JP7593232B2 - Vehicle and vehicle control method - Google Patents

Description

This disclosure relates to a vehicle and a vehicle control method, and more specifically to a control technique for a vehicle equipped with a battery pack.

JP 2010-23636 A (Patent Document 1) discloses a vehicle with multiple battery packs mounted in different positions.

JP 2010-23636 A

In recent years, there has been a trend for battery packs to become larger in vehicles such as electric vehicles or plug-in hybrid vehicles in order to extend the distance that can be traveled using the power stored in the battery pack (the so-called EV distance). On the other hand, the vehicle space in which battery packs can be installed is limited. Therefore, instead of a large battery pack, it is possible to use two smaller battery packs. The two battery packs are connected in series and installed in different positions. For example, one battery pack can be placed outside the vehicle cabin (under the floor, etc.) and the other battery pack can be placed inside the vehicle cabin (in the trunk, etc.).

In a vehicle equipped with two battery packs as described above, since the battery packs are used in different environments, it is possible that one battery pack will deteriorate earlier than the other. Generally, deterioration of a battery pack causes a decrease in the full charge capacity and a decrease in output performance (maximum dischargeable power). In particular, when two battery packs are connected in series, a decrease in the output performance of one battery pack will cause a decrease in the output performance of the two battery packs as a whole, even if the output performance of the other battery pack has not decreased. The same is true for the full charge capacity. Therefore, it is desirable to suppress the deterioration of the two battery packs as a whole as much as possible.

This disclosure has been made to solve the above problems, and the purpose of this disclosure is to suppress the overall deterioration of two battery packs in a vehicle equipped with two battery packs connected in series.

(1) A vehicle according to an aspect of the present disclosure includes a first battery pack, a second battery pack disposed in a position different from the first battery pack and connected in series to the first battery pack, a first temperature adjustment device configured to adjust the temperature of the first battery pack, a second temperature adjustment device configured to adjust the temperature of the second battery pack, and a control device that controls the first and second temperature adjustment devices. When a temperature difference between the temperature of the first battery pack and the temperature of the second battery pack exceeds a reference amount, the control device controls at least one of the first and second temperature adjustment devices so that the temperature difference becomes less than the reference amount.

(2) The first battery pack is located outside the vehicle cabin. The second battery pack is located inside the vehicle cabin.

In configurations such as those in (1) and (2) above, in which the first battery pack is disposed outside the vehicle cabin and the second battery pack is disposed inside the vehicle cabin, the temperature difference between the first battery pack and the second battery pack is likely to become large. Therefore, when the temperature difference exceeds a reference amount, at least one of the first and second temperature adjustment devices is controlled to adjust the temperature difference to less than the reference amount. This reduces the difference in the degree of deterioration depending on the temperature between the first battery pack and the second battery pack. Therefore, according to the configurations in (1) and (2) above, the overall deterioration of the two battery packs can be suppressed.

(3) Each of the first and second temperature adjustment devices includes a cooling device that cools a corresponding one of the first and second battery packs. When the temperature difference exceeds a reference amount, the control device controls the cooling device that corresponds to the hotter battery pack so that the hotter battery pack of the first and second battery packs is cooled.

(4) When the temperature difference exceeds a reference amount, the control device controls the corresponding cooling device so that the high-temperature battery pack is cooled even if the temperature of the high-temperature battery pack is within a temperature range lower than a predetermined high-temperature range.

In the above configurations (3) and (4), when the temperature difference exceeds a reference amount, the high-temperature battery pack is cooled, even if the temperature of the high-temperature battery pack is within a temperature range lower than the predetermined high-temperature range. This makes it possible to suppress the overall deterioration of the two battery packs.

(5) Each of the first and second temperature adjustment devices includes a heating device that heats a corresponding one of the first and second battery packs. When the temperature difference exceeds a reference amount, the control device controls the heating device that corresponds to the battery pack with a lower temperature such that the battery pack with a lower temperature of the first and second battery packs is heated.

(6) When the temperature difference exceeds a reference amount, the control device controls the corresponding heating device so that the low-temperature battery pack is heated even if the temperature of the low-temperature battery pack is within a temperature range higher than a predetermined low-temperature range.

In the above configurations (5) and (6), when the temperature difference exceeds a reference amount, the low-temperature battery pack is heated even if the temperature of the low-temperature battery pack is within a high-temperature range that is lower than a predetermined low-temperature range. This makes it possible to suppress the overall deterioration of the two battery packs.

(7) Each of the first and second temperature adjustment devices includes a cooling device that cools the corresponding battery pack of the first and second battery packs, and a heating device that heats the corresponding battery pack of the first and second battery packs. When the temperature difference exceeds a reference amount, the control device calculates a cooling power amount, which is the power consumption when cooling the high-temperature battery pack so that the temperature difference becomes less than the reference amount, and a heating power amount, which is the power consumption when heating the low-temperature battery pack so that the temperature difference becomes less than the reference amount. When the cooling power amount is smaller than the heating power amount, the control device controls the cooling device corresponding to the high-temperature battery pack so that the high-temperature battery pack is cooled, and when the heating power amount is smaller than the cooling power amount, the control device controls the heating device corresponding to the low-temperature battery pack so that the low-temperature battery pack is heated.

