JPH07105986A - Battery pack - Google Patents

Abstract

PURPOSE:To certainly prevent overcharge and overdischarge of built-in battery cells with the output voltage of a single voltage sensing terminal. CONSTITUTION:A battery pack includes a plurality of built-in battery cells which are rechargeable and is equipped with a cell voltage sensing circuit 3 to sense the voltage of each cell 1. The cell voltage sensing circuit 3 is connected with a voltage sensing terminal 2 via a maximum voltage output circuit 4 or a minimum voltage output circuit 5. The two circuits 4, 5 select only the cell voltage of the battery cell 1 whose voltage exhibits maximum or minimum and give the resultant to the voltage sensing terminal 2 so that the battery cells are precluded from overcharge and overdischarge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery pack which can prevent overcharge or overdischarge of a plurality of battery cells incorporated therein.

[0002]

2. Description of the Related Art In a battery pack, by connecting a plurality of battery cells in series and incorporating the battery cells, the total output of the battery pack can be made the total voltage of each battery cell. You can take it out.
Further, since various voltages can be created by adjusting the number of connected battery cells, it is suitable as a power source for various electric devices. It is desirable that the battery cells contained in this battery pack be rechargeable batteries that can be used any number of times.

When charging the battery cells contained in the battery pack, it is difficult to take out each battery cell from the battery pack, so the output terminals and charging terminals provided on the battery pack are used to connect in series. Often, the charged battery cells are simultaneously charged. At this time, since the battery cells are connected in series, the charging currents flowing through the battery cells are the same. However, even if the charging currents are the same, if the capacities and terminal voltages of the individual battery cells are varied, the battery voltage also begins to rise and reaches full charge.

Therefore, when all the battery cells are to be charged to full charge, the battery cells having a large remaining capacity are fully charged, and thereafter, the charging proceeds and the battery cells having a small remaining capacity are fully charged. Therefore, a battery cell with a large remaining capacity will be overcharged. Further, regarding the battery cells having a high terminal voltage, when the battery cells having a low terminal voltage reach a predetermined voltage increase due to full charge, the voltage of the battery cells having a high terminal voltage further increases. Battery cells that cause such overcharge and abnormal rise in terminal voltage are
There is a risk of significant deterioration and heat generation, resulting in danger.

In order to prevent this adverse effect, a charging circuit has been developed which controls the charging by detecting the voltage of each of a plurality of battery cells (Japanese Patent Laid-Open No. 5-64377).
The charging circuit described in this publication, as shown in FIG.
In order to detect the voltage of each battery cell, the same number of cell voltage detection circuits 3 as the battery cells 1 are provided. The set of cell voltage detection circuits 3 independently detects the voltage of one battery cell.

[0006]

In the charging circuit shown in this figure, when one of the battery cells is fully charged, this is detected by the cell voltage detection circuit and the charging can be terminated. Even if the capacity of each battery cell varies, when one of the battery cells is fully charged, the charging can be stopped and the deterioration of the battery performance can be prevented.

However, the charging circuit of this structure detects the voltage of the battery cells contained in the battery pack and outputs them to the charger independently, so that the same number of voltage detection terminals 2 as the battery cells are provided. Need. However, the battery pack has a drawback that as the number of voltage detection terminals increases, a failure such as a contact failure is more likely to occur. When a contact failure occurs at the voltage detection terminal, the charger cannot accurately detect the charging voltage of each battery cell, and it becomes impossible to reliably prevent overcharge of the battery cell.

Next, when the battery pack is used as a power source for various electric devices, the battery cells contained in the battery pack discharge their remaining capacities. However, if there are variations in the remaining capacity and discharge characteristics of each battery cell,
Variation occurs in the time for which the remaining capacity of each battery cell is consumed. That is, the battery cells connected in series in the battery pack include battery cells that consume the remaining capacity quickly even if they uniformly consume the capacity, and battery cells that still have the remaining capacity. . Therefore, if it is attempted to consume all the remaining capacity of each battery cell in all the battery cells in the battery pack, the battery cell that consumes the remaining capacity quickly becomes over-discharged and causes deterioration. In order to prevent over-discharge, it is necessary to stop using the battery pack in time with the battery cells that consume the remaining capacity. However, in order to realize this structure, the cell voltage and the remaining capacity of each battery cell must be monitored, and a plurality of detection terminals must be provided. If a plurality of detection terminals are provided in this way, there is a drawback in that poor contact is likely to occur, as described above.

