Lifespan management of mixed-chemistry vehicle batteries

Abstract

A method for managing the cycle life of a mixed-chemistry battery pack configured to electrically power a vehicle's traction motor. The method may include determining a drive load requirement to request the mixed-chemistry battery pack to deliver a requested amount of electrical power to the traction motor to propel the vehicle, and converting the drive load requirement into a battery requirement suitable for the mixed-chemistry battery pack to deliver the requested amount of electrical power, while managing the cycle life of the mixed-chemistry battery pack independently of the drive load requirement.

Description

Introduction

[0001] The present disclosure relates to mixed chemistry battery packs, such as, but not necessarily limited to, mixed chemistry vehicle battery packs configured to electrically drive a traction motor of a vehicle.

[0002] A variety of rechargeable energy storage systems (RESSs) may be available for electrically powering a traction motor or other device that converts electrical energy into mechanical energy to propel, drive, operate, or otherwise operate a vehicle. Cycle life, or a cycle life value such as a C-rate, can be used to represent how frequently and / or to what extent a RESS may have been repeatedly charged and / or discharged. As a RESS is used, degradation, reduced efficiency, slower performance, lower capacity, and other potentially performance-limiting effects may occur with increasing cycle time. Description

[0003] A non-limiting aspect of the present disclosure relates to managing the cycle life of rechargeable energy storage systems (RESS), such as, but not necessarily, managing RESS for the purpose of minimizing degradation, reduced efficiency, slower power delivery, lower capacity, and other types of potentially performance-limiting effects resulting from repeated use. The contemplated cycle life management may be beneficial in a variety of RESS, particularly mixed-chemistry packs used to store and provide electrical energy to traction motors or other devices used to propel, drive, operate, or otherwise operate a vehicle.A mixed-chemistry pack may be a pack with multiple subpacks, where one of the subpacks has a different configuration, capability, chemical construction, etc., than the other subpacks. For example, one type of subpack may perform electrochemical reactions suitable for delivering and / or storing electrical energy at different maximum power levels, constant power levels, etc. For example, one subpack may be configured to deliver a lower maximum power than another subpack, but with a longer constant power output.

[0004] One non-limiting aspect of the present disclosure relates to a method for managing the cycle life of a mixed-chemistry battery pack configured to electrically power a traction motor of a vehicle. The method may include determining a propulsion load request made to request the mixed-chemistry battery pack to provide a requested amount of electrical power to the traction motor to propel the vehicle and generating a battery request suitable to provide the requested amount of electrical power from the mixed-chemistry battery pack while managing a cycle life of the mixed-chemistry battery pack independent of the propulsion load request.

[0005] The battery demand can be used to maximize cycle life by prioritizing charging and discharging of the propulsion subpack over the energy subpack.

[0006] The method may include determining a state of charge (SOC) threshold of a propulsion subpack and determining a rated current limit and a maximum current limit for an energy subpack configured to provide a lower maximum power than the propulsion subpack and a longer steady-state power than the propulsion subpack. The battery request may be operable to control the propulsion subpack to provide electrical power to meet the requested amount of electrical power without electrical power assistance from the energy subpack during a first power level that occurs before an SOC of the propulsion subpack reaches an upper limit of the SOC threshold, controlling the energy subpack to provide an assisting amount of electrical power to supplement the propulsion subpack in meeting the requested amount of electrical power,without exceeding the rated current limit during a second power level that occurs after the first power level, when the SOC reaches the upper limit and before a lower limit of the SOC threshold is exceeded, and controlling the energy subpack to provide the assist amount according to a relaxed current limit during a third power level that occurs after the second power level, when the SOC reaches the lower limit and before the SOC exceeds the upper limit, wherein the relaxed current limit is greater than the rated current and equal to or less than the maximum current limit.

[0007] The battery request may be further operable to control the energy subpack to provide the assisting amount without exceeding the rated current limit during a fourth power level that occurs after the third power level when the SOC reaches the upper limit.

[0008] The method may include adjusting the relaxed current limit during the third power level in proportion to the increase in SOC from the lower limit to the upper limit.