(8) When the temperature difference between the high-temperature battery pack and the low-temperature battery pack exceeds a reference amount even if the temperature of each of them is lower than a predetermined high-temperature region and is within a temperature region higher than a predetermined low-temperature region, the control device controls the cooling device corresponding to the high-temperature battery pack so that the high-temperature battery pack is cooled when the amount of cooling power is smaller than the amount of heating power, and controls the heating device corresponding to the low-temperature battery pack so that the low-temperature battery pack is heated when the amount of heating power is smaller than the amount of cooling power.

In the above configurations (7) and (8), when the temperature difference exceeds a reference amount, for example, even if the temperature of each of the high-temperature battery pack and the low-temperature battery pack is lower than a predetermined high-temperature region and is in a temperature region higher than a predetermined low-temperature region, the high-temperature battery pack is cooled or the low-temperature battery pack is heated. This makes it possible to suppress deterioration of the two battery packs as a whole. In addition, of the cooling of the high-temperature battery pack and the heating of the low-temperature battery pack, the one that consumes less power is executed. As a result, even after the temperature of the battery packs is adjusted, more power remains in the battery packs, so the distance that the vehicle can travel (EV distance) can be secured.

(9) In a vehicle control method according to another aspect of the present disclosure, the vehicle includes a first battery pack, a second battery pack disposed at a position different from the first battery pack and connected in series to the first battery pack, a first temperature adjustment device configured to adjust the temperature of the first battery pack, and a second temperature adjustment device configured to adjust the temperature of the second battery pack. The control method includes the steps of acquiring a temperature difference between the temperatures of the first battery pack and the second battery pack, and, if the temperature difference exceeds a reference amount, controlling at least one of the first and second temperature adjustment devices so that the temperature difference is less than the reference amount.

According to the method (9) above, as with the configuration (1) above, the overall deterioration of the two battery packs can be suppressed.

According to the present disclosure, in a vehicle equipped with two battery packs, the overall deterioration of the two battery packs can be suppressed.

1 is a diagram illustrating a schematic overall configuration of a vehicle according to a first embodiment of the present disclosure. FIG. 2 is a circuit block diagram showing the configuration of the vehicle in more detail. FIG. 2 is a diagram for explaining an overview of battery temperature adjustment control in the first embodiment. 4 is a flowchart showing a processing procedure of battery temperature adjustment control in the first embodiment. FIG. 11 is a diagram for explaining an overview of battery temperature adjustment control in embodiment 2. 13 is a flowchart showing a processing procedure of battery temperature adjustment control in the second embodiment. FIG. 13 is a diagram for explaining an overview of battery temperature adjustment control in embodiment 3. 5 is a time chart for explaining a method for calculating the amount of cooling power and the amount of heating power. 13 is a flowchart showing a processing procedure of battery temperature adjustment control in the third embodiment.

The following describes in detail the embodiments of the present disclosure with reference to the drawings. Note that the same or corresponding parts in the drawings are given the same reference numerals and their description will not be repeated.

[First embodiment]
1 is a diagram illustrating a schematic overall configuration of a vehicle according to a first embodiment of the present disclosure. Vehicle 1 is a vehicle equipped with a battery pack, and in this example, is an electric vehicle (EV). Vehicle 1 may be a hybrid vehicle (HV), a plug-in hybrid vehicle (PHV), or a fuel cell vehicle (FCV).

The vehicle 1 includes a first battery pack 11 and a second battery pack 12. In this embodiment, the first battery pack 11 is disposed outside the vehicle compartment (under the floor in this example). The second battery pack 12 is disposed inside the vehicle compartment (in the trunk in this example).

However, the arrangement of the first battery pack 11 and the second battery pack 12 is not limited to the combination of the outside and inside of the vehicle cabin. The first battery pack 11 and the second battery pack 12 only need to be mounted in different positions, and can be arranged in various positions, for example, as described in Patent Document 1.

FIG. 2 is a circuit block diagram showing the configuration of the vehicle 1 in more detail. In addition to the first battery pack 11 and the second battery pack 12, the vehicle 1 includes battery temperature sensors 21, 22, a current sensor 23, a system main relay (SMR) 31, a power control unit (PCU) 32, a motor generator (MG) 33, a DC/DC converter 34, electric heaters 41, 42, cooling fans 51, 52, an inlet 61, an AC/DC converter 62, a charge relay (CHR) 63, a data communication module (DCM) 71, a global pointing system (GPS) receiver 72, an outside air temperature sensor 81, an interior temperature sensor 82, and an electronic control unit (ECU) 9.

Each of the first battery pack 11 and the second battery pack 12 is a battery pack including a plurality of cells (not shown). Each cell is a secondary battery such as a lithium-ion battery or a nickel-metal hydride battery. The first battery pack 11 and the second battery pack 12 are connected in series. Hereinafter, the first battery pack 11 and the second battery pack 12 are also collectively referred to as the "battery". The battery stores power for driving the motor generator 33 and supplies power to the motor generator 33 through the PCU 32. The battery is also charged by power output from the AC/DC converter 62 during plug-in charging of the vehicle 1. Furthermore, the battery is charged by receiving generated power through the PCU 32 when the motor generator 33 generates power (such as during regenerative power generation).

