Temperature protection device and power storage device

Abstract

To inexpensively realize a temperature protection function for a power storage device and to suppress chattering of a current cutoff device.SOLUTION: A temperature protection device S1 for a power storage device 20 includes: a current cutoff device 70 that cuts off a current of the power storage device 20; a drive circuit 80 that drives the current cutoff device 70; a temperature detection circuit 110 that detects a temperature of the power storage device 20 and outputs a detection result to the drive circuit 80; and a setting circuit 120 that sets a hysteresis between a protection temperature at which a protection operation is performed for the power storage device 20 and a recovery temperature at which the protection is released. When the temperature detection circuit 110 detects the protection temperature, the drive circuit 80 opens the current cutoff device 70 to cut off a current, and when the temperature detection circuit 110 detects the recovery temperature, the drive circuit 80 closes the current cutoff device 70 to restore the current cut-off.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a temperature protection device for a power storage device and a power storage device including the same. [Background technology]

[0002] One of the protective functions of a power storage device is protection against temperature abnormalities. Patent Document 1 is a document that discloses a technique for protecting a power storage device from temperature abnormalities. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-166454 Summary of the Invention [Problem to be solved by the invention]

[0004] Fig. 8 shows an example of a thermal protection device. The thermal protection device in Fig. 8 inputs the temperature detected by a temperature sensor (thermistor) circuit 510 to a microcomputer 520. The output voltage of the microcomputer 520 is about 5V, which is not enough to drive the gate of the switch Q10. Therefore, when an abnormal temperature is detected, the gate is driven via a level shift circuit (boost circuit) 530 to control the switch Q10, thereby cutting off the current.

[0005] However, improvements were needed due to the high cost of the microcomputer (integrated circuit) 520 and the level shift circuit 530. Furthermore, when control is achieved using only electronic circuits (hardware) without using a microcomputer (software), chattering can occur when the temperature fluctuates around the threshold, and this needs to be addressed. [Means for solving the problem]

[0006] The thermal protection device for a power storage device includes a current interruption device that interrupts current to the power storage device, a drive circuit that drives the current interruption device, a temperature detection circuit that detects the temperature of the power storage device and outputs the detection result to the drive circuit, and a setting circuit that sets a hysteresis to a protection temperature (first temperature) at which a protection operation for the power storage device is performed and a recovery temperature (second temperature) at which the protection is released. When the temperature detection circuit detects the protection temperature, the drive circuit opens the current interruption device to interrupt the current, and when the temperature detection circuit detects the recovery temperature, the drive circuit closes the current interruption device to restore the current interruption. [Effects of the Invention]

[0007] This configuration allows for the inexpensive realization of a temperature protection function for the power storage device without using a microcomputer or level shift circuit. In addition, a hysteresis function is provided between the protection temperature and the recovery temperature, which helps to suppress chattering in the current interrupter. [Brief explanation of the drawings]

[0008] [Figure 1] Side view of a motorcycle [Figure 2] Block diagram of a motorcycle battery [Figure 3] Exploded perspective view of the battery [Figure 4] Temperature protection circuit diagram (embodiment 1) [Figure 5] Thermistor temperature characteristics [Figure 6] Hysteresis function diagram [Figure 7] Resistance voltage division diagram [Figure 8] FIG. 1 shows a comparative example [Figure 9] Circuit diagram of the temperature protection device (embodiment 2) [Figure 10] Thermistor temperature-resistance characteristics [Figure 11] Circuit diagram of the temperature protection device (embodiment 3) [Figure 12] Hysteresis function diagram DETAILED DESCRIPTION OF THE INVENTION

[0009] (Outline of this embodiment) (1) A thermal protection device for a power storage device according to one embodiment of the present invention includes a current interruption device that interrupts current to the power storage device, a drive circuit that drives the current interruption device, a temperature detection circuit that detects the temperature of the power storage device and outputs the detection result to the drive circuit, and a setting circuit that sets a hysteresis between a protection temperature at which protection of the power storage device is performed and a return temperature at which protection is released. When the temperature detection circuit detects the protection temperature, the drive circuit opens the current interruption device to interrupt the current, and when the temperature detection circuit detects the return temperature, the drive circuit closes the current interruption device to resume the current interruption. In the protection device described in (1), any configuration other than the above is optional and may be used. Furthermore, the current interruption may interrupt both discharging and charging, or may interrupt only one of discharging or charging.

