Device for measuring deterioration of onboard electric power storage unit

Abstract

A device (20) for measuring deterioration of an onboard electric power storage unit comprises a deterioration measurement unit (31), and a time calculation unit (32) that calculates a cumulative elapsed time (T3) after a previous measurement process is performed. The deterioration measurement unit (31) performs the measurement process on the condition that the cumulative elapsed time (T3) exceeds a determined time. The time calculation unit (32) includes a timer (33) and, in a state in which the timer (33) is operating, measures a first elapsed time (T1) using the timer (33). In a state in which the timer (33) is stopped, a charging operation and a discharging operation performed by a charging / discharging unit (for example, the charging unit (22) and the discharging unit (23)) are stopped. The time calculation unit (32) estimates a second elapsed time (T2), during which the timer (33) is stopped, on the basis of a drop in voltage of the electric power storage unit (21) in the state in which the timer (33) is stopped, and calculates the cumulative elapsed time (T3) by adding together the first elapsed time (T1) and the second elapsed time (T2).

Description

Deterioration measurement device for in-vehicle power storage units

[0001] The present disclosure relates to a deterioration measuring device for an in-vehicle power storage unit.

[0002] Conventionally, there are known techniques for measuring the internal resistance of a vehicle battery. For example, Patent Document 1 discloses a power storage system. This power storage system includes a battery, a voltage sensor that detects the voltage value of the battery, a current sensor that detects the current value of the battery, and a control device. The control device derives an estimate of the current internal resistance of the battery based on the voltage value detected by the voltage sensor and the current value detected by the current sensor.

[0003] Japanese Patent Application Laid-Open No. 2023-102052

[0004] When measuring the internal resistance every time a predetermined time has elapsed, it is necessary to determine whether the predetermined time has elapsed. In order to measure the predetermined time using a timer, the timer must be kept running at all times. This raises concerns that the timer may consume a large amount of power.

[0005] An object of the present disclosure is to provide a technique that can calculate the elapsed time since the previous measurement process while suppressing the power consumption by a timer.

[0006] A degradation measurement device for an in-vehicle power storage unit according to the present disclosure is included in an in-vehicle system having a charge / discharge unit that performs a charging operation to charge the power storage unit from a power supply unit and a discharging operation to discharge the power storage unit to a load, and measures a degree of degradation of the power storage unit, and includes: a degradation measurement unit that performs a measurement process to measure the degree of degradation of the power storage unit; and a time calculation unit that calculates a cumulative elapsed time since the previous measurement process was performed, wherein the degradation measurement unit performs the measurement process on the condition that the cumulative elapsed time exceeds a judgment time, the time calculation unit includes a timer that measures a first elapsed time while the timer is operating, and measures a first elapsed time using the timer when the timer is stopped, and the charging operation and the discharging operation by the charging / discharging unit are stopped when the timer is stopped, and the time calculation unit estimates a second elapsed time while the timer is stopped based on a drop in voltage of the power storage unit when the timer is stopped, and calculates the cumulative elapsed time by adding together the first elapsed time and the second elapsed time.

[0007] The technology according to the present disclosure can calculate the elapsed time since the previous measurement process while suppressing the power consumption by the timer.

[0008] Fig. 1 is a schematic diagram illustrating an in-vehicle system including a degradation measurement device for an in-vehicle power storage unit according to a first embodiment. Fig. 2 is an explanatory diagram illustrating a voltage drop in a power storage unit. Fig. 3 is a flowchart of processing performed by a microcomputer in the degradation measurement device for an in-vehicle power storage unit. Fig. 4 is a schematic diagram illustrating an in-vehicle system including a degradation measurement device for an in-vehicle power storage unit according to a second embodiment.

[0009] [Description of Embodiments of the Present Disclosure] In the following, embodiments according to the present disclosure are listed and exemplified.

