Charge state monitoring device and method

Abstract

A state-of-charge monitoring device (100) for monitoring the state of a charging component for an electric vehicle (80) comprises a test sensor (200) held by a charging port (90) and a test probe (202) that interfaces with a counter-charging port (50). The state-of-charge monitoring device includes a control circuit (150) for controlling charging and test operation. The control circuit measures a terminal voltage of the charging port and a sensor voltage of the test sensor to determine the resistance of the charging port and provide a test signal (176). The control circuit includes an electrically isolated switch (160) that receives the test signal and generates a control signal (140) based on the test signal to control charging operation of the charging component. The control circuit executes the test operation simultaneously with the charging operation.

Description

[0001] The subject matter here generally concerns charging systems for electric vehicles.

[0002] Power for recharging EV (electric vehicle) batteries can be supplied through a detachable electrical interface consisting of a charging socket on the vehicle and a charging plug connected to a charging station by a flexible cable. This detachable electrical interface is subject to harsh operating conditions, including frequent cycling (plugging and unplugging), exposure to weather, and damage. These harsh operating conditions can reduce the functionality or electrical performance of the connector by increasing interface resistance. Furthermore, because charging can occur at different locations, the detachable interface occurs between different components, whose individual functionality may also vary. The integrity of the charging interface is important for safe operation.Interfaces with high electrical resistance can lead to excessive resistive heating. Excessive heating can result in slower charging speeds, as a charging inlet temperature sensor detects the excessive heating. It can also damage the charging inlet or charging connector if the charging station does not reduce the charging current quickly enough. The importance of an intact separable interface (with low electrical resistance), combined with the potential for high variability in condition between different charging stations, makes a method for monitoring or measuring the interface condition desirable.

[0003] In one embodiment, a state of charge monitoring device for monitoring a state of a charging component for an electric vehicle is provided. The state of charge monitoring device comprises a charging port configured to be connected to a counter-charging port to perform a charging operation for charging the electric vehicle. The state of charge monitoring device comprises a test sensor held by the charging port. The test sensor comprises a test probe. The test probe is electrically insulated from the charging port. The test probe comprises a test interface configured to interface with a counter-charging port. The state of charge monitoring device comprises control circuitry for the charging component. The control circuitry is operatively connected to the charging port to control the charging operation using the charging port.The control circuit is operatively connected to the test sensor to control a test operation using the test sensor. The control circuit measures a terminal voltage of the charging terminal. The control circuit measures a sensor voltage of the test sensor. The control circuit determines a resistance of the charging terminal and the counter-charging terminal based on the measured terminal voltage and the measured sensor voltage. The control circuit provides a test signal based on the measured resistance. The control circuit includes an electrically isolated switch that receives the test signal. The electrically isolated switch generates a control signal based on the test signal. The control circuit is operatively connected to the charging component to control a charging operation of the charging component based on the control signal.Both the test sensor and the charging port are configured to be connected to the counter-charging port. The control circuit performs the test operation simultaneously with the charging operation.

[0004] The invention will now be described by way of example with reference to the accompanying figures, of which: Fig. 1 illustrates a state of charge monitoring system according to an exemplary embodiment. Fig. 2 is a schematic view of the monitoring device according to an exemplary embodiment. Fig. 3 is a schematic view of the monitoring device according to an exemplary embodiment. Fig. 4 is a schematic view of the monitoring device according to an exemplary embodiment. Fig. 5 is a schematic view of the monitoring device according to an exemplary embodiment. Fig. 6 is a schematic view of the monitoring device according to an exemplary embodiment.

