Battery protection device and battery pack

Abstract

According to the present invention, a measurement circuit measures each voltage of a plurality of cells included in a battery pack and a current flowing through the battery pack. A control circuit controls charging and discharging of the plurality of cells on the basis of a value measured by the measurement circuit. When detecting a non-return type abnormality, the control circuit continues power supplying to the measurement circuit and the control circuit until the voltage of the battery pack drops to a prescribed set voltage while stopping energization with a target load.

Description

Battery protection device and battery pack

[0001] The present disclosure relates to a battery protection device that protects a battery when an abnormality occurs in the battery pack, and to a battery pack.

[0002] In recent years, electric mobility vehicles such as electric bicycles, electric motorcycles, and electric kick scooters have become popular. Electric mobility vehicles use battery packs that include a battery pack in which a plurality of cells are connected in series.

[0003] When cells in a battery pack are charged in a deep-discharged state, copper or iron may precipitate, causing an internal short circuit. Therefore, battery packs generally become unusable when the cell voltage drops below a preset voltage for deep-discharge protection. Many battery packs with deep-discharge protection function minimize current consumption by the internal circuitry as the cell voltage drops, preventing a normal battery pack from becoming unusable due to the deep-discharge protection. For example, over-discharge protection (see, for example, Patent Document 1) is activated before deep-discharge protection, and when the cell voltage drops below the preset voltage for over-discharge detection, the power supply for various ICs is turned off to reduce internal consumption.

[0004] JP 2010-187531 A

[0005] However, if a large variation in cell voltage, which is set as a non-recoverable abnormality, is detected and the battery pack becomes unusable, the over-discharge protection function may suppress internal consumption, causing the cell voltage to remain high, leaving the battery pack in an unusable and unsafe state.

[0006] The present disclosure has been made in light of these circumstances, and its purpose is to provide a technology that prevents unsafe battery packs from being left in an unusable state.

[0007] To solve the above problems, a battery protection device according to one aspect of the present disclosure includes a control circuit that monitors a non-recoverable abnormality in a battery pack, and when the non-recoverable abnormality is detected, the control circuit stops power supply to a target load while continuing to supply power to circuit components in the battery pack until the voltage of the battery pack drops to a predetermined set voltage.

[0008] Any combination of the above components, and conversion of the expression of the present disclosure into an apparatus, system, method, computer program, etc., are also valid aspects of the present disclosure.

[0009] According to the present disclosure, it is possible to prevent an unsafe battery pack from being left in an unusable state.

[0010] The present invention relates to a battery management device for an electric bicycle, and is not limited to the above embodiments.

[0011] FIG. 1 is a diagram illustrating the configuration of a battery pack 1 according to an embodiment. The battery pack 1 includes a battery pack 20 and a battery management device 10. The battery pack 20 includes multiple cells E1-E7 connected in series. While FIG. 1 shows an example of a seven-series battery, the number of series-connected cells is determined by the specifications of the load 2. The cells may be lithium-ion battery cells, nickel-metal hydride battery cells, lead-acid battery cells, or the like. In the following description, an example using lithium-ion battery cells (nominal voltage: 3.6-3.7 V) is assumed.

[0012] A load switch S2 that switches conduction / non-conduction between the battery pack 20 and the load 2 is inserted in the power line connecting the battery pack 20 and the load 2. When the battery pack 1 is used for electric mobility, the load 2 is an inverter and a motor, or a charger.

[0013] In the example shown in FIG. 1 , the load switch S2 is configured by a first transistor Q1 and a second transistor Q2, each configured as an N-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), connected in series in the reverse direction. In an N-channel MOSFET, a parasitic diode is formed in the source-to-drain direction. By connecting two N-channel MOSFETs in series in the reverse direction, it is possible to block current passing through the parasitic diode and form a bidirectional switch. In the example shown in FIG. 1 , discharging current from the battery pack 20 can be cut off by turning off the first transistor Q1, and charging current to the battery pack 20 can be cut off by turning off the second transistor Q2.

