JP2003107139A - Life determining method of secondary battery for motor vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make exchangeable a battery before the end of its battery life by accurately determining battery life. SOLUTION: In this life determining method of a secondary battery for motor vehicle, a current flowing in the battery, a battery temperature, and a residual capacity of the battery are detected at a prescribed sampling cycle, and a parameter value is specified from a detected detection value, and the specified parameter value is operated, and the battery life is determining from the operated total parameter value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the life of a secondary battery for an electric vehicle, and more particularly to a method for determining the life based on the environment in which the battery is used. In the present specification, "for electric vehicles" means not only vehicles such as electric vehicles and electric forklifts that run only on batteries, but also runs on both batteries and engines like hybrid cars, or runs on batteries and human power. Used in a broad sense, including electric bicycles.

[0002]

2. Description of the Related Art An electric vehicle is driven by a motor driven by a battery. For this reason, when the life of the battery is exhausted, the electric vehicle cannot run at all, and the hybrid car cannot accelerate sufficiently, resulting in an extremely bad running condition. This adverse effect can be prevented by determining the life of the battery and detecting it before the life is exhausted. Conventional methods of determining battery life detect the maximum capacity that the battery can be charged. In this method, for example, when the maximum charge capacity of the battery becomes 50% or less of the standard capacity, it can be determined that the life has expired. The maximum charge capacity of the battery can be calculated by integrating the charge capacity from the completely discharged state to the full charge.

[0003]

However, a secondary battery for an electric vehicle, especially a secondary battery for a hybrid car is charged and discharged in a state unfavorable for calculating the maximum charge capacity by this method. This is because, in order to extend the battery life as long as possible, the battery is used between full charge and complete discharge so as not to be fully discharged and not to be fully charged. Batteries have the property of shortening their life when they are completely discharged or fully charged. Therefore, it is difficult to frequently detect the maximum charge capacity of the battery in the actual usage state.

If the battery is completely discharged or fully charged to detect the maximum charge capacity, the battery life is shortened to detect the battery life. Furthermore,
When the battery is completely discharged, the electric vehicle cannot run normally, so it is extremely difficult to set the timing for completely discharging the battery.

Further, in the method of determining the battery life from the maximum charge capacity, when the maximum charge capacity is detected, the chargeable capacity of the battery is detected.
There is no way to guess how long the battery will last. Further, the life of the battery varies greatly depending on the usage environment, but it is not possible to determine the battery life from the usage environment. Further, the method of estimating the battery life from the maximum charge capacity indirectly estimates the life of the battery, and therefore cannot detect how much the battery is damaged. Therefore, it is not possible to infer how the life will end in the future. If the battery life of the secondary battery of an electric vehicle can be accurately determined during a vehicle inspection, for example, the battery can be replaced and the battery can be effectively used until the next vehicle inspection. For this reason, it is important to accurately detect how the battery life is exhausted.

The present invention was developed for the purpose of achieving this. It is an important object of the present invention to provide a method for determining the life of a secondary battery for an electric vehicle that accurately determines the life of the battery and allows the battery to be replaced before the life of the battery is exhausted.

[0007]

According to the method of determining the life of a secondary battery for an electric vehicle of the present invention, the current flowing in the battery, the battery temperature, and the remaining capacity of the battery are detected and detected at a predetermined sampling cycle. The parameter value is specified from the detected value, the specified parameter value is calculated, and the life of the battery is determined from the calculated total parameter value.

According to the method of determining the life of the present invention, the current parameter value is calculated from the battery current and the temperature parameter value is calculated from the battery temperature.
The remaining capacity parameter value can be specified independently from the remaining capacity. In this life determination method, the total parameter value can be calculated by integrating or adding the independently specified current parameter value, temperature parameter value, and remaining capacity parameter value.

According to the method of discriminating the life of the present invention, the composite parameter value can be specified by using the two detection values selected from the detection values of the battery current, the battery temperature and the remaining capacity as variables.
The composite parameter value can be specified by using the detected values of the battery current, the battery temperature, and the remaining capacity as variables. Furthermore,
In the life discriminating method of the present invention, the integrated value of current or the rate of change of current can be used as one of the variables for specifying the parameter value.

The parameter value can be specified from a function having variables of battery current, battery temperature and remaining capacity. Further, the parameter value can be specified from a table having the battery current, the battery temperature, and the remaining capacity as variables.

Further, the life determining method of the present invention uses the secondary battery for an electric vehicle as a battery including a plurality of battery modules, and determines the current flowing in each battery module, the temperature of the battery module, and the remaining capacity of the battery module. It is possible to detect and independently determine the life of each battery module.