[0009] The method may include adjusting the relaxed current limit during the third power level at a predetermined rate as the SOC increases from the lower limit to the upper limit.

[0010] The method may include determining a charge request made to request the energy subpack to provide a charge amount of electrical power to the propulsion subpack for the purpose of charging the propulsion subpack, and generating a charge request operable to control the energy subpack to provide the charge amount of electrical power to the propulsion subpack.

[0011] The method may include determining the charging load request in response to the vehicle being stationary for a predefined period of time, the SOC being at or below the lower limit, and DC fast charging of the propulsion subpack not being available.

[0012] The charging request may be operable to control the energy subpack to provide the charging amount of electrical power without exceeding the rated charging limit.

[0013] The charging request may be operable to control the energy subpack to provide the charging amount of electrical power at a selectable rate.

[0014] The method may include determining a heating load request made to request the power subpack to provide a heating amount of electrical power to the propulsion subpack for the purpose of heating the propulsion subpack, and generating a heating request operable to control the power subpack to provide the heating amount of electrical power to the propulsion subpack.

[0015] The method may include determining the heating load request in response to the vehicle being stationary for a predefined period of time while DC fast charging of the propulsion subpack is unavailable.

[0016] The battery request may be operable to control a converter of the mixed chemistry battery pack to control the electrical power transfer between the propulsion subpack and the energy subpack.

[0017] The converter may be a DC-DC converter connected in parallel between the drive subassembly and the power subassembly.

[0018] One non-limiting aspect of the present disclosure relates to a cycle-life-managed mixed-chemistry battery pack configured to electrically power a traction motor of a vehicle. The pack may include a propulsion subpack, a power subpack, a converter configured to control the transfer of electrical power from the power subpack to the propulsion subpack, and a controller.The controller may be configured to determine a propulsion load request made to request the mixed chemistry battery pack to provide a requested amount of electrical power to the traction motor to propel the vehicle, and generate a battery request suitable for providing the requested amount of electrical power from the mixed chemistry battery pack while managing a cycle life of the mixed chemistry battery pack independent of the propulsion load request.

[0019] The control unit may be configured to maximize cycle life by minimizing charging and discharging of the energy subpack relative to the energy subpack.

[0020] The controller may be configured to determine a state of charge (SOC) threshold of the propulsion subpack and determine a rated current limit and a maximum current limit for the energy subpack configured to provide a lower maximum power than the propulsion subpack and a longer continuous power than the propulsion subpack.

[0021] The battery request may be operable to control the drive subpack to provide electrical power to meet the requested amount of electrical power without electrical power assistance from the energy subpack during a first power level that occurs before a SOC of the drive subpack reaches an upper limit of the SOC threshold, control the energy subpack to provide an assisting amount of electrical power to supplement the drive subpack in meeting the requested amount of electrical power without exceeding the rated current limit during a second power level that occurs after the first power level, when the SOC reaches the upper limit and before a lower limit of the SOC threshold is exceeded, and control the energy subpack to provide the assisting amount according to a relaxed current limit during a third power level,which occurs after the second power stage, when the SOC reaches the lower limit and before the SOC exceeds the upper limit, where the relaxed current limit is greater than the rated current and equal to or less than the maximum current limit.

[0022] The battery request may be operable to control the energy subpack to provide the assisting amount without exceeding the rated current limit during a fourth power level that occurs after the third power level when the SOC reaches the upper limit.

[0023] One non-limiting aspect of the present disclosure relates to a cycle-life-managed electric power system for powering a traction motor of a vehicle. The system may include a mixed-chemistry battery pack having a propulsion subpack, a power subpack, and a converter configured to control the transfer of electric power from the power subpack to the propulsion subpack.The system may further include a controller configured to determine a motive load request made to request the mixed-chemistry battery pack to provide a requested amount of electrical power to the traction motor for the purpose of propelling the vehicle, and to generate a battery request in response to the motive load request, the battery request being capable of providing the requested amount of electrical power from the mixed-chemistry battery pack while managing a cycle life of the mixed-chemistry battery pack.

