WO2012101835A1

WO2012101835A1 - Protection device in lithium ion secondary battery

Info

Publication number: WO2012101835A1
Application number: PCT/JP2011/052448
Authority: WO
Inventors: 敏史江角; 平山　正博
Original assignee: 株式会社イーティーエイコンポーネンツ; 株式会社エルテル
Priority date: 2011-01-28
Filing date: 2011-01-28
Publication date: 2012-08-02

Abstract

Provided is a protection device in a lithium ion secondary battery, which is provided with a circuit protector that is miniaturized to the extent of having a lithium ion secondary battery pack and a control circuit thereof mounted on a same printed board (PCB). The protection device protects the secondary battery, which has a chargeable/dischargeable cell (11), and which is provided with: a battery protection monitoring IC (16), which measures the voltage of the cell, and eliminates overcharge and overdischarge; a switch for controlling the overcharge and the overdischarge; an IC for second protection, which operates in the case where the battery protection monitoring IC cannot perform the control; and a breaker, which opens a circuit when an abnormal current is generated. As the breaker, the circuit protector configured of two opening/closing devices is disposed in a circuit that connects the secondary battery side and the load side with each other, and the circuit protector is provided with a resetting section.

Description

Protection device for lithium ion secondary battery

The present invention relates to a protection device for a lithium ion secondary battery, and particularly to a protection device that can be easily reset.

Lithium-ion secondary batteries (LiBs) are widely used as power sources for all products from lighting equipment, communication equipment, laptop computers to vehicles because they have high energy density and good discharge characteristics. Yes. The lithium ion secondary battery needs to be controlled so as not to be overcharged or overdischarged due to its characteristics.
As a protection device for that purpose, a fuse is conventionally used in a lithium ion secondary battery. However, since fuses are easily blown by a large current for a moment, there is a tendency to use larger specifications (those with large current value ratings). However, in the case of a fuse with a large specification, if an abnormal current occurs, it takes time to shut down, during which time the above secondary battery may be consumed or the circuit may break down. Then, because it will be cut frequently, it is easy to fall into a dilemma as to whether to choose the one with a large specification or the one with a small specification.
An example of a lithium ion secondary battery provided with a protection circuit including a conventional battery protection monitoring IC is shown in FIG. The lithium ion secondary battery in FIG. 7 measures a plurality of cells a and the voltage of each cell, and prevents overcharge when the voltage exceeds the specified voltage and prevents overdischarge when the voltage falls below the specified voltage. Battery protection monitoring IC: b and control switch c. In addition, when the IC: b cannot be controlled for some reason, the IC includes a second protection IC: d, a control switch e, and fuses f1 and f2, and has a protection function against overcharge and overdischarge. It is a working configuration. However, in the above configuration, there is a problem that the fuses f1 and f2 are partially cut or the fact that they are blown cannot be determined. In addition, g shows a charger.
In the above conventional method, a control circuit dedicated to interruption is provided on the IC: b side for ensuring, and the heating elements h1 and h2 are used together with the fuse so as to be easily blown on the fuse side. In order to further reliably cut off the fuses f1 and f2, the fuse may be blown with a delay on the circuit side. However, since the power of the IC: b can be supplied from the fuse side or from the charging side (or discharging side), the certainty is not guaranteed when the power is cut off. In addition, it is possible to cut off the charging side fuse f1 during charging, but during discharging, energy is supplied only from the power source from the secondary battery side, so the secondary battery side fuse f1 is blown first. Then, the charge / discharge side fuse f2 may not be blown.
By the way, the overcharge usually occurs at the time of charging, but at the time of discharging, it may occur at the time of starting or stopping the load depending on the characteristics of the load used. In such a case, a high pressure may be generated although it is a single hour. In such a case, an excessive voltage is applied to the battery, which adversely affects the battery. Of course, it is also conceivable that a potential higher than necessary is applied to the secondary battery. This is a phenomenon that can actually occur when an electric motor or the like is operated with a large battery.
If a secondary battery malfunctions, it can cause a fatal accident if it is used as a power source for a life support device. Even if the abnormal current can be forcibly interrupted by the fuse, to replace the fuse, you must first prepare a fuse with the same specifications, remove the case lid to avoid electric shock, and replace the blown fuse by hand. , Extremely specialized work is required. This work is difficult even in a normal environment, and it may be panicked in an urgent environment, so it is predicted that the work will become more difficult. Thus, the problems associated with the use of fuses are numerous.
In particular, even if a true abnormal current flows, the demerit that it takes time to run out can lead to problems such as the secondary battery and its control circuit being burned out or exploding in the worst case. It is. For this reason, a breaker may be used instead of a fuse in the case where conditions where the merits and demerits contradict each other. However, the conventional breaker has a structure that assumes a commercial power supply, and is heavy and large, so it is not suitable for the lithium ion secondary battery that emphasizes mobility this time. In addition, the design of the conventional breaker is based on the assumption that the reset lever and knob are also attached to the control panel, so it is difficult to say that the design is suitable for lithium secondary batteries. Therefore, a lithium-ion battery is a low voltage circuit (for example, 14.8V with four DC 3.7Vs connected in series) and cannot be used as it is.
For battery systems that place emphasis on mobility, it is desirable to mount the battery pack and its control circuit on the same printed circuit board (PCB) in order to achieve miniaturization. In other words, the specifications required for the protection device in the lithium ion secondary battery are not only electrical numbers, but are small and attached to the PCB as described above, and a reset unit that can be operated immediately by the user after the protection device is activated. Should be prepared.