The battery temperature sensor 21 detects the temperature Tb1 of the first battery pack 11. The battery temperature sensor 22 detects the temperature Tb2 of the second battery pack 12. The current sensor 23 detects the current I input to and output from the battery. Each sensor outputs the detection result to the ECU 9. Although not shown, the battery is also provided with a voltage sensor that detects the voltage of each cell.

The SMR 31 is electrically connected to the battery (both ends of the first battery pack 11 and the second battery pack 12 connected in series). The SMR 31 is opened and closed according to a control command from the ECU 9. This electrically connects the battery to the power line or electrically disconnects it from the power line.

The PCU 32 includes an inverter and a converter (neither shown). The PCU 32 performs bidirectional power conversion between the battery and the motor generator 33 in accordance with control commands from the ECU 9.

The motor generator 33 is, for example, a three-phase AC rotating electric machine with a permanent magnet embedded in a rotor (not shown). The motor generator 33 rotates the drive shaft using power supplied from a battery. The motor generator 33 can also generate power through regenerative braking. The AC power generated by the motor generator 33 is converted to DC power by the PCU 32 and charged into the battery.

The DC/DC converter 34 is a one-way DC/DC converter electrically connected between the battery and the load (specifically, the electric heaters 41, 42 and the cooling fans 51, 52). The DC/DC converter 34 reduces the voltage of the power transmitted from the battery in accordance with a control command from the ECU 9, and supplies the reduced voltage to the load.

The electric heater 41 is, for example, a PTC (Positive Temperature Coefficient) heater, and is configured to heat the first battery pack 11 in accordance with a control command from the ECU 9. The electric heater 42 is, for example, a PTC heater, and is configured to heat the second battery pack 12 in accordance with a control command from the ECU 9.

The cooling fan 51 is configured to cool the first battery pack 11 in accordance with a control command from the ECU 9. The cooling fan 52 is configured to cool the second battery pack 12 in accordance with a control command from the ECU 9.

In this manner, in this embodiment, the first battery pack 11 and the second battery pack 12 can be heated and cooled separately. Note that the electric heaters 41, 42 are an example of a "heating device" according to the present disclosure. The cooling fans 51, 52 are an example of a "cooling device" according to the present disclosure. The "cooling device" according to the present disclosure is not limited to an air-cooled cooling fan, and may be, for example, a cooling mechanism that cools the battery using a cooling liquid (refrigerant).

The inlet 61 is configured to allow insertion of a charging connector provided at the end of a charging cable (not shown). The vehicle 1 is electrically connected to a charger installed outside the vehicle 1 via the charging cable.

The AC/DC converter 62 is electrically connected between the inlet 61 and the charging relay 63. The AC/DC converter 62 converts the AC power supplied from the charger via the inlet 61 into DC power, and outputs the DC power to the charging relay 63. The AC/DC converter 62 also converts the DC power supplied from the battery (or the PCU 32) via the charging relay 63 into AC power, and outputs the AC power to the inlet 61.

The charging relay 63 is electrically connected to the power line connecting the AC/DC converter 62 and the battery. The charging relay 63 is opened/closed in response to a control command from the ECU 9.

The DCM 71 is configured to enable two-way wireless communication with an external server (not shown). Through communication using the DCM 71, the ECU 9 can obtain various information (such as weather forecasts and information related to changes in outside temperature) for the area in which the vehicle 1 is traveling.

The GPS receiver 72 is provided in the navigation system and identifies the position of the vehicle 1 based on radio waves from artificial satellites. The ECU 90 can obtain the planned driving route from the current location of the vehicle 1 to the destination based on the position information of the vehicle 1 identified by the GPS receiver 72 and road map data stored in a memory (not shown).

The outside air temperature sensor 81 detects the outside air temperature Ta of the vehicle 1. The interior air temperature sensor 82 detects the interior air temperature Tc. Each sensor outputs its detection result to the ECU 9.

The ECU 9 includes a processor such as a CPU (Central Processing Unit), memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and input/output ports (none of which are shown) through which various signals are input and output. The ECU 9 controls the devices included in the vehicle 1 based on the input of signals from each sensor and the maps and programs stored in the memory. The ECU 9 may be composed of multiple ECUs divided according to function.

In the vehicle 1 configured as described above, the first battery pack 11 and the second battery pack 12 are used in different environments. The first battery pack 11, which is disposed outside the vehicle cabin, is more susceptible to the outside air temperature Ta than the second battery pack 12. In contrast, the second battery pack 12, which is disposed inside the vehicle cabin, is more susceptible to the inside vehicle temperature Tc than the first battery pack 11. For example, when the outside air temperature is high, the temperature of the first battery pack 11 is likely to rise together with the outside air temperature Ta. On the other hand, since the second battery pack 12 is also cooled by the cooling operation of the air conditioner (not shown), the temperature of the second battery pack 12 is not likely to rise as much as the temperature of the first battery pack 11. Conversely, when the outside air temperature is low, the temperature of the first battery pack 11 is likely to fall together with the outside air temperature Ta. On the other hand, since the second battery pack 12 is also warmed by the heating operation of the air conditioner, the temperature of the second battery pack 12 is not likely to fall as much as the temperature of the first battery pack 11.

