Protection device, power storage device, and method for protecting a power storage element

Abstract

To protect a power storage device by interrupting current to discontinuous excess current.SOLUTION: A protection device 120 of a power storage element 62 comprises a current interruption device 53 which interrupts current of the power storage element 62, and a control unit 130, and has a plurality of conditions with different current thresholds and cumulative thresholds, wherein the control unit 130 calculates a cumulative value N of time in which the current exceeds any of the current thresholds Is and executes current interruption processing S150 for interrupting the current when the calculated cumulative value N exceeds the cumulative threshold Ns associated with the current threshold Is.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a technique for protecting a power storage element from overcurrent.

Background Art

[0002] During assembly work or the like, the terminals of a power storage device may be short-circuited with a tool. The power storage device is provided with a current cutoff device such as a relay or an FET, and when a short circuit occurs, the current is cut off to protect the components constituting the power storage device. Patent Document 1 below describes that the current is cut off when the current continuously exceeds the current threshold for a time longer than a predetermined time.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When determining the cutoff of the current based on the duration during which a current equal to or higher than the current threshold continuously flows, there are cases where a discontinuous overcurrent in which the current temporarily falls below the current threshold cannot be cut off. If there is only one current cutoff condition, the current can only be cut off under one condition, so the protection of the power storage element may be insufficient.

[0005] An object of the present invention is to cut off the current to protect the power storage device against a discontinuous overcurrent.

Means for Solving the Problems

[0006] A protection device for a power storage element according to one aspect of the present invention includes a current interruption device that interrupts the current of the power storage element and a control unit, and has a plurality of conditions with different current thresholds and cumulative thresholds. The control unit calculates a cumulative value of the time when the current exceeds any of the current thresholds, and when the calculated cumulative value exceeds the cumulative threshold corresponding to the current threshold, executes a current interruption process for interrupting the current. A protection device for a power storage element according to another aspect of the present invention includes a current interruption device that interrupts the current of the power storage element, a control unit, and a communication unit, and has a plurality of conditions with different current thresholds and cumulative thresholds. The control unit calculates a cumulative value of the time when the current exceeds any of the current thresholds, and when the calculated cumulative value exceeds the cumulative threshold corresponding to the current threshold, causes the communication unit to transmit an alarm signal.

[0007] This technology can be applied to a method for protecting a power storage element, a protection program, and a recording medium on which the protection program is recorded.

Effects of the Invention

[0008] According to the above aspect, it is possible to protect the power storage element by interrupting the current against a discontinuous overcurrent.

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] The protection device for the energy storage element includes a current interruption device that interrupts the current of the energy storage element and a control unit, has a plurality of conditions with different current thresholds and cumulative thresholds, and the control unit calculates a cumulative value of the time when the current exceeds any of the current thresholds, and when the calculated cumulative value exceeds the cumulative threshold associated with the current threshold, executes a current interruption process for interrupting the current.

[0011] If the cumulative value of the time exceeding the current threshold exceeds the cumulative threshold, a current interruption process is executed, so that the energy storage element can be protected from discontinuous overcurrent. By preparing a plurality of conditions with different current thresholds and cumulative thresholds for the current interruption condition, the combination of the current threshold and the cumulative threshold at which the current can be interrupted increases compared to the case where there is only one condition. Therefore, the protection performance of the energy storage element against overcurrent can be improved compared to the case where there is only one condition. For each condition, the control unit may calculate the cumulative value of the time when the current exceeds the current threshold respectively, and when the calculated cumulative value exceeds the cumulative threshold associated with the current threshold under any one of the conditions, execute a current interruption process for interrupting the current. Among the plurality of conditions, if any one of the conditions exceeds the cumulative threshold, the current interruption process is executed, so that the energy storage element can be protected from overcurrents with different current values and continuous times.

