Patent Publication Number: US-2022239114-A1

Title: Adaptive fast-charging of multi-pack battery system in a mobile platform having dual charge ports

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to and the benefit U.S. Utility patent application Ser. No. 16/780,308 filed Feb. 3, 2020, which is hereby incorporated by reference in its entirety. 
    
    
     INTRODUCTION 
     The present disclosure relates to direct current fast-charging (DCFC) architectures and adaptive charging methodologies for use with motor vehicles and other mobile platforms having dual charge ports. Electric powertrains of the types used to propel battery electric or hybrid electric motor vehicles include one or more rotary electric machines constructed from a wound stator and a magnetic rotor. The stator windings are connected to an alternating current (AC)-side of a power inverter, with a direct current (DC)-side of the same power inverter being connected to positive and negative rails of a DC voltage bus. When the electric machine functions in its capacity as an electric traction motor, control of the ON/OFF conducting states of individual semiconductor switches residing within the power inverter generates an output voltage at a level suitable for energizing the stator windings. Sequential energization of the stator windings generates a rotating magnetic field that ultimately interacts with the rotor&#39;s magnetic field to produce useful machine rotation and torque. 
     The DC voltage bus is electrically connected to an onboard voltage supply. In a high-energy mobile application such as the above-noted battery electric or hybrid electric vehicles, the voltage supply is typically embodied as a high-energy multi-cell battery pack. Voltage capabilities of battery packs commonly used for energizing propulsion functions aboard such vehicles continue to increase in order to satisfy the demand for extended electric driving ranges. Battery charging infrastructure and associated charging methodologies likewise continue to evolve. For example, certain emerging DCFC stations are capable of providing relatively high charging voltages, e.g., 800-1000V or more, while older “legacy” charging stations are generally capable of providing lower charging voltages, for instance 400-500V. As a result, a battery pack and associated power electronics of a mobile platform are limited to a specific maximum charging voltage, which may or may not be available at an encountered DCFC station. 
     SUMMARY 
     A dual port charging architecture and accompanying charging method are described herein that together enable a reconfigurable multi-pack battery system to receive maximum charging power during a direct current fast-charging (DCFC) event. Charging power from a DCFC station is provided to one or both charge ports of the mobile platform at a relatively high or low voltage level. As used herein, the terms “high” and “low” are relative terms. In a non-limiting exemplary embodiment, for instance, 800-1000V or more may be considered high voltage, with low voltage being half of the high voltage level or less, e.g., 400-500V. Such voltage levels are representative of charging voltages of current and emerging DCFC stations. However, lower or higher charging voltages may be contemplated within the scope of the disclosure, and therefore nominal 400V and 800V charging voltages are merely illustrative of the present teachings and not limiting. 
     The battery system used in the present approach has multiple battery packs. The battery system is reconfigurable in the sense that the battery packs may be connected together in a parallel (P-connected) configuration or a series (S-connected) configuration. When connected in series, the battery packs may receive the above-noted high charging voltage. A simplified variation of such a battery system includes two battery packs. The charging voltage in such an embodiment is thus twice the magnitude of the low charging voltage. Additional battery packs may be used, and therefore the S-connected configuration could be more than twice the low charging voltage, as will be appreciated. The disclosed battery system is also capable of independently powering multiple drive systems aboard a mobile platform, e.g., front and rear wheel drive systems, and also of rapidly charging using either of the low or high charging voltages depending upon the configuration of the DCFC station. 
     In an exemplary embodiment, the mobile platform includes a controller, a reconfigurable battery system, and electric powertrain, and first and second charge ports. The battery system includes first and second battery packs, as well as first, second, and third switches having respective ON/OFF conductive states. The ON/OFF conductive states are individually commanded by the controller to selectively connect the first and second battery packs in either a parallel-connected (P-connected) configuration or a series-connected (S-connected) configuration based on a desired operating mode. The first and second charge ports are each connectable to the DCFC station via a corresponding charging cable during a DCFC event in which the first and/or second battery pack recharges via the DCFC station. The first charge port is configured to receive a low charging voltage or a high charging voltage from the DCFC station. The second charge port is configured to receive a low charging voltage that is less than half of the high charging voltage. The controller is configured, when the DCFC station is able to supply the high charging voltage to the first charge port, to selectively establish the S-connected configuration via control of the respective ON/OFF conductive states of the switches, and to thereafter charge the reconfigurable battery system solely via the first charge port. 
     The controller may be configured, when the DCFC station is able to supply the low charging voltage to the first charge port and the second charge port, to selectively establish the S-connected configuration via control of the respective ON/OFF conductive states of the switches, and to thereafter charge the reconfigurable battery system via the first charge port and the second charge port. 
     The controller may also record a diagnostic error code when the DCFC station is not able to supply the high charging voltage and is not able to supply the low charging voltage to the first charge port. 
