Diagnostic device for auxiliary battery

Abstract

To diagnose an auxiliary battery at the proper time.SOLUTION: A diagnostic system of an auxiliary battery comprises: an estimation part 40-1 which estimates travel of a vehicle itself to obtain an estimated travel situation; a prediction part 40-2 which predicts, on the basis of the estimated travel situation estimated by the estimation part 40-1, whether there is a situation where charge and discharge an auxiliary battery 22 can be performed suitable for diagnosis of the auxiliary battery 22; a control part 40-5 which controls a DCDC converter 20 to perform charge and discharge of the auxiliary battery through power exchange between a load 24 and the auxiliary battery at the timing of the situation where charge and discharge of the auxiliary battery 22 can be performed suitable for diagnosis of the auxiliary battery 22 predicted by the prediction part 40-2; and a diagnosis part 40-4 which performs diagnosis through detecting charge and discharge characteristic of the auxiliary battery 22 while the control part 40-5 performs charge and discharge of the auxiliary battery 22 by exchanging power between the load 24 and the auxiliary battery.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a diagnostic device for an auxiliary battery mounted on a vehicle, and more particularly to determining the timing of diagnosis. [Background technology]

[0002] A vehicle is provided with an auxiliary battery as a power source for various auxiliary devices mounted on the vehicle. Since the auxiliary battery deteriorates with use, it is preferable to diagnose the condition of the auxiliary battery. Here, Patent Document 1 describes a device for detecting the battery condition of a backup battery during automatic driving. That is, the battery condition can be grasped by detecting the physical condition such as the internal resistance value, and the detection of the internal resistance can be performed by changing the charge / discharge current of the battery by the output from the DCDC converter. It is also shown that when the physical condition is detected by the DCDC converter, fluctuations in the power consumption state accompanying driving are undesirable, and therefore the detection of the physical condition is prohibited when the fluctuations are large. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-126208 A Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the timing for detecting the battery state is limited, and depending on the driving conditions, diagnosis may not be performed at the appropriate timing. Also, because the output of the DC-DC converter is changed to detect the battery state, appropriate power usage may not be achieved depending on the driving conditions. [Means for solving the problem]

[0005] The present invention provides an auxiliary battery diagnostic device for diagnosing an auxiliary battery in a power supply system in which a DCDC converter, a load, and an auxiliary battery are electrically connected and power can be exchanged between them, the device comprising: an estimation unit that estimates future driving of a vehicle to obtain an estimated driving condition; a prediction unit that predicts whether there is a condition in which the auxiliary battery will be charged or discharged suitable for diagnosing the auxiliary battery based on the estimated driving condition estimated by the estimation unit; a control unit that controls the DCDC converter at a timing when the condition in which the auxiliary battery will be charged or discharged suitable for diagnosing the auxiliary battery predicted by the prediction unit is met, to charge or discharge the auxiliary battery by exchanging power with the load; and a diagnosis unit that detects the charge and discharge characteristics of the auxiliary battery and performs a diagnosis while the control unit is charging or discharging the auxiliary battery by exchanging power with the load.

[0006] Furthermore, the vehicle may have a memory unit that monitors the current flowing through the load during driving, and determines and stores whether there is a situation in which the auxiliary battery is being charged or discharged, which is suitable for diagnosing the auxiliary battery, and the prediction unit may use the determination result stored in the memory unit for making predictions.

[0007] Furthermore, the vehicle may have a traffic information acquisition unit that acquires traffic information, and the prediction unit may determine, based on the traffic information acquired by the traffic information acquisition unit, whether there is a situation in which the auxiliary battery can be charged or discharged, which is suitable for diagnosing the auxiliary battery. Effect of the Invention

[0008] According to the present invention, when there is a diagnosis request, diagnosis of the auxiliary battery can be performed at a location suitable for the diagnosis. [Brief description of the drawings]

[0009] [Figure 1] 1 is a block diagram showing a configuration of a vehicle including a diagnostic device for an auxiliary battery according to an embodiment; [Diagram 2]4 is a diagram showing the relationship between a battery current due to charging and discharging of a battery and a battery voltage. FIG. [Diagram 3] 4 is a chart showing the timing of diagnosis of the auxiliary battery 22. [Figure 4] 13 is a flowchart showing a periodic diagnosis process. [Diagram 5] 1 is a flow chart of a process for performing a diagnosis at a location suitable for the diagnosis. [Figure 6] 11 is a flowchart for performing a diagnosis at a location suitable for the diagnosis, including a determination as to whether or not a set route is being traveled. [Figure 7] 10 is a flowchart illustrating storage of locations suitable for diagnosis when a route to a destination has been set. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiment described herein.

