Patent ID: 12227101

DESCRIPTION OF EMBODIMENT

FIG.1is an explanatory diagram of management system1according to an exemplary embodiment. Management system1is a system that manages information of a plurality of electric vehicles3and information of a plurality of chargers4and that when charger4charges up cells of electric vehicle3, creates a charging plan that contributes to suppression of degradation of the cells. Management system1is a system that is used in delivery companies, bus companies, taxi companies, and the like. Hereinafter, this exemplary embodiment will be described on the assumption that management system1is used in a delivery company. The delivery company owns a plurality of electric vehicles3that can be used for load transportation. In this exemplary embodiment, electric vehicle3is assumed to be a pure electric vehicle (EV) equipped with no internal combustion engine. The plurality of chargers4are not limited to chargers installed in offices or warehouses of the delivery company, but include also chargers installed in various facilities in a delivery area. For example, chargers installed in public facilities, commercial facilities, gas stations, car dealer shops, and freeway service areas are also put under management by the system.

The plurality of electric vehicles3each have a wireless communication function, and are accessible to network2to which management system1is connected. Network2is a general term for such communication paths as the Internet and leased lines, and types of communication media and protocols involved in network2are not matter of concern. As the communication media, for example, a mobile phone network (cellular network), a wireless local area network (LAN), a wired LAN, an optical fiber network, an ADSL network, a CATV network, or the like can be used. As the communication protocols, for example, the transmission control protocol (TCP)/internet protocol (IP), the user datagram protocol (UDP)/IP, or the like can be used.

FIG.2depicts a configuration example of management system1according to the exemplary embodiment. Management system1is composed of a cloud server installed in a data center. Management system1may be composed of the delivery companies' server. Management system1includes processor11and recording unit12. Processor11includes creating unit111, updating unit112, and communication unit113. The function of processor11is implemented by hardware resources and software resources that work together or by hardware resources alone. Usable hardware resources include, a central processing unit (CPU), a graphics processing unit (GPU), a read only memory (ROM), a random access memory (RAM), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), and other large-scale integrated circuits (LSIs). Usable software resources include an operating system, and other programs including an application program.

Recording unit12includes charger information holding unit121, vehicle information holding unit122, and degradation map holding unit123. Recording unit12includes a nonvolatile recording medium, such as a hard disk drive (HDD) and a solid state drive (SSD), and records various programs and data.

Charger information holding unit121holds an identification information item and a charging efficiency of each of a plurality of chargers4to be managed, the identification information item and the charging efficiency being associated with each other. Charger information holding unit121may further hold information on the type numbers, installation locations, and the like of chargers4. As a charging efficiency initial value of each charger4, an initial value listed in a specification table may be entered or the initial value may be left null. For a case of charger4whose specifications are unknown, its charge efficiency initial value is left null.

Vehicle information holding unit122holds an identification information item and a charging efficiency of each of a plurality of electric vehicles3to be managed, the identification information item and a charge efficiency being associated with each other. Vehicle information holding unit122may further hold information on the types, total traveling distances, discharging efficiencies, and the likes of electric vehicles3. As a charging efficiency initial value and a discharging efficiency initial value of each electric vehicle3, initial values listed in the specification table may be entered or both initial values may be left null.

The charging efficiency of charger4, the charging efficiency of electric vehicle3, and the discharging efficiency of electric vehicle3decrease due to time degradation. It should be noted that chargers4with the same type number show different charging efficiency decrease curves, depending on individual differences, environmental conditions, service modes, and the like. Similarly, electric vehicles3of the same type show different charging efficiency decrease curves or discharging efficiency decrease curves, depending on individual differences, environmental conditions, service modes, and the like. The heavier the decrease of the charging efficiency or the discharging efficiency, the greater the charging loss or discharging loss, thereby increasing the heat generation.

Degradation map holding unit123holds a charge cycle degradation characteristic map, a discharge cycle degradation map, and a storage degradation characteristic map for each type of secondary battery. Cycle degradation is degradation that progresses as the number of times of charging/discharging increases. Cycle degradation occurs mainly because of cracking or peeling resulting from expansion or contraction of an active material. Cycle degradation depends on a state of charge (SOC) range, a temperature, and a current rate that are used. In general, cycle degradation accelerates as the SOC range used gets wider, the temperature used gets higher, or the current rate used gets higher.

Storage degradation is deterioration that progresses as time goes by, depending on the temperature of a secondary battery at each point of time and the SOC of the same at each point of time. Storage degradation progresses as time goes by, regardless of whether a charging process or discharging process is in progress. Storage degradation occurs mainly because of formation of a film (solid electrolyte interphase (SEI) film) on the negative electrode. Storage degradation depends on the SOC and the temperature at each point of time. In general, storage degradation accelerates as the SOC at each point of time gets higher or the temperature at each point of time gets higher.

A cycle degradation rate and a storage degradation rate are derived in advance for each type of secondary battery, by battery manufacturer's experiments or simulations.

FIG.3depicts a schematic configuration of electric vehicle3. Electric vehicle3shown inFIG.3is a rear-wheel drive (2WD) EV including a pair of front wheels31f, a pair of rear wheels31r, and motor34serving as a power supply. The pair of front wheels31fare connected by front wheel axle32f, while the pair of rear wheels31rare connected by rear wheel axle32r. Transmission33transmits the rotation of motor34to rear wheel axle32rat a given conversion ratio.