[0014] The battery management device 10 is composed of multiple ICs, which are mounted on a circuit board. In this embodiment, the focus is on the battery protection function of the battery management device 10, so in this specification the battery management device 10 is also referred to as a battery protection device.

[0015] The battery management device 10 includes a power supply circuit 11, a measurement circuit 12, a control circuit 13, a non-volatile memory 14, and a notification lamp LD 1. The power supply circuit 11 steps down the voltage of the battery pack 20 to generate a power supply voltage (e.g., 5.0 V) to be supplied to circuit components inside the battery pack 1 (mainly the measurement circuit 12 and the control circuit 13 in FIG. 1 ).

[0016] The power supply circuit 11 may use a linear regulator (for example, a three-terminal regulator or an LDO (Low Drop Out) regulator) or a switching regulator. Generally, a linear regulator is cheaper and smaller, while a switching regulator has lower loss. In this embodiment, it is assumed that a linear regulator is used.

[0017] An internal power switch S1 is inserted into the power supply line connecting the positive electrode of the battery pack 20 and the input terminal of the power supply circuit 11. By turning off the internal power switch S1, the power supply from the battery pack 20 to the power supply circuit 11 can be cut off.

[0018] The measurement circuit 12 is configured with an AFE (Analog Front End) IC or an ASIC (Application Specific Integrated Circuit). The measurement circuit 12 is connected to each node of the series-connected cells E1-E7 by multiple voltage measurement lines, and measures the voltage between each two adjacent voltage measurement lines to measure the voltage of each cell E1-E7.

[0019] The measurement circuit 12 includes a multiplexer and an A / D converter. The multiplexer outputs the measurement voltages of the multiple cells E1-E7 to the A / D converter in a predetermined order. The A / D converter converts the analog measurement voltages input from the multiplexer into digital values. The measurement circuit 12 transmits the converted digital voltage values ​​of the cells E1-E7 to the control circuit 13 via a communication interface.

[0020] The measurement circuit 12 can measure the current flowing through the battery pack 1. A shunt resistor Rs is connected to the power line connecting the assembled battery 20 and the load 2. A differential amplifier (not shown) amplifies the voltage across the shunt resistor Rs and outputs it to an A / D converter in the measurement circuit 12. The A / D converter converts the analog voltage indicating the current flowing through the assembled battery 20, which is input from the differential amplifier, into a digital value. The measurement circuit 12 transmits the current value converted into a digital value to the control circuit 13 via the communication interface.

[0021] Although not shown, a temperature sensor (e.g., a thermistor) is installed in the battery pack 20, and the temperature sensor outputs the measured temperature of the battery pack 20 to the measurement circuit 12. The measurement circuit 12 converts the measured temperature into a digital value and transmits the converted digital temperature value to the control circuit 13 via the communication interface.

[0022] The control circuit 13 is composed of a microcontroller. The control circuit 13 controls the battery pack 1 based on the voltage values ​​of each cell E1-E7, the current value flowing through the battery pack 20, and the temperature value of the battery pack 20 received from the measurement circuit 12. The control circuit 13 is connected to the non-volatile memory 14 via a communication interface, and the non-volatile memory 14 can be used as an external memory. An EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory can be used as the non-volatile memory 14. The control circuit 13 can store, for example, time-series data of the voltage values, current values, and temperature values ​​received from the measurement circuit 12 in the non-volatile memory 14.

[0023] The control circuit 13 controls the current supplied to the notification lamp LD1, which emits light toward the outside of the battery pack 1, thereby controlling the on / off of the notification lamp LD1. An LED can be used as the notification lamp LD1. In FIG. 1, a configuration is shown in which current is supplied to the notification lamp LD1 from the power supply circuit 11 via the control circuit 13. In this regard, a configuration may be adopted in which the notification lamp LD1 is directly connected to the power supply circuit 11, a switch is provided between the notification lamp LD1 and the power supply circuit 11, and the control circuit 13 controls the on / off of the switch to control the on / off of the notification lamp LD1.

