Patent Description:
An assembled battery includes a plurality of secondary batteries electrically connected to each other. By combining the secondary batteries, a large-capacity assembled battery can be obtained. However, a full charge capacity (an electricity amount accumulated in the secondary battery at a time of full charging) of a secondary battery decreases as the secondary battery deteriorates. For example, <CIT> discloses a deterioration diagnosis method of a battery, which discharges an assembled battery until its voltage (a voltage between terminals) reaches a predetermined discharging end voltage, and estimates a deterioration degree of the assembled battery using data (a discharging curve) indicating a transition of the voltage of the assembled battery from a discharging start voltage to the discharging end voltage. A differential voltage analysis-based online evaluation method for the state of health (SOH) of a battery is known from <CIT>. There, a delta V/delta Q curve is established, a tangent line of the delta V/delta Q curve is made through a certain delta V/delta Q value at the tail end of the delta V/delta Q curve, the slope of the tangent line is in linear negative correlation with the SOH value of the battery, and the larger the slope is, the smaller the SOH value of the battery is. From <CIT> it is known that, in a lithium ion secondary battery system, when a start terminal battery voltage, an end terminal battery voltage, a start terminal SOC or an end terminal SOC in a charge/discharge cycle of a lithium ion secondary battery is detected or estimated as a singular point appearing on a Q-dV/dQ curve, the start terminal battery voltage, the end terminal battery voltage, the start terminal SOC or the end terminal SOC in the charge/discharge cycle of the lithium ion secondary battery is set to a battery voltage or an SOC avoiding the singular point appearing on the Q-dV/dQ curve. The technology disclosed by <CIT>monitors a storage battery by measuring the end voltage and electric current of a storage battery array formed by connecting in series-parallel a plurality of storage batteries, estimates the maximum number of failures of the storage batteries connected in parallel, and determines the available capacity of the storage battery array. This storage battery array failure diagnosis device is connected to an inverter device, and is provided with: a voltage sensor for measuring the end voltage of the storage battery array; an electric current sensor for measuring the electric current that flows to the storage battery array; an integrator for integrating electric current information that has been detected by the electric current sensor to determine the amount of electric charge; and a failure number estimation unit for determining the amount of electric charge at which the change in a value obtained by differentiating the end voltage by the amount of electric charge becomes slow, or the amount of electric charge at which a value obtained by differentiating the end voltage by the amount of charge twice becomes the minimum value, and estimating the maximum number of parallel failed batteries that have been cut off from the amount of charge. <CIT> finally discloses an apparatus that provides real-time monitoring of voltage and differential voltage of both anode and cathode in a battery configured with at least one reference electrode. There, voltage monitors are connected to a computer programmed for receiving anode voltage signals; receiving cathode voltage signals; calculating the derivative of the anode voltage with respect to time or with respect to capacity; and calculating the derivative of the cathode voltage with respect to time or with respect to capacity.

In the deterioration diagnosis method of the battery described in <CIT>, discharging is ended at a timing at which the voltage between the terminals of the assembled battery reaches the discharging end voltage during the discharging. In such a method, since voltages of some of the secondary batteries included in the assembled battery do not reach the discharging end voltage at the end of the discharging, it is difficult to estimate the deterioration degree of each secondary battery included in the assembled battery. Hereinafter, each secondary battery included in the assembled battery is referred to as a "cell".

Therefore, a deterioration diagnosis method of a battery, which ends the discharging at the timing at which voltages of all the cells included in the assembled battery reach the discharging end voltage, can be considered. However, in such a method, it is required that the discharging end voltage is set to an appropriate magnitude. When the discharging end voltage is too low, some cells included in the assembled battery may be over-discharged during the discharging. The over-discharging of a cell accelerates the deterioration of the cell. On the other hand, when the discharging end voltage is too high, sufficient data cannot be obtained during the discharging, and accuracy of estimating a deterioration degree (for example, a full charge capacity) of a cell may decrease.

The present disclosure provides a deterioration diagnosis apparatus of a battery and a deterioration diagnosis method of a battery that set a discharging end voltage to an appropriate magnitude, and estimate, with sufficient accuracy, a deterioration degree of each cell included in an assembled battery while restricting deterioration of a cell during discharging.

A deterioration diagnosis apparatus of a battery according to a first aspect of the present disclosure as set forth in claim <NUM> includes one or more processors. The one or more processors are configured to execute discharging of each of a plurality of cells included in an assembled battery while measuring a voltage of each of the cells, estimate a deterioration degree of each of the cells included in the assembled battery using voltage data indicating a transition of the voltage of each of the cells included in the assembled battery from a discharging start voltage to a predetermined discharging end voltage, and end the discharging when voltages of all the cells included in the assembled battery reach the predetermined discharging end voltage. The predetermined discharging end voltage is a cell voltage at which a change degree of the cell voltage per unit discharging amount starts to sharply rise while the cell voltage is dropping due to the discharging.

In the deterioration diagnosis apparatus of the assembled battery, since the discharging is continued until the voltages of all the cells included in the assembled battery reach the discharging end voltage, it is possible to estimate the deterioration degree of each cell included in the assembled battery using the voltage data indicating the transition of the voltage of each cell included in the assembled battery from the discharging start voltage to the discharging end voltage. Further, in the deterioration diagnosis apparatus of the assembled battery, as described below, the discharging end voltage is set to an appropriate magnitude. Hereinafter, the change degree (an absolute value) of the cell voltage per unit discharging amount is expressed by " |ΔV/ΔQ|". The discharging amount corresponds to a time integral value of a discharging current. The cell is a secondary battery composing the assembled battery. The assembled battery is composed of a plurality of cells electrically connected to each other.

The cell voltage drops during the discharging of the cell. At an initial stage of the discharging, |ΔV/ΔQ| is substantially constant. At a final stage of the discharging, |ΔV/ΔQ| sharply rises due to an increase in reaction resistance. Specifically, |ΔV/ΔQ| starts to sharply rise immediately after the cell voltage reaches a predetermined voltage (hereinafter, also referred to as "a voltage at a change point") during the discharging of the cell. Basically, the accuracy of the deterioration diagnosis becomes higher and the deterioration of the cell becomes easier as a period during which the discharging of the cell is continued is longer. Before |ΔV/ΔQ| starts to sharply rise, by continuing the discharging of the cell, a merit of improving the accuracy of the diagnosis is larger than a demerit of easy deterioration of the cell. On the other hand, after |ΔV/ΔQ| starts to sharply rise, by continuing the discharging of the cell, the demerit of easy deterioration of the cell is larger than the merit of improving the accuracy of the diagnosis. Therefore, by setting, as the discharging end voltage, the cell voltage at which the change degree of the cell voltage per unit discharging amount starts to sharply rise while the cell voltage is dropping due to the discharging, it is possible to promote both ensuring sufficient diagnostic accuracy and restricting deterioration of the cell. As such, with the above configuration, it is possible to estimate, with sufficient accuracy, the deterioration degree of each cell included in the assembled battery while restricting the deterioration of the cell during the discharging.

The voltage at the change point may be a cell voltage at which the change degree of the cell voltage per unit discharging amount is the lowest during the discharging. At the final stage of the discharging of the cell, |ΔV/ΔQ| tends to lower once and then starts to sharply rise. The discharging end voltage may be at or near the voltage at the change point (for example, a voltage slightly lower than the voltage at the change point).

In the first aspect, each of the cells included in the assembled battery may be a lithium-ion secondary battery. The predetermined discharging end voltage may be higher than a voltage at which an entire lithium site in a positive electrode active material of the lithium-ion secondary battery is occupied.

In the lithium-ion secondary battery, a lithium site exists in the positive electrode active material. The site is a crystallographically equivalent grid position. The presence of an atom at the grid position is expressed as occupying the site. The lithium site is a site occupied by lithium. Hereinafter, the voltage at which the entire the lithium site in the positive electrode active material of the lithium-ion secondary battery is occupied is also referred to as a "lithium occupying voltage". In a lithium-ion secondary battery (hereinafter, also referred to as a "ternary LIB") having a positive electrode of a layer-shaped crystal structure expressed by a general formula of LixNiyCozMn(<NUM> - x - z), the lithium occupying voltage is <NUM> V.

When a deterioration degree of only one ternary LIB is estimated in an assembled battery including a plurality of ternary LIBs, the discharging of the assembled battery is ended at a timing at which a voltage of at least one ternary LIB included in the assembled battery reaches the discharging end voltage. In such a deterioration diagnosis apparatus of a battery, by setting the discharging end voltage to <NUM> V, it is possible to estimate, with sufficient accuracy, the deterioration degree of each cell included in the assembled battery while restricting the deterioration of the cell during the discharging.

On the other hand, in the deterioration diagnosis apparatus of the battery, when an assembled battery including a plurality of ternary LIBs is diagnosed, since the deterioration degree of each ternary LIB is estimated in the assembled battery including the ternary LIBs, the discharging of the assembled battery is continued until voltages of all the ternary LIBs included in the assembled battery reach the discharging end voltage. In such a deterioration diagnosis apparatus of a battery, <NUM> V is too low as the discharging end voltage. Therefore, in the above configuration, the discharging end voltage is set to be higher than the lithium occupying voltage.

