JPH0714613A - Memory effect detecting method and device, charging method and device, and portable facsimile machine - Google Patents

Abstract

PURPOSE:To detect the presence of memory effect immediately after full charging by fully charging a secondary battery such as nickel cadmium battery, by discharging it at high current for a specified short time, and by comparing the difference between measured battery voltage and voltage indicated after refreshing which was previously memorized. CONSTITUTION:In a battery charger 100, a battery 110 is fully charged with a system controller 106, and during a full charging period, the output of an A/D converter 108, or battery voltage, is read out and memorized in a peak value memory 104. Peak value is inputted in a comparator 10 and compared with battery voltage in the converter 108, then this operation is repeated. If the battery 110 is fully charged and battery voltage drops, the system judges that charging is completed. Since the drop in battery voltage caused by connection to a testing load 112 is increased by memory effect, the memory effect of the battery 110 can be detected by checking the voltage drop.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method and apparatus for detecting or charging the memory effect of a secondary battery such as a nickel cadmium (NiCd) battery.

[0002]

2. Description of the Related Art When a nickel-cadmium battery or the like is charged after a halfway discharge, a part of the electrode plate does not work effectively for charging / discharging, resulting in a phenomenon in which the apparent capacity is lowered, a so-called memory effect occurs. It is known.

FIG. 6 shows the discharge voltage characteristics of a nickel-cadmium battery with and without the memory effect. When the memory effect does not occur, the battery voltage is almost stable from the start of discharge to the end of discharge as shown by the curve A in the small current discharge. However, when the memory effect occurs, a small current discharge causes the capacity of 5
The battery voltage falls below 1.0V which is the end voltage of the battery before 0% is used up, and the apparent capacity (product of discharge current and discharge time) of the battery is greatly reduced. The effect of the memory effect is remarkable in the large-current discharge, and as shown by the curve C, the battery voltage falls below the end voltage immediately after the discharge is started, and the battery becomes substantially unusable.

Here, the cut-off voltage is a battery voltage at which discharging must be stopped, and is defined by the battery manufacturer.
If discharging is continued under the final voltage, problems such as reversing the polarity of some batteries in the case of assembled batteries occur.

As described above, when the memory effect occurs, the battery is hardly used in the case of discharging a large current. Therefore, for example, a nickel-cadmium battery is used in a thermal recording type facsimile apparatus requiring a large current. If so, the occurrence of memory effect is fatal. For example, when the memory effect occurs, the amount of electricity (product of current and time) that can be taken out from the battery immediately after charging is reduced, so that the number of recordable originals is extremely reduced, and in some cases even one sheet cannot be recorded.
The recording speed becomes extremely slow because the current that can be taken out momentarily is insufficient.

Here, the usage state of the battery in the battery-driven facsimile apparatus will be described. The battery is discharged on reception. In general, one reception does not mean that the battery capacity is exhausted and halfway discharge occurs, but normally, charging is performed in preparation for the next reception. This is a usage situation in which the memory effect is likely to occur as described above. Figure 7
FIG. 4 is a diagram schematically showing changes in battery voltage and capacity in such a usage situation.

Elimination of the above memory effect (refresh)
It is known that the battery may be discharged to a final voltage with a small current of a certain value or less.

FIGS. 5 (a) and 5 (b) show changes in battery voltage and capacity due to the process of refresh-full charge of a battery having a memory effect. A battery having a memory effect recovers its original characteristics by being fully charged after being discharged to a final voltage by a refresh operation with a small current of a certain value or less.

To perform this refresh,
As a premise, it is necessary to detect the occurrence of a memory effect, and the following method has been conventionally devised.

The first method is a method of integrating discharge currents from charging until the battery voltage drops to the final voltage, and determining that a memory effect has occurred when a certain capacity cannot be taken out.

In the second method, the battery voltage is periodically sampled during discharging, so that when the memory effect occurs, the battery voltage drops by two stages (fourth step) that is observed at the end of discharging.
This is a method of detecting the occurrence of a memory effect by observing (see the figure) (Japanese Patent Laid-Open No. 4-186180).

