JP2016075514A - Open-circuit voltage estimation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an open-circuit voltage estimation device which can estimate the open-circuit voltage of a secondary cell with high accuracy.SOLUTION: A differential voltage ΔV between a voltage V1 when a first current I1 flows in a secondary cell B and a voltage V2 when a second current I2 flows is measured, and an inclination r of a linear line L is found by this differential voltage ΔV and a differential current ΔI. With this method, an error in the inclination r can be reduced, as compared with a method in which the inclination of the linear line is found by linking two independently measured points. Although the coordinates of a point M, not just the inclination r, need to be found in order to determine the linear line L, but the linear line L only moves vertically in parallel within the error range of the point M, and therefore it is possible to estimate an open-circuit voltage OCV with high accuracy, as compared with the conventional method in which the error occurring in inclination is large.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an open-circuit voltage estimation device that estimates an open-circuit voltage of a secondary battery.

  For example, in various vehicles such as an electric vehicle (EV) that travels using an electric motor and a hybrid vehicle (HEV) that travels using both an engine and an electric motor, a lithium ion rechargeable battery is used as a power source for the electric motor. And rechargeable batteries such as nickel metal hydride batteries.

  In such a secondary battery, as a method of estimating SOC (State of Charge) which is a charging capacity (that is, remaining capacity), a method of estimating based on an open-circuit voltage of the secondary battery, a current of charge / discharge A method of estimating based on the integrated value is known, and a method of estimating the charge capacity by combining these methods has been proposed (for example, see Patent Document 1). In the charging capacity estimation method described in Patent Document 1, the accuracy of the estimated value is improved by appropriately combining the two methods.

JP 2011-257207 A

  When estimating the charge capacity based on the open voltage as in the method described in Patent Document 1, the secondary battery drops due to internal resistance when a load current or charge current flows. It was difficult to measure. Then, the following methods can be considered as an example of the method of estimating the open circuit voltage of a secondary battery at the time of charging / discharging. First, voltages V01 and V02 when two different currents I01 and I02 flow through the secondary battery during charging and discharging are measured. Further, as shown in FIG. 4, a first measurement point M01 (I01, V01) and a second measurement point M02 (I02, V02) are plotted in a coordinate system in which the horizontal axis is current I and the vertical axis is voltage V. Then, a straight line L0 connecting these two points is obtained. In the straight line L0, the slope r0 corresponds to the internal resistance of the secondary battery, and the voltage at the intersection with the vertical axis is the voltage when the current is 0, that is, the open circuit voltage OCV.

  However, an error may occur in the measured voltage. For example, a voltage within the error range of the error bar shown in FIG. 4 can be a measured value. Since both the first measurement point M01 and the second measurement point M02 may include an error, if the open-circuit voltage OCV is estimated based on these, the accuracy is lowered. In particular, if the measured value of one voltage becomes the maximum value of the error range and the measured value of the other voltage becomes the minimum value, a large error occurs in the slope r0, and the estimation accuracy of the open circuit voltage OCV is low. turn into.

  An object of the present invention is to provide an open-circuit voltage estimation device capable of estimating an open-circuit voltage of a secondary battery with high accuracy.

  In order to solve the problems and achieve the object, the invention described in claim 1 is an open-circuit voltage estimation device for estimating an open-circuit voltage of a secondary battery, and has a first input terminal and a second input terminal. Differential voltage output means for outputting a differential voltage corresponding to a differential value of voltages input to the first input terminal and the second input terminal, and one electrode of the secondary battery connected to the first input A changeover switch exclusively connected to the terminal and the second input terminal, first voltage holding means capable of holding a voltage between the first input terminal and the other electrode of the secondary battery, and the second A second voltage holding means capable of holding a voltage between the input terminal and the other electrode; one electrode of the secondary battery and the first input terminal when a first current flows through the secondary battery; A second current having a magnitude different from that of the first current is connected to the secondary battery. A connection switching control means for controlling the changeover switch so as to connect one electrode of the secondary battery and the second input terminal, and a voltage between the one electrode and the other electrode. Voltage measuring means for measuring the first current, the second current, the differential voltage, a measurement current flowing in the secondary battery during voltage measurement by the voltage measurement means, and a measurement voltage of the voltage measurement means An open-circuit voltage estimation apparatus comprising: an estimation unit that estimates the open-circuit voltage based on the open-circuit voltage.

