JP6658425B2 - Battery system - Google Patents

Description

  The present invention relates to a battery system, and more particularly, to a battery system mounted on an electric vehicle.

  In recent years, a so-called plug-in hybrid vehicle has been put into practical use in which a charging plug connected to a commercial power supply or the like outside the vehicle is attached to a power supply port of the vehicle body so that a vehicle-mounted battery can be charged with external power from the vehicle outside power supply. . For example, in Patent Document 1, in a plug-in hybrid vehicle, when charging external power to a vehicle-mounted battery, a user is asked to select whether or not to perform equalization processing for equalizing voltages of a plurality of battery cells. It is described that the discomfort that the battery charging time feels as being extended by the time required for the equalization processing is suppressed. Further, if the voltage or SOC (State Of Charge) of the battery cells constituting the battery varies due to individual differences, differences in deterioration state, or the like, the SOC range in which the battery can be used is narrowed. It is known to perform an equalization process for equalizing.

JP-A-2005-186339

  Patent Literature 1 describes that, when externally charging a battery, when equalization processing of battery cells is necessary, external charging is performed after the equalization processing is performed. However, in recent years, the battery capacity has been increased in order to extend the distance traveled by the vehicle using only the power of the motor (the so-called EV travel distance), and the charging time required to charge the target SOC with external power is correspondingly increased. Also tend to take longer. Therefore, if the battery cell equalization processing and external charging are performed separately, the total time required for the equalization processing and external charging becomes long, and depending on the usage condition of the vehicle by the user, the equalization processing and external charging may not be performed. Sometimes not enough.

  The present invention provides a battery system capable of determining a start time of an equalization process so as to execute a battery cell equalization process while externally charging a battery in an electric vehicle.

A battery system according to the present invention is a battery system mounted on an electric vehicle and capable of charging external power, and is connected to a battery configured by connecting a plurality of battery cells in series and each battery cell. and equalizing circuit, by controlling the switching elements included in each equalization circuit, and a control device that performs equalization processing of the cell voltage of each battery cell, comprising a control device, the current of each battery cell was calculated for each batteries cell equalization time necessary to complete the equalization process from the SOC and the equalization target SOC,-out based on the charging time of the external power to the battery-and average equivalent time, If it is determined that the charging time is longer than the equalization time, only charging of the external power is performed from [start of charging of external power to {(charging time) − (equalization time)}], and [ From the start of charging external power (Charge time) − (equalization time)｝)], the charging of the external power is continued as it is, the equalization process is performed, and the equalization process is completed at the end of the charging time. If it is determined that the charging time is shorter than the charging time, the equalizing process is started at the same time as the charging of the external power is started. After the charging time is completed, only the equalizing process is continued until the equalizing time ends .

  ADVANTAGE OF THE INVENTION According to the battery system which concerns on this invention, in an electric vehicle, the start time of an equalization process can be determined appropriately so that an equalization process of a battery cell may be performed, performing external charging of a battery. Therefore, since the charging time is not delayed by the execution of the equalization processing, the external charging of the battery can be easily charged to the upper limit SOC, and the opportunity of the equalization processing can be appropriately secured.

It is a figure showing the schematic structure of the battery system which is one embodiment. 3 is a flowchart illustrating an equalization start time determination process according to the first embodiment, which is executed by the control device illustrated in FIG. 1. FIG. 3 is a diagram schematically showing each processing of steps S10 to S20 in the flowchart shown in FIG. 2. 3 is a flowchart illustrating a continuation of the equalization start time determination process illustrated in FIG. 2. It is a flowchart corresponding to FIG. 4 which shows the equalization start time determination processing of 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this description, specific shapes, materials, numerical values, directions, and the like are examples for facilitating the understanding of the present invention, and can be appropriately changed according to uses, purposes, specifications, and the like. Further, when a plurality of embodiments and modified examples are included below, it is assumed from the beginning that these configurations are appropriately combined and used.

  The battery system described below is mounted on an electric vehicle. The electric vehicle refers to a vehicle that can travel by driving the motor with electric power supplied from a vehicle-mounted battery using the motor as a driving power source. Specifically, the electric vehicle may be, for example, a so-called plug-in hybrid vehicle equipped with a motor and an engine, or an electric vehicle (including a fuel cell vehicle) equipped with only a motor as a power source. Good.

  FIG. 1 is a diagram illustrating a schematic configuration of a battery system 10 according to one embodiment. The battery system 10 includes a battery 12, an equalizing circuit 14, and a control device 16.

