JP2002243813A - Arithmetic unit for computing deterioration of capacity of secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arithmetic unit for computing the deterioration of capacity of second battery that does not require any test, etc., for acquiring correlative data. SOLUTION: The battery capacity computing section 603 of this arithmetic unit calculates a change ΔSOC in the charged state of a secondary battery from the integration starting time to the integration ending time of the discharge current Id of the battery, based on the open-circuit voltage E1 at the integration starting time, the open-circuit voltage E2 at the integration ending time, and the correlation between the open-circuit voltages E1 and E2 and the charged state of the battery. In addition, the computing section 603 calculates the deteriorated-time capacity C of the battery based on an integrated discharge current value ΔAh calculated based on the discharge current Id by means of an integrated value computing section 601 and the change ΔSOC. Moreover, the deterioration rate computing section 605 of the arithmetic unit calculates the capacity deterioration rate 5 of the battery based on the calculated deterioration-time capacity C and initial capacity CO of the battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery capacity deterioration calculating device for calculating deterioration of a secondary battery.

[0002]

2. Description of the Related Art One of the characteristics of a secondary battery is that the battery capacity decreases due to aging. That is, the battery capacity of the deteriorated secondary battery is smaller than the initial (new) battery capacity. Therefore, when a secondary battery having such characteristics is mounted on a hybrid vehicle, in order to perform appropriate control according to the deterioration of the battery capacity,
It is necessary to determine the battery capacity deterioration by some method.

Conventionally, when calculating the deterioration of the battery capacity of a secondary battery in a hybrid vehicle, a correlation between the internal resistance deterioration and the capacity deterioration of the battery is obtained in advance by actually performing a test.
This correlation is prepared as a table. Then, the capacity deterioration of the battery is calculated using the internal resistance deterioration obtained from the charge / discharge data during traveling and the correlation table.

[0004]

However, in the above-described battery capacity deterioration calculation method, a test such as running is required in advance to obtain a correlation table which is capacity deterioration calculation data. Further, this correlation differs depending on the constituent materials of the battery, and a test must be performed for each type of battery, which requires a lot of man-hours. Therefore, there is a problem that the production cost is increased to perform this test.

[0005] It is an object of the present invention to provide a battery capacity deterioration calculating device which can reduce a manufacturing cost by eliminating a test or the like for obtaining correlation data.

[0006]

An embodiment of the present invention will be described with reference to FIGS. 1, 2, 6 and 7. FIG. (1) Explaining in connection with FIG. 1 and FIG. 2, the battery capacity deterioration calculating device 6 according to the first embodiment of the present invention
Current sensor 8 for detecting the discharge current Id of the secondary battery 4
Voltage sensor 7 for detecting the open-circuit voltage E of the
A discharge current integrating section 601 for calculating a discharge current integrated value ΔAh based on the discharge current Id detected by the above (a), an open voltage E1 at the start of discharge current integration, and (b) an open voltage E2 at the end of discharge current integration. And (c) the open circuit voltage E of the secondary battery 4
A state-of-charge calculator 603 for calculating a change in state of charge ΔSOC from the start of discharge current integration to the end of discharge current integration based on the correlation between the state of charge and the state of charge;
And a battery capacity calculating unit 603 for calculating the battery capacity C at the time of deterioration based on the discharge current integrated value ΔAh, and the secondary battery capacity C0 based on the battery capacity C at the time of deterioration and the initial battery capacity C0 of the secondary battery 4 stored in advance. The above-described object is achieved by including a deterioration calculation unit 605 for calculating the battery capacity deterioration β of the battery 4. (2) When described in association with FIG. 1, FIG. 2 and FIG.
According to a second aspect of the present invention, in the battery capacity deterioration calculating device 6 according to the first aspect, the discharge current value Id is within a discharge current range where the discharge rate capacity of the secondary battery 4 is substantially constant (0 ≦ Id ≦
X), the calculation of the integrated discharge current value ΔAh is started. (3) Explaining in association with FIG. 2, FIG. 6 and FIG.
According to a third aspect of the present invention, in the battery capacity deterioration calculating device 6 according to the second aspect, the discharge current integrated value ΔAh is a predetermined value ΔAh
0 or more, and the change in the state of charge ΔSOC is a predetermined change amount Y
Until the above, the discharge current integration is performed. (4) Explaining in connection with FIG. 2, the invention of claim 4 detects the battery temperature of the secondary battery 4 in the battery capacity deterioration calculating device 6 according to any one of claims 1 to 3. A temperature sensor 9 and a temperature correction calculator 604 for correcting the deteriorated battery capacity C calculated by the battery capacity calculator 603 to a battery capacity α · C under the same temperature condition as the initial battery capacity C0; Battery capacity α · C corrected in 604
The battery capacity deterioration β is calculated based on the initial battery capacity C0.