In the first aspect, each of the cells included in the assembled battery may be a lithium-ion secondary battery having a positive electrode of a layer-shaped crystal structure expressed by a general formula of LixNiyCozMn(<NUM> - x - z). The predetermined discharging end voltage may be <NUM> V or higher and <NUM> V or lower. With the above configuration, it is possible to estimate, with sufficient accuracy, the deterioration degree of each cell included in the assembled battery while restricting the deterioration of the cell during the discharging. In an embodiment in which each of the cells included in the assembled battery is a ternary LIB, the discharging end voltage may be <NUM> V or higher and <NUM> V or lower.

In the first aspect, each of the cells included in the assembled battery may be a lithium-ion secondary battery having a positive electrode of an olivine-shaped crystal structure expressed by a general formula of LixFePO<NUM>. The predetermined discharging end voltage may be <NUM> V or higher and <NUM> V or lower. With the above configuration, it is also possible to estimate, with sufficient accuracy, the deterioration degree of each cell included in the assembled battery while restricting the deterioration of the cell during the discharging.

In the first aspect, the predetermined discharging end voltage may be a cell voltage at which the change degree of the cell voltage per unit discharging amount becomes a predetermined value or higher while the cell voltage is dropping due to the discharging. The one or more processors may be configured to determine whether the change degree of the cell voltage per unit discharging amount becomes the predetermined value or higher while the cell voltage is dropping due to the discharging of each cell included in the assembled battery, and, upon determining that the change degrees of the cell voltages per unit discharging amount of all the cells included in the assembled battery become the predetermined value or higher, end the discharging. Therefore, the one or more processors may be configured to, upon determining that the change degrees of the cell voltages per unit discharging amount of all the cells included in the assembled battery are the predetermined value or higher, end the discharging.

The one or more processors can determine, based on whether |ΔV/ΔQ| becomes the predetermined value or higher while the cell voltage is dropping due to the discharging, whether |ΔV/ΔQ| has started to sharply rise. With the above configuration, it is easy to end the discharging of the cell when |ΔV/ΔQ| starts to sharply rise while the cell voltage is dropping due to the discharging. The predetermined value is set such that the cell voltage at which |ΔV/ΔQ| becomes the predetermined value or higher while the cell voltage is dropping due to the discharging becomes the cell voltage at which |ΔV/ΔQ| starts to sharply rise while the cell voltage is dropping due to the discharging.

In the first aspect, the assembled battery may be mounted on a vehicle. The one or more processors may be configured to estimate the deterioration degree of the assembled battery using a usage history of the vehicle, and change the predetermined discharging end voltage such that the predetermined discharging end voltage becomes higher as the estimated deterioration degree of the assembled battery is higher.

The cell voltage at which |ΔV/ΔQ| starts to sharply rise while the cell voltage is dropping due to the discharging tends to gradually rise as the battery deteriorates. With the above configuration, it is possible to finely adjust the discharging end voltage according to a change in the cell voltage at which |ΔV/ΔQ| starts to sharply rise. The one or more processors may finely adjust the discharging end voltage within a change width of, for example, <NUM> V. Examples of parameters indicating the usage history of the vehicle can include an integrated mileage of the vehicle, an input/output power amount (an integrated value) of the assembled battery, the number of times that the assembled battery is charged and discharged, and a period of use of the assembled battery (for example, an elapsed time from the start of use). The one or more processors can roughly determine the deterioration degree of the assembled battery (for example, large deterioration / medium deterioration / small deterioration) using usage history information of the vehicle.

In the first aspect, all the cells included in the assembled battery may be connected in series. The one or more processors may be configured to maintain a current value during the discharging of each of the cells.

With the above configuration, it is easy to match the current value during the discharging of each cell included in the assembled battery. As such, it is easy to estimate, with high accuracy, the deterioration degree of the assembled battery.

In the first aspect, the assembled battery may be configured to supply power to an in-vehicle power load. The one or more processors may be configured to execute the discharging by controlling the in-vehicle power load.

With the above configuration, it is possible to easily and appropriately execute the deterioration diagnosis of the assembled battery for the vehicle. The in-vehicle power load that is controlled by the one or more processors during the discharging may include at least one of air conditioning equipment, a seat heater, and a lighting device.

A deterioration diagnosis apparatus of a battery according to a second aspect of the present disclosure as set forth in claim <NUM> includes a storage device and one or more processors. The storage device is configured to manage a discharging end voltage indicating a timing of ending discharging of the battery. The discharging of the battery is executed to acquire data for estimating a deterioration degree of the battery. The one or more processors are configured to store, in the storage device, as the discharging end voltage, a voltage of the battery when a change degree of a voltage per unit discharging amount of the battery after a start of the discharging of the battery becomes a predetermined value or higher. The one or more processors are configured to store the discharging end voltagen association with information indicating the type of the battery. The one or more processors are configured to acquire, from the storage device, the discharging end voltage corresponding to the type of the battery using the information indicating the type of the battery, and discharge the battery based on the discharging end voltage.

With the above configuration, it is possible to manage an appropriate discharging end voltage. The deterioration diagnosis apparatus of the battery can provide an appropriate discharging end voltage to a device (a discharging device) that executes the discharging of the battery to acquire the data for estimating the deterioration degree of the battery. Alternatively, the deterioration diagnosis apparatus of the battery may execute the discharging of the battery by itself to acquire the data for estimating the deterioration degree of the battery. By discharging the battery based on the appropriate discharging end voltage, it is possible to estimate, with sufficient accuracy, the deterioration degree of the battery while restricting the deterioration degree of the battery during the discharging. More specifically, when the voltages of all the cells included in the assembled battery reach the discharging end voltage, by ending the discharging of the assembled battery, it is possible to estimate, with sufficient accuracy, the deterioration degree of each cell included in the assembled battery while restricting the deterioration of the cells during the discharging. The storage device manages the discharging end voltage in association with a type of the battery. The type of the battery may be distinguished using at least one of a battery manufacturer, a model number, and a serial number.

A deterioration diagnosis method of a battery according to a third aspect of the present disclosure as set forth in claim <NUM> is executed by one or more processors. The deterioration diagnosis method includes executing discharging of each of a plurality of cells included in an assembled battery while measuring a voltage of each of the cells, ending the discharging when the voltages of all the cells included in the assembled battery reach a predetermined discharging end voltage, and estimating a deterioration degree of each of the cells included in the assembled battery using voltage data indicating a transition of the voltage of each of the cells included in the assembled battery from a discharging start voltage to the predetermined discharging end voltage. The predetermined discharging end voltage is a cell voltage at which a change degree of the cell voltage per unit discharging amount starts to sharply rise while the cell voltage is dropping due to the discharging.

With the above deterioration diagnosis method of the assembled battery, in the same manner as the deterioration diagnosis apparatus described above, it is also possible to estimate, with sufficient accuracy, the deterioration degree of each cell included in the assembled battery while restricting the deterioration of the cell during the discharging.

The deterioration of the assembled battery may be diagnosed while the assembled battery is mounted on the vehicle. The vehicle may include an internal combustion engine and a motor (hereinafter, also referred to as a "first motor") that executes start processing of the internal combustion engine. The assembled battery of which the deterioration is diagnosed may be mounted on the vehicle and configured to supply power to the first motor. Hereinafter, the internal combustion engine mounted on the vehicle may be referred to as an "engine". The engine may be configured to generate traveling driving power. In addition to the first motor, the vehicle may further include a second motor that receives supply of power from the assembled battery and generates traveling driving power. The first motor may be configured to generate power using drive power output from the engine and supply the generated power to the assembled battery. The start processing of the internal combustion engine is processing for starting the internal combustion engine. The internal combustion engine can be started by receiving assistance from the motor. The start processing may be cranking. The cranking is to start the internal combustion engine by rotating a crankshaft of the internal combustion engine.

A full charge capacity of the assembled battery in an initial state may be <NUM> kWh or smaller. When a capacity of the assembled battery is <NUM> kWh or smaller, a diagnosis with sufficient throughput can be executed by the above-described deterioration diagnosis method using discharging. The full charge capacity of the assembled battery to be diagnosed in the initial state may be <NUM> kWh or larger and <NUM> kWh or smaller, or <NUM> kWh or larger or <NUM> kWh or smaller. The assembled battery to be diagnosed may be a drive battery mounted on a hybrid electric vehicle (HEV).

Embodiments of the present disclosure will be described in detail with reference to drawings. In the drawings, the same or corresponding parts are denoted by the same reference signs and the description thereof will not be repeated. Hereinafter, an electronic control unit is also referred to as an "ECU".

<FIG> is a diagram illustrating a configuration of a vehicle according to an embodiment. With reference to <FIG>, a vehicle <NUM> is a hybrid electric vehicle (HEV). In this embodiment, it is assumed that the vehicle is a front-wheel drive four-wheel vehicle (more specifically, an HEV), but the number of wheels and a drive system can be appropriately changed. For example, the drive system may be four-wheel drive.

The vehicle <NUM> includes a drive battery <NUM>, a voltage sensor 12a, a current sensor 12b, a temperature sensor 12c, a system main relay (SMR) <NUM>, a first motor generator 21a (hereinafter, referred to as an "MG 21a"), a second motor generator 21b (hereinafter, referred to as an "MG 21b"), a power control unit (PCU) <NUM>, and an engine <NUM>.