[0005] Fig. 1 illustrates a state of charge monitoring system 10 according to an exemplary embodiment. The state of charge monitoring system 10 includes a state of charge monitoring device 100 (which may be referred to below as a monitoring device 100). The monitoring device 100 is used to monitor the condition of charging ports used to charge an electric vehicle 80. The state of charge monitoring system 10 measures a charging interface condition when the vehicle 80 is connected to a charging station 20. The state of charge monitoring system 10 can provide a signal that permits or prohibits charging based on the measured condition of that particular detachable interface.The charge state monitoring system 10 reduces dissatisfaction with slow charging speeds, the potential for harmful user intervention (shaking the charging plug to increase the charging speed), or damage to the input and charging plug due to poor interface condition.

[0006] The monitoring device 100 can be installed in the electric vehicle 80 and / or the charging station 20 for charging the electric vehicle 80 to monitor a condition of the charging components, such as controlling charging operation. For example, the monitoring device 100 can permit or prohibit charging operation based on the condition of the charging ports. In an exemplary embodiment, the monitoring device 100 measures an interface resistance at the interface of the charging ports to determine a condition of the charging components. If the interface resistance is too high, the monitoring device 100 can prohibit charging operation, prompting the user to use a different charging station 20 and / or to repair or replace the charging components to improve charging operation.

[0007] The electric vehicle 80 includes a charging inlet 82 having charging ports 90. In one exemplary embodiment, the charging inlet 82 includes a recess configured to receive a charging plug. In various embodiments, the charging inlet 82 may operate as a standard type charging inlet, such as an SAE J1772 inlet. In one exemplary embodiment, the charging ports 90 are pin terminals. However, in alternative embodiments, other types of charging ports may be used. The charging inlet 82 is mounted to the vehicle 80. The charging inlet 82 is electrically connected to a battery 86 of the electric vehicle 80. The charging ports 90 are supplied with power from the charging station 20 to charge the battery 86.

[0008] The charging station 20 includes a charging plug 40 at one end of a charging cable 42. The charging plug 40 is configured to mate with the charging inlet 82. The charging station 20 supplies power to the charging plug 40 to charge the electric vehicle 80. The charging plug 40 may be a Level 1 charging device, a Level 2 charging device, or a Level 3 charging device. In an exemplary embodiment, the charging plug may be a DC fast charging plug. The charging plug 40 may be any type of electric vehicle charging interface that has an array of charging ports, such as a combined charging system (CCS) that has both AC charging ports and DC charging ports. The charging plug 40 includes a handle 44 that holds the charging ports 50. In an exemplary embodiment, the charging ports 50 are charging receptacles.The charging terminals 50 are configured to be received in the recess 84 to connect to the charging terminals 90 of the charging input 82.

[0009] In various embodiments, the monitoring device 100 is part of the electric vehicle 80. For example, the monitoring device 100 may be part of the charging inlet 82. The monitoring device 100 may be part of the battery system. In other various embodiments, the monitoring device 100 is part of the charging station 20. For example, the monitoring device 100 may be part of the charging connector 40. The monitoring device 100 may control the power supply from the charging station 20 to the charging inlet 82. For example, the monitoring device 100 may shut down charging if it determines that the condition of the charging components at the charging interface is unhealthy. For example, charging may be prohibited if there is a high electrical resistance at the charging interface, such as due to damage or deterioration.In an exemplary embodiment, the monitoring device 100 enables individual customers, fleet owners, charging station maintenance companies, or others to assess the condition of the charging connector 40 and determine whether maintenance and / or replacement of the charging connector 40 or its components is required. The monitoring device 100 measures the resistance of the connection in the charging connector 40 to determine the condition of the charging ports 50. In an exemplary embodiment, the monitoring device 100 compares the measured resistance to a known database of connections ranging from good to poor and provides the user with an indication of the condition of the particular charging ports 50 to determine whether the charging ports 50 require service or replacement.The monitoring device 100 may provide the user with an output indicating the status of the charging ports 50, which may be displayed at the charging station 20 and / or within the electric vehicle 80.