[0010] The thermal protection device (1) can inexpensively achieve a thermal protection function for a power storage device without using a microcomputer or level shift circuit. In addition, since it has a hysteresis function between the protection temperature and the recovery temperature, chattering of the current interrupter can be suppressed.

[0011] (2) In the thermal protection device described in (1) above, the drive circuit may include a semiconductor switch that switches the gate voltage of the current interrupter between GND and VDD. The temperature detection circuit may be a series circuit of a thermistor and a resistor. The setting circuit may be configured to automatically set the hysteresis between the protection temperature and the recovery temperature by changing the resistor voltage division ratio of the temperature detection circuit in response to the ON / OFF switching of the semiconductor switch. The configuration of (2) can automatically set the hysteresis between the protection temperature and the recovery temperature in response to the ON / OFF switching of the semiconductor switch. Furthermore, the setting circuit can be configured inexpensively using resistors, switches, etc.

[0012] (3) In the thermal protection device described in (2) above, the thermistor may be a positive temperature coefficient PTC thermistor. Compared to a negative temperature coefficient NTC thermistor, this thermistor has a region in which the resistance value changes more sharply, thereby reducing the variation in the protection temperature. Furthermore, by using a positive temperature coefficient PTC thermistor, the resistance value of the current detection circuit can be increased compared to when a negative temperature coefficient NTC thermistor is used. This also has the advantage of reducing power consumption.

[0013] (4) The temperature protection device according to any one of (1) to (3) may be applied to an electric storage device including an electric storage element and the temperature protection device.

[0014] <Embodiment 1> 1, a battery 20 (an example of a power storage device) according to this embodiment is a battery for a motorcycle mounted on a motorcycle 10. The battery 20 has a rated voltage of 12 volts (V) and can be used to replace (for example, as a retrofit) conventional lead-acid batteries.

[0015] As shown in Fig. 2, a starter 10A, an alternator 10B, and accessories 10C (headlights, a car navigation system, etc.) mounted on a motorcycle 10 are connected to a battery 20. The battery 20 supplies 12V power to the starter 10A to start the engine. The battery 20 is charged by the alternator 10B while the engine is running.

[0016] 3, the battery 20 includes a management unit 53, a plurality of storage cells 3 (an example of a storage element), and a rectangular parallelepiped storage case 40 that houses them. The storage cells 3 may be battery cells such as lithium ion secondary batteries, or may be electrochemical cells such as capacitors.

[0017] Four storage cells 3 are connected in series to form the assembled battery 30. Alternatively, some of the storage cells 3 may be connected in parallel. For example, the assembled battery 30 may have eight storage cells 3 connected in two parallel connections and four in series, or twelve storage cells 3 connected in three parallel connections and four in series.

[0018] The storage case 40 is made of synthetic resin. The storage case 40 includes a case body 41, a lid 42 that closes the opening of the case body 41, a storage section 43 provided in the lid 42, a cover 44 that covers the storage section 43, an inner lid (bus bar frame) 45, and a partition plate 46. The inner lid 45 and the partition plate 46 do not necessarily have to be provided. The energy storage cells 3 are inserted between the partition plates 46 of the case body 41.

[0019] A plurality of metal bus bars 47 (conductive members) are placed on the inner lid 45. The inner lid 45 is placed near the terminal surface on which the cell terminals 32 of the storage cells 3 are provided, and the adjacent cell terminals 32 of adjacent storage cells 3 are connected by the bus bars 47, so that the storage cells 3 are connected in series.

[0020] The storage section 43 is box-shaped and has a protrusion 43a that protrudes outward from the center of one long side in a plan view. A positive terminal 51 and a negative terminal 52 made of metal such as a lead alloy are provided on both sides of the protrusion 43a on the lid section 42. A management unit 53 is stored in the storage section 43. The management unit 53 is connected to the energy storage cells 3 via wiring members and bus bars 47 (not shown). Instead of being stored in the storage section 43, the management unit 53 may be disposed adjacent to the battery pack 30, for example, above or to the side. The management unit 53 may have multiple circuit boards.