The drive battery <NUM> includes a rechargeable secondary battery. The drive battery <NUM> is configured to supply power to the PCU <NUM> (and thus the MGs 21a, 21b). In this embodiment, an assembled battery including a plurality of secondary batteries that are electrically connected to each other is employed as the drive battery <NUM>. A full charge capacity of the drive battery <NUM> in an initial state may be, for example, approximately <NUM> kWh. The secondary batteries included in the drive battery <NUM> may be modularized by a predetermined number. The assembled battery may be composed by combining a plurality of modules. The number of secondary batteries included in the drive battery <NUM> may be <NUM> or more and less than <NUM>, or may be <NUM> or more. In this embodiment, the number of secondary batteries included in the drive battery <NUM> is approximately <NUM>. The drive battery <NUM> is assembled in a form of a battery pack on, for example, a floor panel of the vehicle <NUM>. In this embodiment, the battery pack is formed by installing accessories (a voltage sensor 12a, a current sensor 12b, a temperature sensor 12c, a battery ECU <NUM>, an SMR14, and the like) in a battery case that accommodates the drive battery <NUM>.

Each secondary battery included in the assembled battery is referred to as a "cell". In this embodiment, all the cells included in the assembled battery are connected in series (see, for example, <FIG> described below). In this embodiment, a lithium-ion secondary battery (a ternary LIB) having a positive electrode (a ternary positive electrode) of a layer-shaped crystal structure expressed by a general formula of LixNiyCozMn(<NUM> - x - z) is employed as a cell. However, examples of the cell are not limited to the lithium-ion secondary battery, and may include other secondary batteries (for example, a nickel-hydrogen battery). Further, an all-solid-state secondary battery may be employed as a cell. Examples of the form of assembling the drive battery <NUM> in the vehicle <NUM> are not limited to the battery pack, and may include a packless form.

The voltage sensor 12a detects a voltage of each cell of the drive battery <NUM>. The current sensor 12b detects current flowing through the drive battery <NUM>. The temperature sensor 12c detects a temperature of each cell of the drive battery <NUM>. Each sensor outputs a detection result to the battery ECU <NUM>. The battery ECU <NUM> calculates a State of Charge (SOC) of each cell and an SOC of the drive battery <NUM> using the detection result of each sensor. The SOC indicates a remaining accumulated power amount and represents a ratio of, for example, a current accumulated power amount to an accumulated power amount in a fully charged state from <NUM>% to <NUM>%. The current sensor 12b is provided in a current path of the drive battery <NUM>. In this embodiment, one voltage sensor 12a and one temperature sensor 12c are provided to each cell.

The SMR <NUM> is configured to switch between connection / disconnection of the current path that connects the PCU <NUM> to the drive battery <NUM>. As the SMR <NUM>, for example, an electromagnetic mechanical relay can be employed. When the SMR <NUM> is in a closed state (a connected state), power can be sent and received between the drive battery <NUM> and the PCU <NUM>. On the other hand, when the SMR <NUM> is in an open state (a disconnected state), the current path that connects the drive battery <NUM> to the PCU <NUM> is disconnected. The SMR <NUM> is controlled by an HVECU <NUM>. The SMR <NUM> is switched to the closed state when, for example, the vehicle <NUM> is traveling.

Each of the MGs 21a and 21b is a motor generator that has both a function as a motor that outputs torque by receiving supply of driving power and a function as a generator that generates generated power by receiving torque. As each of the MGs 21a and 21b, an alternating current motor (for example, a permanent magnet type synchronous motor or an induction motor) is used. Each of the MGs 21a and 21b is electrically connected to the drive battery <NUM> via the PCU <NUM>. The MGs 21a, 21b have rotor shafts 43a, 43b, respectively. The rotor shafts 43a, 43b correspond to rotation shafts of the MGs 21a, 21b, respectively.

The vehicle <NUM> further includes a single pinion type planetary gear <NUM>. An output shaft <NUM> of the engine <NUM> is connected to the planetary gear <NUM>. As the engine <NUM>, any internal combustion engine can be employed, but in this embodiment, as the engine <NUM>, a spark-ignition type internal combustion engine including a plurality of cylinders (for example, four cylinders) is employed. The engine <NUM> generates drive power by combusting fuel (for example, gasoline) in each cylinder, and rotates a crankshaft (not shown) common to all cylinders using the generated drive power. The crankshaft of the engine <NUM> is connected to the output shaft <NUM> via a torsional damper (not shown). As the crankshaft rotates, the output shaft <NUM> also rotates. An example of the engine <NUM> is not limited to a gasoline engine, and may include a diesel engine or a hydrogen engine.

The output shaft <NUM> of the engine <NUM> is connected to an input shaft <NUM> of the planetary gear <NUM>. The planetary gear <NUM> has three rotating elements, that is, an input element, an output element, and a reaction force element. More specifically, the planetary gear <NUM> has a sun gear, a ring gear coaxially arranged with the sun gear, a pinion gear that meshes with the sun gear and the ring gear, and a carrier that holds the pinion gear such that it can rotate and revolve. The carrier corresponds to the input element, the ring gear corresponds to the output element, and the sun gear corresponds to the reaction force element. The input shaft <NUM> of the planetary gear <NUM> is connected to the carrier.

The rotor shaft 43a of the MG 21a is connected to the sun gear of the planetary gear <NUM>. Torque is input from the engine <NUM> to the carrier of the planetary gear <NUM>. The planetary gear <NUM> is configured to divide and transfer the torque output by the engine <NUM> to the sun gear (and thus the MG 21a) and the ring gear. When the torque output by the engine <NUM> is output to the ring gear, a reaction force torque output by the MG 21a acts on the sun gear.

The planetary gear <NUM> and MG 21b are configured to combine drive power output from the planetary gear <NUM> (that is, drive power output to the ring gear) and drive power output from the MG 21b (that is, drive power output to the rotor shaft 43b) and transfer the combined power to drive wheels 45a, 45b. More specifically, an output gear (not shown) that meshes with the driven gear <NUM> is installed at the ring gear of the planetary gear <NUM>. Further, a drive gear (not shown) installed at the rotor shaft 43b of the MG 21b also meshes with the driven gear <NUM>. The driven gear <NUM> acts to combine torque output by the MG 21b to the rotor shaft 43b with torque output from the ring gear of the planetary gear <NUM>. The drive torque combined as above is transferred to a differential gear <NUM>, and further transferred to the drive wheels 45a, 45b via the drive shafts 44a, 44b extending to the right and left from the differential gear <NUM>.

A transmission mechanism (not shown) may be provided on a downstream side of the planetary gear <NUM> (for example, between the driven gear <NUM> and the differential gear <NUM>). The transmission mechanism includes a clutch and a brake, and is configured to change a gear ratio (that is, a ratio of rotation speed of an input shaft of the transmission mechanism to rotation speed of an output shaft of the transmission mechanism) depending on a state (engagement / disengagement) of each of the clutch and the brake. The vehicle <NUM> may further include a hydraulic pressure circuit (not shown) that supplies hydraulic pressure to each of the clutch and the brake included in the transmission mechanism. The HVECU <NUM> may switch the state (engagement / disengagement) of each of the clutch and the brake included in the transmission mechanism by controlling the hydraulic pressure circuit. The transmission mechanism may be positioned on the upstream side (for example, between the engine <NUM> and the planetary gear <NUM>) of a power split device (the planetary gear <NUM>).

The vehicle <NUM> further includes a shift lever <NUM> and a P position switch <NUM>. Each of the shift lever <NUM> and the P position switch <NUM> is configured to be able to switch between shift ranges according to a shift operation of a user. The user can select any of a neutral (N) range, a reverse (R) range, a drive (D) range, and a brake (B) range by moving the shift lever <NUM> to a predetermined position. Further, the user can select a parking (P) range by stopping the vehicle <NUM> and pressing the P position switch <NUM>. The HVECU <NUM> switches the shift range of the vehicle <NUM> to a range selected by the user. The HVECU <NUM> controls the hydraulic pressure circuit according to, for example, the shift range.

The vehicle <NUM> further includes a battery ECU <NUM>, a motor ECU <NUM>, an engine ECU <NUM>, and an HVECU <NUM>. In this embodiment, a computer (for example, a microcomputer) is employed as each of the battery ECU <NUM>, the motor ECU <NUM>, the engine ECU <NUM>, and the HVECU <NUM>. The ECUs are connected to each other in a manner capable of executing CAN communication therebetween.

The HVECU <NUM> includes a processor <NUM>, a random access memory (RAM) <NUM>, and a storage device <NUM>. As the processor <NUM>, for example, a central processing unit (CPU) can be employed. The RAM <NUM> functions as a working memory that temporarily stores data processed by the processor <NUM>. The storage device <NUM> is configured to be able to retain the stored information. In addition to the program, the storage device <NUM> stores information (for example, a map, a mathematical formula, and various parameters) used in the program. When the processor <NUM> executes the program stored in the storage device <NUM>, various processes are executed in the HVECU <NUM>.

Although <FIG> illustrates a detailed configuration of only the HVECU <NUM>, each of the other ECUs also includes a processor, a RAM, and a storage device. The number of processors included in each ECU is arbitrary, and any ECU may include a plurality of processors. Further, various processes in each ECU are not limited to execution by software, and may be executed by dedicated hardware (an electronic circuit).

Motor sensors 22a, 22b that detect states (for example, current, a voltage, a temperature, and rotation speed) of the MGs 21a, 21b are provided in the MGs 21a, 21b, respectively. Each of the motor sensors 22a, 22b outputs a detection result to the motor ECU <NUM>. An engine sensor <NUM> that detects a state (for example, an air intake amount, air intake pressure, an air intake temperature, exhaust pressure, an exhaust temperature, a catalyst temperature, an engine coolant temperature, and rotation speed) of the engine <NUM> is provided in the engine <NUM>. The engine sensor <NUM> outputs a detection result to the engine ECU <NUM>. The HVECU <NUM> receives detection values of the motor sensors 22a, 22b and the engine sensor <NUM> from the motor ECU <NUM> and the engine ECU <NUM>, as necessary. Further, the HVECU <NUM> receives a state (for example, a cell voltage, current, a temperature, and an SOC) of the drive battery <NUM> from the battery ECU <NUM>, as necessary.

