JP6895786B2 - Secondary battery status detection device and secondary battery status detection method - Google Patents

Description

The present invention relates to a secondary battery status detecting device and a secondary battery status detecting method.

Patent Document 1 discloses a technique of correcting the temperature characteristic of the internal impedance of a secondary battery to determine the deteriorated state of the secondary battery with high accuracy.

In Patent Document 2, the internal resistance ratio Zr (= Z (resistance at that time) / Z0 (reference resistance when new, etc.)) is obtained, the relative SOC value at each Zr is obtained, and these are associated with each other. The technology for creating a table is disclosed. Since the table created in this way is substantially constant regardless of the type (for example, manufacturer or capacity) or individual of the secondary battery, the SOC of the secondary battery can be detected.

Japanese Unexamined Patent Publication No. 2005-091217 Japanese Unexamined Patent Publication No. 2012-189373

However, in the techniques disclosed in Patent Documents 1 and 2, when the electrolytic solution of the secondary battery decreases due to evaporation or the like, or increases due to replacement fluid or the like, the characteristics of the secondary battery change. There is a problem that the state cannot be detected accurately.

The present invention has been made in view of the above circumstances, and is a secondary battery state estimation device and a secondary battery that can accurately estimate the deterioration state of the secondary battery even when the amount of the electrolytic solution increases or decreases. It is an object of the present invention to provide a method for estimating a battery state.

In order to solve the above problems, the present invention comprises a calculation means for calculating an element value of an element constituting the equivalent circuit model of the secondary battery in a secondary battery state detection device for detecting the state of the secondary battery. A correction means for correcting the element value of the equivalent circuit model calculated by the calculation means to an element value when the secondary battery is in the reference state, and the equivalent circuit in the reference state corrected by the correction means. It has an estimation means for estimating the state of the secondary battery based on the element value of the model, and uses at least the temperature and an index value derived from OCV or OCV as the state values indicating the reference state. It is a feature.
According to such a configuration, it is possible to accurately detect the state of the secondary battery even when the amount of the electrolytic solution is increased or decreased.

Further, the present invention is characterized in that the concentration or specific gravity of the electrolytic solution is used as the index value derived from the OCV.
According to such a configuration, by using an index value that accurately indicates the state of the electrolytic solution, it is possible to accurately detect the state of the secondary battery even when the amount of the electrolytic solution increases or decreases.

Further, in the present invention, the correction means is based on the temperature in the reference state and the index value derived from the OCV or OCV, and the temperature at that time and the index value derived from the OCV or OCV. It is characterized in that the next battery is corrected to the element value when it is in the reference state.
According to such a configuration, it is possible to surely correct the element value in the reference state.

Further, the present invention is characterized in that the reference state is defined as the case where the temperature of the secondary battery is a predetermined value and the SOC of the secondary battery is a predetermined value. To do.
With such a configuration, the reference state can be clearly defined.

Further, the present invention has a storage means for storing an index value derived from the OCV or OCV of the secondary battery measured when it is determined to be in a state close to the reference state, and the correction means is said to be said. The secondary battery is the reference based on the temperature stored in the storage means, the index value derived from the OCV or OCV of the secondary battery, and the temperature at that time and the index value derived from the OCV or OCV. It is characterized in that it is corrected to the element value when it is in a state.
According to such a configuration, when the time scale in which the secondary battery is in the reference state or a state close to the reference state is shorter than the time scale of the change in the electrolytic solution, the secondary battery is accurately based on the updated OCV. The state can be detected.

Further, the present invention is calculated in the calculation step of calculating the element value of the element constituting the equivalent circuit model of the secondary battery and the calculation step in the secondary battery state detection method for detecting the state of the secondary battery. Based on the correction step of correcting the element value of the equivalent circuit model to the element value when the secondary battery is in the reference state, and the element value of the equivalent circuit model in the reference state corrected in the correction step. It is characterized by having an estimation step for estimating the state of the secondary battery, and using at least the temperature and an index value derived from OCV or OCV as the state values indicating the reference state.
According to such a method, it is possible to accurately detect the state of the secondary battery even when the amount of the electrolytic solution is increased or decreased.

