JP2017188277A - Secondary battery state detector, and method for detection of secondary battery state - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly detect the gelation of an electrolyte solution of a secondary battery.SOLUTION: A secondary battery state detector 1 for detecting a secondary battery state comprises: measurement means for measuring an impedance of a secondary battery 14 (including a discharge circuit 15, a voltage sensor 11 and a current sensor 12); and estimation means (a control part 10) for estimating, based on a value of the impedance measured by the measurement means, whether or not an electrolyte solution of the secondary battery is gelated.SELECTED DRAWING: Figure 1

Description

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

  Patent Document 1 discloses a technique for detecting freezing of an electrolytic solution by detecting a change in an open circuit voltage of a secondary battery.

JP 2006-155916 A

  By the way, polarization occurs after the secondary battery is charged or discharged, and it takes a certain time to eliminate this polarization. Since such polarization also affects the open circuit voltage of the secondary battery, it is possible to accurately detect whether or not the electrolyte of the secondary battery is frozen when polarization occurs. There is a problem that it is not possible.

  The present invention has been made in view of the above situation, and provides a secondary battery state detection device and a secondary battery state detection method capable of accurately detecting freezing of the electrolyte of the secondary battery. The purpose is to do.

In order to solve the above-described problems, the present invention provides a secondary battery state detection device that detects a state of a secondary battery, a measurement unit that measures impedance of the secondary battery, and the impedance that is measured by the measurement unit. And estimating means for estimating whether or not the electrolyte solution of the secondary battery is frozen based on the value of.
According to such a configuration, it becomes possible to accurately detect freezing of the electrolyte solution of the secondary battery.

Further, the present invention provides the estimation means when the ratio of the increase in impedance to the decrease in the temperature of the electrolyte is relatively large compared to the case where the electrolyte is not frozen. It is estimated that the electrolytic solution is frozen or freezing has started.
According to such a configuration, freezing of the electrolyte solution of the secondary battery can be accurately detected by a simple determination method.

Further, according to the present invention, the estimation means includes a difference value between the impedance Z1 when the temperature of the electrolytic solution is T1 and the impedance Z2 when the temperature of the electrolytic solution is T2 (<T1) ( When Z2-Z1) is larger than a predetermined threshold Th ((Z2-Z1)> Th), it is estimated that the electrolytic solution is frozen or has started to freeze.
According to such a configuration, freezing of the electrolyte solution of the secondary battery can be accurately detected by simple calculation.

Further, according to the present invention, the estimating means is a ratio of the impedance Z1 when the temperature of the electrolytic solution is T1 and the impedance Z2 when the temperature of the electrolytic solution is T2 (<T1) (Z2 / When Z1) is larger than a predetermined threshold Th ((Z2 / Z1)> Th), it is estimated that the electrolytic solution is frozen or has started to freeze.
According to such a configuration, freezing of the electrolyte solution of the secondary battery can be accurately detected by simple calculation.

Further, in the present invention, the estimation means is a value obtained by the impedance Z1 when the temperature of the electrolytic solution is T1 and the impedance Z2 when the temperature of the electrolytic solution is T2 (<T1). When ((Z2-Z1) / (T2-T1)) is smaller than the predetermined threshold Th (((Z2-Z1) / (T2-T1)) <Th), the electrolyte is frozen or frozen Is estimated to have started.
According to such a configuration, freezing of the electrolyte solution of the secondary battery can be accurately detected by simple calculation.

Further, according to the present invention, the estimating means includes the impedance Z1 when the temperature of the electrolytic solution is T1, the impedance Z2 when the temperature of the electrolytic solution is T2 (<T1), and the electrolytic solution. The value obtained based on the impedance Z3 when the temperature of T3 (<T2) and the impedance Z4 when the temperature of the electrolyte is T4 (<T3) ((Z4-Z3) / ((T4-T3)-(Z2-Z1) / (T2-T1)) is smaller than a predetermined threshold Th (((Z4-Z3) / (T4-T3)-(Z2-Z1) / (T2-T1)) )) <Th), it is estimated that the electrolyte solution is frozen or has started to freeze.
According to such a configuration, freezing of the electrolyte solution of the secondary battery can be accurately detected by simple calculation.

