Patent Publication Number: US-2023150378-A1

Title: Multi-function dc-dc converter for battery electric vehicles

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Chinese Patent Application No. 202111338996.3, filed on Nov. 12, 2021. The entire disclosure of the application referenced above is incorporated herein by reference. 
     INTRODUCTION 
     The information provided in this section is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     The present disclosure relates to battery systems and more particularly to a power control system for battery systems for battery electric vehicles (BEVs) including DC-DC converters. 
     Battery electric vehicles (BEVs) include one or more battery packs each including one or more battery cells. A battery system is used to control charging and discharging of the battery. During operation, one or more electric motors of the BEV are used to provide propulsion for the vehicle. Some BEVs allow a driver to select different modes of operation that may include a sport mode, a normal mode and a range improvement mode. 
     The power stored by the battery pack(s) is depleted after usage and the BEV needs to be recharged. Options for recharging the battery pack(s) include plugging into utility power at a charging station such as a commercial charging station or a home charging station. Other options may include charging one BEV using the power stored in another BEV. 
     As can be appreciated, the battery pack of the BEV may be depleted while the vehicle is not at the home of the owner. Currently, the amount of time that is required to fully recharge the battery pack(s) is typically on the order of 4-12 hours for a full charge depending upon various factors. The charging period is significantly longer than the amount of time that is required to fill a fuel tank of a vehicle including an internal combustion engine (less than 10 minutes). 
     Some BEV(s) have adopted higher voltage battery systems for charging the battery pack(s) more quickly in an effort to reduce charging times. For example, some fast charging systems can charge the battery pack to 80% capacity in less than one hour. Prior to initiating recharging, some of these charging systems may perform battery pre-conditioning such as heating the battery pack(s) to a predetermined temperature to improve charging efficiency. 
     SUMMARY 
     A power control system for a vehicle includes a charge port and a contactor connected to the charge port and including a first plurality of switches. An energy storage system includes a second plurality of switches and one or more battery packs. A bi-directional DC-DC converter is connected between the energy storage system and a plurality of vehicle loads. A controller is configured to control states of the first plurality of switches and the second plurality of switches to configure in a plurality of modes including a range improvement mode; a first charging mode to perform charging at a first voltage level, wherein the one or more battery packs supply power at the first voltage level; a vehicle to vehicle charging mode; a second charging mode to perform charging at a second voltage level that is different than the first voltage level; a battery preconditioning mode; and an accessory load support mode that is operable during charging at a higher one of the first voltage level and the second voltage level and during operation at a higher one of the first voltage level and the second voltage level. 
     In other features, the first plurality of switches of the contactor includes a first switch including a first terminal connected to a first terminal of the charge port, a second terminal connected to a first terminal of the energy storage system and a control terminal connected to the controller. A second switch includes a first terminal connected to a second terminal of the charge port, a second terminal connected to a second terminal of the energy storage system and a control terminal connected to the controller. A third switch includes a first terminal connected to the first terminal of the charge port, a second terminal connected to a first terminal of a first one of the plurality of vehicle loads and a control terminal connected to the controller. A fourth switch includes a first terminal connected to the second terminal of the charge port, a second terminal connected to a second terminal of the first one of the plurality of vehicle loads and a control terminal connected to the controller. 
     In other features, the bi-directional DC-DC converter includes a first capacitor including a first terminal connected to the second terminal of the first switch and a second terminal connected to the second terminal of the second switch; a first power switch including a first terminal connected to the second terminal of the first switch; an inductor including a first terminal and a second terminal; a second power switch including a first terminal connected to a second terminal of the first power switch and the first terminal of the inductor, and a second terminal connected to the second terminal of the second switch; and a second capacitor including a first terminal connected to the second terminal of the inductor and the first one of the plurality of vehicle loads, and a second terminal connected to the second terminal of the second switch. 
     In other features, a fifth switch includes a first terminal connected to the second terminal of the inductor, the first terminal of the second capacitor, and the first one of the plurality of vehicle loads. A fusible link includes a first terminal connected to a second terminal of the fifth switch and a second terminal connected to a second one of the plurality of vehicle loads and the second terminal of the third switch. A sixth switch includes a first terminal connected to the second terminal of the second capacitor and the first one of the plurality of vehicle loads and a second terminal connected to the second one of the plurality of vehicle loads and the second terminal of the fourth switch. 
     In other features, the energy storage system includes a fifth switch of the second plurality of switches including a first terminal connected to the second terminal of the first switch; a sixth switch of the second plurality of switches including a first terminal connected to the second terminal of the first switch; a first fusible link including a first terminal connected to a second terminal of the sixth switch; a first battery pack of the one or more battery packs including a first terminal and a second terminal; a second battery pack of the one or more battery packs including a first terminal and a second terminal; a resistor including a first terminal connected to a second terminal of the fifth switch and a second terminal connected to a second terminal of the first fusible link and the first terminal of the first battery pack, wherein the first terminal of the second battery pack is connected to the second terminal of the first battery pack; a seventh switch of the second plurality of switches including a first terminal connected to the second terminal of the second battery pack; and a second fusible link including a first terminal connected to a second terminal of the seventh switch and a second terminal connected to the second terminal of the second switch. 
     In other features, the energy storage system includes a fifth switch of the second plurality of switches including a first terminal connected to the second terminal of the first switch; a sixth switch of the second plurality of switches including a first terminal connected to the second terminal of the first switch; a first battery pack of the one or more battery packs including a first terminal and a second terminal; a resistor including a first terminal connected to a second terminal of the fifth switch and a second terminal connected to a second terminal of the sixth switch and the first terminal of the first battery pack; a seventh switch of the second plurality of switches including a first terminal connected to the second terminal of the first switch; an eighth switch of the second plurality of switches including a first terminal connected to a second terminal of the seventh switch and a second terminal connected to the second terminal of the first battery pack; a second battery pack of the one or more battery packs including a first terminal and a second terminal; a fusible link including a first terminal connected to the second terminal of the seventh switch and the first terminal of the eighth switch and a second terminal connected to the first terminal of the second battery pack; a ninth switch of the second plurality of switches including a first terminal connected to the second terminal of the second battery pack and a second terminal connected to the second terminal of the second switch; and a tenth switch of the second plurality of switches including a first terminal connected to the second terminal of the first battery pack and a second terminal connected to the second terminal of the second switch. 
     In other features, the bi-direction DC-DC converter includes a capacitor connected to the second terminal of the first switch and the second terminal of the second switch; a first power switch, a second power switch, a third power switch and a fourth power switch each including a first terminal, a second terminal and a control terminal; and an inductor. The first terminal of the first power switch is connected to the second terminal of the first switch. The second terminal of the first power switch is connected to the first terminal of the third power switch and a first terminal of the inductor. The first terminal of the second power switch is connected to a first node. The second terminal of the second power switch is connected to a second terminal of the inductor and a first terminal of the fourth power switch. The second terminal of the fourth power switch is connected a second node. 
