JP2003047165A - Battery charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery charger which enables detecting with very high accuracy time when a secondary battery is in a fully charged state. SOLUTION: The battery charger is provided with a charging circuit 1 which supplies power to a battery unit 2, and a charging control circuit 10 which controls the operation of the charging circuit 1. The charging control circuit 10 calculates a little bit smaller reference voltage value than a peak value, based on the peak value of the battery voltage which is detected when previously charged. Then, the charging control circuit 10 detects the time when the battery voltage of the battery unit 2 corresponds to the reference voltage value, and terminates the charging operation to the charging circuit 1, when a certain time is elapsed from the time of detection.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a charging device for charging a secondary battery such as a nickel-cadmium battery or a nickel-hydrogen battery.

[0002]

2. Description of the Related Art Conventionally, as a method of charging a secondary battery such as a nickel-cadmium battery or a nickel-hydrogen battery, the time at which the secondary battery is in a fully charged state (hereinafter referred to as a fully charged time) is detected. A charging method is known in which charging is terminated at the time of detection. This type of charging method includes a method of detecting a time point at which the battery voltage value at both ends of the secondary battery reaches a peak value as a full charge time point and ending charging at the detection time point, a change in the battery temperature of the secondary battery. Is detected as the point of full charge and the charging is terminated at the point of detection, and the point of time when the difference between the battery temperature of the secondary battery and the ambient temperature increases is detected as the point of full charge and the detection is performed. It is known how to terminate charging at that time. Further, a method of detecting a time when the battery temperature of the secondary battery becomes a certain value or more as a full charge time and ending charging at the detection time, a time when the battery voltage value of both ends of the secondary battery becomes a certain value or more. A method is known in which the charging is detected at the time of full charge and the charging is terminated at the time of detection.

[0003]

However, a charging method for detecting the time when the battery voltage value of the secondary battery reaches the peak value, a charging method for detecting the time when the change in the battery temperature of the secondary battery sharply increases, And in the charging method for detecting the time when the difference between the battery temperature of the secondary battery and the ambient temperature increases,
These points can be easily detected at the time of rapid charging where the charging current value is about 0.5 to 1.0C, but at the time of low current charging when the charging current value is less than 0.5C,
Since it was difficult to detect these time points, the full charge time point of the secondary battery could not be detected with high accuracy. or,
A charging method that detects the battery temperature of the secondary battery and detects the time when the battery temperature becomes a certain value or more, and a battery voltage value of the secondary battery that detects the time when the voltage value becomes the certain value or more In this charging method, the battery temperature and battery voltage value at full charge are different for each secondary battery and change according to the deterioration of the secondary battery over time, so the full charge time of the secondary battery can be detected with high accuracy. I couldn't do it. As described above, in any of the conventional charging methods, there is a problem that the time when the secondary battery is fully charged cannot always be detected with high accuracy. An object of the present invention is to provide a charging device that can always detect with high accuracy the time when the secondary battery is in a fully charged state.

[0004]

The charging device according to the present invention comprises:
It is for charging a battery unit composed of one or more secondary batteries, and comprises a charging circuit for supplying electric power to the battery unit and a charging control circuit for controlling the operation of the charging circuit. Further, in the characteristic configuration of the charging device, the charging control circuit is based on the voltage detection means for detecting the voltage value across the battery unit and the maximum value of the battery voltage value detected by the voltage detection means at the previous charging. A reference value calculating means for calculating a reference voltage value serving as a reference for detecting the time when the battery unit is in a fully charged state, and a reference voltage value calculated by the reference value calculating means after the start of charging as a reference. And a charging end control means for detecting a time point when the battery unit is in a fully charged state from the battery voltage value detected by the voltage detection means and ending the charging operation of the charging circuit at the detection time point.

The battery voltage value at both ends of the battery unit gradually increases as the charging time becomes longer, and becomes substantially constant after reaching the maximum value. Here, when the battery voltage value of the battery unit reaches the maximum value, the battery unit is fully charged. Also, the maximum value of the battery voltage value differs for each secondary battery and changes according to the deterioration of the secondary battery over time. Therefore, the reference voltage value calculating means of the charge control circuit serves as a reference for detecting the full charge state time of the battery unit, based on the maximum value of the battery voltage value detected by the voltage detecting means at the time of the previous charging. Calculate the reference voltage value. Then, after the start of charging, the charging end control means detects the full charge time of the battery unit from the battery voltage value of the battery unit with reference to the reference voltage value, and ends the charging operation of the charging circuit at the detection time.

In the charging device according to the present invention, as described above, the reference voltage value is calculated based on the maximum value of the battery voltage value detected during the previous charging. Therefore, it is possible to calculate an appropriate reference voltage value for each battery unit according to the change in the maximum value due to deterioration over time. Further, since the detection method using the reference voltage value as a reference is adopted for the detection at the time when the battery unit is fully charged, the detection is easy even at the time of low current charging with a small charging current value.

In the above charging device, as described above, an appropriate reference voltage value can be calculated, and since it is easy to detect the time when the secondary battery is fully charged, the time when the secondary battery is fully charged. High accuracy is always obtained for the detection of.

