JP7258450B2 - Vehicle charging controller - Google Patents

Description

The present invention relates to a vehicle charging control device.

2. Description of the Related Art Conventionally, electric vehicles such as hybrid vehicles (HVs) and electric vehicles (EVs) equipped with a motor as a drive source for running are known.

In addition to the high-voltage battery that stores power to drive the motor, the battery system of an electric-powered vehicle includes auxiliary equipment such as a water pump and radiator fan, similar to a conventional vehicle that uses only the engine as a drive source. An auxiliary battery that stores electric power for driving is provided. A DC-DC converter is provided between the high-voltage battery and the auxiliary battery to step down the power output from the high-voltage battery, and the auxiliary battery is charged by the current supplied from the DC-DC converter. be done.

Charging of the auxiliary battery is controlled by an ECU (Electronic Control Unit) including a CPU, memory, and the like. The ECU is connected to a current sensor capable of distinguishing and detecting a charging current for charging the auxiliary battery and a discharging current discharged from the auxiliary battery. In the ECU, the current value of the charging current or the discharging current is obtained from the detection signal of the current sensor, and the amount of charge to or the amount of discharge from the auxiliary battery is calculated by integrating the current value of the charging current or the discharging current. Calculated. Then, the remaining charge (remaining battery charge) of the auxiliary battery is calculated by integrating these electric amounts (charge amount, discharge amount), and SOC (State Of Charge) is calculated.

After the auxiliary battery reaches a fully charged state (SOC 100%), when the auxiliary battery continues to be charged, the water in the electrolyte is electrolyzed, a reactive current flows in the auxiliary battery, and the water Heat is generated by electrolysis. As a measure to prevent this, for example, it has been proposed to stop charging when the auxiliary battery is charged to a certain SOC below full charge (see, for example, Patent Document 1).

JP-A-2003-219570

Due to the detection error of the current sensor, the calculated amount of charge (the amount of current flowing into the battery) may differ from the actual amount of charge. Therefore, a deviation occurs between the calculated SOC value and the actual SOC value, and when this deviation accumulates, the actual SOC value becomes lower than the SOC calculated value by the ECU. In this case, when the charging of the auxiliary battery is stopped because the SOC calculated by the ECU reaches a constant SOC below full charge, the actual SOC of the auxiliary battery is lower than the constant SOC below full charge. , the battery level may continue to be low, accelerating the deterioration of the auxiliary battery.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vehicle charging control device that can achieve both suppression of reactive current and suppression of deterioration of a second battery that is charged with electric power of a first battery.

To achieve the above object, a vehicle charging control device according to the present invention includes a first battery, a DC-DC converter for stepping down the power output from the first battery, and a charging device supplied from the DC-DC converter. A device used in a vehicle equipped with a battery system including a second battery that is charged by current and controlling charging of the second battery, the device comprising: a current value of a charging current and a discharging current from the second battery a current value acquiring means for acquiring a value; a state of charge calculating means for calculating the state of charge of the second battery from the current value acquired by the current value acquiring means; Feedback control means for controlling the DC-DC converter so as to match a predetermined state of less than full charge, and when the duration of control by the feedback control means reaches a predetermined time, the DC-DC converter is controlled. , and refresh charging means for charging the second battery for a predetermined charging time.

According to this configuration, the battery system includes the DC-DC converter that steps down the power output from the first battery, and the second battery is charged by the charging current supplied from the DC-DC converter. .

Each current value of the charging current to the second battery and the discharging current from the second battery is obtained, and the state of charge of the second battery is calculated from each of the obtained current values. Then, the DC-DC converter (charging of the second battery) is feedback-controlled so that the calculated state of charge matches the predetermined state of less than full charge of the second battery. As a result, it is possible to suppress an increase in reactive current due to continued charging of the second battery after the second battery reaches the fully charged state.

Each current value acquired by the current value acquiring means includes an error. Therefore, the calculated value of the state of charge of the second battery may deviate from the actual state of charge. When the deviation accumulates, the actual state of charge of the second battery decreases, and the deterioration of the second battery may be accelerated due to the fact that the state of the actual state of charge continues to be low.

Therefore, when the duration of the feedback control for matching the state of charge calculated by the state of charge calculating means with a predetermined state of less than full charge of the second battery reaches a predetermined time, the second battery is charged (refreshed) for a predetermined charging time. charging) is performed. As a result, it is possible to suppress the continuation of the state where the actual state of charge of the second battery is low, and it is possible to suppress the deterioration of the second battery.

