JP2003134686A - Battery charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery charger which can fully suppress unevenness in charging of each battery when a battery is fully charged until the end of charging and can suppress unevenness in charging of each battery caused by the battery charger as much as possible even when charging is stopped midway. SOLUTION: Charging circuits 11, 12, 13, and 14 are provided to a battery charger in correspondence with each combination of charging terminals 5, 6, 7, 8, and 9 which are adjacent according to the level of electric potential. After a charging current drops due to charging in a first charging state for supplying a current across a combination battery CB by connecting the charging circuits 11 to 14 in series, a charging control means CC of the battery charger CC makes a switching to a second charging state where each of the charging circuits 11 to 14 provides the charging current to the corresponding pair of the charging terminals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for charging an assembled battery formed by combining a plurality of cells in a state where the cells are electrically connected in series at at least one location. .

[0002]

2. Description of the Related Art A battery pack is a battery in which unit cells are combined in series or in parallel to form a single battery, and is used in various devices such as portable personal computers and electric vehicles. As a configuration of a charging device for charging such an assembled battery, a configuration in which a voltage is applied between a positive electrode and a negative electrode of the assembled battery to charge the battery has been generally used.

[0003]

However, in the above-mentioned conventional configuration, due to variations in charge and discharge characteristics of individual cells, one cell is in a fully charged state, while another cell is in an insufficiently charged state. As described above, the degree of charge varies among the unit cells. Therefore, the inventor of the present invention is
As illustrated in FIG. 2, which illustrates a case where four unit cells are connected in series to form an assembled battery, the unit cells 100, 101, 102, 10
The charging circuits 104, 105, 106, corresponding to the respective 3
107, each charging circuit 104, 105, 106,
107 corresponds to the unit cells 100, 101, 102, 1
I devised a configuration to charge 03. However, as a result of the study by the inventor of the present invention, in the configuration of the charging device shown in FIG. 2, when the individual cells are sufficiently charged and are fully charged until they are fully charged, the charging between the single cells is reduced. Although it is possible to charge while suppressing the variation in the degree sufficiently, if the charge is terminated midway before it becomes fully charged, the variation in the degree of charging between individual cells may occur due to the charging device itself. I found out that

The cause will be described with reference to the charging characteristics illustrated in FIG. That is, at the start of charging, the assembled battery is charged with a constant current, and when charging progresses and the terminal voltage of the battery reaches a certain set voltage, thereafter, when charging by a general charging method of charging at the set voltage, Ideally, in the constant current charging region, by charging at a constant current value shown by "Ia" in FIG. 3, the voltage across the unit cell "V
The voltage gradually increases from "b" and when the voltage reaches the set voltage "Va", the voltage "Va" is maintained and charging in the constant voltage region is continued. Therefore, in FIG. 3, the charging proceeds along the route of the straight line C-the straight line A.

However, in reality, the charging circuits 105, 1
Regarding the charging of the single cells 101 and 102 by 06, the charging proceeds along the route of the straight line C-the straight line A, but the charging circuit 10
Regarding the charging of the single cells 100 and 103 by 4, 107, the charging progresses along the route of the straight line C-the straight line B in FIG. It was found that if the operation was stopped halfway, there would be a variation in the degree of charging corresponding to the voltage difference between the straight line A and the straight line B. Here, the charging progresses along the path of the straight line C-the straight line B is that the currents flowing through the respective charging terminals are I1, I2, I3, I4 and I5 as shown in FIG. The loop current formed by
2, i3 and i4, I2, I3 and I4 have loop currents (i1 and i2, i2 and i2) of adjacent loops.
3, i3 and i4) cancel each other and only a weak current flows, whereas a large charging current (current direction is opposite) flows for I1 and I5, causing a voltage drop due to wiring resistance.
It can be explained that even if the output terminal of the charging circuit is at the set voltage "Va", the voltage shifts to the constant voltage charging region while a voltage lower than the voltage drop of the wiring is applied between the terminals of the unit cell.

In addition to this, the charging current "Ia" in the constant current charging region also varies among the individual cells due to variations in the characteristics of the circuit components, etc., which also causes variations in the degree of charging between the individual cells. Will cause it. The present invention has been made in view of the above circumstances, and an object thereof is to perform charging during charging while sufficiently suppressing variation in the degree of charging of each unit cell when the battery is reliably charged until completion of charging. Even when the battery is stopped, the variation in the degree of charging of each cell due to the charging device is suppressed as much as possible.