More specifically, the charging control circuit includes temperature measuring means for measuring the temperature around the battery unit, and the charge control circuit measures the temperature around the battery unit and the battery voltage value detected by the voltage detecting means during charging. And a maximum value relationship storing means for storing a relationship between the maximum value of the battery voltage value and a maximum value of the battery voltage value detected by the voltage detecting means each time charging is completed. Means for updating the relationship stored in the means, the reference value calculating means of the charging control circuit, according to the relationship stored in the maximum value relationship storing means, from the ambient temperature measured by the temperature measuring means. A maximum value corresponding to the temperature is derived, and the reference voltage value is calculated based on the derived maximum value.

The maximum value of the battery voltage value of the battery unit decreases as the ambient temperature of the battery unit increases, while it increases as the ambient temperature of the battery unit decreases. A certain relationship holds with the value. Therefore, in the above specific configuration, the relationship between the ambient temperature of the battery unit and the maximum value of the battery voltage value detected during charging is stored in the maximum value relationship storage means. Then, this relationship is updated each time charging is completed, based on the maximum value of the battery voltage value detected during charging.

During charging, the maximum value corresponding to the temperature is derived from the ambient temperature measured by the temperature measuring means in accordance with the relationship stored in the maximum value relationship storing means as described above, and the derived maximum value is derived. The reference voltage value is calculated based on the value. Here, the relationship is updated based on the maximum value detected during the previous charging. In this way, the reference voltage value is calculated based on the appropriate maximum value according to the ambient temperature of the battery unit. Therefore, a more appropriate reference voltage value can be calculated according to the ambient temperature of the battery unit.

Further, specifically, the relationship stored in the maximum value relationship storing means is expressed by a functional expression having the ambient temperature measured by the temperature measuring means as a variable.

In the specific configuration, the reference value calculating means of the charge control circuit executes the calculation according to the above-mentioned functional expression using the ambient temperature measured by the temperature measuring means as a variable, so as to determine the ambient temperature of the battery unit. Calculate the maximum value. Here, the functional expression is updated based on the maximum value of the battery voltage value detected during the previous charging.

Alternatively, the relationship stored in the maximum value relationship storage means is that a plurality of temperature data representing the ambient temperature of the battery unit and the battery voltage detected by the voltage detecting means at the ambient temperature represented by each temperature data. And a maximum value table including a maximum value of the values, and the updating means of the charge control circuit is configured so that, each time charging is completed, the temperature measuring means among the plurality of maximum values written in the maximum value table. The maximum value of the temperature data corresponding to the ambient temperature measured by is updated to the maximum value of the battery voltage value detected by the voltage detecting means during the charging.

In the specific configuration, the reference value calculating means of the charging control circuit refers to the maximum value table stored in the maximum value relation storing means, and determines the temperature from the ambient temperature measured by the temperature measuring means. The maximum value of the temperature data according to is derived. Then, the updating means of the charging control circuit, every time charging is completed, sets the maximum value of the temperature data corresponding to the ambient temperature at the time of charging, out of the plurality of maximum values written in the maximum value table, The battery voltage value detected during charging is updated to the maximum value. In this way, the table will be updated each time charging is completed. In the above specific configuration, each time charging is completed, only the maximum value of the temperature data corresponding to the ambient temperature at the time of charging is updated. At the measured ambient temperature, the maximum value when the charging was performed last time will be derived. Therefore, regardless of the ambient temperature of the battery unit, it is possible to calculate a more appropriate maximum value according to the ambient temperature of the battery unit, as compared with the configuration in which the functional expression is updated every time charging is completed.

More specifically, the reference value calculation means of the charge control circuit calculates a reference voltage value slightly smaller than the maximum value of the battery voltage value, and the charge end control means After the start of charging, the battery voltage value detected by the voltage detection means and the reference voltage value are compared with each other to detect a time point at which the battery voltage value matches the reference voltage value. And a terminating means for terminating the charging operation of the charging circuit at a time point when a certain time has elapsed from the time point at which it was detected and detecting the time point.

In the specific configuration, a reference voltage value slightly smaller than the maximum value of the battery voltage value of the battery unit is calculated, and after the start of charging, the battery voltage value detected by the voltage detecting means and the reference voltage value. Are compared with each other to detect the time when the battery voltage value matches the reference voltage value. Here, since the reference voltage value is a value slightly smaller than the maximum value,
The coincidence time is detected immediately before the time when the battery voltage value of the battery unit reaches the maximum value. Like this
Since the coincidence time is detected by comparing the battery voltage value and the reference voltage value, the coincidence time can be easily detected even at the time of low current charging with a small charging current value, and high accuracy can be obtained for the detection. .