The present invention was developed with the object of resolving this drawback, and an important object of the present invention is to overcharge a plurality of built-in battery cells with a single voltage detection terminal. Alternatively, it is to provide a battery pack that can reliably prevent over-discharge.

[0010]

The battery pack of the present invention comprises:
In order to achieve the above-mentioned object, the following configurations are provided. The battery pack contains a plurality of rechargeable battery cells 1. Further, the battery pack detects the voltage corresponding to the cell voltage of the battery cell 1 which is the maximum or minimum voltage, from the voltage detection terminal 2
Output from. The voltage corresponding to the cell voltage of the battery cell 1 having the maximum or minimum voltage is a voltage obtained by multiplying the maximum voltage or the minimum voltage by a constant coefficient. When the coefficient is 1, the voltage of the battery cell is output from the voltage detection terminal at the same voltage value.

The battery pack that outputs the maximum voltage of the battery cell has the following structure. The battery pack contains a cell voltage detection circuit 3 that detects the voltage of each battery cell 1. The cell voltage detection circuit 3 has a maximum voltage output circuit 4
Is connected to the voltage detection terminal 2 via. The maximum voltage output circuit 4 selects the maximum voltage from the cell voltages of the individual battery cells 1 and outputs it to the voltage detection terminal 2.

The battery pack that outputs the minimum voltage of the battery cell 1 includes a cell voltage detection circuit 3 that detects the voltage of each battery cell 1 and a voltage detection terminal 2 through a minimum voltage output circuit 5.
Connected to. The minimum voltage output circuit 5 selects the minimum voltage from the cell voltages of the individual battery cells 1 to select the voltage detection terminal 2
Output to

[0013]

According to the battery pack of the present invention, each cell voltage detection circuit 3 detects the cell voltage of each battery cell 1. Then, the maximum voltage output circuit 4 selects only the maximum voltage from the individual cell voltages detected by the cell voltage detection circuits 3 and outputs the voltage corresponding to the maximum cell voltage to the voltage detection terminal 2. . The voltage detection terminal 2 does not separately output the voltage of each battery cell. Only the cell voltage of the battery cell having the maximum or minimum voltage is selected and output. When charging the battery pack, the voltage detection terminal 2 outputs a voltage corresponding to the cell voltage of the battery cell having the maximum voltage. As described above, the battery pack of the present invention that detects and outputs only the maximum voltage from the cell voltages of the individual battery cells reaches the full charge earliest from the plurality of battery cells or the cell voltage increases. For a battery cell, it is possible to know when full charge has arrived and when the cell voltage has risen. Therefore, charging can be stopped before any battery cell is overcharged or abnormally increased in cell voltage. As a result, it is possible to prevent overcharge and abnormal increase in cell voltage for all battery cells, suppress deterioration of the battery cells, and repeatedly use the battery pack for a long period of time.

Further, the voltage detection terminal 2 outputs a voltage corresponding to the cell voltage of the battery cell 1 having the lowest voltage when the battery pack is discharged. The battery cell with the lowest cell voltage among the battery cells 1 when discharging the battery pack is the battery cell 1 that consumes the remaining capacity earliest and is over-discharged when the battery is further discharged. The battery pack of the present invention selects only the minimum voltage from the cell voltages of the battery cell 1 and outputs the voltage corresponding to this to the voltage output terminal 2. Therefore, the discharge can be stopped before any battery cell is over-discharged.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. However, the examples described below exemplify a battery pack for embodying the technical idea of the present invention, and the present invention does not specify the structure of the battery pack as follows.

