JP6155743B2 - Charge state detection device and charge state detection method - Google Patents

Description

  The present invention relates to a technique for estimating the state of charge of a storage element.

  Conventionally, an open circuit voltage (also referred to as an open circuit voltage; hereinafter simply referred to as OCV) of a secondary battery is detected, and an OCV and a charge state (also referred to as remaining capacity; State Of Charge or less) from the detected OCV value. There is a technique for estimating the SOC of a secondary battery using a correlation with (hereinafter simply referred to as SOC) (Patent Document 1).

  In this prior art, the secondary battery waits for the elapse of the standby time until the voltage change amount per unit time of the secondary battery falls below a predetermined amount after the current of the secondary battery falls below the predetermined current value. And the SOC is estimated based on the detected value. That is, in the prior art, the detected value of the terminal voltage of the secondary battery when the condition that the amount of voltage change per unit time is equal to or less than a predetermined amount is uniformly set as the OCV value.

JP 2011-169831 A

  By the way, according to the graph showing the correlation between the OCV and the SOC of a power storage element such as a secondary battery, the SOC change rate, which is the SOC change amount per unit change amount of the OCV, is not always constant and is in the OCV region. May include a high change voltage region having a relatively high SOC change rate and a low change voltage region having a relatively low SOC change rate.

  However, in the above-described prior art, the SOC is estimated using the detected value of the terminal voltage as the OCV value using the same condition regardless of which OCV region the terminal voltage value of the secondary battery belongs to. For this reason, for example, when the detection value of the terminal voltage of the secondary battery belongs to the high change voltage region, the estimation error of the SOC increases due to the detection error of the terminal voltage when the above condition is satisfied, or the detection value of the terminal voltage May belong to the low change voltage region, there may be a disadvantage that it is necessary to wait for an unnecessarily long time until the above condition is satisfied, even though the value is such that a desired accuracy can be obtained.

  In the present specification, the estimation error of the SOC is increased or the standby time is unnecessarily long as compared to the configuration using the same condition regardless of which OCV region the terminal voltage value of the storage element belongs to. Disclosed is a technique capable of estimating the SOC while suppressing this.

  The state-of-charge estimation device disclosed in the present specification includes voltage regions having different charge state change rates, which are change amounts of the charge state with respect to a unit change amount of the open circuit voltage, in the change characteristics between the open circuit voltage and the charge state. A state-of-charge estimation device for estimating a state of charge of a power storage element, comprising: a voltage detection unit that detects a terminal voltage of the power storage element; and a control unit, wherein the control unit has the power storage element equal to or less than a reference current value Region determination processing for determining which of the plurality of voltage regions the detected value of the terminal voltage of the power storage element detected by the voltage detection unit during input / output of A condition setting process for setting, as an estimation condition, a condition for making the terminal voltage of the power storage element more stable as the charging state change rate of the voltage region to which the detection value belongs is higher; If the device determines that the estimated condition is satisfied, it has a configuration for executing an estimation process for estimating the state of charge of the electric storage device.

  According to the invention disclosed in this specification, the estimation error of the SOC becomes larger or less than the configuration using the same condition regardless of which OCV region the terminal voltage value of the storage element belongs to. The SOC can be estimated while suppressing waiting for a necessary long time.

The block diagram which shows the electric constitution of the charge condition estimation apparatus which concerns on one Embodiment. Graph showing terminal voltage and SOC of secondary battery Graph showing the transition of terminal voltage after stopping charging / discharging Flow chart showing integrated SOC estimation process Flowchart showing reset SOC estimation processing Graph showing the transition of terminal voltage after stopping charging / discharging

(Outline of the embodiment)
The charging state estimation device disclosed in the present specification waits until a predetermined estimation condition is satisfied when the storage element is inputting / outputting a reference current value or less, and based on the voltage of the storage element after waiting. The state of charge estimation device estimates the state of charge, and the storage element has a charge state change rate which is a change amount of the charge state with respect to a unit change amount of the voltage in a change characteristic between the voltage and the charge state. A region determination process for determining which of the plurality of voltage regions the voltage belongs to when the storage element is performing input / output of the reference current value or less in a case where a plurality of different voltage regions are included; The condition setting process for setting the estimation condition so that the waiting time becomes longer as the charging state change rate of the voltage region to which the voltage belongs is longer, and the predetermined estimation condition is satisfied. It has a structure having a control unit for executing the estimation process for estimating the state of charge of the electric storage device based on the voltage of the electric storage element when the.

  The charging state estimation device calculates the terminal voltage of the power storage element as the charge state change rate of the voltage region to which the detected value of the terminal voltage of the power storage element detected when the current of the power storage element is equal to or less than a reference value is higher. Conditions for achieving a more stable state are set as estimation conditions. Then, when the charging state estimation device determines that the storage element satisfies the estimation condition, the charging state of the storage element is determined based on the change characteristic from the detected value of the terminal voltage detected by the voltage detection unit when the determination is made. Is estimated. As a result, the estimation error of the SOC is increased or the standby time is unnecessarily long as compared with the configuration using the same condition regardless of which OCV region the terminal voltage value of the storage element belongs to. The SOC can be estimated while suppressing.

