Patent Publication Number: US-2023155400-A1

Title: High-voltage component protection during vehicle recharging

Description:
TECHNICAL FIELD 
     The present disclosure relates to a system and a method for high-voltage component protection during vehicle recharging. 
     INTRODUCTION 
     Many electrical systems in electric vehicles operate at the same high voltages specified for the battery packs of the electric vehicle. A recharging voltage greater than the battery pack high voltages are sometimes used to shorten recharge times. The recharging voltage may be imposed on the electrical systems due to fault conditions. The fault conditions may include loss of isolation and resistive shorts. For example, faults in one electrical system may couple the recharge voltage to the other electrical systems through common chassis connections that are otherwise high-impedance isolated from each other. The faults may generate unwanted chassis currents and/or excessive voltage that may cause nonreversible hardware degradations if exposed to the excessive voltages for a prolonged accumulated time. Accordingly, those skilled in the art continue with research and development efforts in the field of high-voltage component protection during electric vehicle recharging. 
     SUMMARY 
     A protection system for a high-voltage component is provided herein. The protection system includes a switching circuit and a protection controller. The switching circuit is couplable to a plurality of battery packs and the high-voltage component. The switching circuit is configured to change a variable arrangement of the plurality of battery packs between a parallel arrangement and a series arrangement, and transfer power from the plurality of battery packs to the high-voltage component. Each of the plurality of battery packs operates at a battery voltage. The high-voltage component operates at the battery voltage. The high-voltage component includes an input node and a floating chassis ground. The protection controller is coupled to the switching circuit and the high-voltage component. The protection controller is configured to command the switching circuit into the series arrangement in response to a first recharging session, command a first flow of a first current in the first recharging session, measure a measured voltage between the input node and the floating chassis ground of the high-voltage component during the first recharging session, advance a timer while the measured voltage indicates a presence of an improper voltage between the input node and the floating chassis ground, and cancel the first recharging session in response to the presence of the improper voltage for greater than an exposure time. The first recharging session provides a first direct-current fast-charging voltage to the plurality of battery packs in the series arrangement. The first direct-current fast-charging voltage is greater than the battery voltage. 
     In one or more embodiments of the protection system, the protection controller is further configured to command the switching circuit into the parallel arrangement after the first recharging session has been cancelled, and maintain the parallel arrangement of the plurality of battery packs while the protection system has been moved less than a threshold distance since the first recharging session was cancelled due to the improper voltage. 
     In one or more embodiments of the protection system, the protection controller is further configured to enable the series arrangement of the plurality of battery packs in response to the protection system being moved greater than the threshold distance since the first recharging session was cancelled due to the improper voltage. 
     In one or more embodiments of the protection system, the protection controller is further configured to command a flow of current in a second recharging session while the plurality of battery packs are in the parallel arrangement. The second recharging session provides a second direct-current fast-charging voltage to the plurality of battery packs in the parallel arrangement. The second direct-current fast-charging voltage approximately matches the battery voltage. 
     In one or more embodiments of the protection system, the protection controller is further configured to prohibit the series arrangement of the plurality of battery packs in response to the timer exceeding a cumulative time. 
     In one or more embodiments, the protection system includes a maintenance port coupled to the protection controller and configured to receive a notice that service has been performed on the high-voltage component. The protection controller is further configured to enable the series arrangement of the plurality of battery packs in response to the notice. 
     In one or more embodiments of the protection system, the cumulative time is approximately 600 seconds, and the exposure time is approximately 5 seconds. 
     In one or more embodiments of the protection system, the input node of the high-voltage component includes a positive input node and a negative input node. The measured voltage includes a positive measured voltage between the positive input node and the floating chassis ground, and a negative measured voltage between the negative input node and the floating chassis ground. The presence of the improper voltage is determined by the protection controller based on one or more of the positive measured voltage and the negative measured voltage. 
     In one or more embodiments of the protection system, the battery voltage is approximately 400 volts, and the first direct-current fast-charging voltage is approximately 800 volts. 
     A method for fault detection while recharging a vehicle is provided herein. The method includes changing a variable arrangement of a plurality of battery packs of the vehicle from a parallel arrangement to a series arrangement in response to a first recharging session. Each one of the plurality of battery packs operates at a battery voltage. The method includes transferring power from the plurality of battery packs to a high-voltage component of the vehicle. The high-voltage component operates at the battery voltage, and includes an input node and a floating chassis ground. The method further includes commanding a first flow of a first current in the first recharging session with a protection controller of the vehicle. The first recharging session provides a first direct-current fast-charging voltage to the plurality of battery packs in the series arrangement. The first direct-current fast-charging voltage is greater than the battery voltage. The method includes measuring a measured voltage between the input node and the floating chassis ground of the high-voltage component during the first recharging session, advancing a timer while the measured voltage indicates a presence of an improper voltage between the input node and the floating chassis ground of the high-voltage component, and cancelling the first recharging session in response to the presence of the improper voltage at the high-voltage component for greater than an exposure time. 