[0010] Fig. Figure 2 is a schematic view of monitoring device 100 according to an exemplary embodiment. In the illustrated embodiment, monitoring device 100 is part of charging inlet 82. Monitoring device 100 is connected to charging port 90. Fig. 2 shows the charging port 90, which includes a pin 92 received in a socket 52 of the charging port 50. The monitoring device 100 assesses the condition of the charging port 50 and / or the charging port 90 to determine whether charging should or can occur and / or to determine whether maintenance and / or replacement of the charging components is required. The monitoring device 100 measures the resistance of the interface between the charging ports 50, 90.

[0011] The monitoring device 100 includes a control circuit 150 and a test sensor 200 for monitoring the charging components, such as for monitoring the charging port 50 and / or the charging port 90. In an exemplary embodiment, the test sensor 200 includes a test probe 202. The test probe 202 is held by the charging port 90. For example, the test probe 202 may be received in an opening or channel in the pin 92 and extends from the pin 92 to interface with the charging port 50. The charging port 90 has a mating interface along the pin 92 configured to interface with the mating charging port 50, such as with mating elements along the receptacle 52.In an exemplary embodiment, the test probe 202 is electrically insulated from the charging port 90, for example, using a foil, a pad, a sleeve, a coating, an air gap, or other dielectric barrier between the test probe 202 and the charging port 90. The test probe 202 includes a test interface 204 that engages or connects to the charging port 50. In an exemplary embodiment, the test probe 202 is movable relative to the charging port 90 to mate with the mating charging port 50. For example, the test probe 202 may be deflectable or compressible to reliably connect to the charging port 50. In various embodiments, the test probe 202 is a pogo pin. For example, the test probe 202 is spring-loaded to engage the charging port 50.In the illustrated embodiment, the test probe 202 is aligned with the longitudinal axis of the charging port 90 (e.g., the pin axis). For example, the test probe 202 is aligned with and deflectable along a mating axis of the charging ports 50, 90. The test probe 202 may extend forwardly from the distal end of the pin of the charging port 90. The test probe 202 is configured to compress against a bottom end of the receptacle 52, such as against a face at the bottom end of the receptacle 52.

[0012] The control circuit 150 is operatively connected to the charging component (e.g., the charging station 20 and / or the electric vehicle 80) to control the charging process using the charging ports 50, 90. The control circuit 150 is operatively connected to the test sensor 200 to control a test process using the test sensor 200. For example, the control circuit 150 is connected to the charging port 90 with a first line 152, and the control circuit 150 is connected to the test sensor 200 with a second line 154. The control circuit 150 receives signals from the charging port 90 and the test sensor 200 through the lines 152, 154. For example, the control circuit 150 may measure voltage, current, or receive other signals.In an exemplary embodiment, the control circuit measures a terminal voltage of the charging port 90 and a sensor voltage of the test sensor 200 to determine a resistance of the charging port 90 and provide a test signal indicative of or based on the resistance. The resistance can be determined as the voltage difference between the measured voltages of the charging port 90 and the test sensor 200 divided by the charging current. In an exemplary embodiment, the control circuit 150 is a resistance sensor (e.g., a two-wire resistance sensor) configured to determine a resistance measurement of the charging port 50. The control circuit 150 employs a two-wire interface resistance measurement to control the charging process.

[0013] In an exemplary embodiment, control circuit 150 measures a terminal voltage of charging port 50 and measures a sensor voltage of test sensor 200. Control circuit 150 determines a resistance of charging port 50 and charging port 90 based on the measured terminal voltage and the measured sensor voltage divided by the measured charging current. Control circuit 51 includes circuit components 156 for controlling the operation of monitoring device 100. Circuit components 156 may include resistors, capacitors, inductors, transistors, diodes, operational amplifiers, differential amplifiers, integrated circuits, processors, memory, communication components, switches, an electrically isolated switch, a galvanic barrier, an optocoupler, or other types of circuit components.In an exemplary embodiment, control circuit 51 is configured to provide one or more outputs. For example, control circuit 150 may generate a control signal 140 to control the charging operation. In various embodiments, the output may be used to disable or prohibit the charging operation from occurring. For example, control circuit 51 controls the charging operation by stopping the charging operation when the measured resistance is above a threshold resistance. The output may be communicated to the user to provide an indication of the operating status of the charging components, such as with a display on a display device.

