JP2016095959A - Secondary battery state detecting device and secondary battery state detecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery state detecting device and a secondary battery state detecting method, capable of easily and accurately detecting that electrolytic solution of a secondary battery is refilled with water.SOLUTION: A secondary battery state detecting device 1 for detecting a state of a secondary battery 14 mounted on a vehicle comprises: deriving means (control unit 10) for deriving an element value of an equivalent circuit of the secondary battery; calculating means (control unit 10) for calculating open circuit voltage of the secondary battery; and determining means (control unit 10) for determining whether electrolytic solution of the secondary battery is refilled with water from the change of the element value of the equivalent circuit derived by the deriving means and the change of the open circuit voltage calculated by the calculating means.SELECTED DRAWING: Figure 1

Description

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

  As techniques for detecting the amount of the electrolyte solution of the secondary battery, there are conventionally techniques such as Patent Documents 1 to 4.

  Patent Document 1 discloses a technique for obtaining the normal liquid level in the battery tank from the interelectrode resistance of the secondary battery. Patent Documents 2 and 3 disclose an apparatus for detecting a liquid level of a secondary battery using an ultrasonic sensor. Further, Patent Document 4 discloses a technique for determining and warning that the electrolytic solution has decreased when the integrated value of the charging current is larger than a threshold value.

Japanese Patent Laid-Open No. 06-333606 JP 2000-121410 A JP 2000-205931 A JP 2006-344468 A

  By the way, when distilled water or the like is refilled with respect to the electrolyte of the secondary battery, the state of the secondary battery changes. Become. Therefore, it is desirable to accurately detect and grasp the implementation of such refilling.

  However, the technique disclosed in Patent Document 1 has a problem in that the configuration is complicated because the electrolyte is directly measured. In addition, the techniques disclosed in Patent Document 2 and Patent Document 3 have a problem in that the configuration is complicated because the ultrasonic sensor detects the liquid level of the electrolytic solution. In addition, the technique disclosed in Patent Document 4 is intended for detection of liquid reduction, and there is a problem that rehydration cannot be determined.

  An object of the present invention is to provide a secondary battery state detection device and a secondary battery state detection method capable of easily and accurately detecting that water has been replenished with respect to the electrolyte of the secondary battery. .

In order to solve the above-mentioned problems, the present invention relates to a secondary battery state detecting device for detecting a state of a secondary battery mounted on a vehicle, and obtaining means for obtaining an element value of an equivalent circuit of the secondary battery. A calculation means for calculating an open circuit voltage of the secondary battery, a change in the element value of the equivalent circuit obtained by the finding means, and a change in the open circuit voltage calculated by the calculation means And determining means for determining whether or not water has been replenished with respect to the electrolyte solution of the secondary battery.
According to such a configuration, it is possible to easily and accurately detect that water has been replenished with respect to the electrolyte solution of the secondary battery.

Further, according to the present invention, when the conductor resistance that constitutes the equivalent circuit does not change more than a predetermined value and the open circuit voltage is decreased more than a predetermined value, the determination means is refilled. It is characterized by determining.
According to such a configuration, the presence or absence of water replenishment can be easily detected based on the conductor resistance and the open circuit voltage.

Further, according to the present invention, the determination means is configured such that the conductor resistance constituting the equivalent circuit does not change more than a predetermined value, the open circuit voltage changes more than a predetermined value, and the negative electrode reaction resistance is a constant value. At least one of lowering, positive electrode reaction resistance higher than a certain value, negative electrode electric double layer capacity lower than a certain value, and positive electrode electric double layer capacity lower than a certain value was detected. In this case, it is determined that water has been replenished.
According to such a configuration, the presence or absence of water replenishment can be detected more accurately by taking into account other elements of the equivalent circuit in addition to the conductor resistance and the open circuit voltage.

Further, the present invention is characterized by initializing information indicating a state of the secondary battery when it is determined by the determination means that water has been replenished.
According to such a configuration, when water is replenished, the state of the secondary battery changes, so that the state information of the secondary battery is prevented from being erroneously estimated by initializing information indicating the state. it can.

Further, according to the present invention, the information indicating the state of the secondary battery includes element values of the equivalent circuit, usage history of the secondary battery, a charging rate of the secondary battery, and a reference capacity of the secondary battery. It is characterized by being at least one.
According to such a configuration, it is possible to prevent the state of the secondary battery from being erroneously estimated by initializing the use history, the charging rate, and the reference capacity.

Further, the present invention is characterized in that when it is determined by the determination means that water has been replenished, a higher-level device is notified.
According to such a configuration, the host device can also execute processing corresponding to the water replenishment by informing the host device.