In the third method, the battery is discharged for a certain period of time and the voltage at the end of discharge is stored, then the battery is charged, and the time until the completion of charging is shorter than the specified time and stored. It is determined that the memory effect has occurred when the voltage after discharging is below a predetermined voltage (Japanese Patent Laid-Open No. 4-54833).
issue).

[0013]

However, in the first method described above, it is not possible to know whether or not the memory effect will occur unless the charged battery is used up to the end. This is inconvenient for batteries that are charged after discharge.

The second method is also inconvenient in the case of a battery used in a device having a large load fluctuation, such as a facsimile machine, because the two-step drop due to the memory effect cannot be detected with certainty if the load of the battery largely changes. Is.

Further, in the third method, the remaining capacity at the start of charging is also taken into consideration by the voltage after discharging the battery for a certain period of time, but basically, the memory effect occurs due to the length of time until full charging. This is a method of determining the presence or absence. However, it is difficult to accurately detect the occurrence of the memory effect in the case where the battery is used in a facsimile apparatus and is charged after halfway discharge.

The present invention has been made in view of the above problems, and its main purpose is to make it possible to reliably detect the presence or absence of the memory effect immediately after charging, and to promote the progress of the memory effect. It is to prevent the battery from being used in its best condition.

[0017]

In order to solve the above-mentioned problems, in a preferred embodiment of the present invention, after a secondary battery such as a nickel-cadmium battery is fully charged, it is discharged with a large current for a predetermined short time. Battery voltage (V) at that time
To measure. Then, the difference (RV-V) between the measured battery voltage (V) and the previously stored refreshed voltage (RV) of the battery is compared with a predetermined voltage, and a memory effect occurs when the difference is equal to or higher than the predetermined voltage. It is judged that it did. When it is determined that the memory effect has occurred, a small current discharge for battery refresh is performed, followed by a full charge, and then a large current discharge for a predetermined short time, and the battery voltage at that time is measured. , After refreshing this, voltage (RV)
Remember as.

[0018]

When a memory effect occurs, a secondary battery such as a nickel-cadmium battery does not recover its original characteristics even if it is fully charged. Therefore, the battery voltage drops significantly at the time of discharging a large current after the complete charging. On the other hand, when the memory effect is not generated, the original characteristics of the battery are restored by the full charge, so that the battery voltage is less likely to drop when the large current is discharged after the full charge. According to the present invention, the presence / absence of the memory effect can be determined in the fully charged state based on the property related to the memory effect of the secondary battery.

Further, according to the present invention, when the memory effect is detected, refreshing and full charging are performed to restore the original characteristics of the battery, so that the progress of the memory effect is prevented and the battery is used in the best condition. it can.

Further, according to the present invention, when refreshing is performed, the post-refresh voltage (RV) is updated with the battery voltage at the time of discharging a large current after full charging, so that the manufacturing conditions and the number of charge / discharge cycles can be reduced. It is possible to improve the detection accuracy of the memory effect by eliminating the influence of variations in the characteristics of individual batteries due to the difference.

[0021]

1 is a schematic block diagram of a battery charger according to an embodiment of the present invention. This battery charger 100
Is operated by an AC power supply and has not only a function of charging a battery 110 (such as a NiCd battery) that is detachably set, but also a function of detecting a memory effect and refreshing the battery 110. Further, it is possible to supply DC power to an external device, and the connector terminal 1 for that purpose
Have eighteen.

In the battery charger 100, 101 is a power supply circuit for producing a stabilized DC voltage from AC power, which has a charging output 116 of the battery 110 and an external driving output 117 connected to a connector terminal 118. Have.
The power supply circuit 101 may have a known configuration including an AC voltage rectifying / smoothing circuit and a voltage stabilizing circuit.