The vehicle <NUM> includes a monitoring unit 80a that detects a state of an auxiliary battery <NUM> described below. The monitoring unit 80a includes various sensors that detect a state (for example, a temperature, current, and a voltage) of the auxiliary battery <NUM>, and outputs a detection result to the HVECU <NUM>. The HVECU <NUM> can acquire the state (for example, the temperature, current, the voltage, and an SOC) of the auxiliary battery <NUM> based on an output of the monitoring unit 80a. Further, although not shown, other sensors (for example, a vehicle speed sensor, a fuel gauge, an odometer, an accelerator operation amount sensor, and an atmospheric pressure sensor) that indicate a situation of the vehicle <NUM> are also mounted on the vehicle <NUM>. The HVECU <NUM> can grasp information of the vehicle <NUM> based on outputs of various sensors (in-vehicle sensors) mounted on the vehicle <NUM>.

The HVECU <NUM> is configured to output a command (a control command) for controlling the engine <NUM> to the engine ECU <NUM>. The engine ECU <NUM> is configured to control various actuators (for example, a throttle valve, an ignition device, and an injector) (none of them shown) of the engine <NUM> according to the command from the HVECU <NUM>. The HVECU <NUM> can control the engine through the engine ECU <NUM>.

The HVECU <NUM> is configured to output a command (a control command) for controlling each of the MG 21a and the MG 21b to the motor ECU <NUM>. The motor ECU <NUM> is configured to generate a current signal (for example, a signal indicating a magnitude and frequency of current) corresponding to a target torque of each of the MG 21a and the MG21b according to the command from the HVECU <NUM>, and to output the generated current signal to the PCU <NUM>. The HVECU <NUM> can control the motors through the motor ECU <NUM>.

The PCU <NUM> includes, for example, two inverters (not shown) provided to correspond to the MGs 21a, 21b, and a converter (not shown) arranged between each inverter and the drive battery <NUM>. The PCU <NUM> is configured to supply power accumulated in the drive battery <NUM> to each of the MG 21a and the MG 21b, and to supply power generated by each of the MG 21a and the MG 21b to the drive battery <NUM>. The PCU <NUM> is configured to be able to separately control the states of the MGs 21a, 21b, that is, for example, it can turn the MG 21b to a power running state while turning the MG 21a to a power generation state.

The MG 21a is configured to execute start processing of the engine <NUM>. Specifically, when the engine <NUM> is started, the MG 21a that receives supply of power from the drive battery <NUM> executes cranking of the engine <NUM>.

The MG 21a is configured to generate power (that is, engine power generation) using drive power output from the engine <NUM>. The HVECU <NUM> charges the drive battery <NUM> with power generated by the engine power generation such that the SOC of the drive battery <NUM> does not become excessively low while the vehicle <NUM> is traveling. Further, the drive battery <NUM> is also charged with power generated by regenerative braking by the MG 21b.

The vehicle <NUM> is configured to execute HV traveling and EV traveling. The HV traveling is executed by the engine <NUM> and the MG 21b while the engine <NUM> is generating traveling driving power. The EV traveling is executed by the MG 21b when the engine <NUM> is in a stopped state. When the engine <NUM> is in the stopped state, combustion in each cylinder is not executed. When the combustion in each cylinder is stopped, combustion energy (and thus traveling driving power) is not generated in the engine <NUM>.

The vehicle <NUM> further includes an auxiliary battery <NUM>, DC/DC converters <NUM>, <NUM>, an auxiliary relay <NUM>, a high voltage load <NUM>, and a low voltage load <NUM>. The full charge capacity of the auxiliary battery <NUM> is smaller than that of the drive battery <NUM>. A full charge capacity of a battery is an electricity amount accumulated in the battery in a fully charged state and decreases as the battery deteriorates. As the auxiliary battery <NUM>, for example, a lead battery can be employed. However, as the auxiliary battery <NUM>, a secondary battery (for example, a nickel-hydrogen battery) other than the lead battery may be employed. The DC/DC converters <NUM>, <NUM>, the auxiliary relay <NUM>, the high voltage load <NUM>, and the low voltage load <NUM> are controlled by the HVECU <NUM>. The HVECU <NUM> may control these through the battery ECU <NUM>.

The high voltage load <NUM> is an auxiliary machine of a high voltage system. The low voltage load <NUM> is an auxiliary machine of a low voltage system. A drive voltage of the low voltage load <NUM> is lower than a drive voltage of the high voltage load <NUM>. The auxiliary battery <NUM> is an in-vehicle battery of the low voltage system (for example, a <NUM> V system), and is configured to supply power to the low voltage load <NUM>. In this embodiment, the high voltage load <NUM> includes air conditioning equipment and the low voltage load <NUM> includes a lighting device. The air conditioning equipment is configured to heat and cool a cabin of the vehicle <NUM>. The lighting device includes a lighting device that illuminates the inside of the vehicle and a lighting device (for example, a headlight) that illuminates the outside of the vehicle. At least one of the high voltage load <NUM> and the low voltage load <NUM> may further include a seat heater that heats a seat of the vehicle <NUM>.

The DC/DC converter <NUM> is provided between the drive battery <NUM> and the high voltage load <NUM>, steps down power supplied from the drive battery <NUM> and outputs it to the high voltage load <NUM>. The DC/DC converter <NUM> steps down power supplied from the drive battery <NUM> and outputs it to each of the auxiliary battery <NUM> and the low voltage load <NUM>. When the SMR <NUM> is in the open state (the disconnected state), power of the drive battery <NUM> is not supplied to any of the high voltage load <NUM>, the low voltage load <NUM>, and the auxiliary battery <NUM>. An auxiliary relay <NUM> is arranged in a current path that connects the DC/DC converter <NUM> to the low voltage load <NUM>. When the auxiliary relay <NUM> is in the open state (the disconnected state), power is not supplied to the low voltage load <NUM>.

When the SMR <NUM> is in the closed state (the connected state), power can be supplied from the drive battery <NUM> to the auxiliary battery <NUM> through the DC/DC converter <NUM>. For example, when the SOC of the auxiliary battery <NUM> is lower than a predetermined value, the HVECU <NUM> charges the auxiliary battery <NUM> with power of the drive battery <NUM>. Further, the HVECU <NUM> drives the high voltage load <NUM> and the low voltage load <NUM> using power of the drive battery <NUM> according to an instruction from a service tool <NUM> (see <FIG>) in the deterioration diagnosis of the assembled battery (see S16 in <FIG>) described below. At this time, the HVECU <NUM> controls the SMR <NUM>, the DC/DC converters <NUM>, <NUM>, and the auxiliary relay <NUM> such that power of the drive battery <NUM> is supplied to each of the high voltage load <NUM> and the low voltage load <NUM>.

The HVECU <NUM> is configured to execute an SOC limit control to the drive battery <NUM>. The SOC limit control is a control for limiting the SOC of the drive battery <NUM> to within a predetermined SOC range. The HVECU <NUM> limits an input / output of the drive battery <NUM> such that the SOC of the drive battery <NUM> does not leave the SOC range. Specifically, the HVECU <NUM> controls the MGs 21a, 21b, the engine <NUM>, and the DC/DC converters <NUM>, <NUM> such that the SOC of the drive battery <NUM> is within the SOC range. The SOC range is variably set depending on a state of the vehicle <NUM>. The HVECU <NUM> may set an SOC range for protecting the drive battery <NUM> and its peripheral parts using, for example, a map stored in the storage device <NUM>.

The vehicle <NUM> further includes a power switch <NUM>. The power switch <NUM> is used for switching between start / stop of a vehicle system (the HVECU <NUM> and the like). The power switch <NUM> is operated by the user.

The vehicle <NUM> further includes a notification device <NUM>. The notification device <NUM> is configured to send a notification to the user of the vehicle <NUM> in response to a request from the HVECU <NUM>. Examples of the notification device <NUM> can include a meter panel, a head-up display, a navigation display, a warning light, or a speaker. The notification device <NUM> may function as an input device that receives an input from the user. The notification device <NUM> may include a touch panel display or a smart speaker that receives a voice input. The notification device <NUM> may be mounted on a portable device (that is, an electronic device that can be carried by the user), such as a tablet terminal, a smartphone, or a wearable device.

<FIG> is a diagram illustrating a configuration of a deterioration diagnosis apparatus of a battery according to this embodiment. With reference to <FIG> together with <FIG>, in this embodiment, the service tool <NUM> functions as a deterioration diagnosis apparatus of a battery. The service tool <NUM> includes a computer including a processor <NUM>, a RAM <NUM>, and a storage device <NUM>. The storage device <NUM> stores a diagnosis program. The deterioration diagnosis method (see <FIG> described below) of the battery according to this embodiment is executed when the processor <NUM> executes the diagnosis program stored in the storage device <NUM>.

The service tool <NUM> further includes a human machine interface (HMI) <NUM>. The HMI <NUM> includes an input device and a display device. The HMI <NUM> may be a touch panel display. The HMI <NUM> may include a smart speaker that receives a voice input.