     In one or more embodiments, the method includes rearranging the plurality of battery packs to the parallel arrangement after the first recharging session has been cancelled, and maintaining the parallel arrangement of the plurality of battery packs while the vehicle has been driven less than a threshold distance since the first recharging session was cancelled due to the improper voltage. 
     In one or more embodiments, the method includes enabling the series arrangement of the plurality of battery packs in response to the vehicle being driven greater than the threshold distance since the first recharging session was cancelled due to the improper voltage. 
     In one or more embodiments, the method includes commanding a second flow of a second current in a second recharging session while the plurality of battery packs are in the parallel arrangement. The second recharging session provides a second direct-current fast-charging voltage to the plurality of battery packs in the parallel arrangement. The second direct-current fast-charging voltage approximately matches the battery voltage. 
     In one or more embodiments, the method includes prohibiting the series arrangement of the plurality of battery packs in response to the timer exceeding a cumulative time. 
     In one or more embodiments, the method includes enabling the series arrangement of the plurality of battery packs in response to a notice that service has been performed on the vehicle. 
     In one or more embodiments of the method, the cumulative time is approximately 600 seconds, and the exposure time is approximately 5 seconds. 
     A vehicle is provided herein. The vehicle includes a plurality of battery packs, a high-voltage component, a switching circuit, and a protection controller. Each of the plurality of battery packs operates at a battery voltage. The high-voltage component has an input node and a floating chassis ground. The high-voltage component operates at the battery voltage. The switching circuit is coupled to the plurality of battery packs and the high-voltage component, and is couplable to a charging station. The switching circuit is configured to change a variable arrangement of the plurality of battery packs between a parallel arrangement and a series arrangement, and transfer power from the plurality of battery packs to the high-voltage component. The protection controller is coupled to the switching circuit and the high-voltage component, and is couplable to the charging station. The protection controller is configured to command the switching circuit into the series arrangement in response to a recharging session, command a flow of a current from the charging station in the recharging session, measure a measured voltage between the input node and the floating chassis ground of the high-voltage component during the recharging session, advance a timer while the measured voltage indicates a presence of an improper voltage between the input node and the floating chassis ground of the high-voltage component, and cancel the recharging session in response to the presence of the improper voltage from greater than an exposure time. 
     In one or more embodiments of the vehicle, the input node of the high-voltage component includes a positive input node and a negative input node. The measured voltage includes a positive measured voltage between the positive input node and the floating chassis ground, and a negative measured voltage between the negative input node and the floating chassis ground. The presence of the improper voltage is based on one or more of the positive measured voltage and the negative measured voltage. 
     In one or more embodiments, the vehicle includes a sensor configured to measure a speed of the vehicle. The protection controller is further configured to disable the series arrangement of the plurality of battery packs in response to the speed being less than a threshold speed since the recharging session was cancelled due to the improper voltage, and enable the series arrangement of the plurality of battery packs in response to the speed being greater than the threshold speed since the recharging session was cancelled due to the improper voltage. 
     In one or more embodiments of the vehicle, the protection controller is further configured to prohibit the series arrangement of the plurality of battery packs in response to the timer exceeding a cumulative time, and enable the series arrangement of the plurality of battery packs in response to a notice that service has been performed on the vehicle. The above features and advantages and other features and advantages of the present disclosure are readily apparent from the following detailed description of the best modes for carrying out the disclosure when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic plan diagram of a system in accordance with one or more exemplary embodiments. 
         FIG.  2    is a schematic diagram of a protection system in a first extra-high-voltage configuration in accordance with one or more exemplary embodiments. 
         FIG.  3    is a schematic diagram of the protection system in a second extra-high-voltage configuration in accordance with one or more exemplary embodiments. 
         FIG.  4    is a schematic diagram of the protection system in a high-voltage configuration in accordance with one or more exemplary embodiments. 
         FIG.  5    is a schematic diagram of a protection controller in accordance with one or more exemplary embodiments. 
         FIG.  6    is a schematic diagram of a switching circuit in accordance with one or more exemplary embodiments. 
         FIG.  7    is a schematic diagram of an interface between the charging station, the switching circuit, and a vehicle controller in accordance with one or more exemplary embodiments. 
         FIG.  8    is a flow diagram of a method for recharging preparation in accordance with one or more exemplary embodiments. 
         FIG.  9    is a flow diagram of a method for a first recharging session in accordance with one or more exemplary embodiments. 
         FIG.  10    is a flow diagram of a method for a second recharging session in accordance with one or more exemplary embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments of the disclosure generally provide for a system and/or a method to protect high-voltage components in vehicles from isolation faults where a high-voltage (HV) architecture includes a recharge capability at extra-high voltages (EHV) by connecting multiple battery packs in series. While an extra-high voltage (e.g., 800 Vdc) is imposed on the high-voltage components (e.g., 400 Vdc) between high-voltage rails and chassis during the recharge, the system/method senses excessive voltages, measures a cumulative exposure time that the excessive voltages are present, and take corrective action if the excessive voltages do not subside. If the cumulative exposure time is greater than a short limit, the system/method may end the recharging session and disable the extra-high-voltage recharging. The extra-high-voltage recharging may be re-enabled if the vehicle has been moved at least a certain distance away from and/or traveled above a certain speed after leaving the charging station. The re-enabling feature generally extends the extra-high-voltage recharging capability of the vehicle by allowing for transient fault isolation issues. If the cumulative time of exposure for the high-voltage components becomes too long, the system/method may prohibit future extra-high-voltage recharging sessions until maintenance has been performed. 