  The battery 12 is an assembled battery configured by connecting a plurality of battery cells BC1, BC2, BC3,..., BCn (where n is an integer of 4 or more) in series. Here, an example in which four or more battery cells are included will be described, but the number of battery cells may be two or more. For the battery cells BC1, BC2, BC3,..., BCn, for example, chargeable / dischargeable secondary batteries such as lithium ion batteries are used, respectively. Hereinafter, when each of the battery cells BC1, BC2, BC3,..., BCn is referred to without distinction, it is simply referred to as a battery cell BC.

  A power converter 18 is electrically connected to the battery 12 via a positive line PL1 and a negative line NL1. The power converter 18 has a bidirectional AC / DC conversion function. Specifically, in order to drive, for example, a three-phase AC synchronous motor (not shown) serving as a driving power source, a function of converting DC power supplied from the battery 12 to AC power and supplying the same, and It has a function of converting AC power supplied from the motor to DC power for charging the battery. Further, the power conversion device 18 may further have a DC / DC conversion function of raising and lowering the voltage of the DC power.

  System main relays SMR1 and SMR2 are provided on the positive line PL1 and the negative line NL1 between the battery 12 and the power converter 18. When these system main relays SMR1 and SMR2 are turned on, it becomes possible to supply power from the battery 12 to the power converter (ie, the motor). Each of the system main relays SMR1 and SMR2 is controlled on / off in response to a control signal from the control device 16.

  The charger 20 is electrically connected to the positive electrode line PL1 and the negative electrode line NL1 via a positive electrode charging line PCL and a negative electrode charging line NCL closer to the battery 12 than the system main relays SMR1 and SMR2. Charger 20 is electrically connected to a charging port (not shown) provided in the vehicle body. The charging relays CR1 and CR2 are provided on the positive charging line PCL and the negative charging line NCL. The charging relays CR1 and CR2 are turned on / off in response to a control signal transmitted from the control device 16. The controller 16 transmits a control signal for turning on the charging relays CR1 and CR2 when a sensor or the like (not shown) detects that a charging plug connected to an external power supply such as an external commercial power supply is attached to the charging port. I do. Thus, the battery 12 can be charged with the external power supplied from the external power supply.

  The equalizing circuit 14 in the present embodiment is connected to each battery cell BC constituting the battery 12. The equalizing circuit 14 is. For example, it is configured to include discharge resistors R1 and R2 and a switching element FET. The discharge resistor R1 is connected to the positive terminal of each battery cell BC. The discharge resistor R2 is connected to the negative terminal of each battery cell BC.

  The switching element FET is connected between the discharge resistor R1 and the discharge resistor R2. For example, a field effect transistor such as a MOSFET can be suitably used as the switching element FET. The switching element FET is controlled on / off in response to a control signal from the control device 16. More specifically, the switching element FET is turned on in response to a gate-on signal from the control device 16. Then, a short circuit in which a current flows in the order of the discharge resistor R1, the switching device FET, and the discharge resistor R2 is formed for the battery cell BC corresponding to the turned on switching element FET. As a result, the power of the battery cell BC with the switching element FET turned on is consumed by the discharge resistors R1 and R2. As a result, the SOC or voltage of a specific battery cell BC is reduced, and an equalization process for matching with another battery cell BC can be executed.

  Each equalizing circuit 14 is provided with a voltage sensor 22. The voltage sensor 22 is connected in parallel to each battery cell BC. The voltage sensor 22 detects an open-end voltage (cell voltage) of each battery cell, and transmits a detection result to the control device 16. In the present embodiment, the switching element FET and the voltage sensor 22 of each equalizing circuit 14 are configured as an IC covered by a resin mold 23.

  Further, each equalizing circuit 14 is provided with a capacitor 24. Each capacitor 24 has a function of stabilizing the voltage of the battery cell BC detected by the voltage sensor 22.

  The control device 16 is configured by, for example, a computer. As described above, control device 16 controls on / off of system main relays SMR1 and SMR2 and charging relays CR1 and CR2. Further, the control device 16 includes a memory 17. The memory 17 stores in advance programs and data for an equalization process described later. The control device 16 may store a program or data acquired from outside the vehicle by communication or the like. In addition, the control device 16 includes a timer circuit (not shown) for counting the date and time. With this timer circuit, the time of the equalization process described later, the time for charging external power, and the like can be measured.

