JP2002107430A - Method for indicating residual capacity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately indicate the residual capacity of a battery which has become inactive. SOLUTION: In the method for indicating residual capacity, calculating the residual capacity is calculated from a charge capacity of a secondary battery and indicated. In the method for indicating a residual capacity, whether the battery is an inactive battery or not is judged when starting charge. For the battery judged as an inactive battery, the charge efficiency is corrected to a corrected charge efficiency lower than that in a charge state where the inactiveness is eliminated in an activation charge process for charging the inactive battery, and the residual capacity is calculated from the corrected charge efficiency and the charge capacity for indication.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for charging an inactive battery and indicating a remaining capacity.

[0002]

2. Description of the Related Art A secondary battery can be charged to increase the remaining capacity and increase the dischargeable capacity. By the way, a secondary battery becomes inactive if left uncharged for a long time. Immediately after starting charging, the inert battery in this state is practically hardly charged despite the flow of charging current, and the remaining capacity does not increase. After charging for a predetermined time, the inactive state is eliminated, and the charging gradually shifts to normal charging, and the remaining capacity increases.

In the conventional method of calculating and displaying the remaining capacity while charging the inert battery in this state, the remaining capacity is displayed by the characteristics shown in FIG. The remaining capacity is displayed on the assumption that the remaining capacity increases in proportion to the integrated value of the charging current, as shown in FIG. When charging an inert battery, at the beginning of charging, a non-accumulated capacity that does not increase the remaining capacity is provided, and the remaining capacity is not increased until the non-accumulated capacity is reached, and after the charging of the non-accumulated capacity is completed. The remaining capacity is calculated from the integrated value of the charging current and displayed so as to increase. The display method of
A process in which the remaining capacity does not increase even after charging for the first time is defined as a non-integrated capacity. Until the non-integrated capacity is reached, the charging current is not integrated. After the charging of the non-integrated capacity is completed, the remaining capacity is increased in proportion to the charging current. The remaining capacity is calculated by multiplying the integrated value of the charging current by the charging efficiency.

[0004]

As described above, the method of displaying the remaining capacity immediately after charging is started cannot accurately display the remaining capacity of the battery in an inactive state. Further, since the full charge is displayed before the battery is fully charged, there is a disadvantage that the battery is continuously charged even after the full charge is displayed. The method can display the remaining capacity of the battery more accurately than the method, but there is a timing at which the displayed remaining capacity does not increase even though the battery is being charged. There is a wrong disadvantage. Also, the remaining capacity is not increased until the non-cumulative capacity is reached, and immediately after the non-cumulative capacity is completed,
Since the state of charge is displayed by switching to normal charging, there is a disadvantage that the state of charge does not exactly match the increase in the state of charge of the actual battery.

[0005] The present invention has been developed for the purpose of solving such a drawback. An important object of the present invention is to provide a method of displaying the remaining capacity of a secondary battery, which can accurately display the remaining capacity of an inactivated battery so that a user does not make a mistake.

[0006]

According to the present invention, a method of displaying a remaining capacity calculates and displays a remaining capacity from a charged capacity of a secondary battery. The charging capacity can be calculated from an integrated value obtained by integrating the charging current with time. In the constant current charging, the charging capacity can be calculated from the charging time. Further, the display method of the present invention determines whether or not the battery is an inactive battery at the start of charging. A battery determined to be an inactive battery is charged through an activation charging process. In the activation charging step, the corrected charging efficiency is corrected to be lower than the charging state in which the deactivation is eliminated, and the remaining capacity is calculated and displayed from the corrected charging efficiency and the charging capacity.

In the activation charging step, for example, the remaining capacity is calculated and displayed on the assumption that the charging is performed at the corrected charging efficiency obtained by multiplying the normal charging efficiency by the efficiency conversion coefficient. Further, the efficiency conversion coefficient is a numerical value specified using the battery voltage as a parameter, and the efficiency conversion coefficient is reduced as the battery voltage decreases. The efficiency conversion coefficient is calculated by the following equation, for example. Efficiency conversion coefficient = real capacity / (real capacity + no integrated capacity) In this equation, the no integrated capacity is a value specified using the battery voltage as a parameter, and the lower the battery voltage, the larger the no integrated capacity. The real capacity is the maximum remaining capacity when the battery is fully charged with the inactive state eliminated. Further, in order to more accurately calculate and display the remaining capacity, the normal charging efficiency is corrected using the temperature as a parameter.