[0012] The protection device for the energy storage element includes a current interruption device that interrupts the current of the energy storage element, a control unit, and a communication unit, and has a plurality of conditions with different current thresholds and cumulative thresholds. The control unit calculates a cumulative value of the time during which the current exceeds any of the current thresholds, and when the calculated cumulative value exceeds the cumulative threshold corresponding to the current threshold, causes the communication unit to transmit an alarm signal. For equipment powered by the energy storage device (for example, electronic and electrical equipment mounted on a vehicle), there are situations where it is not desirable for the current from the energy storage device to be interrupted and the power supply to fail (power fail). For the purpose of protecting the energy storage device, the purpose of protecting machinery that requires the power of the energy storage device such as a vehicle may be prioritized. In such a case, instead of executing the current interruption process when the interruption condition is satisfied, the fact that the interruption condition is satisfied is notified to equipment outside the energy storage device, that is, an alarm signal is transmitted. By doing so, the control unit can cooperate with equipment outside the energy storage device to determine whether to execute the current interruption process based on the purpose that should be prioritized in situations such as emergencies. Equipment outside the energy storage device can receive the alarm signal from the energy storage device and proceed with preparations for the current interruption process and other problem-solving processes.

[0013] The current interruption device is provided in a current path connecting the energy storage element and an external terminal, and the conditions may at least include a first condition for determining that a short circuit has occurred in the external terminal and a second condition for determining that a short circuit has occurred in a load connected to the external terminal. When there is a short circuit between the external terminals or a load short circuit, the current can be interrupted to protect the energy storage element.

[0014] The control unit counts the time during which the current continuously exceeds the current threshold as the cumulative value, and when the current drops from a state where it exceeds the current threshold, if the time of the drop is less than or equal to the reset time, the cumulative value may be held.

[0015] If the time during which the current is below the current threshold is less than or equal to the reset time, the cumulative value is retained. That is, the cumulative value is not reset, and thereafter, if the cumulative value exceeds the cumulative threshold, the current cutoff process is executed. Therefore, the power storage element can be protected from discontinuous overcurrents.

[0016] The control unit may calculate the cumulative value for each detection period, and if the cumulative value exceeds the cumulative threshold, execute the current cutoff process.

[0017] If the cumulative value exceeds the cumulative threshold within the detection time, the current cutoff process is executed. Therefore, the power storage element can be protected from discontinuous overcurrents.

[0018] <Embodiment 1> 1. Description of Battery 50

[0019] As shown in FIG. 1, the battery 50 includes a battery pack 60, a circuit board unit 65, and a housing 71.

[0020] The housing 71 includes a main body 73 made of a synthetic resin material and a lid 74. The main body 73 is in the shape of a bottomed cylinder. The main body 73 includes a bottom surface portion 75 and four side surface portions 76. An upper opening 77 is formed at the upper end portion by the four side surface portions 76.

[0021] The housing 71 houses the battery pack 60 and the circuit board unit 65. The battery pack 60 has twelve secondary batteries 62. The twelve secondary batteries 62 are connected in 3 parallel and 4 series. The circuit board unit 65 is disposed above the battery pack 60.

[0022] The lid 74 closes the upper opening 77 of the main body 73. An outer peripheral wall 78 is provided around the lid 74. The lid 74 has a protruding portion 79 that is substantially T-shaped in plan view. Of the front portion of the lid 74, the positive external terminal 51 is fixed to one corner, and the negative external terminal 52 is fixed to the other corner.

[0023] As shown in FIGS. 2 and 3, the secondary battery 62 has an electrode body 83 accommodated together with a non-aqueous electrolyte in a rectangular parallelepiped case 82. The secondary battery 62 is a lithium-ion secondary battery as an example. The case 82 has a case body 84 and a lid 85 that closes the upper opening thereof.

[0024] Although not shown in detail, the electrode body 83 has a separator made of a porous resin film disposed between a negative electrode element in which an active material is coated on a base material made of a copper foil and a positive electrode element in which an active material is coated on a base material made of an aluminum foil. All of these are in strip shape, and are wound flatly so as to be accommodated in the case body 84 with the negative electrode element and the positive electrode element being shifted in position to opposite sides in the width direction with respect to the separator.