     Embodiments of the system/method may provide for recharging at multiple different voltage levels. In various embodiments, the vehicle battery packs may be recharged at the regular high-voltage levels of the battery packs. Therefore, the vehicle may recharge at extra-high-voltage charging stations while few or no fault isolation issues are present. Once a detected fault becomes a threat to the high-voltage component, or where the extra-high-voltage charging stations are not available, the vehicle may recharge at regular high-voltage charging stations. 
     Referring to  FIG.  1   , a schematic plan diagram of an example implementation of a system  80  is shown in accordance with one or more exemplary embodiments. The system  80  generally comprises a charging station  90  and a vehicle  100  having a protection system  110 . The protection system  110  includes a switching circuit  112  and a protection controller  114 . The vehicle  100  further includes a maintenance port  116 , a sensor  118 , multiple battery packs  130   a - 130   n , a high-voltage component  140 , and driver controls  150 . 
     The charging station  90  and the protection controller  114  communicate bidirectionally through a control pilot signal (CPS). The control pilot signal is used to sense, initiate, control, and end a recharging session between the charging station  90  and the vehicle  100 . During the recharging session, the charging station  90  may provide a recharging voltage (Vc) and a recharging current (Ic) to the vehicle  100 . The recharging voltage Vc may range from approximately 270 Vdc to approximately 1600 Vdc. The recharging current Ic may range from approximately 6 amperes to approximately 100 amperes. 
     The protection controller  114  may generate a switch control signal (SC) that is transferred to the switching circuit  112 . The switch control signal SC may convey various commands to control an arrangement of the battery packs  130   a - 130   n . The switch control signal SC may also convey information used by the switching circuit  112  to signal an end to a recharging session with the charging station  90 . The maintenance port  116  may couple to external test equipment and present a notice signal (N) from that external test equipment to the protection controller  114 . The notification signal N generally informs the protection controller  114  that a previously-disabled extra-high-voltage recharging session may be enabled. 
     A distance/speed signal (DS) is generated by the sensor  118  and transferred to the protection controller  114 . The distance/speed signal DS may carry data regarding how far and/or how fast the vehicle  100  has moved. A recharge selection signal (RCS) may be generated by the driver controls  150  and received by the protection controller  114 . The recharge selection signal RCS carries commands from the driver indicating what voltage level recharge (e.g., a high-voltage recharge, an extra-high-voltage recharge, or another voltage level recharge) is about to take place. The switching circuit  112  may provide electrical power (PWR) to the high-voltage component  140 . The electrical power PWR may be presented at a regular battery voltage of the battery packs  130   a - 130   n.    
     The charging station  90  implements a direct-current fast charging (DCFS) station. In some embodiments, the charging station  90  may be operational to provide the recharging voltage Vc at a high-voltage level (e.g., approximately 400 Vdc). In other embodiments, the charging station  90  may be operational to provide the recharging voltage Vc at an extra-high-voltage level (e.g., approximately 800 Vdc). Other recharging voltage Vc may be implemented to meet a design criteria of a particular application. 
     The charging station  90  may also be operational to communicate with the protection controller  114  via the control pilot signal CPS. In various embodiments, the charging stations  90  may be compliant with the SAE International J1772 standard and/or the International Electrotechnical Commission (IEC) 61851-1 standard. The charging stations  90  may be DC Level 1 and/or DC Level 2 chargers. Other charging standards may be implemented to meet the design criteria of a particular application. Some charging stations  90  may be placed at fixed locations. Other charging stations  90  may be mobile, for example, mounted on a flatbed truck. 
     The vehicle  100  implements an electric-powered vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. In various embodiments, the electric vehicle  100  may be compliant with the SAE International J1772 standard and/or the International Electrotechnical Commission (IEC) 61851-1 standard. The electric vehicle  100  may implement the DC Level 1 and/or DC Level 2 charging capabilities. Other standards may be implemented to meet the design criteria of a particular application. In various embodiments, the electric vehicle  100  may include, but are not limited to, passenger vehicles, trucks, autonomous vehicles, motorcycles, boats, and/or aircraft. In some embodiments, the electric vehicle  100  may be a stationary object such as a room, a booth and/or a stationary structure. Other types of electric vehicles  100  may be implemented to meet the design criteria of a particular application. 
     The protection system  110  implements a fault isolation protection system. The protection system  110  is operational to change a variable arrangement of the battery packs  130   a - 130   n  between a parallel arrangement and a series arrangement in response to one or more fault detections. The selection of arrangements is based on the voltage levels being used in a current recharging session. The protection system  110  transfers recharging power from the charging station  90  to the battery packs  130   a - 130   n  while the battery packs  130   a - 130   n  are in the parallel arrangement or the series arrangement. The protection system  110  also transfers the electrical power PWR from the battery packs  130   a - 130   n  to the high-voltage component  140  while the battery packs  130   a - 130   n  are in the parallel arrangement or the series arrangement. One or more voltage between a corresponding one or more input nodes of the high-voltage component  140  and a floating chassis ground of the high-voltage component  140  are measured during the recharging session. A timer is advanced while the measured voltage(s) indicate a presence of an improper voltage between the input node(s) and the floating chassis ground. In response to the presence of the improper voltage at the high-voltage component for greater than an exposure time, the recharging session is ended and the battery packs  130   a - 130   n  are configured to the parallel arrangement. 
