JP2002131402A - Tester for secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple tester and a testing method for a secondary battery capable of estimating the life of the battery in a very short time. SOLUTION: The tester for secondary battery comprises a discharging means 12 for giving a constant current load to a battery to be tested 20, a voltage measurement means 17 for measuring the voltage during discharging of the battery to be tested, and a calculation means 14 for estimating the life of the battery based on a voltage value difference measured at least at two points after elapsing of a specific time from the discharge initiation of the battery and discharge characteristic values set in advance. For a power source of each element including the discharging means, the voltage measurement means and the calculation means, the battery to be tested is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection apparatus for estimating the life of a secondary battery with a simple configuration, and more particularly to an inspection apparatus capable of estimating the life of a battery in an extremely short time.

[0002]

2. Description of the Related Art With the spread of portable electronic devices such as personal computers, mobile phones, and electronic organizers, the use of rechargeable secondary batteries as power sources for these devices has been increasing. Such secondary batteries include nickel cadmium batteries, nickel hydrogen batteries,
Various types such as lithium batteries have been developed. Since these secondary batteries are repeatedly charged and discharged, the actual capacity is reduced and the life is reduced as the number of charge and discharge cycles is increased.

In general, when a secondary battery is fully charged, its voltage indicates a standard voltage, so that it is not possible to measure a decrease in the life of the secondary battery. For this reason, in the conventional battery inspection, a method of estimating the life by charging the battery, discharging the battery until the voltage value reaches a predetermined value, obtaining the actual capacity from the voltage value or current value measured during that time, and estimating the service life is known. (No. 2-45476).

[0004]

However, in the above-mentioned conventional inspection apparatus, the life is estimated from the electric capacity of the battery. Therefore, in order to measure the electric capacity required for judging the life, the battery must have a minimum cell voltage. Or it was necessary to discharge to the vicinity, and it took a long time for the measurement.

On the other hand, the voltage after a predetermined time from the discharge is measured, and the drop from the initial voltage is calculated by a calculation formula obtained in advance, so that the deterioration of the secondary battery can be detected in a short time after the discharge. Method for estimating capacity (Japanese Patent Laid-Open No. 11-14711)
No. 7) or the amount of change in the discharge voltage after a short-time discharge from the pre-discharge voltage, and the difference between the product of the internal resistance of the battery and a predetermined current. For estimating the remaining life from the correlation between the internal resistance and the remaining life of the battery (Japanese Patent Laid-Open No. Hei 9-115554)
And so on.

However, secondary batteries have various standard voltages, and even if the standard voltages are the same, the initial voltage varies depending on the type and manufacturer.
In the method of estimating the lifetime from the correlation between the characteristics of the battery and the lifetime obtained in advance, such setting is necessary for each type of battery.

[0007] In the conventional methods for judging deterioration and estimating the life, the voltage before the start of discharge and the voltage after a predetermined time have elapsed are compared. In general, when a fully charged battery is discharged at a constant current, the battery voltage becomes As shown in FIG. 5, it falls rapidly immediately after the start of discharge, and then falls relatively slowly. The voltage value measured at the time of this sudden voltage drop may include a considerable error. Further, since the conventional battery inspection apparatus requires its own power supply, it has been difficult to provide a simple apparatus that can be freely carried.

Accordingly, an object of the present invention is to provide a simple secondary battery inspection apparatus and a simple inspection method capable of estimating the life of a battery in a very short time, for example, several minutes. Another object of the present invention is to provide an inspection apparatus for a secondary battery capable of automatically displaying parameters to be set according to the type and type of a battery to be inspected. Still another object of the present invention is to provide a secondary battery inspection device which has a simple configuration and is portable.

[0009]

Means for Solving the Problems To achieve the above object, the present inventor has determined that the discharge characteristics of a battery are as shown in FIG.
When discharging from a fully charged state, the voltage of the battery immediately drops by about several percent immediately after discharging, and then pays attention to the fact that it gradually drops, and that there is a correlation between the degree of this drop and the service life. The life of the battery is estimated from the voltage difference in a short period immediately after the voltage drop.