After that, the time when a certain time has elapsed from the time when the battery voltage value coincides with the reference voltage value is detected, and the charging operation of the charging circuit ends at the detection time. Here, the fixed time is set to a time required for the battery voltage value of the battery unit to reach the maximum value after the battery voltage value matches the reference voltage value, or a time slightly longer than the time. Also, after the battery voltage value of the battery unit reaches the maximum value as described above,
It becomes almost constant. Therefore, the battery voltage value of the battery unit becomes the maximum value when a certain period of time has passed since the coincidence. In the above-described specific configuration, as described above, the time when the battery voltage value matches the reference voltage value is detected with high accuracy. Further, since the time when the battery voltage value matches the reference voltage value is immediately before the time when the maximum value is reached, the fixed time is set to a short time, and the battery voltage value changes from the time when the battery voltage value matches the reference voltage value to the maximum value. The error between the time to reach and the fixed time is small. Therefore, the fully charged state of the battery unit can be detected with high accuracy.

Further, specifically, the charge control circuit includes an arithmetic constant relation storing means for storing a relation between an ambient temperature of the battery unit and an arithmetic constant used for calculating the reference voltage value, and the reference value is calculated. The means derives an arithmetic constant corresponding to the temperature from the ambient temperature measured by the temperature measuring means according to the relation stored in the arithmetic constant relation storing means, and uses the arithmetic constant for the maximum value of the battery voltage value. The above calculation is performed to calculate the reference voltage value.

Immediately before the battery voltage value of the battery unit reaches its maximum value, the rate of increase of the battery voltage value decreases as the ambient temperature of the battery unit increases, while it increases as the ambient temperature of the battery unit decreases. To do. Therefore,
In the above specific configuration, the relationship between the ambient temperature of the battery unit and the operation constant used for calculating the reference voltage value slightly smaller than the maximum value is stored in the operation constant relationship storage means. Here, the relationship between the ambient temperature of the battery unit and the calculation constant is represented by, for example, a table or a functional expression.

At the time of charging, the operation constant corresponding to the temperature is derived from the ambient temperature measured by the temperature measuring means in accordance with the relationship stored in the operation constant relationship storing means as described above, and the battery of the battery unit is charged. A reference voltage value is calculated by performing a calculation using the calculation constant on the maximum voltage value. As described above, when the reference voltage value is calculated, the arithmetic constant according to the ambient temperature of the battery unit is used, so that the time when the battery voltage value of the battery unit matches the reference voltage value is not related to the ambient temperature of the battery unit. However, the time is substantially the same, and the time from the time when the battery voltage value matches the reference voltage value to the time when the battery voltage value reaches the maximum value is substantially constant. Therefore, the battery voltage value of the battery unit always becomes the maximum value at the time when the above-mentioned fixed time has elapsed from the time when the battery voltage value matches the reference voltage value, regardless of the ambient temperature of the battery unit during charging. In this way, the fully charged state of the battery unit can always be detected with high accuracy.

Furthermore, more specifically, the reference value calculating means calculates the reference voltage value by subtracting the arithmetic constant from the maximum value of the battery voltage value.

As described above, immediately before the battery voltage value of the battery unit reaches the maximum value, the rate of increase of the battery voltage value is
It decreases as the ambient temperature of the battery unit increases, while it increases as the ambient temperature of the battery unit decreases. Therefore, in the above-described specific configuration, as the relationship between the ambient temperature of the battery unit and the arithmetic constant, the arithmetic constant decreases as the ambient temperature rises, while the arithmetic constant increases as the ambient temperature decreases. It is stored in the constant relation storage means.

[0023]

According to the charging device of the present invention, it is possible to always detect with high accuracy the time when the secondary battery is fully charged.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the present invention will be described below.
First, a specific description will be given based on two embodiments.First embodiment The battery unit in which the present invention is implemented is one or more secondary batteries.
Ponds, such as nickel-hydrogen batteries and nickel-cadmium
It consists of a battery, and the positive terminal and
The charging device of the present invention shown in FIG. 1 is connected to the INUS terminal.
It

As shown in the figure, the charging device according to the present invention comprises a charging circuit (1) for converting AC power of AC100V supplied from an external power source (13) into DC power and outputting the DC power. DC power from the battery unit (2) is supplied to the battery unit (2). A charging control circuit (10) composed of a microcomputer is connected to the charging circuit (1), and the charging circuit (1) is
The charging operation is turned on or off according to the charging on / off signal supplied from the charging control circuit (10). Also, the charging circuit
In (1), the charging current value can be set to two values, for example, either 0.05C or 0.2C,
One of the charging current values is set according to the current control signal supplied from the charging control circuit (10). The positive terminal and the negative terminal of the battery unit (2) are connected to the charge control circuit (10), and the battery unit is connected by the charge control circuit (10).
The battery voltage values at both ends of (2) are detected. Battery unit
A constant voltage circuit (12) is connected to the line extending from the positive terminal of (2) to the charge control circuit (10).
The external power supply (13) is connected to 2).

A temperature sensor (11) for measuring the temperature around the battery unit (2) is arranged near the battery unit (2). As the temperature sensor (11),
For example, a thermistor can be adopted. Temperature sensor
The output terminal of (11) is connected to the charging control circuit (10), and the ambient temperature of the battery unit is detected by the charging control circuit (10).

