JP2016211923A - Charging amount estimation method and charging amount estimation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging amount estimation method capable of improving the calculation accuracy of the battery charging amount regardless of the range of the battery charging amount.SOLUTION: In the charging amount estimation method, an open-circuit voltage and a resistance value of an internal resistance of a battery 7 that is charged or discharged are successively estimated. The resistance value of the internal resistance includes a first resistance value and a second resistance value. The charging amount estimation method includes: a step of individually estimating the resistance value of the internal resistance during the charging of the battery 7 and the resistance value of the internal resistance during the discharging of the battery 7; and a step of calculating the charge rate of the battery, on the basis of one of the first and second resistance values of the resistance value of the internal resistance during the charging or discharging.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a charge amount estimation method and a charge amount estimation apparatus that sequentially estimate parameters of a battery that performs charging and discharging.

  Conventionally, in order to calculate a charge amount or a charge rate of a battery to be charged / discharged, a so-called current integration method is used in which a charge amount is calculated by integrating currents flowing through the battery. However, since the current integration method is affected by the charging efficiency of the battery, the error included in the calculated charge amount tends to increase.

  Therefore, in order to calculate the charge amount of the battery to be charged / discharged, calculate the internal resistance corresponding to each frequency by applying alternating current of two types of frequencies, and calculate the charge amount from the calculated internal resistance (Patent Document 1).

  In addition, the internal resistance value at the time of charging and discharging is calculated from the current and voltage after the elapse of a predetermined time after the start of charging / discharging, and the state of charge (charge amount) of the battery is calculated from the calculated internal resistance. (Patent Document 2).

JP-A-61-170678 JP 2013-142649

  However, in the technology described in Patent Document 1, since the internal resistance value at the time of charging and at the time of discharging is handled as the same, when the charge amount is within a certain range, the calculation accuracy of the charge amount is May decrease. In the technique described in Patent Document 2, the internal resistance value is calculated from the current and voltage after a predetermined time has elapsed after the start of charge / discharge. That is, since the internal resistance value is calculated in a certain frequency band, the calculation accuracy of the charge amount may be reduced when the charge amount is within a certain range.

  An object of the present invention made in view of such circumstances is to provide a charge amount estimation method and a charge amount estimation apparatus that can improve the calculation accuracy of the charge amount regardless of the range of the charge amount.

In order to solve the above problem, the charge amount estimation method according to the first aspect of the present invention is:
In the charge amount estimation method for sequentially estimating the resistance value of the internal resistance including the first resistance value and the second resistance value and the open circuit voltage, which is the resistance value of the internal resistance of the battery that performs charging and discharging,
Individually estimating the resistance value of the internal resistance during charging of the battery and the resistance value of the internal resistance during discharging of the battery;
Calculating a charging rate of the battery based on one of the first resistance value and the second resistance value among the resistance values of the internal resistance at the time of charging or discharging.

Further, the charge amount estimation method according to the second aspect of the present invention,
The charge amount is estimated based on the resistance value of the internal resistance at the time of charging.

Further, the charge amount estimation method according to the third aspect of the present invention,
The first resistance value reflects a component having a faster reaction rate between the electrolytic solution of the battery and the electrode than the second resistance value.

Further, the charge amount estimation method according to the fourth aspect of the present invention,
The internal resistance of the battery includes a resistor R0c, a resistor R1c, and a resistor R2c that are effective when charging the battery,
The first and second resistance values when the battery is charged are respectively the resistance values of the resistor R0c and the resistor R2c.

Further, the charge amount estimation method according to the fifth aspect of the present invention,
Further comprising selecting one of the first resistance value and the second resistance value based on a predetermined threshold and an estimated value of the open circuit voltage of the battery;
The step of calculating the charging rate of the battery calculates the charging rate of the battery based on one of the first and second resistance values selected in the selecting step.

Further, the charge amount estimation method according to the sixth aspect of the present invention is:
In the selecting step, when the estimated value of the open circuit voltage of the battery is lower than the predetermined threshold, the first resistance value is selected.

Further, the charge amount estimation method according to the seventh aspect of the present invention,
Further comprising estimating the health of the battery;
The resistance value of the internal resistance is corrected based on the soundness level of the battery.

Further, the charge amount estimation method according to the eighth aspect of the present invention is:
Further comprising measuring the temperature of the battery;
The resistance value of the internal resistance is corrected based on the temperature of the battery.

In order to solve the above problem, a charge amount estimation device according to a ninth aspect of the present invention is:
In the charge amount estimation device that sequentially estimates the resistance value of the internal resistance including the first resistance value and the second resistance value and the open circuit voltage, which is the resistance value of the internal resistance of the battery that performs charging and discharging,
A charging parameter estimator for estimating a resistance value of the internal resistance during charging of the battery;
A discharge parameter estimation unit for estimating a resistance value of the internal resistance during discharge of the battery;
A charge rate estimating unit that calculates a charge rate of the battery based on one of the first and second resistance values among the resistance values of the internal resistance during the charging or discharging.

  According to the charge amount estimation method according to the first aspect of the present invention, the charge amount calculation accuracy can be increased regardless of the charge amount range.

  According to the charge amount estimation method according to the second aspect of the present invention, a more accurate charge amount can be calculated.

  According to the charge amount estimation method according to the third aspect of the present invention, the charge amount can be calculated in a form in accordance with the reaction process inside the battery.

