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WO2016021136A1 - 車載用蓄電システム - Google Patents

車載用蓄電システム Download PDF

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Publication number
WO2016021136A1
WO2016021136A1 PCT/JP2015/003721 JP2015003721W WO2016021136A1 WO 2016021136 A1 WO2016021136 A1 WO 2016021136A1 JP 2015003721 W JP2015003721 W JP 2015003721W WO 2016021136 A1 WO2016021136 A1 WO 2016021136A1
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WO
WIPO (PCT)
Prior art keywords
charging
voltage
battery
state
auxiliary battery
Prior art date
Application number
PCT/JP2015/003721
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English (en)
French (fr)
Inventor
守 向野
岸本　圭司
Original Assignee
パナソニックＩｐマネジメント株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by パナソニックＩｐマネジメント株式会社 filed Critical パナソニックＩｐマネジメント株式会社
Priority to JP2016539826A priority Critical patent/JPWO2016021136A1/ja
Priority to US15/325,894 priority patent/US20170136968A1/en
Publication of WO2016021136A1 publication Critical patent/WO2016021136A1/ja

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R16/00—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for
    • B60R16/02—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements
    • B60R16/03—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for
    • B60R16/033—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for characterised by the use of electrical cells or batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/06—Lead-acid accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/20—Semi-lead accumulators, i.e. accumulators in which only one electrode contains lead
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4207—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells for several batteries or cells simultaneously or sequentially
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H01M10/441—Methods for charging or discharging for several batteries or cells simultaneously or sequentially
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/46—Accumulators structurally combined with charging apparatus
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • H01M10/482—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte for several batteries or cells simultaneously or sequentially
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0068—Battery or charger load switching, e.g. concurrent charging and load supply
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/02—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from AC mains by converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/14—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle
    • H02J7/1423—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle with multiple batteries
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/14—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle
    • H02J7/1469—Regulation of the charging current or voltage otherwise than by variation of field
    • H02J7/1492—Regulation of the charging current or voltage otherwise than by variation of field by means of controlling devices between the generator output and the battery
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/14—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle
    • H02J7/16—Regulation of the charging current or voltage by variation of field
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M2010/4271—Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2310/00—The network for supplying or distributing electric power characterised by its spatial reach or by the load
    • H02J2310/40—The network being an on-board power network, i.e. within a vehicle
    • H02J2310/46—The network being an on-board power network, i.e. within a vehicle for ICE-powered road vehicles
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2310/00—The network for supplying or distributing electric power characterised by its spatial reach or by the load
    • H02J2310/40—The network being an on-board power network, i.e. within a vehicle
    • H02J2310/48—The network being an on-board power network, i.e. within a vehicle for electric vehicles [EV] or hybrid vehicles [HEV]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
    • Y02T10/92—Energy efficient charging or discharging systems for batteries, ultracapacitors, supercapacitors or double-layer capacitors specially adapted for vehicles

Definitions

  • the present invention relates to an in-vehicle power storage system that supplies power to a starter motor and an electrical load of a vehicle.
  • Lead storage batteries are generally used in in-vehicle power storage systems that supply power to vehicle starter motors and electrical loads.
  • Lead-acid batteries are cheaper than nickel-metal hydride batteries, which have different electrical characteristics such as energy density, but are prone to deterioration when repeated deep charge / discharge, and maintain a high SOC (also known as StateSOf Charge, charge rate). It is desirable.
  • SOC also known as StateSOf Charge, charge rate
  • SOC also known as StateSOf Charge, charge rate
  • an in-vehicle power storage system is configured by connecting a lead-acid battery in parallel with a high energy density nickel-metal hydride battery via a switch (see Patent Document 1 below).
  • the nickel-metal hydride battery when charging a lead-acid battery and a nickel-metal hydride battery connected in parallel with each other at a constant voltage, the nickel-metal hydride battery is more excellent in charge acceptability, and often reaches a fully charged state earlier than a lead-acid battery.
  • the present invention provides an in-vehicle device capable of charging a lead storage battery at a constant voltage while suppressing a decrease in charging efficiency after an auxiliary battery of a secondary battery such as a nickel metal hydride battery connected in parallel reaches a fully charged state. It aims at providing the electrical storage system for electricity.
  • An in-vehicle power storage system includes an in-vehicle power supply unit having a lead storage battery and an auxiliary battery connected in parallel with the lead storage battery, a detection unit for detecting a charge state of the lead storage battery and a charge state of the auxiliary battery, When the charging state of the auxiliary battery transitions to the first charging state where charging of the auxiliary battery is to be started, the first voltage is applied to the in-vehicle power source unit and constant voltage charging to the in-vehicle power source unit is started.
  • the state is the lead storage To transition to the third state of charge should stop charging the pond, and a discharge control unit for repeating the second process and the first process.
  • an in-vehicle power storage system capable of charging a lead storage battery at a constant voltage while suppressing a decrease in charging efficiency after an auxiliary battery such as a nickel metal hydride battery connected in parallel reaches a fully charged state. Can be provided.
  • FIG. 1 is a diagram for explaining a vehicle equipped with a vehicle power storage system according to an embodiment of the present invention.
  • FIG. 2 is a diagram for explaining temporal transitions of the charge rates of the lead storage battery and the auxiliary battery of the in-vehicle power supply unit according to the embodiment of the present invention.
  • FIG. 3 is an operation flowchart relating to constant voltage charging control of the in-vehicle power supply unit.
  • the terminal voltage of the storage battery at the time of no load is called OCV (OpenpCircuit Voltage, also called open voltage).
  • OCV OpenpCircuit Voltage, also called open voltage
  • CCV Current Circuit Voltage, also called closed circuit voltage
  • CCV OCV ⁇ Id ⁇ Rd (1)
  • + indicates charging and-indicates discharging.
  • Id ⁇ Rd is called a polarization voltage. The polarization voltage decreases the OCV during discharging and increases the OCV during charging.
  • the voltage is often applied so that the CCV of the lead storage battery is changed from 13.5V to 14.5V.
  • the charging current increases as the difference between CCV and OCV increases and the internal resistance decreases. That is, the time required for constant voltage charging can be shortened as a higher voltage is applied.
  • the nickel metal hydride battery connected in parallel to the lead storage battery is fully charged, for example, if constant voltage charging is continued while a high voltage of 14.5 V is applied, the nickel metal hydride battery is overcharged. There is a fear.
  • the voltage at which the nickel metal hydride battery is not overcharged is applied to perform constant voltage charging of the lead storage battery, the time required for constant voltage charging becomes longer.
  • the lead storage battery needs to be charged and discharged within a high SOC range (for example, 80% or more) in order to suppress the progress of deterioration, and has high OCV and internal resistance during charging.
  • the vehicle power storage system is configured to perform constant voltage charging by applying a high voltage of 14.5 V, for example, and transition the nickel-metal hydride battery in a charging required state to a fully charged state. And a second process of changing the voltage applied to the lead storage battery to a second voltage lower than the first voltage and higher than the OCV of the lead storage battery, and transitioning the fully charged nickel metal hydride battery to the charge required state. Repeat alternately.
  • the high voltage is applied and the constant voltage charge of a lead storage battery is realizable, without putting the nickel-metal hydride battery connected in parallel into the overcharge state, the fall of the charge efficiency with respect to a lead storage battery can be suppressed.
  • FIG. 1 is a diagram for explaining a vehicle 1 equipped with an in-vehicle power storage system 60 according to the present embodiment.
  • the vehicle 1 is assumed to be a hybrid electric vehicle having an engine as a main power source and a motor as an auxiliary power source.
  • the vehicle 1 includes an engine 10, a starter motor 20, an ISG (Integrated Starter Generator) 30, an electrical load 40, an ECU (ElectronicEControl Unit, also referred to as an electronic control unit) 50, and an in-vehicle power storage system 60.
  • the in-vehicle power storage system 60 measures the voltage value of the in-vehicle power supply unit 70 that supplies power to the starter motor 20, the ISG 30, and the electrical load 40, the lead storage battery 71, and the charge / discharge control of the in-vehicle power supply unit 70.
  • the power supply control part 80 which performs is provided.