Further, the life discriminating method of the present invention can output the total parameter value to the outside in response to a request from the outside. Furthermore, the life discriminating method of the present invention preferably outputs a life signal when the total parameter value reaches a set value. Furthermore, in the life determining method of the present invention, the sampling cycle can be set to a fixed cycle or can be changed depending on the usage state of the battery.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. However, the examples described below exemplify a method for determining the life of a secondary battery for an electric vehicle for embodying the technical idea of the present invention, and the present invention specifies the life determining method as follows. do not do.

FIG. 1 is a circuit diagram showing a power supply device for a secondary battery for an electric vehicle, which is used in a method for determining the life of a secondary battery for an electric vehicle. The battery of this power supply device has a plurality of battery modules 1 connected in series to increase the output voltage. The battery module 1 has a plurality of unit cells connected in series. The unit cell is a nickel-hydrogen battery or a lithium ion secondary battery. However, a lead battery or a nickel-cadmium battery can also be used for this unit cell. In the power supply device shown in the figure, a plurality of unit cells are connected in series to form a battery module 1, and the battery life is determined in units of the battery module 1. However, a battery formed by connecting a plurality of unit cells in series is It is also possible to determine the battery life in units of. The life determining method for determining the battery life in units of the battery module 1 is to detect the current, temperature, and remaining capacity flowing in each battery module 1 and determine the life in the unit of unit cell. The flowing current, temperature and remaining capacity are detected.

The power supply unit shown in the figure is used for each battery module 1
Determine the battery life in units of. The plurality of battery modules 1 connected in series do not necessarily have the same life even if the charging and discharging currents are the same. It depends on the temperature environment etc. used by the battery module 1,
This is because the maximum chargeable capacity and the like change, and the remaining capacity also varies.

The power supply device shown in the figure is used for each battery module 1
In addition, a detection circuit 2 for detecting voltage, temperature and remaining capacity is provided. The detection circuit 2 transmits the detected voltage, temperature, and remaining capacity to the main control 3 via the communication bus 4. The detection circuit 2 calculates the remaining capacity of each battery module 1 and transmits the calculated remaining capacity to the main control 3 via the communication bus 4. The battery module 1 in which a plurality of unit cells are connected in series detects the temperature of one unit cell as a representative or detects the temperature of all the unit cells, and calculates the average value or the maximum value thereof through the communication bus 4 And main control 3
To transmit. The circuit that detects the voltage is also the battery module 1.
The entire voltage is detected and transmitted as a voltage signal for the main control 3. However, it is also possible to detect the voltage of the unit cell and transmit the average value to the main control 3 as a voltage signal.

The detection circuit 2 has a built-in A / D converter for converting voltage, temperature and remaining capacity into a digital signal.
The A / D converter converts the detected analog signal into a digital signal and transmits it to the main control 3. The detection circuit 2 converts the detected signal into a digital signal and transmits it to the main control 3 at a constant sampling period. The sampling period is preferably 100 msec. However, the sampling cycle is 10 msec to 1 s
It can also be ec. When the sampling cycle is shortened, the voltage, temperature and remaining capacity can be transmitted to the main control 3 more accurately. When the sampling cycle is lengthened, power consumption can be reduced and an inexpensive A / D converter can be used. The detection circuit 2 does not always need to transmit the digital signal to the main control 3 at a constant sampling period. For example, it is also possible to shorten the sampling cycle when the electric vehicle is running and lengthen the sampling cycle when the electric vehicle is not running to reduce unnecessary power consumption. The detection circuit 2 consumes power only when it detects the voltage, temperature, and remaining capacity and outputs it as a digital signal to the main control 3, thereby reducing the total power consumption. Each battery module 1
The detection circuits 2 connected to each other transmit the detected signals of temperature, voltage, and remaining capacity to the main control 3 with a time lag between them.

Since the battery modules 1 are connected in series, the flowing currents are the same. Therefore, the illustrated power supply device is provided with one current detection circuit 5. This current detection circuit 5 also has a built-in A / D converter.
Therefore, the detected current signal is converted into a digital signal and transmitted to the main control 3 via the communication bus 4. This A / D converter also converts the current signal into a digital signal at a predetermined sampling cycle. When the electric vehicle is running, the current flowing in the battery fluctuates greatly in a short time. Therefore, the current detection circuit 5 has a sampling period as short as possible, for example, 100 mse.
In the cycle of c, the current signal is converted into a digital signal and transmitted to the main control 3. Furthermore, the sampling cycle can be shortened.