The method of displaying the remaining capacity by the above method is as follows.
The remaining capacity of the inert battery can be displayed more accurately. That is, in the activation charging step of the inert battery, the charging efficiency is small without increasing the remaining capacity as a non-integrated capacity as in the related art and without integrating the charging current as a normal charging state. This is because the remaining capacity is displayed after being corrected to the value.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below exemplify a method of displaying the remaining capacity for embodying the technical idea of the present invention, and the present invention does not specify the display method as follows.

Hereinafter, a display device of the remaining capacity will be described in detail by using a nickel-hydrogen battery or a nickel-cadmium battery as a secondary battery to be charged. However, the method for displaying the remaining capacity of the present invention does not specify a secondary battery that displays the remaining capacity by charging, as a nickel-hydrogen battery or a nickel-cadmium battery. This is because the remaining capacity can be displayed in the same manner for all other batteries generated by the inactive battery.

FIG. 2 is a circuit diagram of a display device used in the method for displaying a remaining capacity according to the present invention. The display device includes a voltage detection circuit 2 for detecting a voltage of a secondary battery 1 to be charged, a current detection circuit 3 for detecting a charging current, a temperature sensor 4 for detecting a temperature of the secondary battery 1, and a secondary battery. An arithmetic circuit 5 for calculating the remaining capacity by integrating the charging current of 1 and a display 6 for displaying the remaining capacity calculated by the arithmetic circuit 5 are provided. Further, a charger 9 is connected to the secondary battery 1 in order to charge the secondary battery 1.

The current detection circuit 3 includes a secondary battery 1 and a charger 9
And a current amplifier 8 for amplifying a voltage generated at both ends of the current detection resistor 7. The secondary battery 1 is connected to the current detection resistor 7.
A voltage proportional to the charging current is generated. This is because the product of the resistance value and the current value is the voltage generated at both ends. The current detection resistor 7 has a small resistance value in order to reduce power loss as much as possible. Therefore, the voltage generated at both ends is reduced. A minute voltage generated at both ends of the current detection resistor 7 is amplified by the current amplifier 8. The current amplifier 8 amplifies the voltage of the current detection resistor 7 at a constant amplification factor and inputs the amplified voltage to the arithmetic circuit 5. The output voltage of the current amplifier 8 has a value indicating the charging current of the secondary battery 1. Since the value of the charging current input to the arithmetic circuit 5 is an analog value, it is converted to a digital value by an A / D converter built in the arithmetic circuit 5 or an A / D converter provided in the current detection circuit 3. Input to the arithmetic circuit 5.

The battery voltage detected by the voltage detection circuit 2 is also represented by A /
The data is converted into a digital value by a D converter and input to the arithmetic circuit 5, or is converted into a digital value by an A / D converter built in the arithmetic circuit 5, and is processed by the arithmetic circuit 5. Further, a signal input from the temperature sensor 4 is also converted into a digital value by an A / D converter built in the arithmetic circuit 5 and arithmetically processed by the arithmetic circuit 5.

The calculation circuit 5 calculates the remaining capacity of the secondary battery 1 by integrating the current input from the current detection circuit 3 with a microcomputer such as a CPU. The remaining capacity is calculated by multiplying the integrated value of the current by the charging efficiency. However, the charging efficiency is not always set constant in all states. The inactive battery is determined at the start of charging. The determination of the inactive battery can be detected by the battery voltage. The remaining battery capacity is calculated while correcting the charging efficiency with a battery having a low battery voltage as an inactive battery. For example, nickel-hydrogen batteries and nickel-
In the case of a cadmium battery, a battery having a battery voltage lower than 1 V is regarded as an inactive battery, and if the battery voltage is higher than 1 V, it can be determined that the battery is not an inert battery. In the method of identifying an inactive battery based on the battery voltage, a voltage for determining an inactive battery is changed depending on the type of battery.

For a battery determined to be not an inert battery, the remaining capacity is calculated by multiplying the charging capacity by the normal charging efficiency. The charging capacity is calculated by integrating the charging current with time, that is, the integrated value of the charging current. In constant current charging, the charging capacity can be calculated by multiplying the charging current by the charging time. The normal charging efficiency is corrected based on the battery temperature detected by the temperature sensor 4. FIG. 3 shows the normal charging efficiency with respect to the battery temperature. The normal charging efficiency is set as a constant value in a predetermined temperature range as shown by a polygonal line A, and is set so as to change stepwise when the temperature range is different, or as shown by a curve B, continuously depending on the temperature. Set to change. The normal charging efficiency with respect to the temperature is stored in the storage circuit of the arithmetic circuit. The method of calculating the remaining capacity by correcting the normal charging efficiency with the battery temperature can calculate the remaining capacity more accurately. However, the normal charging efficiency can be a constant value regardless of the battery temperature.

