JP2009244180A - Battery status detection method and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery status detection method and a battery status detection system which determines the discharge capability and the degree of deterioration of a battery by detecting a voltage drop caused by the reactive resistance of the battery. <P>SOLUTION: The battery status detection method measures the voltage V1 of the battery before starting pulse discharge in a first step S1, allows a constant current I0 to be pulse discharged with a frequency of 100 Hz or more in a second step S2, measures the voltage V2 of the battery immediately after the pulse discharge in a third step S3, calculates a voltage drop amount ΔV=V1-V2 from the voltage V1 before the pulse discharge obtained in the first step S1 and the voltage V2 immediately after the end of the pulse discharge obtained in the third step S3 in a fourth step S4, and determines the discharge capability and the degree of deterioration of the battery from the voltage drop amount ΔV in a fifth step S5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a battery state detection method and a battery state detection device that estimate the discharge capacity or the degree of deterioration of a battery.

  In recent years, many electric devices have been mounted in the automobile field, and in particular, the importance of the on-vehicle power source has been further increased with the progress of electric control of safety devices. In addition, in order to respond to energy saving and carbon dioxide emission regulations, it is required to secure an idling stop function and its restart capability at intersections and the like.

  Thus, since the load to a battery increases and the importance is increasing, the necessity of monitoring a battery state and detecting a state is also increasing. In response to this, many techniques for predicting the degree of deterioration (SOH) or discharge capacity (SOF) of a battery have been proposed.

  In Patent Document 1, a battery is discharged at a constant cycle and a current of a constant frequency is supplied. The discharge current waveform and the response voltage waveform at this time are Fourier transformed to obtain respective Fourier transform values, and the Fourier of the voltage response waveform is obtained. The internal impedance is obtained by dividing the converted value by the Fourier transform value of the discharge current waveform. And the deterioration state of a battery is determined from this internal impedance and discharge voltage.

Further, in Patent Document 2, instead of Fourier transform, which requires expensive processing operations, pulse discharge with a rectangular waveform is performed, and the discharge current and response voltage at that time are developed into orthogonal rectangular wave components. Processing is performed at cost. A deterioration state is determined by obtaining a predetermined impedance from the amplitude of a predetermined rectangular wave component of the discharge current and the response voltage.
Japanese Patent No. 3367320 Japanese Patent No. 3960998

  However, in the methods of Patent Documents 1 and 2, the magnitude of the internal impedance during pulse discharge can be estimated, but it is not possible to detect the degree of degradation of reaction resistance that takes time from the start of discharge until a response appears. . In Patent Document 1, the degree of deterioration is determined with further consideration of the average discharge voltage, but even in this case, it takes time until the response appears from the liquid resistance at which the response appears from the start of the discharge and the discharge. The voltage drop due to the reaction resistance cannot be detected separately, and the reaction resistance cannot be clearly and quantitatively determined to determine the discharge capacity / degradation level with high accuracy.

  Therefore, the present invention has been made to solve these problems, and a battery state detection method for determining the discharge capability or the degree of deterioration of a battery with extremely high accuracy by detecting a voltage drop due to the reaction resistance of the battery, and An object is to provide a battery state detection device.

  According to a first aspect of the battery state detection method of the present invention, a predetermined current is pulse-discharged a predetermined number of times at a frequency of 100 Hz or more from a battery, and a voltage difference that is a difference between a voltage before the start of the pulse discharge and a voltage immediately after the end is obtained. It is calculated and the discharge capability or the deterioration degree of the battery is determined from the voltage difference.

  Another aspect of the battery state detection method of the present invention is characterized in that a reaction resistance value is calculated from the voltage difference and the constant current, and a discharge capability or a deterioration degree of the battery is determined from the reaction resistance value. .

  In another aspect of the battery state detection method of the present invention, the voltage before the start of the pulse discharge is an average value of the voltages measured a plurality of times before the start of the pulse discharge, and the voltage immediately after the end of the pulse discharge is The average value of the voltages measured a plurality of times immediately after the end of the pulse discharge.