Preferably, the predetermined time period is set such that charging by the refresh charging means occurs before the actual state of charge of the second battery drops to a predetermined low state of charge.

As a result, it is possible to prevent the actual state of charge of the second battery from lowering to the low state of charge, and to further prevent deterioration of the second battery.

It is preferable that the charging time is set so that the actual state of charge of the second battery becomes equal to or higher than a predetermined state by refresh charging.

As a result, the actual state of charge of the second battery can be restored to a predetermined state or higher, the continuation of the low state of the actual state of charge of the second battery can be prevented, and deterioration of the second battery can be further suppressed. can do.

The vehicle charging control device includes charging start means for controlling the DC-DC converter to start charging the second battery when the battery system is started, and current detection means for detecting the current from the start of charging of the second battery. Charge the second battery to a predetermined state of less than full charge or fully charge the second battery based on the amount of time it takes for the charging current to drop to a predetermined value and the amount of time the battery system has been stopped before starting. and determining means for determining whether the second battery is to be charged to a state of less than full charge. When the charging state is set to a predetermined state and the determination means determines that the second battery is to be fully charged, refresh charging is performed so that the actual charging state of the second battery is fully charged. may be set to

According to this configuration, when the state of charge of the second battery is set to the predetermined state of less than full charge in charging at the time of starting the battery system, the state of charge of the second battery is set to less than full charge in refresh charging. The second battery is charged until a predetermined state is reached. As a result, in refresh charging, it is possible to suppress an increase in reactive current due to continued charging of the second battery after the second battery has reached a fully charged state, thereby reducing the amount of current from the first battery for charging the second battery. It is possible to reduce the amount of electric power taken out. As a result, it is possible to improve the electric power consumption or fuel consumption of the electric vehicle equipped with the battery system.
On the other hand, when the charged state of the second battery 3 is fully charged in the charging at the start of the battery system, the second battery is charged until the charged state of the second battery reaches the fully charged state in the refresh charging. Charging takes place. As a result, it is possible to prevent the second battery from being forced into the second battery so that the actual state of charge of the second battery remains low, thereby suppressing deterioration of the second battery.

According to the present invention, it is possible to achieve both suppression of reactive current and suppression of deterioration of the second battery that is charged with the power of the first battery.

1 is a diagram showing the configuration of a battery system mounted on an electric vehicle together with an ECU according to one embodiment of the present invention; FIG. 4 is a flowchart showing the flow of charging control at startup; FIG. 10 is a diagram showing contents of conditions 1-1 to 1-5; FIG. 10 is a diagram showing the contents of conditions 2-1 and 2-2; FIG. 10 is a diagram showing the contents of conditions 3-1 to 3-5; 4 is a flowchart showing the flow of charging completion determination processing; FIG. 10 is a diagram showing the contents of Conditions 4-1 to 4-4; 4 is a flowchart showing the flow of refresh charge control; FIG. 10 is a diagram showing the contents of conditions 5-1 and 5-2; FIG. 10 is a diagram showing the contents of conditions 6-1 to 6-3;

BEST MODE FOR CARRYING OUT THE INVENTION Below, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Battery system>
FIG. 1 is a diagram showing the configuration of a battery system 1 for an electric vehicle.

A battery system 1 is a power supply system mounted on an electric vehicle and includes a high voltage battery 2 , an auxiliary battery 3 and a DC-DC converter 4 . The electric vehicle is not particularly limited as long as it is a vehicle that uses a drive motor as a drive source for running, and may be a hybrid vehicle (HV) equipped with an engine and a generator motor that generates power with the power of the engine. However, it may be an electric vehicle (EV) that is not equipped with an engine.

The high-voltage battery 2 is an assembled battery that is modularized by connecting a plurality of battery cells in series, and outputs DC power of about 200 to 350 V (volt), for example. Each battery cell consists of a secondary battery such as a lithium ion battery. During power running of the drive motor, the DC power output from the high-voltage battery 2 is converted into AC power by the inverter, and the AC power is supplied to the drive motor. On the other hand, during regenerative operation of the drive motor, AC power generated by the drive motor is converted into DC power by the inverter, and the high-voltage battery 2 is charged with the DC power.