[0007]

By providing the structure according to claim 1, a plurality of cells are combined in a state where the cells are electrically connected in series at at least one location. In a charging device for charging an assembled battery, at least one charging terminal among intermediate charging terminals drawn out from a location where the unit cell and the unit cell are connected in series, which is drawn out from a positive electrode of the assembled battery. In order to perform a charging operation with respect to the charging terminal for the positive electrode and the charging terminal for the negative electrode pulled out from the negative electrode of the assembled battery,
A charging circuit is provided corresponding to each combination of adjacent charging terminals having high and low potentials among these charging terminals, and charging control for switching and controlling the connection state between the charging circuit and the charging terminal. Means is provided, and the charge control means electrically connects the DC outputs of the charging circuits in series and disconnects the electrical connection between the charging circuits and the intermediate charging terminal from the positive electrode. Is set to a first charging state in which charging power is supplied between the charging terminal for charging and the charging terminal for the negative electrode, and the charging current of the charging circuit decreases after charging in the first charging state. Each one
It is configured to perform switching control to a second charging state in which charging power is supplied to a pair of corresponding charging terminals.

That is, in the case of charging an assembled battery formed by combining a plurality of cells in a state where the cells are electrically connected in series at at least one place, the charging circuit is finally charged. By charging in the second charging state in which charging power is supplied to the corresponding pair of charging terminals, the variations in the degree of charging between the single cells can be sufficiently suppressed. However, if the battery is charged in the second charging state from the beginning of the charging period, as described above, the charging device itself may vary the degree of charging between the single cells when the charging is stopped halfway. There is. Therefore, before the charging period in the second charging state, the DC output of each charging circuit is electrically connected in series and the electrical connection between each charging circuit and the intermediate charging terminal is disconnected. , Charging in the first charging state in which charging power is supplied between the positive electrode charging terminal of the assembled battery and the negative electrode charging terminal of the assembled battery, and charging to the extent that the effect of voltage drop due to wiring does not matter. After the current has become sufficiently small, the second charge state is entered.

By charging in such a form, the charging device does not increase the variation in the degree of charging between individual cells, and particularly when charging by constant current charging. In the above, even if the supply current value varies among the charging circuits, the current supplied to the battery pack is limited to the lowest supply current value among the supply current values of the charging circuits. The degree of charge of each single cell does not vary due to the variation in the value. Therefore, when the battery is fully charged until the completion of charging, the degree of charge of each battery due to the charger is maintained even when the charging is stopped during charging while sufficiently suppressing the variation in the charging level of each battery. The variation can be suppressed as much as possible.

Further, by providing the structure according to claim 2, the assembled battery is configured by electrically connecting the unit cells in series, and all the locations where the unit cells and the unit cells are connected in series. All of the charging terminals among the intermediate charging terminals drawn from, the charging terminal for the positive electrode drawn from the positive electrode of the assembled battery and the charging terminal for the negative electrode drawn from the negative electrode of the assembled battery. In order to perform charging operation to the charging terminals, a charging circuit is provided corresponding to each of the combinations of the charging terminals adjacent to each other of the charging terminals having high and low potentials.

That is, the assembled battery to be charged is configured by simple series connection of single cells, and all series connection points are
When the charging terminals are drawn out from the positive electrode and the negative electrode of the assembled battery, a charging circuit is provided corresponding to each unit cell, and charging is performed by switching between the first charging state and the second charging state. As a result, variations in the degree of charge of individual cells can be reliably suppressed, and even if the charging is stopped at the stage when charging is not completed, variations in the degree of charging between cells will increase. Can be prevented.

Further, by providing the structure according to the third aspect, an assembled battery composed of a single cell of a lithium ion battery is charged by the charging device having the above structure. That is, in nickel-hydrogen batteries and lead storage batteries, if the batteries are slightly overcharged, the variation in the degree of charge between the individual batteries tends to converge, but in the lithium-ion battery, once the individual batteries are temporarily charged between the individual batteries. When the degree of charging varies, the variation tends to remain as it is. Therefore, it is particularly suitable to apply the charging device having the above-described configuration to charging an assembled battery composed of single cells of a lithium ion battery.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a charging device of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the charging device CH of the present embodiment targets a battery pack CB configured by combining the single batteries SB for charging.