Further, in this specification, for easy understanding of the claims, the numbers corresponding to the members shown in the embodiments are referred to as "claim column", "action column", and "action column". It is added to the members shown in the section of "Means for Solving the Problems". However, the members shown in the claims are
It is by no means specific to the members of the examples.

The battery pack shown in FIG. 2 has three batteries in a case.
Each battery cell 1, a set of three cell voltage detection circuits 3 and a maximum voltage output circuit 4 are incorporated. The case is provided with a +-output terminal 6 and a single voltage detection terminal 2 that outputs the maximum voltage of the battery cell 1.

The battery cell 1 is a rechargeable secondary battery in which three battery cells 1 are connected in series. In the battery cell 1,
Non-aqueous secondary batteries such as lithium-ion secondary batteries and secondary batteries such as nickel-cadmium batteries and nickel-hydrogen batteries are used, but in order to increase the output voltage with a small number and to make it compact and have a large capacity Is most suitable for a lithium ion secondary battery. The battery cells 1 connected in series have the positive electrode and the negative electrode connected to the output terminal 6.

The cell voltage detection circuit 3 includes three battery cells 1
Independently detect the voltage of. This cell voltage detection circuit 3 includes a differential amplifier 8 having a diode 7 connected to the output side.
Equipped with. The differential amplifier 8 has a + side input terminal connected to the + pole of the battery cell 1 and a − side input terminal connected to the − side of the battery cell 1. The differential amplifier 8 can adjust the output voltage with respect to the voltage of the battery cell 1 by adjusting the amplification factor with the resistance value of the resistor connected to the input side and the output side. Preferably, the differential amplifier 8 outputs the same voltage as the voltage of the battery cell 1 with an amplification factor of 1.

The maximum voltage output circuit 4 is composed of a buffer amplifier 9 which is a differential amplifier. In this maximum voltage output circuit 4, the outputs of the three sets of cell voltage detection circuits 3 are connected to the + side input terminal of the buffer amplifier 9 via the diode 7, and the output terminal 6 is connected to the voltage detection terminal 2. . In order to set the amplification factor of the buffer amplifier 9 to 1, the buffer amplifier 9 has a − side input terminal connected to the output side. The buffer amplifier 9 that constitutes the maximum voltage output circuit 4 is
The maximum voltage of the cell voltage detection circuit 3 is input to the side input terminal via the diode 7. Therefore, the voltage output from the maximum voltage output circuit 4 becomes the maximum voltage of the three battery cells 1. Furthermore, this circuit is based on the cell voltage detection circuit 3
Since the amplification factor of the maximum voltage output circuit 4 is 1,
The maximum voltage of each battery cell 1 is output from the voltage detection terminal 2 as the same voltage. As described above, the battery pack in which the voltage detection terminal 2 outputs the same voltage as the maximum voltage of the battery cell 1 has a feature that circuit adjustment can be easily performed.

As shown in FIG. 2, the battery pack having this structure is charged by the charger 10 which detects the voltage at the voltage detection terminal 2 and controls the charging current. The charger 10 includes a DC power supply 11, a switching element 12 that controls a charging current,
And a comparator 13 for controlling the switching element 12. In the comparator 13, the reference power source 14 is connected to the + side input terminal, the − side input terminal is connected to the voltage detection terminal 2, and the output side is connected to the base of the transistor which is the switching element 12.

This charger performs the following operation to charge the battery pack. At the beginning of charging the battery pack, the switching element 1
2 is turned on. The voltage input to the-side input terminal of the comparator 13 is lower than the voltage of the reference power supply 14,
This is because the comparator 13 outputs a + signal and supplies a base current to the transistor that is the switching element 12 to turn it on. When the charging of the battery cells 1 progresses and one of the battery cells 1 is fully charged, the switching element 12 is turned off and the charging of the battery pack is stopped. When one of the battery cells 1 is fully charged, the voltage output from the voltage detection terminal 2 becomes higher than the voltage of the reference power source 14 of the comparator 13, the output of the comparator 13 becomes negative, and the switching element 12 becomes negative. This is because the base current of does not flow. Therefore, the battery pack and the charger shown in FIG. 2 are stopped when one of the battery cells 1 is fully charged.

