JP4880451B2 - Secondary battery remaining capacity estimation method and apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for estimating the state of charge (SOC) of various secondary batteries represented by lithium ion secondary batteries, and a battery pack incorporating such a remaining capacity estimation apparatus.

  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 driving electric motors for power applications.

  Such a motor-driven application of a secondary battery such as a lithium ion secondary battery includes, for example, 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, but in a hybrid vehicle with a certain drive system, the secondary battery is charged with the electric power obtained by the generator, and when the vehicle is accelerated or uphill, the generator In addition to the electric power, electric power obtained by discharging the secondary battery is supplied to the electric motor. In another type of hybrid vehicle, the driving wheels are directly driven by the engine, and the driving wheels are assisted by the motor output during acceleration or climbing. In these hybrid vehicles, in order to further improve energy efficiency, when braking the vehicle, the motor is operated as a generator to function as a regenerative brake, and the secondary battery is also charged by the energy obtained at that time. I am doing so.

  In the case of a hybrid vehicle, actually, 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 to generate power with the generator, and the secondary battery is charged with the electric power. For example, when the remaining capacity becomes 80% or more, the secondary battery is prevented from being charged any more. Thus, since it is necessary to control charging / discharging according to the remaining capacity of the secondary battery, the remaining capacity of the secondary battery must be constantly monitored. Specifically, the remaining capacity is obtained at time intervals of several tens of milliseconds to several seconds.

  In principle, the remaining capacity of a secondary battery can be determined by the difference between the amount of charged charge and the amount of discharged charge. Conventionally, the value of the charge / discharge current of the secondary battery is measured at regular intervals. Then, the remaining capacity of the secondary battery is obtained by integrating the measured values. Further, 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 It is also performed to estimate the remaining capacity by measuring. However, when a secondary battery is applied to a hybrid vehicle, a large current may flow in a short time due to an inrush current of an electric motor, etc., and an inexpensive, highly linear current sensor with high accuracy may be obtained. If the remaining capacity is obtained by integrating the charge / discharge current values for reasons such as difficulty, a cumulative error that cannot be ignored may occur.

  On the other hand, when the remaining capacity is estimated based on the open circuit voltage of the secondary battery, the problem of error accumulation does not occur. However, since there is a charge / discharge current during normal use of the secondary battery, the open circuit voltage cannot be measured continuously. Therefore, the present inventors, in applications such as hybrid vehicles, discharge and charge are frequently switched in the secondary battery, and the direction of the current flowing through the secondary battery is switched. Has already been proposed in Japanese Patent Application: Japanese Patent Application No. 2003-34967 (Japanese Patent Application Laid-Open No. 2004-245673). In this method, the remaining capacity is continuously calculated by integrating the charging / discharging current of the secondary battery, and at the timing when the charging / discharging current becomes zero, for example, the timing at which charging and discharging are switched, etc. The voltage is measured, the remaining capacity at that time is estimated as an open circuit voltage, and the remaining capacity value calculated by current integration is updated with the estimated value.

  However, strictly speaking, the open circuit voltage is a voltage between the positive electrode and the negative electrode when a sufficient time has elapsed since the charging and discharging of the secondary battery stopped and the battery has reached a thermodynamic equilibrium state. . The terminal voltage of the battery in the state where the current immediately after the end of charging or discharging is zero may deviate from the original open circuit voltage because the inside of the battery has not reached an equilibrium state or a steady state. The degree of deviation from the original open circuit voltage depends on the internal structure of the battery. Therefore, depending on the structure of the secondary battery used, when the remaining capacity is estimated by regarding the terminal voltage at the timing when the charge / discharge current is zero as an open circuit voltage, an error that cannot be ignored may occur. Note that it takes time to reach the equilibrium state because current does not flow to the external circuit.

  Japanese Patent Laid-Open No. 2001-231179 discloses an open circuit voltage corresponding to a suspension time of a secondary battery, determines a charging rate from the voltage value, and determines the amount of charge supplied during charging and before and after charging. Calculate the full charge capacity and remaining capacity from the charge rate, and integrate the change in charge rate converted by the charge amount input and output during operation into the charge rate measured during pause during charge and discharge. Thus, it is disclosed that the current charging rate and the remaining capacity are estimated.