     In other features, a fifth switch includes a first terminal connected to the first node and a second terminal connected first terminals of the vehicle loads. A sixth switch includes a first terminal connected to the second node and a second terminal connected to second terminals of the vehicle loads. 
     In other features, the plurality of vehicles loads include a first vehicle load and a second vehicle load. The first node is connected a first terminal of the first vehicle load and a first terminal of a fifth switch. A second terminal of the fifth switch is connected to a first terminal of the second vehicle load. The second node is connected to a second terminal of the first vehicle load and the second vehicle load. 
     In other features, a fifth switch including a first terminal and a second terminal. A sixth switch includes a first terminal and a second terminal. The plurality of vehicles loads include a first vehicle load and a second vehicle load. The first node is connected a first terminal of the first vehicle loads and a first terminal of a fusible link. A second terminal of the fusible link is connected to a first terminal of the fifth switch. A second terminal of the fifth switch is connected to a second terminal of the third switch and first terminals of the second vehicle load. The second node is connected to a first terminal of the first vehicle load and a first terminal of the sixth switch. A second terminal of the second switch is connected to a second terminal of the second vehicle load and the second terminal of the fourth switch. 
     A power control system for a vehicle includes a charge port and a contactor connected to the charge port and including a first plurality of switches. An energy storage system includes a second plurality of switches and one or more battery packs. A bi-directional DC-DC converter is connected between the energy storage system and a plurality of vehicle loads. A controller is configured to control states of the first plurality of switches and the second plurality of switches to configure in a plurality of modes. The first plurality of switches comprises a first switch including a first terminal connected to a first terminal of the charge port, a second terminal connected to a first terminal of the energy storage system and a control terminal connected to the controller. A second switch includes a first terminal connected to a second terminal of the charge port, a second terminal connected to a second terminal of the energy storage system and a control terminal connected to the controller. A third switch including a first terminal connected to the first terminal of the charge port, a second terminal connected to a first terminal of a first one of the plurality of vehicle loads and a control terminal connected to the controller. A fourth switch includes a first terminal connected to the second terminal of the charge port, a second terminal connected to a second terminal of the first one of the plurality of vehicle loads and a control terminal connected to the controller. 
     In other features, the plurality of modes include a range improvement mode; a first charging mode to perform charging at a first voltage level, wherein one or more battery packs supply power at the first voltage level; a vehicle to vehicle charging mode; a second charging mode to perform charging at a second voltage level that is less than the first voltage level; a battery preconditioning mode; and an accessory load support mode that is operable during charging at a higher one of the first voltage level and the second voltage level and when operating at a higher one of the first voltage level and the second voltage level. 
     In other features, the bi-directional DC-DC converter includes a first capacitor including a first terminal connected to the second terminal of the first switch and a second terminal connected to the second terminal of the second switch; a first power switch including a first terminal connected to the second terminal of the first switch; an inductor including a first terminal and a second terminal; a second power switch including a first terminal connected to a second terminal of the first power switch and the first terminal of the inductor, and a second terminal connected to the second terminal of the second switch; and a second capacitor including a first terminal connected to the second terminal of the inductor and a first one of the vehicle loads, and a second terminal connected to the second terminal of the second switch. 
     In other features, a fifth switch includes a first terminal connected to the second terminal of the inductor, the first terminal of the second capacitor, and the first one of the plurality of vehicle loads. A fusible link includes a first terminal connected to a second terminal of the fifth switch and a second terminal connected to a second one of the plurality of vehicle loads and the second terminal of the third switch. A sixth switch includes a first terminal connected to the second terminal of the second capacitor and the first one of the plurality of vehicle loads and a second terminal connected to the second one of the plurality of vehicle loads and the second terminal of the fourth switch. 
     In other features, the energy storage system includes a fifth switch of the second plurality of switches including a first terminal connected to the second terminal of the first switch. A sixth switch of the second plurality of switches including a first terminal connected to the second terminal of the first switch. A first fusible link includes a first terminal connected to a second terminal of the sixth switch. A first battery pack of the one or more battery packs including a first terminal and a second terminal. A second battery pack of the one or more battery packs includes a first terminal and a second terminal. A resistor includes a first terminal connected to a second terminal of the fifth switch and a second terminal connected to a second terminal of the first fusible link and the first terminal of the first battery pack. The first terminal of the second battery pack is connected to the second terminal of the first battery pack. A seventh switch of the second plurality of switches includes a first terminal connected to the second terminal of the second battery pack. A second fusible link includes a first terminal connected to a second terminal of the seventh switch and a second terminal connected to the second terminal of the second switch. 
     In other features, the energy storage system includes a fifth switch of the second plurality of switches including a first terminal connected to the second terminal of the first switch. A sixth switch of the second plurality of switches includes a first terminal connected to the second terminal of the first switch. A first battery pack of the one or more battery packs includes a first terminal and a second terminal. A resistor includes a first terminal connected to a second terminal of the fifth switch and a second terminal connected to a second terminal of the sixth switch and the first terminal of the first battery pack. A seventh switch of the second plurality of switches includes a first terminal connected to the second terminal of the first switch. An eighth switch of the second plurality of switches includes a first terminal connected to a second terminal of the seventh switch and a second terminal connected to the second terminal of the first battery pack. A second battery pack of the one or more battery packs includes a first terminal and a second terminal. A fusible link includes a first terminal connected to the second terminal of the seventh switch and the first terminal of the eighth switch and a second terminal connected to the first terminal of the second battery pack. A ninth switch of the second plurality of switches includes a first terminal connected to the second terminal of the second battery pack and a second terminal connected to the second terminal of the second switch. A tenth switch of the second plurality of switches includes a first terminal connected to the second terminal of the first battery pack and a second terminal connected to the second terminal of the second switch. 
     In other features, the bi-direction DC-DC converter includes a capacitor connected to the second terminal of the first switch and the second terminal of the second switch. A first power switch, a second power switch, a third power switch and a fourth power switch each include a first terminal, a second terminal and a control terminal. The first terminal of the first power switch is connected to the second terminal of the first switch. The second terminal of the first power switch is connected to the first terminal of the third power switch and a first terminal of an inductor. The first terminal of the second power switch is connected to a first node. The second terminal of the second power switch is connected to a second terminal of the inductor and a first terminal of the fourth power switch. The second terminal of the fourth power switch is connected a second node. 
     In other features, a fifth switch includes a first terminal connected to the first node and a second terminal connected first terminals of the vehicle loads. A sixth switch includes a first terminal connected to the second node and a second terminal connected to second terminals of the vehicle loads. 
