JP2005010032A - Battery remaining amount detection method, small electric device using the method, and battery pack - Google Patents

Abstract

The present invention relates to a small electric device 11 which is normally driven by a built-in secondary battery 10 but can charge the secondary battery 10 by connecting an external power source 7, and has an effective configuration for charge control. In addition, the terminal voltage in the no-load state in the secondary battery 10 is accurately detected, and the full charge capacity reflecting the deterioration state can be accurately estimated.
When power is supplied from the outside, constant current charging of the secondary battery is started, and the voltage and charging current when the terminal voltage becomes a constant value are detected. Further, when the fully charged state is detected, the charging is stopped, the device is driven by the external power source, and the internal resistance is calculated by measuring the voltage value in the substantially no-load state of the secondary battery 10. .
[Selection] Figure 1

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detecting a remaining battery level capable of estimating a capacity when fully charged corresponding to a deteriorated state of a secondary battery, a small electric device such as a mobile phone using the detection method, and a small electric device thereof. The present invention relates to a battery pack to be used.
[0002]
[Prior art]
Conventionally, the remaining battery level is detected by setting the full charge to 100% and the remaining battery charge to 0% when the secondary battery terminal voltage falls below the lower limit. A method of estimating by integrating the discharge amount is common.
[0003]
On the other hand, it is known that a secondary battery deteriorates when it is repeatedly charged and discharged or stored for a long period of time, and the capacity at full charge changes in a decreasing direction according to the degree of deterioration. This full capacity can be detected by accumulating the current capacity from the time of full charge to the end of discharge, but the secondary battery is not always used at once from the full charge state to the end of discharge. In many cases, charging / discharging is repeated in the middle, and it is difficult to detect the full capacity according to the current deterioration state by this method.
[0004]
For such inconvenience, a method is known that utilizes the ability to estimate the capacity at full charge taking into account the degree of deterioration from the value of the internal resistance of the secondary battery. That is, the relationship between the full capacity and the internal resistance is obtained in advance, the internal resistance of the secondary battery is detected during use, and the full capacity is estimated using the detected internal resistance and the relational data described above.
[0005]
As a method for detecting this internal resistance, the open terminal voltage is measured when the secondary battery is not charged / discharged, while the terminal voltage and the discharge when the secondary battery is discharged as a drive power source for an electrical device. The current can be measured individually, and the internal resistance can be obtained from the difference between the terminal voltage in the no-load state and the terminal voltage during discharge and the discharge current. It is also possible to calculate the internal resistance from the difference between the terminal voltage and the discharge current when the electric device is operating in a load state that changes in a plurality of stages.
[0006]
[Problems to be solved by the invention]
However, although the discharge current for driving the electrical equipment is constantly changing irregularly, even if the discharge current of the secondary battery changes, the time delay occurs in the change of the terminal voltage due to the influence of polarization, etc. It is difficult to measure an accurate terminal voltage corresponding to the discharge current.
[0007]
On the other hand, a relatively accurate voltage-current characteristic can be measured by providing a pseudo load inside an electrical device and measuring the terminal voltage while discharging the constant current for a fixed time using this load. However, the provision of a pseudo load leads to an increase in cost and waste of secondary battery power, and still has many problems. Furthermore, as long as driving power is supplied from the secondary battery to the terminal voltage measuring means, the terminal voltage at no load in a strict sense cannot be measured.
[0008]
As a result of consideration in view of such inconvenience, the inventor is configured to supply a power from the outside of the device when charging the secondary battery. Immediately before charging, there is a region where the charging current is constant and the terminal voltage does not change.Accordingly, by using this region to obtain battery information, the secondary battery can be accurately and relatively accurately acquired. It was found that the internal resistance can be calculated.
[0009]
The present invention has been made on the basis of such knowledge, and the configuration for charge control is effective by detecting the terminal voltage and the charging current before and after the detection of the fully charged state using the external power supply for charging. It is an object of the present invention to provide a battery capacity detection method that makes it possible to easily estimate the full charge capacity by using the method, a small electric device using the method, and a battery pack.
[0010]
[Means for Solving the Problems]
The battery remaining amount detection method according to the present invention is applied to the small electric device 11 illustrated in FIG. 1 that uses the secondary battery 10 as an internal power source and can supply power from the outside as necessary.
