JPH0620723A - Secondary battery residual quantity display device and display method - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a secondary battery remaining amount display device and a display method for measuring the charging current amount and the discharging current amount of a secondary battery and displaying the remaining capacity, and the ambient temperature and the discharge current. Correct the measured value in consideration of the error due to the change in discharge efficiency caused by the value and the measurement circuit error such as the variation of parts in the measurement of charge / discharge current, and enable the accurate display of the remaining amount of the secondary battery. With the goal. A secondary battery remaining amount display device including an external memory 8 and a temperature detection circuit 11, wherein the external memory 8 includes a charge / discharge amount measuring circuit that changes discharge efficiency depending on temperature and discharge current value. Store the error as a table, and when discharging,
The discharge accumulated value is corrected using the table of the external memory 8 so that the remaining amount of the secondary battery 1 is accurately displayed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention measures the charging current amount and the discharging current amount of a secondary battery which is repeatedly charged and discharged,
The present invention relates to a secondary battery remaining amount display device and a display method for displaying the remaining capacity.

[0002]

2. Description of the Related Art In a secondary battery such as a nickel-cadmium battery whose output voltage is almost constant, a method of measuring the charging current amount and the discharging current amount and displaying the remaining capacity is used. That is, the current value is obtained by measuring the minute potential appearing at both ends of the resistance through which the charging / discharging current flows, using an individual amplifier circuit. Then, using the product of the charging / discharging current value and the energization time, the remaining capacity is calculated from the difference.

[0003]

However, in the case where the number of times of measurement is large, errors in the amplifier circuit are accumulated due to variations in parts and the like, resulting in errors in display accuracy. Further, the temperature and the discharge current value at the time of discharge are also related to the efficiency of discharge and the error of the remaining amount display.

Therefore, an object of the present invention is to correct the measured value in consideration of an error due to a change in discharge efficiency caused by an ambient temperature and a discharge current value and a measurement circuit error such as a variation of parts in the measurement of charge / discharge current. However, it is possible to accurately display the remaining amount of the secondary battery.

[0005]

In one form of the present invention, as illustrated in FIG. 1, a secondary battery 1, a charger 5 for charging the secondary battery 1, and a temperature for measuring temperature. A detection circuit 11 and a resistor 6 connected in series with the secondary battery 1,
A charging / discharging current detection circuit 2 that receives a voltage across the resistor 6 to detect a charging / discharging current, and an AD converter 3 that receives the outputs of the charging / discharging current detection circuit 2 and the temperature detection circuit 11 and performs analog-to-digital conversion. And a microprocessor unit 4 for receiving the output of the AD converter 3 and processing the data.
And the operation connected to the microprocessor unit 4.
A secondary battery remaining amount display device including a display unit 7 and an external memory 8 is provided. Then, this device has a charging / discharging current detection circuit which is obtained by applying a reference current to the resistor 6 connected in series to the secondary battery 1 as an initial test in the external memory 8 for discharging efficiency according to temperature and current value. The total correction value calculated using the measured current value in 2 is stored as a table, and at the time of discharging, the table of the external memory 8 is used to correct the discharge integrated value and display the remaining amount of the secondary battery 1. To configure.

In another embodiment of the present invention, the secondary battery 1
, A charger 5, a charging / discharging current detection circuit 2 for detecting charging / discharging current, an operation / display unit 7, an external memory 8 and a temperature detection circuit 11, and a secondary battery level display device. The remaining battery residual quantity display method is provided. In this method, the discharge efficiency is corrected by the temperature and current value at the time of charging, the measurement error in the charge / discharge current detection circuit 2 is obtained, and the discharge efficiency is recorrected to charge or discharge the battery. It is configured to display the remaining amount of the secondary battery.

[0007]

With the above-described device or method, the charge amount is obtained by converting the current flowing through the resistor 6 into a voltage by the charge / discharge current detection circuit 2 and converting it into a digital value by the AD (analog / digital) converter 3. The product of the digital value and the charging time is added by the microprocessor unit (MPU) 4, the charge amount is calculated, and displayed on the operation / display unit 7.