That is, the inspection apparatus for a secondary battery according to the first aspect of the present invention includes a discharging unit for applying a constant current load to the battery to be inspected, a voltage measuring unit for measuring a discharge voltage of the battery to be inspected, Calculating means for estimating the life of the battery under test based on a difference between voltage values measured at at least two points after a predetermined time has elapsed from the start of discharging the battery under test and a preset discharge characteristic value. It is.

[0011] Further, the inspection apparatus for a secondary battery according to a second aspect of the present invention comprises a discharging means for applying a constant current load to the battery to be inspected, a voltage measuring means for measuring the voltage of the battery to be inspected,
Calculating means for estimating the life of the battery under test based on a voltage value measured after a lapse of a predetermined time from the start of discharging of the battery under test and a preset discharge characteristic value; , A voltage measuring means and a calculating means.

According to the inspection apparatus for a secondary battery of the present invention according to the first and second aspects, it is possible to avoid a short time in which the battery voltage sharply drops after the start of discharge, typically about 3 minutes, Since the subsequent voltage drop is measured, an accurate inspection with relatively few errors can be performed. In addition, by previously setting the discharge characteristics obtained for a good product (for example, an unused battery), the life can be easily estimated based on the discharge characteristics.

Further, the secondary battery inspection device according to the second aspect does not require a separate power supply as a device, so that the device can have a simple configuration, and can be carried easily and easily at any place. Inspection can be performed. A preferred embodiment of the inspection apparatus for a secondary battery of the present invention is the inspection apparatus for a secondary battery according to the first or second aspect, wherein the calculating means includes:
It is provided with means for calculating a difference between voltage values measured at least at two points after a predetermined time has elapsed from the start of discharging for a non-defective battery of the same type as the battery to be inspected, and displaying the difference as a discharge characteristic value.

In a further preferred aspect of the present invention, the computer has means for correcting the discharge characteristic value. According to a preferred aspect of the present invention, by setting a non-defective product in the inspection apparatus, it is possible to calculate and display a discharge characteristic value used for testing a battery of the same type as the non-defective product. Therefore, even if the characteristic values of various batteries are not set in advance, appropriate discharge characteristic values can be easily set when the type or type of the battery to be inspected changes.

In the method of testing a secondary battery according to the present invention, the battery under test is discharged by applying a constant current load, the voltage of the battery under test at the time of discharge is measured, and the life of the battery under test is determined from the measured voltage value. Is a method of inspecting a secondary battery, which discharges the battery under test, and either when the voltage of the battery under test reaches a preset test voltage or when a predetermined time has elapsed from the start of discharging. A step of starting timing at an earlier time; a step of measuring a voltage V of a battery to be inspected at a time when a predetermined time has elapsed from the start of timing; a discharge characteristic value for a non-defective battery set in advance; Voltage V at
And estimating the life of the battery to be inspected based on the voltage difference between 1 and the voltage V measured at the elapse of the predetermined time.

In one embodiment of the method of testing a secondary battery according to the present invention, in the estimating step, the discharge characteristic value is set in advance for a non-defective battery of the same type as the battery to be inspected after discharge. V1 at the time when the test voltage reaches the predetermined test voltage or when a predetermined time has elapsed since the start of discharge.
And the voltage V2 after the elapse of a predetermined time is ΔV, and the battery life X (%) is expressed by the following equation: X = {[α ｛V- (V1−V− △ V)] / α △ V △ × 10
0 (where α represents an arbitrary correction coefficient).

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a secondary battery inspection apparatus according to the present invention.

FIG. 1 is an external view showing an embodiment of an inspection apparatus for a secondary battery according to the present invention. This inspection apparatus 10 is a simple battery tester having a length of about 180 mm and a width of about 100 mm. Terminals 1 and 2 for connecting a battery are provided, and the battery to be inspected itself serves as a power source of the apparatus, and operates only when the battery to be inspected is connected. The inspection apparatus 10 has switches 3 and 4 for starting and ending the inspection on the upper surface, and a digital setting unit for setting a discharge current, an inspection parameter corresponding to the type and type of the battery, a correction value (offset value), and the like. 5 and a display 6 for displaying the inspection result.