According to the present invention, it is possible to provide a secondary battery state detecting device and a secondary battery state detecting method capable of accurately detecting the state of the secondary battery even when the amount of the electrolytic solution is increased or decreased.

It is a figure which shows the structural example of the secondary battery state detection apparatus which concerns on embodiment of this invention. It is a block diagram which shows the detailed configuration example of the control part of FIG. It is a figure which shows an example of the equivalent circuit model of the secondary battery used in this embodiment. It is a figure which shows the relationship between the relative SOC and ROHM at the time of a normal state or a liquid depletion. It is a figure which shows the relationship between the relative SOC and Rct1 at the time of normal or liquid depletion. It is a figure which shows the relationship between the relative SOC and C1 at the time of normal or the liquid depletion. It is a figure which shows the relationship between the relative OCV and ROHM at the time of a normal state or a liquid depletion. It is a figure which shows the relationship between the relative OCV and Rct1 at the time of a normal state or a liquid depletion. It is a figure which shows the relationship between the relative OCV and C1 at the time of a normal state or a liquid decrease. It is a flowchart for demonstrating operation of Embodiment of this invention. It is a flowchart for demonstrating operation of Embodiment of this invention. It is a flowchart for demonstrating operation of Embodiment of this invention.

Next, an embodiment of the present invention will be described.

(A) Explanation of Configuration of Embodiment of the Present Invention FIG. 1 is a diagram showing a power supply system of a vehicle having a secondary battery state detection device according to the embodiment of the present invention. In this figure, the secondary battery state detection device 1 has a control unit 10, a voltage sensor 11, a current sensor 12, a temperature sensor 13, and a discharge circuit 15 as main components, and determines the charge state of the secondary battery 14. Control. Here, the control unit 10 refers to the outputs from the voltage sensor 11, the current sensor 12, and the temperature sensor 13, detects the state of the secondary battery 14, and controls the generated voltage of the alternator 16. The charging state of the next battery 14 is controlled. The voltage sensor 11 detects the terminal voltage of the secondary battery 14 and notifies the control unit 10. The current sensor 12 detects the current flowing through the secondary battery 14 and notifies the control unit 10. The temperature sensor 13 detects the electrolytic solution of the secondary battery 14 or the ambient temperature, and notifies the control unit 10. The discharge circuit 15 is composed of, for example, a semiconductor switch and a resistance element connected in series, and the secondary battery 14 is commanded by the secondary battery state detection device 1 by controlling the semiconductor switch on / off by the control unit 10. Discharge according to.

The secondary battery 14 is composed of a secondary battery having an electrolytic solution, for example, a lead storage battery, a nickel cadmium battery, a nickel hydrogen battery, or the like, and is charged by an alternator 16 to drive a starter motor 18 to start an engine. At the same time, power is supplied to the load 19. The alternator 16 is driven by the engine 17, generates AC power, converts it into DC power by a rectifier circuit, and charges the secondary battery 14. The alternator 16 is controlled by the control unit 10 so that the generated voltage can be adjusted.

The engine 17 is composed of, for example, a reciprocating engine such as a gasoline engine and a diesel engine, a rotary engine, or the like, is started by a starter motor 18, drives drive wheels via a transmission, gives propulsion to a vehicle, and is an alternator 16. To generate power. The starter motor 18 is composed of, for example, a DC motor, and generates a rotational force by the electric power supplied from the secondary battery 14 to start the engine 17. The load 19 is composed of, for example, an electric steering motor, a defogger, a seat heater, an ignition coil, a car audio, a car navigation system, and the like, and is operated by electric power from the secondary battery 14.

FIG. 2 is a diagram showing a detailed configuration example of the control unit 10 shown in FIG. As shown in this figure, the control unit 10 includes a CPU (Central Processing Unit) 10a, a ROM (Read Only Memory) 10b, a RAM (Random Access Memory) 10c, a communication unit 10d, and an I / F (Interface) 10e. ing. Here, the CPU 10a controls each unit based on the program 10ba stored in the ROM 10b. The ROM 10b is composed of a semiconductor memory or the like and stores the program 10ba or the like. The RAM 10c is composed of a semiconductor memory or the like, and stores data generated when the program 10ba is executed and parameters 10ca such as mathematical formulas or tables described later. The communication unit 10d communicates with an ECU (Electronic Control Unit) or the like, which is a higher-level device, and notifies the higher-level device of the detected information or control information. The I / F 10e converts the signals supplied from the voltage sensor 11, the current sensor 12, and the temperature sensor 13 into digital signals and captures them, and transfers the drive current to the discharge circuit 15, the alternator 16, the starter motor 18, and the like. Supply and control these.