[Structure of Battery Pack CB] The battery pack CB has a structure in which at least one unit cell SB and unit cell S are arranged.
A plurality of unit cells SB with B electrically connected in series
It is configured by combining, and more specifically,
The assembled battery CB is composed of single cells SB of the same type, and all these single cells SB are electrically connected in series and housed in one package. In the present embodiment, four lithium-ion batteries 1, 2, 3, 4 each of which is a single battery SB are used.
An example of an assembled battery CB configured by connecting in series is shown. A plurality of charging terminals are drawn from the assembled battery CB, and three intermediate charging terminals 5, 6 and 7 drawn from all three locations where the unit cells SB and the unit cells SB are connected in series. ,
The positive electrode of the assembled battery CB, that is, the cell SB on the highest potential side
The charging terminal 8 for the positive electrode drawn out from the positive electrode of the (lithium ion battery 1) and the negative electrode drawn out from the negative electrode of the assembled battery CB, that is, the negative electrode of the single battery SB (lithium ion battery 4) on the lowest potential side. The charging terminal 9 and the charging terminal 9 are integrated in one connector 10.

[Structure of Charging Device CH] The charging device CH includes four charging circuits 11, 12, 13, and 14, and each charging circuit and charging terminals 5, 6, 7, and 8 on the assembled battery CB side. Switches 15, 16, 17, 18 as circuit switching means for switching electrical connection and connector 1 on the assembled battery side
The charging device side connector 24 having DC output terminals 19, 20, 21, 22, 23 for connecting to the charging terminals 5, 6, 7, 8, 9 of 0 and a relay or a semiconductor switch. Switch 15, 16, 17, 18
A charging control circuit 25 is provided as a charging control means CC for controlling the opening / closing of the charging circuit 11, 12, 13, 14 and switching the connection state between the charging circuits 11, 12, 13, 14 and the charging terminals 5, 6, 7, 8. .

The charging circuits 11, 12, 13 and 14 charge all of the intermediate charging terminals 5, 6 and 7 drawn out from all the locations where the unit cells SB and the unit cells SB are connected in series. In order to perform charging operation on the charging terminals 5, 6, 7 and the charging terminal 8 for the positive electrode drawn from the positive electrode of the assembled battery CB and the charging terminal 9 for the negative electrode drawn from the negative electrode of the assembled battery CB, The charging terminals 5, 6, 7, 8 and 9 are provided corresponding to respective combinations of adjacent charging terminals having high and low potentials. The charging circuit 11 corresponds to the charging terminal 8 and the charging terminal 5, the charging circuit 12 corresponds to the charging terminal 5 and the charging terminal 6, and the charging circuit 13 corresponds to the charging terminal 6 and the charging terminal. Corresponding to 7 and charging circuit 14
Is provided corresponding to the charging terminal 7 and the charging terminal 9,
The DC outputs of the charging circuits 11, 12, 13, 14 are electrically connected in series.

The charging circuits 11, 12, 13 and 14 have exactly the same circuit configuration, and in this embodiment, they are configured as a constant voltage source having an output current limiting circuit. May be, for example, a switching regulator. The input side of each charging circuit 11, 12, 13, 14 is
It is connected to a commercial AC line via a power switch 26. The charge control circuit 25 includes a logic circuit and other peripheral circuits, but may include a microcomputer chip.

[Charging Control by Charging Control Circuit 25] Next, the control of the charging state by the charging control circuit 25 will be described with reference to the charging characteristics of FIG. Since FIG. 3 shows the charging characteristics of a single battery, the voltage values themselves are different, but the shape of the characteristics is the same. When the power switch 26 is closed while the connector 10 on the assembled battery CB side and the connector 24 on the charging device side are connected, energization of the charging control circuit 25 is started. The charge control circuit 25 closes the switch 15 with the start of energization and maintains the open state of the switches 16, 17, and 18. That is, the DC outputs of the charging circuits 11, 12, 13, 14 are electrically connected in series and the charging circuits 11, 12, 13, 1 are connected.
4, charging electric power is supplied between the positive electrode charging terminal 8 and the negative electrode charging terminal 9 in a state where the electrical connection between the intermediate charging terminal 4 and the intermediate charging terminals 5, 6, 7 is disconnected. Set to the first charge state.

In this initial state, the voltage across the assembled battery CB (that is, the potential difference between the charging terminal 8 and the charging terminal 9) is lower than the sum of the set voltages of the charging circuits 11, 12, 13, and 14. Therefore, each charging circuit 11, 12, 13, 1
The limiting current value of the output current limiting circuit 4 is supplied to the battery pack CB as the charging current Ia, and the battery pack CB is charged by constant current charging. As a result, the voltage across the assembled battery CB is shown in FIG.
Rises along the straight line C at. Each charging circuit 1
When the limiting current value of the output current limiting circuit varies among 1, 12, 13, and 14, the charging current Ia is the minimum limiting current of the limiting current values of the charging circuits 11, 12, 13, and 14. Specified by value.