[0014] In an exemplary embodiment, both the test sensor 200 and the charging port 90 are configured to connect to the mating charging port 50 (the female port) when the charging plug 40 is plugged into the charging inlet 82 of the vehicle 80. The control circuit 51 performs the test operation concurrently with the charging operation. Optionally, the control circuit 51 may perform the test operation once upon initial plugging, such as at the beginning of the charging operation. In other embodiments, the control circuit 51 performs the test operation continuously during the charging operation. In other embodiments, the control circuit 150 performs the test operation at intervals, for example, by pulsing test signals at regular intervals during the charging operation.

[0015] Fig. Figure 3 is a schematic view of the monitoring device 100 according to an exemplary embodiment. In the illustrated embodiment, the monitoring device 100 is part of the charging station 20. The monitoring device 100 is connected to the charging port 50. Fig. 3 shows the charging port 90, which includes the pin 92 received in the socket 52 of the charging port 50. The monitoring device 100 examines the condition of the charging port 50 and / or the charging port 90 to determine whether charging should or can occur and / or to determine whether any maintenance and / or replacement of the charging components is required. The monitoring device 100 measures the resistance of the interface between the charging ports 50, 90.

[0016] The monitoring device 100 includes the control circuitry 150 and the test sensor 200 for monitoring the charging components, such as for monitoring the charging port 50 and / or the charging port 90. In the illustrated embodiment, the test probe 202 is held by the charging port 50. For example, the test probe 202 may be received in an opening or channel formed in the bottom of the receptacle 52 and extends from the bottom into the receptacle 52 to connect to the charging port 90. In an exemplary embodiment, the test probe 202 is electrically insulated from the charging port 50, for example, using a foil, pad, sleeve, coating, air gap, or other dielectric barrier between the test probe 202 and the charging port 50. The test interface 204 of the test probe 202 is configured to engage or connect to the charging port 90.In an exemplary embodiment, the test probe 202 is deflectable to reliably connect to the charging port 90. The test probe 202 may be a spring-loaded pogo pin. In the illustrated embodiment, the test probe 202 is aligned with the longitudinal axis of the charging port 50 (e.g., aligned with the central axis of the receptacle 52). The test probe 202 is configured to connect to the distal end of the pin 92 when the pin 92 is inserted into the receptacle 52.

[0017] The control circuit 150 is operatively connected to the charging component (e.g., the charging station 20 and / or the electric vehicle 80) to control the charging operation using the charging ports 50, 90. The control circuit 150 is operatively connected to the test sensor 200 to control a test operation using the test sensor 200. For example, the control circuit 51 is connected to the charging port 50 by the first line 152, and the control circuit 150 is connected to the test sensor 200 by the second line 154. The control circuit 51 receives signals from the charging port 50 and the test sensor 200 through the lines 152, 154. For example, the control circuit 150 can measure voltage, current, or receive other signals.In an exemplary embodiment, the control circuit 150 is a resistance sensor (e.g., a two-wire resistance sensor) configured to determine a resistance measurement for the charging components.

[0018] In an exemplary embodiment, the control circuit 150 measures a terminal voltage of the charging port 50 and measures a sensor voltage of the test sensor 200. The control circuit 150 determines a resistance of the charging port 50 and the charging port 90 based on the measured terminal voltage and the measured sensor voltage. The control circuit 150 includes circuit components 156 for controlling the operation of the monitoring device 100. The circuit components 156 may include resistors, capacitors, inductors, transistors, diodes, operational amplifiers, differential amplifiers, integrated circuits, processors, memories, communication components, switches, an electrically isolated switch, a galvanic barrier, an optocoupler, or other types of circuit components. In an exemplary embodiment, the control circuit 51 is configured to provide one or more outputs.For example, control circuit 51 may generate control signal 140 to control charging operation. In various embodiments, the output may be used to disable or prohibit charging operation. The output may be communicated to the user to provide an indication of the operating status of the charging components, for example, via a display on a display device.