(B) Description of Operation of Embodiment of the Present Invention Next, the operation of the embodiment of the present invention will be described. In the following, the operation principle of the embodiment of the present invention will be described, and then the detailed operation will be described.

First, the operating principle of the embodiment will be described. FIG. 3 is an equivalent circuit model of the secondary battery 14 used in the embodiment of the present invention. As the equivalent circuit model, the circuit shown in FIG. 3 (A) and the circuit shown in FIG. 3 (B) can be given as examples, but in the following, the circuit shown in FIG. 3 (A) will be given as an example. I will explain. The equivalent circuit model shown in FIG. 3B may be used, or an equivalent circuit model other than this may be used.

In FIG. 3A, the equivalent circuit model has a liquid resistance Rohm, a reaction resistance Rct1, and an electric double layer capacitance C1 as main components. Here, the liquid resistance Rohm is an internal resistance whose main elements are the liquid resistance of the electrolytic solution of the secondary battery 14 and the conductive resistance of the electrodes. The parallel connection circuit of the reaction resistance Rct1 and the electric double layer capacitance C1 is an equivalent circuit corresponding to the anode of the secondary battery 14 and the electrolytic solution in contact with the anode.

4 to 6 show the time when the liquid of each element constituting the equivalent circuit model shown in FIG. 3 (A) is low (when the electrolyte of the secondary battery 14 is low) and the normal time (when the electrolyte of the secondary battery 14 is low). It is a figure which shows the change of the element value by the relative SOC (the SOC obtained by the ratio of the remaining capacity of the secondary battery 14 and the fully charged capacity) in (when the electrolytic solution is not reduced).

FIG. 4 shows the change in the element value with respect to the change in the relative SOC when the liquid resistance Rohm is reduced and when the liquid resistance is normal. More specifically, the change due to the relative SOC of the liquid resistance Rohm at the time of liquid reduction is shown by a circle, and the change due to the relative SOC of the liquid resistance Rohm at the time of normal operation is shown by a quadrangle. As shown in FIG. 4, the element values are significantly different in the region where the relative SOC is low between the liquid reduction state and the normal state.

FIG. 5 shows the change in the element value with respect to the change in the relative SOC when the reaction resistance Rct1 is reduced and when the liquid is normal. More specifically, the change due to the relative SOC of the reaction resistance Rct1 at the time of liquid reduction is shown by a circle, and the change due to the relative SOC of the reaction resistance Rct1 at the time of normal operation is shown by a quadrangle. As shown in FIG. 5, the element values are significantly different in the region where the relative SOC is low and in the region where the relative SOC is high between the liquid reduction state and the normal state.

FIG. 6 shows the change in the element value with respect to the change in the relative SOC when the electric double layer capacity C1 is depleted and when the liquid is normal. More specifically, the change due to the relative SOC of the electric double layer capacity C1 at the time of liquid reduction is shown by a circle, and the change due to the relative SOC of the electric double layer capacity C1 at the time of normal operation is shown by a quadrangle. As shown in FIG. 6, the relative SOC is larger than 40% and the element value is significantly different in the region smaller than 100% between the liquid reduction state and the normal state.

7 to 9 are diagrams showing changes in element values due to the open circuit voltage OCV when the liquid of each element constituting the equivalent circuit model shown in FIG. 3A is low and when the liquid is normal.

FIG. 7 shows the change in the element value with respect to the change in the open circuit voltage OCV when the liquid resistance Rohm is reduced and when the liquid resistance is normal. More specifically, the change of the liquid resistance Rohm due to the open circuit voltage OCV at the time of liquid reduction is indicated by a circle, and the change of the liquid resistance Rohm due to the open circuit voltage OCV at the time of normal operation is indicated by a quadrangle. As shown in FIG. 7, when the open circuit voltage OCV changes, the values of the liquid resistance Rohm are substantially the same at the time of liquid reduction and the normal time.