FIG. 2 is a block diagram showing an outline of a circuit of the inspection apparatus. The inspection device 10 includes a battery 2 to be inspected.
0, a voltmeter 17 connected in series to the battery 20, and a current measuring resistor 1 respectively.
1. a constant current device 12 and a DC / DC power supply 13, a switch 3 for closing a circuit constituted by these elements and starting discharge of a battery, a CPU 14 as a calculating means,
An A / D converter 15 for converting an analog signal input to the PU 14 into a digital signal, a D / A converter 16 for converting a digital signal output from the CPU 14 into an analog signal, and a calculation result of the CPU 14 are displayed. Display 6
And The constant current device 12 constitutes discharging means for applying a constant current load to the battery 20 and discharging it.

The DC / DC power supply 13 receives a voltage from the battery 20 and outputs a constant voltage. The DC / DC power supply 13 supplies a driving voltage to the CPU 14, the A / D converter 15, the D / A converter 16, and the display 6. Apply. The DC / DC power supply 13 is a DC adapter 1
8 and is driven by an external DC power supply.

The CPU 14 is provided with a digital setting unit 5 for setting a discharge current, an inspection parameter corresponding to the type and type of battery, a correction value (offset value), and the like. Inspection parameters are the same as the battery to be inspected,
It is a discharge characteristic value of a battery of the same type, and this discharge characteristic value can be obtained by setting a good battery in this inspection device as described later.

The discharge load current value set by the digital setting unit 5 in the CPU 14 is supplied to the constant current device 12 via the D / A converter 16. As described above, all the circuit elements constituting the inspection apparatus are driven by using the inspection battery as a power supply. The A / D converter 15 converts an analog signal from the voltmeter 17 into a digital signal and inputs the digital signal to the CPU 14. The CPU 14 estimates the life of the battery to be inspected based on the measured voltage value and a preset discharge characteristic value.

The display 6 displays the life of the battery under test estimated by the CPU 14 in a numerical expression such as a percentage of a non-defective battery, "L
A qualitative expression such as “IFE = NG”, an analog expression using a scale of 0 to 100, or a combination thereof is displayed. As a combination, for example, when the percentage is 50% or more, a numerical value is displayed, and when it is lower than that, "NG" is displayed.

Next, the operation of the inspection apparatus for a secondary battery having such a configuration will be described with reference to FIGS. FIG. 3 is a flowchart showing an inspection procedure, and FIG. 4 is a graph showing a change in battery voltage due to discharge.

(1) Determination of Discharge Characteristic Value First, a non-defective battery of the same type and the same type as the battery to be inspected is connected to the inspection device to check the reference discharge characteristics of the battery to be inspected, and the inspection parameters are digitally set. Set to “000” by part 5. Also, the rated current of the battery is set as the discharge current. Next, the start switch 3 is pressed to start the inspection. When the start switch 3 is pressed, the DC / DC power supply 13 is connected to the battery 20, and the current value set in the CPU 14 is sent to the constant current device 12 via the D / A converter 16. A constant current is generated.

Simultaneously with the start of the discharge, the voltage 17 is measured, and the voltage at the start of the discharge (hereinafter referred to as the discharge start voltage) V0
(Step 101). This inspection voltage is a voltage serving as a reference point for comparing discharge patterns under uniform conditions, and is preferably a voltage after a relatively sharp voltage drop immediately after the start of discharge. Specifically, the voltage is set slightly lower than the standard voltage. When the number of cells of the battery type is N, the standard voltage is N ×
Since the voltage is 1.2 V, the inspection voltage is set to a lower value, for example, N × 1.1 V. That is, since the 3.6V battery has three cells, the inspection voltage is 3.3V, and the 4.8V battery has four cells, so the inspection voltage is 4.4V.

Normally, the discharge starting voltage V0 varies from battery to battery.
It is considered that the battery is 3.6V up to 1V, and the test voltage is 3.
The test voltage is set to 3V, and the test voltage is set to 4.4V from 4.2 to 5.3V assuming that the battery is 4.8V. Such a determination can be made by calculation, or a correspondence table between the discharge start voltage and the inspection voltage may be stored in the CPU 14 as a table.