When the voltage across the assembled battery CB approaches the sum of the set voltages of the charging circuits 11, 12, 13, and 14 as the charging progresses, the constant current charging automatically shifts to the constant voltage charging. In the constant voltage charging region, due to the voltage drop between the positive electrode of the charging circuit 11 and the positive electrode of the assembled battery CB and the negative voltage of the negative electrode of the assembled battery CB and the negative electrode of the charging circuit 14,
Charging proceeds along the straight line B in FIG. 3, the voltage across the assembled battery CB gradually rises, and the charging current gradually decreases. The charging control circuit 25 maintains the closed state of the switch 15 when the charging current is sufficiently reduced due to the progress of charging in the first charging state, and the switch 16,
By closing 17 and 18, the charging circuit 11, 12, 13,
Each of 14 controls switching to a second charging state in which charging power is supplied to the corresponding pair of charging terminals. That is, the charging circuit 11 charges the pair of the positive charging terminal 8 and the intermediate charging terminal 5, and the charging circuit 12 charges the pair of the intermediate charging terminal 5 and the intermediate charging terminal 6. The circuit 13 supplies the charging current to the pair of the intermediate charging terminal 6 and the intermediate charging terminal 7, and the charging circuit 14 supplies the charging current to the pair of the intermediate charging terminal 7 and the negative charging terminal 9, respectively. To supply.

The charging control circuit 25 informs the DC output terminal 19 that the charging current in the first charging state has sufficiently decreased.
This is detected by monitoring the potential difference between the potential in the vicinity and the potential in the vicinity of the DC output terminal 23, and for example, the voltage value V that is a sufficiently low charging current value Ith illustrated in FIG.
When the potential difference rises to th, the first charging state is switched to the second charging state. By charging in the second charge state, each lithium ion battery 1, 2, 3,
4 is charged in a well-balanced state to reach full charge, and even when charging is stopped in the middle of the first charging state, the lithium ion batteries 1, 2,
It is possible to prevent the charging degree of 3 and 4 from being varied.

[Other Embodiments] Other embodiments of the charging device of the present invention will be listed below. (1) In the above embodiment, the lithium-ion battery is illustrated as the unit cell SB that constitutes the assembled battery CB.
The charging device of the present invention can be used for charging the assembled battery CB in which various secondary batteries such as Ni-hydrogen battery and Ni-Cd battery are used as the single battery SB. (2) In the above-described embodiment, the assembled battery CB is illustrated as a case where four unit cells SB are connected in series. However, it goes without saying that the number of unit cells to be used may be increased or decreased and the number of unit cells may be parallel. The present invention can be applied even when the connection method of the unit cells is changed in various ways, such as by connecting a plurality of connected unit cells SB in series, and the unit cells SB are provided at at least one location.
The present invention can be applied to any assembled battery in which the unit cell SB and the unit cell SB are electrically connected in series.

(3) In the above-described embodiment, the charging terminals are drawn from all the locations where the unit cells SB and the unit cells SB of the battery pack CB are electrically connected in series, but it is not necessary to connect all of them in series. It is not necessary to draw it out from a place. For example, when a plurality of unit cells SB are connected in series to form a battery pack CB as in the above embodiment, the charging terminals are drawn out from every other series connected place. Is also good. (4) In the above embodiment, the charging circuits 11, 12, 1
3, 14 are configured as a constant voltage source having an output current limiting circuit, and the battery pack C is switched between constant current charging and constant voltage charging.
Although the case of charging B is illustrated, for example, a constant voltage source and a constant current source are separately provided to configure a charging circuit.
The specific configuration of the charging circuit can be changed in various ways. (5) In the above embodiment, the detection of the decrease in the charging current for setting the switching timing from the first charging state to the second charging state is performed by detecting the DC output terminal 19 and the DC output terminal 2.
Although it is performed by detecting the potential difference with respect to No. 3, for example, the required charge amount until full charge is estimated from the voltage across the assembled battery CB at the start of charging, and the actual charge current is integrated to calculate the charge amount. It may be configured to detect that the charging current is sufficiently reduced when the charging amount approaches the required charging amount to some extent, or alternatively, the charging current is directly detected and The determination may be made based on the detected value, and the method for detecting the decrease in the charging current can be variously changed.

