Vehicle charge control device

Abstract

A vehicle charge control device according to the present invention comprises one or more processors and a storage medium in which a program to be executed by the one or more processors is stored. The program includes one or more instructions. The one or more instructions are for causing the one or more processors to execute: a process for monitoring the remaining charge amount of an auxiliary machine battery in a ready-OFF state in which a vehicle cannot travel, a process for starting charging of the auxiliary machine battery when the remaining charge amount of the auxiliary machine battery becomes less than a lower limit threshold value in the ready-OFF state; a process for stopping the charging of the auxiliary machine battery when the remaining charge amount of the auxiliary machine battery reaches an upper limit threshold value, which is a value greater than the lower limit threshold value, in the ready-OFF state; and a process for setting the upper limit threshold value and the lower limit threshold value in accordance with the temperature of the auxiliary machine battery.

Description

Vehicle charging control device

[0001] The present invention relates to the technical field of a vehicle charge control device that controls charging of an on-board battery mounted in a vehicle.

[0002] Electric vehicles that can run without using fuel such as gasoline are becoming more common. Electric vehicles are equipped with a large-capacity traction battery used to propel the vehicle in addition to an auxiliary battery. Because the auxiliary battery is used to start the vehicle system, if the remaining charge of the auxiliary battery becomes too low when the vehicle is in the ready-off state, the vehicle may not be able to start and may become unable to run.

[0003] The following Patent Document 1 discloses an invention in which, when the remaining charge of an auxiliary battery becomes low, the remaining charge of the driving battery is used to charge the auxiliary battery. This prevents an excessive decrease in the remaining charge of the auxiliary battery when the vehicle is in the ready-off state, and makes it possible to avoid a state in which the vehicle cannot be driven.

[0004] Japanese Patent Application Laid-Open No. 2006-174619

[0005] Lithium-ion batteries are sometimes used as auxiliary batteries instead of lead-acid batteries. However, because lithium-ion batteries are more expensive than lead-acid batteries, it is desirable to reduce costs by reducing their capacity. When the capacity of a lithium-ion battery used as an auxiliary battery is reduced, it becomes necessary to charge the auxiliary battery more frequently to prevent the battery from running out while the vehicle is parked.

[0006] However, in charge control of the auxiliary battery, if the SOC is not managed properly, there is a risk that the charge capacity, which has already decreased due to the capacity reduction, may further decrease.

[0007] The present invention has been made in view of the above circumstances, and has an object to suppress further reduction in charge capacity due to deterioration of a low-capacity auxiliary battery.

[0008] A vehicle charging control device according to one embodiment of the present invention comprises one or more processors and a storage medium storing a program executed by the one or more processors, the program including one or more instructions that cause the one or more processors to perform the following processes: monitoring the remaining charge of an auxiliary battery in a ready-off state in which the vehicle cannot be driven; starting charging of the auxiliary battery when the remaining charge of the auxiliary battery in the ready-off state falls below a lower threshold; stopping charging of the auxiliary battery when the remaining charge of the auxiliary battery in the ready-off state reaches an upper threshold that is greater than the lower threshold; and setting the upper threshold and the lower threshold according to the temperature of the auxiliary battery.

[0009] According to the present invention, it is possible to suppress further reduction in charge capacity due to deterioration of the low-capacity auxiliary battery.

[0010] FIG. 1 is a block diagram showing an example of the configuration of a vehicle; FIG. 2 is a block diagram showing an example of the configuration of a control unit; FIG. 3 is a functional block diagram of a control unit; FIG. 4 is a diagram showing an example of setting a lower limit threshold and an upper limit threshold used in SOC management of an auxiliary battery; FIG. 5 is a diagram showing another example of setting a lower limit threshold and an upper limit threshold used in SOC management of an auxiliary battery; FIG. 6 is a diagram showing an example in which a lower limit threshold and an upper limit threshold are changed according to an internal temperature that changes over time; and FIG. 7 is a flowchart showing an example of processing executed by a control unit.