At the time of discharging, the discharging current is converted into a voltage value by the charging / discharging current detection circuit 2 via the resistor 6, converted into a digital value by the AD converter 3, and the product of the digital value and the discharging time. Is added by the MPU 4 to calculate the discharge amount. In this case, referring to the table of the external memory 8 from the temperature data and the discharge current value from the temperature detection circuit 11, the discharge time to be integrated corresponding to the discharge efficiency is shortened, the discharge amount is calculated, and the discharge amount is calculated. Fix it. The corrected discharge amount is subtracted from the charge amount, and the remaining amount of the secondary battery is displayed on the operation / display unit 7.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A block diagram of a secondary battery remaining amount display device as one embodiment of the present invention is shown in FIG. This device includes a secondary battery 1, a resistor 6 connected in series with the secondary battery, a charge / discharge current detection circuit 2 for detecting the voltage across the resistor 6,
It is provided with an AD converter 3 for AD converting the output of the discharge current detection circuit 2, an MPU 4 for receiving the output of the AD converter 3, an operation / display unit 7 connected to the MPU 4, an external memory 8 and a charger 5.

In addition to the above, this device uses a diode 2
1, 22, a temperature detection circuit 11, a charger detection circuit 12, a voltage detection circuit 23, and an output switch 13.
Next, the operation of this device will be described. As a device to be charged including a secondary battery that is charged using this device, for example, a mobile phone or the like is applied.

When the device to be charged is first placed on the charger, terminals for energization and charging are connected to form a circuit as shown in FIG. The power supply line from the charger 5 supplies power to the device to be charged via the diode 21. A charging current is supplied to the secondary battery 1 of the device to be charged through the diode 22. Although the output switch 13 remains closed, the charging current to the secondary battery is supplied through the diode 22 and the power receiving circuit of the device to be charged is energized through the diode 21. The output switch is opened when an overcurrent flows or the detection voltage of the voltage detection circuit 23 drops during the discharging process.

During charging, a current flows through the resistor 6 in the direction of the arrow, and a small voltage is generated across the resistor 6 having a low resistance value. This voltage is amplified by the charging / discharging current detection circuit 2, converted into an appropriate voltage, and converted into a digital voltage value by the AD converter 3. The product of this digital voltage and the charging time is obtained by the MPU 4 and displayed on the operation / display unit 7.

At the time of discharging, the device to be charged is removed from the charger 5, and the energization and charging circuit is cut off. The current charged in the secondary storage battery 1 passes through the resistor 6 and flows to the device to be charged via the output switch. A current flows through the resistor 6 in the opposite direction to that during charging. The voltage across the resistor 6 is amplified by the current detection circuit 2 using an element different from that during charging, AD-converted in the same manner as during charging, and the MPU 4 integrates the discharge current value and the discharge time, and the temperature and discharge current at that time. The discharge efficiency is calculated from the value by referring to a table in the external memory 8 (for example, FIG. 5), corrected, subtracted from the charge amount, and the corrected secondary battery remaining amount is displayed on the operation / display unit. The table of FIG. 5 is created by recorrecting the discharge efficiency of FIG. 4 in consideration of measurement errors of charging and discharging currents.

As the charger to be used, a charger with a full charge detection function is used, which shifts to a minute current (trickle current) of 2 to 3 mA when full charge is detected by the -ΔV detection method or the like. A flow chart of control for displaying the charge amount while charging the secondary battery 1 is shown in FIG. First, when the device to be charged is placed on the charger 5, the process proceeds to the next step, the charging current flows, the charge / discharge current detection circuit 2 performs current-to-voltage conversion, and the AD converter 3 performs digital conversion. Convert to value, MPU
Multiply and add by 4, and display the charge amount in comparison with the previous charge amount. When full charge is detected, the current becomes a trickle current, at which point the full charge current amount is corrected and updated. If the battery is not fully charged, the measured amount is accumulated in the current amount and the ratio of the current amount to the fully charged amount is displayed in percentage.

