JP2009076265A - Battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack capable of easily detecting expansion of a secondary battery while cost is reduced. <P>SOLUTION: The battery pack is provided with a secondary battery 3, a case 2 housing the secondary battery 3, an expansion detecting part 4 arranged between an inner wall of the case 2 and the secondary battery 3 for detecting pressure added by the inner wall of the case 2 and the secondary battery 3, and an abnormality detecting part 532 for detecting abnormalities of the secondary battery 3 when the pressure detected by the expansion detecting part 4 exceeds pressures P1, P3. Then, the expansion detecting part 4 is filled with a material capable of deforming by pressure between electrodes 41, 42 set in opposition, and as a conductive filler 44 with an electric resistance smaller than the material is retained in dispersion in the material, a resistance value is more decreased as the pressure added between the electrodes 41, 42 is more increased. The abnormality detecting part 532 obtains the resistance value between the electrodes 41, 42 as information showing the pressure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a battery pack that encloses a secondary battery.

In recent years, portable battery-driven devices driven by a battery pack such as a portable personal computer, a mobile phone, and a digital camera have been widely used, and the capacity of the battery pack used in such a device has been increasing. And the high capacity | capacitance secondary battery used for such a battery pack expand | swells when it becomes an overcharge. In addition, such a secondary battery may be expanded in a cumulative manner by generating gas inside the package even when charging and discharging are repeated. And if a secondary battery expand | swells too much, a characteristic deterioration and a failure will be caused, or safety | security will fall. Thus, a technique is known in which charging is stopped when the secondary battery expands by detecting expansion of the secondary battery using a pressure sensor or a strain gauge (see, for example, Patent Document 1).
JP-A-6-52901

  By the way, as described above, for example, a semiconductor sensor is used as the pressure sensor or strain gauge for detecting the expansion of the secondary battery. However, since the semiconductor sensor is expensive, if the expansion of the secondary battery is detected using the semiconductor sensor, the cost of the battery pack increases.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a battery pack capable of easily detecting excessive expansion of a secondary battery while reducing cost.

  The battery pack according to the present invention includes a secondary battery, an outer shell that houses the secondary battery, an inner wall of the outer shell, and the secondary battery, and the inner wall of the outer shell and the secondary battery. A bulge detection unit that detects pressure applied by the secondary battery, and an abnormality detection unit that detects an abnormality of the secondary battery when the pressure detected by the bulge detection unit exceeds a preset first pressure The bulge detection unit is filled with a material that can be deformed by pressure between the first and second electrodes that are arranged to face each other, and a conductive filler having a lower electrical resistance than the material is dispersed in the material. The resistance value between the first and second electrodes decreases as the pressure applied between the first and second electrodes increases, and the abnormality detection unit The resistance value between the first and second electrodes is determined by the bulge detection unit. Acquired as information indicating the detected pressure.

  According to this configuration, when the secondary battery expands, the pressure applied to the bulge detection unit disposed between the inner wall of the outer shell and the secondary battery increases. When the pressure applied to the swollenness detecting portion increases, the material filled between the first and second electrodes is compressed, and as a result, the distance between the conductive fillers having low electrical resistance is reduced, resulting in the resistance between the first and second electrodes. The value decreases. Then, the resistance value between the first and second electrodes decreases as the pressure applied between the first and second electrodes increases, thereby indicating the pressure applied to the swell detection unit. When the pressure detected in this way by the swell detection unit exceeds the preset first pressure, the abnormality detection unit detects an abnormality of the secondary battery. In this case, since excessive expansion of the secondary battery can be detected without using an expensive semiconductor sensor, the cost can be easily reduced.

  The swollenness detection unit is further provided in the charge / discharge path so that the charge / discharge path of the secondary battery passes between the first and second electrodes, and the first and second When the current flowing between the electrodes exceeds a preset cutoff current value, it is preferable that the conductive fillers are separated from each other due to the expansion of the material to substantially cut off the charge / discharge path.

  According to this configuration, when the charge / discharge current of the secondary battery exceeds the cut-off current value, the material expands and the conductive fillers are separated from each other, so that the charge / discharge path is substantially cut off. It becomes possible to protect the secondary battery from overcurrent charging / discharging. As a result of detecting the expansion of the secondary battery and protecting the secondary battery from the overcurrent by the expansion detection unit, it is not necessary to separately provide an overcurrent protection element, and the cost can be easily reduced. It becomes.

  The temperature detector further includes a temperature detector, and the blister detector further increases a resistance value between the first and second electrodes as the temperature rises, and the abnormality detector includes the first detector. When the resistance value between the second electrode and the second electrode is less than a first threshold value set as a resistance value indicating the first pressure, the temperature of the secondary battery is detected and the temperature detected by the temperature detection unit It is preferable to increase the first threshold as the value increases.

  According to this configuration, since the resistance value between the first and second electrodes increases as the temperature rises, the resistance value indicating the pressure detected by the swelling detection unit depends on the temperature. Error is included. On the other hand, the influence of the temperature is reduced by increasing the first threshold value, which is a resistance value indicating the first pressure, as the temperature detected by the temperature detection unit increases by the abnormality detection unit. When the resistance value between the first and second electrodes does not satisfy the first threshold value, that is, when a pressure exceeding the first pressure is detected by the swelling detection unit, it is determined that the secondary battery has excessively expanded. An abnormality of the secondary battery is detected. Thereby, the precision which detects the excessive expansion | swelling of a secondary battery improves.

  Further, the swelling detection unit is disposed in a state where a set pressure smaller than the first threshold is applied by the inner wall of the outer shell and the secondary battery, and the pressure detected by the swelling detection unit is It is preferable that a disassembly prohibition unit that prohibits charging of the secondary battery is further provided when the pressure is equal to or lower than a second pressure smaller than the set pressure.

  According to this configuration, the swollenness detection unit is in a state where a set pressure smaller than the first threshold is applied by the inner wall of the outer shell and the secondary battery. Then, when the pressure detected by the swelling detection unit is equal to or lower than the second pressure that is lower than the set pressure, the disassembly prohibition unit prohibits charging of the secondary battery. In this case, for example, when a third party disassembles the outer shell, the pressure applied to the swollen detection unit by the outer shell and the secondary battery decreases. When the pressure detected by the swollenness detection unit is equal to or lower than the second pressure that is lower than the set pressure, the secondary battery is prohibited from being charged by the disassembly prohibition unit, so the battery pack is disassembled and the quality cannot be guaranteed. In some cases, safety can be improved by prohibiting charging of the battery pack.