[0011]
Then, in conjunction with the supply of power from the outside of the device, the charging of the secondary battery 10 is started, and at the same time, the power supply to the electronic circuit other than the secondary battery is switched from the secondary battery 10 to the external power; When it is determined that the charging current and the charging voltage for the secondary battery 10 are substantially constant, a step of detecting first battery information including the terminal voltage and the charging current of the secondary battery 10, and a fully charged state When it is determined that the secondary battery 10 has been reached, the charging of the secondary battery 10 is stopped, and the second battery information including the terminal voltage in the no-load state of the secondary battery 10 after a lapse of a predetermined time from the stop of the charge / discharge. , A step of calculating internal resistance at the time of full charge in the secondary battery 10 from the first and second battery information, and a relationship between the full charge capacity and the internal resistance in the secondary battery 10 are shown. From the internal resistance the calculated three battery information, and a step of estimating the full charge capacity.
[0012]
The detection time of the first battery information is just before the charging of the secondary battery 10 reaches full charge, and the detection time of the second battery information is not affected by the internal resistance or its convergence value can be estimated. It is set longer than the time and shorter than the time until the external power supply is cut off. The internal resistance is calculated by subtracting the terminal voltage V2 in the second battery information from the terminal voltage V1 in the first battery information and dividing by the charging current I1 in the first battery information.
[0013]
In addition, the remaining capacity at full charge is set to 100%, and the remaining capacity is corrected with the estimated full charge capacity, and the charge / discharge capacity during use of the device is integrated with the corrected remaining capacity. By doing so, the absolute value and relative value of the current capacity of the secondary battery can be estimated.
[0014]
A small electric device 11 that performs the above-described battery remaining amount detection method is configured to control a plurality of functional means 1 and the operation timing of each functional means 1 as schematically shown in FIG. Means 2, a secondary battery 10 for driving the functional means 1, and a remaining battery level detection means 3 for detecting the remaining battery level of the secondary battery 10 are provided.
[0015]
The battery remaining amount detecting means 3 includes a battery information measuring means 4 including at least a terminal voltage and a charging current in the secondary battery 10, and a battery remaining amount for estimating the remaining battery capacity from the battery information acquired by the measuring means 4. Estimating means 5 is provided.
[0016]
The control unit 2 starts charging the secondary battery 10 in conjunction with the external power supply, and simultaneously switches the power supply to the functional unit 1 and the remaining battery level detection unit 3 from the secondary battery 10 to external power. Further, when it is determined that the charging of the secondary battery 10 has approached the fully charged state, the measurement unit 4 is instructed to detect the first battery information including the terminal voltage and the charging current, and the fully charged state is set. When it reaches, the charging of the secondary battery 10 is stopped, and after a predetermined time has elapsed since the charging / discharging was stopped, the measurement means 4 includes the terminal voltage in the unloaded state of the secondary battery 10. A control operation for instructing detection of battery information 2 is performed.
[0017]
Further, the remaining battery level estimation means 5 is preliminarily provided with third battery information indicating the relationship between the full charge capacity and the internal resistance in the secondary battery 10, and the secondary battery 10 is obtained from the first and second battery information described above. In addition, the internal resistance at the time of full charge is calculated, and the full charge capacity is estimated from the above-described third battery information and the calculated internal resistance.
[0018]
The secondary battery 10 is housed in a battery case 22 configured to be detachable with respect to the main body case 13 of the device to form a battery pack 23. Further, the battery pack 23 includes a battery information measuring means. 4 and the storage means 6 for storing the first and second battery information measured by the measuring means 4 and the third battery information related to the secondary battery 10 can be configured to be accommodated.
[0019]
【The invention's effect】
In the present invention, as described above, the terminal voltage and the charging current before and after the detection of the fully charged state are detected by using the external power source for charging, so that the configuration for charging control can be effectively used and stable detection can be performed. The operation is performed, and the full charge capacity can be accurately estimated.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the small electric device according to the present invention implemented on the mobile phone 12 as illustrated in FIGS. 2 to 4 are shown below, but the present invention is not limited to this, and the secondary battery 10 such as a pocket-type personal computer or a portable information terminal. It goes without saying that the present invention can be implemented in substantially the same manner for various types of small electric devices that use as a drive source.