  • the starter motor 20, ISG 30, and electrical load 40 are connected in parallel with the in-vehicle power supply unit 70.
  • the starter motor 20 starts the engine 10 when the ignition switch is operated by the user.
  • the ISG 30 has both a power generation function and an electric function.
  • a brake pedal (not shown) is operated and the vehicle 1 is decelerated while the vehicle 1 is traveling, torque is transmitted from the wheels to the ISG 30, and the ISG 30 generates power by the power generation function.
  • the generated power of the ISG 30 exceeds the power consumption of the electrical load 40, the excess is charged in the in-vehicle power supply unit 70. This regenerates energy. If the electric function is not required, the ISG 30 can be replaced with an alternator having only a power generation function.
  • the engine 10 is automatically stopped by the idle stop control of the ECU 50.
  • the vehicle 1 starts, the vehicle 1 is driven by the electric function of the ISG 30 and the engine 10 is started. Further, when an accelerator petal (not shown) is operated while the vehicle 1 is traveling, torque is distributed between the engine 10 and the ISG 30 by assist control of the ECU 50.
  • the ISG 30 generates the distributed torque by an electric function, and drives the vehicle 1 together with the engine 10.
  • the electrical load 40 includes a load such as an electrical component equipped in the vehicle 1 such as an air conditioner and a room light.
  • the electric power supplied from the in-vehicle power supply unit 70 is used as a power source for the electrical load 40.
  • the ECU 50 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) in which a predetermined control program is stored, a RAM (Random Access Memory) in which data is temporarily stored, these Peripheral circuits are provided.
  • ECU 50 is configured to be able to communicate with power supply control unit 80.
  • the ECU 50 controls the overall operation of the vehicle 1 including the engine 10, starter motor 20, ISG 30, and electrical load 40. For example, the ECU 50 automatically stops the engine 10 when a predetermined stop condition such as the vehicle 1 is stopped for a predetermined time at an intersection or the like, and again when a predetermined start condition such as operation release of a brake pedal (not shown) is satisfied.
  • the ECU 50 appropriately refers to the battery state information including the voltage value of the lead storage battery 71 received from the power supply control unit 80 when performing idle stop control or the like. For example, when the ECU 50 determines that sufficient power cannot be supplied to the ISG 30 when the engine 10 is restarted from the idle stop state based on the battery state information when the remaining capacity of the in-vehicle power supply unit 70 is small, the ECU 50 enters the idle stop state. Prohibit migration.
  • the ISG control unit 51 controls the power generation function of the ISG 30 based on an instruction from the power supply control unit 80.
  • the ISG control unit 51 controls the excitation current of a rotor coil (not shown) of the ISG 30 to control the output voltage of the ISG 30.
  • the ISG control unit 51 increases the excitation current of the rotor coil.
  • the power control unit 80 instructs to lower the output voltage of the ISG 30, the ISG control unit 51 reduces the excitation current of the rotor coil.
  • the communication unit 52 performs signal processing (for example, frame formation and conversion to a differential transmission method) for communication with the power supply control unit 80 via a network such as CAN (Controller
  • the communication unit 52 outputs the battery state information received from the power supply control unit 80 to the ISG control unit 51.
  • the in-vehicle power supply unit 70 includes a lead storage battery 71 having a rated voltage of 12 V, and an auxiliary battery 72 that is different from the lead storage battery 71 in electrical characteristics such as energy density and is connected in parallel with the lead storage battery 71. It is assumed that the in-vehicle power supply unit 70 according to the present embodiment uses a nickel-metal hydride battery having a higher energy density than the lead storage battery 71 as the auxiliary battery 72.
  • the rated voltage of the nickel metal hydride battery is 1.2 V / cell. Therefore, auxiliary battery 72 includes ten nickel metal hydride batteries connected in series.
  • the auxiliary battery 72 can also be realized by using a secondary battery such as a lithium ion battery, a capacitor, or the like.
  • the in-vehicle power supply unit 70 is connected in series to the lead storage battery 71, detects the value of the current flowing through the lead storage battery 71, and is connected in series to the auxiliary battery 72, and determines the value of the current flowing through the auxiliary battery 72.
  • a current sensor 74 for detection is included.
  • the current sensors 73 and 74 are constituted by shunt resistors, for example.
  • the in-vehicle power supply unit 70 includes a voltage sensor 75 that is connected in parallel to the lead storage battery 71 and the auxiliary battery 72 and detects the terminal voltage values of the lead storage battery 71 and the auxiliary battery 72 connected in parallel.
  • the power supply control unit 80 includes, for example, a CPU that executes predetermined arithmetic processing, a ROM that stores a predetermined control program, a RAM that temporarily stores data, and peripheral circuits thereof.
  • the power supply control unit 80 includes an acquisition unit 81, a detection unit 82, a charge / discharge control unit 83, a communication unit 84, and a storage unit 85.
  • the acquisition unit 81 performs AD conversion on the current value received from the current sensor 73, obtains a digitized current value (also referred to as Ip, first current value), and outputs the current value to the detection unit 82. Similarly, the acquisition unit 81 obtains a digitized current value (In, also referred to as a second current value) from the current value received from the current sensor 74 and outputs the current value to the detection unit 82. The acquisition unit 81 performs AD conversion on the value of the terminal voltage received from the voltage sensor 75, obtains a digitized voltage value (Vo, also referred to as an overall voltage value), and outputs the voltage value to the detection unit 82.
  • Vo also referred to as an overall voltage value
  • the detecting unit 82 integrates the first current value Ip received from the acquiring unit 81, and detects the charge rate (SOCp) of the lead storage battery 71. Similarly, the detection unit 82 integrates the second current value In received from the acquisition unit 81 and detects the charging rate (SOCn) of the auxiliary battery 72.
  • the detection unit 82 refers to, for example, an IV table indicating the correspondence between the terminal voltage of the lead storage battery 71 and the current flowing in the lead storage battery 71, and the total voltage value Vo received from the acquisition unit 81 and the first current Based on the value Ip, the internal resistance (Rp) of the lead storage battery 71 is detected. Similarly, the detection unit 82 detects the internal resistance (Rn) of the auxiliary battery 72 based on the overall voltage value Vo and the second current value In received from the acquisition unit 81.
  • the detection part 82 substitutes the whole voltage value Vo received from the acquisition part 81, the 1st electric current value Ip, and the detected internal resistance Rp for (1) Formula, and respond
  • the open circuit voltage (OCVp) of the lead storage battery 71 to be detected is detected.
  • the detection unit 82 configures battery state information from the first current value Ip received from the acquisition unit 81 and the calculated charge rate SOCp, and outputs the battery state information to the charge / discharge control unit 83.
  • the charge / discharge control unit 83 Based on the battery state information received from the detection unit 82, the charge / discharge control unit 83 sends an instruction to the ECU 50 via the communication unit 84 and adjusts the output voltage of the ISG 30 to control charging / discharging of the in-vehicle power supply unit 70. .
  • the charge rate SOCp of the lead storage battery 71 and the charge rate SOCn of the auxiliary battery 72 become lower than the lower limits of the respective control target ranges due to the discharge to the electrical load 40 or the like, the charge / discharge control unit 83 outputs the output of the ISG 30 to the ECU 50. An instruction is given to increase the voltage, and the discharge from the in-vehicle power supply unit 70 is limited.
  • the charging / discharging control unit 83 outputs the output voltage of the ISG 30 to the ECU 50. To charge the in-vehicle power supply unit 70.
  • control target range of the charge rate of the lead storage battery 71 (also referred to as the first control target range) is assumed to be 80% to 95% below, and the control target range of the charge rate of the auxiliary battery 72 (second control).
  • the target range is assumed to be 20% to 100%, but is not limited to these ranges.
  • the charge / discharge control unit 83 refers to the threshold value related to the charging rate of the auxiliary battery 72 and determines the charging state of the auxiliary battery 72. More specifically, when the charge rate SOCn of the auxiliary battery 72 is smaller than the first threshold value, the charge / discharge control unit 83 determines that the battery is in a charge state (also referred to as a first charge state) to start charging. To do. When charge rate SOCn of auxiliary battery 72 is larger than the second threshold value, charge / discharge control unit 83 determines that charging is to be stopped (also referred to as second charging state).