  According to the charge amount estimation method according to the fourth aspect of the present invention, the charge amount can be calculated in a form more in line with the reaction process inside the battery.

  According to the charge amount estimation method according to the fifth aspect of the present invention, a more accurate charge amount can be calculated.

  According to the charge amount estimation method according to the sixth aspect of the present invention, a more accurate charge amount can be calculated.

  According to the charge amount estimation method according to the seventh aspect of the present invention, the charge amount can be calculated more easily.

  According to the charge amount estimation method according to the eighth aspect of the present invention, the charge amount can be calculated more easily.

  According to the charge amount estimation device of the ninth aspect of the present invention, the charge amount calculation accuracy can be increased regardless of the range of the charge amount.

It is a figure which shows the structure and connection of the charge amount estimation apparatus which concern on one Embodiment. It is a figure which shows the equivalent circuit of a battery. It is a figure which shows the structure of a charge amount calculating part. It is a figure showing the battery parameter estimation method. It is a figure which shows the correction coefficient of the resistance value of a battery parameter. It is a figure which shows the relationship between an open circuit voltage and the resistance value of a battery parameter. It is a figure which shows the relationship between a charging rate and an open circuit voltage. It is a flowchart of the charge amount estimation method according to an embodiment.

  Hereinafter, an embodiment of a charge amount estimation method and a charge amount estimation apparatus according to the present invention will be described in detail with reference to the drawings.

(Embodiment)
The charge amount estimation method according to an embodiment is executed by a charge amount estimation device. The charge amount estimation device is connected to a battery that performs charge and discharge, and estimates parameters including the resistance value of the internal resistance of the battery and the open circuit voltage (OCV) and the charge amount.

[Charging amount estimation device]
FIG. 1 is a diagram illustrating a configuration of a charge amount estimation device 1 according to an embodiment and a connection circuit with a battery 7. A charge amount estimation apparatus 1 according to an embodiment includes a temperature measurement unit 10, a voltage measurement unit 11, a current measurement unit 12, and a charge amount calculation unit 13. The charge amount calculation unit 13 is connected to the temperature measurement unit 10, the voltage measurement unit 11, and the current measurement unit 12, respectively.

  Each part of the charge amount estimation device 1 is connected to the battery 7. The temperature measurement unit 10 is connected to the temperature measurement location of the battery 7. The voltage measuring unit 11 is connected to the battery 7 in parallel. The current measuring unit 12 is connected to the battery 7 in series. Further, the battery 7 is connected to the load 8 and the charger 9 in parallel. The load 8 is, for example, various control devices, a motor that drives an in-vehicle device, and the like, and consumes electric power that the battery 7 discharges. The charger 9 charges the battery 7 by passing a current in the direction of charging the battery 7.

  The battery 7 that is a target for estimating the charge amount in the charge amount estimation method according to the embodiment is a lead storage battery having a relatively large difference in battery parameters between charge and discharge, but is not limited thereto. The battery 7 may be another rechargeable secondary battery.

  FIG. 2 (a) shows an equivalent circuit of a battery having different battery parameters in the charging direction and the discharging direction. FIG. 2 (a) shows that the battery parameters differ depending on the direction of the current by inserting a diode and limiting the current path in the charging direction and the discharging direction. FIG. 2 (b) is an equivalent circuit showing only circuit elements through which current actually flows when current flows in the discharge direction in the circuit of FIG. 2 (a), that is, circuit elements that are effective during discharge. FIG. 2 (c) is an equivalent circuit showing only circuit elements through which current actually flows when current flows in the charging direction in the circuit of FIG. 2 (a), that is, circuit elements that are effective during charging.

  Circuit elements in the equivalent circuit of FIG. 2 will be described. R represents parasitic resistance (hereinafter also simply referred to as resistance), and C represents parasitic capacitance. A subscript following R or C represents the order of resistance or parasitic capacitance. That is, R0 represents a zeroth-order resistor, and R1 represents a first-order resistor. The order corresponds to the order when an electrical signal (current, voltage, etc.) is approximated by a series. Further, the subscript following the order indicates whether the component is effective during discharging or effective during charging. That is, R0d represents a zero-order resistor that is effective during discharging, and R0c represents a zero-order resistor that is effective during charging. The values of these circuit elements are battery parameters in the equivalent circuit of FIG. That is, the battery parameters include resistors R0c to R2c and R0d to R2d, and parasitic capacitances C1c to C2c and C1d to C2d. The resistance and parasitic capacitance are collectively referred to as the internal resistance of the battery 7. Battery parameters that are effective components during charging and discharging are referred to as charging parameters and discharging parameters, respectively. That is, the charging parameter includes resistors R0c to R2c and parasitic capacitances C1c to C2c, and the discharging parameter includes resistors R0d to R2d and parasitic capacitances C1d to C2d.

  The temperature measurement unit 10 measures the temperature of the battery 7. Usually, the temperature measurement unit 10 measures the surface temperature of the battery 7. The voltage measuring unit 11 measures the terminal voltage of the battery 7. The current measuring unit 12 measures the current flowing through the battery 7. The charge amount calculation unit 13 acquires the temperature of the battery from the temperature measurement unit 10, acquires the terminal voltage of the battery from the voltage measurement unit 11, and acquires the current flowing through the battery from the current measurement unit 12.

