JP6498920B2 - Secondary battery state detection device and secondary battery state detection method - Google Patents

Description

  The present invention relates to a secondary battery state detection device and a secondary battery state detection method.

  Patent Document 1 discloses an open-ended voltage from a secondary battery voltage provided with charge polarization using a correlation between a voltage change rate after a predetermined time from the end of charging and discharging and a voltage correction value for obtaining an open-ended voltage due to polarization. A method of estimating is disclosed.

  In Patent Document 2, voltage current and current are detected using means for detecting battery voltage V and current I, and means for calculating a polarization index indicating the degree of polarization based on activation polarization and concentration polarization of the secondary battery. A method for deriving the battery voltage V under the condition that all the polarization indices satisfy the data measurement conditions is disclosed.

  Patent Document 3 discloses a method of deriving the integrated capacity from the current flowing in the secondary battery and deriving the polarization voltage from the relationship between the rate of change of the integrated capacity and the amount of polarization voltage.

JP 2010-014636 A JP 2005-083970 A JP 2003-197275 A

  In the secondary battery, the relationship between the passage of time and the depolarization behavior after charge / discharge needs to consider the influence based on the activation polarization and concentration polarization in the battery. In particular, the concentration polarization having a slow response may not be resolved even after several tens of hours. Concentration polarization is influenced by different parameters depending on the electrolyte solution and electrode configuration of each secondary battery, such as the electrolyte viscosity, temperature, electrolyte concentration, electrode electric double layer capacity, etc., so the relationship between current, voltage and time There is a problem that it is difficult to accurately predict the elimination behavior of polarization according to the type of the secondary battery only by the formula.

  An object of the present invention is to provide a secondary battery state detection device and a secondary battery state detection method capable of accurately obtaining an open circuit voltage value regardless of the type of secondary battery.

In order to solve the above problems, the present invention provides a secondary battery state detection device for detecting a state of a secondary battery mounted on a vehicle, wherein an element value of an equivalent circuit of the secondary battery, Storage means for storing information indicating a relationship with the polarization voltage value, calculation means for calculating an element value of an equivalent circuit of the secondary battery, and storing the element value calculated by the calculation means in the storage means By applying to the information that has been obtained, the means for obtaining the polarization voltage value, and the polarization voltage value obtained by the means for obtaining is subtracted from the terminal voltage value of the secondary battery. And calculating means for calculating an open circuit voltage value.
According to such a configuration, it becomes possible to accurately obtain the open circuit voltage value regardless of the type of the secondary battery.

According to the present invention, the storage means has a relationship between the polarization voltage value and at least one of an electrolyte resistance value, a reaction resistance value, an electric double layer capacitance value, or a diffusion resistance value constituting the equivalent circuit. The information to be stored is stored, and the obtaining means includes a relationship between the polarization voltage value and at least one of the electrolytic solution resistance value, the reaction resistance value, the electric double layer capacitance value, or the diffusion resistance value. The polarization voltage value is obtained on the basis of information indicating the above.
According to such a configuration, the polarization voltage value can be accurately obtained based on the relationship between the equivalent circuit element value and the polarization voltage value.

Further, the present invention, the storage means, information indicating the relationship between the polarization voltage value and the element values, have been stored for each charging rate of the secondary battery, the Motomede means, said secondary The information corresponding to the charging rate of the battery is obtained from the storage means, and the polarization voltage value is obtained.
According to such a configuration, since the element value and the polarization voltage value are stored for each charging rate, the open circuit voltage can be accurately obtained even when the charging rate changes.

Further, according to the present invention, in the case where two pieces of information having values close to the element value calculated by the calculation unit exist in the storage unit, the obtaining unit corresponds to the low charging rate. It is characterized by selecting and using information .
According to such a configuration, the open circuit voltage can be accurately obtained by preferentially using the relational expression when the charging rate is low.

Further, the present invention is characterized in that the obtaining means corrects the polarization voltage value according to the temperature of the secondary battery.
According to such a configuration, since the polarization voltage value is corrected according to the temperature, the open circuit voltage can be accurately obtained even when the temperature changes.