The HVECU <NUM> further includes a data link connector (DLC) 55a and an interface 55b of the DLC 55a. The DLC 55a is a connector that can be connected to a connector <NUM> of the service tool <NUM>, and is arranged in, for example, the vicinity of a driver seat of the vehicle <NUM>. The service tool <NUM> is an external diagnosis machine used by, for example, a worker (such as a mechanic) in a maintenance shop to grasp a state of a vehicle. Examples of the service tool <NUM> can include a general scan tool (GST). By connecting the connector <NUM> of the service tool <NUM> to the DLC 55a, the service tool <NUM> can read vehicle data stored in the storage device <NUM>.

In the deterioration diagnosis method of the battery according to this embodiment, the service tool <NUM> discharges each cell while measuring a voltage of each cell included in the drive battery <NUM> (the assembled battery). Then, when the voltages of all the cells included in the drive battery <NUM> reach a predetermined discharging end voltage (hereinafter, referred to as "Vend"), the service tool <NUM> ends the discharging. After ending the discharging, the service tool <NUM> estimates a deterioration degree of each cell included in the drive battery <NUM>, using voltage data indicating a transition of the voltage of each cell included in the drive battery <NUM> from a discharging start voltage to Vend.

However, when Vend is too low, some cells included in the assembled battery may be over-discharged during the discharging of the assembled battery. On the other hand, when the Vend is too high, sufficient data cannot be obtained during the discharging of the assembled battery, and accuracy of estimating a deterioration degree (for example, a full charge capacity) of a cell may decrease. Therefore, in the deterioration diagnosis method of the battery according to this embodiment, the cell voltage, at which |ΔV/ΔQ| (that is, the change degree of the cell voltage per unit discharging amount) starts to sharply rise while the cell voltage is dropping due to the discharging, is set as Vend. A method of deciding Vend and a technical significance thereof will be described below (see <FIG> described below).

The service tool <NUM> according to this embodiment includes a discharging unit <NUM> and an estimation unit <NUM>. The discharging unit <NUM> is configured to discharge each cell while measuring the voltage of each cell included in the drive battery <NUM> mounted on the vehicle <NUM>, and to end the discharging when the voltages of all the cells included in the assembled battery reach Vend. The estimation unit <NUM> is configured to estimate a deterioration degree of each cell included in the assembled battery using the voltage data indicating the transition of the voltage of each cell included in the assembled battery from the discharging start voltage to Vend.

<FIG> is a flowchart illustrating the deterioration diagnosis method of the battery according to this embodiment. Processes illustrated in this flowchart are executed when, for example, a predetermined instruction is input from the user to the HMI <NUM> after the connector <NUM> of the service tool <NUM> is connected to the DLC 55a of the vehicle <NUM> in a parked state. However, a condition of starting the process illustrated in <FIG> is not limited thereto, and can be arbitrarily set. Hereinafter, each step in the flowchart is simply referred to as "S". The discharging unit <NUM> of the service tool <NUM> transmits a control command to the HVECU <NUM>, whereby S10 to S18 of <FIG> are executed.

With reference to <FIG> together with <FIG> and <FIG>, in S10, the service tool <NUM> releases an SOC range related to the SOC limit control. As such, the SOC limit (the SOC limit control) of the drive battery <NUM> becomes invalid.

Subsequently in S11, the service tool <NUM> drives the engine <NUM> and charges the drive battery <NUM> with power generated by the engine power generation. By the process of S11, power generated by the MG 21a using drive power output from the engine <NUM> is input to the drive battery <NUM> via the PCU <NUM> and the SMR <NUM>.

In S12, the service tool <NUM> determines whether the voltages of all the cells included in the drive battery <NUM> have become a predetermined start voltage (hereinafter, referred to as "Vstart") or higher. The voltage of each cell included in the drive battery <NUM> is measured by the voltage sensor 12a. Vstart may be a cell voltage indicating that the cell has turned to the fully charged state, or may be a charging upper limit voltage of the cell. The charging upper limit voltage corresponds to an upper limit of a recommended voltage range. When the charging of the cell is continued until the voltage exceeds the charging upper limit voltage, the cell may be over-charged. The over-charging accelerates the deterioration of the cell. Vstart may be <NUM> V or higher and <NUM> V or lower, or may be approximately <NUM> V. Further, the service tool <NUM> may determine whether the voltages of all the cells included in the drive battery <NUM> have become Vstart or higher based on the SOC of the drive battery <NUM>. For example, when the SOC of the drive battery <NUM> has become a predetermined SOC value (for example, <NUM>%) or higher, the service tool <NUM> may determine that the voltages of all the cells included in the drive battery <NUM> have become Vstart or higher.

The processes of S11 and S12 are repeated until the voltages of all the cells included in the drive battery <NUM> become Vstart or higher (NO in S12). When the voltages of all the cells become Vstart or higher (YES in S12), in S13, the service tool <NUM> stops the engine <NUM>. Thereafter, in S14, the service tool <NUM> determines whether the voltages of all the cells included in the drive battery <NUM> have become stable. The process stands by in S14 until the voltage of each cell included in the drive battery <NUM> becomes stable, and, when the voltage of each cell included in the drive battery <NUM> becomes stable (YES in S14), the process proceeds to S15.

In S15, the service tool <NUM> measures a state (a voltage, current, and a temperature) of each cell included in the drive battery <NUM>, and records a measurement result in the storage device <NUM>. Subsequently in S16, the service tool <NUM> discharges the drive battery <NUM> by controlling a power load of the vehicle <NUM>. The drive battery <NUM> is configured to supply power to the power load mounted on the vehicle <NUM>.

Specifically, in S16, the service tool <NUM> controls the power load (for example, at least one of the high voltage load <NUM> and the low voltage load <NUM>) of the vehicle <NUM> such that discharging current of each cell included in the drive battery <NUM> becomes a predetermined value (hereinafter, referred to as "Vd"). In this embodiment, the air conditioning equipment (the high voltage load <NUM>) and the lighting device (the low voltage load <NUM>) are driven by power supplied from the drive battery <NUM>. The service tool <NUM> adjusts power supplied from the drive battery <NUM> to the high voltage load <NUM> and the low voltage load <NUM>, using the DC/DC converters <NUM>, <NUM>, respectively. Then, the service tool <NUM> maintains a current value during the discharging of each cell included in the drive battery <NUM>. Vd may be <NUM> A or higher and <NUM> A or lower, or may be approximately <NUM> A. In this embodiment, the current value during the discharging of each cell is maintained at Vd. In this embodiment, Vd is set to a fixed value (for example, <NUM> A), but Vd may be variable depending on the situation.

In S17, the service tool <NUM> determines whether the voltages of all the cells included in the drive battery <NUM> have reached a predetermined discharging end voltage (Vend).

<FIG> is a graph illustrating an example of a discharging characteristic of the cell included in the drive battery <NUM>. Each of the lines L1 to L3 in <FIG> illustrates an example of a transition of current and a voltage of the drive battery <NUM> (the assembled battery) when S10 to S16 of <FIG> are executed, and the discharging (S16) is continued for a predetermined time. The line L1 illustrates a transition of current of the drive battery <NUM>. The lines L2, L3 respectively illustrate the discharging characteristics (more specifically, the transitions of the cell voltages during the discharging) of a first cell and a second cell included in the drive battery <NUM>. A full charge capacity of the first cell is larger than that of the second cell.

With reference to <FIG>, in a comparison between the transition of a voltage of the first cell (the line L2) and the transition of a voltage of the second cell (the line L3), the voltage of the second cell starts to decrease earlier than that of the first cell and decreases to a voltage lower than a voltage to which the voltage of the first cell decreases. As such, the cell voltage tends to easily decrease during the discharging as a full charge capacity is smaller. When the voltage of the cell decreases too much due to the discharging of the cell, the deterioration of the cell is accelerated. The fact that the discharging of the voltage of the cell is continued until it decreases too much is referred to as "over-discharging".

Hereinafter, with reference to <FIG>, the method of deciding the discharging end voltage (Vend) will be described. <FIG> is a graph for describing an issue that may arise when a discharging lower limit voltage is set as Vend. In <FIG>, a line L11 illustrates a voltage distribution of all cells included in a first assembled battery (hereinafter, referred to as a "first cell voltage distribution"). A line L12 illustrates a voltage distribution of all cells included in a second assembled battery (hereinafter, referred to as a "second cell voltage distribution"). The second cell voltage distribution (the line L12) has wider variations on cell voltages than the first cell voltage distribution (the line L11). The first cell voltage distribution and the second cell voltage distribution are distributions when the discharging is continued until the voltages of all the cells included in the first assembled battery and all the cells included in the second assembled battery reach the discharging lower limit voltage (Vend), respectively.

In <FIG>, the discharging lower limit voltage corresponds to a lower limit value of the recommended voltage range. When the discharging of the cell is continued until the voltage falls below the discharging lower limit voltage, the deterioration of the cell may be accelerated. The fact that the discharging of the cell is continued until the deterioration of the cell may be accelerated corresponds to the above-described "over-discharging". A discharging prohibition voltage corresponds to a dischargeable limit value. When the discharging of the cell is continued until the voltage falls below the discharging prohibition voltage, an abnormality (for example, malfunction or failure) may occur in the cell. In the vehicle <NUM> according to this embodiment, the HVECU <NUM> has a warning flag for self-diagnosis (OBD) in the storage device <NUM>, and when a voltage of any of the cells included in the drive battery <NUM> falls below the discharging prohibition voltage, the HVECU <NUM> is configured to raise the warning flag (for example, a value of the flag is changed from "<NUM>" to "<NUM>"). The discharging lower limit voltage and the discharging prohibition voltage of each cell included in the drive battery <NUM> according to this embodiment are <NUM> V and <NUM> V, respectively.