In this way, temperature variations can occur between the first battery pack 11 and the second battery pack 12 due to differences in the temperature of the usage environment. In general, the higher the temperature of the secondary battery, the faster the deterioration of that secondary battery progresses. Specifically, the output performance of the battery pack decreases (internal resistance increases) and the full charge capacity decreases. Therefore, if an excessively large temperature variation occurs, the deterioration of one battery pack may progress faster than the deterioration of the other battery pack, resulting in a significant difference in the degree of deterioration.

The first battery pack 11 and the second battery pack 12 are connected in series. Therefore, if the output performance of one battery pack decreases, the output performance of the battery (first battery pack 11 and second battery pack 12) as a whole will decrease, even if the output performance of the other battery pack does not decrease. The same applies to the full charge capacity. Therefore, it is desirable to reduce the temperature variation to reduce the difference in the degree of deterioration, thereby suppressing deterioration of the battery as a whole as much as possible. Therefore, in this embodiment, the ECU 9 executes "battery temperature adjustment control" that adjusts the temperature of the first battery pack 11 and/or the second battery pack 12.

<Battery temperature control>
3 is a diagram for explaining an overview of the battery temperature adjustment control in the first embodiment. In this example, the temperature of the battery pack is divided into a high temperature region, a normal temperature region, and a low temperature region. The upper limit temperature in the normal temperature region is written as UL, and the lower limit temperature is written as LL. The upper limit temperature is, for example, a temperature in the range of 40° C. to 50° C. The lower limit temperature LL is, for example, below freezing point.

The high temperature region is a temperature region higher than the upper limit temperature UL of the room temperature region, and is a region in which it is desirable to cool the battery pack in order to protect the battery pack. The low temperature region is a temperature region lower than the lower limit temperature LL of the room temperature region, and is a region in which it is desirable to heat the battery pack in order to protect the battery pack. The room temperature region corresponds to the "temperature region lower than the specified high temperature region" and the "temperature region higher than the specified low temperature region" according to the present disclosure.

The difference between the "battery temperature Tb1" which is the temperature of the first battery pack 11 and the "battery temperature Tb2" which is the temperature of the second battery pack 12 is referred to as the "temperature variation ΔTb". In this embodiment, when the temperature variation ΔTb (absolute value) is greater than the reference amount, the ECU 9 issues a command to cool the hotter battery pack of the first battery pack 11 or the second battery pack 12, even if the battery temperatures Tb1 and Tb2 are within the normal temperature range. In the example of FIG. 3, since the first battery pack 11 is hotter than the second battery pack 12, the first battery pack 11 is cooled by the cooling fan 51. This reduces the temperature variation ΔTb to less than the reference amount, and thus alleviates the situation in which the deterioration of the first battery pack 11 is more likely to progress than the deterioration of the second battery pack 12. This makes it possible to suppress the deterioration of the output performance and/or full charge capacity of the battery as a whole.

<Processing flow>
Fig. 4 is a flowchart showing the procedure of the battery temperature adjustment control in the first embodiment. The flowcharts shown in Fig. 4 and Fig. 6 described later are called from a main routine (not shown) and executed every time a predetermined condition is satisfied (for example, every control period). Each step is realized by software processing by the ECU 9, but may also be realized by hardware (electrical circuitry) arranged in the ECU 9. Hereinafter, steps are abbreviated as S.

In S101, the ECU 9 acquires the battery temperature Tb1 from the battery temperature sensor 21 and the battery temperature Tb2 from the battery temperature sensor 22.

In S102, the ECU 9 determines whether the temperature variation ΔTb between the battery temperature Tb1 and the battery temperature Tb2 exceeds a predetermined reference amount. The reference amount is determined according to the characteristics of the first battery pack 11 and the second battery pack 12. More specifically, based on the results of a prior evaluation test, the temperature difference at which the difference in the degree of deterioration between the first battery pack 11 and the second battery pack 12 becomes large enough to be non-negligible can be determined as the reference amount. The reference amount is, for example, a temperature within a range of 10°C to 20°C. If the temperature variation ΔTb is equal to or less than the reference amount (NO in S102), the subsequent processing is not executed and the processing returns to the main routine.

If the temperature variation ΔTb exceeds the reference amount (YES in S102), the ECU 9 determines whether at least one of the battery temperatures Tb1 and Tb2 is higher than the lower limit temperature LL (S103). If both battery temperatures Tb1 and Tb2 are equal to or lower than the lower limit temperature LL (i.e., within the low temperature region) (NO in S103), it is desirable not to further cool the first battery pack 11 and the second battery pack 12. Therefore, the ECU 9 returns to the main routine without executing any further processing.

If at least one of battery temperature Tb1 and battery temperature Tb2 is higher than lower limit temperature LL (YES in S103), ECU 9 proceeds to S104 and determines whether battery temperature Tb1 is higher than battery temperature Tb2 (S104).