     In other features, the plurality of vehicles loads include a first vehicle load and a second vehicle load. The first node is connected a first terminal of the first vehicle load and a first terminal of the fifth switch. A second terminal of the fifth switch is connected to a first terminal of the second vehicle load. The second node is connected to a second terminal of the first vehicle load and the second vehicle load. 
     In other features, a fifth switch including a first terminal and a second terminal. A sixth switch includes a first terminal and a second terminal. The plurality of vehicle loads include a first vehicle load and a second vehicle load. The first node is connected a first terminal of the first vehicle load and a first terminal of the fusible link. A second terminal of the fusible link is connected to a first terminal of the fifth switch. A second terminal of the fifth switch is connected to a second terminal of the third switch and first terminals of the second vehicle load. The second node is connected to a first terminal of the first vehicle load and a first terminal of the sixth switch. A second terminal of the second switch is connected to a second terminal of the second vehicle load and the second terminal of the fourth switch. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG.  1    is a functional block diagram of an example of a power control system for a battery system of a vehicle according to the present disclosure; 
         FIG.  2 A  is a table illustrating an example of switch states of switches and a buck-boost converter of the battery system during various operating modes according to the present disclosure; 
         FIGS.  2 B to  2 I  show the battery system of  FIG.  1    in various operating modes according to the present disclosure; 
         FIG.  3    is a functional block diagram of an example the battery system according to the present disclosure; 
         FIG.  4    is a functional block diagram of another example of a power control system for a battery system of a vehicle according to the present disclosure; 
         FIG.  5 A  is a table illustrating an example of states of switches and a buck-boost converter of the battery system during various operating modes according to the present disclosure; 
         FIGS.  5 B to  5 H  show the battery system of  FIG.  4    in various operating modes according to the present disclosure; 
         FIG.  6    is a functional block diagram of another example of a power control system for a battery system of a vehicle according to the present disclosure; 
         FIG.  7    is a table illustrating an example of states of switches and a buck-boost converter of the battery system during various operating modes according to the present disclosure; 
         FIG.  8    is a functional block diagram of another example of a power control system for a battery system of a vehicle according to the present disclosure; 
         FIG.  9    is a table illustrating an example of states of switches and a buck-boost converter of the battery system during various operating modes according to the present disclosure; 
         FIG.  10    is a flowchart of a method for operating the battery system according to the present disclosure; 
         FIG.  11    is a functional block diagram of another example of a power control system for a battery system of a vehicle according to the present disclosure; 
         FIG.  12    is a table illustrating an example of states of switches and a buck-boost converter of the battery system during various operating modes according to the present disclosure; 
         FIG.  13    is a functional block diagram of another example of a power control system for a battery system of a vehicle according to the present disclosure; and 
         FIG.  14    is a table illustrating an example of states of switches and a buck-boost converter of the battery system during various operating modes according to the present disclosure. 
     
    
    
     In the drawings, reference numbers may be reused to identify similar and/or identical elements. 
     DETAILED DESCRIPTION 
     While the present disclosure describes a power control system for a battery system including a multi-mode bi-directional DC-DC converter for a battery electric vehicle (BEV), skilled artisans will appreciated that the battery system can be used in hybrid or other vehicles and/or in other applications. 
     The present disclosure describes a power control system including configurable switches and a bidirectional DC-DC converter to provide multiple selectable operating modes. Non-limiting examples of bidirectional DC-DC converter can be a buck-boost converter, a boost converter or a buck converter depending on vehicle applications. DC-DC converter can also be isolated (with transformer) or non-isolated DC-DC converter. Non-isolated DC-DC converters are used in this application as an example. Non-limiting examples of the selectable operating modes include range improvement, battery pre-conditioning, accessory load support, backward DC Fast Charge (DCFC) compatibility, vehicle to vehicle charging, and/or vehicle to X (where X is any other device, utility or other power domain). 
     Referring now to  FIG.  1   , a power control system  10  is shown. In some examples, the power control system  10  is a 400V drive system, although other voltage levels can be used. As will be described further below, the power control system  10  supports various operating modes including range improvement, vehicle-to-vehicle charging, accessory load support, battery preconditioning, and/or backward/forward compatibility. 
     In some examples, the power control system  10  includes a charge port  12  and provides power to first vehicle loads  18  including a one or more sub-modules such as an accessory power module (APM) and/or an air conditioning compressor module (ACCM) and second vehicle loads  22  such as a traction power inverter module (TPIM), although other types of vehicle loads can be used. The power control system  10  further includes contactors  32 , an energy storage system (ESS)  34 , and a buck-boost converter  36 . 
     The contactors  32  include switches S 1  and S 3  having a first terminal connected to a positive terminal of the charge port  12 . The contactors  32  further include switches S 2  and S 4  having first terminals connected to a negative terminal of the charge port  12 . 
     The ESS  34  includes a battery pack  14  and switches SPC, S 5  and S 6 . The switch SPC is a pre-charge contactor. As can be appreciated, the switches can include mechanical relays and/or solid state switches. First terminals of the switches SPC and S 5  are connected to a second terminal of the switch S 1 . A second terminal of the switch SPC is connected by a resistor R 1  to a second terminal of the switch S 5  and a first terminal of a fusible link F 1  (such as a fuse or circuit breaker). 
     A second terminal of the fusible link F 1  is connected to a positive terminal of the battery pack  14  that includes one or more battery cells. A negative terminal of the battery pack  14  is connected to a first terminal of a switch S 6 . A second terminal of the switch S 6  is connected to a second terminal of the switch S 2 . 
     The buck-boost converter  36  includes a capacitor C 1  having a first terminal connected to the first terminal of the switch S 1  and a second terminal connected to the second terminal of the switch S 2 . A first terminal of a power switch T 1  is connected to the second terminal of the switch S 1 . A second terminal of the power switch T 1  is connected to a first terminal of an inductor L 1  and a first terminal of a power switch T 3 . A second terminal of the power switch T 3  is connected to the second terminal of the switch S 2 . 
     The buck-boost converter  36  further includes power switches T 5  and T 6  which form a bidirectional power switch that is used to bypass the DC-DC converter. While an exemplary configuration of a bi-directional switch is shown, other types of bi-directional power switches can be used. This bidirectional DC-DC switch is optional if other switches such as S 1  and S 3  are on and provide the bypass function. The power switch T 5  includes a first terminal connected to the second terminal of the switch S 1  and a second terminal connected to a second terminal of the power switch T 6 . A second terminal of the power switch T 6  is connected to a first terminal of a switch S 9 , a second terminal of the switch S 3 , and to a first terminal of a power switch T 2 . A second terminal of the power switch T 2  is connected to a second terminal of the inductor L 1  and a first terminal of a power switch T 4 . A second terminal of the power switch T 4  is connected to the second terminal of the switch S 2 , a second terminal of the switch S 4  and a first terminal of the switch S 10 . 