Auxiliary battery 3 is a secondary battery used as a power source for load 5 including auxiliary equipment other than the drive motor (for example, water pump, radiator fan, etc.), and is a lead-acid battery that outputs 12V (volt) DC power. consists of

The DC-DC converter 4 is an isolated DC-DC converter with an isolation transformer. The DC-DC converter 4 has a primary side connected to the high voltage battery 2 and a secondary side connected to the auxiliary battery 3 .

In addition, the electric vehicle is equipped with a plurality of ECUs (Electronic Control Units). Each ECU has a microcomputer (microcontroller), and the microcomputer contains, for example, a CPU, nonvolatile memory such as flash memory, and volatile memory such as DRAM (Dynamic Random Access Memory). A plurality of ECUs are connected so as to be capable of two-way communication using CAN (Controller Area Network) communication protocol.

The multiple ECUs include an ECU 6 for controlling the battery system 1 . A current sensor 7 is connected to the ECU 6 to detect the current flowing through the positive terminal of the auxiliary battery 3 . The current sensor 7 employs a sensor capable of distinguishing and detecting a charging current flowing through the positive terminal of the auxiliary battery 3 and a discharging current flowing through the positive terminal of the auxiliary battery 3 . Also, the battery voltage, which is the terminal voltage of the auxiliary battery 3, is input to the ECU 6 .

While the battery system 1 is in operation, the ECU 6 acquires the current value of the charging current or the discharging current from the detection signal of the current sensor 7, and integrates the current value of the charging current or the discharging current to calculate the charge amount or A discharge amount from the auxiliary battery 3 is calculated. Furthermore, the ECU 6 calculates the remaining charge (remaining battery capacity) of the auxiliary battery 3 by integrating the charge amount and the discharge amount, and calculates the SOC (state of charge) indicating the ratio of the remaining charge amount to the charge capacity of the auxiliary battery 3. Charge). The SOC calculated by the ECU 6 is overwritten and stored in the non-volatile memory of the ECU 6 .

<Charging control at startup>
FIG. 2 is a flowchart showing the flow of charge control at startup.

When the battery system 1 is started, the ECU 6 performs start-up charging control. When the ignition switch of the electric vehicle is switched from off to on, the ECU 6 starts the battery system 1 . Further, while the ignition switch is off, the ECU 6 periodically self-starts, acquires the battery voltage of the auxiliary battery 3 (hereinafter simply referred to as "battery voltage"), and detects that the battery voltage reaches a predetermined starting voltage. Determine whether or not it has decreased below. When the battery voltage drops below the starting voltage, the ECU 6 starts the battery system 1 . The battery system 1 stops operating when the relay interposed between the high-voltage battery 2 and the DC-DC converter 4 is turned off, and starts when the relay is switched from off to on. When the battery voltage is higher than the starting voltage, the ECU 6 does not start the battery system 1 and stops its operation.

In the start-up charging control, first, the DC-DC converter 4 is controlled to start charging the auxiliary battery 3 (step S11: start-up charging start). That is, the DC-DC converter 4 is started, the DC power output from the high-voltage battery 2 is stepped down to a predetermined charging voltage, and the stepped-down DC power is supplied from the DC-DC converter 4 to the auxiliary battery 3. As a result, charging of the auxiliary battery 3 is started.

Next, it is determined whether or not all of the conditions 1-1 to 1-5 shown in FIG. 3 are satisfied (step S12). Condition 1-1 is a condition that the battery liquid temperature, which is the temperature of the battery liquid of the auxiliary battery 3, is in the range of A (° C.) or more and B (° C.) or less. A (° C.) and B (° C.) are respectively set to the upper limit value and the lower limit value of the battery fluid temperature range in which the auxiliary battery 3 can be satisfactorily charged. For example, a temperature sensor is provided to detect the ambient temperature of the auxiliary battery 3, and the battery fluid temperature is estimated from the ambient temperature detected by the temperature sensor. Condition 1-2 is a condition that the battery voltage is greater than or equal to C (V). C(V) is set to a value greater than the nominal voltage of auxiliary battery 3 . Condition 1-3 is a condition that the DC-DC converter 4 is operating. Condition 1-4 is a condition that the operation mode of battery system 1 is a charging mode in which auxiliary battery 3 is charged. Condition 1-5 is a condition that the system stop time, which is the time during which the battery system 1 was stopped before starting (the time from the stop of the battery system 1 to the start of the battery system 1), is D (sec) or less. The system stop time is equal to the time the ignition switch is off. D (sec) is set to be longer than the time required for the SOC of auxiliary battery 3 to decrease to a value that promotes deterioration of auxiliary battery 3 due to dark current while the ignition switch is turned off.