If the battery temperature Tb1 is higher than the battery temperature Tb2 (YES in S104), the ECU 9 controls the cooling fan 51 to cool the first battery pack 11 (S105). The ECU 9 continues cooling the first battery pack 11 until a predetermined cooling end condition is met (NO in S106). For example, the ECU 9 determines that the cooling end condition is met when the battery temperature Tb1 drops to the battery temperature Tb2 and the temperature variation ΔTb is eliminated. However, the ECU 9 can determine that the cooling end condition is met when various conditions are met that make the temperature variation ΔTb less than the reference amount. The ECU 9 may determine that the cooling end condition is met when the battery temperature Tb1 drops by a predetermined temperature, or may determine that the cooling end condition is met when a predetermined time has elapsed since the start of cooling the first battery pack 11. When the cooling end condition is met (YES in S106), the ECU 9 stops the cooling fan 51 and ends the cooling of the first battery pack 11 (S107). After that, the ECU 9 returns the process to the main routine.

On the other hand, if battery temperature Tb2 is higher than battery temperature Tb1 (NO in S104), ECU 9 controls cooling fan 52 to cool second battery pack 12 (S108). ECU 9 ends cooling of second battery pack 12 when battery temperature Tb2 drops to battery temperature Tb1 (S110), for example. ECU 9 may end cooling of second battery pack 12 when battery temperature Tb2 drops by a predetermined temperature or when a predetermined time has elapsed since starting cooling of second battery pack 12. ECU 9 then returns processing to the main routine.

As described above, when the temperature variation ΔTb between the battery temperature Tb1 and the battery temperature Tb2 exceeds the reference amount, the deterioration of the relatively high temperature battery pack may progress significantly faster than the deterioration of the relatively low temperature battery pack. Since the first battery pack 11 and the second battery pack 12 are connected in series, when the output performance of the high temperature battery pack decreases due to deterioration, the output performance of the two battery packs as a whole decreases. Therefore, in the first embodiment, when the temperature variation ΔTb exceeds the reference amount, the high temperature battery pack of the first battery pack 11 and the second battery pack 12 is cooled to reduce the temperature variation ΔTb to less than the reference amount. As a result, the rate of deterioration of the high temperature battery pack and the rate of deterioration of the low temperature battery pack become closer to each other, so that the difference in the degree of deterioration is reduced. Therefore, according to the first embodiment, the deterioration of the battery (the first battery pack 11 and the second battery pack 12) as a whole can be suppressed.

[Embodiment 2]
In the first embodiment, a configuration for reducing the temperature variation ΔTb by cooling a high-temperature battery pack is described. In the second embodiment, a configuration for reducing the temperature variation ΔTb by heating a low-temperature battery pack is described. Note that the configuration of the vehicle according to the second embodiment is common to the configuration of vehicle 1 according to the first embodiment (see FIGS. 1 and 2), and therefore the description will not be repeated.

Figure 5 is a diagram for explaining an overview of the battery temperature control in the second embodiment. In the second embodiment, when the temperature variation ΔTb (absolute value) is greater than a reference amount, the ECU 9 issues a command to heat the battery pack with the lower temperature out of the first battery pack 11 and the second battery pack 12, even if the battery temperatures Tb1 and Tb2 are within the normal temperature range. In the example of Figure 5, the second battery pack 12 is heated by the electric heater 42. This reduces the temperature variation ΔTb, and alleviates the situation in which the deterioration of the first battery pack 11 is more likely to progress than the deterioration of the second battery pack 12. This makes it possible to suppress the decrease in the output performance and/or full charge capacity of the battery as a whole.

Figure 6 is a flowchart showing the processing procedure of the battery temperature adjustment control in embodiment 2. The processing of S201 and S202 is equivalent to the processing of S101 and S102 in embodiment 1 (see Figure 4).

In S203, the ECU 9 determines whether at least one of the battery temperatures Tb1 and Tb2 is below the upper limit temperature UL. If both battery temperatures Tb1 and Tb2 are equal to or higher than the upper limit temperature UL (i.e., within the high temperature range) (NO in S203), it is desirable not to further increase the temperature of the first battery pack 11 and the second battery pack 12. Therefore, the ECU 9 returns to the main routine without executing any further processing.

If at least one of the battery temperature Tb1 and the battery temperature Tb2 is lower than the upper limit temperature UL (YES in S203), the ECU 9 proceeds to S204 and determines whether the battery temperature Tb1 is higher than the battery temperature Tb2.

If the battery temperature Tb1 is higher than the battery temperature Tb2 (YES in S204), the ECU 9 controls the electric heater 42 to heat the second battery pack 12 (S205). The ECU 9 continues heating the second battery pack 12 until a predetermined heating end condition is met (NO in S206). The ECU 9 determines that the heating end condition is met, for example, when the battery temperature Tb2 rises to the battery temperature Tb1 and the temperature variation ΔTb is eliminated. However, the ECU 9 can determine that the heating end condition is met when various conditions are met that make the temperature variation ΔTb less than the reference amount. The ECU 9 may determine that the heating end condition is met when the battery temperature Tb2 rises by a predetermined temperature, or may determine that the heating end condition is met when a predetermined time has passed since the start of heating the second battery pack 12. When the heating end condition is met (YES in S206), the ECU 9 stops the electric heater 42 and ends the heating of the second battery pack 12 (S207). After that, the ECU 9 returns the process to the main routine.