Vehicle controller30is a vehicle electronic control unit (ECU) that controls electric vehicle3as a whole, and may be composed of, for example, an integrated vehicle control module (VCM). Vehicle controller30acquires various pieces of sensor information for detecting behavior of electric vehicle3and/or a surrounding environment of electric vehicle3, from sensor unit37in electric vehicle3.

Sensor unit37is a general term for sensors incorporated in electric vehicle3.FIG.3shows, as typical sensors, vehicle speed sensor371, global positioning system (GPS) sensor372, and gyro sensor373.

Vehicle speed sensor371generates a pulse signal proportional to the rotating speed of front wheel axle32for rear wheel axle32r, and transmits the generated pulse signal to vehicle controller30. Vehicle controller30detects the speed of electric vehicle3, based on the pulse signal received from vehicle speed sensor371.

GPS sensor372detects positional information on electric vehicle3, and transmits the detected positional information to vehicle controller30. Specifically, GPS sensor372receives a plurality radio waves from a plurality of GPS satellites, the radio waves including respective times of transmission of the radio waves, and calculates the latitude and longitude of a reception point, based on the times of transmission included respectively in the received radio waves.

Gyro sensor373detects the angular velocity of electric vehicle3, and transmits the detected angular velocity to vehicle controller30. Vehicle controller30integrates the incoming angular velocity from gyro sensor373, thus being able to determine a tilt angle of electric vehicle3.

In addition to these sensors, electric vehicle3is further equipped with various sensors. For example, electric vehicle3is equipped with an accelerator pedal opening sensor, a brake pedal opening sensor, a steering angle sensor, a camera, a sonar, and the like.

Wireless communication unit36carries out signal processing for making wireless access to network2via antenna36a. Usable wireless communication networks that allow electric vehicle3to wirelessly access network2include, for example, a mobile phone network (cellular network), a wireless LAN, an electronic toll collection system (ETC), a dedicated short range communications (DSRC) system, a vehicle-to-infrastructure (V2I) system, and a vehicle-to-vehicle (V2V) system.

FIG.4is an explanatory diagram of a detailed configuration of power supply system40incorporated in electric vehicle3shown inFIG.3. Power supply system40is connected to motor34via first relay RY1and inverter35. In power running mode, inverter35converts DC power, which is supplied from power supply system40, into AC power, and supplies the AC power to motor34. In regeneration mode, inverter35converts AC power, which is supplied from motor34, into DC power, and supplies the DC power to power supply system40. Motor34is a three-phase AC motor. In power running mode, it rotates in accordance with AC power supplied from inverter35. In regeneration mode, motor34converts rotation energy created by deceleration into AC power, and supplies the AC power to inverter35.

First relay RY1is a contactor inserted in a line connecting power supply system40to inverter35. When electric vehicle3is traveling, vehicle controller30sets first relay RY1in an on-state (closed state), thus electrically connecting power supply system40to power equipment of electric vehicle3. When electric vehicle3is not traveling, vehicle controller30, in principle, sets first relay RY1in an off-state (open state), thus breaking the electrical connection between power supply system40and the power equipment of electric vehicle3. In place of the relay, a non-relay type switch, such as a semiconductor switch, may be used.

Electric vehicle3is connected to charger4via charging cable38. This allows power storage unit41in power supply system40to be charged from the outside. In this exemplary embodiment, charger4is assumed to be a quick charger having a power conversion function of converting three-phase AC power, which is supplied from commercial power system5, into DC power. Charger4generates DC power by full-wave rectifying AC power supplied from commercial power system5and further smoothing the rectified AC power through a filter.

Usable quick charging standards include, for example, CHAdeMO (registered trademark), GB/T, and combined charging system (Combo). As of 2019, CHAdeMO (registered trademark) defines maximum power output (specification) as 1000 V×400 A=400 kW. GB/T defines maximum power output (specification) as 750 V×250 A=185 kW. Combo defines maximum power output (specification) as 900 V×400 A=350 kW. CHAdeMO (registered trademark) and GB/T adopt a controller area network (CAN) as a standard communication method. Combo, on the other hand, adopts power line communication (PLC) as a standard communication method.

Charging cable38conforming to the CAN method includes a communication line as well as a power line. When a charging port of electric vehicle3is connected to charger4through charging cable38, vehicle controller30establishes a communication channel for communicating with a controller in charger4. In a case of a charging cable conforming to the PLC method, a communication signal is superposed on a signal transmitted through the power line, and is exchanged between vehicle controller30and the controller in charger4.

Between vehicle controller30and management unit42of power supply system40, a communication channel is established through an in-vehicle network (e.g., CAN). A communication protocol applied between vehicle controller30and the controller in charger4and a communication protocol applied between vehicle controller30and management unit42of power supply system40may be the same or different from each other. When these communication protocols are different from each other, vehicle controller30functions as a gateway.

In electric vehicle3, second relay RY2is inserted in a line connecting power supply system40to charger4. In place of the relay, a non-relay type switch, such as a semiconductor switch, may be used. When charger4charges power storage unit41, vehicle controller30and management unit42operate in cooperation with each other. Vehicle controller30and management unit42set second relay RY2in an on-state (closed state) before charger4starts charging, and sets second relay RY2in an off-state (open state) after charger4finishes charging.

When charger4is an ordinary charger, in general, it charges with single-phase AC power of 100 V/200 V. When charger4charges with AC power, AC power is converted into DC power by an AC/DC converter (not illustrated) interposed between second relay RY2and power supply system40.