[0011] "Overall Configuration" FIG. 1 is a block diagram showing the configuration of a vehicle including a diagnostic device for an auxiliary battery according to an embodiment.

[0012] The vehicle 10 is equipped with a large-capacity main battery 12 that has a high-voltage output of several hundred volts or more. A drive motor 16 is connected to the main battery 12 via an inverter 14, and the power of the main battery 12 is converted to a desired power by the inverter 14 and supplied to the drive motor 16, causing the wheels mechanically connected to the drive motor 16 to rotate and causing the vehicle 10 to travel. During regenerative braking of the vehicle, the main battery 12 is charged by regenerative power from the drive motor 16.

[0013] A DC-DC converter 20 is connected to the main battery 12 and controls power exchange between the main battery 12 and a low voltage system (eg, a 12V system) which is the output voltage of the auxiliary battery 22.

[0014] The high-voltage side of the DCDC converter 20 is connected to the main battery 12, and the low-voltage side is connected to the auxiliary battery 22. The low-voltage side of the DCDC converter 20 and the auxiliary battery 22 are connected by an auxiliary power supply line 26, and various auxiliary devices 24 (24-1 to 24-n) are connected as loads to the auxiliary power supply line 26. Examples of the auxiliary devices 24 include power steering, air conditioners, audio equipment, and various lighting fixtures.

[0015] The auxiliary battery 22 is a secondary battery such as a lithium ion battery or a nickel metal hydride battery, and has a large number of battery cells connected in series and parallel to ensure a predetermined output voltage and battery capacity.

[0016] The auxiliary battery 22 includes a battery cell unit 22-1 consisting of multiple battery cells, an internal relay 22-2 that switches external electrical connections on and off, and a monitoring ECU 22-3 that detects the state of the battery cell unit 22-1, in particular the state of charge (SOC) that indicates the remaining capacity relative to the battery capacity.

[0017] The vehicle 10 also has a current position detection device 30, a navigation device 32, and a communication device 34. The current position detection device 30 is composed of a position detection device such as a GPS, and detects the current location of the vehicle 10. The navigation device 32 has map data and the like, and recognizes the current position on the map, and when a destination is set, stores the set route on the map. Then, when traveling along the set route, the current position and the set route are displayed on the map on a display inside the vehicle, thereby supporting driving.

[0018] The communication device 34 can connect to a traffic information center, a weather forecast site, etc. via a communication line such as a wireless base station or the Internet to obtain various information. In particular, the traffic information center can provide traffic congestion information about the set route to be traveled.

[0019] The vehicle 10 is provided with an overall control unit 40, which controls the operation of the DC-DC converter 20 in accordance with the state of the auxiliary battery 22. The overall control unit 40 has an estimation unit 40-1, a prediction unit 40-2, a memory unit 40-3, a diagnosis unit 40-4, and a control unit 40-5, and performs various processes.

[0020] The current position detection device 30 , the navigation device 32 , and the communication device 34 are connected to a general control unit 40 , and various types of information are provided to the general control unit 40 .

[0021] The estimation unit 40-1 of the general control unit 40 estimates the planned driving route of the vehicle 10 based on information from the navigation device 32, etc. When a destination is set, the set route may be used as the estimated result as it is. The planned driving route may also be estimated based on the driving state of the vehicle 10 and the branching state of the road ahead. Furthermore, the past driving routes of the vehicle 10 may be stored, and the planned driving route may be estimated based on the relationship between the stored driving route and the current driving path. For example, even if the route is not set, when the same route has been traveled many times in the past, the past route may be estimated as the planned driving route. The estimation unit 40-1 may be provided inside the navigation device 32.

[0022] In addition, the communication device 34 can be connected to the outside world via the Internet or the like, and the general control unit 40 can connect to an external site such as an external traffic information center via the communication device 34 and acquire traffic information, i.e., function as a traffic information acquisition unit.

[0023] The prediction unit 40-2 predicts the location where the diagnosis of the auxiliary battery 22 will be performed. In other words, it is preferable to perform the diagnosis of the auxiliary battery 22 when traveling through a location where a predetermined charge / discharge is performed. Therefore, it is determined whether there is a location (area) where a predetermined charge / discharge is performed on the planned traveling route estimated by the estimation unit 40-1, and the location is predicted.

