JPH07140216A - Electric vehicle operable time display device - Google Patents

Abstract

PURPOSE:To decrease stored data by enciphering battery characteristics for the purpose of reducing data to be stored in a ROM, and making calculations using that cipher. CONSTITUTION:The charge and discharge currents, terminal voltages, and temperature of a battery 15 are detected, from the values of which an independent variable of a battery characteristic equation is calculated. Based on an output on the battery characteristic equation and an output current, the current consumed is estimated, and an operable time is computed based on the current consumed and an operating pattern stored in a storage portion 13. The operable time is displayed in a display 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a running time display device for an electric vehicle, and more particularly, to the running time of an electric vehicle by formulating battery characteristics (relationship between electric energy, remaining capacity and current). Regarding what to estimate.

[0002]

2. Description of the Related Art Conventionally, the usable time of a battery is not simply determined by the difference between the rated capacity and the amount of charge / discharge electricity.
It is difficult to accurately estimate the usable time because it depends on the battery temperature, the magnitude of the discharge current, and the charge / discharge pause time. Therefore, temperature, charge / discharge current,
A method of storing the relationship between the voltage (or internal resistance of the battery) and the usable time in a ROM and calling it is disclosed in Japanese Patent Laid-Open No. 2-1.
No. 87679.

[0003]

However, in the case of the method disclosed in the above publication, since the relationship in various running patterns based on the charging / discharging current, voltage, and temperature of the battery is stored in the ROM, the data to be stored is It has the drawback of being huge. Therefore, the present invention has an object to solve the above-mentioned problems, and it is possible to reduce the amount of stored data by formulating a battery characteristic in order to reduce the amount of data to be stored in the ROM and calculating using this formula. An object is to provide a travelable time display device for an electric vehicle.

[0004]

In order to achieve the above-mentioned object, the present invention detects a battery terminal voltage, a voltage detecting means for detecting a battery output current, and a battery temperature. Temperature detecting means, storage means for storing the relationship between the travelable time and the power consumption in a plurality of travel patterns, the independent voltage of the battery characteristic formula prepared in advance based on the terminal voltage, the output current, and the temperature. Calculation means for calculating, estimation means for estimating the consumption current based on the output of the battery characteristic equation calculated by the calculation means and the output current detected by the current detection means, and the estimation means Calculating means for calculating the travelable time based on the consumed current and the travel pattern stored in the storage section, and display means for displaying the travelable time calculated by the calculating means. , And summarized in that comprises a.

[0005]

According to the travel time display device for an electric vehicle of the present invention having the above-mentioned structure, the terminal voltage, the output current, and the temperature of the battery are detected, and the independent variable of the battery characteristic formula is calculated based on the detected values. . Then, the consumption current is estimated from the calculated battery characteristic equation of the independent variable and the output current,
The travelable time is calculated based on the consumed current and the storage pattern stored in the storage unit. The calculated usable time is displayed on the display means.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the running time output device for an electric vehicle of the present invention will be described below. First, a method of deriving a battery characteristic expression of the present invention will be described. Regarding the remaining capacity of the battery, the capacity that can be taken out differs depending on the magnitude of the discharge current and the temperature of the battery case. In order to deal with the characteristics of this battery, the dischargeable capacity was examined with either the discharge current or the battery case temperature fixed.

First, the dischargeable capacity for each discharge current at a battery case temperature of 30 ° C. (constant) was examined.
From this result, the discharge at the discharge current i of 0.2 [CA] was set as the weighting coefficient Ki = 1, and the weighting coefficient Ki depending on the magnitude of the discharge current was obtained. The result is shown in FIG. Next, a discharge test was performed at a constant electric power at each temperature, and the discharge capacity at 30 ° C. was set to 1 to determine the capacity ratio KA at each temperature. The result is shown in FIG.

Therefore, the above weighting coefficient Ki and capacity ratio KA
Independent variable (converted remaining capacity at 0.2 [CA]) SOC of the battery characteristic equation is defined by the following equation.

[0009]

[Equation 1] However, Ah (0.2) is the discharge conversion remaining capacity at 30 ° C. and 0.2 [CA].

Further, considering the experimental result that the battery electrolyte can be homogenized in about 2 hours after the discharge is stopped, the SOC is expressed by the following equation with respect to the discharge stop time t.
Has derived the relationship that the battery electrolyte recovers to SOC0, which is a uniform state.

[0011]

[Equation 2] SOC = SOC + Kt (SOC0-SOC)

[0012]

## EQU3 ## Kt = 1-e- ^{t / Tk}

[0013]

[Equation 4] Here, the discharge pause time t (se
The relationship between c) and the recovery coefficient Kt is shown in FIG.

