Battery pack and electric vehicle

Abstract

A battery pack has a pair of output terminals, a control section, and a plurality of battery units, each of the plurality of battery units has a plurality of battery blocks connected in series and a positive terminal and a negative terminal, the battery block has one battery or a plurality of batteries connected in parallel, a fuse is connected between at least one of the pair of output terminals and the positive terminal or the negative terminal corresponding to the one output terminal, and the fuse is capable of being fused by the control section.

Description

Technical Field

[0001] This invention relates to a battery pack and an electric vehicle. Background Technology

[0002] In recent years, the applications of rechargeable batteries have been continuously expanding. For example, lithium-ion rechargeable batteries, as a representative example of rechargeable batteries, are used not only in various electronic devices, but also in automobiles, motorcycles, electric aircraft, and other fields. Depending on the application, multiple lithium-ion rechargeable batteries are sometimes used instead of a single battery. When multiple lithium-ion rechargeable batteries are used, abnormalities such as internal short circuits may occur in the specified lithium-ion rechargeable batteries. Patent Document 1 described below describes a battery module that ensures safety by using a fuse to disconnect the lithium-ion rechargeable battery that has experienced the relevant abnormality from the circuit.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent document 1: International Publication No. 2012 / 014350. Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] However, in the technology described in Patent Document 1, since the timing of the fuse blowing cannot be controlled, there is a risk that the abnormal lithium-ion secondary battery cannot be disconnected from the circuit.

[0008] Therefore, one of the objectives of this invention is to provide a battery pack and electric vehicle that can reliably disconnect a faulty secondary battery from the circuit by enabling the fuse to blow at the appropriate time.

[0009] Technical solutions for solving technical problems

[0010] The present invention is a battery pack having a pair of output terminals, a control unit and a plurality of battery cells. Each of the plurality of battery cells has a plurality of battery blocks connected in series, a positive terminal and a negative terminal. The battery block has one battery or a plurality of batteries connected in parallel. A fuse is connected between at least one of the output terminals and the positive or negative terminal corresponding to the output terminal. The fuse can be blown by the control unit.

[0011] Invention Effects

[0012] At least according to embodiments of the present invention, by enabling the fuse to blow at an appropriate time, a faulty secondary battery can be reliably disconnected from the circuit. It should be noted that the scope of the present invention is not limited to the effects exemplified in this specification. Attached Figure Description

[0013] Figure 1 This is a diagram to be referenced when explaining the issues that should be considered in one implementation method.

[0014] Figure 2 This is a diagram to be referenced when explaining the issues that should be considered in one implementation method.

[0015] Figure 3 This is a diagram to be referenced when explaining the issues that should be considered in one implementation method.

[0016] Figure 4 This is a diagram to be referenced when explaining the issues that should be considered in one implementation method.

[0017] Figure 5 This is a diagram illustrating a schematic configuration example of a battery pack according to one embodiment.

[0018] Figure 6 A and Figure 6 Figure B is a diagram illustrating an example configuration of a fuse with a heater according to one embodiment.

[0019] Figure 7 This is a diagram illustrating a detailed configuration example of a battery pack according to one embodiment.

[0020] Figure 8 This is a diagram used to illustrate an application example. Detailed Implementation

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the descriptions will be presented in the following order.

[0022] <Issues to be considered in one implementation>

[0023] <One Implementation Method>

[0024] <Variation Example>

[0025] <Application Examples>

[0026] The embodiments described below are preferred examples of the present invention, and the content of the present invention is not limited to these embodiments.

[0027] <Issues to be considered in one implementation>

[0028] First, to facilitate understanding of the present invention, issues that should be considered in one embodiment will be explained.

[0029] Figure 1 This diagram illustrates a typical configuration of a battery pack (battery pack 1). It should be noted that... Figure 1The arrows shown schematically illustrate the flow of current, with their thickness indicating the magnitude of the current. A thicker arrow indicates a larger current, and a thinner arrow indicates a smaller current.

[0030] The battery pack 1 has a battery section 2, a positive terminal TA extending from the positive electrode side of the battery section 2, and a negative terminal TB extending from the negative electrode side of the battery section 2.