According to another aspect of the present invention, there is provided a secondary battery state detection method for detecting a state of a secondary battery mounted on a vehicle, wherein a relationship between an element value of an equivalent circuit of the secondary battery and a polarization voltage value of the secondary battery. A storage step for storing information indicating the storage circuit, a calculation step for calculating an element value of an equivalent circuit of the secondary battery, and the element value obtained in the calculation step is stored in the storage unit. By applying to the information, the obtaining step for obtaining the polarization voltage value, and subtracting the polarization voltage value obtained in the obtaining step from the terminal voltage value of the secondary battery. And a calculation step of calculating an open circuit voltage value.
According to such a method, it is possible to accurately obtain the open circuit voltage value regardless of the type of the secondary battery.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the secondary battery state detection apparatus and secondary battery state detection method which can obtain | require an open circuit voltage value correctly irrespective of the kind of secondary battery.

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 structural example of the control part of FIG. It is a figure which shows an example of the equivalent circuit of a secondary battery. It is a figure which shows the relationship between reaction resistance value and polarization voltage value in a case where a charging rate is 100%. It is a figure which shows the relationship between reaction resistance value and polarization voltage value in case a charging rate is 80%. It is a figure which shows the relationship between the elapsed time and the voltage after completion | finish of charge of a secondary battery. It is a figure which shows the relationship between the elapsed time and voltage after completion | finish of charge of a secondary battery in a different temperature environment. It is a flowchart explaining an example of the process performed in embodiment shown in FIG. FIG. 9 is a flowchart illustrating an example of detailed processing of “OCV estimation processing” in step S <b> 18 of FIG. 8. FIG. It is a figure which shows the relationship between electrolyte solution resistance value and polarization voltage value when a charging rate is 100%. It is a figure which shows the relationship between electrolyte solution resistance value and polarization voltage value in case a charging rate is 80%. It is a figure which shows the relationship between an electrical double layer capacity value and a polarization voltage value in a case where a charging rate is 100%. It is a figure which shows the relationship between an electrical double layer capacity value and a polarization voltage value in case a charging rate is 80%.

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

(A) Description 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 an embodiment of the present invention. In this figure, the secondary battery state detection device 1 includes 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 detects the state of the secondary battery 14. To do. Here, the control unit 10 refers to outputs from the voltage sensor 11, the current sensor 12, and the temperature sensor 13 to detect the state of the secondary battery 14. The voltage sensor 11 detects the terminal voltage of the secondary battery 14 and notifies the control unit 10 of it. The current sensor 12 detects the current flowing through the secondary battery 14 and notifies the control unit 10 of the current. The temperature sensor 13 detects the secondary battery 14 itself or the surrounding environmental temperature, and notifies the control unit 10 of it. The discharge circuit 15 is configured by, for example, a semiconductor switch and a resistance element connected in series, and the secondary battery 14 is intermittently discharged when the control unit 10 performs on / off control of the semiconductor switch.

  The secondary battery 14 is composed of, for example, a lead storage battery, is charged by the alternator 16, drives the starter motor 18 to start the engine, and supplies power to the load 19. The alternator 16 is driven by the engine 17 to generate AC power, convert it into DC power by a rectifier circuit, and charge the secondary battery 14.

  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. The engine 17 is started by a starter motor 18 and drives driving wheels via a transmission to give propulsive force to the vehicle. Drive to generate power. The starter motor 18 is constituted by, for example, a DC motor, generates a rotational force by the electric power supplied from the secondary battery 14, and starts the engine 17. The load 19 is configured by, for example, an electric steering motor, a defogger, an ignition coil, a car audio, a car navigation, and the like, and operates with electric power from the secondary battery 14.

  FIG. 2 is a diagram illustrating a detailed configuration example of the control unit 10 illustrated in FIG. 1. 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 configured by a semiconductor memory or the like, and stores a program 10ba or the like. The RAM 10c is configured by a semiconductor memory or the like, and stores data generated when the program ba is executed, and a parameter 10ca such as a table or a mathematical expression described later. The communication unit 10d communicates with an ECU (Electronic Control Unit) that is a host device and notifies the host device of the detected information. The I / F 10e converts the signal supplied from the voltage sensor 11, the current sensor 12, and the temperature sensor 13 into a digital signal and takes it in, and supplies a driving current to the discharge circuit 15 to control it.

(B) Description of Operation of Embodiment Next, the operation of the embodiment of the present invention will be described with reference to the drawings. In the present embodiment, the polarization voltage value V_SOE is obtained from the relationship between the element value of the element constituting the equivalent circuit of the secondary battery 14 and the polarization voltage value, and the polarization voltage value V_SOE is subtracted from the voltage value V at that time. Thus, an accurate open circuit voltage value OCV is obtained.