[0019] Fig. 4 is a schematic view of monitoring device 100 according to an exemplary embodiment. In the illustrated embodiment, monitoring device 100 is part of charging inlet 82; however, monitoring device 100 may be part of charging station 20 in alternative embodiments. Monitoring device 100 is shown connected to charging port 90. Monitoring device 100 examines the condition of the charging components. For example, monitoring device 100 measures the resistance of the interface between charging ports 50, 90. Monitoring device 100 is used to measure a resistance of charging port 50 using test sensor 200. Fig. Figure 4 illustrates a two-wire resistance measurement circuit for monitoring device 100. Test sensor 200 is used to accurately measure a resistance in charging port 50 to monitor the condition of charging port 50. Test sensor 200 differentiates between a good connection and a bad connection, for example, by comparing the measured resistance to a threshold resistance value and / or a database of known connections. Thus, monitoring device 100 can be used to determine whether charging port 50 requires servicing or replacement.

[0020] In an exemplary embodiment, control circuit 150 includes a voltmeter. A pair of voltage-sensing resistors are connected to the voltmeter to measure the voltage drop across charging port 50.

[0021] In an exemplary embodiment, the control circuit 150 includes an electrically isolated switch 160 that generates the control signal 140 based on the test signals from the test sensor 200. The control signal 140 can be further processed or can be used directly to control operation of the charging system (e.g., to allow or prohibit charging or to control the charging speed). The electrically isolated switch 61 forms a galvanic barrier between the charging components (e.g., the charging ports 50, 90) that are under high voltage and the circuit components or other systems of the vehicle. In an exemplary embodiment, the electrically isolated switch 61 includes an optocoupler 162 that forms an optical connection between the charging side and the isolated side of the control circuit 150. The optocoupler 162 includes an emitter 164 and a phototransistor 166.The emitter 164 may be a diode, such as an IR diode. The emitter 164 is connected to the lines 152, 154 and generates a light output based on the signals from the test sensor 200. The phototransistor 166 receives the optical signals from the emitter 164 and generates a digital output based on the received optical signals. The optocoupler 162 may include other components in alternative embodiments that transmit electrical signals between two isolated circuits using light. In another alternative embodiment, instead of using an optocoupler, the electrically isolated switch 160 may provide isolated circuits employing capacitive components, inductive components, radiating components, acoustic components, or mechanically coupled components.

[0022] In an exemplary embodiment, the optocoupler 162 is activated when the voltage drop across the separable interface increases to a bandgap potential of the emitter 164. The optocoupler 162 provides the required galvanic isolation between the charging port 90 and the vehicle's electrical system. The phototransistor 166 on the isolated side of the optocoupler 162 signals the vehicle to stop charging when a bad condition is determined. The switching potential of the optocoupler 162 can be limited to the existing diode bandgap voltages. In various embodiments, the emitter 164 can be an IR emitter to maintain a low bandgap voltage (e.g., 1.8 V).

[0023] Fig. 5 is a schematic view of the monitoring device 100 according to an exemplary embodiment. In an exemplary embodiment, the monitoring device 100 generates a digital output as the control signal 140 for controlling the charging system. The monitoring device 100 may be part of the charging inlet 82 or the charging plug 40 of the charging station 20. The monitoring device 100 examines the condition of the charging components. For example, the monitoring device 100 measures the resistance of the interface between the charging ports 50, 90. The monitoring device 100 is used to measure a resistance of the charging port 50 using the test sensor 200 and generates the control signal 140 based on the resistance, which is a measure of the condition of the charging components.

