Thermoelectric battery cooling system and process

Abstract

Electrified vehicle arrangement comprising: a first coolant circuit (50) extending from a battery pack (38) to a radiator (18); a second coolant circuit (54) extending from the battery pack (38) to a thermoelectric device (22) powered by an electrical system of an electrified vehicle; and at least one valve (30, 34) configured to allow flow through the first coolant circuit (50) from the battery pack (38) to the radiator for cooling the battery pack (38) under a first operating condition, and configured to allow flow in the second coolant circuit (54) for cooling the battery pack (38) under a second operating condition.

Description

TECHNICAL AREA The present disclosure relates generally to the cooling of batteries of electrified vehicles. In particular, the disclosure relates to the selective cooling of the batteries of electrified vehicles using a thermoelectric device. BACKGROUND In general, electrified vehicles differ from conventional motor vehicles in that they are selectively powered using one or more electric motors powered by batteries. Conventional motor vehicles, in contrast, are powered exclusively by an internal combustion engine. The electric motors can power electrified vehicles instead of, or in addition to, an internal combustion engine. Examples of electrified vehicles include hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), fuel cell vehicles (FCVs), and battery electric vehicles (BEVs). The batteries of electric vehicles may require cooling. Some batteries are liquid-cooled. Typically, a radiator transfers heat energy from these batteries to the surrounding environment. Some electric vehicles employ a cooling device to provide additional cooling for the batteries. This cooling device is connected to the passenger compartment's air conditioning system. From US patent application US 2017 / 0 072 813 A1, a vehicle with a control logic is known that selectively supplies regeneratively generated electrical energy to an electrical heating or cooling system of the battery when defined temperature thresholds are exceeded or fallen below, in particular when the charging power limit of the battery is exceeded. From US patent application US 7 779 639 B2, a vehicle system for hybrid vehicles is known that combines thermoelectric elements with multiple coolant circuits and heat exchangers to selectively heat, cool and dehumidify the vehicle interior, wherein a first coolant circuit is in thermal connection with an electrical side of the hybrid vehicle, and a second circuit is in thermal connection with a fuel-operated side of the hybrid vehicle. German patent application DE 10 2013 206 651 A1 discloses a system and a method for heating a battery in a hybrid vehicle using exhaust gas, wherein an exhaust gas heat recovery (EGHR) device is provided for directing exhaust gas to an EHR heat exchanger for transferring thermal energy to a heat transfer fluid, wherein the heat exchanger transfers thermal energy from the heat transfer fluid to a battery cover plate when the temperature of the battery is below a predetermined temperature, so that the temperature of the battery rises. SUMMARY Based on this prior art, an electrified vehicle arrangement with the features of independent claim 1, an electrified vehicle arrangement with the features of independent claim 7, a vehicle battery pack cooling method with the features of independent claim 10, and a vehicle battery pack cooling method with the features of independent claim 17 are provided. Advantageous embodiments are described in the dependent claims. An electrified vehicle arrangement according to an exemplary aspect of the present disclosure comprises, inter alia, a first coolant circuit extending from a battery pack to a radiator, and a second coolant circuit extending from the battery pack to a thermoelectric device. The thermoelectric device is supplied by an electrical system of an electrified vehicle. At least one valve is configured to allow flow through the first coolant circuit from the battery pack to the radiator for cooling the battery pack under a first operating condition, and is further configured to allow flow in the second coolant circuit for cooling the battery under a second operating condition. In a further non-restrictive embodiment of the above arrangement, the cooler transfers heat energy from the flow in the first coolant circuit to the ambient air outside the electrified vehicle. In a further non-restrictive embodiment of one of the above arrangements, the at least one valve is configured to allow flow through both the first and the second coolant circuits for cooling the battery pack under a third operating condition. In a further non-restrictive embodiment of one of the foregoing arrangements, the arrangement comprises a current control module configured to control the current supplied by the electrical system to the thermoelectric device. In a further non-restrictive embodiment of one of the above arrangements, the first operating condition corresponds to a first temperature and the second operating condition corresponds to a second temperature which is higher than the first operating temperature. In another non-restrictive embodiment of one of the above arrangements, the thermoelectric device is a Peltier device. In a further non-restrictive embodiment that also solves the problem, the arrangement comprises a first coolant circuit extending from a battery pack to a radiator; a second coolant circuit extending from the battery pack to a thermoelectric device; and at least one valve configured to allow flow through the first coolant circuit for cooling the battery pack under a first operating condition, and configured to allow flow in the second coolant circuit for cooling the battery under a second operating condition; and a third coolant