[0025] A positive electrode terminal 87 is connected to the positive electrode element via a positive electrode current collector 86, and a negative electrode terminal 89 is connected to the negative electrode element via a negative electrode current collector 88. The positive electrode current collector 86 and the negative electrode current collector 88 each consist of a flat pedestal portion 90 and a leg portion 91 extending from the pedestal portion 90. A through hole is formed in the pedestal portion 90. The leg portion 91 is connected to the positive electrode element or the negative electrode element. The positive electrode terminal 87 and the negative electrode terminal 89 each consist of a terminal main body portion 92 and a shaft portion 93 protruding downward from the center portion of the lower surface thereof. Among them, the terminal main body portion 92 and the shaft portion 93 of the positive electrode terminal 87 are integrally formed of aluminum (a single material). In the negative electrode terminal 89, the terminal main body portion 92 is made of aluminum and the shaft portion 93 is made of copper, and these are assembled. The terminal main body portions 92 of the positive electrode terminal 87 and the negative electrode terminal 89 are disposed at both ends of the lid 85 via gaskets 94 made of an insulating material, and are exposed outward from the gaskets 94.

[0026] The lid 85 has a pressure release valve 95. As shown in FIG. 2, the pressure release valve 95 is located between the positive electrode terminal 87 and the negative electrode terminal 89. The pressure release valve 95 opens when the internal pressure of the case 82 exceeds a limit value, and reduces the internal pressure of the case 82.

[0027] As shown in FIG. 4, the battery 50 can be mounted on and used in the vehicle 10. The battery 50 may be for starting the engine 20 mounted on the vehicle 10. The vehicle 10 may be an automobile or a motorcycle.

[0028] FIG. 5 is a block diagram showing the electrical configuration of the battery 50. The battery 50 includes a battery pack 60, a current detection resistor 54, a current cutoff device 53, a voltage detection circuit 110, a management unit 130, and a temperature sensor 58 that detects the temperature of the battery pack 60.

[0029] The battery pack 60 is composed of a plurality of secondary batteries 62. There are 12 secondary batteries 62, which are connected in 3 parallel and 4 series. FIG. 5 represents the 3 secondary batteries 62 connected in parallel with one battery symbol. The secondary battery 62 is an example of a "power storage element". The battery 50 has a rated voltage of 12V. The battery 50 with a rated voltage of 12V tends to have a narrow interval between the external terminal 51 of the positive electrode and the external terminal 52 of the negative electrode. Compared with a larger power storage device, a short circuit (dead short) between the terminals due to a metal object such as a tool is likely to occur when assembling the battery to the vehicle.

[0030] The battery pack 60, the current cutoff device 53, and the current detection resistor 54 are connected in series via a power line 55P and a power line 55N. The power line 55P and the power line 55N are examples of current paths.

[0031] The power line 55P is a power line that connects the external terminal 51 of the positive electrode and the positive electrode of the battery pack 60. The power line 55N is a power line that connects the external terminal 52 of the negative electrode and the negative electrode of the battery pack 60.

[0032] The current cutoff device 53 is located on the positive electrode side of the battery pack 60 and is provided on the positive electrode side power line 55P. The current cutoff device 53 is a semiconductor switch such as an FET or a relay. By opening the current cutoff device 53, the current of the battery 50 can be cut off. The current cutoff device 53 is controlled to be closed during normal operation.

[0033] The current detection resistor 54 is located at the negative electrode of the battery pack 60 and is provided on the negative-side power line 55N. By detecting the voltage Vr across both ends of the current detection resistor 54, the current I of the battery pack 60 can be measured.

[0034] The voltage detection circuit 110 can detect the voltage V of each secondary battery 62 and the total voltage Vab of the battery pack 60.

[0035] The management unit 130 is mounted on the circuit board 100 and includes a CPU 131, a memory 133, and four counters 135. The management unit 130 performs monitoring processing of the battery 50 based on the outputs of the voltage detection circuit 1100, the current detection resistor 54, and the temperature sensor 58.