Further, FIG. 3 shows a specific example in which the switching circuit 15 for stopping charging is also incorporated in the battery pack. The battery pack shown in this figure includes two battery cells 1,
Two sets of cell voltage detection circuits 3, a maximum voltage output circuit 4,
It has a built-in switching circuit 15. The cell voltage detection circuit 3 and the maximum voltage output circuit 4 operate in the same manner as the circuit shown in FIG. 2 to output the large voltage of the two battery cells 1 to the voltage detection terminal 2.

The switching circuit 15 includes a switching element 16 connected to the battery cell 1 and a comparator 17 for controlling the switching element 16 on / off. The switching element 16 is a FET, and the comparator 1
On / off control is performed by the output of 7. Comparator 17 is +
When outputting a signal, the switching element 16 is turned on, −
It turns off when a signal is output. Switching element 1
When 6 is turned off, the negative electrode of the battery cell 1 is electrically disconnected from the output terminal 6 and charging is stopped. The comparator 17 connects the − side input terminal to the diode 7 on the output side of the cell voltage detection circuit 3 and the + side input terminal to the reference power supply 18, and compares the output voltage of the cell voltage detection circuit 3 with the reference power supply 18. . The output voltage of the cell voltage detection circuit 3 is the reference power source 1
When the voltage becomes higher than the voltage of 8, the output of the comparator 17 becomes a negative signal, and the voltage of the cell voltage detection circuit 3 becomes the reference power source 1.
Outputs a + signal when higher than 8. Comparator 1
The + signal of 7 turns on the switching element 16, and the − signal turns off the switching element 16. The reference power source 18 connected to the comparator 17 built in the battery pack is
The voltage is preferably slightly higher than that of the reference power source 14 of the charger 10. If the reference power source 18 connected to the comparator 17 of the battery pack is set to be slightly higher than the reference power source 14 of the charger, the switching element 12 of the charger is normally used.
When the charger 10 cannot stop the charging, the switching element 1 built in the battery pack itself is stopped.
It is possible to forcibly stop charging at step 6. For this reason,
The dual protection circuit has the feature that it can prevent overcharging of battery cells more reliably.

However, the reference power source 18 connected to the battery pack comparator 17 can be set to be slightly lower than the reference power source 14 connected to the charger comparator 13.
In the battery pack having this structure, when the battery cell 1 is fully charged, the switching element 16 of the battery pack is turned off and the charging is stopped.
When 6 is not turned off, the switching element 12 of the charger is turned off, and overcharging of the battery cells is protected by both the battery pack and the charger.

Further, the battery pack of the present invention can prevent the over-discharge by detecting the minimum voltage of the battery cell.
This circuit is shown in FIG. The battery pack in this figure
Two battery cells 1 of the same type as the battery pack shown in FIG. 2 are connected in series, and in order to detect the voltage of each battery cell 1, two sets of cell voltage detection circuits 3 are built in. A minimum voltage output circuit 5 is also incorporated to detect the minimum voltage of the voltage detection circuit 3.

The cell voltage detection circuit 3 is a circuit similar to the battery pack shown in FIG. 2, and detects and outputs the voltage of the battery cell 1 in the same manner. The minimum voltage output circuit 5 includes a comparator 19 that compares the output voltages of the two sets of cell voltage detection circuits 3 and outputs a +-signal, a parallel switching circuit 20 that is switched by the comparator 19, and a parallel switching circuit 20. A serial switching circuit 21 that is switched and connects the output side of one of the cell voltage detection circuits 3 to the voltage detection terminal 2 and an inverting amplification circuit 22 that inverts the output signal of the comparator 19 are provided.