[0021] The energy storage cell 3 includes a hollow rectangular parallelepiped case 31 and a pair of cell terminals 32, 32 with opposite polarities provided on one side (terminal surface, top surface) of the case 31. The case 31 accommodates an electrode assembly 33 formed by stacking a positive electrode, a separator, and a negative electrode, and an electrolyte (electrolytic solution) not shown.

[0022] Although not shown in detail, the electrode assembly 33 is constructed by stacking a sheet-shaped positive electrode and a sheet-shaped negative electrode with two sheet-shaped separators in between and winding them (vertical or horizontal). The separators are formed from a porous resin film. Examples of the porous resin film that can be used include porous resin films made of resins such as polyethylene (PE) and polypropylene (PP).

[0023] The positive electrode is an electrode plate in which a positive electrode active material layer is formed on the surface of a long strip-shaped positive electrode substrate made of, for example, aluminum, an aluminum alloy, or the like. The positive electrode active material layer contains a positive electrode active material. The positive electrode active material used in the positive electrode active material layer can be a material capable of absorbing and releasing lithium ions. The positive electrode active material is, for example, LiFePO4, but is not limited thereto, and so-called ternary positive electrode active materials may also be used. The positive electrode active material layer may further contain a conductive additive, a binder, etc.

[0024] The negative electrode is an electrode plate in which a negative electrode active material layer is formed on the surface of a long strip-shaped negative electrode substrate made of, for example, copper or a copper alloy. The negative electrode active material layer contains a negative electrode active material. The negative electrode active material can be a material capable of absorbing and releasing lithium ions. Examples of the negative electrode active material include graphite, hard carbon, and soft carbon. The negative electrode active material layer may further contain a binder, a thickener, and the like.

[0025] The electrolyte housed in the housing case 40 together with the electrode assembly 33 can be the same as that used in conventional lithium-ion secondary batteries. For example, an electrolyte containing a supporting salt in an organic solvent can be used. As the organic solvent, for example, an aprotic solvent such as carbonates, esters, or ethers can be used. As the supporting salt, for example, a lithium salt such as LiPF6, LiBF4, or LiClO4 can be suitably used. The electrolyte may contain various additives such as a gas generating agent, a film-forming agent, a dispersant, or a thickener.

[0026] FIG. 3 shows a prismatic lithium ion battery including a wound electrode assembly 33 as an example of the storage cell 3. Alternatively, the storage cell 3 may be a cylindrical lithium ion battery or a laminated (pouch) lithium ion battery. The storage cell 3 may also be a lithium ion battery including a laminated electrode assembly. The storage cell 3 may also be an all-solid-state lithium ion battery using a solid electrolyte.

[0027] 4 is a block diagram showing the electrical configuration of a portion relating to the temperature protection function of the battery 20. The battery 20 includes a battery pack 30 and a temperature protection device S1. The temperature protection device S1 is a part of the management unit 53.

[0028] The battery pack 30 is composed of four storage cells 3 connected in series. The positive electrode of the battery pack 30 is connected to a positive terminal 51 via a power line 53a. The negative electrode of the battery pack 30 is connected to a negative terminal 52 via a power line 53b.

[0029] The thermal protection device S1 includes a current interruption device 70, a drive circuit 80, a temperature detection circuit 110, and a setting circuit 120. The thermal protection device S1 is composed only of discrete elements (hardware) such as resistors R1 to R4, switches Q1, Q2, Q3, Q4, Q10, Q20, a diode D1, and a thermistor TH1, and does not use a microcomputer (software).

[0030] The current interruption device 70 is disposed on the power line 53b and is composed of a switch Q10 and a switch Q20.

[0031] The switches Q10 and Q20 are N-channel FETs. FET stands for Field Effect Transistor. The source of the switch Q10 is connected to the negative electrode of the battery pack 30, and the drain is connected to the drain of the switch Q20. The source of the switch Q20 is connected to the negative terminal 52 of the battery 20.

[0032] The switch Q10 is a discharge cutoff switch that cuts off discharging, and the switch Q20 is a charge cutoff switch that cuts off charging.