  In the above charging state estimation device, the control unit, after setting the estimation condition and before satisfying the estimation condition, the voltage region to which the detected value of the terminal voltage detected by the voltage detection unit belongs to another voltage region. A change determination process for determining whether or not a change has occurred, and a condition change process for changing the estimation condition to a condition corresponding to the other voltage area when it is determined that the voltage area has been changed. The structure to do may be sufficient.

  In this charging state estimation device, after setting the estimation condition and before satisfying the estimation condition, when it is determined that the voltage region to which the detected value of the terminal voltage detected by the voltage detection unit has been changed to another voltage region The estimation condition is changed to a condition corresponding to another voltage region. Thereby, since the estimation condition can be set more accurately as compared with the configuration in which the estimation condition is not changed according to the change of the voltage region, the state of charge of the storage element can be estimated with higher accuracy.

  In the above-described charging state estimation device, the voltage region may be sandwiched between a region where the charging state change rate is high and a region where the charging state change rate is low.

  According to this state-of-charge estimation device, a region with a high state of charge change is transitioned to an adjacent region by a change determination process and a condition change process, compared to a configuration in which the region is not sandwiched between regions with a low state of charge change. Even if it is a battery with the characteristic which it is easy to do, the charge condition of an electrical storage element can be estimated with high precision.

  In the charging state estimation device, the estimation condition is that a standby time elapses from the stop of charging / discharging. In the condition setting process, the higher the charging state change rate of the voltage region to which the detected value of the terminal voltage belongs is higher. The long waiting time is set as the estimation condition, and in the estimation process, the detected value of the terminal voltage detected by the voltage detection unit when the determination is made, based on the change characteristic, You may estimate the charge condition of an electrical storage element.

  According to this state-of-charge estimation device, the estimation condition is that the standby time elapses after the charge / discharge stop, and the higher the state of charge change in the voltage region to which the detected value of the terminal voltage belongs, the longer the standby time is. Set as the estimation condition. Thereby, it is not necessary to always detect the terminal voltage to determine whether or not the estimation condition is satisfied after the charge / discharge stop, so that the power consumption of the charge state estimation device can be reduced.

  The charging state estimation device includes a temperature detection unit that detects a temperature of the power storage element, and the control unit determines that the temperature of the power storage element detected by the temperature detection unit is lower than a reference temperature value. You may have the structure which does not perform an estimation process.

  According to this state-of-charge estimation device, it is possible to suppress setting a uselessly long standby time compared to a configuration in which estimation processing is performed regardless of the temperature of the storage element.

  Further, the power storage device may include a power storage element and a charge state estimation device.

<One Embodiment>
An embodiment will be described with reference to FIGS. The battery pack 1 according to the present embodiment is mounted on, for example, a conventional engine-driven vehicle (convex vehicle), an electric vehicle, and a hybrid vehicle (hereinafter simply referred to as an automobile), and supplies power to a power source that operates with electric energy. To do.

(Battery pack configuration)
As illustrated in FIG. 1, the battery pack 1 includes a secondary battery 2 and a battery management device (hereinafter referred to as “Battery Management System”). The secondary battery 2 is an example of a power storage element, for example, a single battery. More specifically, it is a lithium ion battery having a negative electrode formed of a graphite-based material and a positive electrode containing an iron phosphate-based material such as LiFePO4. The battery pack 1 is an example of a power storage device, and the BMS 3 is an example of a charge state estimation device.

  The secondary battery 2 is electrically connected through a wiring 4 and a switch 42 to a charging device 40 provided inside or outside the automobile or a load 41 such as a power source provided inside the automobile. . The charging device 40 receives power from an external power source (not shown) and charges the secondary battery 2.

  The BMS 3 includes a control unit 31, an analog-digital converter (hereinafter referred to as ADC) 32, a current sensor 33, a voltage sensor 34, and a temperature sensor 30. The control unit 31 includes a central processing unit (hereinafter referred to as a CPU) 35 and a memory 36 such as a ROM or a RAM. Various programs (including an SOC estimation program) for controlling the operation of the BMS 3 are stored in the memory 36, and the CPU 35 executes an SOC estimation process to be described later according to the program read from the memory 36. Control each part. The control unit 31 is an example of a control unit, and the voltage sensor 34 is an example of a voltage detection unit.

