Temperature control unit for on-vehicle battery

Abstract

To prevent a deterioration in the charging efficiency of an on-vehicle battery having a plurality of batteries.SOLUTION: A plurality of batteries are arranged side by side in at least one of a vehicle fore-and-aft direction and a vehicle width direction. A BECM 81, when a temperature difference between the batteries is equal to or more than a predetermined temperature difference, increases an amount of discharge from the battery having a relatively low temperature compared to an amount of discharge from the battery having a relatively high temperature, and decreases an amount of charge to the battery having a relatively low temperature compared to an amount of charge to the battery having a relatively high temperature.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The technology disclosed herein belongs to the technical field of a temperature control device for an in-vehicle battery. [Background technology]

[0002] Conventionally, efforts have been made to suppress the temperature distribution of an in-vehicle battery.

[0003] For example, Patent Document 1 discloses a cooling control device for a storage battery that includes an estimation unit that estimates the temperature distribution of an electric vehicle and a condition setting unit that sets the operating conditions of the cooling device, and the condition setting unit separately sets the conditions for cooling the storage battery using a first passage and the conditions for cooling the storage battery using a second passage based on the temperature distribution estimated by the estimation unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-43663 A Summary of the Invention [Problem to be solved by the invention]

[0005] Some electrically powered vehicles have a plurality of on-board batteries. When the vehicle has a plurality of batteries, a temperature difference may occur between the batteries depending on the arrangement of the batteries.

[0006] For example, when the batteries are arranged in a line in the front-rear direction of the vehicle, the battery located relatively closer to the front is more likely to be exposed to the wind while the battery located relatively closer to the rear is less likely to be exposed to the wind. This results in a temperature difference between the rear battery and the front battery. Also, when the batteries are arranged in a line in the vehicle width direction, in a situation where sunlight hits one side of the vehicle width direction, the battery located on that side will have a higher temperature than the battery located on the other side.

[0007] Since the charging efficiency of a battery changes depending on the temperature, if there is a temperature imbalance between multiple batteries, there will be differences in the charging efficiency between the batteries when charging while driving. If there is a difference in charging efficiency, the amount of charge will be smaller, which may result in a shorter driving distance.

[0008] In addition, when the temperature of the batteries is high and there is a temperature imbalance between the batteries, the deterioration of a particular battery is accelerated. When the deterioration of a particular battery is accelerated, the charging efficiency of the deteriorated battery deteriorates. In this case, there is also a risk that the charging efficiency will differ between the batteries, resulting in a shorter driving distance.

[0009] As a countermeasure, it is possible to reduce the temperature difference between the batteries by improving the structure and control of the cooling device or by improving the arrangement of the batteries, as in Patent Document 2. However, since the batteries are relatively large, there is a limit to how much the surrounding structure or the arrangement of the batteries themselves can be improved. Furthermore, even if the control of the cooling device is improved, structural changes such as providing a switching valve to adjust the amount of coolant supplied to each battery are unavoidable. For this reason, there is room for improvement in order to obtain sufficient charging efficiency even if temperature deviation occurs among multiple batteries.

[0010] The technology disclosed herein has been made in consideration of these points, and its purpose is to suppress deterioration in the charging efficiency of an on-board battery having multiple cells. [Means for solving the problem]

[0011] In order to solve the above problems, a first aspect of the technology disclosed herein is directed to a temperature control device for an on-board battery having multiple batteries, and includes multiple battery temperature detection units that measure the temperature of each of the batteries, and a controller that controls the charging and discharging of each battery based on the detection results of each battery temperature detection unit, wherein the batteries are arranged in a line in at least one of the fore-and-aft direction and the width direction of the vehicle, and when the temperature difference between the batteries is equal to or greater than a predetermined temperature difference, the controller increases the amount of discharge from the battery with a relatively low temperature compared to the amount of discharge from the battery with a relatively high temperature, and decreases the amount of charge to the battery with a relatively low temperature compared to the amount of charge to the battery with a relatively high temperature.

[0012] The inventors of the present application compared the heat generation of a battery during charging and discharging while driving and found that the heat generation during discharging is greater than that during charging. Therefore, the present disclosure increases the amount of discharge from a battery with a relatively low temperature compared to the amount of discharge from a battery with a relatively high temperature.

[0013] As a result, a battery with a relatively low temperature is more likely to warm up than a battery with a relatively high temperature. Conversely, a battery with a relatively high temperature is more likely to be cooled than a battery with a relatively low temperature. This eliminates the temperature difference between the batteries. By eliminating the temperature difference between the batteries, the difference in charging efficiency between the batteries is also eliminated, making it possible to achieve a high charging efficiency for the entire vehicle battery.

[0014] In addition, as in the above configuration, the charge amount for a battery with a relatively low temperature is set to be smaller than the charge amount for a battery with a relatively high temperature. This allows batteries with high charging efficiency to be charged preferentially, making it possible to maintain high charging efficiency for the entire vehicle battery.