  The battery pack according to the present invention includes a secondary battery, an outer shell that accommodates the secondary battery, a first electrode disposed on an inner wall of the outer shell, and the position at a position facing the first electrode. A swelling detector having a second electrode spaced apart from the first electrode on the outer wall of the secondary battery, and a capacitance generated between the first and second electrodes is a preset reference capacitance And an abnormality detection unit that detects an abnormality of the secondary battery.

  According to this configuration, when the secondary battery expands, the distance between the first electrode and the second electrode in the swell detection unit disposed between the inner wall of the outer shell and the secondary battery decreases. If it does so, the electrostatic capacitance which arises between the 1st and 2nd electrodes will increase. When the electrostatic capacitance generated between the first and second electrodes exceeds a preset reference capacity, the abnormality detection unit detects an abnormality in the secondary battery. In this case, since excessive expansion of the secondary battery can be detected without using an expensive semiconductor sensor, the cost can be easily reduced.

  The battery pack according to the present invention includes a secondary battery, an outer shell that accommodates the secondary battery, a first electrode disposed on an inner wall of the outer shell, and the position at a position facing the first electrode. When a bulge detection unit having a second electrode spaced apart from the first electrode on the outer wall of the secondary battery and the first electrode and the second electrode are electrically connected, the secondary electrode An abnormality detection unit for detecting an abnormality of the battery.

  According to this configuration, when the secondary battery expands, the distance between the first electrode and the second electrode in the swell detection unit disposed between the inner wall of the outer shell and the secondary battery decreases. If it does so, the electrostatic capacitance which arises between the 1st and 2nd electrodes will increase. Then, when the first electrode and the second electrode come into contact with each other and become conductive, the abnormality detection unit detects an abnormality of the secondary battery. In this case, since excessive expansion of the secondary battery can be detected without using an expensive semiconductor sensor, the cost can be easily reduced.

  Moreover, it is preferable that the outer wall of the secondary battery is formed of a metal conductor and used as the second electrode. According to this configuration, since the outer wall of the secondary battery is used as the second electrode, it is not necessary to separately provide the second electrode, and the cost can be easily reduced.

  The battery pack according to the present invention includes a secondary battery, an outer shell that houses the secondary battery, an inner wall of the outer shell, and the secondary battery, and an inner wall of the outer shell, The swell detection unit includes a swell detection unit that changes a conduction state according to an interval with the secondary battery, and an abnormality detection unit that detects an abnormality of the secondary battery based on a continuity state of the swell detection unit. The portion includes third and fourth electrodes provided at intervals, a conductive member disposed so as to cover at least a part of each of the third and fourth electrodes, and the conductive member, A third and a fourth electrode and an elastic member that is held in a vertical direction away from the inner wall of the outer shell, and the abnormality detection unit is electrically connected between the third electrode and the fourth electrode. In addition, an abnormality of the secondary battery is detected.

  According to this configuration, when the secondary battery expands, the distance between the inner wall of the outer shell and the secondary battery is narrowed. Then, the conductive member is pushed in the direction of the third and fourth electrodes by the inner wall of the outer shell and the secondary battery, and the elastic member is deformed so that the conductive member straddles between the third electrode and the fourth electrode. As a result, the third electrode and the fourth electrode are electrically connected. And when the 3rd electrode and the 4th electrode conduct | electrically_connect, abnormality of a secondary battery will be detected by the abnormality detection part. In this case, since excessive expansion of the secondary battery can be detected without using an expensive semiconductor sensor, the cost can be easily reduced.

  Moreover, it is preferable to further include a prohibition control unit that prohibits at least one of charging and discharging of the secondary battery when the abnormality is detected by the abnormality detection unit. According to this configuration, when an abnormality is detected by the abnormality detection unit, the prohibition control unit prohibits at least one of charging and discharging of the secondary battery, thereby improving safety.

  Moreover, it is preferable that the information processing apparatus further includes a notification unit that notifies the occurrence of an abnormality when the abnormality is detected by the abnormality detection unit. According to this configuration, when an abnormality is detected by the abnormality detection unit, the occurrence of the abnormality is notified by the notification unit. For example, an abnormality process is performed on the device side connected to the battery pack, or the user has an abnormality. It becomes possible to know.

  In addition, the secondary battery has a flat and substantially box shape, and the swelling detection unit is disposed between a substantially center of the wall surface of the maximum area of the secondary battery and an inner wall of the outer shell. Is preferred. According to this configuration, the swollenness detection unit is disposed between the approximate center of the wall surface of the maximum area of the secondary battery and the inner wall of the outer shell, that is, at the place where the secondary battery is most likely to swell. Therefore, it becomes easy to detect the expansion of the secondary battery by the expansion detector.

  Since the battery pack having such a configuration can detect excessive expansion of the secondary battery without using an expensive semiconductor sensor, it is easy to reduce the cost.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a perspective view showing an example of the configuration of a battery pack according to an embodiment of the present invention. FIG. 1 shows an example of the structure of the battery pack 1 in a state in which a part of the front wall of the casing 2 (outer shell) of the battery pack 1 is removed and the inside of the casing 2 is visible. 2 is a cross-sectional view showing an XX cross section of the battery pack 1 shown in FIG.

  The housing 2 shown in FIG. 1 has a flat and substantially box shape that is thin in the direction of the thickness d. A battery 3, an overcurrent protection element (swelling detection unit) 4, and a control unit 5 that controls charging / discharging of the battery 3 are accommodated in the housing 2. In addition, a connection connector 6 for connecting the battery pack 1 to an electric device is provided on the side surface of the housing 2. The housing 2 (outer shell) may be configured to enclose the battery 3, the overcurrent protection element 4, and the control unit 5 with a film-like material having high tensile strength. The film-like material is preferably hardly stretchable.

  The battery 3 is a secondary battery such as a lithium ion secondary battery or a nickel hydride secondary battery. The battery 3 is a so-called rectangular battery, and for example, an electrode plate, an electrolytic solution, a separator, and the like are stacked and accommodated in a flat, substantially box-shaped metal case 31. The battery 3 is not limited to a square shape, and may be a cylindrical shape, for example. The housing 2 may contain a battery pack in which a plurality of batteries are connected in series, in parallel, or a mixture of series and parallel.

