Protection device, power storage device, and protection method

Abstract

To suppress the immediate recovery of a current interruption device by the recovery of a cell voltage due to a current interruption.SOLUTION: A protection device for a power storage device 20 includes: a current interruption device 80 that interrupts a current of the power storage device 20; and a control circuit 100 that controls the current interruption device 80. The control circuit 100 interrupts the current by the current interruption device 80 when a low voltage abnormality of the power storage device 20 is detected, and cancels the interruption of the current by the current interruption device 80 when a low voltage abnormality of the power storage device 20 is resolved and a charger 200 is connected to the power storage device 20.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a protection device for a power storage device, a power storage device, and a protection method. [Background technology]

[0002] One of the protection devices for an electricity storage device is a current interruption device. Patent Document 1 discloses a current interruption device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-5985 Summary of the Invention [Problem to be solved by the invention]

[0004] When the cell voltage falls below the protection threshold, the current interruption device cuts off the current, preventing low voltage abnormalities. However, if a low voltage abnormality occurs during discharge, cutting off the current eliminates the voltage drop due to internal resistance, causing the cell voltage to temporarily rise. As a result, if the cell voltage exceeds the protection release threshold, the current interruption device may be reset. Furthermore, as shown in Figure 11, there is concern that this operation (protection operation and its release) may be repeated, leading to an unsafe state in the energy storage device. [Means for solving the problem]

[0005] The protection device for the power storage device includes a current interruption device that interrupts the current of the power storage device and a control circuit that controls the current interruption device. When the control circuit detects a low voltage abnormality in the power storage device, the control circuit interrupts the current using the current interruption device, and when the low voltage abnormality in the power storage device is resolved and a charger is connected to the power storage device, the control circuit cancels the current interruption by the current interruption device. [Effects of the Invention]

[0006] With this configuration, even if the low voltage abnormality of the power storage device is resolved, the current interruption is not released unless a charger is connected to the power storage device. This prevents the current interruption device from immediately returning to normal operation due to the recovery of cell voltage following the current interruption. This prevents the protection operation and its release from being repeated, thereby improving the safety of the power storage device. [Brief explanation of the drawings]

[0007] [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] Battery Schematic [Figure 5] Battery Schematic [Figure 6] Battery Schematic [Figure 7] Battery Schematic [Figure 8] Battery Schematic [Figure 9] Battery Schematic [Figure 10] Truth tables for the electrical status of monitoring ICs, switches, terminals, etc. [Figure 11] Explaining the issues facing this technology DETAILED DESCRIPTION OF THE INVENTION

[0008] (Outline of this embodiment) (1) A 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, and a control circuit that controls the current interruption device. When the control circuit detects a low voltage abnormality in the power storage device, it interrupts the current using the current interruption device, and when the low voltage abnormality in the power storage device is resolved and a charger is connected to the power storage device, it cancels the current interruption by the current interruption device, but does not cancel the current interruption in other cases. In the protection device described in (1), any configuration other than the above is optional and may be used.

[0009] According to the protection device of (1), even if the low voltage abnormality of the energy storage device is resolved, the current interruption is not released unless a charger is connected to the energy storage device. Therefore, it is possible to prevent the current interruption device from immediately returning to normal due to the recovery of cell voltage following the current interruption. This prevents the protection operation and its release from being repeated, thereby improving the safety of the energy storage device.

[0010] (2) In the protection device described in (1) above, the control circuit may include a detection circuit that detects connection of the charger to the power storage device, and a latch circuit. The latch circuit may latch the current interruption device into a current interruption state when the current interruption device interrupts the current due to detection of a low voltage abnormality. The detection circuit may release the latch on the current interruption device when it detects connection of the charger.

[0011] In the configuration (2), when the detection circuit detects the connection of a charger, the latch circuit releases the latch on the current interruption device. Releasing the latch allows the current interruption device to resume conduction, so once the cell voltage recovers, the storage device can be reused.

[0012] (3) In the protection device described in (2), the current interruption device may be a semiconductor switch, and the latch circuit may be a circuit that fixes the semiconductor switch in a current interruption state by prohibiting input of a drive voltage to a gate.

[0013] In the configuration of (3), when the current interruption device interrupts the current due to the detection of a low voltage abnormality, the latch circuit prohibits the input of a drive voltage to the gate of the current interruption device, thereby fixing and latching the current interruption device in the interruption state. Therefore, the current interruption is maintained while the latch is in place.

[0014] (4) In the protection device described in (2) or (3) above, the detection circuit may be a circuit that detects the connection of the charger from a change in voltage at the terminals of the power storage device. According to (4), since the connection of the charger is detected electrically, there is no increase in the number of parts and failures are less likely to occur compared to mechanical detection.

