JP5977119B2 - Secondary battery pack with charge / discharge protection function - Google Patents

Description

  The present invention relates to a battery pack that incorporates a secondary battery and supplies power, and more particularly, to a secondary battery pack having a charge / discharge protection function that stops charging / discharging of a secondary battery in response to an overcurrent during charging / discharging. .

  The battery pack is provided in a state in which current can be passed from the output terminal connected to the positive and negative electrodes of the built-in secondary battery, and can be used by normal charging and discharging. In addition, in order to protect the secondary battery from abnormal states such as overcharge, overdischarge, excessive current, and abnormal temperature rise, it has a charge / discharge protection function that performs control to stop charging / discharging when an abnormal state occurs. That is, a charge / discharge control switch is interposed between the output terminal and the secondary battery, and the charge / discharge control switch is controlled by the protection circuit. When overcharge, overdischarge, or the like is detected, the protection circuit performs control to turn off the charge / discharge control switch and shut off the charge / discharge path.

  FIG. 5 shows a first conventional example of a secondary battery pack having such a charge / discharge protection function. This battery pack includes a secondary battery module 1 including one secondary battery and a protection circuit 2. The protection circuit 2 is connected to the secondary battery module 1 through the positive circuit terminal 3 and the negative circuit terminal 4, and discharges from the secondary battery module 1 to an external load via the positive output terminal 5 and the negative output terminal 6, or Charging of the secondary battery module 1 from the outside is performed.

  A PTC element 7 and a charge / discharge control switch 8 are inserted in a charge / discharge path on the negative electrode side connecting the negative circuit terminal 4 and the negative output terminal 6. The PTC element 7 is used to limit or cut off the current flowing through the charge / discharge path according to a change in resistance value according to the temperature rise due to heat generation of the secondary battery module 1.

  The charge / discharge control switch 8 is configured by connecting a discharge control FET (field effect transistor) 9a and a charge control FET 10a in series. The discharge control FET 9a is connected so that the parasitic diode 9b existing between the drain and the source is in a forward direction with respect to the charging current flowing from the positive electrode output terminal 5 toward the secondary battery module 1. The charge control FET 10a is connected such that the parasitic diode 10b is in the forward direction with respect to the discharge current.

  The voltage monitoring unit 11 is configured by, for example, a protection IC, and a power supply voltage is supplied from the secondary battery module 1 to the power supply terminal VDD via the resistor R1 and the capacitor C. The reference potential terminal VSS is connected to the secondary battery module 1 side of the charge / discharge control switch 8. Further, the overcurrent detection terminal V− is connected to the negative output terminal 6 side of the charge / discharge control switch 8 through the resistor R2.

  Control signals DO and CO from the protection IC 11 are supplied to the gates of the discharge control FET 9a and the charge control FET 10a, respectively. In normal charging and discharging operations, the control signals DO and CO are set to the high level, and the discharge control FET 9a and the charge control FET 10a are controlled to be in the ON state.

  The protection IC 11 detects a voltage between the reference potential terminal VSS and the overcurrent detection terminal VM, and detects a current that equivalently flows in the charge / discharge path from the detected voltage. That is, the current is equivalently detected based on the voltage drop caused by the ON resistance of the discharge control FET 9a and the charge control FET 10a. When a current exceeding a specified current value (that is, overcurrent) flows, the discharge control FET 9a or the charge control FET 10a is turned off to cut off the current.

  By the way, about the charge of a secondary battery, the request of quick charge is increasing. In particular, as the functionality of mobile phones and the like increases, lithium secondary batteries are required to have a higher capacity. Be longer than that. In order to avoid this, it is required to reduce the time required for charging by enabling charging with a larger current value.

  In order to enable charging with a large current, it is desirable to reduce the impedance of the secondary battery pack. Therefore, it is extremely important to reduce the on-resistance of the charge / discharge control switch 8. In order to reduce the resistance of the charge / discharge control switch 8, a configuration of the second conventional example as shown in FIG. 6 has been proposed.

  That is, in the protection circuit 12 of FIG. 6, the charge / discharge control switch 8 in FIG. 5 is configured by two sub control switches 8a and 8b connected in parallel. Other configurations are the same as those in FIG. Thereby, it is possible to reduce resistance. However, when a current flows through such a parallel circuit of the sub-control switches 8a and 8b, the voltage drop due to the on-resistance is small, and the setting level of the current detected as an overcurrent has to be increased.