  Current sensor 33 detects a charging current flowing from charging device 40 to secondary battery 2 during charging and a current value I [A] of a discharging current flowing from secondary battery 2 to load 41 during discharging, and the detected current value An analog detection signal SG1 corresponding to I is transmitted to the ADC 32. Hereinafter, the charging current and the discharging current are collectively referred to as charging / discharging current. The voltage sensor 34 is connected to both ends of the secondary battery 2, detects a voltage value V [V] that is a terminal voltage of the secondary battery 2, and outputs an analog detection signal SG 2 corresponding to the detected voltage value V to the ADC 32. Send to. The voltage sensor 34 can detect an accurate voltage value V in which the influence of the wiring resistance of the wiring 4 is suppressed by directly detecting the terminal voltage without using the wiring 4. The temperature sensor 30 detects the battery temperature T of the secondary battery 2.

  The ADC 32 converts the detection signals SG1, SG2, and SG3 transmitted from the current sensor 33, the voltage sensor 34, and the temperature sensor 30 from analog signals to digital signals, and indicates a current value I, a voltage value V, and a battery temperature T. Data is transmitted to the control unit 31. Then, the control unit 31 stores the digital data in the memory 36.

(OCV-SOC curve of secondary battery)
In FIG. 2, the OCV-SOC curve P of the secondary battery 2 is indicated by a solid line, the charging curve Q of the secondary battery 2 is indicated by a one-dot chain line, and the discharge curve R is indicated by a two-dot chain line. ing.

  The OCV-SOC curve P indicates a change characteristic (correlation) between the OCV and the SOC of the secondary battery 2. The OCV on the OCV-SOC curve P is the terminal voltage of the secondary battery 2 in a stable state, for example, when the amount of voltage change per unit time of the secondary battery 2 is less than a specified amount. This is the terminal voltage of the secondary battery 2. The prescribed amount can be determined in advance by specifications of the secondary battery 2, predetermined experiments, or the like. As shown in FIG. 1, data relating to the OCV-SOC curve is stored in the memory 36.

  The charging curve Q is information indicating the correlation between the terminal voltage and the SOC when the secondary battery 2 is charged at a predetermined charging rate. In FIG. 2, the charging curve when the charging rate is 1C. Q is illustrated. Further, the discharge curve R is information indicating the correlation between the terminal voltage and the SOC when the secondary battery 2 is discharged at a predetermined discharge rate. In FIG. 2, the discharge rate is 1C. A discharge curve R is illustrated.

  According to the OCV-SOC curve P of the secondary battery 2 shown in the figure, the voltage region in which the terminal voltage of the secondary battery 2 can change includes a plurality of voltage regions having different SOC change rates. This SOC change rate is a change amount of SOC per unit change amount of OCV, and is an example of a charge state change rate. Specifically, the different voltage regions include a high change voltage region EH (EH1, EH2) in which the SOC change rate is higher than the reference change rate, and a low change voltage region EL in which the SOC change rate is less than or equal to the reference change rate, It is included.

  Specifically, for example, in the example shown in the figure, the voltage region where the OCV value is about 3.28V to about 3.315V is the first high change voltage region EH1, and the OCV value is about 3.34V to about 3.34V. The voltage region of about 3.35 V is the second high change voltage region EH2. Note that the SOC change rate in the first high change voltage region EH1 and the SOC change rate in the second high change voltage region EH2 are different from each other, specifically, the SOC change rate in the second high change voltage region EH2. Is slightly higher than the SOC change rate in the first high change voltage region EH1.

  The reason why the high change voltage region EH exists may be that the stage structure of the negative electrode formed of the graphite-based material changes in this region. Specifically, since the potential (OCP: Open Circuit Potential) of the negative electrode formed of graphite changes stepwise in the vicinity of SOC 60%, the high change voltage region EH exists. For this reason, in this embodiment, although the positive electrode containing an iron phosphate type material is used, the kind of positive electrode is not specifically limited.

  On the other hand, the voltage region where the OCV value is about 3.28V or less is the first low change voltage region EL1, and the region where the OCV value is about 3.315V to about 3.34V is the second low change voltage region EL2. The region where the OCV value is about 3.35 V or more is the third low change voltage region EL3. The SOC change rates in the respective low change voltage regions EL are different from each other. Specifically, the SOC change rate in the first low change voltage region EL1 is the highest, and the SOC change rate in the third low change voltage region EL3. Is the lowest. Note that the reference change rate can be arbitrarily determined depending on, for example, whether or not the SOC estimation error with respect to the predetermined OCV detection error is within an allowable range.

  According to OCV-SOC curve P, the SOC region in which the SOC of secondary battery 2 can change includes a plurality of SOC regions having different OCV change rates. The OCV change rate is the change amount of the OCV per unit change amount of the SOC. The high change voltage region EH has a relatively low OCV change rate. More specifically, the high change voltage region EH is an SOC region in which the OCV change rate is substantially zero (a region where the SOC is approximately 30% to approximately 64%, and the SOC is approximately 68% to approximately 98%. % Region (hereinafter also referred to as plateau region).

  The low change voltage region EL is a region having a relatively high OCV change rate, that is, a region where the SOC is about 30% or less, a region where the SOC is about 64% to about 68%, and an SOC is about 98% or more. (Hereinafter also referred to as a non-plateau region).

