Method for detecting a function of a plurality of pins in a charging receptacle of a vehicle

Abstract

A method for detecting a function of a plurality of pins (32) in a charging receptacle (30) of a vehicle (10) during a charging cycle, comprising: Supplying a charging current through the pins (32); Monitoring a pin temperature of the pins (32) while supplying the charging current (54); Applying (120) a first step function (56) to the charging current (54); monitoring (118) a first step change (68) in pin temperature during the first step function (56); Comparing (124) the first step change (68) in the pin temperature with a first expected temperature change (70) to generate a first deviation (72); and Comparing (128) the first deviation (72) with a predetermined threshold value: if the first deviation (72) exceeds the predetermined threshold, signaling a maintenance alarm, and if the first deviation (72) is less than the predetermined threshold, logging the first deviation (72); and Calculating the first expected temperature change (70) based on a formula that equates stored energy with a difference between outgoing energy and incoming energy added to generate energy.

Description

The present disclosure relates to methods and mechanisms for determining operability or evaluating the state of vehicles having electric charging capabilities, such as plug-in hybrid and electric vehicles.DE 10 2020 209 581 A1 describes a device for diagnosing a state of a charging interface, comprising a sensor connected to a charging interface for acquiring measurement data of a temperature and / or voltage present at a charging interface, a computing unit and an interface to an output unit. The computing unit is configured to assign measurement data determined by the sensor during a supply of the charging interface with electric current using an assignment table to an identification number, which quantitates a state of the charging interface and outputs the identification number on the output unit.DE 10 2014 016 825 A1 describes a method for detecting an overtemperature in a temperature sensor-free region of a charging socket of a motor vehicle. A temperature value is detected by means of a temperature sensor at a place of installation of the temperature sensor that is different from the region. A configuration value of a current operating configuration in which the charging box is operated is determined, and a temperature specification relating to the temperature sensor-free region is then generated by means of a characteristic diagram which is designed to record the temperature value and the at least one configuration value as input variables and to assign the temperature specification to these input variables.The object of the present invention is to detect and monitor the function of a charge receptacle accurately.The object is achieved by the subject matters of the independent claims.A vehicle according to the invention configured to be able to carry out one or more methods according to the invention for detecting a function of a charge recording during a charging cycle is provided.The methods of the invention include supplying a charging current through the pins; monitoring a pin temperature of the pins during the charging current; and applying a first step function to the charging current. The methods also include monitoring a first step change in pen temperature during the first step function; comparing the first step change in pen temperature to a first expected temperature change to generate a first deviation; and comparing the first deviation to a predetermined threshold. If the first deviation exceeds the predetermined threshold, a maintenance alarm is signaled, and if the first deviation is less than the predetermined threshold, the first deviation is logged. The first expected temperature change is calculated based on a formula that equates a stored energy to a difference between an outflowing energy and an inflowing energy added for energy generation.The methods may include applying a second step function to the charging current; monitoring a second step change in pen temperature during the second step function; comparing the second step change in pen temperature with a second expected temperature change to generate a second deviation; and comparing the second deviation to the predetermined threshold. If the second deviation exceeds the predetermined threshold, the maintenance alarm is signaled, and if the second deviation is less than the predetermined threshold, the second deviation is logged.The use of the first step function may be scheduled not to occur every charge cycle.The step function(s) may be scheduled based on the vehicle history so that detection of a function of the pins occurs only during extended charging cycles.The first expected temperature change may be calculated based on a physical-based thermal model.The above features and advantages, as well as other features and advantages of the present disclosure, will be readily apparent from the following detailed description of the best modes for carrying out the disclosure when taken in conjunction with the accompanying drawings. FIG. 1 is a schematic illustration of a vehicle having one or more rechargeable energy storage systems (RESS) in electrical communication with at least one charge receptacle. FIG. 2A is a schematic diagram of a charging current flowing through the charging receptacle. FIG. 2B is a schematic diagram of temperature measurements of a pin within the charge receptacle as it is exposed to the schematic charge current of FIG. 2A. FIG. 3 is a schematic diagram of a flow chart for determining a state of charge reception. FIG. 4 is a schematic illustration of a load receptacle having one or more faulty pins.In the drawings, like reference numerals refer to similar components wherever possible. All descriptions of the figures relate simultaneously