[0015] In a second aspect of the technology disclosed herein, in the first aspect, the vehicle-mounted battery has a pair of batteries, a first battery and a second battery, and the first battery and the second battery are arranged side by side in the fore-and-aft direction or the width direction of the vehicle, and when the temperature difference between the low-temperature battery, which is the battery that has a relatively low temperature among the first and second batteries, and the high-temperature battery, which is the battery that has a relatively high temperature, is greater than the predetermined temperature difference, the controller makes the amount of discharge from the low-temperature battery greater than the amount of discharge from the high-temperature battery, and makes the amount of charge to the low-temperature battery less than the amount of charge to the high-temperature battery.

[0016] According to this configuration, the control by the controller is simplified, so that deterioration of the charging efficiency of the entire vehicle battery can be more effectively prevented.

[0017] In a third aspect of the technique disclosed herein, in the second aspect, the controller estimates a State of Health (SOH) of the low temperature battery, and sets the predetermined temperature based on the estimated SOH.

[0018] That is, the SOH affects the amount of heat generated during discharge. If the specified temperature difference is small and the amount of heat generated is large, the control time for charging and discharging described above becomes significantly shorter. If the control time for charging and discharging becomes too short, hunting may occur. Therefore, by setting the specified temperature difference based on the SOH as in the above configuration, the control time can be set to a length that does not cause hunting.

[0019] In a fourth aspect of the technology disclosed herein, in the second or third aspect, the SOC (State of Charge) of the first and second batteries is calculated, and when the SOC of the low-temperature battery is less than the first predetermined value, the amount of discharge from the low-temperature battery is made equal to the amount of discharge from the high-temperature battery, even when the temperature difference between the low-temperature battery and the high-temperature battery is equal to or greater than the predetermined temperature difference.

[0020] In other words, when the low temperature battery runs out of power, the high temperature battery will be the main discharger, which may cause the temperature difference to increase excessively. With the above-mentioned configuration, by making the discharge amounts equal, it is possible to suppress the low temperature battery from running out of power while suppressing the temperature difference from increasing excessively.

[0021] In a fifth aspect of the technology disclosed herein, in the fourth aspect, when the SOC of the low-temperature battery is less than a second predetermined value higher than the first predetermined value and the SOC of the high-temperature battery is equal to or greater than the second predetermined value, the controller makes the amount of charge for the low-temperature battery greater than the amount of charge for the high-temperature battery, even when the temperature difference between the low-temperature battery and the high-temperature battery is equal to or greater than the predetermined temperature difference.

[0022] According to this configuration, since charging is suppressed when the SOC is high, it is possible to suppress deterioration of the battery due to excessive charging, and thus to suppress deterioration of charging efficiency due to deterioration of the battery. Effect of the Invention

[0023] As described above, the technology disclosed herein can suppress deterioration in charging efficiency of an on-board battery having multiple cells. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic diagram of a vehicle having a temperature control device according to an exemplary embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a cooling system for a vehicle. [Diagram 3] FIG. 3 is a block diagram showing a control system of the temperature control device. [Figure 4] FIG. 4 is a flowchart showing the processing operation of the PCM. [Diagram 5] FIG. 5 is a flowchart showing a process for setting the predetermined temperature difference. [Figure 6] FIG. 6 is a flowchart showing the processing operation of the specific control. [Figure 7]FIG. 7 is a time chart showing changes in the temperatures of the first and second batteries when the temperature of the first battery is below the first predetermined temperature. [Figure 8] FIG. 8 is a time chart showing changes in the temperatures of the first and second batteries when the temperature of the second battery is higher than the second predetermined temperature. [Figure 9] FIG. 9 is a configuration diagram of a vehicle according to a modified example. [Figure 10] FIG. 10 is a configuration diagram of a vehicle according to still another modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Exemplary embodiments will now be described in detail with reference to the drawings.

[0026] Overall Structure 1 shows a vehicle 1 equipped with a temperature control device according to this embodiment. The vehicle 1 is an automobile capable of running on electric power, such as an electric vehicle or a hybrid vehicle.

[0027] The vehicle 1 has a drive motor 2 as a drive source. Rotation of the drive motor 2 is transmitted to the two wheels (drive wheels 4F) located at the front among the four wheels 4F, 4F, 4R, 4R via a shaft. This allows the vehicle 1 to move (run). The drive motor 2 is a motor generator, and operates as a generator when the vehicle 1 decelerates (regenerates).

[0028] The drive motor 2 is connected to a battery 10 via an inverter 3 , a first converter 5 , and a second converter 6 .

[0029] The battery 10 includes a first battery 11 and a second battery 12. The first battery 11 is located in front of the second battery 12. The first and second batteries 11, 12 are each configured by stacking a plurality of lithium ion battery cells. The rated voltage of the first and second batteries 11, 12 is, for example, 50V or less (specifically, 48V). The first battery 11 and the second battery 12 have the same configuration.

[0030] The first converter 5 is connected to the first battery 11. The second converter 6 is connected to the second battery 12. When the vehicle 1 is running, the first and second converters 5, 6 step down the DC power output from the first and second batteries 11, 12 to a drive voltage for the drive motor 2 and supply it to the inverter 3. When the vehicle 1 is regenerating, the first and second converters 5, 6 step up the DC power from the inverter 3 and charge it to the first and second batteries 11, 12.