[0021]
As shown in FIG. 2, the mobile phone 12 has a display unit 16 including a display screen 14 and a speaker 15, a keyboard 17 and a microphone on the front side of a flat rectangular box-shaped main body case 13. 18 is provided.
[0022]
Further, the side surface of the main body case 13 is provided with a medium control unit 21 into which a rectangular thin plate-like storage medium 20 is removably fitted so that data can be transferred via a predetermined recording medium such as a memory card. ing. On the back side of the main body case 13, a battery pack 23 in which the secondary battery 10 is built in the battery case 22 is detachably attached via the electrodes 24, and is dispersed inside the main body case 13 and the battery case 22. The electronic circuit 25 necessary for control is housed.
[0023]
In addition, a charger 28 that converts the commercial AC voltage input from the power plug 26 into a low-voltage DC voltage and outputs the same is output, and the mobile phone 12 with the battery pack 23 set is attached to the charger 28. Correspondingly, predetermined power can be supplied from the outside to the electronic circuit 25 provided in the mobile phone 12 via the connector 29.
[0024]
FIG. 3 schematically shows the functions of the electronic circuit 25 built in the mobile phone 12 as hardware. In addition to the transmission / reception unit 30 having the basic transmission / reception function as the mobile phone 12, FIG. Various functions to be described later are realized by a control operation using software stored in the control unit 31 and the storage unit 32 provided with a chip microcomputer at the center of control. Since the basic circuit configuration of the mobile phone 12 is substantially the same as that of a conventional multi-function phone, detailed description is omitted.
[0025]
In the present embodiment, the battery case 22 is further provided with a battery remaining amount monitoring unit 33 so that the remaining capacity of the secondary battery 10 can be grasped in real time. In the present embodiment, an example in which the entire battery remaining amount monitoring unit 33 is housed in the battery case 22 is shown, but the present invention is not limited thereto, and a part or all of the battery remaining amount monitoring unit 33 can be provided on the main body case 13 side.
[0026]
Here, FIG. 4 is a block diagram mainly illustrating a configuration relating to charging / discharging of the secondary battery 10 in the battery case 22 in order to clarify the configuration of the battery remaining amount monitoring unit 33 in FIG. 3. The output voltage from the secondary battery 10 is applied to each of the above parts via the discharge circuit 35 whose operation is controlled by the control circuit 34, so that the electronic circuit 25 normally uses the secondary battery 10 as a driving power source. Operate.
[0027]
Further, a commercial AC voltage of 100 to 200 V output from the commercial AC power supply 27 is converted into a low-voltage DC voltage Vd by the AC-DC converter 36 provided in the charger 28, and then provided on the lower surface of the main body case 13, for example. It is applied to the electronic circuit 25 in the main body case 13 and the battery pack 23 through the removable connector 29.
[0028]
The DC voltage Vd sent from the outside of the main body case 13 supplies driving power to each part of the electronic circuit 25 instead of the secondary battery 10 when the input is detected, and at the same time, a charging circuit controlled by the control circuit 34 37 is applied to the secondary battery 10 while controlling the charging voltage and the charging current, so that the accurate remaining battery capacity in the secondary battery 10 can be grasped in conjunction with the above-described discharge circuit 35, or the fully charged state or The secondary battery 10 can be charged up to a previous predetermined charging rate.
[0029]
The battery remaining amount monitoring unit 33 includes a charging current sensor 38 capable of detecting the magnitude of the charging current Ic in the charging circuit 37 and a discharging current sensor 39 capable of detecting the magnitude of the discharging current Id in the discharging circuit 35, respectively. And a programmable control circuit 34 that can detect the terminal voltage Vt of the secondary battery 10 and controls the entire battery remaining amount monitoring unit 33.
[0030]
By controlling the charge / discharge amount with respect to the secondary battery 10 based on the detection values of the sensors 38 and 39 by the program provided in the control circuit 34, the remaining charge / discharge current, for example, is integrated. The current battery remaining capacity can be calculated in real time by an algorithm defined by the program.
