JPH07335266A - Battery assembly and its charger - Google Patents

Abstract

PURPOSE:To prevent overcharging a battery assembly by connecting a bias circuit, containing the second battery of small capacity, in parallel to each of the first unit cell constituting the battery assembly, controlling a charge current in each unit cell, and charging the second unit cell, connected in parallel, with an excessive current. CONSTITUTION:In accordance with advancing a charge, voltage of a unit cell 1 is gradually restored. However, a rise of terminal voltage in each cell is not uniform due to dispersing capacity, and in the unit cell of small capacity, voltage reaches high voltage quickly, but it is slow in a cell of large capacity. When, in this case, a quick one first reaches 3V, a switching circuit 4, connected in parallel to this cell, is actuated to form a bypass circuit, and a charging current to the unit cell 1 is partly guided to a unit cell 2 through this bypass circuit. In this way, when each of all the cells reaches 3V, terminal voltage of a battery assembly is generated 90V, to reach the switching voltage of a charger 5, and it is changed to a fixed voltage charge. When the charging current is decreased to 0 or to approach 0, charging is stopped as fully charged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembled battery in which a plurality of batteries are directly connected and a charging device for the assembled battery.

[0002]

2. Description of the Related Art In recent years, various devices tend to be miniaturized and cordless, so that the demand for batteries is increasing due to these trends. Especially, rechargeable secondary batteries, which can be repeatedly charged and discharged, are widely used in various fields due to their excellent economic efficiency and discharge characteristics, and the demand is increasing.

Regarding the charging characteristics of the secondary battery, for example,
In the case of a non-aqueous secondary battery, the terminal voltage of the battery has a strong correlation with the amount of electricity in the battery. That is, when charging a discharged battery, the terminal voltage rises as the amount of electricity in the battery increases. When the fully charged battery is still charged, the terminal voltage continues to rise. When the terminal voltage becomes higher than the terminal voltage at the time of full charge, the battery capacity decreases and the performance deteriorates. In addition, gas may be generated inside the battery.

As a measure for preventing the performance deterioration due to this overcharging, charging is performed with a constant current in the initial stage of charging, and when the terminal voltage reaches a set voltage as the charging progresses, the charging current is reduced by shifting to constant voltage charging. However, the charging method is used in which the charging is continued and the charging is stopped when the charging current stops flowing or approaches 0. However, when attempting to charge a battery pack connected in series using this method, the charging reaction does not proceed uniformly due to the capacity and internal state of each battery cell that constitutes the battery pack, so the charging reaction is slow. Insufficient charging of items, overcharging of fast-reacting items, resulting in different cell capacities, and as a battery pack, only the capacity of a small cell can be discharged. . Therefore, when the assembled batteries connected in series are charged, it is necessary to arrange the individual cells constituting the assembled batteries in a uniform charged state.

Therefore, Japanese Patent Laid-Open No. 4-366564 proposes a method in which an intermediate terminal is provided to the outside from each terminal connecting the individual cells forming the assembled battery, and the individual cells are charged from the intermediate terminal. There is.

[0006]

However, in the assembled battery configured as described above, since the method of charging each single battery at the time of charging, the charging time of the assembled battery is equal to the number of single batteries. It will only take. Alternatively, there is a problem that a charger for the number of unit cells is required.
Therefore, in view of the above-mentioned conventional problems, it is an object of the present invention to provide an assembled battery and a charging device for the assembled battery, in which the performance is not deteriorated due to the variation in the unit cells.

[0007]

According to the present invention, in an assembled battery in which a plurality of first cells are connected in series, a bypass circuit is connected in parallel to the first cells and the bypass circuit is connected. Has a voltage unit for detecting the terminal voltage of the first unit cell, a switching unit for determining the operation of the bypass circuit, and a second unit cell, and when the assembled battery is charged by a charging device. When the terminal voltage of the first unit cell is detected, and when the detected value reaches a predetermined value, the switching means is activated and the charging current to the first unit cell is changed to the second unit cell. The assembled battery was designed to flow. According to a fourth aspect of the present invention, as a battery charger for an assembled battery, the assembled battery is charged with a constant current at the initial stage of charging and then charged with a constant voltage after the voltage of the assembled battery reaches a predetermined voltage value.