[0007] In the section of the means for solving the above problems, the drawings of the embodiments of the present invention are used to make the present invention easy to understand, but the present invention is not limited to the embodiments of the present invention. Not something.

[0008]

(1) According to the first aspect of the present invention, the battery capacity at the time of deterioration is calculated from the integrated value of the discharge current at the time of discharging and the change of the state of charge. It is calculated from the correlation with the state and the open circuit voltage at the time of discharge. Since the correlation between the open-circuit voltage and the state of charge does not change even if the degree of deterioration of the secondary battery changes, even for a deteriorated secondary battery, even the correlation at the initial stage of the battery is known. For example, the state of charge can be obtained using the correlation. As a result, there is no need to obtain a conventional correlation table between the internal resistance deterioration and the capacity deterioration by a test or the like in advance, and the man-hour and time for obtaining the correlation table can be reduced, and therefore, the manufacturing cost can be reduced. (2) According to the invention of claim 2, in addition to the effect of the invention of claim 1, by starting the calculation of the discharge current integrated value within the discharge current range where the discharge rate capacity becomes substantially constant, The calculation accuracy of the battery capacity, that is, the calculation accuracy of the battery capacity deterioration can be improved. (3) According to the third aspect of the invention, the discharge current integration is performed until the integrated discharge current value is equal to or more than the predetermined value and the change in the state of charge is equal to or more than the predetermined change amount, thereby further calculating the battery capacity deterioration. Accuracy can be improved. (4) According to the invention of claim 4, the battery capacity at the time of deterioration calculated by the battery capacity calculation unit is corrected to a battery capacity under the same temperature condition as the initial battery capacity, and the corrected battery capacity and the initial battery capacity are corrected. Since the battery capacity deterioration is calculated based on the following equation, the calculation accuracy of the battery capacity deterioration can be further improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a hybrid electric vehicle (HE) equipped with a battery capacity deterioration calculating device according to the present invention.
FIG. 5D is a diagram showing a schematic configuration of a drive system of the parallel HEV. The rotor of the electric motor 2 is directly connected to the main shaft of the engine 1. The driving force of the engine 1 and / or the motor 2 is transmitted to the axle via a drive system (not shown). The inverter 3 converts the DC power from the battery 4 composed of a secondary battery into AC power and supplies the AC power to the motor 2, and converts the AC power from the motor 2 into DC power in the power generation mode described later to convert the DC power into DC power.
Supply to

The battery 4 is composed of a plurality of single cells. The cell voltage of each cell is detected by a cell controller 5 and the detected value is output to a battery controller 6. For example, a lithium ion battery or the like is used for the single cell. In the battery controller 6, the cell voltage value sent from the cell controller 5, the total voltage value of the battery 4 detected by the voltage sensor 7, the charge / discharge current value detected by the current sensor 8, and the temperature detected by the temperature sensor 9. The temperature value of the battery 4 is input. The battery controller 6 composed of the microcomputer and its peripheral parts controls the charging and discharging of the battery 4 based on these values, and detects the deterioration of the battery capacity of the battery 4 according to a program described later.

The operation modes of the motor 2 in the parallel HEV include a drive mode for driving the axle and a power generation mode for charging the battery 4. When the battery 4 for supplying electric power to the motor 2 is in a sufficiently charged state when the vehicle is driven, that is, when accelerating, traveling on a flat road, climbing a hill, or the like, the motor 2 is operated in the drive mode and the engine 1 is driven. The vehicle runs with both driving forces of the motor and the motor 2. However, when the state of charge of the battery 4 is low, the motor 2 is operated in the power generation mode, the vehicle is driven by the driving force of the engine 1, the rotor of the motor 2 is rotated, and the power is generated by the motor 2. Charge.