[0036] FIG. 6 is a flowchart of the monitoring process of the battery 50. The monitoring process of the battery 50 is constituted by S10 to S30. The monitoring process of the battery 50 is always executed at a predetermined measurement cycle while the management unit 130 is activated, regardless of whether it is mounted on or removed from the vehicle 10.

[0037] In S10, the management unit 130 measures the current I of the battery pack 60 based on the voltage Vr across both ends of the current detection resistor 54. In S20, the management unit 130 measures the voltage V of each secondary battery 62 based on the output of the voltage detection circuit 110, and in S30, the management unit 130 measures the temperature of the battery pack 60 based on the output of the temperature sensor 58.

[0038] The management unit 130 operates with the battery pack 60 as a power source, and constantly monitors the state of the battery 50 based on the data of the current I, voltage V, and temperature measured at a predetermined measurement cycle, as long as there is no abnormality such as the total voltage Vab of the battery pack 60 falling below the operating voltage.

[0039] When the management unit 130 detects an abnormality in the battery 50, it gives a command to the current cutoff device 53 to cut off the current I and performs a protection operation of the battery 50. The current cutoff device 53 and the management unit 130 are the protection device 120 of the battery 50. The management unit 130 is an example of a control unit.

[0040] 2. External Short Circuit and Battery Protection During assembly work or the like, if the two external terminals 51 and 52 are short-circuited by a metal object such as a tool 200, an overcurrent will flow through the assembled battery 60. When an overcurrent flows, the assembled battery 60 will generate abnormal heat. The value of the overcurrent during discharge due to an external short circuit is extremely large compared to the current value in the case of charging abnormality. However, during engine startup or the like, a very large current value is measured while the discharge is normal. Therefore, it is not easy to determine whether an abnormality such as an external short circuit has occurred or the energy storage device is operating normally only from the current value during discharge. A dead short caused by a tool 200 or the like may occur intermittently, such as when the tool 200 instantaneously separates from the external terminals 51 and 52 and then contacts again. Even if the dead short is instantaneously released, the state of the battery 50 does not recover immediately, and damage remains in the battery 50, such as a significant decrease in the state of charge (SOC).

[0041] Figure 7 is a flowchart of the protection process for the battery 50. The protection process for the battery 50 is composed of S10 to S180. The protection process for the battery 50 is always executed during the startup of the management unit 130, regardless of whether it is mounted on the vehicle 10 or not.

[0042] In S100, the management unit 130 compares the current I measured in the monitoring process with the current threshold Is. The comparison process in S100 is executed every time the current measurement is performed in the monitoring process if the current I is less than or equal to the current threshold Is (S100: NO). The current threshold Is is a threshold for determining whether the current I is an overcurrent or not.

[0043] In the case of an overcurrent (S100: YES), the process proceeds to S110. When the process proceeds to S110, the management unit 130 starts counting by means of a counter 135. The counter 135 is for measuring the cumulative time during which the overcurrent is flowing.

[0044] After starting the count, the process proceeds to S120. When the process proceeds to S120, the management unit 130 compares the current I measured in the next measurement cycle of the monitoring process with the current threshold Is to determine whether the overcurrent continues.

[0045] If an overcurrent continues (S120: YES), the process proceeds to S130. When the process proceeds to S130, the management unit 130 increments the count value N of the counter 135 by "1".

[0046] After that, in S140, the management unit 130 compares the count value N with the cumulative threshold value Ns. If the count value N is less than the cumulative threshold value Ns (S140: NO), the process returns to S120. The cumulative threshold value Ns is a threshold value for determining the accumulation of overcurrent.

[0047] Thereafter, if the overcurrent continues to flow, the count value N is incremented by "1" for each measurement period of the monitoring process. The count value N is the cumulative value of the time during which the current I exceeds the current threshold value Is.

[0048] When the count value N reaches the cumulative threshold value Ns, a YES determination is made in the determination process of S140, and the process proceeds to S150. When the process proceeds to S150, the management unit 130 gives a command to the current cutoff device 53 to cut off the overcurrent (current cutoff process).