[0024] The memory unit 40-3 stores various information. For example, it stores information about past driving routes, set destinations, traffic congestion conditions on the driving routes, driving speed, etc. In addition, for driving patterns that are repeated daily, such as commuting, it is preferable to store the driving conditions in association with the charging and discharging current of the battery.

[0025] The diagnosis unit 40-4 controls the DC-DC converter 20 to control the charging and discharging of the auxiliary battery 22, and measures the battery current and battery voltage of the auxiliary battery 22 at that time to detect the internal resistance of the auxiliary battery 22.

[0026] The control unit 40-5 controls the operation of the DC-DC converter 20, and causes the auxiliary battery 22 to charge and discharge by exchanging electric power with the auxiliary device 24.

[0027] "Diagnosis of auxiliary battery 22" A battery deteriorates with use and the full charge capacity decreases. This deterioration is detected as the physical state of the battery. In this embodiment, the internal resistance of the battery is used as the physical state of the battery. That is, as the internal resistance of a battery increases due to deterioration, the battery is diagnosed by detecting the value of the internal resistance. In this embodiment, the internal resistance of the auxiliary battery 22 is detected, and the auxiliary battery 22 is diagnosed according to the value.

[0028] Here, the internal resistance of a battery can be calculated from the relationship between the battery voltage and the battery current (charge and discharge characteristics). Figure 2 is a diagram showing the relationship between the battery current due to charging and discharging the battery and the battery voltage. As described above, when a battery is charged and discharged, a voltage is generated according to the product of the internal resistance and the battery current, so that if the discharge current is large, the battery voltage drops, and if the charge current is large, the battery voltage rises. Therefore, the internal resistance can be calculated from the relationship: internal resistance = (amount of change in battery voltage) / (amount of change in battery current). At this time, the larger the amount of change in the battery current, the larger the amount of change in the battery voltage, and the accuracy of the detected internal resistance value also improves.

[0029] Therefore, when detecting the internal resistance of a battery, i.e., diagnosing the battery, there is a demand to ensure that the change in the battery current (fluctuation range) is as large as possible and within a specified fluctuation range, for example, the range shown as "Fluctuation Range" in Figure 2.

[0030] "Diagnosis of auxiliary battery 22" In the power supply system according to the embodiment, the auxiliary battery 22 is connected to the DCDC converter 20 by the auxiliary power line 26. Various auxiliary devices 24 are connected to the auxiliary power line 26, and power is supplied to these auxiliary devices 24 via the auxiliary power line 26. Normally, the general control unit 40 controls the operation of the DCDC converter 20 so that the voltage of the auxiliary power line 26 is maintained at a constant value. The DCDC converter 20 may be controlled based on the current value measured in the auxiliary power line 26 or the charge / discharge current of the auxiliary battery 22. The DCDC converter 20 may also have a dedicated control unit and maintain the voltage on the low voltage side.

[0031] By such control, the output from the DC-DC converter 20 to the low voltage side is commensurate with the power consumption of the auxiliary equipment 24 connected to the auxiliary power supply line 26, and the charge / discharge current of the auxiliary battery 22 does not become too large.

[0032] On the other hand, as described above, when diagnosing the auxiliary battery 22, it is necessary to ensure a predetermined fluctuation range for the battery current (charge / discharge current).

[0033] In this embodiment, during running, the auxiliary battery 22 is diagnosed while ensuring a fluctuation range of the charge / discharge current of the auxiliary battery 22.

[0034] <Prediction of suitable locations for diagnosis> As described above, in order to diagnose the auxiliary battery 22, it is necessary to be in a state where the charge / discharge current (battery current) of the auxiliary battery 22 is large. To achieve this, the operation of the DC-DC converter 20 needs to be controlled.

[0035] In this embodiment, the auxiliary battery 22 is charged and discharged based on power consumption according to the driving conditions of the vehicle. Therefore, the auxiliary battery 22 can be diagnosed without reducing the overall energy efficiency of the vehicle 10.

[0036] <Charging the auxiliary battery 22> (i) Supply of charging current from the DC-DC converter 20 When the vehicle 10 is decelerating, a regenerative current is generated by regenerative braking of the drive motor. Normally, this regenerative current is used to charge the main battery 12, but the DC-DC converter 20 can use this regenerative current to charge the auxiliary battery 22.