     A second terminal of the switch S 9  is connected to the second vehicle loads  22  and to a first terminal of a fusible link F 2 . A second terminal of the fusible link F 2  is connected to a first terminal of the second vehicle loads  22 . The second vehicle loads  22  are connected to the second terminal of the switch S 10 . In some examples, the first loads  18  are always connected to battery when a low voltage battery (e.g. 400V) is used. 
     In some examples, the power switches T 1  to T 6  may include voltage-controlled bipolar switching devices in the form of insulated gate bipolar transistors (IGBTs), metal-oxide semiconductor field effect transistors (MOSFETs), silicon carbide (SIC) MOSFET, wideband GaN devices (WBG), or other suitable switches having a control terminal to turn on and off. 
     Referring now to  FIG.  2 A , the positions of the switches during various operating modes are shown. In this example, the drive system and battery assume to be a low voltage system (e.g. 400V). In a normal driving mode in  FIGS.  2 A and  2 B , either the switches S 1  and S 3  is on or bi-directional power switch T 5  and T 6  is on to bypass DC-DC converter. S 5 , S 6  and switches S 9  and S 10  are on, the switch S 2 , S 4  SPC is off and the buck-boost converter  36  is off (in standby mode). The battery directly supplies power to the TPIM  22 . 
     In a range improvement mode in  FIGS.  2 A and  2 C , the switches S 1  to S 4  are off and/or bi-directional power switch T 5  and T 6  is off, switches S 5 , S 6 , S 9 , and S 10  are on, the switch SPC is off and the buck-boost converter  36  is on (in operating mode). 
     In a pre-charging mode in  FIGS.  2 A and  2 D , the switches S 1 , S 2 , S 6  and the SPC are on, the switches S 3 , S 4 , S 5 , S 9 , and S 10  are off, and the buck-boost converter  36  is off. 
     When charging from a 400V grid in  FIGS.  2 A and  2 E , the switches S 1 , S 2 , S 5  and S 6  are on, the switches S 3 , S 4 , S 9 , S 10  and SPC are off and the buck-boost converter  36  is off. 
     When charging from an 800 V grid in  FIGS.  2 A and  2 F , the switches S 1 , S 2 , S 9 , S 10  and SPC are off, the switches S 3  to S 6  and the buck-boost converter  36  are on. 
     When charging an ESS of another vehicle at 400V or 800V in  FIGS.  2 A,  2 G , and  2 H the switches S 1 , S 2 , S 9  and S 10  and SPC are off and the switches S 3  to S 6 , and the buck-boost converter  36  are on. 
     When performing battery preconditioning in  FIGS.  2 A and  2 I , the switches S 1 , S 2 , S 3 , S 4 , S 9 , S 10  and SPC are off and the switches S 5 , S 6  and the buck-boost converter  36  are on. 
     Referring now to  FIG.  3   , a controller  60  executes an application configured to control power switches  68  of the buck-boost converter  36  and switches  64  based upon inputs from sensors  66  (such as current, voltage, temperature, speed, torque, and other sensors), a user interface  72 , other vehicle systems  74 , or other input. In some examples, the user interface  72  allows a driver or occupant to select the mode (such as the range improvement mode) of the battery system using a button, touch panel or other user interface. 
     Referring now to  FIG.  4   , another power control circuit  400  is shown. In some examples, the power control circuit  400  is a 400V drive system with a flexible battery (or flexbatt) battery configuration. The power control circuit  400  supports various modes including range improvement, vehicle-to-vehicle charging, battery preconditioning, and/or 400V accessory load support during 800V charging. 
     The power control circuit  400  includes a charge port  12  and supplies power to the first vehicle loads  18 , the second vehicle loads  22  and/or other vehicle loads. The power control circuit  400  further includes contactors  432 , an energy storage system (ESS)  434  (including a first battery pack  410  and a second battery pack  412 ), and a buck-boost converter  436 . 
     First terminals of switches S 1  and S 3  are connected to a positive terminal of the charge port  12 . First terminals of switches S 2  and S 4  are connected to a negative terminal of the charge port  12 . First terminals of switches S 5 , S 7  and SPC are connected to a second terminal of the switch S 1 . A second terminal of the switch S 7  is connected by a resistor R 1  to a second terminal of the switch SPC and to a first terminal of the first battery pack  410 . A second terminal of the switch S 5  is connected to a first terminal of the switch S 9  and a first terminal of a fusible link F 1 . A second terminal of the switch S 9  is connected to a second terminal of the first battery pack  410  and to a first terminal of a switch S 8 . A second terminal of the second battery pack  412  is connected to a first terminal of a switch S 6 . Second terminals of the switches S 6  and S 8  are connected to a second terminal of the switch S 2 . 
     The buck-boost converter  436  includes a capacitor C 1  having a first terminal connected to the second terminal of the switch S 1  and a second terminal connected to the second terminal of the switch S 2 . A first terminal of a power switch T 1  is connected to the second terminal of the switch S 1  and a first terminal of a bidirectional bypass switch S 0 . A second terminal of the power switch T 1  is connected to a first terminal of an inductor L 1  and a first terminal of a switch T 3 . A second terminal of the power switch T 3  is connected to the second terminal of the switch S 2 . 
     A first terminal of the power switch T 2  is connected to a second terminal of the switch S 0 , a first terminal of the second vehicle loads  22  and a first terminal of a fusible link F 2 . A second terminal of the power switch T 2  is connected to a second terminal of an inductor L 1  and to a first terminal of a power switch T 4 . A second terminal of the power switch T 4  is connected to the second terminal of the switch S 2 , a second terminal of the second vehicle loads  22 , the second terminal of the first vehicle loads  18 , and a second terminal of the switch S 4 . A second terminal of the fusible link F 2  is connected to the first terminal of the switch S 10 . The second terminal of the switch S 10  is connected to the first terminal of vehicle load  18  and second terminal of switch S 3 . 
     Referring now to  FIG.  5 A , the power control circuit  400  operates in various operating modes. In a normal driving mode in  FIGS.  5 A and  5 B , the switches S 1 , S 3  S 5  to S 8  and S 10  are on. The battery directly provides power to TPIM  22  and accessory loads  18 . Switches S 2 , S 4 , S 9  and SPC and the buck-boost converter are off. 
     In a range improvement mode in  FIGS.  5 A and  5 C , the switches S 1  and S 3  are on and switch S 10  is off to support vehicle load  18 , S 9  and SPC are off, switches S 5  to S 8  are on and the buck-boost converter  436  is on. 
