JP7435332B2 - vehicle charging system - Google Patents

Description

The present invention relates to a charging system for charging an assembled battery of a vehicle from an external power source.

Conventionally, when an external power source and a vehicle are connected, a first charging operation is performed with a charging state lower than a fully charged state as a target value, and after the charging state reaches the target value, charging is stopped and charging There is a charging system that performs a second charging operation so as to reach a fully charged state at a scheduled end time (see Patent Document 1).

According to the charging system described in Patent Document 1, the second charging operation is performed so that the power storage device is in a fully charged state at the scheduled charging end time, so the time for maintaining the power storage device in a fully charged state is short. Therefore, deterioration of the power storage device can be suppressed. Furthermore, according to Patent Document 1, the first charging operation is performed immediately when the external power source and the vehicle are connected, so even if the user starts driving the vehicle earlier than the scheduled charging end time, The vehicle can be driven using the electricity stored in the power storage device.

Patent No. 5710775

By the way, in the charging system described in Patent Document 1, when a battery pack in which a plurality of unit cells are connected in series is used as the power storage device, the following problem occurs. In other words, since the first charging operation is performed immediately when the external power source and the vehicle are connected, the SOC (State of Charge: ratio [%] of the current remaining charge to the full charge capacity) of the plurality of cells varies. Charging is performed in the same state. Therefore, even after the second charging operation is completed, there is a possibility that the deviation in SOC (charging ratio) between the plurality of single cells remains large.

The present invention has been made to solve the above problems, and its main purpose is to provide a charging system for a vehicle that charges an assembled battery so that the charging ratio of the assembled battery becomes a predetermined end ratio at a scheduled end time. The object of the present invention is to enable a vehicle to run even at a time earlier than the scheduled end time of charging, and to suppress deviations in charging ratios between single cells at the scheduled end time.

The first means to solve the above problem is
When a battery pack (11) in which a plurality of cells are connected in series is connected to an external power source (31) via a charger (21), the charging ratio of the battery pack reaches the scheduled end time due to multiple stages of charging. A vehicle charging system that charges the assembled battery to a predetermined termination ratio,
During a period in which charging is not being performed from the time when the assembled battery is connected to the external power source via the charger until the start of the final stage of charging of the plurality of stages of charging, an equalization unit (22, 23, 25) that performs equalization to reduce the deviation of the charging ratio to a predetermined deviation or less;
a charging unit (21, 25) that performs the final stage of charging so that the charging ratio of the assembled battery becomes the end ratio at the scheduled end time;
Equipped with.

According to the above configuration, in the vehicle charging system, when an assembled battery consisting of multiple single cells connected in series is connected to an external power source via a charger, the charging ratio of the assembled battery is scheduled to end through multiple stages of charging. The assembled battery is charged to a predetermined end ratio at a certain time. Thereby, since the charging ratio of the assembled battery becomes the end ratio at the scheduled end time, the time during which the charging ratio of the assembled battery is maintained at the end ratio is shortened, and deterioration of the assembled battery can be suppressed. Furthermore, since the assembled battery is also charged during the charging stage earlier than the final charging stage among the multiple stages of charging, the vehicle can be driven even at a time earlier than the scheduled end time. .

Here, if the deviation in the charging ratio between the plurality of single cells is large before charging, there is a possibility that the deviation in the charging ratio between the plurality of single cells will remain large even after the final stage of charging. In this regard, the equalization unit is configured to perform multiple charging operations during a period in which charging is not being performed from the time when the assembled battery is connected to an external power source via the charger until the start of the final stage of charging among multiple stages of charging. Equalization is performed to reduce the deviation of the charging ratio of the single cells to a predetermined deviation or less. Therefore, even if the deviation in charging ratio between multiple single cells is large before charging, it is possible to reduce the deviation in charging ratio between multiple single cells before the start of the final stage of charging. can. Then, the charging unit performs the final stage of charging so that the charging ratio of the assembled battery becomes the end ratio at the scheduled end time. Therefore, it is possible to suppress the deviation in the charging ratio between the single cells at the scheduled end time.

In the second means, the charging unit performs the final stage of charging so that the charging ratio of the assembled battery becomes the end ratio at the scheduled end time after the equalization by the equalizer ends. do.

According to the above configuration, even if the deviation in the charging ratio between the plurality of single cells is large before charging, the deviation in the charging ratio between the plurality of single cells is determined before the start of the final stage of charging. It can be kept below the deviation. Then, after the equalization by the equalization section is completed, the charging section performs the final stage of charging so that the charging ratio of the assembled battery becomes the end ratio at the scheduled end time. Therefore, it is possible to suppress the deviation in the charging ratio between the single cells at the scheduled end time.

In the third means, the slope of the output voltage with respect to the charging ratio of the single cell is larger than the first slope when the charging ratio of the single cell is included in the first range, and the slope of the output voltage with respect to the charging ratio of the single cell is larger than the first slope, The equalization unit satisfies a first relationship that is smaller than the first slope when included in a second range different from the first range, and the equalization unit is configured to , the charging unit calculates the charging ratio of each unit cell, and the charging unit performs the charging at the stage immediately before the equalization is performed by the equalizing unit until the charging ratio of a predetermined unit cell is included in the first range. Exit in the state where it is.