     The switching circuit  112  implements high-powered switches and a controller capable of communicating with the charging station  90 . The switching circuit  112  is operational to arrange selectively the battery packs  130   a - 130   n  in a parallel arrangement or a series arrangement. While in the parallel arrangement, each battery pack  130   a - 130   n  contributes to the electrical power PWR suppled to the high-voltage component  140 , and each battery pack  130   a - 130   n  is recharged by a portion of the recharging current Ic. While in the series arrangement, at least one of the battery packs  130   a - 130   n  provides the electrical power PWR suppled to the high-voltage component  140 , the battery packs  130   a - 130   n  are recharged by the full recharging current Ic. The switching circuit  112  is also operational to communicate with the charging station  90  via the control pilot signal CPS. The control pilot signal CPS may be used to inform the charging station  90  that the vehicle  100  is in a standby state waiting for the recharging session, that the vehicle  100  is present and connected, that the recharging session should begin, that the recharging session should begin with ventilation, that the recharging session should end, and that an error has been detected. 
     The protection controller  114  implements a computer configured to protect the high-voltage component  140  from excessive voltages during the recharging sessions. For an extra-high-voltage recharging session, the protection controller  114  is operational to command the switching circuit  112  to configure the battery packs  130   a - 130   n  into the series arrangement, command the charging station  90  to provide electrical power to recharge the battery packs  130   a - 130   n , sense a measured voltage between one or more of the input nodes and the floating chassis ground of the high-voltage component  140  during the recharging session. The protection controller  114  may advance a timer while the measured voltage indicates a presence of an improper voltage between the input node(s) and the floating chassis ground, cancel the recharging session with the charging station  90  in response to either the presence of the improper voltage for greater than an exposure time or the battery packs  130   a - 130   n  have been recharged, and command the switching circuit  112  to configure the battery packs  130   a - 130   n  into the parallel arrangement after the recharging session has been ended. 
     For a high-voltage recharging session, the protection controller  114  is operational to command the switching circuit  112  to configure the battery packs  130   a - 130   n  in the parallel arrangement, command the charging station  90  to generate a flow of the recharging current Ic in another recharging session, and end the recharging session in response to the battery packs  130   a - 130   n  being recharged. 
     The maintenance port  116  implements a connector accessible by service personnel. The maintenance port  116  is operational to convey the notification signal N from test equipment (not shown) to the protection controller  114 . 
     The sensor  118  implements a distance sensor and/or a speed sensor. For distance, the sensor  118  is operational to measure a running distance traveled by the vehicle  100 . For speed, the sensor  118  is operational to measure a current speed of the vehicle  100 . The distance and/or speed may be reported to the protection controller  114  via the distance/speed signal DS. 
     Each battery pack  130   a - 130   n  implements a rechargeable energy storage system. While recharging, the battery packs  130   a - 130   n  may receive electrical power from the charging station  90 . While recharging and discharging, the battery packs  130   a - 130   n  may present electrical power to the high-voltage component  140 . Each battery pack  130   a - 130   n  operates at a battery voltage Vb (see  FIG.  2   ) In various embodiments, the battery packs  130   a - 130   n  may be implemented in two sets such that the extra-high-voltage may be 2 Vb while the two sets are arranged in series. Each set may contain one or more battery packs  130   a - 130   n  connected in parallel within the set. In some embodiments, the battery packs  130   a - 130   n  may be implemented in three sets such that the extra-high-voltage may be 3 Vb while the three sets are in the series arrangement. Other number of sets may be implemented to meet the design criteria of a particular application. 
     The high-voltage component  140  implements one or more electrical circuits in the vehicle  100  that operate at the battery voltage. The high-voltage component  140  may include, but is not limited to, electrical motors, and pumps. Other high-voltage components  140  may be implemented to meet a design criteria of a particular application. 
     The driver controls  150  implement human-machine-interface actuators and indicators. The driver controls  150  are operational to receive inputs from the vehicle driver, and present information to the driver. One of the inputs includes a selection for the recharge voltage Vc that will be used to recharge the battery packs  130   a - 130   n . The selected recharge voltage (e.g., 400 Vdc or 800 Vdc) may be presented to the protection controller  114  in the recharging selection signal RCS. The driver control  150  may also be operational to present an error indicator to the driver in the event that the extra-high-voltage recharge is selected while the extra-high-voltage recharge is prohibited. 
     Generally, the protection system  110  prevents the high-voltage component  140  from exposure to excessive voltages greater than several hundred volts (e.g., approximately 450 V) from a positive high-voltage rail to vehicle ground, and from a negative high-voltage rail to vehicle ground for more than a few (e.g., 1-10) seconds during a single exposure, and for more than a cumulated time (e.g., 550-650 second) over a lifetime of the high-voltage component  140 . During extra-high-voltage direct-current fast-charging operations, if the protection system  110  detects an excessive positive high-voltage to vehicle ground and/or an excessive negative high-voltage to vehicle ground at the high-voltage component  140  that is greater than the exposure voltage for more than the exposure time limit, a timer is advanced and the series arrangement of the battery packs  130   a - 130   n  is disabled. Thereafter, the protection system  110  allow the battery packs  130   a - 130   n  to be arranged in parallel, but not arranged in series, until after the vehicle  100  speed is greater than a predetermined speed (e.g., approximately 5 kilometers per hour) and/or the vehicle  100  has driven a predetermined distance (e.g., approximately 50 meters). When the accumulated time above the exposure voltage is greater than the cumulative time, the series arrangement of the battery packs  130   a - 130   n  is prohibited and a fault latch is set in the protection controller  114 . The series arrangement of the battery packs  130   a - 130   n , and thus recharging at the extra-high-voltage is prohibited (or locked out) until service has replaced the damaged high-voltage component  140  and the fault latch has been cleared by applying the notification signal N. 
     An example occurrence rate of isolation faults by model year for an existing make of an electric vehicle is provided in Table I as follows: 
     
