WO2005116675A1

WO2005116675A1 - Secondary battery residual-capacity estimating method and apparatus

Info

Publication number: WO2005116675A1
Application number: PCT/JP2005/009257
Authority: WO
Inventors: Mitsunori Ishii; Keiji Katayama
Original assignee: Nec Lamilion Energy, Ltd.; Fuji Jukogyo Kabushiki Kaisha
Priority date: 2004-05-26
Filing date: 2005-05-20
Publication date: 2005-12-08
Also published as: JPWO2005116675A1; JP4880451B2

Abstract

The charging and discharging currents of a secondary battery are monitored, and an integrating arithmetic is executed based on those charging and discharging currents, thereby continuously calculating a first residual capacity value. At the same time, the timing at which the secondary battery switches from its charging to its discharging is detected, and an integration of the discharging current is commenced at the detected timing. When the integrated value reaches a predetermined threshold value, the terminal voltage of the secondary battery is taken and regarded as an open circuit voltage, and a second residual capacity value is determined based on the open circuit voltage. The second residual capacity value is used to update the first residual capacity value. The first residual capacity value then is externally outputted as the residual capacity of the secondary battery.

Description

Specification

Method and apparatus for estimating remaining capacity of secondary battery

Technical field

[0001] The present invention relates to the remaining capacity of various secondary batteries represented by lithium ion secondary batteries (so

The present invention relates to a method and apparatus for estimating a state of charge (C), and a battery pack including such a remaining capacity estimating apparatus.

Background art

[0002] In recent years, secondary batteries such as lithium ion secondary batteries and nickel metal hydride secondary batteries have come to be used as power sources for electric motors for power applications.

[0003] As an application of such a motor drive of a secondary battery such as a lithium ion secondary battery, for example, there is an application in a hybrid vehicle. A hybrid vehicle generally includes an engine that is an internal combustion engine, a generator driven by the engine, a secondary battery, and an electric motor. There are several types of drive systems in hybrid vehicles.However, in some types of drive systems, in the case of hybrid vehicles, the secondary battery is charged with the power obtained from the generator, and when the vehicle accelerates or climbs a hill, In addition to the electric power from the generator, the electric power obtained by discharging the secondary battery is supplied to the motor. In a hybrid vehicle of another drive system, the drive wheels are directly driven by the engine, and the drive of the drive wheels is assisted by the motor output during acceleration or climbing a hill. In these hybrid vehicles, in order to further improve energy efficiency, when braking the vehicle, the electric motor operates as a generator to function as a regenerative brake, and the energy obtained at that time is also used by the secondary battery. To charge the battery.

[0004] In the case of a hybrid vehicle, in practice, control is performed such that the remaining capacity of the secondary battery is always within a predetermined range. Specifically, for example, when the remaining capacity becomes 20% or less, the engine is started, the generator generates power, and the power is used to charge the secondary battery. Then, for example, when the remaining capacity becomes 80% or more, make sure that the secondary battery is not charged any more. As described above, since it is necessary to control charging and discharging according to the remaining capacity of the secondary battery, it is not necessary to constantly monitor the remaining capacity of the secondary battery. Not be. More specifically, the remaining capacity is calculated at tens of milliseconds at intervals of several seconds.

[0005] In principle, the remaining capacity of a secondary battery can be obtained from the difference between the charged amount and the discharged amount. The remaining capacity of the secondary battery was determined by measuring the values of the above and integrating the measured values. Also, when the secondary battery is a lithium ion secondary battery or the like, it is known that there is a certain relationship between the open circuit voltage of the secondary battery and the remaining capacity, and the open circuit voltage of the secondary battery is known. In some cases, the remaining capacity is estimated by measuring the pressure. However, when rechargeable batteries are applied to automobiles and hybrid vehicles, large currents may flow in a short time due to the inrush current of the motor, etc. If it is decided to accumulate the charge / discharge current value to obtain the remaining capacity due to reasons such as difficulty in obtaining a sensor, a non-negligible cumulative error may occur.