  Here, it should be noted that the ON resistances of the discharge control FET 9a and the charge control FET 10a are subject to manufacturing variations and variations due to temperature characteristics. Furthermore, the ON resistances of the discharge control FET 9a and the charge control FET 10a also have a dependency on the gate voltage. As a result, a large variation occurs in the current range in which overcurrent is detected, and there is a problem that the accuracy of overcurrent detection is deteriorated.

  On the other hand, in a device having a very small load current, such as a mobile phone, it is required to detect an overcurrent in a range where the detection current is low for charge / discharge protection. In order to detect an overcurrent with high accuracy at such a low detection current level, it is necessary to reduce variations in overcurrent detection. Therefore, Patent Document 1 discloses a secondary battery pack having the configuration of the third conventional example shown in FIG.

  In the secondary battery pack of FIG. 7, the protection circuit 13 has a configuration in which a chip resistor 14 is added to the protection circuit 11 of FIG. That is, the chip resistor 14 is connected in series with the charge / discharge control switch 8. The chip resistor 14 is inserted in a range in which a voltage is detected by the reference potential terminal VSS and the overcurrent detection terminal VM. Therefore, the voltage monitoring unit 11 causes a voltage drop generated at both ends of the charge / discharge control switch 8 and the chip resistor 14. Based on this, an overcurrent is detected and the charge / discharge protection function is activated. According to this configuration, the low resistance of the charge / discharge control switch 8 can be compensated by the resistance value of the chip resistor 14, and the overcurrent detection level can be lowered. At the same time, since the resistance value of the chip resistor 14 has little variation, the variation in overcurrent detection can be reduced.

JP 2009-77610 A

  Although the configuration disclosed in Patent Document 1 shown in FIG. 7 discloses a current limiting element, the current is limited according to the temperature rise due to heat generation of the secondary battery module 1 as shown in FIG. The PTC element 7 is not described. However, it is practically desirable to provide a thermally responsive element for limiting the current according to the temperature rise of the secondary battery module 1.

  Therefore, in an actual configuration, the PTC element 7 and the overcurrent detection chip resistor 14 are connected in series. For this reason, the resistance of the charge / discharge path increases, and the impedance of the battery pack increases. Further, the increase in the number of circuit components due to the chip resistor 14 causes an increase in cost.

  Therefore, the present invention provides a secondary battery pack capable of appropriately operating a charge / discharge protection function by detecting an overcurrent with high accuracy by a low level detection current without increasing the impedance of the charge / discharge path. The purpose is to provide.

  The secondary battery pack of the present invention has, as a basic configuration, a secondary battery module including one or a plurality of secondary batteries, and a pair of output terminals respectively connected to the electrode terminals of the secondary battery module through a charge / discharge path. A charge / discharge control switch inserted in series in one of the charge / discharge paths, and a current detection unit for detecting a charge / discharge current flowing through the charge / discharge path, wherein the current value detected by the current detection unit is overcurrent A protection IC having a charge / discharge protection function for controlling the charge / discharge control switch to turn off when reaching a basin, and connected in series in the charge / discharge path, in response to an abnormal temperature rise of the secondary battery module A thermally responsive element that limits the charge / discharge current.

In order to solve the above-described problem, the secondary battery pack of the present invention is configured such that the current detection unit detects the charge / discharge current based on a voltage drop at both ends of the thermally responsive element, and temperature characteristics of the resistance value of the actuator element, the voltage variation width of the drop due to the temperature characteristics, the a acceptable range for charge and discharge protection, as the heat responsive element, a combination of bimetal and PTC element A structured breaker is used .

  According to the secondary battery pack having the above configuration, the thermoresponsive element has a charge / discharge current function for a charge / discharge protection function against an overcurrent, in addition to a function for limiting the charge / discharge current according to an abnormal temperature rise of the secondary battery module. It is also used for detection. As a result, without increasing the impedance of the charge / discharge path, it is possible to detect the overcurrent with high accuracy by the low level detection current and appropriately operate the charge / discharge protection function.