  More specifically, in the embodiment of the present invention, when an ignition switch (not shown) is turned on to start the engine 17 and the vehicle is in an operating state, the CPU 10a of the control unit 10 includes the voltage sensor 11 and the current. The voltage value V and current value I of the secondary battery 14 are measured by the sensor 12 at a predetermined cycle, and these measured values are stored in the RAM 10c as the parameter 10ca. The CPU 10a obtains the latest SOC at that time by cumulatively adding the current value I stored in the RAM 10c to the charge rate SOC obtained at a certain time by the processing described later.

  Next, when the vehicle is stopped and the ignition switch is turned off and a predetermined time (for example, 1 hour) elapses, the CPU 10a controls the discharge circuit 15 so as to obtain a predetermined cycle and a predetermined current value. Then, the secondary battery 14 is pulse-discharged. Then, the voltage value and the current value at the time of discharging are detected by the voltage sensor 11 and the current sensor 12, and the electrical voltage of the secondary battery 14 is determined based on the detected voltage value and current value and the voltage value and current value before discharging. A learning process for the element value of the equivalent circuit is executed.

  FIG. 3 is a diagram illustrating an example of an electrical equivalent circuit of the secondary battery 14. In this example, in the equivalent circuit, a reaction resistance Rct and an electric double layer capacitance C connected in parallel are connected in series to an electrolyte resistance (or conductive resistance) Rohm. The CPU 10a of the control unit 10 performs learning processing on such parameters (element values) of the equivalent circuit using an algorithm such as a Kalman filter or a support vector machine. The CPU 10a stores the parameter of the equivalent circuit obtained by the learning process in the RAM 10c as the parameter 10ca.

  Note that the equivalent circuit shown in FIG. 3 is an example, and two or more reaction resistors and electric double layer capacities may exist. Moreover, it is good also as a structure only of the resistor which does not have an electric double layer capacity | capacitance.

  In the RAM 10c, information (for example, a relational expression) indicating the relationship between the element value of the equivalent circuit and the polarization voltage value is stored for each SOC value of the secondary battery 14. FIG. 4 is a diagram showing the relationship between the reaction resistance value Rct and the polarization voltage value V_SOE when the SOC is 100%. In this figure, diamonds and squares show measured values of two secondary batteries (secondary battery type 1 and secondary battery type 2) with different initial capacities, and triangles and crosses are two of the same capacity but different manufacturers. The measured value of the secondary battery (secondary battery type 3 and secondary battery type 4) is shown. A broken line indicates a relational expression obtained from these actually measured values by, for example, the least square method. FIG. 5 is a diagram showing the relationship between the reaction resistance value Rct and the polarization voltage value V_SOE when the SOC is 80%. In this figure, the actual measurement values are the same as those in FIG. 4, and the broken line indicates a relational expression obtained from these actual measurement values by, for example, the least square method. As shown in FIGS. 4 and 5, there is a certain relationship between the reaction resistance value and the polarization voltage value regardless of the initial capacity of the secondary battery and the manufacturer. That is, there is a relationship in which the polarization voltage value decreases as the reaction resistance value increases.

  Note that the actual measurement values shown in FIGS. 4 and 5 can be obtained by the following method, for example. That is, when the SOC of the secondary battery to be measured is 100% and the temperature is 25 ° C., the secondary battery is adjusted and discharged so as to be 5% lower than the target SOC, and the voltage at that time Measure the value and current value. Next, the SOC is charged 5% so as to achieve the target SOC, and the current value and voltage value at that time are measured. For example, when the target SOC is 80%, the battery is charged at 5% after adjusting discharge to 75% (= 80% -5%). Then, the terminal voltage of the secondary battery when 1 hour has elapsed since the end of charging is measured, and the measured value is OCV1. Next, the integrated current value obtained by integrating the current values during the regulated discharge and during charging is added to 100%, which is the SOC value before the start of the regulated discharge, to obtain the true SOC. Then, the obtained SOC is substituted into an expression (for example, a linear function) indicating the relationship between SOC and OCV, and the obtained open circuit voltage value is defined as OCV2, and the polarization voltage value V_SOE (= OCV1- OCV2). Then, an equivalent circuit of the secondary battery at that time is obtained, and the reaction resistance value Rct and the polarization voltage value V_SOE of the obtained equivalent circuit are used as measurement results. Information indicating the relationship between the reaction resistance value Rct thus obtained and the polarization voltage value V_SOE is stored in the RAM 10c for each SOC, for example, as an equation (for example, a linear function).