The present invention has been made paying attention to the above points, and the problem is that the pack of the lithium ion secondary battery and its control circuit are miniaturized to the extent that they are mounted on the same printed circuit board (PCB). It is providing the protection apparatus in a lithium ion secondary battery provided with the circuit protector. Another object of the present invention is to provide a protection device in a lithium ion secondary battery that can be operated immediately and has a reset function that is easy to recover. Another object of the present invention is to use it as a backup power source for use in lighting in case of distress, mobile phone, transceiver, signal light for marine accident work, power cable-less stand-alone equipment using solar panels, and other equipment. It is providing the protection apparatus in the lithium ion secondary battery which can be performed.

In order to solve the above problems, the present invention provides a battery protection monitoring IC having a cell that can be charged and discharged, measuring the voltage of the cell to prevent overcharge and overdischarge, and overcharge and overdischarge control. Protection for protecting a secondary battery in a lithium ion secondary battery having a switch for use, a second protection IC that operates when the IC cannot be controlled, and a circuit breaker that opens a circuit when an abnormal current occurs As a device, a circuit protector comprising two switches as the circuit breaker is arranged in a circuit passing through the secondary battery side and the load side, and the circuit protector includes a reset unit. It was taken.
The lithium ion secondary battery that is the subject of the present invention only needs to have at least one cell, but in general, a battery having a plurality of cells will often be the subject. . The lithium-ion secondary battery has a battery protection monitoring IC that measures the voltage of each cell constituting the battery and prevents overcharge and overdischarge, a control switch, and the IC when the IC becomes uncontrollable. A second protection IC that operates and a circuit breaker that opens the circuit when an abnormal current occurs are provided. Therefore, overcharge and overdischarge during normal use are protected by a battery protection monitoring IC, a control switch, and a second protection IC that operates when the IC cannot be controlled. Is provided with the protection device of the present invention.
In the circuit breaker, a circuit protector composed of two switches is connected to a circuit passing through the secondary battery side and the load side. By using a circuit protector, the protective device can be miniaturized, but as such a circuit protector, for example, our mini-breaker is small and weighs about 5 grams, so a printed circuit board (PCB) It is suitable for mounting on). Of course, the present invention is not limited to the above-described mini-breaker, and can be used in the protective device of the present invention in the same manner as long as it is a small breaker of the same level.
In the above circuit protector, two switches are connected in series to a circuit passing through the secondary battery side and the load side, and the middle (connection end side) and ground side of the two switches are connected. It is desirable to connect to a T-shaped configuration. In the case of the T-shape, one of the two terminals can be shared, the structure is simplified and the number of parts is reduced, which contributes to cost reduction and miniaturization.
As the above-mentioned switches, a switch made of any one of a thermal type, an electromagnetic type and a hybrid type is used. As the thermal switch, for example, a thermal relay using bimetal can be used. As the electromagnetic switches, for example, electromagnetic relays can be used. As hybrid switches, for example, a thermal-magnetic type protector can be used.
As an example of the thermal-magnetic type, there can be mentioned an electrothermal-electromagnetic hybrid structure composed of a combination of a bimetal and an electromagnet. With such a configuration, the trip time can be set in two stages, the electromagnetic coil reacts instantaneously to high overcurrents, and the trip time is delayed until the bimetal reacts to low overcurrents. Can do. For this reason, the hybrid system is suitable for applications that require accurate operations such as communication and process control.
The circuit protector also needs to include a manual return switch as a reset unit. This is a matter to be considered when packaging the protective device in the lithium ion secondary battery of the present invention. By placing a resettable protector by a manual return switch on the end face of the printed circuit board (PCB), The exposed portion required for operation can be minimized. Therefore, it is desirable to arrange connectors for input / output on the end face of the printed circuit board (PCB).
Since the present invention is configured and operates as described above, the circuit protector is miniaturized to such an extent that the pack of the lithium ion secondary battery and its control circuit are mounted on the same printed circuit board (PCB). It is possible to provide a protective device for a lithium ion secondary battery. Further, according to the present invention, it is possible to provide a protection device for a lithium ion secondary battery that can be operated immediately and has a reset part that can be easily restored. In addition, according to the present invention, it is possible to provide a protection device for a lithium ion secondary battery that can be used as a backup power source used in equipment such as lighting in a disaster, a mobile phone, a transceiver, and a signal light for marine accident work. There is an effect that can be done.