According to the above configuration, the slope of the output voltage with respect to the charge ratio of the single cell is larger than the first slope when the charge ratio of the single cell is included in the first range, and A first relationship is satisfied in which the slope is smaller than the first slope when the slope falls within a different second range. Then, the equalization unit calculates the charging ratio of the unit cell based on the first relationship and the detected output voltage of the unit cell. Therefore, in a state where the charging ratio of the single battery is included in the second range, the slope of the output voltage with respect to the charging ratio of the single battery is smaller than the first slope, and the first relationship and the detected output of the single battery are There is a possibility that the charging ratio of each cell cannot be accurately calculated based on the voltage.

In this respect, the charging section ends the charging at the stage immediately before the equalization is performed by the equalization section in a state where the charging ratio of the predetermined unit cell is included in the first range. In a state where the charging ratio of the unit cell is included in the first range, the slope of the output voltage with respect to the charging ratio of the unit cell is larger than the first slope. For this reason, the charging ratio of the single cell is accurately calculated based on the first relationship and the detected output voltage of the single cell, compared to the state where the charging ratio of the single cell is included in the second range. Can be done. Therefore, when the equalization unit performs equalization, it is possible to accurately calculate the charging ratio of each unit cell, and it is possible to improve the accuracy of equalization.

In the fourth means, the slope of the output voltage with respect to the charging ratio of the single cell is larger than the second slope when the charging ratio of the single cell is included in the third range, and the slope of the output voltage with respect to the charging ratio of the single cell is larger than the second slope, satisfies a second relationship that is smaller than the second slope when the temperature of the unit cell is included in a fourth range different from the third range and is included in a predetermined temperature range, and the equalization unit and calculates a charging ratio of the unit cell based on the detected output voltage of the unit cell, and the charging unit performs charging at a stage immediately before performing the equalization by the equalization unit at a predetermined rate. The process ends with the charging ratio of the single battery falling within the third range.

According to the above configuration, the slope of the output voltage with respect to the charge ratio of the single cell is larger than the second slope when the charge ratio of the single cell is included in the third range, and A second relationship is satisfied in which the second slope is smaller than the second slope when the temperature of the cell is included in a different fourth range and the temperature of the unit cell is included in a predetermined temperature range. Then, the equalization unit calculates the charging ratio of the unit cell based on the second relationship and the detected output voltage of the unit cell. Therefore, in a state where the charging ratio of the unit cell is included in the fourth range, depending on the temperature of the unit cell, the slope of the output voltage with respect to the charging ratio of the unit cell may become smaller than the second slope. In that case, there is a possibility that the charging ratio of each unit cell may not be accurately calculated based on the second relationship and the detected output voltage of the unit cell.

In this regard, the charging section ends the charging at the stage immediately before the equalization is performed by the equalization section in a state where the charging ratio of the predetermined unit cell is included in the third range. In a state where the charging ratio of the single battery is included in the third range, the slope of the output voltage with respect to the charging ratio of the single battery is larger than the second slope. Therefore, when the equalization unit performs equalization, it is possible to suppress the accuracy of calculating the charging ratio of each cell from decreasing, and it is possible to suppress the accuracy of equalization from decreasing.

When the final stage of charging of the assembled battery is completed, if the temperature of the assembled battery is too low, the output of the assembled battery will not be stabilized, and if the temperature of the assembled battery is too high, the assembled battery may deteriorate. Further, by charging the assembled battery, the assembled battery generates heat and the temperature of the assembled battery increases.

Therefore, in the fifth means, when the charging section starts the charging step one step before the final step charging, if the temperature of the outside air is lower than a predetermined temperature, the charging section When the charging of the assembled battery is completed with the charging ratio of the assembled battery being the first ratio, and the temperature of the outside air is higher than the predetermined temperature, the charging of the previous stage is completed with the charging ratio of the assembled battery being the first ratio. The process ends with the second ratio being larger than the first ratio.

According to such a configuration, when starting the charging step before the final stage charging, if the outside air temperature is lower than the predetermined temperature, the final stage charging This allows the amount of charge to be charged to the assembled battery to be increased. Therefore, when the temperature of the outside air is lower than the predetermined temperature, the temperature of the assembled battery can be further increased by the final stage of charging. Therefore, when the final stage of charging of the assembled battery is completed, the temperature of the assembled battery can be prevented from becoming too low, and the output of the assembled battery can be stabilized.

Also, when starting the next stage of charging before the final stage of charging, if the outside air temperature is higher than the predetermined temperature, the final stage of charging will cause the assembled battery to The amount of charging can be reduced. Therefore, when the temperature of the outside air is higher than the predetermined temperature, it is possible to suppress the temperature of the assembled battery from increasing during the final stage of charging. Therefore, when the final stage of charging of the assembled battery is completed, it is possible to prevent the temperature of the assembled battery from becoming too high, and it is possible to prevent the assembled battery from deteriorating.

In a sixth means, the charging unit performs the first stage of charging when the assembled battery is connected to the external power source via the charger. According to this configuration, when the assembled battery is connected to an external power source via the charger, electric power can be immediately stored in the assembled battery by the first stage of charging, so that the vehicle can start running at an earlier time. can do.

Specifically, as in the seventh means, the equalization unit controls the charging in the final stage of the plurality of stages of charging from the time when the assembled battery is connected to the external power source via the charger. A configuration in which it is periodically determined whether or not the equalization is necessary during a period in which charging is not performed up to the start time, and the equalization is executed when it is determined that the equalization is necessary. Can be adopted.

If the assembled battery is left in a state where the charging ratio of the assembled battery is high, there is a risk that the assembled battery will deteriorate.