[0031] Battery section 2, for example, has eight secondary batteries and seven fuses. The secondary batteries are, for example, single lithium-ion secondary batteries (hereinafter simply referred to as batteries). Batteries 11 and 12 are connected in series, batteries 13 and 14 are connected in series, batteries 15 and 16 are connected in series, and batteries 17 and 18 are connected in series.

[0032] The midpoints of the connections between batteries 11 and 12, and between batteries 13 and 14, are connected via fuse 21. Additionally, the midpoints of the connections between batteries 13 and 14, and between batteries 15 and 16, are connected via fuse 22. Furthermore, the midpoints of the connections between batteries 15 and 16, and between batteries 17 and 18, are connected via fuse 23.

[0033] A fuse 25 is connected between the positive terminal TA and the positive terminal of battery 11. A fuse 26 is connected between the positive terminal TA and the positive terminal of battery 13. A fuse 27 is connected between the positive terminal TA and the positive terminal of battery 15. A fuse 28 is connected between the positive terminal TA and the positive terminal of battery 17.

[0034] Here, consider the example of an internal short circuit in battery 18. A short-circuit current flows due to the internal short circuit. Specifically, as... Figure 1 As shown, the current discharged from batteries 12, 14, and 16 flows through the loop RP1 on the lower side of battery section 2. The current C12 discharged from battery 12 passes through fuse 21 and combines with the current C14 discharged from battery 14 to form current CA. Current CA passes through fuse 22 and combines with the current C16 discharged from battery 16 to form current CB. Current CB flows through fuse 23.

[0035] The current flowing through fuse 23 is greater than the current flowing through each of fuses 21 and 22 (in short, the current flowing through fuse 23 is three times the current flowing through fuse 21). Therefore, as Figure 2 As shown, fuse 23 blows before fuses 21 and 22.

[0036] Then, as Figure 2As shown, the discharge current from batteries 11 to 16 flows through loop RP2 of battery section 2. The magnitude of the current (current CC) flowing through each of fuses 25, 26, and 27 is approximately equal. On the other hand, the current flowing through fuse 28 is the sum of the currents flowing through each of fuses 25, 26, and 27, resulting in a current of 3 CC. Therefore, as... Figure 3 As shown, fuse 28 blows before each of fuses 25, 26, and 27. This opens the circuit of battery 18, which had an internal short circuit, thus disconnecting it from the electrical circuit within battery pack 1. Therefore, since battery 18 cannot be charged or discharged, overheating and fire can be prevented, ensuring the safety of battery pack 1.

[0037] It should be noted that even if an internal short circuit occurs in a battery other than battery 18, the safety of battery pack 1 is guaranteed in the same way.

[0038] Figure 4 This diagram illustrates a configuration example of a battery pack (battery pack 1A) as described in other examples of general battery packs. Battery pack 1A differs from battery pack 1 in that it has a battery section 2A instead of battery section 2. Battery section 2A includes the aforementioned batteries 15 to 18, and fuses 23, 27, and 28 (the connection relationships of these components are the same as in battery section 2).

[0039] Consider an example where an internal short circuit occurred in battery 18. For example... Figure 4 As shown, after fuse 23 is blown by the current C16 discharged from battery 16, the current CC discharged from battery 15 and battery 16 also flows through fuse 28 via fuse 27.

[0040] The current flowing through fuses 27 and 28 is the same. Therefore, it is unclear which fuse 27 or 28 will blow first. For example, if fuse 27 blows before fuse 28, the battery 18, which has an internal short circuit, cannot be disconnected from the circuit, thus preventing the battery 18 from continuing to charge and discharge. Since it is impossible to predict which battery will experience an internal short circuit, it is practically impossible to make a specific fuse with easily fusible characteristics. Therefore, it is desirable to be able to control the timing of fuse blowing. Furthermore, for example, as... Figure 4 As shown in the circuit, when the number of parallel connections in a series-connected battery pack is two, it is desirable to be able to control the timing at which the fuse connected to each of the battery pack blows. Based on the above points, an embodiment of the present invention will be described.

[0041] <One Implementation Method>

[0042] [Definitions of terms used in this specification]

[0043] First, the definitions of the terms used in this specification are explained.