     In a pre-charging mode in  FIGS.  5 A and  5 D , the switches S 1 , S 2 , S 6 , S 9  and SPC are on and switches S 3 , S 4 , S 5 , S 7 , S 8 , S 10  and the buck-boost converter  436  are off. 
     When charging from the 400 V grid in  FIGS.  5 A and  5 E , the switches S 1 , S 2 , S 5  to S 8  are on, switches S 3 , S 4 , S 9  and SPC are off and the buck-boost converter  436  and S 10  are on to support the vehicle loads  18 . 
     When charging from an 800V grid in  FIGS.  5 A and  5 F , the switches S 1 , S 2 , S 6 , S 7 , and S 9  are on, switches S 3 , S 4 , S 5 , S 8  and SPC are off and the buck-boost converter  436  and S 10  are on to support vehicle load  18 . 
     When charging a second vehicle having a 400V ESS in  FIGS.  5 A and  5 G , the switches S 3  to S 8  are on, the switches S 1 , S 2 , S 9  and SPC are off and the buck-boost converter  436  and switch S 10  are on. 
     During battery preconditioning in  FIGS.  5 A and  5 H , the switches S 2 , S 4 , S 9 , S 10  and SPC are off, and the switches S 5  to S 8  and the buck-boost converter  436  are on. Switch S 1  and S 3  are on if vehicle load  18  is needed. 
     Referring now to  FIG.  6   , a power control system  600  is shown. In some examples, the power control system  600  includes an 800V drive system. The power control system  600  supports various modes including range improvement, accessory load support during driving and charging, charging from different grid voltages (e.g. 400V or 800V), vehicle-to-vehicle charging and/or battery preconditioning. 
     The power control system  600  includes the charge port  12  and provides power to the first vehicle loads  18 , the second vehicle loads  22 , and/or other loads. The power control system  600  further includes contactors  632 , an energy storage system (ESS)  634 , and a buck-boost converter  636 . The contactors  632  include switches S 1  and S 3  having a first terminal connected to a positive terminal of the charge port  12 . The contactors  632  further include switches S 1  and S 4  having first terminals connected to a negative terminal of the charge port  12 . 
     The ESS  634  includes a battery pack  614  and switches SPC, S 5  and S 6 . First terminals of the switches SPC and S 5  are connected to a second terminal of the switch S 1 . A second terminal of the switch SPC is connected by a resistor R 1  to a second terminal of the switch S 5  and a first terminal of a fusible link F 1 . A second terminal of the fusible link F 1  is connected to a positive terminal of the battery pack  614  including one or more battery cells. A negative terminal of the battery pack  614  is connected to a first terminal of a switch S 6 . A second terminal of the switch S 6  is connected to a second terminal of the switch S 2 . 
     The buck-boost converter  636  includes a capacitor C 1  having a first terminal connected to the first terminal of the switch S 1  and a second terminal connected to the second terminal of the switch S 2 . A first terminal of a power switch T 1  is connected to the second terminal of the switch S 1  and a first terminal of a switch S 0 . A second terminal of the power switch T 1  is connected to a first terminal of inductor L 1  and a first terminal of a power switch T 3 . A second terminal of the power switch T 3  is connected to the second terminal of the switch S 2 . 
     A second terminal of the switch S 0  is connected to a first terminal of a power switch T 2 , a second terminal of the switch S 3 , a first terminal of a switch S 12  and a first terminal of the fusible link F 2 . A second terminal of the power switch T 2  is connected to a second terminal of the inductor L 1  and a first terminal of a power switch T 4 . A second terminal of the power switch T 4  is connected to the second terminal of the switch S 2 , a second terminal of the first vehicle loads  18 , and a first terminal of a switch S 11 . 
     A second terminal of the fusible link F 2  is connected to a first terminal of a switch S 10 . A second terminal of the switch S 10  is connected to the second vehicle loads  22 . A second terminal of the second vehicle loads  22  is connected to the second terminal of the switch S 11  and a second terminal of the switch S 4 . 
     Referring now to  FIG.  7   , the positions of the switches during various operating modes are shown. In a normal driving mode, the switches S 1 , S 3 , S 5 , and S 6  are on to provide power to TPIM  22  directly from battery, the switches S 2 , S 4 , S 10 , S 11  and SPC are off and the buck-boost converter  636  and switch  12  are on to support accessory load  18 . 
     In an accessory load support mode, the switches S 1  to S 4  and SPC are off and switches S 5 , S 6 , and S 10  to S 12  are on and the buck-boost converter  636  is on. 
     In a range improvement mode, the switches S 1  to S 4  and SPC are off, switches S 5 , S 6 , and S 10  to S 12  are on, and the buck-boost converter  636  is on. 
     In a pre-charging mode, the switches S 3  to S 5 , S 10  to S 12  are off, switches S 1 , S 2  S 6 , and SPC are on, and the buck-boost converter  636  is off. 
     When charging from a 400V grid, the switches S 3  to S 6 , S 10  and S 11  are on, the switches S 1 , S 2  and SPC are off and the buck-boost converter  636  and S 12  are on support vehicle load  18 . 
     When charging from an 800V grid, the switches S 1 , S 2 , S 5  and S 6  are on, the switches S 3 , S 4 , S 10 , S 11  and SPC are off and the buck-boost converter  636  and S 12  are on to support vehicle load  18 . 
     When charging the ESS of a second vehicle at 400V, the switches S 1 , S 2 , and SPC are off and the switches S 3  to S 6 , and S 9  to S 12  and the buck-boost converter  636  are on. 
     When charging the ESS of a second vehicle at 800V, the switches S 1 , S 2 , S 12 , and SPC are off and the switches S 3  to S 6 , S 10  and S 11  are on, and the buck-boost converter  636  is on. 
     When performing battery preconditioning, the switches S 1  to S 4 , S 10  to S 12  and SPC are off and the switches S 5  and S 6  and the buck-boost converter are on. 
     Referring now to  FIG.  8   , another power control circuit  800  is shown. In some examples, the power control circuit  800  is an 800V drive system with a flexible battery system including two battery packs. The power control circuit  800  supports various modes including range improvement, accessory load support during driving and charging, charging from different grid voltages (e.g. 400V or 800V), vehicle-to-vehicle charging and/or battery preconditioning. 
     The power control circuit  800  include the charge port  12  and supplies power to the second vehicle loads  22 , the first vehicle loads  18  and/or other loads. The power control circuit  800  further includes contactors  832 , an energy storage system (ESS)  834  (including a first battery pack  810  and a second battery pack  812 ), and a buck-boost converter  836 . 