Power supply system40includes power storage unit41and management unit42, and power storage unit41includes a plurality of cells E1-En connected in series. Power storage unit41may be made up of a plurality of power storage modules that are connected in series or connected in series and parallel with each other. The cells are provided as lithium ion battery cells, nickel hydride battery cells, lead battery cells, electric double-layer capacitor cells, lithium ion capacitor cells, or the like. Hereinafter, in this specification, a case of using lithium ion battery cells (with a nominal voltage ranging from 3.6 V to 3.7 V) is assumed. The number of cells E1-En connected in series is determined according to the drive voltage of motor34.

Shunt resistor Rs is connected in series to the plurality of cells E1-En. Shunt resistor Rs functions as a current detection element. A Hall element may be used in place of shunt resistor Rs. A plurality of temperature sensors T1, T2, which detect temperatures of the plurality of cells E1-En, are disposed in power storage unit41. One temperature sensor may be disposed for each battery module or for each of the plurality of cells. As temperature sensors T1, T2, for example, thermistors can be used.

Management unit42includes voltage measurement unit43, temperature measurement unit44, current measurement unit45, and power storage controller46. Nodes of the plurality of cells E1-En connected in series are connected to voltage measurement unit43via a plurality of voltage lines, respectively. Voltage measurement unit43measures respective voltages between pairs of adjacent voltage lines, thereby measuring respective voltages between pairs of adjacent cells of cells E1-En. Voltage measurement unit43transmits the measured voltages between pairs of adjacent cells of cells E1-En to power storage controller46.

Because voltage measurement unit43has a higher voltage than power storage controller46, voltage measurement unit43is connected to power storage controller46through a communication line which is kept insulated in the section between voltage measurement unit43and power storage controller46. Voltage measurement unit43may be configured using an ASIC or a general-purpose analog front-end IC. Voltage measurement unit43includes a multiplexer and an A/D converter. The multiplexer outputs respective voltages between pairs of adjacent voltage lines to the A/D converter in order, with a voltage between the top pair of voltage lines first. The A/D converter converts an incoming analog voltage from the multiplexer, into a digital value.

Temperature measurement unit44includes voltage dividing resistors and an A/D converter. The A/D converter converts a plurality of analog voltages, which are created by dividing voltage signals from the plurality of temperature sensors T1, T2by the plurality of voltage dividing resistors, into digital values in sequence, and outputs the digital values to power storage controller46. Based on the incoming digital values, power storage controller46estimates the temperatures of the plurality of cells E1-En. For example, power storage controller46estimates the temperature of each of cells E1-En, based on a temperature value measured by a temperature sensor that is closest to each of cells E1-En.

Current measurement unit45includes a differential amplifier and an A/D converter. The differential amplifier amplifies a voltage across shunt resistor Rs, and outputs the amplified voltage to the A/D converter. The A/D converter converts the incoming voltage from the differential amplifier into a digital value, and outputs the digital value to power storage controller46. Based on the digital value, power storage controller46estimates a current flowing through the plurality of cells E1-En.

When power storage controller46has a built-in A/D converter and is provided with an analog input port, temperature measurement unit44and current measurement unit45may output analog voltages to power storage controller46, in which the A/D converter in power storage controller46may convert the analog voltages into digital values.

Power storage controller46manages states of the plurality of cells E1-En, based on the voltages, the temperatures, and the currents of the plurality of cells E1-En that are measured by voltage measurement unit43, temperature measurement unit44, and current measurement unit45, respectively. Power storage controller46and vehicle controller30are connected through the in-vehicle network. As the in-vehicle network, for example, a CAN or a local interconnect network (LIN) can be used.

Power storage controller46can be configured using a microcomputer, a nonvolatile memory (e.g., electrically erasable programmable read-only memory (EEPROM), and a flash memory). Power storage controller46estimates an SOC and a state of health (SOH) of each of the plurality of cells E1-En.

Power storage controller46estimates the SOC by a combination of an open circuit voltage (OCV) method and a current integration method. The OCV method is a method by which the SOC is estimated based on an OCV of each of cells E1-En measured by voltage measurement unit43and on an SOC-OCV curve. The current integration method is a method by which the SOC is estimated based on an OCV of each of cells E1-En at the start of charging/discharging and on a current integration value measured by current measurement unit45. The current integration method has a drawback that as a charging/discharging time gets longer, measurement errors by current measurement unit45further accumulate. It is therefore necessary to correct an SOC estimated by the current integration method, by using an SOC estimated by the OCV method.

The SOH is defined as a ratio of a current full charge capacity (FCC) to an initial FCC, and a lower SOH value (value closer to 0%) indicates the further progress of degradation. The SOH may be determined by capacity measurement through full charging/discharging or by adding up a storage degradation measurement and a cycle degradation measurement.

In addition, the SOH may be estimated based on a correlation between a cell and its internal resistance. The internal resistance can be estimated by dividing a voltage drop caused by a given current flowing through the cell for a given time by the value of that current. The internal resistance decreases as the cell temperature rises, and increases as the SOH decreases.

Before electric vehicle3is charged, creating unit111of management system1creates a charging plan, based on the current SOC of electric vehicle3and on a delivery plan. The delivery plan is basically created on the night before the date of delivery. Communication unit113can receive the current SOC of electric vehicle3from electric vehicle3. Based on a delivery route for electric vehicle3to be charged, creating unit111estimates a traveling distance needed for tomorrow's delivery, and estimates an amount of power required for tomorrow's delivery. Creating unit111sets a value given by adding the amount of power required for tomorrow's delivery to a lower limit value of an SOC use range, as a charging target SOC. Creating unit111calculates a required charging amount, based on a difference between the target charging SOC and the current SOC. Creating unit111sets a time right before a departure time fixed in the delivery plan, as a target charging completion time. For example, when the departure time is scheduled for 9:00, the target charging completion time is set as 8:55.