[0044] "Battery": refers to a single battery. It should be noted that in this embodiment, a single lithium-ion secondary battery is used as an example of a battery, but other types of batteries may also be used.

[0045] "Battery block": refers to a block containing one battery or multiple batteries connected in parallel.

[0046] A "battery cell" refers to a unit in which multiple battery cells are connected in series. Each battery cell contains the same number of battery cells.

[0047] "Battery section": refers to a structure that includes multiple battery cells.

[0048] [The battery pack involved in this embodiment]

[0049] (Brief Structure)

[0050] Figure 5 This diagram illustrates a schematic configuration example of the battery pack (battery pack 10) according to this embodiment. The battery pack 10 has a battery section 20. A positive terminal TA is led out from the positive terminal side of the battery section 20. A negative terminal TB is led out from the negative terminal side of the battery section 20. The positive terminal TA and the negative terminal TB correspond to a pair of output terminals.

[0051] The battery pack 10 includes a battery cell 30, a control IC (Integrated Circuit) 35, a fuse 38 with a heater, a battery cell 40, a control IC 45, a fuse 48 with a heater, and a fuse 50. The configuration including the battery cell 30 and the fuse 38 with a heater is connected in parallel with the configuration including the battery cell 40 and the fuse 48 with a heater. It should be noted that in this embodiment, each of the control IC 35 and the control IC 45 corresponds to a control unit.

[0052] As an example of a first battery unit, battery unit 30 has a configuration in which battery blocks 31 and 32 are connected in series. Specific configuration examples of battery blocks 31 and 32 will be described later. Furthermore, battery unit 30 has a positive terminal T1 and a negative terminal T2.

[0053] Control IC 35 is connected to battery cell 30 and heater-equipped fuse 38. Control IC 35 determines the state of each of battery cells 31 and 32. For example, control IC 35 measures the voltage of each of battery cells 31 and 32 to determine whether each battery cell is overcharged. Then, if a battery cell is overcharged, control IC 35 controls the current to the heater of the heater-equipped fuse 38 connected in series with that battery cell. Through this control, the heater-equipped fuse 38 can blow.

[0054] A heater-equipped fuse 38 is connected between the positive terminal TA of one of a pair of output terminals and the corresponding positive terminal of TA, that is, between the positive terminal TA and the positive terminal T1 of the battery cell 30 on the same polarity side. The heater-equipped fuse 38 can be blown under the control of the control IC 35.

[0055] Battery cell 40, as an example of a second battery cell, has battery blocks 41 and 42 connected in series. Specific configurations of battery blocks 41 and 42 will be described later. Additionally, battery cell 40 has a positive terminal T3 and a negative terminal T4.

[0056] Control IC 45 is connected to battery cell 40 and heater-equipped fuse 48. Control IC 45 determines the state of each of battery cells 41 and 42. For example, control IC 45 measures the voltage of each of battery cells 41 and 42 to determine whether each battery cell is overcharged. Then, if a battery cell is overcharged, control IC 45 controls the current to the heater of the heater-equipped fuse 48 connected in series with that battery cell. Through this control, the heater-equipped fuse 48 can blow.

[0057] A heater-equipped fuse 48 is connected between the positive terminal TA of one of a pair of output terminals and the corresponding positive terminal, that is, between the positive terminal TA and the positive terminal T3 of the battery cell 40 on the same polarity side. The heater-equipped fuse 48 can be blown under the control of the control IC 35.

[0058] Fuse 50 is a different type of fuse from fuse 38 and fuse 48 with heaters. As fuse 50, a general fuse such as a current fuse can be used. The connection midpoints of the battery blocks in each of the different battery cells are connected to each other via fuse 50. Specifically, the connection midpoint P1 between battery blocks 31 and 32 in battery cell 30 and the connection midpoint P2 between battery blocks 41 and 42 in battery cell 40 are connected via fuse 50. It should be noted that the connection midpoint in this specification refers to any position in the circuit connection path, and does not necessarily have to be the center of that connection path.