FIG. 8 shows the change in the element value with respect to the change in the open circuit voltage OCV when the reaction resistance Rct1 is reduced and when it is normal. More specifically, the change of the reaction resistance Rct1 due to the open circuit voltage OCV at the time of liquid reduction is shown by a circle, and the change of the reaction resistance Rct1 by the open circuit voltage OCV at the time of normal operation is shown by a quadrangle. As shown in FIG. 8, when the open circuit voltage OCV changes, the values of the reaction resistance Rct1 are substantially the same when the liquid is reduced and when the liquid is normal.

FIG. 9 shows the change in the element value with respect to the change in the open circuit voltage OCV when the electric double layer capacity C1 is depleted and when it is normal. More specifically, the change due to the open circuit voltage OCV of the electric double layer capacity C1 at the time of liquid reduction is shown by a circle, and the change due to the open circuit voltage OCV of the electric double layer capacity C1 at the time of normal operation is shown by a quadrangle. As shown in FIG. 9, when the open circuit voltage OCV changes, the values of the electric double layer capacitance C1 are substantially the same when the liquid is reduced and when the liquid is normal.

As described above, the element values of the elements constituting the equivalent circuit model change between when the liquid is low and when the liquid is normal in relation to the relative SOC, but when the liquid is low and when the liquid is normal in relation to the open circuit voltage OCV. Does not change. Conventionally, the element values of the elements constituting the equivalent circuit model measured at a certain time point (for example, the time point when the electrolyte temperature is θlx and the relative SOC is SOCx) are set to the reference state (the electrolyte temperature is θl0 and the relative SOC). It was corrected to the state of SOC0), and the state of the secondary battery 14 was estimated using the corrected element value.

However, as shown in FIGS. 4 to 6, the relationship between the relative SOC and the element value changes between the time when the liquid is reduced and the time when the liquid is normal. Therefore, it is assumed that the corrected element value is not correct depending on the state of the electrolytic solution. Will be done.

Therefore, in the present embodiment, the open circuit voltage OCV is used as the index value of the reference state instead of the relative SOC. Then, the element values of the elements constituting the equivalent circuit model measured at a certain time point (for example, the time point when the electrolyte temperature is θlx and the open circuit voltage is OCVx) are set to the reference state (the electrolyte temperature is θl0 and the open circuit voltage is set to OCVx). By correcting to OCV0) and estimating the state of the secondary battery 14 using this corrected element value, the state of the secondary battery 14 can be accurately detected regardless of the state of the electrolytic solution. Can be done.

Next, the detailed operation of the embodiment of the present invention will be described.

For example, when the engine 17 is stopped and a predetermined time (for example, several hours) elapses, the CPU 10a of the control unit 10 refers to the output of the temperature sensor 13 and measures the atmospheric temperature θ of the secondary battery 14. Then, the CPU 10a estimates the temperature θl of the electrolytic solution from the atmospheric temperature θ. As a method of estimating the electrolytic solution temperature θl, the thermal equivalent circuit of the secondary battery 14 is obtained, and the electrolytic solution temperature θl is estimated from the thermal resistance and heat capacity of the thermal equivalent circuit and the atmospheric temperature θ. can do.

Next, the CPU 10a obtains the SOC of the secondary battery 14. As a method of obtaining the SOC, for example, a method of obtaining the SOC from the OCV or a method of obtaining the SOC at a certain time point is obtained by adding a value obtained by accumulating the currents flowing in and out by charging / discharging to the SOC obtained at a certain time point. be able to. Of course, the SOC may be obtained by other methods.

Subsequently, the CPU 10a determines whether or not the electrolytic solution temperature θl is the reference temperature (for example, 25 ° C.) and the SOC is the reference SOC (for example, 100%), and both of these conditions are satisfied. The open circuit voltage OCV at that time is measured. Then, the measured open circuit voltage OCV is set to OCV0 indicating the OCV in the reference state, and the electrolyte temperature at that time is set to θl0 indicating the electrolyte temperature in the reference state, and is stored in the parameter 10ca of the RAM 10c. As a method of measuring the open circuit voltage OCV, when the secondary battery 14 is in a stable state (for example, when a predetermined time (for example, several hours) has elapsed after the engine 17 is stopped), the secondary battery 14 is measured. There is a method of measuring the terminal voltage by the voltage sensor 11. Of course, OCV may be obtained by other methods.