[0037] (ii) Regenerative current from auxiliary equipment 24 such as electric power steering In the electric power steering, the steering is performed by the output of the motor, but when a reaction force is received from the tire side, a regenerative current is generated. This regenerative current can be used to charge the auxiliary battery 22. In this case, the DC-DC converter 20 may stop outputting to the low voltage side, but may also increase the charging current of the auxiliary battery 22 at a predetermined output.

[0038] <Discharging of auxiliary battery 22> (i) Output to the high voltage side by the DC-DC converter 20 When the vehicle 10 accelerates, a drive current is supplied to the drive motor 16. Normally, this drive current is generated by discharging the main battery 12, but part of this drive current can be supplied by the discharge current of the auxiliary battery 22 via the DC-DC converter 20.

[0039] (ii) Supplying drive current to auxiliary devices 24 such as electric power steering When turning right or left, the motor drive current for the electric power steering is supplied by the discharge current from the auxiliary battery 22. At this time, it is preferable that the DC-DC converter 20 stops operating.

[0040] <Consideration of driving conditions> (i) During stable driving For example, when the vehicle is on a highway and auto-cruise control is being performed, the vehicle does not accelerate, decelerate, or operate the steering wheel as described above. Therefore, a large fluctuation range is not obtained in the charge / discharge current of the auxiliary battery 22. For this reason, if the auxiliary battery 22 is to be diagnosed, the charge / discharge current of the auxiliary battery 22 is generated in a predetermined pattern (predetermined fluctuation range) by the DCDC converter 20, and the internal resistance of the auxiliary battery 22 is detected based on the voltage of the auxiliary battery 22 at that time.

[0041] (ii) When turning right or left When turning right or left at a relatively wide intersection, the power steering generates a drive current when turning right or left and a regenerative current when returning the steering wheel. At this time, a discharge current and a charge current are generated in the auxiliary battery 22. Therefore, at a large intersection, the fluctuation range of the battery current of the auxiliary battery 22 may exceed a predetermined value.

[0042] (iii) Slopes When going uphill, the output of the drive motor 16 is large, and the drive current is large. When going downhill, the regenerative current is large due to regenerative braking of the drive motor 16. Therefore, by controlling the DCDC converter 20 so that a predetermined range of discharge is performed from the auxiliary battery 22 when going uphill and a predetermined range of charge is performed from the auxiliary battery 22 when going downhill, the auxiliary battery 22 can be charged and discharged according to the running state of the vehicle 10, and the auxiliary battery 22 can be diagnosed at this time.

[0043] (iv) Tunnel during the day When the vehicle is in a tunnel, the headlights are turned on. Therefore, when the vehicle is traveling in a tunnel, the current consumption of the auxiliary device 24 is likely to increase. Therefore, the inside of the tunnel can be used as a sampling point for a large discharge current, and the outside of the tunnel can be used as a sampling point for a charge current.

[0044] (v) Traffic Information When traffic is heavy and congested, there is little change in the driving conditions and little change in the power consumption of the vehicle 10 while driving. Therefore, even if the location is normally suitable for diagnosing the auxiliary battery 22, there is a high possibility that the predetermined fluctuation range for the charge / discharge current cannot be secured.

[0045] <Learning the power consumption status of auxiliary unit 24> (i) Setting destination and route driving In the navigation device 32, when a destination is set and the vehicle is traveling along the set route to the destination, it is advisable to store the charge / discharge currents of the main battery 12 and the auxiliary battery 22 and the current consumption of the auxiliary battery 24 as needed in association with the traveling position, traveling speed, etc.

[0046] If such information is stored, it is possible to analyze the information and determine a location suitable for diagnosing the auxiliary battery 22. Therefore, when traveling along the same set route, it is possible to predict in advance a location suitable for diagnosing the auxiliary battery 22, and the diagnosis can be performed at that location.

[0047] (ii) Frequently traveled roads Even if a route has not been set, it is advisable to determine a location suitable for diagnosing the auxiliary battery 22 while traveling, and if a suitable location is found, to store the location.

[0048] Regardless of whether a set route has been set or not, if it is estimated that the vehicle will travel through that location, then the auxiliary battery 22 can be diagnosed at that location.