  • the lower limit value (20%) of the second control target range can be adopted as the first threshold value
  • the upper limit value (100%) of the second control target range can be adopted as the second threshold value. can do.
  • the charge / discharge control unit 83 determines that the charge state in which charging should be stopped (also referred to as a third charge state) is present.
  • the charge / discharge control unit 83 determines that it is in a charged state (also referred to as a fourth charged state) where charging should be started.
  • the upper limit value (95%) of the first control target range can be adopted as the third threshold value
  • the lower limit value (80%) of the first control target range can be adopted as the fourth threshold value. it can.
  • FIG. 2 is a diagram for explaining temporal transitions of the charging rates of the lead storage battery 71 and the auxiliary battery 72 when the constant voltage charging is performed.
  • the charge rate SOCp of the lead storage battery 71 is smaller than the fourth threshold value, and the charge rate SOCn of the auxiliary battery 72 is smaller than the first threshold value.
  • the charge / discharge control unit 83 determines that the lead storage battery 71 is in the first charge state and the auxiliary battery 72 is in the fourth charge state. Then, the charge / discharge control unit 83 instructs the ECU 50 to increase the output voltage of the ISG 30 to the first voltage. In other words, the charge / discharge control unit 83 performs a process of applying a first voltage to the in-vehicle power supply unit 70 and charging at a constant voltage (also referred to as a first process).
  • a constant voltage also referred to as a first process.
  • 14.5V can be adopted as the first voltage.
  • the charge acceptance of the auxiliary battery 72 is superior to that of the lead storage battery 71. Therefore, as shown in FIG.
  • the rate of increase in the rate is larger in the auxiliary battery 72.
  • the charging rate SOCn of the auxiliary battery 72 becomes larger than the second threshold value. Then, the charge / discharge control unit 83 determines that the charging state of the auxiliary battery 72 has transitioned from the first charging state to the second charging state, and instructs the ECU 50 to lower the output of the ISG 30 to the second voltage. I do.
  • the charge / discharge control unit 83 performs a process of applying the second voltage to the in-vehicle power supply unit 70 and discharging the auxiliary battery 72 to the electrical load 40 or the like (also referred to as a second process).
  • the second voltage is lower than the first voltage, and a voltage included in a range (also referred to as a voltage range) equal to or higher than the open circuit voltage OCVp corresponding to the charging rate of the lead storage battery 71 at the timing T2 is employed.
  • the reason why the output voltage of the ISG 30 is lowered to the second voltage is to temporarily lower the charging rate SOCn of the auxiliary battery 72 because the auxiliary battery 72 is overcharged if constant voltage charging with the first voltage is continued. .
  • the voltage from which the discharge from the auxiliary battery 72 increases and the discharge from the lead storage battery 71 decreases that is, the open circuit voltage OCVp of the lead storage battery 71 as much as possible in the voltage range. It is preferable to employ a close voltage as the second voltage. As long as the voltage is close to the open circuit voltage OCVp of the lead storage battery 71, the second voltage may be higher or lower than the open circuit voltage OCVp.
  • the voltage at which the first current value Ip of the lead storage battery 71 becomes zero by adjusting the output voltage of the ISG 30 while referring to the first current value Ip may be adopted.
  • the second voltage may be a voltage that is smaller than a predetermined value (for example, 5 A) even if the first current Ip is not zero.
  • the predetermined value is a value in which the first current Ip is sufficiently smaller than a value calculated by multiplying the second current value In of the auxiliary battery 72 by the rated capacity ratio (rated capacity of the lead storage battery 71 / rated capacity of the auxiliary battery 72) ( For example, it can be set based on a value smaller than 1/20).
  • the charging rate SOCp of the lead storage battery 71 is hardly reduced, and the charging rate SOCn of the auxiliary battery 72 is mainly reduced. As a result, the time required for constant voltage charging can be shortened.
  • the charging rate SOCn of the auxiliary battery 72 is reduced, and the charging rate SOCp of the lead storage battery 71 is maintained almost as it is. For this reason, at timing T3, the charging rate SOCp of the auxiliary battery 72 becomes smaller than the first threshold value. Then, the charge / discharge control unit 83 determines that the charge state of the auxiliary battery 72 has transitioned from the second charge state to the first charge state, and instructs the ECU 50 to increase the output voltage of the ISG 30 to the first voltage. Give instructions. That is, the charge / discharge control unit 83 executes the first process.
  • the charging / discharging control unit 83 determines that the charging state of the auxiliary battery 72 has transitioned from the first charging state to the second state, the charging / discharging control unit 83 performs the second process and transitions from the second charging state to the first charging state. If determined, the first process is executed. That is, the charge / discharge control unit 83 repeats the first process and the second process every time the charge state of the auxiliary battery 72 transitions.
  • the charging rate SOCp of the lead storage battery 71 becomes larger than the third threshold value.
  • the charge / discharge control unit 83 determines that the state of charge of the lead storage battery 71 has transitioned to the third state, and instructs the ECU 50 to lower the output of the ISG 30 to the third voltage. That is, the charge / discharge control unit 83 completes the charging of the in-vehicle power supply unit 70 and reduces the output voltage of the ISG 30 so that the lead storage battery 71 and the auxiliary battery 72 can be discharged.
  • a voltage of 12 to 13 V can be employed as the third voltage.
  • the communication unit 84 outputs an instruction to the ECU 50 and battery state information received from the charge / discharge control unit 83 to the ECU 50.
  • the storage unit 85 is composed of, for example, a nonvolatile rewritable storage device such as a flash ROM, and stores an IV table and first to fourth threshold values.
  • FIG. 3 is an operation flowchart relating to constant voltage charging control of the in-vehicle power supply unit.
  • the charge / discharge control unit 83 starts constant voltage charging for the in-vehicle power supply unit 70, and compares the charge rate SOCn of the auxiliary battery 72 with the first threshold value (S10). If the charging rate SOCn of the auxiliary battery 72 is smaller than the first threshold value (Y in S10), the charge / discharge control unit 83 instructs the ECU 50 to increase the output voltage of the ISG 30 to the first voltage (S11). ).
  • the charging / discharging control unit 83 compares the charging rate SOCn of the auxiliary battery 72 with the second threshold value (S12). If the charging rate SOCn of the auxiliary battery 72 is larger than the second threshold value (Y of S12), charging / discharging. Control unit 83 compares charge rate SOCp of lead storage battery 71 with the third threshold value (S13). If the charge rate SOCp of the lead storage battery 71 is equal to or less than the third threshold value (N in S13), the charge / discharge control unit 83 instructs the ECU 50 to lower the output voltage of the ISG 30 to the second voltage. On the other hand, if the charge rate SOCp of the lead storage battery 71 is greater than the third threshold (Y in S13), the charge / discharge control unit 83 ends the constant voltage charging for the in-vehicle power supply unit 70.
  • the charging / discharging control unit 83 when the charging state of the auxiliary battery 72 transitions to the first charging state, applies the first voltage to the in-vehicle power source unit 70 to the in-vehicle power source unit 70. The first process of charging at a constant voltage is executed.
  • the charging / discharging control unit 83 applies the second voltage to the in-vehicle power supply unit 70, stops charging the auxiliary battery 72, and the auxiliary battery The 2nd process which discharges to the electrical equipment load 40 etc. from 72 is performed.
  • the charge / discharge control unit 83 repeats the first process and the second process until the state of charge of the lead storage battery 71 transitions to the third state of charge. For this reason, since it is possible to perform constant voltage charging on the lead storage battery 71 at a high voltage while preventing the auxiliary batteries 72 connected in parallel from being overcharged, it is possible to suppress an increase in the required charging time, and as a result, lead A decrease in charging efficiency for the storage battery 71 can be suppressed. Moreover, it is not necessary to insert a switch between the lead storage battery 71 and the auxiliary battery 72, and the connection configuration of the lead storage battery 71 and the auxiliary battery 72 can be simplified and reduced in cost.
  • the detection unit 82 detects the charging rate SOCp of the lead storage battery 71 as the charging state of the lead storage battery 71, and detects the charging rate SOCn of the auxiliary battery 72 as the charging state of the auxiliary battery 72.