[0024] When the control circuit 13 detects any of the normal level abnormalities, such as overcharging, over-discharging, overcurrent, high temperature abnormality, and low temperature abnormality, it sends a load switch S2 disconnect signal to the measurement circuit 12 to turn off the load switch S2. If a predetermined period of time has passed since the load switch S2 was turned off and a safe state has been confirmed, the control circuit 13 sends a load switch S2 close signal to the measurement circuit 12 to turn on the load switch S2. Note that before reconnecting the load 2, a user restart operation may be requested.

[0025] If over-discharge is detected among the above abnormalities, the control circuit 13 causes the measurement circuit 12 to turn off the internal power switch S1 to prevent the voltage of the battery pack 1 from dropping further, which would trigger deep-discharge protection and render the battery pack 1 unusable. This reduces internal consumption of the battery pack 1, thereby preventing a drop in the voltage of the battery pack 1.

[0026] When a charger is connected to the battery pack 1 as the load 2, the charger transmits a start signal to turn on the internal power switch S1. When the internal power switch S1 is turned on, the measurement circuit 12 and the control circuit 13 are started. The control circuit 13 causes the measurement circuit 12 to turn on the load switch S2, thereby enabling the charger to charge the battery pack 20.

[0027] In this way, even if the protection function is activated by detecting a normal level abnormality and the battery pack 1 and the load 2 are disconnected, it is possible to return to the state before the abnormality was detected by satisfying certain conditions. In contrast, non-recoverable abnormalities that cannot be re-recovered are also defined. In this embodiment, the non-recoverable abnormalities defined are cell balance abnormality, deep discharge abnormality, second level overcharge abnormality, current measurement circuit abnormality, pre-charge timeout abnormality, internal ROM abnormality, and EEPROM abnormality.

[0028] A cell balance abnormality is an abnormality in which the voltage difference between any two cells exceeds a predetermined value (e.g., 500 mV). In this embodiment, a cell balancing circuit is not implemented to reduce costs. Therefore, it is not possible to eliminate cell voltage variations through internal control. Large variations in cell voltage significantly reduce the available capacity of the battery pack 1 and increase the variation in deterioration between cells, so this is an irreversible abnormality that requires repair or replacement.

[0029] The deep discharge abnormality is a state in which the voltage is further lower than the overdischarge state, which is a normal level abnormality. In this embodiment, the set voltage for overdischarge detection is set to 2.0 V, and the set voltage for deep discharge detection is set to 1.3 V. The second level overcharge abnormality is a state in which the voltage is further higher than the overcharge abnormality, which is a normal level abnormality. In this embodiment, the set voltage for normal level overcharge detection is set to 4.22 V, and the set voltage for second level overcharge abnormality is set to 4.35 V. Deeply discharged cells or cells charged to the second level overcharge abnormality state are considered to be non-recoverable abnormalities because they may have suffered significant damage.

[0030] A current measurement circuit abnormality is an abnormality in which current is detected even when the load switch S2 is in the off state. Possible abnormalities include an abnormality in the measurement system (shunt resistor Rs or differential amplifier) ​​or an abnormality in the load switch S2. A pre-charge timeout abnormality is an abnormality in which a certain voltage is not reached even after pre-charging for a certain period of time. Pre-charging is a function that automatically charges a cell to a certain voltage with a weak current when the cell voltage drops to prevent over-discharge.

[0031] An internal ROM error is a write error or a read error that occurs in the microcontroller's internal ROM. An EEPROM error is a write error or a read error that occurs in the EEPROM. For example, after the driver writes data to the ROM, it reads the written data from the ROM and checks whether it matches the data before writing. If the data does not match, a write error occurs. The driver also calculates the checksum of the data read from the ROM and checks whether it matches the checksum calculated before writing. If the checksums do not match, a read error occurs.