Further, according to the present invention, the estimating means includes the impedance Z1 when the temperature of the electrolytic solution is T1, the impedance Z2 when the temperature of the electrolytic solution is T2 (<T1), and the electrolytic solution. The value obtained based on the impedance Z3 when the temperature of T3 (<T2) and the impedance Z4 when the temperature of the electrolyte is T4 (<T3) ((Z4-Z3) / The absolute value of (T4-T3) / (Z2-Z1) / (T2-T1)) is greater than a predetermined threshold Th (| (Z4-Z3) / (T4-T3) / (Z2-Z1) / ( When T2-T1) |> Th), it is estimated that the electrolytic solution is frozen or has started to freeze.
According to such a configuration, freezing of the electrolyte solution of the secondary battery can be accurately detected by simple calculation.

Further, according to the present invention, the estimating means sets the impedance at a predetermined past time when the electrolyte of the secondary battery is not frozen as Z1, and sets the current impedance measured by the impedance measuring means as Z2. Sometimes, when the difference value (Z2−Z1) obtained by these is larger than a predetermined threshold Th ((Z2−Z1)> Th), it is estimated that the electrolytic solution is frozen or freezing has started. Features.
According to such a configuration, freezing of the electrolyte solution of the secondary battery can be accurately detected by simple calculation.

Further, according to the present invention, the estimating means sets the impedance at a predetermined past time when the electrolyte of the secondary battery is not frozen as Z1, and sets the current impedance measured by the impedance measuring means as Z2. When these ratios (Z2 / Z1) are larger than a predetermined threshold Th ((Z2 / Z1)> Th), it is estimated that the electrolytic solution is frozen or freezing has started. .
According to such a configuration, freezing of the electrolyte solution of the secondary battery can be accurately detected by simple calculation.

In the present invention, the estimating means sets the impedance at a predetermined measurement time t1 to Z1, sets the open circuit voltage of the secondary battery to V1, and sets the impedance at a predetermined measurement time t2 (> t1) to Z2. When the open circuit voltage of the secondary battery is V2, the value ((Z2-Z1) / (V2-V1)) obtained by these is greater than 0 (((Z2-Z1) / ( In the case of V2-V1))> 0), it is estimated that the electrolytic solution is frozen or freezing has started.
According to such a configuration, freezing of the electrolyte solution of the secondary battery can be accurately detected by simple calculation.

In addition, the present invention has a presentation means for presenting to the outside that the freezing has started when the estimating means estimates that the electrolyte of the secondary battery is frozen or has started freezing. It is characterized by that.
According to such a configuration, it is possible to notify the user that the electrolyte solution of the secondary battery is frozen.

Further, the present invention provides a secondary battery state detection method for detecting a state of a secondary battery, based on a measurement step of measuring the impedance of the secondary battery, and a value of the impedance measured in the measurement step, An estimation step of estimating whether or not the electrolyte of the secondary battery is frozen.
According to such a method, it becomes possible to accurately detect the freezing of the electrolyte solution 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 deterioration estimation method which can detect correctly the freezing of the electrolyte solution of a 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 for demonstrating operation | movement of embodiment shown in FIG. It is a figure for demonstrating operation | movement of embodiment shown in FIG. It is a flowchart for demonstrating operation | movement of embodiment shown in FIG. It is a figure for demonstrating other embodiment. It is a figure for demonstrating other embodiment. It is a figure for demonstrating other embodiment. It is a figure for demonstrating other embodiment. It is a figure for demonstrating other embodiment.

  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 indicates 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 power generation voltage of the alternator 16 to control the power generation voltage. The charging state of the secondary battery 14 is controlled. 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 electrolyte solution of the secondary battery 14 or the ambient 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 constituted by a secondary battery having an electrolytic solution, for example, a lead storage battery, a nickel cadmium battery, or a nickel metal hydride battery. The secondary battery 14 is charged by the alternator 16 and drives the starter motor 18 to start the engine. At the same time, power is supplied 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 alternator 16 is controlled by the control unit 10 and can adjust the generated voltage.