     In some disclosed configurations of the controller, when the DCFC station is able to supply the low charging voltage only to the first charge port, the controller is operable for establishing the P-connected configuration via control of the respective ON/OFF conductive states of the switches, and for thereafter sequentially charging the first and second battery packs via the first charge port using the low charging voltage. 
     An accessory load may be connected to the second charge port during the DCFC event. During the DCFC event, the controller may power the accessory load at the low charging voltage via the second charge port concurrently with charging the reconfigurable battery system at the high charging voltage via the first charge port. 
     An optional fourth switch may be disposed between the second battery pack and the second charge port. The controller may selectively control the ON/OFF conductive state of the fourth switch to enable the second charge port to receive the high charging voltage from the DCFC station. 
     First and second power inverter modules may be connected to the reconfigurable battery system. A first electric machine may be connected to the first power inverter modules and configured to power front road wheels, and a second electric machine may be connected to the second power inverter modules and configured to power the rear road wheels. Or, a single power inverter module may be connected to the reconfigurable battery system, with a plurality of electric machines each respectively connected to the single power inverter module. 
     A method is also disclosed for charging a reconfigurable battery system of an electrical system having first and second battery packs using a DCFC station. The method may include verifying, via the above-noted controller, a connection of first and second charging cables from the DCFC station with respective first and second charge ports of the electrical system. The first charge port is configured to receive either of a low charging voltage or a high charging voltage from the DCFC station, and the second charge port is configured to receive a low charging voltage that is less than half of the high charging voltage. 
     The method may include selectively establishing an S-connected configuration of the first and second battery packs, via the controller, by individually commanding respective ON/OFF conductive states of first, second, and third switches of the reconfigurable battery system, and charging the reconfigurable battery system solely via the first charge port when the DCFC station supplies the high charging voltage to the first charge port. 
     Also disclosed herein is a motor vehicle. An exemplary embodiment of such a motor vehicle includes a controller, road wheels connected to a vehicle body, a rotary electric machine connected to the road wheels, and a power inverter module connected to the above-described battery system. 
     The above summary is not intended to represent every embodiment or aspect of the present disclosure. Rather, the foregoing summary exemplifies certain novel aspects and features as set forth herein. The above noted and other features and advantages of the present disclosure will be readily apparent from the following detailed description of representative embodiments and modes for carrying out the present disclosure when taken in connection with the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of an exemplary mobile platform undergoing a direct current fast-charging (DCFC) operation, with the mobile platform equipped with dual charge ports, an electric powertrain, and a reconfigurable battery system as set forth herein. 
         FIGS. 2A and 2B  are schematic illustrations of different battery systems usable as part of the representative mobile platform of  FIG. 1 . 
         FIGS. 3 and 4  are schematic illustrations of possible embodiments of an electric powertrain that may include the battery systems of  FIGS. 2A and 2B . 
         FIGS. 5 and 6  are flow charts depicting possible embodiments of a fast-charging method using the battery systems of  FIGS. 2A and 2B , respectively. 
         FIG. 7  is a table of operating modes and corresponding switching states for the depicted battery systems. 
         FIG. 8  is another flow chart depicting an exemplary embodiment of an alternative charging method using an additional switch as part of a battery system. 
     
    
    
     The present disclosure is susceptible to modifications and alternative forms, with representative embodiments shown by way of example in the drawings and described in detail below. Inventive aspects of this disclosure are not limited to the particular forms disclosed. Rather, the present disclosure is intended to cover modifications, equivalents, combinations, and alternatives falling within the scope of the disclosure as defined by the appended claims. 
     DETAILED DESCRIPTION 
     Referring to the drawings, wherein like reference numbers refer to the same or like components in the several Figures, a mobile platform  10  having an electric powertrain  20  is depicted schematically in  FIG. 1  in the form of an exemplary motor vehicle. In the illustrated embodiment, the mobile platform  10  is a passenger vehicle having respective front and rear road wheels  14 F and  14 R in rolling contact with a road surface  12 . However, the described solutions may also be used in a wide range of rechargeable electrical systems, such as but not limited to power plants, robots, conveyors, and transport platforms. When the electric powertrain  20  is used in a vehicular application, the present teachings may be readily extended to various types of motor vehicles, aircraft, marine vessels, and trains, trams, subways, or other types of rail vehicles. For illustrative consistency, the mobile platform  10  of  FIG. 1  will be described hereinafter in the context of a motor vehicle without limiting the present teachings. 
     The mobile platform  10  of  FIG. 1  is depicted undergoing a direct current fast-charging (DCFC) operation in which a reconfigurable battery system  22  (see  FIGS. 2A and 2B ) of the electric powertrain  20  is electrically charged via an off-board DCFC station  30  (arrow A) or  130  (arrow B). Such a connection is made between the DCFC station  30  or  130  and dual charge ports  11  of the mobile platform  10 , i.e., respective first and second charge ports P 1  and P 2 , via a length of high-voltage charging cable  32 . Charging plugs  34 A and  34 B forming end connections of the charging cable  32  may be configured as an SAE J1772 or other suitable country-specific or application-specific charge coupler or plug, as will be appreciated by those of ordinary skill in the art, and engaged with a respective one of the dual charge ports  11 . 