If all of the conditions 1-1 to 1-5 are satisfied (YES in step S12), the SOC estimation condition determination flag provided in the volatile memory of the ECU 6 is set to 1 (step S13). If any one of the conditions 1-1 to 1-5 is not satisfied (NO in step S12), the SOC estimation condition determination flag is reset to 0 (step S14). The SOC estimation condition determination flag is reset to 0 when starting charging control is started.

Thereafter, it is determined whether or not condition 2-1 shown in FIG. 4 is satisfied (step S15). Condition 2-1 is a condition that the charging current (hereinafter referred to as "battery current") supplied to auxiliary battery 3 is equal to or less than E (A).

If the condition 2-1 is not satisfied (NO in step S15), then it is determined whether or not the condition 2-2 shown in FIG. 4 is satisfied (step S16). Condition 2-2 is a condition that the battery current is F(A) or less. F(A) is a value smaller than E(A), and is set to a value corresponding to a reactive current flowing through auxiliary battery 3 when auxiliary battery 3 is in a fully charged state (actual SOC 100%). there is

If the condition 2-1 is established (YES in step S15), that is, if the battery current is equal to or less than E (A), the count value of the first counter provided in the volatile memory of the ECU 6 is counted. up (step S17). The first counter is a counter for measuring the time during which a battery current equal to or less than E(A) is supplied to the auxiliary battery 3, and consists of an increment counter that counts up in response to the clock pulse output from the oscillator. The count value of the first counter is reset to 0 when starting charge control is started.

If the condition 2-2 is established (YES in step S16), that is, if the battery current is F(A) or less, the count value of the second counter provided in the volatile memory of the ECU 6 is counted. It is incremented (+1) (step S18). The second counter is a counter for measuring the time during which a battery current of F(A) or less is supplied to the auxiliary battery 3, and consists of an increment counter that counts up in response to the clock pulse output from the oscillator. The count value of the second counter is reset to 0 when starting charging control is started.

Incidentally, if the condition 2-2 is established, the condition 2-1 is judged not to be established. Therefore, condition 2-1 can be rephrased as a condition that the battery voltage is greater than F(A) and equal to or less than E(A).

If neither condition 2-1 nor 2-2 is satisfied (NO in step S16), the first counter and the second counter are not counted up.

After that, it is determined whether or not all of the conditions 3-1 to 3 shown in FIG. 5 or the condition 3-4 is established (step S19). Condition 3-1 is a condition that 1 is set in the SOC estimation condition determination flag. Condition 3-2 is a condition that the battery current is equal to or less than E (A). Condition 3-3 is a condition that the operating time of the DC-DC converter 4 is G (sec) or more and H (sec) or less. G (sec) is set to the time required for the operation of the DC-DC converter 4 to stabilize. H (sec) is the period from the start of charging of the auxiliary battery 3 until the battery current (charging current) is equal to or less than E (A) when the amount of decrease in the SOC of the auxiliary battery 3 while the battery system 1 is stopped is normal. It is set to the time it takes to fall. Condition 3-4 is a condition that the state of the SOC estimation determination flag is 1 one control cycle before. The SOC estimation determination flag is provided in the volatile memory of the ECU 6, and is reset to 0 at the start of the start-time charging control.

If at least one of the conditions 3-1 to 3-3 is not satisfied and the condition 3-4 is not satisfied (NO in step S19), it is determined whether the condition 3-5 shown in FIG. 5 is satisfied. is determined (step S20). Condition 3-5 is a condition that the estimated SOC is I (%) or less. I (%) is set to a value that accelerates the deterioration of auxiliary battery 3 when the SOC of auxiliary battery 3 falls below that value. While the battery system 1 is in operation, the SOC of the auxiliary battery 3 is calculated by the ECU 6 and the calculated SOC is overwritten and stored in the non-volatile memory of the ECU 6 . On the other hand, while the battery system 1 is stopped, the ECU 6 does not calculate the SOC, and the SOC stored in the non-volatile memory of the ECU 6 is not updated. The longer the stop time of the battery system 1, the lower the SOC of the auxiliary battery 3 due to the dark current flowing from the auxiliary battery 3 to the load 5 while the battery system 1 is stopped. Therefore, when the battery system 1 is started, the SOC stored in the nonvolatile memory of the ECU 6 shifts to a value larger than the actual value of the SOC of the auxiliary battery 3 (actual SOC). Therefore, the ECU 6 subtracts a correction value according to the stop time of the battery system 1 from the SOC stored in the nonvolatile memory when the battery system 1 is started, and calculates the subtracted value as the trial SOC of the auxiliary battery 3. During the charging control at the time of starting, the trial calculation SOC is updated by integrating the charge amount of the auxiliary battery 3 .