[0008]

In the assembled battery according to claim 1, a bypass circuit having a second unit cell is connected in parallel to each of the first unit cells constituting the assembled battery, and the first unit cell is fully charged. Since the charging current sometimes flows into the bypass circuit to charge the second single battery, the entire battery pack is not overcharged, the battery life is extended, and the bypassed current can be used. It is possible to suppress heat generation due to the bypass current as compared with the case where a resistor or the like is used. Further, when the power supply of the bypass circuit is assumed to be borne by the second cell in the bypass, the energy utilization rate of the first cell is improved. Furthermore, if the first cell and the second cell are provided in a common battery case and the electrodes are shared, the assembled battery can be made compact.

In the charging device according to the fourth aspect, the assembled battery according to the first aspect is charged with a constant current at the initial stage of charging and with a constant voltage at the final stage of charging. Since the charging current decreases, the value of the bypass current flowing through the second cell can be reduced. Thereby, the energy efficiency of the whole assembled battery can be improved.

[0010]

FIG. 1 shows an embodiment of the present invention. First, the configuration will be described. 30 non-aqueous cells 1, 1a, ...
1b are connected in series and each of the cells 1, 1a,
... 1b is a bypass circuit 10 including a voltage detection circuit 3, a switching circuit 4 and a non-aqueous battery cell 2 in parallel.
0a, ..., 10b are connected to form an assembled battery. The positive and negative electrodes on both ends of the assembled battery are connected to the positive and negative output terminals of the charger 5, respectively. The set voltage of each unit cell 1 is set to 3V, and the operating voltage of the switching circuit 4 is also set to 3V accordingly. The charger 5 is charged by a constant current at the beginning of charging and at a constant voltage at the end of charging, and the switching voltage is set to 90V. The unit cell 2 is in a discharged state at the beginning of charging.

First, when the battery pack in a discharged state is charged by the charger 5, since the terminal voltage of the battery pack is low at the initial stage, the battery charger 5 charges with a constant current. During that time, the terminal voltage of each cell is also low, so the switching circuit 4 is turned off.
In this state, the bypass circuit of unit cell 1 does not operate, and unit cell 1
Only charged. The voltage of the unit cell 1 gradually recovers as the charging progresses. However, the increase in the terminal voltage of each battery is not uniform due to the variation in the capacity, and a single battery with a small capacity reaches a high voltage quickly and a battery with a large capacity rises slowly. When the first one reaches 3V voltage,
The switching circuit 4 connected in parallel to it operates to form a bypass circuit, and a part of the charging current to the unit cell 1 is guided to the unit cell 2 through this bypass circuit.

In this way, the terminal voltage of the assembled battery is 90 when each battery reaches 3V as shown by the solid line in FIG.
The voltage becomes V and reaches the switching voltage of the charger 5, and the charging method changes from constant current charging to constant voltage charging. In this way, the assembled battery is continuously charged at a constant voltage, and when the charging current becomes 0 or close to it, it is determined that the battery is fully charged and the charging is stopped. By doing so, the state of charge of each unit cell 1 becomes uniform as shown by the dotted line in FIG. 2 before the bypass circuit 10 is connected, and as shown by the solid line, and the cycle life of the assembled battery is also as shown in FIG. It greatly extends from the dotted line to the solid line.

A concrete example of the bypass circuit is shown in FIG. The resistor R3 and the diode D are for setting a threshold value for inverting the output of the amplifier A, and constitute a comparator together with the amplifier A. The resistors R1 and R2 form a circuit that divides the terminal voltage of the unit cell 1 and detects the voltage together with the amplifier A. When the detected voltage reaches the threshold value, the output of the amplifier A is inverted. The transistor T that is turned on and off by the output of the amplifier A opens and closes the charging path to the unit cell 2.

