JPH09134741A - Failed battery judging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and accurately judge whether any element cell is in failure in a unit battery or a packaged battery. SOLUTION: A battery concerned is composed of a plurality of element cells. The internal impedance of this battery being discharged is measured, and when the measurement has steeply increased prior to the steep increase immediately before the discharge ending voltage of the battery, it is judged that any element cell is in failure. The number of failed element cells can be known from the number of rises of the internal impedance appearing prior to the steep rise of the internal impedance of the battery.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defective battery determination method for determining whether or not there is a defective single battery in a unit battery or a battery pack composed of a plurality of single batteries.

[0002]

2. Description of the Related Art For lead-acid batteries and the like, a method of accommodating six unit cells in one battery case to form a unit battery is often used. It is also common practice to connect a large number of single cells and use them as an assembled battery. In such a unit battery or assembled battery, there is a problem in that if there is one unit battery or a unit battery that has a low capacity, the performance of the unit battery or assembled battery is deteriorated. Therefore, whether or not there is a defective unit cell in the unit battery or the assembled battery has been conventionally determined by, for example, observing the entire discharge behavior and determining whether there is a rapid change (decrease) in voltage.

[0003]

However, according to the above method, specialized knowledge is required for analysis, and in the case of an assembled battery composed of a large number of cells, the total voltage is high, 1
In many cases, the judgment cannot be made based on the voltage change of about a single cell, and the judgment is extremely difficult. An object of the present invention is to provide a method for easily and accurately determining the presence / absence of a defective single battery in a unit battery or an assembled battery.

[0004]

In order to achieve the above object, the present invention provides a method for determining a defect of a battery composed of a plurality of unit cells as set forth in claim 1, wherein the battery is being discharged. The internal impedance of the battery is measured, and when the internal impedance rapidly increases before the rapid increase immediately before the discharge cutoff voltage of the battery, the presence of a defective cell is determined from this increase. As described in Item 2, determining the existence of a defective cell from the shape of the locus of the internal impedance at the time of discharge in which the rising of the internal impedance appears before the rapid rising of the internal impedance of the battery immediately before the discharge cutoff voltage. Is characterized by. Further, as described in claim 3, in the invention of claim 1 or 2, the number of defective cells is determined based on the number of rises in the internal impedance that appears before the sudden rise in the internal impedance of the battery immediately before the discharge cutoff voltage. Is detected.

[0005]