FIG. 1 is a schematic circuit diagram showing Example 1 of a protection device in a lithium ion secondary battery according to the present invention.
FIG. 2 is a schematic circuit diagram showing a thermal type switch applied to Example 2 of the protection device in the lithium ion secondary battery according to the present invention.
FIG. 3 is a schematic circuit diagram showing an example of a protective device for a lithium ion secondary battery according to the present invention, which is an electromagnetic switch applied thereto.
FIG. 4 is a schematic circuit diagram showing Example 4 of the protection device in the lithium ion secondary battery according to the present invention.
FIG. 5 is a schematic circuit diagram showing Example 5 of the protection device in the lithium ion secondary battery according to the present invention.
FIG. 6 is a timing chart for explaining the operation of the protective device in Example 5.
FIG. 7 is a schematic circuit diagram showing an example of a protection device in a conventional lithium ion secondary battery.

Hereinafter, the present invention will be described in more detail with reference to illustrated embodiments. FIG. 1 shows an example 1 of a protection device 10 in a lithium ion secondary battery, 11 is a lithium ion battery comprising a plurality of cells, and usually takes the shape and structure of a so-called pack. The anode (cathode) and cathode (anode) in the lithium ion battery 11 are connected to

connector terminals

14 and 15 by

wirings

12 and 13, respectively.
Reference numeral 16 denotes a battery protection monitoring IC that measures the voltage for each cell to prevent overcharging, and is connected to the wiring 13 via a charge / discharge switch 17 formed of a MOSFET. Note that the battery protection monitoring IC also serves as protection against a short circuit and large current. The two circuit protectors 20-1 and 20-2 in Example 1 have two sets of two-terminal type