When the assembled battery is charged, the terminal voltage of the unit cell 1 rises. The voltage is divided by the resistors R1 and R2 and then applied to the positive terminal of the amplifier A. When the applied voltage reaches the threshold voltage, the amplifier A is inverted, and accordingly, the transistor T changes from the OFF state to the ON state, and a part of the charging current is shunted from the unit cell 1 and flows to the unit cell 2. Charge it.

The structure of the unit cell is shown in FIG. Positive electrodes 12, 1
An electrode including 3 and a negative electrode 14 sandwiched between them and separators 15 and 16 provided for insulating between the positive electrode and the negative electrode are spirally wound and inserted in a cylindrical case 11.
The case 11 is connected to the negative electrode 14 as a negative electrode terminal. The unit cell 1 is formed by the positive electrode 12 and the negative electrode 14 on the inner periphery of the electrode, and the unit cell 2 is formed by the positive electrode 13 and the negative electrode 14 on the outer periphery. The positive electrodes 12 and 13 are connected to the control circuit 1 by the respective lead wires 17 and 18.
9 and the lead wire 17 is also the positive electrode 2
1 is also connected. A gasket 20 is fitted between the lid 21 and the case 11. The control circuit 19 is composed of the resistors R1, R2, R3, the diode D and the transistor T shown in FIG.

The present embodiment is configured as described above, and since each cell 1 is provided with the bypass circuit including the cell 2, the cell 1 is not overcharged and the cycle life can be extended. . Then, since the bypass current is consumed by the unit cell 2, heat generation due to the bypass current does not occur, and the bypass circuit can be supplied with power from the unit cell 2, and the energy use efficiency of the unit cell 1 is improved. Further, when a bypass circuit including the unit cell 2 is integrated with the unit cell 1,
It is also possible to prevent the assembled battery and the charging device from increasing in size.
Then, the integrated battery units are simply arranged and connected in series like a general cylindrical rechargeable battery, and the handling is easy.

In addition to the above effects, this embodiment can also obtain the following effects. Generally, when a battery reaches the end of its life, its capacity is significantly reduced. The standard is 10
We judge by decrease of%. In other words, whether or not the difference between the maximum capacity and the minimum capacity of each unit cell that constitutes the assembled battery is within 10% is used as a criterion for determination. To obtain the capacity difference, conventionally, the charging current is detected, the detected value is integrated with respect to time in each cell, and the charged amount of electricity is obtained from the integrated area. Although a complicated procedure such as obtaining the capacity difference from the difference has to be taken, according to the embodiment, since the cells with different capacities have different bypassed currents, the charge amount of the cell 2 in the bypass circuit is measured. By doing so, it is possible to obtain the capacity difference between the unit cells 1.

For example, if the cells 1 connected in series have exactly the same capacity and the like, no bypass current is generated and the charging amount of each cell 2 is 0. The result is 0. However, in reality, the terminal voltage of the unit cell 1 having a small capacity with respect to the charging current of the assembled battery shown by the solid line in FIG. 6 reaches the set voltage earlier than others.
As a result, the bypass current is generated, and the current flowing through the unit cell 1 is reduced as compared with the unit cell 1 in which the bypass current is not generated as shown by the dotted line. Therefore, the amount of electricity indicated by the hatched portion in FIG. 6 is charged in the unit cell 2, and this amount of electricity indicates the difference between the capacity of the unit cell 1 connected to it and the capacity of the unit cell 1 having the maximum capacity in the assembled battery. ing. The decrease in the capacity of the unit cell 1 is reflected in the charge amount of the unit cell 2.