  The overcurrent protection element 4 is a so-called PTC (Positive Temperature Coefficient) element. When a current exceeding a predetermined cutoff current value flows through the overcurrent protection element 4 and generates heat, the resistance value increases and the flowing current is substantially increased. It is designed to shut off. The overcurrent protection element 4 can detect the pressure by decreasing the resistance value as the pressure increases. The overcurrent protection element 4 is disposed between the approximate center of the wall surface of the maximum area of the battery 3 and the inner wall surface of the housing 2. Further, the overcurrent protection element 4 is sandwiched between the inner wall surface of the housing 2 and the outer wall surface of the battery 3 in a state where a preset predetermined pressure Ps is applied. It should be noted that substantially interrupting the current means allowing the presence of a leakage current when the current is interrupted.

  FIG. 3 is an explanatory diagram showing an example of the configuration of the overcurrent protection element 4 shown in FIG. The overcurrent protection element 4 shown in FIG. 3 is filled with an insulating material 43 that can be deformed by pressure between the sheet-like electrode 41 (first electrode) and the electrode 42 (second electrode) arranged opposite to each other, The conductive filler 44 is mixed with the material 43, and the conductive filler 44 is dispersed and held by the material 43. Furthermore, the material 43 is expanded by heat. As the material 43, for example, a polymer resin or rubber can be used. For example, a sponge-like foam material can be preferably used. For example, carbon can be used as the conductive filler 44. And the resistance value between the electrodes 41 and 42 is set suitably by adjusting the density | concentration of the electroconductive filler 44 mixed with the material 43 suitably.

  FIG. 4 is an explanatory diagram for explaining a mechanism of pressure detection by the overcurrent protection element 4 shown in FIG. FIG. 4A shows a state where the pressure applied to the overcurrent protection element 4 is low, and FIG. 4B shows a state where the pressure applied to the overcurrent protection element 4 is high. First, as shown in FIG. 4A, the overcurrent protection element 4 holds the conductive fillers 44 in the material 43 dispersedly and held in a state where the applied pressure is low. And the resistance value between the electrodes 41 and 42 increases.

  On the other hand, when pressure is applied to the overcurrent protection element 4, as shown in FIG. 4 (b), the material 43 is deformed by pressure and the interval between the conductive fillers 44 becomes narrower or comes into contact with the electrode 43. The resistance value between 41 and 42 decreases. In this case, as the pressure applied to the overcurrent protection element 4 is higher, the distance between the conductive fillers 44 becomes narrower and the resistance value between the electrodes 41 and 42 decreases, so that the pressure applied to the overcurrent protection element 4 is increased. The resistance value between the electrodes 41 and 42 is detected. Moreover, since the overcurrent protection element 4 does not use a semiconductor, it can be configured at low cost.

  In addition, as shown in FIG. 4A, the overcurrent protection element 4 has a mutual expansion of the conductive filler 44 in the material 43 as in the case where the material 43 is thermally expanded when the temperature rises and the applied pressure is reduced. The distance between the electrodes 41 and 42 increases, and the resistance value between the electrodes 41 and 42 increases. Then, as shown in FIG. 4B, the overcurrent protection element 4 is formed between the conductive fillers 44 in the material 43 as in the case where the material 43 contracts when the temperature decreases and the applied pressure increases. A space | interval becomes narrow and the resistance value between the electrodes 41 and 42 decreases.

  FIG. 5 is a block diagram showing an example of the electrical configuration of the battery pack 1 shown in FIG. A battery pack 1 shown in FIG. 1 includes a control IC (Integrated Circuit) 51, external connection terminals 61, 62, 63, 64, a battery 3, an overcurrent protection element 4, a thermistor 7, a current detection unit 8, and switching elements Q1, Q2. , Q3, temperature fuses F1, F2, and a heater Rh.

  The thermistor 7 corresponds to an example of a temperature detection unit that detects the temperature inside the housing 2. The temperature detector may be any sensor that detects temperature, and is not limited to a thermistor. The current detection unit 8 detects the charge / discharge current of the battery 3 and outputs a signal indicating the current value Is to the control IC 51. The current detection unit 8 is configured using, for example, a shunt resistor, a Hall element, an A / D (analog / digital) converter, or the like. The switching elements Q1, Q2, and Q3 are switching elements such as FET (Field Effect Transistor), for example.

  The external connection terminals 61, 62, 63 and 64 are connection terminals of the connection connector 6. The external connection terminals 61, 62, 63, 64 are connected to a charging device for charging the battery 3, or are driven by a battery such as a mobile phone, a digital camera, or a portable personal computer that is driven by a discharge current from the battery 3 It is a connection terminal for connecting devices. The external connection terminal 61 is connected to the positive electrode of the battery 3 via the temperature fuses F1 and F2, the overcurrent protection element 4, the switching elements Q1 and Q2, and the current detection unit 8. The external connection terminal 62 is connected to the negative electrode of the battery 3, that is, the circuit ground. The external connection terminals 63 and 64 are communication terminals for performing data transmission / reception with a charging device or a battery driving device connected to the battery pack 1.

  The switching element Q1 has a direction in which the anode of the parasitic diode is on the battery 3 side, and the switching element Q2 has a direction in which the anode of the parasitic diode is on the external connection terminal 61 side. The switching element Q1 is used as an overcharge protection switch that cuts off the charging current when the battery 3 is overcharged, and the switching element Q2 is discharged when the discharge current of the battery 3 becomes excessive. Used as an overdischarge protection switch that cuts off current.

  The connection point between the thermal fuse F1 and the thermal fuse F2 is connected to the negative electrode of the battery 3 through the heater Rh and the switching element Q3. The gate of the switching element Q3 is connected to the control IC 51. When the switching element Q3 is turned on according to a control signal from the control IC 51, the heater Rh generates heat and the thermal fuses F1 and F2 are blown.

  The control IC 51 includes, for example, a control unit 53, A / D (analog / digital) converters 54 and 55, and a memory 57. The memory 57 is configured by a nonvolatile memory element such as an EEPROM (Electrically Erasable and Programmable Read Only Memory). The memory 57 stores in advance a data table showing the relationship between the temperature and the resistance value Rs between the electrodes 41 and 42 of the overcurrent protection element 4.

  The input terminal of the A / D converter 54 is connected to the positive electrode of the battery 3, and the output terminal is connected to the control unit 53. The A / D converter 54 detects the terminal voltage of the battery 3, converts it into a digital value, and outputs it to the control unit 53. The input terminal of the A / D converter 55 is connected to both ends of the overcurrent protection element 4, that is, to the electrodes 41 and 42. The A / D converter 55 converts the voltage between the electrodes 41 and 42 into a digital value and outputs the digital value to the control unit 53 as a voltage value Vs.