[0011] 1 shows an example of the configuration of a vehicle 100. The vehicle 100 includes a control unit 1, an on-board battery 2, a PCU (Power Control Unit) 3, a motor 4, a generator 5, and a connector unit 6.

[0012] 3 shows only a portion of the configuration of the vehicle 100, and the vehicle 100 is appropriately equipped with a map locator, various sensors for driving, communication devices, etc., which are not shown.

[0013] The control unit 1 performs overall control of the vehicle 100. The control unit 1 may be provided as a single unit, or may be configured with multiple ECUs (Electronic Control Units). The multiple ECUs may include, for example, a central ECU 1A that performs overall management and control of the vehicle 100, a high-voltage battery ECU 1B that performs charging control of the high-voltage battery, a display control ECU that performs display control of display devices (including meters, etc.) provided in the vehicle 100, an airbag control ECU, an air conditioning control ECU, and so forth.

[0014] As shown in Fig. 2, the control unit 1 or each of the above-mentioned ECUs includes a CPU (Central Processing Unit) 31, a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a bus 34, an input / output interface 35, an input unit 36, an output unit 37, a storage unit 38, a communication unit 39, and a media drive 40. Note that some of these components may be selectively provided for each ECU as appropriate. In other words, it is not necessary for all ECUs to include all of the components shown in Fig. 2.

[0015] The CPU 31 executes various processes in accordance with programs stored in the ROM 32 or programs loaded from the storage unit 38 into the RAM 33. The RAM 33 also stores data and the like necessary for the CPU 31 to execute various processes.

[0016] The CPU 31, ROM 32, and RAM 33 are interconnected via a bus 34. An input / output interface 35 is also connected to the bus 34.

[0017] The input / output interface 35 is connected to an input unit 36, an output unit 37, a storage unit 38, a communication unit 39, and a media drive 40. Signals are input from the input unit 36 ​​from various sensors connected to the control unit 1, etc. The output unit 37 outputs control information for actuators that drive various parts of the vehicle 100 and are connected to the ECU. Note that the output unit 37 may be configured as a display such as an LCD (Liquid Crystal Display) or an organic EL (Electro Luminescence) panel, a speaker, or the like, making it possible to present various types of information to the user.

[0018] The storage unit 38 is configured by a hard disk drive (HDD), a flash memory device, or the like.

[0019] The communication unit 39 performs communication processing for communicating with other ECUs via a Controller Area Network (CAN). The communication unit 39 may also be capable of communicating with a server device or the like via a communication network external to the vehicle 100. Removable media 41 such as a semiconductor memory, a magnetic disk, an optical disk, or a magneto-optical disk is attached to the media drive 40 as needed, and information is written to and read from the removable media 41.

[0020] The central ECU 1A is a control unit that realizes various functions by cooperating with various ECUs and other components. For example, the central ECU 1A issues display instructions to the display control ECU at appropriate times to display desired information to the occupants. The central ECU 1A also cooperates with the airbag control ECU to activate the airbag when a predetermined condition is met, thereby improving the safety of the occupants.

[0021] The control unit 1 controls charging of an in-vehicle battery 2 mounted on the vehicle 100 and manages the state of charge (SOC).

[0022] The vehicle 100 may be equipped with multiple batteries as the on-board battery 2, specifically, a driving battery 2A and an auxiliary battery 2B. The driving battery 2A is the on-board battery 2 with a higher voltage than the auxiliary battery 2B.

[0023] The traction battery 2A is a high-voltage battery of several hundred volts used to drive the vehicle 100. The traction battery 2A supplies power used to drive the wheels and to operate the air conditioning equipment of the vehicle 100. Fig. 1 shows the power supply from the traction battery 2A used to drive the wheels, and does not illustrate the power supply used to operate the other components.

[0024] The high-voltage battery ECU 1B is responsible for managing the driving battery 2A, which has a relatively high voltage, of the in-vehicle battery 2.

