Method of controlling a battery

Abstract

The present application is to calculate the preferred SOC at the time of charging after the vehicle has run. The ECU calculates a running correction amount Dh at the start of external charging. Dh is a value obtained by subtracting a control SOC (SOCs) from an SOC estimation value Es at the time of running. Es is calculated based on the SOC at the end of charging, and SoCs is calculated based on the battery voltage with polarization removed at the time of running stop. A first charging start SOC (SOC1) is calculated by adding Dh to SoCs. A charging control SOC (SOCj) is calculated based on the current cumulative value at the time of external charging and SOC1. A charging allowable current Win is calculated based on SOCj and a temperature TB. The charging current is limited by Win. If SoCs is used in external charging, SoCs becomes a value smaller than the true SOC, and Win can become a larger value, but SOCj is less likely to become a value smaller than the true SOC, and Win can be preferably calculated.

Description

Technical Field

[0001] This invention relates to a battery control method, and more particularly to a battery control method for a vehicle power source that can be externally charged. Background Technology

[0002] Japanese Patent Application Publication No. 2017-227631 (Patent Document 1) discloses a method for suppressing the decrease in the accuracy of the estimation of the State of Charge (SOC) of a battery mounted in a vehicle. In Patent Document 1, an upper limit for the SOC is calculated based on the closed-circuit voltage (CCV) detected during battery charging. When battery charging and discharging cease, the open-circuit voltage (OCV) at which battery polarization is eliminated is estimated, and the SOC is estimated based on the estimated OCV. Then, if the estimated SOC is below the upper limit, the estimated SOC is selected as the battery's SOC; if the estimated SOC is above the upper limit, the upper limit is selected as the battery's SOC.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2017-227631 Summary of the Invention

[0004] State of Charge (SOC) is an indicator of the battery's state of charge. When the battery's full charge capacity is A (Wh or Ah) and the current charge capacity is B (Wh or Ah), it is calculated as SOC = B / A × 100%. The battery's full charge state is defined as 100%, and the fully discharged state is defined as 0%.

[0005] Due to factors such as battery degradation, the full charge capacity decreases. Therefore, sometimes the current full charge capacity is estimated (calculated) and the State of Charge (SOC) is calculated. In this case, the estimated full charge capacity may be greater than the actual full charge capacity.

[0006] As methods for calculating (estimating) SCO, there are known examples using the SOC-OCV characteristic (curve) and examples using the coulomb counting method. In the example using the SOC-OCV characteristic, the battery's OCV is measured, and the SOC is calculated from the measured OCV using the SOC-OCV characteristic. The coulomb counting method calculates the battery's charging and discharging power based on the input and output currents of the battery and estimates the SOC.

[0007] While the vehicle is in motion, the battery charges and discharges. Therefore, it is difficult to detect the Open Voltage Volume (OCV) while the vehicle is in motion, and it is also difficult to calculate the State of Charge (SOC) accurately using the SOC-OCV characteristic. Therefore, when the vehicle is in motion, it is preferable to use the coulomb counting method to estimate the SOC. However, in this case, if the estimated full-charge capacity is greater than the actual full-charge capacity, the SOC relative to the reduction in discharge becomes smaller. Thus, the SOC estimated using the coulomb counting method can sometimes be estimated as greater than the true SOC.

[0008] During vehicle operation, for example, when the stop (parking) time is long and the charging / discharging stop period is also long, it is sometimes possible to determine the voltage after polarization elimination (OCV) of the battery. In this case, the SOC is calculated using the SOC-OCV characteristic, and the SOC estimated by the coulomb counting method is corrected. The corrected SOC is then less than the original SOC. After driving ends, the battery is externally charged. During battery charging, the allowable charging current decreases as the SOC increases. If charging is performed with a current exceeding the allowable charging current, lithium ions may be deposited, for example, in lithium-ion batteries. Therefore, it is desirable to set the allowable charging current based on the SOC during charging and control the charging current to ensure that the charging current does not exceed the allowable charging current.

[0009] If the modified SOC is used as the initial SOC for external battery charging after the vehicle has finished driving, there is a risk that the calculated SOC during charging will be lower than the actual SOC. Therefore, there is a risk that the allowable charging current set based on the SOC will be greater than the preferred value.

[0010] The purpose of this invention is to calculate the optimal State of Charge (SOC) during charging of a vehicle after it has been driven.

[0011] The battery control method of the present invention is a control method for a battery that serves as a power source for a vehicle and is capable of external charging. The battery control method includes: a unit for detecting the battery voltage; and a unit for detecting the input and output current of the battery. The control method includes the following steps: calculating the cumulative value of the input and output current, i.e., the cumulative current value; calculating the estimated SOC value (Es) based on the SOC (SOCf) and the cumulative current value (ΣIB(1)) at the end of external charging; calculating the control SOC (SOCs) based on the SOC (SOCe) and the cumulative current value (ΣIB(2)) calculated based on the battery voltage when the vehicle's specified driving stop is established; calculating the difference between the control SOC (SOCs) and the estimated SOC value (Es), i.e., the driving correction amount (Dh); calculating the SOC (SOC1) at the start of the first charge by adding the driving correction amount (Dh) to the control SOC (SOCs) at the start of external charging; calculating the charging control SOC (SOCj) based on the SOC (SOC1) and the cumulative current value (ΣIB(3)) at the start of the first charge; and calculating the battery's allowable charging current based on the charging control SOC (SOCj).