[0006] On the other hand, when estimating the remaining capacity based on the open circuit voltage of the secondary battery, the problem of accumulation of errors does not occur. However, during normal use of the secondary battery, there is a charge / discharge current, so the open circuit voltage cannot be measured continuously. Therefore, the present inventors have found that in applications such as hybrid vehicles, the discharge and charge of the secondary battery are frequently switched to switch the direction of the current flowing through the secondary battery, and the switching is instantaneous. Paying attention to the fact that the charge / discharge current sometimes becomes zero, we have already proposed a method for accurately estimating the remaining capacity in Japanese Patent Application: Japanese Patent Application No. 2003-34967 (Japanese Patent Application Laid-Open No. 2004-245673). I have. In this method, the remaining capacity is continuously calculated by integrating the charge / discharge current of the secondary battery, and the charge / discharge current of the secondary battery is changed at a timing when the charge / discharge current becomes zero, for example, at a timing when the charge / discharge is switched. Measure the terminal voltage, use it as the open circuit voltage, estimate the remaining capacity at that time, and update the remaining capacity value calculated by current integration with the estimated value.

[0007] Strictly speaking, the open circuit voltage is strictly equal to the positive electrode and negative electrode when a sufficient time has elapsed since charging and discharging of the secondary battery stopped and the battery reached a thermodynamic equilibrium state. Is the voltage between Immediately after charging or discharging is completed, the terminal voltage of the battery when the current is zero does not reach the equilibrium or steady state inside the battery. The circuit voltage force may also be off. The degree of deviation from the original open circuit voltage also depends on the internal structure of the battery. Therefore, depending on the structure of the secondary battery used, if the terminal voltage at the timing when the charge / discharge current is zero is regarded as the open circuit voltage and the remaining capacity is estimated, a non-negligible error may occur. is there. The reason why the time is required to reach the equilibrium state is that no current flows in the external circuit.

[0008] Japanese Patent Application Laid-Open No. 2001-231179 discloses that an open circuit voltage is measured in response to a stop time of a secondary battery, a voltage value of the battery is determined, a charging rate is determined, and a charge amount supplied during charging is determined. The full charge capacity and the remaining capacity are calculated from the charge rates before and after charging, and the change in the charge rate is converted to the charge rate measured during pauses during charge / discharge by the charge amount input / output during operation. It is disclosed to estimate the current state of charge and remaining capacity by integrating the minutes.

[0009] Japanese Patent Application Laid-Open No. 2003-149307 discloses that the remaining capacity is calculated by integrating the charge / discharge current of the battery, the electromotive voltage of the battery is calculated, and the estimated capacity of the battery is calculated from the voltage. It discloses that a correction amount is calculated by a differential force PI (proportional integration) control between the estimated capacity and the remaining capacity to correct the remaining capacity.

[0010] When using a secondary battery such as a lithium ion secondary battery, the use of a single cell of these secondary batteries is rarely necessary. A plurality of single cells are connected in series so that a desired discharge voltage and discharge current can be obtained. And z or a battery pack connected in parallel. In addition to the secondary battery cells, the battery pack often includes, for example, a safety circuit such as an overcharge prevention circuit and a circuit that measures the remaining capacity and outputs the measured value.

[0011] The documents cited in the present specification are listed below.

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-245673

Patent Document 2: Japanese Patent Application Laid-Open No. 2001-231179

Patent Document 3: JP 2003-149307 A

Disclosure of the invention

Problems to be solved by the invention

[0012] As described above, in the conventional method for determining the remaining capacity of the secondary battery, the error is large! /, The latest remaining capacity value cannot be obtained at a required time interval, or the amount of calculation is small. But There remains an issue that needs to be solved.

An object of the present invention is to provide a remaining capacity estimation method capable of estimating the latest remaining capacity of a secondary battery at a desired time interval with a small amount of calculation and with high accuracy.

Another object of the present invention is to provide a remaining capacity estimating apparatus capable of estimating the latest remaining capacity of a secondary battery at a desired time interval with a small amount of calculation and with high accuracy.

[0015] Yet another object of the present invention is to provide a battery pack incorporating such an estimation device.

Means for solving the problem

An object of the present invention is a remaining capacity estimation method for estimating a remaining capacity of a secondary battery, wherein the method monitors a charge / discharge current of the secondary battery, executes an integration operation based on the charge / discharge current, and performs a first operation. The remaining capacity value of the battery was continuously calculated, the timing at which the charge and discharge of the secondary battery were switched was detected, and the terminal voltage of the secondary battery was captured at the time when the timing force was also delayed by a predetermined condition, and was captured. A second remaining capacity value is obtained based on the terminal voltage, the first remaining capacity value is replaced with the second remaining capacity value, and the integration operation in the step of calculating based on the replaced first remaining capacity value is performed. This is achieved by a remaining capacity estimation method in which the first remaining capacity value is continued and the remaining capacity of the secondary battery is used.