[0025] The high-voltage battery ECU 1B is connected to sensors for managing the driving battery 2A, and controls the charging and discharging and temperature of the driving battery 2A based on the detected values ​​from the sensors. Examples of these sensors include a voltage sensor, a current sensor, and a temperature sensor.

[0026] The driving battery 2A is charged based on the DC voltage supplied from the PCU 3. The driving battery 2A supplies the PCU 3 with a power supply voltage for driving the motor 4.

[0027] The PCU 3 is configured to include an inverter, a DC / DC converter, and the like for driving the motor 4. The PCU 3 generates an AC current for driving the motor 4 based on the supplied power supply voltage, and supplies the AC current to the motor 4. The PCU 3 controls the torque of the motor 4 by controlling the AC current. The PCU 3 may also be provided with a regenerative braking function to optimize energy efficiency by utilizing regenerative energy.

[0028] The motor 4 is configured as a motor generator having a power generating function, and drives the wheels based on the supplied AC current.

[0029] The connector unit 6 has a structure that allows insertion of a charging plug provided in charging equipment installed in homes or charging stations. The connector unit 6 outputs AC voltage supplied via the inserted charging plug to the PCU 3. The PCU 3 is equipped with an AC / DC converter and supplies converted DC voltage to the driving battery 2A, thereby charging the driving battery 2A.

[0030] On the other hand, the auxiliary battery 2B is, for example, a 12-volt lithium-ion battery. The auxiliary battery 2B supplies drive power to various auxiliary devices mounted on the vehicle 100. The various auxiliary devices include, for example, various lights, a navigation system, audio equipment, windshield wipers, etc.

[0031] The central ECU 1A is responsible for managing the auxiliary battery 2B, which has a relatively low voltage among the in-vehicle batteries 2, and the like.

[0032] In this embodiment, the central ECU 1A receives information on the SOC from the auxiliary battery 2B, and when the SOC falls below a threshold, starts up various components and controls charging of the auxiliary battery 2B. A generator 5 is used to charge the auxiliary battery 2B.

[0033] The generator 5 includes, for example, a DC / DC converter, and steps down the high voltage supplied from the driving battery 2A and supplies the stepped-down voltage to the auxiliary battery 2B, thereby charging the auxiliary battery 2B. Charging of the auxiliary battery 2B by the generator 5 is performed based on instructions from, for example, the central ECU 1A.

[0034] 2. Functional Configuration The functional configuration of the central ECU 1A is shown in Fig. 3. The central ECU 1A includes a temperature monitoring function F1, a threshold setting function F2, an SOC monitoring function F3, a charge control function F4, and a startup control function F5.

[0035] The temperature monitoring function F1 monitors the internal temperature Tin of the auxiliary battery 2 B. The internal temperature Tin of the auxiliary battery 2 B is estimated based on temperature information obtained from a temperature sensor provided on the surface of or inside the auxiliary battery 2 B, for example.

[0036] The threshold setting function F2 sets a lower limit threshold Th1 and an upper limit threshold Th2 according to the internal temperature Tin of the auxiliary battery 2B obtained by the temperature monitoring function F1.

[0037] The lower limit threshold Th1 is set to, for example, about 30% to 50%, and is the threshold at which charging of the auxiliary battery 2B starts.

[0038] The upper limit threshold Th2 is set to, for example, about 60% to 80%, and is the threshold at which charging of the auxiliary battery 2B is stopped.

[0039] For example, when the internal temperature Tin of the auxiliary battery 2B is lower than the first temperature T1, the threshold setting function F2 sets the lower limit threshold Th1 to 50% and the upper limit threshold Th2 to 80%. Because the output characteristics of the auxiliary battery 2B are likely to deteriorate when the internal temperature Tin is low, the auxiliary battery 2B is managed at a relatively high SOC to avoid a state in which the system of the vehicle 100 cannot be started.