The parallel switching circuit 20 and the series switching circuit 21 are two sets of FETs connected in parallel or in series. There are two sets of the parallel switching circuit 20 and the series switching circuit 21, respectively, and when one is on, the other is off. Two sets of parallel switching circuits 20 are connected to the output side of the comparator 19, but one parallel switching circuit 20 is directly connected and the other parallel switching circuit 20 is connected to the inverting amplifier circuit 2.
2 is connected. The two sets of parallel switching circuits 20 connected in this way are output signals of the comparator 19, and when one is on, the other is off. This is because the +/- reverse signal is input by the inverting amplifier circuit 22.

The serial switching circuit 21 connects the gate of the FET to the source of the parallel switching circuit 20. Therefore, the FET of the serial switching circuit 21
When the parallel switching circuit 20 is turned on, a bias voltage is input to the gate with respect to the drain to turn on. On the contrary, when the parallel switching circuit 20 is turned off, the bias voltage is not input to the gate, and the series switching circuit 21 is turned off.

The minimum voltage output circuit operates as follows to output the minimum voltage of the cell voltage detection circuit to the voltage detection terminal. [When the voltage of the upper battery cell is lower than the voltage of the lower battery cell in FIG. 4] In this state, the output of the comparator 19 becomes +.
This is because the + side input terminal of the comparator 19 becomes larger than the − side input terminal. When the output of the comparator 19 is +, the FET of the parallel switching circuit 20 on the upper side is turned on, and the parallel switching circuit 20 on the lower side is turned off. This is because the bias voltage is applied to the gate of the FET of the upper parallel switching circuit 20. Lower parallel switching circuit 20
Is turned off because the signal whose +/- is inverted by the inverting amplifier circuit 22 is input. When the FET of the upper parallel switching circuit 20 is turned on, the FET of the upper serial switching circuit 21 is also turned on. This is because a bias voltage is applied to the gate of the upper FET. The lower series switching circuit 21 is
It is turned off by the parallel switching circuit 20 in the off state. Therefore, the output of the cell voltage detection circuit 3 connected to the upper battery cell 1 is connected to the voltage detection terminal 2 via the upper series switching circuit 21 that is turned on, and the output of the lower cell voltage detection circuit 3 is , Is electrically disconnected from the voltage detection terminal 2 by the series switching circuit 21 in the off state.

[When the voltage of the lower battery cell is lower than the voltage of the upper battery cell in FIG. 4] In this state, the comparator 19 outputs a-signal, which is inverted by the inverting amplifier circuit 22 to become +. , The lower parallel switching circuit 20 is turned on. The lower parallel switching circuit 20 turns on the lower series switching circuit 21 to connect the lower cell voltage detection circuit 3 to the voltage detection terminal 2.

The upper parallel switching circuit 20 is controlled to be turned off by the minus signal of the comparator 19, so that the upper series switching circuit 21 is turned off.
The upper cell voltage detection circuit 3 is electrically disconnected from the voltage detection terminal 2. That is, the voltage of the lower battery cell 1 having a low voltage is output to the voltage detection terminal 2.

The battery pack shown in FIG. 4 has a voltage detection terminal 2
Is used for the electric device 23 that controls the discharge current by detecting the voltage. The electric device 23 includes a load 24, a switching circuit 25 that controls a discharge current, and a switching circuit 2.
And a comparator 26 for controlling the control unit 5 of FIG. In the comparator 26, the reference power source is connected to the + side input terminal, the − side input terminal is connected to the voltage detection terminal 2, and the switching circuit is connected to the output side. The switching circuit 25 is composed of a switching FET 27 connected to the load and a terminal, and a control FET 28 that controls the switching FET 27 to turn on and off. When the control FET 28 turns on, the switching FET 27 turns off with its gate connected to ground. On the contrary, when the control FET 28 is turned off, the switching FET 27 is turned on without being connected to the ground.

This electric equipment discharges the battery pack by performing the following operation. At the beginning of discharging the battery pack, switching FET
27 is turned on. The voltage input to the-side input terminal of the comparator 26 is higher than the voltage of the reference power supply,
The comparator 26 outputs a signal of-and outputs the control FET2.
This is because 8 is turned off, which turns on the switching FET 27. When the discharge of the battery cell 1 progresses and one of the battery cells 1 is completely discharged, the switching FET 27 is turned off and the discharge of the battery pack is stopped. that is,
When any battery cell 1 is completely discharged, the voltage output from the voltage detection terminal 2 becomes lower than the voltage of the reference power source of the comparator 26, the output of the comparator 26 becomes +, and the control FET 28 is turned on. This is because the switching FET 27 is turned off.

