JP2007057379A - Internal resistance detection method of secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems wherein operation accuracy of an internal resistance R of a secondary battery is poor because of dependency on the accuracy of a current/voltage sensor, and accurate operation of instantaneous R is difficult, and, when a charge/discharge current is constant, operation of R is impossible, and operation accuracy of a battery residual capacity (SOC) at a load time is lowered. <P>SOLUTION: In the first domain wherein a charge/discharge current of the secondary battery is smaller than the first prescribed threshold, the present internal resistance R of the battery is determined from the present residual capacity SOC, by using a correlation map or an operation expression showing the relation between the residual capacity SOC of the secondary battery and the internal resistance R, acquired beforehand. In the second domain wherein the charge/discharge current is over the first prescribed threshold and lower than the second prescribed threshold, the present internal resistance R of the secondary battery is determined from the residual capacity SOC-init at the moment when reaching the second domain and a discharge time DT until the present time of the secondary battery, by using a correlation map or an operation expression showing the relation between the internal resistance R specified in each residual capacity SOC-init at the moment when reaching the second domain of the secondary battery and the discharge time DT, acquired beforehand. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for detecting the internal resistance of a secondary battery, and more particularly to a detection method that improves the detection accuracy of internal resistance.

As an application of a secondary battery, an electric vehicle is drawing attention, and a technique for estimating the internal resistance of the battery in such an application has been developed. For example, the internal resistance (hereinafter also referred to as R) of a secondary battery in a conventional electric vehicle is generally estimated by any one of the following three methods or combinations. “Resistance detection method” (refer to Patent Document 1), “Calculation method of internal resistance of secondary battery and program for realizing the method” (refer to Patent Document 2), and the like.
(1) Sampling the charging / discharging current I and the load voltage V of the battery, performing a regression line calculation, and estimating R from the slope.
(2) Obtain instantaneous R based on battery charge / discharge current I, voltage V, open-circuit voltage estimation EO, and calculation formula: EO = V + I × R.
(3) Apply R to the adaptive filter to improve accuracy.
Japanese Patent Laid-Open No. 2000-21455 (paragraphs 0005-0006, FIG. 6) JP2004-279242 (paragraphs 0008-0009, FIG. 2)

Problems in the method for estimating the internal resistance of the secondary battery described above will be shown below.
Problem of (1) Since I and V used for linear regression depend on the accuracy of the current / voltage sensor, the calculation accuracy of R is poor. Since the calculation frequency (I and V acquisition conditions are met) is low, it cannot follow sudden fluctuations in internal resistance R. When charge / discharge current is constant, R cannot be calculated.
Problem (2) When estimating the open circuit voltage estimation EO from the SOC, if the SOC calculation accuracy is poor, the R calculation accuracy is also poor. Since I and V depend on the accuracy of the current / voltage sensor, the R calculation accuracy is poor.
If the “instantaneous” I and V used in the problem calculation of (3) are not synchronized (the sampling timing is not perfectly matched), the “instantaneous R of actual battery” cannot be obtained accurately. . Since I and V depend on the accuracy of the current / voltage sensor, the R calculation accuracy is poor. Further, when the charge / discharge current is constant, R cannot be calculated. Since the calculation accuracy of R is poor, there is a problem that the calculation accuracy of the remaining battery level (SOC) at the time of load decreases.

In order to solve the above-described problems, a method for detecting the internal resistance of a secondary battery according to the first invention is:
Calculate the current remaining capacity SOC of the secondary battery from the charge / discharge current value,
In the first region (current value <CURLO #) in which the charge / discharge current of the secondary battery is smaller than a predetermined first threshold, the relationship between the remaining capacity SOC of the secondary battery and the internal resistance R acquired in advance. Using a correlation map or an arithmetic expression indicating the current internal resistance R of the battery from the current remaining capacity SOC of the secondary battery,
In the second region (current value ≧ CURLO # and current value <CURHI #) in which the charge / discharge current is equal to or higher than the predetermined first threshold and lower than the predetermined second threshold, the charge / discharge current is acquired in advance, Using the correlation map or the calculation formula showing the relationship between the internal resistance R and the discharge time DT defined for each remaining capacity SOC-init at the moment of reaching the second area of the secondary battery, Remaining capacity SOC-init (for example, stored in a storage device when the area is reached) at the moment of reaching (that is, at the start of discharge) and the discharge time DT of the secondary battery to the present time, the secondary battery For the current internal resistance R of
It is characterized by that.

