacitor) can be used instead of the secondary battery. In the present embodiment, the plurality of single cells 11 are connected in series, but the plurality of single cells 11 connected in parallel may be included in the assembled battery 10.

The monitoring unit 12 detects the voltage of the assembled battery 10 or the voltage of the unit cell 11. When the plurality of single cells 11 constituting the assembled battery 10 are divided into a plurality of blocks, the monitoring unit 12 can detect the voltage of each block. The plurality of blocks are connected in series, and each block includes a plurality of single cells 11 connected in series.

The monitoring unit 12 outputs detection information (voltage) to a PM-ECU (Power Management Electronic Control Unit) 31. A relay IG <b> 1 is connected to the monitoring unit 12. When relay IG1 is on, monitoring unit 12 operates by receiving power from auxiliary battery 51 (corresponding to the second power storage device). Relay IG1 is switched between ON and OFF in response to a control signal from power supply ECU (Electronic Control Unit) 32. The power supply ECU 32 switches the relay IG1 between on and off by flowing a current through the coil of the relay IG1 or not flowing a current.

The system main relay SMR-B is provided on the positive line PL connected to the positive terminal of the assembled battery 10. A positive terminal of the assembled battery 10 is connected to a PCU (Power Control Unit) 22 through a positive line PL. A system main relay SMR-G is provided on the negative electrode line NL connected to the negative electrode terminal of the assembled battery 10. The negative electrode terminal of the battery pack 10 is connected to the PCU 22 via the negative electrode line NL.

System main relay SMR-P and current limiting resistor R are connected in parallel to system main relay SMR-G. System main relay SMR-P and current limiting resistor R are connected in series. The current limiting resistor R is used for suppressing the inrush current from flowing when the assembled battery 10 and the PCU 22 are connected.

System main relays SMR-B, SMR-G, and SMR-P are used when connecting the assembled battery 10 and the PCU 22. System main relays SMR-B, SMR-G, and SMR-P are switched between ON and OFF in response to a control signal from PM-ECU 31. When connecting the assembled battery 10 and the PCU 22, the PM-ECU 31 first switches the system main relays SMR-B and SMR-G from off to on. Thereby, a current can be passed through the current limiting resistor R.

When the precharge of the capacitor (not shown) is completed by the output power of the assembled battery 10, the PM-ECU 31 switches the system main relay SMR-G from OFF to ON, and then turns the system main relay SMR-P from ON to OFF. Switch to. Thereby, the connection between the assembled battery 10 and the PCU 22 is completed, and the system shown in FIG. 1 is in a start-up state (Ready-On). When the PM-ECU 31 confirms that the ignition switch of the vehicle has been switched from OFF to ON, the PM-ECU 31 connects the assembled battery 10 and the PCU 22. Information regarding the on / off of the ignition switch is input to the PM-ECU 31.

The PM-ECU 31 disconnects the connection between the assembled battery 10 and the PCU 22 when it is confirmed that the ignition switch has been switched from on to off. When the connection between the assembled battery 10 and the PCU 22 is disconnected, the PM-ECU 31 switches the system main relays SMR-B and SMR-G from on to off. As a result, the system shown in FIG. 1 enters a stopped state (Ready-Off).

The DC / DC converter 21 is connected to the positive electrode line PL and the negative electrode line NL. Specifically, DC / DC converter 21 is connected to positive line PL located between system main relays SMR-B and PCU 22 and negative line NL located between system main relays SMR-G and PCU 22. ing.

The DC / DC converter 21 steps down the voltage of the assembled battery 10 and supplies the power after stepping down to an auxiliary machine (not shown) or to the auxiliary battery 51. An auxiliary machine is an electronic device mounted on a vehicle, such as an air conditioner, a light, and an audio facility. The DC / DC converter 21 operates in response to a control signal from the PM-ECU 31.

The PCU 22 includes a booster circuit and an inverter. The booster circuit boosts the output voltage of the assembled battery 10 and outputs the boosted power to the inverter. The booster circuit can step down the output voltage of the inverter and output the stepped down power to the assembled battery 10. The inverter converts the DC power output from the booster circuit into AC power, and outputs the AC power to a motor generator (AC motor). The PCU 22 operates in response to a control signal from the PM-ECU 31.