FIG. 2 shows the battery unit (2) during charging.
Represents the change in the battery voltage value of. As shown in the figure, the battery voltage value of the battery unit (2) gradually increases as the charging time increases, and becomes substantially constant after reaching the peak value Vp. Here, when the battery voltage value of the battery unit (2) reaches the peak value Vp, the battery unit (2) is in a fully charged state. Therefore, in the above charging device, when charging is started, a reference voltage value Vb slightly smaller than the peak voltage value Vp is calculated, and the battery voltage value of the battery unit (2) matches the reference voltage value Vb. The time point is detected. here,
The reference voltage value Vb is calculated based on the battery voltage value finally detected at the time of the previous charging, that is, the peak voltage value Vp. Then, a point in time when a certain period of time has passed from the point of coincidence detection is detected, and the charging ends at the point of detection. Here, the fixed time is the time required for the battery voltage value of the battery unit to reach the peak value after it matches the reference voltage value,
Alternatively, the time is set to be slightly longer than that time, for example, one hour.

The charge control circuit (10) shown in FIG.
(Not shown) is built in, and the memory is provided with an area for writing the battery voltage value of the battery unit (2).
In the voltage value writing area of the memory, a peak voltage value when the ambient temperature of the battery unit (2) is a predetermined temperature, for example, 20 degrees, is written. In the initial state of the charging device, the initial value is written in the voltage value writing area. When the charging is started, the charge control circuit (10) calculates the reference voltage value by performing a calculation process described later on the peak voltage value written in the voltage value writing area. In this arithmetic processing, temperature conversion processing is executed based on the ambient temperature of the battery unit (2). At the end of charging, the charge control circuit (10) performs a temperature conversion process on the battery voltage value finally detected at the time of charging, that is, the peak voltage value, and when the ambient temperature of the battery unit (2) is the predetermined temperature. The peak voltage value is calculated, the peak voltage value is overwritten in the voltage value writing area of the memory, and the peak voltage value written in the area is updated. Charge control circuit at the next charge
(10) calculates the reference voltage value based on the peak voltage value updated as described above. In this way, the charge control circuit (1
0) calculates the reference voltage value based on the peak voltage value detected at the previous charging.

A calculation process for calculating the reference voltage value will be described. The above-mentioned reference voltage value is calculated by a calculation process using a functional expression, and assuming that the reference voltage value is Vb and the peak voltage value is Vp, the functional expression is expressed by the following mathematical expression 1, for example.

## EQU1 ## Vb = Vp-α

Here, α is a calculation constant determined according to the ambient temperature of the battery unit as described later.

The peak voltage value Vp is calculated by performing a temperature conversion process on the peak voltage value written in the voltage value writing area of the memory. First, the reason why the temperature conversion process is necessary will be described. FIG. 3 shows changes in the battery voltage value of the battery unit during charging when the ambient temperature of the battery unit is 0 degrees, 20 degrees, and 40 degrees. As shown, the peak voltage value Vp ₀ when the ambient temperature is 0 degrees, the peak voltage value Vp ₂₀ when the ambient temperature is 20 degrees, and the peak voltage value Vp ₄₀ when the ambient temperature is 40 degrees are It is becoming smaller in this order. The peak voltage value written in the voltage value writing area of the memory is the peak voltage value when the ambient temperature of the battery unit is the predetermined temperature as described above. Therefore, it is necessary to convert the peak voltage value into a peak voltage value according to the ambient temperature during charging.

Next, the temperature conversion process of the peak voltage value Vp will be specifically described. FIG. 4 shows the relationship between the ambient temperature of the battery unit and the peak voltage value. Here, FIG. 4 shows the peak voltage value when the ambient temperature of the battery unit is 20 degrees as a reference and the peak voltage value when the ambient temperature is 0 degrees and 40 degrees, respectively. The vertical axis is the difference. As shown in the figure, the peak voltage value when the ambient temperature of the battery unit is 0 degrees is 2
It is 0.1V higher than the peak voltage value when it is 0 degree, and the peak voltage value when the ambient temperature is 40 degree is 0.1V.
Only 1V lower. In this way, since the difference in peak voltage value is proportional to the difference in ambient temperature, a constant relationship is established between the ambient temperature of the battery unit and the peak voltage value.

When the reference of the ambient temperature of the battery unit is 20 degrees, the temperature difference is ΔT, and the ambient temperature of the battery unit is 2
Assuming that the peak voltage value at 0 degrees is Vpo, the peak voltage value Vp is expressed by the following equation 2, for example.

[Equation 2] Vp = a · ΔT + Vpo a: constant

Here, Vpo is the peak voltage value when the ambient temperature of the battery unit is 20 degrees, that is, the peak voltage value written in the voltage value writing area of the memory, and the peak voltage value is as described above. As described above, it is updated every time charging is completed. Therefore, the above functional expression is updated every time charging is completed.