       
         
           
               
             
               
                 TABLE I 
               
             
            
               
                   
               
               
                 Total Population 78000 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Unique Vehicle ID 
                   
                 Average  
               
               
                   
                 Year 
                 Numbers (VINS) 
                 Occurrences 
                 per VIN 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 2017 
                 115 
                 1852 
                 16.10 
               
               
                   
                 2018 
                 118 
                 720 
                 6.10 
               
               
                   
                 2019 
                 208 
                 1579 
                 7.59 
               
               
                   
                 2202 
                 37 
                 778 
                 21.03 
               
               
                   
                 2021 
                 7 
                 377 
                 53.86 
               
               
                   
                   
               
            
           
         
       
     
     Referring to  FIG.  2   , a schematic diagram of an example implementation of the protection system  110  in a first extra-high-voltage configuration is shown in accordance with one or more exemplary embodiments. The charging station  90  generally includes a station controller  92  and a plug  94 . The protection controller  114  includes a vehicle controller  122 . A socket  120  is couplable to the plug  94  to provide bidirectional communication via the control pilot signal CPS, and recharging of the battery packs  130   a - 130   n  with a first recharging current Ic 1  during a first recharging session. The first recharging current Ic 1  may be a variation of the recharging current Ic ( FIG.  1   ). 
     The charging station  90  may present the recharging power as a positive first direct-current fast-charging voltage Vc 1   p  coupled to one end of the series arrangement, and a negative first direct-current fast-charging voltage Vc 1   n  coupled to the opposite end of the series arrangement. The resulting recharging voltage may be referred to as a first direct-current fast-charging voltage Vc 1 , or a first recharging voltage Vc 1  for short. The first recharging voltage Vc 1  may be a variation of the recharging voltage Vc ( FIG.  1   ). 
     The switching circuit  112  is configured to arrange the battery packs  130   a - 130   n  in a series arrangement. Each battery pack  130   a - 130   n  may have a positive terminal  132  and a negative terminal  134 . Each battery pack  130   a - 130   n  operates at a battery voltage Vb. An end battery pack (e.g.,  130   n ) in the series arrangement of the battery packs  130   a - 130   n  may provide the electrical power PWR to the high-voltage component  140 . As such, the high-voltage component  140  may receive electrical power while the battery packs  130   a - 130   n  are being recharged. 
     The high-voltage component  140  generally includes a positive input node  142 , negative input node  144 , and floating chassis ground  146 . The positive input node  142  and the negative input node  144  are coupled across the last battery pack  130   n . The floating chassis ground  146  is coupled to a frame of the vehicle  100  and is isolated from earth ground by the tires. A positive fault isolation path IFp may exist between the positive first direct-current fast-charging voltage Vc 1   p  and the chassis (e.g., the floating chassis ground  146 ) of the high-voltage component  140 . 
     The protection controller  114  may be coupled to the positive input node  142 , the negative input node  144  and the floating chassis ground  146  of the high-voltage component  140 . The protection controller  114  is operational to measure a positive measured voltage Vp between the positive input node  142  and the floating chassis ground  146 . The protection controller  114  is also operational to measure a negative measured voltage Vn between the negative input node  144  and the floating chassis ground  146 . One or both of the positive measured voltage Vp and the negative measured voltage Vn may determine if the positive fault isolation IFp exists, and if so, the extent of the fault. The vehicle controller  122  is in communication with the station controller  92  via the control pilot signal CPS. 
     Under normal conditions (e.g., no isolation fault present), the internal resistance of the high-voltage component  140  may present similar impedances between the floating chassis ground  146  and each of the positive input node  142  and the negative input node  144 . As such, the positive measured voltage Vp and the negative measured voltage Vn should be approximately half (e.g., +200 Vdc and −200 Vdc respectively) of the battery voltage Vb (e.g., 400 Vdc) relative to the floating chassis ground  146 . When the positive isolation fault exists, the positive first direct-current fast-charging voltage Vc 1   p  is pulled down toward the floating chassis ground  146  of the high-voltage component  140 . The extent of the pull is based on the impedance of the positive isolation fault IFp. The pull reduces the positive measured voltage Vp and increases that negative measured voltage Vn. For example, if the positive fault isolation IFp is a short-circuit, the positive measured voltage Vp would be −400 Vdc relative to the floating chassis ground  146  due to the battery pack  130   a , and the negative measured voltage Vn would be −800 Vdc relative to the floating chassis ground  146  due to the series arrangement of the battery packs  130   a - 130   n    
     Once the negative measured voltage Vn is lower than the excessive voltage (e.g., drops 250 volts from −200 Vdc to −450 Vdc) and/or the positive measured voltage Vp falls a similar voltage (e.g., drops 250 volts from +200 Vdc to −50 Vdc), the protection controller  114  may conclude that the positive isolation fault IFp is substantial and activates an internal timer. If the positive isolation fault IFp continues for at least the exposure time, the protection controller  114 , through the vehicle controller  122 , may signal the station controller  92  to end the first charging session. 
     Referring to  FIG.  3   , a schematic diagram of an example implementation of the protection system  110  in a second extra-high-voltage configuration is shown in accordance with one or more exemplary embodiments. The circuitry and voltages shown in  FIG.  3    are similar to the circuitry and voltages shown in  FIG.  2   , expect the high-voltage component  140  is coupled to the top battery pack  130   a , and a negative isolation fault IFn may exist between the negative first direct-current fast-charging voltage Vc 1   n  and the floating chassis ground  146 . 
     As before with no isolation faults present, the positive measured voltage Vp and the negative measured voltage Vn should be approximately half (e.g., +200 Vdc and −200 Vdc respectively) of the battery voltage Vb (e.g., 400 Vdc) relative to the floating chassis ground  146 . When the negative isolation fault exists, the negative first direct-current fast-charging voltage Vc 1   n  is pulled up toward the floating chassis ground  146  of the high-voltage component  140 . The extent of the pull is based on the impedance of the negative isolation fault IFn. The pull increases the positive measured voltage Vp and decreases that negative measured voltage Vn. For example, if the negative fault isolation IFn is a short-circuit, the positive measured voltage Vp would be +800 Vdc relative to the floating chassis ground  146  due to the battery packs  130   a - 130   n , and the negative measured voltage Vn would be +400 Vdc relative to the floating chassis ground  146  due to the battery pack  130   n.    