[0015] <Embodiment> 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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).

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 4 is a block diagram showing the electrical configuration of the battery 20. The battery 20 includes, as its electrical configuration, a battery pack 30, a drive circuit 70, a current interruption device 80, and a control circuit 100. The battery pack 30 is made up of four storage cells 3 connected in series. The drive circuit 70 and the control circuit 100 are part of the management unit 53.

[0029] The positive electrode of the battery pack 30 is connected to the plus terminal 51 via a power line 53a. The negative electrode of the battery pack 30 is connected to the minus terminal 52 via a power line 53b and a current interrupter 80.

[0030] The drive circuit 70 is a circuit that drives the gate G of the current interruption device 80. The current interruption device 80 is disposed on the power line 53b. The current interruption device 80 is a semiconductor switch such as an FET. When the application of the drive voltage to the gate G is stopped, the current interruption device 80 opens and interrupts the current of the battery 20.

[0031] The control circuit 100 monitors the states of the storage cells 3 and the assembled battery 30 based on the results of monitoring the cell voltages and battery voltages of the storage cells 3. If an abnormality in the storage cells 3 or the assembled battery 30 is detected, the control circuit 100 protects the storage cells 3 and the assembled battery 30 by cutting off the current via the current cut-off device 80.

[0032] 2. Low voltage abnormality protection and recovery operation One of the protection items is a low voltage anomaly, which cuts off the current via the current cutoff device 80 when an anomaly occurs in which the cell voltage of the storage cell 3 falls below the protection operation threshold.

[0033] However, if a low voltage abnormality occurs during discharge, cutting off the current eliminates the voltage drop due to internal resistance, causing the cell voltage to temporarily rise. As a result, the cell voltage may exceed the protection operation release threshold, causing the current cutoff device 80 to reset. Furthermore, as shown in Figure 11, this operation (protection operation and its release) may be repeated, potentially putting the battery 20 into an unsafe state.

[0034] Therefore, after current is interrupted due to a low voltage abnormality, the control circuit 100 cancels the current interruption by the current interruption device 80 via the drive circuit 70 if the following two conditions are met, and does not cancel the current interruption in any other cases.

[0035] (1) The low voltage abnormality of storage cell 3 has been resolved. (2) The charger is connected to the battery 20.

[0036] The above control can prevent the current interruption device 80 from immediately returning to normal operation due to the recovery of the cell voltage following the current interruption.

[0037] An example of the drive circuit 70 and the control circuit 100 will be described below with reference to FIGS. The drive circuit 70 is a circuit that drives the gate G of the current interruption device 80. As shown in Fig. 5, the drive circuit 70 is made up of a switch Q6, a switch Q7, a switch Q20, and a diode D3.

[0038] Switch Q6 is a P-channel FET, and switch Q7 is an N-channel FET. FET stands for Field Effect Transistor. Switch Q6 has its source connected to the power supply line L1 and its drain connected to the drain of switch Q7. Switch Q7 has its source connected to ground. Power supply line L1 is drawn from the internal power supply of battery 20, and its voltage is VDD.

[0039] The switch Q20 is a P-channel FET. The source of the switch Q20 is connected to the drains of the switches Q6 and Q7, and the drain is connected to the anode of the diode D3. The cathode of the diode D3 is connected to the gate G of the current interruption device 80 via the input line L2.

[0040] The control circuit 100 includes a cell voltage monitoring IC 110, a battery voltage monitoring IC 120, a reuse prohibition circuit 130, an output circuit 140, a detection circuit 150, and a latch circuit 160.

[0041] The cell voltage monitoring IC 110 monitors the cell voltage of each storage cell 3, and the battery voltage monitoring IC 120 monitors the voltage of the positive terminal 51 of the battery 20. The reuse prohibition circuit 130 is a circuit that prohibits use of the battery 20 under predetermined conditions. The reuse prohibition circuit 130 may be omitted.

[0042] The output circuit (push-pull circuit) 140 is composed of switches Q8 and Q9. Switch Q8 is a P-channel FET, and switch Q9 is an N-channel FET. The source of switch Q8 is connected to VDD, and the drain is connected to the drain of switch Q9. The source of switch Q9 is connected to ground. The drains of switches Q8 and Q9 are connected to the gate of switch Q20 via output line L3. VDD is the internal power supply voltage of battery 20 (the voltage of power supply line L1).