(Transition of terminal voltage after charge / discharge start to charge / discharge stop)
In FIG. 2, charging cases α and β of the secondary battery 2 are shown. In the charging case α, the secondary battery 2 is charged with a specified current from a stable state (point α1) where the OCV value is 3.21 V and the SOC value is 10%. The terminal voltage value of the secondary battery 2 rises from the point α1 to the point α2 after the start of charging, and thereafter rises along the charging curve Q from the point α2.

  For example, when charging is stopped at the point α3, the terminal voltage value of the secondary battery 2 decreases from the point α3 toward the point α4. Since the secondary battery 2 is not charged / discharged while the terminal voltage value of the secondary battery 2 drops from the point α3 to the point α4, the SOC does not substantially change and maintains about 19%.

  In the charging case β, the secondary battery 2 is charged with a specified current from a stable state (point β1) where the OCV value is 3.34V and the SOC value is 75%. The terminal voltage value of the secondary battery 2 rises from the point β1 to the point β2 after the start of charging, and thereafter rises along the charging curve Q from the point β2.

  For example, when charging is stopped at the point β3, the terminal voltage value of the secondary battery 2 decreases from the point β3 toward the point β4. Since the secondary battery 2 is not charged / discharged while the terminal voltage value of the secondary battery 2 drops from the point β3 to the point β4, the SOC does not substantially change and maintains about 85%.

  Here, as indicated by G1 in FIG. 3, the terminal voltage of the secondary battery 2 rapidly approaches the OCV in a short time (T1), and then converges gradually over a long time (T2). In the charging case α of FIG. 2, the time at which the terminal voltage value of the secondary battery 2 reaches the point α5 on the way from the point α3 to the point α4 in FIG. The time when the terminal voltage value of the battery 2 reaches the point β5 in the middle of the decrease from the point β3 to the point β4 in FIG. 2 is T1. The point α5 is a point where the terminal voltage value of the secondary battery 2 is slightly larger than the point α4, and the point β5 is a point where the terminal voltage value of the secondary battery 2 is slightly larger than the point β4.

  The amount of decrease in terminal voltage after the stop of charging / discharging per unit time indicates the rate of decrease in terminal voltage. Therefore, the speed is an example of the voltage change rate. In the graph shown in FIG. 3, the voltage change rate is, for example, a tangent line at the point B1 or the point B2. Since the tangent line becomes gentle with the passage of time, it can be said that the voltage change rate indicates the degree of stability of the terminal voltage. Specifically, the terminal voltage is more stable as the voltage change rate is smaller.

  Further, as indicated by G2 in FIG. 3, the terminal voltage of the secondary battery 2 becomes longer as it approaches the OCV as the temperature of the secondary battery 2 is lower. This is because the influence of the internal resistance of the secondary battery 2 becomes larger than when the temperature of the secondary battery 2 is high.

  Hereinafter, a case will be described in which the SOC value of the secondary battery 2 is estimated when T1 elapses after charging / discharging of the secondary battery 2 is stopped regardless of the high change voltage region and the low change voltage region. In the following, the time from when a charge / discharge is stopped to a time when a terminal voltage for estimating the SOC value of the secondary battery 2 is detected is referred to as a standby time. The reference time point after the charge / discharge is stopped may be after the charge / discharge is stopped or when the voltage region is changed.

  In the case of the charging case α, when the SOC value of the secondary battery 2 is estimated when T1 has elapsed since the charging / discharging of the secondary battery 2 is stopped, based on the terminal voltage value of the secondary battery 2 at the point α5. The SOC value of the secondary battery 2 is estimated. The point α5 belongs to the low change voltage region, and the SOC value at the point α6 on the OCV-SOC curve P becomes the estimated SOC value of the secondary battery 2. The estimated value is about 21%.

  On the other hand, the SOC value at the point α4 on the OCV-SOC curve P becomes the actual value of the SOC of the secondary battery 2, and the actual value is 19%. In the case of the charging case α, an error (hereinafter referred to as an estimation error) S1 between the estimated value and the actual value is about 2%. Therefore, when estimating the SOC value of the secondary battery 2 in the low change voltage region, the error in the SOC value of the secondary battery 2 does not increase even for a relatively short time.

  In the case of the charging case β, when the SOC value of the secondary battery 2 is estimated when T1 has elapsed since the charging / discharging of the secondary battery 2 is stopped, based on the terminal voltage value of the secondary battery 2 at the point β5. The SOC value of the secondary battery 2 is estimated. The point β5 belongs to the high change voltage region, and the SOC value at the point β6 on the OCV-SOC curve P becomes the estimated value of the SOC of the secondary battery 2. The estimated value is about 96%.

  On the other hand, the SOC value at the point β4 on the OCV-SOC curve P becomes the actual value of the SOC of the secondary battery 2, and the actual value is 85%. In the case of charging case β, the estimation error S2 is about 11%. Therefore, when estimating the SOC value of the secondary battery 2 in the high change voltage region, if the time is relatively short, the error in the SOC value of the secondary battery 2 may increase.