[0049] If the overcurrent does not continue, that is, if the current I is below the current threshold value Is (S120: NO), the process proceeds to S160.

[0050] When the process proceeds to S160, the management unit 130 measures the time during which the current I is below the current threshold value Is, and compares the measured time with the reset time TR.

[0051] If the time during which the current is below the current threshold value Is is shorter than the reset time TR, the process proceeds to S170. When the process proceeds to S170, the management unit 130 holds the count value N.

[0052] Thereafter, when the process proceeds to S140 and an overcurrent is detected, the management unit 130 resumes counting by the counter 135, and the count value N is added from the held value.

[0053] On the other hand, when the time during which the current is below the current threshold Is is longer than the reset time TR, the process proceeds to S180. When the process proceeds to S180, the management unit 130 resets the count value N. As a result, the count value N returns to zero.

[0054] FIG. 8 is a diagram showing the waveform of the overcurrent and the transition of the count value N. The waveform of the overcurrent is a continuous waveform that always exceeds the current threshold Is. The count value N is cumulatively added and increases in value after the time t1 when the overcurrent starts to flow, and reaches the cumulative threshold value Ns at the time t2.

[0055] When the count value N reaches the cumulative threshold value Ns at the time t2, the current cutoff process (S150) by the management unit 130 is executed, and the overcurrent is cut off. By cutting off the overcurrent, the battery 50 can be protected.

[0056] FIG. 9 is a diagram showing the current waveform of the overcurrent and the transition of the count value N. The waveform of the overcurrent is a discontinuous pulse-like waveform, and in the periods t2 to t3 and t4 to t5, the current I is below the current threshold Is. Period X 23 、Period X 45 is shorter than the reset time TR.

[0057] During the period from the time t1 when the overcurrent starts to flow to the time t2, the current I exceeds the current threshold Is, and the count value N is added each time S130 is executed, and increases with the passage of time.

[0058] During the period from time t2 to time t3, Period X 23 although the current I is below the current threshold Is, since it is shorter than the reset time TR, the count value N is not reset and is held.

[0059] Between time t3 and time t4, since the current I exceeds the current threshold Is, the count value N is added each time S130 is executed and increases from the held value.

[0060] During the period from time t4 to time t5, Period X 45Since the current I is below the current threshold Is but shorter than the reset time TR, the count value N is not reset and is retained.

[0061] After time t6, since the current I exceeds the current threshold Is, the count value N is incremented each time S130 is executed and increases from the retained value. Then, at time t6, the count value N reaches the cumulative threshold Ns.

[0062] When the count value N reaches the cumulative threshold Ns at time t6, the current cutoff process (S150) by the management unit 130 is executed, and the overcurrent is cut off.

[0063] Even when the current I is below the current threshold Is, if it is within the reset time TR, the count value N is not reset and is retained. Therefore, even for a discontinuous overcurrent where there is a period during which the current I temporarily drops, it is possible to suppress the reset of the count value N each time the current I is below the current threshold Is, and the overcurrent can be cut off when the count value N reaches the cumulative threshold Ns.

[0064] FIG. 10 is a diagram showing the current cutoff conditions. The current cutoff conditions consist of the items of the current threshold Is, the cumulative threshold Ns, and the reset time TR. There are four current cutoff conditions from 1 to 4, and the current threshold Is and the cumulative threshold Ns are different respectively. The reset time TR is common to all conditions 1 to 4.

[0065] The current cutoff condition 1 is a condition for determining that a short circuit has occurred between the two external terminals 51 and 52 (or a condition for cutting off an external short circuit), and the current cutoff conditions 2 to 4 are conditions for determining that a short circuit has occurred in the load connected to the external terminals 51 and 52 (or a condition for cutting off a load short circuit). For the current cutoff condition 1, the current threshold Is is 1450 A and the cumulative threshold Ns is 10 msec. The current cutoff condition 1 has a larger current threshold Is and a shorter cumulative threshold Ns compared to the current cutoff conditions 2 to 4.