On the other hand, if battery temperature Tb2 is higher than battery temperature Tb1 (NO in S204), ECU 9 controls electric heater 41 to heat first battery pack 11 (S208). ECU 9 ends heating of first battery pack 11 when battery temperature Tb1 rises to battery temperature Tb2 (S210), for example. ECU 9 may end heating of first battery pack 11 when battery temperature Tb1 drops by a predetermined temperature or when a predetermined time has elapsed since heating of first battery pack 11 started. ECU 9 then returns processing to the main routine.

As described above, in the second embodiment, when the temperature variation ΔTb exceeds the reference amount, the lower temperature battery pack out of the first battery pack 11 and the second battery pack 12 is heated to reduce the temperature variation ΔTb to less than the reference amount. This makes the rate of deterioration of the high temperature battery pack and the rate of deterioration of the low temperature battery pack closer to each other, thereby reducing the difference in the degree of deterioration. Therefore, according to the second embodiment, as in the first embodiment, the deterioration of the battery as a whole can be suppressed.

In the first and second embodiments, an example has been described in which only one of cooling the high-temperature battery pack and heating the low-temperature battery pack is performed. However, the ECU 9 may control the electric heater to cool the high-temperature battery pack and control the cooling fan to heat the low-temperature battery pack.

[Embodiment 3]
In the third embodiment, a configuration will be described in which either cooling of a high-temperature battery pack or heating of a low-temperature battery pack is appropriately selected depending on the running conditions of the vehicle 1.

Figure 7 is a diagram for explaining an overview of the battery temperature control in the third embodiment. In the third embodiment, when the temperature variation ΔTb exceeds the reference amount (or when the temperature variation ΔTb is predicted to exceed the reference amount), the ECU 9 calculates the amount of power (cooling power amount) α [unit: Wh] consumed to cool the relatively high-temperature battery pack and the amount of power (heating power amount) β [unit: Wh] consumed to heat the relatively low-temperature battery pack. In the example shown in Figure 5, the first battery pack 11 is hotter than the second battery pack 12. Therefore, the cooling power amount α for lowering the battery temperature Tb1 to the battery temperature Tb2 and the heating power amount β for raising the battery temperature Tb2 to the battery temperature Tb1 are calculated.

The ECU 9 compares the amount of cooling power α with the amount of heating power β. If the amount of cooling power α is equal to or less than the amount of heating power β (α≦β), the ECU 9 selects cooling the first battery pack 11. On the other hand, if the amount of cooling power α is greater than the amount of heating power β (α>β), the ECU 9 selects heating the second battery pack 12. For simplicity, the hotter battery pack of the first battery pack 11 and the second battery pack 12 will be abbreviated below as the "hot battery" and the colder battery pack as the "low temperature battery."

Figure 8 is a time chart for explaining the calculation method of the cooling power amount α and the heating power amount β. The horizontal axis represents the elapsed time. The vertical axis represents, from top to bottom, the temperature of each battery pack when the high-temperature battery is cooled, the temperature of each battery pack when the low-temperature battery is heated, and the current input to and output from the battery.

First, the method for calculating the amount of cooling power α will be explained. For comparison, FIG. 8 shows the temperature transition of the high-temperature battery when it is cooled, and the temperature transition of the high-temperature battery when it is not cooled. In the situation shown in this example, the temperatures of the high-temperature battery and the low-temperature battery gradually increase over time.

At the current time t1, for example, the temperature difference between the high-temperature battery and the low-temperature battery (temperature variation ΔTb) exceeds a reference amount, and cooling of the high-temperature battery begins. Then, compared to when the high-temperature battery is not cooled, the temperature rise of the high-temperature battery becomes more gradual, and the temperature variation ΔTb gradually decreases. In this example, the cooling end condition is met when the temperature of the high-temperature battery matches the temperature of the low-temperature battery at time t3.

The ECU 9 calculates the amount of cooling power α according to the environmental temperature of the high-temperature battery and the Joule heat generated in the high-temperature battery, taking into consideration the cooling capacity of the cooling fans 51, 52 in addition to the above cooling end conditions. More specifically, the memory of the ECU 9 stores, for example as a map, the correspondence relationship between the outside air temperature Ta, the vehicle interior temperature Tc, the square value ^I2 (∝Joule heat) of the current input/output to the high-temperature battery, and the amount of temperature change ΔT of the high-temperature battery per unit time. This map is prepared according to the cooling capacity of the cooling fans 51, 52, based on the results of previous experiments or simulations.

The ECU 9 can use, for example, a value detected by the outside air temperature sensor 81 as the outside air temperature Ta. The ECU 9 can also obtain a weather forecast (weather information including the outside air temperature) for the area in which the vehicle 1 is traveling from an external server (not shown) via the DCM 71.

The ECU 9 can use, as the current I, a value according to the driving position of the vehicle 1 identified by the GPS receiver 72. For example, if the vehicle 1 has previously driven along the planned driving route for the current vehicle 1, the ECU 9 can acquire data on the current I by communicating with an external server based on the past driving history of the vehicle 1. If the vehicle 1 has not previously driven along the planned driving route for the current vehicle 1, the ECU 9 can acquire data on the current I from the driving history of many other vehicles of the same model as the vehicle 1 (so-called big data).