to all other figures. FIG. 1 schematically shows a portion of a vehicle 10, which may be, for example and without limitation, an electric vehicle or a hybrid electric vehicle. The vehicle 10 includes a rechargeable energy storage system (RESS) 12 that may include, for example and without limitation, a rechargeable battery or a rechargeable battery pack.A control system or controller 14 is in operative communication with the necessary components of the vehicle 10 to perform the methods, algorithms, and condition evaluations described herein. The controller 14 includes, for example and without limitation, a non-generalized electronic control device having a preprogrammed digital computer or processor, a memory or non-transitory computer readable medium used to store data such as control logic, instructions, look-up tables, etc., and a variety of input / output peripherals, ports, or communication protocols. The controller 14 is configured to execute or implement any of the control logic or instructions described herein.Additionally, the controller 14 may include or be in communication with a variety of sensors, including, but not limited to, those configured to sense or estimate ambient temperature outside the vehicle 10, various coolant temperatures inside the vehicle 10, and other measurement capabilities. The controller 14 may be directed to the specific aspects of the vehicle 10 described herein, or the controller 14 may be part of a larger control system that manages various functions of the vehicle 10.The vehicle 10 includes a communication system 16 capable of sharing information, e.g., determined by the controller 14 or other portions of the vehicle 10, with locations external to the vehicle 10. The communication system 16 may include, for example and without limitation, cellular or Wi-Fi technology that enables signals to be sent to central locations such as cloud storage or communication networks.A coolant circuit 20 or coolant system is in communication with the RESS 12 and includes at least one pump 22. If the vehicle 10 also includes an internal combustion engine, the coolant circuit 20 may also pass through the internal combustion engine, or separate coolant systems may be present for other components of the vehicle 10.A load receptacle 30 having a plurality of pins 32 is in communication with at least the controller 14 and the RESS 12. The charging receptacle 30 cooperates with a charging station, generally via a charging cable, both of which are not shown. The charging cord may include some or all of the features corresponding to the pins 32. The charge receptacle 30 is also in communication with the coolant circuit 20.The load receptacle 30 illustrated by way of example has a total of seven pins 32, some of which are not visible in the figures. The upper set (with respect to FIG. 1 ) is provided for the alternating current charge and the lower set (with respect to FIG. 1 ) is provided for the direct current charge. It should be noted that not all pins 32 are used for conducting the charging current, as some may be used for communication and / or control of the charging current flowing from the charging station through the charging receptacle 30. Moreover, it should be appreciated that the methods and mechanisms described herein may use different charging ports, including those with additional or fewer total pins. For example and without limitation, nine or five pole receptacles may be used, and sockets with only AC or only DC connection may be used.A plurality of temperature sensing devices are embedded in or adjacent to the load receptacle 30 such that the temperature of one or more of the pins 32 may be monitored and communicated to the controller 14. For example, and without limitation, thermocouples may be disposed proximate some or all of the pins 32.The charging receptacle 30 comprises a locking mechanism or a closure 40 which can cooperate with a corresponding locking mechanism on the charging cable. It should be noted that not all charging stations or charging receptacles 30 have the closure 40 or a corresponding structure.Referring now to FIGS. 2A and 2B, and with reference to the other figures, schematic diagrams are shown illustrating mechanisms, methods, or algorithms for testing and / or identifying functionality of the charging station 30. FIG. 2A shows a schematic current graph 50, wherein the y-axis shows the current 51 and the x-axis shows the time 52. The current graph 50 shows the current flowing through the charge receptacle 30 while being exposed to a charge current.As shown in FIG. 2A, a charging current, which may be referred to as a base charging current 54, is supplied via the pins 32. During this time, the vehicle 10 is undergoing a charge cycle directed to charging the RESS 12. The controller 14 also monitors the pin temperature of the pins 32, at least as long as the charging current is flowing. The controller 14, or other control system that manages the charging cycle, applies a first step function 56 to the charging current. It should be noted that the base charge current 54 may be either zero or non-zero. If the base charging current 54 is equal to zero, the state assessment described here can be carried out before the charging cycle is started.FIG. 2B shows a schematic temperature graph 60, wherein the y-axis represents the temperature 61 and the x-axis represents the time 62. The schematic temperature graph 60 shows an expected temperature 64, which may also be referred to as a normal temperature, and a measured temperature 66.During the first step function 56, the controller 14 monitors a first step change 68 in pen temperature. This may be the difference between the temperature during the base charge current 54 and the temperature rise caused by the first step function 56.The temperature rise may be caused by Joule heating, which may be considered the physical