Site-based preventive cooling for direct current fast charging of electric vehicles

Abstract

A method for preventively cooling a traction battery (12) of a vehicle (10) for direct current fast charging (DCFC), the method comprising: in response to detecting, during a drive cycle and prior to arrival at a DCFC station, an expected DCFC event based on vehicle (10) driving history data, requesting start-up by a controller (28) of cooling of the traction battery (12) prior to arrival.

Description

TECHNICAL FIELDThe present disclosure relates to cooling a traction battery for an electric vehicle.GENERAL STATE OF THE ARTElectric vehicles, such as battery-powered electric vehicles ("BEV") and plug-in hybrid vehicles ("PHEV"), include a traction battery, such as a high voltage battery, that acts as a power source for the vehicle. A motor converts electrical energy from the traction battery into torque for vehicle propulsion. When discharged, the traction battery requires charging. Propulsion batteries are rechargeable with energy from the electrical mains. External charging stations provide power to recharge the traction batteries. Recharging can occur at different speeds. For example, DCFC fast charging (DCFC) is a high power charging operation that provides fast charging of vehicles at DCFC stations. Traction batteries may also be charged with normal mains current, via inductive charging, or via other methods. During charging, the temperature of the drive batteries rises due to heat generation. Battery thermal management systems are used to regulate traction battery temperature. These systems allow some temperature rise before high performance cooling is invoked and are typically used for normal ride and load events. Charging the traction battery using DCFC results in an undesired high temperature rise leading to power limiting, an increase in charging time, and a reduced ability to draw long distances from fast charging.In document DE 10 2015 118 466 A1, methods and systems for pre-cooling a traction battery in expectation of recharging at a charging station are described.SUMMARYA vehicle is provided. The vehicle includes a traction battery, a battery cooling system configured to cool the traction battery, and a controller configured to request triggering of the battery cooling system to cool the traction battery prior to arrival at a DCFC station in response to a signal indicative of an expected DCFC event and configured to inhibit triggering in response to an expected duration of the expected DCFC event being less than a predefined duration. The expected DCFC event may be indicated based on collected GPS data or navigation data or may be defined by the state of charge of the battery being below a threshold. The predefined duration of the expected DCFC event is based on a temperature of the traction battery, the state of charge of the traction battery, the ambient temperature, or the cabin climate.According to embodiments of the present disclosure, a method for preventively cooling a traction battery of a vehicle for DCFC fast charging (DCFC) is provided. The method includes, responsive to detecting, during a drive cycle and prior to arrival at a DCFC station, an expected DCFC event based on travel history data of the vehicle, requesting starting by a controller of cooling of the traction battery prior to arrival. The method also includes inhibiting starting cooling of the traction battery in response to an expected duration of the expected DCFC event being less than a predefined duration. The duration of the expected DCFC event is based on a temperature of the traction battery, the state of charge of the traction battery, the ambient temperature, or the cabin climate. The preventative cooling may be based on driving history data that is collected GPS data describing current and previous driving cycles and DCFC events. The collected GPS data may show that the vehicle does not follow a detected worksite, that the vehicle is proximate to and capable of reaching a DCFC station in a predetermined period of time, or that a range is less than a distance to the driver's home or workplace or a previous charging station. The preventive cooling may also be based on travel history data which is navigation data.According to embodiments of the present disclosure, a system for preventively cooling a traction battery of a vehicle to the DCFC is provided. The system includes a traction battery, a battery cooling system configured to cool the traction battery, and a controller configured to detect an expected DCFC event prior to arrival at a DCFC station and request triggering of the battery cooling system to cool the traction battery prior to arrival at the DCFC station. The controller is further configured to inhibit the triggering in response to an expected duration of the DCFC being less than a predefined duration. The predefined duration is based on a temperature of the traction battery, a state of charge of the traction battery, the ambient temperature or the interior climate. The expected DCFC event may be based on collected GPS data or navigation data or may be defined by the state of charge of the battery being below a threshold.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a diagram illustrating an example of an electric vehicle according to an embodiment of the present invention.DETAILED DESCRIPTIONDetailed embodiments of the present invention are disclosed herein as prescribed; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Accordingly, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.FIG. 1 illustrates an example of an electric vehicle 10. In this example, the vehicle 10 is a battery-powered electric vehicle (BEV) lacking an internal combustion engine. However, in certain other embodiments, the vehicle 10 may be a hybrid electric vehicle that includes an internal combustion engine. The vehicle 10 includes a traction battery 12 or battery and an electric motor 14. for example, the battery 12 is a lithium ion battery pack. The motor 14 converts electrical energy from the battery 12 into motor torque for vehicle propulsion. The battery 12 supplies electric