A charging output 102 of the power supply circuit 101 is supplied to a battery 110 via a constant current circuit 102 and a switch 103.
Connected to the positive electrode of. The constant current circuit 102 is a battery 110.
Is a circuit for keeping the charging current for the constant value. The switch 103 is a switch for opening and closing the charging path of the battery 110, and is controlled by the controller 106.

Reference numeral 108 is an A / D converter for converting the voltage value of the battery 110 into a digital value, and its output value is input to the comparator 107 and the controller 106. The comparator 107 compares the output value of the A / D converter 107 with the value given by the controller 106, and returns the comparison result to the controller. A peak value storage memory 104, RV for storing various values used for comparison by the comparator 107.
There are a storage memory 105, an end voltage storage memory 114, and a memory effect determination voltage storage memory 115, which can be accessed by the controller 106. The values stored in each memory will be described later.

111 is a refresh circuit for discharging a low current for refreshing the battery 110,
The battery 110 is connected in parallel via the switch 113.
The switch 113 is closed by the controller at the time of refreshing, and at this time, the discharge path of the refresh circuit 111 is closed. Reference numeral 112 is a test load for passing a large current for judging the memory effect of the battery 110, and 109 is a switch inserted in series with the test load 112.
The switch 109 is closed by the controller 106 for a single time (several microseconds) immediately after the battery 110 is fully charged. Reference numeral 119 is a start button for starting the operation of the battery charger 100.

FIG. 2 is a schematic block diagram of a portable facsimile machine as an example of equipment used in combination with the battery charger 100. The battery charger 100 of the present embodiment can be generally used for charging a secondary battery such as a NiCd battery or a nickel hydrogen battery, which has a problem of memory effect.

This portable facsimile apparatus 200 is capable of facsimile communication using a battery as a power source and a wireless line, and a reading unit 201 for reading a document, a code for performing encoding or decoding of image data. Decoding unit 202, wireless interface unit 203 for interfacing with a wireless line, antenna 210 for transmitting and receiving facsimile signals, recording unit 204 for recording received originals, detection of recording paper in recording unit 204, etc. Sensor section 206, operation section 29 for performing various operations such as transmission / reception, system controller section 205 of a program control system for controlling the entire apparatus, ROM storing fixed information such as programs of this system controller section 205
208, R used for temporary storage of various data
The AM 207, the battery section 211, and the connector terminal 212 connected to the connector 115 of the battery charger 100.
Such a configuration is the same as that of a general facsimile apparatus except that the power supply section is replaced with the battery section 211.

The battery section 211 is used for the facsimile apparatus 200.
In order to supply the operating power of the respective parts, a battery that can be charged by the battery charging part 100 is set. Discharge end detection means for detecting the end of discharge of the battery set in the battery unit 211 is provided. This discharge end detection means is implemented by software in the system controller unit 205 in the example shown here, but is provided as a hardware circuit inside or around the battery unit 211, and the detection output thereof is provided in the system controller unit 2.
You may make it notify to 05. The discharge termination detection means of this software or hardware circuit constantly compares the battery voltage with the termination voltage (the value peculiar to the battery specified by the battery manufacturer), and outputs the termination detection output when the battery voltage drops to the termination voltage. The system controller unit 205 notifies the outside by using the display of the operation unit 209, etc.

Since the connector connection 212 is also connected to the same power supply wiring as the battery of the battery section 211, the battery section 211 is also connected.
Even when the battery is taken out for charging, the power source 101 (FIG. 1) is obtained by directly connecting the connector terminal 118 of the battery charger 100 to the connector 212 (or by connecting via a cable with a connector or the like). More power can be supplied to operate the facsimile apparatus 200.

Next, the operation of the battery charger 100 will be described. FIG. 3 is a flowchart for explaining the operation. When the battery 110 used in the portable facsimile apparatus 200 or other equipment and needs to be charged is set in the battery charger 100 and the start button 119 is pressed, the controller 106 performs the operation shown in FIG. Start control.