Another object of the present invention is a remaining capacity estimating device for estimating a remaining capacity of a secondary battery, a current detecting means for detecting a charging / discharging current in the secondary battery, and a terminal voltage of the secondary battery. A voltage measuring means for detecting the value of the remaining capacity, a memory means for holding the value of the remaining capacity, and an arithmetic means for continuously executing an integration operation on the value stored in the memory means based on the detected charging / discharging current. A timing detecting means for detecting a timing of switching between charging and discharging of the secondary battery based on an output of the current detecting means, and a terminal for taking in and taking in a terminal voltage at a timing delayed by a predetermined condition. A remaining capacity value obtaining means for obtaining a remaining capacity value based on the voltage, wherein the remaining capacity value obtained by the remaining capacity value obtaining means replaces the value in the storage means with a remaining capacity estimating device. Is achieved.

[0018] In a secondary battery, it takes a long time before the open circuit voltage can be measured after the charge / discharge current becomes zero because the charge / discharge current is zero and the current flows to an external circuit. This is because the voltage value is not easily determined. If the current flows from zero again, the voltage of the battery is quickly determined, so such a timing, when there is almost no voltage drop due to the internal impedance of the battery, is captured. By measuring the terminal voltage of the battery, the measured voltage value can be regarded as almost the open circuit voltage of the battery.

Therefore, in the present invention, the timing at which switching between charging and discharging in the secondary battery is detected, the terminal voltage of the secondary battery is measured at a certain time after the timing, and the measured terminal voltage is measured. The remaining capacity value is estimated based on the open circuit voltage of the secondary battery, and the remaining capacity value obtained by the integration operation is updated based on the estimated value. However, when switching from discharging to charging, the battery voltage is not stable unless the current from the switching point is relatively large.Therefore, only the timing at which the charging power switches to discharging is detected, and the terminal is detected at a certain time thereafter. It is preferable to take in the voltage.

[0020] In addition, if the time from when the terminal power is switched to the charging power discharge to the time when the terminal voltage is measured and taken in is kept constant, the error increases depending on the current flow during that period. Therefore, it is preferable to change the timing of taking in the terminal voltage according to the rise of the discharge current from the point of time when the charging power is also switched to the discharge. Specifically, separately from the first integration calculation, which is the integration process of the charge / discharge current for continuously calculating the remaining capacity, the integration process of the discharge current at the time of switching to the charge / discharge, that is, the second integration operation, In this case, the terminal voltage of the secondary battery may be fetched when the integrated current of the second integrated operation reaches a predetermined threshold value. In this way, the more rapidly the discharge current rises, the sooner the terminal voltage is captured, and the difference between the terminal voltage and the open circuit voltage due to the difference in the discharge current pattern. Can be prevented from increasing. If the rise of the discharge current is too slow, that is, if the rise of the discharge current is equal to or less than a predetermined value, the terminal voltage is regarded as an open circuit voltage, and the process of updating the remaining capacity value by the integration operation is not performed. You can also do it. For example, if the power does not reach the predetermined current within the predetermined time after switching to the charging power discharging, the remaining capacity value based on the terminal voltage is not updated. As the predetermined time, for example, 0.1 second is used. As the predetermined current, for example, one hour of the secondary battery is used. The current corresponding to the rated capacity value is used.

[0021] Further, in the present invention, the length of time until switching to charging power discharge and taking in the power terminal voltage in accordance with the charging time immediately before the timing of switching to charging power discharging or the magnitude of the charging current at that time. Can be changed, whereby the accuracy of the remaining capacity estimation can be further improved. Specifically, when the charging time immediately before the timing at which the charging power is switched to the discharging is short, the time until the terminal voltage is taken in is also shortened. Timing force to switch from charge to discharge Force that needs current integrated value for the past.For example, current value is sampled at a predetermined sampling rate and stored in a ring buffer. At the time when the switching is detected, the current value in the ring buffer should be searched for and integrated with the current force in the past.