[0066] Since the magnitudes of the short-circuit currents differ depending on the manner of short-circuit of the load for current interruption conditions 2 to 4, the current threshold value Is is set in three levels, and the smaller the current threshold value Is, the longer the cumulative threshold value Ns.

[0067] The management unit 130 performs the protection processes (S100 to S150) shown in FIG. 7 simultaneously and in parallel using four counters 135 for current interruption conditions 1 to 4, and when the count value N reaches the cumulative threshold value Ns in any of current interruption conditions 1 to 4, the current interruption process of S150 is executed to interrupt the overcurrent.

[0068] By preparing a plurality of current interruption conditions, the combination of the current threshold value Is and the cumulative threshold value Ns increases compared to the case of a single condition. Therefore, the current I can be interrupted in the event of either a short circuit of the external terminal or a load short circuit.

[0069] <Embodiment 2> FIG. 11 is a flowchart of the protection process of the battery 50. The protection process of the battery 50 is always executed while the management unit 130 is activated, regardless of whether it is mounted on or removed from the vehicle 10. The management unit 130 compares the measured current I with the current threshold value Is in the monitoring process (S200). The current threshold value Is is a threshold value for determining whether the current I is an overcurrent.

[0070] When there is an overcurrent (S200: YES), the management unit 130 starts recording the current I (S210). The current I is recorded in the memory 133.

[0071] After starting the recording, the management unit 130 calculates the cumulative time Ta during which the overcurrent has flowed in the detection period W (S220). The cumulative time Ta is the cumulative value of the time during which the current I has exceeded the current threshold value Is within the detection period W.

[0072] As shown in FIG. 12, for example, when there are three periods during which the current I exceeds the current threshold value Is in the detection period W, the total time (Ta1 + Ta2 + Ta3) of the three periods is the cumulative time Ta.

[0073] After that, the management unit 130 determines whether the cumulative time Ta is zero (S230). If the cumulative time Ta is not zero, it determines whether it is greater than or equal to the cumulative threshold Ts (S240).

[0074] When the cumulative time Ta is zero (S230: YES), the management unit 130 ends the recording of the current I (S260). Also, when the cumulative time Ta is greater than or equal to the cumulative threshold Ts (S240: YES), a current cutoff process is performed to cut off the current I by the current cutoff device 53 (S250).

[0075] When the cumulative time Ta is less than the cumulative threshold Ts (S240: NO), it returns to S220. For the next detection period W, the management unit 130 executes the processes of S220 to S240.

[0076] FIG. 13 is a diagram showing the current waveform of the overcurrent and the transition of the cumulative time Ta. The waveform of the overcurrent is a discontinuous pulse-like waveform. At t2 to t3 and t4 to t5, the current I is below the current threshold Is.

[0077] The recording of the current I starts from the time t1 when the current I exceeds the current threshold Is. The management unit 130 calculates the cumulative time Ta for the detection period W1 and compares it with the current cutoff value Ts. If the cumulative time Ta does not exceed the cumulative threshold Ts, for the next detection period W2, the cumulative time Ta is calculated and compared with the cumulative threshold Ts.

[0078] The cumulative time Ta does not reach the cumulative threshold Ts until the detection periods W1 to W8, and reaches the cumulative threshold Ts in the detection period W9. Therefore, at the time t6 when the detection period W9 elapses, the current cutoff process (S250) by the management unit 130 is executed, and the overcurrent is cut off.

[0079] The detection periods W1 to W9 are each shifted by a period Y and are continuous while overlapping each other. By doing so, the detection interval of the cumulative time Ta can be shortened, so that the current cutoff process (S250) can be executed promptly when a short circuit occurs.

[0080] FIG. 14 is a diagram showing current interruption conditions. The current interruption conditions consist of the items of a current threshold value Is, an integrated threshold value Ts, and a detection time W. There are four types, 1 to 4, of current interruption conditions, and the current threshold value Is, the integrated threshold value Ts, and the detection period W are different from each other.