[0031] The inverter 3 converts between DC power and AC power. When the vehicle 1 is traveling, the inverter 3 converts the DC power supplied via the first and second converters 5, 6 into three-phase AC current with different phases and supplies it to the drive motor 2. When the vehicle 1 is regenerating, the inverter 3 converts the AC power generated by the drive motor 2 into DC power and supplies it to the first and second converters 5, 6.

[0032] A first switch 13 is connected to the first battery 11. A second switch 14 is connected to the second battery 12. When both the first switch 13 and the second switch 14 are on, charging of both the first and second batteries 11, 12 and discharging from both the first and second batteries 11, 12 are possible. When the first switch 13 is on and the second switch 14 is off, charging of only the first battery 11 and discharging from only the first battery 11 are possible. When the first switch 13 is off and the second switch 14 is on, charging of only the second battery 12 and discharging from only the second battery 12 are possible.

[0033] As shown in Fig. 2, the vehicle 1 has a cooling device 50 that cools the battery 10. The cooling device 50 cools the battery 10 by an endothermic reaction that occurs when a liquid refrigerant changes phase to a gaseous state. The refrigerant is, for example, an HFO (hydrofluoroolefin) refrigerant, specifically, R1234yf.

[0034] The cooling device 50 includes a first heat exchanger 51 that exchanges heat between the refrigerant and the first battery 11, a second heat exchanger 52 that exchanges heat between the refrigerant and the second battery 12, a compressor 53 that pressurizes the refrigerant flowing out of the first and second heat exchangers 51, 52, a condenser 54 that cools and condenses the refrigerant pressurized by the compressor 53, a fan 55 that draws in outside air, a receiver tank 56 that stores the refrigerant condensed in the condenser 54, and an expansion valve 57 that reduces the pressure of the refrigerant condensed in the condenser 4.

[0035] The compressor 53 pressurizes the refrigerant after heat exchange with the first and second batteries 11, 12. The compressor 3 is, for example, a scroll compressor, and can adjust the pressure of the outflowing refrigerant by adjusting the rotation speed.

[0036] When the vehicle 1 is moving, the condenser 54 cools the refrigerant with air drawn in by at least one of the traveling wind and the fan 55, and when the vehicle 1 is stopped, the condenser 54 cools the refrigerant with air drawn in by the rotation of the fan 55.

[0037] The fan 55 is an electric fan having a small electric motor and rotated by the rotation of the electric motor.

[0038] The expansion valve 57 reduces the pressure of the refrigerant to cause the refrigerant to flow into the first and second heat exchangers 51 and 52. The temperature of the refrigerant that has passed through the expansion valve 57 decreases due to adiabatic expansion. The expansion valve 57 is also used to adjust the flow rate of the refrigerant flowing into the first and second heat exchangers 51 and 52. Specifically, the larger the opening of the expansion valve 57, the larger the flow rate of the refrigerant flowing into the first and second heat exchangers 51 and 52, while the smaller the opening of the expansion valve 57, the smaller the flow rate of the refrigerant flowing into the first and second heat exchangers 51 and 52.

[0039] Control System As shown in Fig. 3, the vehicle 1 has a PCM (Powertrain Control Module) 80, which is a controller that controls the entire power system of the vehicle 1, and a BECM (Battery Energy Control Module) 81, which is a controller that mainly controls charging and discharging of the battery 10. The PCM 80 has one or more processors 80a having a CPU, and a memory 80b having ROM and RAM and storing various programs. The memory 80b is, for example, a non-volatile memory. The BECM 81 has one or more processors 81a having a CPU, and a memory 81b consisting of ROM and RAM and storing various programs. The memory 81b is, for example, a non-volatile memory.

[0040] The BECM 81 includes a first battery temperature sensor SW1 that detects the temperature of the first battery 11, a second battery temperature sensor SW2 that detects the temperature of the second battery 12, a first current sensor SW3 that detects the current of the first battery 11, a second current sensor SW4 that detects the current of the second battery 12, a first voltage sensor SW5 that detects the voltage of the first battery 11, and a second voltage sensor SW6 that detects the voltage of the second battery 12. The first and second battery temperature sensors SW1 and SW2 are disposed, for example, near the centers of the first and second batteries 11 and 12. The first and second current sensors SW3 and SW4 are connected in series to the first and second batteries 11 and 12, respectively. The first and second voltage sensors SW5 and SW6 are connected in parallel to the first and second batteries 11 and 12, respectively.

[0041] The BECM 81 transmits control signals related to charging and discharging the first and second batteries 11, 12 to the PCM 80 based on the signals from the sensors SW1 to SW6.

[0042] The PCM 80 controls the first switch 13, the second switch 14, the inverter 3, the first converter 5, the second converter 6, the compressor 53, the fan 55, and the expansion valve 57 based on a control signal received from the BECM 81.

[0043] The control performed by the BECM 81 is stored as a program in the memory 81b. The control performed by the PCM 80 is stored as a program in the memory 80b.

[0044] Battery temperature control When supplying current to the drive motor 2 and when charging the first and second batteries 11, 12 with power generated by the drive motor 2, the BECM 81 controls charging and discharging of both the first and second batteries 11, 12. In other words, the BECM 81 outputs a control signal to the PCM 80 to turn on both the first and second switches 13, 14.