  That is, regardless of the high change voltage region and the low change voltage region, when the SOC value of the secondary battery 2 is estimated at the same time after the charge / discharge of the secondary battery 2 is stopped, the terminal voltage of the secondary battery 2 is calculated. Is in a high change voltage region, the SOC estimation error becomes large, or when the terminal voltage of the secondary battery 2 belongs to a low change voltage region, it is a value that can obtain a desired accuracy. An inconvenience arises that the user has to wait for an unnecessarily long time.

  Therefore, it is necessary to set the standby time separately for each region so that the error of the SOC value of the secondary battery 2 is approximately the same in the low change voltage region and the high change voltage region. Specifically, in the low change voltage region, the standby time is set to a short standby time, and in the high change voltage region, the standby time is set to a long standby time.

(SOC estimation process flow)
For example, as shown in FIG. 4, the CPU 35 executes an integrated SCO estimation process, triggered by the start of charging / discharging of the secondary battery 2, for example, when the driver turns on a car key. First, the CPU 35 reads the SOC initial value stored in the memory 36 (S1). Then, the CPU 35 integrates the charge / discharge current based on the detection signal SG1 from the current sensor 33 of the secondary battery 2 (S2). CPU35 calculates the value of (DELTA) SOC from the said integrated value (S3), and performs it until it judges that charging / discharging of the secondary battery 2 has stopped (S4).

  If the CPU 35 determines that charging / discharging of the secondary battery 2 is not stopped (S4: NO), the CPU 35 returns to S2 and continues the processing. On the other hand, when the CPU 35 determines that charging / discharging of the secondary battery 2 has stopped (S4: YES), a value obtained by adding the value of ΔSOC to the SOC initial value read from the memory 36 is newly set as the SOC initial value ( S5). Then, the CPU 35 ends the estimation process of the integrated SCO.

  In addition, when there is a request from an external device or a higher-level electronic control unit, the CPU 35 transmits a value obtained by adding the value of ΔSOC to the SOC initial value as the current SOC value.

  Note that “charging / discharging of the secondary battery 2 has stopped” is not limited to the case where the secondary battery 2 has completely stopped charging / discharging (a state in which the switch 42 is opened). Even when the standby current flows through the load 41 to which the secondary battery 2 is connected (for example, less than several mA), the dark current may flow through the BMS 3 (for example, less than several hundred μA). Note that the standby current and dark current are examples of the reference current value.

  On the other hand, while the power is supplied to the BMS 3, the CPU 35 always executes the SOC estimation process for reset described below.

  “Reset” refers to updating the SOC value. Specifically, for example, when the automobile stops, the CPU 35 estimates the SOC value (SOC1) of the secondary battery 2 from the OCV-SOC curve P based on the terminal voltage value of the secondary battery 2, and the SOC described above. Replace the initial value with SOC1. This is because the initial SOC value is often an inaccurate value due to a large integration error of the charge / discharge current.

  However, in the secondary battery 2, as described above, if the standby time until the SOC value of the secondary battery 2 is estimated is set uniformly in any OCV region and the OCV measurement method is executed, the CPU 35 May cause the SOC value to be erroneously detected. For this reason, the value of the SOC estimated from the OCV-SOC curve P by the CPU 35 based on the terminal voltage value of the secondary battery 2 rather than the value of the SOC estimated by the CPU 35 integrating the current of the secondary battery 2. There is a risk that the accuracy is worse.

  Therefore, in the reset SOC estimation process described later, the CPU 35 sets the standby time separately in the low change voltage region and the high change voltage region.

  First, the CPU 35 determines whether charging / discharging of the secondary battery 2 is stopped (S11). When the CPU 35 determines that charging / discharging of the secondary battery 2 has not stopped (S11: NO), the CPU 35 stands by, and when determining that charging / discharging of the secondary battery 2 has stopped (S11: YES), the CPU 35 Then, it is determined whether or not the reset processing condition is satisfied (S12).

  The reset processing conditions include, for example, that the travel distance of the automobile is equal to or greater than the reference travel distance, that the reference reset time has elapsed since the last reset, and that the battery temperature T of the secondary battery 2 is a reference value (for example, 0 ° C. The CPU 35 determines that the mileage of the car is too short to reach the reference mileage, or that the time since the last reset has not passed so much, and the reference reset time. When it is determined that the battery temperature T has not elapsed or when it is determined that the battery temperature T of the secondary battery 2 is lower than the reference value (S12: NO), the flow of reset SOC estimation processing is performed without estimating the SOC. Exit. CPU 35 determines the condition as a limit value that falls within a predetermined SOC estimation accuracy range.