[0010] [1] A degradation measurement device for an in-vehicle power storage unit, which is included in an in-vehicle system having a charge / discharge unit that performs a charging operation to charge the power storage unit from a power supply unit and a discharging operation to discharge the power storage unit to a load, and measures a degree of degradation of the power storage unit, the degradation measurement device having: a degradation measurement unit that performs a measurement process to measure a degree of degradation of the power storage unit; and a time calculation unit that calculates a cumulative elapsed time since the measurement process was last performed, wherein the degradation measurement unit performs the measurement process on a condition that the cumulative elapsed time exceeds a judgment time, the time calculation unit includes a timer that measures a first elapsed time while the timer is operating, and when the timer is stopped, the charging operation and the discharging operation by the charge / discharge unit are stopped, and the time calculation unit estimates a second elapsed time while the timer is stopped based on a drop in voltage of the power storage unit when the timer is stopped, and calculates the cumulative elapsed time by adding together the first elapsed time and the second elapsed time.

[0011] When the timer is stopped, the charging and discharging operations of the charging / discharging unit are stopped, causing the voltage of the power storage unit to decrease due to self-discharge. A certain correlation exists between the voltage decrease of the power storage unit and the elapsed time. By utilizing this correlation, the degradation measurement device for an in-vehicle power storage unit can estimate the second elapsed time during which the timer was stopped based on the voltage decrease of the power storage unit, even when the timer was stopped. Therefore, the degradation measurement device for an in-vehicle power storage unit can calculate the cumulative elapsed time by adding up the first elapsed time and the second elapsed time while suppressing power consumption by the timer.

[0012] [2] The degradation measuring device for an in-vehicle power storage unit according to [1], further comprising a resistance unit provided in parallel with the power storage unit, wherein the power storage unit is discharged to the resistance unit when the charging operation and the discharging operation by the charge / discharge unit are stopped.

[0013] In the degradation measurement device for an in-vehicle power storage unit, when the charging and discharging operations of the charge / discharge unit are stopped, the power storage unit discharges to the resistor unit, which tends to increase the discharge current, making it less likely that a measurement error will occur during the measurement process.

[0014] [3] The deterioration measuring device for an in-vehicle power storage unit according to [2], further comprising a switch unit provided in parallel with the power storage unit and in series with the resistance unit.

[0015] The degradation measuring device for an in-vehicle power storage unit can prevent discharge from the power storage unit to the resistance unit by switching the switch unit to the off state.

[0016] [4] The deterioration measuring device for an in-vehicle power storage unit according to [3], further comprising a switching unit that switches the switch unit to an off state when the voltage of the power storage unit falls below a predetermined voltage.

[0017] The degradation measuring device for an in-vehicle power storage unit can prevent a voltage drop in the power storage unit by stopping discharge from the power storage unit to the resistance unit when the voltage of the power storage unit falls below a predetermined voltage.

[0018] [5] The degradation measuring device for an on-board power storage unit described in any one of [1] to [4], wherein the time calculation unit pre-stores a table showing the correspondence between the second elapsed time and the voltage drop, and estimates the second elapsed time based on the table and the voltage drop.

[0019] The deterioration measuring device for an in-vehicle power storage unit can simplify the configuration for estimating the second elapsed time by using the table.

[0020] [6] The degradation measurement device for an in-vehicle power storage unit described in [5], wherein the time calculation unit stores the table prepared for each range of the degradation level, and estimates the second elapsed time based on the table corresponding to the degradation level measured by the most recent measurement process and the drop in voltage.

[0021] The relationship between the voltage drop of the power storage unit and the second elapsed time may vary depending on the degree of deterioration of the power storage unit. The degradation measuring device for an in-vehicle power storage unit prepares a table for each range of the degree of deterioration and uses the table corresponding to the degree of deterioration to more accurately estimate the second elapsed time.

[0022] [7] The degradation measuring device for an in-vehicle power storage unit described in any one of [1] to [6], wherein the timer is activated when a start switch of the vehicle is on and is stopped when the start switch is off, and the charging operation and the discharging operation by the charging / discharging unit are stopped when the start switch is off.

[0023] The degradation measuring device for an in-vehicle power storage unit can reduce power consumption by stopping the timer and stopping the charging and discharging operations by the charging / discharging unit when the vehicle start switch is in the off state.

[0024] [Details of the embodiments of the present disclosure] 1. First embodiment An in-vehicle system 1 according to the first embodiment is a system mounted on a vehicle. As shown in FIG. 1 , the in-vehicle system 1 includes a power supply unit 10, a load 11, a power path 12, and a diode 13.