  According to a second aspect of the present invention, in the first aspect of the invention according to the first aspect, in the coordinate system in which the estimation unit has a current as one axis and a voltage as the other axis. The slope is calculated based on the ratio of the difference current between two currents and the difference voltage, and a straight line that passes through the coordinates indicating the current during measurement and the measurement voltage and has the slope is obtained. The open circuit voltage is estimated on the basis of the intersection with the other axis.

  The invention described in claim 3 is the invention described in claim 1 or 2, characterized in that the first current and the second current are currents flowing through the secondary battery during discharge. is there.

  The invention described in claim 4 is characterized in that, in the invention described in any one of claims 1 to 3, the current during measurement is equal to the first current or the second current. is there.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, a voltage obtained by amplifying the differential value at a predetermined amplification factor as the differential voltage by the differential voltage output means. It is characterized by being configured to output.

  According to the first aspect of the present invention, the differential voltage output means has the first input terminal and the second input terminal, and the difference between the voltages input to the first input terminal and the second input terminal, respectively. The differential voltage corresponding to the value is output. The changeover switch exclusively connects one electrode of the secondary battery to the first input terminal and the second input terminal. The first voltage holding unit holds a voltage between the first input terminal and the other electrode of the secondary battery. The second voltage holding means holds the voltage between the second input terminal and the other electrode of the secondary battery. The connection switching control means connects one electrode of the secondary battery and the first input terminal when the first current flows through the secondary battery, and the secondary battery when the second current flows through the secondary battery. The changeover switch is controlled so as to connect one of the electrodes and the second input terminal. The voltage measuring means measures a voltage (measurement voltage) between one electrode and the other electrode of the secondary battery when an arbitrary current (current during measurement) flows through the secondary battery. And an estimation means estimates an open circuit voltage based on a 1st electric current, the said 2nd electric current, a difference voltage, a current at the time of measurement, and a measurement voltage.

  Since it did in this way, the voltage between both electrodes when the 1st electric current flows into a secondary battery is hold | maintained by a 1st voltage holding means, and the voltage between both electrodes when a 2nd electric current flows is 2nd. The voltage can be held by the voltage holding means, and the difference value between the two voltages is output as a difference voltage by the difference voltage output means. On the other hand, for example, when the voltage between both electrodes of the secondary battery is directly measured, the voltage changes only between the lowest usable voltage and the highest usable voltage of the secondary battery, The input range of the measuring instrument (for example, an analog-digital converter) needs to be adjusted to 0 or more and the maximum voltage or less, and the minimum use voltage is included as an offset voltage. That is, only a part of the resolution of the measuring instrument can be used. On the other hand, the differential voltage does not include such an offset voltage and becomes a very small value compared to the absolute voltage, so that the resolution of the measuring instrument can be maximized by appropriately amplifying it to match the input range of the measuring instrument. It is possible to detect with high accuracy by using the limit. By detecting this differential voltage with high accuracy, the slope of a straight line representing the relationship between voltage and current can be determined with high accuracy. Thus, the open circuit voltage can be estimated with high accuracy by obtaining the slope of the straight line with high accuracy.

  According to the invention described in claim 2, the estimation means has a slope based on a ratio between the differential current and the differential voltage and measures in a coordinate system having the current as one axis and the voltage as the other axis. A straight line passing through the coordinates indicating the hourly current and the measured voltage is obtained, and the open circuit voltage is estimated based on the intersection of the straight line and the other axis. Thus, for example, in an orthogonal coordinate system having the current I as the horizontal axis and the voltage V as the vertical axis, the slope determined by the differential current ΔI and the differential current ΔV is r (= ΔV / ΔI), A straight line passing through the coordinates (I0, V0) indicating the measurement current I0 and the measurement voltage V0, that is, a straight line represented by V = r · (I−I0) + V0 is obtained. The open circuit voltage can be estimated based on the intersection of the straight line and the vertical axis, that is, the voltage V = −r · I0 + V0 obtained by substituting I = 0 into the relational expression representing the straight line.