     First terminals of switches S 1  and S 3  are connected to a positive terminal of the charge port  12 . First terminals of switches S 2  and S 4  are connected to a negative terminal of the charge port  12 . First terminals of switches S 5 , S 7  and SPC are connected to a second terminal of the switch S 1 . A second terminal of the switch S 7  is connected by a resistor R 1  to a second terminal of the switch SPC and to a first terminal of the first battery pack  810 . A second terminal of the switch S 5  is connected to a first terminal of the switch S 9  and a first terminal of a fusible link F 1 . A second terminal of the switch S 9  is connected to a second terminal of the first battery pack  810  and to a first terminal of a switch S 8 . A second terminal of the second battery pack  812  is connected to a first terminal of a switch S 6 . Second terminals of the switches S 6  and S 8  are connected to a second terminal of the switch S 2 . 
     The buck-boost converter  836  includes a capacitor C 1  having a first terminal connected to the second terminal of the switch S 1  and a second terminal connected to the second terminal of the switch S 2 . A first terminal of a power switch T 1  is connected to the second terminal of the switch S 1  and a first terminal of a switch S 0 . A second terminal of the power switch T 1  is connected to a first terminal of an inductor L 1  and a first terminal of a switch T 3 . A second terminal of the power switch T 3  is connected to the second terminal of the switch S 2 . 
     A second terminal of the power switch T 2  is connected to a second terminal of an inductor L 1  and to a first terminal of a power switch T 4 . A second terminal of the power switch T 4  is connected to the second terminal of the switch S 2 , a second terminal of the first vehicle loads  18 , and a first terminal of the switch S 11 . 
     A second terminal of the switch S 0  is connected to a first terminal of the power switch T 2 , a first terminal of a switch S 12  and a first terminal of the fusible link F 2 . A second terminal of the fusible link F 2  is connected to a first terminal of a switch S 10 . A second terminal of the switch S 10  is connected to the second vehicle loads  22  and to a second terminal of the switch S 3 . A second terminal of the second vehicle loads  22  is connected to a second terminal of the switch S 11  and a second terminal of the switch S 4 . 
     Referring now to  FIG.  9   , the power control circuit  400  operates in various operating modes. In a normal driving mode, the switches S 1 ,S 3 , S 6 , S 7 , S 9 , and are on to provide power to TPIM  22  directly from battery, switches S 2 , S 4 , S 5 , S 8 , S 10 , S 11  and SPC are off, and the buck-boost converter  836  and S 12  are on to support accessory load  18 . 
     In accessory load support mode, switches S 1  to S 5 , S 8  and SPC are off, switches S 6 , S 7 , S 9  to S 12  are on, and the buck-boost converter  836  is on. 
     In a range improvement mode, the switches S 1  to S 5 , S 8  and SPC are off, switches S 6 , S 7 , and S 9  to S 12  are on and the buck-boost converter  836  is on. 
     In a pre-charging mode, the switches S 1  to S 5 , S 7 , S 8 , S 10  to S 12  are off, switches S 6 , S 9  and SPC are on and the buck-boost converter  836  is off. 
     When charging from a 400 V grid, the switches S 3 , S 4 , S 6 , S 7 , and S 9  to S 12  are on, switches S 1 , S 2 , S 5 , S 8  and SPC are off and the buck-boost converter  836  is on. 
     When charging from an 800V grid, the switches S 1 , S 2 , S 6 , S 7 , S 9  and are on and switches S 3 , S 4 , S 5 , S 8 , S 10 , S 11  and SPC are off and the buck-boost converter  836  and S 12  are on to support accessory load  18 . 
     When charging a second vehicle having a 400 V ESS, the switches S 3 , S 4 , S 6 , S 7  and S 9  to S 12  are on, the switches S 1 , S 2 , S 5 , S 8  and SPC are off and the buck-boost converter  836  is on to reduce voltage to 400V to charge second vehicle and support accessory load  18 . 
     When charging a second vehicle having a 800 V ESS, the switches S 3 , S 4 , S 6 , S 7  and S 9  to S 11  are on, the switches S 1 , S 2 , S 5 , S 8 ,S 12  and SPC are off and the buck-boost converter  836  is on to charge second vehicle. 
     During battery preconditioning, the switches S 1  to S 5 , S 8 , S 10  to S 12  and SPC are off, the switches S 6 , S 7 , and S 9  are on and the buck-boost converter  836  is on. 
     Referring now to  FIG.  10   , a method  1000  for operating the battery system is shown. At  1012 , the method determines the operating mode of the battery system. At  1016 , the method determines whether the selected mode is the battery pre-conditioning mode. If  1016  is true, the method continues at  1020  and opens S 1  to S 4  and the buck-boost converter controls AC current to charge the battery pack(s). 
     If  1016  is false, the method continues at  1022  and determines whether the selected mode corresponds to charging from an 800 V grid. If  1022  is true, the method continues at  1026  and determines whether the vehicle has a 400 V charging system. If  1026  is false, the method continues at  1030  and closes switches S 1  and S 2  and opens switch S 3  and S 4 . The battery pack(s) are directly charged from the grid. If  1026  is true, the method continues at  1034  and closes the switches S 3  and S 4  and opens the switches S 1  and S 2 . The buck-boost converter reduces voltage for charging the battery. At the same time, for example, switches S 9  and S 10  in  FIG.  1    are open to isolate the 400V system from 800V grid. 
     If  1022  is false, the method continues at  1038  and determines whether the charging system is charging from a 400 V grid. If  1038  is true, the method continues at  1040  where the method determines whether the vehicle has an 800 V system. If  1040  is false, the method continues at  1044  and closes switches S 1  and S 2  and opens switches S 3  and S 4 . The battery pack(s) is (are) directly charge from the grid. 
     If  1040  is true, the method continues at  1046  and closes the switches S 3  and S 4  and opens the switches S 1  and S 2 . The buck-boost converter boosts voltage for charging the battery pack(s). 
     If  1038  is false, the method continues at  1050  and determines whether vehicle-to-vehicle charging is selected. If  1050  is true, the method continues at  1054  and configures the ESS to either 400 V or 800V depending upon the voltage used by the battery pack(s) of the second vehicle. At  1056 , the switches S 1  and S 2  are opened and the switches S 3  and S 4  are closed. The buck-boost converter controls current to charge the second vehicle battery pack. At the same time, if the vehicle is a 400V drive system and the charged vehicle is 800V, switches S 9  and  510  in  FIG.  1    are open to isolate the 400V system from another ESS with 800V. If  1050  is false, the method continues at  1060  and determines whether the range improvement mode is selected. It  1060  is true, the method continues at  1062  and opens switches S 1  to S 4  and S 9  and closes switches S 5  to S 8 . The buck-boost converter varies bus voltage to a predetermined optimal voltage. 