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, a obtaining step for obtaining an element value of an equivalent circuit of the secondary battery, and the secondary battery. A calculation step for calculating the open circuit voltage of the secondary battery, a change in the element value of the equivalent circuit obtained in the obtaining step, and a change in the open circuit voltage calculated in the calculation step. And a determination step of determining whether or not water replenishment has been performed on the electrolytic solution.
According to such a method, it is possible to easily and accurately detect that water has been replenished with respect to the electrolyte solution of the secondary battery.

  According to the present invention, it is possible to provide a secondary battery state detection device and a secondary battery state detection method capable of easily and accurately detecting that water has been replenished with respect to the electrolyte of the secondary battery. It becomes.

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 the structural example of the equivalent circuit of the secondary battery used in this embodiment. It is a figure which shows the change of the element value of the equivalent circuit before and after performing water replenishment with respect to the electrolyte solution of a secondary battery. It is a figure which shows an example of the process performed in embodiment shown in FIG.

  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 includes, for example, a lead storage battery or the like that has an electrolytic solution and can be replenished with water. The secondary battery 14 is charged by the alternator 16 and drives the starter motor 18 to start the engine and supply power to the load 19. To do. 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 secondary battery 14 is configured such that distilled water or the like can be supplemented to an electrolytic solution such as dilute sulfuric acid stored in the electrolytic cell by a cap provided at the top of the housing. .

  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, and is started by a starter motor 18 to drive driving wheels through a transmission to provide 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 10ba is executed, and a parameter 10ca such as a table or a mathematical expression. 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 CPU 10a of the control unit 10 performs, for example, when a predetermined time (for example, several hours) elapses after an unillustrated ignition switch is turned off by being operated by the driver. The value of the open circuit voltage OCV of the secondary battery 14 is estimated. That is, when the ignition switch is turned off, the polarization voltage is eliminated with time, so the CPU 10a refers to the output of the voltage sensor 11 to measure the terminal voltage and estimate the polarization voltage. The value of the open circuit voltage OCV is estimated from these differences. Further, the CPU 10 a executes a process of learning the values of elements that constitute the equivalent circuit of the secondary battery 14. More specifically, in the present embodiment, an equivalent circuit of the secondary battery 14 as shown in FIG. 3 is assumed, and values of elements constituting the equivalent circuit are obtained by learning processing. The element values of the equivalent circuit and the open circuit voltage OCV values thus obtained are stored in the RAM 10c.

  Next, the CPU 10a obtains the current value of the element of the equivalent circuit and the current value of the open circuit voltage OCV obtained by the learning process, the previous value of the element of the equivalent circuit obtained by the previous process and stored in the RAM 10c, and By comparing the previous value of the open circuit voltage OCV, it is determined whether or not water is replenished to the electrolyte solution of the secondary battery 14. FIG. 4 shows changes in the value of each element of the equivalent circuit before and after water replenishment and the value of the open circuit voltage OCV. In this example, measurement results for secondary batteries # 1 to # 3, which are three lead storage batteries having the same manufacturer and initial capacity, are shown. There is almost no change in the value of the conductor resistance Rohm before and after rehydration. The values of the negative electrode reaction resistance Rct1 are all decreased by water replenishment. The value of the negative electrode electric double layer capacity C1 is decreased by all of the three waters. The positive electrode reaction resistance Rct2 (an element corresponding to the reciprocal of the exchange current density) increases in value due to water replenishment. The value of the positive electrode electric double layer capacity C2 is decreased due to water replenishment. The open circuit voltage OCV decreases in all three values due to water replenishment.

  The CPU 10a (1) the current value is lower than the previous value of the open circuit voltage OCV by a predetermined value or more, (2) the difference between the previous value and the current value of the conductor resistance Rohm is equal to or less than the predetermined value, and If at least one of the following holds, it is determined that water has been replenished.

(3) The current value of the negative electrode reaction resistance Rct1 is smaller than the previous value by a predetermined value or more.
(4) The current value of the positive electrode reaction resistance Rct2 is larger than the previous value by a predetermined value or more.
(5) The current value of the negative electrode electric double layer capacity C1 is smaller than the previous value by a predetermined value or more.
(6) The current value of the positive electrode electric double layer capacity C2 is smaller than the previous value by a predetermined value or more.