  A vehicle equipped with the battery system 10 of the present embodiment is provided with a charging reservation unit 26. The charging reservation unit 26 is configured to be able to transmit and receive signals to and from the control device 16. The charging reservation unit 26 has a function of reserving a time for external charging performed via the charger 20 by a user operation. The charging reservation unit 26 can reserve a charging start time and the like, for example, by using a display unit of an in-vehicle navigation system. Alternatively, the charging reservation unit 26 may be a communication terminal (for example, a smartphone or the like) owned by the user. The user can use the charging reservation unit 26 to make a reservation setting to execute the external charging during the late night time period when the electricity rate becomes low, for example. In order to perform such reserved charging, the charging reservation unit 26 may include a timer circuit (not shown) for counting the date and time, or use a timer circuit included in the control device 16. Is also good.

  In an electric vehicle equipped with the battery 12 configured by connecting a plurality of battery cells BC in series as described above, the voltage or SOC of the plurality of battery cells BC configuring the battery 12 varies due to individual differences and differences in deterioration state. , The SOC range in which the battery can be used is narrowed. More specifically, when there is a variation in the SOC between the battery cells BC due to individual differences or differences in the state of deterioration, a battery cell having a relatively high SOC is charged to the charging target SOC (or use upper limit SOC) at the start of charging. External charging may be stopped and other battery cells may not be charged to the charging target SOC. On the other hand, at the time of discharging in which power is supplied from the battery to the motor in order for the vehicle to travel, if a battery cell having a relatively low SOC reaches the use lower limit SOC, the SOC of the other battery cells does not decrease to the use lower limit SOC. It is possible that the discharge from the battery 12 is limited and the engine starts. If the SOC of the battery cells BC constituting the battery 12 varies as described above, the SOC range in which the battery can be used is limited to a narrow range, which hinders the extension of the EV traveling distance and causes the engine to be started earlier, leading to a reduction in fuel consumption. Therefore, in order to eliminate the variation in the SOC of each battery cell, an equalization process is performed as described later.

  Also, in recent years, the battery capacity has been increased in order to extend the distance traveled by the vehicle using only the power of the motor (so-called EV travel distance). The required charging time also tends to be long. Therefore, if the battery cell equalization processing and external charging are performed separately, the total time required for the equalization processing and external charging becomes long, and depending on the usage condition of the vehicle by the user, the equalization processing and external charging may not be performed. Sometimes not enough.

  Therefore, the battery system 10 of the present embodiment makes it easier for each battery cell to be externally charged to the charge target SOC by performing the equalization process of each battery cell BC as described below, and also to complete the charging time. Can be executed.

  FIG. 2 is a flowchart showing the equalization start time determination processing of the first embodiment, which is executed by the control device 16 shown in FIG. FIG. 3 is a diagram schematically showing each processing of steps S10 to S20 in the flowchart shown in FIG.

  In the process shown in FIG. 2, the charging plug is attached to the vehicle, the battery 12 is in a state where the battery 12 can be externally charged, and the control device 16 causes the variation in SOC between the battery cells BC constituting the battery 12 to be equal to or more than a predetermined value. This processing is performed when it is determined that the equalization processing is necessary due to the increase. Note that since the SOC and the open-end voltage have a correlation in the battery cells BC, even when it is determined that equalization is necessary when the difference between the open-ended voltages between the battery cells BC becomes equal to or greater than a predetermined voltage value. Good.

  Referring to FIG. 2, when it is determined that equalization processing is necessary for battery 12, control device 16 first sets an equalization target SOC in step S10. For example, when the current SOC of the battery 12 is close to the upper limit SOC (for example, 80%), the upper limit SOC can be set as the equalization target SOC. When the current SOC of the battery 12 is close to the use lower limit SOC (for example, 20%), the use lower limit SOC can be set to the equalization target SOC. Alternatively, the control device 16 may set an intermediate SOC between the upper limit SOC and the lower limit SOC according to the current SOC of the battery as the equalization target SOC.

  Next, in Step S12, the control device 16 calculates the current SOC of each battery cell BC. The current SOC of each battery cell BC can be calculated based on the open-end voltage of each battery cell BC detected by the voltage sensor 22 in a state where no current flows through the battery 12. The control device 16 can calculate the current SOC of each battery cell BC with reference to the open-end voltage-SOC map of each battery cell BC stored in the memory 17.