  FIG. 3 is a diagram showing a configuration of the charge amount calculation unit 13. As shown in FIG. The charge amount calculation unit 13 includes a charging parameter estimation unit 14, a discharging parameter estimation unit 15, a selector 16, an OCV calculation unit 17, and an SOC calculation unit 18.

  The charging parameter estimation unit 14 acquires the terminal voltage of the battery 7 from the voltage measurement unit 11, and acquires the current flowing through the battery 7 from the current measurement unit 12. The charging parameter estimation unit 14 estimates charging parameters, OCV, and SOH (State of Health) of the battery 7 based on the acquired terminal voltage and current. The OCV and SOH of the battery 7 estimated by the charging parameter estimation unit 14 are referred to as an OCV estimated value and an SOH estimated value, respectively. A specific estimation method performed by the charging time parameter estimation unit 14 will be described later. The charging parameter estimation unit 14 outputs the estimated value to the selector 16 and the OCV calculation unit 17.

  The discharging parameter estimation unit 15 has the same function as the charging parameter estimation unit 14, but differs in that the discharging parameter of the battery 7 is estimated.

  The selector 16 acquires the current flowing through the battery 7 from the current measuring unit 12, and determines whether the current is a current in the charging direction or a current in the discharging direction. The selector 16 acquires the OCV estimated value and the SOH estimated value of the battery 7 estimated by the charging parameter estimation unit 14 and the discharging parameter estimation unit 15, respectively. The selector 16 determines the OCV estimated value and SOH estimated value of the battery 7 based on the charging parameter or the battery 7 based on the discharging parameter based on the determination result of whether the current direction is the charging direction or the discharging direction. Any one of the OCV estimated value and the SOH estimated value is selected and output to the OCV calculating unit 17.

  The OCV calculating unit 17 acquires the temperature of the battery 7 from the temperature measuring unit 10, and acquires the charging parameter and discharging parameter of the battery 7 from the charging parameter estimation unit 14 and the discharging parameter estimation unit 15. Further, the OCV calculation unit 17 acquires the OCV estimated value and the SOH estimated value of the battery 7 based on either the charging parameter or the discharging parameter that the selector 16 selects and outputs.

  The OCV calculation unit 17 calculates the OCV of the battery 7 based on the acquired information and outputs the value to the SOC calculation unit 18. The OCV calculated by the OCV calculation unit 17 is also referred to as an OCV calculated value in order to distinguish it from the OCV estimated value. A specific method by which the OCV calculation unit 17 calculates the OCV calculation value will be described later. Note that the OCV estimated value of the battery 7 input to the OCV calculating unit 17 is a value estimated by the charging parameter estimating unit 14 or the discharging parameter estimating unit 15, and the accuracy of the value is not high. On the other hand, the OCV calculated value is a value calculated based on the relationship between the resistance value of the internal resistance of the battery 7 and the OCV, as will be described later, and the accuracy of the value is higher than the OCV estimated value.

  The SOC calculation unit 18 calculates the SOC (State of Charge) or the charge amount of the battery 7 based on the OCV calculation value of the battery 7 acquired from the OCV calculation unit 17. The SOC of battery 7 is calculated based on a known relationship between OCV and SOC. The charge amount of the battery 7 is calculated based on the SOC. Specifically, a value obtained by multiplying the full charge amount of the battery 7 by the SOC is calculated as the charge amount of the battery 7.

[Battery parameter estimation method]
A method by which the charging parameter estimation unit 14 estimates the charging parameter and the OCV estimation value will be described. It should be noted that since the discharging parameter estimation unit 15 is also estimated by the same method as the charging parameter estimation unit 14, only the charging will be described here.

  FIG. 4 is a diagram for explaining a battery parameter estimation method in the charging-time parameter estimation unit 14. FIG. 4 (a) is a block diagram including the battery 7, an equivalent circuit 71 of the battery 7, an arithmetic unit 20, and an adaptive mechanism 21. FIG. 4 (b) is a diagram showing a configuration of an equivalent circuit 71 of the battery 7.

  The equivalent circuit 71 of the battery 7 shown in FIG. 4 (b) includes a voltage generation unit representing OCV, a zero-order internal resistance R0, and a set of a primary internal resistance R1 and an internal capacitance C1. Primary internal resistance R1 and primary internal capacitance C1 are connected in parallel. The voltage generator, the 0th-order internal resistance R0, the primary internal resistance R1, and the set of the internal capacitance C1 are connected in series. A current i is input to the equivalent circuit 71, and a terminal voltage v is output between the terminals of the equivalent circuit 71 accordingly.

  In the equivalent circuit 71 of FIG. 4B, the terminal voltage v is the sum of OCV and overvoltage η. The overvoltage η represents a voltage drop due to the internal resistance of the battery 7. The 0th-order resistance R0 that causes the overvoltage η represents a parasitic resistance such as an electrolyte, and the primary resistance R1 and the capacity C1 represent a parasitic resistance and a parasitic capacity that simulate an ion diffusion process inside the electrode, respectively.

  The equivalent circuit 71 shown in FIG. 4 (b) is a so-called first-order Foster-type RC ladder circuit, but it may be a second-order or higher-order Foster-type RC ladder circuit or an n-order Cowell-type circuit. Also good. The equivalent circuit shown in FIG. 2 is a so-called second-order Foster-type RC ladder circuit, which is different from the equivalent circuit 71 shown in FIG. 4 (b), but the basic principle of the parameter estimation method is common. In order to simplify the explanation, a method for estimating the parameters of the equivalent circuit 71 shown in FIG.