[0040] The threshold setting function F2 sets the lower limit threshold Th1 to 30% and the upper limit threshold Th2 to 60% when the internal temperature Tin of the auxiliary battery 2B is equal to or higher than the second temperature T2. If the auxiliary battery 2B is managed at a high SOC when the internal temperature Tin is high, the auxiliary battery 2B will deteriorate significantly. Therefore, the auxiliary battery 2B is managed at a low SOC to prevent the deterioration of the auxiliary battery 2B from accelerating the decrease in capacity due to the deterioration of the auxiliary battery 2B.

[0041] The first temperature T1 and the second temperature T2 may be the same temperature. That is, when the internal temperature Tin of the auxiliary battery 2B is below a certain temperature, the auxiliary battery 2B may be managed at a high SOC, and when the internal temperature Tin is equal to or higher than the certain temperature, the auxiliary battery 2B may be managed at a low SOC (see FIG. 4).

[0042] Alternatively, the first temperature T1 may be set to a temperature lower than the second temperature T2. Specifically, the threshold setting function F2 may set the lower limit threshold Th1 to 40% and the upper limit threshold Th2 to 70% when the internal temperature Tin of the auxiliary battery 2B is equal to or higher than the first temperature T1 and lower than the second temperature T2 (see FIG. 5 ).

[0043] When the temperature of the auxiliary battery 2B is between the first temperature T1 and the second temperature T2, the lower limit threshold Th1 and the upper limit threshold Th2 are set taking into consideration both the deterioration and output characteristics of the auxiliary battery 2B.

[0044] Furthermore, the lower limit threshold Th1 and the upper limit threshold Th2 may be set steplessly according to the internal temperature Tin. For example, the lower limit threshold Th1 may be calculated using the internal temperature Tin according to the following [Equation 1].

[0045] Th1=-(X×Tin)+Y... [Formula 1]

[0046] Here, the unit of the lower threshold value Th1 is "%." Furthermore, "X" and "Y" in [Equation 1] are constants.

[0047] The constant "X" defines how much the SOC management of the auxiliary battery 2B is offset downward for a temperature change of 1 degree. For example, if X = 0.5, the charge amount is managed at a 1% lower level for every 2 degree increase in the internal temperature Tin. For example, if the charge amount was managed between 50% and 80%, a 2 degree increase in the internal temperature Tin will result in the charge amount being managed between 49% and 79%.

[0048] The constant Y may be determined according to the manner of SOC management of the auxiliary battery 2B. For example, if the SOC of the auxiliary battery 2B is to be managed at a low level, the constant Y is set low, and if the SOC is to be managed at a high level, the constant Y is set high. The constant Y may be determined according to the type of the auxiliary battery 2B.

[0049] Alternatively, the upper limit threshold Th2 may be calculated using the internal temperature Tin according to the following [Equation 2].

[0050] Th2=-(X×Tin)+Y+30=Th1+30...[Formula 2]

[0051] Here, the unit of the upper threshold value Th2 is "%".

[0052] The SOC monitoring function F3 receives and manages the SOC from the auxiliary battery 2B, and supplies the SOC of the auxiliary battery 2B to the charge control function F4.

[0053] The charging control function F4 starts or stops charging of the auxiliary battery 2B based on the SOC of the auxiliary battery 2B received from the SOC monitoring function F3. Charging of the auxiliary battery 2B by the charging control function F4 is performed not only in a ready-on state in which the powertrain is activated and the vehicle 100 is ready to run, but also in a ready-off state.

[0054] The charging control function F4 controls the charging of the auxiliary battery 2B based on the lower limit threshold Th1 and upper limit threshold Th2 set by the threshold setting function F2 and the SOC of the auxiliary battery 2B obtained by the SOC monitoring function F3.

[0055] Specifically, the charge control function F4 starts charging the auxiliary battery 2B when the SOC of the auxiliary battery 2B is less than the lower limit threshold Th1.

[0056] When the charging control function F4 starts charging the auxiliary battery 2B in the ready-off state, the charging control function F4 issues instructions to the start-up control function F5 to start up each unit.