[0045] As described above, the first battery 11 is disposed closer to the front of the vehicle than the second battery 12. For this reason, the first battery 11 is more likely to be exposed to the wind caused by running than the second battery 12, and is more likely to become cold than the second battery 12, for example, in winter when the temperature of the wind is low.

[0046] Basically, the charging efficiency decreases as the temperature of the batteries decreases. Therefore, when the temperature of the first battery 11 is lower than that of the second battery 12, even if both the first battery 11 and the second battery 12 are in a chargeable state, the charging efficiency of the first battery 11 is worse than that of the second battery 12. Therefore, when there is a large temperature difference between the first battery 11 and the second battery 12, a large difference in charging efficiency occurs, and the remaining charge of the first battery 11 tends to decrease. When the remaining charge of the first battery 11 decreases, the traveling distance becomes shorter.

[0047] Conversely, the second battery 12 is more likely to become hotter than the first battery 11. If the second battery 12 becomes too hot, this accelerates the deterioration of the second battery 12. If the deterioration of the second battery 12 accelerates, the charging efficiency of the second battery 12 deteriorates. For this reason, even if the temperature of the battery 10 is high, if the temperature difference between the first battery 11 and the second battery 12 is large, a large difference in charging efficiency occurs.

[0048] Therefore, in this embodiment, when the temperature difference between the first battery 11 and the second battery 12 becomes large enough to cause a large difference in charging efficiency, specific control is executed to bias the charging and discharging of the first and second batteries 11, 12.

[0049] FIG. 4 is a flowchart showing a process performed by the BECM 81 to execute specific control.

[0050] First, in step S1, the BECM 81 reads the detection signals from the sensors SW1 to SW6.

[0051] Next, in step S2, the BECM 81 determines whether the first battery temperature T1, which is the temperature of the first battery 11, is higher than the first predetermined temperature Tc1 and lower than a second predetermined temperature Tc2 that is higher than the first predetermined temperature Tc1. The first predetermined temperature Tc1 is a temperature at which the charging efficiency of the battery 10 deteriorates, for example, 0°C. The second predetermined temperature Tc2 is a temperature at which deterioration of the battery 10 accelerates, for example, 55°C. If the first battery temperature T1 is higher than the first predetermined temperature Tc1 and lower than the second predetermined temperature Tc2 (YES), the BECM 81 proceeds to step S3. On the other hand, if the first battery temperature T1 is lower than the first predetermined temperature Tc1 or higher than the second predetermined temperature Tc2 (NO), the BECM 81 proceeds to step S4.

[0052] In step S3, the BECM 81 determines whether the second battery temperature T2, which is the temperature of the second battery 12, is higher than the first predetermined temperature Tc1 and lower than a second predetermined temperature Tc2 that is higher than the first predetermined temperature Tc1. If the second battery temperature T2 is higher than the first predetermined temperature Tc1 and lower than the second predetermined temperature Tc2 (YES), the BECM 81 proceeds to step S8. On the other hand, if the second battery temperature T2 is lower than the first predetermined temperature Tc1 or higher than the second predetermined temperature Tc2 (NO), the BECM 81 proceeds to step S4.

[0053] In step S4, the BECM 81 calculates the first predetermined temperature difference dTh1 and the second predetermined temperature difference dTh2. The first predetermined temperature difference dTh1 is calculated based on the SOH (State of Health), particularly the SOHR (State of Health Resistance), of one of the first and second batteries 11, 12. The SOHR is the deterioration rate of the internal resistance of the battery. The second predetermined temperature difference dTh2 is set based on the first predetermined temperature difference dTh1. The second predetermined temperature difference dTh2 is a value smaller than the first predetermined temperature difference dTh1. The calculation methods of the first predetermined temperature difference dTh1 and the second predetermined temperature difference dTh2 will be described later.

[0054] Next, in step S5, the BECM 81 determines whether the absolute value of the difference between the first battery temperature T1 and the second battery temperature T2 is equal to or greater than the first predetermined temperature difference dTh1. If the absolute value of the difference is equal to or greater than the first predetermined temperature difference dTh1 (YES), the BECM 81 proceeds to step S6. On the other hand, if the absolute value of the difference is less than the first predetermined temperature difference dTh1 (NO), the BECM 81 proceeds to step S8.

[0055] In step S6, the BECM 81 executes the specific control. The specific control changes its control content depending on the SOC (State of Charge) of the first battery 11 and the SOC of the second battery 12. The specific control will be described later.

[0056] Next, in step S7, the BECM 81 determines whether the absolute value of the difference between the first battery temperature T1 and the second battery temperature T2 is equal to or less than the second predetermined temperature difference dTh2. If the absolute value of the difference between the first battery temperature T1 and the second battery temperature T2 is equal to or less than the second predetermined temperature difference dTh2 (YES), the BECM 81 returns. On the other hand, if the absolute value of the difference between the first battery temperature T1 and the second battery temperature T2 is greater than the second predetermined temperature difference dTh2 (NO), the BECM 81 returns to step S6.

[0057] In step S8, the BECM 81 executes normal control. As described above, normal control is control in which both the first and second switches 13, 14 are turned on during both charging and discharging. The BECM 81 returns after step S8.