The operation constant α of the functional expression expressed by the above mathematical expression 1 is determined according to the ambient temperature of the battery unit.
First, the reason why the calculation constant α is determined according to the ambient temperature of the battery unit will be described. As shown in FIG. 3, immediately before the battery voltage value of the battery unit reaches the peak value, the rate of increase in the battery voltage value decreases as the ambient temperature rises, but increases as the ambient temperature decreases. If the calculation constant α is set to a constant value irrespective of the ambient temperature of the battery unit, the time at which the battery voltage value of the battery unit matches the reference voltage value Vb will be different for each ambient temperature, and the battery voltage value will be different. The time from the time when the battery voltage reaches the reference voltage value Vb to the time when the peak value Vp is reached becomes longer as the ambient temperature of the battery unit rises.
It becomes shorter as the ambient temperature of the battery unit decreases.
For this reason, when the ambient temperature of the battery unit is high, the battery voltage value does not reach the peak value Vp at the time point when the battery voltage value of the battery unit coincides with the reference voltage value Vb and when the above-mentioned certain time has elapsed, The battery unit may not reach the fully charged state. On the other hand, when the ambient temperature of the battery unit is low, a long time has passed since the battery voltage value reached the peak value Vp at the time when the above-mentioned certain time has elapsed, and there is a risk of overcharging. Therefore, the calculation constant α is determined according to the ambient temperature of the battery unit.

In the built-in memory of the charge control circuit (10),
The operation constant table shown in FIG. 5 is stored. A plurality of temperature data representing the ambient temperature of the battery unit and the value of the operation constant α corresponding to the ambient temperature represented by each temperature data are written in the table. When calculating the reference voltage value, the calculation constant table is referred to and the calculation constant α for the temperature data corresponding to the temperature is derived from the ambient temperature of the battery unit.

After the charging is started, the charge control circuit (10) shown in FIG. 1 first detects the ambient temperature of the battery unit (2) based on the output signal of the temperature sensor (11), and also has a built-in memory. The peak voltage value is read from the CPU, and the detected ambient temperature and the read peak voltage value are used to perform temperature conversion by the functional expression represented by the above mathematical expression 2, and the peak voltage value Vp corresponding to the ambient temperature at that time is executed. To calculate. Also, FIG.
The arithmetic constant α is derived from the detected ambient temperature by referring to the arithmetic constant table shown in FIG. Next, the charging control circuit
In (10), the reference voltage value Vb is calculated by executing the calculation by the functional expression represented by the above mathematical expression 1 using the calculated peak voltage value Vp and the derived calculation constant α.

Thereafter, the charge control circuit (10) repeats the operation of detecting the battery voltage value of the battery unit (2) and comparing the battery voltage value with the reference voltage value Vb, and the battery voltage value becomes the reference voltage. A time point that matches the value Vb is detected. Then, the time measurement is started from the coincidence detection time point, the time point when a certain time elapses is detected, and the charging circuit (1) ends the charging operation at the detection time point. Here, as described above, the fixed time is set to a time required for the battery voltage value of the battery unit (2) to reach the peak value after it coincides with the reference voltage value, or a time slightly longer than the time. Has been done. Further, the battery voltage value of the battery unit (2) becomes substantially constant after reaching the peak value as described above. Therefore, the battery voltage value of the battery unit (2) reaches a peak value after a certain period of time has elapsed.

The charge control circuit (10) is a battery unit.
Even after detecting the time when the battery voltage value of (2) coincides with the reference voltage value Vb, the operation of detecting the battery voltage value of the battery unit (2) is executed in a predetermined cycle, and the above-mentioned fixed time elapses. At the time of detection, the finally detected battery voltage value, that is, the peak voltage value is temperature-converted into the peak voltage value when the ambient temperature is 20 degrees. Here, the temperature conversion processing is executed by the calculation by the functional expression represented by the above-mentioned mathematical expression 2, and Vo at this time is the battery voltage value detected at the end. Then, the charge control circuit (10) overwrites the peak voltage value obtained by the temperature conversion process in the voltage value writing area of the memory, and updates the peak voltage value written in the area.

In the above charging device, the peak voltage value updated each time charging is completed as described above, that is, the peak voltage value detected at the time of the previous charging, depends on the ambient temperature of the battery unit (2) at that time. The converted peak voltage value Vp is temperature converted, and the reference voltage value Vb is calculated based on the temperature converted peak voltage value Vp. Therefore, the reference voltage value V
b is an appropriate value according to the change in the maximum value due to aged deterioration and the ambient temperature for each battery unit.

After that, the battery voltage value of the battery unit (2) is compared with the reference voltage value Vb to detect the coincidence point of both continuous pressure values. Therefore, even at the time of low current charging with a small charging current value, it is easy to detect the coincidence point, and high accuracy of the detection can be obtained. After that, a point in time when a certain time has elapsed from the point of time of detecting the coincidence is detected, and the charging ends at the point of detection. Here, since a value slightly smaller than the peak voltage value Vp is calculated as the reference voltage value Vb, the fixed time is set to a short time. As described above, the time when the battery voltage value of the battery unit (2) matches the reference voltage value Vb is detected with high accuracy. Further, since the fixed time is set to a short time, the error between the time from the time when the battery voltage value of the battery unit (2) matches the reference voltage value Vb to the peak value and the fixed time is small. . Therefore,
The time when the battery voltage value of the battery unit (2) reaches the peak voltage value, that is, the time when the battery unit (2) is fully charged is detected with high accuracy.