The CPU 14 counts the elapsed time with a built-in clock from the start of discharging, and reads the signal from the voltmeter 17 sequentially to measure the voltage. Then, the voltage measured at the time when the measured voltage becomes equal to or lower than the inspection voltage set as described above (step 102) or at a time t1 (step 103) after a predetermined time, for example, 3 minutes from the start of the discharge, is set to the reference voltage V1. Is stored in the memory (step 104). Therefore, when the test voltage becomes the test voltage before the predetermined time elapses, the test voltage is the reference voltage V1. When the test voltage does not become lower than the test voltage even after the predetermined time elapses, the voltage higher than the test voltage becomes the reference voltage V1. Becomes

The voltage measured at time t2 after a lapse of a predetermined time, for example, 4 minutes, from the measurement of the reference voltage V1 is calculated as V2
(Steps 105 and 106), and a difference ΔV (= V1−V2) from the reference voltage V1 stored in the memory is calculated (step 107). This difference ΔV is calculated as a discharge characteristic value (inspection parameter).
Is displayed on the display 6 (step 108). ΔV is
For example, a three-digit number in mV is displayed.

(2) Inspection of Life of Inspection Battery Next, inspection of a battery of the same type as a non-defective battery whose inspection parameters are determined as described above is started. First, the inspection parameters displayed on the display 6 by the above operation are set by the digital setting unit 5. Thereafter, the user presses the start button 3 to start the inspection. Also in this case, the procedure from step 101 to step 107 is the same. That is, after the discharge starts, when the voltage reaches the inspection voltage or when a predetermined time (here, 3 minutes) has elapsed, the voltage at that time is set as the reference voltage V1, and the voltage measured after the predetermined time (here, 4 minutes) has elapsed. Difference from V ΔV '
(V1-V) is obtained.

As described above, also for the battery to be inspected, the voltage drop Δ from the reference voltage due to the discharge for a predetermined time.
V ′ is obtained, and the life is determined based on the voltage drop ΔV ′ (step 109). If the difference (ΔV′−ΔV) between the voltage drop V ′ and the voltage drop ΔV for the non-defective product is 0, the test battery has the same life as the non-defective product, and the difference ′ between the non-defective product and the voltage drop ΔV is small. It can be estimated that the longer the battery is, that is, the larger the voltage drop after the measurement of the reference voltage V1 is, the shorter the life of the battery is. According to the measurement by the present inventors, although there is some variation depending on the type and type of the battery, the ratio of the difference (ΔV′−ΔV) to the voltage drop ΔV of a non-defective product almost reflects the battery life. Was.

Therefore, here, the CPU 14 calculates the life according to the following equation. X (%) = {[αV− (ΔV′−ΔV)] / α {V} ×
100 ΔV ′ = V1−V In the equation, α represents an arbitrary correction coefficient, for example, 0.6 to 1.
Numerical values up to 5.

The voltage V1 serving as the starting point for calculating ΔV for the non-defective product may not be the same as the voltage V1 serving as the starting point for calculating ΔV ′ for the battery to be inspected. The slight drop in V1 is not a problem because the voltage drop that occurs after the sharp voltage drop of V1 is considered. Rather, in order to be able to measure even a non-defective product in which a voltage drop to the inspection voltage takes a long time, it is more practical to determine V1 at a predetermined time even if the voltage does not reach the inspection voltage.

The correction coefficient can be appropriately set depending on the type and type of the battery. That is, depending on the type or type of battery, if α is set to 1, the life may be calculated to be shorter than the actual life, or conversely, the life may be calculated to be longer. In such a case, the correction coefficient α is set to a numerical value from 0.6 to 1.5, for example, to meet the actual situation.
The correction coefficient can be set in the CPU 14 by the digital setting unit 5. In this case, the numerical value of the correction coefficient 1 may be set as it is, but an integer corresponding thereto (for example, 0 is 1, 0.9 is 2, and 0.8 is 3) is set. Good.

The X (%) obtained by such calculation is displayed on the display 6 as the life (step 110). As described above, the life may be indicated by the numerical value as it is in%. For example, in the case of 50% or less, "LI" is used.
FE = NG ”.