  The engine 17 is constituted by, 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. To generate electric 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 constituted by, for example, an electric steering motor, a defogger, a seat heater, 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 parameters 10ca such as mathematical formulas or tables described later. The communication unit 10d communicates with an upper device such as an ECU (Electronic Control Unit) and notifies the detected information or control information to the upper device. 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 takes them in, and supplies drive current to the discharge circuit 15, the alternator 16, the starter motor 18, and the like. Supply them to control them.

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

  First, the operation principle of the embodiment will be described. FIG. 3 is a diagram illustrating a relationship between the temperature of the electrolytic solution and the impedance of the secondary battery 14 when the secondary battery 14 is a lead storage battery. In FIG. 3, the horizontal axis represents the normalized temperature of the electrolyte solution of the secondary battery 14, and the vertical axis represents the normalized impedance of the secondary battery 14. In FIG. 3, when the temperature of the electrolytic solution of the secondary battery 14 decreases, the impedance gradually increases, and when the electrolytic solution starts freezing, the impedance starts to increase rapidly as shown by the dotted circle. Therefore, in the present embodiment, when the rate of increase in impedance with respect to the decrease in the temperature of the electrolytic solution is relatively large as compared with the case where the electrolytic solution is not frozen (indicated by a dotted circle), It is presumed that the electrolyte has started to freeze.

  Here, the resistance which is a real component of the impedance of the secondary battery 14 is configured by a conductive resistance and a liquid resistance. In general, since the conductor resistance and the liquid resistance are not easily affected by the polarization, when the freezing of the electrolytic solution is estimated using the impedance of the secondary battery 14, the freezing is accurately determined regardless of the presence or absence of the polarization. can do.

  Next, the detailed operation of the embodiment of the present invention will be described. In the embodiment of the present invention, the CPU 10a calculates a value obtained by adding a predetermined margin ΔT (for example, 10 ° C.) to the assumed freezing temperature (for example, −30 ° C.) of the secondary battery 14, The temperature is set to a temperature Tf at which the electrolytic solution freezing monitoring process is started. In the present example, Tf = −20 ° C. (= −30 + 10 ° C.) is obtained.

  Next, as shown in FIG. 4, the CPU 10a measures the impedance Z1 when the temperature of the electrolyte (or environment) of the secondary battery 14 is T1 (for example, 25 ° C.) as the standard temperature. As a method for measuring impedance, for example, a method disclosed in JP2009-002957A can be used. More specifically, for example, after erasing the polarization history by performing a constant current instantaneous discharge cycle satisfying a predetermined condition obtained by an experiment or the like to erase the polarization history, the open circuit voltage is measured and set to Vo. After that, constant current instantaneous discharge by the current I by the discharge circuit 15 is executed, and the minimum voltage Vm at that time is measured. Then, the impedance Z1 is calculated by the following equation (1).

  Z1 = (Vo−Vm) / I (1)

  Since the impedance value varies depending on the temperature, it is desirable to detect the temperature of the electrolyte solution of the secondary battery 14 and correct the impedance value calculated by the above formula (1) to the impedance value at the standard temperature, for example. . The impedance value corrected by the temperature in this way is stored as the parameter 10ca in the RAM 10c, for example.

  Next, when the engine 17 is stopped after the vehicle is stopped, the CPU 10a detects the temperature T of the electrolytic solution with reference to the output of the temperature sensor 13, and the temperature T is equal to or lower than the above-described Tf (T ≦ Tf). In such a case, the freezing monitoring process is executed on the assumption that the electrolytic solution may freeze.

  In the freeze monitoring process, the CPU 10a detects the impedance of the secondary battery 14 at a predetermined cycle by the same process as described above, and sets the detection result to Z2. And the temperature T2 at that time is also detected. The frequency of detecting the impedance is, for example, performed at a long interval when the temperature of the electrolytic solution is sufficiently higher than Tf, and at a short interval when the temperature of the electrolytic solution is close to Tf. You may make it do.