[0025] The power supply unit 10 is, for example, a battery. The power path 12 is an electrical path that supplies power from the power supply unit 10 to the load 11. The diode 13 is provided on the power path 12. The diode 13 allows current to flow from the power supply unit 10 side to the load 11 side and prevents current from flowing from the load 11 side to the power supply unit 10 side.

[0026] The in-vehicle system 1 includes a power storage unit 21, a charging unit 22, a discharging unit 23, a voltage detection unit 24, a temperature detection unit 25, and a microcomputer 26. The charging unit 22 and the discharging unit 23 correspond to examples of a charging / discharging unit.

[0027] The power storage unit 21 includes, for example, one or more capacitors. The power storage unit 21 is, for example, a lithium ion capacitor. The power storage unit 21 functions as a backup power supply.

[0028] Charging unit 22 is provided between power supply unit 10 and power storage unit 21, and performs a charging operation of charging power from power supply unit 10 to power storage unit 21. In the example shown in Fig. 1, charging unit 22 is a switch. The switch may be a semiconductor switch or a mechanical switch. When the switch is in an on state, charging unit 22 is in a state where it performs a charging operation, and when the switch is in an off state, charging unit 22 is in a state where it stops the charging operation.

[0029] Discharge unit 23 is provided between power storage unit 21 and load 11, and performs a discharging operation to discharge power from power storage unit 21 to load 11. In the example shown in Fig. 1, discharge unit 23 is a switch. The switch may be a semiconductor switch or a mechanical switch. Discharge unit 23 is in a state where it performs a discharging operation when the switch is in an on state, and is in a state where it stops discharging when the switch is in an off state.

[0030] The voltage detection unit 24 is configured by, for example, a known voltage detection circuit. The voltage detection unit 24 detects the voltage of the power storage unit 21 at a position closer to the power storage unit 21 than the charging unit 22 and the discharging unit 23. Information indicating the value detected by the voltage detection unit 24 is input to the microcomputer 26.

[0031] The temperature detection unit 25 is configured by, for example, a known temperature sensor. The temperature detection unit 25 detects the temperature of the power storage unit 21 or the temperature around the power storage unit 21. Information indicating the value detected by the temperature detection unit 25 is input to the microcomputer 26.

[0032] The microcomputer 26 controls the charging unit 22 and the discharging unit 23. The microcomputer 26 includes a deterioration measuring unit 31 and a time calculating unit 32.

[0033] The deterioration measurement unit 31 performs a measurement process to measure the deterioration level of the power storage unit 21. The deterioration level of the power storage unit 21 may be, for example, the internal resistance of the power storage unit 21 or the SOH (State of Health) of the power storage unit 21. When the deterioration level of the power storage unit 21 is the internal resistance of the power storage unit 21, the measurement process involves, for example, performing a charging or discharging operation with a constant current and calculating the internal resistance by dividing the voltage change of the power storage unit 21 by the current value. When measuring the voltage of the power storage unit 21, the deterioration measurement unit 31 may measure the voltage of the power storage unit 21 by correcting the detection value of the voltage detection unit 24 with the detection value of the temperature detection unit 25. The SOH is, for example, the rate of increase in the internal resistance of the power storage unit 21 and is calculated by the following formula (1): SOH=R / R0 Formula (1) where R is the current internal resistance of the power storage unit 21 and R0 is the internal resistance of the power storage unit 21 at the start of use. R0 may be stored in advance in the microcomputer 26, or may be a value measured at the start of use. The deterioration measurement unit 31 performs the measurement process on the condition that the cumulative elapsed time T3 since the previous measurement process has been performed exceeds the determination time.

[0034] Time calculation unit 32 calculates cumulative elapsed time T3. Time calculation unit 32 includes timer 33. When timer 33 is operating, time calculation unit 32 measures first elapsed time T1 using timer 33. When timer 33 is stopped, the charging operation by charging unit 22 and the discharging operation by discharging unit 23 are stopped. Time calculation unit 32 estimates second elapsed time T2 while timer 33 is stopped based on the voltage drop of power storage unit 21 while timer 33 is stopped.