As described above, to suppress storage degradation of the secondary battery, reducing a period in which the SOC remains high is effective. Reaching the target SOC right before the start of use of the secondary battery is therefore desirable. In addition, to suppress cycle degradation of the secondary battery at the time of charging, charging the secondary battery at a lower current rate is effective. Charging the secondary battery with a low current suppresses its heat generation, thus suppressing a rise in the temperature of the secondary battery. The rising temperature leads to acceleration of both storage degradation and cycle degradation.

Creating unit111creates a charging plan that contributes to suppression of degradation of the secondary battery, based on the required charging amount and the target charging completion time. Various charging methods can be used in the charging plan. As the simplest charging method, a method of charging with a constant current (CC), i.e., CC method, can be used. Specifically, the required charging amount is divided by a time span between a charging start time and the target charging completion time to calculate a current rate, and the battery is charged with the calculated current rate. A CC-CV method may also be employed, according to which constant current (CC) charging is started as an initial charging process, and when a voltage value lower than the voltage corresponding to the target SOC by a given value is reached, the constant current (CC) charging is switched to constant voltage (CV) charging. Another charging method may also be employed, according to which, to keep the SOC as low as possible, an initial current rate is set low, and then the current rate is increased step by step as the target charge completion time comes near.

Creating unit111may derive an optimum current rate according to the type of the secondary battery and an ambient temperature by referring to the charge cycle degradation characteristic map and the storage degradation characteristic map that are held in degradation map holding unit123. In addition, a pause period may be set in the middle of a charging process. In this manner, various algorithms can be used as charging methods. Any algorithm that contributes to suppression of degradation of the secondary battery and allows reaching the target SOC at the target charge completion time may be used as a charging method.

The above-described methods of creating the charging plan are implemented on the assumption that charging is carried out before the start of delivery. In some cases, however, charging in the middle of delivery becomes necessary. There is a case, for example, where the delivery route is changed and the traveling distance is increased on the day of delivery. In such a case, it is necessary to charge the battery, using charger4installed in a place other than the office or the warehouse. Quick charging is often carried out in this situation. Quick charging involves a higher current rate, thus increasing load on the secondary battery.

Creating unit111creates a charging plan, based on the current SOC of electric vehicle3and on a delivery plan on delivery work of the current time onward of the day. Based on the remaining delivery route of electric vehicle3, creating unit111estimates a traveling distance needed for the remaining delivery and estimates an amount of power required for the remaining delivery. Creating unit111sets a value given by adding the amount of power required for the remaining delivery to the lower limit value of the SOC use range, as a charging target SOC. Creating unit111calculates a required charging amount, based on a difference between the target charging SOC and the current SOC.

Creating unit111estimates a remaining traveling time, based on the traveling distance needed for the remaining delivery route and on an average speed of electric vehicle3. Creating unit111adds a time required for delivery or loading to the remaining traveling time to estimate a remaining work time. Creating unit111subtracts the remaining work time from a scheduled time of returning to the office, thereby setting a target charging completion time for charger4. Creating unit111creates a charging plan that contributes to suppression of degradation of the secondary battery, based on the required charging amount and the target charging completion time. A charging method using an algorithm suitable for quick charging can be used.

When a charging plan is created, a charging efficiency of charger4needs to be taken into consideration. Charging the battery by charger4with a low charging efficiency results in a case where charging is not completed before the target charging completion time. A charging efficiency of electric vehicle3must also be taken into consideration. Charging electric vehicle3with a low charging efficiency also results in a case where charging is not completed before the target charging completion time.

When a charging plan is created, a discharging efficiency of electric vehicle3needs to be taken into consideration. A low discharging efficiency of electric vehicle3leads to a case where electric vehicle3is unable to travel a scheduled distance even if the secondary battery secures an estimated required amount of power.

FIG.5is a diagram that compares time transition of an SOC based on a charging plan with time transition of an SOC at the time of actual charging. A graph on the upper side shows an example without the charging efficiency of charger4and of electric vehicle3. In this example, charging in accordance with the charging plan results in a failure in reaching the target SOC before the target charging completion time. A graph on the lower side shows an example in which the charging plan is corrected with the charging efficiency of charger4and of electric vehicle3into consideration. In this example, the charging plan is corrected according to the charging efficiency of charger4. Specifically, the current rate is corrected according to the charging efficiency of charger4and to the charging efficiency of electric vehicle3. Charging in accordance with the corrected charging plan results in a success in reaching the target SOC before the target charging completion time.

FIG.6is a flowchart showing an example of a process of creating a charging plan and updating a charging efficiency, the process being executed by management system1according to the exemplary embodiment. Communication unit113of management system1receives an identification information item on electric vehicle3and an identification information item on charger4from electric vehicle3connected to charger4, via network2(S10). Based on the received identification information item on charger4, creating unit111refers to charger information holding unit121to acquire a charging efficiency of charger4. Based on the received identification information item on electric vehicle3, creating unit111refers to vehicle information holding unit122to acquire a charging efficiency of electric vehicle3(S11).

Creating unit111creates a charging plan with the charging efficiency of charger4and the charging efficiency of electric vehicle3. Creating unit111, as described above, creates the charging plan based on a required charging amount and a target charging completion time, and corrects a current rate set in the created charging plan, by multiplying the current rate by the reciprocal of the charging efficiency of charger4and the reciprocal of the charging efficiency of electric vehicle3(S12). Communication unit113transmits the charging plan including the corrected current rate, to electric vehicle3via network2(S13).