[0012] According to this method, the estimated SOC (Es) is calculated based on the SOC (SOCf) at the end of external charging and the accumulated current (ΣIB(1)). If the OCV at which the vehicle's specified driving stop is achieved and the battery polarization is eliminated can be estimated based on the battery voltage, the control SOC (SOCs) is calculated based on the SOC (SOCe) and the accumulated current (ΣIB(2)) calculated based on the battery voltage. When external charging of the battery begins, the SOC (SOC1) at the start of the first charge is calculated by adding a driving correction (Dh) to the control SOC (SOCs). The driving correction (Dh) is the difference between the control SOC (SOCs) and the estimated SOC (Es). The charging control SOC (SOCj) is calculated based on the SOC (SOC1) at the start of the first charge and the accumulated current (ΣIB(3)). The allowable charging current of the battery is calculated based on the charging control SOC (SOCj).

[0013] When the battery's full-charge capacity is estimated to be greater than the actual full-charge capacity, the estimated State of Charge (SOC) (Es) is estimated to be greater than the actual SOC. The control SOC (SOCs) is calculated based on the battery voltage at which polarization is eliminated. The battery voltage at which polarization is eliminated is equivalent to the Open Voltage Value (OCV), and the control SOC (SOCs) is close to the actual SOC, becoming a value less than the estimated SOC (Es). If the control SOC (SOCs) is used to perform various controls such as driving control, battery depletion can be appropriately suppressed.

[0014] The allowable charging current is calculated based on the charging control SOC (SOCj). The charging control SOC (SOCj) is calculated based on the SOC (SOC1) at the start of the first charge and the accumulated current value (ΣIB(3)). The SOC (SOC1) at the start of the first charge is calculated by adding a driving correction (Dh) to the control SOC (SOCs) at the start of external charging. The driving correction (Dh) is the difference between the control SOC (SOCs) and the estimated SOC value (Es), thus reducing the possibility that the charging control SOC (SOCj) is calculated to be less than the actual SOC, and suppressing the allowable charging current from becoming greater than the preferred value.

[0015] Preferably, the battery control method may further include the following steps: obtaining the time interval for establishing a predetermined driving stop; and calculating an additional correction amount (Adc) based on the time interval. Then, the SOC (SOC1) at the start of the first charge can be calculated by adding the driving correction amount (Dh) and the additional correction amount (Adc) to the control SOC (SOCs).

[0016] Until the control SOC (SOCs) is updated based on the battery voltage when the battery polarization is eliminated (until the SOCs are calculated using the new SOCe), the control SOC (SOCs) is updated using the current accumulation value (ΣIB(2)). If the interval for correcting the control SOC (SOCs) is long, there is a risk that the control SOC (SOCs) will deviate from the true SOC due to the accumulation of detection errors in the input and output currents.

[0017] According to this method, an additional correction amount (Adc) is calculated based on the time interval for updating the control SOC (SOCs), and the driving correction amount (Dh) and the additional correction amount (Adc) are added to the control SOC (SOCs) to calculate the SOC (SOC1) at the start of the first charge. Therefore, the detection error of the input and output current can be corrected by the additional correction amount (Adc), and the charging allowable current can be prevented from becoming a value greater than the preferred value.

[0018] Preferably, the control method may further include the following steps: determining whether the charging standby time (Tw) from when the vehicle stops to when external charging begins is above a predetermined value. Then, when it is determined that the charging standby time (Tw) is above the predetermined value, the SOC (SOC2) at the start of the second charging can be calculated based on the battery voltage at the start of external charging, and the SOC (SOCb) before correction can be calculated based on the SOC (SOC2) at the start of the second charging and the cumulative current value (ΣIB (3)). The charging SOC (SOCj) is obtained by adding the charging time correction amount (Jh) calculated by the following (Equation 1) to the SOC (SOCb) before correction.

[0019] The correction amount during charging (Jh) = the driving correction amount (Dh) / (the target SOC (SOCt) - the SOC at the start of the second charge (SOC2)) × (the SOC before correction (SOCb) - the SOC at the start of the second charge (SOC2)) ... (Equation 1) In addition, the target SOC (SOCt) is the SOC at the end of external charging.