  According to the third aspect of the present invention, the first current and the second current are currents that flow through the secondary battery during discharging. Since it did in this way, a 1st electric current and a 2nd electric current can be set suitably according to the fluctuation | variation of the magnitude | size of the load connected to the secondary battery. Furthermore, by estimating the open circuit voltage with high accuracy at the time of discharging, it is possible to improve the estimation accuracy of the remaining capacity of the secondary battery, and it is possible to accurately determine the timing that requires charging.

  According to the fourth aspect of the present invention, the measurement current is equal to the first current or the second current. Since it did in this way, a voltage measurement means can measure a voltage substantially simultaneously with holding | maintenance of the voltage by a voltage holding means, and the time which measurement requires can be shortened. Furthermore, when current measuring means for measuring the first current I1 and the second current I2 is provided, the number of times of current measurement can be reduced.

  According to the invention described in claim 5, the differential voltage output means is configured to output a voltage obtained by amplifying the differential value with a predetermined amplification factor as the differential voltage. Since it did in this way, a differential voltage can be obtained as a bigger value, and an open circuit voltage can be estimated still more accurately.

It is a schematic block diagram which shows the open circuit voltage estimation apparatus which concerns on embodiment of this invention. It is a flowchart which shows an example of the open circuit voltage estimation process performed by CPU of the microcomputer with which the open circuit voltage estimation apparatus of FIG. 1 is provided. It is a graph which shows a mode that the open circuit voltage of a secondary battery is calculated | required by the open circuit voltage estimation process of FIG. It is a graph which shows the conventional open circuit voltage estimation method.

  Hereinafter, an open-circuit voltage estimation apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating a schematic configuration of an open-circuit voltage estimation apparatus according to the present embodiment. FIG. 2 is a flowchart illustrating an example of an open-circuit voltage estimation process executed by the CPU of the microcomputer included in the open-circuit voltage estimation apparatus in FIG. FIG. 3 is a graph showing how the open-circuit voltage of the secondary battery is obtained by the open-circuit voltage estimation process of FIG.

  The open-circuit voltage estimation apparatus according to the present embodiment is mounted on, for example, an electric vehicle and connected between electrodes of a secondary battery included in the electric vehicle, and estimates an open-circuit voltage of the secondary battery. Of course, you may apply to the apparatus, system, etc. which were equipped with secondary batteries other than an electric vehicle.

  Such a secondary battery (indicated by symbol B in the figure) has an electromotive force portion e that generates a voltage and an internal resistance r. The secondary battery B generates a voltage V between both electrodes (the positive electrode Bp and the negative electrode Bn), and this voltage V is a voltage generated by an electromotive force generated by the electromotive force unit e (that is, an open circuit voltage OCV) and an internal resistance r Is determined by the voltage Vr generated by the current flowing (V = OCV + Vr). That is, when the current flowing through the secondary battery B becomes 0, the voltage V between both electrodes becomes equal to the open circuit voltage OCV. The negative electrode Bn of the secondary battery B is connected to the reference potential G.

  As shown in FIG. 1, the open circuit voltage estimation device (indicated by reference numeral 1 in the figure) of the present embodiment includes an amplifier 11, a changeover switch 12, a first capacitor 13 as first voltage holding means, and a second The second capacitor 14 as the voltage holding means, the charging / discharging means 15, the voltage measuring means 16, the first analog-digital converter 21, the second analog-digital converter 22, and the microcomputer 40 (hereinafter, “ μCOM40 ”).

  The amplifier 11 is composed of, for example, an operational amplifier, and includes two input terminals (first input terminal In1 and second input terminal In2) and one output terminal (output terminal Out). An amplified voltage Vm obtained by amplifying the difference value of the input voltage with a predetermined amplification factor Av is output from the output terminal. The amplifier 11 corresponds to a differential voltage output unit.