power to the motor 14 through an inverter (not shown) connected between the battery 12 and the motor 14. The battery 12 discharges to supply electrical power to the motor 14. The engine 14 provides torque to a vehicle powertrain to propel one or more wheels 16 of the vehicle 10.The traction battery 12 stores energy and typically provides a high voltage DC output. The traction battery 12 is rechargeable with electrical energy from the electrical grid at a charging station 18. The charging station 18 may provide alternating current or direct current at a normal charging speed or at a high voltage direct current rapid charging (DCFC) speed to the traction battery 12 of the vehicle 10 by electrically connecting through a charging port (not shown). The vehicle 10 may include equipment configured for a fast charging mode. For example, the vehicle 10 may include a quick charging port (not shown) connectable to a quick charging connector (not shown). The plug may include a cable connected to the charging station 18.In one embodiment, the charging station 18 provides relatively high current to the traction battery 12 during the fast charging operation. For example, the charging station 18 is a "DC fast charge" charging station that uses high voltage (e.g., 400-500 V) and high current (e.g., 100-300 A) to charge the battery 12. Using DCFC, the battery 12 can be charged relatively quickly. In other embodiments, the charging station 18 may provide high current or relatively low current.Because of the high current, more heat is generated during the higher voltage charging mode. In some of the charging modes, such as fast charging, the traction battery 12 must be actively cooled to prevent overheating. The temperature of the battery 12 should be maintained within a given range while the battery is operating, such as during discharging and charging. The temperature range depends on the type and characteristics of the battery 12. In particular, the temperature of the battery 12 should not exceed a maximum operating temperature.The temperature of the battery 12 depends on an ambient temperature and the rate of discharge or charge. The following observations can be made while everything else remains the same. The temperature of the battery 12 will be higher with a higher ambient temperature (e.g., a hot summer day) than with a low ambient temperature (i.e., a cold winter night). The temperature of the battery 12 will be higher when the battery is discharged during difficult driving conditions and therefore generates more heat than compared to simple driving conditions. The temperature of the battery 12 will be higher when the battery is charged with high current, which heats the battery quickly, than when the battery is charged with lower current, which heats the battery slowly.The vehicle 10 includes a battery cooling system 20 configured to cool the traction battery 12 by cooling or removing heat from the battery 12 to lower or maintain the battery temperature below the maximum operating temperature. For example, the battery cooling system 20 delivers cooled coolant to the battery 12 and returns warmer coolant to the battery cooling system. The battery cooling system 20 may transfer heat to either the exterior environment or the interior of the vehicle 10 through heat exchangers (e.g., a radiator).The battery cooling system 20 is most effective when the vehicle 10 is moving due to the increased airflow through the heat exchangers. Thus, the cooling capability is greater when the vehicle 10 is powered than when parked at the charging station 18. The battery cooling system 20 is capable of cooling the battery 12 to reduce or maintain the battery temperature below the maximum operating temperature while the vehicle 10 is being propelled.The vehicle 10 further includes a battery temperature sensor 22, an ambient temperature sensor 24, and a battery state of charge (SOC) sensor 26. The ambient temperature sensor 24 is designed to detect the temperature of the surrounding environment. The battery SOC sensor 26 is a processor or the like configured to acquire the SOC of the battery. The battery SOC sensor 26 receives appropriate input information from the battery 12 to determine the battery SOC.The vehicle 10 also includes a controller 28 in electrical communication with the battery cooling system 20 and the sensors 22, 24, and 26. The controller 28 is configured to control the battery cooling system 20 to cool the battery 12 and to decrease and maintain the temperature of the traction battery 12 below the maximum operating temperature. The controller 28 controls the battery cooling system 20 based on trip requests. The start requests are based on battery temperature, ambient temperature, maximum operating temperature, battery SOC, and / or inputs.Preventive cooling of the traction battery 12 to increase the temperature difference between the battery temperature and the maximum operating temperature before the DCFC event at the charging station 18 is desirable. Specifically, the battery 12 heats up rapidly during the DCFC due to the heavy current. The increased amount of heat will not only be too much for the battery cooling system 20 to remove it while the vehicle 10 is parked, but higher temperatures will also result in longer charging times. Since the power consumption of the battery cooling system 20 for preventively cooling the battery 12 is higher when the vehicle is driven, the preventive cooling only occurs upon indication of an expected DCFC event to maximize the daily range and maintain rapid charging.According to embodiments of the present invention, the controller 28 is further configured to request starting of the battery cooling system 20 in anticipation of a DCFC event to pre-emptionally cool the traction battery 12 while the vehicle 10 is being propelled (i.e., during a drive cycle) before arriving at the charging station 18. The controller 28 requests starting of the battery cooling system 20 to preventively cool the traction battery 12 while the vehicle 10 is being driven to the charging station 18 because the battery cooling system 20 has additional cooling capabilities