[0035]

The battery pack of the present invention, when charged,
Only the battery cell voltage with the maximum cell voltage is selected and output to the voltage detection terminal. Therefore, it is possible to know the arrival time of the full charge or the increase time of the cell voltage for the battery cell that has reached the full charge earliest from the plurality of battery cells or has the cell voltage increased. Therefore, when charging
By monitoring the output of the voltage detection terminal, charging can be stopped before overcharging any cell or causing an abnormal rise in cell voltage. It is possible to prevent an abnormal rise in cell voltage. Therefore, the battery pack of the present invention is characterized in that deterioration of battery cells is suppressed and the battery pack can be repeatedly used for a long period of time. Furthermore, when the battery pack of the present invention is discharged, a voltage corresponding to the cell voltage of the battery cell having the lowest voltage is output from the voltage detection terminal. The battery cell with the lowest cell voltage among the battery cells when discharging the battery pack consumes the remaining capacity earliest,
If the battery is further discharged, it will be over-discharged. Since the battery pack of the present invention selects only the minimum voltage from the cell voltages of this battery cell and outputs the voltage corresponding to this to the voltage output terminal, before the battery cell is over-discharged. The discharge can be stopped.

Furthermore, a remarkable feature of the battery pack of the present invention is that the output voltage of a single voltage detection terminal can effectively prevent overcharge or overdischarge of a plurality of battery cells. This is because the battery pack of the present invention selects only the cell voltage of the battery cell having the maximum or minimum voltage and outputs it to the voltage detection terminal. This battery pack
Reduce the number of terminals connected to the charger or electrical equipment,
It has a feature that failures such as contact failure can be minimized and overcharge or overdischarge of battery cells can be effectively prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a conventional DC device that charges a plurality of battery cells.

FIG. 2 is a circuit diagram showing a battery pack and a battery charger of the embodiment of the present invention.

FIG. 3 is a circuit diagram showing a battery pack and a battery charger thereof according to another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a battery pack and a battery charger of another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Battery cell 2 ... Voltage detection terminal 3 ... Cell voltage detection circuit 4 ... Maximum voltage output circuit 5 ... Minimum voltage output circuit 6 ... Output terminal 7 ... Diode 8 ... Differential amplifier 9 ... Buffer amplifier 10 ... Charger 11 ... DC Power supply 12 ... Switching element 13 ... Comparator 14 ... Reference power supply 15 ... Switching circuit 16 ... Switching element 17 ... Comparator 18 ... Reference power supply 19 ... Comparator 20 ... Parallel switching circuit 21 ... Series switching circuit 22 ... Inverting amplification circuit 23 ... Electrical equipment 24 ... load 25 ... switching circuit 26 ... comparator 27 ... switching FET 28 ... control FET

Claims (2)

[Claims] 1. A battery pack having a plurality of rechargeable battery cells (1), which comprises a cell voltage detection circuit (3) for detecting the voltage of each battery cell (1). (3) is connected to the voltage detection terminal (2) via the maximum voltage output circuit (4), and the maximum voltage output circuit (4) outputs only the maximum voltage from the cell voltage of each battery cell (1). A battery pack which is configured to be selected and output a voltage corresponding to the selected voltage to a voltage detection terminal (2). 2. A battery pack having a plurality of rechargeable battery cells (1), which has a cell voltage detection circuit (3) for detecting the voltage of each battery cell (1). (3) is connected to the voltage detection terminal (2) via the minimum voltage output circuit (5), and the minimum voltage output circuit (5) outputs only the minimum voltage from the cell voltage of each battery cell (1). A battery pack which is configured to be selected and output a voltage corresponding to the selected voltage to a voltage detection terminal (2).