Operation: After discharging the unit cell, an alternating current is passed through the unit cell to measure the voltage drop of the AC component generated between the unit cell terminals, and the internal impedance of the unit cell is calculated from the AC current and the voltage drop. It was found that the internal impedance of the unit cell with respect to the discharge time sharply rises immediately before the discharge cutoff voltage as shown by the solid line in FIG. 1, for example. An experiment similar to this was carried out also on a unit battery or an assembled battery of, for example, 12 V, which was configured by connecting, for example, six unit cells in series, each of which had a lower capacity and the remaining capacity was the same. As shown in FIG. 2, the internal impedance of the battery with respect to the discharge time at this time was found to rise sharply immediately before the end of discharge of one low-capacity single cell, and then decreased, and the unit battery or the assembly It was observed that the internal impedance suddenly rose again immediately before the final discharge voltage of the battery. From this result, the sharp rise of the internal impedance immediately before the sudden rise of the internal impedance immediately before the discharge end voltage includes the defective unit cell in the unit battery or the assembled battery even when a plurality of unit cells are combined. It turned out that it is possible to judge whether or not it is. Therefore, the present invention measures the internal impedance during discharge of a battery composed of a plurality of cells, and when the internal impedance changes abruptly before the abrupt change of the internal impedance immediately before the discharge end voltage of the battery. The existence of the defective cell is determined from this change. Further, the existence of a defect is determined from the shape of the locus of the internal impedance at the time of discharge in which the internal impedance rises before the abrupt rise of the internal impedance immediately before the discharge cutoff voltage of the battery. Also, the number of defective single cells is determined by counting the number of sudden rises in the internal impedance that appear before the sudden rise in the internal impedance immediately before the end-of-discharge voltage of the battery.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. A sealed lead-acid battery having a rated capacity of 80 Ah and 12 V in which six unit cells are connected in series is used as a standard battery, and the standard battery 1 is connected to a load 2 as shown in FIG. The standard battery 1 being discharged to 17.5 Hz by an impedance measuring device (made by Yachiyo Denshi Co., Ltd.) 3 connected to the terminal of the standard battery 1.
An alternating current of 0.1 A was passed, and the internal impedance of the standard battery 1 was measured from the voltage drop and the alternating current to a discharge end voltage of 9.0 V. In FIG. 3, 6 is a choke coil. FIG. 4 shows the measured battery voltage of the standard battery 1 (measured by the DC voltmeter 5. The broken line) and its internal impedance (solid line). As shown in the figure, the internal impedance of the standard battery 1 rises sharply immediately before the final discharge voltage. Also, six unit cells of the same type as the standard battery are connected in series, and among these unit cells, the capacity is lower than the remaining unit cells and the capacity is different from each other.
A sealed lead-acid battery using a single battery was used as a test battery 1 ', and was connected to the circuit shown in FIG. 3 instead of the standard battery 1 to measure changes in battery voltage and internal impedance of the battery during discharging. . FIG. 5 shows the battery voltage and internal impedance characteristics with respect to the discharge time of the measurement result. As is clear from FIG. 5, the battery voltage is 9.0 V which is the discharge end voltage.
Immediately before, the internal impedance showed a sharp rise, but before that, it was observed that the internal impedance of the test battery suddenly rose at two locations where the battery voltage dropped stepwise. As shown in FIG. 5, the internal impedance of the test battery 1 ′ at the time of discharging is higher than the internal impedance of the standard battery 1 before the abrupt increase immediately before the discharge end voltage. It can be measured by the measuring device 3, and it can be seen from this increase in internal impedance that there is a defective cell. Further, as the discharge time elapses, the voltage gradually decreases from the unit cell having the lower capacity, so that the discharge time-battery voltage curve gradually decreases as shown in FIG. It is considered that the rising of the internal impedance of ′ appears. Therefore, the test battery 1 ′ at the time of discharging recorded by the recorder 4 connected to the output terminal of the impedance measuring device 4
In the shape of the locus of the internal impedance of, there is a sharp rise before the sharp rise just before the discharge cutoff voltage, so there are defective cells, and because there are two, 2 batteries
You can see that there are individual items.

[0007]

According to the present invention, the present invention has an effect that it is possible to easily and accurately determine the presence or absence of a defective single battery in a unit battery or an assembled battery.

[Brief description of the drawings]

FIG. 1 is a change characteristic diagram of a terminal voltage and an internal impedance of a unit cell during discharging.

FIG. 2 is a change characteristic diagram of a terminal voltage and an internal impedance of an assembled battery or a unit battery including a defective cell during discharging.

FIG. 3 is a circuit diagram for determining a defective battery.

FIG. 4 is a change characteristic diagram of the terminal voltage and the internal impedance of the standard battery during discharging.

FIG. 5 is a change characteristic diagram of the terminal voltage and the internal impedance of the test battery during discharging.

[Explanation of symbols]

1 Standard battery 1'Test battery 2 Load 3 Impedance measuring device 4 Recorder 5 DC voltmeter

Claims (3)

[Claims] 1. A method for determining a defect of a battery composed of a plurality of cells, wherein the internal impedance of the battery during discharging is measured, and the internal impedance is measured before a sharp increase immediately before the discharge end voltage of the battery. A method for determining a defective battery, which is characterized by determining the presence of a defective single battery based on the increase when the amount of battery increases rapidly. 2. A locus of internal impedance at the time of discharge in which a rise of internal impedance appears before abrupt rise of internal impedance of the battery just before the discharge cutoff voltage in a method of determining a defect of a battery composed of a plurality of unit cells. The method for determining a defective battery is characterized by determining the presence of a defective battery cell from the shape of the above. 3. The number of defective cells is detected from the number of rises in the internal impedance that appears before the sudden rise in the internal impedance of the battery immediately before the discharge cutoff voltage. Defective battery determination method.