circuit extending from the radiator to the thermoelectric device, wherein the at least one valve is configured to allow flow through the third coolant circuit for cooling the thermoelectric device under the second operating condition. In a further non-restrictive embodiment of one of the foregoing arrangements, the arrangement comprises a first pump gun and a second pump. The first pump is configured to move a flow through the first coolant circuit under the first operating condition and to move a flow through the second coolant circuit under the second operating condition. The second pump is configured to move a flow through the third coolant circuit under the second operating condition. In a further non-restrictive embodiment of one of the above arrangements, at least a part of the first coolant circuit overlaps at least a part of the second coolant circuit, and the second coolant circuit and the third coolant circuit are separate and distinct from each other. A vehicle battery pack cooling method according to an exemplary aspect of the present disclosure comprises, inter alia, in a first operating condition, cooling a battery pack with a flow moving along a first coolant circuit between the battery pack and a cooler, and in a second operating condition, cooling the battery pack with a flow moving along a second coolant circuit between the battery pack and a thermoelectric device, wherein a part of the first coolant circuit superimposes a part of the second coolant circuit. In a further non-restrictive embodiment of the above method, the method comprises transferring heat energy from a flow within the first coolant circuit to ambient air outside an electrified vehicle at the radiator. In a further non-restrictive embodiment of one of the above methods, the method, under a third operating condition, comprises cooling the battery pack with a flow moving along both the first and the second coolant circuit. In a further non-restrictive embodiment of one of the above methods, the method in the second operating condition comprises supplying the thermoelectric device with current from an electrical system of an electrified vehicle. In a further non-restrictive embodiment of one of the above methods, the second coolant circuit is located completely outside the radiator. In a further non-restrictive embodiment of one of the above methods, the method in the second operating condition comprises cooling the thermoelectric device with a flow moving along a third coolant circuit between the thermoelectric device and the cooler. In another non-restrictive embodiment of one of the above methods, the thermoelectric device is a Peltier device. In a further non-restrictive embodiment that also solves the problem, the vehicle battery pack cooling method comprises, in a first operating condition, cooling a battery pack with a flow moving along a first coolant circuit between the battery pack and a cooler; and in a second operating condition, cooling the battery pack with a flow moving along a second coolant circuit between the battery pack and a thermoelectric device, and switching from the first operating condition to the second operating condition in response to a temperature. In a further non-restrictive embodiment of one of the above methods, the method comprises, in a third operating condition, heating the battery pack with a flow moving along a second coolant circuit between the battery pack and a thermoelectric device. DESCRIPTION OF THE FIGURES The various features and advantages of the disclosed examples will become apparent to a person skilled in the art from the detailed description. The figures accompanying the detailed description can be briefly described as follows: Fig. 1 shows an exemplary battery cooling system operating under a first operating condition. Fig. 2 shows the battery cooling system of Fig. 1 operating under a second operating condition. Fig. 3 shows a highly schematic view of a control arrangement used with components of the battery cooling system of Figs. 1 and 2. DETAILED DESCRIPTION The present disclosure relates generally to the cooling of a battery of an electrified vehicle. In particular, the disclosure relates to the cooling of a battery pack using a cooler and, under certain conditions, to the cooling of the battery pack using a thermoelectric device. The thermoelectric device is used instead of, for example, a cooling device connected to an air conditioning system of a passenger compartment of the vehicle. With reference to Fig. 1, an exemplary battery cooling system 10 comprises a pump 14, a radiator 18, a thermoelectric device 22, a heat exchanger plate 26, a valve 30, and another valve 34. The heat exchanger plate 26 is part of a battery pack 38. Within the battery pack 38, battery cells 42 are arranged on the heat exchanger plate 26. The battery cooling system 10 is integrated into an electrified vehicle. In the electrified vehicle, the battery cells can supply power to 42 motors, which selectively drive one or more sets of vehicle drive wheels. An exemplary vehicle in which the system 10 is integrated is a hybrid vehicle with a first drive system comprising the motor and battery set 38, and a second drive system comprising an internal combustion engine and a generator. The two drive systems can selectively generate torque to drive the vehicle wheels. In another example, the battery pack 38 supplies power to an electric machine that drives the wheels of a battery-electric vehicle, in which the drive wheels are powered exclusively using battery power. The battery cells 42 can heat up during operation and in high-temperature environments. Keeping the temperature of the battery cells 42 below a threshold temperature can improve the efficiency of the battery pack 38. In some examples, the threshold temperature for the battery cells 42 is 50 degrees Celsius. In