     If  1060  is false, the method continues at  1064  and determines whether normal operation mode is selected. If  1064  is true, the method continues at  1068 . At  1068 , switches S 5  to S 8  are closed, switch S 9  is opened and the buck-boost converter is bypassed using either switch S 0  or S 1  to S 4 . The battery directly provides power to the drive system. At  1070 , the motor controller controls torque commands Id and Iq based on voltage, torque and speed and then controls torque. If  1060  is false, the method continues at  1064  and determines whether the vehicle is operating in the normal operating mode. If  1064  is true, the method continues with  1068  and  1070  described above. 
     Referring now to  FIG.  11   , a power control circuit  1100  is shown. In some examples, the battery system is an 800V drive system, although other voltages can be used. The power control circuit  1100  includes a charge port  1112  and provides power to a first vehicle loads  1118  including a one or more sub-modules such as an accessory power module (APM) and/or air conditioning compressor module (ACCM) and second vehicle loads  1122  such as a traction power inverter module (TPIM), although other types of vehicle loads can be used. The power control circuit  1100  further includes contactors  1132 , an energy storage system (ESS)  1134 , and a bi-directional DC-DC converter  1136 . 
     The contactors  1132  include switches S 1  and S 3  having a first terminal connected to a positive terminal of the charge port  1112 . The contactors  1132  further include switches S 2  and S 4  having first terminals connected to a negative terminal of the charge port  1112 . 
     The ESS  1134  includes first and second battery packs  1114  and  1116  and switches SPC, S 5  and S 6 . The switch SPC is a pre-charge contactor. As can be appreciated, the switches can include mechanical relays and/or solid state switches. First terminals of the switches SPC and S 5  are connected to a second terminal of the switch S 1 . A second terminal of the switch SPC is connected by a resistor R 1  to a second terminal of the switch S 5  and a first terminal of a fusible link F 1  (such as a fuse or circuit breaker). 
     A second terminal of the fusible link F 1  is connected to a positive terminal of the first battery pack  1114  that includes one or more battery cells. A negative terminal of the first battery pack  1114  is connected to a positive terminal of the second battery pack  1116 . A negative terminal of the second battery pack is connected to a first terminal of a switch S 6 . A second terminal of the switch S 6  is connected to a fusible link F 2 . The fusible link F 2  is connected to a second terminal of the switch S 2 . 
     The bi-directional DC-DC converter  1136  includes a capacitor C 1  having a first terminal connected to the first terminal of the switch S 1  and a second terminal connected to the second terminal of the switch S 2 . A first terminal of a power switch T 1  is connected to the second terminal of the switch S 1 . A second terminal of the power switch T 1  is connected to a first terminal of an inductor L 1  and a first terminal of a power switch T 2 . A second terminal of the power switch T 2  is connected to the second terminal of the switch S 2 . 
     The bi-directional DC-DC converter  1136  further includes a capacitor C 2  having a first terminal connected to a second terminal of the inductor L 1 , a first terminal of the first vehicle loads  1118  and a first terminal of a switch S 7 . A second terminal of the switch S 7  is connected to a fusible link F 3 . The fusible link F 3  is connected to a first terminal of second vehicle loads  1122  and a second terminal of the switch S 3 . A second terminal of the switch S 8  is connected to a second terminal of the second vehicle loads  1122  and a second terminal of the switch S 4 . 
     In some examples, the power switches T 1  to T 2  may include voltage-controlled bipolar switching devices in the form of insulated gate bipolar transistors (IGBTs), metal-oxide semiconductor field effect transistors (MOSFETs), silicon carbide (SIC) MOSFET, wideband GaN devices (WBG), or other suitable switches having a control terminal to turn on and off. 
     Referring now to  FIG.  12   , the power control circuit  1100  operates in various operating modes. In a normal driving mode, the switches S 1 , S 3 , S 5 , S 6  are on to provide power to TPIM  1122  directly from battery and the bi-directional DC-DC converter  1136  are on to support 400V accessory load  1118  and switches S 7 , S 8 , and SPC are off. 
     In a range improvement mode, the switches S 5  to S 8  and the bi-directional DC-DC converter  1136  are on to reduce voltage to low voltage, for example, 400V, and switches S 1  to S 4  and SPC are off. 
     In accessory load support mode, switches S 1  to S 4 , S 7 , S 8  and SPC are off and switches S 5  and S 6  and the bi-directional DC-DC converter  1136  are on. 
     In a pre-charging mode, the switches S 1 , S 2 , S 6  and SPC are on and switches S 3  to S 5 , S 7  and S 8  and the bi-directional DC-DC converter  1136  are off. 
     When charging from a 400 V grid, the switches S 3  to S 8  and the bi-directional DC-DC converter  1136  are on and switches S 1 , S 2 , and SPC are off. 
     When charging from an 800V grid, the switches S 1 , S 2 , S 5 , S 6  and the bi-directional DC-DC converter  1136  are on to support 400V accessory load and switches S 3 , S 4 , S 7 , S 8  and SPC are off. 
     When charging a second vehicle having a 400 V ESS, the switches S 3  to S 8  and the bi-directional DC-DC converter  1136  are on, the switches S 1 , S 2 , and SPC are off. 
     During battery preconditioning, the switches S 1  to S 4 , S 7 , S 8 , and SPC are off, the switches S 5 , S 6  and the bi-directional DC-DC converter  1136  are on. 
     As can be appreciated from the foregoing, the bidirectional DC-DC converter can be configured in different selectable modes such as range improvement, battery pre-conditioning, accessory load support, backward DC Fast Charge (DCFC) compatibility, V2X charging for a battery electric vehicle. The bidirectional converter functions as buck converter from battery point of view and provides function such as range improvement, battery pre-conditioning, accessory load support, and V2V charging. 
     The bidirectional DC-DC converter functions as boost converter if external source is provided. The bidirectional DC-DC converter functions such as backward DC Fast Charge (DCFC) compatibility, and V2V charging using 400V drive system. 
     For example for an 800V drive system, the architecture in  FIG.  12    can simultaneously achieve range improvement, vehicle to vehicle charging, battery preconditioning, backward compatibility (400V charging for 800V battery). 
     Referring now to  FIG.  13   , a power control system  1200  is shown. In some examples, the power control system  1200  is an 800V drive system, although other voltages can be used. The power control system  1200  includes a charge port  1212  and provides power to a first vehicle loads  1218  including a one or more sub-modules accessory power module (APM) and/or air conditioning compressor module (ACCM) and second vehicle loads  1222  such as a traction power inverter module (TPIM), although other types of vehicle loads can be used. The power control system  1200  further includes contactors  1232 , an energy storage system (ESS)  1234 , and a bidirectional DC-DC converter  1236 . 