On the other hand, when the vehicle is braked, that is, when the vehicle decelerates or descends a slope, the engine 1 and the motor 2 are driven by the rotational force of the wheels via the drive system. At this time, the motor 2 is operated in the power generation mode, and the battery 4 is charged by absorbing regenerative energy.

FIG. 2 is a functional block diagram of a battery controller 6 which is a battery capacity deterioration calculating device. The battery controller 6 includes a calculation unit 60 that performs various calculations for battery control, and a control unit 61 that controls the battery 4 and the inverter 3 based on the calculation results. The calculation unit 60 is an integrated value calculation unit 60
1, an open-circuit voltage calculator 602, a battery capacity calculator 603, a temperature correction calculator 604, and a deterioration rate calculator 605.

The storage unit 62 stores an initial battery capacity C0 of the battery 4 (see FIG. 1), an open circuit voltage and a charging state (state).
A control parameter such as an open-circuit voltage-SOC correlation map indicating a correlation with a charge of charge (hereinafter, referred to as SOC) is stored in advance, and a calculation result of each calculation unit described later is stored. SOC is displayed as a percentage, and when battery 4 is fully charged, SOC = 100%
And the SOC decreases with the discharge.

The integrated value calculating section 601 calculates the integrated discharge current value ΔA from the discharge current value Id detected by the current sensor 8.
Calculate h = ΣId · Δt. Δt is the discharge current value Id
Is the detection interval. The open-circuit voltage calculation unit 602 samples the current value I and the voltage value V when the vehicle is traveling by the current sensor 8 and the voltage sensor 7 and calculates the open-circuit voltage of the battery 4 based on the IV characteristics obtained from the sampled data.

FIG. 3 is a diagram showing an example of the sampling data, in which "x" marks represent the sampling data. L1 is an IV characteristic line obtained from sampling data when calculating open circuit voltage E1 at the start of discharge current integration, and L2 is an IV characteristic obtained from sampling data when calculating open circuit voltage E2 at the end of discharge current integration. It is a straight line. The voltage value at the point where the straight lines L1 and L2 intersect the voltage axis is
An open voltage E1 at the start of integration and an open voltage E2 at the end of integration, respectively.

The battery capacity calculator 603 corresponds to the open circuit voltage E1 at the start of current integration and the open circuit voltage E2 at the end of current integration.
SOC1 (%) and SOC2 (%) are read from the open circuit voltage-SOC correlation map stored in the storage unit 62. FIG. 4 is a diagram showing an example of the correlation between the open circuit voltage and the SOC, and the vertical axis represents S
OC (%) is shown, and the horizontal axis shows open-circuit voltage (V).

The correlation between the open-circuit voltage and the SOC shown in FIG. 4 does not change even if the temperature or the degree of deterioration of the battery 4 changes. Therefore, even if the battery 4 is deteriorated, the SOC can be obtained using the correlation as long as the correlation between the initial batteries is known. That is,
The open circuit voltage is E1 without depending on the deterioration of the battery 4.
In this case, the battery state is SOC1, and when the open circuit voltage is E2, the battery state is SOC2. The storage unit 62 stores a map relating to such a correlation.

The battery capacity calculator 603 calculates the integrated discharge current value ΔAh calculated by the integrated value calculator 601 before and after the integration.
The battery capacity C of the battery 4 is calculated based on the SOC change ΔSOC = SOC1−SOC2. Here, since the product of the battery capacity C (Ah) and ΔSOC (%) is equal to the discharge current integrated value ΔAh while the SOC changes by ΔSOC, the battery capacity C is calculated using the following equation (1). You.