[0024] The controller may be configured to determine a state of charge (SOC) threshold of the propulsion subpack and determine a rated current limit and a maximum current limit for the energy subpack when it is configured to provide a lower maximum power than the propulsion subpack and a longer continuous power than the propulsion subpack. The battery request may be operable to control the propulsion subpack to provide electrical power to meet the requested amount of electrical power without electrical power assistance from the energy subpack during a first power stage that occurs before a SOC of the propulsion subpack reaches an upper limit of the SOC threshold, control the energy subpack to provide a supporting amount of electrical power to supplement the propulsion subpack in meeting the requested amount of electrical power,without exceeding the rated current limit during a second power level that occurs after the first power level, when the SOC reaches the upper limit and before a lower limit of the SOC threshold is exceeded, controlling the energy subpack to provide the assisting amount according to a relaxed current limit during a third power level that occurs after the second power level, when the SOC reaches the lower limit and before the SOC exceeds the upper limit, and controlling the energy subpack to provide the assisting amount without exceeding the rated current limit during a fourth power level that occurs after the third power level, when the SOC reaches the upper limit.

[0025] These features and advantages, as well as other features and advantages of the present teachings, will be readily apparent from the following detailed description of the embodiments of the present teachings, taken in conjunction with the accompanying drawings. It should be understood that, although the following figures and embodiments may be described separately, individual features thereof may be combined to form additional embodiments. Brief description of the drawings

[0026] The accompanying drawings, which may be incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. Fig. 1 shows a schematic view of a vehicle according to a non-limiting aspect of the present disclosure. Fig. 2 shows a schematic view of a mixed chemistry battery pack according to a non-limiting aspect of the present disclosure. Fig. 3 shows a flowchart of a cycle life method in accordance with a non-limiting aspect of the present disclosure. Fig. 4 shows a performance diagram associated with generating a battery request in accordance with one non-limiting aspect of the present disclosure. Detailed description

[0027] As required, detailed embodiments of the present disclosure may be disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or reduced to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for showing one skilled in the art how to variously employ the present disclosure.

[0028] Fig. 1 shows a schematic view of a vehicle 10 in accordance with one non-limiting aspect of the present disclosure. The vehicle 10 may be configured with a drive system, powertrain, or other driveline 12 including an electric motor 14 or other electrically powered device used to propel or otherwise propel the vehicle 10. The vehicle 10 is depicted as a hybrid vehicle because the powertrain 12 optionally includes an internal combustion engine (ICE) 16. The ICE 16 and the electric motor 14 or other electrical-to-mechanical energy conversion device may cooperate to provide mechanical power / torque to the driveline 12 for transmission to one or more of the wheels 20, 22, 24, 26.The driveline 12 may include a transmission 34, a driveshaft 36, a differential 38, axles 40, 42, and / or other components to facilitate the transfer of rotational power from the ICE 16 and / or the engine 14 to the wheels 20, 22, 24, 26. The vehicle 10 is illustrated as including the driveline 12 operable with the front wheels 20, 24 for non-limiting purposes, as the present disclosure fully contemplates its use and application with four-wheel drive automobiles and other non-automotive vehicle types. A controller 44 may be configured to generate control signals associated with directing and otherwise implementing the desired control of the driveline 12, the engine 14, the ICE 16, and / or other features of the vehicle 10, e.g.,the controller 44 may include non-transitory instructions stored on an associated computer-readable storage medium that, when executed with one or more processors, may facilitate the operations, processes, controls, etc. described herein.

[0029] The vehicle 10 is representative of a variety of vehicles and / or other devices that may rely on the conversion of electrical energy to mechanical energy. Such vehicles may be generally referred to as electric vehicles and include a wide range of capabilities for assisting in the conversion of electrical energy to mechanical energy, including electric vehicles of the type that can operate without assistance from the ICE 16. The vehicle 10 may include various configurations for generating, storing, and supplying electrical energy to the electric motor 14 and / or other devices or systems onboard and external to the vehicle 10. The present disclosure contemplates that some or all of the electrical energy may be provided at least in part based on electrical energy supplied by a rechargeable energy storage system (RES).The controller 44 may be configured to manage the operation of the RESS 46 to optimize its lifetime, e.g., by managing charging and discharging to minimize degradation, reduced efficiency, slower power delivery, lower capacity, and other types of potentially performance-limiting effects that may occur with repeated use. Although the present disclosure contemplates use and application with a wide range of RESSs, the RESS 46 is described primarily in terms of its configuration as a mixed-chemistry battery pack 46.

