JP2002162452A - Battery remaining quantity detection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in detection of the percentage of a battery residual quantity by the battery characteristic wherein the battery remaining quantity percentage is not displayed correctly by the change of a battery characteristic with influence on the life time or the like. SOLUTION: Since for the battery, the battery voltage characteristic is generally changed by the influence of the life time or the like, a battery capacity detection circuit determines the degree of the voltage characteristic change of the battery, speculates the voltage characteristic at the last stage of discharge, and decides on x% detection voltage value, by the battery voltage of the voltage remaining quantity Y% (Y=70), at the initial stage of discharge of at the initial stage of the life time, the middle stage of the life time and the last stage of the life time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery remaining amount detecting circuit, and more particularly to a battery remaining amount detecting circuit for detecting a battery capacity corresponding to a change in a voltage characteristic of a battery depending on a battery life.

[0002]

2. Description of the Related Art Conventionally, for detecting the battery capacity, a method utilizing the voltage-current characteristics of a battery has been used, as described in, for example, Japanese Patent Application Laid-Open No. 07-244103.

FIG. 1 is a block diagram showing an embodiment of a battery remaining capacity detecting circuit. When detecting the remaining battery capacity of the secondary battery 1 discharged to the load 5, the battery capacity detection circuit 4 receives the battery voltage and battery current information from the voltage detection circuit 2 and the current detection circuit 3, and calculates (subtracts) the battery capacity. I do.

FIG. 2 is a conceptual diagram showing the operation of the embodiment of the battery remaining capacity detection circuit.

FIG. 2 shows the calculation results of the battery voltage characteristics and the battery capacity detection circuit when the battery is discharged. As shown in FIG. 2, the battery capacity detection circuit 4 determines the remaining capacity of the battery in the A period until the voltage reaches the voltage at the voltage detection point of the remaining capacity x% (hereinafter referred to as x = 5%). Calculation (subtraction) is performed based on the received information to calculate the remaining capacity of the battery.

At the point B where the battery voltage 11 reaches the voltage detection point of the remaining capacity x%, the battery level is detected as the battery remaining amount x%, the battery remaining amount 10 is recognized as x%, and the battery remaining amount is calculated (subtracted).

In FIG. 2, in order to make the calculation of x% by the voltage detection easy to understand, the decrease of the battery remaining amount 10 is not made linear with respect to x%.

However, in this technique, since the remaining battery capacity x% is detected based on the characteristics of the battery, if the battery characteristics change due to the influence of the service life or the like, the remaining battery capacity x% cannot be correctly displayed. Problems arise. FIG. 3 shows the mechanism by which this problem occurs.

FIG. 3 is a conceptual diagram showing a change in battery voltage characteristics due to battery life and a relationship between battery voltage and remaining battery capacity.

As shown in FIG. 3, a battery may change its battery voltage characteristics due to repeated charging and discharging, and generally its voltage characteristics become smoother toward the end of its life. It is. As shown in FIG. 3, when the battery remaining amount x% is detected using the technique of the conventional invention despite the change in the voltage characteristic, the point F at the early stage of the life is correctly left as shown in FIG. Although the amount x% can be detected, there is a problem that the error between the point E at the middle of the life and the point D at the end of the life and the actual remaining capacity of the battery and x% increases as the life proceeds.

[0011]

The first problem with the above-described conventional battery remaining amount detection circuit is that the percentage of the battery remaining amount cannot be displayed correctly.

The reason is that the remaining battery percentage is detected based on the characteristics of the battery, so that the characteristics of the battery change due to the influence of the service life and the like.

An object of the present invention is to provide a circuit for accurately detecting the remaining amount of a battery even when the voltage characteristics of the battery change due to the life or the like.