  • the charge / discharge control unit 83 determines that the charging state of the auxiliary battery 72 has transitioned to the first charging state, and the charging rate SOCn of the auxiliary battery 72 is When it becomes larger than the second threshold value, it is determined that the charging state of the auxiliary battery 72 has transitioned to the second charging state, and when the charging rate SOCp of the lead storage battery 71 becomes larger than the third threshold value, the charging state of the lead storage battery 71 Is determined to have transitioned to the third charging state.
  • the detection unit 82 detects the open circuit voltage OCVp of the lead storage battery 71 corresponding to the state of charge of the lead storage battery 71.
  • the charge / discharge control unit 83 sets the second voltage to be lower than the first voltage and higher than the open circuit voltage OCVp of the lead storage battery 71. At that time, the discharge voltage from the lead storage battery 71 can be reduced by setting the second voltage in the vicinity of the open circuit voltage OCVp of the lead storage battery 71.
  • the discharge current from the lead storage battery 71 can be made zero by setting it higher than the open circuit voltage OCVp of the lead storage battery 71.
  • the charge rate SOCp of the lead storage battery 71 is maintained almost as it is, and the SOCn of the auxiliary battery 72 is decreased, so that it is possible to suppress an increase in the time required for charging the lead storage battery 71.
  • the charge / discharge control unit 83 adjusts the output voltage of the ISG 30 via the ECU 50 so that the first voltage and the second voltage are applied to the in-vehicle power supply unit 70, voltage adjustment when performing constant voltage charging is performed. Easy to do. Since the charge / discharge control unit 83 adjusts the output of the ISG 30 via the ECU 50 so that the second voltage is applied to the in-vehicle power supply unit 70, the discharge from the auxiliary battery 72 to the electrical load 40 can be simplified.
  • the example in which the first to fourth threshold values are fixed has been described.
  • the surface temperature and deterioration state of each of the lead storage battery 71 and the auxiliary battery 72 may be detected, and the first to fourth threshold values may be corrected according to the detected surface temperature and deterioration state.
  • the ECU 50 may be configured to include each functional block of the power control unit 80, and the power control unit 80 may be omitted.
  • An in-vehicle power supply unit having a lead storage battery and an auxiliary battery connected in parallel with the lead storage battery, a detection unit for detecting a charge state of the lead storage battery and a charge state of the auxiliary battery, and a charge state of the auxiliary battery are
  • a first voltage is applied to the in-vehicle power source unit to start constant voltage charging for the in-vehicle power source unit, and the charging state of the auxiliary battery is
  • a first process for transitioning to a second charging state in which charging of the auxiliary battery is to be stopped is performed.
  • the detection unit detects a charge rate of the lead storage battery as a charge state of the lead storage battery, detects a charge rate of the auxiliary battery as a charge state of the auxiliary battery, and the charge / discharge control unit detects the charge rate of the auxiliary battery.
  • the charging rate of the auxiliary battery becomes smaller than the first threshold, it is determined that the charging state of the auxiliary battery has transitioned to the first charging state, and when the charging rate of the auxiliary battery becomes larger than the second threshold, When it is determined that the charging state of the auxiliary battery has transitioned to the second charging state, and the charging rate of the lead storage battery is greater than a third threshold value, it is determined that the charging state of the lead storage battery has transitioned to the third charging state.