[0035] The time calculation unit 32 pre-stores a table showing the correspondence relationship between the second elapsed time T2 and the voltage drop. In this table, a larger second elapsed time T2 corresponds to a larger voltage drop. The time calculation unit 32 estimates the second elapsed time T2 based on the table and the voltage drop. The time calculation unit 32 stores a table prepared for each range of the deterioration level. The larger the deterioration level, the larger the voltage drop corresponding to the same second elapsed time T2. The time calculation unit 32 estimates the second elapsed time T2 based on the table corresponding to the deterioration level measured in the most recent measurement process and the voltage drop. The time calculation unit 32 calculates a cumulative elapsed time T3 by adding up the first elapsed time T1 and the second elapsed time T2.

[0036] The in-vehicle system 1 includes a degradation measurement device 20 for an in-vehicle power storage unit (hereinafter also referred to as the degradation measurement device 20). The degradation measurement device 20 has the above-mentioned power storage unit 21, a charging unit 22, a discharging unit 23, a voltage detection unit 24, a temperature detection unit 25, and a microcomputer 26.

[0037] The microcomputer 26 switches between an ON state and an OFF state. The microcomputer 26 is in the ON state when drive power is supplied, and is in the OFF state when drive power is not supplied. When in the ON state, the microcomputer 26 transitions between an activated state and a sleep state, which consumes less power than the activated state. The microcomputer 26 transitions to the activated state when an activation condition is met. The microcomputer 26 transitions to the sleep state when a sleep condition is met. In this embodiment, the activation condition is that the start switch of the vehicle is switched to the ON state. In this embodiment, the sleep condition is that the start switch of the vehicle is switched to the OFF state. The start switch is a switch for switching the vehicle between a started state and a parked state, and is, for example, an ignition switch or a power switch.

[0038] The microcomputer 26 is always in an ON state, regardless of whether the vehicle's start switch is in an ON state or an OFF state. A start signal indicating the ON / OFF state of the start switch is input to the microcomputer 26 from an external device (e.g., an ECU). The microcomputer 26 determines whether the vehicle's start switch is in an ON state or an OFF state based on the start signal. When the microcomputer 26 determines that the start switch has been switched ON, it determines that the start condition has been met and transitions to the start state. When the microcomputer 26 determines that the start switch has been switched OFF, it determines that the sleep condition has been met and transitions to the sleep state.

[0039] The microcomputer 26 activates the timer 33 when in the activated state and stops the timer 33 when in the sleep state. That is, the timer 33 is activated when the start switch is on and is stopped when the start switch is off.

[0040] The microcomputer 26 causes the charging unit 22 to perform a charging operation when a charging condition is satisfied in the activated state. The microcomputer 26 causes the discharging unit 23 to perform a discharging operation when a discharging condition is satisfied in the activated state. The discharging condition is, for example, when the power supply from the power supply unit 10 to the load 11 is cut off or when the power supply from the power supply unit 10 to the load 11 is insufficient. The microcomputer 26 stops the charging operation by the charging unit 22 and the discharging operation by the discharging unit 23 in the sleep state. In other words, when the start switch is in the off state, the charging operation by the charging unit 22 and the discharging operation by the discharging unit 23 are stopped.

[0041] 2 , when the start switch is in the ON state, the microcomputer 26 causes the charging unit 22 to perform a charging operation and stops the discharging unit 23. Thereafter, when the start switch is switched to the OFF state at timing TM1, the microcomputer 26 measures the voltage V2 of the power storage unit 21 and then stops the charging unit 22. This causes the power storage unit 21 to self-discharge. When the start switch is switched to the ON state at timing TM2, the microcomputer 26 measures the voltage V1 of the power storage unit 21 and then causes the charging unit 22 to resume a charging operation. As a result, the voltage of the power storage unit 21 rises to approximately voltage V2.