If all of the conditions 3-1 to 3-3 are satisfied, or if the condition 3-4 is satisfied (YES in step S19), the SOC estimation determination flag is set to 1 (step S21).

If condition 3-5 is established (YES in step S20), the SOC estimation determination flag is reset to 0 (step S22).

If at least one of the conditions 3-1 to 3-3 is not satisfied, the condition 3-4 is not satisfied, and the condition 3-5 is not satisfied (NO in step S20), the SOC one control cycle before The state of the estimation determination flag is maintained as it is (step S23).

In the starting charging control, the processing from step S12 to steps S21, S22, and S23 is repeated for each control cycle. Then, when a charge completion determination flag provided in the volatile memory of the ECU 6 is set to 1 by a charge completion determination process, which will be described later, the starting charge control is terminated accordingly.

<Charging completion determination process>
FIG. 6 is a flowchart showing the flow of charge completion determination processing.

In parallel with the start-up charging control, the ECU 6 performs charging completion determination processing.

In the charging completion determination process, it is determined whether or not both conditions 4-1 and 4-3 or both conditions 4-2 and 4-4 shown in FIG. 7 are satisfied (step S31). Condition 4-1 is a condition that the time corresponding to the count value of the first counter is J (sec) or longer. J (sec) is set to a time shorter than the time required for the battery current to drop from E (A) to F (A). Condition 4-2 is a condition that the time corresponding to the count value of the second counter is K (sec) or more. K (sec) is set to a time at which the actual SOC of auxiliary battery 3 becomes 100% with certainty by supplying battery current of F (A) or less to auxiliary battery 3 . Condition 4-3 is a condition that the state of the SOC estimation determination flag is 1. Condition 4-4 is a condition that the state of the SOC estimation determination flag is zero.

If both conditions 4-1 and 4-3 are satisfied, or if both conditions 4-2 and 4-4 are satisfied (YES in step S31), that is, the state of the SOC estimation determination flag is 1, and the battery When J (sec) or more has passed since the current dropped below E (A), or when the state of the SOC estimation determination flag is 0 and the battery current drops below F (A) If a time period of K (sec) or more has elapsed since then, 1 is set to the charging completion determination flag provided in the volatile memory of the ECU 6 (step S32). The charge completion determination flag is reset to 0 at the start of the charge completion determination process. When the charging completion determination flag is set to 1, the starting charging control is terminated at that point.

On the other hand, the state of the SOC estimation determination flag is 1, and the battery current has not decreased to E (A) or less, or the time since the battery current has decreased to E (A) or less is J (sec). If it is less than that, the charging completion determination flag is kept reset to 0 (step S33). Also, if the state of the SOC estimation determination flag is 0 and the battery current has not dropped below F (A), or the time since the battery current dropped below F (A) is K (sec). If it is less than that, the charging completion determination flag is kept reset to 0 (step S33). While the state of the charging completion determination flag is 0, the starting charging control is not terminated, and it is repeatedly determined whether both the conditions 4-1 and 4-3 or the conditions 4-2 and 4-4 are satisfied. (step S31).

When the charging completion determination flag is set to 1, it is determined whether or not the state of the SOC estimation determination flag is 1 (step S34). When the state of the SOC estimation determination flag is 1 (YES in step S34), the SOC of the auxiliary battery 3 is set to 98% (step S35), and the charging completion determination process is terminated. On the other hand, when the state of the SOC estimation determination flag is 0 (NO in step S34), the SOC of the auxiliary battery 3 is set to 100% (step S36), and the charging completion determination process is terminated.