  • the on-vehicle power storage system according to Item 1.
  • the detection unit detects an open voltage of the lead storage battery corresponding to a state of charge of the lead storage battery, The charge / discharge control unit sets the second voltage to be lower than the first voltage and to be equal to or higher than an open voltage of the lead storage battery.
  • Item 3. The in-vehicle power storage system according to Item 2.
  • the charge / discharge control unit adjusts an output voltage of a generator connected in parallel to the in-vehicle power source unit so that the first voltage and the second voltage are applied to the in-vehicle power source unit.
  • the charging / discharging control unit discharges the auxiliary battery from the auxiliary battery connected in parallel to the in-vehicle power supply unit, and changes the charging state of the auxiliary battery to the second state so that the output voltage of the generator is changed.
  • the in-vehicle power storage system according to item 4, wherein the power storage system is adjusted.
  • the in-vehicle power storage system according to the present invention is useful for an electric vehicle having an idling stop function and an energy regeneration function.
  • Engine 20 Starter motor 30 ISG 40 Electrical load 50 ECU DESCRIPTION OF SYMBOLS 51 ISG control part 52 Communication part 60 Vehicle-mounted electrical storage system 70 Vehicle-mounted power supply part 71 Lead storage battery 72 Auxiliary battery 73 Current sensor 74 Current sensor 75 Voltage sensor 80 Power supply control part 81 Acquisition part 82 Detection part 83 Charging / discharging control part 84 Communication part 85 memory

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Abstract

　充放電制御部は、補助電池の充電状態が第１充電状態に遷移すると、車載用電源部に第１電圧を印加し、車載用電源部に対して定電圧充電する第１処理を実行する。充放電制御部は、補助電池の充電状態が第１充電状態に遷移すると、車載用電源部に対して第２電圧を印加し、補助電池に対する充電を停止し、かつ、補助電池から電装負荷などに放電させる第２処理を実行する。充放電制御部は、鉛蓄電池の充電状態が第３充電状態に遷移するまで第１処理と第２処理を繰り返す。

Description

車載用蓄電システム
　本発明は、車両のスタータモータや電装負荷に電力を供給する車載用蓄電システムに関する。
　車両のスタータモータや電装負荷に電力を供給する車載用蓄電システムには、鉛蓄電池が一般的に用いられる。鉛蓄電池は、エネルギー密度などの電気特性が異なるニッケル水素電池に比べ、安価であるものの、深い充放電を繰り返すと劣化が進行しやすく、高いＳＯＣ（Ｓｔａｔｅ Ｏｆ Ｃｈａｒｇｅ、充電率とも言う）に維持することが望まれる。近年、燃費の向上のため、車両にアイドルストップ機能やエネルギー回生機能を搭載した車両が普及しつつあるが、これら機能を実現するためには深い充放電が必要となり、鉛蓄電池のみでは、高いＳＯＣに維持することが困難な場合がある。そこで、従来のある方法では、鉛蓄電池にスイッチを介して高エネルギー密度のニッケル水素電池を並列接続して車載用蓄電システムを構成している（下記特許文献１参照）。
特開２００４－３２８９８８号公報
　ところで、並列接続された鉛蓄電池とニッケル水素電池を定電圧充電する場合、ニッケル水素電池のほうが充電受入性に優れているので、鉛蓄電池より早く満充電状態に到達することが多い。ニッケル水素電池が満充電状態に到達した後、鉛蓄電池の充電を継続するには、並列接続されたニッケル水素電池が過充電状態にならないように充電電圧を調整する必要がある。このため、ニッケル水素電池が満充電状態に到達した後は、所望電圧による鉛蓄電池の定電圧充電を実行できないこともあり、鉛蓄電池の充電効率が低下する恐れもある。
　そこで本発明は、並列接続されたニッケル水素電池などの二次電池の補助電池が満充電状態に到達した後、充電効率の低下を抑制しながら、鉛蓄電池を定電圧充電することが可能な車載用蓄電システムを提供することを目的とする。
　本発明に係る車載用蓄電システムは、鉛蓄電池および前記鉛蓄電池と並列接続される補助電池を有する車載用電源部と、前記鉛蓄電池の充電状態および前記補助電池の充電状態を検出する検出部と、前記補助電池の充電状態が、前記補助電池の充電を開始すべき第１充電状態に遷移すると、前記車載用電源部に第１電圧を印加して前記車載用電源部に対する定電圧充電を開始し、前記補助電池の充電状態を、前記補助電池の充電を停止すべき第２充電状態に遷移させる第１処理を実行し、前記補助電池の充電状態が前記第２充電状態に遷移すると、前記定電圧充電を停止し、前記車載用電源部に、前記第１電圧より低い第２電圧を印加して前記補助電池を第１充電状態に遷移させる第２処理を実行し、前記鉛蓄電池の充電状態が、前記鉛蓄電池の充電を停止すべき第３充電状態に遷移するまで、前記第１処理と前記第２処理を繰り返す充放電制御部と、を備える。
　本発明によれば、並列接続されたニッケル水素電池などの補助電池が満充電状態に到達した後、充電効率の低下を抑制しながら、鉛蓄電池を定電圧充電することが可能な車載用蓄電システムを提供することが可能である。
図1は本発明の実施形態に係る車両用蓄電システムが搭載された車両を説明するための図である。 図２は本発明の実施形態に係る車載用電源部の鉛蓄電池と補助電池それぞれの充電率の時間的推移を説明するための図である。 図３は車載用電源部の定電圧充電制御に関わる動作フローチャートである。
　本発明の実施形態を具体的に説明する前に概要について述べる。無負荷時の蓄電池の端子電圧は、ＯＣＶ（Ｏｐｅｎ Ｃｉｒｃｕｉｔ Ｖｏｌｔａｇｅ、開放電圧とも言う）と呼ばれる。一方、充電時又は放電時の蓄電池の端子電圧は、ＣＣＶ（Ｃｌｏｓｅｄ Ｃｉｒｃｕｉｔ Ｖｏｌｔａｇｅ、閉路電圧とも言う）と呼ばれる。蓄電池に流れる電流をＩｄとし内部抵抗をＲｄとすると、ＯＣＶとＣＣＶは下記（１）式で表される関係を有する。
　ＣＣＶ＝ＯＣＶ±Ｉｄ×Ｒｄ　　・・・（１）
　ここで、＋は充電、―は放電を示す。また、Ｉｄ×Ｒｄは分極電圧と呼ばれる。分極電圧は、放電時においてＯＣＶを降下させ、充電時はＯＣＶを上昇させる。