[0057] The start-up control function F5 starts up the high-voltage battery ECU 1B and the driving battery 2A via the high-voltage battery ECU 1B, and also starts up the generator 5, based on instructions from the charge control function F4.

[0058] In response to the start-up control function F5 starting up each part, the charging control function F4 controls the charging of the auxiliary battery 2B using the appropriate voltage obtained by reducing the high voltage from the driving battery 2A using the generator 5.

[0059] The charging control function F4 also stops charging of the auxiliary battery 2B when the SOC of the auxiliary battery 2B is equal to or higher than the upper limit threshold Th2.

[0060] 3. Example of Charging Control An example of charging control by the central ECU 1A is shown in Figure 6. Note that Figure 6 shows the change in the SOC of the auxiliary battery 2B and the change in the lower limit threshold value Th1 and the upper limit threshold value Th2 when the battery internal temperature Tin increases over time. In this example, the lower limit threshold value Th1 and the upper limit threshold value Th2 are set using the above-mentioned [Equation 1] and [Equation 2].

[0061] In the vehicle 100, the powertrain is not started and is in a ready-off state.

[0062] As shown by the dashed line in Figure 6, the internal temperature Tin of the auxiliary battery 2B increases at a constant rate from time t1 to time t2, and the lower limit threshold Th1 and the upper limit threshold Th2 are set to gradually decrease from time t1 to time t3.

[0063] The SOC of the auxiliary battery 2B gradually decreases from time t1 to time t3. This period is a non-charging period in which the auxiliary battery 2B is not charged. Then, at time t3, when the SOC of the auxiliary battery 2B reaches the lower limit threshold Th1, charging of the auxiliary battery 2B begins, and the SOC of the auxiliary battery 2B begins to increase.

[0064] The period from time t3 to time t4 is the charging period for the auxiliary battery 2B.

[0065] Similarly, the period from time t4 to time t5 is a non-charging period for the auxiliary battery 2B.

[0066] In this way, by repeating charging and non-charging periods for the auxiliary battery 2B, it is possible to avoid a state in which the vehicle 100 becomes unable to run due to the SOC dropping too low and making it impossible to restart the system of the vehicle 100, and to prevent deterioration of the auxiliary battery 2B due to the SOC of the auxiliary battery 2B being too high.

[0067] The lower limit threshold Th1 and upper limit threshold Th2, which are used to determine whether to start or stop charging the auxiliary battery 2B, are reset appropriately to appropriate values ​​according to the internal temperature Tin of the auxiliary battery 2B at that time, thereby suppressing deterioration of the auxiliary battery 2B due to changes in the internal temperature Tin and preventing the system of the vehicle 100 from becoming unable to start due to a decrease in output characteristics.

[0068] In addition, in Figure 6, if the internal temperature Tin at time t1 is 30 degrees and the internal temperature Tin at time t2 is 50 degrees, the constant X in the above-mentioned [Equation 1] is set to "1" and the constant Y is set to "80".

[0069] Furthermore, although the example in which the lower limit threshold Th1 and the upper limit threshold Th2 change depending on the internal temperature Tin of the auxiliary battery 2B has been described, the change in the lower limit threshold Th1 and the upper limit threshold Th2 may be limited to a predetermined range. For example, the range of the lower limit threshold Th1 may be set to "20% to 50%," and the range of the upper limit threshold Th2 may be set to "50% to 80%." In this case, even if the lower limit threshold Th1 is calculated to be 10% using the above-described [Equation 1], the lower limit of the range of the lower limit threshold Th1, 20%, may be adopted. Similarly, even if the upper limit threshold Th2 is calculated to be 90% using the above-described [Equation 2], the upper limit of the range of the upper limit threshold Th2, 80%, may be adopted.