  According to another aspect of the battery state detection method of the present invention, a constant current is pulse-discharged a predetermined number of times at a frequency of 100 Hz or more from a battery, and the difference between the voltage before the start of the pulse discharge and the voltage during the current stop period within one cycle of the pulse discharge. The voltage difference for each cycle is calculated, and the voltage difference for each cycle is fitted with the number of pulses using a predetermined function to create a voltage difference approximate expression, and when the pulse discharge is continued from the voltage difference approximate expression A convergence voltage difference is calculated, and a discharge capability or a deterioration degree of the battery is determined from the convergence voltage difference.

  Another aspect of the battery state detection method of the present invention is characterized in that a reaction resistance value is calculated from the convergence voltage difference and the constant current, and a discharge capacity or a deterioration degree of the battery is determined from the reaction resistance value. To do.

  In another aspect of the battery state detection method of the present invention, the predetermined function is an exponential function or an inverse function.

  According to a first aspect of the battery state detection apparatus of the present invention, a voltage measurement unit that measures the voltage of the battery, a current measurement unit that measures a current flowing through the battery, a pulse discharge circuit that pulse-discharges the battery, A control unit that operates a pulse discharge circuit at a predetermined period; a voltage measurement value and a current measurement value of the battery in a predetermined period including a period in which the pulse discharge circuit performs the pulse discharge; And an arithmetic control unit for detecting a battery state by calculating a reaction resistance value of the battery from the measured value of the voltage and the measured value of the current, which is input from the current measuring unit.

  According to another aspect of the battery state detection device of the present invention, the control unit causes the pulse discharge circuit to discharge a predetermined value of current at a frequency of 100 Hz or more from the battery a predetermined number of times in response to a request from the arithmetic control unit. It is characterized by controlling.

  In another aspect of the battery state detection device of the present invention, the control unit controls the start and end of pulse discharge by the pulse discharge circuit in response to a request from the arithmetic control unit.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the battery state detection method and battery state detection apparatus which determine the discharge capability or deterioration degree of a battery with high precision by detecting the voltage drop by the reaction resistance of a battery.

  A configuration of a battery state detection method, a battery state detection device, and a battery power supply system in a preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, about each structural part which has the same function, the same code | symbol is attached | subjected and shown for simplification of illustration and description.

  A first embodiment of the battery state detection method of the present invention will be described below using the flowchart shown in FIG. In the battery state detection method of the present embodiment, the battery discharge state (SOF: State of Function) or the degree of deterioration (SOH: State of Health) is estimated as the battery state. In order to determine the discharge capability or the degree of deterioration of such a battery, in the battery state detection method of this embodiment, the battery is pulse-discharged at a predetermined cycle, and data at that time is acquired and used for the determination.

  In the battery state detection method of the present embodiment, as the first step S1, the battery voltage V1 before the start of pulse discharge is measured and acquired. As the next second step S2, a predetermined pulse discharge is performed from the battery. This pulse discharge can be performed by turning on and off a constant current I0 at a frequency of 100 Hz or more. After performing such a pulse discharge a predetermined number of times, in a third step S3, the battery voltage V2 immediately after the pulse discharge is measured and acquired.

  In the fourth step S4, the voltage drop amount ΔV = V1−, which is the difference between the voltage V1 before the start of the pulse discharge acquired in the first step S1 and the voltage V2 immediately after the end of the pulse discharge acquired in the third step S3. V2 is calculated. In the fifth step, the battery discharge capacity or the deterioration state is estimated from the calculated voltage drop amount ΔV to determine whether the battery state is appropriate.

