JPH10154533A - Battery measuring method and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately estimate a battery discharge characteristic by calculating a characteristic in a prescribed discharge current as data by expressing the relationship between a load and time up to prescribed voltage by at least two kinds of stored discharge currents by a prescribed exponential expression. SOLUTION: A measuring circuit 12 measures electric characteristics such as a discharge current discharged from a secondary battery 11 and battery voltage. A measured value of the measuring circuit 12 is supplied to a control part 14 to control measuring operation, and is stored in a memory 15 connected to the control part 14 according to need. There is also a case where control of an operation condition of a load device 13 is performed by the control part 14. Besides an area to store measured data, a processing program on the basis of a prescribed operation expression is prestored in the memory 15, and in the control part 14, an operation is performed on the measured data on the basis of this processing program, and its operation value is stored. A value calculated by the operation in the control part 14 is displayed by a display part 16 according to need.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery measuring method suitable for measuring characteristics of a battery such as a secondary battery and various electronic devices to which the measuring method is applied.

[0002]

2. Description of the Related Art When a secondary battery (or a primary battery) such as a lithium ion battery, a nickel cadmium battery, or a nickel hydride battery is used, characteristics of the battery and a load device used in combination with the battery are used. It is necessary to select the type and capacity of the battery in consideration of the operating characteristics of the battery. In this case, if the battery is actually connected to the load device and operated, and the change in the battery voltage is measured, the battery duration and the like in the load device can be determined. It takes time and labor to measure, and it is not preferable.

[0003] For this reason, the present applicant stores a plurality of discharge characteristics in a memory by the previously proposed method for measuring a battery (Japanese Patent Application No. 8-92842), and based on the stored characteristics, an arbitrary discharge characteristic. It is shown that the discharge characteristics can be expected at different loads. Specifically, a discharge characteristic at an arbitrary load is predicted by a proportional calculation of a plurality of discharge characteristics stored in advance.

[0004]

However, it has been found that the prediction method based on the proportional calculation proposed earlier has a large error in predicted characteristics. That is, a change in characteristics such as a battery voltage is not generally a linear change, and therefore, a simple proportional calculation results in a large error.

[0005] Further, the prediction method proposed above has a disadvantage that it is not possible to cope with a change in load current during measurement. That is, the prediction method proposed above is based on the premise that the discharge current from the discharge start to the discharge end voltage is kept constant, and cannot cope with load fluctuation.

Further, when an electronic device that performs pulse discharge, such as a portable telephone, is used as a load device, it has been difficult to accurately predict discharge characteristics. That is, the pulse discharge in a mobile phone or the like is a discharge in a very short time as needed, and it is difficult to correct the prediction of the discharge characteristic following the current fluctuation.

The present invention has been made in view of the above circumstances, and has as its object to accurately predict the discharge characteristics of a battery.

[0008]

According to the present invention, the relationship between the load and the time until a predetermined voltage by at least two types of stored discharge currents is stored as data expressed by a predetermined exponential equation. The characteristic at a predetermined discharge current is calculated by the exponential equation calculation.

According to such processing, characteristics at an arbitrary discharge current can be accurately predicted.

[0010]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing a configuration for performing the measurement processing of this embodiment. First, a secondary battery 11 (for example, a lithium ion battery) whose characteristics are to be measured is prepared, and the secondary battery 11 is charged by a predetermined amount. (For example, it is charged to a fully charged state). The charged secondary battery 11 is connected to a measuring circuit 12
And to the load circuit 13 via. The secondary battery 11
May have a built-in circuit attached to the battery, such as a protection circuit.

As the load device 13, various electronic devices (for example, wireless communication terminals, audio devices, video devices, etc.) operated by a power supply from the secondary battery 11 are used. However, in the case of a load device, it may be a simple circuit including a resistor or the like that consumes power with characteristics similar to those of the above-described devices.

The measuring circuit 12 measures electric characteristics such as a discharge current discharged from the secondary battery 11 and a battery voltage. The measurement value in the measurement circuit 12 is supplied to a control unit 14 which is a microcomputer for controlling the measurement operation, and is stored in a memory 15 connected to the control unit 14 as needed. Further, the control unit 14 may control the operation state (power consumption state) of the load device 13.

The memory 15 stores, in addition to an area for storing measured data, a processing program based on a predetermined calculation formula in advance. The control unit 14 calculates measured data based on the processing program. The calculated value is stored. The calculation processing operation will be described later.