  A method for estimating the battery parameters of the battery 7 by the charging parameter estimation unit 14 will be described with reference to the block diagram shown in FIG. In the block diagram of FIG. 4 (a), the adaptive mechanism 21 is also referred to as an adaptive filter. Preferably, the adaptive mechanism 21 uses a Kalman filter, but is not limited thereto.

The charging time parameter estimation unit 14 acquires the terminal voltage of the battery 7 when the current i (k) is input to the battery 7 as the reference signal v (k) from the voltage measurement unit 11 of FIG. The charging parameter estimation unit 14 calculates an output signal v ^ (k) of a voltage output when the current i (k) is input to the equivalent circuit 71 in FIG. 4 (b). The output signal v ^ (k) and the reference signal v (k) are input to the arithmetic unit 20, and the arithmetic unit 20 calculates the difference between the reference signal v (k) and the output signal v ^ (k) to estimate error v. calculating ^~ a ^(k), and outputs estimated error v ^~ a ^(k) to the adaptive mechanism 21. The adaptive mechanism 21 corrects the parameters (R0, R1, C1, OCV) of the equivalent circuit 71 based on the input estimation errors v ^to (k). The charging parameter estimation unit 14 outputs the corrected parameters (R0, R1, C1, OCV) of the equivalent circuit 71.

Preferably, in one embodiment, based on a method for identifying parameters of an equivalent circuit of a battery described in Japanese Patent No. 5319854, parameters of a primary Foster-type RC ladder circuit are sequentially estimated. According to the above method, the transfer function defined by the equations (1) to (5) is obtained. By these equations, the parameters a1, b0, b1, b2 of the transfer function and the parameters of the equivalent circuit are linked.

In the above method, the transfer function parameters a1, b0, b1, and b2 can be estimated based on the current i and the terminal voltage v input to the equivalent circuit. Then, the parameters of the equivalent circuit can be obtained from the estimated parameters as shown in equations (6) to (9).

  Here, the method for estimating the battery parameters in the primary Foster-type RC ladder circuit shown in FIG. 4B has been described as a representative example. The battery parameter can be estimated by increasing the order of the transfer function shown in the above formula (1) even in the case of a Foster type RC ladder circuit of second or higher order without being limited to this example. Even an n-th order Cowell RC ladder circuit can be estimated by using a corresponding transfer function.

  By applying the above-described method to the equivalent circuit of FIG. 2, the charging parameter estimation unit 14 and the discharging parameter estimation unit 15 can estimate the charging and discharging parameters and the OCV estimation value of the battery 7, respectively. Further, the charging parameter estimation unit 14 and the discharging parameter estimation unit 15 can each estimate the SOH estimated value of the battery 7 based on the battery parameters.

[OCV calculation method]
A method in which the OCV calculation unit 17 calculates the OCV calculation value of the battery 7 based on the battery parameters of the battery 7 and the OCV estimated value will be described. It is assumed that the battery parameters of the battery 7 are obtained by estimating the battery parameters for the secondary Foster-type RC ladder circuit in the above-described battery parameter estimation method. That is, in this description, the charging parameter estimation unit 14 has already calculated the resistance value of the internal resistance of the battery 7 (hereinafter also simply referred to as the resistance value) and the OCV estimation value, and the OCV calculation unit 17 calculates these values. It can be acquired.

  The OCV calculation unit 17 calculates the OCV calculation value of the battery 7 from the resistance value of the battery 7 based on the known relationship between the OCV and the resistance value. Here, the resistance value of the battery 7 varies depending on the temperature of the battery 7 and also varies depending on the SOH of the battery 7. In this case, it is difficult to know the relationship between the OCV and the resistance value at different temperatures and different SOHs. Therefore, preferably, the resistance value of the battery 7 acquired from the charging time parameter estimation unit 14 is converted into a resistance value when the temperature of the battery 7 is 25 ° C. and the SOH of the battery 7 is 100%. In this way, it is sufficient to grasp only the relationship between the OCV and the converted resistance value, and the OCV can be calculated more easily and the amount of charge can be further calculated.

  Therefore, before calculating the OCV calculation value of the battery 7, the OCV calculation unit 17 determines the resistance value of the battery 7 when the temperature of the battery 7 is 25 ° C. and the SOH of the battery 7 is 100%. Convert to 7 resistance value. In one embodiment, the temperature is first corrected and then corrected with SOH.