[0058] Calculation of the specified temperature difference Next, a method for calculating the first and second predetermined temperature differences dTh1 and dTh2 will be described. The first predetermined temperature difference dTh1 is set based on the internal resistance calculated from the SOHR of the battery (hereinafter referred to as the low-temperature battery) of the first and second batteries 11, 12, which has a relatively low temperature, and the lower limit time, which is the minimum time that the specific control needs to be continued.

[0059] Although the details will be described later, in the specific control, basically, charging is performed only on the battery (hereinafter referred to as the high-temperature battery) of the first and second batteries 11, 12 that is relatively hot, and discharging is performed only on the low-temperature battery. Therefore, the charging and discharging amounts of the first and second batteries 11, 12 are larger than those in the normal control. When the charging and discharging amounts are larger, hunting is more likely to occur. Hunting is more likely to occur as the on-off cycle of the first and second switches 13, 14 is shorter. Therefore, in order to suppress hunting, it is necessary to continue the specific control for a certain long time. This time is preset as the lower limit time. The lower limit time can be obtained by experiment or the like. The lower limit time is stored in the memory 81b.

[0060] FIG. 5 is a flowchart for calculating the first predetermined temperature difference dTh1.

[0061] First, in step S41, the BECM 81 estimates the SOHR of the low temperature battery based on the current value and voltage value of the low temperature battery in the switched-off state.

[0062] Next, in step S42, the BECM 81 calculates the amount of heat generated during discharge of the low-temperature battery when it is assumed that the specific control is executed. The amount of heat generated is calculated based on the internal resistance calculated from the SOHR estimated in step S42, the current value during discharge, and the lower limit time. Q = RI 2 t It can be obtained by calculating the amount of Joule heat from the formula. Q is the amount of heat generated, R is the internal resistance calculated from SOHR, I is the current value during discharge, and t is the lower limit time. The current value during discharge is the average current value. Note that here, the amount of heat generated when only the low temperature battery is discharged is calculated. As will be described later, in the specific control, there are cases where both the low temperature battery and the high temperature battery are discharged, and the amount of heat generated in that case is lower than the amount of heat generated when only the low temperature battery is discharged.

[0063] Next, in step S43, the BECM 81 calculates a first predetermined temperature difference dTh1 by dividing the amount of heat generated calculated in step S43 by the heat capacity of the low-temperature battery. Since the first and second batteries 11, 12 have the same configuration, the first and second batteries 11, 12 also have the same heat capacity. The heat capacities of the first and second batteries 11, 12 are stored in the memory 81b.

[0064] Next, in step S44, the BECM 81 calculates a second predetermined temperature difference dTh2 based on the first predetermined temperature difference dTh1 calculated in step S44 or step S46. The BECM 81 calculates the second predetermined temperature difference dTh2 so as to be lower than the calculated first predetermined temperature difference dTh1. The second predetermined temperature difference dTh2 may be set to a value lower than the first predetermined temperature difference dTh1 by a determined value, or may be set to a value of a determined ratio (e.g., 60%) of the first predetermined temperature difference dTh1. The BECM 81 returns after step S44. When the second predetermined temperature difference dTh2 calculated based on the first predetermined temperature difference dTh1 is smaller than the resolution of the temperature difference detection by the first and second temperature sensors SW1 and SW2, the second predetermined temperature difference dTh2 may be set to the resolution of the temperature difference detection. For example, when the second predetermined temperature difference dTh2 calculated based on the first predetermined temperature difference dTh1 is 2°C and the resolution of temperature difference detection by the first and second temperature sensors SW1, SW2 is 3°C, the second predetermined temperature difference dTh2 may be set to 3°C.

[0065] In this manner, it is possible to calculate the first predetermined temperature difference dTh1 that enables specific control to be executed while suppressing hunting.

[0066] <Specific Control> Next, the above-mentioned specific control will be described in detail.

[0067] Comparing heat generation during charging and heat generation during discharging, heat generation is more likely during discharging. Therefore, in the specific control, basically, discharging is performed only from the low-temperature battery, while charging is performed only from the battery with the relatively higher temperature (hereinafter referred to as the high-temperature battery) of the first and second batteries 11, 12.

[0068] However, if the low-temperature battery is actively discharged when its SOC is low, the charging power of the low-temperature battery will be depleted and it will be unable to continue generating heat due to discharging. Also, if the high-temperature battery is forced to be charged when its SOC is high, the high-temperature battery will deteriorate, which may lead to a decrease in charging efficiency due to battery deterioration.

[0069] Therefore, in this embodiment, while the basic control is to discharge the low-temperature battery and charge the high-temperature battery, the control content is changed when the SOC of the low-temperature battery is low and when the SOC of the high-temperature battery is high.

[0070] FIG. 6 is a flowchart showing the processing operation of the BECM 81 in the specific control.

[0071] First, in step S61, the BECM 81 determines whether the SOC of the low temperature battery is less than a first predetermined value C1. The first predetermined value C1 is a value of the SOC at which the discharge amount should be suppressed, for example, 40%. If the SOC of the low temperature battery is less than the first predetermined value C1 (YES), the BECM 81 proceeds to step S63. On the other hand, if the SOC of the low temperature battery is equal to or greater than the first predetermined value C1 (NO), the BECM 81 proceeds to step S62.