  In Japanese Patent Application Laid-Open No. 2003-149307, the remaining capacity is calculated by integrating the charging / discharging current of the battery, the electromotive voltage of the battery is calculated, the estimated capacity of the battery is calculated therefrom, and the remaining capacity, the estimated capacity, It is disclosed that a correction amount is calculated from PI difference by PI (proportional integration) control to correct the remaining capacity.

  When a secondary battery such as a lithium ion secondary battery is used, these secondary battery cells are rarely used alone, and a plurality of single cells are connected in series and / or in order to obtain a desired discharge voltage and discharge current. Generally, it is configured as a battery pack connected in parallel. In addition to the secondary battery cell, the battery pack is often provided with a safety circuit such as an overcharge prevention circuit and a circuit that measures the remaining capacity and outputs the measured value.

The documents cited in this specification are listed below.
JP 2004-245673 A JP 2001-231179 A JP 2003-149307 A

  As described above, the conventional method for obtaining the remaining capacity of the secondary battery has a large error, the latest remaining capacity value cannot be obtained at a necessary time interval, or the calculation amount is increased. There are still issues 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 with a small amount of calculation with high accuracy and at a desired time interval.

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

  Still another object of the present invention is to provide a battery pack incorporating such an estimation device.

  An object of the present invention is a remaining capacity estimation method for estimating a remaining capacity of a secondary battery, which monitors a charge / discharge current of the secondary battery, executes an integration operation based on the charge / discharge current, and executes a first remaining capacity. The value is continuously calculated, the timing at which charging and discharging of the secondary battery are switched is detected, the terminal voltage of the secondary battery is taken in at a point delayed from the timing by a predetermined condition, and based on the taken-in terminal voltage The second remaining capacity value is obtained, the first remaining capacity value is replaced with the second remaining capacity value, and the integration calculation in the step of calculating based on the replaced first remaining capacity value is continued. This is achieved by a remaining capacity estimation method in which the remaining capacity value of 1 is used as the remaining capacity of the secondary battery.

  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 charge / discharge current in the secondary battery, and a voltage for detecting a terminal voltage of the secondary battery. Measuring means, storage means for holding the value of the remaining capacity, calculation means for continuously executing integration operation on the value stored in the storage means based on the detected charge / discharge current, and current detection means Based on the output, the timing detection means for detecting the timing at which charging and discharging in the secondary battery are switched, and the remaining capacity value based on the terminal voltage taken in by taking in the terminal voltage at a point delayed by a predetermined condition from that timing A remaining capacity value acquisition means to be obtained, and achieved by a remaining capacity estimation device in which the value in the storage means is replaced by the remaining capacity value obtained by the remaining capacity value acquisition means. .

  In the secondary battery, after the charge / discharge current becomes zero, it takes a long time to measure the open circuit voltage because the charge / discharge current is zero and no current flows to the external circuit. This is because it is difficult to determine the voltage value. If the current starts again from zero, the voltage of the battery will be determined rapidly. Therefore, the timing at which such a voltage drop due to the internal impedance of the battery hardly occurs is detected, and the terminal of the battery at that time If the voltage is measured, the measured voltage value can be regarded as the open circuit voltage of the battery.

  Therefore, in the present invention, the timing at which the secondary battery is switched between charging and discharging is detected, the terminal voltage of the secondary battery is measured at a certain time after that timing, and the measured terminal voltage is measured as the secondary battery. It is assumed that the remaining capacity value is estimated as an open circuit voltage, and the remaining capacity value by the integration calculation is updated with the estimated value. However, when switching from discharging to charging, the battery voltage will not be stable unless the current from the switching point is relatively large. Therefore, only the timing when switching from charging to discharging is detected, and the terminal voltage is taken in at a certain point thereafter. It is preferable to make it.