effect by which passage of current through an electrical conductor generates thermal energy. As those skilled in the art will appreciate, imperfections or degradations in the pins 32 may result in more Joule heating than would be expected with pins 32 that have substantially no such imperfections.The controller 14 compares the first step change 68 of the pen temperature with a first expected temperature change 70 to determine a first deviation 72. This generally quantitates the amount of excess or unexpected heat generated by the pins 32 during the first step function 56.The controller 14 may then compare the first deviation 72 to a predetermined threshold. If the first deviation 72 exceeds the predetermined threshold, the controller 14 may signal a service alert, and if the first deviation 72 is below the predetermined threshold, the controller 14 may log or store the first deviation 72. In some cases, logging the first deviation 72 may include sending the data from a storage external to the vehicle 10 to a cloud or network. The thresholds may be specific to the type of vehicle 10 or generally. Additionally, the thresholds may be updated during the duration of operation of the vehicle 10, e.g., via the cloud network.Depending on the extent of the first deviation 72, the maintenance alarm may include multiple possible actions or warnings. For example, the service alert may alert the operator of the vehicle 10 that he should bring the vehicle 10 to service, or in some cases, prematurely end the charge cycle to prevent further damage to the charge receptacle 30 or other parts of the vehicle 10.Factors that result in degradation or damage to the pins 32 include, but are not limited to: external forces that flex the pins 32, particles that grind the surface of the pins 32, or inadvertent application of heat to the charging tray 30 or the pins 32.Detection of faults, affects, or imperfections in the pins 32 or other components of the vehicle 10 may provide advantages to the vehicle 10, particularly when early detection occurs such that smaller faults are detected before leading to greater issues. Advantages include, but are not limited to, avoiding drive losses or inability to charge the vehicle 10 and the RESS 12, reducing tow and alternative transport costs, and reducing labor costs associated with isolating faults or substantial damage to the systems of the vehicle 10.It should be noted that controller 14 may employ additional step functions in addition to first step function 56 to further test the function of charge receptacle 30 during the charge cycle. Thus, the controller 14 may apply a second step function and compare a second step change in pen temperature with a second expected temperature change to generate a second deviation. Similarly, the controller may compare the second deviation to the predetermined threshold and determine whether the reporting of the maintenance alarm and / or the logging of the temperature deviation is justified.In many cases, the controller 14 will not attempt to test the functionality of the charging station 30 at each charging cycle. For example, and without limitation, use of the pacing stream or other test mechanisms, such as those described herein, may delay completion of the charging operation to analyze functionality. Therefore, it may be advantageous to perform this state analysis occasionally, e.g., and without limitation during extended charge cycles.To determine during which of the charge cycles the functionality of the system is to be tested, the controller 14 may use the history of the vehicle 10 to better determine when an extended charge cycle is likely. For example, the planning methods may analyze the GPS location and history of previous charging cycles to determine that the vehicle 10 is frequently charged for extended periods of time when at home, e.g., overnight, or when in a workplace. Other factors may include, but are not limited to, time of day, ambient temperature, state of charge of the RESS 12, battery power requested, time since the last state assessment, and the type of charging station to which the vehicle 10 is connected.The planning method / function attempts to ensure an uninterrupted charging operation when the operator wishes to travel a few kilometers quickly and without delay, such as during fast-charging while driving, and plans the state monitoring for situations where the operator leaves the vehicle 10 for a longer time for charging. Skilled artisans will appreciate the difference between short and long charge cycles. In one example and without limitation, a predicted charge cycle lasting three hours or longer may be considered an extended charge cycle; or if the vehicle 10 remains connected to the charge station after the RESS 12 is fully charged.Both the first step function 56 and all subsequent step functions may be controlled by the scheduler. In some cases, the planning function may occur outside the vehicle, e.g., within a cloud network, and be communicated to the controller 14. It should be appreciated that the operator of the vehicle 10 may have an irregular stop even when the scheduler estimates the length of the charging cycles so that the controller 14 may abort the state evaluation of the charging systems.To complete the state assessment of the charging station and its pins 32, the controller 14 uses various mechanisms to calculate the first expected temperature change 70. for example, and without limitation, the calculations may be based on a formula that equates the stored energy to the difference between the emanating energy and the incoming energy added to generate energy, which may include a physical-based thermal model.Equation 1 shows the balanced, physically based equation.In Equation 1: . in is the incoming thermal and mechanical energy transfer; . out is the outgoing thermal and mechanical energy transfer, e.g., through the coolant