[0081] The current interruption condition 1 is a first condition for interrupting a short circuit between two external terminals 51 and 52. The current interruption conditions 2 to 4 are second conditions for interrupting a short circuit of a load connected to the external terminals 51 and 52.

[0082] The management unit 130 simultaneously and in parallel performs the protection processes (S200 to S260) shown in FIG. 11 for the current interruption conditions 1 to 4. When the cumulative time Ta reaches the integrated threshold value Ts under any of the current interruption conditions, the current interruption process of S250 is executed to interrupt the overcurrent.

[0083] <Other Embodiments> The present invention is not limited to the embodiments described above and by the drawings. For example, the following embodiments are also included in the technical scope of the present invention.

[0084] (1) In the above embodiment, a secondary battery 62 was exemplified as an example of the power storage element. The power storage element is not limited to the secondary battery 62 and may be a capacitor. The secondary battery 62 is not limited to a lithium ion secondary battery and may be other non-aqueous electrolyte secondary batteries. Also, a lead storage battery or the like can be used. The power storage element is not limited to the case where a plurality are connected in series and parallel, and may be a series connection or a single cell configuration.

[0085] (2) In the above embodiment, the battery 50 was for a vehicle. The use application of the battery 50 is not limited to a specific application. The battery 50 may be used for various applications such as for a moving body (for a vehicle, ship, AGV, etc.) or for industrial use (for an uninterruptible power supply system or a power storage device for a solar power generation system).

[0086] (3) In the above embodiment, the management unit 130 is provided inside the battery 50. The battery 50 only needs to include at least instruments such as the current detection resistor 54 and the voltage detection circuit 110, and the current cutoff device 53, and the management unit 130 may be outside the device of the battery 50.

[0087] (4) In the above embodiment, the current cutoff device 53 is arranged on the positive power line 55P, and the current detection resistor 54 is arranged on the negative power line 55N. Conversely, the current detection resistor 53 may be arranged on the positive power line 55P, and the current detection resistor 54 may be arranged on the negative power line 55N.

[0088] (5) In the above embodiment, for the current cutoff conditions 1 to 4, the protection processes (S200 to S260) are performed simultaneously and in parallel. When the cumulative time Ta reaches the cumulative threshold Ts under any of the current cutoff conditions, the current cutoff process is executed to cut off the overcurrent. In addition to this, among the four current cutoff conditions 1 to 4, the protection process (S200 to S260) may be performed for any one of the current cutoff conditions, and when the count value N reaches the cumulative threshold Ns, the current cutoff process may be executed to cut off the overcurrent. For example, when it is predicted that an external short circuit is likely to occur, the protection process (S200 to S260) may be executed only for the current cutoff condition 1, and when the count value N reaches the cumulative threshold Ns, the current cutoff process may be executed to cut off the overcurrent. When selecting the current cutoff condition, it is preferable to select the current cutoff condition corresponding to the short circuit with a high occurrence probability. The selection of the current cutoff condition is not limited to one, and two may be used. That is, at least one or more conditions may be selected. The management unit 130 may calculate the cumulative value of the time when the current I exceeds any of the current thresholds Is, and when the calculated cumulative value exceeds the cumulative threshold corresponding to the current threshold Is, the current cutoff process may be executed.

[0089] (6) In the above-described embodiment, the control unit calculates the cumulative value of the time during which the current exceeds any of the current thresholds, and when the calculated cumulative value exceeds the cumulative threshold associated with the current threshold, executes a current cutoff process to cut off the current. Alternatively, the control unit may calculate the cumulative value of the time during which the current exceeds any of the current thresholds, and when the calculated cumulative value exceeds the cumulative threshold associated with the current threshold, cause the communication unit to transmit an alarm signal. As shown in FIG. 15, the protection device 120 may include a communication unit 137 controlled by a management unit 130. The housing 71 may include, for example, a communication connector 138 on its lid 74. The communication unit 137 may be communicably connected via the communication connector 138 to a controller outside the battery, such as an ECU (Electronic Control Unit) of a vehicle. Instead of executing the current cutoff process when the cutoff condition is satisfied, the management unit 130 notifies the ECU outside the battery via the communication unit 137 that the cutoff condition is satisfied, that is, transmits an alarm signal, and determines whether to execute the current cutoff process in cooperation with the ECU. Upon receiving the alarm signal, the ECU can proceed with preparations for the current cutoff process, processes for avoiding the current cutoff process, such as stopping the operation of some loads, and other problem-solving processes.