  Further, if the length of time from when the charging is switched to discharging until the terminal voltage is measured and taken is made constant, the error increases depending on the current flow during that period. Therefore, it is preferable to change the timing for taking in the terminal voltage in accordance with how the discharge current rises from the time when switching from charging to discharging. Specifically, separately from the first integration calculation, which is the charge / discharge current integration process for continuously calculating the remaining capacity, the discharge current integration process, i.e. the second The integration calculation is started, and the terminal voltage of the secondary battery may be captured when the current integration value obtained by the second integration calculation reaches a predetermined threshold value. In this way, the faster the discharge current rises, the faster the terminal voltage is taken in, and the difference between the terminal voltage and the open circuit voltage increases due to the difference in the discharge current pattern. Can be prevented. If the rise of the discharge current is too gradual, that is, if the rise of the discharge current is less than or equal to a predetermined value, the terminal voltage is regarded as an open circuit voltage and the process of updating the remaining capacity value by integration is not performed. It can also be done. For example, when the predetermined current is not reached within a predetermined time after switching from charging to discharging, the remaining capacity value based on the terminal voltage is not updated. As the predetermined time, for example, 0.1 second is used, and as the predetermined current, for example, a current corresponding to the one-hour rated capacity value of the secondary battery is used.

  Furthermore, in the present invention, the length of time from switching from charging to discharging to taking in the terminal voltage can be changed according to the charging time immediately before the timing of switching from charging to discharging and the magnitude of the charging current at that time. This can further improve the accuracy of the remaining capacity estimation. Specifically, when the charging time immediately before the timing of switching from charging to discharging is short, the time until the terminal voltage is taken is also shortened. The current integrated value from the timing when switching from charging to discharging is required, but for example, the current value is sampled at a predetermined sampling rate and stored in a ring buffer, and switching from charging to discharging is performed. When the current value is detected, the current value in the ring buffer may be searched and accumulated from that time to the past.

  As described above, in the present invention, every time switching between charging and discharging occurs in the secondary battery, at least every time switching from charging to discharging occurs, the first remaining capacity value based on integration of charging / discharging current is: Since it is updated with a 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 taking in the terminal voltage of the secondary battery with a delay from switching between charging and discharging and considering it as an open circuit voltage, the remaining capacity value is based on the open circuit voltage very close to the original value at that time. As a result, the accuracy of the remaining capacity estimation is further improved. Therefore, according to the present invention, it is possible to obtain the remaining capacity at an arbitrary timing with little influence of the accumulated error and with high accuracy. When considering application to hybrid vehicles, switching between charging and discharging occurs after several tens of minutes at the longest, and the remaining capacity value is updated to an accurate value based on the open circuit voltage. The accumulated error at the time of integrating the discharge current is not so large as to adversely affect the charge / discharge control by the remaining capacity. Further, according to the present invention, it is not necessary to use an expensive sensor with good linearity as a current sensor used for detecting the charge / discharge current, and the overall cost of the configuration for estimating the remaining capacity can be reduced. Can be reduced.

It is a block diagram which shows the structure of the remaining capacity estimation apparatus of one Embodiment of this invention. It is a figure which shows typically operation | movement of remaining capacity estimation. It is a block diagram which shows the structure of the remaining capacity estimation apparatus of another embodiment of this invention. It is a flowchart explaining operation | movement of the remaining capacity estimation apparatus shown in FIG.

  The remaining capacity estimation device 10 shown in FIG. 1 estimates the remaining capacity of the secondary battery 11, and is depicted here as the remaining capacity estimation device 10 incorporated in the battery pack 12. As the secondary battery 11 constituting the battery pack 12, for example, a lithium ion secondary battery can be used. In the following description, it is assumed that a lithium ion secondary battery is used as the secondary battery 11.

  The remaining capacity estimation device 10 includes a current detector 21 that detects a charging current and a discharging current for the secondary battery 11, a voltage measuring unit 22 that measures and outputs a terminal voltage of the secondary battery 11, and a current detector 21 An A / D converter 23 that samples the output and performs analog / digital conversion, and a current zero that detects the timing when the charge / discharge current becomes zero by shaping the output waveform of the current detector 23 to determine the polarity of the charge / discharge current A detection unit 24 and a discharge start detection unit 25 that determines whether the timing when the charge / discharge current becomes zero is the timing of switching from charging to discharging or the timing of switching from discharging to charging, and detects the start of discharging. A remaining capacity value acquisition unit 26 that acquires a remaining capacity value based on the terminal voltage of the secondary battery 11, a remaining capacity storage unit 27 that holds a current value of the remaining capacity, and an A / D converter 3, integration calculation unit 28 that performs integration calculation on the remaining capacity value held in remaining capacity storage unit 27 based on the output from 3, and integration of the current sample value output from A / D converter 23 from charging And a current integration unit 29 that starts at the timing of switching to discharge and outputs a trigger signal to the remaining capacity value acquisition unit 26 when the integration 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 charge / discharge current indicates whether a current is flowing toward the battery or whether a current is flowing from the battery. In other words, it indicates whether the current is charging or discharging.