[0030] Fig. 2 shows a schematic view of the mixed-chemistry battery pack 46 in accordance with one non-limiting aspect of the present disclosure. The mixed-chemistry battery pack 46 may be included as part of a control architecture associated with the exchange of electrical energy with the engine 14 and / or other devices in communication with the vehicle 10. As one of ordinary skill in the art will appreciate, the mixed-chemistry battery pack 46 and the described management thereof may be beneficial in a variety of applications, devices, vehicles, etc., beyond the description provided herein with respect to the vehicle 10. The mixed-chemistry battery pack 46 may be configured to rely at least in part on electrochemical reactions to facilitate the storage and delivery of electrical energy.The mixed-chemistry battery pack 46 may be considered mixed in that it includes a plurality of subpacks 50, 52, each subpack 50, 52 configured to perform electrochemical reactions suitable for storing and delivering electrical energy. Although the present disclosure contemplates the use of a plurality of subpacks 50, 52, the mixed-chemistry battery pack 46 is illustrated as including a first subpack 50 and a second subpack 52. The first subpack 50 may be referred to as the energy subpack 50, and the second subpack 52 may be referred to as the propulsion subpack 52.

[0031] To facilitate managing the cycle life of the mixed-chemistry battery pack 46, the energy and propulsion subpacks 50, 52 may have different configurations, capabilities, chemical designs, etc., for performing the electrochemical reactions associated with delivering and / or storing electrical energy. The associated differences between the subpacks 50, 52 may be selectively determined and utilized to facilitate managing the cycle life of the mixed-chemistry battery pack 46 as a whole. For example, the subpacks 50, 52 may be configured to support different maximum power levels, steady-state power levels, etc. For example, the energy subpack 50 may be configured to deliver a lower maximum power than the propulsion subpack 52, but a longer steady-state power than the propulsion subpack 52.The energy subpack 50 may have a lower maximum power but more energy than the propulsion subpack 52, allowing a smaller propulsion subpack 52 to be used for rapid and demanding power requirements, which in turn may help extend the lifetime of the larger energy subpack 50. The cycle life management presented here may utilize the different characteristics of the subpacks 50 and 52 to facilitate long-term maximization and operation of the mixed-chemistry battery pack 46, e.g., by prioritizing the charging and discharging of the propulsion subpack 52 over the energy subpack 50. The ability to individually control the charging and discharging of the sub-batteries 50, 52, optionally on an unequal or non-uniform basis, may be advantageous for selectively managing their use according to conditions best suited to increasing cycle life.

[0032] The present disclosure contemplates increasing the cycle life of the mixed-chemistry battery pack 46 by selectively and independently managing the discharge and charging of the energy and propulsion subpacks 50, 52, for example, in a manner that utilizes their distinct operating characteristics while simultaneously increasing cycle life. This may be accomplished, for example, by splitting the usage of the subpacks 50, 52 to meet required power requirements in a manner that allows the capabilities of each subpack to be utilized for the purpose of improving the overall cycle life of the mixed-chemistry battery pack 46, for example, by prioritizing the usage of the propulsion subpack 52 over the energy subpack 50, or vice versa. The mixed-chemistry battery pack 46 is illustrated with the energy subpack 50 connected in parallel with the propulsion subpack 52 and a converter 56 interposed therebetween to regulate current flow.For example, the converter 56 may be configured as a DC-DC converter 56, such as a buck converter 56, a switch, or other circuit construct that manages the flow of current from the power subpack 50 to the propulsion subpack 52 and / or from the propulsion subpack 52 to the power subpack 50. The converter 56 may be configured to control the flow of current between the power and propulsion subpacks 50, 52 according to commands received from the controller 44 and / or a motor power controller (MPC) 58. The MPC 58 may be part of the controller 44 and / or a standalone unit configured to operate the mixed-chemistry battery pack 46 according to the management contemplated herein.