due to increased airflow through the heat exchangers. The battery cooling system 20 pre-prophylactically cools the traction battery 12 to further reduce the temperature of the traction battery, which should already be below the maximum operating temperature, below the maximum operating temperature. Like each vehicle feature, the DCFC preventative cooling feature may be selectable by an in-vehicle computer system.The controller 28 detects when a DCFC event is expected and requests starting of the preventive cooling operation from the battery cooling system 20. Such gathering information is referred to with respect to the controller 28 as DCFC event information or "recharge event information.".The vehicle 10 further includes the recharge event notification input 30 for communicating the recharge event information to the controller 28. Multiple methods may be used to communicate the recharge event information to the controller 28, and the recharge event notification input 30 may take various forms, as described below. The recharge event information defining an expected DCFC event may be sensed by a sensor and / or generated and sent to the controller 28 via a signal.The recharge event notification input 30 may be based on the current and previous drive cycles of the vehicle or drive history data to predict when a DCFC event is expected. The vehicle travel history data and / or the traction battery 12 SOC threshold may be used to predict when a DCFC event is expected. The driving history data is based on global positioning system (GPS) collected data and / or navigation data. The current and previous drive cycles may indicate that the vehicle does not follow a known path, that the vehicle is geographically proximate to and capable of reaching a DCFC charging station in a predetermined period of time, and / or the vehicle shows a distance to empty, or range less than the distance to the driver's home or workplace or other location where the vehicle 10 has previously charged. The previous charge may be a non-DCFC event. A DCFC event may also be expected when the SOC of the traction battery 12 falls below a fixed threshold. For example, a DCFC event is not expected when the SOC is above a certain percentage, and thus preventive cooling is not required. Based on the determination that a DCFC event is expected, a recharge event notification input 30 is communicated to the controller 28 to request starting of the battery cooling system 20 to pre-emptionally cool the traction battery 12 prior to arriving at the DCFC charging station.Because the battery temperature may increase during the recharge operation even though the battery cooling system 20 is operating, the recharge operation should be completed before the battery temperature reaches the maximum operating temperature. Thus, the advantages of DCFC can be maintained. Therefore, the battery cooling system 20 cools at a rate to complete recharging before the maximum operating temperature is reached. Further, the battery cooling system 20 may not be triggered during the recharging operation with a temperature difference between the battery temperature and the maximum temperature in triggering recharging due to preventive cooling being large enough depending on the ambient temperature conditions and / or the duration and speed of the recharging operation.Thus, the controller 28 may also be configured to determine whether or not preventive cooling is necessary. Specifically, whether the fast charging operation will be completed in a time period that is less than a predefined duration. Sensors for ambient temperature, traction battery temperature, cabin climate, and / or traction battery SOC are inputs to determine if the DCFC requires longer than a predefined amount of time. If so, then the request from the controller 28 to trigger the battery cooling system 20 to pre-emptively cool the traction battery is not inhibited. If the predefined amount of time is not exceeded, the controller 28 inhibits the battery cooling system 20 from pre-emptive cooling even if a DCFC event is expected. DUC information and other similar conditions may also be used as inputs for determining whether preventive cooling is necessary.In expectation of an expected DCFC event at the charging station 18, the controller 28 is configured to balance (i) the additional electrical energy of the battery 12 consumed by the battery cooling system 20 for the preventative cooling operation with (ii) the distance from the vehicle 10 to the charging station 18 to ensure that the vehicle has the range to reach the charging station. The distance from the vehicle 10 to the charging station 18 is the distance-to-charge (DUC) information in anticipation of the DCFC event at the charging station. Thus, the controller 28 is further configured to control the battery cooling system 20 based on DUC information, in addition to the temperature of the battery, the ambient temperature, the maximum temperature, and / or the battery SOC.Methods and systems have been described for preventively cooling the traction battery of an electric vehicle in expectation of a DCFC event at a charging station while the vehicle is being driven. Preventive cooling prior to DCFC may provide the following advantages: extended battery life when DCFC is regularly performed; reduced time at the DCFC charging station; optimum dimensioning of the battery cooling system with smaller components and lower cost. It is also advantageous that the preventive cooling uses available data to predict DCFC events, allowing the vehicle to be operated more efficiently during normal use (i.e., when a DCFC event is not expected), and allowing the DCFC event to be completed in a minimum time such that long-distance driving is possible in an appropriate time.While exemplary embodiments have been described above, it is not intended that these embodiments describe all possible forms of the invention. The terms used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. In addition, the features of different implemented embodiments may be combined with one another to form further embodiments according to the invention.