The block diagram which shows the circuit structure of the secondary battery pack in one embodiment of this invention Sectional drawing which shows the structure of the breaker which is an element of the secondary battery pack Sectional drawing which shows the structure of the mounting part of the protection circuit board in the secondary battery pack Sectional drawing of the principal part showing the configuration of the mounting portion of the protection circuit board in the secondary battery pack of the conventional example The top view which shows the manufacturing process of the mounting part of the protection circuit board in the secondary battery pack of one embodiment of this invention Block diagram showing a secondary battery pack of a first conventional example Block diagram showing a secondary battery pack of a second conventional example Block diagram showing a secondary battery pack of a third conventional example

  The secondary battery pack of the present invention can take the following aspects based on the above configuration.

  That is, a breaker composed of a combination of a bimetal and a PTC element is used as the thermally responsive element, and between the lead terminals of the breaker, an auxiliary via a main connection portion having a lower resistance than the PTC element and the PTC element. The main connecting portion is conductive by a connecting portion, and is kept in a conductive state when the temperature is lower than a set temperature. In the state exceeding the set temperature, the main connecting portion is operated according to thermal deformation of the bimetal. Can be configured to be in a non-conductive state.

  In this configuration, a protection circuit board on which the protection IC is mounted is mounted facing the electrode terminal of the secondary battery module, and the breaker is on the protection circuit board and one terminal is the protection circuit. The circuit board is mounted so as to be connected to a circuit on the substrate, and the other terminal of the breaker and one of the electrode terminals of the secondary battery module are connected by a metal lead.

  Moreover, a thermal fuse can be used as the thermally responsive element.

  The charge / discharge control switch may include a plurality of sub-control switches connected in parallel, and each of the plurality of sub-control switches may be a series circuit of a discharge control FET and a charge control FET. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Embodiment>
FIG. 1 is a block diagram showing a circuit configuration of a secondary battery pack according to an embodiment of the present invention. Components similar to those of the conventional example shown in FIG. 5 and the like will be described with the same reference numerals.

  The secondary battery pack includes a secondary battery module 1 configured by connecting one or more secondary batteries such as lithium ion batteries, for example. The secondary battery module 1 can be discharged to an external load or charged from the outside via the positive electrode output terminal 5 and the negative electrode output terminal 6 of the protection circuit 15.

  In the negative charge / discharge path connecting the negative circuit terminal 4 and the negative output terminal 6, the breaker 16 and two parallel control switches 8a and 8b connected in parallel are connected in series. A charge / discharge control switch for protecting the secondary battery module 1 from overcurrent is configured by a parallel circuit of the two sub control switches 8a and 8b. The breaker 16 has a configuration in which a bimetal and a PTC element are combined, and a specific structure and operation thereof will be described later.

  Each of the sub-control switches 8a and 8b is configured by connecting a discharge control FET 9a and a charge control FET 10a in series. The breaker 16 is used in place of the PTC element 7 in the conventional example shown in FIG. Therefore, the breaker 16 has a basic function of cutting off the current flowing through the charging / discharging path in accordance with the temperature rise due to heat generation of the secondary battery module 1. Therefore, it is connected in series in the charge / discharge path, and is disposed at a position adjacent to the secondary battery module 1.

  The voltage monitoring unit 17 is configured by, for example, a protection IC, and a power supply voltage is supplied from the secondary battery module 1 to the power supply terminal VDD via the resistor R1 and the capacitor C. The secondary battery module 1 side of the breaker 16 is connected to the reference potential terminal VSS. On the other hand, the negative output terminal 6 side of the breaker 16 is connected to the detection terminal CS of the voltage monitoring unit 17. Thus, in the present embodiment, the voltages at both ends of the breaker 16 are detected through the reference potential terminal VSS and the detection terminal CS, respectively. As a result, the voltage monitoring unit 17 detects an overcurrent based on the voltage drop across the breaker 16. This is a secondary function of the breaker 16 in the present embodiment. For this reason, the connection state with the voltage monitoring unit 17 is different from the PTC element 7 in the conventional example.

  Control signals DO and CO from the voltage monitoring unit 17 are supplied to the gates of the discharge control FET 9a and the charge control FET 10a, respectively. In normal charging and discharging operations, the control signals DO and CO are set to the high level, and the discharge control FET 9a and the charge control FET 10a are controlled to be in the ON state.

  The protection IC 17 detects a voltage between the reference potential terminal VSS and the detection terminal CS, and detects a current that equivalently flows in the charge / discharge path from the detected voltage. That is, the current is equivalently detected based on the voltage drop that occurs across the breaker 16. When a current exceeding a specified current value (that is, overcurrent) flows, the discharge control FET 9a or the charge control FET 10a is turned off to cut off the current.