  If the CPU 10a determines that water has been replenished as a result of the determination based on the determination criteria described above, the CPU 10a notifies the ECU, which is a higher-level device, that the water has been replenished, and also to the user. Notice. As a result, the user can know that water replenishment has been detected. Next, the CPU 10a initializes information indicating the state of the secondary battery 14 stored in the RAM 10c. More specifically, the CPU 10a stores the element value of the equivalent circuit of the secondary battery 14, the usage history of the secondary battery 14, the charging rate, the reference capacity (SOH (State of Health) of the secondary battery 14 stored in the RAM 10c. ))). Thereby, even when a state changes with water replenishment, the influence can be decreased. In addition, when notifying the user of the detection of the refilling water, if the user inputs that the refilling is not performed, the state of the secondary battery 14 stored in the RAM 10c is detected as a false detection. The initialization of the information shown may not be executed.

  As described above, in the present embodiment, the presence / absence of water replenishment of the secondary battery 14 is detected based on the change in the value of the element of the equivalent circuit and the value of the open circuit voltage, and it is determined that the water has been replenished. Since the user is notified to the host device and the user, the user can know that water replenishment has been detected. In addition, since information indicating the state of the secondary battery 14 is initialized when water replacement is detected, information indicating the state is initialized even when the state of the secondary battery 14 changes due to water replenishment. Thus, it is possible to prevent the state from being erroneously determined.

  Note that the learning process of the equivalent circuit and the estimation process of the open circuit voltage are not performed over a long period of time, so that the interval at which the previous value and the current value are measured is not greatly opened. When a predetermined time has elapsed, an equivalent circuit learning process and an open circuit voltage estimation process may be executed.

  Next, details of processing executed in the present embodiment will be described with reference to FIG. The process shown in FIG. 5 is executed, for example, when a predetermined time (for example, several hours) elapses after an unillustrated ignition switch is turned off. When the process shown in FIG. 5 is started, the following steps are executed.

  In step S10, the CPU 10a determines whether or not a predetermined time or more has elapsed since the previous learning process. If it is determined that the predetermined time or more has elapsed (step S10: Yes), the process proceeds to step S11. In the case of (Step S10: No), the process is terminated. For example, if two days or more have elapsed since the previous processing of steps S11 to S13, the determination is Yes and the process proceeds to step S11. Note that this process performs open circuit voltage estimation and equivalent circuit learning at a predetermined period, so that the timing at which the previous value and the current value are obtained is prevented from being unnecessarily separated. Generation of judgment can be prevented.

  In step S11, the CPU 10a executes a process for estimating the value of the open circuit voltage OCV of the secondary battery 14. More specifically, the CPU 10a measures the terminal voltage of the secondary battery 14 with the voltage sensor 11, calculates the polarization voltage, and subtracts it from the measured value, thereby estimating the value of the open circuit voltage OCV.

  In step S <b> 12, the CPU 10 a executes a process of learning the values of elements that constitute the equivalent circuit of the secondary battery 14. More specifically, the CPU 10a drives the discharge circuit 15 to discharge the secondary battery 14 with a predetermined period and a predetermined current, and measures the voltage value and the current value at that time by the voltage sensor 11 and the current sensor 12. For example, by performing learning processing using an algorithm such as a Kalman filter or a support vector machine, the values of elements constituting the equivalent circuit shown in FIG. 3 are obtained.

  In step S13, the CPU 10a stores the value of the open circuit voltage estimated in step S11 and the value of the element of the equivalent circuit learned in step S12 in the RAM 10c. More specifically, the CPU 10a stores the current value of the open circuit voltage estimated in step S11 in the RAM 10c as OCVt, and the conductor resistance, negative reaction resistance, positive reaction resistance, negative electric double layer capacitance learned in step S12. , And the current value of the positive electric double layer capacity is stored in the RAM 10c as Rohmt, Rct1t, Rct2t, C1t, C2t. The value stored in this way is used as the previous value in the next process by the process in step S15.

  In step S14, the CPU 10a determines whether or not the secondary battery 14 is in a fully charged state. If it is determined that the secondary battery 14 is in a fully charged state (step S14: Yes), the process proceeds to step S15. In S14: No), the process ends. More specifically, the CPU 10a charges the secondary battery 14 by substituting the value of the open circuit voltage OCV obtained in step S11 for the relational expression indicating the relationship between the open circuit voltage OCV and the charging rate SOC. The rate SOC is obtained. If the charge rate SOC is 100%, the determination is Yes and the process proceeds to step S15. As described above, when the charging rate is different between the previous time and the current time, the element value and the open circuit voltage of the equivalent circuit may change depending on the charging rate, not the water replenishment. This is to prevent erroneous determination due to such a cause. In addition, instead of 100%, for example, it is determined to be Yes when both charging rates are 90% or more, or when the difference between the previous charging rate and the current charging rate is within several%, Yes is determined. Or you may.