     Once the positive measured voltage Vp is above than the excessive voltage (e.g., increases 250 volts from +200 Vdc to +450 Vdc) and/or the negative measured voltage Vn rises a similar voltage (e.g., increases 250 volts from −200 Vdc to +50 Vdc), the protection controller  114  may conclude that the negative isolation fault IFp is substantial and activates an internal timer. If the negative isolation fault IFn continues for at least the exposure time, the protection controller  114 , through the vehicle controller  122 , may signal the station controller  92  to end the first charging session. 
     Referring to  FIG.  4   , a schematic diagram of an example implementation of the protection system  110  in a high-voltage configuration is shown in accordance with one or more exemplary embodiments. The circuitry and voltages shown in  FIG.  4    are similar to the circuitry and voltages shown in  FIG.  2   , expect the battery packs  130   a - 130   n  are configured in the parallel arrangement, and the charging station  90  present a second current Ic 2  at a second direct-current fast-charging voltage Vc 2  (e.g., 400 Vdc). The second direct-current fast-recharge voltage Vc 2  may be referred to as a second recharging voltage Vc 2  for short. The second recharging voltage Vc 2  may be a variation of the recharging voltage Vc ( FIG.  1   ). The second recharging voltage Vc 2  approximately matches the battery voltage Vb. 
     If either of the positive second direct-current fast-charging voltage Vc 2   p  or the negative second direct-current fast-charging voltage Vc 2   n  is short-circuited to the floating chassis ground  146  of the high-voltage component  140 , one of the positive measured voltage Vp or the negative measured voltage Vn would be driven to zero volts, and the other measured voltage would be +400 Vdc or −400 Vdc relative to the floating chassis ground  146 . In either case, an amplitude of neither the positive measured voltage Vp nor the negative measured voltage Vn would exceed the excessive voltage (e.g., 450 Vdc) and so no threat is posed to the high-voltage component  140 . As such, the protection controller  114  would not stop the charging session and the battery packs  130   a - 130   n  would continue to recharge as planned. 
     Referring to  FIG.  5   , a schematic diagram of an example implementation of the protection controller  114  is shown in accordance with one or more exemplary embodiments. The protection controller  114  generally includes a reference voltage circuit  160 , a positive sensor circuit  162   a , a negative sensor circuit  162   b , a summation circuit  164 , a hardware overvoltage protection circuit  166 , one or more processors  170  (one shown), a memory circuit  172 , a timer  174 , a positive rail isolation resistor Ria, a negative rail isolation resistor Rib, a positive rail sensing resistor Rsa, and a negative rail sensing resistor Rsb. 
     The reference voltage circuit  160  implements a reference voltage generator. The reference voltage circuit  160  is operational to generate a low reference voltage (e.g., +2.5 Vdc) relative to the floating chassis ground  146 . 
     The positive sensor circuit  162   a  implements a voltage sensor. The positive sensor circuit  162   a  is operational to measure a voltage across the positive rail sensing resistor Rsa. The measured voltage is presented to the processor  170  and the summation circuit  164  as a positive voltage value (VP). The positive voltage value VP is a fraction of the positive measured voltage Vp. The fraction is determined by the positive rail isolation resistor Ria and the positive rail sensing resistor Rsa. 
     The negative sensor circuit  162   b  implements another voltage sensor. The negative sensor circuit  162   b  is operational to measure a voltage across the negative rail sensing resistor Rsb. The measured voltage is presented to the processor  170  and the summation circuit  164  as a negative voltage value (VN). The negative voltage value VN is a fraction of the negative measured voltage Vn. The fraction is determined by the negative rail isolation resistor Rib and the negative rail sensing resistor Rsb. 
     The summation circuit  164  implements an adder circuit. The summation circuit  164  is operational to add the positive voltage value VP and the negative voltage value VN to calculate a summed voltage value (VS). The summed voltage value VS is presented to the processor  170  and the hardware overvoltage protection circuit  166 . 
     The hardware overvoltage protection circuit  166  is operational to determine that an overvoltage (e.g., excessive voltage) condition exists. While the overvoltage condition exists, the hardware overvoltage protection circuit  166  is operational to present an overvoltage protection value (VOV) to the processor  170  and assert an overvoltage safety signal (VOS). While the overvoltage conditions is absent, the hardware overvoltage protection circuit  166  de-asserts the overvoltage safety signal VOS. The overvoltage safety signal VOS may be utilized by other circuitry (not shown) to remove the high-voltage power in order to avoid damage. 
     The processor  170  implements one or more central processing units (CPU). The processor  170  is operational to execute software. The software may be stored in non-transitory computer readable media (e.g., nonvolatile memory). The software, when executed by the processor  170 , may cause the processor  170  to monitor the positive measured voltage Vp and/or the negative measured voltage Vn, and take corrective action if either or both show excessive voltages that would indicate an isolation fault that cannot be ignored. Where an isolation fault (e.g., IFp or IFn) posses a risk to the high-voltage component  140 , the processor  170  may command the vehicle controller  122  to notify the station controller  92  in the charging station  90  to end the recharging session. 
     The memory  172  implements one or more memory circuits. The memory  172  is operational to store the software and data used and/or generated by the processor  170 . The memory  172  may include non-transitory computer readable medium and volatile memory. 
     The timer  174  implements a counter. While activated by the processor  170 , the timer  174  accumulates (e.g., counts) time and reports the time back to the processor  170 . The timer  174  may be deactivated (e.g., stops counting) under the control of the processor  170 . The timer  174  may also be reset to an initial (e.g., a zero) count by the processor  170 . 
     In various embodiments, the timer  174  may implement a single timer that reports a current accumulated time. The processor  170  may use the current accumulated time to determine when the exposure time limit has been reached and when the accumulated time limit has been reached. In other embodiments, the timer  174  may implement two timers. One timer may count to the exposure time while active and subsequently report when the exposure time limit has been reached. The other timer may count to the accumulated time while active and subsequently report when the accumulated time limit has been reached. Other forms of timers may be implemented to meet the design criteria of a particular application. 
     The timer  174  allows multiple occurrences of the fault exposure to be measured before the high-voltage component  140  is considered damaged by an isolation fault. For example, where the accumulated time limit is set to 600 seconds, and the exposure time limit is 5 seconds, the high-voltage component  140  may experience a fault exposure at least 120 times before the protection controller  114  locks out (or prohibits) the extra-high-voltage recharging. Allowing for multiple fault exposures may reduce a potential warranty cost. To further reduce the potential warranty cost, various embodiments may implement separate timers for each multiple high-voltage components  140 . Therefore, excessive isolation faults to one of the high-voltage components  140  does not trigger repair/replacement of each high-voltage component  140  at the same time. 
     Referring to  FIG.  6   , a schematic diagram of an example implementation of the switching circuit  112  is shown in accordance with one or more exemplary embodiments. The switching circuit  112  generally includes a pair of charging switches  180   a - 180   b , a pair of parallel switches  182   a - 182   b , and a series switch  184 . The open/closed states of the switches  180   a  to  184  are controlled by the switch control signal SC. 
