JP2002369372A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack which surely detects an abnormal cell surely without deteriorating the cell performance. SOLUTION: The battery pack has constitution where a plurality of protective elements 5 and cell units 7 are connected in parallel. The protective element 5 is constituted by connecting a PTC thermistor 3 for controlling a flowing current in response to a temperature in parallel with a fuse 2 for controlling the maximum value of the flowing current. The cell units 7 are connected in series with the protective element 5. As a result, the cell performance is not deteriorated when the resistance value of the PTC thermistor 3 is increased. A current flows in the abnormal cell, and a voltage applied across both ends containing the cell 1 and the fuse 2 is lowered, so that the presence of the abnormal cell can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembled battery capable of reliably detecting a cell abnormality without deteriorating performance.

[0002]

2. Description of the Related Art A battery mounted on an electric vehicle or the like uses an assembled battery formed by connecting a plurality of cells connected in parallel in series. Each cell is connected in series with a fuse and a positive temperature coefficient (PTC) thermistor. The PTC thermistor has a positive temperature characteristic in which the resistance value increases as the temperature increases.
Normally, a PTC thermistor works as a resistor with a constant low resistance, but when an overcurrent flows, the resistance rapidly increases,
The current can be limited.

[0003]

However, as shown in FIG. 2, in the conventional battery pack in which each cell 1 is simply connected in parallel, when one cell is abnormal and short-circuited, There is a problem that a large current flows from another cell to the abnormal cell.

FIG. 3 shows a conventional battery pack formed by connecting a fuse 2 to each cell 1 in series and connecting a plurality of those connected in parallel to each other in series. In such a configuration, if an abnormality occurs in one cell and short-circuits, when a large current flows from another cell to the abnormal cell, the fuse connected in series with the abnormal cell is blown. The problem that a large current flows can be solved.

However, this configuration has a problem that it is not possible to quickly detect that an abnormality has occurred in a cell. That is, in order to detect an abnormal cell, it is necessary to measure the cell voltages of all the cells or to check the continuity of all the fuses. For this reason, a continuity check mechanism for voltage sensors and fuses is required for the number of cells constituting the battery pack.

FIG. 4 shows a conventional battery pack in which a PTC thermistor 3 is connected in series to a cell 1 and a plurality of PTC thermistors 3 connected in parallel are connected in series. In such a configuration, when an abnormality occurs in one cell and a short circuit occurs, a large current flows from the other cell to the abnormal cell, and the temperature of the PTC thermistor 3 connected in series with the abnormal cell rises. I do. As a result, the temperature of the PTC thermistor 3 has increased.
Since the internal resistance of the abnormal cell increases, it is possible to prevent a large current from flowing through the abnormal cell.

However, if the resistance value of the PTC thermistor 3 connected in series with the cell 1 in which the abnormality has occurred is small,
When the current flows into the abnormal cell, another cell is overdischarged in a short time. Therefore, it is better that the resistance value of the PTC thermistor 3 is as large as possible. However, if the resistance value of the PTC thermistor 3 is increased,
The power consumed by the PTC thermistor 3 increases, and the performance (output) of the battery deteriorates.
Cannot be increased.

An object of the present invention is to provide an assembled battery which can reliably detect abnormal cells without lowering the performance of the battery.

[0009]

FIG. 1 shows an embodiment of the present invention.
The present invention will be described with reference to FIG. (1) A battery pack according to the present invention is configured by connecting a temperature-dependent current limiting element 3 for controlling a current to be conducted according to temperature and a current limiting element 2 for limiting a maximum value of a current to be conducted in parallel. The object is achieved by connecting and connecting a plurality of protection elements 5 and a plurality of cell units 7 each formed of cells 1 connected in series with the protection elements 5. (2) The invention according to claim 2 is the battery pack according to claim 1,
The resistance value of the temperature-dependent current limiting element 3 is
Is larger than the resistance value. (3) The battery according to claim 1 or 2, wherein the resistance value of the current limiting element 2 is determined by a current flowing when the cell 1 has an abnormality.
Is the value at which only the current limiting element 2 connected in series to (4) The battery according to any one of claims 1 to 3, wherein the temperature-dependent current limiting element 3 is in contact with the cell 1 connected in series with the temperature-dependent current limiting element 3. are doing. (5) The invention according to claim 5 is the battery pack according to any one of claims 1 to 4, wherein the current limiting element 2 is a fuse 2. (6) The invention according to claim 6 is the battery pack according to any one of claims 1 to 5, wherein the temperature-dependent current limiting element 3 is a PTC thermistor 3.

