Battery module

Abstract

The invention relates to a battery module. The battery module is configured so as to supply power to a load connected to an output terminal, and is provided with: a power storage unit; a relay provided between the power storage unit and the output terminal and configured to switch between an electrically conductive state and an electrically cut-off state of the power storage unit and the output terminal; and a control unit configured to control a state of the relay, the control unit being configured to control the relay to be in an OFF state under a condition that an output resistance of the battery module is equal to or greater than a first threshold value.

Description

Technical Field

[0001] The present disclosure relates to a battery module that supplies power to a load connected to an output terminal. Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2016-048693 discloses a battery module in which a signal cut-off portion is disposed between a voltage sensing detection terminal electrically connected to an electrode terminal connection portion of a battery cell and a conductive portion connected to the voltage sensing detection terminal. In this battery module, when a short circuit occurs in the conductive portion, the transmission of the detection voltage is interrupted by using the signal cut-off portion, thereby improving safety.

[0003] In the battery module described in Japanese Unexamined Patent Application Publication No. 2016-048693, the battery cell is electrically connected to the conductive portion (i.e., the voltage sensing detection terminal). Therefore, even if the transmission of the detection voltage is immediately interrupted when a short circuit occurs in the conductive portion, the influence of the short circuit sometimes spreads to the battery cell.

[0004] Therefore, in order to further improve the safety of the battery module, it is desirable that the influence caused by a short circuit between output terminals does not spread to the battery cell even when a short circuit occurs in the output terminal or the like. Summary of the Invention

[0005] The present disclosure provides a battery module capable of reducing the influence that spreads to a battery cell when a short circuit occurs between output terminals.

[0006] One aspect of the technology of the present disclosure is a battery module configured to supply power to a load connected to an output terminal, the battery module including: a power storage unit; a relay disposed between the power storage unit and the output terminal and configured to switch between an electrically conductive state and a cut-off state of the power storage unit and the output terminal; and a control unit configured to control the state of the relay, the control unit being configured to control the relay to a cut-off state under a condition that an output resistance of the battery module is equal to or greater than a first threshold.

[0007] The battery module may further include a constant current circuit connected in parallel with the relay. The control unit may be configured to periodically perform control to allow a constant current to flow from the power storage unit to the output terminal via the constant current circuit during a period in which the relay is in a cut-off state, and derive the output resistance based on an outflow current of the power storage unit and a voltage of the output terminal in the control.

[0008] The control unit may also be configured to control the relay to a cut-off state under a condition that the output resistance is less than a second threshold smaller than the first threshold.

[0009] The above control unit may also be configured to control the relay to be in the conducting state under the condition that the above output resistance is equal to or greater than the second threshold and less than the first threshold.

[0010] The above control unit may also be configured to control the relay to be in the cut-off state under the condition that it is detected that the above load is removed from the above output terminal.

[0011] According to the battery module of the present disclosure, under the condition that the output resistance of the battery module is equal to or greater than the first threshold, it is determined that no load is connected to the output terminal of the battery module, and the relay is controlled to be in the cut-off state to electrically disconnect the power storage unit from the output terminal. Through this control, even if a short circuit occurs between the output terminals, the influence of the short circuit on the battery cells can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Hereinafter, the features, advantages, and technical and industrial significance of the embodiments of the present invention will be described with reference to the drawings, in which the same reference numerals denote the same elements, and

[0013] Figure 1 is a schematic configuration diagram of a battery module according to one embodiment of the present disclosure.

[0014] Figure 2 is a flowchart of the connection diagnosis control executed by the battery module.

[0015] Figure 3 is a diagram for explaining an example of the result of the connection diagnosis control. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] In the battery module of the present disclosure, when no load is connected to the output terminal of the battery module, such as in the scenario where the battery module is transported as a single unit, the battery cell stack (power storage unit) and the output terminal are kept in an electrically disconnected state. Thus, even if a short circuit occurs between the output terminals due to external factors, the influence on the battery cell stack can be reduced.