     A designated one of the dual charge ports  11  may be configured as a main/primary charge port capable of receiving either a high charging voltage (V H ) or a low charging voltage (V L ) from the DCFC station  30  or  130 . The other of the dual charge ports  11  may be configured as a secondary port capable of receiving only the low charging voltage (V L ) in certain disclosed embodiments. In a possible dual-voltage embodiment of the DCFC station  30 , for instance, the charging plug  34 A may output either of the low or high charging voltages V L  or V H , with such a dual-voltage capability indicated in  FIG. 1  by the abbreviation “V L /V H ”. The charging plug  34 B may output the low charging voltage (V L ) in the illustrated embodiment. 
     A DCFC event commences with connection of the charging plugs  34 A and  34 B to the respective first and second charge ports P 1  and P 2 , and subsequent detection and verification of such connection by an onboard controller (C)  50  (see  FIG. 3 ). Alternatively, the DCFC station  130  may include a DCFC station  30 A capable of outputting the high charging voltage V H  and a DCFC station  30 B capable of outputting the low charging voltage V L . 
     Referring to  FIGS. 2A and 2B , the battery system  22  may be used as a constituent part of the above-noted electric powertrain  20  of  FIG. 1 . A simplified embodiment of the battery system  22  includes respective first and second battery packs  24 A and  24 B, i.e., BAT- 1  and BAT- 2 . Battery packs  24 A and  24 B may each be embodied as multi-cell high-energy energy storage devices constructed from a lithium ion, zinc-air, nickel-metal hydride, or another application-suitable battery chemistry. The internal and external hardware configurations of the battery packs  24 A and  24 B may vary with the intended application. Although such hardware is omitted for illustrative simplicity, a representative configuration may arrange stacks of foil pouch-style battery cells within a rigid battery case, with the individual cells connected together via conductive bus bars. Cell voltages, temperatures, and other control values are read via a cell sense circuit mounted to such a battery case, with the control values relayed to a battery controller for use in controlling power flow to and from the battery system  22 . 
     The first and second battery packs  24 A and  24 B shown schematically in  FIGS. 2A and 2B  are respectively connected to the first and second charge ports P 1  and P 2  via a set of switches  25 . The switches  25  include at least first, second, and third switches S 1 , S 2 , and S 3 . An optional fourth switch S 4  is included in some embodiments to enable use of the first or charge port P 1  or P 2  as the above-noted main or primary charge port capable of receiving the high charging voltage (V H ). The switches  25 , which are shown as simplified ON/OFF binary switches for simplicity, may be variously embodied as mechanical switches or as solid-state semi-conductor switches, e.g., IGBTs or MOSFETS. Such switches  25  are responsive to ON/OFF state control signals (arrow CC I  of  FIG. 3 ), and thus opened (non-conducting) or closed (conducting) as needed based on pulse width modulation or other suitable switching control commands made by the controller  50  of  FIG. 3  or a separate control unit. 
     In the illustrated embodiment of  FIGS. 2A and 2B , the first charge port P 1  is electrically connected to the positive terminal (+) of the first battery pack  24 A. The second charge port P 2  is connected in a similar manner to the positive terminal of the second battery pack  24 B. The first switch S 1  selectively interconnects the respective first and second charge ports P 1  and P 2 . Negative terminals (−) of battery packs  24 A and  24 B are connected via the second switch S 2 , with the negative terminal of the first battery pack  24 B connected to the positive terminal of the second battery pack  24 B via the third switch S 3 . The optional fourth switch S 4 , which is controlled via a method  300  as set forth in  FIG. 8 , connects the positive terminal of the second battery pack  24 B to the second charge port P 2  to enable use of either charge port P 1  or P 2  as the main/high-voltage port. 
     The representative circuit topology of  FIG. 2A  allows high-voltage fast charging to occur via the first charge port P 1 . Such charging is enabled when respective first and second switches S 1  and S 2  are opened and the third switch S 3  is closed. Alternatively, the first and second charge ports P 1  and P 2  may receive the low charging voltage (V L ) as noted above. For dual port/low-voltage charging, the first and third switches S 1  and S 3  are commanded open and the second switch S 2  is commanded closed. Likewise, single-port charging is enabled via the first charge port P 1  to initially charge the first battery pack  24 A, which may be performed by opening the first and third switches S 1  and S 3  and closing the second switch S 2 . Thereafter, the second battery pack  24 B may be charged by opening the second and third switches S 2  and S 3  and closing the first switch S 1 . These and other switching states are also summarized in  FIG. 7 . As an alternative for single-port charging, both battery packs  24 A and  24 B may be charged simultaneously in a P-connected configuration, with switches S 1  and S 2  closed and switch S 3  open. 