     The contactors  1232  include switches S 1  and S 3  having a first terminal connected to a positive terminal of the charge port  1212 . The contactors  1232  further include switches S 2  and S 4  having first terminals connected to a negative terminal of the charge port  1212 . 
     The ESS  1234  includes first and second battery packs  1214  and  1216  and switches SPC, S 5 , S 6 , S 7 , S 8  and S 9 . The switch SPC is a pre-charge contactor. As can be appreciated, the switches can include mechanical relays and/or solid state switches. First terminals of the switches SPC, S 5  and S 7  are connected to a second terminal of the switch S 1 . A second terminal of the switch SPC is connected by a resistor R 1  to a second terminal of the switch S 7  and a first terminal of the first battery pack  1214 . A second terminal of the first battery pack is connected to a first terminal of a switch S 9  and a first terminal of a switch S 8 . A second terminal of the switch S 5  is connected to a fusible link F 1  and a second terminal of a switch S 9 . The fusible link F 1  is connected to a positive terminal of the second battery pack  1216 . A negative terminal of the second battery pack  1216  is connected to a first terminal of a switch S 6 . Second terminals of the switches S 6  and S 8  are connected to the second terminal of the second switch S 2 . 
     The bidirectional DC-DC converter  1236  includes a capacitor C 1  having a first terminal connected to the first terminal of the switch S 1  and a second terminal connected to the second terminal of the switch S 2 . A first terminal of a power switch T 1  is connected to the second terminal of the switch S 1 . A second terminal of the power switch T 1  is connected to a first terminal of an inductor L 1  and a first terminal of a power switch T 2 . A second terminal of the power switch T 2  is connected to the second terminal of the switch S 2 . 
     The bidirectional DC-DC converter  1236  further includes a capacitor C 2  having a first terminal connected to a second terminal of the inductor L 1 , a first terminal of the first vehicle loads  1218  and a first terminal of a switch S 10 . A second terminal of the switch S 10  is connected to a fusible link F 3 . The fusible link F 3  is connected to a first terminal of second vehicle loads  1222  and a second terminal of the switch S 3 . A first terminal of the switch S 11  is connected to the second terminal of the capacitor C 2 , the second terminal of the power switch T 2 , and second terminals of the switches S 2 , S 6 , and S 8 . A second terminal of the switch S 11  is connected to a second terminal of the second vehicle loads  1222  and a second terminal of the switch S 4 . 
     In some examples, the power switches T 1  to T 2  may include voltage-controlled bipolar switching devices in the form of insulated gate bipolar transistors (IGBTs), metal-oxide semiconductor field effect transistors (MOSFETs), silicon carbide MOSFETS, wideband GaN devices (WBG), or other suitable switches having a control terminal to turn on and off. 
     Referring now to  FIG.  14   , the power control system  1200  operates in various operating modes. In a normal driving mode, the switches S 1 , S 3 , S 6 , S 7  and S 9  are on to provide power directly from battery. The bidirectional DC-DC converter  1236  is on to support accessory load and switches S 2 , S 4 , S 5 , S 8 , S 10 , S 11  and SPC are off. 
     In a range improvement mode, the switches S 6 , S 7 , S 9 , S 10 , S 11  and the bi-directional DC-DC converter  1236  are on and switches S 1  to S 5 , S 8  and SPC are off. 
     In accessory load support mode, switches S 1  to S 5 , S 8  and SPC are off and switches S 6 , S 7 , S 9  to S 11  and the bi-directional DC-DC converter  1236  are on. 
     In a pre-charging mode, the switches S 1 , S 2 , S 6 , S 9  and SPC are on and switches S 3  to S 5 , S 7 , S 8 , S 10 , S 11  and the bi-directional DC-DC converter  1236  are off. 
     When charging from a 400 V grid, the switches S 3 , S 4 , S 6 , S 7 , S 9 , S 10 , S 11  and the bi-directional DC-DC converter  1236  are on and switches S 1 , S 2 , S 5 , S 8  and SPC are off. 
     When charging from an 800V grid, the switches S 1 , S 2 , S 6 , S 7 , and S 9  are on to charge the battery. The bi-directional DC-DC converter  1136  is on to support 400V accessory load  1218  and switches S 3 , S 4 , S 5 , S 8 , S 10 , S 11  and SPC are off. 
     When charging a second vehicle having a 400 V ESS, the switches S 3 , S 4 , S 6 , S 7 , S 9 -S 11  and the bi-directional DC-DC converter  1236  are on, the switches S 1 , S 2 , S 5 , S 8  and SPC are off. 
     During battery preconditioning, the switches S 1  to S 5 , S 8 , S 10 , S 11  and SPC are off, the switches S 6 , S 7 , S 9  and the bi-directional DC-DC converter  1236  are on. 
     For example for an 800V drive system with a flexible battery configuration, the architecture in  FIG.  13    can simultaneously achieve range improvement, vehicle to vehicle charging, battery preconditioning, and 400V accessory load support during 800V charging. 
     The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure. 
     Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.” 
     In the figures, the direction of an arrow, as indicated by the arrowhead, generally demonstrates the flow of information (such as data or instructions) that is of interest to the illustration. For example, when element A and element B exchange a variety of information but information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B may send requests for, or receipt acknowledgements of, the information to element A. 
     In this application, including the definitions below, the term “module” or the term “controller” may be replaced with the term “circuit.” The term “module” may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. 
     The module may include one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces that are connected to a local area network (LAN), the Internet, a wide area network (WAN), or combinations thereof. The functionality of any given module of the present disclosure may be distributed among multiple modules that are connected via interface circuits. For example, multiple modules may allow load balancing. In a further example, a server (also known as remote, or cloud) module may accomplish some functionality on behalf of a client module. 
     The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, data structures, and/or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple modules. The term group processor circuit encompasses a processor circuit that, in combination with additional processor circuits, executes some or all code from one or more modules. References to multiple processor circuits encompass multiple processor circuits on discrete dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple modules. The term group memory circuit encompasses a memory circuit that, in combination with additional memories, stores some or all code from one or more modules. 
     The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory, tangible computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc). 
     The apparatuses and methods described in this application may be partially or fully implemented by a special purpose computer created by configuring a general purpose computer to execute one or more particular functions embodied in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer. 
     The computer programs include processor-executable instructions that are stored on at least one non-transitory, tangible computer-readable medium. The computer programs may also include or rely on stored data. The computer programs may encompass a basic input/output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, etc. 
     The computer programs may include: (i) descriptive text to be parsed, such as HTML (hypertext markup language), XML (extensible markup language), or JSON (JavaScript Object Notation) (ii) assembly code, (iii) object code generated from source code by a compiler, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. As examples only, source code may be written using syntax from languages including C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language 5th revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB, SIMULINK, and Python®.