  The change-over switch 12 is, for example, a one-circuit two-contact (SPDT (single pole double throw)) switch constituted by an analog switch or the like. In the changeover switch 12, one of the two changeover terminals a and b is connected to the first input terminal In1 of the amplifier 11, and the other changeover terminal b is connected to the second input terminal In2 of the amplifier 11. It is connected. The changeover switch 12 has a common terminal c connected to the positive electrode Bp of the secondary battery B (one terminal of the secondary battery). The change-over switch 12 is connected to a later-described μCOM 40, and switches the connection between the two change-over terminals a and b and the common terminal c in accordance with a control signal from the μCOM 40 to change the positive electrode Bp of the secondary battery B to the first. It is exclusively connected to the first input terminal In1 and the second input terminal In2.

  The first capacitor 13 is connected between the first input terminal In1 of the amplifier 11 and the reference potential G, that is, the first capacitor 13 is connected between the first input terminal In1 and the negative electrode Bn of the secondary battery B. It is provided in between. Thus, the voltage between the first input terminal In1 and the negative electrode Bn of the secondary battery B is held in the first capacitor 13.

  The second capacitor 14 is connected between the second input terminal In2 of the amplifier 11 and the reference potential G, that is, the second capacitor 14 is connected between the second input terminal In2 and the negative electrode Bn of the secondary battery B. It is provided in between. Thereby, the voltage between the second input terminal In2 and the negative electrode Bn of the secondary battery B is held in the second capacitor 14.

  The charging / discharging means 15 is connected between the positive electrode Bp of the secondary battery B and the reference potential G (that is, the negative electrode Bn of the secondary battery B), and when the secondary battery B is charged, the secondary battery B The positive electrode Bp is connected to a charging unit (not shown) to flow a charging current. During discharging, the positive electrode Bp is connected to a load (not shown) (for example, an electric vehicle driving motor or a heating electric heater) and secondary. The load current flowing from the battery B to the load is provided so as to be adjustable. The charging / discharging unit 15 is connected to a later-described μCOM 40 and switches charging / discharging of the secondary battery B in accordance with a control signal from the μCOM 40.

  The voltage measuring means 16 is connected between the positive electrode Bp of the secondary battery B and the reference potential G (that is, the negative electrode Bn of the secondary battery B), and a charging current or a load current flows through the secondary battery B. In this case, the voltage V between both electrodes can be measured. The voltage measuring means 16 is connected to a later-described μCOM 40 and measures the voltage V in accordance with a control signal from the μCOM 40.

  The first analog-to-digital converter 21 (hereinafter referred to as “first ADC 21”) quantizes the voltage between both electrodes of the secondary battery B measured by the voltage measuring means 16, and obtains a digital value corresponding to the voltage. The signal shown is output. The second analog-digital converter 22 (hereinafter referred to as “second ADC 22”) quantizes the amplified voltage Vm output from the amplifier 11 and outputs a signal indicating a digital value corresponding to the amplified voltage Vm. In the present embodiment, the first ADC 21 and the second ADC 22 are mounted as individual electronic components. However, the present invention is not limited to this. For example, an analog-digital conversion unit built in the μCOM 40 described later is used. Each voltage may be quantized.

  The μCOM 40 includes a CPU, a ROM, a RAM, and the like, and controls the entire open-circuit voltage estimating apparatus 1. The ROM stores in advance a control program for causing the CPU to function as various means such as connection switching control means and estimation means, and the CPU functions as the various means by executing this control program.

  The μCOM 40 includes a first output port PO1 connected to the changeover switch 12 and a second output port PO2 connected to the charging / discharging means 15. The CPU of the μCOM 40 transmits a control signal to the changeover switch 12 through the first output port PO1, and when the first current I1 flows through the secondary battery B as a charging current or a load current, The first input terminal In1 is connected, and when the second current I2 flows as a charging current or a load current to the secondary battery B, the positive electrode Bp of the secondary battery B and the second input terminal In2 are connected. The changeover switch 12 is controlled. Further, the CPU of the μCOM 40 transmits a control signal to the charging / discharging means 15 through the second output port PO2 to switch between charging and discharging of the secondary battery B, and an appropriate charging current or load current for the secondary battery B. The charging / discharging means 15 is controlled so as to flow.