The value calculated by the operation of the control unit 14 is displayed on the display unit 16 if necessary.

FIG. 2 is a diagram showing an example in which the configuration shown in FIG. 1 is actually configured as a measuring device. In this example, a measuring device 1 having a built-in power supply section 2 is prepared. 1 is connected to the computer device 3. Then, the secondary battery 11 whose characteristics are to be measured is connected to the battery connection terminal 1a of the measuring device 1, and the power input unit of the load device 13 (here, a mobile phone) is connected to the load connection terminal 1b.
Then, the measuring process is performed by the measuring device 1 based on a command from the computer device 3, the measured data is determined by the computer device 3, and the measurement data is determined by the arithmetic processing based on the processing program set in the computer device 3. The measured data is processed, and the processing result is displayed on the display unit 16.
(Display device), stored in a memory or the like in the computer device 3, or printed out from a printer (not shown) connected to the computer device 3.

Next, a description will be given of a process for measuring a battery with the above-described configuration. First, a process of measuring characteristics of a battery to be used is performed. During the battery characteristic processing, a change in voltage when the battery is discharged with at least two types of discharge current values is continuously measured and stored. That is, as shown in the flowchart of FIG. 3, the discharge current, which is the current consumption of the load device 13, is set to the first discharge current value, and the discharge of the secondary battery 11 charged by a predetermined amount is started. A change state of the voltage until the battery voltage reaches the discharge end voltage (hereinafter, this change state is referred to as a discharge curve) is stored (step 10).
1). Next, after charging the secondary battery 11 again to the same charge amount, a second discharge current value different from the first discharge current value is set to start the discharge, and the battery voltage becomes the discharge end voltage. (Step 1)
02).

The first and second discharge current values and the time t from the start of each discharge to the end of discharge voltage t
Using the data of _n , an operation based on the exponential equation stored in the memory in advance is performed, an operation based on the exponential equation is performed, and a constant in the equation is calculated. The exponential equation used here is shown in the following equation.

[0019]

1 / I = A _n exp (B _n t _n ) [where A _n ,
B _n is a constant] where t _n is the discharge time from the start of discharge to the discharge end voltage V _n , and I indicates the discharge current at that time.

Since there are two measured values based on the first and second discharge current values, the constants A _n and B _n of the equation (1) are calculated as follows:
It can be a specific value and the calculated constant _An ,
The value of _Bn is stored in the memory 15.

Next, a process of estimating characteristics when the secondary battery 11 is actually discharged using the values stored as described above will be described with reference to the flowchart of FIG.
First, the discharge current I at that time and the discharge end voltage for stopping the discharge are set (step 111). Then, the set discharge current I is substituted into the above-mentioned [Equation 1], and the calculation process is performed (step 112). At the time of this calculation, the constant A stored in the memory 15 in the above-described processing is used.
_n, using the B _n, by changing the voltage V _n for calculating, with the voltage V _n and the discharge time t _n is a one-to-one correspondence, performs processing for obtaining the discharge curves (step 113).

FIG. 5 is a diagram showing an example of calculating the discharge curve in this way. A discharge curve i ₁ of the first discharging current value I _1, the discharge curve i in the second discharge current value I ₂
Constant A _n calculated based on the ₂ and, in the calculation processing using B _n, it is possible to calculate the discharge curve i ₃ in any of the discharge current, to a predetermined voltage V _n at the discharge current Time can be accurately predicted. That is, the voltage V
The time required to reach _n becomes the time t at the first discharge current value I _1.
n1 and the time t _n2 at the _second discharge current value I ₂ , the discharge time t until the voltage V _n is _reached at an arbitrary discharge current
_n3 can be accurately predicted by an operation using the exponential equation.

[0023] Here will be described the specific processing, the time at which the voltage V _n, a first discharge current value I ₁ at time t _n1
And the time t _n2 at the _second discharge current value I ₂ , and the discharge time t t at an arbitrary discharge current (here, the current value I ₃ ).
_{If n3} , the following three relational expressions are obtained based on the expression (1).

[0024] _{1 / I 1 = A n exp} (B n t n1) 1 / I 2 = A n exp (B n t n2) 1 / I 3 = A n exp (B n t n3)

Here, since the currents I ₁ and I ₂ are actually measured values, they are known values, and the times t _n1 and t _n2 can be determined from the actually measured discharge curve if the voltage V _n is determined. Therefore, the constant A
_n and _Bn are obtained. If the constant value is obtained, the relational expression in the discharge current value I ₃ to be obtained, the constant A _n, by substituting the B _n, is obtained time t _n3 at its current value. Then, by sequentially changing the voltage V _n, it can be calculated discharge curve i ₃ at any discharge current shown in FIG.