[0017] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0018] Embodiment

[0019] Configuration

[0020] Figure 1 is a schematic diagram for explaining the configuration of a battery module 10 according to one embodiment of the present disclosure. Figure 1 The battery module 10 illustrated in the figure is a battery such as a secondary battery that can supply power to a load 30. A load 30 is connected between the positive output terminal 21 and the negative output terminal 22. The battery module 10 is used, for example, by being assembled in a vehicle or the like.

[0021] The battery module 10 includes a power storage unit 11, an output relay 12, a constant current circuit 13, a monitoring unit 14, a control unit 15, a current detection unit 16, and a voltage detection unit 17. In Figure 1 the figure, the power lines for power transfer are represented by solid lines, and the signal lines through which detection values, control instructions, etc. flow are represented by dashed lines.

[0022] The power storage unit 11 is, for example, a secondary battery such as a lithium-ion battery that is configured to be rechargeable. The power storage unit 11 can be a stack structure formed by connecting a plurality of lithium-ion battery cells in series. The positive electrode of the power storage unit 11 is connected to the positive-side output terminal 21 via the output relay 12. The negative electrode of the power storage unit 11 is connected to the negative-side output terminal 22 through the current detection unit 16.

[0023] The output relay 12 is a component provided between the power storage unit 11 and the positive-side output terminal 21 and is used to switch the electrical connection state (conductivity / cutoff) between the power storage unit 11 and the positive-side output terminal 21. For the output relay 12, for example, a relay unit in which two field effect transistors (FET: Field Effect Transistor) are connected in series with the rectification direction of the body diode reversed can be used. The conduction state and the cutoff state of the output relay 12 are controlled by the control unit 15. In addition, the output relay 12 can also be provided between the power storage unit 11 and the negative-side output terminal 22.

[0024] The constant current circuit 13 is a circuit that can output a current of a constant value based on an instruction from the control unit 15. The constant current circuit 13 is connected in parallel with the output relay 12 and has the function of bypassing to connect the power storage unit 11 and the positive-side output terminal 21 when performing the connection diagnosis control described later. Among them, for the constant current circuit 13, a known circuit can be used.

[0025] The monitoring unit 14 is a component for monitoring the state of the power storage unit 11 and is, for example, a monitoring integrated circuit (IC: integrated circuit). The monitoring unit 14 can obtain information on the voltage (such as the voltage of each battery cell) of the power storage unit 11 and information on the current flowing from the current detection unit 16 to the power storage unit 11. The information obtained by the monitoring unit 14 is output to the control unit 15.

[0026] The control unit 15 is a component for controlling the output relay 12 and the constant current circuit 13 and is, for example, a microcomputer. The control unit 15 controls the operations of the output relay 12 and the constant current circuit 13 based on the information related to the state of the power storage unit 11 obtained from the monitoring unit 14 and the voltage between the positive-side output terminal 21 and the negative-side output terminal 22 obtained from the voltage detection unit 17.

[0027] The current detection unit 16 is configured to detect the current flowing out of the power storage unit 11 (outflow current) and the current flowing into the power storage unit 11 (inflow current), and is, for example, a current sensor.

[0028] The voltage detection unit 17 is configured to detect the voltage that appears between the positive output terminal 21 and the negative output terminal 22 (hereinafter referred to as "voltage between output terminals"), and is, for example, a voltage sensor.

[0029] Some or all of the above output relay 12, constant current circuit 13, monitoring unit 14, control unit 15, current detection unit 16, and voltage detection unit 17 operate by receiving power supply from the power storage unit 11.

[0030] Control

[0031] Further refer to Figure 2 and Figure 3 The control of the battery module 10 according to the present embodiment will be described. Figure 2 It is a flowchart for explaining the processing sequence of the connection diagnosis control executed by the control unit 15 of the battery module 10. Figure 3 It is for Figure 2 An example of the result of the connection diagnosis control is shown.