[0031]
Further, the storage circuit 40 and the temperature sensor 41 are integrally incorporated in the battery case 22, and the above-described integration is performed based on the characteristic information of the unit cell provided in the storage circuit 40 and the temperature change information on the battery surface by the temperature sensor 41. In addition to correcting the remaining battery level, the notification information regarding the remaining battery level can be stored. The notification information is displayed on the display screen 14 at an appropriate time, thereby notifying the operator of the current remaining battery level and is used for control of the entire system.
[0032]
The program used for the control of the control circuit 34 includes a battery remaining amount estimation program that describes an algorithm for detecting the remaining battery amount of the battery. As such an algorithm, the remaining capacity is set to 0% at the time of complete discharge when the battery voltage falls below the lower limit value, and the remaining capacity is set to 100% when full charge is detected. However, the method for detecting the remaining battery level is not limited.
[0033]
Furthermore, as a detection method at the time of full charge, a method in which the time change rate of the battery temperature Tc becomes a certain set value or more, and a method in which the battery voltage starts to fall after rising and further falls by a certain set value or more. An algorithm that is optimal for the system is employed, such as a method in which the secondary derivative of the battery voltage with respect to time changes from positive to negative in a region near 100% charge.
[0034]
Furthermore, by using the battery characteristic information stored in advance in the storage circuit 40 in the battery case 22, the secondary battery 10 actually using the above-described full charge detection and charge / discharge amount integration operation. It is made to correspond to. Further, the calculated remaining battery capacity and the time are constantly stored in the storage circuit 40. For example, when the battery case 22 is once removed from the main body case 13 and reattached, the elapsed time during removal is The self-discharge amount is estimated from the discharge characteristics, and the current capacity is corrected by subtracting the self-discharge amount from the remaining battery capacity before the battery case 22 is removed.
[0035]
The present invention has the above-described configuration and has a feature in a configuration in which the battery capacity at the time of full charge is corrected in accordance with the deterioration of the secondary battery 10. More specifically, data indicating the relationship between the internal resistance and the full capacity illustrated in FIG. 5 for the secondary battery 10 is stored in the memory circuit 40 in a predetermined format such as a tabular value or an approximate expression. Keep it.
[0036]
On the other hand, when the secondary battery 10 is charged with a constant current as shown in FIG. 6 and approaches a fully charged state, the terminal voltage becomes substantially constant. Therefore, the current value I1 and the voltage value V1 that are substantially constant are acquired and stored in the storage unit 32.
[0037]
Next, when the fully charged state is detected at time t <b> 1 and charging is stopped, the secondary battery 10 enters a no-load state, and as a result, the terminal voltage rapidly decreases. This voltage drop is related to the polarization voltage after the voltage related to the charge transfer resistance that decreases with a predetermined time constant first converges in about 10 seconds after the voltage increase due to the solution resistance having a quick response decreases. The voltage decreases with a larger time constant.
[0038]
Therefore, the terminal voltage at the time t2 after the elapse of the predetermined time τ after the influence of the voltage increase due to the internal resistance is eliminated after the charging is turned off or the convergence voltage estimated from the voltage decrease curve is obtained and The detection voltage V2 at the time of no load in the secondary battery 10 is used. Therefore, since the internal resistance R1 at that time is obtained by (V1-V2) / I1, the full capacity considering the deterioration state of the secondary battery 10 is applied by fitting the calculated internal resistance R1 to the characteristic curve shown in FIG. C1 is estimated.
[0039]
Note that the waiting time τ from the end of charging until the detection voltage V2 is acquired is sufficiently long until the terminal voltage follows, and until the user of the electrical device removes the mobile phone from the charger 28. A time shorter than the general time is required.
[0040]
However, the solution resistance constituting the internal resistance instantaneously changes, and the charge transfer resistance also changes within about 10 seconds. On the other hand, since it takes several tens of minutes even if the charging time is short, it is rare for the user of the mobile phone to constantly check the charging state, and the mobile phone 12 may be immediately removed from the charger 28 even after charging is completed. Is low. If so, the waiting time τ can be set to about 10 seconds, for example. However, it is also possible to measure the terminal voltage immediately after stopping charging shorter than that and to estimate the convergence value from the measured value.