The PCU 22 is connected to a motor / generator, and the motor / generator receives AC power from the PCU 22 (inverter) and generates kinetic energy for running the vehicle. The motor / generator is connected to wheels, and the kinetic energy generated by the motor / generator is transmitted to the wheels. As a result, the vehicle can be driven by rotating the wheels.

When the vehicle is stopped or decelerated, the motor / generator converts kinetic energy generated during braking of the vehicle into electric energy (AC power). The AC power generated by the motor / generator is output to the PCU 22. The inverter of the PCU 22 converts AC power from the motor / generator into DC power and outputs the DC power to the booster circuit. The output power of the motor / generator is supplied to the assembled battery 10 via the PCU 22, and the regenerative power can be stored in the assembled battery 10. In this embodiment, the booster circuit is used, but the booster circuit may be omitted.

The relay IG3 is connected to the PCU 22. When the relay IG3 is on, the PCU 22 operates by receiving power from the auxiliary battery 51. Relay IG3 switches between ON and OFF in response to a control signal from PM-ECU 31. The PM-ECU 31 switches the relay IG3 between on and off by flowing a current through the coil of the relay IG3 or not flowing a current. A relay IG1 is connected to the PM-ECU 31. When relay IG1 is on, PM-ECU 31 operates by receiving power from auxiliary battery 51.

The charge relay CHR1 is connected to the positive line PL. Specifically, one end of charging relay CHR1 is connected to positive electrode line PL located between assembled battery 10 and system main relay SMR-B. The other end of the charging relay CHR1 is connected to the charger 40. A charging relay CHR2 is connected to the negative electrode line NL. Specifically, one end of the charging relay CHR2 is connected to the negative electrode line NL located between the assembled battery 10 and the system main relay SMR-G. The other end of the charging relay CHR2 is connected to the charger 40.

The charging relay CHR3 is connected in parallel to the charging relay CHR2. The charging relay CHR3 is connected in series with the current limiting resistor R. Charging relays CHR1 to CHR3 are used when connecting assembled battery 10 and charger 40. The current limiting resistor R is used for suppressing the inrush current from flowing when the assembled battery 10 and the charger 40 are connected.

The charging relays CHR1 to CHR3 are switched between on and off in response to a control signal from the PM-ECU 31. When connecting the assembled battery 10 and the charger 40, the PM-ECU 31 first switches the charging relays CHR1 and CHR3 from off to on. Thereby, a current can be passed through the current limiting resistor R.

When the precharge of the capacitor (not shown) included in the charger 40 is completed by the output power of the assembled battery 10, the PM-ECU 31 switches the charging relay CHR3 from OFF to ON after switching the charging relay CHR2 from OFF to ON. Switch off. Thereby, the connection of the assembled battery 10 and the charger 40 is completed. Here, when the assembled battery 10 and the charger 40 are connected, the assembled battery 10 and the PCU 22 are not connected.

In this embodiment, one current limiting resistor R is used, but the present invention is not limited to this. That is, using two current limiting resistors R, the current limiting resistor R can be connected to each of the system main relay SMR-P and the charging relay CHR3. That is, the system main relay SMR-P and one current limiting resistor R can be connected in series, and the charging relay CHR3 and the other current limiting resistor R can be connected in series. In this embodiment, since one current limiting resistor R is used, the number of parts can be reduced as compared with the case where two current limiting resistors R are used.

The charger 40 is used to supply power from the external power source to the assembled battery 10. The external power source is a power source arranged outside the vehicle, and a commercial power source, for example, can be used as the external power source. As a means for supplying power from the external power source to the charger 40, wired or wireless can be used. In the means using a wire, a cable connector (so-called plug) connected to an external power source can be connected to a cable connector (so-called inlet) connected to the charger 40. In addition, wireless means can supply electric power from an external power source to the charger 40 in a non-contact manner using electromagnetic induction or a resonance phenomenon.

The charger 40 converts AC power from an external power source into DC power, and supplies the DC power to the assembled battery 10. Thereby, the assembled battery 10 can be charged. This charging is called external charging. The charger 40 has a bidirectional DC / DC converter 41. The DC / DC converter 41 steps down the output voltage of the assembled battery 10, supplies the reduced power to the auxiliary battery 51, boosts the output voltage of the auxiliary battery 51, and supplies the boosted power to the assembled battery 10. Or to supply. In this embodiment, the DC / DC converter 41 is built in the charger 40, but the DC / DC converter 41 may be provided outside the charger 40.