With reference to <FIG>, in the deterioration diagnosis apparatus of the assembly battery in which the discharging lower limit voltage is set as Vend, when the variations on cell voltages are wide (see, for example, the line L12), the deterioration of some cells included in the assembly battery may excessively progress and the life of the assembly battery may be shortened. Further, when the engine cranking is executed by power supplied by the assembled battery, the voltages of the entire assembled battery decrease as illustrated by a line L13. As such, the voltages of some cells included in the assembled battery may fall below the discharging prohibition voltage, and the warning flag may be raised.

<FIG> is a graph for describing a merit of raising Vend. A line L12 in <FIG> is the same as the line L12 in <FIG>. A line L14 in <FIG> illustrates the second cell voltage distribution at the end of the discharging in the embodiment where Vend is set to a voltage higher than the discharging lower limit voltage.

With reference to <FIG>, by raising Vend to a voltage higher than the discharging lower limit voltage (see, for example, the line L14), a margin from the discharging prohibition voltage becomes large, and the warning flag is less likely to be raised. Further, the number of cells in an over-discharged state is reduced. For this reason, the shortening of the life of the assembled battery is restricted, and a voltage shortage of the assembled battery at the time of engine cranking is restricted. Further, a variation width of cell voltages tends to become wider as a discharging period is longer. Thus, by raising Vend, the variation width of the cell voltages becomes narrow.

<FIG> is a graph for describing a demerit of raising Vend. A line L21 in <FIG> illustrates an example of a transition of the voltages of the cells included in the drive battery <NUM> during the discharging. The transition of the voltage during the discharging is slightly different for each cell, but the tendency is substantially the same.

With reference to <FIG>, when the discharging of the cell is started, the cell voltage gradually decreases. ΔV/ΔQ (corresponding to a slope of the graph), which is a value obtained by differentiating the cell voltage (the vertical axis) with respect to the discharging amount (the horizontal axis), is substantially constant immediately after the start of the discharging, but becomes high on the negative side when the discharging is continued for a while. In the deterioration diagnosis method of the assembled battery according to this embodiment, voltage data (that is, data indicating the transition of the cell voltage) of each cell included in the assembled battery during a discharging period (a period from the start of the discharging to the end of the discharging) is acquired and the deterioration degree of each cell is estimated based on the voltage data. "Qend" in <FIG> illustrates the discharging amount (the discharging amount at the end of the discharging) corresponding to Vend. When Vend is raised, a discharging end timing becomes earlier and the discharging period becomes shorter. When the discharging period becomes shorter, the number of pieces of the voltage data for the deterioration diagnosis of the assembled battery is reduced, and the accuracy of estimating the deterioration degree of the cell decreases.

<FIG> is a graph for describing the method of deciding Vend. The vertical axis of the graph represents -ΔV/ΔQ, and the horizontal axis represents the discharging amount. Since the cell voltage decreases as the discharging amount is increased, ΔV/ΔQ becomes a negative value and -ΔV/ΔQ becomes a positive value. -ΔV/ΔQ indicates the change degree of the cell voltage per unit discharging amount. -ΔV/ΔQ has the same value as |ΔV/ΔQ|. A line L22 in <FIG> illustrates an example of a transition of -ΔV/ΔQ of the cells included in the drive battery <NUM> during the discharging. The transition of -ΔV/ΔQ during the discharging is slightly different for each cell, but the tendency is substantially the same.

With reference to <FIG>, at an initial stage of the discharging of the cell, -ΔV/ΔQ is substantially constant. Thereafter, at a final stage of the discharging, -ΔV/ΔQ sharply rises due to the increase in reaction resistance. At the final stage of the discharging of the cell, -ΔV/ΔQ lowers once, passes through the cell voltage (the voltage at the change point) at which -ΔV/ΔQ becomes the lowest during the discharging, and then starts to sharply rise. A narrowed width (more specifically, a narrowed width of the discharging period per the raised voltage) of the discharging period due to the raising of Vend becomes wider as -ΔV/ΔQ becomes higher. Before |ΔV/ΔQ| starts to sharply rise, a merit of raising Vend is larger than a demerit of raising Vend. After |ΔV/ΔQ| starts to sharply rise, the demerit of raising Vend is larger than the merit of raising Vend. In the deterioration diagnosis method of the battery according to this embodiment, the cell voltage at which -ΔV/ΔQ (that is, the change degree of the cell voltage per unit discharging amount) starts to sharply rise while the cell voltage is dropping due to the discharging is set as Vend. Such Vend may be obtained in advance by experiments or simulation. In the examples illustrated in <FIG> and <FIG>, the length of the discharging period is expressed by the discharging amount, but the length of the discharging period may be expressed by time.

<FIG> is a graph illustrating a discharging characteristic of a lithium-ion secondary battery. Lines L31, L32, and L33 in <FIG> respectively illustrate transitions of the voltages during the discharging of a first lithium-ion secondary battery (hereinafter, referred to as a "first LIB"), a second lithium-ion secondary battery (hereinafter, referred to as a "second LIB"), and a third lithium-ion secondary battery (hereinafter, referred to as a "third LIB"). The first to third LIBs are lithium-ion secondary batteries (more specifically, ternary LIBs) having different deterioration degrees from each other, in order of the third LIB (deterioration degree: high), the second LIB (deterioration degree: intermediate), and the first LIB (deterioration degree: low) from the battery having the highest deterioration degree.

With reference to <FIG>, in a case where the lithium-ion secondary battery employed as each cell of the drive battery <NUM> in this embodiment has been discharged, |ΔV/ΔQ | starts to sharply rise when the voltage of the lithium-ion secondary battery has become <NUM> V. For this reason, in the deterioration diagnosis method of the battery according to this embodiment, <NUM> V is set as Vend. In the lithium-ion secondary battery, the voltage at which the entire lithium site in the positive electrode active material is occupied is <NUM> V. In other words, Vend is set to a voltage higher than the voltage at which the entire lithium site in the positive electrode active material in the lithium-ion secondary battery (the cell) is occupied. As such, the discharging is ended before the entire lithium site in the positive electrode active material is occupied.

The discharging characteristic of the lithium-ion secondary battery changes (see lines L31 to L33) as the lithium-ion secondary battery deteriorates. However, the battery voltage (the voltage of the lithium-ion secondary battery) at which |ΔV/ΔQ | starts to sharply rise during the discharging of the lithium-ion secondary battery does not significantly change even when the deterioration of the lithium-ion secondary battery progresses. In the example illustrated in <FIG>, a change width is within <NUM> V.

As described above, in this embodiment, <NUM> V is set as Vend. With reference to <FIG> again, together with <FIG> and <FIG>, while a voltage of any of the cells included in the drive battery <NUM> is higher than Vend (NO in S17), the processes of S15 to S17 are repeated, and the discharging of the drive battery <NUM> is continued. Then, when the voltages of all the cells included in the drive battery <NUM> become Vend or lower (YES in S17), in S18, the service tool <NUM> ends the discharging of the drive battery <NUM>.

After ending the discharging of the drive battery <NUM> in S18, the service tool <NUM> restarts the SOC limit control. As such, the SOC of the drive battery <NUM> is limited to within the predetermined SOC range, again.

By repeating the above-described processes of S15 to S17, data indicating the state (particularly, the deterioration degree) of the drive battery <NUM> is recorded in the storage device <NUM> of the service tool <NUM>. After the discharging is ended in S18, subsequently in S19, the estimation unit <NUM> of the service tool <NUM> estimates the deterioration degree of each cell included in the drive battery <NUM> using the recorded data of the drive battery <NUM>.

Specifically, the service tool <NUM> acquires a section discharging amount (Ah) from the discharging start voltage to Vend (the discharging end voltage) of each cell using the data (including the voltage data indicating the transition of the cell voltage from the discharging start voltage to the discharging end voltage) acquired in S15. The discharging amount corresponds to a time integral value of a discharging current (A). When the discharging current fluctuates within a section, the section discharging amount can be obtained by integrating the discharging current for each unit time with respect to time. When the discharging current is constant within the section, a value obtained by multiplying the discharging current (A) by the discharging period (h) corresponds to the discharging amount.

As described above, the service tool <NUM> calculates the section discharging amount (that is, the section discharging amount from the discharging start voltage to Vend) of the cell and converts the section discharging amount into the full charge capacity using a predetermined map. A map illustrating a relationship between a temperature of the cell, the section discharging amount, and the full charge capacity may be used to obtain the full charge capacity of the cell. When the temperature of the cell and the section discharging amount are given to the map, the full charge capacity of the cell is output from the map. The temperature of the cell that is used may be the average temperature during the discharging or the temperature at the start of the discharging. The map may be stored in the storage device <NUM> in advance. The map may be a map common to all the cells included in the drive battery <NUM>. The service tool <NUM> may acquire the map from an external server (for example, a server that manages information on various batteries), or may acquire the map from the vehicle <NUM>.

As described above, in S19, the estimation unit <NUM> of the service tool <NUM> estimates the full charge capacity of each cell included in the drive battery <NUM>. The full charge capacity (the electricity amount accumulated in the cell at a time of full charging) of the cell indicates the deterioration degree of the cell. The deterioration degree of the cell becomes higher as the full charge capacity of the cell is smaller. When the process of S19 is executed, a series of processes illustrated in <FIG> ends.