Next, a constant power discharge test was conducted at a battery temperature of 30 ° C., and SOC, power and current data were collected. The relational expression of these three variables, that is, the battery characteristic expression was obtained by the model method. The basic equation required for the model method is expressed as the following equation in consideration of the result of constant power discharge.

[0015]

(Equation 5) (Estimated current) = Wa (AS0 + BSo + CSo
+ DWa + E) where Wa: discharge power / 10, S0 = 1-SOC / 10
0, A, B, C and D are coefficients, and E is a constant. The consumption current (estimated current) can be estimated by this mathematical expression 5.

Here, in order to further improve the estimation accuracy of the estimated current, it is necessary to reselect the basic equation. The least squares method and the conjugate gradient method are used for the optimization method of each coefficient A, B, C, D and the constant E of the basic equation, and the evaluation function J is the mean square of the difference between the measured current value and the estimated current value. (Fig. 5).

That is, as shown in FIG. 5, in step 100, data such as current, voltage, temperature, etc. is obtained from the detector 11. Then, in step 110, S
Calculate OC. In step 120, power consumption is calculated. In step 130, the estimated current value is calculated based on Equation 5. Then, the name coefficients A, B, C, D of the basic equation and the constant E are optimized so as to minimize the evaluation function J from the estimated current value and the actually measured current value.

The characteristic equation for charging is also optimized in the same manner as the coefficient of the basic equation. Here, in the constant power discharge test, it was found that the current sharply increased at the end of discharge as shown in FIG. FIG. 7 shows the relationship between the discharge power and the limiting current value (abruptly rising current value) Ir at which this sudden rising starts. It is considered necessary to avoid using the battery in this vicinity for maintenance of the electrode plate.

Therefore, in the present embodiment, the current running or the discharge power running pattern (Δt second interval) stored in advance.
The current value flowing when the above is repeated is estimated from the battery characteristic formula, and the estimated current value for the discharge power is the limit current value Ir.
When it exceeds, it is determined that traveling under this traveling condition is impossible, and the available traveling time is obtained based on the limiting current value Ir.

FIG. 8 shows the battery charge / discharge test simulating the 10-mode running and the estimated current value estimated by the battery characteristic formula used in the present invention. It can be confirmed from FIG. 8 that the current value is accurately estimated in almost the entire area until the limiting current flows. This makes it easy to understand that the end of discharge can be determined.

[0021]

As described above, according to the present invention, the travelable time can be estimated by obtaining the independent variable of the battery characteristic formula based on the voltage, current and temperature data during running and stopping. It is possible to prevent a situation in which the electric vehicle suddenly becomes unable to travel during traveling.

Further, since it is not necessary to store the traveling patterns based on each of the charging / discharging current, voltage and temperature of the battery in the ROM, the stored data in the storage means is reduced,
There is an effect that a simple ROM can be used.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2A is a diagram showing a constant current discharge test result. (B) is a figure which shows the weighting coefficient for every magnitude | size of discharge current in (a).

FIG. 3 is a diagram showing a result of examining a capacity ratio depending on temperature with reference to 30 ° C. and 0.2 CA discharge.

FIG. 4 is a diagram showing a battery electrolyte recovery degree.

FIG. 5 is a flowchart showing a method for optimizing a battery characteristic expression by a model method.

FIG. 6A is a diagram showing a current value measured during a discharge test at 332 [W]. (B) is a figure which shows the electric current value measured at the time of the discharge test in 837 [W].

FIG. 7 is a diagram showing a relationship between a discharge current and a current value at which the current value suddenly increases during constant power discharge.

FIG. 8 is a diagram showing a current value measured during a battery charge / discharge test simulating a 10-mode running and an estimated current value estimated by a battery characteristic formula obtained by the present invention.

[Explanation of symbols]

11 Detection Unit (Voltage Detection Means, Current Detection Means, Temperature Detection Means) 12 Calculation Unit (Calculation Means, Estimation Means) 13 Storage Unit (Storage Means) 14 Display (Calculation Means, Display Means) 15 Battery 16 Motor Control Device

Claims (1)

[Claims] 1. A voltage detecting means for detecting a terminal voltage of a battery, a current detecting means for detecting an output current of the battery, a temperature detecting means for detecting a temperature of the battery, a travelable time and consumption in a plurality of traveling patterns. Storage means for storing the relationship with the amount of electric power, calculation means for calculating an independent variable of a battery characteristic formula prepared in advance based on the terminal voltage, output current, and temperature, and battery characteristics calculated by this calculation means Based on the current consumption estimated by the estimating means and the running pattern stored in the storage section, and an estimating means for estimating the consumed current based on the output of the equation and the output current detected by the current detecting means. A travelable time display device for an electric vehicle, comprising: a computing means for computing a travelable time; and a display means for displaying the travelable time calculated by the computing means.