[0022] As described above, in the present invention, each time the switching between charging and discharging occurs in the secondary battery, at least each time the switching of the charging power to discharging also occurs, the first remaining capacity is calculated by integrating the charging and discharging current. Since the value is updated with the more accurate second remaining capacity value based on the open circuit voltage, the accumulated error in the integration of the charge / discharge current is reset each time. In particular, by capturing the terminal voltage of the secondary battery with a delay after switching between charging and discharging and treating it as an open circuit voltage, the remaining capacity value is determined based on the open circuit voltage that is very close to the original value at that time. Is obtained, and the accuracy of the remaining capacity estimation is further improved. Therefore, according to the present invention, it is possible to acquire the remaining capacity at an arbitrary timing with less influence of the accumulated error and with good accuracy. No. When considering application to an hybrid vehicle, switching between charging and discharging occurs after a few tens of minutes at the longest, and the remaining capacity value is updated to an accurate value based on the open circuit voltage. The cumulative error in the integration of the charge / discharge current of the battery does not become so large as to have an adverse effect when the charge / discharge is controlled by the remaining capacity. Further, according to the present invention, it is not necessary to use an expensive sensor having good linearity as a current sensor used for detecting a charge / discharge current, and the overall cost of the configuration for estimating the remaining capacity is eliminated. Can be reduced.

Brief Description of Drawings

FIG. 1 is a block diagram showing a configuration of a remaining capacity estimation device according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing an operation of remaining capacity estimation. FIG. 3 is a block diagram showing a configuration of a remaining capacity estimation device according to another embodiment of the present invention.

4 is a flowchart illustrating the operation of the remaining capacity estimating device shown in FIG. 3.

BEST MODE FOR CARRYING OUT THE INVENTION

The remaining capacity estimating device 10 shown in FIG. 1 is for estimating the remaining capacity of the secondary battery 11. Here, the remaining capacity estimating device 10 is illustrated as being incorporated in the nottery pack 12. Have been. For example, a lithium ion secondary battery can be used as the secondary battery 11 included in the battery pack 12. In the following, description will be made assuming that a lithium ion secondary battery is used as the secondary battery 11.

The remaining capacity estimating device 10 includes a current detector 21 for detecting a charging current and a discharging current for the secondary battery 11, a voltage measuring unit 22 for measuring and outputting a terminal voltage of the secondary battery 11, AZD converter 23, which samples the output of detector 21 and converts it to analog Z-digital, and shapes the output waveform of current detector 23, determines the polarity of the charge / discharge current, and detects the timing when the charge / discharge current becomes zero Discharge start to detect the start of discharge by judging whether the current zero detector 24 determines that the timing at which the charge / discharge current becomes zero is the timing of switching from charging to discharging, which is the timing of switching from power discharging to charging. A detecting unit 25, a remaining capacity value obtaining unit 26 for obtaining a remaining capacity value based on a terminal voltage of the secondary battery 11, a remaining capacity storing unit 27 for storing a current value of the remaining capacity, and an AZD converter 23 Based on the output from The integration calculation unit 28 that performs integration calculation on the remaining capacity value held in the capacity storage unit 27, and the integration of the current sample value output from the AZD converter is started at the timing of switching the charging power to discharge as well. A current integrating unit 29 that outputs a trigger signal to the remaining capacity value acquiring unit 26 when the value reaches a predetermined value. Here, the secondary battery 11 may be an assembled battery in which a plurality of unit cells are connected in series. The polarity of the charging / discharging current indicates whether the current is flowing toward the battery or whether the current is flowing from the battery.In other words, it indicates whether the current is charging or discharging. .

[0026] As the current detector 21, an open loop type using a Hall sensor or a type having a shunt resistor and measuring the voltage between both ends can be used. The current detector 21 generates a voltage that is proportional to the magnitude of the charge / discharge current and that is, for example, negative for charging and positive for discharging. The difference between the charge current and the discharge current! It is distinguished by the direction of the current.

[0027] The voltage measuring unit 22 is a device for measuring the voltage between the positive electrode terminal and the negative electrode terminal of the secondary battery as a terminal voltage. The voltage between the positive terminal and the negative terminal of the battery pack is measured as the terminal voltage. The voltage measurement unit 22 outputs the measured terminal voltage as a digital value.

[0028] The current zero detector 24 determines whether the output of the current detector 21 is discharging or charging based on whether the output is positive or negative. During the discharging period, the logical level level is '1'. The timing when the current is zero is detected by using the signal that is “0” in the middle, and the rising timing from “0” to “1” and the rising timing from “1” to “0” in this signal. Each of the falling timings represents a timing at which the charging / discharging current in the secondary battery 11 is zero.As such a current zero detecting unit 24, the non-inverting input terminal has a terminal from the current detector 21. This can be realized by a comparator in which a waveform is input and OV is supplied as a reference potential to the inverting input terminal. Timing of rising to 1 " Detect and, detects the timing of starting discharge therefrom, it sends a trigger for the current integration start on the current integrated unit 29.

