JP5137885B2 - Battery state estimation method and power supply system - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a technical state of a battery state estimation method and a power supply system for estimating a state of deterioration or discharge capability of a battery that supplies power to a load, and more particularly to deterioration or discharge by estimating battery impedance. The present invention relates to a technical field such as a battery state estimation method for estimating capacity.

  Techniques for estimating the deterioration level or discharge capacity of a battery mounted on an automobile or the like have been conventionally known, and for example, there are those described in Patent Document 1.

  In general, since the battery impedance has a strong correlation with the battery degradation level or discharge capability, if the battery impedance can be detected, the battery degradation level or discharge capability can be estimated using the detected impedance. Is possible. By estimating the degree of deterioration or discharge capacity of the battery, it is possible to determine whether the battery has been deteriorated or whether the discharge capacity has been reduced. If the deterioration has progressed or the discharge capacity has been reduced Can prompt the user to replace the battery.

  In a power supply system equipped with a battery, as a method for estimating the deterioration degree or discharge capacity of the battery, a predetermined charging current or discharging current is passed through the battery, the current and voltage at that time are measured, and the measured current and voltage are measured. Conventionally, a method for calculating impedance by a predetermined calculation is known.

  The impedance of the battery is an index that accurately indicates the degree of deterioration and discharge capacity of the battery in an environment where conditions such as a laboratory are prepared, but it is actually used in an environment where it is used as a typical example. In such an environment, impedance measurement of an automobile battery is performed in an environment exposed to noise generated by electrical equipment or the like. Therefore, for example, in the battery deterioration determination method described in Patent Document 1, a method is proposed in which a discharge current having a constant frequency is caused to flow by discharging at a constant cycle, and the impedance is obtained by Fourier transforming the current waveform and voltage waveform of the discharge current. Has been.

Japanese Patent No. 3367320

  However, the conventional impedance measuring method has the following problems. The impedance of the battery is influenced not only by noise and the like but also by the state of charge and polarization of the battery. In order to obtain the impedance with high accuracy excluding such influence, it is preferable to flow the current so that the amount of charge and the amount of discharge are equal, as shown in FIG. 2, for example. Flowing such a current through the battery can be easily realized in an environment such as a laboratory, but in a battery mounted on an actual vehicle, a current that alternately changes between positive and negative as shown in FIG. It cannot be energized. In order to energize such a current, it is necessary to mount a so-called bipolar power supply in the vehicle, resulting in high costs.

  Therefore, in a battery mounted on a vehicle, a method of measuring a current / voltage response due to only discharging as shown in FIG. 3 and calculating an impedance from the measured current / voltage is generally widely used. When the impedance is calculated from the response due to only such discharge, it is known that only the discharge is repeatedly performed on the battery, and therefore the response voltage width gradually decreases as shown in FIG. When the voltage width shows such a response, the impedance calculated by simply dividing the response voltage by the applied current changes as the response voltage changes. Therefore, it is not possible to accurately estimate the degree of deterioration and the discharge capacity of the battery from the impedance thus obtained.

  Accordingly, the present invention has been made to solve such a problem, and a battery state in which a transient change of a response voltage due to repeated discharge can be reduced and a battery deterioration degree or a discharge capacity can be accurately estimated. An object is to provide an estimation method and a power supply system.

In order to solve the above problems, a first aspect of the battery state estimation method according to the present invention estimates the impedance of the battery from the current value and response voltage of the battery when the battery is discharged with a predetermined discharge pattern. A battery state estimation method for determining the degree of deterioration or discharge capacity of the battery using the impedance so that a response voltage at each discharge when the discharge is performed twice or more is substantially constant. The discharge pattern is formed.

According to another aspect of the battery state estimation method of the present invention, the recovery time during which the discharge is suspended is set so that the discharge current width and time width are constant and the response voltage during each discharge is substantially constant. The discharge pattern is formed by adjusting.