In the section of the means for solving the above problems, the present invention is associated with FIG. 1 of the embodiment in order to explain the present invention in an easy-to-understand manner, but the present invention is limited to the embodiment. Not something.

[0011]

According to the present invention, the following effects can be obtained. (1) According to the first to sixth aspects of the present invention, the current limiting element is connected in series with the cell and connected in parallel with the temperature-dependent current limiting element. The resistance value of the current limiting element can be increased,
When an abnormality occurs in a cell, it is possible to prevent a large current from flowing from another cell to the abnormal cell. In addition, abnormal cells can be reliably detected. (2) According to the second aspect of the present invention, when the cell is abnormal, the current limiting element is immediately cut off and current flows through the temperature-dependent current limiting element, thereby preventing overdischarge in other cells. it can. (3) According to the invention of claim 3, when an abnormality occurs in the cell, only the current limiting element connected in series to the cell in which the abnormality has occurred is cut off, so that the abnormal cell can be reliably detected. it can. (4) According to the invention of claim 4, since the temperature-dependent current limiting element is in contact with the cell, the degree of increase in the resistance value of the temperature-dependent current limiting element increases when an abnormality occurs in the cell. , The discharge of other cells can be reduced.

[0012]

FIG. 1 is a diagram showing the configuration of an embodiment of an assembled battery according to the present invention. In the battery pack according to the present invention, the fuse 2 is connected in series for each cell 1, and each fuse 2 is connected in parallel with the PTC thermistor 3. That is, each cell 1 and the PTC thermistor 3 are also connected in series. By configuring the protection element 5 by connecting the fuse 2 and the PTC thermistor 3 in parallel,
When an abnormality occurs in the cell, it plays a role in preventing a large current from flowing through the abnormal cell. Here, the cell 1 and the protection element 5 connected in series with the cell 1 are referred to as a cell unit 7 as a set. That is, the assembled battery of FIG. 1 has a module 6 configured by connecting a plurality of cell units 7 in parallel.
Are connected in series. A voltmeter 4 is connected to both ends of each module 6. The voltage applied to both ends of the cell 1 and the fuse 2 by this voltmeter 4
Alternatively, the voltage applied to both ends of the cell 1 and the PTC thermistor 3 can be measured. Note that the battery pack may be composed of only one module 6.

As described above, it is preferable that the resistance value of the PTC thermistor 3 be as large as possible unless the performance of the battery is considered. When the resistance value of the PTC thermistor 3 is larger than the resistance value of the fuse 2, the current flowing when the cell is normal flows toward the fuse 2. Therefore, of each cell 1,
If one cell 1 becomes abnormal and short-circuits, the other cell 1
Flows through the fuse 2 connected in series with the abnormal cell, and the fuse 2 is blown. At this time PTC
If the resistance value of the thermistor 3 is large, a large current can be prevented from flowing through the abnormal cell.

As described above, when the resistance value of the fuse 2 is smaller than the resistance value of the PTC thermistor 3,
Since the current flowing when the cell is normal flows toward the fuse 2, even if the resistance value of the PTC thermistor 3 is increased, the performance of the battery does not decrease. Therefore, by increasing the resistance value of the PTC thermistor 3, when an abnormality occurs in the cell 1, overdischarge of another cell 1 can be prevented. In order to prevent a decrease in the performance of the battery, it is preferable that the current when the cell is normal flows to the fuse 2 as much as possible. Therefore, it is preferable to reduce the resistance value of the fuse 2 as much as possible. For this reason, the resistance value of the fuse 2 is
Is set to such a value that only the fuse 2 connected in series with the abnormal cell is blown when an abnormality occurs.