  The CPU 10a acquires the mathematical formula measured and stored as described above from the RAM 10c. For example, when the SOC is 80%, a mathematical expression corresponding to the broken line in FIG. 5 is acquired from the RAM 10c. And the reaction resistance value Rct calculated | required by the learning process is acquired from RAM10c, and a polarization voltage value is calculated | required from the acquired reaction resistance value Rct. For example, when the SOC is 80% and the reaction resistance value is 0.002, about 0.12 V can be obtained as the polarization voltage from the broken line in FIG.

  The CPU 10a can obtain the open circuit voltage value OCV (= V−V_SOE) by subtracting the polarization voltage value V_SOE obtained as described above from the terminal voltage value V of the secondary battery 14 at that time. . By obtaining the open circuit voltage value OCV by the method as described above, the open circuit voltage value OCV can be obtained in a short time after the ignition switch is turned off. That is, the polarization voltage of the secondary battery 14 is eliminated over a very long time as shown in FIG. In the example of FIG. 6, the polarization voltage A of the type A secondary battery indicated by the alternate long and short dash line and the polarization voltage B of the type B secondary battery indicated by the solid line are eliminated over 10 hours or more. Since the open circuit voltage is a terminal voltage of the secondary battery in a state where the polarization voltage is eliminated, in order to obtain an accurate open circuit voltage, it is necessary to measure after the polarization voltage is eliminated. As described above, a very long time is required to eliminate the polarization voltage. In this embodiment, the relationship between the reaction resistance value and the polarization voltage value as shown in FIG. 4 and FIG. 5 is obtained, and by using such a relationship, the open circuit voltage of the secondary battery is obtained, for example, The open circuit voltage can be accurately obtained even in a short time (for example, 1 hour) after the ignition switch is turned off. Further, as shown in FIGS. 4 and 5, since the relational expression between the reaction resistance value and the polarization voltage value is established regardless of the initial capacity of the secondary battery or the manufacturer, the initial capacity of the secondary battery or An accurate open circuit voltage can be obtained regardless of the manufacturer.

  In the above description, the temperature of the secondary battery 14 is not considered, but the obtained polarization voltage value V_SOE may be corrected according to the temperature of the secondary battery 14. FIG. 7 shows the difference in elimination of the polarization voltage due to temperature. The solid line shows the state of elimination of the polarization voltage when the temperature of the secondary battery 14 is 65 ° C., the broken line with a long interval shows the state of elimination of the polarization voltage when the temperature is 25 ° C., and the broken line with a short interval shows the temperature Shows the state of elimination of the polarization voltage when -10 ° C. In this example, the case where the temperature is 25 ° C. is resolved earliest, and when the temperature is high and low, the resolution is slow. Therefore, for example, a temperature correction may be performed by obtaining a correction coefficient based on a polarization voltage value depending on temperature and multiplying the polarization voltage value by this correction coefficient.

  Next, details of processing executed in the present embodiment will be described with reference to FIGS. 8 and 9. FIG. 8 is a flowchart for explaining an example of processing executed in the present embodiment. When this process is started, the following steps are executed.

  In step S10, the CPU 10a determines whether or not an unillustrated ignition switch has been turned on by the driver. If it is determined that the ignition switch has been turned on (step S10: Yes), the process proceeds to step S11. In other cases (step S10: No), the same processing is repeated. For example, if the driver gets on the vehicle and operates an ignition switch (not shown) to turn it on, the determination is Yes and the process proceeds to step S11.

  In step S11, the CPU 10a refers to the outputs of the voltage sensor 11 and the current sensor 12, and acquires the voltage value of the terminal voltage of the secondary battery 14 and the charge / discharge current value flowing through the secondary battery 14.

  In step S12, the CPU 10a obtains the SOC value at that time by cumulatively adding the current value obtained in step S11 to the SOC value obtained at a certain time by the process described later. More specifically, for example, the SOC is obtained by substituting the value of OCV obtained by the processing of step S18 into an expression (for example, a primary expression) indicating the relationship between the SOC and the OCV. Then, the current value obtained in step S11 is cumulatively added to this SOC to obtain the latest SOC value at that time.