  The structure of the breaker 16 is demonstrated with reference to sectional drawing of FIG. The breaker 16 is configured such that the leads 19 and 20 are supported by the frame body 18 so that the conduction form between the leads 19 and 20 changes. The outer ends of the leads 19 and 20 projecting outside the frame 18 are connected to the charge / discharge path as shown in FIG.

  In the frame 18, the lead 19 is disposed at the bottom and the lead 20 is disposed at the top, and is opposed to each other with a PTC element 21 and a bimetal 22 interposed therebetween. A bent portion 20a is formed at the end of the lead 20 in the frame 18 and a terminal protrusion 23 is provided at the tip thereof. When the terminal protrusion 23 contacts the lead 19, a first conduction state between the leads 19 and 20 is formed. The connection terminal portion 24 that forms the upper surface of the frame 18 is provided for convenience of connection with the lead 20.

  The bimetal 22 is curved so as to protrude upward as shown in the drawing at room temperature. On the other hand, when the temperature rises, the degree of bending becomes small (the curvature becomes small) and the end portion is displaced upward, so that the bent portion 20a of the lead 20 is pushed up. Accordingly, the terminal protrusion 23 is separated from the lead 19 and the current path through the terminal protrusion 23 is interrupted. As a result, the current path between the leads 19 and 20 is only the connection via the PTC element 21 and the bimetal 22 (second conduction state). In this state, the resistance is extremely high, and the current is substantially cut off, but some current flows. The heat generated thereby stabilizes the form of the bimetal 22 and prevents chattering.

  As is clear from the above operation, the resistance value between the leads 19 and 20 when the current flowing through the charge / discharge path is detected by the protection IC 17 is the first conduction state between the leads 19 and 20 via the terminal protrusion 23. The resistance value at. In the following description, this resistance value is referred to as a resistance value of the breaker 16.

  As described above, the present embodiment also uses the breaker 16 for the protection function against the abnormal temperature rise of the secondary battery module 1 as the current detection unit for the charge / discharge protection function against the excessive current in the charge / discharge path. It is characterized by that. The resistance value of the breaker 16 is generally less dependent on manufacturing variations and temperature than the on-resistance of the FET, and further, there is no problem of dependency on the gate voltage, so the overcurrent detection accuracy is good. It is.

  According to this configuration, since the breaker 16 that is originally used for protection against temperature rise is also used for overcurrent detection, the number of resistance elements is not increased. Therefore, increasing the impedance of the charge / discharge path is avoided. In addition, since the resistance value of the breaker 16 has little temperature dependence, it is possible to detect the overcurrent with high accuracy and to appropriately operate the charge / discharge protection function.

  It is not essential to employ a charge / discharge control switch including two sub control switches 8a and 8b connected in parallel. That is, even when the charge / discharge control switch is constituted by a series circuit of a single discharge control FET 9a and a charge control FET 10a as in the conventional example shown in FIG. However, if a charge / discharge control switch comprising two or more sub-control switches connected in parallel is employed, it is easy to reduce the resistance of the charge / discharge control switch, and an overcurrent detection by the breaker 16 is possible. The accuracy of is not affected. Thereby, the resistance loss of the entire secondary battery pack is reduced, which is advantageous for rapid charging with a large current.

  The breaker 16 can be replaced with another thermal actuator such as a thermal fuse. The thermally responsive element means an element having a function of limiting the current flowing through the charge / discharge path in accordance with the temperature rise due to heat generation of the secondary battery module 1. Such a thermally responsive element needs to have a resistance value large enough to cause a voltage drop sufficient for the protection IC 17 to measure due to the current flowing through the charge / discharge path.

  In addition, a thermoresponsive element having a resistance temperature characteristic within a predetermined range is used. That is, it is necessary that the range of change due to the temperature characteristic of the voltage drop detected by the protection IC 17 is in an allowable range for the charge / discharge protection function that controls the charge / discharge control FETs 9a and 10a to be turned off according to the overcurrent. However, it may be in an allowable range within the range of normal practical conditions of the secondary battery pack. In consideration of such temperature characteristics of the resistance value, the PTC element 7 used for limiting the current of the charging / discharging path at the time of abnormal temperature rise in the conventional example is sufficiently used as the thermally responsive element of the present embodiment. It cannot be said that it has desirable characteristics. This is because the PTC element 7 uses temperature characteristics in which the resistance value rapidly increases or decreases with a slight change in ambient temperature.