  FIG. 2 shows an example of pulse discharge performed in the second step S2 in the process flow of the battery state detection method of the present embodiment. FIG. 2 (a) shows a current pattern (indicated by reference numeral 11) which is a temporal change in the current discharged from the battery, and FIG. 2 (b) corresponds to the current pattern 11 in FIG. 2 (a). A voltage pattern (indicated by reference numeral 12), which is a change in response voltage that changes as shown in FIG.

  In the current pattern 11 shown in FIG. 2A, the magnitude (amplitude) of the current is a constant value I0, and the current is discharged in pulses at a frequency of 100 Hz or more. The number of times of pulse discharge (number of cycles) is N times determined in advance.

  The response voltage pattern 12 when performing the above-described pulse discharge changes in a substantially step shape at the same frequency as the current pattern 11, but the voltage for each cycle decreases as the number of cycles increases at both the upper and lower peaks. I understand. However, the rate of decrease in peak voltage decreases with the number of cycles.

  Since the change due to the repetition of the response voltage pulse as shown in FIG. 2B corresponds to the magnitude of the reaction resistance which takes time until the battery response appears, in the battery state detection method of this embodiment, In the fourth step S4, a voltage drop amount ΔV = V1−V2 between the voltage V1 before the start of the pulse discharge and the voltage V2 immediately after the end of the pulse discharge is calculated. At this time, by setting the frequency of the discharge pulse to 100 Hz or more, it is possible to clearly detect the magnitude of the reaction resistance separately from other resistance components. As the battery reaction resistance deteriorates and the discharge capacity decreases, the voltage drop ΔV increases. Therefore, in the fifth step, the battery discharge state or the deterioration state is estimated based on the voltage drop ΔV. Is appropriate (is the discharge capacity sufficient).

  An example of a method for determining the discharge capacity or the degree of deterioration of the battery will be described below. The voltage drop amount ΔV is compared with a predetermined voltage drop allowable value (= voltage before the start of pulse discharge−allowable minimum voltage), and based on a voltage difference (voltage drop margin) obtained by subtracting the voltage drop amount ΔV from the voltage drop allowable value. The discharge capacity or the degree of deterioration can be determined. That is, when the voltage drop margin is large, it is determined that the discharge capacity is high or the degree of deterioration is low, and when the voltage drop margin is small, it is determined that the discharge capacity is low or the degree of deterioration is high. Further, when the voltage drop amount ΔV exceeds the allowable voltage drop value, it can be determined that the battery needs to be replaced.

  In some cases, the battery can be similarly estimated by predicting a response voltage when discharging is performed with a predetermined discharge pattern from the voltage drop amount ΔV, and comparing the predicted response voltage with a predetermined allowable threshold value. Can be determined.

  In the above embodiment, the allowable voltage drop used for determining the discharge capability or the deterioration level of the battery is assumed to be corrected in accordance with the number of cycles of pulse discharge. That is, if the number of pulse discharge cycles is not sufficient, the determination is made using a voltage that is not sufficiently close to the voltage at which the response voltage pattern shown in FIG. Therefore, when the number of pulse discharge cycles is not sufficient, the discharge capability or the degree of deterioration of the battery can be determined with high accuracy by performing a predetermined correction based on the number of cycles.

  Another method for determining the discharge capacity or the degree of deterioration of the battery will be described below. In this method, the discharge capability or the degree of deterioration of the battery is determined using the reaction resistance value (Rx) of the battery. The reaction resistance value Rx of the battery can be calculated by dividing the voltage drop amount ΔV by the current value I0. The calculated reaction resistance value Rx is compared with a predetermined reaction resistance allowable value, and when the reaction resistance value Rx is sufficiently smaller than the reaction resistance allowable value, it is determined that the discharge capacity is high or the deterioration degree is low, and the reaction resistance value Rx is When it has increased to a value close to the reaction resistance allowable value, it is determined that the discharge capacity is low or the degree of deterioration is high. Further, when the reaction resistance value Rx exceeds the reaction resistance allowable value, it can be determined that the battery needs to be replaced.