[0024] In an exemplary embodiment, the control circuit 150 includes an operational amplifier (opamp) 170. In an exemplary embodiment, the opamp 170 is a differential amplifier that measures and amplifies a voltage drop across the separable interface. The opamp 170 includes a first input 172 from the first line 152 and a second input 174 from the second line 154. The opamp 170 generates a test signal 176 as an output. The test signal 176 may be an analog signal. The test signal 176 is based on a contact resistance 180 at the mating interface between the charging terminals 50, 90. A charging current is represented by the charging source 182. In an exemplary embodiment, the control circuit 150 includes an analog-to-digital converter (ADC) 190. The ADC 190 converts the analog test signal 176 into a digital test signal 192. The digital test signal 192 is passed to the electrically isolated switch 160.The electrically isolated switch 160 generates the control signal 140. The output of the op-amp 170 is sent to the ADC 190, which digitizes the analog value and sends it to the vehicle via the electrically isolated switch 61. The signal sent to the vehicle can be either a simple on-off value indicating a satisfactory interface, a digital bit string corresponding to the measured voltage drop, a PWM (pulse-width modulated) signal proportional to the voltage drop, or another signal type.

[0025] The monitoring device 100 is used to accurately measure a resistance in the charging port 50 to monitor the condition of the charging port 50. The monitoring device 100 differentiates between a good connection and a bad connection, for example, by comparing the measured resistance with a threshold resistance value and / or a database of known connections. Thus, the monitoring device 100 can be used to determine whether the charging port 50 requires servicing or replacement.

[0026] Fig.6 is a schematic view of the monitoring device 100 according to an exemplary embodiment. In an exemplary embodiment, the monitoring device 100 generates an analog output as a control signal 140 for controlling the charging system. The monitoring device 100 can be part of the charging inlet 82 or the charging plug 40 of the charging station 20. The monitoring device 100 examines the condition of the charging components. For example, the monitoring device 100 measures the resistance of the interface between the charging ports 50, 90. The monitoring device 100 is used to measure a resistance of the charging port 50 using the test sensor 200 and generates the control signal 140 based on the resistance, which is a measure of the condition of the charging components.

[0027] In an exemplary embodiment, the control circuit 150 includes the opamp 170. The opamp 170 includes the first input 172 from the first line 152 and the second input 174 from the second line 154. The opamp 170 generates the test signal 176 as an output. The test signal 176 can be an analog signal. The test signal 176 is based on the contact resistance 180 at the mating interface between the charging terminals 50, 90. The test signal 176 is transmitted to the electrically isolated component 160. In an exemplary embodiment, the electrically isolated component 160 is an opamp with a built-in galvanic barrier. The electrically isolated component 160 generates a first output 194 and a second output 196. The electrically isolated component 160 conveys the test signal 176 to the outputs 194, 196, blocking the high voltage present at the input side.The first and second outputs 194, 196 are transmitted to an isolated opamp 198 on the isolated side of the control circuit 150. The isolated opamp 198 generates the control signal 140. In the illustrated embodiment, the control signal 140 is an analog control signal. The electrically isolated component 160 moves the galvanically isolated analog signal from the test opamp 170 on the left side to the isolated opamp 198 on the right side. The isolated opamp 198 converts the differential signal into an analog representation of the voltage differential (e.g., voltage at the charging terminal 50 minus voltage at the test sensor 200) as the output or control signal 140.

[0028] The monitoring device 100 is used to accurately measure a resistance in the charging port 50 to monitor the condition of the charging port 50. The monitoring device 100 differentiates between a good connection and a bad connection, for example, by comparing the measured resistance with a threshold resistance value and / or a database of known connections. Thus, the monitoring device 100 can be used to determine whether the charging port 50 requires servicing or replacement.