  The control unit 53 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) that stores a predetermined control program, and a RAM (Random Access Memory) that temporarily stores data. And an I / O port and peripheral circuits thereof. And the control part 53 functions as the charging / discharging control part 531, the abnormality detection part 532, the prohibition control part 533, the alerting | reporting part 534, and the decomposition | disassembly prohibition part 535 by running the control program memorize | stored in ROM.

  The charging / discharging control unit 531 transmits information necessary for charging the battery 3 such as the terminal voltage of the battery 3 output from the A / D converter 54 and the temperature detected by the thermistor 7, for example, communication not shown. The data is transmitted from the interface circuit to the charging device connected to the outside via the external connection terminals 63 and 64. Alternatively, the charging / discharging control unit 531 calculates a charging voltage and a charging current based on, for example, the terminal voltage of the battery 3 output from the A / D converter 54, the temperature detected by the thermistor 7, and the like. By transmitting a request for the charging voltage and charging current from the communication interface circuit to the externally connected charging device via the external connection terminals 63 and 64, the battery 3 is charged by the charging device. May be.

  In addition, the charge / discharge control unit 531 compares the terminal voltage of the battery 3 input from the A / D converter 54 with a preset overcharge protection voltage value V1. When the terminal voltage of the battery 3 reaches the overcharge protection voltage value V1, the charging / discharging control unit 531 turns off the switching element Q1 and opens the charging / discharging path of the battery 3. Thus, when the terminal voltage of the battery 3 reaches the overcharge protection voltage value V1, the connection between the external connection terminal 61 and the battery 3 is interrupted and the charging is stopped, so that the battery 3 is protected from overcharge. Is done. The overcharge protection voltage value V1 is preset to, for example, 4.35V because the rated voltage of the battery 3 is 4.2V.

  In addition, the charge / discharge control unit 531 compares the terminal voltage of the battery 3 input from the A / D converter 54 with a preset overdischarge voltage value. When the terminal voltage of the battery 3 decreases to the overdischarge voltage value, the charge / discharge control unit 531 turns off the switching element Q2 to open the charge / discharge path of the battery 3. As described above, when the terminal voltage of the battery 3 decreases to the overdischarge voltage value, the battery 3 is disconnected from the circuit and protected from overdischarge. The overdischarge voltage value is set in advance to a minimum voltage value within a range in which the characteristics of the battery 3 are not deteriorated.

  Further, based on the temperature detected by the thermistor 7, the charge / discharge control unit 531 turns off the switching elements Q <b> 1 and Q <b> 2 and stops charging / discharging of the battery 3 when the battery 3 becomes abnormally hot. Thereby, the risk that the battery 3 is deteriorated or damaged by heat generation is reduced.

  The abnormality detection unit 532 detects the pressure value applied to the overcurrent protection element 4 by detecting the resistance value Rs of the overcurrent protection element 4 and converting this resistance value into a pressure. Specifically, for example, the abnormality detection unit 532 includes the voltage value Vs indicating the voltage between the electrodes 41 and 42 acquired by the A / D converter 55 and the charge / discharge current of the battery 3 acquired by the current detection unit 8. And the resistance value Rs of the overcurrent protection element 4 is calculated as Vs / Is.

  Further, the abnormality detection unit 532 uses a constant current circuit (not shown), for example, to flow a constant current Is set in advance to the overcurrent protection element 4, and between the electrodes 41 and 42 acquired by the A / D converter 55. By acquiring the voltage Vs, the resistance value Rs of the overcurrent protection element 4 can be calculated as Vs / Is even when the battery 3 is not charged or discharged.

  For example, when the battery 3 expands due to overcharging and the pressure applied to the overcurrent protection element 4 increases and the resistance value Rs falls below a predetermined resistance value Rth1 (first threshold value), the abnormality detection unit 532 3 is determined to be excessively expanded, and abnormality of the battery 3 is detected.

  In this case, for example, when the expansion of the battery 3 becomes an excessive expansion amount that may cause deterioration or failure, an excessive pressure corresponding to the pressure P1 (first pressure) applied to the overcurrent protection element 4 is obtained. The resistance value Rs of the current protection element 4 is set as the resistance value Rth1. Further, the resistance value Rth1 is set in a range of the resistance value Rs obtained in accordance with, for example, expansion that allows the battery 3 to be used continuously if the battery 3 is discharged and contracted.

  When the abnormality detection unit 532 detects an abnormality in the battery 3, the notification unit 534 connects information indicating that an abnormality has occurred to the outside from the communication interface circuit (not shown) via the external connection terminals 63 and 64. Send to charging device or battery-powered device. For example, a display device such as an LED (Light Emitting Diode) that is turned on when an abnormality of the battery 3 is detected by the abnormality detection unit 532, a buzzer, or the like may be provided as a notification unit.

  Thereby, when the battery 3 is abnormally expanded, information indicating that the abnormality has occurred is transmitted to the externally connected charging device or battery-driven device, so that charging is stopped by the charging device or the battery-driven device is operated by the user. It is possible to notify the occurrence of an abnormality.

  When the abnormality detection unit 532 detects an abnormality in the battery 3, the prohibition control unit 533 turns off the switching elements Q <b> 1 and Q <b> 2 and immediately prohibits charging / discharging of the battery 3. The battery 3 may expand cumulatively by repeating charging and discharging, and does not always expand due to overcharging, but in many cases, the expansion of the battery 3 is considered to be caused by overcharging. Therefore, the prohibition control unit 533 may turn off only the switching element Q1 to prohibit only charging.

  For example, when the battery 3 expands due to overcharging and the pressure applied to the overcurrent protection element 4 increases and the resistance value Rs falls below the resistance value Rth3 smaller than the resistance value Rth1, the prohibition control unit 533 switches the switching element Q3. Is turned on to cause the heater Rh to generate heat and melt the thermal fuses F1 and F2, thereby opening the charge / discharge path of the battery 3 and permanently prohibiting the charge / discharge of the battery 3.

  In this case, for example, when the expansion of the battery 3 reaches an expansion amount that may cause a safety problem such as rupture, the pressure P3 (first pressure) applied to the overcurrent protection element 4 is determined. The resistance value Rs of the overcurrent protection element 4 is set as the resistance value Rth3 (first threshold value).