this example, fluid is moved through the heat exchanger plate 26 to dissipate heat energy from the battery cells 42 and other parts of the battery pack 38. In another example, fluid is moved instead or additionally through areas between the battery cells 42 to dissipate heat energy. Therefore, the battery cooling system 10 is not limited to the fluid cooling path shown. Figure 1 shows the battery cooling system 10 operating under a first operating condition. Under this first operating condition, the system 10 provides a first coolant circuit 50 extending from the heat exchanger plate 26 of the battery pack 38 to the radiator 18 and back. Pump 14 circulates a fluid along the first coolant circuit 50. The fluid absorbs heat from the battery pack 38 as it moves along the first coolant circuit 50 through the heat exchanger plate 26. The heated fluid from the heat exchanger plate 26 then moves along the first coolant circuit 50 and is passed through the radiator 18. In this example, the fluid is a 50 / 50 mixture of water and glycol. However, other fluids and fluid mixtures could also be used. In radiator 18, heat energy is transferred from the fluid in the first coolant circuit to ambient air outside an electrified vehicle with system 10. Under the first operating condition, radiator 18 can provide sufficient cooling for the battery pack 38. A fan can be used to move air through radiator 18. Radiator 18 can be one of several radiators cooled by a single fan. The other radiators can include radiators intended for an internal combustion engine, the transmission oil cooler, etc. Operating system 10 under the first operating condition, fluid at approximately 30 °C can be supplied to the heat exchanger plate in this example. Under many conditions, the fluid supplied to the heat exchanger plate 26 at this temperature will dissipate sufficient heat energy from the battery pack 38 to keep the battery pack 38 at or below the threshold temperature. Under certain conditions, the first coolant circuit 50 may not be able to dissipate sufficient heat energy from the battery pack 38. For example, the vehicle might be operated in a very hot environment where the radiator 18 is unable to transfer sufficient heat energy from the fluid in the first coolant circuit 50 to the ambient air. In response, system 10 switches to operation under a second operating condition. Under the second operating condition, system 10 provides cooling for battery pack 38 if operation under the first operating condition would not provide sufficient cooling. With reference to Fig. 2, the system 10 is shown operating under the second operating condition. Under the second operating condition, the system 10 provides a second coolant circuit 54 extending from the battery pack 38 to the thermoelectric device 22 and back. The system 10 additionally provides a third coolant circuit 58 extending from the radiator 18 to the thermoelectric device 22 and back. In this example, valve 30 and valve 34 are activated to switch the coolant circuits in system 10 from the positions for the first operating condition to the positions for the second operating condition. The second coolant circuit 54 does not overlap with the third coolant circuit 58, so the second coolant circuit 54 and the third coolant circuit 58 are separate and distinct from each other. Valves 30 and 34 can contain solenoids that are energized to activate valves 30 and 34 from the positions for the first operating condition to the positions for the second operating condition. Other valve types could be used in other examples. In this example, the second coolant circuit 54 runs through a cold side 62 of the thermoelectric device 22. The third coolant circuit 58 runs through a hot side 66 of the thermoelectric device. The exemplary thermoelectric device 22 is a Peltier device. When operating under the second operating condition, the system 10 conducts a direct current through a branch 70 of the thermoelectric device 22. The branch 70 is positioned between the cold side 62 and the hot side 66. When current flows through the branch 70, the cold side 62 is cooled and the hot side 66 is heated. As a flow moves along the second coolant circuit through the cold side 62 of the thermoelectric device 22, the fluid is cooled to a temperature suitable for cooling the battery pack 38. The thermoelectric device 22 can provide cooling instead of the cooler 18, particularly at relatively high ambient temperatures. A flow moving along the third coolant circuit 58 transports heat energy from the hot side 66 of the thermoelectric device 22 and transfers the heat energy to ambient air at the cooler 18. A pump 72 separate from the pump 14 can be used to move a flow along the third coolant circuit 58. In this example, when system 10 is operating under the second operating condition, an electrical system of an electrified vehicle, such as battery pack 38, supplies power to a current control module 74. The current control module 74 is integrated into system 10 to regulate current from battery pack 38 to branch 70. Battery pack 38 can power other devices, such as control modules and a DC / DC converter, which then supply power to the current control module 74. Power sources other than battery pack 38 could be used to power the thermoelectric device 22. For example, a 12 V side of a DC / DC converter could be used to power the current control module 74 and branch 70. The power sources may depend, in part, on whether the vehicle is a hybrid or fully electric vehicle. Operating system 10 under the second operating condition thus provides cooling for battery pack 38 when cooler 18 is unable to do so. Cooling under the second operating condition is provided without resorting to a cooling device connected to the vehicle's air conditioning system, and therefore without impairing the air conditioning system's cooling