  Next, the CPU 10a calculates a difference value (Z2−Z1) between the impedances Z1 and Z2, and determines whether or not the difference value (Z2−Z1) is larger than a predetermined threshold Th. As shown in FIG. 4, when the temperature falls below the freezing start point indicated by the broken-line circle, the impedance of the secondary battery 14 increases rapidly. Therefore, when the electrolytic solution starts to freeze, the difference value (Z2−Z1) is At a certain time, the threshold value Th becomes larger than the threshold value Th (for example, 0.4 in the example of FIG. 4).

  If the CPU 10a determines that the difference value (Z2-Z1) is greater than the predetermined threshold Th, the CPU 10a determines that the electrolytic solution has started to freeze, and, for example, via the communication unit 10d, the upper ECU (Electric Control Unit) is notified of the start of freezing. As a result, the host ECU notifies the user, for example, of the start of freezing of the electrolytic solution by visual information or auditory information, for example. Alternatively, when the communication unit 10d can perform communication using infrared rays, radio waves, or the like, a visual indication indicating the start of freezing of the electrolyte with respect to a terminal device (for example, a remote controller or a mobile phone) at hand of the user. Send information or auditory information. Alternatively, when the secondary battery 14 has a freezing prevention heater, the host ECU prevents the electrolyte from freezing by energizing the heater. In addition, since the freezing temperature decreases when the specific gravity of dilute sulfuric acid, which is a component of the electrolytic solution, is large, for example, the engine 17 is started to charge the secondary battery 14, and the specific rate is increased by increasing the charging rate. Alternatively, for example, charging by an external charger (a charger using commercial power) may be started.

  As described above, in the embodiment, the start of freezing of the electrolytic solution is estimated using the fact that the impedance increases when the electrolytic solution freezes. As a result, by using an impedance that is less likely to be affected by polarization compared to the open circuit voltage, it is possible to reliably detect the freezing of the electrolyte even when polarization occurs. Note that when measuring the impedance, it is possible to further reduce the influence of polarization by measuring with a high-frequency current.

  Next, processing executed in the embodiment will be described with reference to FIG. When the flowchart shown in FIG. 5 is started, the following steps are executed.

  In step S10, the CPU 10a adds a predetermined margin ΔT (for example, 10 ° C.) to the assumed freezing temperature (for example, −30 ° C.) of the secondary battery 14, and performs the electrolyte freezing monitoring process. The starting temperature Tf is calculated. The freezing temperature varies depending on the concentration of the electrolytic solution of the secondary battery 14. The concentration of the electrolytic solution varies depending on, for example, the amount of the electrolytic solution, the charging rate, and the state of deterioration. Here, when the amount of the electrolytic solution is decreasing, the concentration increases if the charging rate or the like is constant, and as a result, the freezing temperature decreases. On the other hand, when the charging rate is low or the deterioration progresses, the concentration of the electrolytic solution decreases, and in such a case, the freezing temperature increases. Therefore, an assumed freezing temperature may be appropriately set according to the charging rate and the degree of deterioration. Specifically, the assumed freezing temperature may be set high when the charging rate is low or when the deterioration progresses.

  In step S11, the CPU 10a detects the impedance Z1 of the secondary battery 14 at a predetermined time. More specifically, for example, when the electrolyte reaches a standard temperature (for example, 25 ° C.), the CPU 10a performs the polarization history erasure by performing an instantaneous current discharge cycle, erases the polarization history, and then sets the open circuit voltage. Measured to be Vo. After that, constant current instantaneous discharge by the current I by the discharge circuit 15 is executed, and the minimum voltage Vm at that time is measured. And impedance Z1 is calculated | required by Formula (1) mentioned above.

  In step S12, the CPU 10a detects the temperature T of the electrolytic solution. More specifically, the CPU 10a refers to the output of the temperature sensor 13 and detects the temperature T of the electrolytic solution.