  Here, the resistance value Rs when the pressure P1 corresponding to the expansion amount at which the expansion of the battery 3 may deteriorate or break down is applied to the overcurrent protection element 4 is set as the resistance value Rth1. That the resistance value Rs is lower than the resistance value Rth1 indicates that the pressure applied to the overcurrent protection element 4 exceeds the pressure P1. Furthermore, the resistance value Rs when the pressure P3 corresponding to the expansion amount that may cause a safety problem such as the battery 3 expanding may cause a safety problem is applied as the resistance value Rth3. The resistance value Rs being set and falling below the resistance value Rth3 indicates that the pressure applied to the overcurrent protection element 4 has exceeded the pressure P3.

  The disassembly prohibition unit 535 causes the pressure applied to the overcurrent protection element 4 to decrease due to being sandwiched between the case 2 and the battery 3 by, for example, a third party disassembling the case 2, The resistance value of the current protection element 4 exceeds the preset resistance value Rth2 (second threshold value), that is, the pressure applied to the overcurrent protection element 4 becomes equal to or less than the preset pressure P2 (second pressure). In this case, the switching elements Q1 and Q2 are turned off to immediately prohibit charging / discharging of the battery 3, and the switching element Q3 is turned on to cause the heater Rh to generate heat so that the thermal fuses F1 and F2 are blown. Permanently prohibit charging / discharging. In this case, the pressure P2 is set in advance to a pressure lower than the set pressure Ps. Further, the resistance value Rs of the overcurrent protection element 4 when the pressure P2 is applied to the overcurrent protection element 4 is preset as the resistance value Rth2.

  In addition, the abnormality detection unit 532, the prohibition control unit 533, and the disassembly prohibition unit 535 are data indicating the relationship between the resistance value Rs between the electrodes 41 and 42 of the overcurrent protection element 4 and the temperature stored in the memory 57. Based on the table, the resistance values Rth1, Rth2, and Rth3 are increased as the temperature acquired by the thermistor 7 increases. As a result, the resistance values Rth1, Rth2, and Rth3 of the overcurrent protection element 4 indicate the above-described pressures P1, P2, and P3 regardless of the temperature.

  Next, the operation of the battery pack 1 configured as described above will be described. First, a charging device (not shown) is connected to the external connection terminals 61, 62, 63 and 64, and a charging current is supplied to the battery 3 through the external connection terminals 61 and 62. When the battery 3 expands due to overcharging or the like, or expands and deforms in a round shape, the pressure applied to the overcurrent protection element 4 sandwiched between the housing 2 and the case 31 increases. As shown in FIG. 4B, the pressure of the material 43 is deformed, the interval between the conductive fillers 44 is narrowed, and the resistance value Rs between the electrodes 41 and 42 is decreased.

  At this time, the battery 3 has the largest swelling at the approximate center of the wall surface of the maximum area of the case 31. Therefore, by disposing the overcurrent protection element 4 at a position covering the central point of the wall surface of the maximum area of the case 31, for example, the center point of the wall surface of the maximum area of the case 31, The expansion of 3 can be detected efficiently.

  Even when the casing 2 is made of a film-like material, if the battery 3 wrapped with the film-like material expands, the pressure applied to the overcurrent protection element 4 increases, and the electrode 41 , 42 decreases in resistance value Rs.

  Then, the abnormality detection unit 532 detects the resistance value Rs of the overcurrent protection element 4, and an abnormality is detected when the resistance value Rs falls below the resistance value Rth1. When an abnormality is detected by the abnormality detection unit 532, the notification of the abnormality is performed by the notification unit 534, and the switching element Q1 is turned off by the prohibition control unit 533 so that charging of the battery 3 is prohibited immediately. The possibility that the battery 3 may deteriorate or break down due to overcharging is reduced. Here, the resistance value Rth1 is set in the range of the resistance value Rs obtained according to the expansion that allows the battery 3 to be continuously used if the battery 3 is discharged and reduced, and therefore the battery 3 is discharged. When the pressure applied to the overcurrent protection element 4 decreases and the resistance value Rs becomes equal to or higher than the resistance value Rth1, the prohibition control unit 533 turns on the switching element Q1 to allow the battery 3 to be charged.

  Next, when the expansion of the battery 3 proceeds and the pressure applied to the overcurrent protection element 4 further increases and the resistance value Rs of the overcurrent protection element 4 falls below the resistance value Rth3, the prohibition control unit 533 causes the switching element Q3 to switch. Is turned on, the heater Rh generates heat, and the thermal fuses F1 and F2 are blown to open the charging / discharging path of the battery 3, and the charging / discharging of the battery 3 is permanently prohibited. As a result, when the expansion of the battery 3 reaches an expansion amount that may cause a safety problem such as rupture, the charging / discharging of the battery 3 is permanently prohibited, so that the safety of the battery pack 1 is increased. Improves.

  By the way, the secondary battery accommodated in the battery pack deteriorates as charging and discharging are repeated. Therefore, in recent years, there has been an unskilled person who replaces a secondary battery of a deteriorated battery pack and sells it as a genuine battery pack without permission from the manufacturer of the battery pack. However, such a modified product has a safety problem because an authorized manufacturer of the battery pack cannot perform quality control. In addition, the reliability of the user who purchased the battery pack by believing that it was manufactured by an authorized manufacturer may be lost.

  Therefore, for example, when the battery pack 1 is disassembled, the battery pack 1 is sandwiched between the casing 2 and the battery 3 so that the pressure applied to the overcurrent protection element 4 is eliminated. When the resistance value of the overcurrent protection element 4 exceeds the resistance value Rth2 (second threshold value), the disassembly prohibition unit 535 turns off the switching elements Q1 and Q2 and promptly prohibits charging / discharging of the battery 3 to be safe. Is improved. Furthermore, switching element Q3 is turned on by disassembly prohibition unit 535, heater Rh generates heat, and thermal fuses F1, F2 are blown. Thereby, charging / discharging of the battery 3 is permanently prohibited. Thereby, for example, when an unauthorized recycler tries to disassemble the battery pack 1 and replace the battery 3 with a bad secondary battery, the charging and discharging of the battery 3 is permanent when the housing 2 is disassembled. Therefore, it is possible to reduce the risk that the battery pack 1 loaded with a bad secondary battery will be distributed to the market and cause damage to consumers or the trust of the authorized manufacturer of the battery pack 1 may be impaired. Is done.