Claims

A method for preventively cooling a traction battery (12) of a vehicle (10) for DC fast charging (DCFC), the method comprising: in response to detecting, during a drive cycle and before arrival at a DCFC station, an expected DCFC event based on drive history data of the vehicle (10), requesting starting, by a controller (28), cooling of the traction battery (12) before arrival.The method of claim 1, further comprising inhibiting starting cooling of the traction battery (12) in response to an expected duration of the expected DCFC event being less than a predefined duration.The method of claim 2, wherein the expected duration of the expected DCFC event is based on a temperature of the traction battery (12), the state of charge of the traction battery (12), the ambient temperature, or the cabin climate.The method of claim 2, wherein the driving history data is collected GPS data describing current and previous driving cycles and DCFC events.The method of claim 4, wherein the collected GPS data shows that the vehicle (10) does not follow a detected work path, that the vehicle (10) is proximate to and capable of reaching a DCFC station in a predetermined period of time, or that a range is less than a distance to the driver's home or workplace or a previous charging station (18).The method of claim 2, wherein the driving history data is navigation data.A system for preventively cooling a traction battery (12) for DCFC fast charging (DCFC), the system comprising: a traction battery (12); a battery cooling system (20) configured to cool the traction battery (12); and a controller (28) configured to detect an expected DCFC event prior to arrival at a DCFC station and request starting of the battery cooling system (20) to cool the traction battery (12) prior to arrival at the DCFC station, wherein the expected DCFC event is based on collected GPS data.The system of claim 7, wherein the controller (28) is further configured to inhibit the triggering in response to an expected duration of the DCFC being less than a predefined duration.The system of claim 8, wherein the expected duration of the expected DCFC event is based on a temperature of the traction battery (12), the state of charge of the traction battery (12), the ambient temperature, or the cabin climate.The system of claim 7, wherein the expected DCFC event is based on navigation data.The system of claim 7, wherein the expected DCFC event is defined by the traction battery (12) having a state of charge below a threshold.

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