[0032] During the period when the output relay 12 is in the cut-off state (OFF), the connection diagnosis control shown in Figure 2 is implemented at a specified timing. In a state where no load 30 is connected between the positive output terminal 21 and the negative output terminal 22 of the battery module 10, the control unit 15 controls the output relay 12 to the cut-off state (OFF) and controls the constant current circuit 13 to be non-operational. As a state where no load 30 is connected between the positive output terminal 21 and the negative output terminal 22, a scenario where the battery module 10 is transported as a single unit can be exemplified. As the specified timing, a timing that arrives at a constant cycle can be exemplified.

[0033] In step S201, the control unit 15 operates the constant current circuit 13 to implement constant current control in which a test current flows from the power storage unit 11 toward the positive output terminal 21 for a constant time. The test current is a current with a constant value. The above constant value and constant time are set to appropriate values based on considerations such as the power storage capacity of the power storage unit 11, the capacitance component connected to the power supply target such as the load 30, etc., taking into account avoiding battery depletion, output response performance, etc. If the constant current control related to the constant current circuit 13 is implemented by the control unit 15, the process proceeds to step S202.

[0034] In step S202, the control unit 15 obtains the voltage between the output terminals of the battery module 10 from the voltage detection unit 17 and obtains the discharge current of the power storage unit 11 from the monitoring unit 14. If the control unit 15 has obtained the voltage between the output terminals and the discharge current, the process proceeds to step S203.

[0035] In step S203, the control unit 15 derives an impedance Z as the output resistance of the battery module 10 based on the voltage between the output terminals and the discharge current. The impedance Z can be derived using ordinary laws (such as Ohm's law). The impedance Z can be derived continuously during the constant current control by the constant current circuit 13, or can be derived at the moment when the constant current control ends after a constant time. If the control unit 15 derives the impedance Z, the process proceeds to step S204.

[0036] In step S204, the control unit 15 determines the value of the impedance Z of the battery module 10. This determination is made by comparing the impedance Z with a first threshold value a and a second threshold value b. The first threshold value a is set to a large resistance value that can be judged that no load 30 is connected between the positive output terminal 21 and the negative output terminal 22 of the battery module 10. The second threshold value b is a value smaller than the first threshold value a, and is set to a small resistance value that can be judged that a short circuit occurs between the positive output terminal 21 and the negative output terminal 22 of the battery module 10. For the determination of the value of the impedance Z, in the above step S203, it can be made at any time when the impedance Z is derived continuously, and when the impedance Z is derived at the moment after a constant time, it can be made at the end of the constant current control.

[0037] When the control unit 15 determines that the value of the impedance Z is equal to or greater than the first threshold value a (step S204, a ≤ Z), the process proceeds to step S205. In addition, when the control unit 15 determines that the value of the impedance Z is less than the second threshold value b (step S204, Z < b), the process proceeds to step S206. On the other hand, when the control unit 15 determines that the value of the impedance Z is less than the first threshold value a and is equal to or greater than the second threshold value b (step S204, b ≤ Z < a), the process proceeds to step S207.

[0038] In step S205, since the impedance Z of the battery module 10 is a high resistance value, the control unit 15 determines that the battery module 10 is in a state of "terminal open circuit" where no load 30 is connected between the positive output terminal 21 and the negative output terminal 22. In other words, it is determined that the battery module 10 is not assembled in a vehicle or the like. If the control unit 15 makes a terminal open circuit determination, the process proceeds to step S208.

[0039] In step S206, since the impedance Z of the battery module 10 is a low resistance value, the control unit 15 determines that the battery module 10 is in a "terminal short - circuit" state where the positive - side output terminal 21 and the negative - side output terminal 22 are short - circuited. If the control unit 15 makes a terminal short - circuit determination, the process proceeds to step S208.