[0059] (Regarding fuses with heaters)

[0060] Next, we will describe an example of a fuse with a heater. For example... Figure 6 As shown in Figure A, the fuse 38 with heater has two fuses 38A and fuse 38B connected in series between the positive terminals TA and T1, and a heater 38C connected at one end to the midpoint P38 between fuses 38A and fuse 38B. The heater 38C is a heating element such as a resistance heater.

[0061] One end of fuse 38A (the side opposite to the connection midpoint P38) is grounded via battery E1. The other end of heater 38C is grounded via switch SW1. Switch SW1 is a switch that is turned on / off by control IC 35 and is located near fuse 38A with heater. Battery E1 is, for example, a battery that is in an overcharged state (details will be described later).

[0062] Normally, switch SW1 is open. When it is necessary to blow fuses 38A and 38B, control IC 35 controls the operation of fuse 38 with a heater. Specifically, control IC 35 turns on switch SW1. By turning on switch SW1, current flows... Figure 6 The current flows through the RPA in the current loop of A. Current flows through heater 38C under the control of the relevant control IC 35, causing heater 38C to heat up. Fuses 38A and 38B melt due to their heat. Thus, the fuse 38 with heater is a device that can melt by excessive current flowing through it, just like a conventional current fuse, and that melts fuses 38A and 38B at a predetermined time by current flowing through heater 38C.

[0063] like Figure 6As shown in Figure B, the fuse 48 with heater has two fuses 48A and 48B connected in series between the positive terminals TA and T3, and a heater 48C connected at one end to the midpoint P48 between the fuses 48A and 48B. The heater 48C is a heating element such as a resistance heater.

[0064] One end of fuse 48A (the side opposite to the connection midpoint P48) is grounded via battery E2. The other end of heater 48C is grounded via switch SW2. Switch SW2 is a switch that is turned on / off by control IC 45 and is located near fuse 48 with heater. Battery E2 is, for example, a battery that is in an overcharged state (details will be described later).

[0065] Normally, switch SW2 is open. When it is necessary to blow fuses 48A and 48B, control IC 45 controls the operation of fuse 48 with a heater. Specifically, control IC 45 turns on switch SW2. By turning on switch SW2, current flows... Figure 6 A current flows through the current loop RPB in B. Current flows through heater 48C under the control of the relevant control IC 45, causing heater 48C to heat up. Fuses 48A and 48B melt due to this heat. Thus, the fuse 48 with heater is a device capable of melting due to excessive current flowing through it, similar to a conventional current fuse, and capable of melting fuses 48A and 48B at a predetermined time by current flowing through heater 48C.

[0066] [Detailed configuration example of the battery pack involved in this embodiment]

[0067] Figure 7 This diagram illustrates a detailed configuration example of the battery pack 10 according to this embodiment. The battery unit 30, for example, has 14 battery blocks (battery block 311a, battery block 311b…battery block 311n) connected in series. It should be noted that when it is not necessary to distinguish between the individual battery blocks, they are appropriately referred to simply as battery block 311.

[0068] Battery block 311 has a configuration of four batteries connected in parallel. The number of batteries connected in parallel can be appropriately changed, but the short-circuit current generated when an internal short circuit occurs in one of the batteries will not cause the battery temperature to be set within a certain range.

[0069] Battery cell 40, for example, has 14 battery blocks (battery block 411a, battery block 411b...battery block 411n) connected in series. It should be noted that when it is not necessary to distinguish between individual battery blocks, they are appropriately referred to as battery block 411.

[0070] Battery block 411 has a configuration of four batteries connected in parallel. The number of batteries connected in parallel can be appropriately changed, but the short-circuit current generated when an internal short circuit occurs in one of the batteries will not cause the battery temperature to be set within a certain range.

[0071] Fuse 50 has (number of battery blocks - 1), that is, 13 fuses (fuse 50a, fuse 50b...fuse 50m). For example, the connection midpoint between battery blocks 311a and 311b is connected to the connection midpoint between battery blocks 411a and 411b of battery cell 40 via fuse 50a. The connection midpoints of other battery blocks are also connected to each other via fuses in the same manner.

[0072] Additionally, the battery pack 10 includes an AFE (Analog Front End) 71, an MPU (MicroProcessing Unit) 72, and a charge / discharge control switch 73. The charge / discharge control switch 73 includes a charge control switch 73A and a discharge control switch 73B.