[0042] When the microcomputer 26 determines that the activation conditions are met in the sleep state, it starts the process shown in Fig. 3. First, in step S11, the microcomputer 26 performs activation processing to switch to the activated state. After switching to the activated state, in step S12, the microcomputer 26 measures the voltage V1 of the power storage unit 21. Then, in step S13, the microcomputer 26 calculates a voltage drop of the power storage unit 21 during the sleep state. The voltage drop is calculated by subtracting the voltage V1 from the voltage V2. The voltage V2 is the voltage of the power storage unit 21 measured before transitioning to the sleep state in step S25, which will be described later.

[0043] In step S14, the microcomputer 26 estimates the second elapsed time T2 based on the voltage drop calculated in step S13 and the table described above. In step S15, the microcomputer 26 calculates a cumulative elapsed time T3 by adding together the first elapsed time T1 measured after the previous measurement process and the second elapsed time T2 estimated after the previous measurement process.

[0044] In step S16, the microcomputer 26 determines whether the cumulative elapsed time T3 calculated in step S15 has exceeded the aforementioned determination time. If the microcomputer 26 determines that the cumulative elapsed time T3 has exceeded the determination time, the microcomputer 26 performs a measurement process in step S17 and resets the cumulative elapsed time T3 in step S18.

[0045] If the microcomputer 26 determines in step S16 that the cumulative elapsed time T3 has not exceeded the determination time, or after resetting the cumulative elapsed time T3 in step S18, the microcomputer 26 proceeds to step S21. If the charging conditions are met, the microcomputer 26 causes the charging unit 22 to start a charging operation in step S21. After step S21, the microcomputer 26 starts measuring a first elapsed time T1 in step S22, and determines whether the start switch has been switched to the OFF state in step S23. If the microcomputer 26 determines that the start switch has not been switched to the OFF state, the microcomputer 26 returns to step S23. That is, the microcomputer 26 repeats the processing of step S23 until the start switch is switched to the OFF state.

[0046] When the microcomputer 26 determines that the start switch has been switched to the OFF state, it ends measurement of the first elapsed time T1 in step S24, measures the voltage V2 of the power storage unit 21 in step S25, and stops the charging operation by the charging unit 22 in step S26. Then, in step S27, the microcomputer 26 performs a stop process to transition to a sleep state, and ends the process shown in FIG.

[0047] The following description relates to the effects of the degradation measurement device 20. When the timer 33 is stopped, the charging operation by the charging unit 22 and the discharging operation by the discharging unit 23 are stopped, and the voltage of the power storage unit 21 drops due to self-discharge. A certain correlation exists between the voltage drop of the power storage unit 21 and the elapsed time. Utilizing this correlation, the degradation measurement device 20 can estimate the second elapsed time T2 while the timer 33 is stopped based on the voltage drop of the power storage unit 21, even when the timer 33 is stopped. Therefore, the degradation measurement device 20 can calculate the cumulative elapsed time T3 by adding up the first elapsed time T1 and the second elapsed time T2 while suppressing the power consumption of the timer 33.

[0048] By using the table, deterioration measurement device 20 can simplify the configuration for estimating second elapsed time T2.

[0049] The relationship between the voltage drop of the power storage unit 21 and the second elapsed time T2 may vary depending on the degree of deterioration of the power storage unit 21. The deterioration measurement device 20 prepares a table for each range of the degree of deterioration, and can estimate the second elapsed time T2 more accurately by using the table corresponding to the degree of deterioration.

[0050] When the vehicle start switch is in the off state, the deterioration measurement device 20 can reduce power consumption by stopping the timer 33 and stopping the charging operation by the charging unit 22 and the discharging operation by the discharging unit 23.

[0051] 2. Second Embodiment In the second embodiment, a configuration will be described in which a resistor unit 41 and a switch unit 42 are provided in parallel with the power storage unit 21. In the description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0052] 4, an in-vehicle system 201 of the second embodiment includes a power supply unit 10, a load 11, a power path 12, and a diode 13. The in-vehicle system 201 also includes a degradation measurement device 220 for an in-vehicle power storage unit (hereinafter also referred to as degradation measurement device 220). The degradation measurement device 220 includes a power storage unit 21, a charging unit 22, a discharging unit 23, a voltage detection unit 24, a temperature detection unit 25, and a microcomputer 26.