  Here, referring to FIG. 3, the current SOC of each of the battery cells BC1 to BCn is shown by a rectangular graph. In FIG. 3, the vertical axis indicates the SOC. That is, the higher the height of each rectangle corresponding to each battery cell BC, the higher the current SOC. In the example shown in FIG. 3, the current SOC1 of the battery cell BC1 is the highest, and the current SOC2 and the SOCn of the battery cell BC2 and the battery cell BCn are substantially the same.

  In FIG. 3, the width of each rectangle corresponding to each battery cell BC represents the full charge capacity of each battery cell BC. The full charge capacity of the battery cell BC is a current amount (unit: Ah) corresponding to 100% SOC. In the example shown in FIG. 3, the full charge capacity of the battery cell BC1 is relatively small, the full charge capacity of the battery cell BCn is intermediate, and the full charge capacity of the battery cell BC2 is relatively large. As described above, the variation of the full charge capacity in each battery cell BC is caused by the individual difference between the battery cells BC and the variation of the deterioration state.

  The full charge capacity of each battery cell BC is timely calculated by the control device 16 throughout the usage period of the vehicle, and is updated and stored in the memory 17. The method of estimating the full charge capacity of the battery cell BC is well-known, and a detailed description thereof will be omitted. However, for example, the full charge capacity of each battery cell BC is determined by a current sensor (not shown). Calculation and learning can be performed based on the measured amount of external power charged to the battery 12 and the open-end voltage of each battery cell BC detected by the voltage sensor 22 after the external charging of the battery 12.

  Referring again to FIG. 2, in subsequent step S <b> 14, control device 16 subtracts the current SOC from the equalization target SOC, and calculates differences ΔSOC <b> 1 to n of each battery cell BC up to the equalization target SOC. In FIG. 3, these differences ΔSOC1 to SOCn are indicated by arrows indicated between the equalization target SOC and the current SOC1, current SOC2,..., Current SOCn of each battery cell BC1, BC2,. Expressed by length.

  Referring again to FIG. 2, in subsequent step S16, control device 16 determines whether or not differences ΔSOC1-n of each battery cell BC with respect to equalization target SOC calculated in step S14 are greater than 0 (zero). . Here, when the equalization target SOC is determined at or near the upper limit SOC of the SOC usage range of the battery 12, the differences ΔSOC1 to ΔSOC1 to n of the respective battery cells BC with respect to the equalization target SOC are positive. On the other hand, when the equalization target SOC is determined at or near the lower limit SOC of the SOC usage range of the battery 12, the differences ΔSOC1 to ΔSOC1 to n of the battery cells BC with respect to the equalization target SOC become negative. Alternatively, when the equalization target SOC is determined to be an intermediate SOC between the upper limit SOC and the lower limit SOC, the difference ΔSOC of each battery cell BC may be positive, and some battery cells BC may be negative. .

  If the difference ΔSOC of each battery cell BC is larger than 0 in step S16, the control device 16 proceeds to step S18, and if the difference ΔSOC is 0 or less, the controller 16 proceeds to step S26. Note that, as described later, step S18 and step S26 are processes having the same contents.

  In step S18, the control device 16 multiplies the differences ΔSOC1 to n by the full charge capacities 1 to n of the battery cells BC, respectively, and requires charging until each battery cell BC reaches the equalization target SOC. The current amounts ΔAh1 to ΔAh1 to n are calculated respectively.

  Then, in step S20, the control device 16 extracts the maximum value ΔAhmax among the current amounts ΔAh1 to ΔAh1 to n of the battery cells BC1 to BCn. When the battery cell BC having the maximum value ΔAhmax reaches the equalization target SOC by external charging, if the same amount of current is charged to the other battery cells BC, it exceeds the equalization target SOC. Therefore, the difference between the maximum value ΔAhmax and the amount of current ΔAh1 to n required to reach the equalization target SOC of each battery cell BC is the surplus equalization current amount ΔAh (k that needs to be discharged and consumed for equalization. ) 1 to n.

  In the subsequent step S22, the control device 16 subtracts the current amounts ΔAh1 to Δn required to reach the equalization target SOC of each battery cell BC from the required maximum charge amount ΔAhmax of each battery cell BC, respectively. Calculated current amounts ΔAh (k) 1 to n are calculated for each battery cell BC.

  On the other hand, if it is determined in step S16 that ΔSOC is equal to or less than 0 (NO in step S16), control device 16 determines in step S26 that differences ΔSOC1 to n and full charge capacities 1 to n of each battery cell BC. Are respectively multiplied to calculate the current amounts ΔAh1 to Δn required to be charged until each battery cell BC reaches the equalization target SOC. The process of step S26 is the same as step S18 described above.