[0016] In the activation charging step, the battery whose battery voltage is low and which is determined to be an inactive battery, corrects the charging efficiency to be smaller than the normal charging efficiency and calculates the remaining capacity.
That is, in the activation charging step, the charging efficiency is corrected to a lower charging efficiency than the charging state in which the deactivation is eliminated, and the remaining capacity is calculated from the corrected charging efficiency and the charging capacity. The charging capacity can be calculated by integrating the charging current, or, in the case of constant current charging, the remaining capacity can be calculated by multiplying the charging time by the charging current.

In the activation charging step, in order to correct the charging efficiency to a small value and calculate the remaining capacity, the normal charging efficiency is multiplied by an efficiency conversion coefficient to obtain a corrected charging efficiency, and the corrected charging efficiency is multiplied by the charging capacity. Calculate the remaining capacity. The corrected charging efficiency can be a constant that changes the battery voltage as a parameter. When the battery voltage becomes low, the inactivity of the battery is determined to be severe, and the battery efficiency conversion coefficient is reduced. The efficiency conversion coefficient using the battery voltage as a parameter is calculated by the following equation (1). (1) Efficiency conversion coefficient = real capacity / (real capacity + no integrated capacity) However, in this equation, the no integrated capacity is a value specified using the battery voltage as a parameter. Enlarge. The real capacity is the maximum remaining capacity when the battery is fully charged with the inactive state eliminated.

FIG. 4 illustrates the non-integrated capacity with respect to the battery voltage. The secondary battery 1 of this figure has a battery voltage of 1.2.
When the voltage is lower than V, the battery is determined to be an inactive battery, and the efficiency conversion coefficient is calculated using the non-integrated capacity. Battery voltage is 1.2
If it becomes higher than V, it is determined that the battery is not an inert battery, and the remaining capacity is calculated based on the normal charging efficiency. As the battery voltage decreases, the non-integrated capacity is increased. As the non-integrated capacity increases, the efficiency conversion coefficient decreases from equation (1).
The product of the efficiency conversion coefficient and the normal charging efficiency is the charging efficiency for calculating the remaining capacity of the battery in the activation charging step, that is, the corrected charging efficiency. Therefore, as the battery voltage decreases, the efficiency conversion coefficient decreases, and the rate at which the remaining capacity increases decreases.

FIG. 5 shows a characteristic that the remaining capacity increases as the charging time elapses. In this figure, in the activation charging step, the efficiency conversion coefficient becomes smaller than 1, and the gradient of the increase in the remaining capacity becomes smaller than that in the normal charging step in which the inactive state is eliminated. The figure shows an example in which when the battery voltage rises to 1.2 V, the battery is no longer an inactive battery. In the figure,
In the charging process in which the battery voltage has risen to 1.2 V and the inertness has been eliminated, that is, in the normal charging process, the remaining capacity linearly increases. Because the charging current and the normal charging efficiency are constant, the remaining capacity is calculated by multiplying the integrated value obtained by integrating the charging current with time by the normal charging efficiency as a constant.

The solid line in this figure shows the characteristic that the remaining capacity of a battery identified as an inactive battery increases. The remaining battery capacity of a battery identified as not an inert battery increases linearly from the beginning of charging, as indicated by the chain line in this figure. This is because the charging current and the normal charging efficiency are constant.

The arithmetic circuit 5 outputs the calculated remaining capacity to the display 6 and displays the remaining capacity on the display 6.

The above display device displays the remaining capacity of the secondary battery 1 to be charged in the steps shown in FIG. [Step n = 1] In this step, it is determined whether or not the charger 9 is connected, that is, whether or not the charging of the secondary battery 1 has been started. [Step n = 2] When charging of the secondary battery 1 is started, it is determined in this step whether or not the secondary battery 1 is an inactive battery. The inactive battery is detected by the voltage detection circuit 2 and, when the battery voltage is lower than the set voltage, is determined to be an inactive battery. [Step n = 3] The batteries determined to be inactive batteries are:
The process proceeds to this step. In this step, the arithmetic circuit 5 calculates the corrected charging efficiency. The corrected charging efficiency is calculated by the product of the normal charging efficiency and the efficiency conversion coefficient. The efficiency conversion coefficient is calculated by the above equation (1). That is, the non-integrated capacity is specified from the detected battery voltage, and the efficiency conversion coefficient is calculated from the specified non-integrated capacity by Expression (1). [Step n = 4] The remaining capacity is calculated using the calculated corrected charging efficiency. The remaining capacity is calculated by an integrated value obtained by integrating the charging current with time, and the remaining capacity is calculated by multiplying the charging capacity by the corrected charging efficiency. The calculated remaining capacity is displayed on the display 6. Then, jump to the step of n = 2.