[0033] The commands generated by the MPC 58 for controlling the mixed-chemistry battery pack 46, or more particularly, the converter 56, the power subpack 50, and / or the propulsion subpack 52, may be generated in various forms, including as a signal, such as a pulse-modulated (PWM) signal used to selectively open and close switches or other circuits and components (not shown). The MPC 58 and / or the mixed-chemistry battery pack 46 may include sensors, feedback, and / or other mechanisms (not shown) operable to sense, calculate, predict, and otherwise perform logical operations related to monitoring operations of the mixed-chemistry battery pack 46, the vehicle 10, etc., for the purpose of facilitating the management contemplated herein. For example, the MPC 58 may be configured toThe controller 44 and / or MPC 58 may calculate or otherwise determine a state of charge (SOC) for the subpacks 50, 52, a load requirement or need to provide electrical energy to and / or from the mixed-chemistry battery pack 46, current limits for the subpacks 50, 52, and / or a variety of other variables that may be used in commanding the mixed-chemistry battery pack 46 according to the cycle life management contemplated herein. The controller 44 and / or the MPC 58 may include corresponding non-transitory commands that may be used to generate corresponding commands, instructions, etc.

[0034] Fig. 3 shows a flowchart of a method 64 for cycle life management of the mixed chemistry battery pack 46 in accordance with one non-limiting aspect of the present disclosure. Block 66 relates to a load request process where the MPC 58 may determine a load or other type of request made to request the mixed chemistry battery pack 46 to provide a requested amount of electrical power to the motor 14 or another function onboard the vehicle 10, which may be referred to as a propulsion load request when made to request electrical power to propel the vehicle 10. The propulsion load request may be determined by the MPC 58 directly and / or indirectly via the controller 44. e.g., the controller 44 may receive a request from a driver or other operator, e.g., an autonomous system.Block 68 refers to a battery request process in which the MPC 58 may generate a battery request suitable for controlling the mixed-chemistry battery pack 46 to provide the requested amount of electrical power. The battery request process may include separating the driving load request from the battery request so that the battery request may be generated independently. For example, the battery request may include control parameters generated separately from the parameters defined in the driving load request to enable cycle life management independent of the driving load request. Block 70 refers to a power supply process in which the mixed-chemistry battery pack 46 may be controlled to meet the driving load request, i.e., to deliver the requested power according to the parameters described in the battery request.

[0035] Fig. 4 shows a power graph 74 associated with generating the battery demand in accordance with one non-limiting aspect of the present disclosure. The graph 74 may include a drive graph 76 for representing the desired operation of the drive subunit 52 and an energy graph 78 for representing the desired operation of the power subunit 50. The graphs 76, 78 are illustrated, by way of example, with respect to a horizontal axis 80 denoting time and a vertical axis 82 representing the SOC for the drive graph 76 and the current discharge for the energy graph 78. The horizontal axis 80 may represent a period of time associated with the mixed-chemistry battery pack 46 being controlled during a charging process to provide electrical energy to attempt to meet the drive load demand, e.g., while the powering process of block 70 is ongoing.The mixed SOC and current discharge metrics of the vertical axis 82 may be plotted to reflect the relative changes in the energy and propulsion subpacks 50, 52 over time while the mixed-chemistry battery pack 46 is providing electrical power. The battery demand may be derived from the propulsion and energy graphs 76, 78 and adjusted throughout the power delivery process to facilitate cycle life management of the mixed-chemistry battery pack 46. The battery demand may be generated by the MPC 58 based on the propulsion load demand, but optionally in an independent manner to enable the distribution of electrical power among the sub-batteries 50, 52 based on the selected chemistry, capabilities, etc.the drive and energy subpacks 50, 52, which may vary, the present disclosure contemplates maximizing cycle life by prioritizing charging and discharging of the drive subpack 52 over the energy subpack 50.