[0020] When the charging standby time from when the vehicle stops to when external charging begins is above a predetermined value, the battery polarization can be considered to have been eliminated, and the battery voltage at this time can be considered as the OCV after polarization elimination. According to this method, when it is determined that the charging standby time is above a predetermined value, the SOC (SOC2) at the start of the second charge is calculated based on the battery voltage at the start of external charging. Then, the SOC (SOCb) before correction is calculated based on the SOC (SOC2) at the start of the second charge and the current accumulation value (ΣIB(3)), and the SOC (SOCj) for charging is obtained by adding the charging time correction amount (Jh) calculated by the above (Equation 1) to the SOC (SOCb) before correction. The SOC (SOC2) at the start of the second charge is calculated based on the OCV at the start of charging after polarization elimination, so its accuracy is relatively high. Furthermore, the charging time correction amount (Jh) is a value smaller than the driving correction amount (Dh) at the start of external charging, and becomes a larger value as charging proceeds. Therefore, compared to the case where the charging standby time is less than the specified value, the charging SOC (SOCj) at the beginning of external charging is a smaller value, thus increasing the allowable charging current and shortening the charging time.

[0021] Invention Effects

[0022] According to the present invention, a preferred SOC can be calculated when charging the vehicle after it has been driven. Attached Figure Description

[0023] Figure 1 This is an overall structural diagram of the electric vehicle involved in this embodiment.

[0024] Figure 2 This is a flowchart illustrating an example of SOC calculation and processing when the driving mode is executed by the ECU.

[0025] Figure 3 This is a flowchart illustrating an example of plug-in SOC calculation processing performed by the ECU.

[0026] Figure 4 This is a flowchart representing an example of a current accumulation routine executed by the ECU.

[0027] Figure 5 (A) and Figure 5(B) is a flowchart illustrating an example of SOC calculation processing performed by the ECU in driving mode and SOC calculation processing when plugged in, as described in Implementation 2.

[0028] Figure 6 This is a flowchart illustrating an example of the plug-in SOC calculation process performed by the ECU in Implementation 3. Detailed Implementation

[0029] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, identical or corresponding parts in the drawings will be labeled with the same symbols, and their descriptions will not be repeated.

[0030] (Implementation Method 1)

[0031] Figure 1 This is an overall structural diagram of the electric vehicle 1 according to this embodiment. In this embodiment, the electric vehicle 1 is, for example, an electric car. The electric vehicle 1 includes a motor generator (MG) 10 as a rotary motor, a power transmission gear 20, a drive wheel 30, a power control unit (PCU) 40, a system main relay (SMR) 50, a battery 100, a monitoring unit 200, and an electronic control unit (ECU) 300 as an example of a control device.

[0032] MG10 is, for example, an embedded permanent magnet synchronous motor (IPM motor), which functions as both a motor and a generator. The output torque of MG10 is transmitted to the drive wheel 30 via a power transmission gear 20, which includes a reducer and a differential device.

[0033] When the electric vehicle 1 brakes, the MG10 is driven by the drive wheel 30, and the MG10 functions as a generator. Thus, the MG10 also functions as a braking device for regenerative braking, converting the kinetic energy of the electric vehicle 1 into electrical energy. The regenerative electricity generated by the regenerative braking force in the MG10 is stored in the battery 100.

[0034] PCU40 is a power conversion device that bidirectionally converts power between MG10 and battery 100. PCU40 includes, for example, an inverter and a converter that operate based on control signals from ECU300.

[0035] When battery 100 discharges, the converter boosts the voltage supplied from battery 100 to supply the inverter. The inverter then converts the DC power supplied by the converter into AC power to drive MG10.

[0036] During the charging of battery 100 (when charging is based on regenerative power), the inverter converts the AC power generated by MG10 into DC power and supplies it to the converter. The converter then steps down the voltage supplied by the inverter to a voltage suitable for charging battery 100 and supplies it to battery 100.

[0037] SMR50 is electrically connected to the power line connecting battery 100 and PCU40. When SMR50 is closed (ON) according to a control signal from ECU300, power can be transferred between battery 100 and PCU40. On the other hand, when SMR50 is opened (OFF) according to a control signal from ECU300, the electrical connection between battery 100 and PCU40 is disconnected.

[0038] Battery 100 stores the power used to drive MG10. Battery 100 is a rechargeable DC power source (secondary battery), and is a battery pack composed of multiple individual cells (battery units) 100a connected in series, for example. Battery 100 and individual cells 100a are equivalent to the "battery" of this invention. Individual cell 100a can be a lithium-ion battery having a positive electrode, a negative electrode, a separator, etc. Individual cell 100a can be an all-solid-state lithium-ion battery.

[0039] The monitoring unit 200 includes a voltage sensor 210, a current sensor 220, and a temperature sensor 230. The voltage sensor 210 detects the voltage VB of the single battery 100a (the voltage VB between the terminals of the single battery 100a). The current sensor 220 detects the input / output current (IB) to and from the battery 100 (single battery 100a). The current IB detected by the current sensor 220 has a sign; the current discharging from the battery 100 can be positive (+), and the current charging the battery 100 can be negative (-). The temperature sensor 230 detects the temperatures TB of the single battery 100a. Each detection unit outputs its detection results to the ECU 300.