In this regard, in the eighth means, after the final stage of charging by the charging section is completed, the assembled battery continues to be connected to the external power source via the charger for a predetermined period of time. The battery pack includes a discharging unit that discharges the assembled battery so that the charging ratio of the assembled battery is smaller than the end ratio when the battery is turned on. According to this configuration, if the assembled battery remains connected to the external power source via the charger for a predetermined period of time after the final stage of charging is completed, the user may stop driving the vehicle. It is possible to determine that the battery has been canceled and reduce the charging ratio of the assembled battery. Therefore, it is possible to prevent the assembled battery from being left in a state where the charging ratio of the assembled battery is high, and it is possible to suppress the assembled battery from deteriorating.

Block diagram of electric vehicle charging system Graph showing the relationship between cell OCV and SOC in the first embodiment Flowchart showing the timer charging process procedure Time chart showing aspects of timer charging in the first embodiment Graph showing the OCV of each cell after the first stage of charging is completed Graph showing OCV of each cell after completion of second stage charging in comparative example Graph showing OCV of each cell after equalization Graph showing OCV of each cell after second stage charging Graph showing the relationship between cell OCV and SOC in the second embodiment Time chart showing aspects of timer charging in the third embodiment Time chart showing aspects of SOC reduction processing

(First embodiment)
Hereinafter, a first embodiment embodied in a charging system for an electric vehicle will be described with reference to the drawings. As shown in FIG. 1, the electric vehicle 10 (vehicle) includes a battery pack 11, a charger 21, a battery management unit (BMU) 22, an equalization circuit 23, an input section 24, a controller 25, etc. ing.

The assembled battery 11 is configured by connecting a plurality of cells (single cells) in series. Each cell is composed of a secondary battery such as a lithium ion battery or a nickel battery.

The external power supply 31 is, for example, a 100 [V] single-phase AC commercial power supply. A charging cable 32 is connected to the external power source 31. A charging connector 33 is provided at the tip of the charging cable 32.

A power line 26 is connected to the charger 21 . A charging connector 27 is provided at the tip of the power line 26. Charging connector 27 is connectable to charging connector 33. When the charging connector 33 is connected to the charging connector 27, a connection signal indicating the connection is input from the charging connector 27 to the controller 25. AC power is supplied to the charger 21 from an external power source 31 via a charging cable 32 , charging connectors 33 and 27 , and a power line 26 . Charger 21 converts the supplied AC power into DC power and supplies it to battery pack 11 . As a result, the assembled battery 11 is charged. Charger 21 is controlled by controller 25 .

The battery monitoring unit 22 (hereinafter referred to as "BMU 22") detects the state of the assembled battery 11 based on the detection results of the cell voltage sensor 11a, current sensor 11b, and temperature sensor 11c provided in the assembled battery 11. The cell voltage sensor 11a detects the voltage between the terminals of each cell (output voltage). The current sensor 11b detects the current flowing through the assembled battery 11. The temperature sensor 11c detects the temperature of the assembled battery 11. The BMU 22 transmits the detection results of the cell voltage sensor 11a, current sensor 11b, and temperature sensor 11c to the controller 25. BMU22 is controlled by controller 25.

The equalization circuit 23 is a circuit that individually discharges each cell of the assembled battery 11 and adjusts the SOC (State of Charge) of each cell. SOC (charging ratio) is the ratio [%] of the current remaining capacity to the full charge capacity of the cell. The equalization circuit 23 is controlled by the BMU 22. Note that the equalization circuit 23 may be a circuit that adjusts the SOC of each cell by charging the cell from the cell with a higher SOC to the cell with a lower SOC.

The input unit 24 is a part for inputting a scheduled end time tf of timer charging, which will be described later, through a user's operation. The input section 24 includes a touch panel and a key operation section. The scheduled end time tf input into the input section 24 is transmitted to the controller 25.

The controller 25 is a microcomputer that includes a CPU, ROM, RAM, storage device, input/output interface, and the like. Controller 25 controls charger 21 and BMU 22 based on signals input from charging connector 27 , charger 21 , BMU 22 , and input section 24 . The controller 25 controls the equalization circuit 23 through the BMU 22. When the assembled battery 11 is connected to the external power supply 31 via the charger 21, the controller 25 causes the SOC of the assembled battery 11 to reach SOC2 (predetermined termination ratio) at the scheduled termination time tf through multiple stages of charging. Then, timer charging is performed to charge the assembled battery 11. Note that the equalization circuit 23, BMU 22, and controller 25 constitute an equalization section. The charger 21 and the controller 25 constitute a charging section. The equalization circuit 23, BMU 22, charger 21, and controller 25 constitute a vehicle charging system.

FIG. 2 is a graph showing the relationship between OCV (Open Circuit Voltage) and SOC of a cell. OCV (output voltage) is the voltage between the terminals of a cell when no load is applied to the cell (no device is connected to the cell). As shown in the figure, the OCV and SOC of a cell have a correlation. Therefore, the controller 25 calculates the SOC of each cell based on the graph of FIG. 2 and the OCV detected by each cell voltage sensor 11a.

The slope of the OCV with respect to the SOC of the cell is larger than the first slope g1 when the SOC of the cell is within 0 to 40[%] and 70 to 100[%] (first range). Further, the slope of the OCV with respect to the SOC of the cell is smaller than the first slope g1 when the SOC of the cell is within 40 to 70[%] (second range). The slope of OCV with respect to SOC of a cell satisfies these first relationships.