The relay IG2 is connected to the charger 40. When relay IG2 is on, the power of auxiliary battery 51 is supplied to charger 40. Relay IG2 switches between ON and OFF in response to a control signal from PM-ECU 31. The PM-ECU 31 switches the relay IG2 between ON and OFF by passing a current through the coil of the relay IG2 or not flowing a current.

The auxiliary battery (corresponding to the second power storage device) 51 serves as a power source for operating the system shown in FIG. As the auxiliary battery 51, a secondary battery such as a nickel metal hydride battery or a lithium ion battery can be used. The auxiliary battery 51 can be configured by connecting a plurality of single cells in series. The auxiliary battery 51 may include a plurality of single cells connected in parallel. The nominal voltage of the auxiliary battery 51 is lower than the nominal voltage of the assembled battery 10.

The auxiliary battery 51 also supplies power to the power supply ECU 32. The power supply ECU 32 operates by receiving power from the auxiliary battery 51. Here, a diode 54 is provided in a line connecting the auxiliary battery 51 and the power supply ECU 32. Specifically, the anode of the diode 54 is connected to the auxiliary battery 51, and the cathode of the diode 54 is connected to the power supply ECU 32.

The voltage sensor 52 detects the voltage of the auxiliary battery 51 and outputs the detection result to the PM-ECU 31. A fuse 53 is connected to the auxiliary battery 51. The fuse 53 is used to prevent an excessive current from flowing through the auxiliary battery 51. If an excessive current flows through the auxiliary battery 51 via the fuse 53, the fuse 53 is cut off to cut off the current path.

In a system that operates by receiving power supply from the auxiliary battery 51, in order to ensure the operation of the system, the discharge amount and the charge amount of the auxiliary battery 51 are generally set so as to maintain a balance, The SOC (State of Charge) of the auxiliary battery 51 does not change significantly. When the auxiliary battery 51 is used in this way, the auxiliary battery 51 may have a memory effect. Note that the SOC is the ratio of the current charge capacity to the full charge capacity.

The memory effect is a deterioration phenomenon in which the battery discharge voltage is remarkably lowered when the battery is repeatedly charged before the battery is sufficiently discharged, and as a result, the battery capacity appears to be reduced. Here, it is known that the memory effect can be suppressed by continuing to discharge the battery. In the auxiliary battery 51 mounted on the vehicle, it is difficult to perform a continuous discharge for the reasons described above, and a memory effect may occur.

In the present embodiment, when external charging of the assembled battery 10 is performed using the charger 40, the auxiliary battery 51 is continuously discharged, so that the memory effect is prevented from occurring in the auxiliary battery 51. Yes. Specifically, the auxiliary battery 51 is discharged, and electric power at the time of discharging is supplied to the assembled battery 10.

If the auxiliary battery 51 is discharged, it becomes difficult to supply the power of the auxiliary battery 51 to the auxiliary machine. For this reason, in this embodiment, the power stored in the assembled battery 10 is returned to the auxiliary battery 51. Thereby, it can suppress that SOC of the auxiliary battery 51 falls too much, suppressing a memory effect. A DC / DC converter 41 is used to supply the power of the auxiliary battery 51 to the assembled battery 10 or supply the power of the assembled battery 10 to the auxiliary battery 51.

FIG. 2 is a flowchart for explaining the memory effect suppression processing in this embodiment. The process shown in FIG. 2 is executed by the PM-ECU 31.

In step S101, the PM-ECU 31 determines whether or not the assembled battery 10 is being externally charged. The PM-ECU 31 can determine whether or not the assembled battery 10 is being externally charged by receiving a signal for starting external charging. For example, a signal for starting external charging is input to the PM-ECU 31 by connecting a connector of a cable connected to an external power supply to a connector of a cable connected to the charger 40.

When the PM-ECU 31 determines that the assembled battery 10 is being externally charged, the PM-ECU 31 performs the process of step S102. On the other hand, when the PM-ECU 31 determines that the assembled battery 10 is not being externally charged, the process shown in FIG. As a case where the assembled battery 10 is not being externally charged, for example, the vehicle may be driven using the output of the assembled battery 10. Here, when external charging of the assembled battery 10 is performed, the PM-ECU 31 connects the charger 40 and the assembled battery 10 by controlling on and off of the charging relays CHR1 to CHR3.