  In order to correct the resistance value with temperature, a temperature correction coefficient is defined. For example, using the resistance value R0c_t of the resistor R0c at the time of zero-order charging when the temperature of the battery 7 is t ° C, and the resistance value R0c (25 ° C) when the temperature of the battery 7 is 25 ° C, The temperature correction coefficient (t ° C.) of the resistor R0c = R0c_t ÷ R0c (25 ° C.). FIG. 5 (a) is a graph showing the relationship between the temperature correction coefficient of the resistor R0c and the temperature of the battery 7 during the zero-order charging. The horizontal axis represents the temperature of the battery 7, and the vertical axis represents the temperature correction coefficient. According to this graph, when the temperature of the battery 7 is 25 ° C., the temperature correction coefficient is 1 as defined. When the temperature of the battery 7 is lower than 25 ° C., the temperature correction coefficient is larger than 1, and when the temperature of the battery 7 is higher than 25 ° C., the temperature correction coefficient is smaller than 1. FIG. 5 (a) shows the temperature correction coefficient of the resistor R0c at the 0th-order charging, but the same relationship is defined for the primary and secondary resistors R1c and R2c. The same applies to the resistors R0d, R1d, and R2d during discharge. Preferably, the relationship between the temperature and the temperature correction coefficient of the resistance is a table format or a function format. Preferably, the OCV calculating unit 17 holds data indicating the relationship between the temperature and the temperature correction coefficient of the resistance. Preferably, the data indicating the relationship between the temperature and the temperature correction coefficient of the resistance is stored in a storage unit connected to the OCV calculation unit 17, and the OCV calculation unit 17 acquires data from the storage unit as necessary.

The OCV calculation unit 17 uses the temperature correction coefficient of the resistance and the temperature of the battery 7 to determine the resistance when the temperature of the battery 7 acquired from the charging parameter estimation unit 14 or the discharging parameter estimation unit 15 is t ° C. The resistance value R_t of R (subscript is omitted) is converted into a resistance value R (25 ° C.) when the temperature of the battery 7 is 25 ° C. That is, the following formula (10) is calculated.
R (25 ℃) ＝ R_t ÷ resistance R temperature correction coefficient (t ℃) (10)

  Further, an SOH correction coefficient is defined to correct the internal resistance value with SOH. When the SOH of the battery 7 is x% and the temperature of the battery 7 is 25 ° C., the resistance value R0c (25 ° C., x%) of the resistance R0c at the time of zero-order charging (equal to the above-described R0c (25 ° C.)) ) And the resistance value R0c of the resistor R0c (25 ° C, 100%) when the SOH of the battery 7 is 100% and the temperature of the battery 7 is 25 ° C, the SOH correction coefficient (x %) = R0c (25 ° C., x%) ÷ R0c (25 ° C., 100%). For example, FIG. 5 (b) is a graph showing the relationship between the SOH correction coefficient of the resistor R0c and the SOH of the battery 7 at the zero-order charge. The horizontal axis represents the SOH of the battery 7, and the vertical axis represents the SOH correction coefficient. According to this graph, when the SOH of the battery 7 is 100%, the SOH correction coefficient is 1 as defined. When the SOH of the battery 7 is lower than 100%, the SOH correction coefficient is larger than 1. FIG. 5 (b) shows the SOH correction coefficient of the resistor R0c at the 0th-order charging, but the same relationship is defined for the primary and secondary resistors R1c and R2c. The same applies to the resistors R0d, R1d, and R2d during discharge. Preferably, the relationship between the SOH and the SOH correction coefficient of the resistor is a table format or a function format. Preferably, the OCV calculation unit 17 holds data indicating the relationship between the SOH and the resistance SOH correction coefficient. Preferably, data indicating the relationship between the SOH and the resistance SOH correction coefficient is stored in a storage unit connected to the OCV calculation unit 17, and the OCV calculation unit 17 acquires data from the storage unit as necessary.

The OCV calculating unit 17 uses the resistance SOH correction coefficient and the estimated SOH value of the battery 7 to calculate the resistance value R (25 ° C.) of the resistance R when the temperature of the battery 7 is 25 ° C. , x%) is further converted into a resistance value R (25 ° C., 100%) when the temperature of the battery 7 is 25 ° C. and the SOH of the battery 7 is 100%. That is, the following formula (11) is calculated. Hereinafter, the resistance value R (25 ° C., 100%) is also referred to as a corrected resistance value R_cor.
R (25 ° C, 100%) = R (25 ° C, x%) ÷ SOH correction factor for resistance R (x%) (11)

  The OCV calculation unit 17 calculates the OCV calculation value of the battery 7 using the corrected resistance value R_cor. FIG. 6 is a graph showing the relationship between the corrected resistance value R_cor and OCV. The horizontal axis represents OCV, and the vertical axis represents the correction resistance value. Here, FIGS. 6 (a), 6 (b) and 6 (c) correspond to the 0th-order resistor R0c or R0d, the primary resistor R1c or R1d, and the secondary resistor R2c or R2d, respectively. In each graph, the broken lines represent the resistances R0d, R1d, and R2d during discharging, and the solid lines represent the resistances R0c, R1c, and R2c during charging.

  The OCV calculation unit 17 can calculate the OCV calculation value using either the charging parameter or the discharging parameter. Here, first, a method of calculating the OCV calculation value using the charging parameter will be described.

  According to FIG. 6 (a), the corrected resistance value R0c_cor of the 0th-order resistor R0c during charging decreases to the right when the OCV is smaller than α [V], and increases to the right when the OCV is larger than α [V]. is there. Comparing the absolute values of the slopes of the graphs in these two regions, the absolute values of the slopes of the graphs are larger in the region where OCV is smaller than α [V] than in the region where OCV is larger than α [V]. Therefore, when calculating the OCV calculated value from the corrected resistance value R0c_cor of the resistor R0c, the corrected resistance value R0c_cor is smaller when the OCV is smaller than α [V] than when the OCV is larger than α [V]. The influence of errors is small, and the OCV calculation value can be calculated more accurately. Note that the relationship between the resistance R0c and OCV in FIG. 6 (a) indicates that the lower the SOC, the greater the estimated internal resistance value of the battery 7 during charging.

