JP2017124684A - Power supply system for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply system for a vehicle which can energize an EHC from a power supply system at an extremely-low temperature, and secures battery performance at a normal temperature.SOLUTION: A power supply system for a vehicle comprises: an internal combustion engine; an exhaust emission control device which is arranged in an exhaust emission passage of the internal combustion engine, and purifies exhaust emission at a temperature not lower than a catalyst activation temperature; and heating means which heats the exhaust emission control device. The power supply system also has a power accumulation device of a specified composition having a first lithium ion secondary battery and a second lithium ion secondary battery, a battery temperature measurement device, and a battery selection device which selects a battery used for energization to the heating means. When there is an energization requirement to the heating means, the battery selection device selects a battery used for energization to the heating means from either of the first lithium ion secondary battery and the second lithium ion secondary battery according to the measured temperature of the first lithium ion secondary battery.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a power supply system used in a vehicle including an internal combustion engine and an exhaust purification device.

  In a vehicle equipped with an internal combustion engine, an exhaust gas purification device for purifying exhaust gas discharged when the internal combustion engine is operated with a catalyst is provided in an exhaust passage of the internal combustion engine. This exhaust purification device is a device for oxidizing and reducing harmful components such as HC, CO and NOx contained in the exhaust gas of an internal combustion engine with a three-way catalyst, but the catalyst has not reached the activation temperature (around several hundred degrees Celsius). And exhaust cannot be purified sufficiently. Therefore, in order to sufficiently purify harmful components contained in the exhaust gas, it is necessary to heat the catalyst to the activation temperature before starting the internal combustion engine.

  For this reason, a method for warming the catalyst using electric power before starting the internal combustion engine has been studied. A catalyst heating apparatus using this method is called an electrically heated catalyst (hereinafter also referred to as “EHC”). An EHC includes an electric heater provided on a catalyst.

  Here, when using the method of supplying power from the power supply system to the EHC, when the remaining capacity of the power supply system is insufficient, the internal combustion engine must be started even before the catalyst is heated and reaches the activation temperature. The harmful components contained in the exhaust gas may not be sufficiently purified.

  Therefore, for example, in Patent Document 1, it is determined whether or not the power supply system can supply the energy required for electric heating type catalyst heating and the energy required for running the vehicle, and the energization amount from the power supply system and the operation of the internal combustion engine are determined. A vehicle power supply system that changes the operating point has been proposed. According to this apparatus, since the amount of current supplied to the heating means and the operating state of the internal combustion engine can be integrated and controlled, the energy consumption of the power supply system can be kept low. In addition, since the internal combustion engine can be operated in an operation state suitable for catalyst heating, even if the internal combustion engine must be started before the catalyst reaches the activation temperature, the harmful components contained in the exhaust gas can be discharged. Can be reduced.

  Patent Document 2 includes a positive electrode having a positive electrode active material containing a lithium iron phosphate compound, a negative electrode having a negative electrode active material capable of occluding and releasing lithium ions, an electrolyte, and a cyclic carbonate. EMC) is defined as X wt% and dimethyl carbonate (DMC) is defined as Y wt%. The lithium ion solution provided with a non-aqueous electrolyte satisfying the relationships of 30 ≦ X ≦ 75, 5 ≦ Y ≦ 45 and 50 ≦ X + Y ≦ 80. A secondary battery is disclosed. According to this battery, for example, it is disclosed that it is possible to suppress a decrease in output retention rate at −30 ° C. and a decrease in output retention rate at 20 ° C.

Japanese Patent Laid-Open No. 10-288028 JP 2009-218104 A

  However, in the technique of Patent Document 1, for example, when an extremely low temperature state such as −35 ° C. or lower is reached, there is a possibility that the electrolyte of the battery used in the power supply system is frozen and the power supply system cannot be operated. That is, the EHC cannot be energized, the internal combustion engine must be started before the catalyst reaches the activation temperature, and there is a possibility that harmful components contained in the exhaust gas cannot be sufficiently purified.

  Further, even in the case of a battery as proposed in Patent Document 2, when the electrolyte composition is such that the electrolyte does not freeze at an extremely low temperature of −35 ° C. or lower, the output characteristics at room temperature such as 25 ° C. are reduced. The output performance as a power supply system at room temperature may be deteriorated.