  Then, in step S28, the control device 16 extracts the minimum value ΔAhmin from the current amounts ΔAh1 to ΔAh1 to n of the battery cells BC1 to BCn. When the battery cell BC having the minimum value ΔAhmin reaches the equalization target SOC due to the discharge by the equalization processing, the same amount of current is not reduced to the equalization target SOC only by being discharged from the other battery cells BC. become. Therefore, the difference between the minimum value ΔAhmin and the current amount ΔAh1 to n required to reach the equalization target SOC of each battery cell BC is the surplus equalization current amount ΔAh (k ) 1 to n.

  In subsequent step S30, control device 16 subtracts the equalization-required minimum current amount ΔAhmin of each battery cell BC from current amounts ΔAh1-n required to reach equalization target SOC of each battery cell BC. Thus, the surplus equalization current amounts ΔAh (k) 1 to n are calculated for each battery cell BC.

  Next, in step S32, the control device 16 calculates time required for equalization (hereinafter, referred to as equalized time) T1 to n for each battery cell BC. The equalization times T1 to n of the respective battery cells BC are calculated by dividing the excess equalized current amounts ΔAh (k) 1 to n calculated in steps S22 and S30 by the equalized currents I1 to n, respectively. It is calculated for each of BC1 to BCn. Here, the equalized currents I1 to In can be calculated by dividing the open-circuit voltage of each battery cell BC by the internal resistance (known) of each battery cell BC. During the external charging, the open-circuit voltage of each battery cell BC cannot be obtained by the voltage sensor 22, but the amount of charging current is obtained and monitored by the control device 16. For this reason, it is possible to estimate the changes in the SOC and open-circuit voltage of each battery cell BC from the amount of charging current, and to estimate the changes in the equalized currents I1 to In from the estimated open-circuit voltage. Therefore, the average equalization current from the start to the completion of equalization may be used as the equalization currents I1 to n in step S32, respectively.

  FIG. 4 is a flowchart showing a continuation of the equalization start time determination process shown in FIG. As shown in FIG. 4, in step S34, the control device 16 determines whether or not the charging time Tc for external charging of the battery 12 is longer than the equalization times T1 to Tn. More specifically, it is determined whether or not the charging time Tc is longer than the longest equalization time Tmax among the equalization times T1 to n of the battery cells BC. Here, the charging time Tc can be calculated based on the current SOC of the entire battery 12 and the amount of external power supplied by external charging. When the charging time Tc is set by the user through the charging reservation unit 26, the charging reservation time (for example, 6 hours from 11:00 pm) becomes the charging time Tc.

  When it is determined in step S34 that the charging time Tc is longer than the equalization times T1 to n (YES in S34), the control device 16 proceeds to step S36 from the start of external charging (Tc-T1 to n). It is determined that the equalization processing is started at the time point. Specifically, when the longest equalization time Tmax of the battery cells BC1 to BC is 2 hours and the charging time Tc is 3 hours, the equalization process of each of the battery cells BC1 to BC after one hour from the start of external charging. Is started. The start of the equalization process may be set simultaneously with the start of external charging. In this case, only the external charging is continued after the equalization process ends after the elapse of the longest equalization time Tmax.

  When the start time of the equalization processing is determined in this way, the control device 16 ends the equalization start time determination processing in step S38. Then, control device 16 turns on charging relays CR1, CR2 (see FIG. 1) to start external charging.

  On the other hand, if it is determined in step S34 that the charging time Tc is shorter than the maximum time Tmax of the equalization times T1 to n (NO in S34), the control device 16 starts external charging in the following step S40. It is determined that the equalization process starts at that point. Then, in the following step S42, the control device 16 ends the equalization start time determination processing, and turns on the charging relays CR1 and CR2 to start external charging. In this case, even after the external charging is completed, the equalization process is continued until the equalization time T1 to Tn ends. Alternatively, when the user removes the charging plug from the vehicle and turns on the start switch before the charging of the battery 12 is completed, the control device 16 sets the system main relays SMR1 and SMR2 to the on state to put the battery system 10 in a running state. Start. In this case, the equalization processing is continued until the system is started.

  As described above, according to the battery system 10 of the present embodiment, in the plug-in hybrid vehicle, the start time of the equalization process is appropriately set so as to execute the equalization process of the battery cells BC while performing external charging of the battery 12. Can be determined. Therefore, the charging time is not delayed by the execution of the equalization processing, so that the external charge of the battery 12 can be easily charged to the target SOC, and the opportunity of the equalization processing can be appropriately secured.