The controller 25 causes the equalization circuit 23 through the BMU 22 to perform equalization to reduce the SOC deviation of the plurality of cells of the assembled battery 11 to a predetermined deviation or less. Specifically, the controller 25 determines that the deviation in OCV (SOC) between the cell with the highest OCV (the cell with the most SOC) and the cell with the lowest OCV (the cell with the least SOC) is a predetermined voltage ΔV (a predetermined deviation Cells with a relatively high OCV (cells with a relatively large SOC) are discharged so that the voltage is less than or equal to ΔSOC.

The controller 25 calculates the SOC of the cell based on the first relationship and the detected OCV of the cell. Therefore, in a state where the SOC of the cell is included in the second range, the slope of the OCV with respect to the SOC of the cell is smaller than the first slope g1, and based on the first relationship and the detected OCV of the cell, There is a possibility that the SOC of each cell cannot be calculated accurately. Therefore, the controller 25 causes the equalization to be performed in a state where the SOC of the cell with the lowest SOC (predetermined cell) is included in the first range.

FIG. 3 is a flowchart showing the processing procedure of timer charging. This series of processing is executed by the controller 25 when the charging connector 33 is connected to the charging connector 27 and the scheduled end time tf is inputted by the user into the input section 24.

First, the scheduled charging end time tf is obtained from the input unit 24 (S10). Information about the assembled battery 11 is acquired from the BMU 22 (S11). Based on the acquired information on the assembled battery 11, the start time of the second stage of charging is determined so that the SOC of the assembled battery 11 becomes 100% (predetermined end ratio) at the scheduled end time tf. ts2 is determined (S12).

Specifically, based on the acquired information on the assembled battery 11, the SOC of the cell with the highest SOC is set as the SOC of the assembled battery 11, which is SOCw. The target SOC of the assembled battery 11 in the first stage of charging is SOC1 (for example, 75%). If the SOCw of the assembled battery 11 is less than the target SOC1 (SOCw<SOC1), SOC1 is subtracted from 100% (SOC2), which is the target SOC of the assembled battery 11 due to the second stage of charging, and the SOC1 of the second stage of charging is calculated. The amount of increase ΔSOC2 in the SOC of the assembled battery 11 due to charging is calculated (ΔSOC2=100−SOC1). On the other hand, if the SOCw of the assembled battery 11 is higher than the target SOC1 (SOCw>SOC1), the SOCw is subtracted from 100 [%], which is the target SOC of the assembled battery 11 in the second stage of charging, and The amount of increase ΔSOC2 in the SOC of the assembled battery 11 is calculated (ΔSOC2=100−SOCw).

The time ΔTe2 required to increase the SOC of the battery pack 11 by an increase amount ΔSOC2 by the second stage of charging is calculated. The time ΔTe2 is calculated by dividing the increase amount ΔSOC2 in the SOCw of the assembled battery 11 due to the second stage charging by the increase amount ΔSOCv2 in the SOCw of the assembled battery 11 per unit time during the second stage charging (ΔTe2=ΔSOC2 /ΔSOCv2). Then, a time ΔTe2 before the scheduled charging end time tf is set as the second stage charging start time ts2 (ts2=tf−ΔTe2).

Next, the first stage of charging is started (S13). Information about the assembled battery 11 and a graph showing the relationship between the OCV and SOC of the cell are obtained from the BMU 22 (S14). It is determined whether the first stage of charging can be completed (S15).

Specifically, the SOC of each cell is calculated based on the first relationship in FIG. 2 and the detected OCV of the cell. If the SOC of the cell with the highest SOC is equal to or higher than the target SOC1, and the SOC of the cell with the lowest SOC is included in 70% or higher (first range) (S15: YES), the first stage of charging ends. (S16). On the other hand, if a negative determination is made in S15 (S15: NO), the process is executed again from S14.

Next, based on the information about the assembled battery 11 acquired from the BMU 22, it is determined whether or not equalization of the SOCs of the cells is necessary (S17). Specifically, the deviation in OCV (SOC) between the cell with the highest OCV (the cell with the most SOC) and the cell with the lowest OCV (the cell with the least SOC) is greater than a predetermined voltage ΔV (predetermined deviation ΔSOC). If it is larger, it is determined that equalization is necessary, and if it is smaller than the predetermined voltage ΔV (predetermined deviation ΔSOC), it is determined that equalization is unnecessary. In this determination, if it is determined that cell SOC equalization is necessary (S17: YES), cell SOC equalization is performed as described above (S18). On the other hand, in this determination, if it is determined that equalization of the SOC of the cells is unnecessary (S17: NO), the process proceeds to S19.

That is, in the processing from S16 to S18, charging is performed from the time when the assembled battery 11 is connected to the external power source 31 until the start of the second stage (final stage) of the two stages (multiple stages) of charging. Equalization of the SOCs of a plurality of cells is performed during a period when the battery is not charged (from the end of the first stage charging to the start of the second stage charging).

In the process of S19, it is determined whether the start time ts2 of the second stage charging has arrived (S19). In this determination, if it is determined that the start time ts2 of the second stage charging has not arrived (S19: NO), the process is executed again from S17.

On the other hand, in the determination of S19, when it is determined that the start time ts2 of the second stage charging has arrived (S19: YES), the second stage charging is started (S20). Information about the assembled battery 11, a graph showing the relationship between the OCV and SOC of the cell (the first relationship in FIG. 2), etc. are acquired from the BMU 22 (S21). It is determined whether the second stage of charging can be completed (S22).