First, the controller 106 uses the switch 10
3 is closed to fully charge the battery 110 (ST
1). During this full charge period, the controller 106
First captures the output value (battery voltage) of the A / D converter 108 and writes it in the peak value storage memory 104.
After that, the stored value (peak value) in the peak value storage memory 104 is read out and given to the comparator 107, and the A / D converter 1
08 output value (battery voltage), and if battery voltage> peak value, the output value (battery voltage) of the A / D converter 108 is set as a new peak value in the peak value storage memory 104.
Is rewritten, the peak value after rewriting is given to the comparator 107, and it is again compared with the output value of the A / D converter 108.

As the charging progresses, the battery voltage gradually rises, and the peak value stored in the peak value storage memory 104 is also updated and rises accordingly. When the battery 110 is charged to the fully charged state, the battery voltage drops in reverse (see FIG. 5). As the storage value of the peak value storage memory 104, the peak value of the battery voltage up to that point is stored. The system controller 106 determines the completion of charging by detecting the drop (−ΔV) in the battery voltage after full charging, and switches 10
3 is opened and step ST6 is ended.

Immediately after the completion of this complete charging, the controller 106 turns on the switch 109 for a predetermined single time (several microseconds).
A test pulse TP for closing the battery is generated, a large current is supplied to the battery 110 for a single time through the test load 112, and the battery voltage V at that time is taken in through the A / D converter 108 (ST2, ST3).

The amount of battery voltage drop due to the connection of the test load 112 is larger when the memory effect occurs. Focusing on this characteristic, it is determined whether or not the memory effect occurs in the battery 110. That is, the controller 1
06 obtains the difference between the battery voltage V when the test load is connected and the refreshed voltage RV (stored value of the RV storage memory 105), and this difference and the memory effect determination voltage (memory 115
Value stored in the memory), and when the difference is smaller than the memory effect determination voltage, it is determined that the memory effect has not occurred, and when the difference is equal to or more than the memory effect determination voltage, the memory effect has occurred. (ST
4).

If it is determined that the memory effect has not occurred, the charging operation is terminated and the battery 110 is replaced by the battery charger 10.
It is possible to take out from 0, and set it in a device using it, for example, the battery section 211 of the portable facsimile apparatus 200 in FIG.

When it is determined that the memory effect has occurred, the controller 106 refreshes the battery 110 (ST5). That is, by closing the switch 113, the refresh circuit 111 is activated and the battery 1
10 is discharged at a low current smaller than a certain current value specific to this battery. During this discharge, the controller 106 reads the end voltage stored in the end voltage storage memory 114 and gives it to the comparator 107, and the comparator 107 compares it with the output value (battery voltage) of the A / D converter 108. Let me do it.
The battery voltage gradually decreases as the discharge progresses. When the controller 106 determines from the comparison result of the comparator 107 that the battery voltage has dropped to the cutoff voltage, the switch 113 is opened and the discharge by the refresh circuit 111 is ended.

The controller 106 then proceeds to step ST.
The same full charge operation of the battery 110 as in 1 is performed (ST
6) When this is finished, as in step ST2, the test load 112 is connected to the battery 110 for a single time (several microseconds) to discharge a large current, and the battery voltage at that time is passed through the A / D converter 108. The battery voltage and the cutoff voltage are compared by the comparator 107, and the comparison result is determined (ST7, ST8).

If the battery voltage at the time of the test additional connection is higher than the cut-off voltage, the battery voltage fetched in step ST7 is used as the post-refresh voltage RV to store the RV storage memory 10.
5 is written (ST9), and the charging operation is completed. However, when the battery voltage when the test load is connected is equal to or lower than the cutoff voltage, it is determined that the battery 110 is at the end of its life, and the fact is notified to the outside by lighting the display 121 or the like (ST1
0), the operation ends.

As described above, according to the battery charger 100, the refresh operation and the charge of the battery having the memory effect are automatically performed, and the battery can be used in the best state while preventing the progress of the memory effect. .