## EQU1 ## C = 100 × (ΔAh / ΔSOC) (1)

In the temperature correction calculating section 604, the battery capacity calculated in the battery capacity calculating section 603 is used as the reference temperature T0 (for example,
(T0 = 25 ° C.), the temperature is corrected to the battery capacity C (T0). If the temperature correction coefficient is α, the corrected battery capacity C (T0) is expressed as C (T0) = α · C. FIG. 5 shows the discharge rate capacity (that is, the relationship between the discharge current value and the battery capacity) for different battery temperatures (10 ° C., 20 ° C., and 40 ° C.). In the example shown in FIG. 5, when the battery temperature is 20 ° C., the battery capacity is 3 (Ah), and when the battery temperature rises to 40 ° C., the battery capacity becomes 3.2 (Ah), and the battery temperature becomes 10 (Ah). When the temperature drops to ° C., the battery capacity becomes 2 (Ah).

Since the initial battery capacity C0 of the battery 4 stored in the storage unit 62 is the battery capacity at the reference temperature T0, a battery capacity deterioration rate β to be described later is calculated using the battery capacity C before temperature correction. Then, a calculation error due to a difference in battery temperature occurs. Therefore, in the present embodiment, the battery capacity C calculated by the equation (1) is calculated using the temperature correction coefficient α
The calculation accuracy is improved by calculating the battery capacity deterioration rate β using the corrected battery capacity α · C.

The deterioration rate calculating section 605 calculates the battery capacity deterioration rate β (%) by the following equation (2) based on the temperature-corrected battery capacity α · C and the initial battery capacity C0. Further, equation (3) is obtained by substituting C of equation (1) into equation (2).

Β = 100− (α × C / C0) × 100 (2) β = 100−α × {100 × (ΔAh / ΔSOC)} × 100 / C0 (3)

FIGS. 6 and 7 are flowcharts showing the processing procedure of the battery capacity deterioration rate calculation program executed by the arithmetic unit 60. When the ignition switch of the vehicle is turned on, the battery capacity deterioration rate calculation program is started, and a series of processes shown in FIGS. 6 and 7 are executed at predetermined intervals, for example, at predetermined time intervals or at predetermined traveling distances. . In step S1 of FIG. 6, the integrated current value ΔAh stored in the storage unit 62 is reset to zero. In step S2, the open-circuit voltage E1 at the start of current integration is read from the open-circuit voltage calculator 602 and input to the battery capacity calculator 603.

Next, if the discharge current value Id is detected by the current sensor 8 in step S3, it is determined in step S4 whether the discharge current value Id satisfies a predetermined condition 0 ≦ Id ≦ X. As shown in FIG. 5, the battery capacity changes depending on the magnitude of the current value at the time of discharging, and the battery capacity when discharged at a large current value becomes smaller than when discharged at a small current value. Therefore, if the discharge current value at the time of integration is large, the discharge current has an effect on the battery capacity. Therefore, integration is performed when the discharge current value is smaller than a predetermined current value X (A) at which a substantially constant battery capacity can be obtained. , To improve the calculation accuracy. That is, in step S4, the discharge state (0 ≦ I
Only if d) and the current value Id is less than or equal to X (A), which is hardly affected by the change in capacitance, the process proceeds to step S5; otherwise, the process returns to step S1.

In step S5, the battery state SOC1 corresponding to the open circuit voltage E1 read in step S2 is stored in the storage unit 62.
From the correlation map stored in the storage unit 603
Read to In step S6, the read SOC1 is 4
It is determined whether 0% ≦ SOC1 ≦ 60%. If YES is determined, the process proceeds to step S7. If NO is determined, the process returns to step S1. In the present embodiment, control is performed so that charging starts when the SOC of the battery 4 becomes 30% or less, and ends when the SOC becomes 70%. Therefore, in step S6, the range of SOC1 is set to 40% ≦ SOC1 ≦ so that charging is not started during the calculation of the battery capacity deterioration rate.
It is limited to 60%.

The following steps S7 to S12 are steps relating to discharge current integration.
A series of processes from S12 to S12 are repeatedly executed at the interval time Δt. In step S7, the integrated value calculation unit 60
The discharge current integrated value is calculated by 1 and the result is stored in the storage unit 62. That is, the product of the discharge current detection value Id and the interval time Δt is calculated, and the product Id · Δt
(Id · Δt + ΔAh) of the discharge current integrated value ΔAh read from the storage unit 62 and a new discharge current integrated value ΔA
h is stored in the storage unit 62.