  The disassembly prohibition unit 535 is not limited to the example of permanently prohibiting charging / discharging of the battery 3 by fusing the thermal fuses F1, F2, but for example, information indicating that charging / discharging of the battery 3 is prohibited is stored in the memory 57. If the information that prohibits charging / discharging of the battery 3 is stored in the memory 57, the switching elements Q1 and Q2 are turned off at least once regardless of the resistance value of the overcurrent protection element 4. When the resistance value Rs of the overcurrent protection element 4 exceeds the resistance value Rth2 due to the pressure and the safety of the battery 3 is impaired or the battery pack 1 is disassembled, charging / discharging of the battery 3 is permanently prohibited. You may do it.

  The prohibition control unit 533 and the disassembly prohibition unit 535 are not limited to the example of prohibiting charging of the battery 3 by fusing the temperature fuses F1 and F2 or turning off the switching element Q1, for example, an external connection terminal By transmitting a request signal for stopping the supply of the charging current to a charging device (not shown) connected to 61, 62, 63, 64, for example, from a communication interface circuit (not shown) via the external connection terminals 63, 64. The charging of the battery 3 may be prohibited.

  Further, when an overcurrent flows through the battery 3 and the current value exceeds the cutoff current value of the overcurrent protection element 4, the resistance value of the overcurrent protection element 4 increases and the flowing current is interrupted. Thereby, the battery 3 is protected from charging / discharging by overcurrent.

  As described above, as shown in FIG. 3, the pressure generated by the expansion of the battery 3 can be detected by the overcurrent protection element 4 that does not use a semiconductor, so that the pressure is detected using a semiconductor sensor. However, it is easy to reduce the cost of the battery pack 1. In addition, since the overcurrent protection element 4 for overcurrent protection can be used as a bulge detection unit, it is not necessary to separately provide a bulge detection unit in addition to the overcurrent protection element 4, and it is easy to reduce costs. It becomes.

  In addition, the overcurrent protection element 4 is not necessarily limited to an example in which the overcurrent protection element 4 is disposed at substantially the center of the wall surface of the maximum area of the case 31. Further, the overcurrent protection element 4 provided on the charge / discharge path is not limited to the example used as the swelling detection unit. For example, a swell detector dedicated to pressure detection, which is configured in the same manner as the overcurrent protection element 4 shown in FIG. 3, may be provided at the position of the overcurrent protection element 4 shown in FIG.

  Further, the overcurrent protection element 4 may be configured integrally with the overcurrent protection element 4 and the battery 3 by using, for example, a case 31 made of a metal conductor as the electrode 42. In this case, since it is not necessary to provide the electrode 42 separately, it becomes easy to reduce cost.

(Second Embodiment)
Next, a battery pack according to a second embodiment of the present invention will be described. The battery pack 1 a according to the second embodiment of the present invention is different from the battery pack 1 shown in FIG. 1 in that a pressure switch 4 a (swelling detection unit) is provided instead of the overcurrent protection element 4. The operation of the abnormality detection unit 532a is different from the abnormality detection unit 532 as described later.

  FIG. 6 is an explanatory diagram showing an example of the configuration of the pressure switch 4a shown in FIG. The pressure switch 4a shown in FIG. 6 is arranged to face each other so as to cover at least a part of each of the electrodes 401 and 402, and the electrodes 401 (third electrode) and the electrode 402 (fourth electrode) provided at intervals. The conductive member 403 and the elastic member 404 that holds the conductive member 403 apart from the electrodes 401 and 402 are configured.

  The electrodes 401 and 402 are provided on the outer wall surface of the case 31 of the battery 3. The metal case 31 and the electrodes 401 and 402 are insulated by an insulating means such as an insulating film (not shown). The elastic member 404 is provided so as to straddle the space between the electrodes 401 and 402 so that the top of the arcuate portion contacts the inner wall of the housing 2.

  In addition, a conductive member 403 is attached to the lower part of the arcuate portion of the elastic member 404. As a result, the battery 3 expands and the interval between the inner wall of the housing 2 and the outer wall of the case 31 is narrowed. When pressure is applied to the arcuate portion of the elastic member 404, the elastic member 404 is elastically deformed and the conductive member 403 is deformed. It is displaced in the direction of the electrodes 401 and 402.

  The electrodes 401 and 402 are brought into conduction by contacting the electrodes 401 and 402 so that the conductive member 403 straddles the gap between the electrodes 401 and 402. As the elastic member 404, for example, insulating silicone rubber is preferably used. Silicone rubber does not require the use of various additives that contaminate and corrode electronic components such as electrodes 401 and 402, such as softeners and anti-aging agents used in natural rubber and synthetic rubber, making it heat resistant and flame retardant. Therefore, it is suitable for use as the conductive member 403.

  As the conductive member 403, for example, a conductive silicone rubber in which a conductive filler such as carbon black or metal fine particles is mixed in an insulating silicone rubber is preferably used. Note that the elastic member 404 only needs to have elasticity and insulation. The elastic member 404 may be, for example, natural rubber or synthetic rubber. For example, the leaf spring may be bowed and the leaf spring and the electrodes 401 and 402 may be insulated from each other.

  FIG. 7 is a block diagram showing an example of the electrical configuration of the battery pack 1a shown in FIG. The battery pack 1a shown in FIG. 7 differs from the battery pack 1 shown in FIG. 5 in that the pressure switch 4a is connected to the control unit 53a and that the A / D converter 55 and the current detection unit 8 are not provided. . In this case, the overcurrent protection element 4 is used only for the purpose of protecting the battery 3 from overcurrent.

  Since the other configuration is the same as that of the battery pack 1 shown in FIG. 1, the description thereof will be omitted, and the characteristic points of the present embodiment will be described below. First, when the battery 3 expands and the interval between the inner wall of the housing 2 and the outer wall of the case 31 is narrowed and pressure is applied to the arcuate portion of the elastic member 404, the elastic member 404 is elastically deformed, and the conductive member 403 becomes an electrode. The electrodes 401 and 402 are electrically connected by being displaced in the 401 and 402 directions and contacting the electrodes 401 and 402 so that the conductive member 403 straddles the gap between the electrodes 401 and 402.

  Then, the abnormality detection unit 532a detects conduction between the electrodes 401 and 402, that is, the pressure switch 4a is turned on, and the abnormality of the battery 3 is detected. When an abnormality is detected by the abnormality detection unit 532a, the notification of the abnormality is performed by the notification unit 534 and charging of the battery 3 is prohibited by the prohibition control unit 533, as in the battery pack 1 shown in FIG.