Another aspect of the battery state estimation method of the present invention is characterized in that the discharge pan is formed by sequentially increasing the recovery time so that the response voltage at the time of each discharge becomes substantially constant.

In another aspect of the battery state estimation method of the present invention, when the number of discharges of 2 or more is N, the adjustment parameters are A and B, and the recovery time until the Nth discharge starts is Th (N) The recovery time Th (N) is expressed by the following formula Th (N) = A + B × exp (N)
It is characterized by calculating.

In another aspect of the battery state estimation method of the present invention, the number of discharges of 2 or more is N, the adjustment parameters are C and D, and the recovery time until the Nth discharge is started is Th (N). When the number of discharges N is less than or equal to the predetermined number, the recovery time Th (N) is expressed by the following formula Th (N) = C + D × N
It is characterized by calculating.

A first aspect of a power supply system of the present invention includes a battery, a discharge circuit for discharging the battery at a predetermined current value, a current sensor for measuring the battery current, and a voltage for measuring the battery voltage. A sensor and a control means for controlling the discharge circuit, and the control means has a substantially constant response voltage at each discharge measured using the voltage sensor when the discharge is performed twice or more. The discharge circuit is controlled as described above.

  Another aspect of the power supply system of the present invention is characterized in that the control means outputs a discharge request signal having a constant discharge current width and time width to the discharge circuit every predetermined recovery time. .

  Another aspect of the power supply system of the present invention is characterized in that the control means outputs the discharge request signal to the discharge circuit while sequentially increasing the recovery time.

In another aspect of the power supply system of the present invention, when the number of discharges of 2 or more is N, the adjustment parameters are A and B, and the recovery time until the Nth discharge is started is Th (N), the control The means sets the recovery time Th (N) to the following formula Th (N) = A + B × exp (N)
Characterized in that in calculating and outputs the discharge request signal to the discharge circuit.

In another aspect of the power supply system of the present invention, when the number of discharges of two or more is N, the adjustment parameters are C and D, and the recovery time until the Nth discharge is started is Th (N), the control When the discharge number N is equal to or less than the predetermined number, the means sets the recovery time Th (N) to the following formula Th (N) = C + D × N
Characterized in that in calculating and outputs the discharge request signal to the discharge circuit.

  Advantageous Effects of Invention According to the present invention, it is possible to provide a battery state estimation method and a power supply system that can reduce a transitional change in response voltage due to repetitive discharge and accurately estimate the deterioration degree or discharge capacity of the battery.

It is a graph which shows an example of the discharge pattern used for the state estimation method of the battery which concerns on the 1st Embodiment of this invention. It is a graph which shows an example of the discharge pattern formed so that the amount of charge electricity and the amount of discharge electricity may become equal. It is a graph which shows an example of the discharge pattern only by the conventional discharge. It is a graph which shows a response voltage when using the discharge pattern only by the conventional discharge. It is a graph which shows the recovery time after a fixed pulse discharge. It is a graph which shows the applied current pattern which lengthened recovery time with the frequency | count of discharge. It is a graph which shows a response voltage when using the discharge pattern which lengthened recovery time with the frequency | count of discharge. It is a flowchart which shows the flow of a process of the battery state estimation method which concerns on 1st Embodiment. It is a graph which shows an example of the discharge pattern used for the state estimation method of the battery which concerns on the 2nd Embodiment of this invention. 1 is a block diagram showing a schematic configuration of a power supply system according to an embodiment of the present invention.

  A battery state estimation method and a power supply system according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. Each component having the same function is denoted by the same reference numeral for simplification of illustration and description.