capacity in the vehicle's passenger compartment. In some examples, the thermoelectric device can be used to heat the battery pack 38 instead of cooling it. For instance, in one operating condition different from the second, the thermoelectric device can be supplied with the opposite polarity, so that the cold side 62 becomes a hot side and the hot side 66 becomes a cold side. Fluid moving along the second circuit is then heated at the thermoelectric device 22 and passed through the heat exchanger plate 26 to heat the battery pack 38. Heating the battery pack 38 may be necessary when operating the vehicle in environments with cold ambient temperatures. In some examples, valve 34, valve 30, or both are proportional valves that can be adjusted to positions allowing simultaneous flow through both the first coolant circuit 50 and the second coolant circuit 54 to cool the battery pack 38. In such an example, the portion of the third coolant circuit 58 that extends through the hot side 66 can be omitted. The hot side 66 could then be cooled, for example, by an airflow. With reference to Fig. 3, an exemplary control arrangement 90 is used in conjunction with the system 10 to control the position of the valves 30 and 34 and the flow moved by the pumps 14 and 72. In this example, the control arrangement 90 includes a controller 78 that is functionally connected to the current control module 74. In another example, the current control module 74 is part of the controller 78. The controller 78 can regulate the cooling provided by the thermoelectric device 22 for the battery pack 38 during operation of the system 10 under the second operating condition via the current control module 74. The battery pack 38 can supply power to the current control module 74, or another part of a power supply system of the electrified vehicle can supply power to the current control module 74. The exemplary controller 78 can include a processor that is functionally connected to a memory module. The exemplary processor is programmed to execute a program stored in the memory module. The program can be stored in the memory module as software code. The program stored in the memory section can comprise one or more additional or separate programs, each containing an ordered list of executable instructions for implementing logical functions. These instructions enable the controller 78 to initiate movement of valves 30 and 34 to switch system 10 from the first operating condition to the second operating condition. The instructions also enable the controller 78 to regulate the cooling provided by the thermoelectric device 22. The controller 78 receives temperature data from a temperature sensor 82. The temperature sensor can, for example, measure the temperature of fluid entering the heat exchanger plate 26. If the temperature of this fluid rises above a setpoint, the controller 78 adjusts, among other things, the valves 30 and 34 and the pumps 14 and 72 to switch the system 10 from fluid flow along the first coolant circuit 50 under the first operating condition to fluid flow along the second coolant circuit 54 and the third coolant circuit 58 under the second operating condition. The controller 78 switches the system 10 back from the second operating condition to the first operating condition in response to, for example, a sensor in the arrangement that monitors the temperature of fluid exiting the cooler 18 along the third coolant circuit.When the temperature is low enough to provide adequate cooling of the battery pack 38, the controller 78 switches back to operating the system 10 under the first operating condition, thereby saving power. In addition to the temperature of the fluid entering the heat exchanger plate, the controller 78 can receive other temperature information. For example, ambient temperature measurements, battery cell temperature measurements, and passenger compartment temperature measurements could be used by the controller 78. For the sake of clarity, these other temperature measurements are not shown schematically in Fig. 3. In another example, system 10 switches between the first operating condition and the second operating condition in response to other variables, such as ambient air temperature, the charge level of battery pack 38, the temperature of battery pack 38, etc. For example, system 10 could operate in the first operating condition when the ambient air temperature is less than 30 degrees Celsius, and then switch to the second operating condition when the ambient air temperature reaches 30 degrees Celsius or above. Although this exemplary system 10 in the illustration integrates the third coolant circuit 58 when operating under the second operating condition, the third coolant circuit 58 can be omitted in other examples when the system 10 is operated under the second operating condition. The hot side 66 could, for example, be air-cooled with a fan. Exemplary features of some of the disclosed examples include providing additional cooling for a battery pack without the use of a cooling device, thereby reducing complexity. When packaging the thermoelectric device 22 close to the battery pack 38 in the vehicle, the thermal stress on the thermoelectric device can be reduced by avoiding heat buildup in the coolant lines between the cooling device and the battery pack. In some examples, the system can be operated with a coefficient of performance (COP) comparable to that of systems that use a cooling device to cool the battery pack 38. The foregoing description is illustrative rather than restrictive. Variations and modifications to the disclosed examples, which do not necessarily deviate from the essence of the present disclosure, may be obvious to the person skilled in the art. Thus, the legal scope of protection of the present disclosure can only be determined by considering the following claims.