　定格電圧が１２Ｖの鉛蓄電池に対して定電圧充電を行う場合、鉛蓄電池のＣＣＶが１３．５Ｖから１４．５Ｖになるように電圧を印加することが多い。（１）式から明らかなように、ＣＣＶとＯＣＶとの差が大きくなるほど、また内部抵抗が小さくなるほど充電電流が大きくなる。つまり、高い電圧を印加するほど定電圧充電の所要時間を短縮化できる。
　しかしながら、鉛蓄電池に並列接続されたニッケル水素電池が満充電状態になった後も、例えば、１４．５Ｖの高い電圧を印加したまま定電圧充電を継続すると、ニッケル水素電池が過充電状態になる恐れがある。一方、ニッケル水素電池が過充電状態にならない電圧を印加して鉛蓄電池の定電圧充電を行うと、定電圧充電の所要時間が長くなる。鉛蓄電池は、劣化の進行を抑制するため、高いＳＯＣの範囲内（例えば、８０％以上）で充放電を行う必要があり、充電時のＯＣＶや内部抵抗が高い。そのため、鉛蓄電池に対して定電圧充電を行うときのＣＣＶが低くなると、充電電流が小さくなるから定電圧充電の所要時間が長くなる。鉛蓄電池に対する定電圧充電の所要時間が長くなると充電効率が低下するとも言え、鉛蓄電池に並列接続されたニッケル水素電池が満充電状態になった後も高い電圧を印加したまま定電圧充電を継続することが望まれる。
　そこで本発明の実施形態に係る車両用蓄電システムは、例えば、１４．５Ｖの高い電圧を印加して定電圧充電を実行し、充電必要状態にあるニッケル水素電池を満充電状態に遷移させる第１処理と、鉛蓄電池に印加する電圧を第１電圧より低く、かつ、鉛蓄電池のＯＣＶより高い第２電圧に変更し、満充電状態にあるニッケル水素電池を充電必要状態に遷移させる第２処理を交互に繰り返す。これにより、並列接続されたニッケル水素電池を過充電状態にすることなく、高い電圧を印加して鉛蓄電池の定電圧充電を実現できるので、鉛蓄電池に対する充電効率の低下を抑制できる。
　図１は、本実施形態に係る車載用蓄電システム６０が搭載された車両１を説明するための図である。車両１は、エンジンを主たる動力源とし、モータを補助的動力源とするハイブリッド自動車（Ｈｙｂｒｉｄ　Ｅｌｅｃｔｒｉｃ　Ｖｅｈｉｃｌｅ）を想定する。車両１は、エンジン１０、スタータモータ２０、ＩＳＧ（Ｉｎｔｅｇｒａｔｅｄ　Ｓｔａｒｔｅｒ　Ｇｅｎｅｒａｔｏｒ）３０、電装負荷４０、ＥＣＵ（Ｅｌｅｃｔｒｏｎｉｃ Ｃｏｎｔｒｏｌ Ｕｎｉｔ、電子制御ユニットとも言う）５０、および車載用蓄電システム６０を備える。車載用蓄電システム６０は、スタータモータ２０、ＩＳＧ３０、および電装負荷４０に電力を供給する車載用電源部７０と、鉛蓄電池７１の電圧値などを計測したり、車載用電源部７０の充放電制御を行う電源制御部８０を備える。スタータモータ２０、ＩＳＧ３０、および電装負荷４０は、車載用電源部７０と並列に接続される。
　スタータモータ２０は、ユーザによりイグニションスイッチが操作されるとエンジン１０を始動する。ＩＳＧ３０は、発電機能と電動機能とを兼有する。車両１が走行中に図示しないブレーキペダルが操作されて減速を開始すると、車輪からＩＳＧ３０にトルクが伝えられ、ＩＳＧ３０は、発電機能により発電する。ＩＳＧ３０の発電電力が電装負荷４０の消費電力を超える場合、その超過分が車載用電源部７０に充電される。これによって、エネルギーの回生が行われる。なお、電動機能が必要ない場合、ＩＳＧ３０を発電機能のみ有するオルタネータに置き換えることもできる。
　車両１が停止すると、ＥＣＵ５０のアイドルストップ制御によって、エンジン１０が自動停止する。車両１の発進時には、ＩＳＧ３０の電動機能により、車両１が駆動され、かつ、エンジン１０が始動される。また、車両１が走行中に図示しないアクセルペタルが操作されると、ＥＣＵ５０のアシスト制御によって、エンジン１０とＩＳＧ３０との間でトルクが配分される。ＩＳＧ３０は、配分されたトルクを電動機能により発生し、車両１をエンジン１０とともに駆動する。
　電装負荷４０は、例えば空気調和機及び室内灯等、車両１に装備された電装品等の負荷を含む。車載用電源部７０から供給される電力は、電装負荷４０の電源に使用される。
　ＥＣＵ５０は、例えば、所定の演算処理を実行するＣＰＵ（Ｃｅｎｔｒａｌ　Ｐｒｏｃｅｓｓｉｎｇ　Ｕｎｉｔ）、所定の制御プログラムが保存されたＲＯＭ（Ｒｅａｄ　Ｏｎｌｙ　Ｍｅｍｏｒｙ）、データを一時的に保存するＲＡＭ（Ｒａｎｄｏｍ　Ａｃｃｅｓｓ　Ｍｅｍｏｒｙ）、これらの周辺回路等を備える。ＥＣＵ５０は、電源制御部８０と互いに通信可能に構成される。ＥＣＵ５０は、エンジン１０、スタータモータ２０、ＩＳＧ３０、および電装負荷４０を含む車両１の全体の動作を制御する。例えば、ＥＣＵ５０は、車両１が交差点等で所定時間停止する等の所定の停止条件を満たすとエンジン１０を自動停止し、かつ、図示しないブレーキペダルの操作解除等の所定の始動条件を満たすと再びエンジン１０を始動するアイドルストップ制御を行う。ＥＣＵ５０は、アイドルストップ制御等を行う際、適宜、電源制御部８０から受け取った、鉛蓄電池７１の電圧値などが含まれる電池状態情報を参照する。例えば、ＥＣＵ５０は、電池状態情報に基づき、車載用電源部７０の残容量が少なくアイドルストップ状態からエンジン１０を再始動させる際に、ＩＳＧ３０へ十分な電力を供給できないと判断すると、アイドルストップ状態への移行を禁止する。
　ＩＳＧ制御部５１は、電源制御部８０の指示に基づき、ＩＳＧ３０の発電機能を制御する。ＩＳＧ制御部５１は、ＩＳＧ３０の図示しないロータコイルの励磁電流を制御してＩＳＧ３０の出力電圧を制御する。電源制御部８０よりＩＳＧ３０の出力電圧を高くするように指示されると、ＩＳＧ制御部５１は、ロータコイルの励磁電流を大きくする。一方、電源制御部８０よりＩＳＧ３０の出力電圧を低くするように指示されると、ＩＳＧ制御部５１は、ロータコイルの励磁電流を小さくする。通信部５２は、ＣＡＮ（Ｃｏｎｔｒｏｌｌｅｒ Ａｒｅａ Ｎｅｔｗｏｒｋ）などのネットワークを介して電源制御部８０との間で通信するための信号処理（例えば、フレームの形成や差動伝送方式への変換）を行う。通信部５２は、電源制御部８０から受け取った電池状態情報をＩＳＧ制御部５１に出力する。
　車載用電源部７０は、定格電圧を１２Ｖとする鉛蓄電池７１と、鉛蓄電池７１とエネルギー密度などの電気特性が異なり、鉛蓄電池７１と並列に接続された補助電池７２を含む。本実施形態に係る車載用電源部７０は、補助電池７２として鉛蓄電池７１よりエネルギー密度の高いニッケル水素電池を利用することを想定する。ニッケル水素電池の定格電圧は１．２Ｖ／セルである。したがって、補助電池７２は、直列接続された１０個のニッケル水素電池を含む。なお、補助電池７２は、例えばリチウムイオン電池等の二次電池やキャパシタ等を用いても実現できる。
　車載用電源部７０は、鉛蓄電池７１に直列に接続され、鉛蓄電池７１に流れる電流の値を検出する電流センサ７３と、補助電池７２に直列に接続され、補助電池７２に流れる電流の値を検出する電流センサ７４を含む。電流センサ７３、７４は、例えば、シャント抵抗で構成される。また、車載用電源部７０は、鉛蓄電池７１および補助電池７２に並列に接続され、並列接続された鉛蓄電池７１および補助電池７２の端子電圧の値を検出する電圧センサ７５を含む。
　電源制御部８０は、例えば、所定の演算処理を実行するＣＰＵ、所定の制御プログラムが保存されたＲＯＭ、データを一時的に保存するＲＡＭ、これらの周辺回路等を備える。電源制御部８０は、取得部８１、検出部８２、充放電制御部８３、通信部８４、および記憶部８５を含む。
　取得部８１は、電流センサ７３から受け取った電流の値をＡＤ変換し、デジタル化された電流値（Ｉｐ、第１電流値とも言う）を求め、検出部８２に出力する。同様に、取得部８１は、電流センサ７４から受け取った電流の値からデジタル化された電流値（Ｉｎ、第２電流値とも言う）を求め、検出部８２に出力する。また、取得部８１は、電圧センサ７５から受け取った端子電圧の値をＡＤ変換し、デジタル化された電圧値（Ｖｏ、全体電圧値とも言う）を求め、検出部８２に出力する。
　検出部８２は、例えば、取得部８１から受け取った第１電流値Ｉｐを積算し、鉛蓄電池７１の充電率（ＳＯＣｐ）を検出する。同様に、検出部８２は、取得部８１から受け取った第２電流値Ｉｎを積算し、補助電池７２の充電率（ＳＯＣｎ）を検出する。
　また、検出部８２は、例えば、鉛蓄電池７１の端子電圧と鉛蓄電池７１に流れる電流との対応関係を示すＩ－Ｖテーブルを参照し、取得部８１から受け取った全体電圧値Ｖｏと第１電流値Ｉｐに基づき、鉛蓄電池７１の内部抵抗（Ｒｐ）を検出する。同様に、検出部８２は、取得部８１から受け取った全体電圧値Ｖｏと第２電流値Ｉｎに基づき、補助電池７２の内部抵抗（Ｒｎ）を検出する。また、検出部８２は、例えば、取得部８１から受け取った全体電圧値Ｖｏ、第１電流値Ｉｐ、および検出した内部抵抗Ｒｐを（１）式に代入し、鉛蓄電池７１の充電率ＳＯＣｐに対応する鉛蓄電池７１の開放電圧（ＯＣＶｐ）を検出する。検出部８２は、取得部８１から受け取った第１電流値Ｉｐなどと算出した充電率ＳＯＣｐなどから電池状態情報を構成し、充放電制御部８３に出力する。