[0036] For this purpose, the beginning of a first power level 80 can be used to mark a beginning at which the drive subassembly 52 is able to fully provide the requested amount of electrical power, ie, to meet the drive load requirement without simultaneously drawing electrical power from the energy subassembly 50. Back to Fig. 3, block 82 refers to a setpoint process that may be included as part of the first power stage 80. The setpoint process may include the MPC 58 setting a SOC threshold 86 for the propulsion subpack 52 and thereafter monitoring the SOC of the propulsion subpack 52 to determine if the SOC is approaching the SOC threshold 86, i.e., the SOC of the propulsion subpack 52 may decrease over time if the propulsion subpack 52 continues to be used exclusively for providing the requested amount of electrical power. As in Fig. As shown in Figure 4, the SOC threshold 86 may include an upper limit 88 and a lower limit 90, where the upper limit 88 indicates a SOC value that the propulsion subpack 52 is desired to achieve before the energy subpack 50 is controlled to additionally provide a supporting amount of electrical power. The SOC threshold 86 and / or the upper and lower limits 88, 90 may be selected depending on desired operating conditions, current environmental conditions, vehicle performance strategies, and a variety of other variables that may vary and / or be adjusted in real time or to meet other desired operating capabilities.

[0037] A second power level 94 may correspond to controlling the energy subpack 50 to provide a supporting amount of electrical power to supplement the propulsion subpack 52 in meeting the requested amount of electrical power, which may be accomplished by the energy subpack 50 providing the supporting amount of electrical power without exceeding a rated current limit 96. Return to Fig. 3, block 98 may refer to a current control process in which the MPC 58 determines the rated current for the power subpack 50. The rated current 96 may correspond to a predefined amount of current to be provided by the power subpack 50 during the second power stage 94, i.e., after the SOC of the propulsion subpack 52 reaches the upper limit 88 and before the SOC reaches the lower limit 90. The current control process may determine the rated current 96 according to design parameters, current operating conditions, the state of health (SOH), and / or other design parameters.Block 100 refers to a monitoring process in which the MPC 58 may monitor the SOC of the propulsion subpack 52 to determine whether the assisting amount of electrical power provided at the rated current 96 has caused the SOC to approach or exceed one of the upper and lower limits 88, 90. Block 102 refers to a current adjustment process in which the MPC 58 may initiate a third power stage 104 when the SOC reaches the lower limit 90 and before the SOC exceeds the upper limit 88. The current adjustment process may include initially operating the power subpack 50 at a maximum current 106 in block 102 when the SOC reaches the lower limit 88, and thereafter, as the SOC increases, at a lower, relaxed current 108 in block 110.Like the rated current 96, the maximum and relaxed currents 106, 108 may be design parameters selected according to a variety of operating considerations, including a desirable upper range or limiting of the energy subpack 50 for managing cycle life.

[0038] Returning to Fig. 4, the third power stage 104 may correspond to changing the current limits of the energy subpack 50 from the nominal current 96 to the maximum current 106 and then decreasing from the maximum current 106 to the relaxed current 108 until the SOC reaches the upper limit 88. The third power stage 104 may occur when the assist power provided according to the nominal current 96 during the second power stage 94 causes the SOC to further decrease and approach the lower limit 90. The power output of the energy subpack 50 during the third power stage 104 may be increased accordingly in proportion to a difference between the nominal current 96 and the maximum current 106 and thereafter according to the relaxed current 108, which in turn may alleviate some of the power load on the propulsion subpack 52.The SOC of the propulsion subpack 52 may increase in response to the increasing assist power of the energy subpack 50, so that the relaxed current 108 may be proportionally decreased as the SOC increases and approaches the upper limit 88. When the SOC reaches the upper limit 88, a fourth power stage 114 may begin, after which the minimum current 96 may return to measure the assist power provided by the energy subpack 50.