[0033] The drive circuit 80 is a circuit that drives the gate of the switch Q10 that cuts off discharging in the current interruption device 70. A separate drive circuit is provided for the switch Q20 that cuts off charging. The drive circuit 80 is composed of a diode D1, resistors R3 and R4, and a switch Q1. The switch Q1 is an example of the semiconductor switch of the present invention.

[0034] The anode of diode D1 is connected to VDD via resistor R3. VDD is the internal power supply (internal power supply voltage) of battery 20. Switch Q1 is an NPN transistor. The emitter of switch Q1 is connected to GND, and the collector is connected to the cathode of diode D1. The collector of switch Q1 is also connected to the gate of switch Q10. Resistor R4 is connected between the collector of switch Q1 and GND.

[0035] The temperature detection circuit 110 is a circuit that detects the temperature of the battery pack 30 or its surroundings, and is composed of a resistor R1 and a thermistor TH1. The resistor R1 and thermistor TH1 are connected in series, with the resistor R1 connected to VDD and the thermistor TH1 connected to GND. The connection point A between the resistor R1 and thermistor TH1 is connected to the base of the switch Q1.

[0036] Figure 5 shows the temperature characteristics of thermistor TH1. Thermistor TH1 is a PTC thermistor. PTC thermistors have a positive characteristic where the resistance value increases as the temperature rises. When the Curie temperature is reached, the resistance value of the PTC thermistor increases rapidly.

[0037] As shown in Figure 5, LA represents the temperature characteristics of temperature grade A, LB represents the temperature characteristics of temperature grade B, and LC represents the temperature characteristics of temperature grade C. A thermistor TH1 with temperature characteristics suitable for the specifications can be selected from temperature grades A and B.

[0038] The setting circuit 120 is composed of a switch Q2 and a resistor R2. The switch Q2 is a P-channel FET. The source of the switch Q2 is connected to VDD, and the drain is connected to the connection point A via the resistor R2. The gate of the switch Q2 is connected to the cathode of the diode D1.

[0039] The setting circuit 120 is a circuit that automatically sets the hysteresis Δ for the protection temperature and the recovery temperature by changing the resistor voltage division ratio U of the temperature detection circuit 110 in response to the ON / OFF switching of the switch Q1. The protection temperature (first temperature) is the temperature at which the protection operation is performed, and the recovery temperature (second temperature) is the temperature at which the protection is released. As shown in Figure 6, in the case of high temperature protection, the recovery temperature is lower than the protection temperature.

[0040] 7, the frame line K1 indicates the resistive voltage division until the switch Q1 switches from OFF to ON (Q1: OFF), and the frame line K2 indicates the resistive voltage division until the switch Q1 switches from ON to OFF (Q1: ON). The formula for the resistive voltage division ratio U will be described later.

[0041] 2.Protection against abnormal high temperature <Normal condition (when the temperature of the battery pack 30 is below the protection temperature)> Under normal circumstances, the potential at point A is lower than the ON threshold (approximately 0.6 V) of switch Q1. Therefore, switch Q1 is turned OFF. When switch Q1 is OFF, VDD is applied to gate G via diode D1 and resistor R3, so switch Q10 is closed and maintains a conductive state. This keeps the battery pack 30 in a dischargeable state.

[0042] <When abnormal temperature occurs> When the temperature of the battery pack 30 rises and reaches the Curie temperature, the resistance value of the PTC thermistor TH1 increases. As a result, the resistance voltage division ratio U of the temperature detection circuit 110 gradually increases, and the voltage at point A rises. The voltage at point A is the temperature detection signal (voltage signal) of the battery pack 30, and is input to the base of the switch Q1.

[0043] U=TH1 / (R1+TH1) (1)

[0044] Thereafter, when the temperature of the battery pack 30 reaches the protection temperature, the voltage at point A exceeds the ON threshold (approximately 0.6 V) of the switch Q1, and the switch Q1 turns ON.

[0045] When switch Q1 is turned on, the potential at gate G drops, switch Q10 opens, and discharge is cut off (protective operation).