[0014]

SUMMARY OF THE INVENTION A battery remaining amount detecting circuit according to the present invention sets a battery voltage at an early stage of discharging for detecting a remaining battery capacity of a battery depending on a battery life, and detects a detected battery voltage. The voltage determines the remaining battery voltage at the end of discharging from the remaining battery voltage at the beginning of discharging, and the time at which the detected battery voltage reaches the remaining battery voltage at the last battery is the remaining battery capacity of the battery. When the determination is made, the determination is performed using the characteristic indicating the data of the voltage characteristic change at the end of discharge and the data of the battery characteristic change at the beginning of discharge extracted from a table indicating the relationship between the discharge current and the remaining capacity detection voltage due to the change in battery voltage characteristic due to the battery life. .

[0015]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a remaining battery capacity detection circuit.

Referring to FIG. 1, when detecting the remaining battery capacity of the secondary battery 1 discharged to the load 5, the voltage detection circuit 2 measures the battery voltage of the secondary battery 1 and transmits it to the battery capacity detection circuit 4. . The current detection circuit 3 transmits the current flowing from the secondary battery 1 to the load 5 to the battery capacity detection circuit 4. The battery capacity detection circuit 4 has a function of judging a change in battery characteristics based on the voltage information received from the voltage detection circuit 2 and the current information received from the current detection circuit 3, and detects the remaining capacity x% of the battery from the voltage information and the current information. It has a function to determine the remaining battery level by accumulating the current information.

Next, the operation of the embodiment of the present invention will be described in detail with reference to the drawings.

First, various operations of the battery capacity detection circuit 4 will be described with reference to the drawings. First, the battery capacity detection circuit 4
The function of detecting the remaining battery amount x% of the battery will be described with reference to the drawings.

FIG. 4 is a characteristic diagram showing the characteristics of the battery voltage when the battery is discharged at a constant current of large, medium and small. FIG. 5 is a graph showing the relationship between the battery voltage for detecting the remaining capacity and the discharge current.

In general, as shown in FIG. 4, the battery voltage characteristic changes as the discharge current changes due to small current discharge, medium current discharge, and large current discharge, and the x% detection voltage value also changes. . Therefore, the battery capacity detection circuit 4 has a discharge current-x% remaining amount detection table as shown in FIG. 5, and performs an operation of changing the detection voltage of the battery remaining amount x% with a change in the discharge current.

The operation of the battery capacity detection circuit 4 for determining a change in battery characteristics, which is a feature of the present invention, will be described with reference to FIG.

FIG. 6 is a characteristic diagram showing data on a change in voltage characteristics at the end of discharge and a change in battery characteristics at the beginning of discharge due to the life of the battery in the battery remaining amount detection circuit of the present invention.

As described in FIG. 4, the battery generally changes in battery voltage characteristics due to the influence of the life and the like. Therefore, in the present invention, as shown in FIG. Battery remaining amount Y% (Y = 7 in this description)
The battery capacity detection circuit 4 determines the degree of change in the voltage characteristics of the battery based on the battery voltage at 0), estimates the voltage characteristics at the end of discharging, and determines the x% detection voltage value.

FIG. 7 is a flowchart showing the operation of the battery remaining amount detecting circuit of the present invention.

The discharge of the secondary battery starts (step A1).
And the battery capacity detection circuit 4 calculates the remaining capacity of the battery by integrating and subtracting the battery capacity from the total battery capacity (steps A2 and A3), and the remaining battery capacity is Y% (step A).
The battery voltage is measured at the point of time when 5) is reached, and a change in the voltage characteristics of the battery is determined (step A4).

Next, a voltage for detecting the battery remaining amount x% is determined (step A6). The detection voltage table used at this time changes according to the characteristic change of the life of the battery voltage. FIG. 8 shows the table.

FIG. 8 is a table showing the relationship between the discharge current and the remaining capacity detection voltage due to the change in the battery voltage characteristic of the battery remaining amount detection circuit of the present invention.

The battery capacity detection circuit 4 determines the degree of change in the voltage characteristics of the battery based on the battery voltage at the battery remaining amount Y% (Y = 70 in the present description) at the beginning of the life, the middle of the life, and the end of the life. Estimate the voltage characteristics at the end of discharge, x%
Determine the detection voltage value.

When the battery voltage reaches the detection voltage, the battery capacity is set to x% (steps A7 and A8). Thereafter, the remaining battery level is subtracted until the remaining battery level becomes 0% (step A9 and step A10).