After the processes illustrated in <FIG>, the service tool <NUM> may transmit a diagnosis result (that is, information indicating the full charge capacity of each cell included in the drive battery <NUM>) to the vehicle <NUM>. The diagnosis result received by the vehicle <NUM> may be stored in the storage device <NUM> of the HVECU <NUM>. The notification device <NUM> may send a notification of the diagnosis result in response to a request from the user.

After the processes illustrated in <FIG>, the HVECU <NUM> may start the engine <NUM> by the above-described cranking and charge the drive battery <NUM> with power generated by the engine power generation. The HVECU <NUM> may return the SOC of the drive battery <NUM> to the SOC value before the diagnosis. Alternatively, the HVECU <NUM> may charge the drive battery <NUM> until the vehicle <NUM> turns to a state of being capable of EV traveling.

As described above, the deterioration diagnosis method of the battery according to this embodiment includes the series of processes illustrated in <FIG>.

In the processes illustrated in <FIG>, each cell is discharged while the voltage of each of the cells included in the assembled battery (the drive battery <NUM>) is measured, and the discharging is ended when the voltages of all the cells included in the assembled battery reach the predetermined discharging end voltage (Vend) (S15 to S18). The discharging end voltage (Vend) is the cell voltage (for example, <NUM> V) at which |ΔV/ΔQ | (that is, the change degree of the cell voltage per unit discharging amount) starts to sharply rise while the cell voltage is dropping due to the discharging (see <FIG> and <FIG>). In the processes illustrated in <FIG>, the deterioration degree of each cell included in the assembled battery (the drive battery <NUM>) is estimated using the voltage data indicating the transition of the voltage of each cell included in the assembled battery from the discharging start voltage to the discharging end voltage (Vend) (S19).

<FIG> is a graph illustrating a relationship between the discharging end voltage (Vend) and a coverage ratio. Lines L41, L42, and L43 in <FIG> respectively illustrate the coverage ratio when the deterioration diagnosis of the above-described first LIB, second LIB, and third LIB has been executed by the processes illustrated in <FIG>. Specifically, the coverage ratio is measured while the discharging end voltage (Vend) is changed in the range from <NUM> V to <NUM> V. The coverage ratio corresponds to a ratio of the section discharging amount to the full charge capacity. The coverage ratio is obtained by dividing the section discharging amount calculated in S19 of <FIG> by the full charge capacity. The coverage ratio can be expressed as a percentage. The deterioration degrees of the batteries are in order of the third LIB (deterioration degree: high), the second LIB (deterioration degree: intermediate), and the first LIB (deterioration degree: low) from the highest.

With reference to <FIG>, when Vend is raised above <NUM> V, the coverage ratio sharply decreases (see lines L41 to L43). In the deterioration diagnosis method where Vend is <NUM> V, the coverage ratio is approximately <NUM>%, and the deterioration degree of the cell (the ternary LIB) can be estimated with sufficient accuracy. Further, by raising Vend to <NUM> V, the deterioration of the cell (the ternary LIB) during the discharging is restricted (see <FIG>). As such, with the deterioration diagnosis method of the battery according to the embodiment, it is possible to estimate, with sufficient accuracy, the deterioration degree of each cell included in the assembled battery while restricting the deterioration of the cell during the discharging.

With the deterioration diagnosis method of the battery, the full charge capacity of each cell included in the assembled battery (the drive battery <NUM>) is acquired. For this reason, it is possible to rebuild the assembled battery by replacing only the cell having a high deterioration degree from among the cells in the assembled battery. However, the present disclosure is not limited thereto, and a battery pack including the drive battery <NUM> may be replaced. Whether the assembled battery needs replacing may be determined based on the full charge capacity of a cell having the minimum capacity (a cell having the smallest full charge capacity in the assembled battery).

In the embodiment, <NUM> V is set as the discharging end voltage (Vend). However, the discharging end voltage is not limited thereto, and can be appropriately changed. For example, in an embodiment where each of the cells included in the assembled battery (the drive battery <NUM>) is a lithium-ion secondary battery (an LFP cell) having a positive electrode (a cobalt-free iron phosphate positive electrode) of an olivine-shaped crystal structure expressed by a general formula of LixFePO<NUM>, a voltage selected from a range from <NUM> V or higher and <NUM> V or lower may be set as the discharging end voltage. With the above discharging end voltage, it is also possible to estimate, with sufficient accuracy, the deterioration degree of each cell included in the assembled battery while restricting the deterioration of the cell during the discharging. Further, in the deterioration diagnosis method of the battery according to the embodiment, the discharging end voltage (Vend) is a fixed value (<NUM> V). However, the present disclosure is not limited thereto, and the discharging unit <NUM> may be configured to estimate the deterioration degree of the drive battery <NUM> using the usage history of the vehicle <NUM>, and change Vend such that Vend becomes higher as the estimated deterioration degree of the drive battery <NUM> is higher.

<FIG> is a flowchart illustrating a method of setting the discharging end voltage according to a modified example. The processes illustrated in this flowchart are executed before the process illustrated in <FIG> is started. For example, when a predetermined instruction is input to the HMI <NUM> from the user after the connector <NUM> of the service tool <NUM> is connected to the DLC 55a of the vehicle <NUM> in the parked state, the processes illustrated in <FIG> are executed. Then, the process illustrated in <FIG> is started by a process of S38 described below.

With reference to <FIG> together with <FIG> and <FIG>, in S31, the HVECU <NUM> transmits vehicle history information (that is, information indicating the usage history of the vehicle <NUM>) to the service tool <NUM>. The vehicle history information is sequentially acquired by various sensors mounted on the vehicle <NUM> when the user is using the vehicle <NUM>, and is stored in the storage device <NUM>. In one example, the vehicle history information transmitted in S31 includes the integrated mileage of the vehicle <NUM>.

In S32, the service tool <NUM> receives the vehicle history information. Thereafter, the discharging unit <NUM> of the service tool <NUM> executes the processes of S33 to S38 described below.

In S33, the service tool <NUM> estimates the deterioration degree of the drive battery <NUM> using the vehicle history information. Specifically, it is estimated that the deterioration degree of the drive battery <NUM> becomes higher as the integrated mileage of the vehicle <NUM> is longer. Subsequently, in S34, the service tool <NUM> determines whether the deterioration degree of the drive battery <NUM> is high, intermediate, or low.

When the estimated deterioration degree of the drive battery <NUM> is low ("low" in S34), in S35, the service tool <NUM> sets <NUM> V as the discharging end voltage (Vend). When the estimated deterioration degree of the drive battery <NUM> is approximately intermediate ("intermediate" in S34), in S36, the service tool <NUM> sets <NUM> V as the discharging end voltage (Vend). When the estimated deterioration degree of the drive battery <NUM> is high ("high" in S34), in S37, the service tool <NUM> sets <NUM> V as the discharging end voltage (Vend).

When any of the processes S35 to S37 is executed, in S38, the service tool <NUM> generates a discharging control start trigger used for the deterioration diagnosis of the assembled battery. As such, the process illustrated in <FIG> is started.

As such, according to the processes illustrated in <FIG>, Vend is changed such that Vend becomes higher as the estimated deterioration degree of the drive battery <NUM> is higher. With such an embodiment, it is possible to finely adjust the discharging end voltage (Vend) in accordance with the cell voltage (see <FIG> and <FIG>) at which |ΔV/ΔQ| starts to sharply rise, the cell voltage at which |ΔV/ΔQ| starts to sharply rise being changed depending on the deterioration degree of the drive battery <NUM>.

The processes illustrated in <FIG> may be appropriately changed. For example, the discharging end voltage (Vend) may be the cell voltage at which the change degree of the cell voltage per unit discharging amount while the cell voltage is dropping due to the discharging becomes a predetermined value or higher. Then, the discharging unit <NUM> may be configured to determine whether |ΔV/ΔQ| has become the predetermined value or higher while the cell voltage is dropping due to the discharging of each cell included in the assembled battery, and end the discharging upon determining that |ΔV/ΔQ| of all the cells included in the assembled battery has become the predetermined value or higher.

<FIG> is a flowchart illustrating a modified example of the processes illustrated in <FIG>. The processes illustrated in <FIG> are equivalent to the processes illustrated in <FIG>, except that S17A and S17B are employed instead of S17 (<FIG>). Hereinafter, the processes illustrated in <FIG> will be described, focusing on differences from those illustrated in <FIG>.

With reference to <FIG>, together with <FIG> and <FIG>, in S17A, the service tool <NUM> calculates |ΔV/ΔQ| of each cell by differentiating the cell voltage with respect to the discharging amount in the transition of the voltage mapped (plotted) during the discharging of each cell. In S17B, the service tool <NUM> determines whether |ΔV/ΔQ| of all the cells included in the drive battery <NUM> has become a predetermined value (hereinafter, referred to as "Th") or higher.

<FIG> is a graph for describing a method of setting Th. A line L22 in <FIG> is the same as the line L22 in <FIG>. As illustrated in <FIG>, Th is set such that the cell voltage at which |ΔV/ΔQ| becomes Th or higher while the cell voltage is dropping due to the discharging becomes the cell voltage at which |ΔV/ΔQ| starts to sharply rise while the cell voltage is dropping due to the discharging.

