Method to condition a battery on demand while off charge

A method according to an exemplary aspect of the present disclosure includes, among other things, conditioning a battery of an electrified vehicle while off charge in response to an operator request for improved performance as a tradeoff for decreased range. An electrified vehicle system according to an exemplary aspect of the present disclosure includes, among other things, a battery, an electric machine configured to receive electric power from the battery to drive vehicle wheels, and a system control that generates a control signal to condition the battery while off charge in response to an operator request for improved performance as a tradeoff for decreased range.

TECHNICAL FIELD

This disclosure relates to a method and system for an electrified vehicle where a battery may be conditioned while off charge in response to an operator request for improved performance as a tradeoff for decreased range.

BACKGROUND

The need to reduce automotive fuel consumption and emissions is well known. Therefore, vehicles are being developed that reduce or completely eliminate reliance on internal combustion engines. Electrified vehicles are one type of vehicle currently being developed for this purpose. In general, electrified vehicles differ from conventional motor vehicles because they are selectively driven by one or more battery powered electric machines. Conventional motor vehicles, by contrast, rely exclusively on the internal combustion engine to drive the vehicle.

A high voltage battery pack for powering electric machines and other electrical loads typically includes multiple battery assemblies, or battery arrays, that include a plurality of interconnected battery modules comprised of battery cells. A power output of these high voltage batteries is a function of various factors, one of which is battery temperature. At extreme hot and cold ambient temperatures, the ability of the battery to charge and discharge may be limited. This issue becomes more critical with battery electric vehicles (BEVs) as there is no engine to compensate for the loss of battery power. Thus, the vehicle's performance and drivability can be reduced with these reductions of charge and discharge power limits.

SUMMARY

A method according to an exemplary aspect of the present disclosure includes, among other things, conditioning a battery of an electrified vehicle while off charge in response to an operator request for improved performance as a tradeoff for decreased range.

In a further non-limiting embodiment of the foregoing method, the method includes determining a state of the battery to determine an amount of energy required to bring the battery to a desired level of performance capability.

In a further non-limiting embodiment of either of the foregoing methods, the method includes comparing at least one of battery temperature and battery state of charge to a threshold to determine the state of the battery.

In a further non-limiting embodiment of any of the foregoing methods, the method includes estimating an impact to range based on the amount of energy required to bring the battery to the desired level of performance capability.

In a further non-limiting embodiment of any of the foregoing methods, the method includes communicating to the operator an estimated range available if the battery is conditioned to the desired level of performance capability.

In a further non-limiting embodiment of any of the foregoing methods, the estimating step includes defining a plurality of performance levels and estimating an impact to range for each performance level based on the amount of energy required to bring the battery to each performance level.

In a further non-limiting embodiment of any of the foregoing methods, the method includes communicating to the operator an estimated range available for each performance level.

In a further non-limiting embodiment of any of the foregoing methods, the method includes conditioning the battery in response to an affirmative operator request to have improved performance as a tradeoff for decreased range.

In a further non-limiting embodiment of any of the foregoing methods, the conditioning step includes heating or cooling the battery.

In a further non-limiting embodiment of any of the foregoing methods, the electrified vehicle comprises a battery electric vehicle or plug-in hybrid electric vehicle.

A method according to another exemplary aspect of the present disclosure includes, among other things: generating an operator prompt to allow an operator to approve conditioning a battery of an electrified vehicle for improved performance as a tradeoff for decreased range in response to a next usage or go time for the electrified vehicle, or in response to the electrified vehicle being off charge.

In a further non-limiting embodiment of any of the foregoing methods, the method includes determining a state of the battery to determine an amount of energy required to bring the battery to a desired level of performance capability.

In a further non-limiting embodiment of any of the foregoing methods, the method includes comparing at least one of a battery temperature and battery state of charge to a threshold to determine the state of the battery.

In a further non-limiting embodiment of any of the foregoing methods, the method includes estimating an impact to range based on the amount of energy required to bring the battery to the desired level of performance capability.

In a further non-limiting embodiment of any of the foregoing methods, the method includes communicating to the operator an estimated range available if the battery is conditioned to the desired level of performance capability.

In a further non-limiting embodiment of any of the foregoing methods, the method includes conditioning the battery in response to an affirmative operator request to have improved performance as a tradeoff for decreased range.

A system according to another exemplary aspect of the present disclosure includes, among other things: a battery, an electric machine configured to receive electric power from the battery to drive vehicle wheels, and a system control that generates a control signal to condition the battery while off charge in response to an operator request for improved performance as a tradeoff for decreased range.

In a further non-limiting embodiment of the foregoing system, the system includes an interface configured to allow the operator to communicate a usage schedule to the system control, and wherein the system control is configured to identify a next usage or go time, and if the next usage or go time is during an off charge condition, generate an operator prompt to allow the operator to select an increased performance mode as a tradeoff for decreased range.