The main control 3 is a battery ECU, which calculates digital signals transmitted from the detection circuit 2 connected to each battery module 1 and one current detection circuit 5 to calculate each battery module. The life of 1 is determined. The main control 3 detects the current flowing in the battery module 1, the temperature of the battery module 1, and the remaining capacity of the battery module 1 in a predetermined sampling cycle, and identifies the parameter value from the detected value and identifies the parameter value. The calculated parameter value is calculated, and the life of the battery is determined from the calculated total parameter value.

When the battery reaches the end of life, the main control 3 communicates this to the VCS, which is the general controller 6 of the electric vehicle, via the communication bus 7. Further, in the power supply device shown in the figure, a communication bus 9 for connecting the download device 8 is connected to the main control 3. The download device 8 is a device for downloading the total parameter value calculated by the main control 3. The download device 8 determines the battery life by comparing the downloaded total parameter value with the set value. For example, when the total parameter value is 80% of the set value, it is determined that the remaining battery life is 20%. In this way, the device that can determine the remaining battery life with the download device 8 can detect the remaining battery life during periodic inspections and vehicle inspections, and determine when to replace the battery. For example, a battery with a short life will be unusable within a short period of time after regular inspections and vehicle inspections, and should be replaced during inspections.

FIG. 2 shows a flowchart for the main control 3 to determine the life of the battery module 1. This method calculates the life of the battery module 1 as follows. [Steps n = 1 and 2] Since the main control 3 also performs processing other than life determination, it determines whether 100 msec, which is the sampling cycle, has elapsed after the processing other than life analysis is completed.

[Step n = 3] When the sampling period of 100 msec elapses, the temperature signal and the remaining capacity signal transmitted from the detection circuit 2 via the communication bus 4 and the current signal transmitted from the current detection circuit 5. From the parameter value, the battery module 1 is identified from the parameter value.
Determine the life of. The main control 3 determines the battery life from the calculated total parameter value. When the total parameter value reaches the set value, it is determined that the life has expired. That is, as the battery is used, the calculated total parameter value increases, and when it reaches the set value, it is determined that the battery has reached the end of life.

The main control 3 stores data for specifying the parameter value from the current, temperature and remaining capacity. The data that specifies the parameter value from the current, temperature, and remaining capacity varies depending on the type of battery. Therefore, the main control 3 stores in advance data specifying the parameter values for the current, temperature, and remaining capacity corresponding to the battery of the power supply device. 3 to 5
Shows examples of parameter values for current, temperature, and remaining capacity. FIG. 3 shows parameter values with respect to current values flowing in the battery module 1. The parameter values shown in this figure are
It increases as the current increases. This is because the life of the battery becomes shorter as it is charged and discharged with a large current. Figure 4
Indicates a parameter value with respect to the battery temperature. Since the life of the battery becomes shorter as the temperature becomes higher, the parameter value is made larger as the temperature becomes higher. further,
FIG. 5 shows the parameter value for the remaining capacity. The battery has a shorter life as the remaining capacity increases, and particularly the life becomes shorter as the remaining capacity approaches full charge. Therefore, the parameter value is increased when the remaining capacity approaches 100%.

The main control 3 stores the data for specifying the parameter value from the current, the temperature and the remaining capacity as a function or as a table. For example, the parameter value PA of the current, the parameter value PT of the battery temperature, and the parameter value PSOC of the remaining capacity are specified with the current (A), temperature (T), and remaining capacity (SOC) as variables as follows. It is stored as a function (f). PA = f (A) PT = f (T) PSOC = f (SOC)

The main control 3 specifies the parameter values for the current, temperature and remaining capacity from the stored function or from the table. After that, the main control 3 calculates the total parameter value by integrating the values obtained by multiplying the specified current, temperature, and remaining capacity parameter values.
Since the main control 3 inputs the current, temperature, and remaining capacity at a predetermined sampling cycle, the parameter value is specified every time these signals are input, and the parameter value is multiplied and integrated. That is, every time the sampling period elapses,
The product of the next parameter value is added to the previous total parameter value. Therefore, the total parameter value gradually increases.

In the method of calculating the total parameter value by integrating the product of the parameter values of the current, temperature and remaining capacity, for example, the deterioration of the battery discharged with a large current in a high temperature environment can be determined in an almost ideal state. This is because when a large current is discharged in a high temperature environment, the deterioration of the battery is accelerated. However, the life discriminating method of the present invention can independently specify the parameter values of the current, the temperature, and the remaining capacity, and add them without multiplying the specified parameter values to calculate the total parameter value. This method
The parameter value specified from the remaining capacity is added so that the battery life can be determined.

