JPH05341023A - Residual capacity calculating method for nickel type battery - Google Patents

Abstract

PURPOSE:To calculate the residual capacity with high precision in which the capacity decrement due to self-discharge is taken into account by calculating presumptive]y the self-discharging amount from the calculated residual capacity of the battery and its temperature. CONSTITUTION:An ammeter 4 and temp. sensor 5 to measure the discharge current I and temp. T, respectively, of a Ni-Cd battery 3 and also an ignition switch 6, which senses if electric vehicle is in parking, are connected with a residual capacity meter 1. The data of residual capacity A when the battery 3 is charged fully is assumed as 100%, and the current I and temp. T are sampled, for example at 10msec. intervals. If it is in discharged (charged) condition being judged from the current direction, the electric quantity measured at this time is cumulated on the discharge (charge) electric quantity cumulative value B(C), and this cycle is repeated, for example for 60sec. If the ignition switch 6 is put off and the car is in parking, the self-discharge electric quantity D is calculated presumatively from the capacity A and temp. T. The cumulative values B, C are subtracted/added from/to the capacity A, followed by subtracting of the electric quantity D, to determine a new capacity A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calculating the remaining capacity of a nickel-based battery, and more particularly to an apparatus for displaying the remaining capacity of a nickel-based battery such as Ni-Cd or nickel-hydrogen used as a power source for electric vehicles. Can be applied.

[0002]

2. Description of the Related Art Lead batteries have been generally known as a power source for electric vehicles. In the case of this type of battery, the remaining capacity of the battery has a correlation with the terminal voltage of the battery. Therefore, it is possible to roughly estimate the remaining capacity by monitoring the terminal voltage.

On the other hand, for example, Ni-, which has begun to be adopted as a power source for electric vehicles because of its large charge capacity and the like.
Since the internal resistance of a Cd battery is extremely low, the amount by which the terminal voltage changes in proportion to the amount of discharge is extremely small, so it is extremely difficult to measure the terminal voltage and estimate the remaining capacity of the battery. However, it is necessary to use a highly accurate voltage measuring means. Therefore, Ni-C
For the d battery, the remaining capacity of the battery is initially set to 100% at the time of the first charge completion (full charge) or each time the charge is completed, and the remaining capacity is calculated by sequentially subtracting from it the amount of electricity used. I am trying. The amount of electricity used can be obtained by integrating the measured discharge current every unit time. Of course, if the battery is put in a charged state on the way, the amount of electricity is added to the remaining capacity.

[0004]

By the way, it is known that in nickel-based batteries, self-discharging, which consumes electricity when not in use, is relatively large. For example, a lead battery has 0.5% / day, whereas a Ni-Cd battery has about 1% / day of self-discharge. That is, 1% of electricity is consumed per day even when the vehicle is not used, and the battery capacity becomes zero after 100 days even when the battery is fully charged. This self-discharge cannot be detected from the outside because current flows in the battery, and therefore the self-discharge amount cannot be directly calculated.

The remaining capacity of the battery is
It is an extremely important information for predicting the mileage or the mileage as well as for the safe driving, as it is an index showing how long the drivable state can last.
Therefore, the calculated remaining capacity is desired to be as accurate as possible.

The present invention has been made in view of the above circumstances, and in calculating the remaining capacity of a battery, it is possible to calculate the remaining capacity of a nickel-based battery with high accuracy in which the capacity reduction due to self-discharge is taken into consideration. The purpose is to provide a method.

[0007]

To solve the above problems, according to the present invention, the charging / discharging current of a battery is measured, the charging / discharging electricity quantity is integrated every unit time, and the integrated electricity quantity is preset. In the method of calculating the remaining capacity of a battery by adding or subtracting to the initial value of the remaining capacity of the battery, the self-discharge amount is calculated from the remaining capacity of the battery calculated previously and the temperature of the battery obtained from the temperature sensor. Is provided, and the self-discharge amount is subtracted from the remaining capacity obtained by addition and subtraction at predetermined time intervals.

[0008]

According to the above means, the amount of self-discharge changes depending on the temperature of the battery and also changes according to the remaining capacity of the battery. The self-discharge amount is calculated by using the remaining capacity and the battery temperature obtained by the measurement as variables, and by subtracting this from the remaining capacity obtained by addition and subtraction, the remaining capacity always has data corrected by the self-discharge amount. become.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings showing a preferred embodiment of the present invention.

FIG. 1 illustrates a method according to the invention, for example Ni--
FIG. 2 is a block diagram showing a calculation processing flow when applied to a remaining capacity display device for a Cd battery, and FIG. 2 is a block diagram showing a configuration example of the remaining capacity display device.

The battery remaining capacity display device comprises a remaining capacity meter 1 and a display unit 2. Ni is used for the remaining capacity meter 1.
-Cd Ammeter 4 for measuring the discharge current of the battery 3, Ni-C
A temperature sensor 5 that measures the temperature inside the d battery 3 and an ignition switch 6 that detects whether or not the electric vehicle is parked are connected. Reference numeral 7 is an electric motor controller for controlling the drive electric motor of the electric vehicle.