Further, the internal resistance detection method of the secondary battery according to the second invention is:
The calculated internal resistance R is corrected according to the temperature of the secondary battery using a calculation means (calculation circuit, CPU, MPU, DSP, etc.),
It is characterized by that.

Further, the internal resistance detection method of the secondary battery according to the third invention is:
The secondary battery is mounted on an electric vehicle.
It is characterized by that.
As described above, the solution of the present invention has been described as a method. However, the present invention can be realized as a device, a program, and a storage medium storing the program substantially corresponding to these, and the scope of the present invention. It should be understood that these are also included.

  According to the first invention, it is possible to follow the increase in the internal resistance of the battery due to the transient phenomenon ideally and in real time, and it is possible to accurately estimate the internal resistance R and the remaining capacity SOC of the battery. Further, even when the charge / discharge current is constant, the internal resistance R can be accurately calculated. In the first region (that is, the low current region), since the internal resistance hardly changes with the passage of time, the SOC-R correlation is established (slope = small). Therefore, in this first region, the SOC-R Calculation can be performed with high accuracy using the correlation. Next, in the second region (that is, the medium current region), a proportional relationship (slope = large) is established with respect to time vs. internal resistance. Therefore, in this second region, this time vs. internal resistance correlation is used. Thus, the calculation can be performed with high accuracy. In the present invention, the case where a current higher than that in the second region flows is excluded from the calculation target, but the first reason is that the system output of the vehicle ( This is because there is almost no scene where a constant current or more (for example, 100 A) flows, and there is no practical problem even if a configuration in which this constant current or more is excluded as the upper limit is used. The second reason is that in a high current region exceeding the second region, a proportional relationship is not established with respect to time versus internal resistance (diffusion limit). In other words, the present invention maintains high calculation accuracy by performing calculations only in each region where these correlations are well established.

  In addition, according to the second aspect of the invention, the variation in the internal resistance R of the battery accompanying the change in battery temperature is corrected, and the calculation accuracy of the internal resistance R is improved. In particular, in applications such as electric vehicles, a large current is used, so the temperature of the secondary battery varies considerably, and the effect of performing such temperature correction processing is great.

  In addition, electric vehicles such as electric vehicles are expected to be used rapidly in the future, and in such applications, high-capacity secondary batteries are frequently charged and discharged with a high voltage current. In order to calculate this, it is necessary to obtain the internal resistance R in a timely and accurate manner. According to the third invention, the secondary battery mounted on such an electric vehicle It becomes possible to obtain the internal resistance R in a timely and accurate manner.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiment described below is an example embodying the present invention, and does not limit the technical scope of the present invention. For example, the present invention will be described on the assumption that the present invention is applied to an electric vehicle. However, the present invention can be widely applied to other uses using a secondary battery.
FIG. 1 is a configuration diagram of a high-power system for an electric vehicle suitable for use in the internal resistance measuring method according to the present invention. An assembled battery 101 as a power source configured by connecting a plurality of cells 107 in series includes an inverter 106 and a high-voltage harness 102 and 111 connected to the positive electrode (+) side and the negative electrode (−) side. Electric power is supplied to the vehicle driving motor 117 via the inverter and the motor power harness 117H. The high-voltage harnesses 102 and 111 are provided with relays 103 and 110 for starting / cutting off power supply. The relay is turned on / off by a relay control signal from a relay control signal line 113 of the battery control device 109. Shall. Based on the input signal from the total voltage sensor 104 via the current sensor input signal line 114 and the input signal from the current sensor 105 via the total voltage sensor input signal line 115, the battery control device 109 The total voltage BATVOL and the current input / output current BATCUR are sampled at a specified period.