     Alternatively, the circuit topology of  FIG. 2B  may be used to connect an optional accessory load (ACC)  26  to the second charge port P 2  during a DCFC event in which the first charge port P 1  is used to charge the multi-pack battery system  22 . That is, using the dual charging ports  11  of  FIG. 1 , the first charge port P 1  may be used to charge one or both of the battery packs  24 A and/or  24 B depending on the present charge mode, while the second charge port P 2  is used to supply power directly to the connected accessory load  26  at the level of the low charging voltage V L . Such a load may be variously embodied as an air conditioning compressor, a heater, a pump, or another accessory that an operator of the mobile platform  10  of  FIG. 1  may wish to operate concurrently with ongoing charging of the respective first or second battery pack(s)  24 A or  24 B. Under extreme cold or hot weather conditions, where the battery packs  24 A and  24 B cannot be charged due to potential exposure to lithium plating or battery aging, the ACC  26  can take power directly from the DCFC station  30  or  130  to warm up or cool down the battery packs and vehicle cabin. After the battery temperature reaches a desired charging temperature through pre-heating or cooling, then the first charge port P 1  is used to charge the battery packs  24 A and/or  24 B. 
     Referring to  FIGS. 3 and 4 , the battery system  22  of  FIGS. 2A and 2B  may be used as a constituent part of the electric powertrain  20 , e.g., of a motor vehicle or another mobile platform  10 . Power flow to and from the battery system  22  is provided via programmed operation the controller  50 . In a simplified embodiment of the electric powertrain  20 , the battery system  22  may be disposed between separate first and second traction power inverter modules  27 - 1  and  27 - 2 , which are connected to positive and negative bus rails  31   +  and  31   − . For clarity, the traction power inverter modules  27 - 1  and  27 - 2  are respectively labeled TPIM- 1  and TPIM- 2 . A respective link capacitor Cl and C 2  and resistor R 1  and R 2  are connected in parallel with the TPIMs  27 - 1  and  27 - 2 . 
     Each of the TPIMs  27 - 1  and  27 - 2  energizes a respective rotary electric machine  28 - 1  and  28 - 2  with an alternating current voltage (VAC), with the electric machines  28 - 1  and  28 - 2  respectively labeled M 1  and M 2 . Motor torque (arrow T M ) from the electric machines  28 - 1  and  28 - 2  is then directed to a connected load, e.g., a transmission (not shown) and/or the road wheels  14 F and  14 R of  FIG. 1 . The architecture of  FIG. 3  may also provide added flexibility by enabling battery packs  24 A and  24 B of different configurations, voltage capabilities, and/or battery chemistries to be used in different drive systems. For example, the battery pack  24 B may power the road wheels  14 R via the electric machine  28 - 2 , while the battery pack  24 A may independently power the road wheels  14 F via the electric machine  28 - 1 . 
     As part of the electric powertrain  20  shown in  FIGS. 3 and 4 , the controller  50  is equipped with a processor (P) and memory (M), with the memory (M) including application-suitable amounts of tangible, non-transitory memory, e.g., read only memory, whether optical, magnetic, flash, or otherwise. The controller  50  also includes application-sufficient amounts of random-access memory, electrically-erasable programmable read only memory, and the like, as well as a high-speed clock, analog-to-digital and digital-to-analog circuitry, and input/output circuitry and devices, as well as appropriate signal conditioning and buffer circuitry. 
     The controller  50  is programmed to execute instructions embodying the methods  100 ,  200 , and  300  as set forth below, with the controller  50  controlling the ON/OFF states of the various switches  25  of  FIGS. 2A and 2B  as part of such methods. To that end, the controller  50  is configured to receive input signals (arrow CC I ) indicative of a drive-requested or autonomously-requested operating mode of the first and/or second battery packs  24 A and/or  24 B, and in response to such a requested mode, to output control signals (arrow CC O ) to the multi-pack battery system  22  and thereby establish a particular combination of switching states of the switches  25 . 
     Some of the input signals (arrow CC I ) may be determined during a DCFC event during ongoing wired and/or wireless communication between the controller  50  and the DCFC station  30  or  130  of  FIG. 1 , as will be appreciated by those of ordinary skill in the art. Such communication generally occurs upon connection of the mobile platform  10  to the DCFC station  30  or  130 , such as when the DCFC station  30  or  130  communicates its maximum charging voltage to the controller  50 , and when the controller  50  provides information about the current state of charge, voltage capacity, chemistry, and other battery information to the DCFC station  30  or  130 . 
     In a drive/propulsion mode, an operator-requested or autonomously-determined propulsion request may likewise cause the controller  50  to selectively establish a parallel-connected (P-connected) configuration of the respective first and second battery packs  24 A and  24 B. During certain DCFC events, the controller  50  may selectively reconfigure the first and second battery packs  24 A and  24 B to a series-connected (S-connected) configuration to take advantage of an available high charging voltage V H . Depending on the particular configuration of the electric powertrain  20 , propulsion of the mobile platform  10  in the S-connected configuration at the high charging voltage V H  may be a possible operating mode. 