　充放電制御部８３は、検出部８２から受け取った電池状態情報に基づき、通信部８４を介してＥＣＵ５０に指示を送り、ＩＳＧ３０の出力電圧を調整して車載用電源部７０の充放電を制御する。電装負荷４０などへの放電により、鉛蓄電池７１の充電率ＳＯＣｐおよび補助電池７２の充電率ＳＯＣｎがそれぞれの制御目標範囲の下限より低くなると、充放電制御部８３は、ＥＣＵ５０に対してＩＳＧ３０の出力電圧を上げるように指示し、車載用電源部７０からの放電を制限する。
　他方、ＩＳＧ３０からの充電により、鉛蓄電池７１の充電率ＳＯＣｐおよび補助電池７２の充電率ＳＯＣｎがそれぞれの制御目標範囲の上限より高くなると、充放電制御部８３は、ＥＣＵ５０に対してＩＳＧ３０の出力電圧を下げるように指示し、車載用電源部７０への充電を制限する。
　説明の便宜上、以下では、鉛蓄電池７１の充電率の制御目標範囲（第１制御目標範囲とも言う）は８０％から９５％を想定し、補助電池７２の充電率の制御目標範囲（第２制御目標範囲とも言う）は２０％から１００％を想定するが、これら範囲に限定されない。
　充放電制御部８３は、補助電池７２の充電率の関するしきい値を参照し、補助電池７２の充電状態を判断する。具体的に説明すると、充放電制御部８３は、補助電池７２の充電率ＳＯＣｎが、第１しきい値より小さいと、充電を開始すべき充電状態（第１充電状態とも言う）にあると判断する。充放電制御部８３は、補助電池７２の充電率ＳＯＣｎが、第２しきい値より大きいと、充電を停止すべき充電状態（第２充電状態とも言う）にあると判断する。ここで、第１しきい値として、第２制御目標範囲の下限値（２０％）を採用することができ、第２しきい値として、第２制御目標範囲の上限値（１００％）を採用することができる。同様に、充放電制御部８３は、鉛蓄電池７１の充電率ＳＯＣｐが、第３しきい値より大きいと、充電を停止すべき充電状態（第３充電状態とも言う）にあると判断する。充放電制御部８３は、鉛蓄電池７１の充電率ＳＯＣｐが、第１しきい値より小さいと、充電を開始すべき充電状態（第４充電状態とも言う）にあると判断する。第３しきい値として、第１制御目標範囲の上限値（９５％）を採用することができ、第４しきい値として、第１制御目標範囲の下限値（８０％）を採用することができる。
　充放電制御部８３は、補助電池７２が第１充電状態にあり、鉛蓄電池７１が第４充電状態にあると判断すると、車載用電源部７０に対して定電圧充電を実行する。図２は、この定電圧充電を行ったときの、鉛蓄電池７１と補助電池７２それぞれの充電率の時間的推移を説明するための図である。ここで、Ｓ１＝５％＜Ｓ２＝３０％＜Ｓ３＝８０％＜Ｓ４＝９５％＜Ｓ５＝１００％である。以下、図２を参照しながら、充放電制御部８３が実行する定電圧充電の具体的な説明を行う。
　タイミングＴ１において、鉛蓄電池７１の充電率ＳＯＣｐが第４しきい値より小さく、補助電池７２の充電率ＳＯＣｎが第１しきい値より小さいものとする。この場合、タイミングＴ１において、充放電制御部８３は、鉛蓄電池７１は第１充電状態にあり、補助電池７２は第４充電状態にあると判断する。すると、充放電制御部８３は、ＩＳＧ３０の出力電圧を、第１電圧まで高くするようにＥＣＵ５０に対して指示を行う。すなわち、充放電制御部８３は、車載用電源部７０に対して第１電圧を印加し、定電圧充電する処理を行う（第１処理とも言う）。ここで、第１電圧として、例えば、１４．５Ｖを採用することができる。
　鉛蓄電池７１の充電率ＳＯＣｐと補助電池７２の充電率ＳＯＣｎはともに増加するが、補助電池７２の充電受入性は鉛蓄電池７１より優れているため、図２に示すように、単位時間当たりの充電率の上昇度は、補助電池７２のほうが大きくなる。このため、タイミングＴ２において、補助電池７２の充電率ＳＯＣｎは第２しきい値より大きくなる。すると、充放電制御部８３は、補助電池７２の充電状態が第１充電状態から第２充電状態に遷移したと判断し、ＩＳＧ３０の出力を、第２電圧まで低くするようにＥＣＵ５０に対して指示を行う。すなわち、充放電制御部８３は、車載用電源部７０に対して第２電圧を印加し、補助電池７２から電装負荷４０などに放電させる処理を行う（第２処理とも言う）。ここで、第２電圧は、第１電圧より低く、タイミングＴ２における鉛蓄電池７１の充電率に対応する開放電圧ＯＣＶｐ以上の範囲（電圧範囲とも言う）に含まれる電圧が採用される。
　ＩＳＧ３０の出力電圧を第２電圧まで低くする理由は、第１電圧による定電圧充電を継続すると補助電池７２が過充電となるので、一時的に、補助電池７２の充電率ＳＯＣｎを下げるためである。定電圧充電の所要時間を短縮化するためには、補助電池７２からの放電が多くなり、鉛蓄電池７１からの放電が少なくなる電圧、つまり、電圧範囲のうち鉛蓄電池７１の開放電圧ＯＣＶｐにできるだけ近い電圧を第２電圧として採用することが好ましい。鉛蓄電池７１の開放電圧ＯＣＶｐに近い電圧であれば、第２電圧は、開放電圧ＯＣＶｐより高くてもよく、低くてもよい。第２電圧は、第１電流値Ｉｐを参照しながらＩＳＧ３０の出力電圧を調整し、鉛蓄電池７１の第１電流値Ｉｐがゼロになるときの電圧が採用されてもよい。第２電圧は、第１電流Ｉｐがゼロでなくても、所定値（例えば、５Ａ）より小さい場合の電圧が採用されてもよい。所定値は、第１電流Ｉｐが、補助電池７２の第２電流値Ｉｎに定格容量比（鉛蓄電池７１の定格容量／補助電池７２の定格容量）を乗じて算出した値より十分小さくなる値（例えば、１／２０より小さくなる値）に基づき設定することができる。第１電流Ｉｐが所定値より小さければ、鉛蓄電池７１の充電率ＳＯＣｐはほとんど減少せず、主に補助電池７２の充電率ＳＯＣｎが減少することになる。結果、定電圧充電の所要時間を短縮化できる。
　車載用電源部７０に対して第２電圧を印加することで、図２に示すように、補助電池７２の充電率ＳＯＣｎは減少し、鉛蓄電池７１の充電率ＳＯＣｐはほぼそのまま維持される。このため、タイミングＴ３において、補助電池７２の充電率ＳＯＣｐは第１しきい値より小さくなる。すると、充放電制御部８３は、補助電池７２の充電状態が第２充電状態から第１充電状態に遷移したと判断し、ＩＳＧ３０の出力電圧を、第１電圧まで高くするようにＥＣＵ５０に対して指示を行う。すなわち、充放電制御部８３は、第１処理を実行する。
　以降、充放電制御部８３は、補助電池７２の充電状態が第１充電状態から第２状態に遷移したと判断すると第２処理を実行し、第２充電状態から第１充電状態に遷移したと判断すると第１処理を実行する。つまり、充放電制御部８３は、補助電池７２の充電状態が遷移するごとに、第１処理と第２処理を繰り返す。
　これにより、タイミングＴ８において、鉛蓄電池７１の充電率ＳＯＣｐが第３しきい値より大きくなる。すると、充放電制御部８３は、鉛蓄電池７１の充電状態が第３状態に遷移したと判断し、ＩＳＧ３０の出力を、第３電圧まで低くするようにＥＣＵ５０に対して指示を行う。すなわち、充放電制御部８３は、車載用電源部７０に対する充電を完了し、鉛蓄電池７１および補助電池７２それぞれが放電可能になるように、ＩＳＧ３０の出力電圧を下げる。ここで、第３電圧として、例えば、１２～１３Ｖの電圧を採用することができる。
　図１に戻る。通信部８４は、充放電制御部８３から受け取ったＥＣＵ５０に対する指示や電池状態情報をＥＣＵ５０に出力する。記憶部８５は、例えば、フラッシュＲＯＭ等の不揮発性の書き換え可能な記憶装置で構成され、Ｉ－Ｖテーブルや第１～４しきい値を記憶する。
　以上の構成による車載用蓄電システム６０の動作を説明する。図３は、車載用電源部の定電圧充電制御に関わる動作フローチャートである。充放電制御部８３は、車載用電源部７０に対する定電圧充電を開始し、補助電池７２の充電率ＳＯＣｎを第１しきい値と比較する（Ｓ１０）。補助電池７２の充電率ＳＯＣｎが第１しきい値より小さければ（Ｓ１０のＹ）、充放電制御部８３は、ＩＳＧ３０の出力電圧を第１電圧まで高くするようにＥＣＵ５０に対して指示する（Ｓ１１）。充放電制御部８３は、補助電池７２の充電率ＳＯＣｎを第２しきい値と比較する（Ｓ１２）補助電池７２の充電率ＳＯＣｎが第２しきい値より大きければ（Ｓ１２のＹ）、充放電制御部８３は、鉛蓄電池７１の充電率ＳＯＣｐを第３しきい値と比較する（Ｓ１３）。鉛蓄電池７１の充電率ＳＯＣｐが第３しきい値以下であれば（Ｓ１３のＮ）、充放電制御部８３は、ＩＳＧ３０の出力電圧を第２電圧まで低くするようにＥＣＵ５０に対して指示する。他方、鉛蓄電池７１の充電率ＳＯＣｐが第３しきいより大きければ（Ｓ１３のＹ）、充放電制御部８３は、車載用電源部７０に対する定電圧充電を終了する。