[0053] Furthermore, the degradation measurement device 220 has a resistor unit 41, a switch unit 42, and a switching circuit 43. The resistor unit 41 is provided in parallel with the power storage unit 21. The switch unit 42 is provided in parallel with the power storage unit 21 and in series with the power storage unit 41. The switch unit 42 may be configured with a semiconductor switch or a mechanical switch. In a state in which the charging operation by the charging unit 22 and the discharging operation by the discharging unit 23 are stopped, if the switch unit 42 is in an on state, the power storage unit 21 is discharged to the resistor unit 41, and if the switch unit 42 is in an off state, the discharge from the power storage unit 21 to the resistor unit 41 is stopped.

[0054] The switching circuit 43 corresponds to an example of a switching unit. The switching circuit 43 switches the on / off state of the switch unit 42. The switching circuit 43 controls the switch unit 42 to the on state when the voltage of the power storage unit 21 is equal to or higher than a predetermined voltage, and switches the switch unit 42 to the off state when the voltage of the power storage unit 21 falls below the predetermined voltage. The predetermined voltage is greater than 0 V and less than the fully charged voltage of the power storage unit 21.

[0055] The switching circuit 43 includes, for example, a comparator. The detection value of the voltage detection unit 24 is input to the switching circuit 43. The switching circuit 43 determines whether the voltage of the power storage unit 21 (specifically, the detection value of the voltage detection unit 24) is equal to or higher than a predetermined voltage. If the switching circuit 43 determines that the voltage of the power storage unit 21 is equal to or higher than the predetermined voltage, it outputs an ON signal and controls the switch unit 42 to the ON state. If the switching circuit 43 determines that the voltage of the power storage unit 21 is lower than the predetermined voltage, it outputs an OFF signal and controls the switch unit 42 to the OFF state.

[0056] In the degradation measurement device 220 of the second embodiment, the switching circuit 43 only needs to operate when at least the charging operation by the charging unit 22 and the discharging operation by the discharging unit 23 are stopped, and when it is determined that the voltage of the power storage unit 21 exceeds the predetermined voltage, the switching circuit 43 causes the power storage unit 21 to discharge to the resistance unit 41. With this configuration, when the charging operation by the charging unit 22 and the discharging operation by the discharging unit 23 are stopped, the discharge current tends to be large, making it less likely that a measurement error will occur in the measurement process.

[0057] Furthermore, the switching circuit 43 switches the switch unit 42 to the off state when the voltage of the power storage unit 21 falls below a predetermined voltage. With this configuration, the degradation measurement device 220 can prevent a voltage drop in the power storage unit 21 by stopping the discharge from the power storage unit 21 to the resistor unit 41 when the voltage of the power storage unit 21 falls below the predetermined voltage.

[0058] <Other Embodiments> The present disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of features of the above-described or below-described embodiments is possible within a range that does not contradict. Furthermore, any feature of the above-described or below-described embodiments may be omitted unless explicitly stated as essential. Furthermore, the above-described embodiments may be modified as follows.

[0059] In each of the above embodiments, the deterioration measurement device 20, 220 is configured to have the charging unit 22 and the discharging unit 23, but the charging unit 22 and the discharging unit 23 may be provided external to the deterioration measurement device 20, 220. Furthermore, while the deterioration measurement device 20, 220 is configured to control the charging unit 22 and the discharging unit 23, the deterioration measurement device 20, 220 may be configured to control the charging unit 22 and the discharging unit 23 by a device external to the deterioration measurement device 20, 220.

[0060] In the above embodiments, the degradation measurement device 20, 220 is configured to calculate the cumulative elapsed time T3 after estimating the second elapsed time T2, but the degradation measurement device 20, 220 may calculate the cumulative elapsed time T3 at the point when it finishes measuring the first elapsed time T1. Alternatively, the degradation measurement device 20, 220 may determine whether the cumulative elapsed time T3 has exceeded the determination time at the point when it finishes measuring the first elapsed time T1 and calculates the cumulative elapsed time T3.