Although the remaining capacity meter 1 is not shown, the ammeter 4
, A read-only memory that stores the program for performing the arithmetic processing of FIG. 1, an analog-digital converter that converts the analog value of the discharge current measured by the Random access memory used for, etc., central processing unit, various interfaces for normalizing voltage signals from ammeter 4, temperature sensor 5 and ignition switch 6 and supplying drive current to display unit 2, and operating these interfaces. It is composed of a DC / DC converter that obtains a DC voltage suitable for the operation.

Next, a method for calculating the remaining capacity of the Ni-Cd battery 3 will be described with reference to FIG. 1. In Step 10, the Ni-Cd battery is fully charged (fully charged).
At that time, the remaining capacity (A) data is initialized to 100%. In steps 11 and 12, the battery charge / discharge current (I) and battery temperature (T) are sampled, for example, every 10 milliseconds. In step 13, it is determined from the measured current direction whether the battery is in a charging state or a discharging state.

If the battery is in the discharged state, in step 14, the accumulated electricity quantity (B) is integrated with the electricity quantity measured this time, and this accumulation is repeated for 60 seconds, for example. If the battery is in the charged state, in step 15, the charge amount integrated value (C) is integrated with the measured amount of electricity this time, and this integration is repeated for 60 seconds, for example.

Step 16 is to set an interval for updating the display of the state of charge of the battery, which is set to, for example, 60 seconds in order to prevent the display output from flickering. In step 17, it is determined whether the ignition switch is off, that is, whether the electric vehicle is parked. If the electric vehicle is parked, the self-discharged electricity amount (D) is calculated in step 18 to drive the vehicle. If so, step 18 is passed.

As shown in FIG. 3, the self-discharge electric quantity (D) has a characteristic that it becomes smaller as the discharge rate becomes larger, that is, the remaining capacity becomes smaller, and becomes larger as the temperature becomes higher even at the same discharge rate. Since these relationships are obtained in advance, it is possible to easily estimate and calculate the self-discharged electricity amount (D) from the remaining capacity (A) obtained by the calculation and the battery temperature (T) obtained by the measurement. it can.

Next, at step 19, the discharge electricity quantity integrated value (B), the charge electricity quantity integrated value (C) and the self-discharge electricity quantity (D) are added to or subtracted from the previously calculated remaining capacity (A). Then, a new remaining capacity (A) is obtained, and in step 20, the discharge electricity amount integrated value (B) and the charge electricity amount integrated value (C) are obtained.
Is reset to zero, and in step 21, the remaining capacity corrected by the self-discharged electric quantity is displayed and output.

It should be noted that the remaining capacity meter 1 is always functioning, but if the consumed electricity amount is not negligible as compared with the self-discharged electricity amount, in step 19,
The electricity consumption of the remaining capacity meter 1 is also subtracted.

[0019]

As described above, according to the present invention, when the remaining capacity of the nickel-based battery is obtained by subtracting the integrated value of the discharge current corresponding to the amount of electricity used from the initial value at the completion of charging, By calculating the self-discharged amount of electricity, which is the amount of electricity consumed even when it is not used such as when parking, and subtracting this amount of electricity, the calculated remaining capacity of the battery and the actual remaining capacity Since there is no difference in the capacity, it is possible to calculate the remaining capacity with high accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing a remaining capacity calculation processing flow in a remaining capacity display device to which a remaining capacity calculation method for a nickel-based battery according to the present invention is applied.

FIG. 2 is a block diagram showing a configuration example of a remaining capacity display device to which a method for calculating a remaining capacity of a nickel-based battery according to the present invention is applied.

FIG. 3 is a diagram showing an example of self-discharge characteristics of a nickel-based battery.

[Explanation of symbols]

 1 Remaining capacity meter 2 Display section 3 Ni-Cd battery 4 Ammeter 5 Temperature sensor 6 Ignition switch 7 Motor controller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyasu Suzuki 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor Kazuo Natori 2-4-1 Nishitsujikeoka, Chofu-shi, Tokyo Tokyo (72) Inventor Noboru Fujiwara 2-4-1, Nishitsutsujigaoka, Chofu-shi, Tokyo Inside the Technical Research Institute, Tokyo Electric Power Co., Inc.

Claims (1)

[Claims] 1. A battery is obtained by measuring a charge / discharge current of a battery, adding up an amount of charge / discharge electricity every unit time, and adding / subtracting the added amount of electricity to a preset initial value of the remaining capacity of the battery. In the method of calculating the remaining capacity of, the self-discharge amount is estimated and calculated from the previously calculated remaining capacity of the battery and the temperature of the battery obtained from the temperature sensor, and this self-discharge amount is added or subtracted at predetermined time intervals. A method for calculating the remaining capacity of a nickel-based battery, which is characterized in that a subtraction process is performed from the remaining capacity obtained by.