     The electric powertrain  20 A of  FIG. 4  depicts an alternative configuration to the electric powertrain  20  shown in  FIG. 3  in which a single inverter such as TPIM  27 - 1  is used to power multiple electric machines  28 - 1 , . . . ,  28 -n, . . . ,  28 -m (M 1 , . . . , M 2 , . . . M 3 ) sharing the same voltage bus. Such an embodiment, with respective first and second switches S 1  and S 2  open and third switch S 3  closed, may run the TPIM  27 - 1  at the higher voltage level V H . For operation at the low charging voltage V L , which occurs in the P-connected configuration, the respective first and second switches S 1  and S 2  are commanded closed and the third switch S 3  is commanded open. The various electric machines  28 - 1 , . . .  28 -n, . . .  28 -m may be used to power different loads, such as individual front or rear road wheels  14 F or  14 R of the exemplary mobile platform  10  of  FIG. 1  or other devices aboard the mobile platform  10 . 
     Referring to  FIG. 5 , the battery system  22  described above with reference to  FIGS. 2A-4  may be controlled via the controller  50  according to a method  100 . As with the methods  200  and  300  described below, the method  100  may be embodied as computer-executable instructions recorded in memory (M) of the controller  50  and executed by the processor (P). A corresponding logic table is shown in  FIG. 7  depicting the ON/OFF switching states of the switches  25  and the resulting operating modes. 
     In an exemplary embodiment of the method  100  commencing with block B 102 , the controller  50  verifies connection of the charging plugs  34 A and  34 B from the DCFC station  30  or  130  (see  FIG. 1 ) with the respective first and second charge ports P 1  and P 2 . The controller  50  thereafter verifies the status or charge capability of the first and second charge ports P 1  and P 2  (P 1 , P 2  STAT) upon such a connection. Verification in block B 102  may occur automatically via an electronic handshake and a subsequent exchange of charging needs and capabilities information between the controller  50  and the DCFC station  30  or  130  of  FIG. 1 , as will be readily appreciated by those of ordinary skill in the art. An actual physical connection and communications protocol used for subsequent information exchange is dependent upon the relevant charging standard being employed. The result of block B 102  is knowledge by the controller  50  of the maximum charging voltage that can be supplied to the first and charge ports P 1  and P 2  by the DCFC charge station  30  or  130 . The method  100  proceeds to block B 104 . 
     At block B 104 , the controller  50  next determines whether the first charge port P 1  is configured to receive the high charging voltage V H , i.e., whether the DCFC station is able to supply the high charging voltage V H  to the first charge port P 1  (P 1 =V H ?). The method  100  proceeds to block B 106  when the first charge port P 1  is connected to receive the high charging voltage V H , with the method  100  otherwise proceeding to block B 107 . 
     Block B 106  of method  100 , which is used when an accessory load  26  ( FIG. 2B ) is not concurrently powered during a DCFC event, may entail temporarily deactivating the second charge port P 2  (P 2 =DEACT) via the controller  50 . That is, with the first charge port P 1  configured and connected to receive the high charging voltage V H , the second charge port P 2  is not required during the imminent DCFC event. Deactivation of the second charge port P 2  may include preventing a flow of electrical power to the second charge port P 2 , such as by instructing the DCFC station  30  or  130  that the second charge port P 2  is not available for charging, and/or unplugging or otherwise disconnecting the second charge port P 2  from the DCFC station  30  or  130 , etc. The method  100  thereafter proceeds to block B 108 . 
     Block B 107 , which is analogous to block B 106 , includes determining whether the first charge port P 1  is instead configured and connected to receive the low charging voltage V L  from the DCFC station  30  or  130  of  FIG. 1  (P 1 =V L ?) The method  100  proceeds to block B 109  when this is the case, with the method  100  otherwise continuing on with block B 113  in the event the first charge port P 1  is not configured to receive the low charging voltage V L . 
     At block B 108 , the controller  50  establishes the S-connected configuration of the battery system  22 . For example, the controller  50  may command the respective first and second switches S 1  and S 2  to open, and the third switch S 3  to close (S 1 , S 2 =O, S 3 =X), where “O” and “X” indicate respective open and closed states. The method  100  then proceeds to block B 110 . 
     At block B 109 , the controller  50  determines whether the second charge port P 2  is configured and connected to receive the low charging voltage V L  (P 2 =V L ?). If so, the method  100  proceeds to block B 111 , with the method  100  otherwise continuing with block B 115  when the second charge port P 2  is not configured to receive the low charging voltage V L . 
     At block B 110 , the controller  50  commences a DCFC event at the high charging voltage V H , with power flow to the battery system  22  occurring through the first charge port P 1 . The method  100  is then complete, resuming anew with block B 102 . 