Upon receiving the charging plan including the current rate, vehicle controller30of electric vehicle3transmits the current rate as a current command value, to charger4via the communication line in charging cable38. Vehicle controller30turns on second relay RY2. Charger4supplies power to electric vehicle3at the current rate specified by the current command value.

During charging, vehicle controller30of electric vehicle3acquires the measurement value of a charging current flowing through power storage unit41and the measurement value of a charging voltage applied to power storage unit41, from power storage controller46. When the acquired charging voltage value reaches a voltage corresponding to a target SOC included in the charging plan, vehicle controller30turns off second relay RY2to end the charging.

During the charging, vehicle controller30transmits the acquired charging current measurement value to management system1via network2. Communication unit113of management system1receives the charging current measurement value transmitted from electric vehicle3(S14).

Updating unit112calculates the charging efficiency of charger4connected to electric vehicle3, based on the current command value included in the charging plan, the charging current measurement value, and the charging efficiency of electric vehicle3(S15). Specifically, the charging efficiency of charger4is calculated by (Equation 1) shown below. It is desirable that an average of a plurality of charging current measurement values that are taken in a given period in which the current command value remains unchanged be used as the charging current measurement value.
Charging efficiency of charger 4=charging current measurement value/(current command value*charging efficiency of electric vehicle 3)  (Equation 1)

When the charging efficiency of electric vehicle3is unknown, the charging efficiency of charger4can be calculated, using the following (Equation 2) to (Equation 4).
Charging current measurement value 1(known)=charging efficiency of chargerA(unknown)*charging efficiency of electric vehicleA(unknown)*current command value 1(known)  (Equation 2)
Charging current measurement value 2(known)=charging efficiency of chargerB(known)*charging efficiency of electric vehicleA(unknown)*current command value 2 (known)  (Equation 3)
Charging efficiency of chargerA(unknown)=(charging current measurement value 1(known)*charging efficiency of chargerB(known)*current command value 2 (known))/charging current measurement value 2(known)*current command value 1 (known)  (Equation 4)

Electric vehicle A and charger A represent electric vehicle3and charger4that are involved in the current charging process. Charger B is one of chargers4that electric vehicle A used in the past. Charger B may be, for example, charger4installed in an office and used most frequently by electric vehicle A, or may be charger4used most recently to charge electric vehicle A.

Current command value 1 represents a current command value used in the current charging process, and charging current measurement value 1 represents a charging current measured in the current charging process. Current command value 2 represents a current command value used in a charging process using charger B, and charging current measurement value 2 represents a charging current measured in the charging process using charger B.

When the charging efficiency of charger4is calculated using the above (Equation 2) to (Equation 4), it is necessary to hold current command value 2 and charging current measurement value 2 as a charging efficiency calculation history, in recording unit12of management system1or in the nonvolatile memory of vehicle controller30of electric vehicle3for a given period.

Updating unit112reads a charging efficiency of charger4held in charger information holding unit121, and calculates a new charging efficiency of charger4, based on the read charging efficiency that is the pre-updating charging efficiency and on the charging efficiency of charger4having been calculated this time. Updating unit112updates the charging efficiency of charger4held in charger information holding unit121, with the newly calculated charging efficiency (S16). Specifically, the new charging efficiency of charger4is calculated by using the following (Equation 5).
New charging efficiency of charger 4=(charging efficiency of charger 4 having been calculated this time*α(0<α≤1))+(pre-updating charging efficiency of charger 4*(1−α))  (Equation 5)

Setting α=1 results in a process of replacing the existing charging efficiency of charger4with the charging efficiency of the charger4having been calculated this time. α being smaller than 1 results in a moving average process in which the charging efficiency value having been calculated this time contributes less as α gets closer to 0. Because the charging efficiency of charger4depends also on environmental conditions, such as temperature, the charging efficiency should desirably be updated by the moving average process, based on a plurality of pieces of sample data. The equation may be manipulated such that as the interval between the current date of calculation and the previous date of calculation gets longer, α is brought closer to 1 to increase the degree of contribution of the charging efficiency value having been calculated this time.

Updating unit112calculates the charging efficiency of electric vehicle3, based on the current command value included in the transmitted charging plan, the received charging current measurement value, and the charging efficiency of charger4connected to electric vehicle3(S17). Specifically, the charging efficiency of electric vehicle3is calculated by the following (Equation 6).
Charging efficiency of electric vehicle 3=charging current measurement value/(current command value*charging efficiency of charger 4)  (Equation 6)

When the charging efficiency of charger4is unknown, the charging efficiency of electric vehicle3can be calculated using the following (Equation 7) to (Equation 9).
Charging current measurement value 1(known)=charging efficiency of electric vehicleA(unknown)*charging efficiency of chargerA(unknown)*current command value 1(known)  (Equation 7)
Charging current measurement value 2(known)=charging efficiency of electric vehicleB(known)*charging efficiency of chargerA(unknown)*current command value 2(known)  (Equation 8)
Charging efficiency of electric vehicleA(unknown)=charging current measurement value 1(known)*charging efficiency of electric vehicleB(known)*current command value 2(known)/charging current measurement value 2(known)*current command value 1(known)  (Equation 9)

Electric vehicle A and charger A represent electric vehicle3and charger4that are involved in the current charging process. Electric vehicle B represents one of electric vehicles3that were charged with charger A in the past. Electric vehicle B may be, for example, electric vehicle3charged most frequently with charger A, or electric vehicle3charged most recently with charger A.