[0039] Returning to Fig.3, block 116 relates to controlling the energy subpack 50 to provide the supporting amount of electrical power without exceeding the rated current 96. If the SOC continues to rise above the upper limit 88, the rated current 96 may optionally be adjusted and / or the supporting use of the energy subpack 50 may be discontinued. In the event that demand increases or other situations occur that cause the SOC to continue to decrease toward the lower limit 90, the above processes may be repeated; e.g., the energy subpack 50 may be deployed to provide supporting electrical power in addition to the propulsion energy subpack 50, i.e., according to the minimum, relaxed, and / or maximum currents 96, 106, 108.While the foregoing cycle life management techniques may primarily rely on the use of the power subpack 50 to provide auxiliary electrical power to supplement the electrical power provided by the drive subpack 52, which may require appropriate control of the inverter 56, other techniques for sharing the power supply between the power and drive subpacks 52 are also contemplated in the present disclosure.

[0040] As previously mentioned, one aspect of the present disclosure relates to a parallel mixed-chemistry battery pack in which a "drive" cell / subpack is directly connected to a load, while a "power" cell / subpack is connected to the load via a DC-DC converter. This provides the ability to "isolate" the load on the power cells from the road load requirement, thereby supporting a method for reducing the load on the power cells so that the cycle life of that cell type can be maximized. The power cells used in mixed-chemistry packs may be advanced chemistry cells with relatively short cycle life (e.g., LMB, Si anode). This method provides an approach to improving the cycle life of the power cells by reducing the discharge rate C, where possible, e.g., where the requirements can be met with the drive cell.The approach considered may include isolating the battery charge from the road load so that the discharge current can be maintained at a lower level, controlling the discharge of the energy cells so that the SOC of the drive cell can be maintained at the target level at the same time, and allowing the energy cells to slowly charge the drive cells under certain conditions when the vehicle is not in motion.

[0041] In cold ambient conditions, the propulsion cells may experience SOC limitations if the cell temperature is too low. In such a scenario, when the vehicle is not moving, power from the energy cells may be used to maintain the propulsion cell temperature above a minimum threshold (customer-selectable feature). This may include determining the MPC of a warming load request issued to request the energy subpack to provide a warming amount of electrical power to the propulsion subpack for the purpose of warming the propulsion subpack, and generating a warming request used to control the energy subpack to provide the warming amount of electrical power to the propulsion subpack.The warm-up load request may be determined in response to the vehicle being stationary for a predefined period of time while the propulsion subpack DC fast charge is unavailable.

[0042] A variable converter current limiting algorithm is implemented with the MPC to limit the discharge current of the energy cells as much as possible while ensuring that the drive cells remain within the SOC target window. When the vehicle is stationary, the drive cells are at the minimum SOC limit (vehicle in range extension mode) and DC fast charging (DCFC) is not available, the drive cells can be charged by the energy cells at a controlled rate (customer-selectable feature).This may include determining, by the MPC, a charge load request made to request the energy subpack to provide a charging amount of electric power to the propulsion subpack to charge the propulsion subpack, and generating a charging request operable to control the energy subpack to provide the charging amount of electric power to the propulsion subpack. The charging request may be determined in response to the vehicle being stationary for a predefined period of time, the SOC being at or below the lower limit, and DC fast charging of the propulsion subpack not being available. The charging request may be to control the energy subpack to provide the charging amount of electric power without exceeding the rated charging limit and / or at a selectable rate.

[0043] The terms "consisting of," "including," and "having" are all-inclusive and therefore specify the presence of certain features, steps, operations, elements, or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, or components. The order of steps, processes, and operations may be changed where possible, and additional or alternative steps may be used. The term "or" as used in this description includes all combinations of the listed elements. The term "each of" includes every possible combination of the listed items, including "each of" the listed items. "A," "a," "the," "at least one," and "one or more" are used interchangeably to indicate that at least one of the items is present.There may be more than one of these elements unless the context clearly indicates otherwise. All values ​​of parameters (e.g., quantities or conditions), unless expressly stated otherwise or in light of the context, including the appended claims, are to be understood as being modified in all cases by the term "via," regardless of whether "via" actually appears before the value or not. A component "configured" to perform a particular function is capable of performing the specified function without modification, rather than merely having the potential to perform the specified function after further modifications. In other words, if the described hardware is expressly configured to perform the specified function, then it is specifically selected, created, implemented, used, programmed, and / or designed to perform the specified function.