  In step S13, the CPU 10a stores the SOC value obtained in step S12 in the RAM 10c.

  In step S14, the CPU 10a determines whether or not an unillustrated ignition switch has been turned off by the driver. If it is determined that the ignition switch has been turned off (step S14: Yes), the process proceeds to step S15. In other cases (step S14: No), the process returns to step S11 and the same process as described above is repeated. For example, if the driver stops the vehicle and operates an ignition switch (not shown) to turn it off, the determination is Yes and the process proceeds to step S15.

  In step S15, the CPU 10a determines whether or not a predetermined time (for example, 1 hour) has elapsed since the ignition switch was turned off, and determines that the predetermined time has elapsed (step S15: If yes, the process proceeds to step S16, otherwise the same process is repeated (step S15: No). For example, if one hour has elapsed since the ignition switch was turned off, the determination is Yes and the process proceeds to step S16.

  In step S <b> 16, the CPU 10 a controls the discharge circuit 15 to pulse discharge the secondary battery 14 with a predetermined cycle and a predetermined current value, and the voltage value and current value at that time are determined by the voltage sensor 11 and the current sensor 12. The detection is performed with reference to the output, and the process of learning the element value of the equivalent circuit of the secondary battery 14 is executed. More specifically, the CPU 10a learns the element values of the elements constituting the equivalent circuit shown in FIG. 3 based on, for example, voltage values and current values detected using an algorithm such as a Kalman filter or a support vector machine. .

  In step S17, the CPU 10a stores the element value of the equivalent circuit obtained by the learning process in step S16 in the RAM 10c as the parameter 10ca.

  In step S18, the CPU 10a executes a process for estimating the OCV. As a result, an accurate OCV can be obtained. Details of this process will be described later with reference to FIG.

  In step S19, the CPU 10a determines whether or not to continue the process. If it is determined that the process is to be continued (step S19: Yes), the process returns to step S10 and the same process as described above is repeated. In step S19: No, the process ends.

  Next, the OCV estimation process shown in step S18 of FIG. 8 will be described in detail with reference to FIG.

  In step S30, the CPU 10a acquires the SOC value stored in the RAM 10c in step S13 of FIG. For example, 80% is acquired as the SOC value.

  In step S31, the CPU 10a refers to the output of the temperature sensor 13 and acquires the temperature of the secondary battery 14. For example, 30 ° C. is acquired as the temperature of the secondary battery 14.

  In step S32, the CPU 10a acquires from the RAM 10c a relational expression (an expression indicating a relation between the reaction resistance value and the polarization voltage value) corresponding to the SOC value acquired in step S30. In the present example, since the SOC value is 80%, for example, the relational expression corresponding to the broken line shown in FIG. 5 is acquired.

  In step S33, the CPU 10a acquires the reaction resistance value Rct stored in step S15 from the RAM 10c. For example, 0.002Ω is acquired as the reaction resistance value Rct.

  In step S34, the CPU 10a applies the reaction resistance value Rct acquired in step S33 to the relational expression acquired in step S32 to obtain the polarization voltage value V_SOE. In the present example, by applying 0.002Ω as the reaction resistance value Rct to the relational expression corresponding to the broken line in FIG. 5, 0.12 V is obtained as the polarization voltage value V_SOE.

  In step S35, the CPU 10a executes a process of correcting the polarization voltage value V_SOE obtained in step S34 according to the temperature obtained in step S31. More specifically, a temperature correction coefficient is obtained from the temperature characteristics shown in FIG. 7, and a relational expression or table indicating a correspondence relationship between the temperature and the temperature correction coefficient is stored in the RAM 10c. Then, temperature correction can be performed by acquiring a temperature correction coefficient corresponding to the temperature acquired in step S31 and multiplying the polarization voltage value V_SOE. In this example, since the temperature is 30 ° C., for example, if 1.25 is obtained as the temperature correction coefficient, 0.15 V (= 0.12 × 1.25) is obtained as the polarization voltage value after correction.

  In step S36, the CPU 10a refers to the output of the voltage sensor 11 and acquires the voltage value V of the secondary battery 14 at that time. For example, 12.5 V is obtained as the voltage at that time.