Since the rate of decrease of the electrolytic solution is very slow, for example, the treatment may be executed about once every few months. Of course, a frequency other than the above may be used (for example, about once a month).

Next, a case of detecting the state of the secondary battery 14 will be described. When the engine 17 is stopped and a predetermined time (for example, several hours) elapses, the CPU 10a measures the atmosphere temperature θ of the secondary battery 14 from the output of the temperature sensor 13 by the same method as in the above case, and the atmosphere. The electrolyte temperature θl is estimated from the temperature θ.

Further, the CPU 10a obtains the open circuit voltage OCV of the secondary battery 14. The method for obtaining the OCV is the same as in the above case. In the CPU 10a, the electrolyte temperature θl and the open circuit voltage OCV at that time obtained as described above are set to θlx and OCVx.

Next, the CPU 10a reads out the electrolyte temperature θl0 in the reference state and the open circuit voltage OCV0 in the reference state, which are stored in the RAM 10c as the parameter 10ca.

Subsequently, the CPU 10a calculates the element values of the elements constituting the equivalent circuit model shown in FIG. 3 by the learning process. The element values calculated in this way are the element values at the electrolytic solution temperature θlx and the open circuit voltage OCVx at that time. Specifically, Rohmx, Rct1x, and C1x are obtained. As the element value learning process, there is a method using an extended Kalman filter as described later. Of course, other methods may be used.

Next, the CPU 10a sets the element values Rohmx, Rct1x, and C1x at the electrolytic solution temperature θlx and the open circuit voltage OCVx obtained by the learning process described above to the element values Rohm0, The process of correcting to Rct10 and C10 is executed.

More specifically, by substituting Rohmx, Rct1x, C1x, θlx, OCVx, θl0, OCV0 for the following equations (1) to (3), the corrected element values Rohm0, Rct10, and C10 are obtained. ..

Rohm0 = f1 (Rohmx, θlx, OCVx, θl0, OCV0) ... (1)

Rct10 = f2 (Rct1x, θlx, OCVx, θl0, OCV0) ... (2)

C10 = f3 (C1x, θlx, OCVx, θl0, OCV0) ... (3)

Note that f1 () to f3 () are multivariable functions in which the variables in parentheses are independent variables. Such functions f1 () to f3 () can be obtained, for example, by actual measurement. In addition, instead of obtaining it as a function (mathematical expression), for example, a table may be generated from the measured values, and Rohm0, Rct10, and C10 may be obtained based on this table.

By the above processing, Rohm0, Rct10, and C10 in the reference state can be obtained. The CPU 10a obtains the SOH (State of Health) as the state of the secondary battery 14 based on Rohm0, Rct10, and C10 in the reference state thus obtained. For example, the SOH can be obtained by comparing Rohm0 when the secondary battery 14 is new with Rohm0 at that time. Of course, the SOH may be obtained by a method other than this. In the above description, SOH has been taken as an example, but an index other than SOH may be detected.

Next, the process executed in the embodiment of the present invention will be described with reference to FIGS. 10 to 12.

FIG. 10 is a flowchart for explaining the process executed in the embodiment of the present invention. The process shown in FIG. 10 is executed, for example, when the engine 17 is stopped. When the processing of the flowchart shown in FIG. 10 is started, the following steps are executed.

In step S10, the CPU 10a of the control unit 10 refers to the output of the temperature sensor 13 and detects the atmospheric temperature θ of the secondary battery 14.

In step S11, the CPU 10a estimates the electrolyte temperature θl based on the atmospheric temperature θ detected in step S10. For example, a thermal equivalent model of the secondary battery 14 (a model composed of heat capacity, thermal resistance, etc.) is created, and the above-mentioned atmospheric temperature θ is applied to the thermal equivalent model to obtain an electrolytic solution temperature θl.

In step S12, the CPU 10a of the control unit 10 refers to the output of the voltage sensor 11 and detects the terminal voltage V of the secondary battery 14.