[0040] The electric vehicle 1 includes a charging interface 60, and the battery 100 can be externally charged using an electric vehicle supply equipment (EVSE) 400. The charging interface 60 is configured to connect to a connector 420 at the front end of a charging cable 410 provided on the EVSE 400. The charging interface 60 is electrically connected to the power lines connected to the battery 100, and external charging of the battery 100 is performed by closing a charging relay 70. In this embodiment, the EVSE 400 outputs DC power and charges the battery 100 (external charging), but it can also be configured to supply AC power from the EVSE 400 and charge the battery 100. In this case, the electric vehicle 1 includes a charger that converts AC power to DC power. The state in which the connector 420 is connected to the charging interface 60 is also referred to as the "plug-in state," and is a state in which the battery 100 can be externally charged.

[0041] ECU 300 includes a Central Processing Unit (CPU) 301 and a memory (e.g., including Read Only Memory (ROM) and Random Access Memory (RAM)) 302. ECU 300 controls various devices to bring the electric vehicle 1 to a desired state based on signals received from the monitoring unit 200, signals from various sensors (not shown) (e.g., throttle opening signal, vehicle speed signal, etc.), mappings stored in memory 302, and programs. ECU 300 controls PCU 40, EVSE 400, etc., and controls the input and output current (charging and discharging current) of battery 100. ECU 300 can be composed of multiple ECUs, such as a battery ECU, a driving control ECU, etc.

[0042] The Human Machine Interface (HMI) device 600 includes an input device and a display device. The HMI device 600 may include a touchscreen display. The input device outputs signals corresponding to input from the user to the ECU 300. The display device may include an instrument panel and / or a central display, and displays information received from the ECU 300.

[0043] ECU300 calculates the SOC of battery 100. The calculated SOC is used for the charge and discharge control of battery 100, the display of remaining battery capacity (SOC display) in HMI device 600, etc. Figure 2This is a flowchart illustrating an example of SOC calculation processing performed by ECU300 in a driving mode. This flowchart is processed repeatedly for each specified period when the battery is not plugged in. In step (hereinafter, step "S") 10, an estimated SOC value Es is calculated. The estimated SOC value Es is calculated based on the cumulative value ΣIB(1) of the SOC at the end of the last external charging and the current (input / output current) IB of the battery 100. Hereinafter, the SOC at the end of the external charging is also referred to as "SOCf". SOCf will be discussed later. Figure 3 The SOC calculation process is set during plug-in. The cumulative value of the current (input / output current) IB, ΣIB (1), is obtained through the following... Figure 4 The current accumulation routine is used to calculate the cumulative value ΣIB(1). The cumulative value is the cumulative value of the current IB from the end of the charging of the battery 100. The current IB detected by the current sensor 220 has a negative (-) sign when charging and a positive (+) sign when discharging. Therefore, the cumulative value ΣIB(1) increases in the negative direction when charging and increases in the positive direction when discharging.

[0044] In S10, the SOC estimate Es is calculated, for example, by “Es=SOCf-(ΣIB(1) / CP)×100”. CP is the full charge capacity of battery 100, as described later. Figure 3 The SOC calculation is performed during the plug-in process.

[0045] In S11, it is determined whether the electric vehicle 1 has reached the specified state of stopping. In this embodiment, the specified state of stopping is determined when the OCV after polarization elimination of the battery 100 can be estimated with high accuracy. For example, if the stopping time of the electric vehicle 1 is longer than a specified time T, the specified state of stopping is determined. Figure 2The diagram at the lower left shows the "polarization characteristics" of battery 100, with voltage VB on the vertical axis and time on the horizontal axis. This polarization characteristic represents the characteristics of battery 100 during discharge. As battery 100 discharges, voltage VB decreases. If the electric vehicle 1 stops moving at time t0, the discharge of battery 100 stops. If the discharge of battery 100 stops (current IB becomes 0), the polarization of battery 100 gradually disappears over time, and voltage VB increases. If the voltage VB at time t1 after a certain time from time t0 is set as OCV1 and the voltage VB at time t2 after a certain time from time t1 is set as OCV2, then the polarization-eliminated OCV (hereinafter referred to as "OCVe") can be calculated, for example, by "OCVe = OCV2 + (OCV2 - OCV1) × α". Time t1, time t2, and α are set through prior experiments or simulations to ensure accurate calculation of OCVe. In this embodiment, the time from time t0 to time t2 is set to a predetermined time T. In S11, if the predetermined time T has elapsed since the electric vehicle 1 stopped, it is determined that the predetermined driving stop has been achieved, and the process proceeds to S12. If the electric vehicle 1 starts driving before the predetermined time T has elapsed after stopping, it is determined to be negative, and the process proceeds to S14.

[0046] In S12, OCVe (OCVe = OCV2 + (OCV2 - OCV1) × α) is calculated based on OCV1 and OCV2 detected by voltage sensor 210. Then, SOCe is calculated based on OCVe. SOCe is the SOC calculated using the SOC-OCV characteristic. Figure 2 The mapping of the SOC-OCV characteristics shown in the lower right corner is stored in memory 302, and SOCe is calculated from OCVe using this mapping. After setting the flag F1 to 1, the process proceeds to S13.