  In step S37, the CPU 10a obtains the open circuit voltage value OCV (= V−V_SOE) by subtracting the polarization voltage value V_SOE corrected in temperature in step S35 from the voltage value V obtained in step S36. For example, in this example, the open circuit voltage value is 12.35 V (= 12.5−) by subtracting the polarization voltage value 0.15 V, which is temperature-corrected in step S35, from the voltage value 12.5 V obtained in step S36. 0.15) is obtained.

  According to the above processing, the polarization voltage value V_SOE is obtained based on the relational expression between the reaction resistance value Rct and the polarization voltage value V_SOE, and the OCV is obtained from the obtained polarization voltage value V_SOE. The OCV can be accurately obtained in a short time after is turned off. Further, since the relational expression between the reaction resistance value Rct and the polarization voltage value V_SOE is established regardless of the initial capacity of the secondary battery 14 and the manufacturer, the OCV can be accurately obtained regardless of the type of the secondary battery 14. Can do. In the above embodiment, since the polarization voltage value V_SOE is corrected by the temperature correction coefficient, the accurate polarization voltage value V_SOE can be obtained regardless of the temperature of the secondary battery 14.

(C) Description of Modified Embodiment It goes without saying that the above embodiment is merely an example, and the present invention is not limited to the case described above. For example, in the above embodiment, the polarization voltage value V_SOE is obtained using only the reaction resistance constituting the equivalent circuit, but other than this, for example, the electrolyte resistance (or conductive resistance), the electric double layer capacitance, etc. Alternatively, a diffusion resistance element (a resistance element included in the reaction resistance element) may be used. FIG. 10 is a diagram showing the relationship between the electrolyte resistance value and the polarization voltage value when the SOC is 100% and the temperature is 25 ° C. FIG. 11 is a diagram showing the relationship between the electrolytic solution resistance value and the polarization voltage value when the SOC is 80% and the temperature is 25 ° C. In these figures, the horizontal axis represents the electrolyte resistance value (Ω), and the vertical axis represents the polarization voltage value (V). As shown in these figures, a relationship similar to the reaction resistance value also exists between the electrolyte resistance value and the polarization voltage value. For this reason, even when the electrolytic solution resistance is used instead of the reaction resistance value, the same effect as described above can be obtained.

  FIG. 12 is a diagram showing the relationship between the electric double layer capacitance value and the polarization voltage value when the SOC is 100% and the temperature is 25 ° C. FIG. 13 is a diagram showing the relationship between the electric double layer capacitance value and the polarization voltage value when the SOC is 80% and the temperature is 25 ° C. In these drawings, the horizontal axis represents the electric double layer capacitance value (F), and the vertical axis represents the polarization voltage value (V). As shown in these figures, a relationship similar to the reaction resistance value also exists between the electric double layer capacitance value and the polarization voltage value. For this reason, even when the electric double layer capacitance value is used instead of the reaction resistance value, the same effect as described above can be obtained.

  Instead of using a single element constituting an equivalent circuit, a plurality of these elements may be used in combination. As an example, in the case of a combination of the two, a relational expression between the reaction resistance value, the electric double layer capacitance value, and the polarization voltage value V_SOE may be obtained, and the polarization voltage value V_SOE may be obtained based on this relational expression. . Of course, it may be a combination other than these, or a combination of three. Further, a relational expression between a value obtained by multiplying a plurality of element values by a weighting coefficient and the polarization voltage value V_SOE may be obtained, and the polarization voltage value V_SOE may be obtained based on this relational expression. .

  In the above example, as shown in FIG. 4 and FIG. 5, the case where the SOC is 100% and 80% has been described as an example, but other relational expressions relating to the SOC value are prepared in the RAM 10c, You may make it obtain | require a polarization voltage value also using those relational expressions. For example, a relational expression with an SOC value of 60% to 100% may be prepared in units of 5%, and a relational expression with the closest SOC value at that time may be selected and used. Alternatively, two relational expressions having close SOC values at that time may be selected, and a polarization voltage value corresponding to the SOC value at that time may be obtained by interpolating these relational expressions.

  As is clear from the comparison between FIG. 4 and FIG. 5, since the error between the broken line and the actual measurement value is smaller when the SOC value is smaller than when the SOC value is large, measurement corresponding to different SOC values is possible. If a value exists, the measured value when the SOC value is small may be used preferentially. According to such a method, the polarization voltage value can be obtained more accurately.