In the above description, two types of data, a value measured at the _first discharge current value I ₁ and a value measured at the second discharge current value I ₂ , are set as original data. However, the constants A _n and B _n of Expression 1 may be obtained based on data measured with three or more types of discharge currents. However, in this case, the constants _An and _Bn may not be one value, and the constants _An and _Bn are set by the approximation processing. That is, as shown in the flowchart of FIG.
After storing the data of the discharge curve measured with the discharge currents of the kinds or more (step 121), each measured value is
One exponential curve is obtained using a predetermined approximation method such as a linear regression method (step 122). Then, based on the exponential curve, a constant A
_n and _Bn are calculated (step 123).

FIG. 7 is a characteristic diagram showing a processing example at this time. For example, as a correspondence between the actually measured voltage and the discharge time,
When the three types of values t _n1 , t _n2 , and t _n3 are dispersed, an exponential curve exp1 is obtained by an operation using an approximation method such as a linear regression method of the three types of values t _n1 , t _n2 , and t _n3. ,
The constants _An and _Bn are calculated from the values on the exponential curve exp1. By processing like this,
It is possible to predict a discharge curve based on three or more types of actually measured values. In this case, as the number of measured data increases, the approximated exponential curve has a more accurate value, and more accurate prediction can be performed.

Next, the processing when the current changes during the discharge will be described with reference to the flowchart of FIG. 8 and the characteristic diagram of FIG. Here, after discharging for a predetermined time at the first current value, the discharge current is changed to the second current value, and when the subsequent discharge is performed, the change point of the current value reaches the discharge end voltage. Is predicted. At this time, first, an integrated value of the energy discharged by the first current is calculated (step 131). Integrated value of the discharge energy is obtained in decreasing volume of the discharge current and the battery voltage and the discharge time, for example, the relationship between the voltage and the time during discharge in the first current value, be a discharge curve i ₄ shown in FIG. 9 , the change point of the current is that it is time t _1, that is multiplied by the first current to the area of the range E ₁ showing hatched becomes the integrated value of the energy.

If the current value changes to the second current value at the timing t ₁ (here, the current value changes small), the integrated value of the same discharge energy at this second current value (FIG. 9) the value obtained by multiplying the second current to the area of the range E ₁ showing hatched) calculates the timing t ₂ of the start of discharge obtained (step 132). Then, a difference time t ₀ between the timing t ₁ and the timing t ₂ is calculated (step 133), and the discharge curve i ₅ at the second current value is calculated as
The discharge curve i ₆ indicated by the broken line in FIG. 9 is set by parallel movement by the difference time t _{0, and} the predicted curve after the timing t ₁ is set as the discharge curve i ₆ (step 13).
4).

By performing such processing, even when the discharge current changes in the middle, the discharge characteristics can be accurately predicted to the end. In the example of FIG. 9, when the discharge current value decreases at the timing t ₁ (that is, when the load decreases), the battery voltage temporarily increases. In addition, here, the processing in the case where the current value decreases in the middle has been described, but if the current value increases, conversely, in the direction of adding the time by the calculated difference time,
It is necessary to translate the position of the discharge curve in parallel.

Next, how to deal with the case where the connected load device is a device that performs pulse discharge will be described with reference to the flowchart of FIG. 10 and the characteristic diagram of FIG. In the case of this pulse discharge, as a process of first measuring a discharge curve, the maximum current I _max of the pulse and the minimum current I
_min and its potential difference ΔV are detected (step 141),
Calculating the average current I _av of the maximum current I _max and the minimum current I _min (step 142). Then, based on the respective values, a calculation process of correcting the discharge end voltage by a correction formula prepared in advance is performed (step 143). The correction equation used here is as follows.

[0032]

V _E = V _E0 ｛1 + ΔV × (I _max -I _av ) /
(I _max −I _min )｝ where V _E is the corrected discharge end voltage, and V _E0 is the actual discharge end voltage.

By making such corrections, the discharge end voltage at the time of pulse discharge can be properly corrected, and the discharge state at the time of pulse discharge can be accurately predicted.