[Step n = 5] The remaining capacity of a battery determined to be not an inactive battery is calculated using normal charging efficiency. In this step, the remaining capacity is calculated by multiplying the integrated value obtained by integrating the charging current with time by the normal charging efficiency. The calculated remaining capacity is displayed on the display 6. The remaining capacity is calculated in this step until the secondary battery 1 is fully charged, and the calculated remaining capacity is displayed on the display 6. [Step n = 6] When the secondary battery 1 is fully charged, the charging is completed in this step.

The above-described remaining capacity display device detects the battery voltage of the secondary battery being charged at a fixed timing, specifies the non-integrated capacity that changes from the detected battery voltage, and determines the non-integrated capacity from this non-integrated capacity. The efficiency conversion coefficient is calculated, and the remaining capacity is calculated using the efficiency conversion coefficient. According to the display method of the present invention, when charging is started, the battery voltage is detected, and the corrected charging efficiency in all steps of the activation charging step can be calculated. The arithmetic circuit for realizing this stores the efficiency conversion coefficient in the activation charging process as a function using the battery voltage detected first as a parameter. This method specifies an efficiency conversion coefficient in all steps of the activation charging process from the detected battery voltage based on a stored function, calculates a corrected charging efficiency from the specified efficiency conversion coefficient, and calculates the corrected charging efficiency. Is used to calculate and display the remaining capacity.

[0025]

The method for displaying the remaining capacity of the present invention has a feature that the remaining capacity of an inactivated battery can be accurately displayed without being mistaken. That is, the display method of the remaining capacity of the present invention determines whether or not the battery is an inactive battery at the start of charging. In the activation charging step of charging the battery determined to be the inactive battery, the inactive charging process is performed. This is because the corrected charging efficiency is corrected to be lower than the canceled charging state, and the remaining capacity is calculated and displayed from the corrected charging efficiency and the charging capacity.
According to the display method of the present invention, in the activation charging step, the remaining capacity is calculated with the corrected charging efficiency corrected low, so that the remaining capacity can be displayed more accurately even in a battery in an inactive state. For this reason, the remaining capacity can be displayed in a state closer to the actual remaining capacity so that the user does not make a mistake from immediately after the start of the charging until the full charge is displayed.

[Brief description of the drawings]

FIG. 1 is a graph showing a method of calculating a remaining capacity while charging a conventional inert battery.

FIG. 2 is a circuit diagram of a display device used for a method of displaying a remaining capacity according to an embodiment of the present invention.

FIG. 3 is a graph showing normal charging efficiency with respect to battery temperature.

FIG. 4 is a graph showing a non-integrated capacity with respect to a battery voltage.

FIG. 5 is a graph showing characteristics of battery voltage and remaining capacity with respect to charging time.

FIG. 6 is a flowchart showing a process of displaying the remaining capacity of the secondary battery to be charged by the display device shown in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Secondary battery 2 ... Voltage detection circuit 3 ... Current detection circuit 4 ... Temperature sensor 5 ... Operation circuit 6 ... Display 7 ... Current detection resistance 8 ... Current amplifier 9 ... Charger

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Claims (5)

[Claims] 1. A method for calculating and displaying a remaining capacity from a capacity for charging a secondary battery, comprising: determining an inactive battery at the start of charging; and charging the battery determined as the inactive battery. , A remaining capacity is calculated from the corrected charging efficiency and the charged capacity and is displayed by correcting the corrected charging efficiency to be lower than the charged state in which the inactivity has been eliminated. 2. The activated charge process according to claim 1, wherein the remaining charge is calculated and displayed as being charged at the corrected charge efficiency obtained by multiplying the normal charge efficiency by the efficiency conversion coefficient. How to display the remaining capacity. 3. The method according to claim 2, wherein the efficiency conversion coefficient changes using the battery voltage as a parameter, and the efficiency conversion coefficient decreases as the battery voltage decreases. 4. The method for displaying a remaining capacity according to claim 3, wherein the efficiency conversion coefficient is represented by the following equation. Efficiency conversion coefficient = real capacity / (real capacity + no integrated capacity) However, in this equation, the no integrated capacity is a value specified using the battery voltage as a parameter, and the lower the battery voltage, the larger the no integrated capacity. The real capacity is the maximum remaining capacity when the battery is fully charged with the inactive state eliminated. 5. The method according to claim 2, wherein the normal charging efficiency is corrected using temperature as a parameter.