<effect>
In the starting charging control, for example, after all of conditions 1-1 to 1-5 are satisfied and the SOC estimation condition determination flag is set to 1, the operation time of the DC-DC converter 4 is G (sec) or more and H ( sec) When the battery current drops below E (A) within the following range, the first counter starts counting up, and all conditions 3-1 to 3-3 are met to estimate the SOC. 1 is set to the determination flag. When the SOC estimation determination flag is set to 1, the condition 3-4 is established thereafter, so that the state in which the SOC estimation determination flag is set to 1 is maintained.

If the estimated SOC at the start of the start-up charging control is equal to or less than I (%), the condition 1-5 is satisfied, so the SOC estimation determination flag remains reset to 0. Thereafter, charging of the auxiliary battery 3 progresses, and even if the estimated SOC exceeds I (%) and the condition 3-5 is no longer satisfied, the SOC estimation determination flag remains unchanged unless all of the conditions 3-1 to 3-3 are satisfied. Since the state is maintained at the state of the SOC estimation determination flag one control cycle before, the state in which the SOC estimation determination flag is reset to 0 continues. When all of the conditions 3-1 to 3-3 are satisfied, the SOC estimation determination flag is set to 1, and thereafter, the SOC estimation determination flag is set to 1 due to the establishment of the condition 3-4. maintained.

In the charging completion determination process, when the SOC estimation determination flag is set to 1, the time corresponding to the count value of the first counter, that is, the time after the battery current has dropped below E (A) is J (sec). ) is reached. Then, when the time after the battery current drops below E (A) reaches J (sec), 1 is set to the charge completion determination flag. When the charging completion determination flag is set to 1, the starting charging control is terminated, and the charging of the auxiliary battery 3 (starting charging) is terminated. J (sec) is set to a time shorter than the time required for the battery current to drop from E (A) to F (A). As a result, when the charging of the auxiliary battery 3 is completed, the battery current has not decreased to F(A), and the auxiliary battery 3 has not reached the fully charged state and is in a predetermined state of less than full charge. . Therefore, it is possible to suppress an increase in reactive current due to continued charging of the auxiliary battery 3 after the auxiliary battery 3 reaches a fully charged state, and the power from the high voltage battery 2 for charging the auxiliary battery 3 can be suppressed. can be reduced. As a result, it is possible to improve the electric power consumption or fuel consumption of the electric vehicle in which the battery system 1 is mounted.

In this case, the SOC of the auxiliary battery 3 is set to 98%. This allows the calculated value of the auxiliary battery 3 to substantially match the actual SOC.

On the other hand, in the start-up charging control, if the system stop time exceeds D (sec), the condition 1-5 is not established, so the SOC estimation condition determination flag is not set to 1, and the SOC estimation condition determination flag is set to 0. left as is. In this case, the condition 3-1 is not satisfied, and the SOC estimation determination flag one control period before is 0, so the condition 3-4 is also not satisfied. Therefore, when the estimated SOC is equal to or less than I (%), the condition 3-5 is satisfied, the SOC estimation determination flag is kept reset to 0, and the estimated SOC is greater than I (%). Also, since the state of the SOC estimation determination flag is maintained at the state of the SOC estimation determination flag one control cycle earlier, the state in which the SOC estimation determination flag is reset to 0 continues.

Further, even if all of the conditions 1-1 to 1-5 are established and the SOC estimation condition determination flag is set to 1, the battery If the current does not fall below E (A), condition 3-2 is not satisfied, so the SOC estimation determination flag is not set to 1, and if the estimated SOC is below I (%), Even if the condition 3-5 is established, the SOC estimation determination flag is kept reset to 0, and the estimated SOC is greater than I (%), the state of the SOC estimation determination flag is the SOC estimation one control cycle before. Since the state of the determination flag is maintained, the state in which the SOC estimation determination flag is reset to 0 continues.

In the charge completion determination process, when the SOC estimation determination flag is set to 0, the time corresponding to the count value of the second counter, that is, the time after the battery current has dropped below F (A) is K (sec). ) is reached. Then, when the time after the battery current drops below F (A) reaches K (sec), 1 is set to the charge completion determination flag. When the charging completion determination flag is set to 1, the starting charging control is terminated, and the charging of the auxiliary battery 3 (starting charging) is terminated. F(A) is set to a value corresponding to a reactive current flowing through auxiliary battery 3 when auxiliary battery 3 is in a fully charged state. Therefore, auxiliary battery 3 is push-charged by continuing charging of auxiliary battery 3 until the elapsed time from when the battery current drops to F (A) or less reaches K (sec). As a result, it is possible to prevent the actual SOC of the auxiliary battery 3 from continuing to be low, thereby suppressing deterioration of the auxiliary battery 3 .