[0046] Furthermore, when switch Q1 is turned ON, switch Q2 is turned ON, and resistors R1 and R2 are connected in parallel. This causes the resistor voltage division ratio U of the temperature detection circuit 110 to change and increase, causing the voltage at point A to rise even if there is no change in the temperature of the battery pack 30. This voltage increase is used to implement a hysteresis function.

[0047] U=TH1 / (R12+TH1) (2) R12 is the combined resistance of R1 and R2. R1>R12

[0048] Thereafter, as the temperature of the battery pack 30 drops below the protection temperature, the increased voltage at point A gradually decreases. As the temperature further decreases and the battery pack 30 drops to the recovery temperature, the voltage at point A falls below the ON threshold of switch Q1 (approximately 0.6 V), and switch Q1 turns OFF.

[0049] When switch Q1 is turned off, VDD is applied to gate G via diode D1 and resistor R3, so switch Q10 is closed and maintains a conductive state, returning the battery pack 30 to a dischargeable state (protection release).

[0050] Figure 8 is a comparative example of a thermal protection device. In the thermal protection device of Figure 8, the temperature detected by a temperature sensor circuit (thermistor) 510 is input to a microcomputer 520. The output voltage of the microcomputer is about 5V, which is not enough to drive the gate of switch Q10. Therefore, the gate is driven via a level shift circuit (boost circuit) 530 to control switch Q10.

[0051] This technology makes it possible to inexpensively implement a temperature protection function for the battery 20 using only discrete elements (hardware), without using expensive components such as a microcomputer (software) 520 or a level shift circuit 530. Furthermore, as shown in FIG. 6, a hysteresis function Δ is provided between the protection temperature and the recovery temperature, thereby suppressing chattering of the switch Q10. In the above example, the switch Q10 that cuts off discharging is turned off when the battery pack 30 exceeds the protection temperature. However, a configuration may also be adopted in which the operation of the switch Q1, similar to that of the switch Q10, is used to turn off the switch Q20 that cuts off charging. Alternatively, both Q10 and Q20 may be turned off.

[0052] <Embodiment 2> 9 is a circuit diagram of the thermal protection device S2. The thermal protection device S2 of the second embodiment differs from the thermal protection device S1 of the first embodiment in the temperature detection circuit 210. Specifically, an NTC thermistor TH2 with a negative characteristic is used instead of the PTC thermistor TH1 with a positive characteristic. A negative characteristic is a characteristic in which the resistance value decreases as the temperature rises. In addition, the positions of the NTC thermistor TH2 and the resistor R1 are swapped, with the NTC thermistor TH2 being placed on the VCC side and the resistor R1 being placed on the ground side.

[0053] Similar to the thermal protection device S1 of the first embodiment, the thermal protection device S2 of the second embodiment can protect the battery 20 by detecting an abnormal temperature (high temperature abnormality) in the battery pack 30 and turning off the switch Q10.

[0054] 10 is a graph comparing the temperature-resistance characteristics of the PTC thermistor TH1 and the NTC thermistor TH2. Compared to the NTC thermistor TH2, the PTC thermistor TH1 has a region where the change in resistance with temperature is steeper.

[0055] By turning on switch Q1 in the region where the resistance value of PTC thermistor TH1 changes sharply, it is possible to reduce variation in the protection temperature more than with NTC thermistor TH1. In Figure 10, X indicates the variation in the protection temperature, and Y indicates the range of thermistor resistance due to variation in the ON threshold of switch Q1.

[0056] <Embodiment 3> 11 is a circuit diagram of the thermal protection device S3. The thermal protection device S3 of the third embodiment differs from the thermal protection device S1 of the first embodiment in the temperature detection circuit 310. Specifically, an NTC thermistor TH2 with a negative characteristic curve is used instead of the PTC thermistor TH1 with a positive characteristic curve. The positions of the NTC thermistor TH2 and resistor R1 are the same as those of the first embodiment, with resistor R1 located on the VDD side and NTC thermistor TH2 located on the GND side.

[0057] If the positive-temperature coefficient PTC thermistor TH1 is replaced with the negative-temperature coefficient NTC thermistor TH2, the relationship between temperature and voltage is reversed, and the lower the temperature of the battery pack 30, the higher the voltage at point A. Therefore, the temperature protection device S3 functions as a low-temperature protection circuit that cuts off the current when a low-temperature abnormality is detected.