[0031]

As described above, the first effect of the battery remaining amount detection circuit of the present invention is that the remaining battery capacity can be accurately detected even when the voltage characteristics of the battery change.

The reason is that the data of the change in the characteristics of the battery voltage due to the life is used to measure the voltage characteristics at the beginning of discharge and predict the voltage characteristics at the end of discharge.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment of a remaining battery capacity detection circuit.

FIG. 2 is a conceptual diagram showing an operation of the embodiment of the remaining battery capacity detection circuit.

FIG. 3 is a conceptual diagram showing a change in battery voltage characteristics due to battery life and a relationship between battery voltage and remaining battery capacity.

FIG. 4 is a characteristic diagram showing characteristics of a battery voltage when the battery is discharged with a large, medium, and small constant current.

FIG. 5 is a graph showing a relationship between a battery voltage for detecting a remaining capacity and a discharge current.

FIG. 6 is a characteristic diagram showing data of a voltage characteristic change at the end of discharge and a battery characteristic change at the beginning of discharge depending on the battery life of the battery remaining amount detection circuit of the present invention.

FIG. 7 is a flowchart showing the operation of the battery remaining power detection circuit of the present invention.

FIG. 8 is a table showing a relationship between a discharge current and a remaining capacity detection voltage according to a change in battery voltage characteristics of the battery remaining amount detection circuit of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Secondary battery 2 Voltage detection circuit 3 Current detection circuit 4 Battery capacity detection circuit 5 Load

Claims (6)

[Claims] 1. A battery remaining amount detecting circuit for detecting a battery voltage and detecting a remaining battery amount using data of a change in battery voltage characteristics depending on a battery life. 2. A battery level detection battery voltage for detecting the remaining battery capacity of the battery depending on the battery life is set in advance, and when the detected battery voltage reaches the battery level, the remaining battery level is determined. A battery remaining amount detection circuit that determines that the battery capacity is reached. 3. A battery voltage at the beginning of discharge for detecting the remaining battery capacity of the battery depending on the battery life is set in advance, and the detected battery voltage is calculated based on the battery voltage at the initial discharge at the end of discharge. A remaining battery capacity of the battery when the detected battery voltage reaches the battery voltage at the end of discharging. 4. A battery voltage at the beginning of discharge for detecting the remaining battery capacity of the battery depending on the battery life is set in advance, and the detected battery voltage is calculated based on the battery voltage at the initial discharge at the end of discharge. When the remaining battery capacity of the battery is determined when the time when the detected battery voltage reaches the battery voltage at the end of discharge is determined as the remaining battery capacity of the battery, a change in the voltage characteristic at the end of discharge due to the battery life and A battery remaining amount detection circuit, wherein the detection is performed using characteristics indicating data of a change in battery characteristics at an initial stage of discharging. 5. A battery voltage at the beginning of discharge for detecting the remaining battery capacity of the battery depending on the battery life is set in advance, and the detected battery voltage is calculated based on the battery voltage at the early stage of discharge from the battery voltage at the end of discharge. The remaining battery capacity of the battery is determined, and when the detected battery voltage reaches the remaining battery capacity battery voltage at the end of discharging is determined as the remaining battery capacity of the battery, the discharge current due to the battery voltage characteristic change due to the battery life is determined. And a remaining capacity detection voltage using a characteristic extracted from a table indicating a relationship between the remaining capacity detection voltage and a voltage characteristic change at the end of discharge and a change in battery characteristic at the beginning of discharge. 6. When the discharge of the secondary battery starts, a battery capacity detection circuit calculates the remaining capacity of the battery by integrating and subtracting the battery capacity from the total battery capacity, and calculates the remaining capacity of the battery at the time of initial discharge reaching Y%. The battery voltage characteristic is measured by using a table showing the relationship between the discharge current and the remaining capacity x% detection voltage due to the change in the battery voltage characteristic, and the end-of-discharge voltage for detecting the remaining battery amount x% is determined. A remaining battery level detection circuit.