[0043] The battery 20 also has a bypass line L4 and a switch Q70. The bypass line L4 bypasses the battery pack 30 and the current interruption device 80 and connects the two terminals 51 and 52. The switch Q70 is provided on the bypass line L4.

[0044] The switch Q70 is a P-channel FET, and has its source connected to the positive terminal 51 and its drain connected to the negative terminal 52. The gate of the switch Q70 is connected to the gate G of the current interruption device 80.

[0045] The detection circuit 150 is a circuit that detects the connection of the charger 200 (FIG. 9) to the battery 20 by utilizing a change in voltage of the negative terminal 52. The detection circuit 150 is connected to the negative terminal 52 via a signal line L5.

[0046] In this example, when the negative terminal 52 is at GND potential, the B output of the detection circuit 150 is VDD, and when the negative terminal 52 is at VDD potential, the B output of the detection circuit 150 is GND. The B output is the voltage at the output terminal of the detection circuit 150, that is, the output of the detection circuit 150. VDD is an example of a high-level signal, and GND is an example of a low-level signal.

[0047] The latch circuit 160 is a circuit that, when the current of the battery 20 is interrupted, fixes the current interruption device 80 in an interrupted state by prohibiting the input of VDD (drive voltage) to the gate G. The latch circuit 160 is composed of a switch Q5, a first resistor R1, and a second resistor R2.

[0048] The switch Q5 is a P-channel FET. The source of the switch Q5 is connected to the power supply line L1, and the drain of the switch Q5 is connected to the output line L3 via the first resistor R1. The drain of the switch Q5 is also connected to the gates of the switches Q6 and Q7.

[0049] The gate of the switch Q5 is connected to the output of the reuse prohibition circuit 130. It is also connected to the B output of the detection circuit 150 via a second resistor R2.

[0050] The operation of the control circuit 100 will be described with reference to Figures 6 to 10. In Figures 6 to 10, a thick line indicates that the voltage of that line is VDD. A dashed line indicates that the voltage of that line is ground potential. VDD is the internal power supply voltage of the battery 20. In the following, the output of the reuse prohibition circuit 130 is considered to be high impedance for convenience (to facilitate understanding of the technology).

[0051] <Normal time (normal time)> 6 is a block diagram showing the electrical control state of the battery 20 under normal conditions. Under normal conditions, the current interruption device 80 is closed, so the negative terminal 52 of the battery 20 is at GND potential. When the negative terminal 52 is at GND potential, the B output of the detection circuit 150 is at VDD. When the B output is at VDD, the switch Q5 is turned off.

[0052] Furthermore, the cell voltage monitoring IC 110 outputs a conduction signal (VDD) to the output circuit 140. While the conduction signal is being output, the switch Q8 is turned OFF and the switch Q9 is turned ON. As a result, the output line L3 becomes the GND potential, so the switch Q6 is turned ON, the switch Q7 is turned OFF, and the switch Q20 is turned ON.

[0053] When the switch Q6 is turned ON and the switch Q20 is turned ON, the diode D3 becomes conductive, and VDD is applied to the gate G of the current interruption device 80. As a result, the current interruption device 80 remains CLOSE (conductive).

[0054] <When undervoltage protection is activated> 7 is a block diagram showing the electrical control state during low voltage protection operation of the battery 20. The low voltage protection operation is an operation to cut off the current of the battery 20 upon detection of a low voltage abnormality (an abnormality in which the cell voltage falls below the protection operation threshold).

[0055] Upon detecting a low voltage abnormality, the cell voltage monitoring IC 110 outputs a shutdown signal (GND) to the output circuit 140. While the shutdown signal is being output, the switch Q8 is ON and the switch Q9 is OFF. As a result, the output line L3 becomes the VDD potential, and the switch Q20 is turned OFF.

[0056] When switch Q20 is turned OFF, diode D3 becomes non-conductive, and the application of drive voltage VDD to gate G of current interruption device 80 is cut off. This causes current interruption device 80 to open (current interruption). Also, when diode D3 becomes non-conductive, switch Q70 turns ON. As a result, negative terminal 52 is connected to positive terminal 51 through bypass line L4, and negative terminal 52 becomes the VDD potential.

[0057] When the negative terminal 52 is at VDD, the B output of the detection circuit 150 switches to the GND potential. When the B output becomes the G potential, the switch Q5 turns ON, and further the switch Q6 turns OFF and the switch Q7 turns ON.

[0058] When switch Q6 is turned OFF and switch Q7 is turned ON, the source of switch Q20 is fixed to GND potential, which fixes switch Q20 to OFF, preventing VDD (drive voltage) from being applied to gate G, and latching current interrupt device 80 to OPEN (current interruption).