  Further, the OCV estimation process shown in step S18 of FIG. 8 is executed after one hour has elapsed since the ignition switch was turned off, but may be set to a time other than one hour.

  In the process shown in FIG. 9, the obtained polarization voltage value is corrected using the temperature coefficient. For example, a relational expression corresponding to both the SOC value and the temperature value is obtained, and this relational expression is obtained. May be used in consideration of the temperature characteristics. Specifically, the relational expression shown in FIG. 5 with an SOC of 80% is obtained in units of 5 ° C. from 0 ° C. to 50 ° C., and the relational expression is selected based on the temperature and SOC at that time. Good.

  4 and 5 may be slightly changed due to deterioration of the secondary battery 14. Therefore, a relational expression corresponding to deterioration due to aging is prepared, and the aging of the secondary battery 14 is prepared. The polarization voltage value may be obtained using a relational expression corresponding to a change (for example, SOH (State of Health)).

  In the above embodiment, the case where the relational expression indicating the relation between the reaction resistance value Rct and the polarization voltage value V_SOE is used as an example has been described. The table may be used.

  In the above embodiment, as the equivalent circuit of the secondary battery 14, the equivalent circuit shown in FIG. 3 is used. However, other equivalent circuits may be used. For example, the number of reaction resistors and electric double layer capacities connected in parallel may be two or more. Further, an equivalent circuit having only a resistor having no electric double capacitance may be used.

DESCRIPTION OF SYMBOLS 1 Secondary battery state detection apparatus 10 Control part (calculation means, search means, calculation means)
10a CPU
10b ROM
10c RAM (storage means)
10d Communication unit 10e I / F
DESCRIPTION OF SYMBOLS 11 Voltage sensor 12 Current sensor 13 Temperature sensor 14 Secondary battery 15 Discharge circuit 16 Alternator 17 Engine 18 Starter motor 19 Load

Claims (6)

In a secondary battery state detection device that detects the state of a secondary battery mounted on a vehicle,
Storage means for storing information indicating a relationship between an element value of an equivalent circuit of the secondary battery and a polarization voltage value of the secondary battery;
Calculating means for calculating an element value of an equivalent circuit of the secondary battery;
Applying the element value calculated by the calculating means to the information stored in the storage means, thereby obtaining the polarization voltage value;
Calculating means for calculating an open circuit voltage value by subtracting the polarization voltage value obtained by the obtaining means from a terminal voltage value of the secondary battery;
A secondary battery state detection device comprising: The storage means stores information indicating a relationship between the polarization voltage value and at least one of an electrolyte resistance value, a reaction resistance value, an electric double layer capacitance value, or a diffusion resistance value constituting the equivalent circuit. And
The obtaining means includes the polarization voltage value based on information indicating a relationship between at least one of the electrolyte resistance value, the reaction resistance value, the electric double layer capacitance value, or the diffusion resistance value and the polarization voltage value. Find the voltage value,
The secondary battery state detection device according to claim 1. The storage means stores information indicating the relationship between the element value and the polarization voltage value for each charging rate of the secondary battery,
The obtaining means obtains the polarization voltage value by obtaining information corresponding to the charging rate of the secondary battery from the storage means.
The secondary battery state detection device according to claim 2. The obtaining means selects and uses the information corresponding to the low charging rate when two pieces of information having values close to the element value calculated by the calculating means exist in the storage means. The secondary battery state detection device according to claim 3, wherein:   5. The secondary battery state detection device according to claim 1, wherein the obtaining unit corrects the polarization voltage value according to a temperature of the secondary battery. 6. In a secondary battery state detection method for detecting a state of a secondary battery mounted on a vehicle,
A storage step of storing information indicating a relationship between an element value of an equivalent circuit of the secondary battery and a polarization voltage value of the secondary battery in a storage unit;
A calculation step of calculating an element value of an equivalent circuit of the secondary battery;
A step of obtaining the polarization voltage value by applying the element value obtained in the calculation step to the information stored in the storage unit;
A calculation step of calculating an open circuit voltage value by subtracting the polarization voltage value obtained in the obtaining step from the terminal voltage value of the secondary battery;
A secondary battery state detection method comprising:

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