[0040] In step S207, since the impedance Z of the battery module 10 is an intermediate resistance value, the control unit 15 determines that the battery module 10 is in a "terminal connection" state where a load 30 is connected between the positive - side output terminal 21 and the negative - side output terminal 22. In other words, the control unit 15 determines that the battery module 10 is assembled in a vehicle or the like. If the control unit 15 makes a terminal connection determination, the process proceeds to step S209.

[0041] In step S208, the control unit 15 controls the output relay 12 to the cut - off state (OFF). By this control, the power storage unit 11 and the positive - side output terminal 21 are electrically disconnected. If the control unit 15 controls the output relay 12 to the cut - off state (OFF), the process proceeds to step S201.

[0042] In step S209, the control unit 15 controls the output relay 12 to the conduction state (ON). By this control, the power storage unit 11 and the positive - side output terminal 21 are electrically connected, and power can be supplied from the battery module 10 to the load 30. If the control unit 15 controls the output relay 12 to the conduction state (ON), the connection diagnosis control ends.

[0043] In addition, when the battery module 10 is assembled in a vehicle or the like and the connection diagnosis control ends, if the control unit 15 can detect that the battery module 10 is removed from the vehicle or the like, the above - mentioned connection diagnosis control can be started again.

[0044] Figure 3 shows an image of terminal open - circuit determination, terminal short - circuit determination, and terminal connection determination based on the comparison of the impedance Z of the battery module 10 with the first threshold value a and the second threshold value b.

[0045] Function / Effect

[0046] As described above, in the battery module 10 according to one embodiment of the present disclosure, an output relay 12 and a constant current circuit 13 connected in parallel are provided between the power storage unit 11 and the positive-side output terminal 21, and connection diagnosis control of the output terminal using the test current related to the constant current circuit 13 is performed. If the result of the connection diagnosis control determines that a load 30 is connected between the positive-side output terminal 21 and the negative-side output terminal 22 of the battery module 10, the control unit 15 turns on the output relay 12. Through this control, power supply from the battery module 10 to the load 30 can be performed.

[0047] On the other hand, in the battery module 10 according to the present embodiment, if the result of the connection diagnosis control determines that a load 30 is not connected between the positive-side output terminal 21 and the negative-side output terminal 22 of the battery module 10, or determines that the positive-side output terminal 21 and the negative-side output terminal 22 of the battery module 10 are short-circuited, the control unit 15 cuts off the output relay 12. Through this control, even if a short circuit occurs between the output terminals of the battery module 10, the influence of the short circuit on the power storage unit 11 can be reduced.

[0048] The battery module of the present disclosure can be used in cases where it is desired to prevent the influence of a short circuit between output terminals from spreading to battery cells.

Claims

1. A battery module configured to supply electric power to a load connected to an output terminal, characterized in that: The battery module comprises: Power storage unit; a relay provided between the power storage unit and the output terminal and configured to switch an electrical conduction state and a disconnection state between the power storage unit and the output terminal; and a control unit configured to control the state of the relay, The control unit is configured to control the relay to be in an off state under the condition that the output resistance of the battery module is equal to or greater than a first threshold value.

2. The battery module according to claim 1, characterized in that: Also comprising a constant current circuit connected in parallel with the relay, The control unit is configured to periodically control a constant current to flow from the power storage unit to the output terminal via the constant current circuit while the relay is in the disconnected state, and derive the output resistance based on the outflow current of the power storage unit and the voltage of the output terminal during the control.

3. The battery module according to claim 1 or 2, characterized in that: The control unit is configured to control the relay to be in an off state under the condition that the output resistance is lower than a second threshold value that is lower than the first threshold value.

4. The battery module according to claim 3, characterized in that: The control unit is configured to control the relay to be in an on state under the condition that the output resistance is equal to or greater than the second threshold value and less than the first threshold value.

5. The battery module according to claim 4, characterized in that: The control unit is configured to control the relay to an off state under a condition that it is detected that the load is removed from the output terminal.

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