  Therefore, the present invention has been made in view of the above-described conventional problems, and the object thereof is to allow the EHC to be energized from the power supply system at an extremely low temperature such as −35 ° C. and at a normal temperature such as 25 ° C. The object is to provide a vehicle power supply system that guarantees output performance.

  A vehicle power supply system disclosed herein includes an internal combustion engine, an exhaust purification device that is provided in an exhaust passage of the internal combustion engine and performs exhaust purification at an activation temperature of a catalyst or higher, and a heating unit that heats the exhaust purification device, And a battery used for energizing the heating means, the first lithium ion secondary battery and the second lithium ion secondary battery. A battery selection device that selects from any of the lithium ion secondary batteries, and when the measured temperature of the first lithium ion secondary battery is equal to or higher than a preset threshold, the battery selection device is the first If the measured temperature of the first lithium ion secondary battery is lower than a preset threshold value, the battery selection device may select the second lithium ion secondary battery. And selects the ion secondary battery.

The first lithium ion secondary battery and the second lithium ion secondary battery include LiPF ₆ , ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC). The volume ratio of DMC in the electrolyte solution of the first lithium ion secondary battery is 40 vol% or more, and the volume ratio of DMC in the electrolyte solution of the second lithium ion secondary battery. The volume ratio of DMC in the electrolyte solution of the second lithium ion secondary battery is 5 vol% or more and 35 vol% or less, and the volume ratio of EC in the electrolyte solution of the first lithium ion secondary battery is The volume ratio of EC in the electrolyte solution of the second lithium ion secondary battery is 30 vol%.

  According to such a configuration, the second lithium ion secondary battery is used as the lithium ion secondary battery involved in the heating means even at an extremely low temperature of −35 ° C. in response to the start request of the internal combustion engine. Since the electrolyte of the power supply system does not freeze, it is possible to energize the EHC from the power supply system. Therefore, it is possible to prevent the internal combustion engine from being started before the catalyst reaches the activation temperature, and it is possible to sufficiently purify harmful components contained in the exhaust gas.

  Moreover, since the said 1st lithium ion secondary battery excellent in output characteristics is used as a lithium ion secondary battery which concerns on the output performance of a heating means or a vehicle except at the time of extremely low temperature, the performance of a power supply system is ensured. be able to.

  In a preferred aspect of the vehicle power supply system disclosed herein, the vehicle power supply system includes an electric motor and the power storage device that stores electric power for driving the electric motor and is charged and discharged as the vehicle travels. A remaining capacity measuring device that measures the remaining capacity of the second lithium ion secondary battery, and a lithium ion secondary that is charged when the power storage device is charged, based on the measured remaining capacity of the second lithium ion secondary battery. A battery selection device for selecting a secondary battery. When the remaining capacity of the second lithium ion secondary battery is less than a preset threshold value, the second lithium ion secondary battery is charged when the power storage device is charged, and the second lithium ion secondary battery is charged. When the remaining capacity of the battery is greater than or equal to a preset threshold, the first lithium ion secondary battery is charged when the power storage device is charged.

  According to such a configuration, since the second lithium ion secondary battery is charged with priority over the first lithium ion secondary battery, before the catalyst provided in the exhaust passage of the internal combustion engine reaches the activation temperature. Therefore, it is possible to prevent the internal combustion engine from starting into a state that must be started.

1 is an overall view of a vehicle in an embodiment of the present invention. 1 is an overall view showing a power supply system according to an embodiment of the present invention. It is a schematic diagram showing the relationship between the composition (volume ratio) and the freezing point in an electrolytic solution in which the volume ratio of EC: DMC: EMC is represented by 30: X: (70-X). It is a schematic diagram which shows the relationship between the temperature and the electrical conductivity in the electrolyte solution whose volume ratio of EC: DMC: EMC is represented by 30: X: (70-X). It is a flowchart which shows the process sequence of ECU in one Embodiment of this invention. It is a time chart for demonstrating control of ECU in one Embodiment of this invention. It is a flowchart which shows the process sequence of ECU in one Embodiment of this invention. It is a flowchart which shows the process sequence of ECU in one Embodiment of this invention.