Thus, the life of the battery can be obtained within a few minutes from the start of the discharge, 4 to 7 minutes in the example described above. After the measurement is completed, the end switch 4 is pressed to open the circuit of FIG. Since this inspection device uses the battery itself as a power source,
If the end switch 4 is not depressed, the discharge will continue as it is. Therefore, pressing the end switch 4 prevents further discharge. Alternatively, as a function of the CPU 14, it is possible to provide a function of turning off the switch at the same time as the calculation of the life and the end of the display. As a result, the discharge can be reliably terminated, and the consumption of the battery can be prevented.

Although the embodiment of the inspection apparatus of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various changes can be made. For example, in the above-described embodiment, the voltage difference obtained for the non-defective product is displayed as an inspection parameter, and is set by the digital setting unit 5 when the test target battery is inspected. You may make it set to the memory in CPU14. The numerical values used in the above description are merely examples, and can be arbitrarily changed.

[0038]

According to the present invention, when estimating the service life from the voltage drop at the time of discharge of the secondary battery, the error value can be obtained by using the voltage values measured at least at two points after the elapse of a predetermined time after the start of discharge. Inspection can be performed with a small quantity of Further, according to the present invention, parameters used for estimating the life can be obtained and set for non-defective products of the same type as the battery to be inspected, so that various batteries can be easily inspected. Further, according to the present invention, it is possible to provide an inspection device which has a simple configuration and is easy to carry by using the battery to be inspected as a power source of the device.

[Brief description of the drawings]

FIG. 1 is an external view showing an embodiment of a secondary battery inspection device according to the present invention.

FIG. 2 is a circuit diagram showing an embodiment of a secondary battery inspection device according to the present invention.

FIG. 3 is a flowchart showing an embodiment of a method for inspecting a secondary battery according to the present invention.

FIG. 4 is a view for explaining an embodiment of the inspection method for a secondary battery of the present invention.

FIG. 5 is a diagram showing a discharge curve of a secondary battery.

[Explanation of symbols]

 12 ... constant current device (discharge means) 14 ... CPU (calculation means) 17 ... voltmeter (voltage measurement means) 20 ... battery to be tested

Claims (6)

[Claims] 1. A discharging means for applying a constant current load to a battery to be tested, a voltage measuring means for measuring a discharge voltage of the battery to be tested, and at least two points after a lapse of a predetermined time from the start of discharging of the battery to be tested. Calculating means for estimating the life of the battery to be inspected based on the difference between the voltage values measured in step (a) and a preset discharge characteristic value. 2. The inspection apparatus for a secondary battery according to claim 1, wherein the battery to be inspected is used as a power source for each element including the discharging unit, the voltage measuring unit, and the calculating unit. 3. The calculating means calculates a difference between voltage values measured at least at two points after a lapse of a predetermined time from the start of discharging for a non-defective battery of the same type as the battery to be inspected, and calculates the difference as a discharge characteristic value. 2. The inspection apparatus for a secondary battery according to claim 1, further comprising means for displaying as V. 4. The inspection apparatus for a secondary battery according to claim 3, wherein said calculation means includes means for correcting said discharge characteristic value. 5. A battery to be tested is discharged by applying a constant current load thereto.
A method for testing a secondary battery, comprising measuring a voltage of a battery under test at the time of discharging and estimating the life of the battery under test from the measured voltage value, wherein the battery under test is discharged and the voltage of the battery under test is reduced. A step of starting timing at a time when a predetermined test voltage is reached or a predetermined time has elapsed from the start of discharging, whichever is earlier; and a voltage V of the battery to be inspected at a time when a predetermined time has elapsed from the start of timing. And estimating the life of the battery to be inspected based on a preset discharge characteristic value of the non-defective battery and a voltage difference between the voltage V1 at the time of starting the timing and the voltage V measured after a predetermined time has elapsed. And a method for inspecting a secondary battery. 6. In the estimating step, the discharge characteristic value is a predetermined value from the time when the voltage of the non-defective battery reaches a predetermined test voltage after discharge or the start of discharge for a non-defective battery of the same type as the battery to be inspected. The difference ΔV between the voltage V1 at the time when the time has elapsed and the voltage V2 after the elapse of the predetermined time further
And the battery life X (%) is given by the following equation: X = {[α ｛V- (V1-V- △ V)] / α △ V｝ × 10
6. The inspection method for a secondary battery according to claim 5, wherein the value is obtained by 0 (where α represents an arbitrary correction coefficient).