  Next, the internal resistance characteristics of the secondary battery which is an example of this patent will be described with reference to FIGS. 1, 2, 3 and 4. FIG. FIG. 2 is a correlation diagram showing the relationship between the discharge time and the internal characteristics of the secondary battery. When the discharge start SOC is set to SOC1 to 4 # under the conditions of a constant battery temperature BATTEMP # and discharge current <CURHI #, the internal resistances R1 to R4 of the battery are proportional to the discharge time. However, the slopes A1 to A4 of the change in the internal resistance are different depending on SOC1 to 4 #, which are the SOC at the start of discharge and the SOC at the moment of reaching the target discharge current region. In other words, this correlation diagram is a correlation map showing the relationship between the internal resistance R and the discharge time DT defined for each remaining capacity SOC-init at the moment of reaching the discharge target region in the secondary battery.

A method for obtaining the inclinations A1 to A4 of changes in internal resistance will be specifically described below.
Specific example When starting discharge SOC = SOC1 #:
R1 = A1 x t + RINT1 #
The slope An is obtained from SOC # k, which is the SOC at the start of discharge.
FIG. 3 shows the correlation between the SOC and the internal resistance characteristics of the secondary battery shown in FIG. FIG. 4 shows the correlation between the temperature and the internal resistance characteristics of the secondary battery shown in FIG. FIG. 5 shows a correlation between the discharge start SOC and the slope A of the secondary battery shown in FIG. As shown in these figures, the internal resistance defined for each SOC at the start of discharge and the discharge time have a strong positive correlation and change with a constant slope A. The present invention utilizes this characteristic. It is.

この求めたBATSOCに基づきSOC対傾きAの相関マップ（図５）を参照して傾きAを演算する。更に、負荷開始時内部抵抗推定RINT＝RINT＃とする。このSOC対傾きAの相関マップを表としての一例を表で示すと以下のようになる。

Next, the internal resistance calculation logic in the embodiment shown in FIG. 1 will be described using the flowchart of FIG. As shown in the figure, in step S601, the battery control device 109 is turned on by starting the vehicle, and the internal resistance calculation is started. In step S602, the total voltage BATVOL and charge / discharge current BATCUR of the battery module are obtained based on the A / D inputs from the voltage sensor 104 and the current sensor 105. In step S603, the battery remaining capacity BATSOC is calculated. In step S604, an initial internal resistance RINT is obtained by referring to a correlation map of SOC vs. internal resistance (FIG. 3) based on the obtained BATSOC. An example of a correlation map of SOC vs. internal resistance is shown in the table below. At this time, RINT is calculated based on the SOC, assuming that RINT is an internal resistance when there is no load (TIME = 0 sec).

Based on the obtained BATSOC, the slope A is calculated with reference to the correlation map of SOC vs. slope A (FIG. 5). Further, the internal resistance estimation RINT = RINT # at the start of load. An example of the SOC vs. slope A correlation map as a table is as follows.

In step S605, if a shirt down request is received from the vehicle controller 116 via the communication 116S, the process proceeds to step S616, and otherwise, the process proceeds to step S606. In step S606, if charge / discharge current | BATCUR | ≧ CURLO #, the process proceeds to S607, and otherwise, the process proceeds to S603. In step S607, if charge / discharge current | BATCUR | <CURHI #, the process proceeds to S608, and otherwise, the process proceeds to S614. In step S608, the intercept RINT # = RINT and the slope A # = A, which are initial internal resistances. In step S604, the internal resistance RINT is calculated once for the sake of convenience, but in practice, the internal resistance RINT is constantly updated according to the SOC at that time. That is, R≈RINT when going from the first region (low current region) to the second region (medium current region), and even if RINT is used as the intercept of the following arithmetic expression in the second region, there is a problem. Absent. That is,
Resistance R = A # × time (s) + RINT (Internal resistance at 0 sec)
Can be obtained. In step S609, if the TIMUP counter is not 0 for measuring the discharge time, the TIMUP counter is started after clearing to TIMUP = 0. In step S610, the battery internal resistance R at load is calculated (internal resistance R = slope A # × discharge time TIMUP + initial internal resistance RINT #).