Preferred embodiments of the present invention will be described below with reference to the drawings. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. In the present specification, the “lithium ion secondary battery” refers to a secondary battery using lithium ions as a charge carrier and a non-aqueous electrolyte as an electrolyte. Moreover, although it demonstrates using a hybrid vehicle (henceforth "HV vehicle") as one aspect | mode of a present Example, it is not limited to it.

  FIG. 1 is a block diagram of a vehicle 1 in the present embodiment. The vehicle 1 includes an internal combustion engine 10, a first MG (Motor Generator) 20, a second MG 30, a power split device 40, a speed reducer 50, a power control unit (hereinafter referred to as "PCU") 60, Power storage device 70, drive wheel 80, and electronic control unit (Electronic Control Unit, hereinafter referred to as “ECU”) 200 are provided.

  The internal combustion engine 10 is an internal combustion engine that generates a driving force for rotating a crankshaft by combustion energy generated when an air-fuel mixture is burned. First MG 20 and second MG 30 are motor generators driven by alternating current.

  The vehicle 1 is a vehicle that travels by power output from at least one of the internal combustion engine 10 and the second MG 30. The driving force generated by the internal combustion engine 10 is divided into two paths by the power split device 40. That is, one is a path transmitted to the drive wheel 80 having the speed reducer 50 and the other is a path transmitted to the first MG 20.

  Power split device 40 includes a planetary gear including a sun gear, a pinion gear, a carrier, and a ring gear. The pinion gear engages with the sun gear and the ring gear. The carrier supports the pinion gear so as to be capable of rotating, and is connected to the crankshaft of the internal combustion engine 10. The sun gear is connected to the rotation shaft of the first MG 20. The ring gear is connected to the rotation shaft of second MG 30 and speed reducer 50.

  PCU 60 is controlled by a control signal from ECU 200. PCU 60 converts the DC power supplied from power storage device 70 into AC power that can drive first MG 20 and second MG 30. PCU 60 outputs the converted AC power to first MG 20 and second MG 30, respectively. Thus, first MG 20 and second MG 30 are driven by the electric power stored in power storage device 70. PCU 60 can also convert AC power generated by first MG 20 and second MG 30 into DC power and charge power storage device 70 with the converted DC power.

  The power storage device 70 is a direct current power source that stores electric power for driving the first MG 20 and the second MG 30, and includes a lithium ion secondary battery that includes lithium ions and the like. Note that a detailed configuration of the power storage device 70 applied to the present embodiment will be described later.

  Further, the vehicle 1 includes an exhaust passage 130. Exhaust gas discharged from the internal combustion engine 10 is discharged to the atmosphere through the exhaust passage 130.

  In the middle of the exhaust passage 130, an electrically heated catalyst (Electrical Heated Catalyst, hereinafter referred to as “EHC”) 140 is provided. The EHC 140 is a catalyst device configured such that the catalyst can be electrically heated by an electric heater.

  The EHC 140 is connected to the PCU 60 via the switching device 100. Switching device 100 includes a relay that electrically connects and disconnects EHC 140 and PCU 60 based on a control signal from ECU 200. When DC power from the PCU 60 is supplied to the EHC 140 in a state where the EHC 140 and the PCU 60 are electrically connected (a state where the relay provided in the switching device 100 is closed), the EHC 140 is heated.

  Here, power supply system 300 including power storage device 70 and PCU 60 according to the present embodiment will be briefly described with reference to FIG. FIG. 2 is a block diagram of the vehicle power supply system according to the present embodiment. In FIG. 2, power supply system 300 includes power storage device 70, PCU 60, and first temperature sensor 210. Here, power storage device 70 includes a first lithium ion secondary battery 250 and a second lithium ion secondary battery 260, and PCU 60 includes an SOC management circuit 240 and a temperature management circuit 230.

  The first temperature sensor 210 measures the temperature of the first lithium ion secondary battery 250, and the secondary battery used by the temperature management circuit 230 to transmit power to the EHC according to the temperature is used as the first lithium ion battery. Selection is made from either the secondary battery 250 or the second lithium ion secondary battery 260.

  In addition, the SOC management circuit manages the SOCs of the first lithium ion secondary battery 250 and the second lithium ion secondary battery 260, and transmits a charging current from the first MG during charging according to each SOC. Is selected from either the first lithium ion secondary battery 250 or the second lithium ion secondary battery 260, or the charge ratio for transmitting power to both is determined. The SOC is a battery capacity ratio (State of Charge, hereinafter referred to as “SOC”), and represents a remaining charge capacity ratio when the fully charged state of the battery is 100%.