  In step S15, the CPU 10a acquires the value of the element and the value of the open circuit voltage that are learned or estimated by the previous process and stored in the RAM 10c. More specifically, in the previous process, the previous value of the open circuit voltage estimated by the process of step S11 is OCVp, and the conductor resistance, the positive reaction resistance, the negative reaction resistance, and the last learned by the process of step S12, The previous values of the negative electrode electric double layer capacitance and the positive electrode electric double layer capacitance are Rohmp, Rct1p, Rct2p, C1p, and C2p.

  In step S16, the CPU 10a obtains a difference between the previous value OCVp of the open circuit voltage acquired in step S15 and the current value OCVt of the open circuit voltage estimated in step S11 and sets it as ΔOCV (= OCVt−OCVp).

  In step S17, the CPU 10a obtains a difference between the previous value Rohmp of the conductor resistance acquired in step S15 and the current value Rohmt of the conductor resistance learned in step S12, and sets it as ΔRohm (= Rohmt−Rohmp).

  In step S18, the CPU 10a obtains a difference between the previous value Rct1p of the negative electrode reaction resistance acquired in step S15 and the current value Rct1t of the negative electrode reaction resistance learned in step S12 and sets it as ΔRct1 (= Rct1t−Rct1p).

  In step S19, the CPU 10a obtains a difference between the previous value Rct2p of the positive electrode reaction resistance acquired in step S15 and the current value Rct2t of the positive electrode reaction resistance learned in step S12 and sets it as ΔRct2 (= Rct2t−Rct2p).

  In step S20, the CPU 10a obtains a difference between the previous value C1p of the negative electric double layer capacity acquired in step S15 and the current value C1t of the negative electric double layer capacity learned in step S12, and ΔC1 (= C1t−C1p) To do.

  In step S21, the CPU 10a obtains a difference between the previous value C2p of the positive electric double layer capacity acquired in step S15 and the current value C2t of the positive electric double layer capacity learned in step S12, and ΔC2 (= C2t−C2p) To do.

  In step S22, the CPU 10a determines whether or not ΔOCV <Th1 and ΔRohm <Th2 is satisfied, and if it is determined that both of these conditions are satisfied (step S22: Yes), the process proceeds to step S23. In the case (step S22: No), the process is terminated. More specifically, the current value is lower than the previous value of the open circuit voltage by a predetermined value or more (ΔOCV <Th1), and the previous value and the current value of the conductor resistance are not changed by the predetermined value or more ( If ΔRohm <Th2), the determination is Yes and the process proceeds to step S23. That is, when water is replenished to the electrolyte solution of the secondary battery 14, the open circuit voltage OCV is decreased as shown in FIG. 4, while the conductor resistance Rohm hardly changes. Determine the presence or absence.

  In step S23, the CPU 10a proceeds to step S24 if at least one of ΔRct1 <Th3, ΔRct2> Th4, ΔC1 <Th5, and ΔC2 <Th6 is satisfied (step S23: Yes), and otherwise (step S23). In S24: No), the process ends. More specifically, as shown in FIG. 4, when water is replenished, Rct1 decreases, Rct2 increases, C1 decreases, and C2 decreases, so when at least one of these holds true Determines that water has been replenished (Yes), and proceeds to step S24.

  In step S24, the CPU 10a notifies the higher-level device that water replacement has been detected. More specifically, the CPU 10a notifies the ECU (not shown), which is a higher-level device, that the water replacement has been detected via the communication unit 10d. When the ECU receives such a notification, for example, the ECU notifies the user that water replenishment has been detected and notifies the display device. Thereby, the user can know that water replenishment has been detected.

  In step S <b> 25, the CPU 10 a executes a process for initializing information indicating the state of the secondary battery 14. More specifically, the CPU 10a determines the element value of the equivalent circuit of the secondary battery 14 stored in the RAM 10c, the usage history of the secondary battery 14, the charging rate of the secondary battery 14, and the reference capacity of the secondary battery 14. Initialize information such as.

  According to the above process, for example, when the process shown in FIG. 5 is performed after the electrolyte solution of the secondary battery 14 is replenished, the element value of the equivalent circuit acquired before the replenishment and When the open circuit voltage value is the previous value, the element value of the equivalent circuit and the open circuit voltage value acquired after rehydration are the current values, and these changes satisfy the conditions of step S22 and step S23, In step S24, the higher-level device is notified, and information indicating the state of the secondary battery 14 is initialized in step S25.