The process described above can be applied to a measurement device as shown in FIG. 2 to measure the characteristics of the battery, and also to a prediction process when the battery is actually used. For example, in a memory of a portable battery-powered computer device such as a notebook personal computer,
In addition to storing a discharge curve of a battery connected to the device, a processing program for performing the above-described prediction process is stored, and an operation of predicting a remaining time that can be used up to a discharge end voltage of the battery is calculated by the computer device. It may be executed by the microprocessor as needed to display the remaining time of the battery. By doing this,
The processing of this example can be realized using a circuit included in the computer device.

The memory 15, the measuring circuit 12, and the control unit 14 shown in FIG. 1 are integrated into a housing (a so-called battery pack) that houses the secondary battery 11, so that this housing When the body is used by attaching it to various electronic devices (for example, a video camera, a mobile phone, etc.), the control unit 14 can calculate information such as a remaining time in which the device can be driven. improves.
In this case, the display unit is attached to the battery pack and displayed, and the calculated information is sent to the connected device side to display the remaining battery time and the like on the display unit of the device. Is also good.

In the above-described embodiment, the case where the secondary battery is used for discharging is described. However, it is needless to say that the present invention can be applied to the case where various primary batteries are discharged.

[0037]

According to the measuring method of the present invention, the relationship between the load and the time until a predetermined voltage by at least two kinds of stored discharge currents is converted into data expressed by a predetermined exponential equation. By calculating the characteristic up to a predetermined voltage at a predetermined discharge current by calculating the exponential formula, it is possible to accurately predict the discharge characteristic at an arbitrary discharge current.

In this case, as an exponential equation showing the relationship between the discharge time t _n to the predetermined voltage V _n and the discharge current I, 1 / I = A _n exp (B _n t _n ) [where A _n , _Bn are constants], so that good characteristics can be predicted by a simple calculation.

In the case described above, when discharging is performed with three or more types of discharge currents, a constant is calculated based on a value obtained by approximating a measured value by a predetermined calculation.
A more accurate prediction based on a large amount of measurement data becomes possible.

In the case described above, when calculating the characteristic up to a predetermined voltage at a predetermined discharge current, when the discharge current changes, the integrated value of the discharge energy until the current value changes, and the change Based on the difference from the discharge time calculated from the integrated value of the discharge energy at the subsequent current value, the time for calculating the characteristics up to the predetermined voltage is changed, so that the discharge current during the discharge is changed. Even when there is a change, accurate prediction can be made.

Further, according to the measuring device of the present invention, there is provided storage means for storing a plurality of discharge characteristics of the battery by expressing it in a predetermined exponential formula, and storing the detected load current.
By calculating the characteristic up to a predetermined voltage by substituting it into the exponential equation stored in the storage means, it becomes possible to accurately predict the characteristic at an arbitrary discharge current.

In this case, 1 / I = A _n exp (B _n t) is an exponential equation showing the relationship between the discharge current t and the discharge time t _n up to the predetermined voltage V _n stored in the storage means. _n ) (where A _n and B _n are constants), it is possible to perform good characteristic prediction with a simple arithmetic processing configuration.

In the above case, when the discharge current detected by the discharge current detecting means changes from the first current value to the second current value, the integrated value of the discharge energy until the current value changes, In a calculation process based on a difference from a discharge time calculated from an integrated value of the discharge energy at a later current value, by performing a process of changing and predicting a time for calculating a characteristic up to a predetermined voltage, Even if the discharge current changes during the discharge, a measuring device that can accurately predict the discharge end voltage can be obtained.

In the case described above, a notifying means for notifying the characteristics calculated by the calculating means in a predetermined manner is provided so as to function as a measuring device for measuring the characteristics of the connected battery. The characteristics can be easily measured when an arbitrary battery is connected to an arbitrary load device.

In the case described above, the storage means and the arithmetic means provided in the computer are used as the storage means and the arithmetic means, and a processing program for performing the exponential calculation is stored in the storage means of the computer. By measuring the characteristics of the battery that drives the computer device, it is possible to accurately determine, for example, the remaining time that can be driven by the battery mounted on the computer device using a circuit included in the computer device. become.

In the case described above, the storage means, the discharge current detection means, and the calculation means are integrated into a housing for accommodating the secondary battery, so that this housing can be mounted on various electronic devices. At the time of use, information such as the remaining time in which the device can be driven can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a processing configuration according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing an example in which the processing of one embodiment is realized by a measuring device.

FIG. 3 is a flowchart illustrating a characteristic measurement process according to an embodiment.