[0090] (7) The present technology can be applied to a protection program for a power storage element. The protection estimation program for a power storage element is a program that causes a computer to execute the following processes. The current cutoff condition for cutting off the current of the power storage element has a plurality of conditions with different current thresholds and cumulative thresholds. The control unit calculates the cumulative value of the time during which the current exceeds any of the current thresholds, and when the calculated cumulative value exceeds the cumulative threshold associated with the current threshold, is a program that causes a current cutoff process for cutting off the current to be executed. The present technology can be applied to a recording medium on which a protection program for a power storage element is recorded. The computer is, as an example, the management unit 130. The power storage element is, as an example, the secondary battery 62. The protection program can be recorded on a recording medium such as a ROM.

Explanation of Reference Numerals

[0091] 10 vehicles 50 batteries (power storage devices) 53 current cut-off device 54 current detection resistor 60 battery packs 62 secondary battery (power storage element) 120 protection device 130 management unit (control unit) 131 CPU 133 memory 135 counter N count value (accumulated value) Ns accumulated threshold value Is current threshold value Ta accumulated time (accumulated value) Ts accumulated threshold value

Claims

1. A protection device for a storage element, comprising: A current interruption device that interrupts the current of the storage element; A control unit, the control unit calculates an accumulated value of a time during which the current exceeds a current threshold, and when the calculated accumulated value exceeds an accumulation threshold corresponding to the current threshold, executes a current interruption process to interrupt the current; The control unit counts only the accumulated time during which an overcurrent in which the current continuously exceeds the current threshold flows as the accumulated value, and when the current falls below the current threshold from a state exceeding the current threshold, does not reset the accumulated value if the time during which the current fell below the current threshold is equal to or shorter than a reset time.

2. A protection device for a storage element, comprising: A current interruption device that interrupts the current of the storage element; A control unit; A communication unit, the control unit calculates a cumulative value of a time during which the current exceeds a current threshold, and when the calculated cumulative value exceeds a cumulative threshold corresponding to the current threshold, causes the communication unit to transmit a warning signal; The control unit counts only the accumulated time during which an overcurrent in which the current continuously exceeds the current threshold flows as the accumulated value, and when the current falls below the current threshold from a state exceeding the current threshold, does not reset the accumulated value if the time during which the current fell below the current threshold is equal to or shorter than a reset time.

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

4. The power storage device according to claim 3, A storage device rated at 12V.

5. A method for protecting an energy storage element, comprising: a control unit that calculates an accumulated value of a time during which the current exceeds a current threshold, and when the calculated accumulated value exceeds an accumulated threshold corresponding to the current threshold, executes a current interruption process to interrupt the current; the control unit counts only the accumulated time during which an overcurrent in which the current continues to exceed the current threshold flows as the accumulated value, and when the current falls below the current threshold from a state exceeding the current threshold, does not reset the accumulated value if the time during which the current fell below the current threshold is equal to or shorter than a reset time.

6. A method for protecting an energy storage element, comprising: a control unit that calculates a cumulative value of a time during which the current exceeds a current threshold, and when the calculated cumulative value exceeds a cumulative threshold corresponding to the current threshold, the control unit causes a communication unit to transmit an alarm signal; the control unit counts only the accumulated time during which an overcurrent in which the current continues to exceed the current threshold flows as the accumulated value, and when the current falls below the current threshold from a state exceeding the current threshold, does not reset the accumulated value if the time during which the current fell below the current threshold is equal to or shorter than a reset time.

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