Current command value 1 represents a current command value used in the current charging process, and charging current measurement value 1 represents a charging current measured in the current charging process. Current command value 2 represents a current command value that is used when electric vehicle B is charged, and charging current measurement value 2 represents a charging current that is measured when electric vehicle B is charged.

When the charging efficiency of electric vehicle3is calculated using the above (Equation 7) to (Equation 9), it is necessary to hold current command value 2 and charging current measurement value 2 as a charging efficiency calculation history, in recording unit12of management system1or in the nonvolatile memory of vehicle controller30of electric vehicle3for a given period.

Updating unit112reads a charging efficiency of electric vehicle3that is the target vehicle, the charging efficiency being held in vehicle information holding unit122, and calculates a new charging efficiency of electric vehicle3, based on the read charging efficiency that is the pre-updating charging efficiency and on the charging efficiency of electric vehicle3having been calculated this time. Updating unit112updates the charging efficiency of electric vehicle3held in vehicle information holding unit122, with the newly calculated charging efficiency (S18). Specifically, the new charging efficiency of electric vehicle3is calculated by the following (Equation 10).
New charging efficiency of electric vehicle 3=(charging efficiency of electric vehicle 3 having been calculated this time*β(0<β≤1))+(pre-updating charging efficiency of electric vehicle 3*(1−β))  (Equation 10)

Setting β=1 results in a process of replacing the existing charging efficiency of electric vehicle3with the charging efficiency of electric vehicle3having been calculated this time. β being smaller than 1 results in a moving average process in which the charging efficiency value having been calculated this time contributes less as β gets closer to 0. Because the charging efficiency of electric vehicle3depends also on environmental conditions, such as temperature, the charging efficiency should desirably be updated by the moving average process, based on a plurality of pieces of sample data. The equation may be manipulated such that as the interval between the current date of calculation and the previous date of calculation gets longer, β is brought closer to 1 to increase the degree of contribution of the charging efficiency value having been calculated this time.

With reference to the above (Equation 1) to (Equation 4) and (Equation 5) to (Equation 9), examples of calculating the charging efficiency of charger4and the charging efficiency of electric vehicle3on the basis of the current command value and the charging current measurement value have been described. In this calculation process, a power command value and a charging power measurement value may be used in place of the current command value and the charging current measurement value. A depth of discharge (DOD) may also be used.

FIG.7is a flowchart showing an example of a process of creating a charging plan and updating a discharging efficiency, the process being executed by management system1according to the exemplary embodiment. Communication unit113of management system1receives an identification information item on electric vehicle3and an identification information item on charger4from electric vehicle3connected to charger4, via network2(S20). Based on the received identification information item on charger4, creating unit111refers to charger information holding unit121to acquire a charging efficiency of charger4. Based on the received identification information item on electric vehicle3, creating unit111refers to vehicle information holding unit122to acquire a charging efficiency and a discharging efficiency of electric vehicle3(S21).

Creating unit111creates a charging plan with the charging efficiency of charger4, the charging efficiency of electric vehicle3, and the discharging efficiency of electric vehicle3. Creating unit111, as described above, creates a charging plan based on a required charging amount and a target charging completion time. Creating unit111corrects an amount of power required for traveling, by multiplying an amount of power required for traveling a scheduled delivery route, the amount of power being the basis of calculation of the required charging amount, by the reciprocal of the discharging efficiency of electric vehicle3. In addition, creating unit111corrects a current rate set in the created charging plan, by multiplying the current rate by the reciprocal of the charging efficiency of charger4and the reciprocal of the charging efficiency of electric vehicle3(S22). Communication unit113transmits the charging plan including the corrected current rate, to electric vehicle3via network2(S23).

Upon receiving the charging plan including the current rate, vehicle controller30of electric vehicle3transmits the current rate as a current command value, to charger4via the communication line in charging cable38. Vehicle controller30turns on second relay RY2. Charger4supplies power to electric vehicle3at the current rate specified by the current command value.

During charging, vehicle controller30of electric vehicle3acquires the measurement value of a charging current flowing through power storage unit41and the measurement value of a charging voltage applied to power storage unit41, from power storage controller46. When the acquired charging voltage value reaches a voltage corresponding to a target SOC included in the charging plan, vehicle controller30turns off second relay RY2to end the charging.

When the vehicle having finished delivery returns to the office, vehicle controller30transmits power consumption representing an amount of power consumed in the current delivery work, to management system1via network2. Communication unit113of management system1receives the power consumption transmitted from electric vehicle3(S24).

Updating unit112calculates a discharging efficiency of electric vehicle3, based on an amount of power required for pre-correction traveling, the amount of power being estimated at the time of creating the charging plan, and on the received power consumption (S25). Specifically, the discharging efficiency of electric vehicle3is calculated by the following (Equation 11).
Discharging efficiency of electric vehicle 3=power consumption/estimated amount of power required for pre-correction traveling  (Equation 11)

Updating unit112reads a discharging efficiency of electric vehicle3that is the target vehicle, the discharging efficiency being held in vehicle information holding unit122, and calculates a new discharging efficiency of electric vehicle3, based on the read discharging efficiency that is the pre-updating discharging efficiency and on the discharging efficiency of electric vehicle3having been calculated this time. Updating unit112updates the discharging efficiency of electric vehicle3held in vehicle information holding unit122, with the newly calculated discharging efficiency (S26). Specifically, the new discharging efficiency of electric vehicle3is calculated by the following (Equation 12).
New discharging efficiency of electric vehicle 3=(discharging efficiency of electric vehicle 3 having calculated this time*γ(0<γ≤1))+(pre-updating discharging efficiency of electric vehicle 3*(1−γ))  (Equation 12)