In addition, when the high-temperature battery is the first battery pack 11 arranged outside the vehicle cabin, the outside air temperature Ta has a large influence on the temperature of the high-temperature battery, while the effect of the vehicle interior temperature Tc on the temperature of the high-temperature battery is relatively small. Therefore, the map may not include the vehicle interior temperature Tc (i.e., the map may define the correspondence relationship between the outside air temperature Ta, the squared value of the current ^I2 , and the amount of temperature change ΔT of the high-temperature battery per unit time). On the other hand, when the high-temperature battery is the second battery pack 12 arranged inside the vehicle cabin, the effect of the outside air temperature Ta on the temperature of the high-temperature battery is relatively small. Therefore, the map may not include the outside air temperature Ta (the map may define the correspondence relationship between the vehicle interior temperature Tc, the squared value of the current ^I2 , and the amount of temperature change ΔT of the high-temperature battery per unit time).

By referring to the map, the ECU 9 can calculate the temperature change amount ΔT of the high-temperature battery per unit time from the outside air temperature Ta detected by the outside air temperature sensor 81 and/or the interior temperature Tc detected by the interior temperature sensor ⁸² , and the squared value I2 of the current detected by the current sensor 23. Therefore, the ECU 9 can estimate the temperature transition of the high-temperature battery during the period from time t1 to time t3 based on the temperature change amount Δ per unit time.

Furthermore, the ECU 9 can calculate the amount of cooling power Δα per unit time from the specifications of the cooling fans 51 and 52. Therefore, the ECU 9 can calculate the amount of cooling power α by integrating the amount of cooling power Δα per unit time over the period from the current time until the cooling end condition is met.

Although cooling and heating are different, the ECU 9 can calculate the heating power amount β in a similar manner, so a detailed description of the calculation method for the heating power amount β will not be repeated. In the example shown in FIG. 8, the heating end condition is satisfied at time t2 prior to time t3 at which the cooling end condition is satisfied.

The ECU 9 compares the amount of cooling power α and the amount of heating power β, and adjusts the temperature of the battery pack in a manner that consumes less power. That is, the ECU 9 cools the high-temperature battery when the amount of cooling power α is equal to or less than the amount of heating power β, and heats the low-temperature battery when the amount of heating power β is smaller than the amount of cooling power α. This cooling or heating also reduces the temperature variation ΔTb, and thus, as in the first and second embodiments, mitigates the situation in which the high-temperature battery is more likely to deteriorate than the low-temperature battery. This makes it possible to suppress a decrease in the output performance and/or full charge capacity of the battery as a whole.

Note that in FIG. 8, it has been described that cooling or heating is started because the temperature variation ΔTb has exceeded the reference amount at the current time t1, but the timing at which cooling or heating is started is not limited to this. Cooling or heating may be started before the temperature variation ΔTb exceeds the reference amount. In other words, the ECU 9 may start cooling or heating when it is predicted that the temperature variation ΔTb will exceed the reference amount.

Figure 9 is a flowchart showing the processing procedure for battery temperature adjustment control in embodiment 3. The processing of S301 and S302 is equivalent to the processing of S101 and S102 in embodiment 1 (see Figure 4).

If the temperature variation ΔTb exceeds the reference amount or if the temperature variation ΔTb is predicted to exceed the reference amount (YES in S302), the ECU 9 determines whether the temperature of the high-temperature battery is higher than the upper limit temperature UL (S303). If the temperature of the high-temperature battery is higher than the upper limit temperature UL (YES in S303), the ECU 9 controls the cooling fan (one of the cooling fans 51 and 52 corresponding to the high-temperature battery) to cool the high-temperature battery (S304).

If the temperature of the high-temperature battery is equal to or lower than the upper limit temperature UL (NO in S303), the ECU 9 determines whether the temperature of the low-temperature battery is lower than the lower limit temperature LL (S305). If the temperature of the low-temperature battery is lower than the lower limit temperature LL (YES in S305), the ECU 9 controls the electric heater (one of the electric heaters 41 and 42 that corresponds to the low-temperature battery) to heat the low-temperature battery (S306).

If the temperature of the high-temperature battery is equal to or lower than the upper limit temperature UL and the temperature of the low-temperature battery is equal to or higher than the lower limit temperature LL (NO in S305), i.e., if both the high-temperature battery and the low-temperature battery are in the normal temperature range, the ECU 9 calculates the amount of cooling power α for cooling the high-temperature battery and the amount of heating power β for heating the low-temperature battery (S307). This calculation method has been described in detail in FIG. 8, so the description will not be repeated here.

In S308, the ECU 9 determines whether the cooling power amount α is equal to or less than the heating power amount β. If the cooling power amount α is equal to or less than the heating power amount β (YES in S308), the ECU 9 controls the cooling fan corresponding to the high-temperature battery to cool the high-temperature battery (S309). On the other hand, if the cooling power amount α is greater than the heating power amount β (NO in S308), the ECU 9 controls the electric heater corresponding to the low-temperature battery to heat the low-temperature battery (S310).

Although this is not shown due to space limitations, the ECU 9 ends the cooling of the high-temperature battery when a cooling end condition is met while the high-temperature battery is being cooled. Also, the ECU 9 ends the heating of the low-temperature battery when a heating end condition is met while the low-temperature battery is being heated. After that, the process returns to the main routine.