(First embodiment)
A battery state estimation method according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 5 to 8. It has been explained that when only discharging is repeatedly performed on the battery, the response voltage width gradually decreases as shown in FIG. 4. This is due to the influence of polarization and stratification inside the battery. There is a predetermined time until such influence is reduced to return to a stable state. Further, there is a characteristic that the time required to return to a stable state becomes longer as the number of discharges is increased. As an example, FIG. 5 shows the result of measuring the recovery time required to return to the original voltage after performing a constant pulse discharge. As shown in the figure, it can be seen that the recovery time after discharge becomes longer as the number of discharges increases, and that the amount of increase in the recovery time increases at an accelerated rate as the number of discharges increases.

  Therefore, in the battery state estimation method of the present embodiment, the time interval for discharging from the battery is increased with the number of discharges in consideration of the characteristics of the battery recovery time as shown in FIG. As shown in FIG. 6, when the applied time width (hereinafter referred to as T1) and the current width (hereinafter referred to as I1) are constant, the application interval is appropriately increased along with the number of discharges. Then, as shown in FIG. 7, the response voltage can be made substantially constant.

  As described above, when a constant response voltage is obtained for a constant applied current (application time width T1 and current width I1 are constant), a constant value is obtained as an impedance by dividing the response voltage by the applied current. It is done. In this case, since the battery is not in a stable state in which polarization, stratification, and the like are eliminated, it does not have an impedance at the time of stabilization. Therefore, the impedance calculated as described above is hereinafter referred to as metastable impedance. There is a one-to-one relationship between the impedance at the time of stabilization and the degree of deterioration or the discharge capability of the battery. Using this relationship, the degree of deterioration of the battery or the discharge capability can be detected from the impedance at the time of stabilization.

  However, in the battery state estimation method according to the present embodiment, a constant response voltage is obtained with respect to a constant applied current. Therefore, even between the metastable impedance at this time and the deterioration degree or discharge capacity of the battery. A one-to-one relationship is established. Therefore, in the battery state estimation method of the present embodiment, the relationship between the impedance at the time of metastable and the degree of deterioration or discharge capacity of the battery is obtained in advance, and this is used to determine the degree of deterioration of the battery from the impedance at the time of metastable. Alternatively, the discharge capacity is detected. As the relationship between the metastable impedance and the battery deterioration level or discharge capacity, the battery deterioration level or discharge capacity is calculated using the relational expression F (X) (X is metastable impedance) created in advance below. Shall be estimated.

In the battery state estimation method of the present embodiment, the relationship between the number of discharges and the recovery time until the start of discharge shown in FIG.
Th (N) = A + B × exp (N) (1)
Here, N represents the number of discharges, and Th (N) represents the recovery time until the Nth discharge is started. In the present embodiment, the change in the recovery time shown in FIG. 5 is approximated using an exponential function, and the equation (1) is optimally approximated using the recovery time data shown in FIG. Parameters A and B are determined. An example of the discharge pattern in which the recovery time Th (N) is determined using the equation (1) is shown in FIG.

  When the battery is discharged using the discharge pattern 10 shown in FIG. 1, the measured response voltage becomes a substantially constant value. Then, the metastable impedance X can be calculated from the measured response voltage and the discharge current shown in FIG. From this, it is possible to determine the degree of deterioration or the discharge capacity of the battery using the relational expression F (X).

  The battery state estimation method of this embodiment will be described in detail with reference to the flowchart shown in FIG. Here, the relational expression Th (N) between the number of discharges of Formula (1) and the recovery time until the start of discharge, and the relational expression F (X) between the impedance X at the time of metastable and the deterioration degree or discharge capability of the battery are It is created in advance, and the state of the battery is estimated using this.

  When the battery state detection is started, first, the number of discharges N is initialized to 1 in step S1. In the next step S2, the battery is discharged with the discharge width I1 and the discharge time width T1. In step S3, the response voltage is measured during the discharge period performed in step S2. In step S4, the measured response voltage is stored in a predetermined memory or the like during the discharge period of step S2. In the example of the response voltage shown in FIG. 7, for example, the lowest response voltage can be selected as the response voltage to be stored. Alternatively, the average value of the measured voltage during the discharge period can be used. Regardless of which response voltage is used, a relational expression F (X) between the impedance X and the degree of deterioration of the battery or the discharge capacity needs to be created in advance.