[0029] When a trigger is input from the discharge start detection unit 25, the current integration unit 29 starts integration of the current sample value output by the AZD converter 23, and obtains the remaining capacity at the timing when the integrated value reaches a predetermined value. A trigger signal is output to the module 26, and immediately thereafter, the integration is stopped and the integrated value is reset to zero. The predetermined value here is set to indicate the timing at which the terminal voltage of the rechargeable battery 11 becomes closest to its original open circuit voltage after the charge / discharge current becomes zero. Is a threshold value determined in advance in accordance with. The current integrator 29 also receives a signal indicating the timing at which the current becomes zero from the current zero detector 24.At the time that this signal is input, the current integrator 29 stops the current integration, and the current integration is stopped. Reset the value to zero. Therefore, after the start of integration, if the secondary battery 11 switches from discharging to charging before reaching the above-described predetermined value, the current integrating unit 29 stops the integration without outputting a trigger signal and returns to zero. Will be reset to When switching from charging to discharging, the current integrator 29 receives the signal from the current zero detector 24 and discharges it. Force input by both triggers from power start detection unit 25 In this case, current integration unit 29 starts current integration immediately after being reset to zero.

[0030] When the open circuit voltage of the secondary battery 11 is input, the remaining capacity value acquiring unit 26 obtains and outputs the remaining capacity value corresponding to the open circuit voltage. The voltage value measured by the measurement unit 22 and the trigger signal generated by the current integration unit 29 are input. Then, the terminal voltage value of the secondary battery 11 is fetched at the timing when the trigger signal is input, the fetched terminal voltage is regarded as an open circuit voltage, and the remaining capacity value corresponding to the open circuit voltage is output. Actually, a look-up table showing the relationship between the open circuit voltage value and the remaining capacity of the lithium ion secondary battery is provided, and the captured voltage value is referred to as the open circuit voltage value, and the remaining capacity value is referred to. Is output. If the secondary battery whose remaining capacity is to be estimated is a secondary battery other than a lithium-ion secondary battery, a lookup table corresponding to the characteristics of the secondary battery shall be provided.

In the present embodiment, the timing of estimating the remaining capacity value by regarding the terminal voltage of the secondary battery 11 as an open circuit voltage in the remaining capacity value acquiring unit 26 is not the timing at which the charge / discharge current becomes zero. Thus, the time when the timing force is also delayed, specifically, the time when the integrated value in the current integrating unit 29 reaches a predetermined value. As described above, the terminal voltage at a timing later than the terminal voltage at the timing when the charge / discharge current becomes zero is not used as the open-circuit voltage is referred to as the open-circuit voltage. As described in the item, at the timing of switching between charging and discharging in the secondary battery 11, the terminal voltage of the secondary battery 11 may be shifted from the original open circuit voltage. When the charging / discharging current flows to the secondary battery 11 after the charging / discharging current becomes zero, at a certain timing, the terminal voltage at that time coincides with the original open circuit voltage. In the present embodiment, the terminal capacity is taken in at such a delayed timing and regarded as an open circuit voltage, so that the remaining capacity can be accurately estimated. In particular, by detecting the timing at which the charging power switches to discharging, the terminal voltage at the time when the integrated amount of the discharging current at the timing power reaches a predetermined value is used as the open circuit voltage, thereby estimating the remaining capacity. Make it more accurate.

[0032] The remaining capacity storage unit 27 that holds the current remaining capacity of the secondary battery 11 also functions as an arithmetic memory when the remaining capacity is calculated by integrating the charge / discharge current by the integration calculator 28. The remaining capacity storage section 27 outputs the current remaining capacity (SOC) to the outside in real time. Furthermore, the value of the remaining capacity in the remaining capacity storage unit 27 is replaced with the output value when the trigger signal is output and the remaining capacity value is output from the remaining capacity value acquisition unit 26. I have. The integration operation unit 28 performs an integration operation on the remaining capacity value stored in the remaining capacity storage unit 27 according to the output of the AZD converter 23 for each sampling of the AZD converter 23. Here, if the value of the remaining capacity stored in the remaining capacity storage unit 27 is [SOC], at the time of discharging,

[SOC] [SOC] — (magnitude of discharge current) ... h)

To update the [SOC], and when charging,

[SOC] [SOC] + (magnitude of charging current) X charging efficiency · · · (2)

[SOC] is updated by! / Since the sampling of the AZD converter 23 is performed at a constant time period, addition and subtraction of a current amount are equivalent to addition and subtraction of a charge amount. The reason why the charging efficiency is multiplied at the time of charging is that not all of the charge amount corresponding to the charging current is stored in the secondary battery 11. Charging efficiency is generally a function of temperature. Therefore, the integration operation may be performed by changing the value of the charging efficiency according to the temperature.