  The prohibition control unit 533 stops the supply of charging current to a charging device (not shown) connected to the external connection terminals 61, 62, 63, 64 by fusing the thermal fuses F 1, F 2, turning off the switching element Q 1, and the like. The charging of the battery 3 is prohibited by transmitting a request signal to be transmitted.

  In this case, as shown in FIG. 6, the pressure switch 4a can detect the expansion of the battery 3 without using an expensive semiconductor sensor, so that the battery pack is more effective than the case where the pressure is detected using the semiconductor sensor. It becomes easy to reduce the cost of 1a. Moreover, since the abnormality detection part 532a should just detect abnormality of the battery 3 when the electrodes 401 and 402 of the pressure switch 4a conduct | electrically_connect, the process of the abnormality detection part 532a rather than the battery pack 1 shown in FIG. It can be simplified.

(Third embodiment)
Next, a battery pack according to a third embodiment of the present invention will be described. The battery pack 1 b according to the third embodiment of the present invention is different from the battery pack 1 shown in FIG. 1 in that a swell detection unit 4 b is provided instead of the overcurrent protection element 4.

  FIG. 8 is an explanatory diagram showing an example of the configuration of the swelling detection unit 4b shown in FIG. FIG. 8A shows a normal state, and FIG. 8B shows a state where the battery 3 expands and the case 31 expands. 8 includes an electrode 411 (first electrode) disposed on the inner wall surface of the housing 2 and an insulating sheet 412 attached to the surface of the battery 3 in the electrode 411 on the case 31 side. I have.

  The case 31 is made of a metal conductor. The case 31 is connected to the positive electrode of the battery 3. The case 31 may be configured to be connected to the ground. In this case, the case 31 corresponds to an example of a second electrode, and the electrode 411, the insulating sheet 412, and the case 31 correspond to an example of a swollen detection unit.

  As a result of the electrode 411 and the case 31 being arranged to face each other, a capacitance is generated between the electrode 411 and the case 31. The distance between the case 31 and the electrode 411 is set so that the capacitance between the electrode 411 and the case 31 becomes a preset reference capacity in a normal state where the battery 3 is not expanded. The battery 3 is fixed to the housing 2 so that the distance between the electrode 411 and the case 31 set in this way is maintained in a state where the battery 3 is not expanded. The capacitance between the electrode 411 and the case 31 increases as the distance between the electrode 411 and the case 31 decreases.

  FIG. 9 is a block diagram showing an example of the electrical configuration of the battery pack 1b shown in FIG. The battery pack 1b shown in FIG. 9 is different from the battery pack 1a shown in FIG. 7 in that the pressure switch 4a is not provided, and that the swelling detection unit 4b and the capacitance detection unit 9 are provided. The abnormality detection unit 532b is different in operation from the abnormality detection unit 532a as described later.

  Since the other configuration is the same as that of the battery pack 1 shown in FIG. 1, the description thereof will be omitted, and the characteristic points of the present embodiment will be described below. The swelling detection unit 4b shown in FIG. 9 functions as a variable capacitor, for example, by arranging the case 31 and the electrode 411 so as to face each other. A case 31 that functions as one electrode of the variable capacitor is connected to, for example, the positive electrode of the battery 3, and the other electrode 411 is connected to the capacitance detection unit 9.

  The capacitance detection unit 9 detects the capacitance of the bulge detection unit 4b and outputs a signal indicating the capacitance to the abnormality detection unit 532b. The capacitance detection unit 9 detects a current flowing through the bulge detection unit 4b by supplying a periodic signal having a preset frequency to the bulge detection unit 4b, for example. And the electrostatic capacitance detection part 9 detects the electrostatic capacitance of the swelling detection part 4b based on the periodic signal of the said periodic signal, and the electric current which flows into the swelling detection part 4b, for example.

  And as shown in FIG.8 (b), when the battery 3 expand | swells and the space | interval of the outer wall of the case 31 and the electrode 411 becomes narrow, the electrostatic capacitance of the swell detection part 4b will increase. Next, the electrostatic capacitance detection unit 9 detects the electrostatic capacitance of the swelling detection unit 4b, and a signal indicating the electrostatic capacitance is output to the abnormality detection unit 532b.

  Further, when the capacitance of the swelling detection unit 4b detected by the capacitance detection unit 9 exceeds a preset reference capacity, the abnormality detection unit 532b detects an abnormality of the battery 3. When an abnormality is detected by the abnormality detection unit 532b, the notification of the abnormality is performed by the notification unit 534 and charging of the battery 3 is prohibited by the prohibition control unit 533, as in the battery pack 1 shown in FIG.

  The prohibition control unit 533 stops the supply of charging current to a charging device (not shown) connected to the external connection terminals 61, 62, 63, 64 by fusing the thermal fuses F 1, F 2, turning off the switching element Q 1, and the like. The charging of the battery 3 is prohibited by transmitting a request signal to be transmitted.

  In this case, as shown in FIG. 8, the swelling detection unit 4b can detect the expansion of the battery 3 without using an expensive semiconductor sensor, so that the battery is detected rather than the case where the pressure is detected using the semiconductor sensor. It becomes easy to reduce the cost of the pack 1b. Further, since the case 31 is used as an electrode, it is not necessary to provide a separate electrode, and the cost can be easily reduced. In addition, the swelling detection part 4b is not restricted to the example which uses the case 31 as a 2nd electrode, It is good also as a structure which arrange | positions a 2nd electrode separately in the position facing the electrode 411 in the outer wall surface of the case 31. FIG.

  Further, for example, as shown in FIG. 10A, a bulge detection unit 4c in which the insulating sheet 412 (at least a part thereof) is removed from the bulge detection unit 4b may be used instead of the pressure switch 4a shown in FIG. . Then, in a normal state where the battery 3 is not expanded, the battery 3 is fixed to the housing 2 in a state where the case 31 and the electrode 411 are separated so as not to contact each other. In this case, when the battery 3 expands, the distance between the inner wall of the housing 2 and the outer wall of the case 31 is reduced, and the electrode 411 and the outer wall of the case 31 are in contact with each other as shown in FIG.