In step S13, the CPU 10a estimates the open circuit voltage OCV from the terminal voltage V detected in step S12. For example, when the secondary battery 14 becomes stable (for example, when a predetermined time (for example, several hours) has passed since the engine 17 was stopped), the effects of stratification and polarization are reduced. Therefore, the terminal voltage V at that time can be regarded as the open circuit voltage OCV. The open circuit voltage OCV may be obtained by eliminating the effects of stratification and polarization by calculation in consideration of the time elapsed since the engine 17 was stopped.

In step S14, the CPU 10a estimates the SOC at that time. For example, the CPU 10a can obtain the SOC by applying the OCV estimated in step S13 to the relational expression between the OCV and the SOC. The SOC may be obtained by a method other than this.

In step S15, the CPU 10a determines whether or not the electrolytic solution temperature θl estimated in step S11 is 25 ° C., which is the reference temperature, and if θl = 25 ° C. (step S15: Y), the step S16 is performed. The process proceeds, and in other cases (step S15: N), the process ends.

In step S16, the CPU 10a determines whether or not the SOC estimated in step S14 is 100%, which is the reference SOC, and if SOC = 100% (step S16: Y), the process proceeds to step S17. In other cases (step S16: N), the process ends.

In step S17, the CPU 10a stores the OCV estimated in step S13 in the parameter 10ca of the RAM 10c as OCV0 which is the reference OCV.

In step S18, the CPU 10a stores the θl estimated in step S11 in the parameter 10ca of the RAM 10c as θl0, which is a reference θl.

According to the above processing, OCV0 and θl0, which are OCV and θl in the reference state (SOC = 100% and θl = 25 ° C.), can be measured and stored in the RAM 10c.

Next, with reference to FIG. 11, a process of detecting the state of the secondary battery 14 based on OCV0 and θl0 stored by the flowchart shown in FIG. 10 will be described. The process shown in FIG. 11 is executed, for example, when a predetermined time (for example, several hours) has elapsed since the engine 17 was stopped. When the process shown in FIG. 11 is started, the following steps are executed.

In step S30, the CPU 10a of the control unit 10 refers to the output of the temperature sensor 13 and detects the atmospheric temperature θ of the secondary battery 14.

In step S31, the CPU 10a estimates the electrolyte temperature θl based on the atmospheric temperature θ detected in step S10. For example, a heat equivalent model of the secondary battery 14 is created, and the electrolytic solution temperature θl is obtained by applying the above-mentioned atmospheric temperature θ to the heat equivalent model.

In step S32, the CPU 10a of the control unit 10 refers to the output of the voltage sensor 11 and detects the terminal voltage V of the secondary battery 14.

In step S33, the CPU 10a estimates the open circuit voltage OCV from the terminal voltage V detected in step S32. For example, when the secondary battery 14 becomes stable, the influence of stratification and polarization is reduced, so that the terminal voltage V at that time can be regarded as the open circuit voltage OCV. The open circuit voltage OCV may be obtained by eliminating the effects of stratification and polarization by calculation in consideration of the time elapsed since the engine 17 was stopped.

In step S34, the CPU 10a substitutes the electrolytic solution temperature θl estimated in step S31 and the open circuit voltage OCV estimated in step S33 into θlx and OCVx indicating the electrolytic solution temperature and the open circuit voltage at that time, respectively.

In step S35, the CPU 10a reads out OCV0 and θl0 stored in the parameter 10ca of the RAM 10c by the processes shown in steps S17 and S18 of FIG.

In step S36, the CPU 10a executes a process of learning the element values of the elements constituting the equivalent circuit model in θlx and OCVx. As a result, Rohmx, Rct1x, C1x are obtained. The details of this process will be described later with reference to FIG.

In step S37, the CPU 10a executes a process of correcting the element values Rohmx, Rct1x, and C1x obtained in step S36 to the element values at OCV0 and θl0 read in step S35. More specifically, the element values Rohm0, Rct10, and C10 at OCV0 and θl0 are corrected by using the above-mentioned equations (1) to (3).

In step S38, the CPU 10a estimates the state of the secondary battery 14 based on the element values of the equivalent circuit model corrected in step S37. For example, SOH is estimated as the state of the secondary battery 14. Of course, other than SOH may be estimated.