  As the current detector 21, an open loop type using a Hall sensor or a type having a shunt resistor and measuring a voltage at both ends thereof can be used. The current detector 21 is proportional to the magnitude of the charge / discharge current and generates a voltage that is negative for charge and positive for discharge, for example. The difference between the charging current and the discharging current is distinguished by the direction of the current with respect to the secondary battery 11.

  The voltage measuring unit 22 measures the voltage between the positive electrode terminal and the negative electrode terminal of the secondary battery as a terminal voltage. If the assembled battery is used as the secondary battery 11, the voltage measuring unit 22 The voltage between the positive terminal and the negative terminal is measured as the terminal voltage. The voltage measuring unit 22 outputs the measured terminal voltage as a digital value.

  The zero current detector 24 discriminates whether the current detector 21 is discharged or charged depending on whether the output of the current detector 21 is positive or negative. The logic level is “1” during the discharging period, and during the charging period. By using a signal that is “0”, the timing when the current is zero is detected. The rise timing from “0” to “1” and the fall timing from “1” to “0” in this signal both represent the timing when the charge / discharge current in the secondary battery 11 is zero. ing. Such a zero current detection unit 24 can be realized by a comparator in which the waveform from the current detector 21 is input to the non-inverting input terminal and 0 V is supplied as the reference potential to the inverting input terminal. . The discharge start detection unit 25 detects the rising timing of the above-described signal from “0” to “1” in the current zero detector 24, detects this as the discharge start timing, and starts current integration. Is sent to the current integrating unit 29.

  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 from the A / D converter 23, and acquires the remaining capacity at the timing when the integration value reaches a predetermined value. A trigger signal is output to the unit 26, and immediately after that, the integration is stopped and the integrated value is reset to zero. The predetermined value here represents the timing at which the terminal voltage of the secondary battery 11 is closest to its original open circuit voltage after the charge / discharge current becomes zero, and the type and internal configuration of the secondary battery 11. The threshold value is predetermined according to the above. The current integration unit 29 also receives a signal indicating the timing when the current becomes zero from the current zero detection unit 24. At the time when this signal is input, the current integration unit 29 stops the current integration, and the integrated value is obtained. Reset to zero. Therefore, when the secondary battery 11 is switched from discharging to charging after starting the integration before reaching the predetermined value described above, the current integration unit 29 stops the integration without outputting a trigger signal, Will be reset to zero. When switching from charging to discharging, both the signal from the current zero detection unit 24 and the trigger from the discharge start detection unit 25 are input to the current integration unit 29. At this time, the current integration unit 29 No. 29 starts current integration immediately after being reset to zero.

  When the open circuit voltage of the secondary battery 11 is input, the remaining capacity value acquiring unit 26 obtains and outputs a remaining capacity value corresponding to the open circuit voltage. Here, the voltage measuring unit 22 The measured voltage value and the trigger signal generated by the current integrating unit 29 are input. And the terminal voltage value of the secondary battery 11 is taken in at the timing when the trigger signal is inputted, the taken-in terminal voltage is regarded as an open circuit voltage, and the remaining capacity value corresponding to the open circuit voltage is outputted. Actually, it has a look-up table showing the relationship between the open circuit voltage value and the remaining capacity of the lithium ion secondary battery, and refers to this look-up table with the captured voltage value as the open circuit voltage value, and the remaining capacity value Is output. When the secondary battery that is the target of the remaining capacity estimation is a secondary battery other than the lithium ion secondary battery, a lookup table corresponding to the characteristics of the secondary battery is provided.