While |ΔV/ΔQ| of any of the cells included in the drive battery <NUM> is lower than Th, the service tool <NUM> makes a negative determination in S17B of <FIG>, repeats the processes of S15 to S17B, and continues the discharging of the drive battery <NUM>. Then, when |ΔV/ΔQ| of all the cells included in the drive battery <NUM> becomes Th or higher (YES in S17B), in S18, the service tool <NUM> ends the discharging of the drive battery <NUM>.

As such, the discharging unit <NUM> can determine whether |ΔV/ΔQ| starts to sharply rise, based on whether |ΔV/ΔQ| has become the predetermined value or higher while the cell voltage is dropping due to the discharging. With the processes illustrated in <FIG>, it is possible to easily determine whether |ΔV/ΔQ| starts to sharply rise while the cell voltage is dropping due to the discharging. Then, when |ΔV/ΔQ| starts to sharply rise, the discharging unit <NUM> can end the discharging of the cell.

<FIG> is a diagram illustrating a modified example of the service tool <NUM> illustrated in <FIG>. With reference to <FIG>, a service tool 200A further includes a management unit <NUM> and a data acquisition unit <NUM> in addition to the discharging unit <NUM> and the estimation unit <NUM>. The management unit <NUM> is configured to manage Vend. Vend corresponds to the discharging end voltage indicating the timing of ending the discharging of the battery, which is executed to acquire the data for estimating the deterioration degree of the battery. The data acquisition unit <NUM> stores, in the management unit <NUM>, as the discharging end voltage, the voltage of the battery when |ΔV/ΔQ| (the change degree of the voltage per unit discharging amount of the battery) has become a predetermined value (Th) or higher after the start of the discharging of the battery. The management unit <NUM> in the service tool 200A is embodied by a storage device 203A. The data acquisition unit <NUM> in the service tool 200A is embodied by the processor <NUM> and a diagnosis program stored in the storage device 203A.

<FIG> is a flowchart illustrating processes related to data acquisition executed by the service tool 200A illustrated in <FIG>. The data acquisition unit <NUM> of the service tool 200A transmits a control command to the HVECU <NUM> in a state where the vehicle <NUM> in an unused state (for example, before shipment) is connected to the service tool 200A, whereby S41 to S47 of <FIG> are executed.

With reference to <FIG> together with <FIG>, in S41, the service tool 200A prepares for the discharging of the drive battery <NUM>. In S41, the service tool 200A may execute the above-described processes of S10 to S14 of <FIG>.

Subsequently in S42, the service tool 200A discharges the drive battery <NUM>. The process of S42 may be equivalent to that of S16 of <FIG>.

Subsequently in S43, the service tool 200A measures a state (a voltage, current, and a temperature) of each cell included in the drive battery <NUM>, and records a measurement result in the storage device 203A. The process of S43 may be equivalent to that of S15 of <FIG>.

Subsequently in S44, the service tool 200A calculates |ΔV/ΔQ| of each cell by differentiating the cell voltage with respect to the discharging amount in the transition of the voltage during the discharging of each cell included in the drive battery <NUM>. Then, in S45, the service tool 200A determines whether |ΔV/ΔQ| of all the cells included in the drive battery <NUM> has become Th or higher. The processes of S44 and S45 may be equivalent to those of S17A and S17B of <FIG>, respectively.

When |ΔV/ΔQ| of all the cells included in the drive battery <NUM> becomes Th or higher (YES in S45), in S46, the service tool 200A specifies a battery voltage at which |ΔV/ΔQ | starts to sharply rise while the battery voltage is dropping due to the discharging from the discharging amount (Qend) when |ΔV/ΔQ| of all the cells included in the drive battery <NUM> has become Th or higher. Then, the service tool 200A decides the specified battery voltage to be Vend. Vend may be the voltage (for example, the average cell voltage) of the drive battery <NUM> when |ΔV/ΔQ| of all the cells included in the drive battery <NUM> has become Th or higher.

Subsequently in S47, the service tool 200A ends the discharging of the drive battery <NUM>. The process of S47 may be equivalent to that of S18 of <FIG>.

Subsequently in S48, the data acquisition unit <NUM> of the service tool 200A stores, in the management unit <NUM>, the discharging end voltage (Vend) in association with information indicating the type of the battery composing the drive battery <NUM>. The service tool 200A may acquire the information indicating the type of the battery from the vehicle <NUM>. The information indicating the type of the battery may be stored in the storage device <NUM> in advance. In one example, the information indicating the type of the battery includes a battery manufacturer and a model number. The service tool 200A can discriminate, based on the battery manufacturer and the model number, the type of the battery (for example, a lithium-ion secondary battery / a nickel-hydrogen secondary battery) composing the drive battery <NUM>. The discharging end voltage (Vend) may be stored in the management unit <NUM> by executing a series of processes illustrated in <FIG> to the batteries mounted on vehicles other than the vehicle <NUM>. The management unit <NUM> manages a discharging end voltage (Vend) of a plurality of types of batteries. The management unit <NUM> manages the discharging end voltage (Vend) in association with information indicating the type of the battery in each battery. When the process of S48 is executed, the series of processes illustrated in <FIG> ends.

<FIG> is a flowchart for describing a method of setting the discharging end voltage based on the data that is acquired using the processes illustrated in <FIG>. The processes illustrated in this flowchart are executed before the process illustrated in <FIG> is started. For example, when a predetermined instruction is input from the user to the HMI <NUM> after the service tool 200A is connected to the vehicle <NUM> that has been used, the processes illustrated in <FIG> are executed. Then, the process illustrated in <FIG> is started by a process of S54 described below.

With reference to <FIG> together with <FIG>, in S51, the HVECU <NUM> transmits, to the service tool 200A, the information (for example, the battery manufacturer and the model number of the battery composing the drive battery <NUM>) indicating the type of the battery composing the drive battery <NUM>.

In S52, the service tool 200A receives the information indicating the type of the battery. Thereafter, the discharging unit <NUM> of the service tool 200A executes the processes of S53 and S54 described below.

In S53, the service tool 200A acquires, from the management unit <NUM>, the discharging end voltage (Vend) corresponding to the type of the battery composing the drive battery <NUM> using the information indicating the type of the battery, and sets it. Thereafter, in S54, the service tool 200A generates a discharging control start trigger used for deterioration diagnosis of the assembled battery. As such, the process illustrated in <FIG> is started. In the processes illustrated in <FIG>, the battery is discharged based on an appropriate discharging end voltage (that is, Vend set in S53) corresponding to the type of the battery mounted on the vehicle <NUM>. As such, it is possible to estimate, with sufficient accuracy, the deterioration degree of the battery while restricting the deterioration of the cell during the discharging.

The functions of the discharging unit <NUM> and the estimation unit <NUM> may be implemented in the vehicle <NUM>. <FIG> is a diagram illustrating a modified example of the HVECU <NUM> illustrated in <FIG>. With reference to <FIG>, an HVECU 50A mounted on the vehicle <NUM> may include the discharging unit <NUM> and the estimation unit <NUM>. In such an embodiment, the HVECU 50A mounted on the vehicle <NUM> executes the processes illustrated in <FIG>. The discharging unit <NUM> and the estimation unit <NUM> in the HVECU 50A may be embodied by the processor <NUM> and a program (for example, a diagnosis program stored in a storage device 53A) executed by the processor <NUM>. However, each of the discharging unit <NUM>, the estimation unit <NUM>, and the data acquisition unit <NUM> that are described above may be embodied by dedicated hardware (an electronic circuit).

In the above embodiment, the assembled battery mounted on the HEV which does not include an inlet for a plug-in is a target of the deterioration diagnosis. However, the present disclosure is not limited thereto, and an assembled battery mounted on a plug-in hybrid electric vehicle (PHEV) which includes an inlet for a plug-in may be a target of the deterioration diagnosis. Further, an assembled battery mounted on other xEVs (for example, a BEV, an FCEV, a range extender EV) may be a target of the deterioration diagnosis. The xEV is a vehicle that uses power as all or part of a drive power source.

It is not essential that all the cells are connected in series in the assembled battery of which the deterioration is diagnosed by any of the above-described methods (see <FIG>). The structure of the assembled battery of which the deterioration is diagnosed is arbitrary. <FIG> is a diagram illustrating a modified example of the assembled battery illustrated in <FIG>. For example, an assembled battery <NUM> illustrated in <FIG> may be a target of the deterioration diagnosis. The assembled battery <NUM> includes N parallel cell blocks (that is, parallel cell blocks CB-<NUM> to CB-N). Each of the parallel cell blocks CB-<NUM> to CB-N includes a plurality of cells connected in parallel. The number of cells connected in parallel in each parallel cell block is arbitrary, but in the example illustrated in <FIG>, it is three. The parallel cell blocks CB-<NUM> to CB-N are connected in series via a power line.

Claim 1:
A deterioration diagnosis apparatus (<NUM>) of a battery, the deterioration diagnosis apparatus (<NUM>) comprising one or more processors (<NUM>) configured to:
execute discharging of each of a plurality of cells included in an assembled battery (<NUM>) while measuring a voltage of each of the cells;
estimate a deterioration degree of each of the cells included in the assembled battery (<NUM>) using voltage data indicating a transition of the voltage of each of the cells included in the assembled battery (<NUM>) from a discharging start voltage to a predetermined discharging end voltage (Vend), the predetermined discharging end voltage (Vend) being a cell voltage at which a change degree of the cell voltage per unit discharging amount starts to sharply rise while the cell voltage is dropping due to the discharging; and
end the discharging when voltages of all the cells included in the assembled battery (<NUM>) reach the predetermined discharging end voltage (Vend).