Further, the operation constant α of the functional expression represented by the above mathematical expression 1 is determined to a value corresponding to the ambient temperature of the battery unit (2) as described above. For example, when the ambient temperature of the battery unit is 0 degrees, the calculation constant α ₀ shown in FIG.
When the value of 1 and the ambient temperature of the battery unit are 40 degrees, the value of 0.06 is determined as the arithmetic constant α ₄₀ .
Therefore, the battery voltage value of the battery unit (2) is the reference voltage value V
As shown by the broken line in the figure, the point of time that coincides with b is almost the same regardless of the ambient temperature of the battery unit (2), and the point of time when the battery voltage value reaches the peak voltage value from the time point when it coincides with the reference voltage value Vb. The time until is almost constant. Therefore, regardless of the ambient temperature of the battery unit (2) at the time of charging, the battery voltage value of the battery unit (2) has always passed the fixed time from the time when the battery voltage value coincides with the reference voltage value Vb. At this time, the peak value is reached, and the fully charged state of the battery unit (2) is always detected with high accuracy.

6 and 7 show a specific charging control procedure by the charging control circuit (10). The charge control circuit (10) has a provisional charge timer for measuring the time of provisional charging performed at a charging current value of 0.05C, and a duration of main charging performed at a charging current value of 0.2C. The main charging timer and the full charging timer for measuring the time from the time when the battery voltage value of the battery unit (2) matches the reference voltage value during the main charging are built in. As shown in the figure, first, in step S1, temporary charging is started with a charging current value of 0.05 C, and then in step S2, a temporary charging timer is set.
Succeedingly, in a step S3, it is determined whether or not the battery voltage value of the battery unit (2) is equal to or more than a predetermined threshold value. here,
When the battery unit (2) is composed of, for example, two secondary batteries having a rated voltage value of 1.2 V, the threshold value is 2.
A value of 2V is set. If NO is determined in step S3, the process proceeds to step S4, it is determined whether 5 minutes have elapsed from the start of temporary charge based on the output value of the temporary charge timer, and if NO is determined Returns to step S3.

When the battery voltage value of the battery unit (2) becomes equal to or higher than the threshold value within 5 minutes after the start of the temporary charging, it is determined as YES in step S3 at that time, and 7, the process proceeds to step S6. On the other hand, if the battery voltage value of the battery unit (2) does not become equal to or higher than the threshold value within 5 minutes after the provisional charging is started, the result in step S4 is YES after 5 minutes. Then, the procedure proceeds to step S5, the temporary charging is terminated, and the above procedure is terminated.

In step S6 of FIG. 7, after the main charging is started with the charging current value of 0.2C, the main charging timer is set in step S7, and in step S8, the reference voltage value is calculated as described above. . Subsequently, in step S9, it is determined based on the output value of the main charging timer whether or not 5 hours have elapsed from the start of main charging. If NO is determined, the process proceeds to step S10, and the battery unit (2 After detecting the battery voltage value of), the process proceeds to step S11. Step S
At 11, it is determined whether or not the detected battery voltage value matches the reference voltage value, and if the result is NO, the process returns to step S9. In this way, the determination as to whether the battery voltage value of the battery unit (2) matches the reference voltage value is repeated. Here, the judgment is executed, for example, in a cycle of 5 seconds.

If the battery voltage value of the battery unit (2) coincides with the reference voltage value within 5 hours after the start of the main charging, it is determined as YES in step S11 at that time and step S12 Move to. Step S12
Then, set the full charge timer, then step S13
Then, based on the output value of the full charge timer, it is determined whether or not one hour has passed from the coincidence time point, and if it is determined to be no, the process proceeds to step S14, and based on the output value of the main charge timer. It is determined whether 5 hours have elapsed from the start of main charging. If it is determined NO, the process proceeds to step S15, the battery voltage value of the battery unit (2) is detected, and then the process returns to step S13.

Then, if one hour elapses from the time when the battery voltage value of the battery unit (2) coincides with the reference voltage value before five hours have elapsed from the start of the main charging, then at step S13, YES is obtained. Then, the process proceeds to step S16. On the other hand, if 5 hours have elapsed from the start of the main charging before 1 hour has elapsed from the time when the battery voltage value of the battery unit matches the reference voltage value, then YES is determined in step S14 at that point. Then, the process proceeds to step S16. In step S16, the battery voltage value finally detected in step S15, that is, the peak voltage value is temperature-converted into a peak voltage value when the ambient temperature is 20 degrees, and the peak voltage value thus obtained is stored in the internal memory. After overwriting the voltage value storage area of, the main charging is ended in step S17, and the above procedure is ended.