  In the present embodiment, the remaining capacity value acquisition unit 26 regards the terminal voltage of the secondary battery 11 as an open circuit voltage and estimates the remaining capacity value, not the timing at which the charge / discharge current becomes zero. More specifically, it is the time when the integrated value in the current integrating unit 29 reaches a predetermined value. As described above, the terminal voltage at the timing when the charge / discharge current becomes zero is not set as the open circuit voltage, but the terminal voltage at the timing later than that is set as the open circuit voltage. However, as described above, the terminal voltage of the secondary battery 11 may be deviated from the original open circuit voltage at the timing at which charging and discharging are switched in the secondary battery 11. When the charge / discharge current flows through the secondary battery 11 after the charge / discharge current becomes zero, the terminal voltage at that time coincides with the original open circuit voltage at a certain timing. In this embodiment, the terminal voltage is taken in at such a delayed timing and regarded as an open circuit voltage, so that the remaining capacity can be estimated accurately. In particular, the remaining capacity can be estimated more accurately by detecting the timing of switching from charging to discharging and using the terminal voltage when the integrated amount of discharge current from that timing reaches a predetermined value as the open circuit voltage. To be able to.

The remaining capacity storage unit 27 that holds the current remaining capacity of the secondary battery 11 also functions as a calculation memory when calculating the remaining capacity by integrating the charge / discharge current by the integration calculation unit 28. The current remaining capacity (SOC) is output to the outside in real time. Further, when the trigger signal is output and the remaining capacity value is output from the remaining capacity value acquiring unit 26, the remaining capacity value in the remaining capacity storage unit 27 is replaced with the output value. For each sampling of the A / D converter 23, the integration calculation unit 28 performs integration calculation on the remaining capacity value stored in the remaining capacity storage unit 27 according to the output of the A / D converter 23. Here, if the value of the remaining capacity stored in the remaining capacity storage unit 27 is set to [SOC], during discharge,
[SOC] ← [SOC] − (size of discharge current) (1)
To update [SOC] and when charging,
[SOC] ← [SOC] + (charge current magnitude) × charge efficiency (2)
[SOC] is updated. Since the sampling of the A / D converter 23 is performed at a constant time period, the addition and subtraction of the current amount is equivalent to the addition and subtraction of the 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 calculation 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 estimation 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 A / D converter 23. The A / D converter 23 and the integration calculation unit 28 calculate the above equation (1) for the remaining capacity value [SOC] stored in the remaining capacity storage unit 27 for each sampling in the A / D converter 23. ), Integration calculation 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 A / D converter 23.

  The voltage signal from the current detector 21 is also input to the current zero detection unit 24 where the waveform is shaped, and a signal whose logic level is “1” during the discharge period and “0” during the charge period. Then, the discharge start detection unit 25 detects the discharge start timing, and the current integration unit 29 starts the integration of the discharge current, that is, the integration of the shaded portion in the figure, in response to the detected timing. The integrated current value is represented by the area of the shaded portion in the figure. When the current integrated value reaches a predetermined value, a trigger signal is output from the current integrating unit 29 to the remaining capacity value acquiring unit 26, and the remaining capacity value acquiring unit 26 performs a lookup table at the timing when the trigger signal is input. , The remaining capacity value in which the terminal voltage of the secondary battery 11 at that time is regarded as an open circuit voltage is obtained. Then, the remaining capacity value [SOC] stored in the remaining capacity storage unit 27 is replaced with the acquired remaining capacity value.

  The terminal voltage of the secondary battery 11 at the timing when the integrated value of the discharge current after switching from charging to discharging reaches a predetermined value is substantially the same as the value of the open circuit voltage of the secondary battery 11 at that time. Since the remaining capacity value acquisition unit 26 outputs such an accurate remaining capacity value, according to the remaining capacity estimation device 10, the secondary capacity is continuously calculated by integrating the charge / discharge current. While the remaining capacity of the battery 11 is continuously calculated, the remaining capacity value used in the integration calculation is updated with an accurate remaining capacity value at the timing of switching from discharging to charging. As a result, accumulation of errors in the integration calculation is eliminated, and an accurate remaining capacity at that time can be known at any time.

  The above-described remaining capacity estimation device 10 of the present embodiment is generally implemented using a microcomputer. In that case, each function 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 is realized by a microcomputer. Specifically, the microcomputer continuously executes the integration calculation by the charge / discharge current, and the output signal such as the above-described comparator is input to the input capture terminal of the microcomputer, and the rising edge and the falling edge are detected. If an edge is detected, an interrupt task is generated so that the above-described processing is performed.