  In step S5, it is determined whether or not the number of discharges N has reached the target number (Nmax). If the target number has not been reached, the process proceeds to step S6. In step S6, 1 is added to the number N of discharges, and a recovery time Th (N) until the Nth discharge is started in the next step S7 is calculated. In step S8, the process waits for the recovery time Th (N) to elapse. When the recovery time Th (N) elapses, the process returns to step S2 and the processes up to step S4 are repeated.

  On the other hand, if it is determined in step S5 that the number of discharges N has reached the target number of times Nmax, the process proceeds to step S9, and all the response voltages stored in step S4 are read. In step S10, an average value Va of the read response voltages is calculated. In the state estimation method of the present embodiment, a substantially constant response voltage can be obtained regardless of the number of discharges N. Here, the average value is calculated in order to reduce the variation in the measured value of the response voltage. When the variation in the measured value of the response voltage is sufficiently small, the process of step S10 is not necessarily required, and any one of the response voltages may be used.

In step S11, the impedance X is calculated from the response voltage Va calculated in step S10 and the discharge width I1 by the following equation.
X = Va / T1 (2)
In step S12, using the impedance X calculated by the above equation, F (X) is determined (compared with a predetermined threshold value) to determine the degree of deterioration or the discharge capacity of the battery.

  In the above processing flow, the discharge width I1 is used to calculate the impedance X in step S11. However, instead of this, a current measurement value can also be used. In that case, the current is measured together with the response voltage in step S3, and the current measurement value is stored in the memory together with the response voltage in step S4. Thus, in step S11, the impedance X can be calculated using the current measurement value stored in the memory.

  As described above, according to the battery state estimation method of the present embodiment, it is possible to reduce the transient change of the response voltage due to repeated discharge and to make it almost constant. It becomes possible to estimate the deterioration degree or discharge capacity of the battery with high accuracy.

(Second Embodiment)
A battery state estimation method according to the second embodiment of the present invention will be described with reference to FIG. In the battery state estimation method of the present embodiment, the following equation (3) is used instead of equation (1) of the first embodiment for the relationship between the number of discharges N and the recovery time until the start of discharge.
Th (N) = C + D × N (when N ≦ Nb) (3)
Or Th (N) = A + B × exp (N) (when N> Nb) (4)

  Formula (3) is such that the recovery time Th (N) is approximated by a linear expression of the number of times of discharge N when the number of times of discharge N is equal to or less than the predetermined number of times Nb. When the number of discharges N is greater than the predetermined number Nb, the recovery time Th (N) is calculated by an exponential function of the number of discharges N shown in Equation (4), as in the first embodiment. An example of the discharge pattern used in the battery state estimation method of the present embodiment is shown in FIG. In the figure, the initial discharge pattern 20a in which discharge is started is obtained by calculating the recovery time using the above equation (3), and the discharge pattern 20b is obtained by calculating the recovery time using the above equation (4). It is calculated.

  In the battery state estimation method of the present embodiment, when the number of discharges is small, the recovery time Th (N) is calculated by calculating the recovery time using the linear expression shown in the equation (3). It is possible to reduce the load on the arithmetic processing device to be used.

  An embodiment of the power supply system of the present invention will be described below with reference to FIG. FIG. 10 is a block diagram showing a configuration of the power supply system 100 of the present embodiment. The power supply system 100 includes a battery 101, an alternator 102 that charges the battery 101, a discharge circuit 103 that discharges the battery 101 with a predetermined discharge current, and a battery state estimation device 110 that estimates the state of the battery 101. ing. A load 105 is connected to the battery 101.