loop 20 or convective heat transfer to the ambient air; . g is thermal energy generation, e.g., by Joule heat; and . st is the stored thermal energy that raises the temperature of the pins 32.Equations 2-5 include parts of Equation 1.In equations 2-5: R = electrical resistance; I = electrical current; h = convection heat transfer coefficient, where h amb is the ambient air and h f is the liquid; T is the measured temperature of the charging receptacle pins 32; T amb is the temperature of the ambient air; T f is the temperature of the cooling liquid; A 1 is the surface area between the charging receptacle 30 and the ambient air; A 2 is the surface area between the charging receptacle 30 and the cooling liquid; and ρVc is the thermal capacity. Substituting Equations 2-5 into Equation 1, Equation 6 is obtained.Transformation of equation 6 and use of the Pauchen parameters P 1, P 2 and P 3 yields the following equation 7, wherein: P 1= ρVc; P 2= h amb* A 1; and P 3= H f* A 2.From Equation 7, the controller 14, or a subsystem thereof, may determine the expected temperature 64 and calculate the first deviation 72 from the difference between the first step change 68 and the first expected temperature change 70. Equation 7 may also be useful for determining the effective resistance of one or more pins 32. It should be appreciated that onboard calculations may be performed, for example and without limitation, by modeling functions or lookup tables.Referring to FIG. 3 and to all other figures, a schematic flow diagram is shown illustrating mechanisms, methods, or algorithms for testing and / or identifying the functionality of the charging receptacle 30. A method 100 is illustrated in FIG. 3 and illustrates one way to assess the state of the charge receptacle 30 in addition to other parts of the vehicle 10 as described herein.Step 110: Start / Initialize.The method 100 may begin operation when invoked by the controller 14, run continuously, or be repeated in a loop.Step 112: Connected to the station and ready to charge?The method 100 determines whether the vehicle 10 is connected to a charging station and ready to begin charging the RESS 12. If these conditions are not met, the method returns to the start step 110, which may include a repetition or pause before restarting. Alternatively, the starting step 110 may also be initialized only when the vehicle 10 is connected to the charging station and ready for charging.Step 114: State Assessment Scheduler.The method 100 communicates with the scheduler, either onboard the vehicle 10 or via a communication network. This helps in deciding whether to test the vehicle 10.Step 116: Allowed Conditions Met?If the condition of the state assessment scheduler is not met, the method returns to the start step 110, which may include a repetition or pause before restarting. If the conditions are met, the method 100 continues to step 118.Step 118: Monitor temperature.In this step, the method 100 monitors many temperature conditions including, without limitation: ambient air, cooling liquid, and charging reservoir 30, which may contain one or more of the individual pins 32. These conditions form the basis during the initial charging phase.Step 120: apply step function and monitor temperature.After determining the base, the method 100 applies step conditions. For example, the controller 14 may apply the first step function 56 to the charging current, as shown in FIG. 2A. The method 100 then monitors the changing temperature conditions in the charge receptacle 30 during and probably also after the first step function 56, for example with one or more thermocouples that effectively measure the charge receptacle 30.Step 122: Determine expected temperature and resistance.The method 100 determines the expected temperature, e.g., based on the physical-based model, and may also determine the resistance through the one or more pins 32 or the entire charge receptacle 30. The method 100 uses the expected temperature and resistance in subsequent computations and / or determinations.Step 124: Estimating the deviation from healthy recording.The method 100 estimates the deviation from a healthy, i.e., normally functioning, charge receptacle 30. the method 100 may use a comparison between the expected temperature and the measured temperature to derive the deviation, such as the first deviation 72 shown in FIG. 2B. Alternatively, the method 100 may compare the calculated resistance to an expected resistance based on the current and voltage conditions coming from the charging station.Step 126: Determine Capture / Pen State and Generate Report (optional).The method 100 may include a step of determining the overall state of the charging receptacle 30 or individual pins 32. This state assessment can in turn be logged or otherwise reported, e.g. to the cloud network. The determination of the state of the recording and the notification of the state determination can also be considered as an overlapping step, which comprises steps 124- 132. In many cases, summary messages can be sent to the operator of the vehicle 10 if the charge receptacle 30 is completely healthy.Step 128: Exceed predetermined thresholds?The method 100 may compare the temperature deviation, resistance deviation, or both calculated in step 120 to predetermined thresholds. As those skilled in the art will appreciate, these variations may be vehicle specific and may be based on, for example, the type and size of the RESS 12, the configuration of the charge receptacle 30, the powertrain, and other system configurations.Step 130: Continue charging.If the determination in step 128 is negative, i.e., the answer is "no," represented by a "-" in the flowchart, the method 100 allows the vehicle 10 to continue the charging operation. In such a situation, the method 100 may have determined that it is generally not harmful to continue the charge cycle for the