  The first lithium ion secondary battery 250 and the second lithium ion secondary battery 260 include LiPF6, ethylene carbonate (hereinafter referred to as “EC”), dimethyl carbonate (hereinafter referred to as “DMC”) in the electrolytic solution. )) And methyl ethyl carbonate (hereinafter "EMC").

  Here, in the first lithium ion secondary battery 250, the ratio of DMC in the entire electrolyte is 40 vol% or more, and the volume ratio of EC in the entire electrolyte is 30 vol%. The volume ratio of DMC in the entire electrolyte of the second lithium ion secondary battery 260 is 5 vol% or more and 35 vol% or less, and the volume ratio of EC in the electrolyte is 30 vol%.

  According to the above configuration, the electrolytic solution of the second lithium ion secondary battery 260 is less likely to freeze under an extremely low temperature condition than the electrolytic solution of the first lithium ion secondary battery 250. This will be described with reference to FIG. FIG. 3 is a schematic diagram showing the relationship between the composition of the electrolytic solution and the freezing point where the volume ratio of EC: DMC: EMC is represented by 30: X: (70-X).

  From FIG. 3, the configuration of the electrolyte solution of the second lithium ion secondary battery is such that the volume ratio of DMC is 5 vol% or more and 35 vol% or less, so that the freezing point is −40 ° C. or less, while the first lithium ion secondary battery The freezing point of the electrolyte of the secondary battery is −35 ° C. or higher. Therefore, if it is a 2nd lithium ion secondary battery, even if it is extremely low temperature conditions, such as -35 degreeC, electrolyte solution does not freeze and it is possible to supply electric power.

  Also, with the above configuration, the first lithium ion secondary battery 250 has higher output performance at room temperature such as 25 ° C. than the electrolyte solution of the second lithium ion secondary battery 260. The reason for this will be described with reference to FIG. FIG. 4 shows the electrical conductivity when the volume ratio of EC: DMC: EMC is changed to 15, 30, 45 in the electrolyte represented by 30: X: (70-X). It is the figure which showed the relationship of temperature. From this figure, it can be seen that the higher the volume ratio of DMC, the higher the electrical conductivity, and the more remarkable it is in an environment of 10 ° C. or higher. The volume ratio of DMC in the electrolytic solution in the first lithium ion secondary battery 250 is 40 vol% or higher, which is higher than the electrolytic solution in the second lithium ion secondary battery 260. Therefore, the electrical conductivity of the electrolyte solution of the first lithium ion secondary battery 250 is higher than that of the electrolyte solution of the second lithium ion secondary battery 260 at room temperature, and is excellent in output characteristics.

  Therefore, for example, at an extremely low temperature of −35 ° C. or lower, the EHC can be appropriately operated by using the second lithium ion secondary battery 260 as a secondary battery used for transmitting power to the EHC. In the temperature range higher than −35 ° C., the first lithium ion secondary battery 250 is used as a secondary battery to be used for transmitting power to the EHC. A secondary battery can be used efficiently.

  In addition, the SOC management circuit 240 measures the charge capacities of the first lithium ion secondary battery 250 and the second lithium ion secondary battery 260, and the first lithium ion secondary battery is charged during charging according to the measured capacity. The charging rate distributed to the secondary battery 250 and the second lithium ion secondary battery 260 may be changed. Depending on the measured capacity, the charge ratio distributed to the first lithium ion secondary battery 250 and the second lithium ion secondary battery 260 during charging is changed, so that the charge capacity necessary for the operation of the EHC is changed. The first lithium ion secondary battery 250 in the normal temperature region can be charged while preferentially securing the second lithium ion secondary battery 260.

  ECU 200 incorporates a CPU (Central Processing Unit) and a memory (not shown), executes predetermined arithmetic processing based on the information stored in the memory, and controls each device of vehicle 1 based on the result.

  In the vehicle 1 having the above configuration, the ECU 200 determines whether or not the EHC 140 needs to be heated based on the EHC temperature before the internal combustion engine 10 is started. If it is determined that the EHC 140 needs to be heated, EHC energization is performed.