When an abnormality occurs in the cell 1, as in the conventional battery pack having only the cell 1 and the PTC thermistor 3 connected in series, a current flows from the cell 1 other than the abnormal cell to the abnormal cell. Since the voltage value of the voltmeter 4 decreases, abnormality of the battery can be reliably detected. That is, it is not necessary to provide the voltmeter 4 for each cell, and by providing one voltmeter 4 at both ends of the module 6,
Battery abnormality can be detected. In an assembled battery in which only the cell 1 and the PTC thermistor 3 are connected in series, P
When the resistance value of the TC thermistor 3 is increased, there is a problem that the performance of the battery is reduced. However, in the assembled battery according to the present invention, the performance of the battery is not reduced as described above. Further, when an abnormality of the battery is detected by measuring the voltage value of the voltmeter 4, an abnormal cell can be detected by checking the blown fuse 2.

In order to reduce the discharge of cells other than the abnormal cell when the cell is abnormal, it is necessary to minimize the current flowing through the abnormal cell. For this purpose, when an abnormality occurs in a cell, a PT connected in series with the abnormal cell is used.
It is better to increase the resistance value of the C thermistor 3 as soon as possible. As described above, the resistance of the PTC thermistor 3 increases as the temperature rises. Therefore, if the PTC thermistor 3 is brought into contact with the cell 1 connected in series with the PTC thermistor 3, the degree of increase in the resistance value of the PTC thermistor 3 becomes large when the cell is abnormal. That is, when the cell is abnormal, the temperature of the cell 1 also rises. Therefore, the degree of temperature rise of the PTC thermistor 3 becomes larger and the degree of increase of the resistance value becomes larger than when the PTC thermistor 3 is not in contact with the cell 1.

The present invention is not limited to the above embodiment. For example, another overcurrent protection device may be used instead of the fuse 2. In addition, a device other than the PTC thermistor 3 can be used as long as the amount of current to be conducted according to the temperature can be controlled. Further, in the above-described embodiment, the case where only one abnormal cell occurs has been described, but the same effect can be obtained even when abnormality occurs in two or more cells.

As described above in detail, according to the battery pack of the present invention, the fuse 2 is connected in series with the cell 1, and the PTC thermistor 3 connected in series with the cell 1 and the fuse 2 are connected in parallel. , The resistance value of the PTC thermistor 3 can be increased without deteriorating the performance of the battery, and when an abnormality occurs in the cell 1, a large current flows from the other cell 1 to the abnormal cell. Can be prevented. Further, by measuring the voltage applied to both ends of the cell 1 and the protection element 5, it is possible to reliably detect the abnormal cell. Further, if the PTC thermistor 3 is kept in contact with the battery, when the cell 1 becomes abnormal,
The degree of increase in the resistance value of the TC thermistor 3 also increases, and the discharge of other cells 1 can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a configuration of a conventional assembled battery in which cells are simply connected in parallel.

FIG. 3 is a diagram showing a configuration of a conventional battery pack in which cells and fuses are connected in series and connected in parallel;

FIG. 4 is a diagram showing a configuration of a conventional battery pack in which cells and a PTC thermistor connected in series are connected in parallel;

[Explanation of symbols]

1 ... cell, 2 ... fuse, 3 ... PTC thermistor, 4 ...
Voltmeter, 5: protection element, 6: module, 7: cell unit

Claims (6)

[Claims] 1. A protection element comprising a temperature-dependent current limiting element for controlling a current to be conducted in accordance with a temperature and a current limiting element for limiting a maximum value of a current to be conducted, connected in parallel, and said protection element. An assembled battery comprising a plurality of cell units connected in parallel with each other, the cells being composed of cells connected in series. 2. The battery pack according to claim 1, wherein a resistance value of the temperature-dependent current limiting element is larger than a resistance value of the current limiting element. 3. The battery pack according to claim 1, wherein the resistance value of the current limiting element is connected in series to the abnormal cell by a current flowing when the abnormal cell occurs. The battery pack according to claim 1, wherein only the current limiting element is turned off. 4. The battery pack according to claim 1, wherein the temperature-dependent current limiting element is in contact with a cell connected in series with the temperature-dependent current limiting element. Battery. 5. The battery pack according to claim 1, wherein said current limiting element is a fuse. 6. The battery pack according to claim 1, wherein said temperature-dependent current limiting element is a PTC thermistor.