     At block B 111 , the controller  50  initiates double-port fast charging (P-V L -Ch) of the battery system  22  at the low charging voltage V L  via the first and second charge ports P 1  and P 2 . In order to do this, the controller  50  commands the respective first and third switches S 1  and S 3  to open and the second switch S 2  to close, with such a state also depicted in  FIG. 7 . 
     Block B 113  is reached from block B 107  when the first charge port P 1  is not configured to receive the high or low charging voltage V H  or V L . As this does not ordinarily occur, such a result may be treated by the controller  50  as an error state (E). Block B 113  may include, responsive to the error state, interrupting power flow to the battery system  22  and unplugging from the DCFC station  30  or  130 . Block B 113  may also include recording a diagnostic error code in memory (M) of the controller  50  that is indicative of the error state. The method  100  is complete, thereafter resuming with block B 102  after taking necessary corrective action to address or clear the anomaly. 
     At block B 115 , the controller  50  opens the respective first and third switches S 1  and S 3  and closes the second switch S 2  (S 1 , S 3 =O, S 2 =X). Once the indicated switching states are established, the controller  50  commences charging of the first battery pack  24 A (V L -BAT-1). The method  100  proceeds to block B 117  once the first battery pack  24 A has fully charged. 
     Block B 117  is analogous to block B 115  and includes charging the second battery pack  24 B (V L -BAT-2). Prior to charging the second battery pack  24 B, the controller  50  commands the first switch S 1  to close and the respective second and third switches S 2  and S 3  to open (S 1 =X, S 2 , S 3 =O). Thus, blocks B 115  and B 117  of method  100  together entail sequentially charging the first and second battery packs  24 A and  24 B, i.e., the first battery pack  24 A is charged first, followed by the second battery pack  24 B. The method  100  is then complete, resuming anew with block B 102 . 
     Referring to  FIG. 6 , the method  200  may be used as an alternative approach to the method  100  of  FIG. 5  whenever the optional accessory load  26  of  FIG. 2B  is to be powered concurrently with a DCFC event. With the exception of block B 211 , the various logic blocks of method  200  are analogous to corresponding blocks of method  100 , and thus are summarized below for simplicity. 
     At block B 202 , the controller  50  of  FIG. 3  first verifies the status of the first and second charge ports P 1  and P 2  of the mobile platform  10  shown in  FIG. 1 . As part of block B 202 , the controller  50  may determine whether a human or autonomous operator of the mobile platform  10  of  FIG. 1  has requested simultaneous powering of accessory load  26  of  FIG. 2B . The controller  50  proceeds to block B 204 , where the controller  50  determines if the first charge port P 1  is configured and connected to receive the high charging voltage V H  from the DCFC station  30  or  130  (P 1 =V H ?). If so, the method  200  proceeds to block B 209 . The method  200  proceeds instead to block B 205  whenever the first charge port P 1  is not configured and connected to receive the high charging voltage V H . 
     Block B 205  entails determining, once again via operation of the controller  50  of  FIG. 3 , whether the first charge port P 1  is configured and connected to receive the low charging voltage V L  from the DCFC station  30  or  130  of  FIG. 1  (P 1 =V L ?). The method  200  proceeds to block B 206  when the first charge port P 1  is so configured, and to block B 213  in the alternative whenever the first charge port P 1  is not configured to receive the low charging voltage V L . 
     At block B 206 , the controller  50  opens the respective first and third switches S 1  and S 3  and closes the second switch S 2 . The controller  50  thereafter initiates fast-charging of the battery system  22  via the first charge port P 1  (P 1 -V L -Ch). Charging in this particular embodiment may occur at the low charging voltage V L . 
     Block B 209  entails determining via the controller  50  whether the second charge port P 2  is configured and connected to receive the low charging voltage V L . The method  200  proceeds to block B 210  when the first and second charge ports P 1  and P 2  are both configured to receive the low charging voltage V L  from the DCFC station  30  or  130 , and to block B 213  in the alternative when the second charge port P 2  is not configured to receive the low charging voltage V L . 
     The controller  50  simultaneously executes blocks B 210  and B 212 . In block B 210 , the controller  50  opens the respective first and second switches S 1  and S 2  and closes the third switch S 3 . The method  200  proceeds to block B 211  to conduct series/S-connected charging of the battery system  22  at the high charging voltage V H , with such a charging mode abbreviated “V H -Ch” in  FIGS. 6 and 7 . 
     Block B 212  in this particular embodiment is reached from block B 209 , and entails directly powering the accessory load (ACC)  26  of  FIG. 2B  at the level of the low charging voltage V L , with this occurring via the second charge port P 2 . For instance, an operator of the mobile platform  10  depicted in  FIG. 1  may wish to run an air conditioning compressor or a blower motor to condition a passenger cabin of the mobile platform  10  during the ongoing fast-charging process, with such an accessory load  26  energized via the second charge port P 2  in this particular embodiment. 