Setting γ=1 results in a process of replacing the existing discharging efficiency of electric vehicle3with the discharging efficiency of electric vehicle3having been calculated this time. γ being smaller than 1 results in a moving average process in which the discharging efficiency value having been calculated this time contributes less as γ gets closer to 0. Because the discharging efficiency of electric vehicle3depends also on environmental conditions, such as temperature, the discharging efficiency should desirably be updated by the moving average process, based on a plurality of pieces of sample data. The equation may be manipulated such that as the interval between the current date of calculation and the previous date of calculation gets longer, γ is brought closer to 1 to increase the degree of contribution of the discharging efficiency value having been calculated this time.

FIG.8depicts a schematic configuration of electric vehicle3according to a modification. Electric vehicle3according to the modification is an electric vehicle equipped with detachable/replaceable battery pack P1serving as a power source. Compared with electric vehicle3with full-spec capability, this electric vehicle3has lower power output and is limited in occupant capacity and maximum speed. Electric vehicle3according to the modification includes battery mounting unit47in which battery packs P1are placed. Battery mounting unit47has a plurality of mounting slots. The plurality of battery packs P1fitted in the plurality of mounting slots are connected in parallel with each other. The greater the number of battery packs P1placed in the battery mounting unit47is, the higher the battery capacity becomes.

As described above, according to this exemplary embodiment, the charging plan is created with the charging efficiency of charger4and the charging efficiency of electric vehicle3. A charging plan contributing to suppression of degradation of the secondary battery, therefore, can be created meticulously with high accuracy. In a case where a shift between the charging plan and the actual time transition of charging exists, correction for eliminating the shift is required in the next charging process and other charging processes to follow. However, because charger4and electric vehicle3have their unique charging efficiencies, respectively, using a different unit of charger4or electric vehicle3in each charging process leads to a problem that the shift is not eliminated. In particular, a vehicle for delivery business needs to be charged in the middle of its delivery work in many cases, in which various types of chargers4are expected to be used.

According to this exemplary embodiment, the charging efficiency of charger4and the charging efficiency of electric vehicle3are collectively managed by the database of management system1. By accessing management system1at the time of charging electric vehicle3, therefore, the shift between the charging plan and the actual time transition of charging can be reduced. Reducing the shift allows creation of a charging plan that contributes to suppression of degradation of the secondary battery.

In addition, the charging efficiency of charger4and the charging efficiency of electric vehicle3are updated in each charging process. As a result, the charging efficiency of charger4and the charging efficiency of electric vehicle3can be kept at the optimum charging efficiency value. Even if a different unit of charger4or electric vehicle3is used in each charging process, therefore, a highly accurate charging plan can be created constantly. In a case where charger4is a charger used for a certain unit of electric vehicle3for the first time, if this charger4has already been used to charge a different unit of electric vehicle3, a highly accurate charging plan can be created by accessing management system1.

By collectively managing the discharging efficiencies of electric vehicles3by the database of management system1, the secondary battery can be charged with the optimal amount of power with little excess or deficiency. Collective discharging efficiency management is particularly effective for an application in which, as indicated inFIG.8, combinations of electric vehicle3and the secondary battery vary. A proper charging plan can be created according to the discharging efficiency of electric vehicle3in which the secondary battery is incorporated. By updating the discharging efficiency of electric vehicle3for each delivery work, the discharging efficiency of electric vehicle3can be kept at the optimum discharge efficiency value. Discharging efficiency updating can also be used for the purpose of identifying electric vehicle3whose discharging efficiency is declining. This also allows management of vehicle maintenance periods and tire replacement periods.

According to this exemplary embodiment, management system1manages the charging efficiency of charger4, the charging efficiency of electric vehicle3, and the discharging efficiency of electric vehicle3, and creates the charging plan. This reduces the load on vehicle controller30of electric vehicle3. Software for vehicle controller30of electric vehicle3is updated less frequently, and adding functions is achieved in most cases by merely updating software for management system1. Hence actual implementation of the system is easy.

The present disclosure has been described above according to the exemplary embodiment. It will be understood by those who are skilled in art that the exemplary embodiment is merely an example, that combinations of constituent elements and processes included in the exemplary embodiment may be modified in various forms, and that such modifications are also within the scope of the present disclosure.

In the above-described exemplary embodiment, the case of the delivery vehicle having the delivery plan to follow has been described. The present disclosure may also be applied to services with an undetermined traveling distance, such as a car-sharing service. In such a case, the target SOC in the charging plan may be set as the upper limit value of the SOC use range.

The exemplary embodiment may be specified by the following items.

[Item 1]

Management system (1) includes:charger information holding unit (121) that holds an identification information item and a charging efficiency of each of a plurality of chargers (4), the identification information item and the charging efficiency being associated with each other;communication unit (113) that, from electric vehicle (3) connected to charger (4), receives an identification information item on charger (4) via network (2); andcreating unit (111) that creates a charging plan for electric vehicle (3), based on a required charging amount and a target charging termination time,wherein creating unit (111) refers to charger information holding unit (121) and specifies a charging efficiency of charger (4) connected to electric vehicle (3), based on the received identification information item, and creates a charging plan in which the charging efficiency of charger (4) is taken into consideration, andcommunication unit (113) sends the created charging plan to electric vehicle (3) via network (2).