In a further non-limiting embodiment of either of the foregoing systems, the system control determines a state of the battery to determine an amount of energy required to bring the battery to a desired level of performance capability, estimates an impact to range based on the energy requirement to condition the battery, and communicates to the operator an estimated range available if the battery is conditioned to the desired level of performance capability.

In a further non-limiting embodiment of any of the foregoing systems, the system includes a heating system and a cooling system wherein, in response to an operator selection of improved performance capability, the system control is configured to activate the heating or cooling system while off charge to place a temperature of the battery within a desired range to achieve the desired level of performance capability for the next usage or go time.

DETAILED DESCRIPTION

This disclosure details exemplary methods of conditioning a battery for an electrified vehicle while off charge in response to an operator request for improved performance as a tradeoff for decreased range. These and other features are discussed in greater detail in the following paragraphs of this detailed description.

FIG. 1schematically illustrates an example electrified vehicle10that includes a battery12, an electric machine14, and a pair of wheels16. The electric machine14can receive electric power from the battery12. The electric machine14converts the electric power to torque that drives the wheels16. The battery12is a high voltage traction battery in some embodiments.

The example electrified vehicle10is an all-electric vehicle, i.e. a battery electric vehicle (BEV). In other examples, the electrified vehicle10is a hybrid electric vehicle or plug-in hybrid electric vehicle (PHEV), which can selectively drive the wheels16with torque provided by an internal combustion engine instead of, or in addition to, the electric machine. Other electrified vehicles with a fuel cell where thermal management is also important.

The battery12will periodically require recharging. A charging station18can provide power to recharge the battery12. The charging station18includes a cord set20that can engage a port22of the electrified vehicle10to electrically couple the electrified vehicle10to the charging station18. When the electrified vehicle10and the charging station18are electrically coupled, power can move from a grid power source24to the electrified vehicle10. The power from the grid power source24recharges the battery12.

The example electrified vehicle10includes a system to control operation of the battery12and electric machine14, as well as to interface with an operator of the vehicle10. The system includes a controller30and an operator interface32that communicate with each other. The controller30can include a processor, memory, and one or more input and/or output (I/O) device interface(s) that are communicatively coupled via a local interface. The local interface can include, for example but not limited to, one or more buses and/or other wired or wireless connections. The local interface may have additional elements, which are omitted for simplicity, such as controllers, buffers (caches), drivers, repeaters, and receivers to enable communications. Further, the local interface may include address, control, and/or data connections to enable appropriate communications among the aforementioned components.

The controller30may be a hardware device for executing software, particularly software stored in memory that may include one or more separate programs, each of which includes an ordered listing of executable instructions for implementing logical functions. The controller30can be a custom made or commercially available processor, a central processing unit (CPU), an auxiliary processor among several processors associated with the computing device, a semiconductor based microprocessor (in the form of a microchip or chip set) or generally any device for executing software instructions. The memory can include any one or combination of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, VRAM, etc.)) and/or nonvolatile memory elements (e.g., ROM, hard drive, tape, CD-ROM, etc.).

The interface32can include various input and output devices that may communicate with the controller input and output interfaces. The interface32, for example, may be a touch screen within the vehicle10via which information can be communicated to the operator or through which the operator can communicate to the controller30. In additional, the interface32may also include a wireless communication interface where the vehicle controller30and operator can communicate via a mobile device such as a smart phone or tablet, or an internet browser for example.

The battery12is an exemplary electrified vehicle battery. The battery12may be a high voltage traction battery pack that includes a plurality of battery assemblies (i.e., battery arrays or groupings of battery cells) capable of outputting electrical power to operate the electric machine14. In one non-limiting embodiment, the electrified vehicle10operates in an Electric Vehicle (EV) mode where the electric machine14is used for vehicle propulsion, thereby depleting the battery12state of charge up to its minimum allowable value under certain driving patterns/cycles.

In one example, when the vehicle is not in use, the operator preferably places the cord20in the charge port22such that the charging station18can replenish the depleted battery power. Optionally, there are wireless charging systems that do not require a plug connection for charging. However, often during usage, the vehicle10is parked at a location that does not include a charging station, which means the vehicle is off charge.

As discussed above, one exemplary method of the disclosure is directed toward a method of conditioning the battery12for a BEV10to allow an operator to select a mode that provides greater vehicle performance as a tradeoff for decreased range. In one example, the controller30determines a state of the battery to determine an amount of energy that is required to bring the battery to a desired level of performance capability. In one example, the state of the battery is determined based on the battery state of charge and/or a battery temperature. The desired level of performance can be based on a desired speed capability, acceleration capability, etc. for example. As shown inFIG. 2, the controller30first detects when a next usage time (NUT) or go time is available as indicated at100. In one example, an operator communicates with the controller30via the interface32to identify one or more go times/NUTs that are scheduled for the vehicle10each day or for a plurality of days. When the vehicle is charging, the controller30can then initiate battery heating or cooling based on when the operator is scheduled to use the vehicle next, such that desired levels of vehicle performance can be achieved. However, if the next usage time occurs while the vehicle is not charging, then the controller30traditionally does not initiate battery heating or cooling for improved performance as this could adversely affect vehicle range.