Specifically, the SOC of each cell is calculated based on the first relationship in FIG. 2 and the detected OCV of the cell. If it is determined that the SOC (SOCw) of the cell with the highest SOC is not 100 [%] (the target SOC of the assembled battery 11 due to the second stage of charging) (S22: NO), execute again from the process of S21. . On the other hand, when it is determined that the SOC (SOCw) of the cell with the highest SOC has reached 100% (S22: YES), the second stage of charging is ended (S23). Then, this series of processing ends (END).

Note that the processing from S16 to S18 corresponds to the processing performed by the equalization section, and the processing from S19 to S23 corresponds to the processing performed by the charging section.

FIG. 4 is a time chart showing an aspect of timer charging.

At time t11, traveling of electric vehicle 10 is ended. At time ts1, when the charging connector 33 is connected to the charging connector 27 and the user inputs the scheduled end time tf into the input unit 24, the first stage of charging is started.

In the first stage of charging, the assembled battery 11 is charged until the SOCw of the assembled battery 11 exceeds 40 to 70 [%] (second range) and reaches the target SOC1. Note that while the assembled battery 11 is being charged and discharged, the BMU 22 is activated.

At time tf1, when the SOCw of the assembled battery reaches the target SOC1 in the first stage of charging, the first stage of charging ends. Between time tf1 when the first stage charging ends and time ts2 when the second stage charging starts, the BMU 22 is activated periodically and cell equalization is performed as necessary.

At start time ts2, second stage charging is started. At the scheduled end time tf, the SOCw of the battery pack 11 reaches 100%, and the timer charging of the battery pack 11 ends. At time t12, electric vehicle 10 starts running.

FIG. 5 is a graph showing the OCV of each cell after the first stage of charging is completed. OCV1 is an OCV corresponding to the target SOC1 in the first stage of charging, and OCV2 is an OCV corresponding to the target SOC of 100[%] (SOC2) in the second stage of charging. When the electric vehicle 10 finishes running, there are variations in the OCV (SOC) of the cells that make up the assembled battery 11. Even at the end of the first stage of charging, a state in which the OCVs of the cells forming the assembled battery 11 vary is maintained.

FIG. 6 is a graph showing the OCV of each cell after the second stage of charging is completed in the comparative example. Even at the end of the second stage of charging, a state in which there are variations in OCV (SOC) of the cells forming the assembled battery 11 is maintained. Therefore, only the OCV of cell 4 with the highest OCV is OCV2, and the OCVs of the other cells are lower than OCV2.

FIG. 7 is a graph showing the OCV of each cell after equalization is performed after the first stage of charging in FIG. 5 is completed. Cells 1, 4, 6, n with relatively high OCV (large SOC) are discharged, and cells 1, 4, 6, n with the highest OCV (cell with the highest SOC) and cell 5 (with the lowest OCV) are discharged. The deviation of the OCV (SOC) from the cell with the lowest SOC is less than or equal to the predetermined voltage ΔV (predetermined deviation ΔSOC).

FIG. 8 is a graph showing the OCV of each cell after the second stage of charging is completed in this embodiment. Even at the end of the second stage of charging, the variation in OCV of the cells constituting the assembled battery 11 remains small, as in the case after equalization.

The present embodiment described in detail above has the following advantages.

- In the charging system of the electric vehicle 10, when the assembled battery 11 in which a plurality of cells are connected in series is connected to the external power source 31 via the charger 21, the SOCw of the assembled battery 11 is increased by charging in multiple stages (two stages). The assembled battery 11 is charged so that it reaches 100% (SOC2) at the scheduled end time tf. As a result, the SOCw of the assembled battery 11 becomes 100 [%] at the scheduled end time tf, so the time during which the SOCw of the assembled battery 11 is maintained at 100 [%] is shortened, and deterioration of the assembled battery 11 is suppressed. Can be done. Furthermore, since the assembled battery 11 is also charged by the charging in the stage (first stage) before the final stage (second stage) of charging in multiple stages, the battery pack 11 is charged at the time tf1 earlier than the scheduled end time tf. Even if there is a problem, the electric vehicle 10 can be made to run.

- The controller 25 is configured to perform charging from the time when the assembled battery 11 is connected to the external power source 31 via the charger 21 (time ts1) until the start of the final stage of charging among the multiple stages of charging (start time ts2). During the period when it is not being performed (times tf1 to ts2), equalization is performed to reduce the SOC deviations of a plurality of cells to a predetermined deviation ΔSOC or less. Therefore, even if the SOC deviation between multiple cells is large before charging, it is possible to reduce the SOC deviation between multiple cells to a predetermined deviation ΔSOC or less before starting the final stage of charging. can. After the equalization is completed, the controller 25 causes the final stage of charging to be performed so that the SOCw of the assembled battery 11 becomes 100% at the scheduled end time tf. Therefore, as shown in FIG. 8, the deviation in SOC between cells at the scheduled end time tf can be suppressed, and the SOC of more cells can be reduced to 100% (in a fully charged state) compared to the comparative example in FIG. ) can be approached.

