JPH11341693A - Set battery having overcharge protective circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a set battery having an overcharge protective circuit which is simple in structure and is very practical. SOLUTION: In a set battery 1 constituted of a serial combination of a plurality of battery modules 2, each of which is built up of a plurality of single batteries serially connected in succession from 1 onwards, each of the battery modules 2 is parallelly connected with a constant-voltage protective circuit 7 for bypassing charging current at the time the battery module 2 is overcharged. When the battery module 2 becomes overcharged and the terminal voltage increases, the constant-voltage protective circuit 7 is turned ON to bypass the charging current thereby further suppressing overcharging of the single batteries in an overcharged state. Furthermore, by detecting the increase in temperature of the constant-voltage protective circuit 7, signals can be processed without an electric insulation circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an assembled battery,
In particular, it relates to the overcharge protection circuit.

[0002]

2. Description of the Related Art For example, in a battery for supplying running energy of an electric vehicle such as a Li-ion battery, a large number of assembled batteries (usually several hundreds) are required from the viewpoints of wiring resistance loss, downsizing of an inverter circuit and a motor, and the like. Of cells (battery cells) are connected in series, but since the capacity and charging characteristics of each cell vary during charging, each cell has charge management, especially an assembled battery having overcharge protection. It is carried out.

More specifically, since there is a correlation between the open-circuit voltage of a unit cell and its charging capacity, the open-circuit voltage is estimated from the terminal voltage and current detected during charging, and thereby the overcharge detection is performed. Is detected, and when overcharging is detected, the charging current to the assembled battery is cut off.

[0004]

However, in the above-described conventional battery pack for a vehicle, since the number of battery modules is large, a large number of detected terminal voltages must be processed by a signal processing circuit including an A / D converter. Since the terminal voltage of each part of the assembled battery is high, an electric insulation circuit must be interposed each time to transmit the terminal voltage of each cell to the low-voltage controller. At the same time, the current must be processed in combination with the detected current, so that a controller that operates at high speed is required. For this reason, there has been a problem that the scale of the overcharge protection circuit is large and the cost burden is heavy.

The present invention has been made in view of the above problems, and has as its object to provide an assembled battery having an overcharge protection circuit having a simple configuration and excellent practicability.
Further, when one cell is overcharged, charging of the assembled battery is interrupted regardless of the capacity of the other cells constituting the assembled battery, and there is a problem that the charging is not performed sufficiently. Was.

The present invention has been made in view of the above problems, and has a simple configuration and excellent practicability. Further, it is possible to suppress an increase in the circuit scale and to prevent a part of fully charged single cells from being hindered. It is an object of the present invention to provide an assembled battery having an overcharge protection circuit capable of charging another unit cell.

[0007]

According to an assembled battery having an overcharge protection circuit according to the present invention, a plurality of battery modules each consisting of a plurality of unit cells connected in series from one to one are connected in series. In the assembled battery, a constant voltage protection circuit for bypassing the charging current when the battery module was overcharged was connected in parallel to each battery module.

In this case, when the cell of any of the battery modules is overcharged and its terminal voltage rises, the constant voltage protection circuit becomes conductive and bypasses the charging current. Further overcharging of the charged cells can be prevented from progressing. Further, the charging current bypassing the constant voltage protection circuit acts as a normal charging current in another battery module in which the unit cell is not yet in the overcharged state, so that other circuit scales that have not yet reached full charge. Some of the fully charged cells can be charged afterwards without any increase, while other cells can be charged without hindrance.
The charge / discharge capacity of the assembled battery can be improved.

According to a second aspect of the present invention, in the battery pack having the overcharge protection circuit according to the first aspect, a diode that conducts by an overcharge voltage of the battery module and a current-limiting resistance element are connected in series. The temperature of these diodes or resistance elements is detected by a temperature sensor, and the charging current of the assembled battery is regulated when the temperature rises due to overcharging.

In this way, charging can be stopped due to overcharging without employing an expensive electrical insulation circuit. According to the third aspect of the present invention, in the battery pack having the overcharge protection circuit according to the second aspect, the temperature of the unit cell is further detected by the temperature sensor. When a battery abnormality occurs, it can be detected.

According to the fourth aspect of the present invention, in the battery pack having the overcharge protection circuit according to the second aspect, the output terminals of the respective temperature sensors are connected in series or in parallel to output a composite signal. The circuit scale can be simplified without impairing the overcharge detection function. According to a fifth aspect of the present invention, in the battery pack having the overcharge protection circuit according to the first aspect, the light emitting diode is turned on by the overcharge voltage of the battery module, and the light emission is detected to detect the overcharge. Regulate the charging current of the assembled battery.

That is, according to this configuration, since the light emitting diode itself has an overcharge voltage detecting function and a function of a conventional electric insulation circuit, overcharge is performed without newly adding an electric insulation circuit (photocoupler or the like). Detection and protection can be performed, and the circuit configuration can be simplified. According to the configuration described in claim 6, in the assembled battery having the overcharge protection circuit according to claim 5, the light emission of the plurality of light emitting diodes is further transmitted to a single light receiving diode through a common optical transmission path (for example, an optical fiber). send. With this configuration, the overcharge detection circuit system can be significantly simplified compared to the related art.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a battery pack having an overcharge protection circuit according to the present invention will be specifically described below with reference to the following examples.