  As described above, according to the embodiment of the present invention, water is replenished to the electrolyte of the secondary battery 14 based on the value of the element of the equivalent circuit of the secondary battery 14 and the value of the open circuit voltage. Since it has been determined whether or not water has been added, the presence or absence of water replenishment can be reliably detected with a simple configuration. In addition, when water replenishment is detected, information indicating the state of the secondary battery 14 is initialized. Therefore, it is possible to reliably cope with a state change caused by water replenishment and to accurately detect the state of the secondary battery. Can do. In addition, since the open circuit voltage estimation process and the equivalent circuit learning process are executed at a predetermined cycle based on the determination in step S10, these processes are not executed for a long period of time. Therefore, it is possible to prevent erroneous changes from accumulating and erroneous determinations.

(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 determination is made based on the reaction resistances Rct1, Rct2 and the electric double layer capacitances C1, C2 in step S22 of FIG. 5, but the electric double layer capacitances C1, C2 are determined based on the reaction resistance Rct1. , Rct2, the measurement error is large, so that the electric double layer capacitances C1, C2 may be excluded from the determination targets, and the determination may be made based only on the reaction resistances Rct1, Rct2. When excluding the electric double layer capacitances C1 and C2 from the determination targets, not only the process proceeds to step S24 when any of the conditions (ΔRct1 <Th3 or ΔRct2> Th4) regarding the reaction resistances Rct1 and Rct2 is satisfied, The process may proceed to step S24 when both of these conditions are satisfied. In some cases, the determination in step S23 of FIG. 5 may be omitted, and the presence / absence of water replenishment may be determined only by the determination in step S22.

  Also, ΔOCV, ΔRohm, ΔRct1, ΔRct2, ΔC1, and ΔC2 are multiplied by a weighting coefficient (including “0”) and added, and the obtained result is compared with a predetermined threshold value to make a determination. Also good.

  Further, in the above embodiment, the determination is made when the secondary battery 14 is fully charged. For example, the processing is performed when the charge rate SOC at the time of measuring the previous value and the current value is equal. May be executed. For example, when the charge rate SOC when measuring the previous value is 90%, the current value may be measured and determined when the SOC becomes 90%.

  Further, in the process shown in FIG. 5, the information indicating the state of the secondary battery 14 is initialized immediately after notifying the host device. If it is certain, information indicating the state of the secondary battery 14 may be initialized.

DESCRIPTION OF SYMBOLS 1 Secondary battery state detection apparatus 10 Control part 10a CPU (a search means, calculation means, determination means)
10b ROM
10c RAM
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 (7)

In a secondary battery state detection device that detects the state of a secondary battery mounted on a vehicle,
Obtaining means for obtaining an element value of an equivalent circuit of the secondary battery;
Calculating means for calculating an open circuit voltage of the secondary battery;
Whether the secondary battery electrolyte has been replenished from the change in the element value of the equivalent circuit obtained by the obtaining means and the change in the open circuit voltage calculated by the calculation means Determining means for determining
A secondary battery state detection device comprising:   The determination means determines that water replenishment has been performed when the conductor resistance constituting the equivalent circuit does not change more than a predetermined value and the open circuit voltage has decreased by a predetermined value or more. The secondary battery state detection device according to claim 1. The determination means has no change of a conductor resistance constituting the equivalent circuit more than a predetermined value, and the open circuit voltage changes more than a predetermined value,
The negative electrode reaction resistance becomes lower than a certain value, the positive electrode reaction resistance becomes higher than a certain value, the negative electrode electric double layer capacity becomes lower than a certain value, and the positive electrode electric double layer capacity becomes lower than a certain value. The secondary battery state detection device according to claim 2, wherein when at least one is detected, it is determined that water has been replenished.   The secondary battery state according to any one of claims 1 to 3, wherein information indicating a state of the secondary battery is initialized when it is determined that the water is replenished by the determination unit. Detection device.   The information indicating the state of the secondary battery is at least one of an element value of the equivalent circuit, a usage history of the secondary battery, a charging rate of the secondary battery, and a reference capacity of the secondary battery. The secondary battery state detection apparatus of Claim 4 characterized by these.   The secondary battery state detection device according to any one of claims 1 to 5, wherein when it is determined that water has been replenished by the determination means, a higher-level device is notified. In a secondary battery state detection method for detecting a state of a secondary battery mounted on a vehicle,
A obtaining step for obtaining an element value of an equivalent circuit of the secondary battery;
A calculation step of calculating an open circuit voltage of the secondary battery;
Whether the secondary battery electrolyte has been replenished based on the change in the element value of the equivalent circuit obtained in the obtaining step and the change in the open circuit voltage calculated in the calculation step A determination step for determining
A secondary battery state detection method comprising:

Images