[0058] Since charging the storage cell 3 at low temperatures can easily cause electrodeposition, the thermal protection device S3 is configured to cut off charging using switch Q20 when it detects an abnormally low temperature. For this reason, the drive circuit 320 of the thermal protection device S3 is different from that of the thermal protection device S1.

[0059] The drive circuit 320 includes a switch Q1, a resistor R3, a switch Q3, a diode D1, and a resistor R4. The switch Q1 is an NPN transistor. The switch Q1 has an emitter connected to GND and a collector connected to VDD via a resistor R3.

[0060] Switch Q3 is a P-channel FET with its gate connected to GND, its source connected to the collector of switch Q1, and its drain connected to the anode of diode D1, whose cathode is connected to the gate of switch Q20. Resistor R4 is connected between the gate and source of switch Q20.

[0061] When the temperature of the battery pack 30 drops below the protection temperature, the voltage at point A exceeds the ON threshold, turning switch Q1 ON. When switch Q1 turns ON, the gate and source of switch Q3 have the same potential, turning switch Q3 OFF.

[0062] When switch Q3 is turned off, the charge on the gate is discharged through resistor R4, and switch Q20 opens, cutting off charging (protection operation).

[0063] After charging is cut off, if the temperature of the battery pack 30 rises and exceeds the recovery temperature, the voltage at point A falls below the ON threshold, turning switch Q1 OFF. When switch Q1 turns OFF, switch Q3 turns ON. This closes switch Q20, enabling charging (protection release). Note that, in the case of low temperature protection, the protection temperature is lower than the recovery temperature, as shown in Figure 12.

[0064] <Other embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments, for example, are also included within the technical scope of the present invention.

[0065] (1) In the above embodiment, the battery 20 is for a motorcycle. However, the use of the battery 20 is not limited to a motorcycle, and it may be for a four-wheeled motor vehicle or for a moving body other than a vehicle.

[0066] (2) In the above embodiment, the current interruption device 70 is disposed at the negative electrode of the battery pack 30, but it may also be disposed at the positive electrode.

[0067] (3) In the above embodiment, the current interruption device 70 is configured from two switches Q10 and Q20, but it may be configured from just one of the switches Q10 or Q20.

[0068] (4) In the above embodiment, the temperature detection circuit 110 is configured with a resistor R1 and a thermistor TH, but other configurations are possible as long as they can detect temperature. Similarly, the setting circuit 120 may be configured differently as long as it is possible to set the hysteresis Δ between the protection temperature and the recovery temperature. [Explanation of symbols]

[0069] 20 Battery (energy storage device) 30 battery packs 70 Current interrupter 80, 320 drive circuit 110, 210, 310 Temperature detection circuit 120 Setting circuit S1, S2, S3 temperature protection device TH1 PTC thermistor TH2 NTC thermistor

Claims

1. A temperature protection device for an electricity storage device, a current interruption device that interrupts the current of the power storage device; a drive circuit that drives the current interruption device; a temperature detection circuit that detects the temperature of the power storage device and outputs the detection result to the drive circuit; a setting circuit for setting a hysteresis between a protection temperature at which a protection operation for the power storage device is performed and a recovery temperature at which the protection is released, When the temperature detection circuit detects a protection temperature, the drive circuit opens the current interruption device to interrupt the current; When the temperature detection circuit detects a return temperature, the temperature protection device closes the current interruption device to return to the current interruption state.

2. 2. The thermal protection device of claim 1, the drive circuit includes a semiconductor switch that switches a gate voltage of the current interruption device between GND and VDD; the temperature detection circuit is a series circuit of a thermistor and a resistor, The temperature protection device wherein the setting circuit automatically sets the hysteresis between the protection temperature and the recovery temperature by changing the resistor voltage division ratio of the temperature detection circuit in response to the switching on and off of the semiconductor switch.

3. 3. The thermal protection device of claim 2, The temperature protection device, wherein the thermistor is a positive temperature coefficient PTC thermistor.

4. A power storage device comprising: a power storage element; and the temperature protection device according to claim 1 or 2.

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