[0072] In step S62, the BECM 81 determines whether the SOC of the high-temperature battery is equal to or greater than a second predetermined value C2. The second predetermined value C2 is a value of the SOC at which the charge amount should be suppressed, e.g., 80%. If the SOC of the high-temperature battery is equal to or greater than the second predetermined value C2 (YES), the BECM 81 proceeds to step S64. On the other hand, if the SOC of the high-temperature battery is less than the first predetermined value C2 (NO), the BECM 81 proceeds to step S65.

[0073] In step S63, the BECM 81 outputs a control signal to the PCM 80 so that charging is performed only on the low temperature battery and discharging is performed from both the low temperature battery and the high temperature battery. When charging, the PCM 80 turns on the switch connected to the low temperature battery and turns off the switch connected to the high temperature battery. When discharging, the PCM 80 turns on both the switch connected to the low temperature battery and the switch connected to the high temperature battery. After step S63, the BECM 81 returns.

[0074] In step S64, the BECM 81 outputs a control signal to the PCM 80 so as to perform both charging and discharging only on the low-temperature battery. The PCM 80 turns on the switch connected to the low-temperature battery and turns off the switch connected to the high-temperature battery during both charging and discharging. The BECM 81 returns after step S64.

[0075] In step S65, the BECM 81 outputs a control signal to the PCM 80 so that charging is performed only on the high temperature battery and discharging is performed from the low temperature battery. When charging, the PCM 80 turns on the switch connected to the high temperature battery and turns off the switch connected to the low temperature battery. When discharging, the PCM 80 turns on the switch connected to the low temperature battery and turns off the switch connected to the high temperature battery. After step S65, the BECM 81 returns.

[0076] In this way, discharging the low-temperature battery as much as possible can promote heat generation in the low-temperature battery and promote cooling of the high-temperature battery. Also, charging the high-temperature battery as much as possible can suppress deterioration of the charging efficiency of the entire battery 10.

[0077] 7 is a time chart showing charging and discharging of the first and second batteries 11, 12 and changes in the first and second battery temperatures T1, T2 when the battery temperatures are low. Here, it is assumed that the first battery 11 is a low-temperature battery and the second battery 12 is a high-temperature battery. It is also assumed that the SOC of the first battery 11 and the SOC of the second battery 12 are both equal to or greater than a first predetermined value C1 and less than a second predetermined value C2.

[0078] First, in an initial state, the vehicle 1 is stopped and neither the first nor the second battery 11, 12 is being charged or discharged. At this time, the first battery temperature T1 is less than the first predetermined temperature Tc1. The difference between the first battery temperature T1 and the second battery temperature T2 is less than the first predetermined temperature difference dTh1.

[0079] Next, at time t11, the vehicle 1 starts traveling. Since there is almost no difference between the first battery temperature T1 and the second battery temperature T2, the BECM 81 executes normal control. As a result, discharge occurs from both the first and second batteries 11, 12. Since the first battery 11 is more susceptible to the wind caused by traveling than the second battery 12, the first battery temperature T1 is less likely to rise than the second battery temperature T2.

[0080] Next, at time t12, when the difference between the first battery temperature T1 and the second battery temperature T2 becomes equal to or greater than the first predetermined temperature difference dTh1, the BECM 81 executes the specific control. Since discharging is currently in progress, only the first battery 11 is discharged, and the second battery 12 is not discharged. At this time, since it is necessary to supply the necessary power to the drive motor 2 only from the first battery 11, the discharge amount increases compared to normal control. Discharging only from the first battery 11 causes the first battery temperature T1 to rise significantly.

[0081] Next, the vehicle 1 is braked and regenerative charging begins at time t13. At this time, only the second battery 12 is charged, and the first battery 11 is not charged. Since only the second battery 12 is charged, the second battery temperature T2 rises while the first battery temperature T1 hardly rises at all. Furthermore, since the temperature rise during charging is smaller than during discharging, the rate at which the second battery temperature T2 rises during charging is slower than the rate at which the first battery temperature T1 rises during discharging.

[0082] Next, when discharging starts again at time t14, only the first battery 11 is discharged, and no discharge occurs from the second battery 12. This causes the first battery temperature T1 to rise significantly again.

[0083] Then, at time t15, when the difference between the first battery temperature T1 and the second battery temperature T2 becomes equal to or smaller than the second predetermined temperature difference dTh2, the BECM 81 stops the specific control and executes normal control, thereby discharging both the first and second batteries 11, 12.

[0084] Thereafter, at time t16, when the difference between the first battery temperature T1 and the second battery temperature T2 again becomes equal to or greater than the first predetermined temperature difference dTh1, the BECM 81 executes the specific control again.

[0085] 8 is a time chart showing charging and discharging of the first and second batteries 11, 12 and changes in the first and second battery temperatures T1, T2 when the battery temperatures are high. Here, it is assumed that the first battery 11 is a low-temperature battery and the second battery 12 is a high-temperature battery. It is also assumed that the SOC of the first battery 11 and the SOC of the second battery 12 are both equal to or greater than a first predetermined value C1 and less than a second predetermined value C2.