  The battery state estimation device 110 includes a current sensor 111, a voltage sensor 112, a control unit 113, and a memory 114. The battery state estimation methods of the first embodiment and the second embodiment are processed using the control means 113. That is, a discharge request signal having a discharge width I1 and a discharge time width T1 is output from the control means 113 to the discharge circuit 103 to be discharged, and the current and response voltage therebetween are measured using the current sensor 111 and the voltage sensor 112, respectively. In addition, the recovery time until the start of discharge is calculated by the control means 113, and when the recovery time is reached, the discharge request signal is output to the discharge circuit 103 again to cause discharge. The current and response voltage measured by the current sensor 111 and the voltage sensor 112 are stored in the memory 114, and are used to calculate the impedance X after all discharges are completed.

  In the power supply system of this embodiment configured as described above, it is possible to accurately estimate the state of the battery 101 using the battery state estimation method of the first embodiment and the second embodiment. It is possible to appropriately notify the user of the degree of deterioration or the discharge capacity of the battery 101.

  The description in the present embodiment shows an example of the battery state estimation method and the power supply system according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of the battery state estimation method and the like in the present embodiment can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Power supply system 101 ... Battery 102 ... Alternator 103 ... Discharge circuit 105 ... Load 110 ... Battery state estimation apparatus 111 ... Current sensor 112 ... Voltage sensor 113 ... .Control means 114 ... memory

Claims (10)

Estimating the impedance of the battery from the current value and response voltage of the battery when the battery is discharged with a predetermined discharge pattern, and using the impedance to determine the degree of deterioration or the discharge capacity of the battery A method,
A battery state estimation method, wherein the discharge pattern is formed so that a response voltage at each discharge when the discharge is performed twice or more is substantially constant. The discharge pattern is formed by adjusting the recovery time during which the discharge is suspended so that the discharge current width and time width are constant and the response voltage at the time of each discharge is substantially constant. The battery state estimation method according to claim 1. 3. The battery state estimation method according to claim 2, wherein the discharge period is formed by sequentially increasing the recovery time so that the response voltage at the time of each discharge becomes substantially constant. When the number of discharges of 2 or more is N, the adjustment parameters are A and B, and the recovery time until the Nth discharge is started is Th (N), the recovery time Th (N) is expressed by the following formula Th (N ) = A + B × exp (N)
The battery state estimation method according to claim 2, wherein the battery state estimation method is further calculated. When the number of discharges equal to or greater than 2 is N, the adjustment parameters are C and D, and the recovery time until the Nth discharge is started is Th (N). Th (N) is expressed by the following formula Th (N) = C + D × N
The battery state estimation method according to any one of claims 2 to 4, wherein the battery state estimation method is further calculated. Battery,
A discharge circuit for discharging the battery at a predetermined current value;
A current sensor for measuring the current of the battery;
A voltage sensor for measuring the voltage of the battery;
Control means for controlling the discharge circuit,
The control means controls the discharge circuit so that a response voltage at each discharge measured using the voltage sensor when the discharge is performed twice or more becomes substantially constant. system. The power supply system according to claim 6, wherein the control unit outputs a discharge request signal that makes a discharge current width and a time width constant to the discharge circuit every predetermined recovery time. The power supply system according to claim 7, wherein the control unit outputs the discharge request signal to the discharge circuit while sequentially increasing the recovery time. When the number of discharges of 2 or more is N, the adjustment parameters are A and B, and the recovery time until the Nth discharge is started is Th (N), the control means sets the recovery time Th (N) to The following formula Th (N) = A + B × exp (N)
The power supply system according to claim 7 or 8, wherein the discharge request signal is output to the discharge circuit after being calculated by the following equation. When the number of discharges equal to or greater than 2 is N, the adjustment parameters are C and D, and the recovery time until the Nth discharge is started is Th (N), the control means has the number of discharges N equal to or less than a predetermined number When the recovery time Th (N) is expressed by the following formula Th (N) = C + D × N
The power supply system according to claim 7, wherein the discharge request signal is calculated and output to the discharge circuit.

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