- The controller 25 ends the charging at the stage immediately before performing equalization (first stage) in a state where the SOC of the predetermined cell (the cell with the lowest SOC) is included in the first range. In a state where the SOC of the cell is within the first range (70 to 100 [%]), the slope of the output voltage with respect to the SOC of the cell is larger than the first slope g1. Therefore, compared to the state where the SOC of the cell is included in the second range (40 to 70 [%]), the first relationship in FIG. 2 and the detected cell output voltage (voltage between terminals) Based on this, the SOC of the cell can be accurately calculated. Therefore, when the controller 25 executes equalization, the SOC of each cell can be calculated accurately, and the accuracy of equalization can be improved.

- The controller 25 causes the first stage of charging to be performed when the assembled battery 11 is connected to the external power source 31 via the charger 21. According to this configuration, when the assembled battery 11 is connected to the external power source 31 via the charger 21, power can be immediately stored in the assembled battery 11 by the first stage of charging, so that the electric vehicle 10 runs can be made possible.

(Second embodiment)
The second embodiment will be described below, focusing on the differences from the first embodiment. Note that the same parts as in the first embodiment are given the same reference numerals, and the description thereof will be omitted. In this embodiment, the slope of the OCV with respect to the SOC of the cell satisfies the second relationship shown in FIG. 9, which is different from the first relationship shown in FIG.

FIG. 9 is a graph showing the relationship between OCV and SOC of a cell. As shown in the figure, the OCV and SOC of a cell have a correlation. Therefore, the controller 25 calculates the SOC of each cell based on the graph in FIG. 9 and the OCV detected by each cell voltage sensor 11a.

The slope of the OCV with respect to the SOC of the cell is larger than the second slope g2 when the SOC of the cell is included in 0 to 60 [%] and 75 to 100 [%] (third range). In addition, the slope of OCV with respect to SOC of the cell is determined when the SOC of the cell is included in the range of 60 to 75 [%] (fourth range) and the temperature of the assembled battery 11 is included in the range of 25 to 45 degrees Celsius (predetermined temperature range). , it becomes smaller than the second slope g2. Note that the slope of the OCV with respect to the SOC of the cell is the second range when the SOC of the cell is within 60 to 75% (fourth range) and the temperature of the assembled battery 11 is between -30°C and 0°C. The slope becomes larger than the slope g2. The slope of OCV with respect to SOC of a cell satisfies these second relationships.

In FIG. 3, the controller 25 executes the same processing as in the first embodiment from S10 to S13.

Then, information on the assembled battery 11, a graph showing the relationship between the OCV and SOC of the cell (second relationship in FIG. 9), etc. are acquired from the BMU 22 (S14). It is determined whether the first stage of charging can be completed (S15).

Specifically, the SOC of each cell is calculated based on the second relationship in FIG. 9 and the detected OCV of the cell. If the SOC of the cell with the highest SOC is equal to or higher than the target SOC1, and the SOC of the cell with the lowest SOC is included in 75% or higher (third range) (S15: YES), the first stage of charging ends. (S16). On the other hand, if a negative determination is made in S15 (S15: NO), the process is executed again from S14.

After that, the controller 25 executes the same processing as in the first embodiment from S17 to S23.

According to the above configuration, the controller 25 performs charging at the stage immediately before performing equalization (first stage charging) when the SOC of the cell with the lowest SOC (predetermined cell) is included in the third range. end in the state. In a state where the SOC of the cell is included in the third range, the slope of the OCV with respect to the SOC of the cell is larger than the second slope g2. Therefore, when the controller 25 executes equalization, it is possible to suppress a decrease in the accuracy of calculating the SOC of each cell, and it is possible to suppress a decrease in the accuracy of equalization.

(Third embodiment)
The third embodiment will be described below, focusing on the differences from the first embodiment. Note that the same parts as in the first embodiment are given the same reference numerals, and the description thereof will be omitted.

When the second stage (final stage) of charging of the assembled battery 11 is finished, if the temperature of the assembled battery 11 is too low, the output of the assembled battery 11 will not be stable, and if the temperature of the assembled battery 11 is too high, the assembled battery 11 may deteriorate. Further, by charging the assembled battery 11, the assembled battery 11 generates heat, and the temperature of the assembled battery 11 increases.

Therefore, in this embodiment, as shown in FIG. 10, the controller 25 controls the outside air to When the temperature is lower than the predetermined temperature, the previous stage of charging is ended with the SOCw of the assembled battery 11 being SOC3 (first ratio). On the other hand, if the temperature of the outside air is higher than the predetermined temperature, the previous stage of charging is ended in a state where the SOCw of the assembled battery 11 is SOC4 (second ratio), which is larger than SOC3.

According to this configuration, when starting the charging step before the final charging step, if the outside air temperature is lower than a predetermined temperature (low temperature) or higher than the predetermined temperature (high temperature), In comparison, the amount charged to the assembled battery 11 can be increased by the final stage of charging. Therefore, when the temperature of the outside air is lower than the predetermined temperature, the temperature of the assembled battery 11 can be further increased by the final stage of charging. Therefore, when the final stage of charging of the battery pack 11 is completed, the temperature of the battery pack 11 can be prevented from becoming too low, and the output of the battery pack 11 can be stabilized.

Also, when starting the charging step before the final charging step, when the outside air temperature is higher than the predetermined temperature (high temperature), compared to when it is lower than the predetermined temperature (low temperature), By charging at the final stage, the amount of charge to the assembled battery 11 can be reduced. Therefore, when the temperature of the outside air is higher than the predetermined temperature, it is possible to suppress the temperature of the assembled battery 11 from increasing due to the final stage of charging. Therefore, when the final stage of charging of the battery pack 11 is finished, it is possible to prevent the temperature of the battery pack 11 from becoming too high, and it is possible to prevent the battery pack 11 from deteriorating.