[0032] Current measurement circuit abnormalities, pre-charge timeout abnormalities, internal ROM abnormalities, or EEPROM abnormalities may indicate a hardware abnormality that is difficult to repair on its own, and are events that require repair or replacement as non-recoverable abnormalities.

[0033] When a non-recoverable abnormality is detected, the control circuit 13 causes the measurement circuit 12 to turn off the load switch S2, stopping the flow of current to the load 2. When a non-recoverable abnormality is detected, the control circuit 13 continues the supply of power from the power supply circuit 11 to the measurement circuit 12 and the control circuit 13 until the voltage of the battery pack 1 drops to a predetermined set voltage. The control circuit 13 may calculate the voltage of the battery pack 1 (i.e., the voltage across the assembled battery 20) by summing the voltages of multiple cells E1-E7, or may measure the voltage across the assembled battery 20 by resistively dividing it. The predetermined set voltage is set to a voltage higher than the power supply voltage of the measurement circuit 12 by a certain value. In this embodiment, it is set to 6 V.

[0034] When the voltage of the battery pack 1 drops to a set voltage due to internal consumption after a non-recoverable abnormality is detected, the control circuit 13 causes the measurement circuit 12 to turn off the internal power switch S1 to stop internal consumption. If the voltage of the battery pack 1 is below the set voltage when a non-recoverable abnormality is detected, the control circuit 13 immediately turns off the internal power switch S1.

[0035] The control circuit 13 controls the internal current consumption until the voltage of the battery pack 1 drops to the set voltage so that it remains within a certain range. If the internal current consumption increases, the voltage drop due to the internal resistance of the cells increases, potentially causing a momentary voltage fluctuation that temporarily hits the set voltage. In this case, there is a risk that internal consumption will end before the battery pack 1's actual voltage drops to the set voltage, leaving the voltage high. On the other hand, if the internal current consumption is too small, it will take a long time for the battery pack 1's voltage to drop to the set voltage, resulting in a longer unsafe period. The control range of the internal current consumption after a non-recoverable abnormality is detected is preset by the designer, taking into account the cell type, the capacity of the battery pack 1, and the results of experiments and simulations.

[0036] The control circuit 13 can adjust the internal current consumption after a non-recoverable abnormality is detected by adjusting the current flowing through the notification lamp LD1. The control circuit 13 turns on the notification lamp LD1 when it wants to increase the internal current consumption, and turns off the notification lamp LD1 when it wants to decrease the internal current consumption. Note that, as will be described later, if multiple notification lamps LD1 are installed, the control circuit 13 can adjust the internal current consumption by controlling the number of notification lamps LD1 that are turned on.

[0037] FIG. 2 is a flowchart showing the flow of the self-shutdown process performed by the battery management device 10 according to the embodiment. The control circuit 13 monitors for the presence or absence of a non-returnable abnormality (S10). While no non-returnable abnormality is detected (N in S10), the control circuit 13 monitors whether the minimum voltage of the cells E1-E7 included in the battery pack 20 is below 2.0 V (S11). If the minimum voltage of the cells E1-E7 is below 2.0 V (Y in S11), the control circuit 13 causes the measurement circuit 12 to turn off the load switch S2 (S12). Then, the control circuit 13 causes the measurement circuit 12 to turn off the internal power switch S1 to shut off internal consumption (S13). Then, when certain conditions, such as the passage of a predetermined period of time, are met, the internal circuitry is restarted (S14), and the battery pack 1 becomes usable again.