  The μCOM 40 has a first input port PI1 to which a signal output from the first ADC 21 is input, and a second input port PI2 to which a signal output from the second ADC 22 is input. The signals input to the first input port PI1 and the second input port PI2 are converted into information in a format that can be recognized by the CPU of the μCOM 40 and sent to the CPU. The CPU of the μCOM 40 detects the voltage V and the amplified voltage Vm between both electrodes of the secondary battery B based on the information. As will be described later, the CPU uses the amplified voltage Vm, the differential current that is the differential value of the current flowing in the secondary battery B, the measured voltage of the voltage measuring means 15, and the current at the time of voltage measurement by the voltage measuring means 15 (measurement time). The open circuit voltage of the secondary battery B is estimated based on the current), and the charge capacity (remaining capacity) of the secondary battery B is estimated based on the open circuit voltage.

  The μCOM 40 has a communication port (not shown). This communication port is connected to an in-vehicle network (for example, CAN (Controller Area Network)), and is connected to a display device such as a terminal device for vehicle maintenance through the in-vehicle network. The CPU of the μCOM 40 transmits a signal indicating the estimated charge capacity to the display device through the communication port and the in-vehicle network, and displays the charge capacity of the secondary battery B on the display device based on the signal. Alternatively, the CPU of the μCOM 40 transmits a signal indicating the estimated charging capacity to a display device such as a combination meter mounted on the vehicle through the communication port and the in-vehicle network, and the secondary battery B based on the signal in the display device. May be displayed.

  Next, an example of the open-circuit voltage estimation process in the μCOM 40 included in the open-circuit voltage estimation apparatus 1 described above will be described with reference to the flowchart of FIG. 2, and the calculation performed by the μCOM 40 in the open-circuit voltage estimation process will be described with reference to FIG. 3. I will explain.

  When the CPU of the μCOM 40 (hereinafter simply referred to as “CPU”) receives a discharge start command for the secondary battery B from the electronic control device mounted on the vehicle through the communication port, for example, when the vehicle starts running or accelerates, A discharge start control signal is transmitted to the charge / discharge means 15 through the two output port PO2. In response to this control signal, the charging / discharging means 15 connects the secondary battery B to the traveling motor and starts discharging the secondary battery B. And it progresses to the open circuit voltage estimation process shown in FIG.

  In the open circuit voltage estimation process, when the discharge of the secondary battery B is started, the CPU transmits a control signal for connecting the other switch terminal b and the common terminal c to the switch 12 through the first output port PO1. (S110). The changeover switch 12 connects the positive electrode Bp of the secondary battery B and the second input terminal In2 of the amplifier 11 by connecting the other changeover terminal b and the common terminal c in accordance with this control signal. Thereby, the second capacitor 14 is connected between the positive electrode Bp and the negative electrode Bn of the secondary battery B, and the charge flows from the secondary battery B into the second capacitor 14.

  Next, the CPU stands by until the second current I2 flows through the secondary battery B (S120). Then, after a certain amount of time has elapsed, the voltage between both electrodes of the secondary battery B when the second current I2 flows is held in the second capacitor 14. Note that the second current I2 may be measured or estimated from the size of the load. For example, a current measuring unit for measuring the load current is provided and the measurement result is input to the μCOM 40. The CPU may determine that the second current I2 has flowed, or the μCOM 40 stores in advance the relationship between the load magnitude and the load current, and when the load magnitude reaches a predetermined value, the second current I2 The CPU may determine that has flowed. The magnitude of the second current I2 may not be determined in advance. For example, the CPU determines that the load current that flows immediately after the start of the discharge of the secondary battery B or after a predetermined time has elapsed as the second current I2, and You may measure the magnitude | size of this electric current by a measurement means.