  Then, the CPU 35 detects the terminal voltage value V of the secondary battery 2 based on the detection signal SG2 from the voltage sensor 34 (S13). Then, the CPU 35 refers to the OCV-SOC curve information stored in the memory 36, and determines whether or not the terminal voltage value is in the high change voltage region (S14).

  When the CPU 35 determines that the terminal voltage value is in the high change voltage region (S14: YES), the CPU 35 sets the standby time to a long standby time (for example, 24 hours) (S15), and the terminal voltage value changes to high. If it is determined that the voltage is not in the voltage range (S14: NO), the standby time is set to a short standby time (eg, 3 hours) (S16). Then, the CPU 35 starts time measurement (S17). The memory 36 stores a long standby time corresponding to the high change voltage region and a short standby time corresponding to the low change voltage region in association with each other.

  Thereafter, the CPU 35 detects the terminal voltage value V of the secondary battery 2 (S18), and determines whether or not there is a change in the voltage region determined in S14 (S19). When the CPU 35 determines that the voltage region has been changed (S19: YES), the CPU 35 changes the standby time according to the change of the voltage region (S20). For example, when the CPU 35 determines that the terminal voltage value V of the secondary battery 2 has changed from the high change voltage region to the low change voltage region, the CPU 35 changes the standby time from the long standby time to the short standby time. Thereafter, the CPU 35 newly starts time measurement based on the changed standby time (S21). Note that the process of S19 is an example of a change determination process, and the process of S20 is an example of a condition change process.

  After the process of S21 or when the CPU 35 determines that the voltage region has not been changed (S19: NO), the CPU 35 determines whether or not the standby time has elapsed since the start of time measurement (S22).

  If the CPU 35 determines that the standby time has not elapsed since the time measurement start (S22: NO), the CPU 35 returns to S18 and detects the terminal voltage value V of the secondary battery 2 again. On the other hand, if the CPU 35 determines that the standby time has elapsed since the start of time measurement (S22: YES), the CPU 35 detects the terminal voltage value V of the secondary battery 2 (S23), and calculates the SOC according to the detected terminal voltage value. Estimate (S24). Then, the CPU 35 stores the estimated value of the SOC in the memory 36 as the SOC initial value (S25). The SCO estimation process is terminated. Note that the process of S24 is an example of an estimation process.

  Next, the effect of setting the standby time separately in the low change voltage region and the high change voltage region will be described with reference to FIG.

  First, in the charging case α, the charging of the secondary battery 2 is stopped at the point α3 (S11: YES), and since the point α3 is in the EL1 (S14: NO), the CPU 35 sets the standby time to the short standby time. (S16). Thereafter, when the standby time has elapsed (S22: YES), the terminal voltage value V of the secondary battery 2 decreases and reaches the point α5, but the voltage region remains EL1 (S19: NO).

  Therefore, the CPU 35 determines the SOC of the secondary battery 2 based on the terminal voltage value V of the secondary battery 2 at the point α5 when the standby time has elapsed after the charging of the secondary battery 2 is stopped (S23). Is estimated at the point α6 (about 21%) (S24). When the CPU 35 estimates the SOC value of the secondary battery 2 at the point α4, the estimated value is about 19%, so that the CPU 35 estimates the SOC value of the secondary battery 2 at the point α6. Thus, the estimation error S1 is about 2%.

  Next, in the charging case β, the charging of the secondary battery 2 is stopped at the point β3 (S11: YES), and since the point β3 is in the EL3 (S14: NO), the CPU 35 sets the standby time to the short standby time. Set (S16). Thereafter, when the terminal voltage value V of the secondary battery 2 decreases to reach the point β5, the CPU 35 determines that the voltage range of the terminal voltage value has been changed from EL3 to EH2 (S19: YES), and the standby time Is set to a long standby time (S20).

  Thereafter, the terminal voltage value further decreases, and when the standby time elapses after the CPU 35 sets the standby time to the long standby time (S22: YES), the terminal voltage value decreases to a point β6 that is as close as possible to the point β4. Then, based on the terminal voltage value V of the secondary battery 2 at the point β6 (S23), the CPU 35 estimates the SOC value of the secondary battery 2 at the point β7 (about 87%) (S24). When the CPU 35 estimates the SOC value of the secondary battery 2 at the point β4, the estimated value is about 85%, so that the CPU 35 estimates the SOC value of the secondary battery 2 at the point β7. Thus, the estimation error S2 is about 2%.

  Further, in the charging case γ, the charging of the secondary battery 2 is stopped at the point γ3 (S11: YES), and the point γ3 is in the EH2 (S14: YES), so the CPU 35 sets the standby time to the long standby time. (S15). Thereafter, when the terminal voltage value V of the secondary battery 2 decreases to reach the point γ5, the CPU 35 determines that the voltage range of the terminal voltage value has been changed from EH2 to EL2 (S19: YES), and the standby time Is set to a short standby time (S20).