  In step S13, the CPU 10a determines whether or not the temperature T of the electrolytic solution detected in step S12 is higher than the temperature Tf set in step S10 to start the freeze monitoring process, and if T> Tf is satisfied (step S13). In step S13: Y), the process returns to step S11 to repeat the same process as described above. In other cases (step S13: N), the process proceeds to step S14. For example, when the temperature T of the electrolytic solution is equal to or lower than Tf, it is determined as N and the process proceeds to step S14.

  In step S14, the CPU 10a detects the impedance Z2 of the secondary battery 14 at that time (current). More specifically, the CPU 10a detects the impedance Z2 of the secondary battery 14 by the same process as in step S11 described above.

  In step S15, the CPU 10a calculates a difference value (Z2-Z1) between the impedance Z2 obtained at step S14 and the impedance Z1 obtained at step S11 at the predetermined time, and the difference value is larger than the threshold Th. It is determined whether ((Z2-Z1)> Th). If it is determined that it is large (step S15: Y), the process proceeds to step S16. Otherwise (step S15: N), the process returns to step S11. Repeat the same process as described above.

  In step S16, the CPU 10a outputs a freeze detection signal. More specifically, the CPU 10a outputs a freeze detection signal to a host device (not shown) via the communication unit 10d. As a result, the host device notifies the user that freezing has been detected, or in order to prevent the freezing from progressing, the engine 17 is started to increase the charging rate, or the secondary battery 14 is The heater for warming can be energized.

  According to the above processing, freezing of the electrolyte solution of the secondary battery 14 can be accurately detected regardless of the polarization state, for example. When freezing is detected, the progress of freezing can be prevented by notifying the user or starting the engine 17.

(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 presence / absence of freezing is estimated by comparing the difference value (Z2−Z1) between the impedance Z1 obtained in step S11 of FIG. 5 and the impedance Z2 obtained in step S14 and the threshold Th. However, in addition to this, for example, the presence or absence of freezing may be estimated based on a comparison between the ratio of impedances Z1 and Z2 (Z2 / Z1) and the threshold Th. That is, as shown in FIG. 4, when the freezing has not started, the impedances Z1 and Z2 have substantially the same value, and thus Z2 / Z1≈1, but when the freezing starts, Z2> Z1, so Z2 / Z1 is a value greater than 1. Therefore, it may be determined that freezing has started when Z2 / Z1 is equal to or greater than a predetermined threshold Th greater than 1.

  Further, based on the impedance Z1 detected in step S11 and the electrolyte temperature T1 at that time, and the impedance Z2 detected in step S14 and the electrolyte temperature T2 at that time shown in FIG. The slope of the curve ((Z2-Z1) / (T2-T1)) may be calculated, and the presence or absence of freezing may be determined based on this slope. FIG. 6 is a diagram showing the relationship between the temperature of the electrolyte solution of the secondary battery 14 and the value of ((Z2-Z1) / (T2-T1)). In addition, the horizontal axis of FIG. 6 shows the normalized temperature of the electrolyte solution of the secondary battery 14, and the vertical axis shows the value of ((Z2-Z1) / (T2-T1)). As shown in FIG. 6, when the electrolytic solution is not frozen, the slope is close to zero. When the electrolytic solution starts to freeze, as indicated by a broken-line circle, the value first fluctuates to a minus value and then greatly fluctuates to a plus or minus value. Therefore, the value of ((Z2-Z1) / (T2-T1)) is compared with a predetermined threshold Th, and when ((Z2-Z1) / (T2-T1)) <Th, freezing starts. You may make it estimate that it was.

  Further, as shown in FIG. 7, impedances Z1, Z2 and temperatures T1, T2 are obtained at times t1, t2 (t1 <t2), and impedances Z3, Z4 and temperatures T3, T3 are obtained at times t3, t4 (t3 <t4). T4 is obtained, and based on these values, a value of ((Z4-Z3) / (T4-T3)-(Z2-Z1) / (T2-T1)) is calculated, and ((Z4 When -Z3) / (T4-T3)-(Z2-Z1) / (T2-T1)) <Th, it may be estimated that freezing has started. More specifically, in FIG. 7, the value of ((Z4-Z3) / (T4-T3)) at the time when freezing starts is changed to the previous value of ((Z2-Z1) / (T2-T1)). In comparison, since the values are small, these difference values become negative values. Therefore, the presence or absence of freezing can be determined by comparing the difference value with the threshold value Th. In FIG. 7, the horizontal axis indicates the normalized time, and the vertical axis indicates the value of ((Z4-Z3) / (T4-T3)-(Z2-Z1) / (T2-T1)). .