[0014]

Embodiment 1 An assembled battery having an overcharge protection circuit according to Embodiment 1 will be described with reference to FIG. FIG. 1 is a block diagram showing an assembled battery having this overcharge protection circuit. Reference numeral 1 denotes an assembled battery, which is configured by connecting a number of battery modules 2 in series. In this embodiment, each battery module 2 is composed of one unit cell.

Reference numeral 3 denotes a charge control circuit which converts an input voltage into a voltage optimal for charging the assembled battery 1 and applies the converted voltage to the assembled battery 1. Reference numeral 4 denotes a constant voltage protection circuit connected in parallel to each battery module (that is, each cell) 2. The constant voltage protection circuit 4 includes an overcharge heating circuit 7 in which a constant voltage diode 5 and a current limiting resistance element 6 are connected in series by an overcharge voltage of the battery module 2 connected in parallel, and a constant voltage diode. 5 and a temperature sensor 8 for detecting a temperature rise of the resistance element 6. As shown in FIG. 2, the temperature sensor 8 is in close contact with the outer peripheral surface of each unit cell 2, and the overcharge heat generating circuit 7 is in close contact with the temperature sensor 8. Thereby, the temperature sensor 8 can detect the heat generation of both the unit cell 2 and the overcharge heat generation circuit 7.

The temperature sensor 8 may be a normal thermistor, but may be a temperature-electrical resistance conversion element such as PTC whose electric resistance changes suddenly at a predetermined temperature or higher. It is preferable that a temperature-electric resistance conversion element of a type in which the electric resistance rapidly increases when the temperature exceeds a predetermined temperature is used in series connection like the temperature sensor 8 shown in FIG. 1, and when the temperature exceeds a predetermined temperature, the electric resistance rapidly decreases. It is preferable that the temperature-electrical resistance conversion element of the following type be used in parallel connection.

Reference numeral 9 denotes a controller incorporating a microcomputer, which is driven by a low-voltage power supply (not shown).
A total voltage detector 91, a temperature detector 92, a current detector 93,
A total voltage detector 91 detects a total voltage of the battery pack 1 to be inputted, a temperature detector 92 detects a total electric resistance (current) of each temperature sensor 8, and a current detector 93.
Detects the charging current of the assembled battery 1 from the current sensor 10,
The charging unit 3 instructs the charging control circuit 3 to stop the charging operation based on the determination result regarding the overcharge by the determination unit 94.

The operation of this device will be described below. In addition,
The threshold voltage of the constant voltage diode 5 is set equal to a predetermined overcharge voltage of the cell (battery module) 2. Also, the increase in the terminal voltage of the cell 2 during the overcharge state after the full charge of the cell 2 is not so large,
In order to improve the sensitivity of heat detection by the temperature sensor 8, the resistance value of the current limiting resistor element 6 is set sufficiently small. FIG. 4 in this embodiment shows a voltage-current characteristic of the overcharge heating circuit 7, that is, a series resistance of the constant voltage diode 5 and the resistance element 6, in a solid line in FIG. Indicated by That is, in this embodiment, when the overcharge further proceeds, the unit cell 2 absorbs the charging current to prevent the current to the overcharge heating circuit 7 from becoming excessive.

If all the cells (battery modules) 2 have not reached full charge during charging, the constant voltage diode 5 is cut off, and the charging current may bypass the overcharge heating circuit 7. Therefore, the temperature sensors 8 are all in the low resistance state, and the controller 9 determines that no overcharge has occurred. During charging, if any cell (battery module) 2 is overcharged and its terminal voltage exceeds the threshold voltage of the constant voltage diode 5, an overcharged heating circuit 7
When the charging current detours, the temperature sensor 8 that senses the temperature rise becomes a high resistance, the controller 9 determines that overcharging has occurred, and outputs a warning or a charge stop command to the charging control circuit 3.

When overcharging is detected by the temperature sensor 8 in a range where the total voltage does not increase so much, a charge stop command is not output to the charge control circuit 3 but the current capacity allowed by the constant voltage diode 5 is used. It is preferable to continue charging within the range of. In this way, another battery module 2 that has not yet reached full charge can be charged with a predetermined constant current. After that, many battery modules 2
Is fully charged, the total voltage of the assembled battery 1 exceeds a predetermined threshold value. Accordingly, it is determined that the charging of the assembled battery 1 is completed, and the charge control circuit 3 may be instructed to stop charging. In addition, it is also possible to instruct the charge control circuit 3 to stop charging based on the past accumulated charge / discharge amount calculated by the current sensor 10.