Here, regarding the judgment of the memory effect, FIG.
Further description will be made with reference to. FIG. 4 shows step ST of FIG.
2 shows the change in the battery voltage when the test pulse TP is generated. (A) is a case where the memory effect is not generated in the battery, and (b) is a case where the memory effect is generated.

If the memory effect has not occurred, (a)
As described above, the drop amount of the battery voltage when the test load is connected is relatively small, and the difference between the battery voltage V and the refreshed voltage RV at that time is smaller than the memory effect determination voltage. But,
When the memory effect occurs, the battery voltage drops significantly when the test load is connected, and the difference from the refreshed voltage RV exceeds the memory effect determination voltage. In other words, depending on the presence or absence of the memory effect, the magnitude of the discharge current and the memory effect determination voltage when the test load is connected are selected so as to satisfy the above relationship.

It is also possible to set the refreshed voltage RV to a predetermined fixed value. However, even in the case of the same type of battery, due to differences in manufacturing conditions, the number of charge / discharge cycles, etc., considerable variations in the battery voltage when the discharge test load is connected are recognized. Therefore, after the refresh, the voltage R
If V is set to a fixed value, it is easily affected by such variations and it is difficult to determine the optimum value. On the other hand, as described above, if the post-refresh voltage RV measured by applying a test load in a fully charged state after refreshing is used, a highly accurate memory effect that eliminates the influence of variations in individual batteries can be obtained. It becomes possible to detect.

[0043]

As is apparent from the above description, the present invention has the effects listed below. (1) According to the present invention, since it is possible to determine the presence or absence of the memory effect immediately after the battery is fully charged, the method is half-finished as compared with the method using the integrated value of the current until the battery is completely discharged or the charging time until the battery is fully charged. This is convenient for the purpose of detecting the memory effect of a battery, such as discharging and charging repeatedly. Further, since it is not the method of detecting the two-step drop of the battery voltage in the actual load state, the influence of the load change of the battery can be essentially avoided. (2) According to the present invention, when the memory effect is detected and refresh is performed, the post-refresh voltage (RV) is updated with the battery voltage at the time of large current discharge after full charge.
It is possible to eliminate the influence of variations in the characteristics of individual batteries due to differences in manufacturing conditions and the number of heavy discharge cycles, and to detect the memory effect with high accuracy. (3) According to the present invention, when the memory effect is detected,
Refreshing and full charging are performed to restore the original characteristics of the battery, so that the progress of the memory effect can be prevented and the battery can be used in the best condition. As a result, in equipment such as a battery-driven facsimile machine, it is possible to avoid performance degradation of the equipment due to the memory effect of the battery. (4) According to the charging device of the present invention, it is possible to take out the battery from the device and perform the charging and the memory effect detection while maintaining the device such as the facsimile device in the operable state.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a battery charger that performs memory detection and battery charging according to the present invention.

FIG. 2 is a block diagram showing an example of a portable facsimile apparatus according to the present invention.

FIG. 3 is a flowchart for explaining the operation of the battery charging device.

FIG. 4A is a diagram showing a change in battery voltage due to a test load when a memory effect is not occurring. FIG. 4B is a diagram showing a change in battery voltage due to connecting a test load when a memory effect is occurring.

FIG. 5 (a) is a diagram showing a change in battery voltage due to a process of refreshing a battery having a memory effect-a full charge process; and (b) is a diagram showing a change in battery capacity according to the same process.

FIG. 6 is a diagram showing a change in discharge characteristics of a battery due to a memory effect.

FIG. 7 is a diagram showing changes in general voltage and capacity of a driving battery during operation of a facsimile device.