<Refresh charge control>
FIG. 8 is a flowchart showing the flow of refresh charge control.

When the battery system 1 is in operation and the operation mode of the battery system 1 is a mode other than the charge mode, that is, the fuel economy mode, the ECU 6 performs refresh charge control. In the fuel efficiency mode, the ECU 6 feedback-controls charging of the auxiliary battery 3 (operation of the DC-DC converter 4) so that the SOC of the auxiliary battery 3 is maintained at 98%.

In refresh charging control, it is determined whether or not both conditions 5-1 and 5-2 shown in FIG. 9 are satisfied (step S41). Condition 5-1 is a condition that the duration of the fuel consumption mode is L (sec) or more. L (sec) is set to a time during which the actual SOC of auxiliary battery 3 does not drop to a predetermined low SOC (97%, for example) even if the fuel consumption mode is continued. Condition 5-2 is that the state of the refresh completion flag provided in the volatile memory of the ECU 6 is "1". At the end of the start-up charge control, 1 is set to the refresh completion flag.

The process does not proceed until both conditions 5-1 and 5-2 are satisfied (NO in step S41), and when both conditions 5-1 and 5-2 are satisfied (YES in step S41), 1 is set to the refresh start flag provided in the ECU 6, and the refresh start flag provided in the volatile memory of the ECU 6 is reset to 0 (step S42).

Further, the DC-DC converter 4 is controlled to start refresh charging of the auxiliary battery 3 (step S43: start of refresh charging).

Then, the count value of the third counter provided in the volatile memory of the ECU 6 is incremented (+1) (step S43). The third counter is a counter that measures the time during which the auxiliary battery 3 is refresh-charged (hereinafter referred to as "refresh charge time"), and counts up in response to the clock pulse output from the oscillator. Consists of an increment counter. The count value of the third counter is reset to 0 at the start of refresh charge control.

Thereafter, it is determined whether both conditions 6-1 and 6-2 shown in FIG. 10 are satisfied, or whether condition 6-1 is not satisfied and condition 6-3 is satisfied (step S45). Condition 6-1 is a condition that the state of the SOC estimation determination flag is 1. Condition 6-2 is a condition that the refresh charge time is M (sec) or longer. M (sec) is set to a time sufficient for auxiliary battery 3 to reach a predetermined state of less than full charge (for example, SOC of 98%) by refresh charging. Condition 6-3 is a condition that the refresh charging time is N (sec) or more. N (sec) is a value larger than M (sec), and is set to a time sufficient for auxiliary battery 3 to be fully charged by refresh charging.

Until both conditions 6-1 and 6-2 are satisfied, or condition 6-1 is not satisfied and condition 6-3 is satisfied, the refresh charging of the auxiliary battery 3 is continued, and the third counter Counting up continues (step S44).

If both conditions 6-1 and 6-2 are satisfied (YES in step S45), that is, if the state of the SOC estimation determination flag is 1 and the refresh charging time has reached M (sec), the refresh charging ends. Then (step S46), the refresh start flag is reset to 0, and the refresh end flag is set to 1 (step S47). At this time, since the state of the SOC estimation determination flag is 1, the determination as to whether or not the state of the SOC estimation determination flag is 1 is affirmative (YES in step S48), and the SOC of the auxiliary battery 3 is 98%. (step S49), the refresh charging control is terminated.

If the condition 6-1 is not satisfied and the condition 6-2 is satisfied (YES in step S45), that is, the state of the SOC estimation determination flag is 0 and the refresh charging time reaches N (sec). If so, refresh charging is terminated (step S46), the refresh start flag is reset to 0, and the refresh end flag is set to 1 (step S47). At this time, since the state of the SOC estimation determination flag is 0, the judgment as to whether or not the state of the SOC estimation determination flag is 1 is denied (NO in step S48), and the SOC of the auxiliary battery 3 is 100%. (step S49), the refresh charging control is terminated.

<Action>
In the fuel efficiency mode, charging of the auxiliary battery 3 is feedback-controlled so that the SOC of the auxiliary battery 3 is maintained at 98%. When the duration of the fuel economy mode reaches L (sec) or longer, the auxiliary battery 3 is refresh-charged. Refresh charging can prevent the actual SOC of auxiliary battery 3 from continuing to be low, and can prevent deterioration of auxiliary battery 3 .