In step S39, the CPU 10a executes a control process based on the state of the secondary battery 14 estimated in step S38. For example, when the SOH is estimated and the SOH is less than a predetermined threshold value, it is presented to the user that the deterioration is progressing, and the replacement of the secondary battery 14 is urged. Of course, other processing may be executed.

As described above, according to the process shown in FIG. 11, the state of the secondary battery 14 can be accurately estimated.

FIG. 12 is a diagram illustrating an example of learning processing of the equivalent circuit model shown in step S36 of FIG. When the process of FIG. 12 is started, the following steps are executed.

In step S50, the CPU 10a _{substitutes the variable T n} indicating the time with the value obtained by adding ΔT to the previous value T _n-1. As ΔT, for example, several msec to several hundred msec can be used.

In step S51, the control unit 10, voltage sensor 11, current sensor 12 and, based on the detection signal from the temperature sensor 13 measures current _{I n,} the voltage _{V n,} a temperature theta _n.

In step S52, the CPU 10a _{applies the voltage V n} measured in step S51 to the following equation (4) to calculate the _{voltage drop ΔV n.}

ΔV _n = V _{n −} OCV ・ ・ ・ (4)

In step S52, the CPU 10a updates _{the Jacobian F n from} the nth observed value and the previous state vector estimated value based on the following equation (5). Note that diag () indicates a diagonal matrix.

F _n = diag (1-ΔT / Rct1 _n · C1 _n , 1,1,1,1) ... (5)

In step S54, the CPU 10a sets ΔV _{n obtained by calculation in step S52 as the actually measured observation value Y n} of the extended Kalman filter as shown by the following equation (6).

Y _n = ΔV _n ... (6)

In step S55, the CPU 10a obtains the state vector X _{n + 1} | _n one period ahead based on the following equation (7).

X _{n + 1} | _n = F _n · X _n + _Un ... (7)

Here, X _n and _Un are represented by the following equations (8) and (9). Note that T indicates a transposed matrix.

X _n ^T = (ΔV2, Rohm, Rct1, C1, V0) ... (8)

^{_{U n T = (Δt · I}} n / C1,0,0,0,0) ··· (9)

By _{defining H n} ^T as the following equation (10), the observation equation and the predicted observed value Y _{n + 1} | _n can be defined as the equation (11).

^{_{H n T = (1, I}} n, 0,0,0) ··· (10)

Y _n = H _n ^T・ X _n ... (11)

In step S56, the CPU 10a performs the Kalman gain calculation and the extended Kalman filter calculation by the Kalman gain calculation and the filtering calculation based on _{the predicted value X n + 1} | _n of the state vector one period ahead, the measured observed value Y _{n + 1,} and the predicted observed value Y _{n + 1} | _n. The optimum state vector X _n is sequentially estimated, and the adjustment parameter (of the equivalent circuit model) is updated to the optimum one from _{the estimated state vector X n.}

As described above, according to the process shown in FIG. 12, the element values of the elements constituting the equivalent circuit model of the secondary battery 14 can be obtained.

(C) Description of Modified Embodiment The above embodiment is an example, and it goes without saying that the present invention is not limited to the cases described above. For example, in the above embodiment, the case where the equivalent circuit model shown in FIG. 3A is used has been described as an example, but for example, the equivalent circuit model shown in FIG. 3B may be used. Further, an equivalent circuit model other than these may be used.

Further, in the above embodiments, the case where the electrolytic solution is reduced is described as an example, but the present invention may be applied when the solution is increased by replacement fluid. That is, the liquid reduction proceeds slowly because it occurs due to evaporation of the electrolytic solution or the like. However, since the replacement fluid is caused by the act of replenishing the electrolytic solution (for example, distilled water), a sudden change occurs. Therefore, in order to deal with such a case, for example, when the element value, the OCV, or the like suddenly changes, it is determined that the replacement fluid has been performed, and the processes of FIGS. 10 to 12 are executed. You may. According to such a configuration, the state of the secondary battery 14 can be accurately detected even when the fluid is replenished. When the replacement fluid is replenished, in order to immediately update OCV0 and θl0, the processes of steps S17 and S18 may be executed without executing the processes of steps S15 and S16 of FIG. Good.