[Explanation of symbols]

 100 Battery Charger 101 Power Supply Circuit 102 Constant Current Circuit 103 Switch 104 Peak Value Storage Memory 105 RV Storage Memory 106 Controller 107 Comparator 108 A / D Converter 109 Switch 110 Battery 111 Refresh Circuit 112 Test Load 113 Switch 114 Final Voltage Storage Memory 115 memory effect determination voltage storage memory 118 connector terminal 200 portable facsimile apparatus 211 battery section 212 connector terminal

Claims (7)

[Claims] 1. A step 1 of performing a full charge of a secondary battery.
Then, following the step 1, a step 2 of performing a predetermined large current discharge of the secondary battery for a predetermined short time and measuring a battery voltage (V) at that time, and a reference battery voltage of the secondary battery ( RV) and the battery voltage (V) measured in step 2 (RV-V) are compared with a predetermined determination voltage to determine whether or not the memory effect of the secondary battery occurs. A method for detecting a memory effect of a secondary battery, which comprises: 2. The battery voltage when the same large-current discharge as in step 2 is performed after the secondary battery is sequentially refreshed and fully charged is used as the reference battery voltage (RV). The method of detecting a memory effect according to claim 1. 3. A step 1 of fully charging the secondary battery.
Then, following the step 1, a predetermined large current discharge of the secondary battery is performed for a predetermined short time, and a battery voltage (V) at that time is measured, and a refreshed voltage (RV) stored in advance. The difference (RV-V) with the battery voltage (V) measured in step 2 is compared with a predetermined determination voltage, and when the difference is equal to or higher than the determination voltage, it is determined that a memory effect has occurred. , Step 4 of discharging a predetermined small current for refreshing the secondary battery when it is determined that the memory effect has occurred in Step 3, and full charging of the secondary battery following Step 4. Step 5 to be performed, Step 6 to perform the same large current discharge and battery voltage measurement of the secondary battery as in Step 1 after Step 5, and the battery voltage measured in Step 6 after the refresh A method of charging a secondary battery comprising a step 7 for re-stored as the pressure (RV). 4. A power supply means for supplying a charging current of a secondary battery, a test load means for discharging a predetermined large current of the secondary battery, and a storage means for storing a voltage after refresh and a memory effect determination voltage. , Step 1 of completely charging the secondary battery with a charging current supplied from the power supply means, and a large current discharge of the secondary battery through the test load means for a predetermined short time following the step 1. And step 2 of obtaining the battery voltage (V) at that time,
The refreshed voltage (R
V) and the battery voltage (V) obtained in step 2 (RV-V) is compared with the memory effect determination voltage stored in the storage means, and the difference is the memory effect determination voltage. A memory effect detecting device having a control unit that performs control including Step 3 for determining that a memory effect has occurred when the above is true. 5. A power supply means for supplying a charging current of a secondary battery, a test load means for discharging a predetermined large current of the secondary battery, and a small current discharge for refreshing the secondary battery. For refreshing, a storage means for storing the refreshed voltage and the memory effect determination voltage, a step 1 for completely charging the secondary battery with a charging current supplied from the power source means, and a step 1 following the step 1. For a predetermined short time to discharge the secondary battery with a large current through the test load means and obtain the battery voltage (V) at that time, and the refreshed voltage (RV) stored in the storage means. ) And the battery voltage (V) obtained in step 2 (RV-V) are compared with the memory effect determination voltage stored in the storage means, and the difference is stored in the memory. When it is determined that the memory effect has occurred when the voltage is equal to or higher than the effect determination voltage, and when it is determined that the memory effect has occurred, a small current discharge of the secondary battery is performed through the refreshing means. Then, the step 4 of refreshing the secondary battery is performed, the step 5 is followed by the step 5 of fully charging the secondary battery by the power supply means, and the step 5 is followed by the step of performing the predetermined short time. A step 6 of discharging a large current of the secondary battery through a test load means and acquiring a battery voltage at that time, and a step of re-storing the battery voltage acquired by the step 6 as the post-refresh voltage in the storage means. And a control means for performing control including 6. The charging device according to claim 5, further comprising an external terminal for supplying DC power from the power supply unit to an external device. 7. A battery unit having a secondary battery set therein, and a terminal connected to an external terminal of the charging device according to claim 6, wherein the secondary battery is set in the terminal or the battery unit. A portable facsimile machine supplied with operating power.