[0073] The AFE71 is a type of protection IC that measures the voltage of each battery cell, the charging current flowing through the circuitry within the battery pack 10, and the discharging current. The AFE71 then sends the measurement results to the MPU72, which acts as the higher-level IC.

[0074] The MPU72 provides unified control over the protection actions and other functions of the battery pack 1. Furthermore, the MPU72 communicates with the electronic device (host device) using the battery pack 10 via the communication terminal COM.

[0075] The charge / discharge control switch 73 is a switch controlled by AFE 71 to be turned on / off. For example, a FET (Field Effect Transistor) can be used as the charge / discharge control switch 73. The charge / discharge control switch 73 is connected in series with the positive terminal TA and either a heater-equipped fuse 38 or a heater-equipped fuse 48 on the positive side power line PLA.

[0076] [Example of battery pack operation]

[0077] (On / off control of the charge / discharge control switch)

[0078] Next, an example of the operation of the battery pack 10 according to this embodiment will be described. First, the on / off control of the charge / discharge control switch 73 will be explained.

[0079] As described above, AFE71 sends the measured results of the voltage of each battery cell, the charging current flowing through the circuit in the battery pack 10, and the discharging current to MPU72. Based on the sent measurement results, MPU72 determines whether it is necessary to cut off the current path. When it is necessary to cut off the current path, MPU72 outputs a control command to AFE71. According to the control command, AFE71 appropriately switches the charging control switch 73A and the discharging control switch 73B on / off, thereby cutting off the current path.

[0080] For example, when MPU72 determines that the battery section 20 is normal and can be charged and discharged without problems, MPU72 controls AFE71 to turn on the charging control switch 73A and the discharging control switch 73B. Furthermore, when the voltage of the battery section 20 reaches the overcharge prohibition voltage or other situations requiring charging to be prohibited, MPU72 controls AFE71 to at least turn off the charging control switch 73A. Similarly, when the voltage of the battery section 20 reaches the over-discharge prohibition voltage or other situations requiring discharging to be prohibited, MPU72 controls AFE71 to at least turn off the discharging control switch 73B. Finally, when the battery section 20 is deeply discharged and reaches the recharge prohibition region, MPU72 controls AFE71 to turn off the charging control switch 73A and the discharging control switch 73B, thereby stopping charging and discharging.

[0081] (Fuse control with heater)

[0082] Next, the fuse control of fuse 38 and fuse 48 with heaters will be explained. It should be noted that, for ease of explanation, the following description will use... Figure 5 Using the configurations of battery cells 30 and 40 shown as examples, the fuse control of the heater-equipped fuse will be explained. Furthermore, a scenario where an internal short circuit occurs in the battery block 42 of battery cell 40 will be described.

[0083] After an internal short circuit occurs in battery block 42, current from battery block 32 flows through fuse 50, causing fuse 50 to blow. Then, current from battery cell 30 flows through battery cell 40 via fuse 38 with heater and fuse 48 with heater.

[0084] Here, if the heater-equipped fuse 48 blows before the heater-equipped fuse 38, the battery block 42, which has an internal short circuit, can be electrically disconnected. Therefore, the safety of the battery pack 1 can be guaranteed even when the charging voltage is applied to the battery pack 1 via the positive terminal TA and the negative terminal TB. On the other hand, if the heater-equipped fuse 38 blows before the heater-equipped fuse 48, the battery block 42 cannot be electrically disconnected. In this state, if the battery pack 1 is charged, the voltage of the battery block 42 does not rise because of the internal short circuit, only the voltage of the battery block 41 rises. Due to the rise in the voltage of the battery block 41, the battery block 41 becomes overcharged (the voltage is greater than or equal to a threshold (e.g., 4.3V in the case of a battery).

[0085] The control IC 45 detects the overcharge state of the battery block 41. Upon detecting the overcharge state, the control IC 45 determines that the fuse 48 with a heater, which is connected in series with the overcharged battery block 41, needs to be activated. Then, the control IC 45 controls the flow of current through the fuse 48 with the heater (by turning on the aforementioned switch SW2). This control allows current to flow through the heater 48C using the power of the battery block 41, enabling the thermal fuses 48A and 48B to be blown. Therefore, the battery cell 40, including the battery block 42, can be electrically disconnected.