In step S102, the PM-ECU 31 determines whether the travel distance of the vehicle is longer than a threshold value (distance). The PM-ECU 31 can acquire the travel distance of the vehicle using the output of the travel meter. The travel distance of the vehicle can be, for example, a travel distance from 0 km to the present. Further, when the memory effect suppression process shown in FIG. 2 is performed, the travel distance from the time when the memory effect suppression process was performed last time to the present time can be set as the travel distance of the vehicle.

Threshold value (distance) is a threshold value related to travel distance. The threshold value (distance) is a travel distance of the vehicle when the memory effect is assumed to occur in the auxiliary battery 51, and can be specified in advance by an experiment. Information about the threshold (distance) can be stored in a memory. The PM-ECU 31 can read information on the threshold value (distance) from the memory and perform the process of step S102.

When the travel distance is longer than the threshold value (distance), the PM-ECU 31 determines that the memory effect is occurring in the auxiliary battery 51 and performs the process of step S103. When the travel distance is shorter than the threshold (distance), the PM-ECU 31 determines that the memory effect has not occurred in the auxiliary battery 51 and ends the process shown in FIG.

In this embodiment, whether or not the memory effect is generated in the auxiliary battery 51 is determined by comparing the travel distance of the vehicle and the threshold value (distance), but the present invention is not limited to this. That is, it is only necessary to determine whether or not the memory effect is generated in the auxiliary battery 51.

For example, by comparing the accumulated time with a threshold value (time), it is possible to determine whether or not a memory effect has occurred. The accumulated time can be acquired using a timer. The accumulated time can be, for example, an elapsed time from when the vehicle is used for the first time until the present time. When the memory effect suppression process shown in FIG. 2 is performed, the accumulated time can be the elapsed time from when the memory effect suppression process was last performed to the present time.

Threshold value (time) compared with the accumulated time is a threshold value related to time, and is an elapsed time assumed to cause a memory effect. The threshold value (time) can be specified in advance by an experiment, and information on the threshold value (time) can be stored in a memory. The PM-ECU 31 can read information on the threshold value (time) from the memory and determine whether or not the memory effect is occurring.

In step S103, the PM-ECU 31 calculates the amount of charge power of the assembled battery 10. The amount of charge power is the amount of power until the assembled battery 10 is fully charged from the current charged state by charging the assembled battery 10. The charge power amount of the assembled battery 10 can be calculated based on, for example, the current SOC of the assembled battery 10 and the full charge capacity [Ah] of the assembled battery 10. Since the full charge capacity of the assembled battery 10 is known in advance, if the SOC of the assembled battery 10 is specified, the charge power amount of the assembled battery 10 can be calculated.

Since SOC and OCV (Open Circuit Voltage) are in a correspondence relationship, if the OCV of the assembled battery 10 is specified, the SOC corresponding to the OCV can be specified. The correspondence relationship between the SOC and the OCV can be obtained in advance by experiments. On the other hand, it is also possible to calculate the SOC of the assembled battery 10 by detecting the current value when the assembled battery 10 is charged / discharged and integrating the current value.

Further, in step S103, the PM-ECU 31 determines whether or not the charge power amount is smaller than a threshold value (power amount). The threshold value (power amount) is a threshold value related to the charging power amount. When the charge power amount is smaller than the threshold value (power amount), it becomes difficult to store the electric energy in the assembled battery 10 when the auxiliary battery 51 is discharged.

Therefore, in the process of step S103, it is determined whether or not the electric energy when the auxiliary battery 51 is discharged can be stored in the assembled battery 10 by comparing the charging power amount and the threshold value (power amount). Yes. The threshold value (power amount) can be set as appropriate based on the viewpoint that can ensure the discharge of the auxiliary battery 51. Here, when external charging is performed, the SOC of the battery pack 10 is likely to be in a reduced state, and the amount of charging power tends to be larger than the threshold value (power amount).

For example, the threshold value (power amount) can be set to zero. When the SOC of the assembled battery 10 is 100%, the assembled battery 10 cannot be charged and the amount of charge power is zero. Therefore, the threshold value (power amount) can be set to 0. Information about the threshold (power amount) can be stored in a memory. The PM-ECU 31 can read information on the threshold value (electric energy) from the memory and perform the process of step S103.