  According to FIG. 6 (b), the correction resistance value R1c_cor of the primary resistance R1c during charging is substantially flat with respect to the change in the OCV value. Therefore, it is difficult to calculate the OCV from the corrected resistance value R1c_cor.

  According to FIG. 6 (c), the correction resistance value R2c_cor of the secondary resistance R2c during charging decreases to the right when the OCV is smaller than α [V], and increases to the right when the OCV is larger than α [V]. is there. Comparing the absolute values of the slopes of the graphs in these two regions, the absolute values of the slopes of the graphs are larger in the region where OCV is larger than α [V] than in the region where OCV is smaller than α [V]. Therefore, when calculating the OCV calculation value from the corrected resistance value R2c_cor, the effect of the correction resistance value R2c error is greater when OCV is larger than α [V] than when OCV is smaller than α [V]. The OCV calculation value can be calculated more accurately.

  From the above, the OCV calculating unit 17 calculates the OCV calculated value from the corrected resistance value R0c_cor of the resistor R0c when OCV is smaller than α [V], and the resistor R2c when OCV is larger than α [V]. It is preferable to calculate the OCV calculation value from the corrected resistance value R2c_cor.

  As described above, it is preferable to properly use the resistance value for calculating the OCV calculation value from among the resistance values included in the battery parameters in accordance with the OCV. Here, in order to use the resistance value properly, the OCV calculation unit 17 selects a resistance value to be used for calculating the OCV calculation value by dividing the case using the OCV estimation value. That is, the OCV calculation unit 17 determines which resistance value to use based on the OCV estimation value acquired from the charging parameter estimation unit 14. In this way, if the resistance value is properly used according to the OCV estimated value, the OCV calculated value can be calculated more accurately and the charge amount can be calculated more accurately.

  Next, a method for calculating the OCV calculation value using the discharge parameter will be described.

  According to FIG. 6 (a), the corrected resistance value R0d_cor of the zero-order resistor R0d during discharge rises to the right in the region where OCV is smaller than α [V], and is almost flat in the region where OCV is larger than α [V]. is there. Therefore, when calculating the OCV calculated value from the corrected resistance value R0d_cor, the effect of the error in the corrected resistance value R0d_cor is greater when OCV is smaller than α [V] than when OCV is larger than α [V]. The OCV calculation value can be calculated more accurately.

  According to FIG. 6 (b), the corrected resistance value R1d_cor of the primary resistance R1d during discharging is substantially flat with respect to the change in the OCV value. Therefore, it is difficult to calculate the OCV from the corrected resistance value R1d_cor.

  According to FIG. 6 (c), the corrected resistance value R2d_cor of the secondary resistance R2d during discharge decreases to the right when the OCV is smaller than α [V], and increases to the right when the OCV is larger than α [V]. is there. Comparing the absolute values of the slopes of the graphs in these two regions, the absolute values of the slopes of the graphs are larger in the region where OCV is larger than α [V] than in the region where OCV is smaller than α [V]. Therefore, when calculating the OCV calculated value from the corrected resistance value R2d_cor, the effect of the corrected resistance value R2d_cor is more affected when OCV is larger than α [V] than when OCV is smaller than α [V]. The OCV calculation value can be calculated more accurately.

  From the above, the OCV calculating unit 17 calculates the OCV calculated value from the corrected resistance value R0d_cor of the resistor R0d when OCV is smaller than α [V], and the resistor R2d when OCV is larger than α [V]. It is preferable to calculate the OCV calculation value from the corrected resistance value R2d_cor.

  In addition, when calculating the OCV calculation value using the discharge time parameter, as in the case of using the charge time parameter, the OCV calculation unit 17 determines which resistance value based on the OCV estimation value obtained from the discharge time parameter estimation unit 15. It is preferable to determine whether to use.

  As described above, the OCV (OCV calculated value) of the battery 7 can be accurately calculated by using the resistance value and the OCV estimated value of either the battery 7 during charging or discharging. As a value used for the case division, a predetermined threshold value can be appropriately determined depending on the relationship between the resistance value of the battery 7 and the OCV. The OCV calculation unit 17 calculates the OCV according to the case depending on whether the OCV estimated value is larger or smaller than a predetermined threshold.

  In one embodiment, the resistance value of the zeroth-order resistor R0c or R0d is also referred to as a first resistance value, and the resistance value of the second-order resistor R2c or R2d is also referred to as a second resistance value. That is, the resistance value of the internal resistance of the battery 7 includes the first resistance value and the second resistance value. The OCV calculation unit 17 calculates the OCV calculation value based on the relationship between either the first resistance value or the second resistance value and the OCV in both cases of charging and discharging. Preferably, the OCV calculation unit 17 selects the resistance value of the 0th-order resistor R0c or R0d, that is, the first resistance value when the estimated OCV value is smaller than a predetermined threshold, and the first resistance value and the OCV The OCV calculation value is calculated based on the relationship. Preferably, the OCV calculation unit 17 selects the resistance value of the secondary resistance R2c or R2d, that is, the second resistance value when the OCV estimated value is larger than the predetermined threshold value, and the second resistance value and the OCV Based on the relationship, the OCV calculation value is calculated. Thus, by calculating either the first or second resistance value and calculating the OCV calculated value, it is possible to calculate a more accurate OCV calculated value and to calculate a more accurate charge amount.