Claims

Electrified vehicle arrangement comprising: a first coolant circuit (50) extending from a battery pack (38) to a radiator (18); a second coolant circuit (54) extending from the battery pack (38) to a thermoelectric device (22) powered by an electrical system of an electrified vehicle; and at least one valve (30, 34) configured to allow flow through the first coolant circuit (50) from the battery pack (38) to the radiator for cooling the battery pack (38) under a first operating condition, and configured to allow flow in the second coolant circuit (54) for cooling the battery pack (38) under a second operating condition. Arrangement according to claim 1, wherein the cooler (18) transfers heat energy from the flow in the first coolant circuit (50) to the ambient air outside the electrified vehicle. Arrangement according to claim 1, wherein the valve (30, 34) is configured to allow flow through both the first (50) and the second coolant circuit (54) for cooling the battery pack (38) under a third operating condition. Arrangement according to claim 1, further comprising a current control module (74) configured to control the current supplied by the electrical system to the thermoelectric device (22). Arrangement according to claim 1, wherein the first operating condition corresponds to a first temperature and the second operating condition corresponds to a second temperature which is higher than the first temperature. Arrangement according to claim 1, wherein the thermoelectric device (22) is a Peltier device. Electrified vehicle arrangement comprising: a first coolant circuit (50) extending from a battery pack (38) to a radiator (18); a second coolant circuit (54) extending from the battery pack (38) to a thermoelectric device (22);and at least one valve (30, 34) configured to allow flow through the first coolant circuit (50) for cooling the battery pack (38) under a first operating condition, and configured to allow flow in the second coolant circuit (54) for cooling the battery pack (38) under a second operating condition, and a third coolant circuit (58) extending from the radiator (18) to the thermoelectric device (22), wherein the at least one valve (30, 34) is configured to allow flow through the third coolant circuit (58) for cooling the thermoelectric device (22) under the second operating condition. Arrangement according to claim 7, further comprising a first pump (14) and a second pump (72), wherein the first pump (14) is configured to move a flow through the first coolant circuit (50) under the first operating condition and to move a flow through the second coolant circuit (54) under the second operating condition, wherein the second pump (72) is configured to move a flow through the third coolant circuit (58) under the second operating condition. Arrangement according to claim 8, wherein at least a part of the first coolant circuit (50) is superimposed on at least a part of the second coolant circuit (54) and the second coolant circuit (54) and the third coolant circuit (58) are separate and distinct from each other. Vehicle battery pack cooling method comprising: in a first operating condition, cooling a battery pack (38) with a flow moving along a first coolant circuit (50) between the battery pack (38) and a radiator (18); and in a second operating condition, cooling the battery pack (38) with a flow moving along a second coolant circuit (54) between the battery pack (38) and a thermoelectric device (22), wherein a part of the first coolant circuit (50) superimposes a part of the second coolant circuit (54). The method of claim 10, which further comprises transferring heat energy from a flow within the first coolant circuit (50) to ambient air outside an electrified vehicle at the radiator (18). The method according to claim 10, which further comprises, in a third operating condition, cooling the battery pack (38) with a flow moving along both the first (50) and the second coolant circuit (54). The method according to claim 10, which further comprises, in the second operating condition, supplying the thermoelectric device (22) with current from an electrical system of the electrified vehicle. Method according to claim 10, wherein the second coolant circuit (54) is located completely outside the radiator (18). The method according to claim 10, which further comprises, in the second operating condition, cooling the thermoelectric device (22) with a flow moving along a third coolant circuit (58) between the thermoelectric device (22) and the cooler (18). Method according to claim 10, wherein the thermoelectric device (22) is a Peltier device. Vehicle battery pack cooling method comprising: in a first operating condition, cooling a battery pack (38) with a flow moving along a first coolant circuit (50) between the battery pack (38) and a radiator (18); and in a second operating condition, cooling the battery pack (38) with a flow moving along a second coolant circuit (54) between the battery pack (38) and a thermoelectric device (22), and switching from the first operating condition to the second operating condition in response to a temperature. The method according to claim 10, which further comprises, in a third operating condition, heating the battery pack (38) with a flow moving along a second coolant circuit (54) between the battery pack (38) and a thermoelectric device (22).

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