charge receptacle 30, the RESS 12, or other components of the vehicle 10.Step 132: Generate error message.If the determination in step 128 is affirmative -- i.e., the answer is "yes" as represented by a "+" in the flowchart -- method 100 generates an error message. This may include, for example and without limitation: signaling to the vehicle operator, e.g., via an onboard light, a messaging system, or a portable device app; and / or notifying a fleet manager when the vehicle 10 is part of a fleet.Depending on the severity of the threshold being exceeded, step 132 may also include interrupting the charge cycle. In particular, if optional step 126 determines that the state of charge receptacle 30 is severely impaired, method 100 may decide that it is best to shut down the charge cycle without further delay. This would likely generate additional error messages, including alerting service or repair personnel for the vehicle 10 and / or the charging station.Step 134: End / Loop.After either step 130 or step 132, the method 100 ends. In many configurations, the method 100 loops continuously or periodically while the charge cycle is in operation.Referring to all other figures, a load receptacle 150 is shown in FIG. 4 illustrating some possible damage to the load receptacles described herein. Those skilled in the art will appreciate that the charging receptacle 150 is wholly or partially similar to the charging receptacle 30 shown in FIG. 1.The load receptacle 150 includes a plurality of pins 152 that are substantially undamaged. However, the charging receptacle 150 also has a damaged pin 153. The damaged pin 153 may be broken by an improperly oriented charging cord inserted into the charging receptacle 150. In addition, the damaged pin 153 may have caused an electric arc so that the housing of the charging receptacle 150 is fused around the damaged pin 153.Additional methods for assessing the state of charge recordings, such as the charge recording 150 or the charge recording 30, can comprise an image analysis of the respective charge recording. For example, the driver of the vehicle may be prompted to take a photograph of the charge receptacle 150 at regular intervals, or may take the photograph whenever ready for it. Thereafter, the photograph is sent to a cloud network for image processing, for example and without limitation. The cloud network may use any number of techniques, including, without limitation, human verification, image recognition, or artificial intelligence to identify possible damage to the charging receptacle 150.If the cloud network or similarly equipped systems determine that the charging receptacle 150 is likely damaged, a service alert may be signaled or sent. The maintenance alert may include, for example and without limitation: signaling to the vehicle operator, e.g., via an onboard light, a messaging system, or a portable device app; notifying a fleet manager when the vehicle 10 is part of a fleet; or notifying service or repair personnel.The smartphone or personal device camera may use an app or upload images for analysis over the Internet. Possible damage that can be detected includes, among others, minute combustion traces caused by electric arcs, abraded particles, cracks, or melting points.As shown in FIG. 1, the vehicle 10 includes the coolant circuit 20. The flow chart in FIG. 3 illustrates a similar algorithm or method for evaluating the coolant circuit 20.The method for evaluating the coolant circuit 20 includes monitoring temperature similar to the method 100 shown in FIG. 3. However, in step 120, the controller 14 maintains the charging current constant while pacing the flow of the liquid coolant through the coolant circuit 20 and monitoring the temperature change during the coolant step, rather than applying a step to the charging current.The cooling agent step may be performed as an increase or decrease. If, for example, the coolant flow through the coolant circuit 20 increases, it is to be expected that the temperature of the pins 32 in the charging receptacle 30 falls. However, if the coolant circuit 20 is not functioning properly, the temperature lowering may not be fully realized.A deviation may be calculated from the difference between the measured temperature and the expected temperature of the pins 32. This deviation may be compared by the controller 14 to thresholds to assess the state of the coolant circuit 20, similar to the methods shown in FIG. 3.As shown in FIG. 1, the charging receptacle 30 includes the closure 40 that cooperates with a corresponding locking mechanism on the charging cable. However, the shutter 40 of the charging cable shutter may be damaged or may no longer function properly.It can therefore be advantageous to check the state of the closure 40 and / or of the charging cable closure.In many interactions, the shutter 40 and charging cord shutter must successfully snap into one another before the charging cycle can begin or be initiated. Therefore, the controller 14 knows whether the shutter 40 and the charging cable shutter are successfully locked. Therefore, state evaluations may be performed for the shutter 40, the corresponding charging cable shutter, or both.For example, if the closure 40 normally successfully locks onto the first or second attempt, but requires five attempts to lock onto a particular charging station, this indicates that the charging cord closure may be damaged or otherwise malfunctioning. The controller 14 can then signal via a communication network that the charging station may have to be checked and / or repaired. Similarly, and without limitation, the controller 14 may determine that the closure 40 is not functioning properly if the closure 40 has difficulty successfully engaging a charging station that normally engages the first or second attempt and send a maintenance message or reminder to inspect and / or repair the closure 40.