  Further, in some cases, the battery can be similarly detected by predicting a response voltage when discharging with a predetermined discharge pattern determined from the reaction resistance value R and comparing the predicted response voltage with a predetermined allowable threshold value. Can be determined.

  Also in the above embodiment, when the number of pulse discharge cycles is not sufficiently large, either the reaction resistance value Rx or the reaction resistance allowable value is corrected in advance based on the number of cycles. Thereby, it becomes possible to determine the discharge capability or the deterioration degree of the battery with high accuracy.

  A second embodiment of the battery state detection method of the present invention will be described below using the flowchart shown in FIG. In the battery state detection method of the present embodiment, the voltage of the battery before the start of pulse discharge is obtained by measuring a plurality of times in the first step S11 shown in FIG. 3, and in the second step S12, the obtained plurality of voltages are obtained. An average value is obtained and is set as V1.

  After a predetermined pulse discharge is performed from the battery in step S13, the voltage of the battery immediately after the pulse discharge is measured and acquired a plurality of times in the fourth step S14, and in the fifth step S15, the acquired plurality of voltages are acquired. An average value is obtained and is set as V2. In subsequent 6th step S16 and 7th step S17, the process similar to step S4, S5 of 1st Embodiment is performed, and the discharge capability or deterioration degree of a battery is determined.

  As described above, in this embodiment, a plurality of voltages before and after the pulse discharge are obtained as voltages used for detecting the state of the battery, and an average value of each is obtained, thereby reducing variation in data and improving accuracy. A high voltage value is used.

  A third embodiment of the battery state detection method of the present invention will be described below using the flowchart shown in FIG. In the battery state detection method of the present embodiment, a response voltage during a period in which no current is discharged is measured for each period of pulse discharge as shown in FIG. 2, and this response voltage is determined from a voltage V1 before the start of pulse discharge. The voltage drop amount (hereinafter referred to as the voltage drop amount per cycle) is calculated.

When the voltage drop amount for each cycle is calculated for all cycles, this is fitted using a predetermined function with the number of pulse discharges as a variable to create a voltage drop approximation formula. This predetermined function has convergence and proportionality.
From this voltage drop approximation formula, calculate the amount of convergence voltage drop when pulse discharge is continued, that is, the amount of convergence voltage drop when the number of pulses is infinite, and from this amount of convergent voltage drop, the discharge capacity or deterioration degree of the battery Determine.

  In the flowchart shown in FIG. 4, as the first step S21 of the battery state detection method of the present embodiment, the battery voltage V1 before the start of pulse discharge is measured and acquired. When predetermined pulse discharge is started from the battery in the next second step S22, the following third step S23 to fifth step S25 are repeated for the number of pulse discharge cycles.

  In the third step S23, the response voltage V2i when the current is not discharged in the i-th cycle is measured and acquired. In the fourth step S24, the difference ΔVi = V1−V2i between the voltage V1 before the start of the pulse discharge and the response voltage V2i is calculated and set as the voltage drop amount per cycle. In the fifth step S25, it is determined whether or not the pulse discharge has ended. If the pulse discharge is continuing, the process returns to the third step S23 and the next cycle is performed. On the other hand, if it is determined in the fifth step S25 that the pulse discharge has ended, the process proceeds to the next sixth step S26.

  In the sixth step S26, the predetermined voltage drop amount ΔVi calculated in the fourth step S24 is fitted using a predetermined function having the pulse discharge frequency i as a variable, and this is used as a voltage drop approximation formula. In the seventh step S27, the convergence voltage drop amount ΔV∞ when the number of pulse discharges i is set to infinity is calculated from this voltage drop approximation formula, and in the eighth step S28, the discharge capacity of the battery is calculated from this convergence voltage drop amount ΔV∞. Alternatively, the deterioration state is estimated to determine whether the battery state is appropriate.