When the charged electric energy is smaller than the threshold value (electric energy), the PM-ECU 31 determines that the auxiliary battery 51 cannot be discharged, and ends the process shown in FIG. On the other hand, when the charging power amount is larger than the threshold value (power amount), PM-ECU 31 determines that auxiliary battery 51 can be discharged, and performs the process of step S104.

In step S104, the PM-ECU 31 discharges the auxiliary battery 51. The discharge current of the auxiliary battery 51 flows to the assembled battery 10 via the DC / DC converter 41. Thereby, the assembled battery 10 can be charged. Here, when the power of the auxiliary battery 51 is supplied to the assembled battery 10, the power supply from the external power source to the assembled battery 10 can be stopped. Specifically, the PM-ECU 31 can prevent the charging current from the external power source from flowing into the assembled battery 10 by controlling the operation of the charger 40.

In step S105, the PM-ECU 31 determines whether or not the discharge power amount of the auxiliary battery 51 is greater than the threshold value (power amount) used in step S103. PM-ECU 31 can calculate the amount of electric power discharged from auxiliary battery 51 based on the discharge current value of auxiliary battery 51 and the voltage detected by voltage sensor 52.

When the discharge power amount of the auxiliary battery 51 is smaller than the threshold value (power amount), the PM-ECU 31 determines that the discharge power of the auxiliary battery 51 can continue to be supplied to the assembled battery 10, and the process of step S104 I do. When the discharge power amount of the auxiliary battery 51 is greater than the threshold value (power amount), the PM-ECU 31 determines that the discharge power of the auxiliary battery 51 cannot be supplied to the assembled battery 10, and the process of step S106 I do.

In step S106, the PM-ECU 31 stops the discharge of the auxiliary battery 51. By stopping the discharge of the auxiliary battery 51, the charging of the assembled battery 10 is also stopped. In the present embodiment, the auxiliary battery 51 is discharged until the amount of power when the auxiliary battery 51 is discharged reaches a threshold value (power amount), but is not limited thereto. For example, the discharge of the auxiliary battery 51 can be stopped before the electric energy when the auxiliary battery 51 is discharged reaches a threshold value (electric energy).

In step S107, the PM-ECU 31 discharges the assembled battery 10. The discharge current of the assembled battery 10 flows to the auxiliary battery 51 via the DC / DC converter 41. Thereby, the auxiliary battery 51 can be charged. Here, when the power of the assembled battery 10 is supplied to the auxiliary battery 51, the power supply from the external power source to the assembled battery 10 can be stopped.

In step S108, the PM-ECU 31 determines whether or not the amount of electric power when charging the auxiliary battery 51 (charged electric energy) has reached the amount of electric power when discharging the auxiliary battery 51 (discharged electric energy). Is determined. Here, the electric energy when the auxiliary battery 51 is discharged is the electric energy from the discharge of the auxiliary battery 51 in the process of step S104 to the completion of the discharge of the auxiliary battery 51 in the process of step S106. It is. The charge power amount of the auxiliary battery 51 can be calculated from the current value of the auxiliary battery 51 and the voltage detected by the voltage sensor 53.

When the charge power amount of the auxiliary battery 51 has not reached the discharge power amount of the auxiliary battery 51, the PM-ECU 31 continues the process of step S107. On the other hand, when the charge power amount of the auxiliary battery 51 reaches the discharge power amount of the auxiliary battery 51, the PM-ECU 31 performs the process of step S109. In step S109, the PM-ECU 31 stops discharging the assembled battery 10, in other words, charging the auxiliary battery 51. After the auxiliary battery 51 is discharged and charged, power from an external power source can be supplied to the assembled battery 10.

In this embodiment, the amount of electric power when discharging the auxiliary battery 51 and the amount of electric power when charging the auxiliary battery 51 are equal, but this is not restrictive. In other words, the amount of power when discharging the auxiliary battery 51 may be different from the amount of power when charging the auxiliary battery 51. Here, when the electric energy for charging the auxiliary battery 51 is larger than the electric energy for discharging the auxiliary battery 51, the SOC of the assembled battery 10 is the same as when the auxiliary battery 51 starts discharging. It may be lower than the SOC. In this case, by charging the assembled battery 10 using electric power from the external power source, it is possible to compensate for the decrease in the SOC of the assembled battery 10.