     The charging switches  180   a - 180   b  may receive the positive direct-current fast-charging voltage Vcp and the negative direct-current fast-charging voltage Vcn from the socket  120 . While the charging switches  180   a - 180   b  are open, the switching circuit  112  electrically disconnects the battery packs  130   a - 130   n  and the high-voltage component  140  from the charging station  90 . While the charging switches  180   a - 180   b  are closed. electrical power from the charging station  90  is available to recharge the battery packs  130   a - 130   n.    
     The parallel switch  182   a  is disposed between the positive terminals  132  of the battery packs  130   a - 130   n  and the parallel switch  182   b  is disposed between the negative terminals  134  of the battery packs  130   a - 130   n . While the parallel switches  182   a - 182   b  are open, the battery packs  130   a - 130   n  are electrically isolated from each other and thus available to be connected in series. While the parallel switches  182   a - 182   b  are closed and the series switch  184  is open, the battery packs  130   a - 130   n  are electrically connected together in parallel. 
     The series switch  184  is disposed between the positive terminal  132  of the battery pack  130   n  and the negative terminal  134  of the battery pack  130   a . While the series switch  184  is open, the battery packs  130   a - 130   n  are available to be connected in parallel. While the series switch  184  is closed and the parallel switches  182   a - 182   b  are open, the battery packs  130   a - 130   n  are arranged in series. 
     Referring to  FIG.  7   , a schematic diagram of an example implementation of an interface between the charging station  90 , the switching circuit  112 , and the vehicle controller  122  is shown in accordance with one or more exemplary embodiments. While the plug  94  and the socket  120  are engaged, the charging station  90  may provide the charging current Ic through a pair of pins in the plug  94  and the socket  120 . A chassis ground is shared through a third pin in the plug  94  and the socket  120 . A fourth pin carries the control pilot signal CPS between the station controller  92  and the vehicle controller  122 . A proximity signal (PS) is generated by the vehicle controller  122  and presented through a fifth pin of the plug  94  and the socket  120  to a proximity switch  96  in the plug  94 . The proximity switch  96  is mechanically linked to a latch release actuator (not shown) on the plug  94 . During recharging, the latch release actuator is released and the proximity switch  96  is closed. Therefore, the vehicle controller  122  sees a first load to the chassis ground. When the latch release actuator is grabbed, the proximity switch  96  is open, the vehicle controller  122  sees a different load to the chassis ground, and signals the station controller  92  to stop the recharging session before the power pins are disconnected. 
     Referring to  FIG.  8   , a flow diagram of an example implementation of a method  200  for recharging preparation is shown in accordance with one or more exemplary embodiments. The method (or process)  200  is implemented by the system  80 . The method  200  includes steps  202  to  214 , as illustrated. The sequence of steps is shown as a representative example. Other step orders may be implemented to meet the criteria of a particular application. 
     In the step  202 , before the recharging session begins, the switching circuit  112  configures the battery packs  130   a - 130   n  in the parallel arrangement for normal operations. The protection controller  114  may receive the recharge selection signal RCS from the driver controls  150  in the step  204 . If extra-high-voltage (EHV) recharging (e.g., 800 Vdc) is selected, the protection controller  114  determines if the extra-high-voltage recharging is enabled in the step  206 . If the extra-high-voltage recharging is selected but not enabled (prohibited), an error signal is presented to the driver in the step  208 . Thereafter, the switching circuit  112  and the protection controller  114  maintain the battery packs  130   a - 130   n  in the parallel arrangement in the step  210  and the method  200  returns to the step  202 . 
     If the extra-high-voltage recharging is selected and enabled, the protection controller  114  commands the switching circuit  112  to configure the battery packs  130   a - 130   n  in the step  212  into the series arrangement. While transitioning to and while in the series arrangement, the switching circuit  112  transfers the power from at least one battery pack  130   a - 130   n  to the high-voltage component  140  in the step  214 . If a high-voltage (HV) recharging (e.g., 400 Vdc) is selected at the step  204 , the switching circuit  112  and the protection controller  114  maintain the battery packs  130   a - 130   n  in the parallel arrangement in the step  210 . The method  200  subsequently returns to the step  202  where electrical power is still presented by the battery packs  130   a - 130   n  to the high-voltage component  140 . 
     Referring to  FIG.  9   , a flow diagram of an example implementation of a method  220  for a first recharging session is shown in accordance with one or more exemplary embodiments. The method (or process)  220  may be implemented by the system  80 . The first recharging session of the method  220  is an extra-high-voltage recharging. The method  220  includes steps  222  to  266 , as illustrated. The sequence of steps is shown as a representative example. Other step orders may be implemented to meet the criteria of a particular application. 
     In the step  222 , the protection system  110  waits for the charging station  90  to signal a readiness for the first recharging session at the extra-high voltage. Once the charging station  90  is ready, the vehicle controller  122  commands the switching circuit  112  to close the charging switches  180   a - 180   b , and commands the charging station  90  to begin recharging in the step  224 . The vehicle  100  receives the first recharging current Ic 1  in the step  226 . 
     In the step  228 , the protection controller  114  measures one or both measured voltages Vp and/or Vn between the input node(s)  142 / 144  and the floating chassis ground  146  of the high-voltage component  140  during the first recharging session. A check is performed by the protection controller  114  at the step  230  to determine if an improper (excessive) voltage is detected. If no improper voltage is detected, the timer  174  is not advanced (e.g., the counting is stopped) and continuation of the recharging is checked in the step  232 . If the recharging should continue, the method  220  loops back to the step  228  to continue monitoring the measure voltages Vp and/or Vn. 
     If the first recharging session should be ended per the step  232 , the vehicle controller  122  may signal the station controller  92  to end the first charging session in the step  234 . The protection controller  114  commands the switching circuit in the step  236  to place the battery packs  130   a - 130   n  in the parallel arrangement and open the recharging switches  180   a - 180   b . Thereafter, the charging station  90  may be disconnected from the vehicle in the step  238  and the method  220  ends. 
     Upon detection of an improper voltage at the step  230 , the protection controller  114  may advance the timer  174  in the step  240  while the measured voltages Vp and/or Vn indicate the presence of the improper voltage between the input node(s)  142 / 144  and the floating chassis ground  146  of the high-voltage component  140 . If the improper voltage is sensed for less time than the exposure threshold per the step  242 , the method  220  returns to the step  228  and continues to monitor the input voltages Vp and/or Vn. A threshold for the exposure time may be determined by short-term overvoltage capabilities of high-voltage components  140  that are commonly used among electrification programs. 