In the above processing flow, the response voltage V2i measured in the third step S23 is stored in the memory, and it is determined in the fifth step S25 that the pulse discharge has ended, and then the voltage drop for each cycle in the fourth step S24. The amount ΔVi = V1−V2i may be calculated.
In addition, the determination of the discharge capability or the deterioration level of the battery in the eighth step S28 can be performed by comparing the converged voltage drop amount ΔV∞ with the allowable voltage drop value as in the first embodiment, or the convergence. The reaction resistance value of the battery may be calculated from the voltage drop amount ΔV∞, and this may be used.

In the sixth step S26, an exponential function or a reciprocal function can be used as a function for fitting the periodical voltage drop amount ΔVi. As a voltage drop approximation expression using an exponential function, for example, the following expression can be used.

  The parameters A1 and A2 are determined by fitting the above equation to the number of periods i and the amount of voltage drop ΔVi for each period using the least square method or the like. Thereby, the convergence voltage drop amount ΔV∞ calculated in the seventh step S27 can be set to A2. As an example, FIG. 5 shows a result obtained by approximating the voltage drop amount ΔVi for each cycle in (Equation 1). From the figure, it can be seen that by using an exponential function (curve indicated by reference numeral 21 in FIG. 5) as the voltage drop approximation formula, the periodical voltage drop amount ΔVi (indicated by reference numeral 22 in FIG. 5) can be approximated with high accuracy.

FIG. 6 shows an embodiment using an inverse function as a function for fitting the periodical voltage drop amount ΔVi. FIG. 6 shows the result of approximating the voltage drop amount ΔVi for each cycle using the reciprocal function of the following equation.

  The parameters B1, B2, and B3 are determined by fitting the above equation to the number of periods i and the voltage drop amount ΔVi for each period using a least square method or the like. Thereby, the convergence voltage drop amount ΔV∞ calculated in the seventh step S27 can be set to B3. 6 that even when an inverse function (curve indicated by reference numeral 31 in FIG. 6) is used as the voltage drop approximation formula, the periodical voltage drop amount ΔVi (indicated by reference numeral 32 in FIG. 6) can be approximated with high accuracy. .

  FIG. 7 shows a schematic configuration of the battery state detection device and the battery power supply system according to the embodiment of the present invention. FIG. 2 is a block diagram showing a schematic configuration of the battery power supply system 100 and the battery state detection device 110 according to the present embodiment. The battery power supply system 100 includes a battery 101, a voltage measurement unit 102, a current measurement unit 103, and the battery state detection device 110 of the present embodiment.

  In addition, the battery state detection device 110 according to the present embodiment includes an arithmetic control unit 111, a storage unit 112, a pulse discharge circuit 113, and a control unit 114. The control unit 114 can control the pulse discharge circuit 113 so that a predetermined current is pulse-discharged a predetermined number of times at a frequency of 100 Hz or more from the battery 101 in accordance with a request from the arithmetic control unit 111.

  The arithmetic control unit 111 performs any one of the processes from the first embodiment to the third embodiment of the battery state detection method of the present invention described above. The calculation control unit 111 is configured to be able to input a voltage measurement value and a current measurement value from the voltage measurement unit 102 and the current measurement unit 103, respectively. In addition, the controller 114 can set conditions for causing the pulse discharge circuit 113 to perform pulse discharge, that is, conditions such as the frequency of pulse discharge, the number of discharges, and the discharge current value. The start instruction is also given.

  With the configuration as described above, the battery power supply system 100 and the battery state detection device 110 according to the present embodiment cause the battery 101 to perform pulse discharge in response to an instruction from the arithmetic control unit 111, and measure the voltage and current during the voltage measurement. For example, the state of the battery 101 can be detected by reading the voltage from the storage unit 112 after the pulse discharge is completed. Furthermore, a voltage drop tolerance, a reaction resistance tolerance, a voltage drop approximation equation fitting parameter, and the like used for state detection may be stored in the storage unit 112 and read and used when necessary.