thermal relays

18 and 19 as switches and are arranged in series together with the switching

units

21 and 22, and The circuit protectors 20-1 and 20-2 are connected to the ground side by an intermediate wiring 23 between them (connection end side), and are T-shaped wirings sharing the terminals. In addition, the circuit of the protection device 10 in the lithium ion secondary battery uses a second protection IC 24 and a control switch 25 made of a MOSFET, in order to cope with the case where the IC 16 can no longer be controlled. A circuit can also be opened and closed in the intermediate wiring 23.
A mini-breaker (model number: 1620) made by our company is suitable for the circuit protectors 20-1 and 20-2. This mini breaker is equipped with a manual return switch as a reset part, and the resettable breaker by the manual return switch is arranged on the end face of the printed circuit board (PCB) as a circuit protector to minimize the exposed part necessary for external operation. The connector for input / output is also arranged on the end face of the printed circuit board (PCB). Furthermore, the potential between the external terminal 26 and the ground can be monitored by installing the external terminal 26 in the intermediate wiring 23 between the circuit protectors. Reference numeral 27 denotes a charger, which is connected to the connector terminal 14 side of the wiring 12.
In the protective device 10 of Example 1, the thermal relays 18 and 19 of the same standard are used, and the circuit on the battery side and the load side can be shut off by using a T-shaped wiring with a common terminal connected in series. it can. That is, since current flows to the battery side through the two circuit protectors 20-1 and 20-2 during normal charging, the circuit protector 20 does not flow to the control switch 25 side and becomes overvoltage or short-circuited. -1, 20-2, or both, trips and breaks the circuit. In particular, in the event of an abnormality due to overcharge, in order to cut off the current to the lithium ion battery 11 side, control is performed so that the current flows to the control switch 25 side to protect the lithium ion battery. Even when the control by the IC 16 is impossible, the circuit protector 20-1 trips and protects the lithium ion battery 11. Further, when the overvoltage state continues thereafter, the control switch 25 may be destroyed, but the circuit protector 20-2 prevents this, so the control switch 25 is protected.
When the battery protection monitoring IC 16 returns to normal or when a load-side abnormality is removed, unlike the conventional fuse, it can be manually restored, so that convenience is high. Moreover, since the electric potential between it and the ground (15) can be monitored by the external terminal 26, for example, when the electric potential is 0V, both circuit protectors 20-1 and 20-2 are operating, It can be determined that the circuit on the battery side and the load side are shut off.
FIG. 2 shows Example 2 of the present invention, and the circuit protector 30 is the same as the circuit protectors 20-1 and 20-2 used in Example 1 described above. This is an example of a thermal switch, and the two

thermal relays

18 and 19 are of the same standard, and they are connected in series with the switching units 28 and 29 and combined with a manual return switch 31 that trips two poles simultaneously. Thus, the circuit protector 30 of Example 2 is configured.

Reference numerals

32a, 32b, and 32c denote three terminals. Since the trip mechanism of the thermal relays 18 and 19 is bimetal and does not trip for a certain period of time against temporary inrush power, the device can be effectively protected. Therefore, it is optimal for applications such as motors, transformers, and low voltage wiring.
FIG. 3 shows Example 3 of the present invention, which is an example in which the circuit protectors 20-1 and 20-2 are electromagnetic (magnetic type) switches as switches. The electromagnetic circuit protector 30 'of the third example is an electromagnetic coil wound around the outer periphery of the pipe, a movable iron core disposed in the pipe, a spring, a fixed iron core, silicon oil sealed in the pipe, and opened and closed outside the pipe. It has the

magnetic relays

33 and 34 comprised with the operating plate connected with the engaging end of the mechanism part, and also the operating iron piece connected with the operating plate. Similarly to Example 2, the

magnetic relays

33 and 34 are provided with a manual return switch 37 that is combined with the open /

close portions

35 and 36 and trips two poles simultaneously.