[0086] The same procedure is followed even when an internal short circuit occurs in a battery block other than battery block 42. For example, if an internal short circuit occurs in battery block 32 and an overcharged state of battery block 31 is detected, the control IC 35 controls the operation of the fuse 38 with a heater. Furthermore, the same procedure is followed even if an internal short circuit occurs in any of the batteries constituting battery blocks 311 or 411.

[0087] [Effect]

[0088] Based on the above-described embodiment, the following effects can be obtained, for example.

[0089] Because it can reliably disconnect battery cells that have experienced internal short circuits, it can prevent overheating, fires, and other problems caused by internal short circuits in battery cells, thus ensuring the safety of the battery pack.

[0090] In the specific example above, assuming that no battery cell is overcharged when the heater-equipped fuse 48 blows before the heater-equipped fuse 38, the control to blow the heater-equipped fuse 38 is not performed. Therefore, battery cell 30 can continue to be used.

[0091] <Variation Example>

[0092] The embodiments of the present invention have been described in detail above, but the content of the present invention is not limited to the above embodiments, and various modifications can be made based on the technical concept of the present invention.

[0093] In one embodiment described above, the control IC can determine the necessity of activating the heater-equipped fuse by identifying a state other than overcharging. For example, the control IC can determine the state of voltage balance between the battery cells. During charging, if the voltage of one series-connected battery cell rises while the voltage of the other battery cell remains relatively constant, an internal short circuit occurs in the other battery cell, and the control IC can determine that the heater-equipped fuse needs to be activated. Even without charging, if the voltage difference between the battery cells reaches a certain level, it can be determined that an internal short circuit has occurred, requiring the heater-equipped fuse to activate. Through such control, abnormal batteries can be disconnected earlier. Additionally, the control IC can also determine whether there are battery cells whose voltage remains relatively constant even during charging; if such battery cells exist, it determines that the heater-equipped fuse needs to be activated. These conditions can also be combined to determine whether the heater-equipped fuse needs to be activated.

[0094] In one embodiment described above, an example of using the power of an overcharged battery pack to activate a fuse with a heater was illustrated, but the method is not limited to this. For example, a constant current source can be provided in the battery pack, from which current flows through the heater of the fuse with a heater, thereby heating the heater. Furthermore, of the plurality of fuses with heaters in the battery pack, some or all of the fuses with heaters can be connected between the negative terminal of the battery pack and the negative terminal of the battery cell. Additionally, fuses with heaters can be connected between the positive terminal of the battery pack and the positive terminal of the battery cell, and between the negative terminal of the battery pack and the negative terminal of the battery cell, to prevent malfunction of the fuses with heaters.

[0095] In one embodiment described above, the AFE can autonomously determine the necessity of protection action based on measurement results such as voltage, rather than the control of the MPU, and appropriately switch the charge / discharge control switch on / off according to the determination result. Alternatively, the MPU can send the measurement results from the AFE to the electronic equipment side, where a microcomputer determines the necessity of protection action.

[0096] In one embodiment described above, the control IC can communicate with the AFE and the MPU. For example, the control IC can communicate with the MPU to notify the MPU that a specified fuse with a heater has blown. The MPU can then notify the user through a display, sound, or by providing an error message to prompt for replacement of the fuse with the heater.

[0097] In one embodiment described above, the charge / discharge control switch can be connected in series with the negative terminal TB on the power line PLB on the negative side, and with a heater-equipped fuse connected to the negative side of the battery cell. Furthermore, the configuration of the control IC and AFE integrated, as well as the battery pack configuration, can be appropriately modified without departing from the spirit of the invention. Additionally, the number of connected battery cells, the number of connected battery blocks, and the configuration of the battery blocks (number of batteries, connection method) in the above embodiment can be appropriately modified.

[0098] The items described in the above-described embodiments and variations can be appropriately combined. Furthermore, the materials and processes described in the embodiments are merely examples, and the scope of this invention is not limited to the illustrated materials.