Claims

A method of detecting a function of a plurality of pins (32) in a charging receptacle (30) of a vehicle (10) during a charging cycle, comprising: supplying a charging current through the pins (32); monitoring a pin temperature of the pins (32) during the supplying of the charging current (54); applying (120) a first step function (56) to the charging current (54); monitoring (118) a first step change (68) of the pin temperature during the first step function (56); comparing (124) the first step change (68) of the pin temperature with a first expected temperature change (70) to generate a first deviation (72); and comparing (128) the first deviation (72) to a predetermined threshold: if the first deviation (72) exceeds the predetermined threshold, signaling a service alarm, and if the first deviation (72) is less than the predetermined threshold, logging the first deviation (72); and calculating the first expected temperature change (70) based on a formula that equates a stored energy to a difference between an emanating energy and an incoming energy added to generate energy.The method of claim 1, further comprising: applying a second step function to the charging current; monitoring a second step change in the pen temperature during the second step function; comparing the second step change in the pen temperature with a second expected temperature change to generate a second deviation; and comparing the second deviation with the predetermined threshold: if the second deviation exceeds the predetermined threshold, signaling the maintenance alert, and if the second deviation is less than the predetermined threshold, logging the second deviation.The method of claim 1, further comprising: scheduling the first step function (56) such that it does not occur at each charge cycle.The method of claim 3, further comprising: planning the first step function (56) based on the vehicle history such that the detection of a function of the pins (32) occurs during extended charging cycles.The method of claim 1, further comprising: calculating the first expected temperature change (70) based on a physical-based thermal model.The method of claim 2, further comprising: planning the first step function (56) and the second step function based on the vehicle history, wherein the first step function (56) and the second step function do not occur at each charging cycle, and wherein detecting a function of the pins (32) occurs during extended charging cycles.A vehicle (10) comprising: a rechargeable energy storage system (RESS) (12) selectively undergoing a charge cycle; a charge receptacle having a plurality of pins; a controller (14) in communication with the RESS (12) and the charge receptacle, the controller (14) configured to identify a function of the charge receptacle (30) during the charge cycle by: supplying a charge current through the pins (32); monitoring a pin temperature of the pins (32) during the supplying of the charge current; applying (120) a first step function (56) to the charge current; monitoring (118) a first step change (68) in the pin temperature during the first step function (56); comparing (124) the first step change (68) of the pen temperature with a first expected temperature change (70) to produce a first deviation (72); and comparing (128) the first deviation (72) with a predetermined threshold: if the first deviation (72) exceeds the predetermined threshold, signaling a service alarm, and if the first deviation (72) is less than the predetermined threshold, logging the first deviation (72); and calculating the first expected temperature change (70) based on a formula that equates stored energy to a difference between emanating energy and incoming energy added to produce energy.The vehicle of claim 7, wherein the controller (14) is further configured to identify a function of charge acceptance during the charging cycle by: applying a second step function to the charging current; monitoring a second step change in pen temperature during the second step function; comparing the second step change in pen temperature with a second expected temperature change to generate a second deviation; and comparing the second deviation with the predetermined threshold: if the second deviation exceeds the predetermined threshold, signaling the maintenance alert, and if the second deviation is less than the predetermined threshold, logging the second deviation.The vehicle of claim 7, wherein the controller (14) is further configured to identify a charge acceptance function during the charge cycle by: scheduling the first step function (56) such that it does not occur at each charge cycle.

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