[0049] In particular, if the location is one that is frequently passed by, it is preferable because the diagnosis of the auxiliary battery 22 can be performed whenever necessary.

[0050] (iii) Learning It is advisable to learn and store suitable locations for diagnosing the auxiliary battery 22 whenever the vehicle 10 is traveling. This allows a diagnosis to be performed relatively quickly when it is necessary.

[0051] Timing of diagnosis FIG. 3 is a chart showing the timing of diagnosis of the auxiliary battery 22.

[0052] When a diagnosis is performed, the date and time of the diagnosis is stored in the general control unit 40, and timing starts without a diagnosis execution request. Then, after a predetermined period (several months) has elapsed, a diagnosis execution request is generated, and the state becomes one in which a diagnosis execution request is made.

[0053] When a diagnosis execution request is received, the general control unit 40 finds a timing at which the diagnosis can be executed, and executes the diagnosis. When the diagnosis is executed, the date and time of the diagnosis are stored, and the clock starts without a diagnosis execution request.

[0054] In this manner, the auxiliary battery 22 can be diagnosed periodically.

[0055] "Diagnostics Processing" <Regular checkups> FIG. 4 is a flow chart showing the operation of the general control unit 40 in the periodic diagnosis process shown in the timing chart of FIG.

[0056] First, the time is measured from the previous diagnosis (S11), and it is determined whether a predetermined period of time has elapsed (S12). If NO, the process returns to S11.

[0057] If the answer is YES in S12, a request to perform diagnosis is generated (S13). Then, it is determined whether a diagnosis completion signal has been received (S14), and if the answer is NO, the process returns to S13.

[0058] If S14 is YES, the diagnosis of the auxiliary battery 22 has been performed, and the time measurement is reset (S15). Then, it is determined whether the process is finished (S16), and if NO, the process returns to S11. S16 may be set to YES when the auxiliary battery 22 is replaced, for example. For a brand new auxiliary battery 22, an initial diagnosis may be performed and the initial internal resistance value may be stored, and then the process of S11 may be started. The initial internal resistance value may be used as a reference value, and the degree of deterioration may be diagnosed by comparing it with subsequent internal resistance values. For example, the degree of deterioration may be determined by the percentage increase in the initial internal resistance value.

[0059] <Diagnosis implementation> FIG. 5 is a flow chart showing the operation of the general control unit 40 in the process of performing a diagnosis at a location suitable for the diagnosis.

[0060] It is determined whether there is a diagnosis execution request (S21), and if NO, diagnosis is not necessary and the process ends. If the determination in S21 is YES, the current driving conditions are acquired (S22). The driving conditions include the current location, traveling direction, driving speed, etc.

[0061] Next, traffic information is acquired (S23). The traffic information includes congestion information, etc. Then, it is determined whether the location is suitable for diagnosis (S24). That is, it is determined whether it is appropriate to perform diagnosis based on the current driving conditions. If this determination is NO, the process returns to S22. For example, if it is determined that the vehicle is entering an intersection and will turn right or left, the determination in S24 can be YES.

[0062] In addition, the judgment in S24 is made by having the estimation unit 40-1 estimate the future driving of the vehicle to obtain an estimated driving condition, and the prediction unit 40-2 determines a location suitable for diagnosis by predicting whether there is a condition in which the auxiliary battery will be charged or discharged, which is suitable for diagnosing the auxiliary battery, based on the estimated driving condition obtained by the estimation unit 40-1, and sets the result to YES when the current location reaches the suitable location.

[0063] If the determination in S24 is YES, the diagnosis is performed by detecting the internal resistance of the auxiliary battery 22 (S25). Then, it is determined whether the diagnosis is completed (S26), and if completed (YES in S26), the process ends.

[0064] FIG. 6 is a flowchart showing a process for performing a diagnosis at a location suitable for the diagnosis, including a determination as to whether or not the vehicle is traveling along a set route.

[0065] It is determined whether the vehicle is traveling along a set route (S31), and if the result is YES, it is determined whether a location suitable for diagnosis is stored on the set route (S32). If the result of S32 is YES, the stored location suitable for diagnosis is read out (S33).

[0066] If the determination in S31 is NO, the driving route at this time is estimated (34). If the route has been estimated in S34 or if the determination in S32 is NO, it is determined whether there is a place suitable for diagnosing the road to be traveled from now on (S35). If the determination in S32 is NO, the determination is made on the set route to be adopted as the estimated route, and in the case of S34, the determination is made on roads that may be traveled in the direction of travel. If the determination in S35 is NO, there is no place to be diagnosed, so the process ends.