Further, as a second method of the life discriminating method of the present invention, one composite parameter value is specified with three variables of current, temperature and remaining capacity as variables, and the total parameter value is obtained by adding the composite parameter values. Can also be calculated. The main control 3 of the power supply device that determines the battery life by this method is, for example, a composite parameter value (PAL
L) is stored as the following function f (A, T, SOC), or a table that specifies one composite parameter value with three variables of current, temperature, and remaining capacity is stored. PALL = f (A, T, SOC) This function [f (A, T, SOC)] is a function for calculating a composite parameter value with three variables of current, temperature, and remaining capacity as variables. This function [f (A, T, SOC)] is measured in advance and stored in the main control 3 as a function capable of specifying the battery life from the current, temperature and remaining capacity. This function [f (A, T, SOC)] changes depending on the type of battery. Therefore, the function [f (A, T, SOC)] that matches the battery type of the power supply device is measured in advance, and the measured function is stored in the main control 3.

The main control 3 receives digital signals of current, temperature, and remaining capacity from the detection circuit 2 and the current detection circuit 5 in the sampling cycle. Therefore, each time these digital signals are input, a current is supplied. Specify the composite parameter value (PALL) from the temperature, temperature, and remaining capacity. The specified composite parameter value (PALL) is added to the previous total parameter value. Also in this method, the life of the battery is determined by comparing the total parameter value with the set value.

Further, the main control 3 has a current,
Specify the composite parameter value using the two parameters of temperature and remaining capacity as parameters, add the specified composite parameter values,
Alternatively, the total parameter value can be calculated by integrating the values multiplied by the composite parameter value. This third method of determining life is based on current and temperature and is a composite parameter value (PA,
T) is specified, the composite parameter value (PA, SOC) is specified from the current and the remaining capacity, and the composite parameter value (PT, SOC) is specified from the temperature and the remaining capacity. These composite parameter values are stored in the main control 3 as a function shown below or as a table. PA, T = f (A, T) This function specifies a composite parameter value with current and temperature as variables. PA, SOC = f (A, SOC) This function specifies the composite parameter value with the current and the remaining capacity as variables. PT, SOC = f (T, SOC) This function specifies a composite parameter value with temperature and remaining capacity as variables.

The main control 3 calculates the total parameter value by adding the specified composite parameter values (PA, T), (PA, SOC), (PT, SOC). In addition, the specified composite parameter values (PA, T), (PA, SOC), (P
It is also possible to calculate the total parameter value by accumulating the product of (T, SOC). However, the method of calculating the total parameter value by integrating the products of the specified composite parameter values (PA, T), (PA, SOC), (PT, SOC) is to calculate the product of these composite parameter values. Then, the total parameter value is calculated to specify the composite parameter value so that the life can be determined.

Furthermore, the fourth life judging method uses the integrated current value as one of the variables for specifying the parameter value. In this method, the main control 3 stores a function or table for specifying a parameter value from the integrated current value. Also, the rate of change of current can be used as one of the variables that specify the parameter value. In this method, the main control 3 stores a function or a table that specifies a parameter value from the rate of change of current. The parameter value for the rate of change of the current is specified from the stored function or table. The parameter value specified from the integrated current value or the current change rate is added to the total parameter value calculated from the current, temperature, and remaining capacity. It is also possible to calculate the total parameter value by multiplying the parameter value specified from the integrated current value and the current change rate by the parameter value specified from the current, temperature and remaining capacity.

[Step n = 4] The total parameter value is compared with the set value to determine whether or not the battery life has been reached. In this step, the total parameter value is compared with the set value, and when the total parameter value reaches the set value, it is determined that the battery life has been reached. [Step n = 5] When the total parameter value reaches the set value and the battery life is reached, in this step, the main control 3 informs the VCS, which is the general controller 6 of the electric vehicle, that the battery life has expired. Communication is performed via the communication bus 7. [Step n = 6 to 7] After that, when the download request is received from the download device 8, the main control 3 transmits the total parameter value to the download device 8. N = 1 when no download request is received
Jump to the step.

[0033]

The method of determining the life of the secondary battery for an electric vehicle of the present invention has a feature that the life of the battery can be accurately determined. The life determining method of the present invention specifies the parameter value from the battery current, the battery temperature, and the remaining capacity of the battery detected in a predetermined sampling cycle, and the battery life is calculated by the total parameter value calculated from the specified parameter value. This is because it is determined. The life determination method of the present invention can determine the battery life without calculating the maximum charge capacity by completely discharging or fully charging the battery as in the prior art, or in other words, determining the battery life without adversely affecting the battery. Secondary battery,
In particular, it is convenient for determining the battery life of a battery that is used between full charge and complete discharge, such as a secondary battery for a hybrid car.