[0061] In the above embodiments, the measurement process is performed when it is determined that the cumulative elapsed time T3 has exceeded the judgment time, but the measurement process may also be performed at a predetermined timing after the cumulative elapsed time T3 has exceeded the judgment time. For example, if the degradation measurement device 20, 220 determines that the cumulative elapsed time T3 has exceeded the judgment time when it finishes measuring the first elapsed time T1, the degradation measurement device 20, 220 may then switch the vehicle start switch to the OFF state, and then switch the start switch to the ON state again before performing the measurement process.

[0062] In the above embodiments, the measurement process is performed when the start switch is switched to the ON state, but the measurement process may be performed at another timing. For example, when the start switch is switched to the OFF state, the measurement process may be performed before the charging unit 22 and the discharging unit 23 are stopped.

[0063] In the second embodiment, the microcomputer 26 may be configured to be able to control the switch unit 42. With this configuration, for example, the microcomputer 26 controls the switch unit 42 to the off state when the start switch is in the on state, thereby making it possible to reduce unnecessary power consumption by the resistor unit 41.

[0064] The second embodiment may be configured without the switch unit 42 .

[0065] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, and is intended to include all modifications within the scope indicated by the claims or within the scope equivalent to the claims.

[0066] DESCRIPTION OF SYMBOLS 1...In-vehicle system 10...Power supply unit 11...Load 12...Power path 13...Diode 20...Deterioration measuring device for in-vehicle power storage unit 21...Power storage unit 22...Charging unit (charging / discharging unit) 23...Discharging unit (charging / discharging unit) 24...Voltage detection unit 25...Temperature detection unit 26...Microcomputer 31...Deterioration measuring unit 32...Time calculation unit 33...Timer 41...Resistance unit 42...Switch unit 43...Switching circuit (switching unit) 201...In-vehicle system 220...Deterioration measuring device for in-vehicle power storage unit T1...First elapsed time T2...Second elapsed time T3...Cumulative elapsed time TM1...Timing TM2...Timing

Claims

1. A degradation measurement device for an in-vehicle power storage unit that is included in an in-vehicle system having a charge / discharge unit that performs a charging operation to charge the power storage unit from a power supply unit and a discharging operation to discharge the power storage unit to a load, and that measures a degree of degradation of the power storage unit, the degradation measurement device having: a degradation measurement unit that performs a measurement process to measure a degree of degradation of the power storage unit; and a time calculation unit that calculates a cumulative elapsed time since the previous measurement process was performed, wherein the degradation measurement unit performs the measurement process on the condition that the cumulative elapsed time exceeds a judgment time, the time calculation unit includes a timer that measures a first elapsed time while the timer is operating, and measures a first elapsed time while the timer is stopped, and the charging operation and the discharging operation by the charge / discharge unit are stopped while the timer is stopped, based on a drop in voltage of the power storage unit while the timer is stopped, and calculates the cumulative elapsed time by adding together the first elapsed time and the second elapsed time.

2. The degradation measuring device for an in-vehicle power storage unit according to claim 1, further comprising a resistance unit provided in parallel with the power storage unit, wherein the power storage unit is discharged to the resistance unit when the charging and discharging operations by the charge / discharge unit are stopped.

3. The deterioration measuring device for an in-vehicle power storage unit according to claim 2, further comprising a switch unit provided in parallel with the power storage unit and in series with the resistance unit.

4. The deterioration measuring device for an in-vehicle power storage unit according to claim 3, further comprising a switching unit that switches the switch unit to an off state when the voltage of the power storage unit falls below a predetermined voltage.

5. The degradation measuring device for an in-vehicle power storage unit according to any one of claims 1 to 4, wherein the time calculation unit pre-stores a table showing the correspondence relationship between the second elapsed time and the voltage drop, and estimates the second elapsed time based on the table and the voltage drop.

6. The degradation measuring device for an in-vehicle power storage unit according to claim 5, wherein the time calculation unit stores the table prepared for each range of the degradation level, and estimates the second elapsed time based on the table corresponding to the degradation level measured by the most recent measurement process and the voltage drop.

7. The degradation measuring device for an in-vehicle power storage unit according to any one of claims 1 to 4, wherein the timer is activated when a start switch of the vehicle is on and is stopped when the start switch is off, and the charging operation and the discharging operation by the charge / discharge unit are stopped when the start switch is off.

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