[0038] If a non-recoverable abnormality is detected in step S10 (Y in S10), the control circuit 13 causes the measurement circuit 12 to turn off the load switch S2 (S15). The control circuit 13 determines whether the voltage of the battery pack 1 is 6.0 V or less (S16). If the voltage of the battery pack 1 is higher than 6.0 V (N in S16), the control circuit 13 keeps the internal power switch S1 on to continue internal consumption (S17). The process transitions to step S16. If the voltage of the battery pack 1 is 6.0 V or less (Y in S16), the control circuit 13 causes the measurement circuit 12 to turn off the internal power switch S1 to shut off internal consumption (S18).

[0039] The off state of the internal circuit based on the detection of a non-reset type abnormality is an off state that cannot be restored by user operation, so the user takes the battery pack 1 to a service center of the manufacturer or retailer. At the service center, the battery pack 1 is disassembled and repaired or parts replaced. If repair or part replacement is not possible, the battery pack 1 itself is replaced.

[0040] 3 is a diagram showing a schematic view of the exterior of a battery pack 1 for an electric bicycle 2a according to an embodiment. The battery pack 1 is detachable from the mounting slot of the electric bicycle 2a or the mounting slot of a charger (not shown). The housing of the battery pack 1 is provided with multiple notification lamps LD1 to indicate the remaining battery charge. The more the remaining battery charge, the more notification lamps LD1 light up. In this embodiment, when a non-recoverable abnormality is detected, the control circuit 13 controls the number of notification lamps LD1 that light up according to the target internal current consumption, regardless of the remaining charge of the battery pack 1.

[0041] As described above, this embodiment can prevent the unsafe battery pack 1, including cells that maintain a high voltage, from being left in an unusable state. Furthermore, by utilizing existing functions, the unsafe prevention function can be implemented reasonably without requiring additional costs. Furthermore, by including the notification lamp LD1 in the internal consumption load, the internal current consumption can be adjusted to an appropriate range.

[0042] Furthermore, in a battery pack 1 that does not incorporate a cell balancing circuit, the cell balance abnormality cannot self-correct for cell variations, and therefore is considered a non-recoverable abnormality. Unlike deep discharge abnormalities, cell balance abnormalities, measurement system abnormalities, and control system abnormalities can occur even when the cell voltage is high. By implementing the unsafety prevention function according to this embodiment, the energy of high-voltage cells can be gradually released, thereby improving the safety of the battery pack 1.

[0043] The present disclosure has been described above based on the embodiments. The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of the respective components and processing steps, and that such modifications are also within the scope of the present disclosure.

[0044] In the above embodiment, when a non-recoverable abnormality is detected while the voltage of the battery pack 1 is high, an example is described in which internal consumption is performed by the measurement circuit 12, the control circuit 13, and the notification lamp LD1. In this regard, a separate discharge resistor for internal consumption when a non-recoverable abnormality is detected may be provided in the battery pack 1.

[0045] In the above-described embodiment, an example has been described in which the battery pack 1 according to the present disclosure is mounted on an electric mobility such as an electric bicycle. In this regard, the battery pack 1 according to the present disclosure can also be mounted on a full-size electric vehicle, a low-speed electric vehicle (such as a golf cart or a land car), an electric ship, a rail vehicle, a multicopters (drones), a stationary power storage system, or a consumer electronic device (such as a smartphone or a notebook PC).

[0046] The embodiment may be specified by the following items.

[0047] [Item 1] A battery protection device (10) comprising a control circuit (13) that monitors a non-recoverable abnormality in a battery pack (1), wherein the control circuit (13) stops current flow to a target load (2) when the non-recoverable abnormality is detected, while continuing to supply power to circuit components in the battery pack (1) until the voltage of the battery pack (1) drops to a predetermined set voltage.

[0048] This makes it possible to prevent the unsafe battery pack (1) from being left in an unusable state.