Next, if the discharge current value Id is detected by the current sensor 8 in step S8, it is determined in step S9 whether the discharge current value Id satisfies a predetermined condition 0 ≦ Id ≦ X. If YES is determined in step S9, the process proceeds to step S10. If NO is determined, the integration of the discharge current is interrupted and the process returns to step S1. In step S10,
The open-circuit voltage E2 is read from the open-circuit voltage calculator 602 and is input to the battery capacity calculator 603. In step S11, the battery state SOC2 corresponding to the open circuit voltage E2 read in step S10 is read from the correlation map stored in the storage unit 62 to the battery capacity calculation unit 603.

In step S12, the absolute value | SOC1− of the difference between SOC1 at the start of integration and SOC2 obtained in step S11.
It is determined whether SOC2 | is equal to or greater than a predetermined value Y (%). Here, if the change in the SOC at the time of integrating the discharge current is too small, the calculation accuracy deteriorates. Therefore, in order to improve the accuracy, the integration is performed until the change in the SOC becomes equal to or more than the predetermined value Y. That is, if NO is determined in step S12, step S
7, and if YES is determined, step S13 in FIG.
Proceed to. The predetermined value Y is set, for example, to 20%.

When the process proceeds from step S6 to step S7, the discharge current integration is performed using the discharge current value Id detected in step S3 in step S7, but the process returns from step S12 to step S7. , The discharge current integration is performed using the discharge current value Id detected in the previous step S8. That is, step S
8 and the interval time Δt detected in step 8
Is calculated from the storage unit 62 to obtain the sum of the product calculated by the previous discharge current integration from the storage unit 62, and the sum is stored in the storage unit 62 as a new discharge current integration value ΔAh. I do.

In step S13, it is determined whether or not the obtained discharge current integrated value ΔAh is equal to or greater than a predetermined value ΔAh0. This is for determining whether or not the discharge current integrated value ΔAh is large enough to prevent the battery capacity calculation accuracy from deteriorating, and is provided for improving the calculation accuracy as in the process of step S12. The predetermined value ΔAh0 is, for example, 0.4 (A
h). If YES is determined in step S13, the process proceeds to step S14, and if NO is determined, the process returns to step S1. In step S14, the discharge current integrated value ΔAh calculated in step S7 is compared with the SO before and after the integration.
The current battery capacity C of the battery 4 is calculated from ΔSOC, which is the change in C, using the above-described equation (1).

Next, in step S15, the battery temperature T of the battery 4 is detected by the temperature sensor 9. In step S16, the battery capacity C is temperature-corrected by the correction coefficient α based on the detected battery temperature T, and the corrected battery capacity α · C is calculated. In step S17, based on the corrected battery capacity α · C calculated in step S16 and the initial battery capacity C0 previously stored in the storage unit 62, the above-described equation (2) is used.
Alternatively, the battery capacity deterioration rate β (%) is calculated by equation (3).

As described above, in the present embodiment,
Utilizing that the correlation between the open-circuit voltage and the SOC does not change regardless of the temperature or the degree of deterioration of the battery 4, the open-circuit voltage-SOC correlation is used to calculate the SOC from the change in the open-circuit voltage during vehicle running.
The change ΔSOC was calculated. And SOC is ΔSO
The discharge current integrated value ΔAh during the change by C is calculated, and the battery capacity deterioration rate β is obtained from the discharge current integrated value ΔAh and ΔSOC as shown in Expression (3). for that reason,
According to the present invention, a running test or the like for obtaining a correlation between the internal resistance deterioration and the capacity deterioration, which has been conventionally performed, can be omitted. In addition, by storing the initial battery capacity C0 and the correlation map for each type in advance in the storage unit 62 in accordance with the type of the secondary battery constituting the battery 4, it is possible to support various types of secondary batteries. .

In the above-described embodiment, the parallel HEV
However, the present invention is not limited to this and can be applied to various battery capacity deterioration calculating devices for secondary batteries. The method of calculating the open-circuit voltages E1 and E2 is not limited to the above-described method of estimating from the IV characteristics obtained at the time of charge and discharge. The open circuit voltage obtained by the above may be used.