  Further, in the battery system 10 of the present embodiment, whether the current SOC of the battery 12 (specifically, the SOC of each battery cell BC) is at or near the upper limit SOC, or at or near the lower limit SOC, or the upper limit SOC and the lower limit SOC The equalization process of the battery 12 can be performed regardless of whether the battery 12 is at an intermediate position with the SOC. Therefore, the equalization process of the battery 12 can be performed in a timely manner.

  FIG. 5 is a flowchart illustrating the equalization start time determination processing according to the second embodiment. In this example, the processes in steps S10 to S32 are the same as those in the above embodiment, and a description thereof will be omitted.

  As shown in FIG. 5, in step S44, the control device 16 determines that the time difference obtained by subtracting the charging time Tc from the maximum time Tmax among the equalized times T1 to n of the battery cells BC calculated in step S32 is 0. It is determined whether it is larger. In this determination, when the time difference is greater than 0, that is, when the maximum time Tmax of the equalization times T1 to n is longer than the charging time Tc (YES in S44), the control device 16 sets the switching element FET of the equalization circuit 14 to Is set to on-duty 1 (that is, full ON (maintaining ON state)). Then, in the following step S42, the control device 16 ends the equalization start time determination processing, and turns on the charging relays CR1 and CR2 to start external charging. This process is the same as step S42 of the first embodiment described above.

  On the other hand, if it is determined in step S44 that the time difference is smaller than 0, that is, the maximum time Tmax of the equalization times T1 to n is shorter than the charging time Tc (NO in S44), the control device 16 continues. In step S46, a value obtained by dividing the equalization time T1 to n of each battery cell BC by the charging time Tc is set as the on-duty of the switching element FET of the equalization circuit 14. This on-duty is set for each equalizing circuit 14 corresponding to each battery cell BC. By setting the on-duty of the switching element FET in this way, the equalization currents I1 to n of the respective battery cells BC are suppressed, and the equalization times T1 to n are extended. As a result, the equalization time T1 to n in each of the battery cells BC1 to BC can be set to the same time as the charging time Tc. Thereby, the equalization process of each battery cell BC can be executed in accordance with the start and end of the external charging.

  Then, the control device 16 ends the equalization start time determination process in the following step S38, and starts the external charging by turning on the charging relays CR1 and CR2 (see FIG. 1), and also starts the equalization process. In the present embodiment, when the battery 12 is charged up to the target SOC (or upper limit SOC), the equalization processing of each battery cell BC is also ended at the same time.

  The same effect as in the first embodiment can be achieved by the equalization start time determination processing of the present embodiment.

  It should be noted that each of the above-described embodiments and their modified examples are merely examples, and it is needless to say that various changes and improvements can be made within the matters described in the claims of the present application and equivalents thereof. Absent.

  Reference Signs List 10 battery system, 12 battery, 14 equalization circuit, 16 control device, 17 memory, 18 power conversion device, 20 charger, 22 voltage sensor, 23 resin mold, 24 capacitor, 26 charge reservation unit, CR1, CR2 charging relay , FET switching element, I1-n equalization current, PCL positive charge line, NCL negative charge line, NL1 negative line, PL1 positive line, R1, R2 discharge resistance, SMR1, SMR2 system main relay.

Claims (1)

A battery system mounted on an electric vehicle and capable of charging external power,
A battery configured by connecting a plurality of battery cells in series,
An equalizing circuit connected to each of the battery cells,
A control device that performs a cell voltage equalization process of each of the battery cells by controlling a switching element included in each of the equalization circuits,
The control device includes:
Calculating, for each of the battery cells, an equalization time required for completing the equalization process from the current SOC of each of the battery cells and the equalization target SOC;
-Out based on the charge time of the external power and the equalization time to the battery,
If it is determined that the charging time is longer than the equalization time, the external power is not charged until the time [from the start of charging the external power to {(the charging time) − (the equalization time)}}. Only charging is performed, and after [the time of {(the charging time)-(the equalization time)} from the start of charging of the external power], the charging of the external power is continued as it is, and the equalization process is performed. The equalization process is also completed with the end of the charging time,
When it is determined that the charging time is shorter than the equalization time, the equalization process is started together with the start of charging of the external power, and after the completion of the charging time, the equalization time is terminated. Continuing only the equalization process ,
Battery system.

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