     In response to the improper voltage being sensed for greater than exposure time in the step  242 , the protection controller  114  signals the vehicle controller  122  to instruct the station controller  92  to cancel the first recharging session in the step  244 . The protection controller  114  disables the series arrangement of the battery packs  130   a - 130   n  in the step  246  in response to the cancellation of the first recharging session due to the improper voltage. The protection controller  114  also commands the switching circuit  112  in the step  248  to rearrange the battery packs  130   a - 130   n  from the series arrangement to the parallel arrangement and open the recharging switches  180   a - 180   b  after the first recharging session has been cancelled. 
     Another time check is performed by the protection controller  114  in the step  250 . If the high-voltage component  140  has been subjected to improper voltages for greater that a cumulative time, the protection controller  114  prohibits the series arrangement in the step  252 . (The battery packs  130   a - 130   n  were previously configured in the parallel arrangement in the step  248 .) The protection controller  114  waits in the step  254  to receive the notification through the maintenance port  116  that the appropriate repairs have been completed. While no notification is received, the protection controller  114  and the switching circuit  112  maintain the battery packs  130   a - 130   n  in the parallel arrangement in the step  256 . Once the notification is received, the protection controller  114  enables the series arrangement in the step  258 . The method  220  subsequently ends in the step  260 . 
     Where the cumulative time limit has not been reached in the step  250 , the sensor  118  measures a distance and/or top speed that the vehicle  100  has traveled (or moved) since the first recharging session was cancelled due to the improper voltage in the step  262 . If the distance/speed traveled is less than a threshold distance/threshold speed per the step  254 , the protection controller  114  and the switching circuit  112  maintain the battery packs  130   a - 130   n  in the parallel arrangement in the step  266  and the method  220  returns to the step  262  to continue measuring the distance traveled. After the distance/speed traveled is greater than the threshold distance/threshold speed per the step  264 , the protection controller  114  enables the series arrangement in the step  258  and the method  220  ends in the step  260 . 
     The function of disabling the extra-high-voltage recharge may encourage the driver to move the vehicle  100  away from a potentially bad charging station  90 . The driver should be informed that the extra-high-voltage recharging function is re-enabled after the vehicle speed is over a threshold speed and/or the vehicle location has moved over a certain distance. Having the vehicle  100  drive away from a potentially bad charging station  90  may reduce the occurrence rate of the high-voltage component  140  experiencing the improper voltages. The function of automatically enabling the high-voltage recharging in response to the extra-high-voltage recharging being disabled and/or prohibited generally provides a convenience to the driver. 
     Referring to  FIG.  10   , a flow diagram of an example implementation of a method  280  for a second recharging session is shown in accordance with one or more exemplary embodiments. The method (or process)  280  may be implemented by the system  80 . The second recharging session of the method  280  is a high-voltage recharging. The method  280  includes steps  282  to  296 , as illustrated. The sequence of steps is shown as a representative example. Other step orders may be implemented to meet the criteria of a particular application. 
     In the step  282 , the protection system  110  waits for the charging station  90  to signal a readiness for the second recharging session at the high voltage. Once the charging station  90  is ready, the vehicle controller  122  commands the switching circuit  112  to close the recharging switches  180   a - 180   b , and commands the charging station  90  to begin recharging in the step  284 . The vehicle  100  receives the second recharging current Ic 2  in the step  286 . The second recharging current Ic 2  may be a variation of the recharging current Ic ( FIG.  1   ). 
     A check may be performed in the step  288  to determine if the second recharging session should continue. If the conclusion is to continue charging per the step  290 , the method  280  may return to the step  286  and the vehicle  100  continues to receive the second recharge current Ic 2 . If the second recharging session should end, the vehicle controller  122  may signal the station controller  92  to end the second charging session in the step  292 . The protection controller  114  and the switching circuit  112  maintain the battery packs  130   a - 130   n  in the parallel arrangement per the step  294  and open the recharging switches  180   a - 180   b . Thereafter, the charging station  90  may be disconnected from the vehicle in the step  296  and the method  280  ends. 
     Various embodiments sense different isolation faults, including loss of isolation and resistive short, by direct voltage sensing between high-voltage rails (or inputs) and a chassis ground of the high-voltage component  140 . A delay between sensing excessive voltages and taking protective action enables full utilization of short-term overvoltage capabilities of the high-voltage component  140  to save cost, weight, and size. The direct voltage sensing does not rely on accurately measuring the isolation resistance of the connected electrical systems, nor measuring noisy ground fault currents to trigger the protection. 
     Embodiments of the system  80  generally provides machines and/or methods for protection of high-voltage components  140  from isolation faults during extra-high-voltage recharging. The protection generally includes changing a variable arrangement of the battery packs  130   a - 130   n  from the parallel arrangement to the series arrangement in preparation for the first recharging session, and transferring electrical power from the battery packs  130   a - 130  to the high-voltage component  140  in both arrangements. Once the charging station  90  is ready, a first flow of the first recharging current Ic 1  in the first recharging session from the charging station  90  to the vehicle  100  is commanded, and the measured voltage(s) Vp and/or Vn between the input nodes  142 / 144  and the floating chassis ground  146  of the high-voltage component  140  are measured during the first recharging session. The protection controller  114  advances the timer  174  while the measured voltages Vp/Vn indicate the presence of an improper voltage between the input nodes  142 / 144  and the floating chassis ground  146 . The first recharging session is canceled in response to the presence of the improper voltage at the high-voltage component  140  for greater than an exposure time, and the battery packs  130   a - 130   n  are rearranged from the series arrangement to the parallel arrangement after the first recharging session has been cancelled. 
     All numerical values of parameters (e.g., of quantities or conditions) in this specification, including the appended claims, are to be understood as being modified in all instances by the term “about” whether or not “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows some slight imprecision (with some approach to exactness in the value; about or reasonably close to the value; nearly). If the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. In addition, disclosure of ranges includes disclosure of all values and further divided ranges within the entire range. Each value within a range and the endpoints of a range are hereby all disclosed as separate embodiments. 
     While the best modes for carrying out the disclosure have been described in detail, those familiar with the art to which this disclosure relates will recognize various alternative designs and embodiments for practicing the disclosure within the scope of the appended claims.