[0070] 7 shows an example of processing executed by the central ECU 1A. In step S101, the central ECU 1A determines whether the vehicle 100 is in a ready-on state. If it is determined that the vehicle 100 is in a ready-on state, the central ECU 1A proceeds to step S102, where it performs SOC management of the auxiliary battery 2B in the ready-on state, thereby starting and stopping charging as appropriate.

[0071] After completing the process of step S102, the central ECU 1A executes the process of step S101 again. That is, while the vehicle 100 is in the ready-ON state, the central ECU 1A continuously performs SOC management in the ready-ON state while detecting a state change to ready-OFF.

[0072] If the ready-off state is detected in step S101 (step S101: No), for example, if the vehicle 100 transitions to a parked state, the central ECU 1A proceeds to step S103 and acquires the internal temperature Tin and remaining charge (SOC) of the auxiliary battery 2B.

[0073] Next, in step S104, the central ECU 1A sets a lower limit threshold Th1 and an upper limit threshold Th2 based on the internal temperature Tin. As described above, if a range of values ​​is set for each of the lower limit threshold Th1 and the upper limit threshold Th2, the central ECU 1A determines whether the calculated lower limit threshold Th1 and the upper limit threshold Th2 fall within the predetermined range, and if not, sets the lower limit threshold Th1 and the upper limit threshold Th2 so that they fall within the predetermined range.

[0074] Next, in step S105, the central ECU 1A performs branching processing based on the result of comparison between the SOC of the auxiliary battery 2B and the lower limit threshold value Th1.

[0075] Specifically, if it is determined in step S105 that the SOC of the auxiliary battery 2B is less than the lower threshold value Th1 (step S105: Yes), the central ECU 1A determines in step S106 whether charging of the auxiliary battery 2B has already started.

[0076] If it is determined that charging of the auxiliary battery 2B has not yet started (step S106: No), the central ECU 1A starts charging of the auxiliary battery 2B in step S107. At this time, the central ECU 1A activates each unit to charge the auxiliary battery 2B using the driving battery 2A as described above.

[0077] On the other hand, if it is determined that charging of the auxiliary battery 2B has already started (step S106: Yes), the central ECU 1A maintains the status quo in step S108, that is, continues charging of the auxiliary battery 2B.

[0078] After completing the process of step S107 or step S108, the central ECU 1A returns to the process of step S101 again.

[0079] That is, when the vehicle 100 is in the ready-off state and the SOC of the auxiliary battery 2B is less than the lower limit threshold Th1, the central ECU 1A continues to charge the auxiliary battery 2B.

[0080] In step S105, when it is determined that the SOC of the auxiliary battery 2B is equal to or higher than the lower limit threshold Th1 (step S105: No determination), the central ECU 1A proceeds to branch processing of step S109.

[0081] In the branching process of step S109, the central ECU 1A compares the SOC of the auxiliary battery 2B with the upper limit threshold Th2, and determines whether the SOC is equal to or greater than the upper limit threshold Th2.

[0082] If it is determined that the SOC is equal to or greater than the upper limit threshold Th2 (step S109: Yes), the central ECU 1A stops charging of the auxiliary battery 2B in step S110. If charging of the auxiliary battery 2B has already been stopped, this state is maintained.

[0083] After executing the charging stop process in step S110, the central ECU 1A returns to the process in step S101 again.

[0084] On the other hand, if it is determined in step S109 that the SOC is less than the upper threshold value Th2 (step S109: No), that is, if it is determined that the SOC of the auxiliary battery 2B is between the lower threshold value Th1 and the upper threshold value Th2, the central ECU 1A proceeds to step S108 and performs processing to maintain the current state. At this time, if the auxiliary battery 2B is being charged, i.e., if it is in the charging period, the central ECU 1A continues charging the auxiliary battery 2B. If the auxiliary battery 2B is not being charged, i.e., if it is in the non-charging period, the central ECU 1A continues to stop charging the auxiliary battery 2B.

[0085] After completing the process of step S108, the central ECU 1A returns to the branch process of step S101.