FIG. 4 is a flowchart illustrating a characteristic calculation process according to one embodiment.

FIG. 5 is a characteristic diagram illustrating a processing example according to one embodiment;

FIG. 6 is a flowchart illustrating a characteristic calculation process when three or more types of actually measured values are used according to an embodiment.

FIG. 7 is a characteristic diagram showing an example of an exponential curve according to one embodiment.

FIG. 8 is a flowchart showing a process when a discharge characteristic changes according to an embodiment.

FIG. 9 is a characteristic diagram illustrating an example of a correction process at the time of a load change according to an embodiment;

FIG. 10 is a flowchart showing a process at the time of pulse discharge according to one embodiment.

FIG. 11 is a characteristic diagram showing an example of correction processing at the time of pulse discharge according to one embodiment.

[Explanation of symbols]

1 measuring device, 2 power supply unit, 3 computer device, 1
1 secondary battery, 12 measurement circuit, 13 load circuit, 14
Control unit, 15 memory, 16 display unit

Claims (10)

[Claims] 1. A battery measuring method for measuring a discharging state of a battery, wherein the prepared battery is discharged with at least two types of discharging currents, and a voltage-time change characteristic up to a predetermined voltage due to the discharging at each current. The relationship between the time until a predetermined voltage and the load by the stored at least two types of discharge currents and the load is defined as data expressed by a predetermined exponential equation. Calculating the constant of this exponential formula from the calculation of the above, and calculating the characteristic at a predetermined discharge current by calculating the exponential formula using the calculated constant. . 2. The battery measurement method according to claim 1, wherein the exponential equation showing the relationship between the discharge time t _n and the discharge current I up to the discharge end voltage V _n is: 1 / I = A _n exp (B _n t _n ) where A _n and B _n are constants. 3. The battery according to claim 1, wherein when the battery is discharged with three or more types of discharge currents, the constant is obtained based on a value obtained by approximating the measured value by a predetermined calculation. Measuring method. 4. The battery measuring method according to claim 1, wherein when calculating the characteristic up to the predetermined voltage at the predetermined discharge current, the discharge current is changed from a first current value to a second current value. When the current value changes, the integrated value of the discharge energy at the first current value until the current value changes is calculated, and the discharge time at which the integrated value of the discharge energy is obtained by the discharge at the second current value is calculated. A battery measurement method in which the time for calculating the characteristic up to the predetermined voltage is changed by the difference between the calculated discharge time at the second current value and the time discharged at the first current value. Method. 5. An electronic device for measuring a discharge state of a connected battery, wherein a voltage up to a predetermined voltage when the connected battery or a battery having the same characteristics as the battery is discharged with at least two types of discharge currents. Storage means for storing the relationship between the time up to a predetermined voltage and the load based on the change with time and expressing the relation by a predetermined exponential formula, discharge current detection means for a connected battery; An electronic device comprising: a calculating means for calculating a characteristic by substituting the discharge current detected by the means into the exponential equation stored in the storage means. 6. The electronic apparatus according to claim 5, wherein the exponential equation indicating a relationship between a discharge time t _n and a discharge current I up to a predetermined voltage V _n stored in the storage means is: _{/ I = a n exp (B} n t n) [where a _n, B _n are constants] electronic device so as to use. 7. The electronic device according to claim 5, wherein when the discharge current detected by the discharge current detecting means changes from a first current value to a second current value, the arithmetic processing by the arithmetic means includes: A process of calculating an integrated value of discharge energy at a first current value until the current value changes, and calculating a discharge time at which the integrated value of the calculated discharge energy is obtained by discharging at a second current value And the discharge time at the calculated second current value and the first
An electronic device which performs processing for changing the time for calculating the characteristic up to the predetermined voltage by a difference from the time for discharging at the current value. 8. The electronic device according to claim 5, further comprising a notifying unit that notifies the characteristic calculated by the calculating unit in a predetermined manner, and functions as a measuring device that measures the characteristic of the connected battery. Electronic equipment. 9. The electronic device according to claim 5, wherein the storage means and the calculation means include a storage means and a calculation means provided in a computer device, and the storage means of the computer device uses the exponential formula. An electronic device that stores a processing program to be operated and measures characteristics of a battery that drives the computer device. 10. The electronic device according to claim 5, wherein said storage means, said discharge current detection means, and said calculation means are integrally incorporated in a housing for accommodating a secondary battery.