  Next, when the second current I2 flows through the secondary battery B and a predetermined time has elapsed, the CPU determines that the charge accumulation in the second capacitor 14 has been completed, and switches the changeover switch 12 through the first output port PO1. On the other hand, a control signal for connecting one switching terminal a and the common terminal c is transmitted (S130). The change-over switch 12 connects the positive electrode Bp of the secondary battery B and the first input terminal In1 of the amplifier 11 by connecting one switch terminal a and the common terminal c in accordance with a control signal from the CPU. . Thereby, the first capacitor 13 is connected between the positive electrode Bp and the negative electrode Bn of the secondary battery B, and the charge flows from the secondary battery B into the first capacitor 13.

  Next, the CPU stands by until a first current I1 having a magnitude different from that of the second current I2 flows through the secondary battery B (S140). When a certain amount of time elapses after the first current I1 flows, the first capacitor 13 holds the voltage between both electrodes of the secondary battery B when the first current I1 flows. The first current I1 may be measured or estimated from the size of the load in substantially the same manner as the second current I2. Further, the magnitude of the first current I1 may not be determined in advance, and the magnitude of the differential current from the second current I2 may be determined in advance.

  Next, the CPU detects the amplified voltage Vm output from the amplifier 11 based on information obtained from the signal input to the second input port PI2, and obtains it from the signal input to the first input port PI1. Based on the received information, the measurement voltage V0 output from the voltage measurement means 16 is detected (S150). At this time, since the first current I1 flows through the secondary battery B, the measured voltage V0 is equal to the voltage V1 across the first capacitor 13.

  Next, the CPU divides the detected amplified voltage Vm by the amplification factor Av of the amplifier 11 to thereby obtain a differential voltage ΔV between the voltage V1 across the first capacitor 13 and the voltage V2 across the second capacitor 14. (= V1−V2) is obtained, and the difference voltage ΔV is further divided by the difference current ΔI (= I1−I2) between the first current I1 and the second current I2 (S160). That is, as shown in FIG. 3, in a rectangular coordinate system having the current I as the horizontal axis and the voltage V as the vertical axis, a straight line representing the relationship between the load current and the voltage V (= OCV + Vr) between both electrodes of the secondary battery B. Is calculated.

  Next, the CPU determines coordinates indicating the measurement voltage V0 and the current during measurement I0 (that is, equal to the first current I1) (S170). That is, the position of the point M (I1, V1) is determined in the orthogonal coordinate system shown in FIG.

  Next, the CPU obtains a straight line L passing through the point M shown in FIG. 3 and having an inclination r, and obtains the coordinates of the intersection of this straight line and the vertical axis (S180). That is, as a relational expression representing the straight line L, V = r · (I−I1) + V1 is obtained, and I = 0 is substituted into this equation, and the open circuit voltage OCV = −I1 · r + V1 is estimated. finish. And after completion | finish of an open circuit voltage estimation process, CPU estimates the charge capacity of the secondary battery B based on this open circuit voltage OCV and the relationship between the open circuit voltage and charge capacity memorize | stored previously, and through a communication port. The charging capacity is transmitted to another device or the like.

  The CPU that executes the processes of steps S110 and S130 in the flowchart of FIG. 2 corresponds to connection switching control means, and the CPU that executes the processes of S160 to S180 corresponds to estimation means.

  According to this embodiment, there are the following effects. That is, by obtaining the differential voltage ΔV from the amplified voltage Vm amplified by the amplifier 11, the slope r of the straight line L can be obtained with high accuracy from the differential voltage ΔV and the differential current ΔI, and two points measured independently. The error of the slope r can be reduced as compared with the method of obtaining the slope of the straight line by connecting. Further, in order to determine the straight line L, it is necessary to obtain not only the inclination r but also the coordinates of the point M. Although an error as indicated by an error bar in FIG. The open circuit voltage OCV can be estimated with high accuracy as compared with the conventional method in which the error in the tilt is large.

  Further, by estimating the open circuit voltage OCV based on the first current I1 and the second current I2 that are load currents at the time of discharging the secondary battery B, the variation in the size of the load connected to the secondary battery B can be reduced. Accordingly, the first current and the second current can be set as appropriate. Furthermore, by estimating the open circuit voltage OCV with high accuracy at the time of discharging, the estimation accuracy of the remaining capacity of the secondary battery B can be improved, and the timing at which charging is required can be accurately determined.