  Next, an example of the mounting structure of the thermally responsive element in the secondary battery pack of the present embodiment will be described with reference to FIG. 3A. FIG. 3A is an example of the arrangement of the thermal response element unique to the present invention, and is adopted when the breaker 16 is used as the thermal response element. According to this arrangement, as described later, an advantage of simplifying the battery pack manufacturing process can be obtained. For comparison, FIG. 3B shows a structure in which a PTC element 7 is used as a thermally responsive element and arranged in the same manner as the conventional example. 3A and 3B are cross-sectional views showing the structure in the vicinity of the electrode terminals of the secondary battery pack.

  3A and 3B, the outer can 25 is a thin square formed of, for example, aluminum or an aluminum alloy, and a unit cell is configured by incorporating a power generation element therein. In the figure, only the upper side where the lower side of the outer can 25 is cut off is shown. The upper part of the power generation element is sealed by the upper insulating plate 26, and the positive electrode tab 27 and the negative electrode tab 28 extending from the power generation element penetrate through the upper insulating plate 26 and are exposed upward.

  The upper end of the positive electrode tab 27 is welded to the outer can 25 and is electrically connected to the positive terminal 29 bonded to the upper surface of the peripheral edge of the outer can 25. The upper end of the negative electrode tab 28 is welded to the internal lead 30. The internal lead 30 is held by the outer can 25 via an insulator 31, and a negative electrode terminal 32 is provided on the insulator 31 and is electrically connected to the internal lead 30.

  A cover 33 is attached to the top of the outer can 25 to form a space between the upper surface of the outer can 25. A protection circuit board 34 on which the protection circuit 15 (see FIG. 1) is mounted is attached to the upper inner surface of the cover 33 so as to be positioned above the space. When the cover 33 is attached to the outer can 25, the external connection output terminals 35 (including the positive output terminal 5 and the negative output terminal 6 of FIG. 1) attached to the protection circuit board 34 are located on the cover 33. Exposed from the end face. The positive circuit terminal 3 provided on the lower surface of the protection circuit board 34 is connected to the positive terminal 29. Similarly provided negative circuit terminal 4 is connected to negative terminal 32 with breaker 16 or PTC element 7 interposed.

  3A, the breaker 16 is mounted on the protective circuit board 34, and one terminal of the breaker 16 is connected to the negative circuit terminal 4 at that time. One end of the negative electrode lead 36 is connected in advance to the other terminal of the mounted breaker 16 by, for example, welding. Further, one end of a positive electrode lead 37 is connected to the positive circuit terminal 3 in advance, for example, by welding. Thereby, when the protective circuit board 34 is mounted, the other end of the negative electrode lead 36 is welded to the negative electrode terminal 32, whereby the connection between the negative electrode circuit terminal 4 and the negative electrode terminal 32 can be completed in a simple process. Similarly, by welding the other end of the positive electrode lead 37 to the positive electrode terminal 29, the connection between the positive electrode circuit terminal 3 and the positive electrode terminal 29 can be completed in a simple process.

  On the other hand, in the configuration of the conventional example shown in FIG. 3B, the negative circuit terminal 4 is formed by welding one lead terminal 38 of the PTC element 7 to the negative circuit terminal 4 and welding the other lead terminal 39 to the negative terminal 32. And the negative electrode terminal 32 are connected. Therefore, in order to connect the negative circuit terminal 4 and the negative terminal 32 when the protective circuit board 34 is mounted, it is necessary to perform welding in two steps, which is more complicated than the above-described configuration using the breaker 16.

  This process is employed because it is difficult to mount the PTC element 7 on the protection circuit board 34 in the conventional process. That is, the PTC element has a large change from the initial characteristics due to external heat factors such as reflow during mounting. Therefore, when mounting on the protection circuit board 34, there is a concern that the planned effect cannot be exhibited. As a result of not being able to adopt the process of mounting on the protection circuit board 34, when the protection circuit board 34 is mounted, the connection between the negative circuit terminal 4 and the negative terminal 32 must be made by two-step welding.

  A method of mounting the protective circuit board 34 on the outer can 25 in the case of the configuration of the present embodiment as shown in FIG. 3A will be described with reference to FIG. 4 showing the manufacturing process of the mounting portion.