FIG. 2 schematically shows the operation of the remaining capacity estimating apparatus 10.

The current detector 21 constantly monitors the charge / discharge current for the secondary battery 11 and supplies a voltage signal corresponding to the detected current to the AZD converter 23. The AZD converter 23 and the multiplying operation unit 28 calculate the remaining capacity value [SOC] stored in the remaining capacity storage unit 27 by the above equation (1), An integration operation is performed by adding or subtracting the charge / discharge current according to (2). As a result, the latest remaining capacity value is stored in the remaining capacity storage unit 27 for each sampling in the AZD variable.

[0035] The voltage signal from the current detector 21 is also input to the current zero detection unit 24, where the waveform is shaped, and the logic level is "1" during the discharge period and "0" during the charge period. The discharge start timing is detected by the discharge start detection unit 25, and in response to the detected timing, the current integration unit 29 integrates the discharge current, that is, Start integration. The current integrated value is represented by the area of the hatched portion in the figure. When the current integration value reaches a predetermined value, a trigger signal is output from the current integration unit 29 to the remaining capacity value acquisition unit 26, and the remaining capacity value acquisition unit 26 searches for the lookup signal at the timing when the trigger signal is input. By referring to the table, a remaining capacity value is obtained by regarding the terminal voltage of the secondary battery 11 at that time as an open circuit voltage. Then, the remaining capacity value [SOC] stored in the remaining capacity storage unit 27 is replaced with the obtained remaining capacity value.

The terminal voltage of the secondary battery 11 at the timing when the integrated value of the discharge current has reached a predetermined value after switching to the charging power discharge is the open circuit voltage of the secondary battery 11 at that time. Since the remaining capacity value acquiring unit 26 outputs such an accurate remaining capacity value, the remaining capacity estimating apparatus 10 according to the remaining capacity estimation device 10 The remaining capacity of the secondary battery 11 is continuously calculated, and at the timing when the discharger also switches to charging, the remaining capacity value used in the integration operation is updated with the accurate remaining capacity value. . As a result, the accumulation of errors in the integration operation is eliminated, and it becomes possible to know the exact remaining capacity at that time at any time.

[0037] The above-described remaining capacity estimating apparatus 10 of the present embodiment is generally implemented using a microcomputer. In this case, the functions of the edge detection unit 25, the remaining capacity value acquisition unit 26, the remaining capacity storage unit 27, the integration calculation unit 28, and the current integration unit 29 are realized by a microcomputer. Specifically, the microcomputer continuously performs the integration operation based on the charging / discharging current, and the output signal of the above-described comparator or the like is input to the input capture terminal of the microcomputer, and the rising edge and the falling edge are input. Should be detected, and if an edge is detected, an interrupt task should be generated so that the above processing is performed!

FIG. 3 shows a remaining capacity estimating device according to another embodiment of the present invention.

In FIG. 1, the remaining capacity estimating device captures the terminal voltage of the secondary battery 11 at the timing when the integrated value of the discharge current from the point of switching from charge to discharge reaches a predetermined value, and determines the open circuit voltage and However, in order to further improve the accuracy of the estimated value of the remaining capacity, the remaining capacity estimator shown in Fig. 3 uses the charging period immediately before switching from charging to discharging. The timing for taking in the terminal voltage is changed according to the length of the charging time between the charging periods or according to the current value of the charging current during such a charging period. Specifically, when the charging time is short or the charging current amount is small, the time interval between switching from charging to discharging and taking in the terminal voltage is shortened. Further, when the rise of the discharge current is too small and the integrated current value does not reach a predetermined value due to a weak force, the remaining capacity value is not updated by regarding the terminal voltage as an open circuit voltage. For example, if the discharge current value does not reach the predetermined current value within the predetermined time after switching to charging / discharging, the remaining capacity value that does not consider the terminal voltage as the open circuit voltage is not updated. . The predetermined time here is, for example, about 100 milliseconds, and the predetermined current value is, for example, a current value corresponding to a one-hour rated capacity value of the secondary battery.