  When the terminal voltage value of the secondary battery 2 further decreases and reaches the point γ6, the CPU 35 determines that the voltage range of the terminal voltage value has been changed from EL2 to EH1 (S19: YES), and the standby time Is set to a long standby time (S20). Thereafter, the terminal voltage value further decreases, and when the standby time has elapsed (S22: YES), the terminal voltage value decreases to a point γ7 that is as close as possible to the point γ4.

  Thereafter, the CPU 35 estimates the SOC value of the secondary battery 2 at the point γ8 (about 46%) based on the terminal voltage value V of the secondary battery 2 at the point γ7 when the standby time has elapsed (S23). (S24). When the CPU 35 estimates the SOC value of the secondary battery 2 at the point γ4, the estimated value is about 44%, so that the CPU 35 estimates the SOC value of the secondary battery 2 at the point γ8. Thus, the estimation error S3 is about 2%.

  Finally, in the discharge case δ, the discharge of the secondary battery 2 is stopped at the point δ3 (S11: YES), and since the point δ3 is in the EL1 (S14: NO), the CPU 35 sets the standby time to the short standby time. Set (S16). Thereafter, when the standby time has elapsed (S22: YES), the terminal voltage value V of the secondary battery 2 decreases and reaches the point δ5, but the voltage region remains EL1 (S19: NO).

  Therefore, the CPU 35 determines the SOC of the secondary battery 2 based on the terminal voltage value V of the secondary battery 2 at the point δ5 when the standby time has elapsed since the charging of the secondary battery 2 is stopped (S23). Is estimated at the point δ6 (about 25%) (S24). When the CPU 35 estimates the SOC value of the secondary battery 2 at the point δ4, the estimated value is about 27%, so that the CPU 35 estimates the SOC value of the secondary battery 2 at the point δ6. Thus, the estimation error S4 is about 2%.

(Effect of this embodiment)
In the present embodiment, the standby time is divided into a low change voltage region and a high change voltage region. Thereby, it is possible to estimate the SOC while suppressing the estimation error of the SOC from increasing or waiting for an unnecessarily long time.

<Other embodiments>
The technology disclosed in the present specification is not limited to the embodiments described with reference to the above description and drawings, and includes, for example, the following various aspects.

  In the above embodiment, when the CPU 35 detects the current value I of the secondary battery 2 by the current sensor 33 and determines that the current value I is less than the reference current value, the secondary battery 2 is less than or equal to the reference current value. It is determined that the input / output is performed, in other words, the reset processing condition is satisfied. However, the present invention is not limited to this, and the CPU 35 is configured to perform charge stop and discharge stop control. When the charge stop control and the discharge stop control are executed, the secondary battery 2 has an input that is less than the reference current value. You may judge that it is outputting. Further, when receiving a charge stop signal or a discharge stop signal from an external device such as a charger, the CPU 35 may determine that the secondary battery 2 is inputting / outputting a reference current value or less. With these configurations, it is not necessary to detect the current value I of the secondary battery 2 by the current sensor 33.

  In the above embodiment, when the CPU 35 determines that the voltage region has changed, the CPU 35 newly sets the standby time. However, the present invention is not limited to this, and the CPU 35 may set a time obtained by subtracting the standby time set in S16 from the standby time set in S20 as the standby time.

  In the above embodiment, the CPU 35 sets the voltage region according to the OCV value. However, the present invention is not limited to this, and the CPU 35 may set the voltage region according to the battery temperature of the secondary battery 2 or the deterioration of the secondary battery 2.

  In the said embodiment, the control unit 31 which has one CPU35 was mentioned as an example as an example of a control part. However, the control unit is not limited thereto, and includes a configuration including a plurality of CPUs, a configuration including hardware circuits such as an application specific integrated circuit (ASIC) and a field-programmable gate array (FPGA), and both hardware circuits and CPUs. The structure provided with may be sufficient. For example, a configuration in which at least two of the area determination process, the condition setting process, and the estimation process are executed by separate CPUs and hardware circuits may be used.

  In the above embodiment, as an example of the charge state estimation program, the program stored in the memory 36 having the RAM and the ROM is taken as an example. However, the charge state estimation program is not limited to this, and may be stored in a non-volatile memory such as a hard disk device or a flash memory, or a storage medium such as a CD-R.

  In the embodiment described above, a single battery is taken as an example of the power storage element. However, the present invention is not limited to this, and the power storage element may be a plurality of cells connected in series or in parallel, and the number of cells can be changed as appropriate. Further, the power storage element is not limited to the positive electrode active material being an iron phosphate-based material, and is not necessarily limited to having a negative electrode formed of a graphite-based material. In short, any active material that changes stepwise in the correlation between OCV and SOC may be used. If the storage element has two minute change regions with an OCV change rate equal to or less than a reference value and a sharp change region between the two minute change regions and the OCV change rate higher than the reference value, preferable. The storage element may be another secondary battery such as a lead battery or a manganese-based lithium ion battery. Furthermore, the storage element is not limited to a secondary battery, and may be a capacitor or an electric double layer capacitor.