     Referring briefly to  FIG. 7 , six exemplary operating modes are listed in table form under a mode column (Md), with open (O) and closed (X) switching states of the various switches  25  shown in  FIGS. 2A and 2B  depicted for each mode. Mode  1  (V H -Ch) is a series/S-connected charging mode occurring at the high charging voltage V H , with the respective first and second switches S 1  and S 2  in an open state and the third switch S 3  in a closed state. Mode  2  (P-V L -Ch) is a parallel/P-connected charging mode conducted at the low charging voltage V L , with respective first and third switches S 1  and S 3  open and the second switch S 2  closed in this particular mode. Modes  3  and  4  correspond to individual charging of the first and second battery packs  24 A and  24 B, respectively, at the low charging voltage V L . 
     Also depicted in  FIG. 7  are two possible electric propulsion modes for the mobile platform  10  shown in  FIG. 1 , i.e., Modes  5  and  6 . Mode  5  (V H -S) is a series/S-connected propulsion mode conducted at the high charging voltage V H . In such a mode, the respective first and second switches S 1  and S 2  are commanded open and the third switch S 3  is commanded closed. Mode  6  (V L -P) is a parallel/P-connected propulsion mode conducted at the low charging voltage V L , i.e., with the first and second battery packs  24 A and  24 B connected in parallel. In Mode  6 , the switching states of switches S 1 , S 2 , and S 3  are opposite the corresponding switching states in Mode  5 , i.e., first and second switches S 1  and S 2  are commanded closed by the controller  50  and the third switch S 3  is commanded open. 
     As noted above and as shown in  FIGS. 2A and 2B , the battery system  22  may optionally include the optional fourth switch S 4 . When used, switch S 4  may be positioned between the second charge port P 2  and the second battery pack  24 B. Inclusion of the fourth switch S 4  provides added control flexibility by allowing either of the first or second charge ports P 1  or P 2  to receive the high charging voltage V H  from the DCFC station  30  or  130 , as opposed to relying on the first charge port P 1  for this purpose. Thus, the inclusion of the fourth switch S 4 , albeit at the cost of a slight increase in programming complexity, provides a greater amount of control freedom when charging the battery system  22  via the DCFC station  30  or  130  of  FIG. 1 . 
       FIG. 8  is a flow chart for a method  300 . Method  300  is adapted for use with either of the representative circuit topologies of  FIGS. 2A and 2B  whenever the optional fourth switch S 4  is included. While some of the logic blocks of  FIG. 8  are analogous to corresponding logic blocks of  FIGS. 5 and 6 , the flexibility of using either of the first or second charge ports P 1  or P 2  to receive the high charging voltage V H  necessitates the use of additional logic flow decisions and possible control outputs of method  300 . 
     In an exemplary embodiment of such a method  300 , block B 302  entails verifying the status of the respective first and second charge ports P 1  and P 2  and connection of the same to the DCFC station  30  or  130  of  FIG. 1 , e.g., automatically via an electronic handshake between the controller  50  and the DCFC station  30  or  130 , as will be appreciated by those of ordinary skill in the art and noted above with reference to method  100 . The method  300  then proceeds to block B 304 . 
     Block B 304  includes using the controller  50  to determine whether the first charge port P 1  is configured and connected to receive the high charging voltage V H  from the DCFC station  30  or  130  (P 1 =V H ?). If such is the case, the method  300  proceeds to block B 306 , with the method  300  otherwise continuing on to block B 305  when the first charge port P 1  is not configured to receive the high charging voltage V H . 
     At block B 305 , the controller  50  determines whether the second charge port P 2  is configured and connected to receive the high charging voltage V H  from the DCFC station  30  or  130  (P 2 =V H ?). If so, the method  300  proceeds to block B 307 , with the method  300  otherwise continuing on to block B 310  when the second charge port P 2  is not configured to receive the high charging voltage V H . 
     Block B 306  entails deactivating the second charge port P 2  via the controller  50 . That is, with the first charge port P 1  configured to receive the high charging voltage V H , the second charge port P 2  is not needed in a subsequent charging action. The method  300  proceeds to block B 308 . 
     Block B 307  may entail deactivating the first charge port P 1  (DEACT P 1 ) via the controller  50  before proceeding to block B 309 . 
     At block B 308 , the controller  50  opens the first, second, and fourth switches S 1 , S 2 , and S 4  and closes the third switch S 3 . The controller  50  proceeds to block B 325  once the indicated switching states have been established. 
     At block B 309 , the controller  50  opens the respective second and fourth switches S 2  and S 4  and closes the first and third switches S 1  and S 3 . The controller  50  thereafter proceeds to block B 325 . 
     Block B 310  includes determining whether the first charge port P 1  is configured to receive a charging voltage from the DCFC station  30  or  130  of  FIG. 1  at the low charging voltage V L  (P 1 =V L ?). The method  300  proceeds to block B 312  when this is the case, with the method  300  otherwise continuing with block B 311 . 