According to Item 1, a highly accurate charging plan in which the charging efficiency of connected charger (4) is taken into consideration can be created.

[Item 2]

Management system (1) according to Item 1, further including vehicle information holding unit (122) that holds an identification information item and a charging efficiency of each of a plurality of electric vehicles (3), the identification information item and the charging efficiency being associated with each other,wherein communication unit (113) receives an identification information item on electric vehicle (3) from electric vehicle (3) connected to charger (4), via network (2), andcreating unit (111) refers to vehicle information holding unit (122) and specifies a charging efficiency of electric vehicle (3), based on the received identification information item on electric vehicle (3), and creates a charging plan in which a charging efficiency of charger (4) and the charging efficiency of electric vehicle (3) are taken into consideration.

According to Item 2, a highly accurate charging plan in which the charging efficiency of connected charger (4) and the charging efficiency of electric vehicle (3) are taken into consideration can be created.

[Item 3]

Management system (1) according to Item 2, whereincommunication unit (113) receives a measurement value of a charging current or charging power in electric vehicle (3) connected to charger (4), via network (2), andmanagement system (1) further includes updating unit (112) that calculates a charging efficiency of charger (4), based on a current command value or a power command value included in a charging plan transmitted to electric vehicle (3), on the measurement value of the charging current or of the charging power, and on a charging efficiency of electric vehicle (3), and updates a charging efficiency of charger (4) held in charger information holding unit (121), based on the calculated charging efficiency.

According to Item 3, the charging efficiency of charger (4) can be kept at an optimum value.

[Item 4]

Management system (1) according to Item 3, wherein updating unit (112) calculates a charging efficiency of electric vehicle (3), based on a current command value or a power command value included in a charging plan transmitted to electric vehicle (3), on the measurement value of the charging current or of the charging power, and on a charging efficiency of charger (4) connected to electric vehicle (3), and updates a charging efficiency of electric vehicle (3) held in vehicle information holding unit (122), based on the calculated charging efficiency.

According to Item 4, the charging efficiency of electric vehicle (3) can be kept at an optimum value.

[Item 5]

Management system (1) according to Item 3 or 4, whereinvehicle information holding unit (122) further holds an identification information item and a discharging efficiency of each of the plurality of electric vehicles (3), the identification information item and the discharging efficiencies being associated with each other,communication unit (113) receives an identification information item on electric vehicle (3) and power consumption representing an amount of power consumed for traveling, from electric vehicle (3) to which the charging plan has been transmitted, via network (2), andupdating unit (112) calculates a discharging efficiency of electric vehicle (3), based on an amount of power required for traveling, the amount of power being estimated when a charging plan having been transmitted to electric vehicle (3) is created, and on the power consumption, and updates a discharging efficiency of electric vehicle (3) held in vehicle information holding unit (122), based on the calculated discharging efficiency.

According to Item 5, the discharging efficiency of electric vehicle (3) can be kept at an optimum value.

[Item 6]

Management system (1) according to Item 5, wherein creating unit (111) refers to vehicle information holding unit (122) and specifies a discharging efficiency of electric vehicle (3), based on an identification information item on electric vehicle (3) connected to charger (4), and creates a charging plan in which the discharging efficiency of electric vehicle (3) is taken into consideration.

According to Item 6, a highly accurate charging plan in which the discharging efficiency of electric vehicle (3) is taken into consideration can be created.

[Item 7]

Management system (1) according to any one of Items 1 to 6, wherein power storage unit (41) incorporated in electric vehicle (3) is detachable.

According to Item 7, even if a combination of electric vehicle (3) and power storage unit (41) changes, a highly accurate charging plan can be created.

[Item 8]

A management program causing a computer to execute the processes of:receiving an identification information item on charger (4) from electric vehicle (3) connected to charger (4), via network (2);referring to charger information holding unit (121) that holds an identification information item and a charging efficiency of each of a plurality of chargers (4), the identification information item and the charging efficiencies being associated with each other, and specifying a charging efficiency of charger (4) connected to electric vehicle (3), based on the received identification information item;creating a charging plan for electric vehicle (3), based on a required charging amount, a target charging termination time, and the charging efficiency of charger (4); andtransmitting the created charging plan to electric vehicle (3) via network (2).

According to Item 8, a highly accurate charging plan in which the charging efficiency of connected charger (4) is taken into consideration can be created.

[Item 9]

Electric vehicle (3) including:motor (34);power storage unit (41) that supplies power to motor (34); andcontroller (30) that communicates with management system (1) according to any one of Items 1 to 7 to control a process of charging power storage unit (41) by charger (4).

According to Item 9, highly accurate charging in which the charging efficiency of connected charger (4) is taken into consideration can be carried out.

REFERENCE MARKS IN THE DRAWINGS

1management system2network3electric vehicle4charger5commercial power system11processor111creating unit112updating unit113communication unit12recording unit121charger information holding unit122vehicle information holding unit123degradation map holding unit124calculation history holding unit30vehicle controller31ffront wheel31rrear wheel32ffront wheel axle32rrear wheel axle33transmission34motor35inverter36wireless communication unit36aantenna37sensor unit371vehicle speed sensor372GPS sensor373gyro sensor38charging cable40power supply system41power storage unit42management unit43voltage measurement unit44temperature measurement unit45current measurement unit46power storage controller47battery mounting unitE1, E2, En cellRY1first relayRY2second relayT1first temperature sensorT2second temperature sensorRs shunt resistorP1battery pack