  In the above embodiment, the secondary battery 2 having a characteristic in which a plurality of high change voltage regions and low change voltage regions exist is taken as an example. However, the present invention is not limited to this, and a secondary battery having a characteristic in which only one high change voltage region or a low change voltage region is present or a secondary battery having three or more properties may be used.

  In the above embodiment, when it is determined that the current value I is less than the reference current value (for example, less than several mA), the CPU 35 determines whether or not the reset processing condition is satisfied. However, the present invention is not limited to this, and the reference current value may be slightly higher than several mA.

  In the above embodiment, the SOC value is estimated based on the terminal voltage value V of the secondary battery 2 after the standby time has elapsed since the time measurement start. However, the present invention is not limited to this, and the SOC value may be estimated based on the voltage change rate and the terminal voltage value V of the secondary battery 2.

  In the above embodiment, the first high change voltage region EH1 and the second high change voltage region EH2 have the same standby time. However, the present invention is not limited to this, and EH1 and EH2 may have different standby times. Similarly, the 1 low change voltage region EL1, the 2 low change voltage region EL2, and the third low change voltage region EL3 may have different standby times. And threshold values, such as EH1 and EH2, can be suitably changed according to a battery characteristic, and are not limited to the value of the said embodiment.

  In the above embodiment, when the CPU 35 determines that the standby time has not elapsed since the time measurement start (S22: NO), the CPU 35 returns to S18 and detects the terminal voltage value V of the secondary battery 2 again. However, the present invention is not limited to this, and the CPU 35 may not detect the terminal voltage value V of the secondary battery 2 again when it is determined that the standby time has not elapsed since the time measurement start.

  1: Battery pack 2: Secondary battery 3: BMS 31: Control unit 33: Current sensor 34: Voltage sensor 35: CPU 36: Memory

Claims (8)

A charging state estimation device that waits until a predetermined estimation condition is satisfied when a storage element is performing input / output below a reference current value, and estimates a charging state based on a voltage of the storage element after the standby. In the change characteristics between the voltage and the charge state, the storage element includes a plurality of voltage regions having different charge state change rates that are the change amount of the charge state with respect to the unit change amount of the voltage.
A region determination process for determining which of the plurality of voltage regions the voltage belongs to when the storage element is performing input / output less than or equal to the reference current value;
A condition setting process for setting the estimation condition so that the waiting time becomes longer as the charging state change rate of the voltage region to which the voltage belongs is higher;
A charge state estimation device including a control unit that executes an estimation process for estimating a charge state of the power storage element based on a voltage of the power storage element when the predetermined estimation condition is satisfied. The charging state estimation device according to claim 1,
The controller is
After setting the estimation condition and before satisfying the estimation condition, it is determined whether or not the voltage region to which the detection value detected by the voltage detection unit that detects the voltage of the power storage element has been changed to another voltage region. Change decision processing,
A charging state estimation device having a configuration for executing a condition changing process for changing the estimation condition to a condition corresponding to the other voltage area when it is determined that the voltage area has been changed. The charging state estimation device according to claim 2,
The charging state estimation device, wherein the voltage region is sandwiched between regions where the charge state change rate is high and regions where the charge state change rate is low. The charging state estimation device according to claim 2 ,
The estimation condition is that a standby time elapses after the charge / discharge stop,
In the condition setting process, the higher the charging state change rate of the voltage region to which the detection value detected by the voltage detection unit is higher, the longer the standby time is set as the estimation condition,
In the estimation process, a charging state estimation device that estimates a charging state of the power storage element based on the change characteristic from the detection value detected by the voltage detection unit when the determination is made. The charge state estimation device according to any one of claims 1 to 4,
A temperature detection unit for detecting the temperature of the electricity storage element;
The controller is
A charge state estimation device having a configuration in which the estimation process is not executed when it is determined that the temperature of the power storage element detected by the temperature detection unit is lower than a reference temperature value.   The state of charge estimation device according to any one of claims 1 to 5, wherein the power storage element is a lithium ion battery having a positive electrode containing an iron phosphate material. A storage element;
An automobile comprising: the charging state estimation device according to any one of claims 1 to 6. A charging state estimation method for waiting until a predetermined estimation condition is satisfied when a storage element is performing input / output of a reference current value or less, and estimating a charging state based on the voltage of the storage element after waiting. In the change characteristics between the voltage and the charge state, the storage element includes a plurality of voltage regions having different charge state change rates that are the change amount of the charge state with respect to the unit change amount of the voltage.
A region determining step of determining which of the plurality of voltage regions the voltage belongs to when the storage element is performing input / output of the reference current value or less;
A condition setting step for setting the estimation condition so that the waiting time becomes longer as the charging state change rate of the voltage region to which the voltage belongs is higher;
A charge state estimation method comprising: an estimation step of estimating a charge state of the power storage element based on a voltage of the power storage element when the predetermined estimation condition is satisfied.

Images