[0041]
When the remaining battery capacity monitoring unit 33 is operated so that the remaining capacity at the time when the full capacity is corrected is 100% and the charge / discharge current is integrated, the integrated value is sequentially subtracted from the full capacity C1. As a result, the current remaining capacity is estimated not only as a relative value but also as an absolute value.
[0042]
In the above-described configuration, when the battery pack 23 is attached to the main body case 13 of the mobile phone 12, the remaining battery power is monitored using the electrical device information stored in the storage circuit 40 in the battery pack 23 and the battery pack 23 information. By initializing the unit 33, the detection of full charge of the secondary battery 10 and the accumulation operation of the charge / discharge amount are performed in correspondence with the mobile phone 12 and the secondary battery 10 that are actually used.
[0043]
Further, the calculated remaining battery capacity and the time are constantly stored in the storage circuit 40. For example, when the battery case 22 is once removed from the main body case 13 and reattached, the elapsed time during removal is The self-discharge amount is estimated from the discharge characteristics, and the current capacity is corrected by subtracting the self-discharge amount from the remaining battery capacity before the battery case 22 is removed.
[0044]
Furthermore, when the charger 28 is connected to the mobile phone 12 and charged, and when the battery is fully charged, the full capacity in the deteriorated state is estimated and the remaining capacity is corrected by the value. That is, every time the battery is fully charged by the charging operation, the battery remaining amount is subjected to absolute correction in consideration of the capacity change due to the deterioration of the battery.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a basic configuration of the configuration of the present invention.
FIG. 2 is a perspective view showing an example in which the present invention is implemented in a mobile phone.
FIG. 3 is a block diagram schematically showing a configuration of an electronic circuit.
FIG. 4 is a block diagram illustrating a configuration of a battery remaining amount monitoring unit.
FIG. 5 is a characteristic curve illustrating the relationship between the internal resistance and the full capacity of the secondary battery.
FIG. 6 is a graph showing a change in terminal voltage when the secondary battery is fully charged.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Function means 2 Control means 3 Battery remaining charge detection means 4 Measurement means 5 Estimation means 6 Storage means 7 External power supply 10 Secondary battery 11 Small electric equipment 12 Mobile phone 13 Main body case 14 Display screen 15 Speaker 16 Display part 17 Keyboard 18 Microphone DESCRIPTION OF SYMBOLS 19 Operation part 20 Storage medium 21 Medium control part 22 Battery case 23 Battery pack 24 Electrode 25 Electronic circuit 26 Power plug 27 Commercial alternating voltage 28 Charger 29 Connector 30 Transmission / reception part 31 Control part 32 Storage part 33 Battery residual quantity monitoring part 34 Control Circuit 35 Discharge circuit 36 AC-DC converter 37 Charging circuit 38 Charging current sensor 39 Discharging current sensor 40 Memory circuit 41 Temperature sensor

Claims (8)

A method for detecting a remaining battery level in a small electric device that uses a secondary battery as an internal power source and can supply power from the outside as required.