  FIG. 3 shows a remaining capacity estimation apparatus according to another embodiment of the present invention.

  In the remaining capacity estimation device shown in FIG. 1, the terminal voltage of the secondary battery 11 is taken in at the timing when the integrated value of the discharge current from the time when switching from charging to discharging becomes a predetermined value, and is regarded as an open circuit voltage. In order to further improve the accuracy of the estimated value of the remaining capacity, the remaining capacity estimating apparatus shown in FIG. 3 depends on the length of the charging time in the charging period immediately before switching from charging to discharging, or so The timing for taking in the terminal voltage is changed in accordance with the current value of the charging current during a long charging period. Specifically, when the charging time is short or when the amount of charging current is small, the time interval from switching from charging to discharging until 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 readily reach a predetermined value, the remaining capacity value is not updated with the terminal voltage regarded as an open circuit voltage. For example, when the discharge current value does not reach a predetermined current value within a predetermined time after switching from charging to discharging, the remaining capacity value is not updated with the terminal voltage regarded as an open circuit voltage. . The predetermined time here is, for example, about 100 milliseconds, and the predetermined current value is, for example, a current value corresponding to the one-hour rated capacity value of the secondary battery.

  The remaining capacity estimation apparatus shown in FIG. 3 is the same as the remaining capacity estimation apparatus shown in FIG. 1 except that a ring buffer 30 and a trigger signal generation section 31 are provided instead of the current integration section 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 calculation 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 A / D converter 23. When the number of current sample values to be stored exceeds the memory capacity of the ring buffer 30, the oldest sample is stored. The value is rewritten to the latest sample value, and thereby, each current sample value that goes back from the latest time point to the past is stored in the ring buffer 30 by the capacity of the ring buffer 30. Become. The reason why the ring buffer is provided instead of simply providing a circuit for current integration is that the past current sample value is used in order to change the condition for generating the trigger signal according to the past charging time or the amount of charging current. It is because it is necessary to hold.

  The trigger signal generator 31 outputs the trigger signal to the remaining capacity value acquisition unit 26. The trigger signal output condition changes according to the charging time immediately before the timing of switching from charging to discharging, and further, the discharging is performed. When the rise of the current is too small, the output of the trigger signal is suppressed. The trigger signal generation unit 31 receives a trigger from the discharge start detection unit 25 and also receives a signal indicating the timing when the current becomes zero from the current zero detection unit 24, and the current of the remaining capacity estimation device shown in FIG. Similar to the integration unit, the signal is reset by a signal from the zero current detection unit 24, and current integration is started by a trigger from the discharge start detection unit 25.

  FIG. 4 is a flowchart showing the operation of the trigger signal generator 31. First, in step 101, it is determined whether or not it is a timing for switching from charging to discharging, that is, whether or not a trigger is input from the discharge start detector 25. If it is not the timing of switching from charging to discharging, it waits until such timing is reached, and if it is the timing of switching from charging to discharging, the trigger signal generating unit 31 stores it in the ring buffer 30 in step 102. The obtained current sample value is searched to determine whether the current value of each sample corresponds to charging or discharging, and the duration of the previous charging, that is, the charging time is examined. Then, the trigger signal generation unit 31 determines the threshold value of the current integrated value so that the threshold value of the current integrated value becomes small when the charging time immediately before the timing of switching from charging to discharging is short. To do. In this case, when 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 for storing the current sample value for the predetermined time. That's fine. 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 and integrating the current sample values newly stored in the ring buffer 30. In step 104, it is determined whether or not a predetermined elapsed time has elapsed after the start of integration. If not, the process proceeds to step 106, and if the predetermined elapsed time has elapsed, step 104 is performed. In 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 value. As the predetermined elapsed time, for example, 100 milliseconds is used, and as the predetermined lower limit value, for example, a current value corresponding to the hourly rated capacity of the secondary battery 11 is used. If the current value of the discharge current is less than the lower limit value, this corresponds to the case where the rise of the discharge current is too gradual, so the process is aborted. In step 106, it is determined whether or not the current integrated value has reached the threshold value determined in step 102. If not, the process returns to step 104 for further current integration, and if it has been reached. In step 107, after outputting the trigger signal, the process is terminated.