[0086] First, in an initial state, the vehicle 1 is stopped and neither the first nor the second battery 11, 12 is being charged or discharged. At this time, the second battery temperature T2 is higher than the second predetermined temperature Tc2. The difference between the first battery temperature T1 and the second battery temperature T2 is less than the first predetermined temperature difference dTh1.

[0087] Next, at time t21, the vehicle 1 starts traveling. Since there is almost no difference between the first battery temperature T1 and the second battery temperature T2, the BECM 81 executes normal control. As a result, discharge occurs from both the first and second batteries 11, 12. Since the first battery 11 is more exposed to the wind during traveling than the second battery 12, the second battery temperature T2 is less likely to drop than the first battery temperature T1.

[0088] Next, at time t22, when the difference between the first battery temperature T1 and the second battery temperature T2 becomes equal to or greater than the first predetermined temperature difference dTh1, the BECM 81 executes the specific control. Since discharging is currently in progress, only the first battery 11 is discharged, and the second battery 12 is not discharged. At this time, since it is necessary for only the first battery 11 to supply the necessary power to the drive motor 2, the discharge amount increases compared to normal control. As the second battery 12 is no longer discharged, the second battery 12 becomes easier to cool, and the second battery temperature T2 drops significantly.

[0089] Next, the vehicle 1 is braked and regenerative charging begins at time t23. At this time, only the second battery 12 is charged, and the first battery 11 is not charged. Since only the second battery 12 is charged, the second battery temperature T2 becomes less likely to drop than the first battery temperature T1.

[0090] Next, when discharging starts again at time t24, only the first battery 11 is discharged, and no discharge occurs from the second battery 12. This causes the second battery temperature T2 to drop significantly again.

[0091] Then, at time t25, when the difference between the first battery temperature T1 and the second battery temperature T2 becomes equal to or smaller than the second predetermined temperature difference dTh2, the BECM 81 stops the specific control and executes the normal control, thereby discharging both the first and second batteries 11, 12.

[0092] Thereafter, at time t26, when the difference between the first battery temperature T1 and the second battery temperature T2 again becomes equal to or greater than the first predetermined temperature difference dTh1, the BECM 81 executes the specific control again.

[0093] In this manner, the temperature difference between the first cell 11 and the second cell 12 can be reduced, and the charging efficiency of the first cell 11 and the charging efficiency of the second cell 12 can be made as high and uniform as possible. As a result, deterioration of the charging efficiency can be suppressed.

[0094] Effects of the embodiment Therefore, in this embodiment, the vehicle includes first and second battery temperature sensors SW1 and SW2 that measure the temperatures of the first and second batteries 11 and 12, respectively, and a BECM 81 that controls the charging and discharging of the first and second batteries 11 and 12 based on the detection results of the first and second battery temperature sensors SW1 and SW2. The first battery 11 and the second battery 12 are arranged side by side in the vehicle front-rear direction, and the BECM 81 discharges only the low-temperature battery and charges only the high-temperature battery when the temperature difference between the low-temperature battery, which is relatively low, and the high-temperature battery, which is relatively high, of the first and second batteries 11 and 12, is equal to or greater than a first predetermined temperature difference dTh. As a result, the low-temperature battery is more likely to heat up than the high-temperature battery, and the temperature difference between the first battery 11 and the second battery 12 is eliminated. Also, the high-temperature battery is more likely to cool down than the low-temperature battery, and the temperature difference between the first battery 11 and the second battery 12 is eliminated. By eliminating the temperature difference between the first battery 11 and the second battery 12, the difference in charging efficiency between the first battery 11 and the second battery 12 is eliminated, and the charging efficiency of the entire in-vehicle battery can be made high. Also, the charging amount for the low-temperature battery is made smaller than the charging amount for the high-temperature battery. This allows the battery with the highest charging efficiency to be charged preferentially, making it possible to make the charging efficiency of the entire in-vehicle battery high.

[0095] In this embodiment, the BECM 81 estimates the SOHR of the low-temperature battery and sets the first predetermined temperature difference dTh1 based on the estimated SOHR. This makes it possible to set the time during which the specific control is executed long enough to prevent hunting from occurring. As a result, the specific control can be executed with high accuracy.

[0096] In this embodiment, the BECM 81 calculates the SOC of the first and second batteries 11, 12, and when the SOC of the low temperature battery is less than the first predetermined value C1, the BECM 81 makes the amount of discharge from the low temperature battery equal to the amount of discharge from the high temperature battery even when the temperature difference between the low temperature battery and the high temperature battery is equal to or greater than the first predetermined temperature difference dTh. This makes it possible to prevent the temperature difference from becoming excessively large while suppressing the power depletion of the low temperature battery.

[0097] When the SOC of the low temperature battery is less than a second predetermined value C2 higher than the first predetermined value C1 and the SOC of the high temperature battery is equal to or greater than the second predetermined value C2, the BECM81 makes the charge amount of the low temperature battery greater than the charge amount of the high temperature battery, even when the temperature difference between the low temperature battery and the high temperature battery is equal to or greater than the first predetermined temperature difference dTh1. This suppresses charging when the SOC is high, thereby suppressing deterioration of the high temperature battery due to excessive charging. As a result, it is possible to suppress deterioration of charging efficiency due to deterioration of the high temperature battery.