Reference numerals

38a, 38b, and 38c denote three terminals. When an overcurrent flows, the movable iron core is attracted to the fixed iron core, the magnetic resistance is reduced, the operating iron piece is attracted, the operating plate is moved, the engagement end of the open / close mechanism is released, and the movable contact opens in conjunction with this. The circuit is interrupted. Therefore, when a current such as a short circuit accident current flows, the operating iron piece is immediately drawn and tripped. Note that the sealing of the silicone oil is for the purpose of giving a time delay characteristic to the movement of the movable iron core due to its viscosity.
When the electromagnetic type is compared with the thermal type, it has the following characteristics.
1) Not affected by ambient temperature.
Since the operating current of the circuit protectors 20-1 and 20-2 is determined only by the magnitude of the current and does not change depending on the ambient temperature, there is no need for temperature correction of the rated current.
2) Immediate re-restoration Even after a shut-off operation (trip), if the current is less than the rated current, it can be re-reacted immediately without requiring standby time.
3) Immediate shut-off characteristics When a large current flows through the coil, it does not wait for the movement of the movable iron core, and the working iron piece is absorbed instantly and the working plate is moved.
Although not shown, hybrid protectors can also be applied as the circuit protectors 20-1 and 20-2 in the present invention. This is an example of a thermal-electromagnetic hybrid structure, and as already mentioned by combining a bimetal and an electromagnetic coil, the trip time can be set in two stages. The electromagnetic coil reacts instantaneously to a high overcurrent, and the trip time can be delayed for a low overcurrent.
FIG. 4 shows Example 4 of the present invention. In Example 4, two circuit protectors 20-1 and 20-2 are replaced with one T-shaped (three-terminal type) protector 40. Since the other configuration is the same as that of Example 1, reference numerals are used and detailed description will not be repeated. The details of one T-shaped (three-terminal type) protector 40 are substantially shown in FIG. 2 or FIG. By using this protector 40, the battery side and load side circuits can be interrupted by three instead of four. Our company has already manufactured a small circuit breaker that can trip two poles at the same time. By using this technology together, the T-shaped (3-terminal) with the internal circuit configuration shown in Figs. Type) Circuit protector can be manufactured easily. The tripping of two poles at the same time and the combination of the T-shaped wiring bring a great advantage to the lithium battery protection circuit, and it is possible to expect a great demand.
FIG. 5 shows Example 5 of the present invention. Example 5 is an example of a stacked lithium ion secondary battery 42 in which one battery pack 41 shown in FIG. 1 or FIG. 4 is connected in parallel and stacked. The individual battery packs 41 and 41 are sequentially connected to the wiring 12 of the battery pack 41 of the next layer by extending the intermediate wiring 23 to constitute one parallel-type stacked lithium ion secondary battery 42 as a whole. .
In the laminated lithium ion secondary battery 42 in which such battery packs 41 are laminated, when the battery pack 41 of each layer is in an overvoltage or short-circuit state, two circuit protectors (these are denoted by reference numerals 20-1 and 20-). 2 or 20-3 or 20-4) or one or both of them may trip and break the circuit. For example, in overcharge, the circuit protector 20-1 on the first layer trips and the other circuit protector 20-2 and the circuit protectors 20-3 and 20-4 on the second layer do not trip when shutting off. Considering the case, even if the potential between the external terminal 43 and the ground is measured for the purpose of grasping the circuit state of the first layer, the circuit protector 20-2 is not tripped. A voltage is applied. That is, the external terminal 44 cannot correctly measure the potential of the first layer circuit (see the timing chart in FIG. 6). For the above reasons, a laminated battery pack always requires a circuit protector that trips two poles simultaneously. In addition to the above-described stacking in parallel connection, stacking in series connection is also conceivable. In that case, a battery pack is configured by a pair of protectors and one control IC.
The protection device for a lithium ion secondary battery according to the present invention is capable of mounting the battery pack and its control circuit on the same printed circuit board (PCB), and has an object without impairing the miniaturization of the lithium ion secondary battery. Can be achieved. Therefore, the design suitable for the lithium ion secondary battery can be summarized with a margin, and it is also suitable as a lithium ion secondary battery with emphasis on mobility, coupled with the fact that so-called reset can be easily performed, It will have excellent properties for practical use. The lithium-ion secondary battery equipped with the protection device of the present invention can be used as a power source for all products as described at the beginning of this document, and since it is easy to reset, it is a harsh that does not have alternative means such as sea and mountains It is suitable as a battery for equipment used in various situations. Also, paying attention to the fact that the circuit protector has several hundreds of reset endurance cycles and that the LiBs itself has a very long characteristic retention period (about 10 years), various connectors and reset knobs exposed to the outside have been made waterproof. If a completely sealed structure is adopted, it can be used in a flooded state as a resettable marine work battery.

Claims

A battery protection monitoring IC that has a cell that can be charged and discharged, measures the voltage of the cell to prevent overcharge and overdischarge, a switch for overcharge and overdischarge control, and the IC cannot be controlled. In a lithium ion secondary battery provided with a second protection IC that operates in a normal state and a circuit breaker that opens a circuit when an abnormal current occurs, a protection device for protecting the secondary battery,
A circuit protector consisting of two switches as the circuit breaker is arranged in a circuit passing through the secondary battery side and the load side,
The circuit protector includes a reset unit, and a protection device for a lithium ion secondary battery.
The circuit protector connects two switches in series to the circuit that passes the secondary battery side and the load side, and connects the connection end side of the two switches and the ground side to form a T-shape. The protection device for a lithium ion secondary battery according to claim 1, which has a configuration of a mold.
The protection device for a lithium ion secondary battery according to claim 1 or 2, wherein the switches are any one of a thermal type, an electromagnetic type, and a hybrid type.