The remaining capacity estimating device shown in FIG. 3 is different from the remaining capacity estimating device shown in FIG. 1 in that a ring buffer 30 and a trigger signal generating unit 31 are provided instead of the current integrating unit 29. In the present embodiment, the functions of the edge detection unit 25, the remaining capacity value acquisition unit 26, the remaining capacity storage unit 27, the integration operation unit 28, the ring buffer 30, and the trigger signal generation unit 31 can be realized by a microcomputer.

The ring buffer 30 sequentially stores the current sample values from the AZD converter 23. When the number of current sample values to be stored exceeds the memory capacity of the ring buffer 30, the ring buffer 30 is the oldest. The sample value is rewritten to the newest sample value, so that each current sample value whose current point in time goes back to the past is stored in the ring buffer 30 by the capacity of the ring buffer 30. Will be. The reason why a ring buffer is provided instead of simply providing a circuit for current integration is that in order to change the trigger signal generation condition according to the past charging time or charging current amount, the past current This is because it is necessary to hold the sample values.

[0042] The trigger signal generation unit 31 outputs a trigger signal to the remaining capacity value acquisition unit 26. However, the output condition of the trigger signal changes according to the charging time immediately before the timing of switching to the charging power discharge. Further, when the rising of the discharge current is too small, the output of the trigger signal is suppressed. The trigger is also input to the trigger signal generator 31 and the discharge start detector 25, and the current zero detector 24 indicates the timing at which the current becomes zero. The signal is also input, and is reset by a signal from the current zero detection unit 24, and the current integration is started by a trigger from the discharge start detection unit 25, similarly to the current integration unit of the remaining capacity estimation device shown in FIG. .

FIG. 4 is a flowchart showing the operation of the trigger signal generator 31. First, in step 101, it is determined whether the charging power is also the timing power for switching to discharging, that is, whether a trigger from the discharging start detection unit 25 has been input. If it is not the timing of switching from charging to discharging, the process waits until such timing is reached, and if it is the timing of switching from charging to discharging, in step 102, the trigger signal generation unit 31 stores in the ring buffer 30 The stored current sample value is searched to determine whether the current value of each sample corresponds to charging or discharging, and the duration of the immediately preceding charging, that is, the charging time is examined. Then, when the charging time immediately before the timing of switching from charging to discharging is short, the trigger signal generating unit 31 sets the threshold value of the current integrated value so that the threshold value of the current integrated value becomes small. To determine. In this case, if the charging time is longer than a predetermined time, the threshold value of the current integrated value is set to a constant value, so that the ring buffer 30 has a storage capacity sufficient to store the current sample value for the predetermined time. If there is. As the predetermined time, for example, a time corresponding to 20 samples represented by current sampling is used.

Next, in step 103, the trigger signal generator 31 starts integrating the discharge current.

The integration of the discharge current is performed by taking in a current sample value newly stored in the ring buffer 30 and integrating it. Then, in step 104, it is determined whether or not the predetermined elapsed time has elapsed since the start of the integration. If the elapsed time has not elapsed, the process directly proceeds to step 106, and if the predetermined elapsed time has elapsed, In step 105, it is determined whether the current value of the discharge current at that time is equal to or greater than a predetermined lower limit. As the predetermined elapse time, for example, 100 milliseconds is used, and as the predetermined lower limit, for example, a current value corresponding to the one-hour rated capacity of the secondary battery 11 is used. If the current value of the discharge current is less than the lower limit, it corresponds to a case where the rise of the discharge current is gradual or too strong, so the process is terminated. In step 106, it is determined whether or not the integrated current value has reached or reached the value determined in step 102. If not, the process returns to step 104 for further current integration. If the current value has been reached, a trigger signal is output in step 107, and the process ends.

The processing of the trigger signal generating unit 31 as described above is executed every time the charging power also detects the switching timing to the discharging.

Claims

The scope of the claims

[1] A remaining capacity estimation method for estimating the remaining capacity of a secondary battery,

The charge / discharge current of the secondary battery is monitored, and an integration operation based on the charge / discharge current is executed to continuously calculate a first remaining capacity value,

Detecting the timing of switching between charging and discharging in the secondary battery, capturing the terminal voltage of the secondary battery at a point in time delayed by a predetermined condition, and determining a second remaining voltage based on the captured terminal voltage; Calculating the capacity value and replacing the first remaining capacity value with the second remaining capacity value;

A remaining capacity estimating method, wherein an integration operation in the calculating step based on the first remaining capacity value after replacement is continued to make the first remaining capacity value the remaining capacity of the secondary battery.