On the other hand, when the power of the auxiliary battery 51 is supplied to the assembled battery 10 or the power of the assembled battery 10 is supplied to the auxiliary battery 51, power loss occurs due to the conversion efficiency of the DC / DC converter 41. Resulting in. For this reason, when the auxiliary battery 51 is charged, when the SOC of the auxiliary battery 51 is returned to the SOC before the discharge of the auxiliary battery 51, the SOC of the assembled battery 10 is reduced by the amount of power loss. Sometimes. In this case, by supplying power from the external power source to the assembled battery 10, it is possible to compensate for the decrease in the SOC of the assembled battery 10.

When the auxiliary battery 51 is discharged and charged, the charge / discharge characteristics of the auxiliary battery 51 can be acquired. The charge / discharge characteristics of the auxiliary battery 51 include the relationship between the current and voltage of the auxiliary battery 51 and the OCV of the auxiliary battery 51. Here, after the process of step S109 is completed, the auxiliary battery 51 can be further discharged and charged. The process of discharging and charging auxiliary battery 51 is the same as the process of steps S104 to S109.

When the auxiliary battery 51 is further discharged and charged, the charge / discharge characteristics of the auxiliary battery 51 can be acquired again. Then, by comparing the charge / discharge characteristics acquired at the first time with the charge / discharge characteristics acquired at the second time, it is possible to confirm whether or not the memory effect is suppressed. If the voltage drop is eliminated by comparing the charge / discharge characteristics, it can be confirmed that the memory effect is suppressed. When it is determined that the memory effect is not suppressed, the auxiliary battery 51 can be discharged and charged (steps S104 to S109) again.

In the present embodiment, the range in which the SOC of the auxiliary battery 51 is changed by the discharge of the auxiliary battery 51 can be set as appropriate. Specifically, the number of times the auxiliary battery 51 is discharged and charged can be reduced as the amount of change in the SOC of the auxiliary battery 51 increases. For example, if the change amount of the SOC of the auxiliary battery 51 is set to about 90%, the memory effect may be suppressed by performing the discharge and charge processing of the auxiliary battery 51 only once.

On the other hand, the smaller the amount of change in the SOC of the auxiliary battery 51, the more discharge and charging processes of the auxiliary battery 51 can be performed. By repeatedly performing discharge and charge processing of the auxiliary battery 51, the memory effect can be easily suppressed.

In this embodiment, it is determined (predicted) whether or not the memory effect is generated in the auxiliary battery 51 in the process of step S102, but the present invention is not limited to this. Specifically, the auxiliary battery 51 is periodically discharged and charged (steps S103 to S109) without determining whether or not the memory effect is generated in the auxiliary battery 51. Can do. Even in this case, the memory effect can be suppressed.

According to the present embodiment, the memory effect generated in the auxiliary battery 51 can be suppressed by charging the auxiliary battery 51 after discharging it. In addition, by storing the electric energy when the auxiliary battery 51 is discharged in the assembled battery 10 and returning the electric energy stored in the assembled battery 10 to the auxiliary battery 51, the electric energy can be used without waste. it can.

The charger 40 is generally provided with a DC / DC converter for converting the voltage of the external power source into a voltage corresponding to the assembled battery 10. By simply changing the DC / DC converter to a bidirectional DC / DC converter, the memory effect suppression process can be performed. Thereby, it is not necessary to change the system shown in FIG. 1 significantly, and an increase in cost can be suppressed.

In this embodiment, the auxiliary battery 51 is discharged and charged using the DC / DC converter 41 built in the charger 40, but the present invention is not limited to this. Specifically, the auxiliary battery 51 can be discharged and charged using the DC / DC converter 21. In this case, the DC / DC converter 21 and the auxiliary battery 51 may be connected, and even in a system that does not include the charger 40, the memory effect suppression process can be performed. Here, when the auxiliary battery 51 is discharged and charged, it is necessary to connect the assembled battery 10 and the DC / DC converter 21 by driving the system main relays SMR-B, SMR-G, and SMR-P.