The processing of the trigger signal generation unit 31 as described above is executed every time the timing for switching from charging to discharging is detected.

Claims (14)

A remaining capacity estimation method for estimating a remaining capacity of a secondary battery,
Monitoring the charge / discharge current of the secondary battery, continuously calculating the first remaining capacity value by performing an integration operation based on the charge / discharge current,
Wherein detecting a timing at which the charge-discharge and is switched in the secondary battery, the seeking second remaining capacity value based on the terminal voltage of your Keru the secondary battery at the time delayed by a predetermined condition from the timing Replacing the first remaining capacity value with a second remaining capacity value;
A remaining capacity estimation method in which the integration calculation in the step of calculating based on the first remaining capacity value after replacement is continued to set the first remaining capacity value as the remaining capacity of the secondary battery. And starts integration of the discharge current value from the previous Symbol timing that switched to the discharge from the charging before Symbol rechargeable battery, Keru you at the time the integrated value of the discharge current value reaches the threshold value of the secondary battery based on the terminal voltage Ru seek the second remaining capacity value, the method of claim 1. The method according to claim 2 , wherein the threshold value is changed according to a length of a charging period immediately before the timing at which the secondary battery is switched from charging to discharging or a charging current in the charging period. When the rise of the discharge current immediately after the timing of switching from charging to discharging in the secondary battery is equal to or less than a predetermined value, the replacement of the first remaining capacity value by the second remaining capacity value is executed. The remaining capacity estimation method according to claim 2 or 3 , wherein: The method according to any one of claims 1 to 4 wherein the secondary battery is a lithium-ion secondary battery. 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;
Based on the detected charge / discharge current, calculation means for continuously executing integration calculation on the value held in the storage means;
Timing detection means for detecting timing at which charging and discharging in the secondary battery are switched based on the output of the current detection means;
A remaining capacity value acquiring means for obtaining a remaining capacity value based on the terminal voltage at the time delayed by a predetermined condition from the timing,
Have
Wherein the remaining capacity value acquiring unit is determined the residual capacity value, said value in said memory means is replaced, the remaining capacity estimating apparatus. And starts integration of the discharge current value from the timing of switching to the discharge from the charging before Symbol secondary battery, a trigger signal generating means integrated value of the discharge current value to generate a trigger signal at the time the threshold is reached In addition ,
The remaining capacity value obtaining means, said trigger device signals is determined the residual capacity value based on the terminal voltage at the time of the occurrence, according to claim 6. The device according to claim 7 , wherein the threshold value changes in accordance with a length of a charging period immediately before the timing at which the secondary battery is switched from charging to discharging or a charging current in the charging period. When the rise of the discharge current immediately after the timing of switching to the discharge from the charging of the secondary battery is below a predetermined value, the trigger signal generating means does not generate the trigger signal, to claim 7 or 8 The device described. 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;
Based on the detected charge / discharge current, calculation means for continuously executing integration calculation on the value stored in the storage means;
Timing detection means for detecting timing at which charging and discharging in the secondary battery are switched based on the output of the current detection means;
Anda remaining capacity value acquiring means for obtaining a remaining capacity value based on the terminal voltage at the time delayed by a predetermined condition from the timing,
A battery pack in which the value in the storage means is replaced by the remaining capacity value obtained by the remaining capacity value acquisition means. And starts integration of the discharge current value from the timing of switching to the discharge from the charging before Symbol secondary battery, a trigger signal generating means integrated value of the discharge current value to generate a trigger signal at the time the threshold is reached In addition ,
The remaining capacity value obtaining means, said trigger device signals is to determine the residual capacity value based on the terminal voltage at the time of the occurrence, the battery pack according to claim 10. The battery pack according to claim 11 , wherein the threshold value changes in accordance with a length of a charging period immediately before the timing at which the secondary battery is switched from charging to discharging or a charging current in the charging period. When the rise of the discharge current immediately after the timing of switching to the discharge from the charging of the secondary battery is below a predetermined value, the trigger signal generating means does not generate the trigger signal, to claim 11 or 12 The battery pack described. Any battery pack according to one of the secondary battery according to claim 10 or 13 which is a lithium ion secondary battery.

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