Further, in the above embodiment, the element values of the elements constituting the equivalent circuit model are obtained based on the equations (1) to (3), but based on the following equations (12) to (14). The element value may be obtained.

Rohm0 = f1 (Rohmx, Rct1x, C1x, Tlx, OCVx, Tl0, OCV0) ... (12)

Rct10 = f2 (Rohmx, Rct1x, C1x, Tlx, OCVx, Tl0, OCV0) ... (13)

C10 = f3 (Rohmx, Rct1x, C1x, Tlx, OCVx, Tl0, OCV0) ... (14)

Further, in the above embodiment, the reference state is determined based on the temperature θ and the open circuit voltage OCV. For example, the concentration (for example, mass% or weight%) or specific gravity of the electrolytic solution of the secondary battery 14 is determined. The reference state may be obtained based on. The concentration or specific gravity of the electrolytic solution may be measured directly by arranging a sensor in the electrolytic solution of the secondary battery 14. Alternatively, the concentration or specific density may be estimated as an index value based on the open circuit voltage OCV.

Further, in the flowchart shown in FIG. 10, the case where the electrolytic solution temperature is 25 ° C. and the SOC is 100% is stored in the RAM 10c as a reference state, but the case of other values is stored as a reference state. Alternatively, the value when the temperature and SOC are within a predetermined range may be stored.

1 Secondary battery state detection device 10 Control unit (calculation means, correction means, estimation means)
10a CPU
10b ROM
10c RAM
10d communication unit 10e I / F
11 Voltage sensor 12 Current sensor 13 Temperature sensor 14 Rechargeable battery 15 Discharge circuit 16 Alternator 17 Engine 18 Starter motor 19 Load

Claims (5)

In the secondary battery state estimation device that estimates the deterioration state of the secondary battery,
A calculation means for calculating the element values of the elements constituting the equivalent circuit model of the secondary battery based on the measurement results of the current and voltage of the secondary battery, and
A correction means for correcting the element value of the equivalent circuit model calculated by the calculation means to the element value when the secondary battery is in the reference state.
It has an estimation means for estimating the deterioration state of the secondary battery based on the element value of the equivalent circuit model in the reference state corrected by the correction means.
At least the temperature and the concentration or specific gravity of the OCV or the electrolytic solution are used as the state values indicating the reference state.
A secondary battery state estimation device characterized by this. The correction means includes the temperature in the reference state, the concentration or specific gravity of the OCV or the electrolytic solution, and the temperature and the OCV at the time when the element value of the equivalent circuit model of the secondary battery is calculated by the calculation means. The secondary battery state estimation device according to claim 1, wherein the secondary battery is corrected to an element value when the secondary battery is in the reference state based on the concentration or specific gravity of the electrolytic solution. The reference state is the a the temperature is the predetermined value of the secondary battery, and a case where SOC of the secondary battery is 100% to claim 1 or 2, characterized in that the reference state The described secondary battery state estimation device. A storage means for storing the OCV or concentration or specific gravity of the electrolyte of the measured secondary battery when it is determined the reference shape on purpose,
The correction means calculates the temperature stored in the storage means, the concentration or specific gravity of the OCV or the electrolytic solution of the secondary battery, and the element value of the equivalent circuit model of the secondary battery by the calculation means. The secondary battery according to claim 3 , wherein the secondary battery is corrected to an element value when the secondary battery is in the reference state based on the temperature and the concentration or specific gravity of the OCV or the electrolytic solution at a certain time. State estimator . In the secondary battery state estimation method for estimating the deterioration state of the secondary battery,
A calculation step of calculating the element values of the elements constituting the equivalent circuit model of the secondary battery based on the measurement results of the current and voltage of the secondary battery, and
A correction step for correcting the element value of the equivalent circuit model calculated in the calculation step to the element value when the secondary battery is in the reference state, and a correction step.
It has an estimation step of estimating the deterioration state of the secondary battery based on the element value of the equivalent circuit model in the reference state corrected in the correction step.
At least the temperature and the concentration or specific gravity of the OCV or the electrolytic solution are used as the state values indicating the reference state.
A method for estimating the state of a secondary battery.

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