The power controlled by the DC / DC converter 41 tends to be lower than the power controlled by the DC / DC converter 21. For this reason, when the memory effect suppression process is performed, the power loss in the DC / DC converter 41 tends to be smaller than the power loss in the DC / DC converter 21. Therefore, in order to suppress power loss, it is preferable to use the DC / DC converter 41 rather than the DC / DC converter 21. On the other hand, if the memory effect suppression process is performed using the DC / DC converter 21, the processing time can be shortened as compared to the case where the memory effect suppression process is performed using the DC / DC converter 41.

In the present embodiment, when the battery pack 10 is externally charged, the memory effect suppression process is performed, but the present invention is not limited to this. That is, the timing for performing the memory effect suppression process does not have to be when the battery pack 10 is being externally charged. For example, even when the vehicle is left unattended and the connection between the assembled battery 10 and the PCU 22 is cut off, the memory effect suppressing process can be performed. Specifically, when a predetermined time elapses with the vehicle left unattended, the PM-ECU 31 can be activated to perform the processing described in this embodiment (the processing shown in FIG. 2).

Claims

A first power storage device that outputs the running energy of the vehicle;
A second power storage device that outputs driving power of an auxiliary device mounted on the vehicle;
A DC / DC converter that converts an output voltage from the second power storage device to the first power storage device and converts an output voltage from the first power storage device to the second power storage device;
A controller that performs charge / discharge processing for charging the second power storage device by discharging the first power storage device after charging the first power storage device by discharging the second power storage device via the DC / DC converter; ,
A power storage system comprising:
2. The power storage system according to claim 1, wherein the controller performs the charging / discharging process when it is determined that a memory effect is generated in the second power storage device.
3. The power storage system according to claim 1, wherein the controller performs the charging / discharging process when an amount of electric power that can charge the first power storage device is higher than a threshold value.
The power storage system according to any one of claims 1 to 3, wherein the controller performs the charging / discharging process when the first power storage device is charged using power from an external power source.
5. The power storage system according to claim 4, wherein the controller supplies power from the external power source to the first power storage device after performing the charge / discharge process.
The power storage system according to claim 4 or 5, further comprising a charger that includes the DC / DC converter and supplies power from the external power source to the first power storage device.
The controller charges the second power storage device until the amount of power when charging the second power storage device reaches the power amount when discharging the second power storage device in the charge / discharge process. The power storage system according to any one of claims 1 to 6, wherein the power storage system is characterized in that:
The controller is
When performing the charge / discharge process, the charge / discharge characteristics of the second power storage device are acquired,
The power storage system according to any one of claims 1 to 7, wherein a plurality of the charge / discharge characteristics acquired when the charge / discharge processing is performed a plurality of times are compared.
The electrical storage system according to any one of claims 1 to 8, wherein a nominal voltage of the second electrical storage device is lower than a nominal voltage of the first electrical storage device.
The power storage system according to any one of claims 1 to 9, wherein the second power storage device is a nickel metal hydride battery or a lithium ion battery.
A control method for controlling charging / discharging between a first power storage device that outputs travel energy of a vehicle and a second power storage device that outputs drive power of an auxiliary device mounted on the vehicle,
Converting an output voltage from the second power storage device to the first power storage device, and charging the first power storage device by discharging the second power storage device;
Converting the output voltage from the first power storage device to the second power storage device after charging the first power storage device, and charging the second power storage device by discharging the first power storage device;
A control method characterized by that.
The control method according to claim 11, wherein the charge / discharge process is performed when the first power storage device can store the output power of the second power storage device.
The control method according to claim 11 or 12, wherein the charge / discharge process is performed when the first power storage device is charged using electric power from an external power source.
14. The control method according to claim 13, wherein after the charge / discharge process is performed, electric power from the external power supply is supplied to the first power storage device.
In the charge / discharge process, the second power storage device is charged until the amount of power when charging the second power storage device reaches the amount of power when discharging the second power storage device. Item 15. The control method according to any one of Items 11 to 14.
When performing the charge / discharge process, the charge / discharge characteristics of the second power storage device are acquired,
The control method according to any one of claims 11 to 15, wherein a plurality of the charge / discharge characteristics acquired when the charge / discharge treatment is performed a plurality of times are compared.
The control method according to any one of claims 11 to 16, wherein a nominal voltage of the second power storage device is lower than a nominal voltage of the first power storage device.