     Block B 311  entails deactivating the first charge port P 1  via the controller  50  (DEACT P 1 ) before proceeding to block B 315 . As shown in  FIG. 8 , the controller  50  at block B 315  determines whether the second charge port P 2  is configured and connected to receive the low charging voltage V L  from the DCFC station  30  or  130  (P 2 =V L ?), analogously to above-described block B 305 . If so, the method  300  proceeds to block B 319 , with the method  300  otherwise returning to block B 317 . 
     Block B 312  includes determining whether the second charge port P 2  is configured to receive the low charging voltage V L  from the DCFC station  30  or  130  (P 2 =V L ?). If so, the method  300  proceeds to block B 314 , with the method  300  otherwise continuing on to block B 325  when the second charge port P 2  is not configured and connected to receive the low charging voltage V L . 
     At block B 314 , the controller  50  opens the respective first and third switches S 1  and S 3  (S 1 , S 3 =O) and closes the respective second and fourth switches S 2  and S 4  (S 2 , S 4 =X). The controller  50  thereafter proceeds to block B 316 . 
     At block B 316 , the controller  50  next initiates dual-port fast charging of the battery system  22  in a parallel/P-connected configuration, which is abbreviated P-V L -Ch in  FIG. 8 . The method  300  is complete, resuming anew with block B 302 . 
     At block B 317 , the controller  50  may record an error code corresponding to an error state of second charge port P 2  (E, P 2 ), and then may disconnect the second charge port P 2  (DISCON P 2 ). The method  300  thereafter returns to block B 302 . 
     Block B 319  entails closing the respective first and second switches S 1  and S 2  (S 1 , S 2 =X) and opening the respective third and fourth switches S 3  and S 4  (S 3 , S 4 =O). The controller  50  thereafter charges the first battery pack  24 A at the low charging voltage V L , i.e., V L -BAT-1. The method  300  then proceeds to block B 321 . 
     At block B 321 , the controller  50  opens the respective first and third switches S 1  and S 3  (S 1 , S 3 =O) and closes the respective second and fourth switches S 2  and S 4  (S 2 , S 4 -X). The controller  50  thereafter initiates charging of the second battery pack  24 B at the low charging voltage V L , i.e., V L -BAT-2. The method  300  is then complete, resuming anew with block B 302 . 
     Block B 325  includes unplugging or disconnecting charge port P 2  (DISCON P 2 ) and then proceeding to block B 327 . 
     Block B 327  entails opening the respective first and third switches Si and S 3  (S 1 , S 3 =O) and closing the respective second and fourth switches S 2  and S 4  (S 2 , S 4 =X). The controller  50  thereafter initiates charging of the first battery pack  24 A at the low charging voltage V L , i.e., V L -BAT-1, and then proceeds to block B 329 . 
     At block B 329 , the controller  50  closes the respective first and fourth switches S 1  and S 4  (S 1 , S 4 =X) and opens the respective second and third switches S 2  and S 3  (S 2 , S 3 =O). The controller  50  thereafter charges the second battery pack  24 B at the low charging voltage V L , i.e., V L -BAT-2. 
     Although for clarity the methods  100 ,  200 , and  300  are described separately above with reference to  FIGS. 5, 6, and 8 , respectively, the collective logic of the methods  100 ,  200 , and  300  may be implemented as alternative loops of a single control algorithm or program. For instance, the controller  50  may be programmed with the number of switches  25  in the battery system  22 , including whether the optional fourth switch S 4  is used. The controller  50  is thus configured to determine whether or not an operator or autonomous logic has requested that the accessory load  26  of  FIG. 2B  remain powered during a particular charging operation of the battery system  22 . Using such information, the controller  50  may then determine the particular control logic subroutine to implement. 
     The above disclosure therefore provides a flexible dual-port charging architecture for achieving maximum power charging of the battery system  22  used aboard the mobile platform  10  of  FIG. 1 . Charging may occur using the low and/or high charging voltages V L  or V H , respectively, and using either of the DCFC stations  30  or  130 . Additionally, the disclosed solutions provide added flexibility to use the separate first and second battery packs  24 A and  24 B to power independent drive systems. By using the described first and second charge ports P 1  and P 2  on the mobile platform  10 , one charge port P 1  or P 2  may be used to support the accessory load  26  of  FIG. 2B  while the other charge port P 2  or P 1  receives a charging voltage for recharging the individual cells of the battery system  22 . These and other advantages will be readily appreciated by those of ordinary skill in the art in view of the foregoing disclosure. 
     While some of the best modes and other embodiments have been described in detail, various alternative designs and embodiments exist for practicing the present teachings defined in the appended claims. Those skilled in the art will recognize that modifications may be made to the disclosed embodiments without departing from the scope of the present disclosure. Moreover, the present concepts expressly include combinations and sub-combinations of the described elements and features. The detailed description and the drawings are supportive and descriptive of the present teachings, with the scope of the present teachings defined solely by the claims.