[2] The method according to claim 1, wherein the secondary battery is a lithium ion secondary battery.

[3] A remaining capacity estimation method for estimating the remaining capacity of a secondary battery,

The timing at which the secondary battery switches to charging power discharge is detected, and the timing power discharge current value integration is started, and when the integrated value of the discharge current value reaches and reaches the value, the secondary battery is discharged. Capturing a terminal voltage, obtaining a second remaining capacity value based on the captured terminal voltage, replacing the first remaining capacity value with the second remaining capacity value,

4. The method according to claim 3, wherein the threshold value is changed according to a length of a charging period immediately before the timing or a charging current during the charging period.

[5] The method according to claim 3, wherein when the rise of the discharge current immediately after the timing is equal to or less than a predetermined value, the replacement of the first remaining capacity value with the second remaining capacity value is not performed. The remaining capacity estimation method described. 6. The method according to claim 3, wherein the secondary battery is a lithium ion secondary battery.

[7] A remaining capacity estimating device for estimating a remaining capacity of a secondary battery,

Current detection means for detecting a charge / discharge current in the secondary battery,

Voltage measuring means for detecting a terminal voltage of the secondary battery,

Storage means for holding a value of the remaining capacity;

Calculating means for continuously performing an integration calculation on the value stored in the storage means based on the detected charging / discharging current;

Timing detection means for detecting a timing of switching between charging and discharging in the secondary battery based on an output of the current detection means;

Remaining capacity value acquiring means for acquiring the terminal voltage at a point in time delayed by a predetermined condition from the timing and obtaining a remaining capacity value based on the acquired terminal voltage,

A remaining capacity estimating device, wherein the remaining capacity value obtained by the remaining capacity value obtaining means replaces the value in the storage means.

[8] A remaining capacity estimating device for estimating a remaining capacity of a secondary battery,

Storage means for holding a value of the remaining capacity;

Timing detecting means for detecting a timing at which the secondary battery switches from charging to discharging based on an output of the current detecting means;

Trigger signal generating means for starting integration of the timing force discharge current value, generating a trigger signal when the integrated value of the discharge current value reaches a threshold, and

A residual capacity value obtaining means for obtaining a residual capacity value based on the terminal voltage obtained by capturing the terminal voltage when the trigger signal is generated,

A remaining capacity estimating apparatus, wherein the value in the storage means is replaced by the remaining capacity value obtained by the remaining capacity value obtaining means, and the integration operation is continued. 9. The device according to claim 8, wherein the threshold value changes according to a length of a charging period immediately before the timing or a charging current during the charging period.

10. The apparatus according to claim 8, wherein the trigger signal generating means does not generate the trigger signal when the rising of the discharge current immediately after the timing is equal to or less than a predetermined value.

Secondary batteries,

Storage means for holding a value of the remaining capacity;

Remaining capacity value acquisition means for acquiring a remaining capacity value based on the acquired terminal voltage at a time point delayed by a predetermined condition from the timing,

A battery pack wherein the value in the storage means is replaced by the remaining capacity value obtained by the remaining capacity value obtaining means.

12. The battery pack according to claim 11, wherein the secondary battery is a lithium ion secondary battery. Secondary batteries,

Storage means for holding a value of the remaining capacity;

Calculating means for continuously executing an integration calculation on the value stored in the storage means based on the detected charging / discharging current;

Timing detecting means for detecting a timing at which the secondary battery switches from charging to discharging, based on an output of the current detecting means;

The timing force starts accumulating the discharge current value, and the accumulated value of the discharge current value becomes a threshold, A trigger signal generating means for generating a trigger signal when the value reaches a value, and a remaining capacity value for obtaining a remaining capacity value based on the terminal voltage taken in at the time when the trigger signal is generated. Obtaining means,

A battery pack wherein the value in the storage means is replaced by the remaining capacity value obtained by the remaining capacity value obtaining means, and the integration operation continues.

14. The battery pack according to claim 13, wherein the threshold value changes according to a length of a charging period immediately before the timing or a charging current during the charging period.

15. The battery pack according to claim 13, wherein the trigger signal generating means does not generate the trigger signal when the rising of the discharge current immediately after the timing is equal to or less than a predetermined value.

16. The battery pack according to claim 13, wherein the secondary battery is a lithium ion secondary battery.