　　本発明の実施形態によれば、充放電制御部８３は、補助電池７２の充電状態が第１充電状態に遷移すると、車載用電源部７０に第１電圧を印加し、車載用電源部７０対して定電圧充電する第１処理を実行する。充放電制御部８３は、補助電池７２の充電状態が第１充電状態に遷移すると、車載用電源部７０に対して第２電圧を印加し、補助電池７２に対する充電を停止し、かつ、補助電池７２から電装負荷４０などに放電させる第２処理を実行する。充放電制御部８３は、鉛蓄電池７１の充電状態が第３充電状態に遷移するまで第１処理と第２処理を繰り返す。このため、並列接続された補助電池７２が過充電になることを防止しながら、鉛蓄電池７１に対する定電圧充電を高い電圧で実行できるので、充電所要時間が長くなることを抑制でき、結果として鉛蓄電池７１に対する充電効率の低下を抑制できる。また、鉛蓄電池７１と補助電池７２との間にスイッチを挿入する必要がなくなり、鉛蓄電池７１と補助電池７２の接続構成を簡易、低コスト化できる。また、補助電池７２の過充電を防止するためスイッチを開放する必要がなくなり、スイッチ開放時の動作音を起因とする利用者の不快感を解消でき、スイッチの開閉に伴う電気的なノイズの発生を抑制できる。検出部８２は、鉛蓄電池７１の充電状態として鉛蓄電池７１の充電率ＳＯＣｐを検出し、補助電池７２の充電状態として補助電池７２の充電率ＳＯＣｎを検出する。充放電制御部８３は、補助電池７２の充電率ＳＯＣｎが第１しきい値より小さくなると、補助電池７２の充電状態が第１充電状態に遷移したと判断し、補助電池７２の充電率ＳＯＣｎが第２しきい値より大きくなると、補助電池７２の充電状態が第２充電状態に遷移したと判断し、鉛蓄電池７１の充電率ＳＯＣｐが第３しきい値より大きくなると、鉛蓄電池７１の充電状態が第３充電状態に遷移したと判断する。このため、鉛蓄電池７１と補助電池７２の充電状態に応じた充放電制御を実現でき、鉛蓄電池７１や補助電池７２が過充電状態あるいは過放電状態となることを確実に防止できる。検出部８２は、鉛蓄電池７１の充電状態に対応する鉛蓄電池７１の開放電圧ＯＣＶｐを検出する。充放電制御部８３は、第２電圧を第１電圧より低く、かつ、鉛蓄電池７１の開放電圧ＯＣＶｐより高くなるように設定する。その際に、第２電圧を鉛蓄電池７１の開放電圧ＯＣＶｐ近傍に設定することで、鉛蓄電池７１からの放電電流を小さくできる。鉛蓄電池７１の開放電圧ＯＣＶｐより高く設定することで、鉛蓄電池７１からの放電電流をゼロにできる。結果、第２処理において鉛蓄電池７１の充電率ＳＯＣｐはほぼそのまま維持され、補助電池７２のＳＯＣｎは減少することになるので、鉛蓄電池７１に対する充電所要時間が長くなることを抑制できる。充放電制御部８３は、第１電圧および第２電圧が車載用電源部７０に印加されるようにＥＣＵ５０を介してＩＳＧ３０の出力電圧を調整するので、定電圧充電を実行する際の電圧調整が簡単にできる。充放電制御部８３は、車載用電源部７０に第２電圧が印加されるようにＥＣＵ５０を介してＩＳＧ３０の出力を調整するので、補助電池７２から電装負荷４０などへの放電を簡単にできる。
　以上、本発明を実施の形態をもとに説明した。この実施の形態は例示であり、それらの各構成要素や各処理プロセスの組み合わせにいろいろな変形例が可能なこと、またそうした変形例も本発明の範囲にあることは当業者に理解されるところである。
　上述の実施の形態では第１～４しきい値を固定する例を説明した。この点、鉛蓄電池７１および補助電池７２それぞれの表面温度や劣化状態を検出し、検出した表面温度や劣化状態に応じて第１～４しきい値を補正してもよい。
　また、上述の実施の形態では車両１は、ＥＣＵ５０とは別に、電源制御部８０を備えている例を説明した。この点、ＥＣＵ５０が、電源制御部８０の各機能ブロックを備えるように構成して、電源制御部８０をなくしてもよい。
　なお、本実施の形態に係る発明は、以下に記載する項目によって特定されてもよい。
［項目１］
　鉛蓄電池および前記鉛蓄電池と並列接続される補助電池を有する車載用電源部と、前記鉛蓄電池の充電状態および前記補助電池の充電状態を検出する検出部と、前記補助電池の充電状態が、前記補助電池の充電を開始すべき第１充電状態に遷移すると、前記車載用電源部に第１電圧を印加して前記車載用電源部に対する定電圧充電を開始し、前記補助電池の充電状態を、前記補助電池の充電を停止すべき第２充電状態に遷移させる第１処理を実行し、前記補助電池の充電状態が前記第２充電状態に遷移すると、前記定電圧充電を停止し、前記車載用電源部に、前記第１電圧より低い第２電圧を印加して前記補助電池を第１充電状態に遷移させる第２処理を実行し、前記鉛蓄電池の充電状態が、前記鉛蓄電池の充電を停止すべき第３充電状態に遷移するまで、前記第１処理と前記第２処理を繰り返す充放電制御部と、を備える車載用蓄電システム。
［項目２］
　前記検出部は、前記鉛蓄電池の充電状態として前記鉛蓄電池の充電率を検出するとともに、前記補助電池の充電状態として前記補助電池の充電率を検出し、前記充放電制御部は、前記補助電池の充電率が第１しきい値より小さくなると、前記補助電池の充電状態が前記第１充電状態に遷移したと判断するとともに、前記補助電池の充電率が第２しきい値より大きくなると、前記補助電池の充電状態が第２充電状態に遷移したと判断し、前記鉛蓄電池の充電率が第３しきい値より大きくなると、前記鉛蓄電池の充電状態が第３充電状態に遷移したと判断する、項目１に記載の車載用蓄電システム。
［項目３］
　前記検出部は、前記鉛蓄電池の充電状態に対応する前記鉛蓄電池の開放電圧を検出し、
　前記充放電制御部は、前記第２電圧を前記第１電圧より低く、かつ、前記鉛蓄電池の開放電圧以上になるように設定する、
項目２に記載の車載用蓄電システム。
［項目４］
　前記充放電制御部は、前記第１電圧および前記第２電圧が前記車載用電源部に印加されるように、前記車載用電源部に並列接続される発電機の出力電圧を調整する、項目３に記載の車載用蓄電システム。
［項目５］
　前記充放電制御部は、前記補助電池から前記車載用電源部に並列接続される電装負荷に放電させて前記補助電池の充電状態を前記第２状態に遷移させるように、前記発電機の出力電圧を調整する、項目４に記載の車載用蓄電システム。
　本発明に係る車載用蓄電システムは、アイドリングストップ機能やエネルギー回生機能を有する電動車両等に有用である。
　　１０　　エンジン
　　２０　　スタータモータ
　　３０　　ＩＳＧ
　　４０　　電装負荷
　　５０　　ＥＣＵ
　　５１　　ＩＳＧ制御部
　　５２　　通信部
　　６０　　車載用蓄電システム
　　７０　　車載用電源部
　　７１　　鉛蓄電池
　　７２　　補助電池
　　７３　　電流センサ
　　７４　　電流センサ
　　７５　　電圧センサ
　　８０　　電源制御部
　　８１　　取得部
　　８２　　検出部
　　８３　　充放電制御部
　　８４　　通信部
　　８５　　記憶部

Claims (5)

  1. 　鉛蓄電池および前記鉛蓄電池と並列接続される補助電池を有する車載用電源部と、
    　前記鉛蓄電池の充電状態および前記補助電池の充電状態を検出する検出部と、
    　前記補助電池の充電状態が、前記補助電池の充電を開始すべき第１充電状態に遷移すると、前記車載用電源部に第１電圧を印加して前記車載用電源部に対する定電圧充電を開始し、前記補助電池の充電状態を、前記補助電池の充電を停止すべき第２充電状態に遷移させる第１処理を実行し、前記補助電池の充電状態が前記第２充電状態に遷移すると、前記定電圧充電を停止し、前記車載用電源部に、前記第１電圧より低い第２電圧を印加して前記補助電池を前記第１充電状態に遷移させる第２処理を実行し、前記鉛蓄電池の充電状態が、前記鉛蓄電池の充電を停止すべき第３充電状態に遷移するまで、前記第１処理と前記第２処理を繰り返す充放電制御部と、
    　を備える車載用蓄電システム。
  2. 　前記検出部は、前記鉛蓄電池の充電状態として前記鉛蓄電池の充電率を検出するとともに、前記補助電池の充電状態として前記補助電池の充電率を検出し、
    　前記充放電制御部は、前記補助電池の充電率が第１しきい値より小さくなると、前記補助電池の充電状態が前記第１充電状態に遷移したと判断するとともに、前記補助電池の充電率が第２しきい値より大きくなると、前記補助電池の充電状態が前記第２充電状態に遷移したと判断し、前記鉛蓄電池の充電率が第３しきい値より大きくなると、前記鉛蓄電池の充電状態が前記第３充電状態に遷移したと判断する、
    　請求項１に記載の車載用蓄電システム。
  3. 　前記検出部は、前記鉛蓄電池の充電状態に対応する前記鉛蓄電池の開放電圧を検出し、
    　前記充放電制御部は、前記第２電圧を前記第１電圧より低く、かつ、前記鉛蓄電池の開放電圧以上になるように設定する、
    請求項２に記載の車載用蓄電システム。
  4. 　前記充放電制御部は、前記第１電圧および前記第２電圧が前記車載用電源部に印加されるように、前記車載用電源部に並列接続される発電機の出力電圧を調整する、
    　請求項３に記載の車載用蓄電システム。
  5. 　前記充放電制御部は、前記補助電池から前記車載用電源部に並列接続される電装負荷に放電させて前記補助電池の充電状態を前記第２状態に遷移させるように、前記発電機の出力電圧を調整する、
    　請求項４に記載の車載用蓄電システム。
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