  In addition, the description in this Embodiment shows an example of the battery state detection method and battery state detection apparatus which concern on this invention, and is not limited to this. The detailed configuration and detailed operation of the battery state detection method and the like in the present embodiment can be changed as appropriate without departing from the spirit of the present invention.

It is a flowchart which shows the flow of a process of the battery state detection method which concerns on the 1st Embodiment of this invention. It is a figure which shows the change of the voltage and electric current of the battery at the time of pulse discharge, (a) A current pattern and (b) a voltage pattern are shown. It is a flowchart which shows the flow of a process of the battery state detection method in the 2nd Embodiment of this invention. It is a flowchart which shows the flow of a process of the battery state detection method in the 3rd Embodiment of this invention. It is a figure which compares the voltage drop approximate expression using an exponential function, and the voltage drop amount for every period. It is a figure which compares the voltage drop approximate expression using a reciprocal function, and the voltage drop amount for every period. It is a block diagram which shows the schematic structure of the battery state detection apparatus and battery power supply system which concern on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Battery power supply system 101 Battery 102 Voltage measurement part 103 Current measurement part 110 Battery state detection apparatus 111 Operation control part 112 Storage part 113 Pulse discharge circuit 114 Control part

Claims (9)

A predetermined current is pulse-discharged a predetermined number of times at a frequency of 100 Hz or more from the battery
Calculate a voltage difference that is the difference between the voltage before the start of the pulse discharge and the voltage immediately after the end,
The battery state detection method characterized by determining the discharge capability or the deterioration degree of the battery from the voltage difference. Calculate a reaction resistance value from the voltage difference and the constant current,
The battery state detection method according to claim 1, wherein a discharge capability or a deterioration degree of the battery is determined from the reaction resistance value. The voltage before the start of the pulse discharge is an average value of the voltage measured a plurality of times before the start of the pulse discharge,
3. The battery state detection method according to claim 1, wherein the voltage immediately after the end of the pulse discharge is an average value of voltages measured a plurality of times immediately after the end of the pulse discharge. A predetermined current is pulse-discharged a predetermined number of times at a frequency of 100 Hz or more from the battery
The difference between the voltage before the start of the pulse discharge and the voltage during the current stop period within one cycle of the pulse discharge is calculated as the voltage difference for each cycle,
Fitting the voltage difference for each period with the number of pulses using a predetermined function to create a voltage difference approximation formula,
Calculate the convergence voltage difference when the pulse discharge is continued from the voltage difference approximation formula,
The battery state detection method characterized by determining the discharge capacity or the deterioration degree of the battery from the convergence voltage difference. Calculate a reaction resistance value from the convergence voltage difference and the constant current,
The battery state detection method according to claim 4, wherein a discharge capability or a deterioration degree of the battery is determined from the reaction resistance value.   The battery state detection method according to claim 4, wherein the predetermined function is an exponential function or an inverse function. A voltage measuring unit for measuring the voltage of the battery;
A current measuring unit for measuring a current flowing through the battery;
A pulse discharge circuit for pulse discharging the battery;
A controller for operating the pulse discharge circuit at a predetermined period;
The measured voltage value and the measured current value of the battery for a predetermined period including the period for performing the pulse discharge in the pulse discharge circuit are input from the voltage measuring unit and the current measuring unit, respectively, and the measured voltage value and A battery state detection apparatus comprising: an arithmetic control unit that detects a battery state by calculating a reaction resistance value of the battery from the measured value of the current. 8. The control unit according to claim 7, wherein the control unit controls the pulse discharge circuit so that a constant current is pulse-discharged a predetermined number of times at a frequency of 100 Hz or more from the battery in response to a request from the arithmetic control unit. Battery state detection device. The battery state detection device according to claim 7 or 8, wherein the control unit controls start and end of pulse discharge by the pulse discharge circuit in response to a request from the arithmetic control unit.

Images