[0049] [Item 2] The battery protection device (10) according to Item 1, wherein the circuit components include the control circuit (13) and a measurement circuit (12) that measures the voltages of the plurality of cells (E1-E7) included in the battery pack (1) and the current flowing through the battery pack (1), and the control circuit (13) controls charging and discharging of the plurality of cells (E1-E7) based on the values ​​measured by the measurement circuit (12), and when the non-recoverable abnormality is detected, stops the flow of current to the target load (2) while continuing the supply of power to the measurement circuit (12) and the control circuit (13) until the voltage of the battery pack (1) drops to a predetermined set voltage.

[0050] According to this, when a non-recoverable abnormality is detected, the voltage of the battery pack (1) is internally consumed by the measurement circuit (12) and the control circuit (13) up to a predetermined set voltage, thereby increasing the safety of the battery pack (1).

[0051] [Item 3] The battery protection device (10) according to Item 2, wherein the circuit components include a notification lamp (LD1) that emits light toward an outside of the battery pack (1), and when the non-recoverable abnormality is detected, the control circuit (13) stops power supply to the target load (2) while continuing to supply power to the notification lamp (LD1) until the voltage of the battery pack (1) drops to a predetermined set voltage.

[0052] According to this, when a non-recoverable abnormality is detected, the voltage of the battery pack (1) is internally consumed by the notification lamp (LD1) up to a predetermined set voltage, thereby increasing the safety of the battery pack (1).

[0053] [Item 4] The battery protection device (10) according to Item 2, wherein the plurality of cells (E1-E7) are connected in series, and when a voltage difference between the plurality of cells (E1-E7) exceeds a predetermined set value as the non-recoverable abnormality, the control circuit (13) continues supplying power to the circuit components in the battery pack (1) until the voltage of the battery pack (1) drops to a predetermined set voltage.

[0054] This can improve the safety of the battery pack (1) when the balance between the multiple cells (E1-E7) is significantly lost.

[0055] [Item 5] A battery pack (1) comprising: at least one cell (E1-E7); and the battery protection device (10) according to any one of items 1 to 4.

[0056] This makes it possible to prevent the unsafe battery pack (1) from being left in an unusable state.

[0057] 1 Battery pack, 2 Load, 2a Electric bicycle, 20 Assembled battery, E1-E7 Cells, 10 Battery management device, 11 Power supply circuit, 12 Measurement circuit, 13 Control circuit, 14 Non-volatile memory, LD1 Notification lamp, Rs Shunt resistor, Q1 First transistor, Q2 Second transistor, S1 Internal power switch, S2 Load switch.

Claims

1. A battery protection device comprising a control circuit that monitors a non-returnable abnormality within a battery pack, and when the control circuit detects a non-returnable abnormality, the control circuit cuts off current flow to a target load while continuing to supply power to circuit components within the battery pack until the voltage of the battery pack drops to a specified set voltage.

2. The battery protection device of claim 1, wherein the circuit components include the control circuit and a measurement circuit that measures the voltage of at least one cell included in the battery pack and the current flowing through the battery pack, and the control circuit controls the charging and discharging of the at least one cell based on the value measured by the measurement circuit, and when the non-recoverable abnormality is detected, stops the flow of current to the target load while continuing the supply of power to the measurement circuit and the control circuit until the voltage of the battery pack drops to a predetermined set voltage.

3. A battery protection device as described in claim 2, wherein the circuit components include a notification lamp that emits light toward the outside of the battery pack, and when the non-recoverable abnormality is detected, the control circuit stops the flow of current to the target load while continuing to supply power to the notification lamp until the voltage of the battery pack drops to a predetermined set voltage.

4. The battery protection device of claim 2, wherein the at least one cell is a plurality of cells connected in series, and when a voltage difference between the plurality of cells exceeds a predetermined set value as the non-recoverable abnormality, the control circuit continues to supply power to the circuit components in the battery pack until the voltage of the battery pack drops to a predetermined set voltage.

5. A battery pack comprising: a battery protection device according to any one of claims 1 to 3; and at least one cell.

6. A battery pack comprising: the battery protection device according to claim 4; and a plurality of said cells.

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