[0099] <Application Examples>

[0100] The battery pack 10 of the present invention can be mounted on power tools, electric vehicles, various electronic devices, etc., or used to supply power.

[0101] As an example of applying the present invention to an energy storage system for electric vehicles. Figure 8 The diagram schematically illustrates a hybrid vehicle (HV) configuration employing a series hybrid system. A series hybrid system is a vehicle that uses electricity generated by a generator powered by an engine, or electricity temporarily stored in a battery, to drive via an electric drive conversion device.

[0102] The hybrid vehicle 600 is equipped with an engine 601, a generator 602, an electric drive power conversion device (DC motor or AC motor, hereinafter referred to as "motor 603"), drive wheels 604a and 604b, wheels 605a and 605b, a battery 608, a vehicle control device 609, various sensors 610, and a charging port 611. The battery 608 is equipped with the battery pack 10 of this invention.

[0103] The electric motor 603 powered by battery 608 operates, and the rotational force of motor 603 is transmitted to drive wheels 604a and 604b. The rotational force generated by engine 601 allows electricity generated by generator 602 to be stored in battery 608. Various sensors 610 control engine speed or the opening of a throttle valve (not shown) via vehicle control unit 609.

[0104] The hybrid vehicle 600 decelerates via a braking mechanism (not shown), the resistance during deceleration being applied as a rotational force to the electric motor 603. The regenerative electricity generated by this rotational force is stored in the battery 608. The battery 608 can also be charged by connecting to an external power source via the hybrid vehicle 600's charging port 611. Such an HV vehicle is called a plug-in hybrid electric vehicle (PHV or PHEV).

[0105] It should be noted that the secondary battery involved in this invention can also be applied to miniaturized primary batteries as a power source for the tire pressure monitoring system (TPMS) built into the wheels 604 and 605.

[0106] The above description uses a series hybrid electric vehicle as an example, but the invention can also be applied to hybrid electric vehicles using both an engine and an electric motor in a parallel configuration, or a combination of series and parallel configurations. Furthermore, the invention can also be applied to electric vehicles (EVs or BEVs) and fuel cell vehicles (FCVs) that operate solely on a drive motor that does not use an engine. Additionally, the invention can be applied to electric bicycles.

[0107] Explanation of reference numerals in the attached figures

[0108] 10: Battery pack; 30, 40: Battery cells; 31, 32, 41, 42: Battery blocks; 35, 45: Control IC; 38, 48: Fuse with heater; 38C, 48C: Heater; 73: Charge / discharge control switch; TA: Positive terminal of battery pack; TB: Negative terminal of battery pack; T1, T3: Positive terminal of battery cell; T2, T4: Negative terminal of battery cell.

Claims

1. A battery pack having a pair of output terminals, a control unit, and multiple battery cells, The plurality of battery cells includes at least a first battery cell and a second battery cell, each of the first battery cell and the second battery cell having a plurality of battery blocks connected in series, a positive terminal and a negative terminal. The battery block has one battery or multiple batteries connected in parallel. A fuse with a heater is connected between at least one of the pair of output terminals and the positive terminal corresponding to that output terminal. The fuse with a heater can be blown by the control unit. The first battery cell and the second battery cell are connected in parallel. The different fuses with heaters are connected to each of the positive terminals of the first battery cell and the second battery cell. The control unit determines whether the battery pack is in an overcharged state. If an overcharged state of the battery block is detected, the heater-equipped fuse connected to the battery cell of the battery block having the overcharged state is caused to blow before the heater-equipped fuse connected to the battery cell of the battery block not having the overcharged state.

2. The battery pack according to claim 1, wherein, The control unit determines whether each of the plurality of battery blocks is in the overcharge state.

3. The battery pack according to claim 1 or 2, wherein, The battery pack has multiple control units. The control unit is connected to each of the plurality of battery cells.

4. The battery pack according to claim 1 or 2, wherein, The connection midpoints of the battery blocks in each of the different battery cells are connected to each other via a different fuse than the fuse with heater.

5. The battery pack according to claim 1 or 2, wherein, A charge / discharge control switch is connected in series between one of the pair of output terminals and the fuse with heater.

6. An electric vehicle having a battery pack according to any one of claims 1 to 5.

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