If the battery voltage value does not match the reference voltage value within 5 hours after the main charging is started, it is determined as YES in step S9 when 5 hours have elapsed, and step S16 is performed. Move to. Step S16
Then, the battery voltage value finally detected in step S10, that is, the peak voltage value is temperature-converted into a peak voltage value when the ambient temperature is 20 degrees, and the peak voltage value thus obtained is converted into the voltage of the internal memory. After overwriting the value storage area, the main charging is ended in step S17, and the above procedure is ended.

According to the above procedure, the temporary charging is first performed, and the main charging is started when the battery voltage value of the battery unit (2) becomes equal to or higher than the predetermined threshold value. On the other hand, when the battery voltage value of the battery unit (2) does not exceed the predetermined threshold value within 5 minutes, it is determined that the battery unit (2) is defective and the charging is completed. If the battery voltage value of the battery unit (2) coincides with the reference voltage value within 5 hours after the start of the main charging and one hour has passed from the coincidence time,
Charging ends when one hour has passed. If 5 hours have elapsed from the start of main charging while repeatedly determining whether the battery voltage value of the battery unit (2) matches the reference voltage value after the start of main charging, 5 hours have elapsed. Charging is forcibly terminated at the point. In addition, when 5 hours have elapsed from the start of main charging while the time measurement of 1 hour is being performed from the time when the battery voltage value of the battery unit (2) matches the reference voltage value, the time point when 5 hours have elapsed The charging is forced to end with. In this way, overcharging is prevented because the charging is forcibly terminated when 5 hours have elapsed from the start of the main charging.

According to the charging apparatus of this embodiment, as described above, the time when the battery unit (2) is in the fully charged state can be detected with high accuracy at all times.

[0051]Second embodiment In the charging device of the first embodiment, when calculating the reference voltage value,
Performing the operation by the functional expression represented by the above equation 2
Depending on the ambient temperature of the battery unit, the peak voltage
For calculating the value, the charging device of the present embodiment is
Referring to the peak voltage value table shown in FIG.
It derives the peak voltage value according to the ambient temperature of the
is there.

The structure of the charging device of this embodiment is the same as that of the charging device of the first embodiment shown in FIG. 1 except for the charging control circuit. In the built-in memory of the charge control circuit of this embodiment, FIG.
The peak voltage value table shown in is stored. The table is provided with a temperature range data writing column and a voltage value writing column. In the temperature range data writing column,
A plurality of temperature range data representing the range of the ambient temperature of the battery unit (2) is written in advance. On the other hand, in the voltage value writing column, the peak voltage value in the temperature range represented by each temperature range data is written. In the initial state of the charging device, the initial value is written in the voltage value writing field.

When calculating the reference voltage value Vb, the charge control circuit refers to the peak voltage value table and refers to the peak voltage value Vp for the temperature range data from the ambient temperature of the battery unit (2) to the temperature. And the operation constant table shown in FIG. 5, the operation constant α corresponding to the ambient temperature of the battery unit (2) is derived. Then, the charge control circuit calculates the reference voltage value Vb by using the peak voltage value Vp and the calculation constant α to perform the calculation by the functional expression represented by the above mathematical expression 1.

Thereafter, the charge control circuit detects the time when the battery voltage value of the battery unit (2) matches the reference voltage value Vb, as in the first embodiment, and a certain time has elapsed from the detection time. At this point, the charging circuit (1) ends the charging operation. Further, the charge control circuit overwrites the battery voltage value detected at the time of charging, that is, the peak voltage value, in the voltage value writing field of the peak voltage value table shown in FIG. At this time, the peak voltage value is written in the voltage value writing field for the temperature range data according to the ambient temperature at the time of charging. In this way, the table will be updated each time charging is completed.

In the charging device of this embodiment, at the end of charging, only the peak voltage value for the temperature range data according to the ambient temperature at the time of charging is updated, so the reference voltage value V
When b is calculated, the peak voltage value at the time of previous charging at the ambient temperature detected at that time is derived. Therefore, a more appropriate peak voltage according to the ambient temperature of the battery unit (2) can be obtained as compared with the first embodiment in which the functional expression is updated every time charging is completed, regardless of the ambient temperature of the battery unit (2). The value Vp will be calculated. As a result, a more appropriate reference voltage value Vb is calculated, and higher accuracy can be obtained for detection when the battery unit (2) is fully charged.

The configuration of each part of the present invention is not limited to the above-described embodiment, and various modifications can be made within the technical scope described in the claims. For example, in the first and second embodiments, the charge control circuit refers to the calculation constant table shown in FIG. 5 when calculating the reference voltage value Vb, and calculates the calculation constant α from the ambient temperature of the battery unit (2). However, in spite of this, it is also possible to adopt a configuration in which the arithmetic constant α is calculated by executing arithmetic processing using a functional expression having the ambient temperature of the battery unit (2) as a variable. It is possible. In the first and second embodiments, the reference voltage value Vb is calculated using an arithmetic expression that subtracts the arithmetic constant α from the peak voltage value Vp of the battery unit (2). Regardless of this, it is also possible to adopt a configuration in which the reference voltage value Vb is calculated using an arithmetic expression that multiplies the peak voltage value Vp by the arithmetic constant α.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a charging device according to the present invention.