By the way, if the capacity of the unit cell 2 is about 10% of the capacity of the unit cell 1, as described above, when the unit cell 2 is fully charged, the unit cells 1 connected in parallel with it have a limited life. Can be determined. In this embodiment, the unit cell 2
Since the non-aqueous secondary battery is used for the battery, there is a one-to-one relationship between the terminal voltage of the battery and the amount of electricity inside it. Therefore, by detecting the terminal voltage corresponding to full charge, the unit cell Can determine that he has reached the end of his life. In addition,
The unit cell 2 is not limited to the non-aqueous system, and any battery can be used as long as the terminal voltage correlates with the internal quantity of electricity.

[0020]

As described above, according to the present invention, a bypass circuit including a second battery having a small capacity is connected in parallel to each of the first cells forming the assembled battery, and a charging current is supplied to each of the cells. By controlling and charging the excess current to the second cell connected in parallel, the cycle life of the assembled battery is improved and the bypassed current can be used, and the energy of the first cell can be saved. It is possible to obtain an effect that the utilization factor is improved and at the same time, the heat generation due to the bypass current can be suppressed.

Furthermore, if the first cell and the second cell are provided in a common battery case and the electrodes are shared, the assembled battery can be made compact. Moreover, by measuring the capacities of the batteries connected in parallel, it is possible to easily measure the difference in charging capacity between the cells connected in series, and it is possible to easily determine the life of the unit cell 1 by the difference in capacity. it can. Since the charging means for charging the assembled battery charges at a constant current at the initial stage of charging and at a constant voltage at the final stage of charging, the bypass current value can be reduced. As a result, the second cell can receive the bypass current without generating heat.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a terminal voltage of each unit cell.

FIG. 3 is a diagram showing the relationship between the capacity of a battery pack and the number of cycles.

FIG. 4 is a circuit diagram showing a configuration of a bypass circuit.

FIG. 5 is a diagram showing a structure of an assembled battery.

FIG. 6 is a diagram showing a relationship between a bypass current and a capacity difference.

[Explanation of symbols]

 1, 1a, 1b, 2 Single cell 3 Voltage detection circuit 4 Switching circuit 5 Charger 10, 10a, 10b Bypass circuit 11 Case 12, 13 Positive electrode 14 Negative electrode 15, 16 Separator 17, 18 Lead wire 19 Control circuit 20 Gasket 21 Lid R1, R2, R3 resistance A amplifier D diode T transistor

Claims (4)

[Claims] 1. In an assembled battery in which a plurality of first cells are connected in series, a bypass circuit is connected in parallel to the first cells, and the bypass circuit is the first circuit.
The voltage detecting means for detecting the terminal voltage of the unit cell, the switching means, and the second unit cell, and the terminal voltage of the first unit cell when the battery pack is charged by the charging device. When it is detected and the detected value reaches a predetermined value,
An assembled battery, wherein the switching means is activated so that a charging current to the first unit cell flows to the second unit cell. 2. The assembled battery according to claim 1, wherein power supply to the bypass circuit is performed by the second unit cell. 3. The set according to claim 1, wherein the electrode of the first unit cell and the electrode of the second unit cell are provided in a common battery case and share a positive electrode or a negative electrode. battery. 4. In an assembled battery in which a plurality of first cells are connected in series, a bypass circuit is connected in parallel to the first cells, and the bypass circuit comprises the first cells.
The voltage detecting means for detecting the terminal voltage of the unit cell, the switching means, and the second unit cell, and the terminal voltage of the first unit cell when the battery pack is charged by the charging device. When it is detected and the detected value reaches a predetermined value,
What is claimed is: 1. A battery pack charging apparatus configured to operate the switching means so that a charging current for the first cell flows into the second cell, wherein the battery pack is charged with a constant current at the initial stage of charging. A battery charger for an assembled battery, comprising: a charging circuit that charges the battery at a constant voltage after the terminal voltage of the battery reaches a predetermined voltage value.