If all the cells (battery modules) 2 are not overdischarged during discharging, the constant voltage diode 5 is cut off and the discharge current does not bypass the overcharge heating circuit 7. , The temperature sensors 8 are all in the low resistance state, and the controller 9 determines that no overdischarge has occurred. At the time of discharging, if any of the cells (battery modules) 2 is overdischarged and the discharge current bypasses the overcharge heating circuit 7, the temperature sensor 8 that senses the temperature rise becomes high resistance and the controller 9 Determines that overdischarge has occurred,
An alarm is generated or a load (not shown) is cut off.

FIG. 3 shows a flowchart of the above operation. In FIG. 3, VthL is a threshold voltage equal to the total voltage of the assembled battery 1 in a state where some of the cells 2 are overcharged, and VthH is a value in which most of the cells 2 are overcharged. The threshold voltage is equal to the total voltage of the assembled battery 1 in the closed state.

[0023]

Embodiment 2 Another embodiment of the present invention will be described with reference to the block diagram shown in FIG. Overcharge light emitting circuits 7a are connected in parallel to both ends of a battery module 2 formed by connecting two unit cells in series. This overcharged light emitting circuit 7a has only the light emitting diode 11 connected in series to the overcharged heating circuit 7 shown in FIG. 1, and the sum of the forward conduction voltage of the light emitting diode 11 and the breakdown voltage of the constant voltage diode 5 is equal to the battery. It is set equal to the overcharge voltage of module 2. Note that, as a part or all of the threshold voltage of the constant voltage diode 5, the forward voltage drop of an inexpensive PN junction diode or the forward voltage drop of a light emitting diode may be used. It is.

When the light emitting diode 11 is energized due to overcharging, the light emission enters the inside of the optical fiber 12 from the bent portion of the optical fiber 12 disposed close to the light emitting diode 11, and the light is emitted therefrom.
While being totally reflected inside, light is emitted from the end to the light receiving diode 13. The overcharge light emitting circuit 7a is provided for each battery module 2 and has a common optical fiber 12
Is sent to one light receiving diode 13. This makes it possible to detect overcharge more quickly than in the overcharge protection circuit of the first embodiment.

[Brief description of the drawings]

FIG. 1 is a block diagram of an assembled battery having an overcharge protection circuit according to a first embodiment.

FIGS. 2A and 2B show the overcharge heating circuit 5 shown in FIG. 1, wherein FIG. 2A is a plan view and FIG. 2B is a side view.

FIG. 3 is a flowchart showing an operation of the controller 9 shown in FIG.

FIG. 4 is a voltage-current characteristic diagram of the overcharge heating circuit 5 shown in FIG.

FIG. 5 is a circuit diagram illustrating a main part of an assembled battery having an overcharge protection circuit according to a second embodiment.

[Explanation of symbols]

1 is an assembled battery, 2 is a cell (battery module), 4 is a constant voltage protection circuit (part of the overcharge protection circuit), 5 is a constant voltage diode, 6 is a resistance element, 7 is an overcharge heating circuit, and 8 is The temperature sensor 9 is a controller (the rest of the overcharge protection circuit,
Current control means), 7a is an overcharged light emitting circuit, 13 is a light receiving diode

Claims (6)

[Claims] An overcharge comprising: an assembled battery formed by connecting a plurality of battery modules each consisting of a plurality of unit cells connected in series from one to one in series; and an overcharge protection circuit for preventing each battery module from being overcharged. In the battery pack having a protection circuit, the overcharge protection circuit includes a constant voltage protection circuit that is connected in parallel to the battery modules and bypasses a charging current flowing through the battery pack when the battery module is overcharged. A battery pack having an overcharge protection circuit. 2. The assembled battery having an overcharge protection circuit according to claim 1, wherein the constant voltage protection circuit connects a diode, which conducts by an overcharge voltage of the battery module, and a resistance element for limiting current in series. And an overcharge detection circuit having a temperature sensor for detecting a temperature rise of the diode or the resistance element for current limiting. An assembled battery having an overcharge protection circuit, comprising current regulating means for regulating a charging current of the assembled battery. 3. The assembled battery having an overcharge protection circuit according to claim 2, wherein the temperature sensor also detects the temperature of the unit cell. 4. An assembled battery having an overcharge protection circuit according to claim 2, wherein the output terminals of the plurality of temperature sensors provided for each of the battery modules are connected in series or in parallel to each other to control the current. An assembled battery having an overcharge protection circuit, which is output to a means. 5. The assembled battery having an overcharge protection circuit according to claim 1, wherein the constant voltage protection circuit includes an overcharge light-emitting circuit including a light-emitting diode that is turned on by an overcharge voltage of the battery module; An overcharge detection circuit having a light receiving diode for detecting, wherein the constant voltage protection circuit has current regulating means for regulating a charging current of the battery pack by an output signal of the light receiving diode. An assembled battery having a circuit. 6. The assembled battery having the overcharge protection circuit according to claim 5, wherein light emitted from the plurality of light emitting diodes provided for each of the plurality of battery modules is received by the common light receiving diode. A battery pack having an overcharge protection circuit.