In addition, when the charging of the stage before the second stage (final stage) is finished with the SOCw of the assembled battery 11 being SOC3 (first ratio) and SOC4 (second ratio), , the SOC of the cell (SOCw of the assembled battery 11) is preferably included in the first range in FIG. 2 or the third range in FIG.

Note that each of the embodiments described above can be modified and implemented as follows. The same parts as in each of the above embodiments are given the same reference numerals, and a description thereof will be omitted.

- At the end of the second stage (final stage) of charging, the SOCw of the assembled battery 11 is not limited to 100 [%], but may be set to 95 [%] or 90 [%] (a predetermined end ratio).

- The controller 25 may end the second stage (final stage) of charging a predetermined time before the scheduled end time tf of timer charging input by the user.

- If the assembled battery 11 is left in a state where the SOCw of the assembled battery 11 is large, there is a possibility that the assembled battery 11 will deteriorate. Therefore, as shown in FIG. 11, the controller 25 maintains a predetermined state in which the assembled battery 11 is connected to the external power source 31 via the charger 21 after the final stage charging (second stage charging) is completed. If the discharge continues beyond time Te3, the assembled battery 11 is discharged so that the SOCw of the assembled battery 11 is made smaller (for example, to 90[%]) than 100[%] (predetermined termination ratio). (SOC reduction processing). Note that the equalization circuit 23, BMU 22, and controller 25 constitute a discharge section.

According to this configuration, if the assembled battery 11 continues to be connected to the external power source 31 via the charger 21 for more than the predetermined time Te3 after the final stage of charging is completed, the user It is possible to reduce the SOCw of the assembled battery 11 by determining that the electric vehicle 10 has stopped running. Therefore, it is possible to prevent the assembled battery 11 from being left in a state where the SOCw of the assembled battery 11 is large, and it is possible to suppress deterioration of the assembled battery 11.

- When the charging connector 33 is connected to the charging connector 27, the controller 25 may start the first stage of charging even if the scheduled end time tf is not input by the user to the input unit 24. Then, after the user inputs the scheduled end time tf into the input unit 24, the second stage charging start time ts2 may be determined.

- The controller 25 performs charging at the stage immediately before performing equalization (first stage), when the SOC of the cell whose SOC is close to the average value or the cell whose SOC is the highest (predetermined cell) is in the first range or the third range. It may also be terminated in a state where it is included in . Further, the controller 25 can also terminate the charging at the stage immediately before performing equalization, regardless of whether the SOC of a predetermined cell is included in the first range or the third range.

- Timer charging is not limited to two stages of charging, but may be performed through three or more stages of charging. In that case, the controller 25 performs charging during the period between charging stages, that is, from the time when the assembled battery 11 is connected to the external power source 31 until the start of the final charging stage among the multiple stages of charging. It is sufficient to perform equalization during the period when the Note that if the controller 25 determines that the time from when the assembled battery 11 is connected to the external power source 31 via the charger 21 to the scheduled end time tf is longer than the predetermined time Te4 (for example, 8 hours), Equalization may be performed before the first stage of charging. Even in that case, after equalization, the assembled battery 11 is charged by a stage of charging that is earlier than the final stage of charging among multiple stages of charging, so the time tf1 is earlier than the scheduled end time tf. It is also possible to enable the electric vehicle 10 to travel.

- Not limited to a configuration that periodically determines whether or not equalization is necessary during a period when charging is not being performed, but also a configuration that determines once whether or not equalization is necessary after each stage of charging is completed. Good too.

- After starting to equalize the SOCs of cells in the process of S18 in FIG. 3, by the time the SOC deviations of multiple cells become equal to or less than the predetermined deviation (equalization ends), the second stage of the process of S19 is performed. It may be determined that charging start time ts2 has arrived. In that case, even if the SOC deviations of the plurality of cells are not equal to or less than the predetermined deviation, equalization may be interrupted in the process of S20 and second stage charging may be started (executed). Even with this configuration, if the SOC deviation between the plurality of cells is large before charging, it is possible to reduce the SOC deviation between the plurality of cells before the start of the second stage (final stage) charging. can. Then, at the scheduled end time tf, the SOCw of the assembled battery 11 can be set to 100% (end ratio).

In particular, when the outside air is at high temperature in the second embodiment and the third embodiment, the time from the end of the first stage charging to the start of the second stage charging tends to be short. Therefore, if the second stage charging start time ts2 is reached by the time the SOC deviations of a plurality of cells become equal to or less than a predetermined deviation (equalization ends), the second stage charging can be started (executed). is valid.

- As the external power source 31, a 200 [V] three-phase AC commercial power source or the like may be used.

- Each of the above embodiments can be applied not only to the electric vehicle 10 that includes a motor as a drive device, but also to a hybrid vehicle that includes an engine and a motor as a drive device.

DESCRIPTION OF SYMBOLS 10... Electric vehicle, 11... Assembled battery, 21... Charger, 22... Battery monitoring unit (BMU), 23... Equalization circuit, 25... Controller, 31... External power supply.