[0047] In S13, after calculating the SOC for control, proceed to S16. Hereinafter, the SOC for control will also be referred to as "SOCs". SOcs is calculated based on the cumulative value ΣIB(2) of SOCe and current IB, for example, by "SOCs = SOCe - (ΣIB(2) / CP) × 100". The cumulative value ΣIB(2) is calculated by... (The rest of the text is missing). Figure 4 The current accumulation routine is used to calculate the cumulative value ΣIB (2), which is the cumulative value of the current IB since the most recent calculation of SOCe.

[0048] In S14, it is determined whether the flag F1 is 1. When the flag F1 is 1, it is determined to be positive, and proceeds to S13. When the flag F1 is 0, it is determined to be negative, and proceeds to S15. In S15, after setting the SOC estimate Es to SOCs, it proceeds to S16.

[0049] In step S16, the allowable charging current Win and allowable discharging current Wout of battery 100 are calculated based on SOCs and temperature TB, and the current routine ends. Win is the upper limit (limit value) of the input current of battery 100, and Wout is the upper limit (limit value) of the output current of battery 100. ECU300 controls PCU40 to ensure that the charging current of battery 100 does not exceed Win and the discharging current of battery 100 does not exceed Wout. For example, to suppress lithium deposition, the higher the SOCs and the lower the temperature TB, the smaller the value of Win can be calculated.

[0050] Figure 3 This is a flowchart illustrating an example of the SOC calculation process performed by ECU 300 during plug-in operation. This flowchart begins processing when the battery is plugged in. In S20, it is determined whether external charging of the battery 100 has started. For example, if ECU 300 and EVSE 400 are ready to charge and external charging has started, it is determined to be positive in S20. If a timed charging schedule has been reserved with ECU 300, it can be determined that external charging has started when the set start time arrives. If external charging has not started while the battery is plugged in, S20 is repeated.

[0051] If external charging begins, proceed to step S21 to calculate the driving correction amount Dh. The driving correction amount Dh is calculated by subtracting the SOCs from the SOC estimate Es (Dh = Es - SOCs). The driving correction amount Dh is the amount obtained by subtracting the SOCs from the SOC estimate Es at the end of this trip (when the vehicle stops).

[0052] In the following S22, the SOC at the start of the first charge is calculated. Hereinafter, the SOC at the start of the first charge will also be referred to as SOC1. SOC1 is calculated by adding the driving correction amount Dh to SOCs (SOC1 = SOCs + Dh).

[0053] In S23, the SOC for charging control is calculated. Hereinafter, the SOC for charging control will also be referred to as "SOCj". SOCj is calculated based on the cumulative value ΣIB(3) of SOC1 and the current (input / output current) IB of battery 100. The cumulative value ΣIB(3) is obtained through the following... Figure 4 The current accumulation routine is used to calculate the cumulative value ΣIB(3), which is the cumulative value of the current IB from the start of external charging of battery 100. SOCj is calculated, for example, by “SOCj=SOC1-(ΣIB(3) / CP)×100”.

[0054] In S24, the allowable charging current Win of battery 100 is calculated based on SOCj and temperature TB. Win is the upper limit (limit value) of the input current of battery 100; the charging current during external charging is limited by Win. ECU300 controls EVSE400, etc., to ensure that the charging current of battery 100 does not exceed Win. Figure 3 As shown in the diagram, Win is set to decrease as SOCj increases to suppress lithium deposition. Furthermore, Win can be calculated so that it decreases as the temperature TB decreases.

[0055] In the next step, S25, it is determined whether external charging has ended. External charging ends when the SOC of battery 100 rises to the target SOC. Hereinafter, the target SOC will also be referred to as "SOCt". SOCt can be a value preset by the user or a fixed value (e.g., representing the SOC value of a fully charged battery). ECU 300... Figure 2 The SOC-OCV characteristic is used to determine the charging end OCV corresponding to SOCt. Then, ESU300 obtains the OCV of battery 100 by excluding the voltage drop caused by battery current from the voltage VB detected by voltage sensor 210. For example, the value of the product of voltage VB, current IB, and internal resistance is calculated as OCV. Then, when the calculated OCV is greater than or equal to the charging end OCV, it is determined that external charging has ended and proceeds to S26. If external charging has not ended, it is determined as negative and returns to S23. In addition, when the calculated OCV is greater than or equal to the charging end OCV, ECU300 stops the power supplied from EVSE400 and disconnects the charging relay 70.

[0056] In S26, the full charge capacity CP is calculated and SOCf is set. Then, after setting flag F1 to 0, the current process ends. CP is calculated, for example, by “CP=100×ΣIB(3) / (SOCt-SOCS)”. In processing S26, ΣIB(3) becomes the value representing the cumulative value of the charging current from the start of external charging to the end of external charging, and SOCs is not updated from the value at the end of this driving (when parked). ECU300 sets SOCt to SOCF.