However, as the range for BEVs10continues to be extended, it is desirable to provide operators with a choice to have increased performance rather than increased range. Once it has been determined that the next usage time occurs while the vehicle is not charging, the controller30starts an analysis to determine whether the battery can be conditioned as indicated at102. The method first determines if the vehicle10is in an off charge condition as indicated at104. If the vehicle is off charge, the controller30then determines a current state of the battery12. For example, controller30determines if the available power from the battery12is limited due to the current temperature of the battery12as indicated at106. In one example, there are two temperature thresholds for step106, which include a first threshold T1below which the battery would need heating, and a second threshold T2above which the battery needs cooling. Note that T1is lower temperature value than T2. In other words, if the battery temperature is between the two thresholds no thermal management/conditioning is required. The controller30may also determine if the available energy from the battery12is limited due to the battery state of charge C, as indicated at108, where the state of charge C has to be greater than a threshold C1. In other words, the current battery temperature and the current state of charge are compared to respective thresholds to determine whether conditioning would be required to place the battery in an appropriate condition to provide the desired performance level at the next “go time.”

If the controller30determines that the battery temperature meets threshold requirements, and that the battery state of charge meets the threshold, then conditioning can be done as the current state of the battery is sufficient for the desired level of performance. For example, if a determination is made that the battery temperature is within the predetermined temperature range bounded by T1and T2, and the battery state of charge is higher than a predetermined state of charge threshold C1, a determination is made as to the amount of energy that would be required to place the battery12in a condition to provide the desired level of performance as indicated at110. In one example, the amount of energy required is based on providing a full or maximum level of performance for the vehicle. In another example, a plurality of performance levels are identified and amounts of energy are determined for each level of performance.

Based on this determination, controller30will estimate the remaining range of the vehicle10if the battery12was to be conditioned for the desired increased performance level as indicated at112. For example, the controller30will determine the current available range and the estimated impact to the range, i.e. the amount of range reduction, which will result if conditioning is selected by the operator. The controller30will then prompt the operator, as indicated at114, to select between conditioning the battery12to a limited or increased performance mode in light of the estimated impact to vehicle range. The controller30does this by communicating information to the operator via the interface32. In one example, the information includes the amount of the range reduction and the range that would be available if conditioning the battery12were to occur.

If the operator affirmatively selects the increased performance level as a tradeoff for decreased range, the controller30will then determine the temperature at which the battery12needs to be in order to achieve the desired performance level as indicated at116. In one example, the vehicle includes a heating system40and a cooling system42(FIG. 1) which are controlled by the controller30. If heating is required, the controller30will issue a control signal to activate the heating system40as indicated at118inFIG. 2. If cooling is required, the controller30will issue a control signal to activate the cooling system42as indicated at120. The battery12is then subsequently cooled or heated until the desired temperature range is achieved. Any type of heating or cooling system can be used to heat/cool the battery12.

If heating is required, the controller30will identify a target battery cooling temperature as indicated at122. The controller30will then determine a heater duty cycle to achieve the target battery coolant temperature as indicated at124. The controller30will then issue control signals to control valve(s), pump(s), and/or other heating system components to perform the heater duty cycle as indicated at126.

If cooling is required, the controller30will identify a target battery coolant temperature as indicated at128. The controller30will then determine a cooling duty cycle to achieve the target battery coolant temperature as indicated at130. The controller30will then issue control signals to control valve(s), pump(s), and/or other air conditioner system components to perform the cooling duty cycle as indicated at132.

This method is useful for situations when the vehicle is located in a high temperature or low temperature environment for a significant time while off charge. For example, if the operator drives to an airport for a trip, the vehicle may be in an off charge condition for several days. The operator may have communicated to the controller30the estimated go time/NUT for when the operator is returning from the trip. The controller30can then, based on this go time/NUT, determine the current state of the battery and offer the operator a choice of having an increased performance level available.

In this example, the operator may have indicated that the operator is planning to return to home upon arrival at the airport. If the vehicle has been in an extremely cold environment for several days, the controller30can then determine the energy that would be required to heat the battery to place the battery within a temperature range to provide one or more various levels of performance. The controller30can also determine the impact to the range that would result from the energy required to thermally condition the battery. The controller can then communicate to the operator how much range would be available for each level of performance and allow the user to approve or disapprove of the condition strategy.