FIG. 2 is a graph showing changes in the battery voltage value of the battery unit during charging.

[Fig. 3] Ambient temperature of the battery unit is 0 degrees, 20 degrees, and 40 degrees.
6 is a graph showing a change in a battery voltage value of a battery unit during charging in degrees.

FIG. 4 is a graph showing the relationship between the ambient temperature of the battery unit and the peak voltage value.

FIG. 5 is a diagram showing an arithmetic constant table stored in a built-in memory of the charge control circuit of the first embodiment.

FIG. 6 is a flowchart showing the first half of a charging control procedure by the charging control circuit of the present invention.

FIG. 7 is a flowchart showing the latter half of the above procedure.

FIG. 8 is a diagram showing a peak voltage value table stored in a built-in memory of the charge control circuit of the second embodiment.

[Explanation of symbols]

(1) Charging circuit (10) Charge control circuit (11) Temperature sensor (12) Constant voltage circuit (13) External power supply (2) Battery unit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masashi Arikuma             1-1 Sanyo-cho, Daito City, Osaka Prefecture Sanyo Tech             No Sound Co., Ltd. (72) Inventor Katsuhiro Hirai             1-1 Sanyo-cho, Daito City, Osaka Prefecture Sanyo Tech             No Sound Co., Ltd. F term (reference) 2G016 CA00 CB33 CC01 CC04 CC10                       CC13 CC23 CC27                 5G003 AA01 BA01 CA15 CA20 CB06                       CC02 GC05                 5H030 AA03 AS18 BB01 FF27 FF43                       FF44 FF52

Claims (7)

[Claims] 1. A charging device for charging a battery unit consisting of one or more secondary batteries, comprising a charging circuit for supplying electric power to the battery unit and a charging control circuit for controlling the operation of the charging circuit. In the charging device, the charging control circuit includes a voltage detecting unit that detects a voltage value across the battery unit and a battery unit that detects a voltage value based on the maximum value of the battery voltage value detected by the voltage detecting unit during the previous charging. A reference value calculation unit that calculates a reference voltage value that serves as a reference for detecting the time point when the battery is fully charged, and a voltage detection unit that uses the reference voltage value calculated by the reference value calculation unit as a reference after starting charging. And a charging end control means for detecting a time point when the battery unit is in a fully charged state from the detected battery voltage value and ending the charging operation of the charging circuit at the detection time point. And charging device. 2. A temperature measuring means for measuring a temperature around a battery unit is installed, wherein the charge control circuit has a maximum temperature of the battery unit and a maximum value of a battery voltage value detected by the voltage detecting means at the time of charging. And a maximum value relationship storage means for storing the relationship between the maximum value relationship storage means and a maximum value relationship storage means each time charging is completed, based on the maximum value of the battery voltage value detected by the voltage detection means at the time of charging. The reference value calculation means of the charging control circuit changes from the ambient temperature measured by the temperature measurement means to the temperature according to the relationship stored in the maximum value relationship storage means. The charging device according to claim 1, wherein a corresponding maximum value is derived, and the reference voltage value is calculated based on the derived maximum value. 3. The charging device according to claim 2, wherein the relationship stored in the maximum value relationship storing means is represented by a functional expression having a variable of the ambient temperature measured by the temperature measuring means. 4. The relationship stored in the maximum value relationship storage means includes a plurality of temperature data representing an ambient temperature of a battery unit and a battery voltage detected by the voltage detecting means at the ambient temperature represented by each temperature data. And a maximum value table including a maximum value of the values, and the updating means of the charge control circuit is configured so that, each time charging is completed, the temperature measuring means among the plurality of maximum values written in the maximum value table. The charging device according to claim 2, wherein the maximum value of the temperature data corresponding to the ambient temperature measured by is updated to the maximum value of the battery voltage value detected by the voltage detection means during the charging. 5. The reference value calculating means of the charging control circuit,
A reference voltage value that is slightly smaller than the maximum value of the battery voltage value is calculated based on the maximum value, and the charging end control means, after the start of charging, the battery voltage value detected by the voltage detection means and the reference voltage value. And detecting means for detecting a time point when the battery voltage value matches the reference voltage value, and detecting a time point when a certain time has elapsed from the time point detected by the detecting means, and charging at the detection time point. The charging device according to any one of claims 1 to 4, further comprising a termination unit that terminates a charging operation of the circuit. 6. The charge control circuit includes an arithmetic constant relation storing means for storing a relation between an ambient temperature of the battery unit and an arithmetic constant used for calculating a reference voltage value, and the reference value calculating means is an arithmetic constant. In accordance with the relationship stored in the relationship storage means, an operation constant corresponding to the temperature is derived from the ambient temperature measured by the temperature measurement means, and an operation using the operation constant is performed on the maximum value of the battery voltage value. The charging device according to claim 5, wherein the reference voltage value is calculated. 7. The charging device according to claim 6, wherein the reference value calculation means calculates the reference voltage value by subtracting the arithmetic constant from the maximum value of the battery voltage value.