  As described in the explanation of the equivalent circuit parameters in FIG. 4 (b), the 0th-order resistor R0c or R0d represents the resistance of the electrolyte or the like, and the first-order resistor R1c or R1d simulated the ion diffusion process inside the electrode. Represents resistance. Also, the secondary resistance R2c or R2d included in the equivalent circuit of FIG. 2 represents a resistance simulating the ion diffusion process inside the electrode.

  Here, the reaction between the battery electrolyte and the electrode can be divided into a fast reaction that depends on the resistance of the electrolyte and the like, and a slow reaction that depends on the ion diffusion process inside the electrode. That is, the resistance value of the 0th-order resistor R0c or R0d representing the resistance of the electrolyte solution, that is, the first resistance value is the resistance value of the second-order resistor R2c or R2d representing the ion diffusion process inside the electrode, that is, the second resistance. It reflects the component whose reaction rate between the battery electrolyte and the electrode is faster than the value. Thus, by calculating the OCV calculation value by properly using the first and second resistance values, it is possible to calculate the OCV calculation value in accordance with the reaction process inside the battery and further calculate the charge amount. In addition, by using an equivalent circuit including a 0th to 2nd order resistance as an equivalent circuit of the battery, it is possible to calculate an OCV calculation value in a form more in line with a reaction process inside the battery, and further calculate a charge amount.

  Preferably, two or more predetermined threshold values are set. In this case, it is divided into three or more cases. In this way, OCV can be calculated more accurately.

  According to FIG. 6 (a), when OCV is smaller than α [V], the absolute value of the slope of the resistance value of the zeroth-order resistor R0c during charging is the resistance of the zeroth-order resistor R0d during discharging. Greater than absolute value slope. Therefore, in one embodiment, it is possible to calculate a more accurate OCV calculation value and further calculate the charge amount by using the resistance value of the resistor R0c during charging than using the resistance value of the resistor R0d during discharging.

[SOC calculation method]
A method in which the SOC calculation unit 18 calculates the SOC based on the relationship between the SOC and the OCV will be described. FIG. 7 is a graph showing the relationship between SOC and OCV. The horizontal axis represents OCV, and the vertical axis represents SOC. According to the graph of FIG. 7, the SOC calculation unit 18 can calculate the SOC by converting the OCV calculation value acquired from the OCV calculation unit 17.

  In addition, the SOC calculation unit 18 calculates the charge amount of the battery 7 from the calculated SOC. Specifically, the charge amount of the battery 7 is calculated by multiplying the known full charge amount of the battery 7 by the SOC.

  As described above, the charge amount estimation device 1 according to an embodiment can calculate the charge amount of the battery 7.

[Flowchart of charge amount estimation method]
Next, a charge amount estimation method executed by the charge amount estimation apparatus 1 according to an embodiment will be described with reference to the flowchart shown in FIG.

  First, the temperature measurement unit 10, the voltage measurement unit 11 and the current measurement unit 12 of the charge amount estimation apparatus 1 of FIG. 1 respectively measure and detect the temperature of the battery 7, the terminal voltage of the battery 7, and the current of the battery 7 ( Step S1). In other words, the temperature, voltage and current of the battery 7 are detected by a sensor.

  Next, the charge amount calculation unit 13 of the charge amount estimation device 1 acquires the temperature of the battery 7, the terminal voltage of the battery 7, and the current of the battery 7 from the temperature measurement unit 10, the voltage measurement unit 11, and the current measurement unit 12, respectively. To do. The charging parameter estimation unit 14 and the discharging parameter estimation unit of the charging amount calculation unit 13 in FIG. 2 individually estimate the charging and discharging parameters of the battery 7, respectively. Further, the charging parameter estimation unit 14 and the discharging parameter estimation unit estimate the OCV estimated value and the SOH estimated value of the battery 7 (step S2). The method for estimating the parameter is as described above.

  Next, the OCV calculation unit 17 of the charge amount calculation unit 13 acquires a charging or discharging parameter from the charging parameter estimation unit 14 or the discharging parameter estimation unit 15. Further, the OCV calculating unit 17 acquires the OCV estimated value and the SOH estimated value of the battery 7 at the time of charging or discharging selected according to the direction of the current flowing through the battery 7 from the selector 16 (step S3). Further, the temperature of the battery 7 is acquired from the temperature measuring unit 10.

  Next, the OCV calculation unit 17 corrects the resistance value R of the battery 7 based on the temperature of the battery 7, and calculates a resistance value R (25 ° C.) corresponding to the case where the temperature of the battery 7 is 25 ° C. ( Step S4).

  Next, the OCV calculation unit 17 corrects the resistance value R (25 ° C., x%) of the battery 7 whose temperature is corrected in step S4 based on the estimated SOH value of the battery 7 and corrects the battery 7 A resistance value R (25 ° C., 100%) corresponding to the case where the SOH of 7 is 100% is calculated (step S5).

  Next, the OCV calculation unit 17 determines whether or not the OCV estimated value of the battery 7 is larger than a predetermined threshold (step S6).

  When the OCV estimated value of the battery 7 is smaller than the predetermined threshold value (step S6: NO), the OCV calculating unit 17 calculates the relationship between the resistance value of the zeroth-order resistor R0c or R0d and OCV shown in FIG. OCV is calculated (step S7).