A flow chart showing the measurement process in the discharge mode is shown in FIG. When recognizing that the device to be charged is removed from the charger, the charger detection circuit 12 operates and shifts to the discharge mode, and the thermal efficiency value shown in FIG. 4 is selected by monitoring the current temperature and discharge current. When the integration cycle at the time of charging is set to 1, at the time of discharging, the MPU is shortened by the ratio of the efficiency value.
It is decided that the internal counter capacity has apparently decreased. When the discharge current flows, it is converted into a voltage in the same way as during charging, and it is subtracted and compared with the full charge amount to display the remaining amount. FIG. 4 is calculated in advance from the characteristic data of the battery.

The thermal efficiency values in the external memory can be weighted by testing the changes in the measured values due to variations in the parts of the charge / discharge current detection circuit 2 during manufacturing, and this table is shown in FIG. This figure is a table obtained by subtracting 5% from the table of FIG. 4 showing the standard efficiency values, assuming that the error in the measured values due to variations in parts and the like is -5%. For example, the table of FIG. 5 is used to correct the discharge amount. In this case, the error of the charging / discharging current detection circuit is determined in consideration of both charging and discharging.

[0017]

According to the present invention, the measurement value is corrected in consideration of the measurement circuit such as the error due to the change of the discharge efficiency caused by the ambient temperature and the discharge current value and the variation of parts in the measurement of the charge / discharge current, It is possible to accurately display the remaining amount of the secondary battery.

[Brief description of drawings]

FIG. 1 is a block diagram showing a secondary battery remaining amount display device as one embodiment of the present invention.

FIG. 2 is a flow chart showing a measurement process in a charging mode of the embodiment.

FIG. 3 is a flow chart showing a measurement process in a discharge mode of the embodiment.

FIG. 4 is a diagram showing an example of standard discharge efficiency values in Examples.

FIG. 5 is a diagram showing an example of a standard discharge efficiency value including a measurement circuit error in the example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Secondary battery 2 ... Charge / discharge current detection circuit 3 ... AD converter 4 ... MPU 5 ... Charger 6 ... Resistor 7 ... Operation / display section 8 ... External memory 11 ... Temperature detection circuit 12 ... Charger detection section 13 ... Output switches 21, 22 ... Diode 23 ... Voltage detection circuit

Claims (2)

[Claims] 1. A secondary battery (1), a charger (5) for charging the secondary battery (1), a temperature detection circuit (11) for measuring temperature, and the secondary battery (1). A resistor (6) connected in series, a charging / discharging current detecting circuit (2) for detecting a charging / discharging current by receiving a voltage across the resistor (6), and a charging / discharging current detecting circuit (2) A for receiving the output of the temperature detection circuit (11) and converting it from analog to digital
D converter (3), microprocessor unit (4) for receiving data from the AD converter (3) and processing data, and operation / display unit (7) connected to the microprocessor unit (4) A secondary battery residual amount display device comprising: and an external memory (8), wherein the external memory (8) has a discharge efficiency depending on a temperature and a current value, and the secondary battery (1) has an initial test. The total correction value calculated by using the measured current value in the charge / discharge current detection circuit (2) obtained by applying the reference current to the resistor (6) connected in series is stored as a table, and the Using the table in memory (8),
A secondary battery remaining amount display device which corrects the integrated discharge value and displays the remaining amount of the secondary battery (1). 2. A secondary battery (1), a charger (5), a charge / discharge current detection circuit (2) for detecting a charge / discharge current,
A secondary battery level display method using a secondary battery level display device comprising an operation / display unit (7), an external memory (8) and a temperature detection circuit (11), wherein the temperature during discharge And the discharge efficiency is corrected by the current value, the measurement error in the charge / discharge current detection circuit (2) is calculated, and the discharge efficiency is corrected again, and the remaining amount of the charged or discharged secondary battery is displayed. How to display the remaining battery level.