Further, since the life judging method of the present invention judges the battery life from a plurality of parameter values of the battery current, the battery temperature, and the remaining capacity, the battery usage environment and the damage to the battery are taken into consideration. The battery life, which greatly changes due to these factors, can be effectively determined. As described above, the life determining method of the present invention directly estimates the life of the battery by using a plurality of parameter values, so that it is possible to accurately determine the battery life and replace the ideal battery before the battery life is exhausted. It will be possible.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power supply device used in a method for determining the life of a secondary battery for an electric vehicle according to an embodiment of the present invention.

FIG. 2 is a flowchart in which the main control determines the battery life.

FIG. 3 is a graph showing an example of a parameter value with respect to a current value flowing in a battery.

FIG. 4 is a graph showing an example of parameter values with respect to battery temperature.

FIG. 5 is a graph showing an example of parameter values with respect to remaining capacity.

[Explanation of symbols]

1 ... Battery module 2 ... Detection circuit 3 ... Main control 4 ... communication bus 5 ... Current detection circuit 6… General controller 7 ... communication bus 8 ... Download device 9 ... communication bus

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2G016 CA03 CB12 CB22 CB31 CC03                       CC04 CC07 CC09 CC10 CC16                       CC26                 5G003 AA01 BA01 DA04 EA08 FA06                       GC05                 5H030 AA06 AS08 FF22 FF42 FF52                 5H115 PA15 PC06 PG04 PI16 SE06                       TI02 TI05 TI06 TI10

Claims (15)

[Claims] 1. A current flowing in a battery, a battery temperature, and a remaining capacity of the battery are detected at a predetermined sampling cycle, a parameter value is specified from the detected value detected, and the specified parameter value is calculated and calculated. Method for determining the life of a battery for an electric vehicle, which determines the life of the battery from the obtained total parameter value. 2. The life determination of the secondary battery for an electric vehicle according to claim 1, wherein the current parameter value is independently specified from the battery current, the temperature parameter value is specified from the battery temperature, and the remaining capacity parameter value is independently specified from the remaining capacity. Method. 3. The method for determining the life of a secondary battery for an electric vehicle according to claim 2, wherein the current parameter value, the temperature parameter value, and the remaining capacity parameter value are integrated to calculate a total parameter value. 4. The method of determining the life of a secondary battery for an electric vehicle according to claim 2, wherein the current parameter value, the temperature parameter value, and the remaining capacity parameter value are added to calculate the total parameter value. 5. The method for determining the life of a secondary battery for an electric vehicle according to claim 1, wherein the composite parameter value is specified by using two detection values selected from the detection values of the battery current, the battery temperature and the remaining capacity as variables. . 6. The method of determining the life of a secondary battery for an electric vehicle according to claim 1, wherein the composite parameter value is specified by using the detected values of the battery current, the battery temperature, and the remaining capacity as variables. 7. The method for determining the life of a secondary battery for an electric vehicle according to claim 1, wherein the integrated value of the current is used as one of the variables for specifying the parameter value. 8. The method for determining the life of a secondary battery for an electric vehicle according to claim 1, wherein the rate of change in current is used as one of the variables for specifying the parameter value. 9. The method for determining the life of a secondary battery for an electric vehicle according to claim 1, wherein the parameter value is specified from a function having the battery current, the battery temperature, and the remaining capacity as variables. 10. The method of determining the life of a secondary battery for an electric vehicle according to claim 1, wherein the parameter value is specified from a table having battery current, battery temperature and remaining capacity as variables. 11. The battery includes a plurality of battery modules, and the current flowing through each battery module, the temperature of the battery module, and the remaining capacity of the battery module are detected,
The method of determining the life of a secondary battery for an electric vehicle according to claim 1, wherein the life of each battery module is independently determined. 12. The method of determining the life of a secondary battery for an electric vehicle according to claim 1, wherein the total parameter value is output to the outside in response to a request from the outside. 13. The method for determining the life of a secondary battery for an electric vehicle according to claim 1, wherein a life signal is output when the total parameter value reaches a set value. 14. The method of determining the life of a secondary battery for an electric vehicle according to claim 1, wherein the sampling cycle is a fixed cycle. 15. The method for determining the life of a secondary battery for an electric vehicle according to claim 1, wherein the sampling cycle is changed depending on the state of use of the battery.