  Then, the abnormality detection unit 532a detects that the electrode 411 and the case 31 are electrically connected, and charging of the battery 3 is prohibited. In this case, since the swelling detector 4c is configured only by attaching the electrode 411 to the inner wall surface of the housing 2, it is easier to reduce the cost than the pressure switch 4a shown in FIG.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for a battery pack used as a power source for a battery-mounted device such as an electronic device such as a portable personal computer, a digital camera, or a mobile phone, a vehicle such as an electric vehicle or a hybrid car.

It is a perspective view which shows an example of a structure of the battery pack which concerns on one Embodiment of this invention. It is sectional drawing which shows the XX cross section of the battery pack shown in FIG. It is explanatory drawing which shows an example of a structure of the overcurrent protection element used for the battery pack which concerns on the 1st Embodiment of this invention. It is explanatory drawing for demonstrating the mechanism of the pressure detection by the overcurrent protection element shown in FIG. (A) shows a state where the pressure applied to the overcurrent protection element is low, and (b) shows a state where the pressure applied to the overcurrent protection element is high. It is a block diagram which shows an example of the electrical constitution of the battery pack which concerns on the 1st Embodiment of this invention. It is explanatory drawing which shows an example of a structure of the pressure switch used for the battery pack which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows an example of the electrical constitution of the battery pack which concerns on the 2nd Embodiment of this invention. It is explanatory drawing which shows an example of a structure of the swelling detection part used for the battery pack which concerns on the 3rd Embodiment of this invention. (A) shows a normal state, and (b) shows a state where the battery expands and the case expands. It is a block diagram which shows an example of the electrical constitution of the battery pack which concerns on the 3rd Embodiment of this invention. It is explanatory drawing which shows the modification of the pressure switch shown to FIG. 6, FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b Battery pack 2 Case 3 Battery 4 Overcurrent protection element 4a Pressure switch 4b, 4c Swelling detection part 5 Control unit 6 Connector 7 Thermistor 8 Current detection part 9 Capacitance detection part 31 Case 41, 42, 401, 402, 411 Electrode 43 Material 44 Conductive filler 53, 53a Control unit 54, 55 A / D converter 57 Memory 61, 62, 63, 64 External connection terminal 403 Conductive member 404 Elastic member 412 Insulating sheet 531 Charge / discharge control unit 532, 532a, 532b Abnormality detection unit 533 Prohibition control unit 534 Notification unit 535 Disassembly prohibition unit F1, F2 Thermal fuse Ps Set pressure Q1, Q2, Q3 Switching element Rh Heater

Claims (11)

A secondary battery,
An outer shell for housing the secondary battery;
A swell detector that is disposed between the inner wall of the outer shell and the secondary battery, and detects a pressure applied by the inner wall of the outer shell and the secondary battery;
An abnormality detection unit that detects an abnormality of the secondary battery when the pressure detected by the swelling detection unit exceeds a preset first pressure;
The swelling detection unit
The first and second electrodes arranged opposite to each other are filled with a material that can be deformed by pressure, and conductive filler having a lower electric resistance than that of the material is dispersed and held in the material. And the resistance value between the first and second electrodes decreases as the pressure applied between the second and second electrodes increases.
The abnormality detection unit
A battery pack, wherein the resistance value between the first and second electrodes is acquired as information indicating the pressure detected by the swelling detection unit. The swelling detection unit
Further, the charge / discharge path of the secondary battery is interposed in the charge / discharge path so as to pass between the first and second electrodes, and a current flowing between the first and second electrodes is preset. 2. The battery pack according to claim 1, wherein when the cut-off current value is exceeded, the conductive fillers are separated from each other due to expansion of the material to substantially cut off the charge / discharge path. A temperature detection unit for detecting the temperature;
The swelling detection unit
Furthermore, the resistance value between the first and second electrodes increases as the temperature increases,
The abnormality detection unit
When a resistance value between the first and second electrodes is less than a first threshold value set as a resistance value indicating the first pressure, an abnormality of the secondary battery is detected and detected by the temperature detection unit. The battery pack according to claim 1, wherein the first threshold value is increased as the measured temperature increases. The swelling detection unit
The inner wall of the outer shell and the secondary battery are disposed in a state where a set pressure smaller than the first threshold is applied,
The decomposition | disassembly prohibition part which prohibits charge of the said secondary battery when the pressure detected by the said swelling detection part is below 2nd pressure smaller than the said setting pressure is further provided. The battery pack according to any one of the above. A secondary battery,
An outer shell for housing the secondary battery;
Swell detection having a first electrode disposed on the inner wall of the outer shell and a second electrode disposed on the outer wall of the secondary battery at a position facing the first electrode and spaced from the first electrode. And
A battery pack, comprising: an abnormality detection unit that detects an abnormality of the secondary battery when an electrostatic capacitance generated between the first and second electrodes exceeds a preset reference capacity. A secondary battery,
An outer shell for housing the secondary battery;
Swell detection having a first electrode disposed on the inner wall of the outer shell and a second electrode disposed on the outer wall of the secondary battery at a position facing the first electrode and spaced from the first electrode. And
A battery pack, comprising: an abnormality detection unit that detects an abnormality of the secondary battery when the first electrode and the second electrode are electrically connected. The battery pack according to claim 1, wherein an outer wall of the secondary battery is configured by a metal conductor and is used as the second electrode. A secondary battery,
An outer shell for housing the secondary battery;
A swell detector that is disposed between the inner wall of the outer shell and the secondary battery, and whose conduction state changes according to the distance between the inner wall of the outer shell and the secondary battery;
An abnormality detection unit that detects an abnormality of the secondary battery based on a conduction state of the swelling detection unit;
The swelling detection unit
Third and fourth electrodes provided at a distance from each other;
A conductive member disposed so as to cover at least a part of each of the third and fourth electrodes;
The conductive member includes the third and fourth electrodes, and an elastic member that holds the conductive member so as to be vertically separated from the inner wall of the outer shell,
The abnormality detection unit
The battery pack, wherein an abnormality of the secondary battery is detected when the third electrode and the fourth electrode are electrically connected. 9. The apparatus according to claim 1, further comprising a prohibition control unit that prohibits at least one of charging and discharging of the secondary battery when the abnormality is detected by the abnormality detection unit. The battery pack described. The battery pack according to any one of claims 1 to 9, further comprising a notifying unit that notifies the occurrence of an abnormality when the abnormality is detected by the abnormality detecting unit. The secondary battery has a flat and substantially box shape,
The swelling detection unit
The battery pack according to any one of claims 1 to 10, wherein the battery pack is disposed between a substantially center of a wall surface of a maximum area of the secondary battery and an inner wall of the outer shell.

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