(6) In the above embodiment, among all the intermediate charging terminals 5, 6, 7, the charging terminal 8 for the positive electrode of the assembled battery CB and the charging terminal 9 for the negative electrode of the assembled battery CB. The charging circuits 11, 12, 13, and 14 are provided corresponding to the combinations of the adjacent charging terminals depending on the level of the potential of the charging terminals. For example, among the three intermediate charging terminals 5, 6, and 7, The charging terminal 6 is selected from among the charging terminals 6, the charging terminal 8 for the positive electrode, and the charging terminal 9 for the negative electrode, and the total corresponding to each combination of the charging terminals adjacent to each other according to the potential level. May be configured to include two charging circuits. For the charging terminal 8 for the positive electrode and the charging terminal 9 for the negative electrode, the existence of the charging circuit connected to these charging terminals is essential. However, the charging circuit is not connected to the intermediate charging terminal. May be that. That is, at least one charging terminal of the intermediate charging terminals drawn out from the location where the cells are connected in series,
In order to charge the positive electrode charging terminal drawn out from the positive electrode of the assembled battery and the negative electrode charging terminal drawn out from the negative electrode of the assembled battery, the potential of one of these charging terminals It suffices that a charging circuit is provided corresponding to each combination of high and low adjacent charging terminals.

[0025]

According to the configuration of the first aspect, the charging device switches between the single cells by switching to the second charging state after the charging current is reduced by the charging in the first charging state. Does not increase the variation in the degree of charging of the battery pack, and especially when charging by constant current charging, even if the supply current value varies between charging circuits, the battery pack Since the current supplied to the charging circuit is limited to the lowest supply current value among the supply current values of the charging circuits, the degree of charging of each unit cell does not vary due to the dispersion of the supply current value. . Therefore, when the battery is fully charged until the charging is completed, while sufficiently suppressing the variation in the degree of charging of each single battery,
Even when charging is stopped during charging, it has become possible to suppress variations in the degree of charging of individual cells due to the charging device as much as possible.

Further, according to the configuration of the above-mentioned claim 2, the assembled battery to be charged is configured by simple series connection of the unit cells, and the charging circuit is provided corresponding to each unit cell. , The variation in the degree of charge of individual cells is surely suppressed, and the variation in the degree of charge between cells is prevented from expanding even if the charging is stopped at the stage when the charging is not completed. it can. Further, according to the configuration of the above-mentioned claim 3, by applying the present invention to the charging of the assembled battery of the lithium ion battery in which variations in the degree of charging tend to occur between the single cells, the charging of individual lithium ion batteries can be performed. It is possible to reliably suppress the variation in the degree, and to prevent the variation in the degree of charging between the single cells from expanding even if the charging is stopped at the stage where the charging is not completed.

[Brief description of drawings]

FIG. 1 is a schematic circuit configuration diagram of a charging device according to an embodiment of the present invention.

FIG. 2 is a schematic circuit configuration diagram of a conventional charging device.

FIG. 3 is a diagram illustrating charging characteristics.

[Explanation of symbols]

CC charging control means CB battery pack SB single battery 1,2,3,4 lithium-ion battery 5,6,7 Intermediate charging terminals 8 Charging terminal for positive electrode 9 Charging terminal for negative electrode 11, 12, 13, 14 Charging circuit

Claims (3)

[Claims] 1. A charging device for charging an assembled battery configured by combining a plurality of cells in a state in which the cells are electrically connected in series at at least one location, the battery comprising: From at least one charging terminal of the intermediate charging terminals drawn out from the location where the unit cells are connected in series, the charging terminal for the positive electrode drawn from the positive electrode of the assembled battery, and the negative electrode of the assembled battery. In order to perform a charging operation on the drawn charging terminal for the negative electrode, a charging circuit is provided corresponding to each of the combinations of the charging terminals adjacent to each other at high and low potentials of these charging terminals, Charging control means for switching and controlling the connection state between the charging circuit and the charging terminal is provided, and the charging control means electrically connects in series the DC output of each charging circuit and each charging circuit. And a first charging state in which charging power is supplied between the charging terminal for the positive electrode and the charging terminal for the negative electrode in a state where the electrical connection between the intermediate charging terminal and the intermediate charging terminal is disconnected, After the charging current decreases due to the charging in the first charging state, each of the charging circuits is configured to perform switching control to the second charging state in which charging power is supplied to the corresponding pair of charging terminals. Charging device. 2. The assembled battery is configured by electrically connecting the unit cells in series, and among the intermediate charging terminals drawn out from all locations where the unit cells and the unit cells are connected in series. All charging terminals,
In order to charge the positive electrode charging terminal drawn out from the positive electrode of the assembled battery and the negative electrode charging terminal drawn out from the negative electrode of the assembled battery, the potential of one of these charging terminals The charging device according to claim 1, wherein a charging circuit is provided corresponding to each combination of high and low adjacent charging terminals. 3. The charging device according to claim 1, wherein the unit cell is a lithium ion battery.