  Further, when the first current I1 flows through the secondary battery B, the voltage measuring means 16 measures the voltage between both electrodes of the secondary battery B to obtain the measured voltage V0. It is equal to the current I1, and the measurement voltage V0 can be measured immediately after the charging of the first capacitor 13 is completed, and the time required for the measurement can be shortened. Furthermore, when current measuring means for measuring the first current I1 and the second current I2 is provided, the number of times of current measurement can be reduced.

  In addition, this invention is not limited to the said embodiment, Including other structures etc. which can achieve the objective of this invention, the deformation | transformation etc. which are shown below are also contained in this invention.

  For example, in the embodiment, the open-circuit voltage OCV is estimated based on the first current I1 and the second current I2 that are load currents when the secondary battery B is connected to the traveling motor and discharged. The first current and the second current may be a load current when the secondary battery is connected to another load, may be a current flowing through the secondary battery during charging, or may be a current during discharging. The current at the time of charging may be combined.

  Moreover, in the said embodiment, when the 1st electric current I1 flows into the secondary battery B, the voltage measurement means 16 shall measure the voltage between the both electrodes of the secondary battery B, However, A voltage measurement means is arbitrary The voltage may be measured when the current flows, and may be measured when the second current I2 flows. Moreover, the structure which measures the load current by a current measurement means, and measures a voltage by a voltage measurement means at the same time may be sufficient as the current measurement means which measures the load current of the secondary battery B may be provided.

  In addition, the best configuration, method and the like for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of materials, quantity, and other detailed configurations. Therefore, the description limiting the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such is included in this invention.

DESCRIPTION OF SYMBOLS 1 Open circuit voltage estimation apparatus 11 Amplifier (differential voltage output means)
12 switch 13 first capacitor (first voltage holding means)
14 Second capacitor (second voltage holding means)
16 Voltage measurement means 40 Microcomputer (connection switching control means, estimation means)
B Secondary battery

Claims (5)

An open-circuit voltage estimation device for estimating an open-circuit voltage of a secondary battery,
Differential voltage output means having a first input terminal and a second input terminal, and for outputting a differential voltage corresponding to a differential value of voltages input to the first input terminal and the second input terminal,
A changeover switch for exclusively connecting one electrode of the secondary battery to the first input terminal and the second input terminal;
First voltage holding means capable of holding a voltage between the first input terminal and the other electrode of the secondary battery;
Second voltage holding means capable of holding a voltage between the second input terminal and the other electrode;
When a first current flows through the secondary battery, one electrode of the secondary battery and the first input terminal are connected, and a second current having a magnitude different from the first current flows through the secondary battery. Connection switching control means for controlling the changeover switch so as to connect one electrode of the secondary battery and the second input terminal.
Voltage measuring means for measuring a voltage between the one electrode and the other electrode;
The open-circuit voltage is estimated based on the first current, the second current, the differential voltage, a measurement current that flows through the secondary battery during voltage measurement by the voltage measurement unit, and a measurement voltage of the voltage measurement unit. An open-circuit voltage estimation device comprising: an estimation unit.   In the coordinate system having the current as one axis and the voltage as the other axis, the estimating means is inclined based on a ratio between the difference current between the first current and the second current and the difference voltage. And calculating a straight line passing through the coordinates indicating the current during measurement and the measured voltage and having the slope, and estimating the open-circuit voltage based on the intersection of the straight line and the other axis. The open-circuit voltage estimation apparatus according to claim 1.   3. The open-circuit voltage estimation device according to claim 1, wherein the first current and the second current are currents that flow through the secondary battery during discharging. 4.   The open-circuit voltage estimation apparatus according to claim 1, wherein the measurement current is equal to the first current or the second current.   The said differential voltage output means is comprised so that the voltage which amplified the said difference value with the predetermined amplification factor as said difference voltage may be output, The any one of Claims 1-4 characterized by the above-mentioned. Open voltage estimation device.

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