[0059] <Cell voltage recovery> 8 is a block diagram showing the electrical control state during cell voltage recovery of battery 20. Cell voltage recovery occurs when the voltage drop due to internal resistance disappears due to current interruption, causing the cell voltage to temporarily rise.

[0060] When the cell voltage recovers and exceeds the protection operation release threshold, the cell voltage monitoring IC 110 outputs a re-conduction signal (VDD) to the output circuit 140. While the re-conduction signal is being output, the switch Q8 is turned OFF and the switch Q9 is turned ON, causing the output line L3 to go to GND potential.

[0061] However, as long as the B output maintains the GND potential, switch Q5 remains ON, switch Q6 remains OFF, switch Q7 remains ON, and switch Q20 remains OFF. When switch Q20 remains OFF, diode D3 is not conducting, so drive voltage VDD is not applied to gate G, and current interruption device 80 remains OPEN (current interruption).

[0062] <Connecting the charger after cell voltage recovery> 9 is a block diagram showing the electrical control state of the battery 20 when a charger is connected after cell voltage recovery. When the charger 200 is connected between the positive terminal 51 and the negative terminal 52, the negative terminal 52 becomes negative potential.

[0063] When the negative terminal 52 is at a negative potential, the B output of the detection circuit 150 switches to VDD. When the B output is VDD, the switch Q5 turns OFF, and furthermore, the switch Q6 turns ON and the switch Q7 turns OFF. When the switch Q6 turns ON and the switch Q7 turns OFF, the source of the switch Q20 is connected to the power line L1, and the latch is released.

[0064] By releasing the latch, the diode D3 becomes conductive and the drive voltage VDD is applied to the gate G. This causes the current interruption device 80 to close and become conductive again.

[0065] According to this technology, even if the low voltage abnormality of the battery 20 is resolved, the current interruption is not released unless the charger 200 is connected to the battery 20. This prevents the current interruption device 80 from immediately returning to normal operation due to the recovery of the cell voltage following the current interruption. As a result, as shown in FIG. 11, the protection operation and its release are not repeated, thereby improving the safety of the battery 20.

[0066] <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.

[0067] (1) In the above embodiment, the battery is for a motorcycle. However, the use of the battery is not limited to motorcycles, and the battery may be for a four-wheeled vehicle or for a moving body other than a vehicle.

[0068] (2) In the above embodiment, the control circuit 100 is configured from the cell voltage monitoring IC 110, the battery voltage monitoring IC 120, the reuse prohibition circuit 130, the output circuit 140, the detection circuit 150, and the latch circuit 160. The circuit configuration of the control circuit 100 is not limited to the example of the embodiment as long as it can perform the following: If a low voltage abnormality of the battery 20 is detected, the current is cut off. When the low voltage abnormality of the battery 20 is resolved and a charger is connected to the battery 20, the current cutoff is released. [Explanation of symbols]

[0069] 20 Battery (electricity storage device) 30 battery packs 32 Energy storage cells 70 Drive circuit 80 Current interrupter 100 control circuit 110 Cell voltage monitoring IC 140 Output circuit 150 Detection circuit 160 Latch Circuit 200 charger

Claims

1. A protection device for an electricity storage device, a current interruption device that interrupts the current of the power storage device; a control circuit for controlling the current interruption device, The control circuit When a low voltage abnormality of the power storage device is detected, the current is interrupted by the current interruption device, A protection device that cancels the current interruption by the current interruption device when the low voltage abnormality of the storage device is resolved and a charger is connected to the storage device, and does not cancel the current interruption in other cases.

2. 2. The protection device of claim 1, The control circuit a detection circuit that detects connection of the charger to the power storage device; a latch circuit, The latch circuit When the current interruption device interrupts the current due to the detection of a low voltage abnormality, the current interruption device is latched in a current interruption state; A protection device that releases the latch for the current interruption device when the detection circuit detects connection of the charger.

3. 3. The protection device according to claim 2, the current interruption device is a semiconductor switch, The latch circuit is a circuit that fixes the semiconductor switch in a current-blocking state by prohibiting input of a drive voltage to the gate.

4. 4. The protection device according to claim 2 or claim 3, The protection device, wherein the detection circuit is a circuit that detects connection of the charger based on a change in voltage at the terminal of the power storage device.

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

6. A method for protecting an electricity storage device, comprising: If a low voltage abnormality is detected in the storage device, the current is cut off by the current cutoff device, When the low voltage abnormality in the power storage device is resolved and a charger is connected to the power storage device, the current interruption by the current interruption device is cancelled.

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