[0057] Figure 4 This is a flowchart illustrating an example of a current accumulation routine executed by ECU300. This flowchart, for example, repeats the process at predetermined time intervals Δt. Additionally, in... Figure 4 Below, the illustration shows the "SOC shift" in this embodiment. First, in S30, it is determined whether flag F1 has changed from 1 to 0. Flag F1 in Figure 2 Set to 1 in S12, Figure 3In S26, it is set to 0. Flag F1 changes from 1 to 0 when external charging of battery 100 ends. After external charging ends, the current accumulation routine ( Figure 4 When processed for the first time, it is judged as positive in S30 and proceeds to S31. If the flag F1 is 1 or 0, it is judged as negative and proceeds to S33.

[0058] In S31, the accumulated value ΣIB(1) is reset, and after setting ΣIB(1) to "0", the process proceeds to S32. In S33, it is determined whether the prescribed driving stop of electric vehicle 1 is met. This process is the same as that in S11 ( Figure 2 The same process applies: if the result is affirmative in S11, proceed to S34. If the result is not affirmative in S11, proceed to negative in S34 and proceed to S35.

[0059] In S34, the accumulated value ΣIB(2) is reset, and after setting ΣIB(2) to "0", the process proceeds to S32. In S35, it is determined whether external charging of battery 100 has started. This process is consistent with S20 ( Figure 3 The same process applies: if the condition is affirmative in S20, proceed to S36; if the condition is negative in S20, proceed to S32. In S36, reset the cumulative value ΣIB(3). After ΣIB(3) is set to "0", proceed to S32.

[0060] In S32, the cumulative values ​​ΣIB(1), ΣIB(2), and ΣIB(3) are calculated by accumulating the input current (IB), and the current routine ends. ΣIB(1) is the cumulative value of the current IB from the end of charging of battery 100. ΣIB(2) is the cumulative value of the current IB from the time SOCe was last calculated. ΣIB(3) is the cumulative value of the current IB from the time external charging of battery 100 begins. The current IB is accumulated by multiplying the current IB detected by current sensor 220 by the interruption interval (specified time Δt) of the current accumulation routine. Regarding the current IB, the current of the charging battery 100 is negative (-), and the current discharging from battery 100 is positive (+), so it increases in the negative direction during charging and in the positive direction during discharging.

[0061] In this embodiment, such as Figure 4As shown in the "SOC Shift" section below, the estimated SOC value Es (reference dashed line) decreases as the battery 100 discharges while the electric vehicle 1 is in motion. The dotted line represents the actual SOC of the battery 100. When the calculated full charge capacity CP is greater than the actual full charge capacity, the estimated SOC value Es is smaller relative to the decrease in discharge capacity. Therefore, the estimated SOC value Es is calculated as a value greater than the actual SOC. The solid line represents the control SOC (SOCs). At times ta, tb, and tc, if the specified driving stop is achieved (a positive determination in S11 and S33), a new control SOC (SOCs) is calculated using OCVe (OCV after polarization elimination), and then SOCs is updated using the cumulative value ΣIB (2) (S12). Thus, SOCs is calculated in a manner close to the actual SOC. If the battery 100 is plugged in at time t0 and external charging begins, the driving correction amount Dh is added to the SOCs to calculate the SOC (SOC1) at the start of the first charge (S22).

[0062] In the section on "SOC Shift," the thin solid line represents the shift of SOCs assuming SOCs are also calculated during plug-in, and the thin dashed line represents the shift of the estimated SOC Es assuming the estimated SOC Es is also calculated during plug-in. The SOC at the start of external charging is set to SOC1. Therefore, the charging control SOC (SOCj) shifts from SOC1 as a base point, as shown by the double-dotted line, until the battery is 100% fully charged, becoming a value greater than the actual SOC. Therefore, by calculating the allowable charging current Win based on SOCj, lithium-ion deposition can be suppressed. Conversely, if Win is calculated using SOCs (thin solid line) during plug-in, it is assumed that SOCs are less than the actual SOC, and lithium-ion deposition cannot be suppressed.

[0063] (Implementation Method 2)

[0064] In the above-described embodiment 1, in S11 ( Figure 2 When the determination in S11 is positive, a new SOCs is calculated using OCVe (OCV after polarization elimination), and then the SOCs are updated at any time using the cumulative value ΣIB (2). In driving mode, if the interval in S11 where the determination is positive is long, there is a risk that the SOCs will deviate from the true SOC due to detection errors of the current sensor 220, etc. When the deviation between the SOCs and the true SOC is large, the SOCj may be insufficient if the SOCj is calculated based on the SOC1 obtained by adding the driving correction amount Dh to the SOCs. In Implementation 2, when the interval in S11 where the determination is positive is long, the risk is eliminated by calculating the SOC1 using the additional correction amount.