Claims (8)

When a battery pack (11) in which a plurality of cells are connected in series is connected to an external power source (31) via a charger (21), the charging ratio of the battery pack reaches the scheduled end time due to multiple stages of charging. A vehicle charging system that charges the assembled battery to a predetermined termination ratio,
During a period in which charging is not being performed from the time when the assembled battery is connected to the external power source via the charger until the start of the final stage of charging of the plurality of stages of charging, an equalization unit (22, 23, 25) that performs equalization to reduce the deviation of the charging ratio to a predetermined deviation or less;
a charging unit (21, 25) that performs the final stage of charging so that the charging ratio of the assembled battery becomes the end ratio at the scheduled end time;
Equipped with
The slope of the output voltage with respect to the charging ratio of the unit cell is larger than the first slope when the charging ratio of the unit cell is included in the first range, and the slope of the output voltage with respect to the charging ratio of the unit cell is larger than the first slope when the charging ratio of the unit cell is included in the first range. satisfies a first relationship that is smaller than the first slope when included in two ranges,
The equalization unit calculates a charging ratio of each unit cell based on the first relationship and the detected output voltage of the unit cell,
A vehicle charging system, wherein the charging unit finishes charging at a stage immediately before the equalization is performed by the equalization unit in a state in which a predetermined charging ratio of the unit cell is included in the first range. . When a battery pack (11) in which a plurality of cells are connected in series is connected to an external power source (31) via a charger (21), the charging ratio of the battery pack reaches the scheduled end time due to multiple stages of charging. A vehicle charging system that charges the assembled battery to a predetermined termination ratio,
During a period in which charging is not being performed from the time when the assembled battery is connected to the external power source via the charger until the start of the final stage of charging of the plurality of stages of charging, an equalization unit (22, 23, 25) that performs equalization to reduce the deviation of the charging ratio to a predetermined deviation or less;
a charging unit (21, 25) that performs the final stage of charging so that the charging ratio of the assembled battery becomes the end ratio at the scheduled end time;
Equipped with
The slope of the output voltage with respect to the charging ratio of the single cell is larger than the second slope when the charging ratio of the single cell is included in the third range, and when the charging ratio of the single cell is different from the third range, 4 range and satisfies a second relationship that is smaller than the second slope when the temperature of the unit cell is included in a predetermined temperature range,
The equalization unit calculates a charging ratio of the unit cell based on the second relationship and the detected output voltage of the unit cell,
The charging unit is configured to charge the vehicle by terminating the charging at a stage immediately before the equalization is performed by the equalization unit in a state where a predetermined charging ratio of the unit cell is included in the third range. system. When a battery pack (11) in which a plurality of cells are connected in series is connected to an external power source (31) via a charger (21), the charging ratio of the battery pack reaches the scheduled end time due to multiple stages of charging. A vehicle charging system that charges the assembled battery to a predetermined termination ratio,
During a period in which charging is not being performed from the time when the assembled battery is connected to the external power source via the charger until the start of the final stage of charging of the plurality of stages of charging, an equalization unit (22, 23, 25) that performs equalization to reduce the deviation of the charging ratio to a predetermined deviation or less;
a charging unit (21, 25) that performs the final stage of charging so that the charging ratio of the assembled battery becomes the end ratio at the scheduled end time;
Equipped with
The charging unit is configured to perform the charging in the previous stage to charge the assembled battery if the temperature of the outside air is lower than a predetermined temperature when starting the charging in the stage preceding the final stage of charging. When the ratio is the first ratio and the temperature of the outside air is higher than the predetermined temperature, the previous stage of charging is changed to a state where the charging ratio of the assembled battery is higher than the first ratio. A vehicle charging system that ends with two ratios. If the assembled battery continues to be connected to the external power source via the charger for more than a predetermined time after the final stage of charging by the charging unit is completed, the assembled battery The vehicle charging system according to any one of claims 1 to 3 , further comprising a discharging unit (22, 23, 25) that discharges the assembled battery so that the charging ratio is smaller than the end ratio. When a battery pack (11) in which a plurality of cells are connected in series is connected to an external power source (31) via a charger (21), the charging ratio of the battery pack reaches the scheduled end time due to multiple stages of charging. A vehicle charging system that charges the assembled battery to a predetermined termination ratio,
During a period in which charging is not being performed from the time when the assembled battery is connected to the external power source via the charger until the start of the final stage of charging of the plurality of stages of charging, an equalization unit (22, 23, 25) that performs equalization to reduce the deviation of the charging ratio to a predetermined deviation or less;
a charging unit (21, 25) that performs the final stage of charging so that the charging ratio of the assembled battery becomes the end ratio at the scheduled end time;
Equipped with
If the assembled battery continues to be connected to the external power source via the charger for more than a predetermined time after the final stage of charging by the charging unit is completed, the assembled battery A vehicle charging system comprising: a discharging unit (22, 23, 25) that discharges the assembled battery so that the charging ratio is smaller than the end ratio. The charging unit performs the final stage of charging so that the charging ratio of the assembled battery becomes the end ratio at the scheduled end time after the equalization by the equalizer ends . 5. The vehicle charging system according to any one of Item 5 . The vehicle charging system according to any one of claims 1 to 6 , wherein the charging unit performs a first stage of charging when the assembled battery is connected to the external power source via the charger. The equalization unit is configured to: during a period when charging is not being performed from the time when the assembled battery is connected to the external power source via the charger until the start of the final stage of charging among the plurality of stages of charging; The vehicle charging method according to any one of claims 1 to 7 , wherein it periodically determines whether or not the equalization is necessary, and executes the equalization when it is determined that the equalization is necessary. system.

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