  Further, as shown in FIG. 8, impedances Z1, Z2 and temperatures T1, T2 are obtained at times t1, t2 (t1 <t2), and impedances Z3, Z4 and temperatures T3, T3 are obtained at times t3, t4 (t3 <t4). T4 is obtained, and based on these values, a value of ((Z4-Z3) / (T4-T3) / (Z2-Z1) / (T2-T1)) is calculated, and ((Z4 When -Z3) / (T4-T3) / (Z2-Z1) / (T2-T1))> Th, it may be estimated that freezing has started. More specifically, in FIG. 8, ((Z4-Z3) / (T4-T3)) at the time when freezing starts is absolute compared to the previous ((Z2-Z1) / (T2-T1)). Since the value is large, the presence or absence of freezing can be estimated by comparing the absolute value with the threshold Th. In FIG. 8, the horizontal axis indicates the normalized time, and the vertical axis indicates the value of ((Z4-Z3) / (T4-T3) / (Z2-Z1) / (T2-T1)). .

  As shown in FIG. 9, when the impedance Z1 at a predetermined time t1 (for example, when a new secondary battery 14 is mounted) is used as a reference, the impedance Z2 at the time t2 (> t1) When the difference value (Z2−Z1) is larger than the predetermined threshold Th, it may be estimated that freezing has started. Of course, instead of the difference value, the ratio (Z2 / Z1) and the predetermined threshold Th may be used to determine that freezing has started when (Z2 / Z1)> Th. In addition, the horizontal axis of FIG. 9 has shown the normalized time, and the vertical axis | shaft has shown the value of (Z2-Z1).

  Also, as shown in FIG. 10, the impedance Z1 and the open circuit voltage V1 at a certain time t1 are obtained, and the impedance Z2 and the open circuit voltage V2 at a time t2 (> t1) are obtained, and based on these values ((Z2 -Z1) / (V2-V1)) is obtained, and when this value is larger than a predetermined threshold Th (for example, Th = 0), it may be determined that freezing has started. In addition, the horizontal axis of FIG. 10 shows the normalized time, and the vertical axis shows the value of ((Z2-Z1) / (V2-V1)).

  In the above embodiment, the description has been made by paying attention to the real number component of the impedance. However, the determination of freezing may be performed with reference to the imaginary number component. For example, an equivalent circuit configured by connecting resistance elements in series to a resistance element and a capacitor element connected in parallel is an equivalent circuit of the secondary battery 14, and the equivalent circuit is used as, for example, a learning process or a fitting process. Thus, each element value which is a constituent element is obtained. Then, the presence or absence of freezing may be determined based on the obtained change in the element value.

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

Claims (12)