[0065] Figure 5This is a flowchart illustrating an example of SOC calculation processing in driving mode and SOC calculation processing when plugged in, performed by ECU 300 in Implementation 2. Figure 5 (A) is the SOC calculation and processing in the driving mode of Implementation Method 2. Figure 2 In the flowchart, process S12A is added between S11 and S12. Other processes are similar to... Figure 2 The process is the same as the flowchart, so its description is omitted. If the determination is affirmative in S11, proceed to S12A. In S12A, obtain the elapsed time TE from the last affirmative determination in S11 to the current affirmative determination in S11, accumulate the elapsed time TE, and calculate the cumulative time ΣTE. The elapsed time TE is equivalent to the elapsed time from the last SOCs calculation via OCVe to the current SOCs calculation via OCVe. The cumulative elapsed time ΣTE is equivalent to an example of the "time interval for establishing the prescribed driving stop" in this invention. If the process of S12A ends, proceed to S12.

[0066] Figure 5 (B) is the SOC calculation process during plug-in in Implementation Method 2. Figure 3 In the flowchart, process S21A is added between S21 and S22. The content of the process in S22 is changed, but the other processes are the same. Figure 3 The process is the same as in the flowchart, so its description is omitted. In S21A, which is processed after S21, the additional correction amount Adc is calculated based on the cumulative time ΣTE calculated in S12A. For example, a mapping with ΣTE and Adc as parameters is stored in memory 302, and Adc is obtained from ΣTE using this mapping. This mapping is preset according to the design value of the current sensor 220 (e.g., detection accuracy), for example, it is set such that the longer ΣTE is, the larger the value of Adc is.

[0067] In the next step, S22, the State of Charge (SOC) at the start of the first charge (SOC1) is calculated. In Embodiment 2, SOC1 is calculated by adding a driving correction amount Dh and an additional correction amount Adc to the SOCs (SOC1 = SOCs + Dh + Adc). In Embodiment 2, SOC1 is the value of SOCs at the end of the last trip (before becoming plugged in) with the driving correction amount Dh and the additional correction amount Adc added. If SOC1 is calculated, proceed to S23.

[0068] According to Embodiment 2, an additional correction amount Adc is calculated based on the accumulated time ΣTE, and the additional correction amount Adc is added to the driving correction amount Dh to obtain SOC1. Therefore, considering the detection error of the current sensor 220, the SOC at the start of external charging is set to SOC1. Thus, even if the interval for recalculating SOCs is long, the charging control SOC (SOCj) will be greater than the actual SOC until the battery 100 is fully charged. Therefore, by calculating the charging allowable current Win using SOCj, lithium-ion deposition can be suppressed. Furthermore, in Embodiment 2, the current accumulation routine is used in the same way as in Embodiment 1. Figure 4 The flowchart.

[0069] (Implementation Method 3)

[0070] Figure 6 This is a flowchart illustrating an example of the plug-in SOC calculation process performed by the ECU 300 in Embodiment 3. In Embodiment 3, the SOC calculation process and current accumulation routine in driving mode are used in the same manner as in Embodiment 1. Figure 3 and Figure 4 The flowchart. The SOC calculation process during plug-in in Implementation 3 is relative to... Figure 3 The flowchart (Implementation Method 1) adds process S20a between S21 and S22, and adds S20f between S25 and S23. Furthermore, in Figure 3 S20b to S20d are added to the flowchart. The following section discusses... Figure 3 The flowcharts illustrate different processing methods.

[0071] In Implementation Method 3, after calculating the driving correction amount Dh in S21, the process proceeds to S20a. In S20a, it is determined whether the charging standby time Tw is greater than or equal to a predetermined value α. The charging standby time Tw is the time from when the vehicle stops (when parked) to when external charging begins (the time from when the vehicle stops until S20 determines that it is affirmative). The predetermined value α is the sufficient time required to eliminate polarization after the charging and discharging of the battery 100 stops (after the current IB becomes 0), and is set through prior experiments, etc. The predetermined value α can be obtained by mapping the state of charge (SOC) and temperature (TB) of the battery 100 as parameters. If the charging standby time Tw is greater than or equal to the predetermined value α, the process is affirmative, and the process proceeds to S20b. If the charging standby time Tw is less than the predetermined value α, the process is negative, and the process proceeds to S22.

[0072] In S20b, the SOC at the start of the second charge is calculated based on the voltage VB. Hereinafter, the SOC at the start of the second charge will also be referred to as "SOC2". Furthermore, the flag F2 is set to 1. Additionally, the flag F2 is set to 0 in S26. The ECU 300 uses the voltage VB detected by the voltage sensor 210 as the OCV and calculates according to... Figure 2 The SOC obtained from the SOC-OCV characteristics is set as SOC2.

[0073] In S20c, the SOC before correction is calculated. Hereinafter, the SOC before correction will also be referred to as "SOCb". SOCb is calculated based on the cumulative value ΣIB(3) of SOC2 and current (input and output current) IB. SOCb is calculated, for example, by "SOCb=SOC2-(ΣIB(3) / CP)×100".