As described above, in the third embodiment as well, when the temperature variation ΔTb exceeds (is predicted to exceed) the reference amount, the temperature variation ΔTb between the two battery packs is reduced by cooling the high-temperature battery or heating the low-temperature battery. This makes the rate at which the high-temperature battery deteriorates closer to the rate at which the low-temperature battery deteriorates, thereby reducing the difference in the degree of deterioration. Thus, according to the third embodiment, as in the first and second embodiments, deterioration of the battery as a whole can be suppressed.

Furthermore, in the third embodiment, the temperature of the battery pack is adjusted in a manner that consumes less power. This reduces the power consumed by the battery for cooling or heating, allowing more power to remain in the battery after cooling or heating is completed. This makes it possible to minimize the reduction in the EV distance of the vehicle 1 that accompanies temperature adjustment.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is indicated by the claims rather than the description of the embodiments above, and is intended to include all modifications within the meaning and scope of the claims.

1 vehicle, 11 first battery pack, 12 second battery pack, 21, 22 battery temperature sensor, 23 current sensor, 31 SMR, 32 PCU, 33 motor generator, 34 DC/DC converter, 41, 42 electric heater, 51, 52 cooling fan, 61 inlet, 62 AC/DC converter, 63 charging relay, 71 DCM, 72 GPS receiver, 81 outside air temperature sensor, 82 vehicle interior temperature sensor, 9 ECU.

Claims (9)

A first battery pack;
a second battery pack arranged at a position different from that of the first battery pack and connected in series to the first battery pack;
a first temperature adjustment device configured to adjust the temperature of the first battery pack;
a second temperature adjustment device configured to adjust the temperature of the second battery pack;
a control device that controls the first and second temperature adjustment devices,
A vehicle, wherein the control device controls at least one of the first and second temperature adjustment devices so that, when a temperature difference between the temperature of the first battery pack and the temperature of the second battery pack exceeds a reference amount, the temperature difference becomes less than the reference amount. the first battery pack is disposed outside a vehicle compartment;
The vehicle according to claim 1 , wherein the second battery pack is disposed inside the vehicle compartment. each of the first and second temperature adjustment devices includes a cooling device that cools a corresponding one of the first and second battery packs;
3. The vehicle according to claim 1, wherein when the temperature difference exceeds the reference amount, the control device controls a cooling device corresponding to the battery pack having a higher temperature among the first and second battery packs so that the battery pack having a higher temperature is cooled. The vehicle according to claim 3, wherein the control device controls the corresponding cooling device so that the high-temperature battery pack is cooled when the temperature difference exceeds the reference amount, even if the temperature of the high-temperature battery pack is within a temperature range lower than a predetermined high-temperature range. each of the first and second temperature adjustment devices includes a heating device that heats a corresponding one of the first and second battery packs;
3. The vehicle according to claim 1, wherein the control device controls a heating device corresponding to a battery pack having a lower temperature among the first and second battery packs so that the battery pack having a lower temperature is heated when the temperature difference exceeds the reference amount. The vehicle according to claim 5, wherein the control device controls the corresponding heating device so that the low-temperature battery pack is heated when the temperature difference exceeds the reference amount, even if the temperature of the low-temperature battery pack is within a temperature range higher than a predetermined low-temperature range. Each of the first and second temperature adjustment devices includes:
a cooling device for cooling a corresponding one of the first and second battery packs;
a heating device for heating a corresponding one of the first and second battery packs;
When the temperature difference exceeds the reference amount, the control device
calculating a cooling power amount, which is the power consumption when cooling the hotter battery pack of the first and second battery packs so that the temperature difference becomes less than a reference amount, and a heating power amount, which is the power consumption when heating the colder battery pack of the first and second battery packs so that the temperature difference becomes less than a reference amount;
When the amount of cooling power is smaller than the amount of heating power, a cooling device corresponding to the high-temperature battery pack is controlled so that the high-temperature battery pack is cooled;
3. The vehicle according to claim 1, further comprising: a heating device for controlling the battery pack having a lower temperature so that the battery pack having a lower temperature is heated when the amount of heating electric power is smaller than the amount of cooling electric power. When the temperature difference exceeds the reference amount, even if the temperatures of the high temperature battery pack and the low temperature battery pack are in a temperature range lower than a predetermined high temperature range and higher than a predetermined low temperature range, the control device
When the amount of cooling power is smaller than the amount of heating power, a cooling device corresponding to the high-temperature battery pack is controlled so that the high-temperature battery pack is cooled;
The vehicle according to claim 7 , wherein when the amount of heating power is smaller than the amount of cooling power, a heating device corresponding to the battery pack having a lower temperature is controlled so that the battery pack having a lower temperature is heated. A method for controlling a vehicle, comprising:
The vehicle is
A first battery pack;
a second battery pack arranged at a position different from that of the first battery pack and connected in series to the first battery pack;
a first temperature adjustment device configured to adjust the temperature of the first battery pack;
a second temperature adjustment device configured to adjust the temperature of the second battery pack;
The control method includes:
obtaining a temperature difference between a temperature of the first battery pack and a temperature of the second battery pack;
If the temperature difference exceeds a reference amount, operating at least one of the first and second temperature adjustment devices so that the temperature difference becomes less than the reference amount.

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