In the starting charging control, when the SOC estimation determination flag is set to 1 and the time after the battery current drops below E (A) reaches J (sec), the starting charging of the auxiliary battery 3 is started. is terminated, that is, when the charging of the auxiliary battery 3 is terminated in a predetermined state of less than full charge, the refresh charging control is executed at the time when the refresh charging time reaches M (sec), which is shorter than N (sec). , the refresh charging of the auxiliary battery 3 is terminated. Therefore, it is possible to suppress an increase in reactive current due to continuation of charging of the auxiliary battery 3 after the auxiliary battery 3 reaches a fully charged state. It is possible to reduce the amount of electric power taken out. As a result, it is possible to improve the electric power consumption or fuel consumption of the electric vehicle in which the battery system 1 is mounted.

In this case, the SOC of the auxiliary battery 3 is set to 98%. This allows the calculated value of the auxiliary battery 3 to substantially match the actual SOC.

On the other hand, in the starting charging control, the auxiliary battery 3 is started when the time after the SOC estimation determination flag is set to 0 and the battery current drops below F (A) reaches K (sec). When the time charging is terminated, that is, when the charging of the auxiliary battery 3 is terminated in a fully charged state, the refresh charging control determines that the refresh charging time is a time sufficient to charge the auxiliary battery 3 to a fully charged state. When the time reaches N (sec), refresh charging of the auxiliary battery 3 is terminated. As a result, it is possible to suppress the fact that the auxiliary battery 3 is forced to be pushed and the state of the actual SOC of the auxiliary battery 3 is low, and the deterioration of the auxiliary battery 3 can be suppressed.

In this case, the SOC of the auxiliary battery 3 is set to 100%. This allows the calculated value of the auxiliary battery 3 to substantially match the actual SOC.

<Modification>
Although one embodiment of the present invention has been described above, the present invention can also be implemented in other forms.

For example, E (A), F (A), J (sec), K (sec), M (sec) and N (sec) may be variably set according to the battery liquid temperature of the auxiliary battery 3. good. E(A) and F(A) may be set, for example, to monotonically increase (non-monotonically decrease) as the battery fluid temperature increases. Also, J (sec), K (sec), M (sec) and N (sec) may be set, for example, to monotonically decrease as the battery fluid temperature increases. As a result, E (A), F (A), J (sec), K (sec), M (sec) and N (sec) can be set to values corresponding to the battery fluid temperature. Regardless, the auxiliary battery 3 can be satisfactorily charged to a predetermined state of less than full charge or to a fully charged state.

In the above-described embodiment, the state in which the SOC of the auxiliary battery 3 is 98% was taken up as an example of the predetermined state in which the auxiliary battery 3 is less than fully charged. may be in a state where the SOC takes a value other than 98%, such as a state where the SOC is 97%, as long as the SOC of the auxiliary battery 3 is less than 100%.

In addition, various design changes can be made to the above configuration within the scope of the matters described in the claims.

1: Battery system 2: High voltage battery (first battery)
3: Auxiliary battery (second battery)
4: DC-DC converter 6: ECU (vehicle charging control device, current value acquisition means, state of charge calculation means, feedback control means, refresh charging means)

Claims (3)

A vehicle equipped with a battery system that includes a first battery, a DC-DC converter that steps down the power output from the first battery, and a second battery that is charged with a charging current supplied from the DC-DC converter. A device for controlling charging of the second battery,
a current value acquiring means for acquiring the current value of the charging current and the current value of the discharging current from the second battery;
state of charge calculation means for calculating the state of charge of the second battery from the current value acquired by the current value acquisition means;
feedback control means for controlling the DC-DC converter such that the state of charge calculated by the state of charge calculation means matches a predetermined state of less than full charge of the second battery;
refresh charging means for controlling the DC-DC converter to charge the second battery for a predetermined charging time when the duration of control by the feedback control means reaches a predetermined time. charge control device. 2. The vehicle according to claim 1, wherein said predetermined time is set so that said second battery is charged by said refresh charging means before the actual state of charge of said second battery drops to a predetermined low state of charge. charging controller. 3. The charging control device for a vehicle according to claim 1, wherein said charging time is set so that the actual charging state of said second battery is equal to or higher than said predetermined state by charging by said refresh charging means.

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