[0074] In the following S20d, the SOC (SOCj) for charging control is calculated. SOCj is obtained by adding the charging correction amount Jh to SOCb (SOCj=SOCb+Jh). The charging correction amount Jh can be calculated according to the following (Equation 1).

[0075] Jh=Dh / (SOCt-SOC2)×(SOCb-SOC2)……(Formula 1)

[0076] During charging, the correction amount Jh is a value less than the driving correction amount Dh at the start of external charging, and becomes a larger value as charging progresses. If SOCj is calculated in S20d, then proceed to S24.

[0077] If external charging is not yet complete and is determined negatively in S25, proceed to S20f. In S20f, determine if flag F2 is 1. If flag F2 is 1, determine positively and return to S20c. If flag F2 is 0, determine negatively and return to S23. Thus, in S24, if determined positively in S20a, calculate Win based on the SOCj calculated in S20d; if determined negatively in S20a, calculate Win based on the SOCj calculated in S23.

[0078] exist Figure 6Below, the diagram shows the "SOC shift" when the flag F2=1. In Embodiment 3, when the charging standby time Tw is a predetermined value α or more and the polarization of the battery 100 is eliminated, the SOC calculated based on the voltage VB is set as the SOC at the start of the second charge (SOC2). When the charging standby time Tw is a predetermined value α or more and the polarization of the battery 100 is eliminated, it is considered that the SOC calculated using the voltage VB based on the SOC-OCV characteristic is close to the true SOC. Therefore, as shown by the double-dotted line, the charging control SOC (SOCj) is approximately shifted to the true SOC represented by the single-dotted line by adding Jh, which increases as charging progresses, with SOC2 as the base point. Therefore, by calculating the charging allowable current Win based on SOCj, lithium ion deposition can be suppressed. Furthermore, since SOCj is close to the true SOC, the charging current at the beginning of external charging can be increased, and it is expected that the charging time will be shortened.

[0079] It should be considered that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the invention is set forth in the claims, not in the description of the above embodiments, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0080] Symbol Explanation

[0081] 1-Electric vehicle, 10-Electric generator (MG), 20-Power transmission gear, 30-Drive wheel, 40-PCU, 50-SMR, 60-Charging interface, 100-Battery, 100a-Single battery, 200-Monitoring unit, 210-Voltage sensor, 220-Current sensor, 230-Temperature sensor, 300-ECU, 400-EVSE, 420-Connector.

Claims

1. A method for controlling a battery, wherein the battery is a power source for a vehicle and is capable of external charging, the method for controlling the battery being characterized by comprising: A unit for detecting the voltage of the battery, i.e., the battery voltage; and A unit for detecting the input and output current of the battery. The control method includes the following steps: Calculate the cumulative value of the input and output currents, i.e., the cumulative current value; The estimated SOC value is calculated based on the SOC at the end of external charging and the accumulated current value. The control SOC is calculated based on the SOC calculated from the battery voltage and the accumulated current value when the specified driving stop of the vehicle is established. The difference between the control SOC and the estimated SOC is the driving correction amount. When the external charging begins, the driving correction amount is added to the control SOC to calculate the SOC at the start of the first charging. Calculate the SOC for charging control based on the SOC at the start of the first charge and the accumulated current value; and The allowable charging current of the battery is calculated based on the SOC used for charging control.

2. The battery control method according to claim 1, characterized in that, The control method further includes the following steps: Obtain the time interval at which the specified driving stop is established; and The additional correction amount is calculated based on the aforementioned time interval. The calculation of the SOC at the start of the first charge is performed by adding the driving correction amount and the additional correction amount to the control SOC.

3. The battery control method according to claim 1, characterized in that, The control method further includes the following steps: Determine whether the charging standby time from the time the vehicle stops to the time the external charging begins is above a predetermined value. When it is determined that the charging standby time is above the specified value. At the start of the external charging, the SOC at the start of the second charging is calculated based on the battery voltage. The SOC before correction is calculated based on the SOC at the start of the second charge and the accumulated current value. The charging control SOC is obtained by adding the charging correction amount calculated by Equation 1 below to the original SOC. Correction amount during charging = Correction amount during driving / (Target SOC for charging - SOC at the start of the second charge) × (SOC before correction - SOC at the start of the second charge) ... (Equation 1) The target SOC is the SOC at which the external charging ends.

4. The battery control method according to claim 1, characterized in that, The current accumulation value used in calculating the SOC estimate is the current accumulation value accumulated from the end of the external charging of the battery. The current accumulation value used in calculating the SOC for control is the current accumulation value accumulated from the time the specified driving stop is established. The current accumulation value used when calculating the SOC for charging control is the current accumulation value accumulated from the start of external charging.

5. The battery control method according to claim 1 or 2, characterized in that, The specified driving stop time is the time when the charging and discharging of the battery stops, and the OCV (Optical Characteristic Value) at which the polarization of the battery is eliminated can be estimated based on the battery voltage.

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