In the secondary battery state detection device for detecting the state of the secondary battery,
Measuring means for measuring the impedance of the secondary battery;
Estimating means for estimating whether or not the electrolyte of the secondary battery is frozen based on the impedance value measured by the measuring means;
A secondary battery state detection device comprising:   The estimation means determines that the electrolyte solution is frozen when the rate of increase in the impedance with respect to a decrease in the temperature of the electrolyte solution is relatively large compared to the case where the electrolyte solution is not frozen. The secondary battery state detection device according to claim 1, wherein it is estimated that the battery is frozen or has started to freeze.   The estimation means has a predetermined difference value (Z2−Z1) between the impedance Z1 when the temperature of the electrolytic solution is T1 and the impedance Z2 when the temperature of the electrolytic solution is T2 (<T1). 3. The secondary battery state detection device according to claim 2, wherein the electrolyte solution is estimated to be frozen or freezing started when the threshold value Th is greater than (Th 2)> Th. .   The estimation means is configured such that a ratio (Z2 / Z1) of the impedance Z1 when the temperature of the electrolytic solution is T1 and the impedance Z2 when the temperature of the electrolytic solution is T2 (<T1) is a predetermined threshold value. 3. The secondary battery state detection device according to claim 2, wherein when it is larger than Th ((Z 2 / Z 1)> Th), it is estimated that the electrolytic solution is frozen or freezing has started.   The estimation means obtains a value ((Z2−Z1)) obtained from the impedance Z1 when the temperature of the electrolytic solution is T1 and the impedance Z2 when the temperature of the electrolytic solution is T2 (<T1). / (T2-T1)) is smaller than a predetermined threshold Th (((Z2-Z1) / (T2-T1)) <Th), it is estimated that the electrolyte is frozen or has started to freeze. The secondary battery state detection device according to claim 2.   The estimation means includes the impedance Z1 when the temperature of the electrolytic solution is T1, the impedance Z2 when the temperature of the electrolytic solution is T2 (<T1), and the temperature of the electrolytic solution is T3 (< T2) and the impedance Z4 when the temperature of the electrolyte is T4 (<T3) ((Z4-Z3) / (T4-T3) − When (Z2-Z1) / (T2-T1)) is smaller than a predetermined threshold Th (((Z4-Z3) / (T4-T3)-(Z2-Z1) / (T2-T1))) <Th) The secondary battery state detection device according to claim 2, wherein it is estimated that the electrolytic solution is frozen or has started to freeze.   The estimation means includes the impedance Z1 when the temperature of the electrolytic solution is T1, the impedance Z2 when the temperature of the electrolytic solution is T2 (<T1), and the temperature of the electrolytic solution is T3 (< T2) and the impedance Z4 when the electrolyte temperature is T4 (<T3) and the value ((Z4-Z3) / (T4-T3) / The absolute value of (Z2-Z1) / (T2-T1)) is greater than a predetermined threshold Th (| (Z4-Z3) / (T4-T3) / (Z2-Z1) / (T2-T1) |> 3. The secondary battery state detection device according to claim 2, wherein in the case of Th), it is estimated that the electrolytic solution is frozen or has started to freeze.   The estimation means is obtained by setting the impedance at a predetermined past time when the electrolyte of the secondary battery is not frozen as Z1 and the current impedance measured by the impedance measurement means as Z2. The difference value (Z2-Z1) is larger than a predetermined threshold value Th ((Z2-Z1)> Th), and it is estimated that the electrolyte solution is frozen or has started to freeze. The secondary battery state detection apparatus as described in.   The estimation means sets the impedance at a predetermined past time when the electrolyte of the secondary battery is not frozen as Z1, and the ratio when the current impedance measured by the impedance measurement means as Z2 ( 3. The method according to claim 2, wherein when Z2 / Z1) is greater than a predetermined threshold Th ((Z2 / Z1)> Th), it is estimated that the electrolyte is frozen or has started to freeze. Secondary battery state detection device.   The estimation means sets the impedance at a predetermined measurement time t1 to Z1, sets the open circuit voltage of the secondary battery to V1, sets the impedance at a predetermined measurement time t2 (> t1) to Z2, and sets the secondary When the open circuit voltage of the battery is V2, the value ((Z2-Z1) / (V2-V1)) obtained by these is larger than 0 (((Z2-Z1) / (V2-V1))> The secondary battery state detection device according to claim 2, wherein in the case (0), it is estimated that the electrolytic solution is frozen or has started to freeze.   When the estimation means estimates that the electrolyte solution of the secondary battery is frozen or has started to freeze, it has a presentation means for presenting to the outside that the freezing has started. Item 11. The secondary battery state detection device according to any one of Items 1 to 10. In the secondary battery state detection method for detecting the state of the secondary battery,
A measurement step of measuring the impedance of the secondary battery;
An estimation step for estimating whether or not the electrolyte of the secondary battery is frozen based on the impedance value measured in the measurement step;
A secondary battery state detection method comprising:

Images