  First, as a preparation process for mounting the protection circuit board 34, the breaker 16 and the positive electrode lead 37 are solder-mounted on the protection circuit board 34 as shown in FIG. Next, as shown in FIG. 4B, one end of the negative electrode lead 36 is welded to the connection terminal portion 24 of the breaker 16.

  In order to mount the prepared protective circuit board 34 on the outer can 25, as shown in FIG. 4C, the other end of the negative lead 36 and the end of the positive lead 37 protruding from the protective circuit board 34 are provided. Are simultaneously welded to the negative electrode terminal 32 and the positive electrode terminal 29, respectively. Next, the negative electrode lead 36 and the positive electrode lead 37 are bent at the center, so that the protective circuit board 34 is mounted on the outer can 25 as shown in FIG. By configuring so that this state is maintained, the mounting is completed.

  In the above process, welding for attaching the protective circuit board 34 to the upper portion of the outer can 25 is only one process. Thus, the battery pack manufacturing process can be simplified by adopting the structure in which the breaker 16 is used as the thermally responsive element and the breaker 16 is mounted on the protection circuit board 34.

  The secondary battery pack according to the present invention also functions as a thermal actuator to detect the current in the charging / discharging path, so that the overcurrent can be accurately detected at a low detection current level without increasing the impedance of the charging / discharging path. It is possible to detect and appropriately operate the charge / discharge protection function, and it is useful as a battery pack used for a device having a small load current such as a mobile phone.

DESCRIPTION OF SYMBOLS 1 Secondary battery module 2, 12, 13, 15 Protection circuit 3 Positive circuit terminal 4 Negative circuit terminal 5 Positive output terminal 6 Negative output terminal 7, 21 PTC element 8 Charge / discharge control switch 8a, 8b Sub control switch 9a Discharge control FET
9b Parasitic diode 10a Charge control FET
10b Parasitic diode 11, 17 Protection IC
14 Chip resistor 16 Breaker 18 Frame body 19, 20 Lead 20 a Bending part 22 Bimetal 23 Terminal protrusion 24 Connection terminal part 25 Outer can 26 Upper insulating plate 27 Positive electrode tab 28 Negative electrode tab 29 Positive electrode terminal 30 Internal lead 31 Insulator 32 Negative electrode terminal 33 Cover 34 Protection circuit board 35 Output terminal 36 Negative electrode lead 37 Positive electrode leads 38, 39 Lead terminal

Claims (5)

A secondary battery module including one or more secondary batteries;
A pair of output terminals respectively connected to the electrode terminals of the secondary battery module via a charge / discharge path;
A charge / discharge control switch inserted in series in one of the charge / discharge paths;
A charge / discharge protection that includes a current detection unit that detects a charge / discharge current flowing through the charge / discharge path, and controls the charge / discharge control switch to be turned off when a current value detected by the current detection unit reaches an overcurrent region. A protection IC having a function;
In a secondary battery pack comprising a thermally responsive element connected in series in the charge / discharge path and limiting the charge / discharge current according to an abnormal temperature rise of the secondary battery module,
The current detection unit is configured to detect the charge / discharge current based on a voltage drop at both ends of the thermally responsive element;
The temperature characteristic of the resistance value of the thermoresponsive element is a range in which the change width of the voltage drop caused by the temperature characteristic is acceptable for the charge / discharge protection function ,
A secondary battery pack, wherein a breaker configured by combining a bimetal and a PTC element is used as the thermally responsive element . Before SL between breaker lead terminals are conductively by an auxiliary connecting portion via the main connection portion and the PTC element of lower resistance than the PTC element,
When the temperature is lower than the set temperature, the main connection portion is kept in a conductive state. When the temperature exceeds the set temperature, the main connection portion is turned off by an action according to thermal deformation of the bimetal. The rechargeable battery pack according to claim 1 constituted. A protection circuit board on which the protection IC is mounted is mounted opposite to the electrode terminal of the secondary battery module, the breaker is on the protection circuit board, and one terminal is a circuit of the protection circuit board. Implemented to be connected,
The secondary battery pack according to claim 1, wherein the other terminal of the breaker and one of the electrode terminals of the secondary battery module are connected by a metal lead. The secondary battery pack according to claim 1, wherein a thermal fuse is used as the thermally responsive element. The charge / discharge control switch includes a plurality of sub-control switches connected in parallel,
The secondary battery pack according to claim 1, wherein each of the plurality of sub control switches is a series circuit of a discharge control FET and a charge control FET.

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