In conjunction with the external power supply, starting charging the secondary battery, and simultaneously switching power supply to the electronic circuit other than the secondary battery from the secondary battery to external power;
Detecting the first battery information including the terminal voltage and the charging current of the secondary battery when it is determined that the charging current and the charging voltage for the secondary battery are substantially constant;
When it is determined that a fully charged state has been reached, charging to the secondary battery is stopped, and a second voltage including a terminal voltage in a no-load state in the secondary battery after a lapse of a predetermined time from the stop of the charging / discharging. Detecting battery information;
Calculating the internal resistance at the time of full charge in the secondary battery from the first and second battery information;
Estimating a full charge capacity from third battery information indicating a relationship between a full charge capacity and an internal resistance in the secondary battery, and the calculated internal resistance;
A remaining battery level detection method. The detection time of the first battery information is immediately before the charging of the secondary battery reaches full charge,
The detection time of the second battery information is set longer than the time when the influence of the internal resistance is eliminated or the convergence value can be estimated, and shorter than the time until the external power supply is cut off. And
The internal resistance is calculated by subtracting the terminal voltage in the second battery information from the terminal voltage in the first battery information and dividing the result by the charging current in the first battery information. Battery level detection method. The remaining capacity at the time of full charge is set to 100%, and the remaining capacity is corrected with the estimated full charge capacity,
3. The battery according to claim 1, wherein the absolute value and the relative value of the current capacity of the secondary battery can be estimated by integrating the charge / discharge capacity during use of the device with the corrected remaining capacity. Remaining amount detection method. A plurality of functional means; a control means for regulating the operation timing of each functional means; a secondary battery for driving the functional means; and a remaining battery level detecting means for detecting the remaining battery level of the secondary battery; A small electrical device comprising
It is possible to supply predetermined power as needed from the outside of the small electric device,
The battery remaining amount detecting means
Battery information measuring means including at least a terminal voltage and a charging current in the secondary battery;
Battery remaining amount estimating means for estimating the battery remaining amount from the battery information acquired by the measuring means,
The control means includes
In conjunction with the power supply from the outside of the device, the charging of the secondary battery is started, and at the same time, the power supply to all the electronic circuits is switched from the secondary battery to the external power,
When it is determined that the charging of the secondary battery is close to a fully charged state, the measurement unit is instructed to detect first battery information including a terminal voltage and a charging current,
When the fully charged state is reached, the charging to the secondary battery is stopped, and after a predetermined time has elapsed from when the charging / discharging is stopped, the terminal voltage in the no-load state of the secondary battery is included with respect to the measuring means. Performing a control operation instructing detection of the second battery information;
The battery remaining amount estimating means includes
Third battery information indicating a relationship between the full charge capacity and internal resistance in the secondary battery is provided in advance,
An internal resistance at the time of full charge in the secondary battery is calculated from the first and second battery information, and a full charge capacity is estimated from the third battery information and the calculated internal resistance. Small electrical equipment. The detection time of the first battery information is immediately before the charging of the secondary battery reaches full charge,
The detection time of the second battery information is set longer than the time when the influence of the internal resistance is eliminated or the convergence value can be estimated, and shorter than the time until the external power supply is cut off. And
5. The calculation of the internal resistance is performed by subtracting the terminal voltage in the second battery information from the terminal voltage in the first battery information and dividing by the charging current in the first battery information. Small electrical equipment. The remaining capacity at the time of full charge is set to 100%, and the remaining capacity is corrected with the estimated full charge capacity,
The small electric device according to claim 4 or 5, wherein a current capacity of the secondary battery can be estimated by integrating a charge / discharge capacity during use of the device with the corrected remaining capacity. The secondary battery is housed in a battery case configured to be detachable with respect to a main body case of the device to form a battery pack,
Further, in the battery pack, there are at least storage means for storing the battery information, and storage means for storing first and second battery information measured by the measurement means and third battery information related to the secondary battery. The small electric device according to any one of claims 4 to 6, wherein the small electric device is housed. A battery pack comprising a secondary battery housed in a battery case that is detachably attached to a device body containing a plurality of functional means and a control means for regulating the operation timing of each functional means in the main body case. There,
From the outside of the main body case, it is possible to supply predetermined power as necessary, and a battery remaining amount detection means is provided,
The battery remaining amount detecting means
Battery information measuring means housed in the battery case and including at least a terminal voltage and a charging current in the secondary battery;
In the main body case or in the battery case, the battery remaining amount estimating means for estimating the remaining battery capacity from the battery information acquired by the measuring means,
The control means includes
In conjunction with power supply from the outside of the main body case, the charging to the secondary battery is started, and at the same time, the power supply to all electronic circuits is switched from the secondary battery to external power,
When it is determined that the charging of the secondary battery is close to a fully charged state, the measurement unit is instructed to detect first battery information including a terminal voltage and a charging current,
When the fully charged state is reached, the charging to the secondary battery is stopped, and after a predetermined time has elapsed from when the charging / discharging is stopped, the terminal voltage in the no-load state of the secondary battery is included with respect to the measuring means. Performing a control operation instructing detection of the second battery information;
The battery remaining amount estimating means includes
Third battery information indicating a relationship between the full charge capacity and internal resistance in the secondary battery is provided in advance,
An internal resistance at the time of full charge in the secondary battery is calculated from the first and second battery information, and a full charge capacity is estimated from the third battery information and the calculated internal resistance. Battery pack.

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