  In step S611, if the charge / discharge current | BATCUR | ≧ CURLO #, the process proceeds to S612, and otherwise, the process proceeds to S603. In step S612, if TIMUP counter <DISTIME #, the process proceeds to S613; otherwise, the process proceeds to S614. In step S613, if the charge / discharge current | BATCUR | ≧ CURHI #, the process proceeds to 614. Otherwise, the process proceeds to 610. In step S614, R = R (previous value) is held. In step S615, if a shirt down request is received from the vehicle controller 116 which is a host controller, the process proceeds to S616, and otherwise, the process proceeds to S610. In step S616, the internal resistance calculation is terminated.

FIG. 7 is a flowchart showing a process for correcting the temperature deterioration of the secondary battery. As shown in the figure, in step S701, an internal resistance correction logic based on temperature is started. In step S702, the average battery temperature BATTEMP is obtained based on the A / D input from the thermistor 108 via the temperature detection signal line 112. In step S703, the temperature deterioration coefficient RREK is calculated with reference to the battery temperature one deterioration coefficient map (FIG. 4) based on the temperature BATTEMP of the secondary battery. In step S704, if the R operation has been performed, the process proceeds to S705A, and otherwise, the process proceeds to S705B. In step S705A, the corrected battery internal resistance BATRES is calculated as follows.
Corrected internal resistance BATRES = Internal resistance before correction R x Temperature degradation coefficient RREK
In step S706B, BATRES = RINTIAL #. In step S707, if a shirt down request is received from the vehicle controller 116, the process proceeds to S708, and otherwise, the process proceeds to 703. In step S707, the internal resistance correction calculation based on temperature ends.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each member, each means, each step, etc. can be rearranged so that there is no logical contradiction, and a plurality of members, means, steps, etc. can be combined or divided into one. Is possible.

It is the figure which showed the component of the drive system of an electric vehicle. It is the graph (correlation map) which showed the correlation with the discharge time of a secondary battery, and internal resistance. It is the graph (correlation map) which showed correlation with SOC of a secondary battery, and internal resistance. It is the graph (correlation map) which showed the correlation of the temperature of a secondary battery, and internal resistance. It is the graph (correlation map) which showed the correlation of SOC and inclination A at the time of the discharge start of a secondary battery. It is the flowchart which showed the internal resistance calculation logic in this invention. 3 is a flowchart showing an internal resistance correction logic based on temperature in the present invention.

Explanation of symbols

101 battery pack
102,111 High-voltage harness
103,110 Relay
104 Total voltage sensor
105 Current sensor
106 Inverter
107 cells
108 thermistor
109 Battery control device
112 Temperature detection signal line
113 Relay control signal line
114 Current sensor input signal line
115 Total voltage sensor input signal line
116 Vehicle controller
116S signal line
117 Vehicle drive motor
117H Motor power harness

Claims (3)

A method for detecting the internal resistance of a secondary battery,
In the first region where the charging / discharging current of the secondary battery is smaller than a predetermined first threshold, a correlation map or an arithmetic expression indicating the relationship between the remaining capacity SOC of the secondary battery and the internal resistance R acquired in advance. Is used to determine the current internal resistance R of the battery from the current remaining capacity SOC of the secondary battery,
In the second region where the charge / discharge current is not less than the predetermined first threshold value and less than the predetermined second threshold value, the remaining at the moment of reaching the second region of the secondary battery acquired in advance. Using a correlation map or an arithmetic expression indicating the relationship between the internal resistance R and the discharge time DT defined for each capacity SOC-init, the remaining capacity SOC-init at the moment of reaching the second region and the secondary battery Obtain the current internal resistance R of the secondary battery from the discharge time DT up to now,
The internal resistance detection method of the secondary battery characterized by the above-mentioned. The internal resistance detection method of the secondary battery according to claim 1,
The obtained internal resistance R is corrected according to the temperature of the secondary battery,
The internal resistance detection method of the secondary battery characterized by the above-mentioned. In the internal resistance detection method of the secondary battery according to claim 1 or 2,
The secondary battery is mounted on an electric vehicle.
The internal resistance detection method of the secondary battery characterized by the above-mentioned.

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