  Here, depending on the temperature of the first lithium ion secondary battery 250, there is a possibility that power cannot be transmitted to the EHC. If the internal combustion engine 10 is started in such a state, the exhaust purification performance cannot be ensured, and harmful components contained in the exhaust may not be sufficiently purified.

  Therefore, the ECU 200 according to the present embodiment uses the secondary battery to transmit power to the EHC according to the measured temperature of the first lithium ion secondary battery 250 when the EHC is energized before the internal combustion engine 10 is started. Is selected.

  FIG. 5 is a flowchart showing a control procedure of the ECU 200 when EHC energization is performed. The flowchart of FIG. 5 is repeatedly executed at a predetermined cycle while the internal combustion engine 10 is stopped. FIG. 6 is a time chart when EHC energization is performed. In addition, the process determination method of ECU200 demonstrated below is an example to the last, Comprising: It is not limited to this.

  In step S10, ECU 200 determines whether EHC energization is necessary based on the EHC temperature. If EHC energization is not necessary (NO in step S10), the process proceeds to step S50, and the control is returned to the main routine.

  If EHC energization is required (YES in step S10), ECU 200 measures the temperature of first lithium ion secondary battery 250 in step S20 through PCU 70, and selects a secondary battery to be used for EHC energization. . Specifically, it is determined whether or not the measured temperature of the first lithium ion secondary battery 250 is equal to or higher than a preset threshold value Tb.

  When the measured temperature of first lithium ion secondary battery 250 is equal to or higher than threshold value Tb (YES in step S20, time t1), EHC energization is performed using first lithium ion secondary battery 250. If the measured temperature of the first lithium ion secondary battery 250 is lower than the threshold (NO in step S20, time t2), EHC energization is performed using the second lithium ion secondary battery 260.

  In step S30, the ECU 200 measures the temperature of the EHC, and if the measured temperature of the EHC is equal to or higher than a preset threshold value Th (time t3), the control proceeds to step S40, and after the EHC energization ends, The process proceeds to step S50 and returns to the main routine. If the measured EHC temperature is lower than the preset threshold value Th in step S30, the control proceeds to step S50, and the control is returned to the main routine.

  As described above, the ECU 200 according to the present embodiment performs the EHC energization using the measured temperature of the first lithium ion secondary battery when the EHC energization is performed before the internal combustion engine 10 is started. Determine the battery. As a result, the EHC can be energized from the power supply system even at an extremely low temperature, and the battery performance at normal temperature can be ensured while appropriately ensuring the exhaust purification performance after the start of the internal combustion engine 10. .

  Next, a control procedure of the ECU 200 after the internal combustion engine 10 in the HV vehicle is started will be described. FIG. 7 is a flowchart showing a control procedure of the ECU 200 after the internal combustion engine 10 is started. The flowchart in FIG. 7 is repeatedly executed at a predetermined cycle after the internal combustion engine 10 is started. In addition, the process determination method of ECU200 demonstrated below is an example to the last, Comprising: It is not limited to this.

  In step S110, ECU 200 measures the temperature of first lithium ion secondary battery 250 through PCU 60, and selects a secondary battery used for power. Specifically, it is determined whether or not the measured temperature of the first lithium ion secondary battery 250 is lower than a preset threshold value. The power represents the start of an internal combustion engine or an air conditioner, traveling in an HV vehicle, and the like.

  If the measured temperature of the first lithium ion secondary battery 250 is lower than the threshold (NO in step S110), power is secured using the second lithium ion secondary battery 260, and then control proceeds to step S120. Returned to the main routine. If the measured temperature of first lithium ion secondary battery 250 is equal to or higher than the threshold (YES in step S110), power is secured using the first lithium ion secondary battery, and then control proceeds to step S120. Proceed and control is returned to the main routine.

  As described above, ECU 200 according to the present embodiment determines the lithium ion secondary battery that obtains power using the measured temperature of the first lithium ion secondary battery after starting internal combustion engine 10. As a result, power can be secured more appropriately than lithium ion secondary batteries even at extremely low temperatures, and battery performance at room temperature can be ensured.

  Next, a control procedure of ECU 200 during charging of the HV vehicle will be shown. FIG. 8 is a flowchart showing a control procedure of ECU 200 during charging. The flowchart in FIG. 8 is repeatedly executed at a predetermined cycle when the power storage device 70 is charged regardless of whether or not the vehicle is traveling. In addition, the process determination method of ECU200 demonstrated below is an example to the last, Comprising: It is not limited to this.