  When the OCV estimated value of the battery 7 is larger than the predetermined threshold value (step S6: YES), the OCV calculation unit 17 calculates the relationship between the resistance value of the secondary resistor R2c or R2d and OCV shown in FIG. OCV is calculated (step S8).

  Next, the SOC calculation unit 18 of the charge amount calculation unit 13 acquires the OCV of the battery 7 from the OCV calculation unit 17, and calculates the SOC of the battery 7 from the relationship between the SOC and the OCV shown in FIG. 7 (step S9 ). Further, the charge amount of the battery 7 is calculated by multiplying the full charge amount of the battery 7 by the SOC.

  As described above, according to the charge amount estimation method shown in the flowchart of FIG. 8, the SOC and the charge amount of the battery 7 can be calculated.

(Modification)
According to the charge amount estimation method according to an embodiment, the OCV calculation unit 17 calculates the OCV calculation value from the battery parameter and the OCV estimation value estimated by the charge parameter estimation unit 14 or the discharge parameter estimation unit 15, and calculates the SOC. The unit 18 calculated the SOC and charge amount of the battery 7. On the other hand, the charging parameter estimation unit 14 or the discharging parameter estimation unit 15 may be configured to estimate the SOC of the battery 7. The configuration in this case will be described as a modified example.

  When the charging parameter estimation unit 14 or the discharging parameter estimation unit 15 estimates the SOC of the battery 7 and calculates the SOC estimation value (in this modification), the OCV calculation unit 17 in FIG. 3 calculates the SOC. It functions as a part to do. That is, the OCV calculation unit 17 calculates the SOC from the estimated SOC value based on the relationship between the resistance value of the zeroth-order or second-order resistor and the SOC.

  Further, in the case of this modification, the SOC calculation unit 18 in FIG. 3 functions as a part for calculating OCV. That is, the SOC calculation unit 18 calculates the OCV from the SOC calculated by the OCV calculation unit 17 based on the relationship between the SOC and the OCV.

  Even in the configuration of the present modification, the SOC can be calculated more accurately as in the embodiment described above.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various changes or modifications based on the present disclosure. Therefore, it should be noted that these variations or modifications are included in the scope of the present invention. For example, the functions included in each component, each step, etc. can be rearranged so that there is no logical contradiction, and a plurality of components, steps, etc. can be combined into one or divided. It is.

1 Charge estimation device
10 Temperature measurement unit
11 Voltage measurement section
12 Current measurement section
13 Charge calculation unit
14 Charging parameter estimator
15 Discharge parameter estimation unit
16 Selector
17 OCV calculator
18 SOC calculator
20 Calculator
21 Adaptation mechanism
7 batteries
71 Battery equivalent circuit
8 Load
9 Charger

Claims (9)

In the charge amount estimation method for sequentially estimating the resistance value of the internal resistance including the first resistance value and the second resistance value and the open circuit voltage, which is the resistance value of the internal resistance of the battery that performs charging and discharging,
Individually estimating the resistance value of the internal resistance during charging of the battery and the resistance value of the internal resistance during discharging of the battery;
Calculating a charging rate of the battery based on one of the first resistance value and the second resistance value among the resistance values of the internal resistance at the time of charging or discharging. The charge amount estimation method according to claim 1,
The charge amount estimation method which calculates the said charge amount based on the resistance value of the internal resistance at the time of the said charge. In the charge amount estimation method according to claim 1 or 2,
The charge amount estimation method, wherein the first resistance value reflects a component having a faster reaction rate between the battery electrolyte and the electrode than the second resistance value. In the charge amount estimation method according to any one of claims 1 to 3,
The internal resistance of the battery includes a resistor R0c, a resistor R1c, and a resistor R2c that are effective when charging the battery,
The charging amount estimation method, wherein the first and second resistance values when charging the battery are resistance values of the resistors R0c and R2c, respectively. The charge amount estimation method according to any one of claims 1 to 4,
Further comprising selecting one of the first resistance value and the second resistance value based on a predetermined threshold and an estimated value of the open circuit voltage of the battery;
The step of calculating the charging rate of the battery calculates the charging rate of the battery based on one of the first and second resistance values selected in the selecting step. . In the charge amount estimation method according to claim 5,
In the selecting step, when the estimated value of the open circuit voltage of the battery is lower than the predetermined threshold, the first resistance value is selected. The charge amount estimation method according to any one of claims 1 to 6,
Further comprising estimating the health of the battery;
The charge amount estimation method, wherein the resistance value of the internal resistance is corrected based on a soundness level of the battery. The charge amount estimation method according to any one of claims 1 to 7,
Further comprising measuring the temperature of the battery;
The charge amount estimation method according to claim 1, wherein the resistance value of the internal resistance is corrected based on a temperature of the battery. In the charge amount estimation device that sequentially estimates the resistance value of the internal resistance including the first resistance value and the second resistance value and the open circuit voltage, which is the resistance value of the internal resistance of the battery that performs charging and discharging,
A charging parameter estimator for estimating a resistance value of the internal resistance during charging of the battery;
A discharge parameter estimation unit for estimating a resistance value of the internal resistance during discharge of the battery;
A charge amount estimation apparatus comprising: a charge rate estimation unit that calculates a charge rate of the battery based on one of the first resistance value and the second resistance value among the resistance values of the internal resistance during charging or discharging.

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