[0086] That is, when the vehicle 100 is in the ready OFF state, the central ECU 1A determines whether the vehicle 100 has transitioned to the ready ON state, and manages the SOC of the auxiliary battery 2B by starting and stopping charging as appropriate so that the SOC of the auxiliary battery 2B does not fall outside the range between the lower threshold value Th1 and the upper threshold value Th2.

[0087] 5. Summary The vehicle 100 described above includes the control unit 1 as a vehicle charge control device, specifically, the central ECU 1A and the high-voltage battery ECU 1B.

[0088] The control unit 1 includes one or more processors (CPU 31) and a storage medium (ROM 32, RAM 33, or storage unit 38) storing a program executed by the one or more processors, the program including one or more instructions that cause the one or more processors to perform at least the following four processes: The four processes are a process of monitoring the remaining charge (SOC) of the auxiliary battery 2B in the ready-off state in which the vehicle 100 cannot run (step S103); a process of starting charging of the auxiliary battery 2B when the remaining charge of the auxiliary battery 2B in the ready-off state falls below the lower threshold value Th1 (step S107); a process of stopping charging of the auxiliary battery 2B when the remaining charge of the auxiliary battery 2B in the ready-off state reaches an upper threshold value Th2 that is greater than the lower threshold value Th1 (step S110); and a process of setting the upper threshold value Th2 and the lower threshold value Th1 according to the temperature (e.g., internal temperature Tin) of the auxiliary battery 2B (step S104). For example, if the auxiliary battery 2B is an in-vehicle battery 2 such as a lithium-ion battery, which deteriorates more rapidly as the internal temperature Tin increases and whose remaining charge decreases, and whose output characteristics deteriorate as the internal temperature Tin decreases and whose remaining charge decreases, by varying the lower limit threshold Th1 and the upper limit threshold Th2 of the SOC management in accordance with the internal temperature Tin, it is possible to both suppress deterioration of the auxiliary battery 2B and prevent deterioration of the output characteristics. Note that, although the example in which the internal temperature Tin of the auxiliary battery 2B is used to vary the lower limit threshold Th1 and the upper limit threshold Th2 is shown, the surface temperature of the auxiliary battery 2B or the temperature of the space in which the auxiliary battery 2B is located may be used instead of the internal temperature Tin.

[0089] The auxiliary battery 2B as the on-board battery 2 mounted on the vehicle 100 may be a lithium-ion battery. If a lithium-ion battery is used as the auxiliary battery 2B, managing the SOC at a high value when the internal temperature Tin is high will further reduce the capacity that has already been reduced to reduce battery costs. For such an auxiliary battery 2B, by varying the lower limit threshold Th1 and the upper limit threshold Th2 in accordance with the internal temperature Tin as described above, it is possible to suitably suppress further reduction in the capacity of the auxiliary battery 2B, which has already been reduced in capacity.

[0090] REFERENCE SIGNS LIST 1 Control unit (vehicle charging control device) 1A Central ECU (vehicle charging control device) 1B High-voltage battery ECU (vehicle charging control device) 2B Auxiliary battery 31 CPU (processor) 32 ROM (storage medium) 33 RAM (storage medium) 38 Storage unit (storage medium) 100 Vehicle Th1 Lower limit threshold Th2 Upper limit threshold Tin Internal temperature (temperature)

Claims

1. A vehicle charging control device comprising: one or more processors; and a storage medium storing a program executed by the one or more processors, the program including one or more instructions that cause the one or more processors to execute the following processes: monitoring the remaining charge of an auxiliary battery in a ready-off state in which the vehicle cannot be driven; starting charging of the auxiliary battery when the remaining charge of the auxiliary battery in the ready-off state falls below a lower threshold; stopping charging of the auxiliary battery when the remaining charge of the auxiliary battery in the ready-off state reaches an upper threshold that is greater than the lower threshold; and setting the upper threshold and the lower threshold according to the temperature of the auxiliary battery.

2. The vehicle charging control device according to claim 1, wherein the auxiliary battery is a lithium ion battery.

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