  In step S210, ECU 200 determines whether or not there is a charging request using the SOC of first lithium ion secondary battery 250 and the SOC of second lithium ion secondary battery 260 through PCU 70. If there is no charge request (NO in step S210), the process proceeds to step S240, and control is returned to the main routine.

  If there is a charge request (YES in step S210), the SOC of second lithium ion secondary battery 260 is calculated in step 220, and it is determined whether the calculated SOC is equal to or greater than a preset threshold value.

  If the SOC of second lithium ion secondary battery 260 is equal to or greater than a preset threshold value (YES in step S220), first lithium ion secondary battery 250 is charged, and then control proceeds to step S240, where the main routine Returned to If the SOC value is less than the threshold value (NO in step S220), the second lithium ion secondary battery 260 is charged, and then control proceeds to step S240, where the process returns to the main routine.

  As described above, ECU 200 according to the present embodiment determines a lithium ion secondary battery to be charged based on the SOC of second lithium ion secondary battery 260 and a preset threshold value when charging the HV vehicle. . As a result, the second lithium ion secondary battery can be proactively charged rather than the first lithium ion secondary battery, so that the charge amount of the second lithium ion secondary battery is below the threshold value. The power can be secured even at extremely low temperatures.

  In the present embodiment, the battery to be charged is determined based on the SOC of the second lithium ion secondary battery 260, but if necessary, the SOC of the first lithium ion secondary battery 250 is calculated, Charging may be controlled, for example, by charging the SOC of the first lithium ion secondary battery 250 and the SOC of the second lithium ion secondary battery 260 at the same time.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Vehicle, 10 Internal combustion engine, 20 1st MG, 30 2nd MG, 40 Power split device, 50 Reducer, 60 PCU, 70 Power storage device, 80 Drive wheel, 100 Switching device, 130 Exhaust passage, 140 EHC, 200 ECU, 210 First temperature sensor, 230 Temperature management circuit, 240 SOC management circuit, 250 First lithium ion secondary battery, 260 Second lithium ion secondary battery, 300 Power supply system

Claims (2)

A power supply system used in a vehicle, comprising: an internal combustion engine; an exhaust purification device that is provided in an exhaust passage of the internal combustion engine and purifies exhaust gas at an activation temperature of a catalyst or higher; and a heating unit that heats the exhaust purification device. ,
A power storage device comprising a first lithium ion secondary battery and a second lithium ion secondary battery;
A battery temperature measuring device for measuring the temperature of the first lithium ion secondary battery;
A battery selection device that selects a battery used for energization of the heating means from either the first lithium ion secondary battery or the second lithium ion secondary battery;
Have
The first lithium ion secondary battery and the second lithium ion secondary battery include an electrolytic solution containing LiPF ₆ , ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC). Have
The volume ratio of DMC in the electrolyte solution of the first lithium ion secondary battery is 40 vol% or more,
The volume ratio of DMC in the electrolyte solution of the second lithium ion secondary battery is 5 vol% or more and 35 vol% or less,
The volume ratio of EC in the electrolyte solution of the first lithium ion secondary battery is 30 vol%,
The volume ratio of EC in the electrolyte solution of the second lithium ion secondary battery is 30 vol%,
When there is an energization request to the heating means for the power storage device,
When the measured temperature of the first lithium ion secondary battery is equal to or higher than a preset threshold, the battery selection device selects the first lithium ion secondary battery,
When the measured temperature of the first lithium ion secondary battery is lower than a preset threshold value, the battery selection device selects the second lithium ion secondary battery. .
A vehicle power supply system comprising: an electric motor; and the power storage device that stores electric power for driving the electric motor and is charged and discharged as the vehicle travels,
An SOC measuring device for measuring the SOC of the second lithium ion secondary battery;
A battery selection device that selects a lithium ion secondary battery to be charged when charging the power storage device from the measured SOC of the second lithium ion secondary battery,
When the SOC of the second lithium ion secondary battery is greater than or equal to a preset threshold, the first lithium ion secondary battery is charged when the power storage device is charged,
2. The vehicle power supply system according to claim 1, wherein when the SOC of the second lithium ion secondary battery is less than a preset threshold value, the second lithium ion secondary battery is charged when the power storage device is charged.