Claims

[1] Charge state monitoring device (100) for monitoring the condition of a charging component for an electric vehicle (80), the charge state monitoring device comprising: a charging port (90) configured to be connected to a counter-charging port (50) to perform a charging operation for charging the electric vehicle; a test sensor (200) held by the charging port, the test sensor comprising a test probe (202), the test probe being electrically isolated from the charging port, the test probe comprising a test interface (204) configured to interface with a counter charging port; a control circuit (150) for the charging component, wherein the control circuit is operatively connected to the charging port to control the charging operation using the charging port, wherein the control circuit is operatively connected to the test sensor to control a test operation using the test sensor, wherein the control circuit measures a terminal voltage of the charging port, wherein the control circuit measures a sensor voltage of the test sensor, wherein the control circuit determines a resistance of the charging port and the counter-charging port based on the measured terminal voltage and the measured sensor voltage, wherein the control circuit provides a test signal (176) based on the measured resistance, wherein the control circuit comprises an electrically isolated switch (160) that receives the test signal,wherein the electrically isolated switch generates a control signal (140) based on the test signal, wherein the control circuit is operatively connected to the charging component to control a charging operation of the charging component based on the control signal;, wherein both the test sensor and the charging terminal are configured to be connected to the counter-charging terminal, wherein the control circuit performs the test operation simultaneously with the charging operation. [2] The charging station condition monitoring device (100) of claim 1, wherein the control circuit (150) uses a two-wire interface resistance measurement to control the charging operation. [3] The charging station condition monitoring device (100) according to claim 1, wherein the test probe (202) is movable with respect to the charging port (90) to be connected to the counter-charging port (50). [4] The charging station condition monitoring device (100) according to claim 1, wherein the checking operation takes place during the charging operation. [5] The charging station condition monitoring device (100) according to claim 1, wherein the control circuit (150) controls the charging operation by stopping the charging operation when the measured resistance is above a limit resistance. [6] The charging station condition monitoring device (100) according to claim 1, wherein the charging terminal (90) is a pin terminal and the counter-charging terminal (50) is a socket terminal, the test probe (202) is received in the socket terminal, with the pin terminal to connect to the socket terminal. [7] The charging station condition monitoring device (100) according to claim 1, wherein the charging terminal (90) is a female terminal and the counter-charging terminal (50) is a male terminal, wherein the test probe (202) is arranged in a socket (52) of the female terminal to connect to the male terminal when the male terminal is inserted into the socket. [8] The charging station condition monitoring device (100) according to claim 1, wherein the charging port (90) has a mating interface, wherein the control circuit (150) measures the resistance of the mating interface. [9] The charging station condition monitoring device (100) according to claim 1, wherein the control circuit (150) measures a charging current of the charging terminal (90), the resistance being determined as the voltage difference divided by the charging current. [10] The charging station condition monitoring device (100) of claim 1, wherein the electrically isolated switch (160) is an optocoupler (162). [11] The charging station condition monitoring device (100) of claim 1, wherein the control circuit (150) comprises an operational amplifier (170) that receives the sensor voltage from the test sensor (200) and receives the terminal voltage from the charging terminal (90), the operational amplifier providing the test signal (176) as an output (194). [12] The charging station condition monitoring device (100) according to claim 1, wherein the control circuit (150) comprises a differential amplifier that receives the sensor voltage and the terminal voltage. [13] The charging station condition monitoring device (100) according to claim 1, wherein the control signal (140) generated by the control circuit (150) is a pulse width modulated signal. [14] The charging station condition monitoring device (100) according to claim 1, wherein the control signal (140) generated by the control circuit (150) is an on / off value to control the charging operation. [15] The charging station condition monitoring device (100) according to claim 1, wherein the control circuit (150) comprises an analog-to-digital converter, wherein the control signal (41) generated by the control circuit is a digital signal (192). [16] The charging station condition monitoring device (100) according to claim 1, wherein the control signal (140) generated by the control circuit (150) is an analog signal (176).

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