[0098] (Other embodiments) The technology disclosed herein is not limited to the above-described embodiment, and may be substituted without departing from the spirit and scope of the claims.

[0099] For example, in the above-described embodiment, the first cell 11 and the second cell 12 are arranged side by side in the vehicle front-rear direction. However, as shown in FIG. 9, the first cell 11 and the second cell 12 may be arranged side by side in the vehicle width direction. Even when the first cell 11 and the second cell 12 are arranged side by side in the vehicle width direction, for example, when sunlight is hitting one of the left and right sides of the vehicle 1 or when the exhaust pipe is arranged biased to one of the left and right sides of the vehicle 1, a temperature difference occurs between the first cell 11 and the second cell 12. Therefore, even when the first cell 11 and the second cell 12 are arranged side by side in the vehicle width direction, the effect of the specific control can be exerted.

[0100] In the above embodiment, the BECM 81 basically discharges only from the low-temperature battery and charges only from the high-temperature battery. However, the BECM 81 may discharge and charge at least one of the low-temperature battery and the high-temperature battery, and adjust the ratio. For example, 80% of the discharge amount may be supplied from the low-temperature battery and 20% from the high-temperature battery. Also, 20% of the charge amount may be supplied to the low-temperature battery and 80% to the high-temperature battery. In this way, the control to adjust the ratio of the charge amount and the discharge amount is possible by controlling the first converter 5 and the second converter 6.

[0101] In the above embodiment, the battery 10 includes only two batteries, the first battery 11 and the second battery 12. However, the battery 10 may include three or more batteries as shown in FIG. 10. In this case, the BECM 81 executes the specific control when the difference between the temperature of the hottest battery and the temperature of the coldest battery becomes equal to or greater than the first predetermined temperature difference dTh1. At this time, only the coldest battery is discharged, and the batteries other than the coldest battery are charged. The ratio of the discharge amount and the charge amount may be adjusted according to the temperature of the batteries. For example, when there are three batteries as shown in FIG. 10, 70% of the discharge amount may be supplied from the coldest battery, 20% from the battery with the middle temperature, and 10% from the hottest battery.

[0102] The above-described embodiments are merely illustrative and should not be construed as limiting the scope of the present disclosure. The scope of the present disclosure is defined by the claims, and all modifications and variations within the scope of the claims are within the scope of the present disclosure. [Industrial Applicability]

[0103] The technology disclosed herein is useful as a temperature control device for an on-board battery having multiple batteries. [Explanation of symbols]

[0104] 10 batteries 11 First battery 12 Second battery 81 BECM (controller) SW1 1st battery temperature sensor (battery temperature detection section) SW2 Second battery temperature sensor (battery temperature detection section)

Claims

1. A temperature control device for an in-vehicle battery having a plurality of batteries, a plurality of battery temperature detection units each measuring a temperature of each of the batteries; a controller that controls charging and discharging of each battery based on the detection results of each battery temperature detection unit; The batteries are arranged side by side in at least one of a vehicle front-rear direction and a vehicle width direction, a controller that controls the discharge amount of the battery having a relatively low temperature to be greater than the discharge amount of the battery having a relatively high temperature when the temperature difference between the batteries is equal to or greater than a predetermined temperature difference, and controls the charge amount of the battery having a relatively low temperature to be less than the charge amount of the battery having a relatively high temperature.

2. The temperature control device for an in-vehicle battery according to claim 1, the vehicle-mounted battery includes a pair of batteries, a first battery and a second battery, The first battery and the second battery are arranged side by side in a vehicle front-rear direction or a vehicle width direction, A temperature control device for an on-board battery, characterized in that when a temperature difference between a low-temperature battery, which is the battery that has a relatively low temperature among the first and second batteries, and a high-temperature battery, which is the battery that has a relatively high temperature, is equal to or greater than the predetermined temperature difference, the controller makes the amount of discharge from the low-temperature battery greater than the amount of discharge from the high-temperature battery, and makes the amount of charge to the low-temperature battery less than the amount of charge to the high-temperature battery.

3. The temperature control device for an in-vehicle battery according to claim 2, The controller: Estimating a state of health (SOH) of the low-temperature battery; A temperature control device for an in-vehicle battery, comprising: a temperature control device for controlling a temperature of the in-vehicle battery;

4. The temperature control device for a battery according to claim 2 or 3, The controller: Calculating the SOC (State of Charge) of each of the first and second batteries; a temperature control device for an on-board battery, characterized in that when the SOC of the low-temperature battery is less than the first predetermined value, the amount of discharge from the low-temperature battery is equal to the amount of discharge from the high-temperature battery, even when the temperature difference between the low-temperature battery and the high-temperature battery is equal to or greater than the predetermined temperature difference.

5. 5. The battery temperature control device according to claim 4, a controller that controls a charging amount of the low-temperature battery to be greater than a charging amount of the high-temperature battery when the SOC of the low-temperature battery is less than a second predetermined value higher than the first predetermined value and the SOC of the high-temperature battery is equal to or greater than the second predetermined value, even when a temperature difference between the low-temperature battery and the high-temperature battery is equal to or greater than the predetermined temperature difference.

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