[0044] While various embodiments have been described, the description is intended to be exemplary and not restrictive, and it will be apparent to those skilled in the art that many other embodiments and implementations are possible that fall within the scope of the embodiments. Any feature of one embodiment may be used in combination with, or in place of, another feature or element in another embodiment, unless expressly limited. Accordingly, the embodiments are not to be limited except in accordance with the appended claims and their equivalents. Also, various modifications and changes may be made within the scope of the appended claims.Although various modes for carrying out the many aspects of the present teachings have been described in detail, those familiar with the art to which these teachings relate will recognize various alternative aspects for carrying out the present teachings that fall within the scope of the appended claims. It is intended that everything contained in the above description or shown in the accompanying drawings be considered illustrative and exemplary of the entire range of alternative embodiments that one of ordinary skill in the art would recognize as being implied, structurally and / or functionally equivalent, or otherwise obvious based on the content included therein, and not as limited solely to the embodiments expressly shown and / or described.

Claims

[1] A method for managing the cycle life of a mixed-chemistry battery pack configured to electrically power a traction motor of a vehicle, the mixed-chemistry battery pack including a power subpack connected in parallel with a propulsion subpack, the method comprising: Determining a drive load request made to request the mixed chemistry battery pack to provide a requested amount of electrical power to the traction motor for the purpose of propelling the vehicle; and Generating a battery request in response to the propulsion load request, the battery request being capable of providing the requested amount of electrical power from the mixed chemistry battery pack while managing a cycle life of the mixed chemistry battery pack independent of the propulsion load request. [2] The method of claim 1, wherein: the battery requirement is operable to maximize cycle life by prioritizing charging and discharging of the propulsion subpack over the energy subpack. [3] The method of claim 1, further comprising: Determining a state of charge (SOC) threshold for the drive subpack; Determining a rated current limit and a maximum current limit for the energy subpack, wherein the energy subpack is configured to provide a lower maximum power than the drive subpack and a longer constant power than the drive subpack; the battery requirement operable to: controlling the propulsion subpack to provide electric power to meet the requested amount of electric power without electric power assistance from the energy subpack during a first power level that occurs before a SOC of the propulsion subpack reaches an upper limit of the SOC threshold; Controlling the energy subpack to provide a supporting amount of electrical power to supplement the propulsion subpack in meeting the requested amount of electrical power without exceeding the rated current limit during a second power level that occurs after the first power level when the SOC reaches the upper limit and before a lower limit of the SOC threshold is exceeded; and Controlling the energy subpack to provide the assist amount according to a relaxed current limit during a third power stage occurring after the second power stage when the SOC reaches the lower limit and before the SOC exceeds the upper limit, wherein the relaxed current limit is greater than the rated current and equal to or less than the maximum current limit. [4] The method of claim 3, further comprising: the battery demand is operable to control the energy subpack to provide the assisting amount without exceeding the rated current limit during a fourth power level that occurs after the third power level when the SOC reaches the upper limit. [5] The method of claim 4, further comprising: Adjusting the relaxed current limit during the third power stage in proportion to the increase in SOC from the lower limit to the upper limit. [6] The method of claim 4, further comprising: Adjust the relaxed current limit during the third power stage at a predetermined rate as the SOC increases from the lower limit to the upper limit. [7] The method of claim 3, further comprising: Determining a charge load request made to request the energy subpack to provide a charge amount of electrical power to the propulsion subpack for the purpose of charging the propulsion subpack; and Generating a charge request operable to control the energy subpack to provide the charge amount of electrical energy to the propulsion subpack. [8] The method of claim 7, further comprising: Determining the charging load request in response to the vehicle being stationary for a predefined period of time, the SOC being at or below the lower limit, and DC fast charging of the propulsion subpack being unavailable. [9] The method of claim 7, wherein: the charging request is operable to control the energy subpack to provide the charging amount of electrical power without exceeding the rated charging limit. [10] The method of claim 7, wherein: the charging request is operable to control the energy subpack to provide the charging amount of electrical power at a selectable rate.

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