In the correspondence between the embodiment described above and the elements of the claims, the battery capacity C is the battery capacity at the time of deterioration, the battery 4 is the secondary battery, the battery controller 6 is the battery capacity deterioration calculating device, The integrated value calculating section 601 constitutes a discharge current integrating section, the battery capacity calculating section 603 constitutes a charge state computing section, and the battery capacity deterioration rate β constitutes battery capacity deterioration.

[Brief description of the drawings]

FIG. 1 is a diagram showing a hybrid electric vehicle (HEV) including a battery capacity deterioration calculation device according to the present invention, and is a diagram showing a schematic configuration of a drive system of a parallel HEV.

FIG. 2 is a functional block diagram of a battery controller having a function as a battery capacity deterioration calculation device.

FIG. 3 is a diagram illustrating an example of sampling data.

FIG. 4 is a diagram illustrating an example of a correlation between an open circuit voltage and SOC.

FIG. 5 is a diagram showing a relationship between a discharge current value and a battery capacity.

FIG. 6 is a flowchart illustrating a processing procedure of a battery capacity deterioration rate calculation program executed by a calculation unit 60;

FIG. 7 is a flowchart showing processing subsequent to FIG. 6;

[Explanation of symbols]

 Reference Signs List 1 engine 2 motor 3 inverter 4 battery 5 cell controller 6 battery controller 7 voltage sensor 8 current sensor 9 temperature sensor 60 calculation unit 61 control unit 62 storage unit 601 integrated value calculation unit 602 open voltage calculation unit 603 battery capacity calculation unit 604 temperature correction Calculation part 605 Deterioration rate calculation part

Continued on the front page F-term (reference) 2G016 CA03 CB01 CB11 CB12 CB21 CB22 CC01 CC03 CC04 CC07 CC13 CC24 CC27 CF06 5G003 AA07 BA01 DA07 EA08 FA06 GB06 GC05 5H030 AA03 AA04 AA09 AS08 BB10 FF22 FF41 FF42 FF43 FF43 FF43 FF44 FF42 FF43 FF42

Claims (4)

[Claims] 1. A current sensor for detecting a discharge current of a secondary battery, a voltage sensor for detecting an open voltage of the secondary battery, and a discharge current integrated value is calculated based on the discharge current detected by the current sensor. And (c) an open voltage at the start of discharge current integration, (b) an open voltage at the end of discharge current integration, and (c) a correlation between the open voltage of the secondary battery and the state of charge. A charge state calculation unit that calculates a change in state of charge from the start of discharge current integration to the end of discharge current integration; and a battery capacity calculation that calculates a battery capacity during deterioration based on the change in charge state and the integrated value of discharge current. And a deterioration calculator for calculating the battery capacity deterioration of the secondary battery based on the battery capacity at the time of deterioration and the initial battery capacity of the secondary battery stored in advance. Degradation Apparatus. 2. The battery capacity deterioration calculating device according to claim 1, wherein the discharge current integrating unit is configured to control when the discharge current value is within a discharge current range in which a discharge rate capacity of the secondary battery is substantially constant. Calculating the discharge current integrated value. 3. The battery capacity deterioration calculating device according to claim 2, wherein the discharge current integrating unit is configured such that the discharge current integrated value is equal to or greater than a predetermined value and the change in the state of charge is equal to or greater than a predetermined change amount. A battery capacity deterioration calculation device characterized by performing a discharge current integration up to this point. 4. The battery capacity deterioration calculation device according to claim 1, wherein a temperature sensor for detecting a battery temperature of the secondary battery, and a battery capacity deterioration calculation unit that calculates a battery capacity when the battery capacity is deteriorated. A temperature correction calculating unit for correcting the battery capacity to a battery capacity under the same temperature condition as the initial battery capacity, wherein the battery capacity deterioration is corrected based on the battery capacity corrected by the temperature correction calculating unit and the initial battery capacity. A battery capacity deterioration calculation device, wherein the calculation is performed.