[0067] If the answer is YES in S35, traffic information is acquired (S36). As described above, traffic information includes congestion information, and the location is judged to be suitable for diagnosis by taking the traffic information into consideration. That is, it is judged whether it is OK to perform diagnosis based on the current driving conditions (S37). If the answer is NO, the process ends, and if the answer is YES, it is judged whether a suitable location for diagnosis has been reached (S38). If the answer is NO, the process returns to S31, and if the situation has not changed, the process returns to the judgment in S38.

[0068] If the determination in S38 is YES, a diagnosis is performed by detecting the internal resistance of the auxiliary battery 22 (S39).

[0069] In this manner, diagnosis of the auxiliary battery 22 can be performed at a location suitable for the diagnosis.

[0070] FIG. 7 is a flow chart for explaining the storage of locations suitable for diagnosis when a route to a destination has been set.

[0071] First, it is determined whether a route has been set (S41). If the determination is NO, the process ends.

[0072] If the determination in S41 is YES, the driving conditions are detected (S42) and it is determined whether or not the conditions are suitable for diagnosis (S43). If the determination in S43 is YES, locations suitable for diagnosis are stored (S44). When storing of locations suitable for diagnosis in S44 is completed or if the determination in S43 is NO, it is determined whether driving of the set route has been completed (S45), and if NO, the process returns to S42 and is repeated. If the determination in S45 is YES, the process is terminated.

[0073] In this way, when traveling along a set route, it is possible to store locations suitable for diagnosis. These locations suitable for diagnosis can be stored together with the set route, and the next time the same route is set, the locations suitable for diagnosis can also be read out. Therefore, when a diagnosis is requested, a diagnosis can be performed promptly.

[0074] In the above process, a location suitable for diagnosis is stored when a route is set in S41, but even if a route is not set, a location suitable for diagnosis may be stored automatically or when a switch for storing is turned on, etc. In this way, when a diagnosis request is made, a diagnosis of the auxiliary battery 22 can be performed when traveling through the stored location. [Explanation of symbols]

[0075] 10: vehicle, 12: main battery, 14: inverter, 16: drive motor, 20: DCDC converter, 22: auxiliary battery, 22-1: battery cell section, 22-2: built-in relay, 22-3: monitoring ECU, 24: auxiliary, 26: auxiliary power line, 30: current position detection device, 32: navigation device, 34: communication device, 40: overall control unit, 40-1: estimation section, 40-2: prediction section, 40-3: memory section, 40-4: diagnosis section, 40-5: control section.

Claims

1. A diagnostic device for an auxiliary battery in a power supply system in which a DC-DC converter, a load, and an auxiliary battery are electrically connected and power can be exchanged between them, the diagnostic device comprising: an estimation unit that estimates future travel of the vehicle to obtain an estimated travel situation; a prediction unit that predicts whether there is a situation in which the auxiliary battery is to be charged or discharged, which is suitable for diagnosing the auxiliary battery, based on the estimated traveling situation estimated by the estimation unit; a control unit that controls the DCDC converter to charge and discharge the auxiliary battery by exchanging power with the load at a timing when the auxiliary battery is in a state where charging and discharging is performed that is suitable for diagnosing the auxiliary battery as predicted by the prediction unit; a diagnosis unit that detects and diagnoses a charge / discharge characteristic of the auxiliary battery while the control unit is causing the auxiliary battery to charge and discharge by exchanging power with the load; Equipped with Diagnostic device for auxiliary batteries.

2. 2. The diagnostic device for an auxiliary battery according to claim 1, moreover, a storage unit that monitors a current flowing through the load during running, and determines whether there is a situation in which the auxiliary battery is being charged or discharged that is suitable for diagnosing the auxiliary battery, and stores the determined result; The prediction unit uses the determination result stored in the storage unit for prediction. Diagnostic device for auxiliary batteries.

3. 3. The diagnostic device for an auxiliary battery according to claim 1, Further, a traffic information acquisition unit for acquiring traffic information is provided, The prediction unit determines whether there is a situation in which the auxiliary battery is to be charged or discharged, which is suitable for diagnosing the auxiliary battery, based on the traffic information acquired by the traffic information acquisition unit. Diagnostic device for auxiliary batteries.

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